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SECTION 9

MISCELLENEOUS

UAB School of Engineering - ECTC 2014 Proceedings - Vol. 13 227

Proceedings of the Fourteenth Annual Early Career Technical Conference The University of Alabama, Birmingham ECTC 2014 November 1 – 2, 2014 - Birmingham, Alabama USA

INFLUENCE OF FLUID RHEOLOGY ON THE PISTON CYLINDER OIL FILM DEVELOPMENT AND PRESSURE DISTRIBUTION CONSIDERING

MEDIUM SPEED EFFECTS IN INITIAL ENGINE START UP

Chaudhri Usman Lamar University

Beaumont, TX, USA

Kendrick Aung Lamar University

Beaumont, TX, USA

ABSTRACT This paper investigates the friction and the wear between

piston and cylinder liner during idling conditions with no or very little load applied. A 2-D non-Newtonian piston skirts lubrication model and analysis at the time of engine start up is presented. The well established Maxwell model has been used to describe viscoelasticity encountered during initial engine startup. The analysis of Lubricant Rheology between piston and cylinder liner by using characteristic lubricant relaxation times in an order of magnitude analysis is done by using the perturbation method. At low to medium engine start up speeds, the effects of Viscoelasticity on lubricant velocity and pressure fields are examined and the influence of film thickness on lubricant characteristics is investigated. Numerical simulations show that piston eccentricities, hydrodynamic pressures and film thickness profiles are functions of low to medium engine start up speeds.

INTRODUCTION Initial Engine Start up is a critical occasion because less

engine oil is present and there is a large piston to bore radial clearance. The initial start up of automobile engines used to cover preliminary low speed 4-stroke cycles prior to engine warm up at medium to high speeds. But automotive vehicles in the present day are started out at high rpm’s to achieve the stable situation without delays; however these high operating cycles invite start up adhesive wear among interacting piston skirts and liner surfaces in the absence of lubricating oil film. With the evolution of advanced machine elements that experience severe operating conditions, the increasing use of non-Newtonian fluids has been emphasized. The viscosity index improvers in the engine lubricants enhance the performance of base stocks for different conditions of crucial engine operations [1]. The lubricant’s viscosity should prevent

start up wear, and at the same time its mobility should facilitate smooth engine start up under the normal temperature conditions. In the past, a Sinh law based Ree-Eyring type lubricant that focused on shear thinning effects was modeled, but the model was contrary to the fact, which suggested that such characteristics cannot truly be modeled by that law [2]. Some researchers neglected the viscoelastic effects in compression and in shear while employing the thermal non-Newtonian Ree-Eyring lubrication model [3]. The non-Newtonian behavior of engine oils was modeled using various techniques. However, lately the attention of many researchers has been centered on the viscoelastic behavior of oils [4]. Newtonian fluid flow between interacting surfaces in relative motion causes shearing of layers and contributes towards an increase in the energy dissipation. While in a viscoelastic model, energy storage is characterized by lubricant elasticity and energy dissipation as lubricants viscous effect. A Maxwell type Viscoelastic fluid model of flow between the opposing surfaces facilitates reduction in energy dissipation [5].

This study develops a hydrodynamic lubrication model of the piston skirts. The viscoelastic characteristics of a non-Newtonian engine lubricant are incorporated in the lubrication model. A low viscosity grade engine oil, 1000 rpm crank shaft rotation speed and a piston-to-bore radial clearance of 10 mm are some of the inputs of the basic numerical model. Two other numerical models are developed and simulated to generate the results. An initial Start up speed of 1500 rpm is considered for the first case, whereas 2000 rpm is used in the second lubrication model.

In this study the following assumptions are considered for modeling the phenomenon [6].

1. Laminar flow and Turbulent effects are neglected. 2. Leakage at the sides and edges is neglected. 3. Pressure at the inlet is zero.


4. Lubricant is incompressible 5. Thermal effects are neglected. 6. Surface roughness and waviness are neglected. 7. Squeeze and cavitation effects are neglected.

NOMENCLATURE FG = Gas force

FIC = Inertia force due to piston mass FIP = Inertia force due to piston pin mass

Ipis = Piston inertia about its center of mass M = Moment acting on piston skirts

Mf = Friction moment acting on skirt surface P = Pressure

Ph = Hydrodynamic pressure a = Vertical distance from skirt top to the piston-pin

b = Vertical distance from skirt top to piston center of gravity et , eb = Piston eccentricities at skirts top and bottom surface

h = Film Thickness hm = Mean Film Thickness

hd = Deborah film thickness mpis = Mass of piston

mpin = Mass of piston-pin r = Crank radius

𝛚 = Constant crankshaft speed, corresponds to the engine speed

τ = Shear stress η = Kinematic viscosity

θ = Skirt angle Φ = Connecting rod angle

ψ = Crank angle

MATHEMATICAL MODEL

Piston and Cylinder bore are two components of the Power Cylinder system. The chemical Energy in the fuel is converted to kinetic energy during combustion and transmitted from the combustion chamber, through the piston, pin and connecting rod to the crank shaft. The geometric placement of the power cylinder system allows the linear motion of the piston to be converted in to rotational motion of the crank shaft. The angle of the connecting rod causes lateral motion of the piston, and interaction with the bore, combined with lateral motion and friction at the wrist pin bearing tends to cause piston tilt as shown in figure 1.

Figure 1. Schematic of Piston Cylinder System (a) and (b)

[7].

Apart from the primary piston axial motion its small secondary transverse eccentric displacements along the direction perpendicular to the axis of cylinder known as piston slap are incorporated in the equations of piston motion. Piston skirt eccentricities at the skirt top and bottom are calculated by considering piston inertia, hydrodynamic force, hydrodynamic friction force and moments in the form of equations similar to that defined by Zhu et al [7]:

�mpis �1− a

L�+ mpis �1− b

L� mpis

aL

+ mpisbL

IpisL

+ mpis(a − b) �1 − bL� mpis(a − b) b

L−

IpisL

� � eteb� =

�F + Fs + Ff tan∅M + Ms + Mf

� (1)

Where Fs= tan (FG+FIP+FIC) And Ms= FGCP - FICCG Piston geometry parameters are shown in Table 1 below.

Table 1. Input parameters including piston geometry [5] S/N

Parameter

Value S/N

Parameter

Value 1 Length (a) 12.5m

m 6 Pin off-set 1mm

2 Length (b) 15 mm 7 Clearance (C)

0.01mm

3 Mass mpin 0.09 kg 8 Crank radius (r)

41.8mm

4 Mass mpis 0.295kg 9 Radius (R) 41.5mm

5 Skirt Length (L)

33.8mm 10

Connecting rod length (l)

133mm


The magnitude of the gas force is a function of crank rotation angles for the 720 degree cycle. The gas force magnitude profile is shown below.

Figure 2.Gas Pressure Force Diagram.[5]

CALCULATION OF HYDRODYNAMIC PRESSURES The following 2-D Reynolds equation is used to calculate

the hydrodynamic pressures and forces. [6]. ∂∂x∗

�h∗3 ∂p∗

∂x∗�+ �R

L�2 ∂∂y∗

�h∗3 ∂p∗

∂y∗� = ∂h∗

∂x∗ (2) Boundary conditions to solve the Reynolds equation are: ∂p∂xx=0

= ∂p∂xx=π

= 0 ; (3) Where p = 0 when x 1 ≤ x ≤ x2 And p(x,0) = p(x,L) = 0

CALCULATION OF FILM THICKNESS

The lubricant film thickness without considering the bulk elastic deformation of piston skirts is given by [7]. h = C + et(t)cos x + [eb(t) - et(t)]ycos x

VISCOELASTIC FLUID MODEL An upper convected Maxwell model is applied to present

solutions for the unsteady flow induced by a constantly accelerating plate between two side walls perpendicular to the plate and by incorporating constant density, viscosity and a small fluid relaxation time. The continuity, momentum and constitutive equations for the incompressible non Newtonian fluid flow are solved by using a regular perturbation method. Specifically, we assume an asymptotic solution in the form of a double perturbation expansion in powers of 𝜀 and De. The leading term in the conventional lubrication solution is denoted by [ℓ] while the two perturbation corrections are denoted by [𝜀] and [De].

The leading term of Partial derivative of pressure is obtained from the simple Reynolds equation. ∂∂x�h3�� ∂ph

∂x�+ ∂

∂y�h3�� ∂ph

∂y� = 6ηU dh�

dy (4)

The correction term of the pressure is obtained by taking double derivative of leading term of velocities [6]. ∂P(ε)

∂x= 2 ∂2U(ℓ)

∂x2+ ∂2U(ℓ)

∂y2 (5)

which gives ∂P(ε)

∂x= 12�h

3−hmh3

�+ 2(3hmh3

+ 2h2

) dhdx

(6) For the Deborah term of pressure, modified Reynolds equation is solved [6], which gives, ∂P(De)

∂x= −18 hm

2

h5dhdx

+ 18 hmh4

dhdx− 4

h3dhdx− 12 hd

h3 (7)

where

ℎ𝑑 = {38�

ℎ𝑚2

ℎ14 −

ℎ22

ℎ04�−

12�

hmh1

3−hmh0

3�+16�

1h1

2−1

h02�

∫ 1ℎ3(𝑥)𝑑𝑥10

} (8)

Now total dpdx

is calculated. dpdx

= ∂P(ℓ)

∂x+ ∂P(ε)

∂x+ ∂P(De)

∂x (9)

The resulting expression is used in the calculation of shear stress, which will further give hydrodynamic friction force. NUMERICAL SOLUTION

To define the piston motion, eq. (1), represents a pair of mathematical relationships and incorporates the expressions for the forces and moments on the right side. The two non-linear second order differential equations of piston motion constitute an initial value problem to determine the time based piston secondary eccentricities. By using the assumed values of et, eb, at the previous time step as initial values for the current time step, the mean hydrodynamic film thickness is calculated. The average Reynolds equation and the oil film thickness equation are solved simultaneously by using the finite difference method and Gauss Seidel iterative numerical scheme. Afterwards all the forces and moments in eq. (1) are calculated. The accelerations are computed and satisfied from the solution of velocities at the previous and present time steps. If these are not satisfied then the present solution of velocities are adjusted using Runge– Kutta iterative scheme. When the satisfactory values of eccentric displacement rates are achieved, the piston position at the end of the current time step is obtained.


RESULTS AND DISCUSSION The basic non-Newtonian hydrodynamic lubrication fluid

flow model is simulated using Matlab to generate the results for discussion. 11x11 mesh size is used to generate the results that show the secondary eccentric displacements of the piston, hydrodynamic film thickness profiles and the pressure fields respectively. ECCENTRICITIES OF THE PISTON SKIRT

In figure 3(a), (b), (c) and (d), the Et and Eb profiles represent the dimensionless eccentricities of the top and bottom skirt surfaces of the piston. The Et and Eb curves are plotted with respect to three horizontal lines i.e., the upper line, the mid line and the lower line. The upper line and the lower line represent the non thrust and the thrust sides of the liner. The middle line shows the concentric position of the piston with respect to the cylinder liner. The Et and Eb curves are plotted against the 720o crank angle rotation. If the Et or the Eb curve touches either the upper line at 1.0 or the lower line at -1.0, then a solid to solid contact gets established between the skirt and liner surfaces and wear will take place. Piston eccentricity curves in the four stated speeds generally follow the same path such that initially concentric piston motion in the induction stroke, lateral eccentric displacements predetermined towards the non thrust side during the induction and compression strokes and speedy directional eccentric shift towards the thrust side at a piston position near the end of compression stroke.

Figure 3(a) Eccentricities of Piston Skirts at 1000 rpm

At 1000 rpm, the instantaneous directional shift in the eccentric displacement of the piston skirts top surface during the compression and expansion strokes keeps a considerable distance to the lower line where it remains till the end of the exhaust stroke at 720o

Figure 3(b) Eccentricities of Piston Skirts at 1500 rpm.

At 1500 rpm, the piston eccentricities Et and Eb during the expansion and exhaust stroke came very close to the lower line but still there is less possibility of solid to solid contact.

Figure 3(c) Eccentricities of Piston Skirts at 2000 rpm.


At 2000 rpm, the piston eccentricities Et and Eb during the expansion and exhaust stroke almost touched the lower line hence increasing the possibility of solid to solid contact and leading towards the piston skirt and liner wear.

Figure 3(d) Eccentricities of Piston Skirts at 2500 rpm.

At 2500 rpm, the piston eccentricities Et and Eb during the expansion and exhaust stroke cross passed the lower line making physical contact of piston skirts with cylinder liner more certain.

HYDRODYNAMIC FILM THICKNESS The maximum and minimum film thickness profiles as a

function of 720o cycle are shown in figure 4(a),(b),(c) and (d).The film thickness increases due to the eccentric displacements of the skirts before the piston completes the induction stroke. The secondary piston displacements contribute towards enhancing the film thickness. In the expansion stroke, the thrust generated by the combustion process tend to reduce the film thickness drastically.

Figure 4(a) Hydrodynamic Film Profiles at 1000 rpm

The magnitude of the maximum and the minimum film thickness profiles did not show any drastic change between 1000 and 1500 rpm.

Figure 4(b) Hydrodynamic Film Profiles at 1500 rpm

From 2000 rpm to 2500 rpm the decrease in film thickness was observed which highlights the damaging effect of high rpm engine initial start up on the load carrying capacity as shown in figure 4(c) and 4(d).

Figure 4(c) Hydrodynamic Film Profiles at 2000 rpm


Figure 4(d) Hydrodynamic Film Profiles at 2500 rpm

HYDRODYNAMIC PRESSURE FIELDS The hydrodynamic Pressures develop over the surface of the piston skirts at each degree of piston travel. 3 D pressure profiles are plotted at some of the important positions to analyze the pressure gradient and intensities. The pressure profiles showed the same trend at 1000, 1500 and 2000 rpm as shown in figure 5(a) through 5(d) and pressure profiles at 2500 rpm showed zero value and hence are not plotted here.

Figure 5(a): Pressure Profiles at 90o crank angle

Figure 5(b): Pressure Profiles at 180o Crank angle

In the induction stroke, the low intensity positive pressures

build up gradually and are slanted towards the top surface of the skirts. Figure 5(b) and 5(c) show gentle slopes, which indicate the rising pressures. After the mid compression stroke, the cyclic speed of the piston decreases but the gas force is still increasing.

Figure 5(c): Pressure Profiles at 270o Crank angle


The effects of moving piston inertia on the transverse side and a change in the direction of eccentric displacement vectors towards the thrust side shifts the positive pressures towards the bottom surface of the skirts as shown in figure 5(d).

Figure 5(d): Pressure Profiles at 360o Crank angle

SUMMARY/CONCLUSIONS

A 2-Dimensional non-Newtonian piston skirts hydrodynamic lubrication fluid flow model was developed to study the effects of medium to high initial engine start up speeds on hydrodynamic film thickness profile. The initial engine start up speed at medium range i.e., 1000 rpm is the one at which chances of adhesive wear of piston skirts surface are minimized due to the maximum improvement in the secondary eccentric motion of the piston, on the other hand, at 2500rpm the reverse seems to be true. Similarly the maximum and minimum hydrodynamic film thickness profiles are reduced considerably at 2500rpm. To optimize the engine start up speed in a few initial cycles based on the findings of the present study suggests that speeds above 2000rpm would cause surface to surface contact and hence adhesive wear could occur which can considerably reduce the engine life. In addition, the present non-linear transient analysis agrees qualitatively with the linear analysis of the previous study by Qasim et al. [9]. ACKNOWLEDGEMENTS The authors would like to pay gratitude to The Lamar University, TX, USA for supporting this project.

REFERENCES [1] A.Berker, M.G.Bouldin, S.J. Kleis, W.E.Vanarsdale, “Effects of polymer on Flow in Journal Bearing,” Journal of Non-Newtonian Fluid Mechanics, 0377-0257/95,1995. [2] Kumar.P,Khunsari MM,Bair S. “Full EHL simulations using the actual Ree-Eyring model for shear thinning lubricants”. ASME Journal of Tribology, 2009:011802-1-6131. [3] Yang.P, Wen.S , “The behavior of non-Newtonian thermal EHL film in line contacts at dynamic loads”. Journal of Tribology, 1992:114(1),81-95. [4] Sara J. Hupp, “Defining the role of Elastic lubricants and micro textured surfaces in lubricated , sliding friction”, PhD thesis, Massachusetts Institute of Technology, feb 2008. [5] Corina Fetecau, D. Vieru, A. Mahmood, “On the Energetic balance for the flow of a Maxwell fluid due to a constantly accelerating plate,” Acta Mech 2003,89-96-2009. [6] Gwidon,W. Stachowiak, W. Batchelor, “Engineering Tribology”,Third Edition,pp115-116. [7] Dong Zhu,Herbert S Cheng,Takayuki Arai, Kgugu Hamai., "A numerical analysis for Piston Skirts in mixed lubrication," ASME Journal of Tribology,114-553:62 [8] Rong Zhang and Xin Kai Li. “Non Newtonian effects on lubricant thin film flows” Journal of Engineering Mathematics (2005) 51: 1-13. [9] Syed Adnan Qasim, Usman F.Chaudhri, M. Afzaal Malik, “Analyzing Viscoelastic effects in Pistons skirt EHL at small radial clearances in initial engine startup”. Tribology International, 45 (2012) 16-29.



SOME PROJECT MANAGEMENT CHALLENGES WHEN PLANNING TO CONDUCT VERTICAL TRANSPORTATION STUDY

Magdalena Krstanoski, MSc.ME

Doctoral Candidate Ss. Cyril and Methodius University Faculty of Mechanical Engineering,

Skopje, Macedonia

ABSTRACT This paper discusses some project management aspects

when planning to conduct traffic study, when many aspects of the projects are not defined yet. When carefully implemented and documented, vertical transportation analysis, can contain valuable source of information about the project initial intend, and can serve as a base to understand the concept of the vertical transportation study later in the process. Traffic study (vertical transportation analysis) is a complex process of researching all elements related to the available information about the project that may affect the horizontal, and the vertical communication in the building. The importance of the areas, such as: understanding the concept, time, methods of communications, addressing questions, and selection of assumptions, as well as further revisiting and challenging the assumptions as more information about the project becomes available, are aiding to the process of making decisions in the path of suggesting solutions for the given project. Herein, the challenges that elevator planning designer is facing are observed, and some factors that directly or indirectly influence the process are analyzed.

MOTIVATION Attention to the traffic studies increased with the rising

trend of high rise buildings. Although it appears to be not so visible part of a project, it is of significant importance, develops a need of focused attention, and a special approach.

The reason is that, not only the need or inquiry for traffic study may involve concept design, beginning of the project initial phase or around the time before drawings are send to approval, but also, when projects have already been built, and there are modernization plans, building use changes, or occupancy changes.

The proposed concept design often needs to be further clarified, or the initial vertical transportation intent to be revisited. As the initial traffic study is not given much attention as it really deserves, often facing with time constraints, many

areas that need to be considered, remain not observed. Identifying unobserved and undocumented areas may appear as key elements in researching the vertical transportation service once building is put in service, and may arise as a possible non-observed source for further resolution. This paper may serve as basis for concept planning and investigates challenges when planning to conduct vertical transportation study.

UNDERSTANDING THE CONCEPT AND IDENTIFYING OBJECTIVES

Planning and organizing the tasks requires identifying objectives, and may include two approaches:

- Based on prior experience and best practices - tasks that most likely are to be followed;

- Based on project unique requirements, or new project – tasks with a new approach path to explore and address the unknowns;

In both cases definition of sequences of work is important, known vs. unknown data to be investigated, assumptions and possibilities to be explored, and time frame to accomplish the tasks to be estimated.

Identifying objectives is the key tool to organize the process. This needs to reflect the situation at present and to give an understanding of possible future outcome.

Achieving the results is related to the operational character of the objectives[1], per Drucker’s, objectives:

“They must be capable of being converted into specific targets and specific assignments.” (Peter Drucker 1974) [1].

Drucker[1] also calls for balancing the objectives[1], and decisions for risks to be taken in favor of the results[1]. In the case of a traffic study management, risks to be taken can be translated into exploring possibilities, and selecting the assumptions based on the project study, and observation. Identifying the priorities[1] by what comes first, and scheduling the task activities, helps us to understand the objectives by employing a thoughtful process to go over each segment to measure the possible paths to achieve results.


In 1971 in the fifth edition of “Mechanical and Electrical Equipment for Buildings” W. McGuinness and B. Stein [2] wrote about the inner relations between architecture and engineering [2]. They noted the necessity of considering several elements at the same time, such as: building use in relation to the elevator service, elevator spaces factors such as elevator (elevator banks) lobbies locations and arrangement, shafts and machine rooms in relation to the architecture, and the elevator selection in relation to the economy. [2]

Strakosch [3] as well, noted the importance of at the same time analyzing, and understanding peoples’ movement, i.e. pedestrians flow, human factors and pedestrians traffic demands [3]. All elements are to be considered concurrently, meaning they are to be observed or analyzed as one connected whole rather than as separate elements.

Determining the need for a traffic study and the reasons behind it, must evolve from understanding the current concept, addressing the concerned areas, and reviewing details to develop paths that can possibly lead to solutions, diligently research criteria for making assumptions, and evaluating the results.

To understand the concept, and as general starting point, areas that need consideration and investigation need to be clearly defined. Depending on the project’s objectives, and project phase, a focus on key critical factors (impact of the selection of the assumptions) as related to the general elements/steps is important. Following general steps and review processes in order to understand the project includes review of the available drawings (plans, sections) and specifications, analyze the available data (human factors, project location, market research), observation, evaluation, comparison study, methods to measure current pedestrian flow (See Fig.1).

Figure 1. General steps in order to understand the

concept

METHODS OF COMMUNICATION Communication commences when a need and/or an inquiry

about vertical transportation for particular project is put on the table.

In the past and up to date, project information and drawings have been communicated and delivered in several ways: traditional drawings (depending of the project and location of the party that inquire about traffic study and location of the designer), delivered or sent as a copy, or by exchanging drawings, providing link to the FTP server (or inviting to share one specific link via common server, online file transferring platform for sharing large files), or other storage media, or shared by e-mail that in most cases may require more than one email. Furthermore, as the new technology evolves, other methods of sharing the project information include: project websites, visualization, BIM, or other (See Figure 2).

All of the above requires certain document management, or digital data management that will allow storage, and data sharing if applicable, with the project participants. The file format varies, and in some cases, compatibility of the programs, and version of certain programs between the sender and the recipient, may affect the time to commence the project study, due to the additional time required to access the drawings set. When time is of essence, and limited time is available for the project, this may possible create challenges and delays in communication, if not foreseen ahead of time. Formats such as pdf files are most likely to be easily communicated; other formats are used as well. For ex. Sharing CAD or granting access to common media, where only CAD files are utilized, may possibly create additional delays in communication, in case both parties have not previously agreed on the version to be used for review, or if another party needs additional time to print/plot the drawings in order to conduct the review.

Figure 2. Methods of communication of the project documents

Depending on the

project phase Review and evaluation

Data

Observation and Project Data

Measure; Evaluate

• Plans, Section • Specifications

• Past &Present • Human factors • Market

Research • Building Purpose • Occupancy Type • Elevator

Placement • Elevator usage

Methods of communication of the project data

Traditionall ways of communication

- Printed drawings delivered or exchanged - Link to share (FTP server, common server, online file transfering platform, storage media & granted access for sharing files)

-E-mail communication and drawings exchange

Other

- Conference calls, project reviews via

screen sharing - BIM , CAD


TIME MANAGEMENT Time is an important dimension [1], in the management,

closely related to the decisions for action. Per Drucker [1]: “…The time dimension endows the managerial decision

with its special characteristics. It is the act in which the manager integrates present and future.” [1], (Peter F. Drucker 1974) [1].

Observing the time factor, Parkinson’s Law [4], – “work expands so as to fill the time available for its completion” [4], appears to be a reasonable approach when planning a traffic study.

Time is a deplete-able resource, and if not diligently dedicated to the task, may very well influence the end outcome, where time is needed to investigate all the aspects, review and evaluate all the available data, to elaborate the steps and rationale, or produce the results, and evaluate the process.

Depending on the given time frames with the inquiry for the traffic study, the time required to produce one may be limited. Planning on a limited time faces time constraints for review of the available data, and is related to the urgency of the inquiry and the ability to establish priorities in a fast-pace environment. At the same time, limited time planning, may suffer from insufficient time for detail approach, lack of effective completeness of action, and necessity of extra time at hand to double-check the action to assure the action’s rational and accuracy (See Fig.3).

To effectively achieve the objective, limited time planning needs to focus on known data and values, and to observe, explore and analyze possibilities and assumptions that will timely lead to accomplishing the goal, based on defined objectives.

For some large and involved projects, such as mixed-use projects (for ex. shopping malls with mixed-use occupancies, having different segment areas connected to the mall, such as hotels, residential and office areas, fitness facilities, conference rooms), the time for traffic study must be carefully planned.

As the Parkinson’s Law [4] theoretically may apply in the traffic study concept analysis time frame, the same is dependant on many factors, and generally may be viewed as a sum of times needed to accomplish the segments of work, plus additional time to double check the assumptions, paths, and conclusions.

In comparison with the general project management, where time frames to communicate the project status and reports are related to the sequence of work, and availability of human resources involved in the project, in case of planning vertical transportation study many times is in the hands of a single designer, who need to coordinate, organize, conduct and communicate his work with other parties.

Fig.3 Limited time planning, may suffer from insufficient time for detail approach, completeness of action and lack of time to double-check the action to assure the action’s

rational and accuracy Identification of the factors that affect time resource,

depending of the project objectives, in addition to the review of the available project data, may involve further research areas related to: project location, market analysis, human factors, traffic analysis, applicable regulations, budget, approvals, and administrative factors (See Fig.4).

Reviewing and investigating human factors, movements in and about the building, building purpose and occupancy type, building location and project location, are just few elements that influence the initial start-up time in the process of researching for design solution. Further the process involves time to understand the critical factors (impact of selecting, and support the reason of selecting particular assumptions), and likelihood that decision to reflect the future outcome. In addition, time to conduct the actual traffic study, and explore the possibilities, as well as time to double check the process, all the above that will ultimately lead to rendering a value of opinion.

Timely planning Limited-Time planning challenges


Figure.4 Areas that may affect the time aspects of

planning of the traffic study

SELECTION OF ASSUMPTIONS Analyzing, and selecting assumptions, based on the

available project information is not a simple process. Selection of the assumptions and possibilities depends on the vertical transportation planner’s skills, creativity, experience, coordination skills, research and technical background.

The decision regarding assumptions to be researched and employed is closely related to the likelihood of the vertical transportation design outcome to picture the project in the future. By assessing the impact of the assumptions, elaborating the criteria developed for decisions to adopt each assumption, and grounds for selecting the possible assumptions that lead to certain decisions, may further open paths for possibilities.

This approach may later lead to identifying indicators that will measure the effectiveness of the decision based on the assumptions employed. Herein “later” is a time dependant factor, part of the time management planning (See Firg.3).

Selection of assumptions is related to the ability to research, recognize key areas, identify risks, support the selection with applicable references and make choices.

Davidoff and Reiner [5] define planning as “a process for determining appropriate future action through a sequence of choices.” [5] (Paul Davidoff and Thomas A. Reiner 1962) [5].

Regarding choices, they further relate choices with the “exercise of judgments” [5], addressing the “three levels” [5], choices are made:

“ …..first, the selection of ends and criteria; second,

the identification of a set of alternatives consistent with these general prescriptives, and the selection of a desired alternative; and, third, guidance of action toward determined ends. Each of these choices requires the

exercise of judgment; judgment permeates planning.” [5] (Paul Davidoff and Thomas A. Reiner 1962) [5].

This concept generally applies in the process of vertical

transportation planning, where expressing a value of judgment based on prior research, selection of assumptions, processes and directions towards achieving effective goals influence the end result.

Selection of the assumptions, and traffic study analysis is time dependant, subject to change should any new information or corrected data that was listed as known or unknown, about the project becomes available. Then a new study must be conducted that will consider the new information.

ADDRESSING IMPORTANT QUESTIONS There is industry publishing in the area of traffic study,

where many important aspects of the industry and questions, such as population for typical buildings for estimating elevators requirements, and elevator planning are covered (W. McGuiness and B. Stein [2], G. Strakosch [3], G. Barney [6], J. DeChiara, J. Panero and M. Zelnik [7]).

On the other hand, project management aspects in planning vertical transportation study are left to the designers, which study reports covering information that pertains to the quality and quantity of the service of the proposed concept. But many times the bases of the assumptions, and referenced sources are not included.

When basic project data that refers to population per floor is not known, many times there are methods same to be calculated based on the referenced industry data available, by researching project information, noting the questions arisen and carefully selecting assumptions.

Hypothetically speaking, in many instances questions need additional analysis and consideration, such as whether acceptable vertical transportation service can be achieved if the originally proposed number of the elevators is reduced, and how to achieve acceptable vertical transportation quality and quantity of service, with more economically favored solutions.

Defining per floor population is the key element. If information about population per floor is not provided to the designer, but other related data is available on the floor plans (although the list is longer, but to name a few, for ex. floor area, rentable area, number and type of units in the residential or hotel section, parking spots, etc), and if, based on that information, the population per floor was estimated, without explaining the path, more important questions to be asked are “How the population per floor was established?” and “What assumptions are taken into consideration when population per floor was established?” and “What reference source served as a base for the population per floor to be estimated?”

The necessity for vertical transportation designers to explain the reasoning behind their made assumptions, referenced sources, or reasoning behind their specified choice provides valuable information as of the origin of the project

Time related factors

Traffic study concept

Project data

Market analysis

Geographical area Human factors Applicable

regulations

Project administration

Approvals

Budget


communication with the project team and vertical transportation designer. It also provides everyone an opportunity to understanding later in the process of the reasons behind the decision of their opinion, once project is build and if revisiting the origin of study is necessary, if needed.

CONCLUSIONS Traffic study is an important element when designing a

building. Vertical transportation designers need to consider many factors related to the vertical transportation to understand the project, prior conducting the mathematical aspect of the study. On the other hand, the designer’s input project information depends on the data about the project that have been furnished to the designer by others (depending on the project phase, project information, concept, plans, drawings, specifications).

It is not an individual process but rather a coordinated process that requires addressing important right questions to be asked, in order designer to gain understanding of the building to further proceed with the traffic study. It is also a continuous process; if information originally utilized in the study process changed, than new study must be conducted that will reflect the new data.

The intent of this paper is to initiate the importance of the process of planning of the traffic study, for traffic study designers to dedicate time to understand the project in order to make valuable assessments, plan time to make right assumptions, and create an extra time for evaluation of the assumptions closely reflecting the project status, that can lead to picture the future, based on today’s information, if done diligently. At the same time, this paper discusses the significance designers to include the basis for the made assumptions and referenced sources for selecting project applicable assumptions in their study, the information that once the project is built, may possibly answer questions about the basis the study was conducted.

REFERENCES [1] Peter F. Drucker, 1974, Management: tasks, responsibilities, practices, Harper & Row, Publishers, Inc., 10 East 53rd Street, New York, N.Y. 10022 ISBN 0-06-011092-9, pp. 43-45; 99—102; 117-120; [2] William J. McGuinness, Benjamin Stein, 1971, Mechanical and Electrical Equipment for Buildings, Fifth Edition, Published by John Wiley and Sons Inc., ISBN 0-471-58431-2, pp.890; pp.899; pp.908-912; [3] George R. Strakosch, 1998, The Vertical Transportation Handbook, Third Edition, John Wiley & Sons, Inc., 605 Third Avenue, New York, NY 10158-0012, ISBN 0-471-16291-4, pp.4, pp.247-249. Pp.283-285; pp.303-304; [4] Merriam-Webster’s Collegiate Dictionary, Eleventh Edition, Merriam-Webster, Incorporated Springfield, Massachusetts, U.S.A., pp.901; [5] Paul Davidoff and Thomas A. Reiner, 1962, A Choice

Theory of Planning, Journal of the American Institute of Planners; [6] Gina Barney, 2003, Elevator Traffic Handbook, Theory and Practice, Spon Press Taylor & Francis Group, London and New York, ISBN 0-415-27476-1, pp.128-132; pp.200; [7] J. DeChiara, J. Panero & M. Zelnik, 1991, Time-saver standards for interior design and space planning, McGraw-Hill, Inc. United States of America, ISBN 0-07-016299-9, pp.1060;



DESIGN AND DEVELOPMENT OF AIR POWERED ENGINE

Shalin Shah, Nisarg Patel, Kirtan Khajanchi Student

Vimal Savsani Assistant Professor

Pandit Deendayal Petroleum University

Gandhinagar, Gujarat, INDIA

ABSTRACT There are millions of cars on roads already, so it would be

illogical to withdraw them all and implement this technology, so it is better to modify the existing technology, which is possible with just a few minor modifications. The aim was to convert 2-S internal combustion engine to an efficient air engine with minimum cost. There were 3 primary concerns which needed to be addressed for materializing the same. First was blocking the induction port to prevent any leakage of air. Second, to determine the position of air supply from a place where maximum work could be extracted. Third and the most important part was the design of a timing circuit to precisely decide the time of entry of air and the duration for air supply. After the modification, it is necessary to check whether the engine performs as per the requirement. So, the engine performance based on different parameters needs to be observed. For experimental purpose, a compressor was used to supply air to the engine. First and foremost, the range of a vehicle of a given air tank capacity assuming constant pressure condition was established. Also the duration for which it will run and derived from that, its velocity over the course were found. Coherently it is necessary to check the change in the variation of distance and velocity if pressure drop in the tank is considered. Last and pivotal, the engine performance parameters most important of which was efficiency. For that, polytropic expansion in the piston was considered to obtain the work done using moving boundary condition and maximum possibility for doing work was calculated considering isothermal tank capacity. From moving boundary work, net power and torque could be calculated. It could easily be seen that torque output at certain pressures was more than the spark ignition engine itself. The most obvious trend that was observed was that, with the decreasing pressure work output, efficiency, power and torque decrease almost linearly. There is scope for further development of this project. As it is intended for mobile applications, an air-tank could be designed of composite materials which are much lighter than steel. Also, this engine will run at considerably lower speeds, hence a hybrid system

can provide a two-fold advantage of speed and mileage at reduced costs.

NOMENCLATURE BDC Bottom Dead Centre dt Tank Diameter dw Wheel Diameter D Range of Vehicle EPO Exhaust Port Open lt Tank Length m Reduction in Mass of Air in Tank M Total Mass of Air in Tank n Polytropic Index N Total Number of Rotations of Shaft P Power Developed at Shaft P1 Tank Pressure P2 Exhaust Pressure Pi Initial Pressure Pf Final Pressure r Number of Rotations Possible R Gas Constant t Run Time of the Vehicle T Torque Produced at Shaft T1 Tank Temperature TDC Top Dead Centre V Velocity of Vehicle Vf Final Volume (After Expansion) Vi Initial Volume (Before Expansion) Vs Swept Volume Vt Tank Volume Weng Work Obtained from Engine Wtank Energy Available in Tank ρi Initial Density (Before Expansion) ρf Final Density (After Expansion) η Engine Efficiency

INTRODUCTION The principle of compressed-air propulsion is to pressurize

the storage tank and then connect it to something very like a reciprocating steam engine of the vehicle[1]. Instead of


mixing fuel with air and burning it in the engine to drive pistons with hot expanding gases, compressed air vehicles use the expansion of compressed air to drive their pistons. The concept of air-powered engines is not at all recent. In fact, it had been used for certain mining vehicles and torpedo propulsion as early as 1903. Since the early 1990’s Guy Negre has been trying to sell air-car designs in different countries through his company Motor Development International[2]. But, as far as the application of the concept of modifying the existing engine is concerned, Jem Stansfield, an English inventor has been able to convert a regular scooter to a compressed airmoped. The range of the vehicles was approximately 7 miles with a top speed of 18 miles per hour[3]. There have been attempts for designing a new engine as well as modifying an existing engine. But, the air-powered engine in general has some inherent merits and demerits. The prominent merits are: The fuel i.e. air, itself is non-combustible and non-

polluting. In addition to that, the price of the fuel is lower than conventional fuels[4].

There are just a few auxiliary systems, so the overall cost is reduced and maintenance becomes easy and cheap.

Air is compressed at the refueling station, hence there is no transportation cost of the fuel. Further, the refueling rates are much higher as compared to other non-conventional options [2].

The environmental impact of these engines is almost negligible. The fuel and the storage medium have no effect on the environment at all.

There are always two sides of a coin. The other side i.e. the demerits are: The energy density of the fuel is considerably low,

hence making it unsuitable for high speed applications. As the fuel is utilized, pressure drop in the tank occurs.

This affects the range as well as the maximum velocity of the automobile.

As there is expansion of air in the engine, in lower temperatures, the engine may ice-up[1].

Pressure in the tank is considerably high. Hence in case of a mishap, there is a serious threat of the bursting of the air-tank.

Keeping in mind the above points, the air engine is appropriate for:

Automobiles in mining industry where even a small spark can lead to a catastrophe.

Companies that use compressed air in their processing, like the textile industry. After processing, the air exhausted is still at high pressures. Here the air

engine can be coupled with a generator and the power produces can be used to run other small systems. This will lead to considerable amount of savings.

A pneumatic hybrid. The major demerit is the energy density. If speed is required, a coupling with other system is necessary for high speeds. This will give the advantage of economy and environment friendliness as well as the need for high speed[5-7].

DEVELPOMENT OF AIR-ENGINE Converting an internal combustion engine to air-engine

requires certain modification and additional parts as well. The components of the air-engine setup are:

2-stroke reciprocating engine Flywheel Solenoid valve IR sensors Arduino Board Motor Driver Battery Pressure Gauge Piping Electrical Wires Connectors Aluminum Plate

Figure 1:Experimental Setup

The objective was to make an efficient reciprocating air engine. The lightest available engine which met the requirement was a 2-S 50 cc Kinetic Luna engine. This engine

Pressure Gauge

Solenoid Valve

IR sensor

Arduino Board

Motor Driver

Flywheel

Battery

Engine


could easily be modified because of its simple nature many of which, one of many is the absence of cam and cam shafts obviating the requirement for major modification. The modified engine is shown in Figure1. There were mainly three modifications required in the engine.

1. Blocking the induction port 2. Induction port for from a place where maximum work

could be extracted 3. Designing a timing circuit for the supply of air

There is an induction port for the supply of fuel in a 2-S engine. The supply of air is made through a different port, hence the induction ports needs to be blocked to prevent any leakage of air. This port has been blocked off between the combustion chamber and fuel chamber by using a thin 1 mm aluminum plate. For additional protection from leakage m-seal has been applied to prevent losses as far as possible.

Compressed air will be able to extract maximum work only when it will be above the piston at the Top Dead Center (TDC). The most ideal place for induction would be in place of the spark plug. As there would be no need of the spark plug and removing that will leave a big hole to be filled. Hence, this becomes the most ideal place for entry of air. Using proper connectors, compressed air is induced directly from the top.

The timing circuit is the most crucial component of the entire air engine functioning. This will determine the exact position of the piston where the air will be induced and for the time duration it needs to be supplied. This is accomplished by using proper sensors and a controller. For the experiment IR (infrared) sensors with varying range have been used. There are two sensors used. One for switching on the air supply and the other one to shut off the same. The sensor is mounted on two S-shaped 2mm thick aluminum plates machined according to the need of height and ability to attach it to the existing engine. A L-plate of the same material are used for acting as the obstacle to be sensed by the sensor. The S-shaped plates are at an angle which is nearly 1000 i.e. an angle smaller than the angle between Top Dead Centre and Exhaust Port Opening. It is mounted on the shaft in such a way that the first sensor on the S-shaped plated is sensed just after the piston crosses the Top Dead Center. The IR sensor is connected to the controller. Here this being an arduino kit. The arduino kit collects the signals from both the sensors and relays the information to the solenoid valve for its operation. The arduino kit itself can only manage voltages up to 5 V. For this reason motor driver to manage the high voltages and function as per the programing of freeduino (arduino) board is utilized. The motor driver is connected to the battery which is responsible for the supply of voltage to IR

sensors as well as the solenoid valve. The arduino board receives the signal from the sensor and signals the solenoid valve to switch on and off. IR sensors are connected to both, the motor driver which will supply the required current and to the controller board to which it is supply the sensed signal. The motor driver is connected to the solenoid valve as well. The Arduino which received the signal from the sensors are relayed to the motor driver which read the signal and supply power to solenoid valve. The battery used is a 12 V 1.2 A power source which is enough to power all the components of the circuit. The connections of this timing circuit are as shown in the Figure 2.

Figure 2: Timing Circuit

After these modifications, the engine is ready to run.

Different connections to connect all the components listed above The main objective was to check the performance of engine for mobile use hence special storage tanks are required for air, but here it was for experimental purpose, so compressed air obtained directly from a compressor is used. The air from the compressor is supplied at a certain pressure. An initial push is needed to start the engine as an exciter is not connected. The compressed air will then take over for supplying power. This air is supplied to the solenoid valve. In between there is a pressure gauge attached. This will account for the pressure losses occurring in the pipe between the compressor and the pressure gauge. The pipe needs to be connected with the help to certain connectors. First of all the pipe from the compressor needs to be connected to the P.U. pipe connecting it to the pressure


gauge. This pipe cannot be directly connected to the pressure gauge as that requires special pipes. A copper pipe is used for this connection. At the both endstwo connectors are attached. One end will be the pipe carrying the supply of air from the compressor while the other end will be connected to the inlet pipe to the engine. After that using a P.U. pipe, the compressed air is supplied to the solenoid valve. This valve will be operated by the arduino kit and motor driver which receives its signal from the IR sensor. When the obstacle reaches the first IR sensor, the signal will be passed onto the arduino which will give signal to the motor driver to give power to the solenoid valve with the help of battery. As the valve opens, air finally enters the combustion chamber when the piston has just crossed TDC and pushes the piston downwards giving movement to the shaft. The shaft rotates so does the obstacle attached on it. As soon as the piston approaches its EPO, the IR sensor will sense it and a signal will be passed to shut off the solenoid valve. The air from the combustion chamber will exhaust from the exhaust port. A flywheel of balanced weight and appropriate mass attached to the shaft rotates along with it. This will ensure that the cycle is completed and the piston reaches TDC to reinitiate the next cycle. This is the path of air-flow from compressor to exhaust. Schematic diagram of the experimental setup is shown in Figure 3.

Figure 3: Schematic Diagram of Setup

For experimental analysis of the engine, pressure of

compressed air and angular velocity obtained at the shaft need to be measured. A tachometer was used to measure the shaft speed. The readings were taken for variable pressure after allowing the pressure to stabilize. Further calculations for engine performance were done based on this values obtained.

MATHEMATICAL MODELLING A mathematical model is necessary to check the engine

performance parameters like range, velocity, torque, power, efficiency etc.

Figure 4: P-V Diagram

For the calculation the atmospheric conditions are taken as

standard temperature and pressure and the tank temperature is taken the same as atmospheric. The expansion of gases is assumed to be polytropic. In the Figure 4, Process 1 to 2: Polytropic Expansion of air Process 2 to 3: Isobaric Compression of air Calculation for effect of pressure on range and velocity Assuming the dimension of a tank having dimensions :

Length of tank (lt) = 1 m

Diameter of tank (dt) = 0.5 m

Volume of tank (Vt)

= 𝜋4

dt2 lt (1)

= 0.196349 m3 Swept volume (Vs) = 𝐴𝑛𝑔𝑙𝑒𝑏𝑒𝑡𝑤𝑒𝑒𝑛𝑇𝐷𝐶𝑎𝑛𝑑𝐸𝑃𝑂

𝐴𝑛𝑔𝑙𝑒𝑏𝑒𝑡𝑤𝑒𝑒𝑛𝑇𝐷𝐶𝑎𝑛𝑑𝐵𝐷𝐶Volume of Combustion Chamber (2)

= 27.66 cc This is the volume of air required for one rotation of the shaft. So, from this we can calculate the number of maximum rotations possible from a tank of the above specified capacity assuming it has enough pressure to move the piston.


Number of rotations possible (r) = 𝑉𝑜𝑙𝑢𝑚𝑒𝑜𝑓𝑡𝑎𝑛𝑘

𝑆𝑤𝑒𝑝𝑡𝑉𝑜𝑙𝑢𝑚𝑒 (3)

= 7098.68 rotations

Assuming a wheel diameter (dw) of 0.5 m, we can get the range and velocity of the vehicle Range of the vehicle (R) = π dw r (4) = 11.1439 km Velocity of the vehicle will change with change in angular velocity which is directly dependent on pressure. For calculating velocity we will need run time of the engine. Run time will change with change in pressure. Run Time (t) = 𝑁𝑢𝑚𝑏𝑒𝑟𝑜𝑓𝑟𝑒𝑣𝑜𝑙𝑢𝑡𝑖𝑜𝑛𝑠

𝐴𝑛𝑔𝑢𝑙𝑎𝑟𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 (5)

= 19.446 minutes Velocity of vehicle (v)

= 𝑅𝑡 (6)

= 34.38 km/h Calculation for effect of pressure drop on range and velocity The tank capacity is same as mentioned above. Angular velocity changes with change in the pressure. So, if the tank starts losing air mass, the pressure will drop which will result in a change of distance travelled and the average velocity. Calculating the same for first pressure drop. Volume of tank (Vt) = 0.1963 m3

Initial Density (ρi) at 11 bar = 12.84 kg/m3

Final Density (ρf) at 10.5 bar = 12.26 kg/m3

Reduction in mass of air in tank (m) = (ρi -ρf) Vt (7)

= 0.1139 kg Volume of air supplied = 𝑚

(ρi+ρf2 )

(Considering average density) (8)

= 8.78 x 10-3 m3 We know the swept volume for work done = 27.66 x 10-6 m3

Total Rotations for this amount of volume (9) = 𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑎𝑖𝑟 𝑠𝑢𝑝𝑝𝑙𝑖𝑒𝑑

𝑆𝑤𝑒𝑝𝑡 𝑣𝑜𝑙𝑢𝑚𝑒

= 328.05 rotations Total distance travelled for this amount of rotations = π dw (Total Rotations) (10) = 0.515 km Velocity will become = 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒𝑇𝑟𝑎𝑣𝑒𝑙𝑙𝑒𝑑𝑇𝑜𝑡𝑎𝑙𝑅𝑜𝑡𝑎𝑡𝑖𝑜𝑛𝑠

𝐴𝑛𝑔𝑢𝑙𝑎𝑟𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 (11)

= 34.38 km/h Calculation for Engine Performance Parameters Assuming polytropic expansion of air for ideal gas, we can find the net energy available in tank for expansion from any pressure to ambient pressure i.e. 1 bar. For the sample calculation let us assume pressure in tank to be 11 bar and at 25o C. Isothermal expansion coefficient for air (n) = 1.3. Wtank = 𝑛𝑅𝑇1

𝑛−1 ((𝑝1

𝑝2)(n-1)/n – 1) [8] (12)

= 273.91 kJ/kg Work done by piston can be obtained from moving boundary condition. For that we require initial volume and pressure and final volume and pressure. Initial Pressure = 11 bar = 1100 kPa Initial Volume = 𝑉𝑜𝑙𝑢𝑚𝑒𝑜𝑓𝐶𝑜𝑚𝑏𝑢𝑠𝑡𝑖𝑜𝑛𝐶ℎ𝑎𝑚𝑏𝑒𝑟

𝐶𝑜𝑚𝑝𝑟𝑒𝑠𝑠𝑖𝑜𝑛𝑅𝑎𝑡𝑖𝑜 (13)

= 6.225 x 10-6 m3

Final Pressure = 1 bar = 100 kPa Final Volume = Swept volume for work done = 27.66 * 10-6 m3 So, moving boundary work = 𝑃𝑖𝑉𝑖−𝑃𝑓𝑉𝑓

𝑛−1 (14)

= 0.0136 kJ/kg This is the work done in one stroke or one rotation. Total number of rotations previously found are 7098.Hence, total work done will become Weng = 0.0136 * 7098 (15) = 96.56 kJ/kg


We now have energy available in tank and energy obtained from the air engine from moving boundary work. The efficiency can be found by η (eff.) = 𝑊𝑒𝑛𝑔

𝑊𝑡𝑎𝑛𝑘 (16)

= 35.25 % Total mass of air in the tank at 11 bar for the vessel of given volume will be ρi= 12.24 Vt = 0.19 M = ρiVt (17) = 2.52 kg Actual total work done can be calculated using the mass and work obtained from moving boundary condition Wat = Weng M (18) = 243.35 kJ We know the run time t = 19.45 min. Hence, the power can be calculated as we know the actual total work done P =𝑊𝑎𝑡

𝑡 (19)

= 0.208 kW Since we know the power produced by the engine and the angular velocity at which it is rotating, torque available will be: T = 60 𝑃

2 𝜋 𝑁 (20)

= 5.45 N-m

RESULTS AND DISCUSSION Table1: Effect of Pressure on Range and Velocity

Pressure Angular Velocity

Number of Revolutions

Run Time Distance* Velocity

(bar) (rpm) (min) (km) (km/h)

11 365 7098 19.4466 11.1439 34.38 10.5 355 7098 19.9944 11.1439 33.44

10 338 7098 21.0000 11.1439 31.84 9.5 320 7098 22.1813 11.1439 30.14

9 304 7098 23.3487 11.1439 28.64 8.5 283 7098 25.0813 11.1439 26.66

8 263 7098 26.9886 11.1439 24.77 7.5 235 7098 30.2043 11.1439 22.14

7 217 7098 32.7097 11.1439 20.44 6.5 184 7098 38.5761 11.1439 17.33

6 166 7098 42.7590 11.1439 15.64 5.5 153 7098 46.3922 11.1439 14.41

5 132 7098 53.7727 11.1439 12.43

*Assuming diameter of wheel = 0.5 m

As it can be very lucidly observed from Table 1, with the decrease in pressure, the angular velocity measured at the shaft decreases. Here, run time is the duration for which the air in the tank will last to give power to the shaft. Number of revolutions will remain the same as the volume utilized will be the same. Hence the distance travelled will be the same. So, the time within which the air is utilized will change. Higher the pressure, more will be the rotational speed, hence the same distance will be travelled in lesser time. From the simple relation between time and distance, we know that for the same distance, with increase in time, velocity will decrease. This is the reason for a downward trend in the velocity column.

Table 2:Effect of Pressure Drop on Range and Velocity

Pressure Angular Velocity

Density Mass of Air Used

Number of Revolutions

Distance Travelled

Velocity

(bar) (rpm) (kg/m^3) (kg) (km) (km/h)

11 365 12.84 - - - 10.5 355 12.26 0.1139 328.0506 0.515039 34.3804

10 338 11.67 0.1158 350.0225 0.549535 31.3394 9.5 320 11.09 0.1139 361.7782 0.567992 28.8691

9 304 10.51 0.1139 381.207 0.598495 25.9387 8.5 283 9.92 0.1158 409.9872 0.64368 22.9119

8 263 9.34 0.1139 427.5219 0.671209 20.4544 7.5 235 8.75 0.1158 463.0203 0.726942 17.5515

7 217 8.17 0.1139 486.6472 0.764036 14.9215 6.2 184 7.59 0.1139 522.4664 0.820272 12.8339

6 166 7 0.1158 574.0944 0.901328 9.9036 5.5 153 6.42 0.1139 613.5671 0.9633 8.36

5 132 5.83 0.1158 683.7582 1.0735 6.9143 4.5 111 5.25 0.1139 743.1472 1.166741 5.4885

Total 6345.268 9.962071 Average 18.4513

Figure 5:Volume of Air Used at each Pressure Drop

Figure 5 clearly depicts that the volume of air used for each

pressure drop increases. However, it can be seen from Table 1, the mass of air consumed remains nearly the same. This may be

0.009000

0.011000

0.013000

0.015000

0.017000

0.019000

0.021000

11

10.5

10

9.

5 9 8.

5 8 7.

5 7 6.

2 6 5.

5 5

Vol

ume

of A

ir (m

^3)

Pressure (bar)

Volume of Air Used at each Pressure Drop


attributed to the fact of varying density at each pressure. Increased consumption in volume will lead to an increase in the number of revolutions of the shaft too. Directly affecting the distance travelled by the vehicle. Also, as seen in the previous results, the velocity of vehicle changes at each pressure. Thus the average velocity of the vehicle will also decrease. The most important aspect that needs to be noticed is that the distance travelled by the vehicle decreases. This is directly related to the fact that the number of revolutions have decreased. If we find a percentage value, that comes out to be nearly 18 percent which is a considerable reduction.

Table 3: Engine Performance Parameters

Pressure Engine Work

Energy in Tank

Efficiency Net Work Produced

Power Torque

(bar) (kJ/kg) (kJ/kg) (%) (kJ) (kW) (Nm)

11 96.57 273.92 35.25 243.35 0.209 5.459

10.5 89.20 267.03 33.41 224.79 0.187 5.043 10 81.84 259.89 31.49 206.24 0.164 4.627

9.5 74.48 252.47 29.50 187.68 0.141 4.210 9 67.11 244.75 27.42 169.12 0.121 3.794

8.5 59.75 236.68 25.24 150.56 0.100 3.378 8 52.38 228.25 22.95 132.01 0.082 2.961

7.5 45.02 219.39 20.52 113.45 0.063 2.545 7 37.65 210.08 17.92 94.89 0.048 2.129

6.2 25.87 194.04 13.33 65.20 0.028 1.463 6 22.93 189.78 12.08 57.78 0.023 1.296

5.5 15.56 178.64 8.71 39.22 0.014 0.880 5 8.20 166.69 4.92 20.66 0.006 0.463

Figure 6: Power v/s Angular Velocity

Figure 7:Pressure v/s Energy in Tank

Figure 8: Pressure v/s Net Work Produced

Figure 9: Pressure v/s Efficiency

From Figures 6, 7, 8 and 9, we can easily see the

interdependency of the parameters. With the decrease in pressure, the tank energy decreases, so does work obtained from engine. But the decrease in engine work is lesser, and hence the efficiency of the engine decreases. As a result of

0.00000

0.05000

0.10000

0.15000

0.20000

0.25000

100 150 200 250 300 350 400

Pow

er (k

W)

Angular Velocity (rpm)

Power v/s Angular Velocity

4 5 6 7 8 9

10 11 12

150.0000 175.0000 200.0000 225.0000 250.0000 275.0000

Pres

sure

(bar

)

Energy in Tank (kJ)

Pressure v/s Energy in Tank

4 5 6 7 8 9

10 11 12

0.0000 50.0000 100.0000 150.0000 200.0000 250.0000

Pres

sure

(bar

)

Net Work Produced (kJ)

Pressure v/s Net Work Produced

4 5 6 7 8 9

10 11 12

0.00000 10.00000 20.00000 30.00000 40.00000

Pres

sure

(bar

)

Efficiency (%)

Pressure v/s Efficiency


decreased engine work, power decreases, so does the torque almost in a linear pattern. Hence we can see that with the increase in pressure, all the engine performance parameters will increase and will give a better engine performance.

CONCLUSIONS Experimentation on the modified engine yields many

results. It can be seen that increased pressure leads to an

increased linear velocity. But as the volume of air inside the tank is same, the distance travelled will be the same. This points to the fact that there will be a variation in the run time of the vehicle.

When it is not possible to maintain the pressure inside the tank, there will be a pressure drop as air is utilized. There will be a decrease in the distance travelled by a considerable amount. Due to pressure drop, the velocity at each stage will also change and the average velocity will become nearly half of the maximum velocity at maximum pressure for this experimental analysis.

The engine performance parameters change with the change in pressure. A change in the tank pressure will affect the tank isothermal capacity and the work obtained at shaft. Lower the pressure, lower will be the work done. Similar trends will be seen in the power output and torque available at shaft and consequently the efficiency too.

The torque produced at 10 bar and higher is more than that produced in Spark Ignition engine itself.

REFERENCES [1] B. S. Patel, R S Barot, Karan Shah, Pushpendra Sharma. “Air Powered Engine”. National Conference on Recent Trends of Engineering and Technology. May, 2011. India [2] Yu-Ta Shen, Yean-Ren Hwang. “Design and implementation of an air-powered motorcycle”. Applied Energy;2009;86;1105-1110. [3] Robinson T. Electric and hybrid vehicle technology. UK: International Press; 1997. [4] S.S. Verma. “Air Powered Vehicles”. The Open Fuels and Energy Science Journal. 2008;1; 54-56. [5] K. David Huang, Sheng-Chung Tzeng, Wei-Chuan Chang. ”Energy-Saving Hybrid Vehicle using Pneumatic-Power System”. Applied Energy 2005; 81: 1-18. [6] Huang KD, Tzeng SC, Ma WP, Chang WC. Hybrid pneumatic-power systemwhich recycles exhaust gas of an internal-combustion engine. Applied Energy; 2005;82:117–32. [7] K. David Huang, Sheng-Chung Tzeng. “Development of a hybrid pneumatic-power vehicle". Applied Energy; 2005; 80; 47-59. [8] Yunus Cengel, Michael Boles. Thermodynamics: An

Engineering Approach, Seventh Edition, Tata McGraw Hill; 2010


ISBN 978-1-4951-3251-3


UAB - ECTC 2014 PROCEEDINGS - Section 9 Page · UAB School of Engineering - ECTC 2014 Proceedings -...

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Transcript of UAB - ECTC 2014 PROCEEDINGS - Section 9 Page · UAB School of Engineering - ECTC 2014 Proceedings -...