21

Experimental Investigation of Direct Air Injection Scavenged Two Stroke Engine

M. Ayaz Afsar 1, Mr. Prafulla V. Pawar 2 Mr.Pratik Dahule3,Mr.S.Papinwar4 +

1 Lecturer in Mechanical Deptt.B.N.College of Engg. Pusad(INDIA) 234Final year student, Mechanical Deptt. B.N.College of Engg. Pusad(INDIA)

Abstract. In view of better utilization of payload capacity, a rapid shift towards use of 2 wheelers for individual transportation is clearly seen in recent years & the rate of production of such 2 wheelers is sharply rising up in our country. 2 stroke engines have the advantage of low specific weight, simplicity of operation & less cost. However it has inherent drawbacks of poor scavenging & relatively high exhaust emissions. The concept of making hole in transfer port by direct injection of air stream is an attractive proposition for eliminating those drawbacks. In this paper an attempt has been made to study performance & emissions characteristics of a single cylinder direct injection using scavenging. The variation of BSFC, NOx, Smoke & particulate emission with brake power have been studied for both scavenging and without scavenging and results of work shows an improvement in the performance and emissions characteristics of engine with scavenging. This paper reports a comparative analysis of experimental investigations carried out on a single cylinder 2 stroke S.I.Engine in carburetor with and without scavenging.

Keywords: scavenging, two stroke S.I. engine, BSFC, DAI

1. Introduction A two stroke engine is one which complete its cycle of operation in one revolution of the crankshaft or in

two strokes of the piston. In many two stroke engines the mechanical construction is greatly simplified by using the piston as a slide valve in conjunction with intake and exhaust ports cut in the side of the cylinder. Two stroke engines are most simple in construction as there are very few moving parts and but more difficult to analyze because of overlapping the inlet and exhaust. As there are only two strokes for performing four basic operations, the overlapping processes cannot be avoided. During the downward stroke, expansion is carried out during part of stroke and during remaining part of stroke; the exhaust and charging are carried out simultaneously. This process is also continued during the upward motion of the piston for part of stroke, and for remaining part of stroke, the compression is carried out. However, when applied to spark ignition engine the two stroke cycle has certain disadvantages which have restricted its use to small engines suitable for motor cycles, scooter, lawn movers, outboard engines, etc. In spark ignition engine the charge consists of mixture of air and fuel. During scavenging, as both inlet and outlet ports are open simultaneously for some time, some part of the fresh charge containing fuel escapes with exhaust. This results in high fuel consumption or lower thermal efficiency.

2. Problem Identification The gas exchange or scavenging process is common to all internal combustion engines. Its function is to

effect expulsion of the products of combustion from the engine cylinder and their replacement by fresh air charge in preparation for the next working cycle. Here problem occurring is the power loss due to poor scavenging which may rise by the short circuiting scavenging process. Also it results in reduction of fuel + Corresponding author. Tel.: + (091- 9423654442);. E-mail address: ( ayazafsar123 @rediffmail.com).

2009 International Symposium on Computing, Communication, and Control (ISCCC 2009) Proc .of CSIT vol.1 (2011) © (2011) IACSIT Press, Singapore

22

efficiency. In which the fresh charge coming from the scavenge manifold directly goes out of the exhaust ports without removing any residual gas. This is a dead loss and its occurrence must be avoided.

3. Problem Formulation A detailed knowledge of the scavenging process becomes necessary during the development process,

when the performance and in particular the emission output of two-stroke engines needs to be qualified and evaluated. In order to improve the performance of I.C.Engine shorcircuiting should be avoided.This is possible only when air provide a barrier for the fresh charges to be mixed with the residual gases.In this paper an attempt is made to regulate the natural flow of air for scavenging This paper presents an experimental approach to describe the composition of the flow at the exhaust port by means of flow visualization and to quantify the relative changes of the scavenging losses imposed

4. Methodology • Modification of engine for the purpose of scavenging A drill was made in the engine for the air

passage to avoid short circuiting phenomenon in the engine. • Development of Test-Rig i.e.design of various components such as frame, air box and dynamometer • Performance evaluation of 2Stroke Engine without Direct air injection and calculation of the various

engine parameters such as brake power, brake specific fuel consumption, brake thermal efficiency • Performance evaluation of 2Stroke Engine with Direct air injection and calculation of the various

engine parameters such as brake power, brake specific fuel consumption, brake thermal efficiency

5. Experimental Setup The experimental setup for performance evaluation of direct air injection scavenged engine is as shown

in fig1.

Fig.1. Experimental Setup

1-Engine Frame, 2-Crank Case, 3-Caburettor, 4-Air Box, 5-Fuel Tank, 6-Burrete, 7-Exhaust Of Engine, 8-Puc Machine Setup, 9-Rope Brake Dynamometer, 10-Air Box Stand, 11-Machine Stand, 12-Hole Provided For Direct Air Injection, 13-Tachometer

6. Observation • Diameter of orifice = 32mm • Swept volume = 150cc • Cv of fuel = 42500kj/kg • Specific gravity of fuel = 0.8 • Cp of water = 4.1868kj/kgk • Diameter of brake drum = 30cm

23

• Speed of engine = 1500 rpm • Room temp = 302k

Table 1. Comparative Performance Evaluation Of Various Parameters On Varing Load

Sr. No.

Load Speed (RPM)

Brake Power (Watt)

Mass Of Fuel (Kg/Sec)

BSFC (Kg/KWhr)

Thermal Efficiency

Load (Kg)

Without DAI

With DAI

Without DAI

With DAI

Without DAI

With DAI

Without DAI

With DAI

Without DAI

With DAI

1 00 115 170 00 00 9.34 9.17 00 00 00 00 2 0.5 110 160 8.48 12.3 8.77 8.67 0.037 0.025 2.25 3.304 3 1 106 151 16.3 23.3 8.69 8.62 0.019 0.013 4.37 6.27 4 1.5 102 154 23.6 35.6 8.62 8.54 0.013 0.009 6.36 9.69

Table 2.Exhaust Emmisions

Sr. No. Emmisions Without DAI Scavenging

With DAI Scavenging

1 CO (% by Vol) 1.43 1.21 2 HC (ppm) 1840 1156

7. Result The performance of the engine and the combustion parameters of engine by using petrol as a fuel are

represented as below.

7.1. Combustion Parameter There is increase in BP of the engine because of injection of outside air in to the cylinder.

7.2. Exhaust Emission The emissions of hydrocarbons are decreased by almost 38% where as carbon monoxide emission

decrease by 18%. This shows that the modified engine can be more esuriently.

24

8. Conclusion The significant conclusion from the present experimetal investigation are summarized as follows:- • The engine can be successful operated with the modified engine having a direct air injection upto the

maximum speed of 5500 rpm. • Improvement in BSFC and more complete combustion of the modified engine were observed as

compares to the conventional engine. • The CO and UBHC emissions levels were less than conventional engine. The CO emissions were

reduced by 18% at rated power output & UBHC emissions were reduced by 38% at rated power output.

9. Acknowledgement We are thankful to the Principal, Prof.N.M.Gatphane, for providing all the facilities. We are indeed thankful to

Prof.A.M.Wankhade, H.O.D. of Mechanical Engg. Department for his time to time suggestions and other faculty members who gave necessary help as required.

10. References [1] Bryan Willson, Justin Mick and Stephanie Mick. “Development of an Externally-Scavenged Direct-Injected

Two- Stroke Cycle Engine”, Colorado State University, SAE International, International Off- Highway & Powerplant Congress & Exposition Milwaukee,. September 11-13, 2000 Wisconsin.

[2] CUDINAM.( 2004) “Model testing the two-phase scavenging system in a two-stroke petrol engine”, Proceedings of the Institution of Mechanical Engineers. Part D, Journal of automobile engineering, vol. 218.

[3] David Shawcross, Colin Pumphrey and David Arnall.( March 6–9, 2000) “A Five-Million Kilometer, 100-Vehicle Fleet Trial, of an Air-Assist Direct Fuel Injected, Automotive 2-Stroke Engine”, Orbital Engine Co. Pt. Ltd., SAE 2000 World Congress Detroit, Michigan.

[4] Miles, P. C.; Green, R. M.; Witze, P. O. (11-14 Jul. 1994) “Comparison of in-cylinder scavenging flows in a two- stroke cycle engine under motored and fired conditions.” Presented at the 7th International Symposium on Applications of Laser Techniques to Fluid Mechanics, Lisbon, Portugal.

[5] Dr. Mathur M.K., Sharma, “Testing and Performance”, Textbook of Internal Combustion Engine, Seventh Edition, Dhanpat Rai & Co Ltd, p.p.556-575.

[6] Dr. V Ganesan, “Performance Parameters and Characteristics”, Textbook of Internal Combustion Engine, Third Edition, Tata McGraw-Hill Publishing Co Ltd, p.p.386-534.