PROJECT SYNOPSIS ON

“AIRCRAFT PROPELLERS”

Submitted by

MOHAMMAD ASAD ANSARI

MOHAMMAD ISHRAT JAVED SIDDIQUI

DANYAL SAGIER SIDDIQUI

HEMANT KUMAR CHANDRA

B.TECH 4th year (2013-2014)

(MECHANICAL ENGINEERING)

UNITED COLLEGE OF ENGINEERING AND RESERCH ALLAHABAD

Introduction

Propellers

Internal Combustion Engines

Gas Turbine Engines

Chemical Rockets

Non-Chemical Space Propulsion Systems

AER 710 Aerospace Propulsion

OBJECTIVE The main objective of the project is to understand the functioning and constructional details of the aircraft propeller. This project is an attempt to throw some light on the use of mechanical engineering designing of blade, analysis of operating force, analysis of material use and stress distribution in an aircraft propeller.

The project also intend to understand the wide application and history in the development of aircraft propeller. Aircraft propeller is widely used in most of the aircraft carrier. It is also used in many of the military operations in World War 2nd in most of the fighter planes as well as bomber planes.

C-130

Nieuport N.28C-1

Introduction to the Propeller• The rotating blade of a propeller shares

similar characteristics to a wing passing through the air

• A propeller blade generates thrust F through an aerodynamic lift force component, demands an engine torque Q to overcome aerodynamic drag, and will stall if the local resultant angle of attack of the blade exceeds max

• Additional factors: trailing vortex generation, tip losses, compressibility

Martin MB-2

Small Pressure Increase here

Greater Pressure Decrease here

The result isMORE LIFT

How lift is increased

PROPELLER SYSTEM

Small Pressure Increase here

Greater Pressure Decrease here

The result isMORE LIFT

How lift is increased

PROPELLER SYSTEM

Direction of travel

Aerofoil incline

The difference in direction of travel and aerofoil incline is called:-

The ANGLE of ATTACK

How lift is increased

PROPELLER SYSTEM

PROPELLER SYSTEMHow the blade tip travel produces the HELIX ANGLE

Forward Speed

RPMRPM

Faster Forward Speed

Changes in FORWARD SPEED and RPM will change the Helix Angle

How an increase in FORWARD SPEED changes the HELIX ANGLE

PROPELLER SYSTEM

All propeller blades are actuated by the same mechanical linkage

PROPELLER SYSTEM

Sliding Piston

Hard Stops

Fine Pitch

Coarse Pitch

Direction of

Rotation

Direction of Flight

Propeller Blade

Actuating Lever

Actuating Link

DH-98 Mosquito

Forces acting on wing airfoil section (above) and propeller blade section (below)

Momentum-Blade Element Theory

• Logically, the next level of analysis would look at a given propeller blade’s aerodynamic performance from hub to blade tip

• one can discretize the blade into a finite number of elements, while applying momentum conservation principles

Momentum-Blade Element Theory (Summary)

• The above equations for CT and CP can be integrated from the hub station (x = xh) to the blade tip (x = 1) using a numerical approach as one moves along the blade of varying and c, calculating the various pertinent parameters (C , Cd, i , etc.) in conjunction

Thrust

Power

Propeller Propulsive Efficiency

• Define as useful thrust power over overall shaft power:

Spr P

FV

JCC

dnCVdnC

P

T

P

Tpr

53

42

Also, via substitution:

A variable pitch propeller will have better efficiency over thecourse of the flight mission, relative to a fixed pitch prop.

Chart illustrating propeller propulsive efficiency for an example propeller

Compressibility Tip Loss• Depending on the blade airfoil section

design, drag divergence (compressibility) effects will become evident when the propeller blade’s resultant tip speed VR,tip exceeds a local flow Mach number Matip of around 0.85 (critical value, Macr)

• As a result, one would not typically be cruising at much greater than a flight Mach number Ma of around 0.6

22)(

MaandMatip

)1.0

(10015 crtip

alminpr,noprMaMa

Dommasch correlation:

Blade tip Mach number:

Modern high-speed blades may be thinner, and sweptor curved along the blade length, to mitigate the issues with compressibility and compression wavedevelopment at higher local flow Mach numbers

Activity Factor• Activity factor (AF) is a design parameter

associated with the propeller blade’s geometry. The more slender the blade (larger radius, smaller chord), the lower the AF value:

xxdcAF

hx p

d16

100000 31

pdcAF 1563

Typically see higher AF props on turboprop engines.

Blade Number• One has the option of setting the number

of blades, B, for a given application. While one has a minimum of 2 blades to choose from, one can presently go as high as around 8 blades on the high-performance end for an unducted propeller

• On occasion, one also sees the use of two contra-rotating rows of blades, to get more thrust delivery from one engine