ed 2 propeller 7

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REPORT 7 PROPELLER SIZING

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7 PROPELLER SIZING

7.1 Introduction

The function of the propeller is to convert brake horse power from the engine into

thrust. The primary purpose is to convert engine power to axial thrust through torque transferto the propeller.

Fixed pitch: The propeller is made in one piece. Only one pitch setting is possible and is usually

two blades propeller and is made of wood or metal

Constant speed: During operation, the constant speed propeller will automatically change its

blade angle to maintain a constant engine speed. If engine power is increase, the blade angle is

increased to make the propeller absorb the additional power while the rpm remain constant.

7.2 Propeller Size Determination

The propeller diameter for a two bladed propeller is given by[1]

(7.1)

where HP is power available in horse power

The takeoff gross weight from third weight estimate is 1283.496 gm

The maximum power loading (as obtained from Report 3),

Propeller is selected from the propeller catalogue available in the adamone[6]

website

Table 7.1 Propeller sizing details

Propeller name, type APCE,Fixed

No of blades 2

Diameter 11 in

Pitch 5.5 in


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Now the battery is chosen to suit the propeller sizing requirements[6]

Table 7.2 Specifications of battery

Battery Name ThunderPower 2100 15/20c

Series, Parallel 2,1

Cell Capacity 2100mAh

Max Current 42 A

Volt Per Cell 3.7 V

Cell Resistance 0.0086

Pack Voltage 7.4 V

Pack Weight 92 gm

7.3 PROPELLER THEORY

In a simple blade element theory the forces acting on the blade are as shown in the fig.

below

Fig 7.1: The forces acting on the blade element[1]


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where

is the angle of attack

is the helix angle

is the geometric pitch angle of the blade

dT is the elemental thrust on blade element

dQ is the propeller torque

dL is the lift force acting on the blade element

dD is the drag force acting on the blade element

The static rpm for the selected APCE propeller is given in the adamone website[6]

The static rpm of the propeller[6]

= 6785 rpm

7.4 Propeller Performance

The various performance parameters of the propeller are investigated as follows

Table 7.3 Propeller performance evaluation parameters

Climb velocity , 10.556 m/s

Static rotational speed 6785 rpm

Static rotational speed , n 113.083 rps

Diameter, D 11 in

Pitch 5.5 in

7.4.1Helix angle

The helix angle of the propeller is found using the following relation

( ) ( ) (7.2)

Where =2n is angular speed at radius r.


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7.4.2. Advance ratio

The advance ratio for the propeller is given by[1]

(7.3)

7.4.3 Thrust coefficient

The thrust coefficient of the propeller is given by[1]

(7.4)

Fig 7.2 Thrust coefficient vs advance ratio for different blade angle[4]

Assume an blade angle =15 deg


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7.4.4 Power coefficient

The power coefficient of the propeller is given by

(7.4)

From the propeller chart shown below

Fig 7.3. Power coefficient vs. advance ratio for propellers[4]

P = 138.75 W

7.4.5. Speed coefficient

The speed coefficient of the propeller is given by

(7.5)

7.4.6. Propeller Efficiency

The propeller efficiency of the blade is given by

(7.6)


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Table 7.4 Propeller performance for the entire mission

Phase V

aircraft

Helix

angle

Advance

ratio

Thrust

coefficient

Power

coefficient

Speed

coefficient

Propeller

efficiency

Takeoff 11.6373 6.86 0.3683 0.09 0.048 0.676 69.056

Climb 10.556 6.07 0.3341 0.092 0.046 0.618 66.82

Cruise 15.1719 8.69 0.4801 0.068 0.04 0.8219 81.16

Turn 14.310 8.20 0.4529 0.072 0.041 0.8579 79.53

Landing 12.4468 7.15 0.393 0.08 0.042 0.7408 74.85

7.5 Conclusion

The propeller is selected based on the maximum power loading estimated(Report 3) and

performance parameters of the propeller were investigated and tabulated for various phases of

the flight. Based on the parameters computed, the propeller is selected as Fixed pitch type

APCE 11 X 5.5 having two blades.


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List of Symbols

1. CT - Thrust coefficient of propeller

2. CP - Power coefficient of propeller

3. CS - Speed coefficient of propeller

4. D - Propeller diameter

5. dD - Drag force acting on the element

6. dL - Lift force acting on the element

7. dT -Thrust acting on the element

8. dQ - Propeller torque

9. J - Advance ratio

10.n - static rotational speed

11.P - Power available

12.r - radius of propeller

13.Vclimb - Climb velocity

14.W - Weight

15. - Angle of attack

16. - Blade angle

17. - Helix angle

18. - Rotational speed of propeller

List of Figures

7.1 Forces acting on the blade element

7.2 Thrust coefficient versus Advance ration for the propellers

7.3 Power coefficient versus Advance ratio for the propellers

List of Tables

7.1 Propeller sizing details

7.2 Battery specifications

7.3 Propeller performance evaluation parameters

7.4 Propeller performance parameters


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7.6 REFERENCES

1. Daniel P. Raymer, Aircraft Design: A Conceptual Approach, 2nd edition AIAA

Educational series, 1989.

2. John D Anderson Jr., Aircraft Performance and Design, 4th reprint 2011, McGraw-Hill, New York.

3. John D Anderson Jr., Fundamentals of Aerodynamics, McGraw-Hill, New York.

4. McCormick, Aerodynamics of V/STOL flight

5.Jan Roshkam.,Airplane Aerodynamics and Performance,

6. http://adamone.rchomepage.com
http://adamone.rchomepage.com/http://adamone.rchomepage.com/http://adamone.rchomepage.com/

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