Motor/Prop Matching Lecture 14 ME EN 415 Andrew Ning - - PowerPoint PPT Presentation

ME EN 415 Andrew Ning aning@byu.edu

Motor/Prop Matching

Lecture 14

Motor/Prop Matching

Ω Q

motor prop

Ω Ω η T

motor prop prop

Ω η

motor prop

Ω η

motor prop

Thrust Constraint

see simulation on JuliaBox

see simulation on JuliaBox 1) What parameters most improve motor efficiency? 2) Assume the motor and prop are not well

• matched. Which motor parameter(s) are most

useful in shifting the efficiency curve? 3) What about the motor parameters?

Other Design Considerations

single twin

tractor pusher

CHAPTER J

0 Propulsion and Fuel System Integration 317

Tractor Fuselage

Wing

Pod

• Fig. 10.25 Propeller location matrix.

However, the pusher configuration suffers several disadvantages. First, the propeller has reduced efficiency because it is forced to work with dis- turbed airflow off the fuselage, wing, and tails. Also, with weight to the rear the tails need to be larger. The pusher propeller might require longer landing gear because the aft location causes the propeller to dip closer to the runway as the nose is lifted for takeoff. The propeller should have at least 9 in. { 23 em} of clearance in all attitudes. The pusher propeller is also more likely to be damaged by rocks thrown up by the wheels. A pusher location for a turboprop propeller can create problems due to the engine exhaust impinging upon the propeller. The Cessna Skymaster and Rutan Defiant use a combination of pusher and tractor engines on the fuselage to eliminate engine-out yawing. Wing mounting of the engines is normally used for multi-engine designs. Wing mounting of engines reduces wing structural weight through a span-loading effect and reduces fuselage drag by removing the fuselage from the propeller wake. Wing mounting of engines introduces engine-out controllability pro- blems that force an increase in the size of the rudder and vertical tail.