1. Basics of A Turboprop Engine
P M V Subbarao
Professor
Mechanical Engineering Department
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2. Economy Flying AN 12 : CRUISE SPEED : 520 km/h PAYLOAD : 18000 KG
Range: 2400 km
Maximum altitude: m

3. Requirements of Economic Flying
In recent years, interest in highly efficient flight transportation is renewed.
This has spurred investigation into very high bypass ratio fans.
Some economic optimization of turbofan cycle shows a bypass ratio of 100.
The weight of cowl and drag due to the cowl will have high penalty on total cost if bypass ratio is greater than 25.
This led to thinking of high bypass ratio open turbofan engines.
Turboprops.

4. Philosophy of Fuel Economy

5. Turboprop Engine : Just for Fuel Economy1 1’ 2 3 4 6 7 5
p04 =r0p,comp p0∞ = p05
T04= =t0p,comp T0∞
p02=p01= p03 = p0∞
T02=T01 = T03 = T0∞

6. Three Spool Turboprop Engine
VU

7. Actuator disc theory for Propeller1 JU JD 1 p
pJU
pJD
VU
VD
p0U
p0JU
p0JD
p0D

8. Power Consumed by Propeller
The ideal shaft power can be found using the integral energy equation on the control volume:

9. Shaft Power Balance for Turboprop
Law of Turboprop

10. Propeller (Reaction) Power
Propeller work coefficient:
The work coefficient of a propeller depends on compressor pressure ratio and turbine pressure ratio.
The compressor pressure ratio and turbine pressure ratio are two independent design variables for a turboprop.