- Define specific fuel consumption?
Answer : It is the rate of fuel consumed per unit work output. efficiency decreases with increase in specific fuel consumed its unit is kg/k whr.
2.Define propulsive efficiency? of the engine.
Propulsive efficiency defined as the ratio of propulsive power or thrust power to the power output
3.what are the condition for maximum propulsive efficiency?
For max.propulsive efficiency the jet velocity must be twice more than free stream velocity for which the propulsive efficiency 66.7%.
- What is multispool engine?
Aircraft flying at the high speed should operate at the high speed temperature. So they used high pressure compressor and turbine.this is known as multispool engines.
5.Define intercooler?
In multistage compressor,the compressed air coming out of the first stage is cooled to the intial temperature with the help of the heat exchanger before being passed to the next stage this heater exchanger is called intercooler.
6.Draw the PV and TS diagram for an open joules cycle with inter cooler,reheater and regenerator?
7.Define specific impulsive?
It is defined as the thrust produced per unit weight flow rate through the propulsive device.
8.Define specific thrust?
Specific thrust is defined as the the thrust produced per unit mass flow rate through the propulsive device.
- Give the classification of air breathing engine?
Air breathing engine may be classified into turbojet engine, turboprop engine, pulsejet and ramjet engine.
10.Define work ratio?
Work ratio is defined as the ratio of net work done by the engine to the work done by the turbine.
- Define thrust augmentation?
Increasing the thrust output of the aircraft power plant for a short interval of the time to achieve better take-off performance, higher rate of climb etc..is called thrust augmentation.
- What are the various types of thrust augmentation?
The after burner, injection of water, alcohol mixtures and the bleed burn cycle are the different types of thrust augmentation
- Give the advantage of turbojet engine?
*it is suitable for long distance flight at high speed and altitude.
*lower frontal area and shorter landing gears.
*lower weight per unit thrust at design speed and altitude.
*pressure rise through the inlet diffuser is sufficient.
*reheat can be employed for increased thrust.
14.What are the disadvantage of turbojet engine?
- *it requires a long run way.
- *TSFC is comparatively high at low speed and altitude.
- *uneconomical on short distance flight.
- *lower thrust and propulsive efficiency at lower speed.
- What are the advantage of turboprop engine?
It is produced high thrust at lower speed. so it require short run way.
*The TSFC is based on thrust is low.
*propulsive efficiency within the range of operation is high.
*Thrust reversal is easily achieved with variable pitch propeller blades.
16.What are the disadvantage of the turboprop engine?
*Application is limited to power speed and altitude.
*Due to large diameter propeller the landing gear should be long.
*engine is heavier and more complicated.
*higher weight per unit thrust.
- Why doesn’t ramjet engine need a compressor and turbine?
Flight speed of the ramjet engine is very high, say M=2 to 4.due to this pressure rise in diffuser(Ram pressure) is very high, at this flight speed contribution of the compressor to the total static pressure rise insignificant. Thus the ram jet engine has a no compressor and turbine.
static pressure at the energy at the inlet of the compressor without a loss of total pressure.
22.Define ram recover point?
It is the velocity of the aircraft at which the ram pressure is equal to the fractional pressure lose. For a good inlet duct the ram recover point is less.
- What are the factor affecting the design of an inlet?
*inlet total pressure ratio.
*Drag to the design speed.
