The transmission efficiency of a turbojet engine is determined by the ratio of which of the following?
Compressor work to turbine work
Turbine work to compressor work
Net-work output to compressor work
Net-work output to turbine work
At what speed does the flow usually enter the burner in a ramjet engine?
Subsonic
Sonic
Supersonic
Hypersonic
The specific thrust of a ramjet engine ……… with Mach number at a given maximum temperature of the cycle.
continuously increases
continuously decreases
initially increases and then decreases
initially decreases and then increases
Consider the following statements regarding the specific fuel consumption of the ramjet engine;
i. It decreases continuously with the Mach number for a given maximum total temperature of the cycle.
ii. It initially increases and then decreases with the Mach number for a given maximum total temperature.
iii. It decreases with an increasing maximum total temperature of the engine for a given Mach number.
iv. It increases with an increasing maximum total temperature of the engine for a given Mach number.
of these, the correct statement(s) is/are
i only
i and iv only
i and iii only
ii and iv only
Which of the following options includes all the rotating components typically used in a turbofan engine configuration?
Compressor, Turbine, Propelling nozzle
Fan, Compressor, Combustor
Diffuser, Fan, Turbine
Fan, Compressor, Turbine
Common Data for Questions Q6 to Q11
The component performance parameters for a turbojet engine flying at a speed equivalent to Mach 0.7 and an altitude of 8000 m are as follows:
Compressor pressure ratio = 7.5
Turbine Inlet temperature = 1200 K
Isentropic efficiency of compressor = 0.88
Isentropic efficiency of turbine = 0.91
Isentropic efficiency of intake = 0.94
Isentropic efficiency of propelling nozzle = 0.95
Mechanical transmission efficiency = 0.99
Combustion pressure loss = 4 % of combustion delivery pressure
Fuel- Air ratio = 0.0194
Universal gas constant (R) = 287 J/kgK
At 8000 m altitude,
Pressure = 0.3565 bar, Temperature = 236.2 K and Sound speed = 308.1 m/s.
For Air, specific heat at constant pressure = 1.005 kJ/kgK and Specific heat ratio = 1.4
For Gas, Specific heat at constant pressure = 1.147 kJ/kgK and Specific heat ratio = 1.33
Based on above data, answer the given sub-questions.
Real total temperature (K) at the exit of a compressor is
259
318
427
489
Total pressure (bar) at the exit of a turbine is
1.26
1.31
1.52
1.74
Critical nozzle pressure ratio is
1.92
2.17
2.46
2.83
Flow velocity (m/s) at the nozzle outlet is
512
571
603
654
Specific thrust (N-s/kg) produced by the nozzle is
501
536
593
618
Specific fuel consumption (kg/h-N) is
0.118
0.151
0.172
0.193