List of top Propulsion Questions asked in GATE AE

A uniform rigid prismatic bar of total mass $ m $ is suspended from a ceiling by two identical springs as shown in the figure.
Let $ \omega_1 $ and $ \omega_2 $ be the natural frequencies of mode I and mode II respectively (with $ \omega_1<\omega_2 $).
The value of $ \omega_2/\omega_1 $ is _________ (rounded off to one decimal place).

A rocket operates at an absolute chamber pressure of 20 bar to produce thrust $F_1$. The hot exhaust is optimally expanded to 1 bar (absolute pressure) using a convergent-divergent nozzle with exit to throat area ratio $\left(\frac{A_e}{A_t}\right)$ of 3.5 and thrust coefficient, $C_{F,1} = 1.42$. The same rocket when operated at an absolute chamber pressure of 50 bar produces thrust $F_2$ and the thrust coefficient is $C_{F,2}$. Which of the following statement(s) is/are correct?

Which of the following is NOT always true for a combustion process taking place in a closed system?

A convergent nozzle fed from a constant pressure, constant temperature reservoir, is discharging air to atmosphere at 1 bar (absolute) with choked flow at the exit (marked as $Q$).
Flow through the nozzle can be assumed to be isentropic.
If the exit area of the nozzle is increased while all the reservoir parameters and ambient conditions remain the same, then at steady state

In a static test, a turbofan engine with bypass ratio of 9 has core hot exhaust speed 1.5 times that of fan exhaust speed. The engine is operated at a fuel–air ratio of $f=0.03$. Both the fan and the core streams have no pressure thrust. The ratio of fan thrust to thrust from the core engine is (round off to one decimal place).

In a single stage turbine, the hot gases come out of stator/nozzle at a speed of 500 m/s and at an angle of 70 degrees with the turbine axis as shown. The design speed of the rotor blade is 250 m/s at the mean blade radius. The rotor blade angle, $ \beta $, at the leading edge is _________ degrees (round off to one decimal place).

A high-pressure-ratio multistage axial compressor encounters an extreme loading mismatch during starting. Which of the following technique(s) can be used to alleviate this problem?

The region of highest static temperature in a rocket engine and the region of highest heat flux are _______, respectively.

The point of maximum entropy on a Fanno-curve in a Temperature–Entropy (T–s) diagram represents the

At the design conditions of a single-stage axial compressor, the blade angle at rotor exit is $30^\circ$. The absolute velocities at rotor inlet and exit are 140 m/s and 240 m/s, respectively. The relative flow velocities at rotor inlet and exit are 240 m/s and 140 m/s, respectively. Find the blade speed $U$ at the mean radius (round off to two decimal places).