List of top Propulsion Questions asked in GATE AE

The figure below shows a compressor stage with station numbers 1, 2, and 3 as indicated. If \(p_{0i}\), \(T_{0i}\), and \(C_i\) refer to the average values of total pressure, total temperature, and absolute flow speed, respectively, at the \(i^{th}\) station, select the CORRECT option considering losses.

In an ideal turbofan engine shown in the figure below, the compressor is driven by the high pressure turbine, and the fan is driven by the low pressure turbine. The stations 0, 2, 3, 4, 4.5, and 5 refer to free-stream, compressor inlet, compressor outlet, combustor exit, high pressure turbine exit, and low pressure turbine exit, respectively, and the subscript 't' refers to the total condition. Also, \(\tau_r = T_{t0}/T_0\), \(\tau_c = T_{t3}/T_{t2}\) and \(\tau_\lambda = T_{t4}/T_0\). The total temperature ratio of the high pressure turbine \((T_{t4.5}/T_{t4})\) is given by ______.

A multi-stage axial compressor can be operated at two points, A and B, both of which lie on the same speed line, as shown in the figure below. If \(\eta\) is the isentropic efficiency of the compressor, select the statements that is/are TRUE.

The figure below shows the blading of the rotors of two different axial turbomachines under their typical operating conditions, labelled as Configuration I and Configuration II. Which of the following statements is/are TRUE?

In the figure shown below, the flow at the nozzle exit is .

The figure below depicts two ideal gas turbine cycles, cycle 1-2-3-4-1 and cycle 1-2-3'-4'-1, on a \(T\)-\(s\) diagram. Which one of the following statements is FALSE?

A centrifugal compressor has a constant-width radial diffuser. The diameters at the diffuser inlet and outlet are \(0.2\) m and \(0.3\) m, respectively. The flow at the diffuser inlet and outlet is assumed to be steady and uniform. The average velocity at the diffuser inlet and outlet are \((60\,\hat{e}_r + 75\,\hat{e}_{\theta})\) m/s and \((u\,\hat{e}_r + 50\,\hat{e}_{\theta})\) m/s, respectively. If the flow through the diffuser is treated as steady and incompressible, the value of \(u\) is _______ (rounded off to the nearest integer).

A gas mixture at a pressure of \(800\) kPa and a density of \(5\) kg/m\(^3\) enters a turbine stage. The temperature of the gas at the nozzle exit and the stage exit are \(790\) K and \(750\) K, respectively. Assume the specific heats are constant for the gas mixture in the range of temperatures considered. The specific heat at constant pressure is \(0.72\) kJ/kg-K and the ratio of specific heats is \(1.33\). The value of the degree of reaction of the turbine stage is _______ (rounded off to 2 decimal places).

Isobutane (\(C_4H_{10}\)) is burnt completely in pure oxygen as per the reaction given below. Given that the standard heats of formation (in kcal/mole) of isobutane, carbon dioxide, and water vapour are -31.489, -94.052, and -60.150, respectively, the heat of reaction is ________ kcal (rounded off to 2 decimal places).
\[ C_4H_{10} + 6.5\,O_2 \to 4\,CO_2 + 5\,H_2O \]

A furnace of 250 MW rating is used to melt and raise the temperature of aluminium from 25\(^{\circ}\)C to 900\(^{\circ}\)C. Aluminium has a solid-state specific heat, latent heat, and liquid-state specific heat of 0.9 kJ/kg-K, 390 kJ/kg, and 1.108 kJ/kg-K, respectively, and the furnace has 70% efficiency. The melting point of aluminium is 660\(^{\circ}\)C. The amount of aluminium that can be processed per hour is ________ kg (rounded off to 1 decimal place).

Which of the following process(es) is/are involved in the compression of air in an ideal ramjet engine?

An ideal rocket has characteristic exhaust velocity of 1200 m/s, mass flow rate of 75 kg/s, thrust coefficient of 1.5, and nozzle throat area of 0.025 \(\text{m}^2\). The chamber pressure in kPa and the specific impulse due to gravity in seconds are ________, respectively. Assume that the acceleration due to gravity is 9.8 \(\text{m/s}^2\).

Consider a launch vehicle of mass 10 tons being launched vertically. The vehicle has 8 tons of propellant, which burns completely at a constant rate over 50 s. If the engine specific impulse is 250 s, and the acceleration due to gravity at sea level is \(g_0\), the acceleration experienced by the vehicle at lift-off is ________.

For a given air-standard power, the propulsive efficiency of a turbofan engine is more than that of a turbojet engine. Which of the following is/are the reason(s) for this?

Which one of the following makes an ideal air-standard Stirling cycle?

Which propulsion system is most suitable for high-speed supersonic aircraft?