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Thermodynamics & Marine Diesel Engines(31)Marine Steam Turbines, Gas Turbines & Boilers(12)Engine Dynamics & Marine Auxiliary Machinery & Systems(5)

Thermodynamics & Marine Diesel Engines

31 Questions

GATE→2026→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q1

MCQ[1 Mark]

If the indicated power of an IC engine at NO-LOAD condition is 0.5 kW, then the friction power is kW.

(A)

1

(B)

2

(C)

0.5

(D)

0

Explanation

GATE→2026→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q2

MSQ[1 Mark]

Which of the following factors affect(s) knocking in a Diesel engine?

(A)

Injection timing

(B)

Cetane number of the fuel

(C)

Spark timing

(D)

Compression ratio

Explanation

GATE→2026→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q3

MSQ[1 Mark]

Which of the following processes is/are used for heat addition in an air-standard dual cycle?

(A)

Isochoric

(B)

Isobaric

(C)

Isentropic

(D)

Isothermal

Explanation

GATE→2026→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q4

MSQ[1 Mark]

Which ONE or MORE of the following can be caused by scavenging in a two-stroke Diesel engine?

(A)

Dilution of incoming fuel-air mixture

(B)

Loss of incoming air

(C)

Pushing out exhaust gases by incoming air

(D)

Autoignition

Explanation

GATE→2026→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q5

NAT[1 Mark]

Consider two insulated tubes with air flowing steadily through them. The flow rate and temperature of the air are $0.1\text{ kg/s}$, $20^\circ\text{C}$ in tube 1 and $0.2\text{ kg/s}$, $25^\circ\text{C}$ in tube 2. If the two streams are allowed to mix adiabatically, the steady-state temperature of the mixed stream is °C (rounded off to one decimal place). Assume a constant $C_p$ for air.

Explanation

GATE→2026→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q6

NAT[1 Mark]

Consider a reversible heat engine with a thermal efficiency of 55%. The engine is reversed and operated as a heat pump between the same temperature reservoirs. If the heat supplied from the low temperature reservoir is 45 kJ/cycle, then the absolute value of heat rejected is kJ/cycle (answer in integer).

Explanation

GATE→2026→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q7

MCQ[2 Marks]

The dry bulb temperature (DBT) of atmospheric humid air is $30^\circ\text{C}$. The dew point temperature (DPT) is also $30^\circ\text{C}$ and the humidity ratio is $0.025\text{ kg water vapor / kg dry air}$. The relative humidity (RH) of the air is %.

(A)

100

(B)

25

(C)

50

(D)

0

Explanation

GATE→2026→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q8

MSQ[2 Marks]

Consider two engines operating on Otto and Diesel air-standard cycles with the same compression ratio. Which of the following is/are TRUE about the thermal efficiency ($\eta$) and the peak pressure ($p_{peak}$)?

(A)

$\eta_{otto} < \eta_{Diesel}$

(B)

$\eta_{otto} > \eta_{Diesel}$

(C)

$(p_{peak})_{otto} > (p_{peak})_{Diesel}$

(D)

$(p_{peak})_{otto} = (p_{peak})_{Diesel}$

Explanation

GATE→2025→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q9

MSQ[1 Mark]

Which of the following components is/are NOT found in a two-stroke marine diesel engine?

(A)

Crankshaft

(B)

Piston

(C)

Spark plug

(D)

Air-inlet valve

Explanation

GATE→2025→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q10

MCQ[2 Marks]

A closed system is undergoing a reversible process 1-P-2 from state 1 to 2, as shown in the figure, where X and Y are thermodynamic properties. An irreversible process 2-Q-1 brings the system back from 2 to 1.\nThe net change in entropy of the system and surroundings during the above-mentioned cycle are respectively.

(A)

positive and negative

(B)

negative and positive

(C)

zero and negative

(D)

zero and positive

Explanation

GATE→2025→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q11

MCQ[2 Marks]

An ideal Brayton cycle (1-2-3-4) consisting of two isentropic and two isobaric processes is shown in the T-s plot, where T is the temperature and s is the specific entropy of the system. Which one of the following plots represents the corresponding actual cycle $1-2'-3-4'$ (denoted by dashed lines) between the same two pressures $p_{1}$ and $p_{2}$?

(A)

Plot A

(B)

Plot B

(C)

Plot C

(D)

Plot D

Explanation

GATE→2025→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q12

NAT[2 Marks]

Consider the psychrometric process denoted by the straight line from state 1 to 2 in the figure. The specific humidity, Dry Bulb Temperature (DBT) and Wet Bulb Temperature (WBT) at the two states are shown in the table. The latent heat of vaporization of water $(h_{fg})$ is $2440\text{ kJ/kg}$.\nIf the flow rate of air is $1\text{ kg/s}$, the rate of heat transfer from the air is kW (rounded off to two decimal places).

Explanation

GATE→2025→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q13

NAT[2 Marks]

Consider a weightless, frictionless piston with a 2 kg mass placed on it as shown in the figure. At equilibrium in position 1, the cylinder contains 0.1 kg of air. The piston cross-sectional area is $0.01\text{ m}^2$. The ambient pressure in the surroundings outside the piston-cylinder arrangement is 0 bar (absolute). When the mass above the piston is removed instantaneously, it moves up and hits the stop at position 2 which is 0.1 m above the initial position.\nAssuming $g=9.81\text{ m/s}^2$, the thermodynamic work done by the system during this process is J (answer in integer).

Explanation

GATE→2025→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q14

NAT[2 Marks]

A two-stroke four-cylinder large marine diesel engine has a cylinder bore of 600 mm and stroke length of 2400 mm. The brake thermal efficiency $(\eta_{bth})$ is 45% and fuel consumption rate $(\dot{m}_{f})$ is $0.265\text{ kg/s}$ at an engine speed (N) of 100 rpm. Assuming the calorific value of fuel is $42\text{ MJ/kg}$, the brake mean effective pressure (bmep) is bar (rounded off to one decimal place).

Explanation

GATE→2024→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q15

MSQ[1 Mark]

Which of the following statement(s) is/are correct for a thermodynamic closed system?

(A)

The entropy change is positive for a reversible adiabatic process

(B)

The entropy change is positive for a reversible cycle

(C)

The entropy change is positive for a reversible isothermal heat addition process

(D)

The entropy change is negative for a reversible isothermal heat rejection process

Explanation

GATE→2024→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q16

MCQ[2 Marks]

Which one of the following psychrometric processes is represented by the line 1-2 in the figure?

(A)

Cooling and humidification

(B)

Heating and humidification

(C)

Sensible cooling

(D)

Sensible heating

Explanation

GATE→2024→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q17

NAT[2 Marks]

A 4-cylinder, 4-stroke diesel engine operating at 3000 rpm has a compression ratio r of 12 and cut-off ratio $r_c$ of 2.5. The temperature rise during the heat addition process is 2400 K. Given mass flow rate or fuel parameters, $\gamma = 1.4$ and $C_p = 1.004\text{ kJ/kg-K}$. The power output of the engine is kW

Explanation

GATE→2024→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q18

NAT[2 Marks]

Consider a gas turbine combustor with air as the working fluid. The flow enters the device at 500 K and leaves at 1400 K with a mass flow rate of $0.1\text{ kg/s}$. Neglect changes in kinetic energy and potential energy. Given $C_{v} = 0.717\text{ kJ/kg-K}$ and $R = 0.287\text{ kJ/kg-K}$. The heat addition rate is kW (rounded off to the nearest integer).

Explanation

GATE→2024→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q19

NAT[2 Marks]

A new absolute temperature scale is proposed based on a Carnot engine operating between hot and cold reservoirs of temperatures $T_{L}$ and $T_{H}$ respectively. Let $Q_{L}$ and $Q_{H}$ be the respective heat transfers, with the relation given by $\frac{T_{L}}{T_{H}}=\frac{Q_{L}}{Q_{H}}$. On the new scale, the difference between the steam and ice points of water is 500 units and the efficiency of the engine is 0.268. The steam point of water on this scale is units (rounded off to the nearest integer).

Explanation

GATE→2023→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q20

MCQ[1 Mark]

A closed system undergoing a thermodynamic cycle consisting of two reversible isothermal and two reversible adiabatic processes is shown in the following figure. If $\delta Q$ is the infinitesimal heat transfer and T is the instantaneous temperature, then the value of the contour integral $\oint \frac{\delta Q}{T}$

(A)

is positive

(B)

is negative

(C)

is zero

(D)

cannot be determined

Explanation

GATE→2023→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q21

NAT[1 Mark]

A Carnot heat engine operates between two reservoirs of temperatures $900^{\circ}\text{C}$ ($T_H$) and $30^{\circ}\text{C}$ ($T_L$). If the heat transferred during one cycle to the engine from $T_H$ is 150 kJ, then the energy rejected to $T_L$ is kJ (round off to the nearest integer)

Explanation

GATE→2023→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q22

MCQ[2 Marks]

A vertical frictionless piston-cylinder arrangement contains air of mass 1 kg. During a process, 50 J of heat is transferred from outside to the system such that the piston is raised slowly by 0.1 m from its initial equilibrium position. The mass of the piston is 1 kg, and the diameter is 0.1 m. Assume that $g=9.81\text{ m}/\text{s}^2$, and $P_{atm}=100\text{ kPa}$.\nThe change in internal energy of the air in J (round off to two decimal places) lies between

(A)

28.45 and 28.55

(B)

-28.55 and -28.45

(C)

-29.55 and -29.45

(D)

129.45 and 129.55

Explanation

GATE→2023→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q23

MCQ[2 Marks]

An insulated nozzle has an inlet cross-sectional area of $314\text{ cm}^2$. Air flows through the nozzle with an inlet temperature of 300 K at a steady rate of $1.256\text{ m}^3/\text{s}$. The velocity at the exit is greater than that at the inlet by $210\text{ m}/\text{s}$. Assume a constant $C_p = 1.004\text{ kJ}/\text{kg-K}$.\nThe temperature (in K) of air at the exit of the nozzle lies between

(A)

330 and 331

(B)

269 and 270

(C)

320 and 321

(D)

277 and 278

Explanation

GATE→2023→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q24

NAT[2 Marks]

Saturated liquid water ($m=1\text{ kg}$) initially at $0.101\text{ MPa}$ and $100^{\circ}\text{C}$ is heated at constant pressure until the temperature increases to $500^{\circ}\text{C}$. Assume a constant $C_p$ of steam = $1.9\text{ kJ}/\text{kg-K}$, and enthalpy of vaporization, $h_{fg}=2257\text{ kJ}/\text{kg}$ at $0.101\text{ MPa}$.\nThe change in entropy of the water is kJ/K (round off to two decimal places)

Explanation

GATE→2023→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q25

NAT[2 Marks]

An air-standard diesel cycle, as shown in the following figure with a compression ratio of 16, has an initial pressure 0.9 bar and temperature 300 K. Assume $\gamma=1.4$ and $C_p=1.004\text{ kJ}/\text{kg-K}$. If the heat added during the constant pressure process is $900\text{ kJ}/\text{kg}$, then the peak temperature during the cycle is K (round off to the nearest integer)

Explanation

GATE→2022→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q26

MCQ[1 Mark]

In a diesel engine, the ignition is initiated by the

(A)

spark

(B)

preheating of the fuel

(C)

heating due to the compression of intake air

(D)

preheating of the intake air

Explanation

GATE→2022→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q27

MCQ[1 Mark]

In an internal combustion engine, supercharging is the process of supplying intake air at a pressure

(A)

higher than that of the ambient

(B)

lower than that of the fuel

(C)

higher than that of the fuel

(D)

lower than that of the ambient

Explanation

GATE→2022→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q28

MSQ[1 Mark]

Which of the following are TRUE for pressure, temperature and density of a thermodynamic system?

(A)

path functions

(B)

point functions

(C)

inexact differentials

(D)

exact differentials

Explanation

GATE→2022→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q29

MSQ[2 Marks]

An Otto cycle has states 1 and 2 at the beginning and the end of the compression stroke, respectively. The states 3 and 4 are at the beginning and the end of the expansion stroke, respectively.\nLet the compression ratio of the cycle be r, specific heat ratio of air be $\gamma$, specific heat of air at constant volume be $C_{v}$, and P, v, and T be pressure, specific volume and temperature of the air, respectively. Then, which of the following expressions represent the thermal efficiency of the cycle?

(A)

$1-\frac{1}{r^{\gamma-1}}$

(B)

$1-\frac{T_{3}-T_{4}}{T_{2}-T_{1}}$

(C)

$\frac{(P_{3}v_{3}-P_{4}v_{4})-(P_{2}v_{2}-P_{1}v_{1})}{C_{v}(T_{3}-T_{2})(\gamma-1)}$

(D)

$1-r^{\gamma-1}$

Explanation

GATE→2022→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q30

NAT[2 Marks]

An air standard Otto cycle has a compression ratio of 6 and a mean effective pressure of 1000 kPa. Assume that the specific heat ratio $\gamma$ as 1.4 and specific gas constant R as 0.287 kJ/kgK for the air. If the pressure and temperature at the beginning of the compression stroke are 100 kPa and 300 K, respectively, then the specific work output of the cycle is kJ/kg (rounded off to one decimal place).

Explanation

GATE→2022→Thermodynamics and Marine Engineering→Thermodynamics & Marine Diesel Engines

Q31

NAT[2 Marks]

If methane ($\text{CH}_{4}$) gas reacts with air at a stoichiometric proportion, then the air-fuel ratio of the combustion process is (rounded off to one decimal place).

Explanation

Marine Steam Turbines, Gas Turbines & Boilers

12 Questions

GATE→2026→Thermodynamics and Marine Engineering→Marine Steam Turbines, Gas Turbines & Boilers

Q32

MCQ[2 Marks]

Identify the p-h diagram that denotes a vapor compression refrigeration cycle with flash intercooling from the following. The pressure and specific enthalpy of the working fluid are represented by p and h respectively.

(A)

Diagram A

(B)

Diagram B

(C)

Diagram C

(D)

Diagram D

Explanation

GATE→2025→Thermodynamics and Marine Engineering→Marine Steam Turbines, Gas Turbines & Boilers

Q33

MCQ[1 Mark]

Which one of the following is the most common type of gear assembly used for coupling steam turbine and propeller shafts?

(A)

Spur

(B)

Single helical

(C)

Double helical

(D)

Worm

Explanation

GATE→2025→Thermodynamics and Marine Engineering→Marine Steam Turbines, Gas Turbines & Boilers

Q34

MSQ[1 Mark]

Which of the following boiler arrangements will ensure that there is NO contamination of the primary feed system?

(A)

Steam-to-steam generator

(B)

Double evaporation boiler

(C)

Water tube boiler

(D)

Fire tube boiler

Explanation

GATE→2024→Thermodynamics and Marine Engineering→Marine Steam Turbines, Gas Turbines & Boilers

Q35

MSQ[1 Mark]

Which of the following boiler/reactor types are utilized in marine propulsion plants?

(A)

Boiled water reactor boiler (Pressurized water reactor steam generator)

(B)

Water tube boiler

(C)

Fire tube boiler

(D)

Option D

Explanation

GATE→2024→Thermodynamics and Marine Engineering→Marine Steam Turbines, Gas Turbines & Boilers

Q36

MSQ[1 Mark]

Consider an ideal Rankine cycle as shown in the figure. The overall efficiency of the cycle can be improved by

(A)

increasing the pressure at which heat is added

(B)

decreasing the pressure at which heat is rejected

(C)

employing an intercooler

(D)

superheating the steam

Explanation

GATE→2024→Thermodynamics and Marine Engineering→Marine Steam Turbines, Gas Turbines & Boilers

Q37

MCQ[2 Marks]

Which one of the following p-h plots represents the ideal vapour compression cycle with intercooling? Here, p and h denote pressure and specific enthalpy respectively.

(A)

Plot A

(B)

Plot B

(C)

Plot C

(D)

Plot D

Explanation

GATE→2023→Thermodynamics and Marine Engineering→Marine Steam Turbines, Gas Turbines & Boilers

Q38

MCQ[1 Mark]

The vapor quality of steam in the turbine of a Rankine cycle can be improved by employing

(A)

regeneration of steam

(B)

intercooler

(C)

reheating

(D)

cogeneration

Explanation

GATE→2023→Thermodynamics and Marine Engineering→Marine Steam Turbines, Gas Turbines & Boilers

Q39

MCQ[1 Mark]

In a marine steam power cycle employing regeneration, the feed water heater for waste heat recovery is placed after the

(A)

boiler

(B)

turbine

(C)

condenser

(D)

pump

Explanation

GATE→2023→Thermodynamics and Marine Engineering→Marine Steam Turbines, Gas Turbines & Boilers

Q40

NAT[2 Marks]

A simple vapor compression refrigeration cycle with ammonia as the working fluid operates between $30^{\circ}\text{C}$ and $-10^{\circ}\text{C}$ as shown in the following figure. The saturated liquid and vapor enthalpies at $30^{\circ}\text{C}$ and $-10^{\circ}\text{C}$ are provided in the table below. If the COP of the cycle is 5.6, the specific enthalpy at the inlet to the condenser is kJ/kg (round off to the nearest integer)\nTable values: h_f(30°C)=320, h_g(30°C)=1460, h_f(-10°C)=130, h_g(-10°C)=1420.

Explanation

GATE→2022→Thermodynamics and Marine Engineering→Marine Steam Turbines, Gas Turbines & Boilers

Q41

MCQ[2 Marks]

If $\Delta h_{m}$ and $\Delta h_{f}$ are the enthalpy drops across the moving and fixed blades of a turbine stage, then the degree of reaction is

(A)

$\frac{\Delta h_{m}}{\Delta h_{f}}$

(B)

$\frac{\Delta h_{f}}{\Delta h_{m}}$

(C)

$\frac{\Delta h_{m}}{\Delta h_{m}+\Delta h_{f}}$

(D)

$\frac{\Delta h_{f}}{\Delta h_{m}+\Delta h_{f}}$

Explanation

GATE→2022→Thermodynamics and Marine Engineering→Marine Steam Turbines, Gas Turbines & Boilers

Q42

MSQ[2 Marks]

For a simple vapour compression refrigeration, which of the following thermodynamic cycles (1-2-3-4) are possible? Here, T, P, s and h indicate temperature, pressure, specific entropy and specific enthalpy, respectively.

(A)

Cycle A (T-s)

(B)

Cycle B (P-h)

(C)

Cycle C (P-h variant)

(D)

Cycle D (T-s variant)

Explanation

GATE→2022→Thermodynamics and Marine Engineering→Marine Steam Turbines, Gas Turbines & Boilers

Q43

NAT[2 Marks]

In a vapour compression refrigeration cycle using R134 as the refrigerant, the enthalpies are (i) $240\text{ kJ}/\text{kg}$ at the beginning of the compression, (ii) $275\text{ kJ}/\text{kg}$ at the end of the compression and (iii) $96\text{ kJ}/\text{kg}$ at the beginning of the throttling.\nThen the coefficient of performance of the cycle is (rounded off to one decimal place).

Explanation

Engine Dynamics & Marine Auxiliary Machinery & Systems

5 Questions

GATE→2025→Thermodynamics and Marine Engineering→Engine Dynamics & Marine Auxiliary Machinery & Systems

Q44

MCQ[1 Mark]

For marine engine shafts subjected to high radial and axial thrust loads, which one of the following types of bearings is the most suitable?

(A)

Deep groove ball

(B)

Sealed ball

(C)

Tapered roller

(D)

Needle

Explanation

GATE→2025→Thermodynamics and Marine Engineering→Engine Dynamics & Marine Auxiliary Machinery & Systems

Q45

MCQ[1 Mark]

In ships, a flash evaporator is used to obtain

(A)

distilled water

(B)

low viscosity lubricating oil

(C)

high-temperature heavy oil

(D)

air for space heating

Explanation

GATE→2024→Thermodynamics and Marine Engineering→Engine Dynamics & Marine Auxiliary Machinery & Systems

Q46

MCQ[1 Mark]

Which one of the following is characteristic of marine diesel engines?

(A)

Option A

(B)

Option B

(C)

Option C

(D)

Option D

Explanation

GATE→2024→Thermodynamics and Marine Engineering→Engine Dynamics & Marine Auxiliary Machinery & Systems

Q47

MCQ[1 Mark]

Which one of the following reduces the ratio of vibratory response amplitude to the forcing amplitude, in large stationary engine shaft design?

(A)

Reduction in axial vibrations of the rotating shaft

(B)

Increase in the fundamental frequency of the rotating shaft

(C)

Decrease in the rotational speed of shaft

(D)

Operating the shaft at a speed exceeding the critical speed

Explanation

GATE→2022→Thermodynamics and Marine Engineering→Engine Dynamics & Marine Auxiliary Machinery & Systems

Q48

MCQ[1 Mark]

The most desirable property amongst the following for a lubricating oil is

(A)

high density

(B)

high dynamic viscosity

(C)

low density

(D)

low dynamic viscosity

Explanation