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Steam and Gas Turbines MCQs (Multiple-Choice Questions)

Steam and Gas Turbines are two of the most essential concepts in the field of power production; they convert fluid to mechanical energy, which results in the generation of electricity. These turbines are used in power plants, small-scale decentralized power generation, and aircraft.

Explore and practice the most popular multiple-choice questions with answers on Steam and Gas Turbines. These Steam and Gas Turbines MCQs are written for beginners as well as advanced that are helpful to learn, test, and enhance the knowledge of Steam and Gas Turbines. This set of MCQs covers its basic to advance including steam and gas turbine types, different types of cycles (Rankine, baryton cycle, Carnot cycle), classification of turbines, superheated, saturated and unsaturated steam, reheating effect, and many more.

List of Steam and Gas Turbines MCQs

1. Amongst which of the following is a correct definition of steam turbine?

  1. Steam turbines convert steam's electrical energy into mechanical energy
  2. Steam turbines convert steam's chemical energy into mechanical energy
  3. Steam turbines convert steam's kinetic energy into mechanical energy
  4. Steam turbines convert steam's thermal energy into mechanical energy

Answer: D) Steam turbines convert steam's thermal energy into mechanical energy.

Explanation:

A steam turbine is a device that converts steam's thermal energy into mechanical energy. It is then utilized to power a generator or other machines.

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2. Gas turbine works on ____ cycle.

  1. Otto cycle
  2. Baryton cycle
  3. Carnot cycle
  4. Rankine cycle

Answer: B) Baryton cycle

Explanation:

Baryton cycle is a cycle that mainly consists of four processes: compression, combustion, expansion, and exhaust, and in gas turbines all these processes are followed. The Baryton cycle is also known as the constant pressure cycle.

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3. Amongst which of the following shows the purpose of compressors in gas turbines?

  1. A compressor is used to reduce the pressure of incoming air
  2. A compressor is used to increase the pressure of incoming air
  3. A compressor is used to reduce the pressure of outgoing air
  4. None of the above

Answer: B) A compressor is used to increase the pressure of incoming air.

Explanation:

A compressor's main function is to increase the pressure of incoming air. Its primary goal is to compress the air and increase its energy level, which is essential for combustion and electricity generation.

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4. High-pressure steam is used in the ____ steam turbine to turn the blades.

  1. Condensing steam turbine
  2. Non-condensing steam turbine
  3. Impulse turbine
  4. Reaction turbine

Answer: B) Non-condensing steam turbine

Explanation:

High-pressure steam is used in the non-condensing steam turbine to turn the blades. The other name for the non-condensing steam turbine is the back-pressure steam turbine. This type of turbine requires extremely little or no cooling water.

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5. Amongst which of the following steam turbine types extracts the most energy from the steam?

  1. Condensing steam turbine
  2. Non-condensing steam turbine
  3. Impulse turbine
  4. Reaction turbine

Answer: A) Condensing steam turbine

Explanation:

Condensing steam turbine type extracts the most energy from the steam, which uses a condenser to condense the exhaust steam. The steam is then routed via tubes containing water from the cooling system.

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6. Amongst which of the following component of the impulse turbine is a pipe that supplies water to the impulse turbine?

  1. Nozzle
  2. Breaking jet
  3. Penstock
  4. Bucket

Answer: C) Penstock

Explanation:

This turbine's penstock is a pipe or duct that supplies water to the impulse turbine.

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7. Amongst which of the following turbine is responsible for changing the velocity of the water jet?

  1. Astern steam turbine
  2. Non-condensing steam turbine
  3. Impulse turbine
  4. Cross-compound steam turbine

Answer: C) Impulse turbine

Explanation:

An impulse turbine is a device that alters the velocity of a fluid jet, such as water or steam. The presence of high-pressure fluid (which was passed through the nozzle) converts pressure energy into high-velocity kinetic energy.

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8. Amongst which of the following type of turbines are also known as reversing turbines?

  1. Astern steam turbine
  2. Non-condensing steam turbine
  3. Reaction turbine
  4. Cross-compound steam turbine

Answer: A) Astern steam turbine

Explanation:

The astern turbine creates reverse thrust for propulsion systems.

Astern turbines can reverse the direction of rotation by modifying the steam flow or changing the blade angle, and therefore it is also known as reversing turbine.

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9. Do reaction turbines employ nozzles in the same way as impulse turbines do?

  1. Yes
  2. No

Answer: B) No

Explanation:

Reaction turbines, unlike impulse turbines, do not employ nozzles. The flow of steam in a reaction turbine is controlled by a series of fixed blades known as nozzles or diaphragms.

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10. How many varieties of gas turbines are there based on the path of the working fluid?

  1. 5
  2. 4
  3. 6
  4. 3

Answer: D) 3

Explanation:

Gas turbines are classified into three types based on the path of the working fluid:

  • Open-cycle Gas Turbine
  • Closed-cycle Gas Turbine
  • Semi-closed Cycle Gas Turbine

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11. Amongst which of the following is also referred to as a continuous combustion gas turbine?

  1. Open-cycle Gas Turbine
  2. Closed-cycle Gas Turbine
  3. Semi-closed Cycle Gas Turbine
  4. None of the above

Answer: A) Open-cycle Gas Turbine

Explanation:

Open cycle gas turbine is widely employed in mechanical drive systems and aircraft propulsion. In OCGT, outside air is taken into the compressor and compressed to a higher pressure. It is also referred to as a continuous combustion gas turbine because here the combustion of fuel takes place continuously.

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12. Amongst which of the following gas turbines isolates and reuses the working fluid?

  1. Open-cycle Gas Turbine
  2. Closed-cycle Gas Turbine
  3. Semi-closed Cycle Gas Turbine
  4. None of the above

Answer: B) Closed-cycle Gas Turbine

Explanation:

Instead of the surrounding air, the closed cycle gas turbine uses working fluids such as helium and hydrocarbon mixtures, which internally go through some thermodynamic cycle within the closed loop, resulting in the reuse of the working fluid.

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13. Is each spool of a multi-spool gas turbine has its compressor?

  1. Yes
  2. No

Answer: A) Yes

Explanation:

True, in a multi-spool gas turbine, each spool has its compressor, turbine stages, and rotor shaft. The reason for using several spools is that each spool can function independently and control each compressor, resulting in higher performance.

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14. Amongst which of the following is not a type of gas turbine?

  1. Multi-spool gas turbine
  2. Double spool gas turbine
  3. Open-cycle gas turbine
  4. Closed-cycle gas turbine

Answer: B) Double spool gas turbine

Explanation:

There is no such turbine named a double spool gas turbine. Based on the design, the gas turbines are either single-spool gas turbines or multi-spool gas turbines.

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15. Amongst which of the following is true about the reciprocating engine?

  1. Reciprocating engines have the same power-to-weight ratio as gas turbine engines
  2. Reciprocating engines have a higher power-to-weight ratio than gas turbine engines
  3. Reciprocating engines have a lower power-to-weight ratio than gas turbine engines
  4. None of the above

Answer: C) Reciprocating engines have a lower power-to-weight ratio than gas turbine engines.

Explanation:

Reciprocating engines are commonly called piston engines. When compared with gas turbines, reciprocating engines have a lower power-to-weight ratio; they are heavier or give power output.

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16. Amongst which of the following combustors has many independent combustion chambers arranged in a circular configuration?

  1. Annular
  2. Reverse flow combustor
  3. Rich-Burn, Quick-Mix, Lean-Burn (RQL) Combustor
  4. Can annular

Answer: D) Can annular

Explanation:

Can annular is a type of combustor that has many independent combustion chambers arranged in a circular configuration. In the field of industrial gas turbines, can annular combustors are widely employed.

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17. The airflow pattern in the can combustor is ____.

  1. Radial inward-outward pattern
  2. Axial radial pattern
  3. Opposite airflow pattern
  4. None of the above

Answer: A) Radial inward-outward pattern

Explanation:

The airflow in the can combustors is a radial inward-outward pattern. In this design, the air is normally drawn into each combustion chamber and flows towards the center of the engine core, and the hot exhaust gases are ejected outward towards the turbine section.

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18. Do Can-annular combustors use separate fuel injectors for each combustion chamber?

  1. Yes
  2. No

Answer: A) Yes

Explanation:

Yes, Can-annular combustors use separate fuel injectors for each combustion chamber. The fuel injectors are in charge of injecting fuel into the combustion chamber, which ensures effective fuel mixing.

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19. Amongst which of the following is true about axial flow turbine?

  1. It converts chemical energy into mechanical energy
  2. It converts kinetic energy into mechanical energy
  3. It converts fluid (gas or liquid) energy into mechanical energy
  4. None of the mentioned

Answer: C) It converts fluid (gas or liquid) energy into mechanical energy.

Explanation:

The principle of an axial flow turbine is that it converts fluid (gas or liquid) energy into mechanical energy. The blades of an axial flow turbine are designed to efficiently transform the fluid's energy into rotational motion.

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20. Turbojet is based on which of the following principles?

  1. Otto cycle
  2. Baryton cycle
  3. Carnot cycle
  4. Rankine cycle

Answer: B) Baryton cycle

Explanation:

A turbojet engine is a type of jet engine, that works on the baryton cycle principle.

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21. How many airflows does a turbofan engine have?

  1. 6
  2. 5
  3. 4
  4. 2

Answer: D) 2

Explanation:

Turbofan engine has two separate airflows: the primary airflow and the bypass airflow. The primary air flow works the same as it works in traditional gas turbines engine. The bypass airflow, on the other hand, is drawn into the engine and routed around the exterior of the engine core.

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22. In high bypass engines, the thrust is derived primarily from the ____.

  1. Engine core
  2. Fan
  3. Combustor
  4. Compressor

Answer: B) Fan

Explanation:

In high bypass engines, the thrust is derived primarily from the fan, whereas in low bypass engines, it is derived from the engine core. High bypass engines are widely utilized in commercial aviation, especially big commercial airliners, but low bypass engines are often found in military fighter planes and some business jets.

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23. What are the two primary components of a turboprop engine?

  1. Compression ring and fan
  2. Combustor and fuel injector
  3. Core engine and propeller
  4. Propeller and combustor

Answer: C) Core engine and propeller

Explanation:

The core engine and propeller are the two primary components of a turboprop engine. The compressor, combustion chamber, turbine, and exhaust section comprise the core engine, whereas the propeller turns the mechanical power generated by the core engine into thrust.

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24. In terms of bypass ratio, turbofan engines have a ____ bypass ratio.

  1. Larger
  2. Smaller
  3. Moderate
  4. None of the mentioned

Answer: A) Larger

Explanation:

In terms of bypass ratio, turbofan engines have a higher bypass ratio. The bypass ratio (BPR) is the ratio of flow bypassing the core to flow flowing through the core. In turbofan engines, a significant percentage of the incoming air is bypassed around the main engine, resulting in a higher bypass ratio.

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25. Amongst which of the following type of turbine is typically installed to extract the additional energy from high-pressure steam?

  1. Topping Turbine
  2. Back-Pressure Turbine
  3. Condensing Turbine
  4. Extraction Turbine

Answer: A) Topping Turbine

Explanation:

The topping turbine is installed to extract the additional energy from high-pressure steam. Topping turbines are an important component in combined cycle power plants, which use both gas turbines and steam turbines to generate electricity.

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26. Marine compound power plants consist of ____.

  1. Steam turbine
  2. Gas turbine
  3. Both A and B
  4. None

Answer: C) Both A and B

Explanation:

Marine compound power plant consists of both steam and gas turbines. Steam turbines are noted for their high efficiency in changing thermal energy into mechanical work, whilst gas turbines provide rapid response times.

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27. In ____ engines, waste energy is recovered and utilized.

  1. Steam engine
  2. Expansion engine
  3. Suction engine
  4. Turbo compound engine

Answer: D) Turbo compound engine

Explanation:

In a turbo compound engine, waste energy is recovered and utilized. It is a type of internal combustion engine (ICE), which is in charge of transforming the fuel's chemical energy into mechanical work.

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28. Amongst which of the following factors can decrease the engine efficiency and power output of a gas turbine?

  1. Lower ambient temperature
  2. Higher ambient temperature
  3. Proper fuel quality
  4. None of the above

Answer: B) Higher ambient temperature

Explanation:

Higher ambient temperatures can reduce engine efficiency and power output. When the temperature rises, the molecules expand, resulting in a lower mass flow rate of air entering the engine, which reduces the amount of fuel that can be burned and the power that can be created, ultimately leading to lower engine efficiency and power output.

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29. Land-based gas turbines are of how many types?

  1. 5
  2. 4
  3. 2
  4. 6

Answer: C) 2

Explanation:

There are two types of land-based gas turbines: (1) heavy frame engines and (2) aero-derivative engines.

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30. Based on speed, which of the following types of turbines is slower?

  1. Heavy-frame industrial gas turbines
  2. Aeroderivative gas turbines
  3. Both A and B
  4. None

Answer: A) Heavy-frame industrial gas turbines

Explanation:

Heavy-frame industrial gas turbines have a slower rotational speed than aero-derivative gas turbines because they are intended for large-scale industrial applications, and if the slower rotational speed is present, larger turbine components such as the rotor and blades can be used.

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31. Amongst which of the following process is not utilized in the Carnot cycle?

  1. Isothermal heat addition
  2. Adiabatic expansion
  3. Isothermal heat rejection
  4. Adiabatic Exhaustion

Answer: D) Adiabatic Exhaustion

Explanation:

Adiabatic exhaustion process is not utilized in the Carnot cycle. Carnot cycle has four processes: isothermal heat addition, adiabatic expansion, isothermal heat rejection, and adiabatic compression.

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32. Carnot cycle is reversible or irreversible?

  1. Reversible
  2. Irreversible

Answer: B) Irreversible

Explanation:

Carnot cycle is an irreversible cycle which means the processes can be reversed, but real-world processes are not entirely reversible, and there are always some irreversible losses and inefficiencies due to factors like friction, and heat transfer losses.

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33. Rankine cycle is employed in ____ power plants.

  1. Steam turbine
  2. Gas turbine
  3. Both
  4. None

Answer: C) Both

Explanation:

Rankine cycle is employed in steam turbine power plants and not in gas turbine power plants. The rankine cycle is widely used in steam power plants to generate electricity. In this cycle, high-pressure steam is generated by heating water, which is then expanded through a turbine to generate mechanical power.

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34. Rankine cycle converts ____.

  1. Chemical energy to mechanical energy
  2. Mechanical energy to heat energy
  3. Heat energy to mechanical energy
  4. Heat energy to chemical energy

Answer: C) Heat energy to mechanical energy

Explanation:

The rankine cycle converts heat energy to mechanical energy.

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35. How can you improve the efficiency of the Rankine cycle?

  1. By compressing the steam
  2. By reheating the steam
  3. By compressing ambient air
  4. All of the above

Answer: B) By reheating the steam

Explanation:

Reheating the steam improves overall efficiency by maximizing the consumption of heat energy and increasing the work output of the cycle.

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36. Amongst which of the following cycle is known as a mixed cycle?

  1. Reheat cycle
  2. Carnot cycle
  3. Dual cycle
  4. Rankine cycle

Answer: C) Dual cycle

Explanation:

Dual cycle is commonly known as a mixed cycle; it is the combination of the otto cycle and the Deisel cycle. The Dual Cycle starts with an adiabatic compression stroke, which compresses the air-fuel combination in the cylinder.

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37. Amongst which of the following processes occurs first in a dual cycle?

  1. Isentropic compression
  2. Constant volume heat addition
  3. Isentropic expansion
  4. None of the above

Answer: A) Isentropic compression

Explanation:

In a dual cycle, the process starts with the isentropic compression of the air-fuel combination in the cylinder; this compression process is often believed to be adiabatic and reversible, increasing by working fluid pressure and temperature.

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38. For better efficiency the steam rate should be ____.

  1. Higher
  2. Lower
  3. Steam rate does not affect efficiency
  4. None of the mentioned

Answer: B) Lower

Explanation:

For better efficiency, the steam rate should be lower. Lowering the steam rate enables for more efficient use of the thermal energy in the steam, resulting in less heat loss.

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39. The cross-sectional area of which type of nozzle drops constantly from its entrance to its exit?

  1. Convergent Nozzle
  2. Divergent Nozzle
  3. Convergent-Divergent Nozzle
  4. All of the above

Answer: A) Convergent Nozzle

Explanation:

The cross-sectional area of the Convergent nozzle drops constantly from its entrance to its exit. This form is intended to improve the velocity of a fluid flowing through it while decreasing the pressure.

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40. In which of the following conditions divergent nozzle is used?

  1. Backpressure >= critical pressure ratio
  2. Backpressure = critical pressure ratio
  3. Backpressure < critical pressure ratio
  4. None of the above

Answer: C) Backpressure < critical pressure ratio.

Explanation:

Divergent nozzle is utilized in a situation when back pressure is less than the critical pressure ratio. When the backpressure is less than the critical pressure ratio, the flow through the diverging nozzle can expand to supersonic speeds, enhancing thrust or flow efficiency in certain applications.

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41. Amongst which of the following is true about diffusers?

  1. Diffusers reduce the velocity of fluids and decrease pressure
  2. Diffusers increase the velocity of fluids and increase pressure
  3. Diffusers reduce the velocity of fluids and increase pressure
  4. None of the mentioned

Answer: C) Diffusers reduce the velocity of fluids and increase pressure.

Explanation:

Diffusers are ducts that reduce the velocity of fluids and increase pressure. Diffusers are extensively employed in a variety of applications, including ventilation systems and air conditioning because they transform the kinetic energy of the fluid into an increase in pressure.

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42. If the density of the fluid changes in response to changes in pressure caused by flow, then the fluid is commonly called ____.

  1. Incompressible
  2. Compressible
  3. Exhaustible
  4. Combustors

Answer: B) Compressible

Explanation:

If the density of the fluid changes in response to changes in pressure caused by flow, then the fluid is commonly called as compressible. Changes in pressure cause matching changes in density in a compressible fluid, indicating that the fluid can be compressed.

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43. When the Mach number is ____, the flow is to be supersonic?

  1. Less than 1
  2. Greater than 1
  3. Equal to 1
  4. Equal to 0

Answer: B) Greater than 1

Explanation:

The Mach number is the ratio of flow velocity to sound speed. When the Mach number is more than one, the flow is in the subsonic region. The Mach number is greater than one in the supersonic zone, indicating that the flow velocity is greater than the speed of sound.

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44. Amongst which of the following factor does not affect the nozzle efficiency?

  1. The fluid's nature and condition,
  2. Friction
  3. The velocity of a fluid.
  4. None of the mentioned

Answer: D) None of the mentioned

Explanation:

The fluid's nature and condition, Friction, and velocity of fluid are all these three factors that affect the nozzle efficiency. Some other factors which also affect the nozzle efficiency are:

  • The nozzle material
  • The nozzle's size and shape
  • Finish the nozzle
  • Divergence angle

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45. If all the molecules of the steam remain in the gaseous state then this type of steam is commonly known as ____.

  1. Unsaturated steam
  2. Saturated steam
  3. Superheated steam
  4. None of the above

Answer: C) Superheated steam

Explanation:

If all the molecule of the steam remains in a gaseous state, then this type of steam is commonly known as superheated steam. Superheated steam is steam that has been heated over its saturation point without the presence of liquid water.

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46. What is the other name of wet steam?

  1. Saturated steam
  2. Fixed steam
  3. Heated steam
  4. Unsaturated steam

Answer: D) Saturated steam

Explanation:

Wet steams are commonly known as unsaturated steam. Wet steam is steam that contains a combination of water droplets and vapor. It's created when steam isn't vaporized and still has some liquid water in it.

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47. Does steam have more energy?

  1. Superheated steam
  2. Saturated steam
  3. Both
  4. None

Answer: A) Superheated steam

Explanation:

Superheated steam has more energy than saturated steam. The extra energy in superheated steam results from the additional heat applied to saturated steam to raise its temperature over the saturation point; the higher the temperature of superheated steam, the larger the kinetic energy of the steam molecules, and thus the greater the energy content.

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48. Amongst which of the following has lower density?

  1. Superheated steam
  2. Saturated steam
  3. Both
  4. None

Answer: A) Superheated steam

Explanation:

When superheated steam is heated to a greater temperature, its molecules gain kinetic energy and move more rapidly, resulting in a lower density than saturated steam.

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