Power Plant Cpl - IR

The impeller is made of aluminium alloy forging because it is a strong and lightweight material that is commonly used in applications where high strength and low weight are required. Aluminium alloys have excellent corrosion resistance and good mechanical properties, making them suitable for use in impellers, which are rotating components used in pumps and turbines. The forging process further enhances the strength and durability of the impeller, making it an ideal choice for this application.

The correct answer is a. Subsonic airflow. Subsonic airflow refers to the air velocity entering the compressor that is below the speed of sound. This means that the air is traveling at a relatively slower speed compared to the speed of sound, which is approximately 343 meters per second at sea level. In subsonic airflow, the air molecules are not compressed to a point where they reach or exceed the speed of sound.

The thrust of gas turbine engines is affected by various factors during operations. These factors include air speed, air temperature, air pressure, and altitude. Air speed affects the amount of air entering the engine and thus influences the thrust. Higher air temperature reduces the density of the air, resulting in lower thrust. Air pressure also affects the density of the air and consequently impacts the thrust. Altitude affects the air density, with higher altitudes having lower air density, leading to reduced thrust. Therefore, these four factors are important in determining the thrust of gas turbine engines during operations.

The air entering the engine is primarily used for combustion, which is the process of burning fuel to generate power. Combustion requires a mixture of fuel and air in the correct proportions for efficient and complete burning. Therefore, 75% of the air is used for this purpose. The remaining 25% is not specified in the question, but it is commonly used for other purposes such as cooling the engine and diluting the exhaust gases.

The correct answer is a. Avigas. Avigas, also known as aviation gasoline, is the type of fuel used in gas turbine engines. It is specifically designed for use in aircraft engines and has a higher octane rating compared to regular gasoline. Avigas is formulated to meet the specific requirements of aviation engines, providing efficient and reliable performance in aeronautical applications.

The correct answer is a. The compressor pressure ratio is defined as the ratio of the total pressure at the compressor outlet to the total pressure at the compressor inlet. This ratio represents the amount of pressure increase that the compressor is able to achieve. By comparing the total pressures at the inlet and outlet, we can determine the efficiency and performance of the compressor.

The compressor bleed valve serves as an anti-compressor stall device. Stall occurs when the airflow through the compressor is disrupted, leading to a decrease in performance and potentially damaging the engine. The bleed valve helps prevent stall by releasing excess air pressure from the compressor, ensuring smooth and uninterrupted airflow. This allows the compressor to operate efficiently and prevents any potential damage or loss of power.

The thermodynamic process during compression is an isothermal process. In an isothermal process, the temperature of the system remains constant while the pressure and volume change. During compression, the gas is being compressed, which results in a decrease in volume. Since the temperature remains constant, the pressure increases proportionally to maintain the equilibrium. This process is commonly used in refrigeration and air conditioning systems to compress gases.

The inlet duct of a subsonic aircraft is designed to use a convergent shape. A convergent duct is used to accelerate the incoming airflow and increase its velocity before it enters the engine. This is necessary to ensure efficient combustion and optimal engine performance. By narrowing the duct, the airflow is compressed and its velocity is increased, allowing for better fuel-air mixing and combustion. This design is especially important for subsonic aircraft as they operate at speeds below the speed of sound.

The function of the variable inlet guide vanes is to reduce the compressor pressure ratio. These vanes are adjustable and can change the angle of the incoming air, which in turn affects the pressure ratio of the compressor. By reducing the pressure ratio, the vanes help to optimize the performance and efficiency of the compressor. This adjustment allows for better control and regulation of the air flow, ensuring that the compressor operates within its designed parameters.

The purpose of the compressor stator on an axial flow compressor is to decrease the air velocity and increase the air pressure. The stator vanes in the compressor help to redirect the flow of air and convert the kinetic energy of the air into pressure energy. By slowing down the air and increasing its pressure, the stator prepares the air for further compression in the compressor rotor. This allows for more efficient compression and higher overall pressure ratios in the compressor.

There are two combustion chamber drain valves installed at the bottom side of the combustion chamber.

The correct answer is a. Intake, Compression, combustion, Exhaust. This is the correct sequence of steps in the turbine engine cycle. The intake phase involves drawing in air, which is then compressed to increase its pressure. Next, fuel is injected and ignited, causing combustion to occur. Finally, the exhaust gases are expelled from the engine.

Rocket engines are often referred to as Non Air Breathing engines because they do not require atmospheric oxygen for combustion. Unlike other jet engines such as ramjets, pulse jets, and turbojets, rockets carry their own oxidizer, usually in the form of liquid oxygen, which allows them to operate in the vacuum of space where there is no air. Rockets generate thrust by expelling high-speed exhaust gases from their engines, providing the necessary propulsion for space exploration and satellite launches.

A subsonic inlet duct is designed to increase the air velocity entering a system. This is achieved by carefully shaping the duct to minimize air resistance and maximize the flow rate. As the air flows through the duct, its velocity increases due to the decreasing cross-sectional area of the duct. This increased velocity can be beneficial in various applications, such as improving the performance of an engine or increasing the efficiency of a ventilation system.

The components of a centrifugal compressor are the inducer, impeller, diffuser, and compressor manifold. The inducer is responsible for increasing the velocity of the fluid, the impeller imparts kinetic energy to the fluid, the diffuser converts kinetic energy into pressure energy, and the compressor manifold collects the compressed fluid and directs it to the outlet. Therefore, option a is the correct answer.

The highest pressure location at the engines is the inlet duct. This is because the inlet duct is responsible for directing air into the engine, and as the air enters the engine, it is compressed, resulting in an increase in pressure. Therefore, the highest pressure is found at the inlet duct.

The diffuser is used for flame propagation during start on engines that use Can type or Can annular combustion chambers. The diffuser helps to slow down and increase the pressure of the incoming air, creating the ideal conditions for the flame to ignite and propagate. It also helps to distribute the air evenly across the combustion chamber, ensuring efficient combustion. The flame tube, swirl vanes, and interconnector are not directly involved in flame propagation during start.

The method of introducing fuel into the combustion chamber is through a carburetor. A carburetor is a device that mixes air and fuel in the correct ratio for combustion in an internal combustion engine. It atomizes the fuel into tiny droplets and mixes it with the incoming air, creating a combustible mixture that can be ignited in the combustion chamber.

The diffuser section is located at the mid frame of the engines. This is where the airflow from the compressor enters and expands, slowing down and increasing in pressure. The diffuser section helps to convert the high-velocity, low-pressure air into low-velocity, high-pressure air before it enters the combustion chamber. This is an important step in the engine's operation as it ensures efficient combustion and optimal engine performance. The other options mentioned (b, c, and d) are incorrect as they do not accurately describe the location of the diffuser section.

The function of a diffuser on a centrifugal compressor is to increase air pressure. A diffuser is a component that is placed after the impeller of the compressor. It slows down the high-velocity air coming out of the impeller and converts its kinetic energy into pressure energy. This increase in pressure allows the compressor to deliver compressed air at a higher pressure than the incoming air.

The propeller hub is limited to not exceeding one Mach Number when the propeller rotates at maximum RPM. This is because as the propeller spins faster, the tips of the blades can approach or even exceed the speed of sound, resulting in a phenomenon called supersonic flow. To prevent this, the hub, which is closer to the center of rotation, is designed to limit the speed and ensure that it stays below the critical Mach Number.

Louvers are used to prevent the long flame in the combustion liner. Louvers are essentially angled plates or slats that are installed in the combustion liner to control the flow of air and fuel mixture. By adjusting the position of the louvers, the airflow can be regulated to ensure that the flame remains stable and does not extend beyond the desired length. This helps to maintain the efficiency and safety of the combustion process. Swirl vanes, reverse flow secondary air pass through the shortening flame holes, and reverse flow secondary air pass through the louvers are not mentioned as methods to prevent long flames in the combustion liner.

The correct answer is a. Air passage for fuel nozzle. Louvers at the combustion liner serve the purpose of providing an air passage for the fuel nozzle. This allows the fuel to mix with the air and be properly ignited, ensuring efficient combustion in the engine. The louvers help to direct the airflow towards the fuel nozzle, creating the ideal conditions for combustion to occur.

The purpose of the combustion drain valve is to drain water contamination in the combustion chamber. This is important because water can disrupt the combustion process and lead to engine damage. By draining the water, the valve helps to ensure that the combustion chamber remains clean and free of any contaminants that could negatively affect the engine's performance.

The gas turbine engine design with a reverse flow combustion chamber is implemented to increase engine efficiency. This design allows for better mixing of fuel and air, resulting in more complete combustion and improved thermal efficiency. By increasing the efficiency of the engine, it can generate more power while consuming less fuel, leading to improved overall performance and reduced fuel consumption.

The correct answer is a. Piston and type compressor. Piston and type compressors are commonly used on aircraft gas turbine engines. These compressors work by using pistons to compress the air and then transfer it to the combustion chamber. This type of compressor is known for its efficiency and reliability in providing the necessary compressed air for the engine's operation.

The correct answer is a. Low noise level. This is not an advantage of Turbo Fan over Turbo Jet because Turbo Fan engines are known for their quieter operation compared to Turbo Jet engines. Turbo Fan engines have an additional fan that helps in reducing noise by diverting some of the air around the engine core. Therefore, low noise level is not a disadvantage of Turbo Fan engines.

The correct answer is a. 3 psi. This means that the pressure operated combustion drain valve is designed to resist the valve spring at a pressure of 3 pounds per square inch. This pressure is sufficient to keep the valve closed and prevent any leakage or loss of combustion gases.

The purpose of the rotor blades of an axial compressor is to increase the air velocity. As the air passes through the rotor blades, it gains speed and kinetic energy. This increased velocity is important for the compressor to effectively compress the air and provide it to the combustion chamber at a higher pressure. By increasing the air velocity, the rotor blades contribute to the overall efficiency and performance of the compressor.

The correct answer is a. Single spool and Twin spool engines. This answer is correct because it accurately identifies the two types of turbofan engines. A single spool engine has one compressor spool, while a twin spool engine has two compressor spools. The number of compressor spools affects the engine's efficiency and performance.

Thrust Specific Fuel Consumption (TSFC) is a measure of an engine's efficiency in converting fuel into thrust. It is calculated by dividing the fuel flow rate by the thrust produced by the engine. Therefore, the correct answer is a) Fuel flow multiplied by Thrust.

In the event of a compressor stall, shutting down the engines is the correct procedure for recovery. This is because a compressor stall is a disruption in the airflow through the engine, which can lead to a loss of thrust and potentially damage the engine. Shutting down the engines helps to prevent further damage and allows for inspection and necessary repairs before restarting the engines.

Compressor stall is caused by a disruption in the airflow through the compressor. In the case of a bird strike, the bird can be sucked into the engine and cause damage to the compressor blades. This damage can disrupt the smooth airflow, leading to a compressor stall.

Secondary air is used for the combustion process. It is introduced into the combustion chamber to provide additional oxygen to the fuel-air mixture, ensuring complete combustion and increasing the efficiency of the process. This additional air helps to maintain a stable flame and prevent unburned fuel from being released into the environment. Therefore, the purpose of secondary air is to support and enhance the combustion process.

The location of the Hush Kit is in the engine inlet.

According to the regulation, every gas turbine engine should have one igniter per engine. This means that each engine should be equipped with a single igniter for proper functioning. Having multiple igniters may not be necessary or required by the regulation. Therefore, the correct answer is a. One igniter per engine.

The propulsive force on the jet engines is obtained from a rotating propeller. Jet engines work by sucking in air, compressing it, and then combusting it with fuel. The resulting high-pressure gases are then expelled through a nozzle at the back of the engine, creating a forward thrust. In this process, the propeller plays a crucial role in compressing the air and generating the necessary force for propulsion.

The highest pressure of gas in a Gas Turbine Engine is in the Inlet compressor. The compressor is responsible for compressing the incoming air before it enters the combustion chamber. This compression increases the pressure of the gas, allowing for more efficient combustion and power generation in the engine. Therefore, the highest pressure is achieved in the inlet compressor stage.

The power turbine on a turbo prop absorbs heat energy from the combustion process at a rate of 20 to 25%. This means that only a small portion of the heat energy produced by combustion is converted into mechanical energy by the power turbine. The remaining heat energy is either lost as waste or used for other purposes within the engine system.

The compressor is the engine component that comes into contact with the highest gas temperature. As the compressor takes in air from the environment, it compresses it and raises its temperature before sending it to the combustion chamber. In the combustion chamber, fuel is added and ignited, resulting in a high-temperature gas mixture. Therefore, the compressor is the component that encounters the highest gas temperature in the engine.

The temperature probes or temperature sensors of the engine are located in the engine inlet. This is the part of the engine where air enters, and measuring the temperature at this point is important for monitoring the performance and efficiency of the engine. By placing the temperature sensors in the engine inlet, engineers can gather data on the temperature of the incoming air, which can be used to make adjustments and optimize the engine's operation.

Hush Kit refers to a device or system that is used to reduce noise. It is not specifically a suppressor or absorber, but rather a general term for any equipment or technology that helps to decrease or minimize noise levels. Therefore, option a, "Noise reducer," is the correct meaning of Hush Kit.

The correct answer is a. Turbojet. A turbojet is a type of gas turbine engine used on aircraft. It is designed to produce a high-speed jet of exhaust gases that provides thrust for the aircraft. It consists of a compressor, combustion chamber, turbine, and nozzle. Turbojets are commonly used in military aircraft and some commercial aircraft that require high speeds. Turboprop and turbofan engines are also used on aircraft, but they have different designs and purposes. Therefore, the correct answer is a. Turbojet.

The correct sequence of starting a gas turbine engine is to first turn the starter on, then turn the ignition on, and finally turn the fuel on. This sequence ensures that the engine is properly primed and ready to start. Starting with the starter on allows the engine to spin up to the required speed, then turning the ignition on provides the spark needed for combustion, and finally turning the fuel on allows the engine to receive fuel and sustain the combustion process.

The function of a turbine rotor is to convert heat energy into pressure energy. This means that the turbine rotor takes the heat energy generated by a heat source, such as steam or hot gases, and uses it to increase the pressure of a fluid. This increase in pressure can then be used to drive other processes or machinery. The conversion of heat energy into pressure energy is a key function of turbines and is essential for their operation.

At least one igniter plug should be installed in the combustion chamber. This is because the igniter plug is responsible for igniting the fuel-air mixture in the combustion chamber, which is necessary for the engine to start and run. Without an igniter plug, the fuel-air mixture would not ignite, and the engine would not be able to function properly. Therefore, it is essential to have at least one igniter plug installed in the combustion chamber.

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The correct answer is a. Accelerating mass air through combustion process. This is because in a jet engine, the process of combustion occurs, which produces high-pressure and high-temperature gases. These gases are then expelled at a high velocity through a nozzle, creating a thrust force that propels the aircraft forward. This acceleration of mass air is the fundamental principle behind the propulsion force of a jet engine.

The principle of jet propulsion is based on Newton's third law, which states that for every action, there is an equal and opposite reaction. This means that when a jet engine expels high-speed exhaust gases backwards, the aircraft is propelled forward. Pascal's principle, on the other hand, relates to fluid mechanics and the transmission of pressure in enclosed fluids. Therefore, Pascal's principle is not directly related to the principle of jet propulsion.