Volume 2 - 2014 2A651 CDC

The section of a jet engine that introduces and burns fuel is called the combustion section. In this section, fuel is mixed with compressed air and ignited, producing a high-temperature and high-pressure gas. This gas then expands and flows through the turbine, where it generates power to drive the compressor and other engine components. The combustion section is a critical part of the jet engine's operation, as it is responsible for converting the chemical energy in the fuel into mechanical energy that propels the aircraft forward.

A barometer is the correct instrument to measure barometric pressure. A barometer is designed specifically for this purpose and is used to measure the atmospheric pressure in a given area. It consists of a sealed container filled with mercury or aneroid capsules that are sensitive to pressure changes. By measuring the height of the mercury column or the displacement of the capsules, the barometer can provide an accurate reading of the barometric pressure. A potentiometer is used to measure electrical potential difference, a pyrometer is used to measure high temperatures, and a barometer is used to measure barometric pressure.

The highest point of temperature in an engine is reached in the combustion section. This is where the fuel is burned, generating a high amount of heat and energy. The combustion section is designed to withstand and control these high temperatures, ensuring efficient combustion and power generation in the engine.

Before installing separable bearings, it is crucial to ensure that the bearings are a matched set. This means that the bearings are specifically designed to work together and have the same specifications and dimensions. Using mismatched bearings can lead to uneven load distribution, increased friction, and premature failure of the bearings. Therefore, it is essential to check that the bearings are a matched set to ensure optimal performance and longevity of the bearings.

Kerosene has a heat content of 18,500 British thermal units (Btu) per pound. This means that when one pound of kerosene is burned, it releases 18,500 Btu of heat energy.

In a jet engine, the required velocity for air and gases is greater when exiting than when entering. This is because the engine works on the principle of thrust, which is generated by expelling a large volume of air at a high velocity. By increasing the velocity of the exhaust gases, the engine is able to produce a greater amount of thrust, allowing the aircraft to move forward. Therefore, the correct answer is greater velocity exiting than entering.

Newton's third law of motion states that for every action, there is an equal and opposite reaction. In the case of an operating jet engine, the action is the expulsion of high-speed exhaust gases from the rear of the engine. The reaction to this action is the forward thrust generated by the engine. As the exhaust gases are expelled with a high velocity in one direction, the engine experiences an equal and opposite force in the opposite direction, propelling the aircraft forward. Therefore, the correct answer is forward thrust.

A divergent duct is designed to gradually increase in size, causing the gas to expand and slow down as it passes through. This decrease in velocity leads to an increase in pressure. Therefore, a divergent duct would decrease the velocity and increase the pressure of a gas as it passes through.

The purpose of an augmentor (afterburner) in a jet engine is to increase the maximum thrust capability of the basic engine. This is achieved by injecting additional fuel into the exhaust stream and igniting it, which increases the temperature and velocity of the exhaust gases. This increased energy output results in a higher thrust output from the engine, allowing for greater acceleration or speed.

The compressor section of a jet engine continually supplies air and maintains pressure. The compressor takes in air and compresses it before sending it to the combustion chamber. This compressed air is essential for the combustion process and provides the necessary pressure for efficient combustion and thrust generation in the engine.

The fuel control is the engine component that meters fuel for combustion. It regulates the flow of fuel into the engine based on the demand and operating conditions. It ensures that the correct amount of fuel is delivered to achieve optimal combustion and power output. The pressure and drain valve, fuel nozzle, and fuel pump are also important components in the fuel system, but they do not directly meter the fuel for combustion like the fuel control does.

When two or more turbine wheels are used in a jet engine, the component that is placed directly in front of each turbine wheel is the turbine stator (nozzle diaphragm). The turbine stator is responsible for directing the flow of exhaust gases onto the turbine blades, which in turn drives the turbine wheel. This component helps to optimize the efficiency and performance of the turbine system in the jet engine.

The most commonly used bearing removal tools are arbor presses and bearing pullers. Arbor presses are used to apply force to remove bearings, while bearing pullers are designed specifically for extracting bearings from their housings. These tools are preferred because they provide a safe and efficient way to remove bearings without causing damage to the surrounding components. Hammers and drift pipes are not commonly used for bearing removal as they can cause excessive force and potentially damage the bearings or the equipment.

The purpose of the exhaust duct is to straighten exhaust gas-flow. This means that the exhaust gas, which may be turbulent or uneven, is directed and aligned in a straight path through the duct. This helps to improve the efficiency of the exhaust system by reducing pressure drop and minimizing turbulence. Straightening the exhaust gas-flow also ensures that it exits the system smoothly and without any obstructions, allowing for better performance and reduced emissions.

The total temperature (Tt2) sensor on an F100-PW-220 engine sends electronic signals to the digital electronic engine control (DEEC). The DEEC is responsible for monitoring and controlling various engine parameters, including fuel flow, compressor speed, and turbine temperature. By receiving signals from the Tt2 sensor, the DEEC can adjust the engine's performance accordingly to optimize efficiency and ensure safe operation.

The statement describes the phenomenon of lift production on an airfoil, which is best explained by Bernoulli's principle. According to Bernoulli's principle, as the velocity of a fluid (in this case, air) increases, its pressure decreases. This principle applies to the flow of air over an airfoil, where the increased velocity of air above the curved upper surface creates a lower pressure compared to the slower-moving air below the airfoil. This pressure difference generates an upward force, known as lift, which allows the airfoil (such as an airplane wing) to generate upward motion.

Fuel for an engine represents potential energy. When fuel is burned in the engine, it releases energy in the form of heat, which is then converted into mechanical energy to power the engine. This potential energy stored in the fuel is what allows the engine to perform work and generate power.

The general flow of gases from the combustion chamber is parallel to the axis of the rotor shaft. This means that the gases flow in the same direction as the rotor shaft, creating a straight and consistent flow. This flow is important for the overall operation and efficiency of the system.

When discussing the location of parts in a jet engine, it is important to refer to them from the perspective of standing at the rear of the engine. This is because the rear of the engine is typically used as a reference point for describing the positions of different components. It provides a consistent frame of reference for engineers and technicians working on the engine, ensuring clear communication and accurate understanding of the engine's layout.

Foot-pounds and inch-pounds are units of measure for work because work is defined as the product of force and distance. In this case, the force is measured in pounds and the distance is measured in feet or inches. Work is the amount of energy transferred when a force is applied over a distance, so foot-pounds and inch-pounds are appropriate units for measuring work.

The correct answer is interlocking stainless-steel bands. This is because an annular-type combustion chamber is typically made up of multiple stainless-steel bands that interlock with each other to form the inner and outer surfaces of the chamber. This design allows for efficient combustion and containment of the high temperatures and pressures generated during the combustion process.

After a failed start, the fuel that accumulates is drained overboard by a drain system. This means that the excess fuel is removed from the system and disposed of outside the aircraft. This is a common practice to prevent any potential hazards or damage that may occur from the accumulation of fuel.

The constructional feature of an axial-flow compressor casing that is being described here is the split along the horizontal centerline. This means that the casing is divided into two halves along its horizontal center, allowing for easy access to the internal components of the compressor for maintenance and repairs. This split design simplifies the disassembly and reassembly process, making it more convenient for technicians to work on the compressor.

The correct answer is reaction-impulse. This answer is correct because the question asks for the three types of turbine and vane assemblies used in jet engines, and the options provided are impulse, reaction, fir tree, shrouded, unshrouded, and reaction-impulse. Out of these options, the correct answer is reaction-impulse as it combines both the impulse and reaction types of turbine and vane assemblies.

The stator generator of an F100-PW-220 engine is mounted on the gearbox module. The gearbox module is responsible for transferring power from the engine to various components, including the generator. This allows the generator to convert mechanical energy into electrical energy, which can then be used for various purposes within the engine or aircraft system.

Nicks are a type of defect that appear on bearings as a result of bearing parts striking together. Nicks are small, localized areas of damage or chipping on the surface of the bearing. This can occur when there is excessive load, misalignment, or improper lubrication, causing the parts of the bearing to collide and create small chips or dents. Nicks can lead to increased friction, wear, and potential failure of the bearing if not addressed.

The leading edge vanes on an F100-PW-220 engine are hollow so that anti-icing air can flow through them. This is important because during flight, ice can accumulate on the leading edge of the engine, which can disrupt the airflow and potentially damage the engine. By allowing anti-icing air to flow through the hollow vanes, the ice can be prevented from forming or quickly melted, ensuring the engine operates efficiently and safely.

The most probable cause of a flameout of a jet engine flying at 40,000 feet with a constant engine rpm of 50 percent is that the rpm is too low. When the rpm is too low, it can lead to insufficient fuel flow and inadequate combustion, causing the flame to go out. This can result in a loss of engine power and a flameout.

The parts on a can-annular combustion section must be removed in a specific order because of the combustion chamber crossover tubes. These tubes connect the individual combustion chambers in a can-annular configuration, allowing for the flow of gases between them. Removing the crossover tubes first ensures that the combustion chambers are properly isolated and prevents any potential damage or disruption to the fuel nozzle, transition liner, or combustion chamber outer case.

When an aircraft is taxiing at a steady speed, it demonstrates Newton's first law of motion, also known as the law of inertia. According to this law, an object at rest or in motion will continue to stay in that state unless acted upon by an external force. In this case, the aircraft will continue to move at a steady speed unless a force, such as braking or engine power, is applied to change its motion. This demonstrates the principle of inertia, which is a fundamental concept of Newton's first law of motion.

Before inspecting new jet engine bearings, it is necessary to remove the preservative coating. This is because the preservative coating is applied to protect the bearings during storage and transportation. If the preservative coating is not removed before inspection, it may interfere with the ability to properly assess the condition of the bearings. Therefore, removing the preservative coating is an essential step to ensure accurate inspection and assessment of the new jet engine bearings.

The greatest enemy of antifriction bearings, next to contamination and improper lubrication, is improper removal. This means that if the bearings are not removed properly, it can cause damage to the bearings and affect their performance. This can lead to premature failure of the bearings and result in costly repairs or replacements. It is important to follow proper procedures and techniques when removing antifriction bearings to ensure their longevity and efficient operation.

In a jet engine, the temperature of compressed air needs to be raised in order to increase the energy. This is because increasing the temperature of the air increases its kinetic energy, which in turn increases the energy available for propulsion and thrust. By raising the temperature, the air molecules move faster and collide with more force, resulting in a more powerful and efficient jet engine.

A gas turbine is a type of engine that converts the energy from a flow of gas into mechanical energy. Combustion efficiency refers to the effectiveness of the combustion process in converting fuel into useful energy. A higher percentage indicates a more efficient combustion process, meaning that a larger proportion of the fuel is being converted into usable energy. Therefore, the percentage of combustion efficiency of a gas turbine is usually between 95 and 100, as this range represents a high level of efficiency in converting fuel into energy.

The recommended method of expanding a bearing race before installation is to use a hot-oil bath. This is because heating the bearing race in a hot-oil bath causes it to expand, making it easier to install onto the shaft or housing. The hot oil helps to evenly distribute heat and prevent damage to the bearing race. Using a coal furnace or oscillating heater may result in uneven heating and potential damage to the bearing race. A hydraulic-oil bath is not typically used for expanding bearing races.

The advantage of the modular engine concept is that it eliminates the need to return whole engines to the depot for overhaul. This means that instead of having to take out the entire engine for maintenance or repair, only the specific module that needs attention can be removed and replaced. This saves time and resources, as well as reduces downtime for the engine.

A turbo-supercharger is essentially a high-capacity air pump. It is a device that increases the air pressure and density entering the engine, which in turn increases the amount of oxygen available for combustion. This results in improved engine performance and power output. The turbo-supercharger achieves this by using a turbine to harness the energy from the engine's exhaust gases and drive a compressor that compresses the incoming air. Therefore, the turbo-supercharger acts as a high-capacity air pump, supplying more air to the engine for improved performance.

A jet engine gets its name from its design because it utilizes an exhaust-gas-driven turbine wheel to drive its compressor. This means that the turbine wheel is powered by the exhaust gases produced by the engine, which in turn drives the compressor to provide the necessary airflow for combustion and propulsion. This design is a key characteristic of jet engines and distinguishes them from other types of engines.

The augmentor spray rings on an F100-PW-220 engine are pressure sensitive and can adjust their fuel nozzle openings in response to fuel pressure. This means that the fuel nozzle openings will be adjusted based on the pressure of the fuel, allowing for proper fuel flow and combustion within the engine. This adjustment ensures that the engine operates efficiently and effectively.

The correct answer is "increases." In a divergent design of a diffuser, the cross-sectional area of the flow passage increases, causing the velocity of the air to decrease. According to Bernoulli's principle, as the velocity decreases, the pressure increases. Therefore, in a divergent diffuser, the air pressure increases.

The most common type of fuel nozzle system is pressure-atomizing. This type of system uses high pressure to atomize the fuel into small particles, allowing for efficient combustion. It is widely used in various applications, including gas turbines, industrial burners, and oil-fired boilers. Pressure-atomizing systems offer better fuel atomization and control compared to other types, resulting in improved combustion efficiency and reduced emissions.

When small particles of foreign material become lodged between the rollers of bearings, it can cause grooves to appear on the surface. These grooves can lead to increased friction, reduced efficiency, and potential damage to the bearing over time. Pits, bands, and brinelling are not the correct answers because they do not specifically refer to the defect caused by foreign material lodged between the rollers.

The efficiency of a jet engine is commonly measured in terms of thermal efficiency, which refers to the ratio of the useful work output (in this case, the propulsive power generated by the engine) to the energy input (the fuel burned). This measure indicates how effectively the engine converts the energy from the fuel into useful work, making it a suitable term to describe the efficiency of a jet engine. Energy and momentum are not specific measures of engine efficiency, while propulsive efficiency refers to the ratio of the useful work output to the energy flow through the engine, which is a different concept from thermal efficiency.

The correct answer is compression. In a jet engine, the air temperature gradually rises across the compressor to the diffuser outlet. This is because the compressor compresses the incoming air, increasing its pressure and temperature. As the air is compressed, its molecules are forced closer together, resulting in an increase in temperature. This compressed and heated air is then used for combustion in the combustion chamber, leading to the generation of thrust in the engine.

The product of thermal efficiency and propulsive efficiency is overall efficiency. Thermal efficiency measures the effectiveness of converting thermal energy into useful work, while propulsive efficiency measures the effectiveness of converting the work done by the engine into useful thrust. Multiplying these two efficiencies together gives the overall efficiency, which represents the effectiveness of converting thermal energy into useful thrust. Therefore, overall efficiency is the correct answer.

Excessive bearing wear can usually be detected by roughness of the metal. When a bearing is worn excessively, the metal surfaces become rough and uneven. This roughness can be felt by touching the bearing or observed visually. It is a common sign of wear and indicates that the bearing is no longer functioning properly. Pits, bands, and misalignment are not necessarily indicative of excessive bearing wear, making roughness of the metal the correct answer.

When handling jet engine bearings, it is important to change cotton gloves frequently because they get soaked with sweat. Sweat can cause the gloves to become wet and damp, which can lead to discomfort and reduced grip. Additionally, the moisture from sweat can potentially damage the bearings or affect their performance. Therefore, changing the gloves frequently helps to maintain a dry and secure grip while handling the bearings.

The correct answer is three because a jet engine bearing can experience three different types of loads: radial loads, axial loads, and moment loads. Radial loads act perpendicular to the axis of rotation, axial loads act parallel to the axis of rotation, and moment loads act to twist or bend the bearing. These three types of loads are important to consider in order to ensure the proper functioning and durability of the jet engine bearing.

When there is more moisture in the air, it displaces some of the dry air molecules, resulting in a decrease in the overall density of the air. This is because water molecules are lighter than the average air molecule. Therefore, the correct answer is "More moisture, less dense."

The excess airflow that is not burned in the combustion section is used to mix with and cool the burned gases. This is because the combustion process in an engine produces hot gases that need to be cooled down before being expelled as exhaust. The excess airflow is directed towards the burned gases to mix with them and lower their temperature, preventing damage to the engine components and reducing emissions.