Volume 2. Engine Theory And Construction

A barometer is used to measure barometric pressure, which is the pressure exerted by the atmosphere. It consists of a glass tube filled with mercury or aneroid cells that expand or contract based on the pressure changes. The height of the mercury column or the position of the aneroid cells indicates the atmospheric pressure. Potentiometer is used to measure electrical potential difference, psychrometer is used to measure humidity, and pyrometer is used to measure high temperatures. Therefore, the correct instrument for measuring barometric pressure is a barometer.

Inertia is the correct answer because it refers to the tendency of an object at rest to stay at rest and an object in motion to keep moving in a straight line at a constant speed. This property is a fundamental concept in physics and is related to the mass of an object. Inertia is responsible for the resistance an object exhibits to changes in its state of motion.

The section of a jet engine that introduces and burns fuel is the combustion section. In this section, fuel is mixed with compressed air and ignited, creating a high-temperature and high-pressure gas. This gas expands rapidly and moves through the turbine, driving it and producing thrust. The combustion section is crucial for the overall functioning of the jet engine as it generates the energy needed to propel the aircraft forward.

When handling jet engine bearings, it is important to change cotton gloves frequently because they can get soaked with sweat. Sweat can make the gloves damp, which can affect their effectiveness in providing a good grip and protection. Additionally, damp gloves can cause discomfort and may lead to skin irritation. Therefore, changing the gloves regularly helps to maintain a dry and comfortable working environment.

According to Bernoulli's principle, as the velocity of a fluid (in this case, air) increases, the pressure exerted by the fluid decreases. When air flows over an airfoil, the shape of the airfoil causes the air to move faster over the top surface, resulting in lower pressure above the airfoil compared to the pressure below it. This pressure difference creates lift, which is the upward force that allows an aircraft to stay airborne. Therefore, Bernoulli's principle best describes the combination of decreased pressure above an airfoil and increased pressure below it, resulting in lift.

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 gases onto the turbine wheel, which helps to extract energy from the gases and convert it into mechanical energy to drive the engine. It acts as a stationary guide for the gases before they enter the turbine wheel, ensuring efficient operation of the turbine system.

The stationary vanes positioned between rotor discs in a compressor are used to direct air and increase pressure. These vanes act as a guide for the airflow, ensuring that it flows in the desired direction and is compressed effectively. By directing the air, the vanes help to increase the pressure within the compressor, which is essential for efficient operation. This process allows the compressor to generate higher pressure levels, which is necessary for various applications such as power generation, air conditioning, and industrial processes.

Pressure-atomizing is the most common type of fuel nozzle system. This system uses pressure to atomize the fuel into small particles, allowing for efficient combustion. It is widely used in various applications such as gas turbines, boilers, and industrial burners. The fuel is injected into the combustion chamber under high pressure, where it mixes with air and ignites. This type of system offers better fuel efficiency, improved combustion control, and reduced emissions compared to other nozzle systems.

The recommended method of heating inner races of bearings before installing them is a hot-oil bath. This method involves immersing the bearings in a bath of heated oil, which allows for even and controlled heating. The hot oil ensures that the bearings reach the desired temperature without causing any damage or uneven heating. This method is commonly used in industries where precision and accuracy are crucial, as it helps to expand the bearings and ease their installation onto shafts or housings.

The gases in a jet engine are directed onto the first-stage turbine wheel blades by the turbine stator. The turbine stator is a stationary set of blades that guide the flow of gases from the combustion chamber towards the turbine wheel blades. It helps to control the direction and velocity of the gases, ensuring that they hit the turbine wheel blades at the correct angle and with sufficient force to drive the turbine and generate power.

The excess airflow that is not burned in the combustion section is used to cool the burner surfaces. This is because the combustion process generates a significant amount of heat, and if the burner surfaces are not cooled, they can become damaged or even melt. Therefore, the excess airflow is directed towards the burner surfaces to remove heat and maintain their integrity.

After a failed start, the fuel that accumulates is drained overboard by a drain system. This is done to remove the excess fuel and prevent any potential hazards. Draining the fuel overboard ensures that it does not enter the fuel control system again, which could cause further issues. Instead of allowing the fuel to evaporate or burn on the next start attempt, it is safer and more efficient to drain it using a drain system.

The purpose of the exhaust duct is to straighten the exhaust gas-flow. This means that the duct is designed to remove any turbulence or irregularities in the flow of exhaust gases, ensuring that they move in a smooth and straight path. Straightening the exhaust gas-flow is important for efficient and effective exhaust system performance, as it helps to minimize back pressure and improve the overall flow dynamics. By straightening the exhaust gas-flow, the duct can help to optimize engine performance and reduce emissions.

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. However, it can interfere with the inspection process and potentially mask any defects or damage that may be present on the bearings. Therefore, removing the preservative coating ensures a thorough and accurate inspection can be conducted.

A divergent duct would decrease the velocity and increase the pressure of a gas as it passes through. In a divergent duct, the cross-sectional area gradually increases along the flow direction. This causes the gas to expand, resulting in a decrease in velocity and an increase in pressure. The gradual expansion allows the gas to slow down and increase in pressure, making a divergent duct suitable for applications where pressure increase is desired, such as in diffusers or exhaust systems.

A divergent design of a diffuser increases air pressure. This is because a divergent diffuser gradually expands the flow area, allowing the air to slow down and increase in pressure. As the air flows through the divergent diffuser, it experiences a decrease in velocity and an increase in pressure due to the expansion of the flow area. Therefore, the divergent design of a diffuser has the effect of increasing air pressure.

The correct answer is combustion chamber cross over tubes. The combustion chamber cross over tubes connect the different combustion chambers in a can-annular combustion section. They allow for the flow of combustion gases between the chambers, ensuring even distribution of heat and pressure. Therefore, they need to be removed in a specific order to maintain the integrity and functionality of the combustion section.

The given answer, "reaction-impulse," is the correct answer because it accurately identifies a type of turbine and vane assembly used in jet engines. The term "reaction-impulse" refers to a combination of both impulse and reaction turbines. Impulse turbines are driven by the impact of a high-velocity jet of fluid, while reaction turbines are driven by the pressure difference between the inlet and outlet of the turbine. A reaction-impulse turbine combines the principles of both types of turbines to maximize efficiency and power output in jet engines.

The purpose of an augmentor (afterburner) in a jet engine is to increase the basic engine thrust. The augmentor is a device that injects additional fuel into the exhaust stream, which ignites and increases the temperature and velocity of the exhaust gases. This increased energy in the exhaust gases leads to a higher thrust output, providing a significant boost in performance and acceleration for the jet engine.

Arbor presses and bearing pullers are the most commonly used tools for bearing removal. Arbor presses are used to apply pressure and force to remove bearings from shafts or housings, while bearing pullers are specifically designed to grip and extract bearings from their seating. These tools are preferred because they provide a controlled and efficient method for removing bearings without causing damage to the surrounding components. Drift pipes and hammers are not as commonly used for bearing removal, as they are more likely to cause accidental damage or misalignment during the removal process.

The radial drive shaft on an F108 engine connects the core engine to the accessory drive assembly. This assembly is responsible for driving various accessories such as generators, pumps, and compressors, which are essential for the operation of the engine. It transfers power from the engine's core to these accessories, allowing them to function properly.

The overall reduction ratio of the RGB's main reduction gear train on the T56 turboprop engine is 13.54 to 1.

The total gear reduction ratio of the RGB is 13.54:1. This means that for every 13.54 revolutions of the input gear, the output gear will make one revolution. This indicates that the output gear rotates at a slower speed than the input gear, resulting in a higher torque output.

Kerosene has a heat content of approximately 18,500 BTUs per pound. This means that when one pound of kerosene is burned, it releases 18,500 BTUs of heat energy. This high heat content makes kerosene a suitable fuel for various applications, such as heating and power generation.

The correct answer is turbine. In a jet engine, the turbine is responsible for extracting energy from the hot combustion gases and converting it into mechanical energy to drive the compressor and other engine accessories. It consists of a series of blades that are driven by the high-velocity gases from the combustion chamber. This mechanical energy is then used to drive the compressor, which compresses incoming air, and the exhaust gases are expelled through the exhaust section. The diffuser is not a major section of a jet engine, but rather a component that slows down and increases the pressure of the air before it enters the combustion chamber.

Directing air around the plug helps prevent igniter plug fouling by keeping the plug cooler and reducing the build-up of carbon deposits. This allows for a more efficient combustion process and ensures that the plug remains clean and functional. Gold plating, split electrode, and ceramic coating on the plug may have other benefits in engine design but do not specifically address the prevention of igniter plug fouling.

Swirl-type fuel nozzles are designed to provide a high flame speed. This is because the swirling motion of the fuel and air mixture created by these nozzles promotes better mixing and faster combustion. The increased turbulence and mixing result in a more efficient and intense flame, leading to a higher flame speed.

The reduction geartrain is responsible for reducing the engine rotor speed to the rpm required for accessories. This component helps to match the speed of the engine with the speed requirements of the accessories, ensuring they operate efficiently and effectively. By reducing the speed through a series of gears, the reduction geartrain allows the engine to power the accessories at the appropriate speed without putting excessive strain on the engine or the accessories.

A turboprop engine produces thrust by accelerating a large mass of air by a small amount. This is achieved by using a gas turbine engine to drive a propeller. The engine takes in air, compresses it, and then mixes it with fuel and ignites it. The resulting hot gases expand and pass through a turbine, which drives the compressor and the propeller. As the propeller rotates, it accelerates a large mass of air behind it, creating thrust that propels the aircraft forward. This method is efficient for low-speed aircraft and provides good fuel economy.

Vane-type fuel pumps used in jet engines are similar to sliding-vane air compressors. Both types of pumps use a set of vanes that slide in and out of slots in a rotor to create a pumping action. This design allows for a continuous flow of fluid or air, making it efficient for high-pressure applications like jet engines. The vanes in both pumps also create a seal against the pump housing, preventing any leakage. Therefore, the similarity between vane-type fuel pumps and sliding-vane air compressors lies in their design and functionality.

After air is drawn into the guide vanes of a centrifugal compressor, it is subjected to two forces: rotational force, which is the result of the spinning motion of the compressor impeller, and centrifugal force, which is the outward force that pushes the air away from the center of rotation. These two forces work together to compress the air and increase its pressure.

The correct answer is the compressor assembly. In a turboprop engine, the compressor assembly is responsible for compressing the incoming air before it enters the combustion chamber. This compressed air is then mixed with fuel and ignited to create the necessary combustion for generating power. The compressor assembly plays a crucial role in the overall functioning of the engine by ensuring proper air intake and compression, thereby increasing the efficiency and performance of the engine. The power unit and torquemeter assembly are also important components of a turboprop engine, but they are not the major sections as mentioned in the question.

The fuel control is responsible for metering the fuel for combustion in an engine. It regulates the flow of fuel to ensure the correct amount is delivered to the combustion chambers. This component plays a crucial role in maintaining the proper air-fuel ratio for efficient combustion and optimal engine performance. The P&D valve, fuel pump, and fuel nozzles are all important components in the fuel system, but they do not specifically meter the fuel for combustion like the fuel control does.

The correct answer is that the impeller is a forged single unit. This means that the impeller is manufactured as a single piece, rather than being assembled from multiple parts. This constructional feature provides several advantages, including increased strength and durability, improved efficiency, and reduced maintenance requirements. By being forged as a single unit, the impeller can withstand the high rotational speeds and pressures required for centrifugal compression without the risk of failure or damage that may occur with a multi-part design.

Grooves appear on bearings as a result of small particles of foreign material becoming lodged between the rollers. These grooves can cause uneven wear and damage to the bearing, leading to reduced performance and potential failure.

Excessive bearing wear can usually be detected by the roughness of metal. When the bearing is worn out, the smooth surface of the metal becomes rough due to friction and abrasion. This roughness can be felt by touching the bearing or observed visually. It indicates that the bearing is no longer functioning properly and needs to be replaced. Pits, bands, and misalignment can also be signs of bearing wear, but the roughness of metal is a more reliable indicator in most cases.

The primary airflow in the F108 engine passes through the booster, core engine, and low-pressure turbine. However, it does not pass through the accessory gearbox. The accessory gearbox is responsible for driving various engine accessories such as generators, hydraulic pumps, and fuel pumps, but it does not play a role in the primary airflow of the engine.

The LPT shaft assembly connects the fan shaft with the LPT rotor. The LPT (Low Pressure Turbine) rotor is responsible for extracting energy from the hot gases exiting the combustion chamber and converting it into rotational energy. This rotational energy is then transferred to the fan shaft, which drives the fan blades to provide the necessary thrust for the engine. Therefore, the LPT rotor is the correct answer as it is directly connected to the fan shaft via the LPT shaft assembly.

The type of horsepower that is delivered to the propeller for useful work is brake horsepower. Brake horsepower refers to the actual power output of an engine or motor, measured at the output shaft. It represents the power available to do useful work, such as turning the propeller in this case.

The secondary airflow on the F108 engine produces 80% of the total engine thrust.

This statement describes Newton's second law of motion, which states that an unbalanced force acting on an object will cause the object to accelerate in the direction of the force. The acceleration is directly proportional to the force applied and inversely proportional to the mass of the object. This law is commonly expressed as F = ma, where F is the force, m is the mass, and a is the acceleration.

Nicks are a type of defect that appear on bearings as a result of bearing parts striking together. When two parts of a bearing make contact with each other, it can cause small chips or nicks to form on the surface. These nicks can lead to increased friction, wear, and potential failure of the bearing over time. Therefore, nicks are a common type of defect that can occur on bearings.

The stationary (stator) vane blades on the T56 compressor are used to increase pressure. These blades are fixed in place and help to redirect the airflow coming from the rotating blades of the compressor. By changing the direction of the airflow, the stator blades increase the pressure of the air as it passes through the compressor. This increased pressure is important for the efficient operation of the engine and for achieving the desired power output.

The correct answer is "Accessory, compressor, combustion, and power turbine section." This answer accurately identifies the four modules of the T700 engine. The accessory section refers to the components that provide auxiliary functions such as electrical power generation. The compressor section is responsible for compressing incoming air. The combustion section is where fuel is burned to generate power. And finally, the power turbine section extracts energy from the hot exhaust gases to drive the compressor and accessory section.

The "fir tree" method of attaching turbine blades to the turbine rotor disc is preferred because there is a significant temperature differential between the turbine rotor disc and the blades. This method allows for the differential expansion and contraction of the blades and disc due to the temperature difference, ensuring a secure and stable attachment.

When the aircraft is on the ground and the engine is stopped, the propeller brake is applied. This means that the brake is activated to prevent the propeller from spinning freely. Applying the propeller brake ensures that the propeller remains stationary and prevents any accidental movement or rotation, which could be dangerous during ground operations or maintenance activities.

When the rectangular teeth on the exciter wheels are aligned at zero torque, it means that there is no torque being transmitted. This indicates that the torquemeter is in a neutral or zero position. This alignment allows for accurate measurement of torque, as any change in torque will cause the teeth to move out of alignment and provide a reading on the torque indicator. Therefore, when the rectangular teeth are aligned at zero torque, it ensures proper functioning and accurate measurement of torque by the torquemeter.

The T700 engine AGB routes oil and fuel through internal passages. This means that the oil and fuel flow through channels or tubes that are located within the engine itself, rather than being transported through external lines or passages. Internal passages provide a more direct and efficient route for the oil and fuel to reach the necessary components of the engine, ensuring proper lubrication and fuel delivery.

The AE2100D3 power plant major assemblies consist of the PGB (Power Gearbox), torquemeter assembly, power section, and accessory drives. These components are responsible for generating and transferring power in the engine. The nacelle structure, on the other hand, refers to the outer casing or housing of the engine, which provides protection and aerodynamic shape. While important for the overall functioning and safety of the engine, the nacelle structure does not directly contribute to the power generation or transfer process. Therefore, the correct answer is nacelle structure.

The forward end of the shaft on a centrifugal compressor is hollow in order to provide a passage for the main fuel supply. This allows the fuel to flow through the hollow shaft and reach the combustion chamber where it can be ignited to produce power. Without this passage, the fuel would not be able to reach the combustion chamber and the engine would not be able to function properly.