Questions and Answers
What is the primary function of the screen and spacer filter?
What is the purpose of the threaded element in a thread filter?
Why is an oil bypass valve necessary in an oil filter?
What type of filter is typically used as a pressure filter?
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What is the purpose of the perforated tube in a screen and spacer filter?
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Where is a thread filter typically located?
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What determines the degree of filtration in a thread filter?
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What happens to the other channel when both channels are serviceable and the active channel alternates with each engine start?
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What is the purpose of the dual sensors fitted on valves and actuators?
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What happens if both channels of the EEC fail?
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What is the function of the Engine Rating Plug?
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What is the purpose of the hydromechanical unit?
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What is the function of the electrical hydraulic servo valve (EHSV)?
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What happens in one system upon dual channel failure?
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What is attached to the engine fan case with a lanyard?
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What primarily changes the mass of air induced through the engine?
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How does the FCU adjust the fuel flow to the engine?
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Which of the following is NOT an input for the typical FCU?
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What effect does a mismatch between airflow and fuel flow have on engine performance?
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Which condition is adjusted by the servo system in the fuel control unit?
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What is the role of the HP fuel pump in the engine fuel system?
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What modern technology automatically compensates for fuel density in engines?
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What happens to engine speed during rapid acceleration if airflow is not properly adjusted?
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Which of the following statements accurately describes the primary purpose of a combustor drain valve?
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What mechanism triggers the opening of a combustor drain valve after engine shutdown?
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What is the primary concern regarding a malfunctioning combustor drain valve?
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What is the primary reason for the current regulations prohibiting the dumping of fuel from aircraft in flight?
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What is the primary function of a fuel recycling system?
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What is the purpose of introducing bleed air into the dump port of a fuel recycling system?
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What is the function of the float valve in a fuel recycling system?
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Which of the following is NOT a potential outcome of a malfunctioning drain valve?
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What role does the air balance chamber play in relation to the compressor thrust bearing?
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In what scenario might an engine not require an air balance chamber?
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What is the primary use of customer bleed air in turbine engines?
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How is low-pressure bleed air characterized in a gas turbine engine?
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What is the function of the pre-cooler in relation to engine bleed air?
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What role does the fan air temperature sensor play in the cooling process?
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What happens to the fan air after passing through the heat exchanger in the cooling process?
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What is a distinguishing feature of high-pressure bleed air?
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What is the primary function of a gas turbine system?
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What is the purpose of the combustion chamber in a gas turbine system?
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What is a major advantage of gas turbine systems?
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In which industry are gas turbines used to power pumps and compressors?
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What is the purpose of the turbine in a gas turbine system?
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What is a challenge associated with gas turbine systems?
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What is a benefit of gas turbines in terms of environmental impact?
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What is the purpose of the generator in a gas turbine system?
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Study Notes
Screen and Spacer Filters
- Utilize disc-shaped elements stacked on an element support.
- Oil flows through both sides of filter discs separated by a spacer into a perforated tube.
- Commonly used as pressure filters, positioned downstream of the pump.
Thread Filters
- Serve as “last chance” filters before oil enters bearings.
- Feature an inner threaded element and an unthreaded outer casing.
- Filtration efficiency can be adjusted by selecting pitch of threads; finer pitches provide better filtration.
Oil Filter Bypass
- Mandatory design for oil filters to allow full oil flow even if blocked.
- Typically achieved through an oil bypass valve that diverts oil when the filter is clogged.
- Airflow changes due to altitude, temperature, and speed affect engine fuel-air ratio.
Fuel Flow Variation
- High-Pressure (HP) fuel pump output adjusted through:
- Piston stroke variation for piston type pumps.
- Recirculation of excess fuel for gear type pumps.
- Pump output adjustments respond to throttle movement, air temperature, pressure changes, rapid accelerations, and engine performance signals.
Engine Electronic Control (EEC)
- Modern systems with two redundant channels for reliability, each with its own processor and sensors.
- Active channel alternates with each engine start; can operate even with some faults.
- EEC controls subsystems such as fuel and air oil coolers, bleed valves, and turbine cooling systems.
Drain Valves
- Mechanical devices in combustor to prevent fuel accumulation by opening based on pressure changes.
- According to operation, valve prevents risks of hot starts or after-fires due to fuel residue.
- Essential for maintenance and effective engine starting procedures.
Drain Tanks and Recycling Systems
- Current regulations mandate that dumped fuel be captured; direct ground dumping is prohibited.
- Recycling methods include returning fuel to the aircraft supply or using bleed air to expel fuel through nozzles.
- Balanced systems prevent compressor forward thrust by utilizing air pressure in balance chambers.
Customer Bleed Air Systems
- Extracted from the engine compressor for aircraft functions like anti-icing and cabin pressurization.
- Low-pressure bleed air comes from early compressor stages, while high-pressure air is sourced from later stages.
Pre-cooler Functionality
- Hot engine bleed air is cooled before use in aircraft systems.
- Utilizes cold airflow from the engine’s fan area as a cooling medium through a heat exchanger.
- Controlled by a fan air temperature sensor affecting the position of the Fan Air Modulating Valve for optimal air cooling.
Overview
- Gas turbine systems utilize a turbine in internal combustion engines for power generation.
- Widely employed in power generation, oil and gas, and aerospace sectors.
- Notable for high efficiency and superior power-to-weight ratios.
Components
- Compressor: Ingests air, compresses it, and mixes it with fuel.
- Combustion Chamber: Site of fuel ignition, releasing significant energy.
- Turbine: Transforms energy from combustion into mechanical energy.
- Generator: Converts mechanical energy into electrical energy, primarily in power generation.
Working Principle
- Air enters the compressor where it undergoes compression.
- Fuel is injected and combined with the compressed air in the combustion chamber.
- Ignition of the air-fuel mixture generates energy.
- Resulting hot gases expand through the turbine, producing power.
- The turbine drives the generator, creating electrical energy from mechanical input.
Advantages
- Achieves a high power-to-weight ratio, enhancing mobility and efficiency.
- Efficiency rates can reach up to 40%, making them cost-effective.
- Produces lower emissions compared to traditional fossil fuel power systems.
- Quick startup and responsive operations make them versatile.
- Capable of using diverse fuels, such as natural gas and biofuels.
Applications
- Power Generation: Central to producing electricity in various power plants.
- Oil and Gas: Vital for powering pumps and compressors in extraction processes.
- Aerospace: Essential for jet engines, providing thrust for aircraft.
- Industrial: Powers mechanical equipment like compressors and pumps in industrial settings.
Challenges and Limitations
- Maintenance costs can be significantly high over the system's lifetime.
- Initial investment is considerable, posing a barrier to adoption.
- Some designs exhibit limited fuel flexibility, restricting operational versatility.
- Noise and vibration produced can present significant operational challenges.
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Description
Learn about screen and spacer filters, their working principle, and applications. Understand how they function as pressure filters in oil systems.
