Gas Turbine Engine Oil Coolers

Questions and Answers

What is the primary function of the flyweights in the governor?

To directly control the fuel metering valve position

To regulate hydraulic pressure in the system

To initiate fuel flow based on temperature

To adjust the opening of the governor valve based on rpm changes (correct)

How does a hydro-pneumatic fuel control unit (FCU) differ from a hydromechanical FCU?

The hydro-pneumatic FCU has a pneumatic coupling instead of mechanical linkage (correct)

The hydro-pneumatic FCU is only used in high-altitude engines

The hydromechanical FCU relies solely on temperature sensors

The hydro-pneumatic FCU uses an electric actuator

What happens to the metering valve when there is a rise in rpm?

The metering valve closes slightly (correct)

The metering valve opens wide

The metering valve remains in a fixed position

The metering valve opens fully

What role does the pneumatic computing section play in a hydro-pneumatic FCU?

It calculates fuel flow rates based on multiple variables Signup and view all the answers

What is the effect of closing the governor valve on acceleration control pressure?

Accreditation control pressure (Px) increases Signup and view all the answers

How does the bellows assembly respond to decreased N1 rpm?

It opens the metering valve slightly Signup and view all the answers

What influences the fuel flow rates in a hydro-pneumatic FCU?

N1 rpm and power lever position along with compressor discharge air Signup and view all the answers

What occurs to the governor pressure (Py) when the governor valve is closed?

Governor pressure (Py) increases along with total compressor pressure (Pc) Signup and view all the answers

What is the primary influence on the hydro-pneumatic fuel control unit for maintaining the correct air-fuel ratio?

Compressor discharge pressure Signup and view all the answers

Which component ensures a constant pressure drop across the metering head in the fuel control unit?

The fuel pressure regulator Signup and view all the answers

What characteristic of Tt2 sensors is used in fuel control systems?

They sense inlet duct temperature Signup and view all the answers

What happens to the governor valve when the power lever is advanced?

It closes off the Py bleed Signup and view all the answers

What is the function of excess fuel in the hydro-pneumatic fuel control system?

It is bypassed back to the pump inlet Signup and view all the answers

How do the pressures Px and Py affect turbine temperatures under hot conditions?

They reduce the acceleration rate Signup and view all the answers

What role do the flyweights play when the power lever is advanced?

They droop in, changing valve positions Signup and view all the answers

Which input is NOT part of the hydro-pneumatic fuel control unit?

Output voltage Signup and view all the answers

What is the primary function of oil jets in a gas turbine engine?

To distribute oil to various engine components requiring lubrication Signup and view all the answers

How does an air-cooled oil cooler regulate the temperature of the oil?

By controlling the quantity of air that passes through the cooler Signup and view all the answers

What type of lubrication system is primarily used by oil jets under high pressure loads?

Fluid stream lubrication system Signup and view all the answers

Which component ensures that air is directed through an air-cooled oil cooler?

Thermostatically controlled air scoop Signup and view all the answers

Which statement about the oil jets' operation is correct?

They use a calibrated orifice to create an oil spray. Signup and view all the answers

In which scenario is an air/oil mist spray primarily utilized?

In larger engines requiring a wider lubrication area from a single jet Signup and view all the answers

What happens when the bypass valve of a fuel-cooled oil cooler is open?

Oil bypasses the cooler and moves to the lubrication system directly. Signup and view all the answers

What type of valve systems do air-cooled oil coolers use?

Bypass and thermostatic valve systems Signup and view all the answers

What is the primary function of the combustor drain valve?

To prevent fuel accumulation in the combustor. Signup and view all the answers

What happens to the combustor drain valve during engine operation?

It is closed by gas pressure. Signup and view all the answers

How is the combustor drain valve opened after the engine is shut down?

By spring pressure. Signup and view all the answers

What could occur if the combustor drain valve is not functioning properly?

A hot start or after-fire may happen. Signup and view all the answers

What modern systems have been developed to manage dump fuel from the drain tank?

Recycling systems that return fuel to the aircraft fuel supply. Signup and view all the answers

What occurs when a drain tank becomes full in the described system?

An educator type flow system drains the tank. Signup and view all the answers

Which method is currently prohibited for handling dump fuel?

Dumping fuel onto the ground. Signup and view all the answers

What occurs to dump fuel when bleed air is introduced into the dump port?

It is pushed out of the fuel nozzles. Signup and view all the answers

What role does the governor play in engine operation?

It maintains on-speed RPM when the desired RPM is reached. Signup and view all the answers

How does the system manage changes in altitude?

Using an evacuated bellows to reset the metering valve position. Signup and view all the answers

What ensures smooth deceleration in the fuel system?

The deceleration bellows. Signup and view all the answers

What is the primary purpose of flow control units in fuel systems?

To regulate fuel flow by bypassing excess fuel. Signup and view all the answers

What best describes the function of Electro‑Hydromechanical Control Systems?

They utilize a combination of electronic circuits and mechanics for precision. Signup and view all the answers

What are the benefits of electronic engine control systems?

They enhance reliability while reducing maintenance costs. Signup and view all the answers

Which type of electronic engine control system offers full authority over engine functions?

Full Authority Digital Engine Control (FADEC). Signup and view all the answers

What is the function of sensors in the fuel control system?

To measure ambient temperature and adjust discharge pressure. Signup and view all the answers

Study Notes

Fuel-Cooled Oil Cooler

Functions with a bypass valve that can be open or closed to regulate oil flow.

Air-Cooled Oil Coolers

Operate similarly to fuel-cooled oil coolers, using air to cool oil.
Incorporate bypass and thermostatic valves for temperature regulation.
Air scoop directs airflow through the cooler based on oil temperature.

Oil Jets

Distribute oil for lubrication after it passes through the pressure pump and filter.
Utilize calibrated orifices to create an oil spray or fluid stream.
Direct-lubrication oil jets target bearings and gears; some engines use air/oil mist for wider lubrication coverage.

Hydro-Pneumatic Fuel Control

Maintains proper air-fuel ratios using compressor discharge pressures.
Controls RPM, acceleration, and flow rates via pneumatic and electronic systems.
Employs unmetered fuel pressure from the fuel pump, regulated for constant flow.

Sensor Technology

Tt2 sensors (bimetallic discs) monitor inlet duct temperature.
Have a direct impact on fuel metering which influences turbine temperature management.

Power Lever Position Dynamics

Advanced power levers affect governor valve operation, impacting RPM and fuel flow.
Governing system uses flyweights and bellows to modulate metering valve openings for maintaining engine speed.

Differences in Fuel Control Types

Hydro-pneumatic systems lack mechanical linkages, using pneumatic connections instead for more precise fuel flow control than hydromechanical systems.

Governor Section Mechanisms

Responds to power lever inputs to regulate acceleration and maintain desired RPM.
Incorporates automated altitude and temperature adjustment capabilities for effective performance under varying conditions.

Electro-Hydromechanical Control System

Also known as electronic fuel controls due to predominance of electronic components.
Aims at enhancing engine life, reliability, fuel efficiency, and reducing maintenance demands.
Includes systems like Supervisory Electronic Engine Control and Full Authority Digital Engine Control (FADEC).

Combustor Drain Valves

Mechanical valves that prevent fuel buildup in the combustion chamber during engine operation.
Open upon pressure reduction after shutdown to allow safe fuel drainage, avoiding risks during subsequent starts.

Drain Tank Regulations

International standards prevent direct dumping of fuel, mandating capture and recycling systems.
Innovations include returning drained fuel to the aircraft's fuel supply or using bleed air to manage fuel dumping and prolong combustion before starvation.

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Description

Explore the concepts related to fuel-cooled and air-cooled oil coolers in gas turbine engines. This quiz will test your understanding of bypass valves and their functions. Perfect for students pursuing training in aerospace engineering.