Engine protection devices - aircraft engine, Other Engineering

Assignment Help:

Engine protection devices :

Described below are typical protection devices that will override any excessive demands made on the engine by the pilot or by the control units.

TOP TEMPERATURE LIMITER.

Turbine gas temperature is measured by thermocouples in the jet pipe. When maximum temperature is reached, these pass a signal to an amplifier, which limits pump stroke by reducing pump servo pressure or moves the throttle valve in series with the pilot.

POWER LIMITER.

A power limiter is fitted to some engines to prevent over-stressing due to excessive compressor outlet pressure during high-speed, low altitude running. The limiter (see figure) takes the form of a half-ball valve which is opened against a spring force when compressor outlet press (P3) reaches its maximum value. The half-ball valve bleeds off air pressure to the ACU control capsule, thus causing the ACU to reduce pump stroke.

1399_engine protaction device.png

OVERSPEED GOVERNOR.

The engine is protected against over-speeding by a governor, which, in hydro-mechanical systems, is usually fitted on the fuel pump and acts by bleeding off pump servo fuel when the governed speed is reached. On two-spool engines, the pump is driven from the HP shaft and the LP shaft is protected by either a mechanical governor or an electro-mechanical device, again acting through the hydro-mechanical control system. There are two types of pump-driven governors:

Centrifugal Governor.

The centrifugal type of governor uses the centrifugal pressure of fuel in radial drillings in the fuel pump rotor to deflect a diaphragm at maximum speed. The diaphragm operates on a half-ball valve to reduce pump servo pressure and thus pump stroke. The disadvantage of this type is that it needs to be reset if fuel specific gravity changes. It is seldom used on modern engines.
1115_engine protaction device1.png 
Centrifugal governors using bob weights are used as LP shaft governors on some engines. They will return fuel to low pressure when the LP shaft overspeeds see figure.

1934_engine protaction device2.png

Hydro-mechanical Governor.

In the hydro-mechanical governor the pump drive shaft rotates a rotor containing a half-ball valve on a lever arm (shown in the figure). As engine speed increases, centrifugal force closes the valve, increasing the pressure of fuel in the governor housing (governor pressure) by restricting its flow to LP. When the maximum speed is reached, governor pressure is high enough to deflect a diaphragm, which opens the half-ball valve acting on pump servo. A hydro-mechanical governor does not require adjustment for changes in fuel specific gravity.

978_engine protaction device3.png


Related Discussions:- Engine protection devices - aircraft engine

Engineering physics, Consider a conical pendulum with a bob of mass m=80kg ...

Consider a conical pendulum with a bob of mass m=80kg on a string of length L=10 m that makes an angle of 5 deg. with the vertical. Determine the horizontal and vertical component

Four stroke diesel engine, FOUR STROKE DIESEL ENGINE: T he cycle of ev...

FOUR STROKE DIESEL ENGINE: T he cycle of events that takes place in a four -stroke diesel engine has been shown. Unlike the petrol which drawn in a mixture of air and petrol,

Metallurgy assignment, Hi I need someone to help me to do a metallurgy assi...

Hi I need someone to help me to do a metallurgy assignment

Static aeroelasticity, An object, such as an aerofoil, moving through a flu...

An object, such as an aerofoil, moving through a fluid disturbs the surrounding flow field. The fluid velocity varies along the aerofoil surface creating a variation in pressure as

Derivatives- vertical spread, Let C (K ) denote a European vanilla Call opt...

Let C (K ) denote a European vanilla Call option with strike price K . Assume that all options are identical except for strike price, and strike prices satisfy K ??Question 1 [5 m

Principles of sprinkler systems-fire safety engineering, Principles of Spri...

Principles of Sprinkler Systems-Fire safety Engineering Sprinkler systems may be installed in a building to achieve a number of different objectives.  Very often the primary r

Modified accelerated cost recovery system , Modified Accelerated Cost Recov...

Modified Accelerated Cost Recovery System (MACRS) Although SLN is the most commonly used depreciation method in the U.S. for purpose of financial reporting, MACRS is the only

DSP HW1, With x[n] denoting the input signal and y[n] denoting the output s...

With x[n] denoting the input signal and y[n] denoting the output signal, give the difference equation relating the input signal to the output signal in the discrete-time domain, gi

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd