Induction Systems
9. What kind of inlet duct is often used on turbine-powered helicopters?
A bell-mouthed inlet duct.
7. What is meant by a convergent inlet duct for a turbine engine?
A convergent duct is one whose cross-sectional area becomes smaller in the direction the air flows.
8. What is meant by a divergent inlet duct for a turbine engine?
A divergent duct is one whose cross-sectional area becomes greater in the direction the air flows.
15. How does an engine air inlet vortex destroyer help prevent foreign object damage to the engine?
A high-velocity stream of compressor bleed air is blown out in front of the engine to break up the vortices that form in front of the engine when it is operating at high power on the ground.
How do venture-type particle separators, found on many turbine powered helicopters, function?
A venture is used to accelerate the flow of incoming air and debris through a curved intake. The debris gains too much inertia to allow it to follow the curved intake towards the engine, and is channeled away from the compressor.
How and at what point does an internally driven supercharger boost air pressure?
An (engine driven) impeller compresses the fuel/air mixture after it leaves the carburetor.
13. What is usually installed in a large reciprocating engine between the turbosupercharger and the carburetor?
An intercooler. This is an air-to-air heat exchanger.
How is induction ice categorized?
As impact ice, fuel evaporation ice, and throttle ice.
Is carburetor throttle ice more likely to occur at a higher or lower power setting? Why?
At a lower power setting because the throttle is partly closed , offering a larger surface area for ice accumulation.
What could happen if the carburetor heat is applied at high engine power?
Detonation
What are the most common ways to control a waste gate?
Either mechanically with linkages to the throttle or a separate control or by an actuator that is driven by oil pressure.
What are the most common methods used for anti-icing of turbine engine inlet ducts?
Engine bleed air and electric heating elements.
What is used to power a turbocharger?
Engine exhaust gas directed onto the turbocharger turbine.
5. What is used to drive most of the external superchargers used on modern reciprocating engines?
Exhaust gases.
1. Where is the heat taken from that is used to heat the induction air in a reciprocating engine?
From a muff that is installed around some part of the exhaust system.
2. Where does the alternate air come from that is used with a pressure carburetor or a fuel injection system?
From inside the engine cowling.
What causes fuel evaporation ice?
Fuel evaporation ice is formed because of the decrease in air temperature resulting from evaporation of the fuel after it is introduced into the airstream.
4. Does the application of carburetor heat cause the fuel-air mixture to become richer or to become leaner?
Heated air causes the fuel-air mixture to become richer.
12. How do some turbine engines prevent ice formation on the inlet guide vanes?
Hot compressor bleed air flows through hollow inlet guide vanes.
14. In what position should the carburetor heat control be placed when starting a reciprocating engine?
In the Cold position.
3. Where does carburetor ice normally form in a carburetor?
In the throat of the carburetor on and around the throttle valve.
What are two types of supercharged induction systems?
Internally driven and externally driven.
How does induction icing affect engine performance?
It causes a reduction in power and possible erratic operation.
What is the function of a divergent-shaped jet engine inlet during subsonic flight?
It causes the airflow to decrease with a subsequent increase in pressure.
What function does a turbocharger waste gate perform?
It controls the amount of exhaust gas either into or around the turbocharger, thus controlling the boot pressure of the turbocharger.
Where are bellmouth inlet ducts typically found?
On helicopter engines.
What is a common method to used to prevent induction system ice in a reciprocating engine?
Raise the temperature of the induction air with a preheater.
6. What controls the speed of a turbocharger compressor?
The amount of exhaust gas that is forced to flow through the turbine. This is controlled by the position of the waste gate.
What could result if the waste gate on turbocharger system does not fully close?
The engine may not be able to produce its rated power at certain altitudes, and the aircraft my not be capable of reaching critical altitude.
What could happen if the induction system becomes obstructed?
The engine may not be able to produce its rated power or it may not run at all. This also may be an indication of a dirty air inlet filter.
What may be the indication of leaking intake pipes?
The engine runs rough at low RPM.
In a pressurized reciprocating aircraft, what component in the turbocharger system is used to limit the amount of turbocharger airflow used for cabin pressurization?
The sonic venturi.
What could cause a turbocharger engine to surge?
There could be a waste gate or controller malfunction.
What happens to engine power when the carburetor heat is applied?
There is a noticeable drop in power.
11. Why do some turbine engines use variable inlet guide vanes?
These variable inlet guide vanes are automatically adjusted to direct the air into the engine in such a way that it keeps the RPM vs. velocity proper for the most efficient operation.
10. What is the danger of operating an aircraft reciprocating engine with too high a carburetor air temperature?
Too high a carburetor air inlet temperature can cause the fuel-air mixture to reach its critical temperature and detonate.
Name the three components on the induction system of a reciprocating engine?
he air scoop, carburetor or fuel control, and the intake manifold.
