134 (4-1) orl Flashcards
Defined the term sonic subsonic and super sonic
Sonic is Mach one or the speed of sound abt 760mph
subsonic is a speed below the speed of sound
supersonic is a speed greater than the speed of sound
Why must the airflow be subsonic while flowing through the engine
Supersonic air flows can’t go through the engine or else it will cause shockwaves that will choke the compressor that may lead to blade damage. Supersonic is not compressible because a solid
What is the function of the engine diffuser
Function is to decrease in velocity and increase in pressure the diffuser section generates the highest amount of pressure
What is the shape of a subsonic and supersonic diffuser? Explain why they must be shaped differently
Subsonic - divergent shape : As the intake air passes through the duct it spreads out. As the air spreads out, it’s velocity decreases and it’s pressure increases
Supersonic - convergent-divergent shape : Convergence section of the Inlet will first slow the speed of the air to subsonic by forming a shockwave.
Why do some inlet ducts have a movable wage or Spike incorporated into them
This is for supersonic aircraft. It change geometry to accommodate a wide range of flight speed. These techniques ensure that the demand for engine airflow Is met Precisely to optimize efficiency at all flight conditions
What role do diffusion and diffusers play in controlling velocity and pressure
To decrease velocity and increase in static pressure. Radio to actual flow. This prepares the air for entry into combustion section at low velocity to allow proper mixing With fuel. The diffusion process is assisted by located immediately behind the last stag of the compressor
Who Normandy designs and supplies in the inlet duct
Airframe manufacturers normally designs and supply the inlet duct, however, engine performance is taken into consideration of the engine design
What is meant by ram recovery and ram recovery speed
Ram recovery is when the inlet total pressure is equal to the ambient air pressure. It affects that have positive pressure efficiency.
Ram recovery speed is the speed at which Ram effect counters the reduced air mass, to the point where ambient pressure is obtain this speed is typically around 160mph. There is no ram recovery speed on turboprops and shaft
Why must inlet duct repairs be done very carefully?
Repairs must be done very carefully to retain the ducks smooth streamline aerodynamic shape. If small amounts of airflow distortion can result in Appreciable loss in engine efficiency or you can be responsible for otherwise unexplainable compressor surge
What are blow-in-doors and explained their functions
They are used on single engine entrance ducks, they are used during times when they need a high thrust operation at Low airspeed example take off. They are spring loaded doors they add additional more air to the force of the engine. Also helps prevent compressor stalls
What is a Bellmouth duct and when is it used
It has a conversion shape allowing more air to enter the Inlet of the engine it is usually installed on the engine body established on the ground test stand to lead the outside air into the face of the fan and compressor and on helicopters. Reduce turbulence
How does a particle separator operates. What type of aircraft installation use them?
They are use on small turboprops and turboshaft engines that operate in unprepared landings for example the PT six and ST six. It protects the engine from excessive ingestion of sand and dust preventing the compressor blades from erosions and the increase in TBO’s. Has sharp turns to create centrifugal force to separate the air and debris around the sharp turns. Inertia sparates debris from air. Clean air 2 enigne
What is meant by high bypass ratio Turbofan engines
It refers to the Ratio of the air that bypass the core of the engine and is directed to the fan to make thrust. A bypass ratio is 4:1 or greater (4 parts of air goes to the fan and 1 part goes to the engine core) is considered high. Fan thrust and engine thrust : total thrust
What is the function of the inlet guide vanes and why Are they made hollow
During low airspeeds they are close to direct air at an optional angle, for the critical angle of attack and control the mass of the airflow through engine. For the first few stages are hollow because of Ice build up it prevents deicing. hollow for oil passage too. Oil takes away power less dense
