Table of Contents
Why is afterburner mode limited?
Limitations. Due to their high fuel consumption, afterburners are only used for short duration high-thrust requirements. These include heavy-weight or short runway take-offs, assisting catapult launches from aircraft carriers, and during air combat.
What would the effect on engine thrust be if the area of the exhaust nozzle was increased?
If the nozzle opening is too big, thrust is being wasted. Adjusting the area of the exhaust nozzle changes both the engine performance and the exhaust gas temperature. When the velocity of the exhaust gases at the nozzle opening becomes Mach 1, the flow passes only at this speed—it does not increase or decrease.
How does an afterburner engine work?
The idea behind an afterburner is to inject fuel directly into the exhaust stream and burn it using this remaining oxygen. This heats and expands the exhaust gases further, and can increase the thrust of a jet engine by 50\% or more. Therefore most planes use afterburners sparingly.
What factors affect thrust?
The factors affecting thrust of a gas turbine engine include air density, altitude, airspeed, ram effect and engine RPM. The effect of these factors is not restricted to any particular gas turbine engine; although a certain engine may be able to compensate for an effect better than another.
Why does thrust decrease with airspeed?
When you’re flying faster than L/D max, more power is needed to compensate for increasing parasite drag. As you accelerate, drag load increases as well. Because of this, more power is required at higher airspeed for acceleration. This lack of efficiency at high airspeeds also decrease thrust and power available.
How does a jet engine nozzle work?
Like any other nozzle, the jet nozzle works by compressing the air as it moves through the nozzle. This creates pressure, which is used in propulsion. As the pressure goes up, the speed at which the air is expelled increases as well. Thus, the nozzle improves the thrust used to push the aircraft through the air.
What is the function of nozzle in jet engine?
Nozzle converts the high pressure and low velocity of the gases into the high velocity and low pressure at the outlet. Nozzle restricts the flow somewhat before allowing gas to expand and thus it creates additional pressure that results in additional thrust. It has much higher power to weight ratio than the piston engine.
Do turbofan engines lose thrust during takeoff?
The drop in thrust during takeoff is even more marked for engines of higher bypass ratio and for this reason it is preferable to quote turbofan thrusts at a typical takeoff speed rather than at static conditions.
How can I explore the design and operation of a turbojet?
You can explore the design and operation of a turbojet engine by using the interactive EngineSim Java applet. Set the Engine Type to “Turbojet” and you can vary any of the parameters which affect thrust and fuel flow. You can also explore how thrust is generated within the nozzle by using the nozzle simulator program which runs on your browser.
What determines the amount of mass flow in a turbojet?
The amount of mass flow is usually set by flow choking in the nozzle throat. The nozzle of the turbojet is usually designed to take the exhaust pressure back to free stream pressure.