Jet engines perform better at higher altitudes due to reduced air density and drag. Turbine engines produce high thrust at low altitudes but have better efficiency at 100% power. Specific fuel consumption is used to measure engine performance and is important for multi-engine aircraft in case of engine failure.
Jet or turbine engines provide power for commercial and general aviation aircraft around the world. Propeller-driven aircraft have operational altitude limitations due to prop performance, but jet engine performance tends to increase at higher altitudes. Turbine engine performance is measured by fuel consumption, thrust, and drag at various operating altitudes.
A turbine engine will produce a large amount of thrust at low altitudes due to the high density of the air. As the plane climbs, the air density will decrease until the plane reaches normal cruising altitudes, often above 30,000 feet (9,100 meters). Although the air density is much lower at these altitudes, the aircraft can travel faster due to reduced drag or air friction.
The high thrust of the jet at lower altitudes is a disadvantage to engine efficiency. A jet aircraft sailing at lower altitudes must reduce power significantly to avoid overspeed and airframe damage. The resulting lower thrust with high air density creates poor performance of the jet engine, and fuel consumption will be higher.
Jet engine performance is optimized when the turbine operates near 100 percent power. This occurs because only a part of the engine’s thrust is due to the combustion of the fuel. A large proportion of thrust is the air compressed by the compressor section of the turbine and passing through the engine or bypassing the combustion process. Most turbine engines are called bypass engines, because only part of the airflow is used for fuel combustion, with the rest bypassing the combustion section.
As air enters the engine’s intake, it passes through a series of rotors and blades that compress the air to a higher pressure as it passes through a smaller cross section. Higher pressure air is used for both bypass thrust and combustion air. A discharge nozzle is designed to accelerate the air exiting the rear of the engine as pressure is converted to velocity, resulting in thrust that pushes the aircraft forward. The combustion gases also drive a series of vanes connected to a shaft that drives the inlet compressor section.
Jet engine performance is often measured by specific fuel consumption. This is defined as the amount of fuel used divided by the net thrust of the engine. Net thrust is the total thrust of the engine minus the amount of thrust produced by ram effects, or air passing through the engine due to flight speed. Specific fuel consumption provides designers with standard values of engine performance that can be compared for different altitudes and speeds.
It is also important to understand jet engine performance for situations where one engine fails in multi-engine aircraft. The remaining engine must produce enough thrust at a specified altitude to allow controlled flight until a landing can be made. Also, the non-running motor creates drag due to the air passing through it, an effect called a windmill. Designers must include engine performance in engine performance requirements.
Protect your devices with Threat Protection by NordVPN
