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VNTs offer higher flow rates and higher peak efficiency compared to other variable geometry designs. [3] Sliding Wall Turbines are commonly found in heavy-duty engines. The vanes do not rotate, but instead, their effective width is changed. This is usually done by moving the turbine along its axis, partially retracting the vanes within the housing.
The fuel consumption per mile or per kilometre is a more appropriate comparison for aircraft that travel at very different speeds. [ citation needed ] There also exists power-specific fuel consumption , which equals the thrust-specific fuel consumption divided by speed.
A turbocharger's performance is closely tied to its size, [30] and the relative sizes of the turbine wheel and the compressor wheel. Large turbines typically require higher exhaust gas flow rates, therefore increasing turbo lag and increasing the boost threshold.
Concorde, a supersonic transport, managed about 17 passenger-miles to the Imperial gallon, which is 16.7 L/100 km per passenger; similar to a business jet, but much worse than a subsonic turbofan aircraft. Airbus states a fuel rate consumption of their A380 at less than 3 L/100 km per passenger (78 passenger-miles per US gallon). [52]
A revised turbocharger offers up to 20-percent quicker response at lower engine speeds compared to previous 4G63. The 4B11T offers a broader torque curve, producing more torque than the 4G63 at all engine speeds, helped by the engine's square bore and stroke design, both measure 86 mm (3.39 in).
Propulsive efficiency is defined as the ratio of propulsive power (i.e. thrust times velocity of the vehicle) to work done on the fluid. In generic terms, the propulsive power can be calculated as follows:
Estimates made in 1964 for the Concorde design at Mach 2.2 showed the penalty in range for the supersonic airliner, in terms of miles per gallon, compared to subsonic airliners at Mach 0.85 (Boeing 707, DC-8) was relatively small.
The type of jet engine used to explain the conversion of fuel into thrust is the ramjet.It is simpler than the turbojet which is, in turn, simpler than the turbofan.It is valid to use the ramjet example because the ramjet, turbojet and turbofan core all use the same principle to produce thrust which is to accelerate the air passing through them.