[Rolls Royce] TPR参数介绍（原创）

A widely used parameter for thrust indication is LP speed (N1).Whilst simple to measure and accurate in itself it is not, however, the mostaccurate or consistent measurement of engine thrust. As a result, N1 ratedengines need to be over boosted to ensure the certified thrust levels aredelivered regardless of conditions. This means an N1 rated engine is generallyworking harder than it needs to therefore affecting its rate of deteriorationand time on wing.

For this reason RR has, up until the introduction of the Trent900and Trent 1000, used Engine Pressure Ratio (EPR) to present thrust on theaircraft. Whilst being more complex than N1 speed to calculate EPR provides amore accurate and consistent indication of thrust that is unaffected byhumidity and LP Compressor deterioration.

Turbofan Power Ratio is a new thrust representing parameter, whichhas been patented by Rolls Royce, and is based on the accuracy principles ofEPR.

The latest engine designs (Trent 900 and Trent 1000) have asignificantly higher bypass ratio, when compared to the previous Trent designs(Trent 500,700 and 800), but a lower pressure ratio across the LP compressor.

If EPR were to be used the calculation would be

adversely affected

by thelower pressure ratio thereby, as stated earlier, making the range between idleand max very small.

A measure of core engine power, TPR is similarly unaffected byhumidity changes and fan condition variations and is better suited than EPR foraccurate thrust indication and control on low fan pressure ratio engines, hencethe move to this parameter on the latest design of Trent engines.

表征推力指示用到的最广泛的参数是低压转子转速（N1），N1参数本身比较容易获取且精度较高，但不能精确和连续的表征推力。因此，当使用N1控制发动机推力时，发动机工作将更剧烈以确保在各种情况下有足够的推力值，这样就会缩短发动机的在翼时间和寿命。

因此，R&R在Trent900和Trent1000之前的发动机，使用EPR（enginepressure ratio）表征发动机推力。EPR（P49.5/P20）的计算比N1复杂，但提供了更为精确和连续的推力指示，同时推力控制不受空气湿度和低压压气机性能衰退的影响。

R&R公司的新专利——TPR（turbofan power ratio）——作为表征发动机推力的新参数（通过P20、T20、TGT和P30计算），是基于EPR更为精确的计算参数。

最新设计的发动机（Trent900和Trent1000）具有更高的涵道比（bypassratio），但与先前的Trent系列相比（Trent500，700和800），具有较低的风扇压比。若使用EPR控制发动机推力，低风扇压比对参数计算会产生负面影响，导致慢车位与最大推力之间的范围非常小。而TPR，作为新的控制发动机推力的参数，不仅兼具了EPR控制不会受到空气湿度和风扇状态变化影响的特点，而且比EPR更能精确的控制低风扇压比（low fan pressure ratio）发动机，因此采用TPR作为Trent新设计发动机的参数。