桨扇发动机性能预测

在飞机的方案论证阶段以及尔后飞机与发动机的性能匹配过程中都需要知道桨扇发动机的性能。本文主要讨论桨扇发动机性能的预测方法,并给出计算得到的飞行特性和转速特性。 一、设计点的选取 1.桨扇发动机设计点 起飞和巡航是运输机的主要飞行任务。发动机的尺寸主要也是根据这两个飞行任务选取。以往,涡扇发动机是将海平面上的起飞条件作为设计点,只要起飞推力够了,巡航推力一定满足。但桨扇发动机由于函道比较大(>50),推力随马赫数下降很快,一般选10000米高度上的巡航马赫数作为设计点。 

PERFORMANCE PREDICTION OF A PROPFAN

The airplane/engine performance matching of a propfan requires that the engine performancesare evaluated over the entire range of Mach numbers and altitudes. The problem of the critical engine sizing requirements is considered firstly, an aerodynamic model is then provided to estimate the propfan efficiency trend and to determine the pressure drop in each expansion unit under the off-design conditions. Based on this model, two curves,ηB = f(SHP/D2)and -ηBR = f(J), are recommended to reduce the propfan efficiency map, and a redistributioncurve of the generalized pressure ratio over each expansion unit is obtained. According to these curves the off-design performances of a propfan,inclusive of the flight, take-off, and throttle characteristics, are predicted.