Thrust performance, which can be obtained by indoor sea level test facility, plays a critical role in jet and turbofan engine performance. In this study, to obtain the aerodynamic characteristics in test cell and the final thrust correction coefficient, a standard turbofan engine is chosen as the testing engine, which is mounted separately on a fixed contracting or adjustable Laval nozzle. Experimental results show that the aerodynamic performance of intake is poor if no guide vanes are implemented. In this situation, inhomogeneity of intake flow is up to 97%. Besides, the flow would separate in the upstream of the engine, which is also proven by the CFD simulation results.
With the flow separating upstream of the test engine, the traditional intake momentum correction method by using ideal horizontal intake condition could result in greater correction error of intake momentum. Thus, a new formula is derived in the present paper to correct the intake momentum with flow separation by mechanic control system. Comparisons of thrust performance and specific fuel consumption are conducted between the result corrected by new formula suited for flow separation condition and those obtained from the performance data of the same engine tested in the sea level condition. And good agreement has been achieved. Thus it is proven that the new thrust correction method is correct and reliable.
Result of this study indicates that: 1) intake flow separation has a great influence on thrust measurement in jet engine test facility, which will result in the 1.4 to 2 times greater correction error. Thus, guide vanes should be implemented at inlet tower corner in preventing from the flow separation. 2) The new correction method derived in this paper is very effective to correct the engine thrust performance with the flow separation upstream of the test engine.
Reference and Limit Governors for Limit Protection of Turbofan Engines
