Airworthiness Assessment Of Fan Aft Noise For Civil Aircraft Engine Based On Boeing Algorithm

With the wide application of the high bypass ratio engine and the improvement of engine design, the exhaust gas speed of the jet engine was gradually reduced, and this makes a significant reduction of jet noise, which is eighth order function of exhaust gas velocity. Compared with the fan noise, the jet noise is of less importance in total engine noise, and for the high bypass ratio turbofan engine, the fan noise almost plays the same role as that of the jet noise in the engine noise. Researches show that the fan noise radiates not only forward but also to the backward. And for some airplanes fan aft noise, which almost dominates total fan noise, makes roughly the same contribution as that of the engine jet gas during their taking off. As a result, it is of great significance to study the fan aft noise.Based on Boeing Fan Noise(BFN) Algorithm, a sort of fan aft noise prediction method is explained in detail in this paper. And in addition, predictions and visualization analysis platform for fan aft noise has been developed with the help of science and technology software MATLAB. To verify and validate the accuracy and precision of the algorithm, one type of engine is taken as an example to compare simulated results with static test data and a series of researches have been done, including sound pressure level characteristics, trends and related visual analysis. In addition, thanks to data obtained in our workshop with the same motor, the influence of fan aft noise for the whole engine is studied under take-off, landing and sideline fan rotation speed condition. At last, noise airworthiness assessment is analyzed in this paper. The results can be useful and may serve as a reference for the civil aviation authority.