Estimation Of Fan Noise Contours During Takeoff

At present,all aircraft manufacturers launching new models of aircraft must pass the airworthiness certification in terms of noise before entering the market.The importance of environmentally relevant airworthiness certification items such as noise and emissions is almost equal to the airworthiness certification in terms of performance.During the take-off of the aircraft,the engine noise is much larger than the aerodynamic noise brought by the fuselage,and the noise generated by the fan components is an important part of the engine noise.This article analyzes the components of fan noise,uses Heidmann fan noise model as the core of the noise prediction algorithm,and Matlab software as the calculation tool to perform noise prediction on the fan components of the engine.First,calculate the noise of the fan component under static conditions,and combine the data provided by the ANP database to analyze and calculate the inevitable loss of the sound in the air propagation process and the impact caused by the Doppler effect.The distance of the source can be obtained by calculating the actual takeoff flight path of the aircraft.The effects of atmospheric sound attenuation and Doppler effect are substituted on the fan noise prediction model for dynamic correction,making the prediction results more realistic.The finite sensory noise level EPNL is used as the calculation result,because EPNL is only a process quantity,which is more in line with the subjective feeling of the human ear.Taking Boeing 737-800 aircraft as an example to calculate the noise,by comparing with the noise data of the European Experimental Center,it can be concluded that the noise calculation model is more reasonable and accurate,and has application value.Take multiple points on the ground,use the same method to calculate the noise at multiple predicted points,and generate contour maps from the obtained data to visually show the environment caused by the noise of fan components on the ground during takeoff influences.In view of the environmental assessment of the reconstruction and expansion of the airport,the contour line of airport environmental noise is one of the items,so it isalso of practical significance to calculate the contour line of aircraft noise.By analyzing the calculated data of the noise value,the EPNL value of the effective perceived noise level of the fan component obtained from the multiple predicted points on the ground will change as the horizontal distance increases.The results show that the Heidmann fan noise model algorithm is highly accurate when used to predict the engine fan noise of an actual civil aircraft,and it can provide a reference for the method of noise prediction during aircraft airworthiness certification.