Dynamic Estimation Of Engine Core Noise Based On Airworthiness Approach

With the popularity of civil aviation transportation and the improvement of passengers' comfort requirement,aircraft noise issues have become increasingly prominent.At the same time,international standards for aircraft noise have become more and more stringent.At present,ICAO has proposed a new fifth stage noise standard.During the critical period when China's domestically-built large aircraft is being recharged and the national aviation industry is rejuvenated,it is important to establish a set of airworthiness noise prediction and assessment systems of civil aircraft precisely and effectively.In order to meet the future noise targets and develop an airworthy noise prediction capability for aeroengines,this paper aims to develop a comprehensive noise prediction model that combines the engine's core noise source,noise propagation,and flight trajectory.After a detailed investigation and study of the related cutting-edge technology currently,this paper proposes a calculation framework for the core engine airworthiness noise,the dynamic prediction of the aircraft's core engine noise within the approach verification point and the surrounding area was also given.For starters,this paper studies the composition and generation mechanism of core engine noise;and then uses MATLAB software to estimate the static far-field nondimensionalized mean square sound pressure of combustion and turbine separately,according to the GECOR model and the Peart & Dunn model in NASA's latest aircraft noise prediction manual——ANOPP2.After which it is integrated and corrected to the sound pressure level(SPL)of the core engine in the approach state,analyze the frequency characteristics,angle characteristics,proportions of the engine noise,and discuss the core engine noise specialties during airworthy approaching.And then it is converted into the effective perceived noise level(EPNL)according to the requirements of airworthiness regulations.Specific examples verify the accuracy and reliability of the algorithm,and its relative error is about 2%.Based on this,a program is developed to dynamically estimate the core engine noise in the approach state,calculate the perceived noise level(PNL)at each prediction point in the 4km×3.9km area around the approach certification point,draw a three-dimensional noise contour;the effective perceived noise level at each prediction point in the same area is also calculated as well as the arrival core engine noise footprint,meanwhile,the accurate prediction and visual display of the approach core engine noise is realized.This model can be used for rapid assessment of aircraft's core engine noise during airworthy approach,so that manufacturers can control the aircraft core engine noise during the design phase to meet the airworthiness requirements;it also offers a new idea to determine the start point of the airworthiness certification test for approach in advance during airworthiness determination tests;at the same time,it can visually display the dynamic changes of the core engine noise in the vicinity of the airport,the distribution of noise contours,and its range of influence during the airworthy approach,so that people can clearly discover the changes in core engine noise as the approach procedure progresses.