| With the continuous development of industry,the number of airspace routes increases continuously.And the environmental pollution caused by the exhaust gas which is emitted by aero engines is becoming more and more serious.Due to the insufficient fuel combustion,there are a large number of non-volatile particulate matter(nv PM)in the exhaust gas which causes environment pollution.In order to accurately quantify the particulate matter emitted by the engine,the International Civil Aviation Organization has issued relevant recommended standards and also conducted research on the sampling measurement standards.The particles in the sampling system have a certain loss because of the particle characteristics,which reduces the reliability of the measurement mass and the number concentration results.Therefore,the measurement results need to be corrected.Starting from the five particle loss mechanisms : diffusion,thermophoresis,bend,inertia,and electrostatics,the exhaust gas measurement and particle loss correction process at the engine emission plane are studied in detail,and the corresponding loss values caused by different particle loss characteristics are quantified.And based on the measurement process of particulate matter,corrects the calculation methods.The corresponding calculation code was written in MATLAB.And the user interface was designed by using APP Designer,and the application program for calculating loss correction was developed,which makes it more convenient to use APP to correct the measurement results.On this basis,the loss correction method is improved,and the correction results calculated under different working conditions and different types of typical engines are compared.A comparative analysis of the emission number and mass concentration correction results of different powers under the LTO cycle of the CFM56-7B26/3 engine found that the original calculation method assumes that the standard deviation is a constant is inappropriate.The new method improves the calculation tools and introduces more true values.It is concluded that the number concentration correction factor is greatly affected by the geometric mean diameter,and its trend is consistent with the original method but overall is smaller than the correction result of the original method,and as the engine power increases,The difference gradually becomes smaller,and the number correction factor is negatively correlated with engine thrust.As for the mass correction factor,the results obtained by the new correction method are not greatly affected by the geometric mean diameter,and similar to the results of the original method,the mass correction factor is also negatively correlated with the engine thrust.Further explore the correction method,and compare the measurement results of different types of typical engine emission particulate matter,the results shows that the number and mass correction factors obtained by different correction methods and the measurement results of different types of engines are all at the larger mass and large particle size.There is the same trend,and the difference is small,and when the ratio of number to mass concentration is larger,the errors of the results obtained by various calculation methods become larger and show a scattered state,that is,the emission results corresponding to the small particle size are not relatively concentrated in the large particle size.And among those methods,the result obtained by the correction method of substituting the fitted data into the calculation process have better robustness,which makes the result trend and regularity stronger,and also increases the convenience of the calculation tool.In summary,using MATLAB to make the correction calculation process into a more convenient application program,on this basis,the loss correction method has been improved and compared in different directions,which adds a lot of improvement ideas and calculation experiences for the study of particle measurement loss correction schemes. |
