Noise Identification Of High Pressure Common Rail Diesel Engine Based On Acoustic Holography

With the rapid growth of vehicle ownership and the number of construction machinery and agricultural machinery,diesel engines will face challenges such as strict noise and exhaust emission limits,low fuel consumption,and high reliability.Diesel engines will also be more important than quality,noise and emissions.High demands.The internal combustion engine is a multi-noise coupling power plant,and noise control has always been a difficult point in the field of internal combustion engine research.The premise of noise control is to accurately identify and locate noise sources.In addition to measuring "propagating waves",the near-field acoustic holography method can also measure near-field "evanescent waves".It has good advantages in low-frequency space and is widely used in acoustics.Source identification.Therefore,the development of a noise source test and noise analysis system based on the theory of near-field acoustic holography is of great significance for the noise control of high-pressure common rail diesel engines.The subject is based on the theory of near-field acoustic holography,using a laboratory-developed test system to collect noise and sound source identification of high-pressure common rail diesel engines on the bench,analyze the problems existing in the original test system program,and propose an optimization plan.Completed the development and testing of the following modules,redesigned the program framework and selected the While+ event structure;added functional modules including monocular vision system,sound quality analysis,and sound image matching modules;rewritten data acquisition and signal storage modules;optimized the corresponding modules,Integrate the written subsystem and optimize the entire test system,as follows:(1)Visual subsystem programming and test verificationAnalyze the theory of visual imaging and write a visual module based on the visual function in Labview.The main functions of the visual module include: image acquisition,image calibration,image processing and image storage.After the visual module is written,use the industrial camera and industrial network cable to connect the computer host and the display to verify whether the visual system can realize the writing function.The test proves that the visual module can complete the corresponding function.(2)Compilation of noise acquisition subsystemAnalyze the type of engine noise signal,and select spectrum analysis,cepstrum analysis,energy spectrum analysis,double spectrum analysis,wavelet and wavelet packet analysis to process the engine signal.The system derives the time-frequency analysis algorithm,and uses Labview to compile modules such as signal acquisition,signal processing,and signal storage.(3)Compile the sound image matching module and verify the function of the system through known sound sourcesThe sound image matching module belongs to the result post-processing.The image calibration knows the conversion relationship between the world coordinates and the image coordinates.The near-field acoustic holography method reconstructs the sound pressure distribution of the sound source surface,and uses the known overlap relationship to overlap the sound source surface reconstruction results on the image.So as to realize the visualization of the sound field.Using the test system to collect known sound source signals,it is verified that the system can realize sound source localization and sound image matching functions.(4)Bench testSet up the test system hardware and software on the engine bench,scan and reconstruct the primary/secondary thrust side sound sources under two atmospheric pressures and three speeds,and perform corresponding signal analysis on the oil pan and generator noise sources.The whole test system development and research results show that:(1)The developed test system has a friendly human-machine interface and a more concise program block diagram;the added sound quality analysis module,visual module,and sound image matching module can realize corresponding functions;(2)In the same atmospheric environment,the engine sound pressure level of the tested model increases as the speed increases;compared with different atmospheric environments,the engine sound pressure level becomes smaller under standard atmospheric pressure.(3)The radiated noise of the test model mainly appears in the oil pan,generator,air pump,intercooler intake pipe,exhaust pipe,tripod,turbocharger,intake manifold,flywheel housing,valve chamber cover Wait.(4)The loudness amplitude of the test model between the benches appears in 0.9Bark-2.1Bark;the roughness amplitude appears in 10Bark-12Bark;the sharpness amplitude appears in 19Bark-20 Bark.