Rapid Measurement For Engine Compression Ratio Based On Acoustic Method

As an important parameter of an engine, compression ratio is determinedby the structure size of the engine and affects the engine performance.Currently titration is widely used for measuring compression ratio. With thedisadvantage of low accuracy and efficiency, titration cannot meet therequirements of high precision and rapid measurement. Measuringcompression ratio rapidly and accurately can support evaluating andmonitoring engine manufacture level, guiding quality improvement andprocess optimization. Therefore, measuring compression ratio has greatsignificance for both design and manufacture of engine.According to the above problem, this paper studies dynamic measurementmethod for engine cylinder volume based on Helmholtz resonator. Rapidmeasurement system for compression ratio is developed and applied to engineplant. Measuring compression ratio provides guidance for production lineplanning and quality control.The main research contents include:(1) Established measurement modelfor cylinder volume based on Helmholtz resonant and verify the accuracy ofthe model;(2) Studied rapid measurement technology for Helmholtz resonatorfrequency. Developed an algorithm based on FFT and solved the problem ofunsteadiness in dynamic measurement;(3) Developed rapid measurementsystem for compression ratio. The control system is programmed underLabVIEW and automatic, precision measurement for compression ratio isrealized;(4) Conducted measurement system analysis (MSA) for the system.The bias of volume was within0.3%and repeatability reached+/-0.1mL (±3),which converted to compression ratio is±0.02. The equipment was applied inengine plant to evaluate and monitor engine manufacturing level and guide the quality control by measuring compression ratio. Factory application shows thatthe measurement system is convenient and reliable. It can provide evaluationand guidance for optimizing key process.