Detection of the Disorder of Small Sized Diesel Engine by Exhaust Sound Radiated from the Funnel Outlet

Abstract

A 4 cycle diesel engine, whose rated power is 25ps {18.4kW}, is used in this experimental study. Valve clearance of the exhaust valve and injection pressure of fuel valve are selected as an abnormal portion, and its standard values are 0.4mm (clearance) and 190kg/cm² {18.6MPa} (pressure) .
A series of experiments are carried out for various valve clearance ranging from 0.1 to 1.45mm (valve clearance experiment) and injection pressure ranging from 100 to 305kg/cm² (injection pressure experiment) . The spectral analysis of sound from funnel outlet is made by an FFT analyzer. Using the analyzed data, multivariate analysis is made to infer the degree of the clearance and the pressure, thus ten categories (clearance or pressure) are obtained and which category a given sample belongs to is determined by the Mahalanobis' generalized distance.
As a result in the valve clearance experiment, 91.2 percent of cases are judged correct to sample cases (sample size is 400) .
In the injection pressure experiment, 95.0 percent of cases are judged correct to sample cases (sample size is 400) when the revolution is 800rpm and the load is 2/4, in case of the transformed data obtained by converting measured data at various loads into 4/4 load data by use of regression equation, 97.6 percent of cases are judged correct to sample cases (sample size is 500) .