図示平均有効圧の計測誤差に及ぼす指圧計動特性の影響

概要

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In the study, a method for predicting IMEP (Indicated Mean Effective Pressure) measurement error induced by dynamic characteristics of pressure indicators such as strain gauge, semi-conductor and piezoelectric type is proposed. A simple lumped element model is used for evaluating the frequency response of the indicators and combined with a new IMEP equation proposed by author, instead of conventional numerical integration, which gives us an useful information that IMEP is governed by fundamental and second harmonics among pressure wave-form having frequency lower than several hundred Hz. The prediction results show that for keeping the error within ±1% for Diesel engine, first order system of piezoelectric type requires time constant more than 60 times as long as a period of the engine revolution. It is also confirmed that second order system such as an indicator with connecting passage requires natural frequency more than from 17 (damping ratio ζ=0.01) to 85 (ζ=0.1) times as high as frequency of the engine revolution.