Abstract
Pressure diagrams represent important data, given that indicated mean effective pressure (IMEP), maximum in-cylinder pressure, heat release rate, and which directly expresses volume of work for each cycle, can be derived from them. Generally, in measurement of pressure diagrams, piezo-electric pressure sensor is used together with charge amplifier. However, the high-accuracy pressure sensors used in engine development have problems in terms of sensor life and mounting in the combustion chamber. So, in this paper, because of solving a problem, the prototype piezo-electric sensor to mount the outside of engine was manufactured. A present method of employing prototype sensors outside the combustion chamber to measure signals originating in combustion in the cylinders to determine the equivalent IMEP, which is strongly correlated with IMEP, would be calculated. In order to accurately determine IMEP, it is important that the detection of the 1st- and 2nd-order frequency components of engine speed. Measuring system using prototype sensor was improved low frequency characteristics owing to high sensitivity and high insulation resistance of prototype sensor. The prototype sensor mounted cylinder head of a four-stroke cycle single cylinder side valve engine and measured equivalent IMEP, the correlation coefficient between IMEP and equivalent IMEP was about 0.99. In the same way as single cylinder engine, the prototype sensor mounted cylinder block of a four-stroke cycle multi-cylinder engine and measured equivalent IMEP, the correlation coefficient between IMEP and equivalent IMEP was about 0.96. Therefore, the present method can expect to apply multi-cylinder engine.
