Search Results

The effects of recirculated exhaust gas on the wear of piston and piston rings were investigated by the experiment with a two-cylinder, four-cycle, indirect injection diesel engine operating at 75% load and 1600 rpm. For the purpose of comparison between the wear rates of the two cylinders with and without EGR, the recirculated exhaust gas was sucked into one of two cylinders after the soot contents in exhaust emissions were removed by an intentionally designed cylinder-type scrubber equipped with 6 water injectors (A water injector has 144 nozzles of 1.0 mm diameter), while only the fresh air was inhaled into the other cylinder. These experiments were carried out with the fuel injection timing fixed at 15.3° BTDC.

Optical fiber pressure sensors developed recently have merits of compact size, installation ease and relatively low cost. However, they are normally not suitable for IMEP measurement due to the insufficient measuring accuracy in low frequency range, which is vital for the measurement of indicated mean effective pressure (IMEP). On the other hand, it is confirmed that the IMEP is determined by the frequency components which are equivalent to, or twice greater than those of the engine speeds included in the indicated pressure wave form. The IMEP calculation method discussed in the following is capable of accurate calculation of IMEP, by checking the characteristics of the pressure sensor in advance and correcting the primary and secondary components of frequency properly. This paper describes the correction method and reports the measured results obtained in actual engine operations.

A rapid compression-expansion machine which can simulate the combustion processes in diesel engines is developed. The configuration of the combustion chamber is a 100 mm bore and a 90 mm stroke, and the compression ratio is 15. The piston is driven by an electro-hydraulic system with a thrust of 90 kN and the maximum frequency of 20 Hz. The whole system composed of a hydraulic actuator, a fuel injection system, and a valve driving unit is sequentially controlled by a computer. The reproducibility of the stop position of the piston at the end of compression is achieved with an accuracy of ±0.1 mm by employing a hydraulic-mechanical brake mechanism. The experiment shows that the combustion in the expansion stroke is achieved, and that the combustion characteristics such as the rate of heat release and indicated output as well as the exhaust emission can be measured.