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This paper investigates the combined effect of EGR and emulsified fuels on engine performance. The influence of intake air temperature (25∼86°C) on engine performance was examined prior to uncooled EGR experiments. Compared with gas oil, emulsified fuel gave simultaneous improvements in NOx concentration, smoke density, and specific fuel consumption (BSFC) over the tested range. The effect of EGR on engine performance were investigated with various water to fuel ratios at two load conditions (BMEP=0.52MPa and 0.26MPa). It was confirmed that at 11% EGR with the emulsified fuel at the rated output resulted in a significant reduction in NOx concentration without worsening smoke density and BSFC.

An automatic failure diagnosis system for engines where we apply motoring test bed and sampled firing test set is proposed in this paper. Focusing on the inspection items where sound signals can be employed, we propose a new approach utilizing wavelet transform, FFT analysis and cepstrum analysis to anomaly characterization. For three important items, namely tappet clicks, misfire and mismatching, the following results have been obtained. (1) For tappet clicks, motoring test is more effective than firing test in recognizing the features of the anomaly. Wavelet transform is more reliable and convenient than FFT analysis to extract the features. (2) For misfire, cepstrum analysis is simple and effective to detect the features. (3) For abnormal combustion sound due to time mismatching, FFT analysis can be applied to extract the features. Further studies are required for finding more effective methods.