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A prototype of measurement device that compresses a sample of engine oil at constant temperature and calculates its void fraction from the magnitude of volume change and pressure was proposed. During compression, the oil sample was pressurized to several hundreds of kPa above atmospheric pressure. Because the gas can be regarded as an ideal gas at this pressure level, the estimation of void fraction can be based on a simple formula derived from the ideal gas law, the law of conservation of mass and Henry’s law. The calibration line is represented by a linear equation of the void fraction, and from the coefficient of void fraction or the constant term the volume fraction of the dissolved gas in the initial state can be known. That is, by experimentally determining the calibration line, not only void fraction but also the volume fraction of the dissolved gas in the initial state can be known. Then, the results of measurement principle confirmation tests were given.

The Microwave Discharge Igniter (MDI) was developed to create microwave plasma for ignition improvement inside combustion engines. The MDI plasma discharge is generated using the principle of microwave resonance with microwave (MW) originating from a 2.45 GHz semiconductor oscillator; it is then further enhanced and sustained using MW from the same source. The flexibility in the control of semiconductors allows multiple variations of MW signal which in turn, affects the resonating plasma characteristics and subsequently the combustion performance. In this study, a wide range of different MW signal parameters that were used for the control of MDI were selected for a parametric study of the generated Microwave Plasma. Schlieren imaging of the MDI-ignited propane flame were carried out to assess the impact on combustion quality of different MW parameters combinations.

The chemiluminescence emission intensity can be measured with high temporal resolution, leading to understanding the chemical reaction. Time-series chemiluminescence measurements of OH*, CH* and C2* were carried out to understand flame propagation speed, its thickness and A/F ratio of combustion status. The optical piston head (quartz) allows us to visualize combustion chamber. It is found that the chemiluminescence intensity ratio of CH*/OH* and C2*/OH* can estimate local A/F. The A/F measured by O2 sensor was used for evaluation and the results indicate this method can be applicable to estimate A/F.