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In order to clarify the diesel fuel spray characteristics inside the cylinder, we developed two novel techniques, which are preparation of same level of temperature and pressure ambient as inside cylinder and quantitative measurement of vapor concentration. The first one utilizes combustion-type constant-volume chamber (inner volume 110cc), which allows 5 MPa and 873K by igniting the pre-mixture (n-pentane and air) with two spark plugs. In the second technique, TMPD vapor concentration is measured by using Laser Induced Exciplex Fluorescence method (LIEF). The concentration is compensated by investigation of the influence of ambient pressure (from 3 to 5 MPa) and temperature (from 550 to 900 K) on TMPD fluorescence intensity. By using two techniques, we investigated the influence of nozzle hole diameter, injection pressure and ambient condition on spray characteristics.

In order to clarify the state of spray and mixture formation in a diesel engine cylinder, the formation technique of high temperature and high pressure conditions in a constant-volume chamber was developed. This technique reproduces actual cylinder conditions (for example, 5MPa and 873K at TDC in NA engines with a compression ratio of 16) by filling ambience formation mixture into the chamber and pre-igniting the mixture. LIEF (Laser Induced Exciplex Fluorescence) technique was applied to the analysis of vapor-liquid separation as the measurement of spray. However, the light emission from various aromatic compounds by laser irradiation makes it difficult to apply the technique to the evaluation of the actual fuel. Therefore the preparation technique of the fuel for this LIEF technique was developed to have a mixture formation state on fuel properties.