Mataji Tateishi

Compression Ignition and Spray Combustion Characteristics of Alcohol Fuels in a DI Diesel Engine

Entablishment of recycling energy system utilizing biomass as the storage of solar energy must be expected for the fundamental solution of global problems such as petroleum exhaustion and climate change. Final goal of this study is to realize a compression ignition and spray combustion engine system with higher efficiency and controllability using biomass-based alcohol fuels such as Methanol and Ethanol. As the first step of this research, in order to make clear the ignition and combustion characteristics of alcohol fuels, five kinds of alcohols and gas oil were tested in a small sized DI Diesel engine with glow-assisted ignition system. The test results show that difficulties of controlled ignition of alcohols are due to difficulties of mixture formation of suitable mixing ratio and attainment of required temperature of mixture for spontaneous ignition at the same time and place in a spray. Combustion rate and duration after ignition are affected with average mixing ratio of fuel sprays at the ignition timing.

Fuel Spray Motion in Air Flow.

In direct injection diesel engines the intense swirling air motion in the cylinder is useful for a higher air fuel mixing rate. Therefore, we have investigated fuel spray motion in air flow with a uniform velocity distribution in order to explain the effect of the air swirl on the fuel spray motion in the cylinders of direct injection diesel engines, and concluded that the spray movement affected by the lateral air motion is controlled by the momentum of the fuel injection, the momentum of the air motion, the effective diameter of the fuel injection nozzle and factors of air entrainment. Then, the equation of the fuel spray motion locus in lateral air flow is obtained.

Prediction of cavitation erosion in diesel engine fuel injection systems

A new system developed by the authors to predict the cavitation erosion of the fuel injection system utilizes ultrasonic wave issued by collapse of cavities in the system. This prediction system can replace the conventional time-consuming endurance test and thus greatly contributes to the saving of cost and time. The technical features of this system include: (1) Detection of ultrasonic wave through the fuel injection pipe wall using a piezoelectric sensor, with the ultrasonic wave signal intensity in a higher frequency range increasing with the cavitation intensity, i.e., the level of energy released by the collapse of cavities; (2) the system output representing effective cavitation intensity which is given after being processed from the raw state in a high pass filter; and (3) capability of dealing with a higher level of accuracy than by the conventional method.