An experimental study was undertaken to investigate the possibility of reducing diesel particulates in the exhaust by aspirating small quantities of gaseous hydrogen in the intake of a diesel engine. A single cylinder, direct injection type diesel engine was used in the experiments. Hydrogen flow rates equivalent to about 10% of the total energy substantially reduced smoke emissions at part loads. At the full rated load, reduction in smoke levels was limited; this is believed to be due to the lower amounts of excess air available in the cylinder. It was found that the engine thermal efficiency was dependent on the portion of hydrogen energy, out of the total input energy, supplied to the engine. There was no significant change in the hydrocarbon emissions but oxides of nitrogen in the exhaust increased with an increase in hydrogen energy. A/F EitOpeak NOMENCLATURE air-fuel ratio (kg/kg) rate of hydrogen energy supply (KJ/s) rate to total energy supply (KJ/s) angle when peak pressure occurs (deg) fuel air equivalence ratio (q~ < 1 is lean)

AbstraetmA high-pressure hydrogen injector was designed and developed in the laboratory. The injector was hydraulically operated by a separate pump. Measurement of injection characteristics on a bench stand showed very repetitive performance of the injector. The injection system was used to supply hydrogen fuel to a singlecylinder spark ignition engine. Results of the tests showed that the engine performance was superior to that achieved with carbureted gasoline fuel. BMEPMBT P NOMENCLATURE brake mean effective pressure, kPa min. spark advance in crank degrees for best torque maximum difference in peak cylinder pressure, kPa average peak cylinder pressure, kPa