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An experimental investigation was carried out to assess the effect on engine operation of the addition of 20% hydrogen by volume to natural gas. Blends of hydrogen and natural gas are referred to as hythane in this report. Three groups of testing were conducted. All the tests were conducted at light loads similar to those in urban driving. The first group of tests were conducted using a 2.0 liter Nissan four cylinder engine to measure the increase in flame front propagation rate when fueled with hythane as compared to pure methane (simulating natural gas). The second group of tests were conducted with a 1.6 liter Toyota four cylinder engine to measure the changes in emissions and thermal efficiency comparing hythane operation to pure methane operation.

An experimental screening of non-nitrogen containing ignition improvers was conducted to investigate the possible use of diesel/alcohol fuel blends in an unmodified CI engine. The five non-nitrogen containing ignition improvers were: Di-Tertiary Butyl Peroxide; O,O-t-Amyl-O (2-Ethyl hexyl) monoperoxycarbonate; 1,1 Bis-(t-butylperoxy)-3,3,5-trimethylcyclohexane; Tertiary Butyl Hydroperoxide; and t-Amyl Perbenzoate. Alcohol content tested ranged from 10% to 100% by volume. For diesel/alcohol fuel blends containing more than 10% alcohol, BTEs similar to pure diesel could only be achieved with the addition of an ignition improver additive. Since diesel/alcohol blends separate with water addition, additives to improve water addition phase stability were also investigated. The blend employing the preferred ignition improver additive was found to have a greater ability to stay in solution than a control diesel blend without the additive.

Present research efforts are pursuing the development of complex fuel delivery systems in an effort to successfully incorporate existing combustion chambers and coolant systems designed for hydrocarbon fuels into a hydrogen-fueled engine design. This paper presents the hypothesis that fundamental redesign of the combustion chamber shape and coolant passages can solve the hydrogen engine design problems more economically than redesign of the fuel delivery system. The differences in knock with hydrogen fuel and with hydrocarbon fuel are discussed. It is concluded that the combustion chamber shapes designed to reduce knock with hydrocarbon fuel actually promote knock with hydrogen fuel.