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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.

The objective of the project reflected in this summary paper is to document an experimental design data-base on hydrogen-fueled automotive engines. The effort, sponsored by the U.S. Department of Energy, is directed toward possible future designs of airbreathing piston engines using hydrogen. To this end, pertinent performance and emissions (NOx only) characteristics of 16 engine configurations are presented graphically. Configurational variations of a 1600 cc automotive test engine included: throttled and unthrottled operation (i.e., quantity and quality power level control); central manifold, port, direct cylinder injection [not included]; single and divided combustion chambers; exhaust gas recirculation (EGR), water induction and air injection; and certain other features.

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.

The following report covers the design, and testing of a dedicated hydrogen-fueled engine. Subsequent modifications to the design are also covered. Both part-load and full-load data were taken under laboratory conditions. The engine design included a billet aluminum single combustion chamber cylinder-head with one intake valve, two sodium cooled exhaust valves, and two spark plugs. The cylinder-head design also included drilled cooling passages. The fuel-delivery system initially employed two modified Siemens electrically actuated fuel injectors. Subsequent modifications allowed operation with a premixed hydrogen-air mixture. The exhaust system included two separate headers, one for each exhaust port. The piston/ring combination was designed specifically for hydrogen operation.