Development status and insight on a “research level” piezoelectric direct injection fuel injection system for prototype hydrogen Internal Combustion Engines (ICEs) is described. Practical experience accumulated from specialized material testing, bench testing and engine operation have helped steer research efforts on the fuel injection system. Recent results from a single cylinder engine are also presented, including demonstration of 45% peak brake thermal efficiency.
Developing ICEs to utilize hydrogen can result in cost effective power plants that can potentially serve the needs of a long term hydrogen roadmap. Hydrogen direct injection provides many benefits including improved volumetric efficiency, robust combustion (avoidance of pre-ignition and backfire) and significant power density advantages relative to port-injected approaches with hydrogen ICEs. Early, mid or late-cycle direct injection timing approaches allow engine developers maximum flexibility to optimize power density, efficiency and emissions.
Specific hydrogen-related issues with injector sub-components and materials are discussed as well as ongoing research. As will be seen, hydrogen operation creates unique materials related challenges. The technical discussion looks at the effect of hydrogen's low mass / energy density, high sonic velocity and low viscosity. These physical attributes directly affect component size, material choice and tribology.