The hydrogen internal combustion engine offers the opportunity to achieve similar performance and comfort characteristics as a conventional gasoline fuelled engine. In order to improve power density and vehicle range new ways in engine design and in charging hydrogen engines were investigated. The engine used for the discussed test series was a specially designed single-cylinder engine with external and internal mixture formation and a flexible charging system allowing to simulate different charging methods. Thermodynamic analysis as well as CFD-simulation were used to optimise engine design and operation strategy. Engine operation at high loads was investigated and operation strategies were developed for low fuel consumption and extremely low NOx emissions. At full load operation, engine loads over 18 bar indicated mean effective pressure were achieved. The hydrogen combustion at stoichiometric mixtures has a lower thermodynamic efficiency compared to gasoline combustion. This is due to the higher flame temperatures (about 3000 deg K) resulting in increased wall-heat losses and exhaust temperatures. For part load, the hydrogen engine has a significant higher efficiency compared to current technology gasoline and diesel engines. The high thermodynamic efficiency results from the very lean fuel-air mixture (lambda = 4). Although the thermodynamic efficiency of the hydrogen engine is below the one of a diesel engine, the hydrogen engine has a higher indicated efficiency. The main reasons are the higher burning velocity resulting in lower losses due to non-ideal combustion process and significantly lower gas exchange losses due to unthrottled operation. Compared to a gasoline engine, the indicated efficiency of the hydrogen engine is approx. 8 % higher, which results in a better fuel consumption of 25 %. In conclusion, the hydrogen powered internal combustion engine allows power density and power output on the same level of current gasoline engines. At the same time at low to medium-high loads fuel efficiency is above current Diesel engines. This is possible in combination with virtually no pollutant emissions. The key is the capability to burn stoichiometric mixtures (for power density and NOx reduction in a catalyst at high load) and unthrottled operation over nearly the complete operating range (for fuel efficiency). This has been achieved with currently available technology. The IC-engine is still undergoing rapid development and future advances in IC-engine technology will certainly lead to further improvements also for hydrogen applications.
Potentials of a charged SI-hydrogen engine
2003
9 Seiten, 17 Bilder, 11 Quellen
Conference paper
English
Potentials of a charged SI-hydrogen engine
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