Lean-burn hydrogen spark-ignited engines: The mechanical equivalent to the fuel cell
- Lawrence Livermore National Lab., CA (United States)
Hydrogen-fueled, spark-ignited, homogeneous- charge engines offer a near-term alternative to fuel cells. Hydrogen in a spark-ignited engine can be burned at very low equivalence ratios, so that NO{sub x} emissions can be reduced to less than 10 ppm without catalyst. HC and CO emissions may result from oxidation of engine oil, but by proper design are negligible (a few ppm). Lean operation also results in increased indicated efficiency due to the thermodynamic properties of the gaseous mixture contained in the cylinder. The high effective octane number of hydrogen allows the use of a high compression ratio, further increasing engine efficiency. In this paper, a simplified engine model is used for predicting hydrogen engine efficiency and emissions. The model uses basic thermodynamic equations for the compression and expansion processes, along with an empirical correlation for heat transfer, to predict engine indicated efficiency. A friction correlation and a supercharger/turbocharger model are then used to calculate brake thermal efficiency. The model is validated with many experimental points obtained in a recent evaluation of a hydrogen research engine. The results present information that can be used to predict engine performance for vehicular applications, and are expected to serve as a first-order guide for engine sizing (number of cylinders) and control strategy selection. The results indicate that hydrogen lean-burn spark-ignited engines can provide Equivalent Zero Emission Vehicle (EZEV) levels in either a series hybrid or a conventional automobile.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 541036
- Report Number(s):
- CONF-9610275--; ISBN 0-7918-1516-1
- Country of Publication:
- United States
- Language:
- English
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