Addition of hydrogen to gasoline can dramatically improve efficiency and emissions of homogeneous charge, spark ignition engines. Reforming is the way to obtain hydrogen on board the vehicle, directly from gasoline. Gas containing hydrogen, carbon monoxide and nitrogen would be obtained through partial oxidation of a rich gasoline/air mixture. In this article, the effect of some different kinds of reformer gas upon emissions, efficiency and combustion process is shown and the importance of the relative amounts of active and inert species is analysed. Reformer technology is currently being developed mainly for fuel cell applications. There, CO presence is highly undesirable. Analysing the effect of gas composition on combustion is important to decide whether the same reforming technology as in fuel cells applications can be used in engine applications or ad-hoc reformers need to be developed. At first, the general behaviour of the engine when fuelled with various gasoline-reformer gas mixtures at low load is investigated. Engine stability, pollutant emissions and engine efficiency are shown. Under these conditions engine-out emissions are dramatically reduced to near-zero levels, which could be easily brought down to zero by means of a simplified catalyst. The efficiency gain measured in the engine seems to be enough to compensate or even overcome the energy losses occurring in the reforming process. On the fundamentals side, in-cylinder investigation techniques were used to gain in-depth understanding of the combustion process. These include cylinder pressure indication, ion sensors and optical fibres. In this way heat release, flame propagation and flame speed have been studied. The presence of CO in the reformer gas is shown to be beneficial to the combustion process, unless very high fractions of hydrogen can be achieved in the reforming process. For internal combustion engine applications, it seems more meaningful to limit the degree of partial oxidation (thus the energy losses in the reformer) and leave a substantial fraction of CO in the reformer gas.
Combustion of reformer gas/gasoline mixtures in spark ignition engines: Effect of the reformer gas composition upon emissions, efficiency and combustion process
Verbrennung von Synthesegas/Benzin-Mischungen in Verbrennungsmotoren: Einfluss der Reformergas-Zusammensetzung auf Emissionen, Wirkungsgrad und Verbrennungsprozess
2006
12 Seiten, 10 Bilder, 2 Tabellen, 22 Quellen
Aufsatz (Konferenz)
Englisch
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