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As an efficient hydrogen carrier, ammonia itself is also a promising zero-carbon fuel that is drawing more and more attention. As the combustion of pure ammonia is hard to achieve on SI engines, in this study, spark- ignited micro-gasoline-jet was utilized to ignite the premixed ammonia/air mixture in a constant volume combustible vessel at different premixed ammonia/air excess air coefficient and backpressure (represented by ammonia partial pressure). The flame image was captured by a high-speed camera and the transient pressure change in the vessel was measured by an engine cylinder pressure sensor.

The first firing cycle is very important for cold-start. Misfire of the first firing cycle can lead to significant HC emissions and affect the subsequent cycles. The first firing cycle for Gasoline SI engine have been reported in many studies. Liquefied petroleum gas (LPG) as an alternative fuel has been widely used in commercial vehicles during the last decade. However, the properties of the first firing cycle for LPG SI engine have been seldom reported. This paper presents an investigation of the characteristics of transient HC emissions of the first firing cycle during cold start on a LPG SI engine. A fast-response flame ionization detector (FFID) was applied to measure transient HC emissions of the first firing cycle in the exhaust port of the engine. At the same time, the transient cylinder pressure and instantaneous crankshaft speed of the engine were measured and recorded.