Experimental and modeling study of hydrogen/syngas production and particulate emissions from a natural gas-fueled partial oxidation engine

In this study, a combustion model was first applied to conditions representing varying compression ratios and equivalence ratios to investigate engine exhaust composition from partial oxidation (POX) of natural gas in reciprocating engines. The model was experimentally validated over a range of equivalence ratios from 1.3 to 1.6 with a spark-ignited single cylinder engine fueled by natural gas. The modeling results matched well with engine gaseous emission data over the experimental range. The model was also extended to higher equivalence ratios to predict H2H2 and CO production at engine conditions and stoichiometries representative of homogeneous charge compression ignition (HCCI) engine operation. Secondly, over the same experimental range of equivalence ratios, particulate samples were taken to determine both total particulate mass production (g/hp h) via gravimetric measurement as well as particle size distribution and loading via a scanning mobility particle sizer (SMPS). While experiments indicate hydrogen yields up to 11% using spark ignition (SI), modeling results indicate that greater than 20% H2H2 yield may be possible in HCCI operation. Over the experimental range, rich-burn particulate matter (PM) production is no greater than that from typical lean-burn operation. Finally, an energy balance was performed over the range of engine experimental operation.