Use of catalytic reforming to aid natural gas HCCI combustion in engines: experimental and modelling results of open-loop fuel reforming

Methane reforming is achieved here by reaction with engine exhaust gas and air in a small scale monolith catalytic reactor. The benchmark quantity of H2 required to enhance the feasibility and engine load range of HCCI combustion is 10%. For low temperature engine exhaust gas, typical for HCCI engine operating conditions, experiments show that additional air is needed to produce this quantity. Experimental results from an open-loop fuel exhaust gas reforming system are compared with two different models of basic thermodynamic equilibria calculations. At the low reactor inlet temperatures needed for the HCCI application (approx. 400∘C) the simplified three-reaction thermodynamic equilibrium model is in broad agreement with experimental results, while for medium (550-650∘C) inlet temperature reforming with extra air added, the high hydrogen yields predicted from the multi-component equilibrium model are difficult to achieve in a practical reformer.