Various effects of reformer gas enrichment on natural-gas, iso-octane and normal-heptane HCCI combustion using artificial inert species method

Various effects of reformer gas enrichment on natural-gas, iso-octane and normal-heptane HCCI combustion using artificial inert species method

Natural gas

Methane

Combustion

Mixtures

Synthesis gas

Specific heat

Internal combustion engines

Polyols

Heptane

Reformer gas (syngas) addition to main fuel is a practical solution for combustion timing control in HCCI engines. This study emphasizes the understanding of various effects of reformer gas (RG) addition, with composition of 75%vol H2 and 25%vol CO, in HCCI combustion by developing an artificial inert species method and using a detailed chemical kinetics multi-zone model. Three fuels (iso-octane, n-heptane, and natural gas) with different autoignition characteristics were used in this study. The developed multi-zone model was validated for mentioned fuels at various percentages of RG using six experimental cases of a single-cylinder CFR engine. The results showed that increasing reformer gas fraction in the fuel mixture advanced methane fuel combustion timing, retarded the combustion of n-heptane and had insignificant effect on iso-octane combustion. Thermal effect of RG in all fuels resulted in earlier start of combustion (SOC) because of the mixture specific heat ratio enhancement. The SOC for methane and iso-octane fuels was advanced by RG addition due to the chemical effect of RG. However, the chemical effect of RG for methane fuel is more significant. By adding 30% RG to methane fuel, H2 advanced the SOC by 5.6 CA and CO retarded it by 1.4 CA due to chemical effect and also the interaction effect of CO and H2 advanced the SOC by 1.8 CA. For iso-octane fuel, adding 30% RG, both CO and H2 advanced the SOC by 0.4 CA due to their chemical effect. On the other hand, in n-heptane fuel, H2 is almost responsible for all of the chemical effects of RG for retardation of SOC. 2017 Elsevier Ltd

7-19

159

Energy Conversion and Management

2018

Reyhanian, Masoud

Hosseini, Vahid

journalArticle

1968904

10.1016/j.enconman.2017.12.074