Brake Specific Energy Consumption (BSEC) and Emission Characteristics of the Direct Injection Spark Ignition Engine Fuelled by Hydrogen Enriched Compressed Natural Gas at Various Air-Fuel Ratios

摘要

Research on improving fuel consumption and emission characteristics of the internal combustion engine (ICE) become necessary as a result of increases conventional fuel energy prices couple with environmental protection and depletion. Hydrogen enriched compressed natural gas (CNG-H_2) is the best alternative fuel to be utilized in ICE. In view of the aforementioned problem caused by conventional fuel, hydrogen enriched compressed natural gas (CNG-H_2) might have the potential to achieve good fuel consumption and low engine emission. Thus, the primary aim of this research is to experimentally study the brake specific energy consumption (BSEC) and exhaust emission characteristics of the direct injection spark ignition engine fuelled by a mixture of hydrogen gas and compressed natural gas. The experiment was carried out part-throttle, constant engine speed of 2000 rpm, various hydrogen gas (0, 20, 28, 38 and 46% by volume) and various air-fuel ratios (λ = 0.9, 1.0 and 1.2 which represent rich, stoichiometric, and lean mixtures respectively). The results showed that increasing the relative percentage hydrogen gas increases the BSEC. More so, BSEC of about 42% increment at lean mixture (λ = 1.2) was observed in comparison with stoichiometric mixture (λ = 1.0). While the emission concentrations of BSCO and BSUHC, decreased with increasing percentage of hydrogen gas. Their emission shows a reduction of approximately 94% and 26% when comparing between rich and stoichiometric mixture respectively. In addition, BSNOx emission concentrations increases as the percentage hydrogen gas increases due to the fact that hydrogen fraction increase the turbulence within the engine cylinder. Thus, it can be concluded that CNG-H_2 is a very good alternative fuel technique to achieve significant reduction in basic pollutant emissions associated with DI-HCNG engine such as BSCO and BSUHC emissions.