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Through an addition of a small amount of hydrogen to the main fuel, combustion process can be considerably enhanced in internal combustion engines producing significantly lower levels of exhaust emissions. This improvement in combustion can be mainly attributed to the faster and cleaner burning characteristics of hydrogen in comparison to conventional liquid and gaseous fuels. An oxygen-enrichment of a fuel-air mixture also improves thermal efficiency and reduces especially particulate, carbon monoxide and unburned hydrocarbon emissions in exhaust. This contribution describes the results of experimental investigation where a small amount of hydrogen and oxygen is produced by Hydrogen Generating System through the electrical dissociation of water and are added to the intake of a compression ignition engine operating on a commercial diesel fuel. It is shown that level of exhaust emissions including NOx can be moderately reduced using such a pre-treatment method in diesel engines.

One of the main features of methane fueled spark ignition engines is their relatively slow flame propagation rates in comparison to liquid fuel applications which may lead to relatively lower power output and efficiency with increased emissions and cyclic variations. This is especially pronounced at operational equivalence ratios that are much leaner than the stoichiometric value. The addition of some hydrogen and oxygen to the methane may contribute towards speeding the combustion process and bring about significant improvements in performance and emissions. It has been suggested that the addition to the methane of products of water electrolysis generated in situ on board of a vehicle may produce such improvements.

There are distinct operational mixture limits beyond which satisfactory spark ignition engine performance can not be maintained. The values of these limit mixtures which depend on the mode of their determination, are affected by numerous operational and design factors that include the type of engine and fuel used. Simple approximate methods are presented for predicting these limits. Good agreement is shown to exist between the calculated and the corresponding experimental values over a range of operating conditions while operating on the gaseous fuels: methane, propane and hydrogen. The experimentally observed operational limits deviate very substantially from the corresponding accepted flammability limit values for quiescent conditions evaluated at the average temperature and pressure prevailing at the instant of the spark passage.

Ever increasing price of the fossil fuels, and fast depletion of the petroleum reserves world wide, have greatly encouraged the utilization of the alternative and renewable fuels for the production of electricity and motive power. Among the alternative renewable fuels, landfill gases which were produced by the anaerobic decomposition of organic waste in the landfills and solid waste dump sites were underutilized and overlooked in the past. Lately, there has been an increased interest in this research as the utilization of the landfill gas would provide energy independence, generate revenue and create environmental benefits. They are used both in the internal combustion engines and gas turbines for energy production needs. However because of the low heating value (Btu) content in the landfill gases, competitive energy market and other issues, they were not considered for the energy production in the past in most of the cases.

The current rapidly growing interests on utilization of various alternative fuels, including low heating value fuels such as land filled gases and biogases, are prompted due to the energy security concerns and the environmental advantages. It is nevertheless augmented due to the recent high price of the conventional petroleum based fuels. Generally, the low heating value (Btu) fuels contain substantial amounts of the diluents such as carbon dioxide, nitrogen, water vapor and other trace gases in the fuel composition. This paper describes the results of the investigation of knock in a single cylinder variable compression ratio spark ignition engine fueled with gaseous fuels such as natural gas, methane and hydrogen in the presence of different amounts of diluents specifically carbon dioxide in the fuel mixture in order to represent closely the general composition of land filled and biogases in practice.