Combustion in a heavy-duty direct-injection engine using hydrogen–methane blend fuels

Adding hydrogen to the fuel in a direct injection natural gas engine offers the potential significantly to reduce local and global air pollutant emissions. This work reports on the effects of fuelling a heavy-duty engine with late-cycle direct injection of blended hydrogen– methane fuels and diesel pilot ignition over a range of engine operating conditions. The effect of hydrogen on the combustion event varies with operating condition, providing insight into the fundamental factors limiting the combustion process. Combustion stability is enhanced at all conditions studied; this leads directly to a significant reduction in emissions of combustion byproducts, including carbon monoxide, particulate matter, and unburned fuel. Carbon dioxide emissions are also significantly reduced by the lower carbon–energy ratio of the fuel. The results suggest that this technique can significantly reduce both local and global pollutant emissions associated with heavy-duty transport applications while requiring minimal changes to the fuelling system

Hydrogen-methane blend fuelling of a heavy-duty, direct-injection engine

Combining hydrogen with natural gas as a fuel for internal combustion engines provides an early opportunity to introduce hydrogen into transportation applications. This study investigates the effects of fuelling a heavy-duty engine with a mixture of hydrogen and natural gas injected directly into the combustion chamber. The combustion system, developed for natural gas fuelling, is not modified for blended hydrogen operation. The results demonstrate that hydrogen can have a significant beneficial effect in reducing emissions without affecting efficiency or requiring significant engine modifications. Combustion stability is enhanced through the higher reactivity of the hydrogen, resulting in reduced emissions of unburned methane. The fuel’s lower carbon:energy ratio also reduces CO2 emissions. These results combine to significantly reduce tailpipe greenhouse gas (GHG) emissions. However, the effect on net GHG’s, including both tailpipe and fuelproduction emissions, depends on the source of the hydrogen. Cleaner sources, such as electrolysis based on renewables and hydro-electric power, generate a significant net reduction in GHG emissions. Hydrogen generated by steam-methane reforming is essentially GHG neutral, while electrolysis using electricity from fossil-fuel power plants significantly increases net GHG emissions compared to conventional natural gas fuelling

The influence of fuel composition on a heavy-duty, natural-gas direct-injection engine

This work investigates the implications of natural gas composition on the combustion in a heavy-duty natural gas engine and on the associated pollutant emissions. In this engine system, natural gas is injected into the combustion chamber shortly before the end of the compression stroke; a diesel pilot that precedes the natural gas injection provides the ignition source. The effects of adding ethane, propane, hydrogen, and nitrogen to the fuel are reported here. The results indicate that these additives had no significant effect on the engine’s power or fuel consumption. Emissions of unburned fuel are reduced for all additives through either enhanced ignition or combustion processes. Black carbon particulate matter emissions are increased by ethane and propane, but are virtually eliminated by including nitrogen or hydrogen in the fuel

The effects of fuel dilution in a natural-gas direct-injection engine

This study reports the effects of fuelling a heavy-duty single-cylinder research engine with pilot-ignited late-cycle direct-injected natural gas diluted with 0, 20, and 40 per cent nitrogen. The combustion duration is unaffected while its intensity is reduced and its stability is increased. Emissions of nitrogen oxides, particulate matter, hydrocarbons, and carbon monoxide are all reduced, with no effect on the engine’s performance and efficiency. The results indicate the benefits of increased in-cylinder turbulence and are of particular relevance when considering fuel composition variations with non-conventional sources of gaseous fuels