Search Results

Particulate matter (PM) emission of non-road diesel engines is more and more stringently restricted by US, EU, Japan, etc. In order to achieve these emission regulations, diesel particulate filter (DPF) system is applied. However DPF system requires extra fuel consumption in order to burn accumulated particles. Furthermore, since it is difficult to install large DPF systems in limited packaging space of non-road applications, compact DPF system is desirable. Reducing soot emission with engine technology is effective for reducing PM emission, which results in reducing extra fuel consumption and downsizing or removing of DPF system. Soot emission level mainly depends on excess air ratio (EAR), and can be reduced by keeping EAR high (lean combustion). However, lean combustion under the limited amount of air and maximum in-cylinder pressure requires decrease in fuel injection quantity, and yields decrease in engine power.

The chemical composition of marketed gasoline varies depending on the crude oil, refinery processes of oil refineries, and season. The combustion characteristics of HCCI engines are very sensitive to the fuel composition, and a fuel standard for HCCI is needed for HCCI vehicles to be commercially viable. In this paper, the effects of the structure of the fuel components on auto-ignition characteristics and HCCI engine performance were investigated. The engine employed in the experiments is a research, single cylinder HCCI engine with a compression ratio of 14.7. The intake manifold was equipped with a heater attachment allowing control of the intake air temperature up to 150 °C at 2000 rpm. Thirteen kinds of hydrocarbons, 4 kinds of paraffins, 3kinds of naphthenes, and 6 kinds of aromatics, were chosen for the investigation, and 20vol% of each of the pure hydrocarbons was blended with the 80 vol% of PFR50 fuel.

Reductions in combustion noise are necessary in high load diesel engine operation and multiple fuel injections can achieve this with the resulting reductions in the maximum rate of pressure rise. In 2014, Dr. Fuyuto reported the phenomenon that the combustion noise produced in the first combustion can be reduced by the combustion noise of the second fuel injection, and this has been named “Noise Cancelling Spike Combustion (NCS combustion)”. To investigate more details of NCS combustion, the effects of timings and heating values of the first and second heat releases on the reduction of overall combustion noise are investigated in this paper. The engine employed in the research here is a supercharged, single cylinder DI diesel engine with a high pressure common rail fuel injection system.

This research investigates the influences of the injection timing, injection pressure, and compression ratio on the combustion and exhaust emissions in a single cylinder 1.0 L DI diesel engine operating with ultra-high EGR. Longer ignition delays due to either advancing or retarding the injection timing reduced the smoke emissions, but advancing the injection timing has the advantages of maintaining the thermal efficiency and preventing misfiring. Smokeless combustion is realized with an intake oxygen content of only 9-10% regardless of the injection pressure. Reduction in the compression ratio is effective to reduce the in-cylinder temperature and increase the ignition delay as well as to expand the smokeless combustion range in terms of EGR and IMEP. However, the thermal efficiency deteriorates with excessively low compression ratios.

To execute the computational fluid dynamics coupling with fuel chemistry in internal combustion engines, simplified chemical kinetic models which capture the low-temperature oxidation kinetics would be required. A steady-state analysis was applied to see the complicated reaction mechanism of alkylperoxy radicals by assuming the steady state for hydroperoxyalkyl (QOOH) and hydroperoxyalkylperoxy (OOQOOH) radicals. This analysis clearly shows the systematic trend of the reaction rate for the chain-branching and non-branching process of alkylperoxy (ROO) radicals as a function of the chain length and the carbon class. These trends make it possible to classify alkylperoxy radicals by their chemical structures, and suggest a reduced low-temperature oxidation chemistry.

In a DI diesel engine, THC emissions increase significantly with lower compression ratios, a low coolant temperature, or during the transient state. During the transient after a load increase, THC emissions are increased significantly to very high concentrations from just after the start of the load increase until around the 10th cycle, then rapidly decreased until the 20th cycle, before gradually decreasing to a steady state value after 1000 cycles. In the fully-warmed steady state operation with a compression ratio of 16 and diesel fuel, THC is reasonably low, but THC increases with lower coolant temperatures or during the transient period just after increasing the load. This THC increase is due to the formation of over-lean mixture with the longer ignition delay and also due to the fuel adhering to the combustion chamber walls. A low distillation temperature fuel such as normal heptane can eliminate the THC increase.