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This study investigated effects of gas inhomogeneity induced by droplets of fuels and oils on the auto ignition timing and temperature in the direct-injection spark ignition (DISI) engine by means of detailed numerical calculation using multi zone model. Recent researchers pointed out that droplets are made of fuels and oils which mix on the cylinder liner and released from the cylinder liner [1]. During the compression stroke released droplets reach the auto ignition temperature before flame propagation induced by spark ignition. It is called Pre-ignition. In combustion chamber, there is inhomogeneity caused by temperature and mixture distribution. In this study, the effects of gas inhomogeneity produced by droplet on the auto ignition timing and temperature have been investigated using Multi-Zone model of CHEMKIN-PRO by changing initial temperature and initial equivalence ratio. Especially, the volume of first ignition zone is focused on.

In practical lean burn engines used to date, the use of a stratified air-fuel configuration, with a comparatively rich mixture in the vicinity of the spark plugs, has resulted in the stable combustion of an overall lean mixture. However, because a comparatively rich mixture is burned during the first half of combustion, NOx emissions are not reduced sufficiently. This research focused on a form of lean burn with homogeneous premixture that would be able to balance low NOx emissions with combustion controllability. It is widely known that homogeneous lean premixed gas has poor flame propagation characteristics. To determine the dominant cause of this, this study investigated the combustion properties of a single-cylinder engine while changing the compression ratio and intake temperature. As a result, the primary cause of combustion fluctuation, the abnormal cycle has a low TDC temperature compared to that of other cycles.

This study examined a high-speed, high-powered diesel engine featuring a pent-roof combustion chamber and straight ports, with the objective of improving the specific power of the engine while minimizing any increase in the maximum cylinder pressure (Pmax). The market and contemporary society expect improvements in the driving performance of diesel-powered automobiles, and increased specific power so that engine displacement can be reduced, which will lessen CO2 emissions. When specific power is increased through conventional methods accompanied with a considerable increase in Pmax, the engine weight is increased and friction worsens. Therefore, the authors examined new technologies that would allow to minimize any increase in Pmax by raising the rated speed from the 4000 rpm of the baseline engine to 5000 rpm, while maintaining the BMEP of the baseline engine.

Alternative combustion crossing stoichiometric air fuel ratio was investigated to utilize a 4-way catalyst system with LNT (lean NOx trap). The chemical mechanism of restricting soot formation reactions with low combustion temperature was combined with the physical mechanism of reducing smoke by lowering local equivalence ratio to enable low smoke rich and near rich combustion. A new combustion chamber for spatially and timely mixture formation phasing was developed to combine the two mechanisms and allow smooth EGR changing over a wide load range. Through this investigation, rich and near rich combustion to effectively utilize a 4-way catalyst system was realized. In addition, conditions suitable for LNT sulfur regeneration were realized from light to medium load.

A new diesel engine system adopting alternative combustion with rich and near rich combustion, and an airflow-dominant control system for precise combustion control was used with a 4-way catalyst system with LNT (lean NOx trap) to achieve Tier II Bin 5 on a 2.2L TDI diesel engine. The study included catalyst temperature control, NOx regeneration, desulfation, and PM oxidation with and without post injection. Using a mass-produced lean burn gasoline LNT with 60,000 mile equivalent aging, compliance to Tier II Bin 5 emissions was confirmed for the US06 and FTP75 test cycles with low NVH, minor fuel penalty and smooth transient operation.

An airflow-dominant control system was developed to provide precise engine and exhaust treatment control with low air fuel ratio alternative combustion. The main elements of the control logic include a real-time state observer for in-cylinder oxygen mass estimation, a simplified packaging scheme for all air-handling and fueling parameters, a finite state machine for control mode switching, combustion control models to maintain robust alternative combustion during transients, and smooth rich/lean switching during lean NOx trap (LNT) regeneration without post injection. The control logic was evaluated on a passenger car equipped with a 4-way catalyst system with LNT and was instrumental in achieving US Tier II Bin 5 emission targets with good drivability and low NVH.

In order to further reduce exhaust gas emissions, an investigation was carried out with premixed charge compression ignition (PCCI) combustion mode using conventional diesel fuel. Past research was carried out with early injection into shallow-dish piston bowl, combined with a narrow nozzle angle setting. Early injection significantly reduced NOX emissions, but some of the fuel spray adhered to the piston bowl surface creating a fuel wall-film which was a major cause in increasing soot, HC and CO emissions and fuel consumption [1]. As a possible solution to this issue, PCCI combustion mode operation on a direct injection diesel engine was investigated with fuel injection timing set close to top dead center (TDC). As a result, regardless of the fuel injection timing, increasing EGR reduced NOx emissions. In terms of fuel consumption, soot, HC and CO, however, fuel injection timing close to TDC was superior to earlier injection, due to the reduction in the fuel wall-film formation.

In order to further reduce exhaust gas emissions, an investigation was carried out concerning premixed charge compression ignition (PCCI) combustion, which is achieved by the early injection of conventional diesel fuel to the combustion chamber. The engine used for the experiments was a single cylinder version of a modern passenger car type common rail engine with a displacement of 550(cm3). An injector with a narrower corn angle was used to prevent interaction of the spray and the cylinder liner. Also, the compression ratio was decreased in order to avoid an excessively advanced ignition situation. Additionally, a large degree of cooled exhaust gas recirculation (EGR) was applied. These measures led to a significantly reduction in NOX emissions. However, a fuel wall-film, which was formed on the surface of the piston bowl wall, caused increases in soot, HC and CO emissions.

It is a generally accepted fact that the advantage of diesel engines over their gasoline-powered counterparts is superior fuel consumption. However, attempts to use diesel engines as car powerplants have been hampered by the associated increase in toxic emissions. Research was carried out with the objectives of achieving the lowest fuel consumption for a diesel-powered passenger vehicle in the 1,590kg equivalent inertia weight class while also meeting the 2005 European diesel exhaust emissions standards (EURO IV). This paper starts with a description of the experiments on combustion and the results of the simulations and experiments using a visualization apparatus, followed by a description of the fuel consumption, emissions and power performance of the engine when fitted in an actual vehicle. To begin with, the relationship between engine displacement and fuel consumption was investigated.

To enable non-throttling operation of gasoline S.I. engine, we have manufactured engines equipped with a newly developed Hydraulic Variable-valve Train (HVT), which can vary its intake-valve closing-timing freely. The air-intake control ability of HVT engine is equivalent to conventional throttling engines. Combustion becomes unstable, however, under non-throttling operation at idling. For the countermeasure, newly designed combustion chamber has been developed. The reduction of pumping loss by the HVT depends on engine speed rather than load, and amounts to about 80 % maximum. A conventional engine-management system is not applicable for non-throttling operation. Therefore, new management system has been developed for load control.

For the prediction of frictional mean effective pressure (Pmf), the experimental data of over 300 engines, including super high speed engines whose maximum revolutional speeds were up to 16000 rpm, were analyzed. It was found that Pmf is nearly proportional to a non-dimensional number given by piston stroke (S), mean equivalent crank diameter (Dcm) and cylinder bore (B). Its proportional constant consists of an engine speed dependent term and a constant term. We focused on the influence of pumping loss on the first term and made a tribological study on the second term. As a result of this research, regardless of cylinder configuration or maximum engine speed, Pmf can be estimated at the stage of engine designing.

Many papers are written on the frictional loss of each component in an engine, such as piston, crankshaft or bearings, but few papers describe on the total engine friction in detail. In this paper, the total engine friction is analyzed using the engine friction data of 145 HONDA mass produced motorcycle in-line engines, including single-, 2- and 4-cylinder configurations measured by the motoring method. Consequently, it is shown that the total engine friction, that is the frictional mean effective pressure (Pmf), is mainly influenced by the following dimensions; cylinder bore, piston stroke, crank pin and journal diameters. Thus the empirical equation for the total engine friction is derived, and it becomes thereby possible to reduce the total engine friction as well as to estimate it.