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A series calculation methodology from the injector nozzle internal flow to the in-cylinder fuel spray and mixture formation in a diesel engine was developed. The present method was applied to a valve covered orifice (VCO) nozzle with the recent common rail injector system. The nozzle internal flow calculation using an Eulerian three-fluid model and a cavitation model was performed. The needle valve movement during the injection period was taken into account in this calculation. Inside the nozzle hole, cavitation appears at the nozzle hole inlet edge, and the cavitation region separates into two regions due to a secondary flow in the cross section, and it is distributed to the nozzle exit. Unsteady change of the secondary flow caused by needle movement affects the cavitation distribution in the nozzle hole, and the spread angle of the velocity vector at the nozzle exit.

To meet the future demands on internal combustion engines regarding efficiency emissions and durability all design parameters must be optimized together. As a result of progress in material engineering fuel injection technology turbo charging technology exhaust gas after treatment there arise a multiplicity of possible parameters, such as: design parameters (compression ratio, dimensioning depending on peak firing pressure and mean effective pressure), injection system (rate shaping, split injection, injection pressure, hole diameter), air management (turbo charging with or without VTG, EGR rate) combustion optimization (timing, air access ratio). The interaction of all these parameters can not be over-looked without simulation and optimization tools. This is valid for the concept layout, the optimization and the application process later on.

Phosphor thermometry was used during fuel injection in an optical engine with the glass piston of reentrant type. SiO2 coated phosphor particle was used for the gas-phase temperature measurements, which gave much less background signal. The measurements were performed in motored mode, in combustion mode with injection of n-heptane and in non-combustion mode with injection of iso-octane. In the beginning of injection period, the mean temperature of each injection cases was lower than that of the motored case, and temperature of iso-octane injection cases was even lower than that of n-heptane injection cases. This indicates, even if vaporization effect seemed to be the same at both injection cases, the effect of temperature decrease changed due to the chemical reaction effect for the n-heptane cases. Chemical reaction seems to be initiated outside of the fuel liquid spray and the position was moving towards the fuel rich area as the time proceeds.

Generally, soot emissions increase in diesel engines with smaller bore sizes due to larger spray impingement on the cavity wall at a constant specific output power. The objective of this study is to clarify the constraints for engine/nozzle specifications and injection conditions to achieve the same combustion characteristics (such as heat release rate and emissions) in diesel engines with different bore sizes. The first report applied the geometrical similarity concept to two engines with different bore sizes and similar piston cavity shapes. The smaller engine emitted more smoke because air entrainment decreases due to the narrower spray angle. A new spray design method called spray characteristics similarity was proposed to suppress soot emissions. However, a smaller nozzle diameter and a larger number of nozzle holes are required to maintain the same spray characteristics (such as specific air-entrainment and penetration) when the bore size decreases.

Over the last few years there has been much interest in DiMethyl Ether (DME) as an alternative fuel for diesel cycle engines. It combines the advantages of a high cetane number with soot free combustion, which makes it eminently suitable for compression ignition engines. However, due to the fact that it is a gas under ambient conditions, it requires special fuel handling and a specially designed fuel injection system, which until recently, was not available. The use of the digital hydraulic operating system (DHOS), combined with a fuel handling system designed to cope with the properties of DME, enables the fuel to be safely and conveniently handled, In addition, the flexibility of the injection system enables injection pressures to be chosen according to the needs of the combustion.

A detailed investigation of the influence of intake port design on the in-cylinder flow structure during the intake and compression strokes, the mixing of the residual gas and a non-premixed intake charge, and the extent and pattern of charge inhomogenity near the time of combustion is described. The engine geometry is typical of the current lean-burn design and the study includes comparison of a helical (swirl) port and an idealized direct (no swirl) port designs. The results show marked dependence of the in-cylinder charge mixing characteristics on the intake port design. It is found that combinations of intake port design and manifold fuel injection timing produce favourably-stratified or irregularly-mixed charge distributions at the time of spark ignition. The consequences with respect to combustion characteristics are pointed out.

Diesel emissions are significant issue worldwide, and emissions requirements have become so tough that. the application of after-treatment systems is now indispensable in many countries To meet even more stringent future emissions requirements, it has become apparent that the improvement of market fuel quality is essential as well as the development in engine and exhaust after-treatment technology. Japan Clean Air Program II (JCAP II) is being conducted to assess the direction of future technologies through the evaluation of current automobile and fuel technologies and consequently to realize near zero emissions and carbon dioxide (CO2) emission reduction. In this program, effects of fuel properties on the performance of diesel engines and a vehicle equipped with two types of diesel NOx emission after-treatment devices, a Urea-SCR system and a NOx storage reduction (NSR) catalyst system, were examined.

Alternative fuels, especially fuels based on biological matter, are gaining more and more attention. Not only as a pure substitute of oil but also in terms of a possibility for further reduction in emission and as an option to improve the global CO2 balance. For improving the engine performance (emissions, fuel consumption, torque and drivability) the adjustment of fuel injection, the fuel evaporation process and the combustion process itself is paramount. In order to exploit the full potential of alternative fuels excellent knowledge of the fuel properties, including the impact on ignition and flame propagation, is required. This needs suitable tools for analysis of the fuel injection and combustion process. These tools have to support the optimization of the combustion system and the dynamic engine calibration for lowest emissions and most efficient use of fuel. As the term “Alternative Fuels” covers a very wide area a brief overview on available fuel types will be made.

The subject of this paper is the discussion of a non-dimensional combustion model that relies on the concept of mixing controlled combustion (MCC Heat Release Rate) avoiding the detailed description of the individual mixture formation and fuel oxidation processes. For diffusion combustion in today's direct injection diesel engines it can be shown that the rate of heat release (ROHR) is controlled mainly by two items, i.e. the instantaneous fuel mass present in the cylinder charge and the local density of turbulent kinetic energy. Both items can be derived from the injection process, the instantaneous fuel mass being the difference of fuel injected minus fuel burnt and the turbulent kinetic energy being produced mainly by the momentum of the fuel sprays. Following this strategy, the injection process is now understood as the most important controlling factor for the heat release rate.

DiMethyl Ether (DME) has been shown to be a very attractive fuel for low emission direct injection compression ignition (DICI) engines. It combines the advantages of the high efficiencies of diesel cycle engines with soot free combustion. However, its greatest drawback is the need to develop new fuel injection and handling systems. Previous approaches have been common rail type injection systems which have shown great potential in reducing harmful exhaust emissions and achieving good engine performance and efficiency due to good control of both the fuel injection characteristics and temperature. The concept also has proven benefits with respect to convenient and safe fuel handling. The logical evolution of this concept simplifies the fuel system and avoids special components for DME handling such as high pressure rail pumps while retaining all the benefits of the common rail principle.

Single cylinder engine testing was carried out to clearly understand the test results of multi-cylinder engines reported by the Diesel WG in JCAP (Japan Clean Air Program) (1), (2), (3) and (4). In this tests, engine specifications such as fuel injection pressure, nozzle hole diameter, turbo-charging pressure, EGR rate, and fuel properties such as 1-, 2-, 3-ring aromatics content, n-,i-paraffins content, and T90 were parametrically changed and their influence on the emissions were studied. PM emission generally increased in each engine condition with increased aromatic contents and T90. In particular, multi ring aromatics brought about large increases in PM regardless of the engine conditions. The influence of fuel properties on NOx emission is smaller than the influence on PM emission. Some other fuels that have various side chain structures of 1-ring aromatics, normal paraffins only and various naphthene contents were also investigated.

Fuel injection is a key process influencing the performance of Gasoline Direct Injection (GDI) Engines. Injecting fuel at elevated temperature can initiate flash boiling which can lead to faster breakup, reduced penetration, and increased spray-cone angle. Thus, it impacts engine efficiency in terms of combustion quality, CO2, NOx and soot emission levels. This research deals with modelling of flash boiling processes occurring in gasoline fuel injectors. The flashing mass transfer rate is modelled by the advanced Hertz-Knudsen model considering the deviation from the thermodynamic-equilibrium conditions. The effect of nucleation-site density and its variation with degree of superheat is studied. The model is validated against benchmark test cases and a substantiated comparison with experiment is achieved.

A new clean diesel combustion concept has been proposed and its excellent performance with respect to gas emissions and fuel economy were demonstrated using a single cylinder diesel engine. It features the following three items: (1) low-penetrating and highly dispersed spray using a specially designed injector with very small and numerous orifices, (2) a lower compression ratio, and (3) drastically restricted in-cylinder flow by means of very low swirl ports and a lip-less shallow dish type piston cavity. Item (1) creates a more homogeneous air-fuel mixture with early fuel injection timings, while preventing wall wetting, i.e., impingement of the spray onto the wall. In other words, this spray is suitable for premixed charge compression ignition (PCCI) operation, and can decrease both nitrogen oxides (NOx) and soot considerably when the utilization range of PCCI is maximized.

A Large-Eddy-Simulation (LES) approach is applied to the calculation of multiple SI-engine cycles in order to study the causes of cycle-to-cycle combustion variations. The single-cylinder research engine adopted in the present study is equipped with direct fuel-injection and variable valve timing for both the intake and exhaust side. Operating conditions representing cases with considerably different scatter of the in-cylinder pressure traces are selected to investigate the causes of the cycle-to-cycle combustion variations. In the simulation the engine is represented by a coupled 1D/3D-CFD model, with the combustion chamber and the intake/exhaust ports modeled in 3D-CFD, and the intake/exhaust pipework set-up adopting a 1D-CFD approach. The adopted LES flow model is based upon the well-established Smagorinsky approach. Simulation of the fuel spray propagation process is based upon the discrete droplet model.

The worldwide trend to increasingly stringent exhaust emissions standards, together with consumer requirements, are forcing both vehicle and engine manufacturers, as well as manufacturers of ancilliary equipment, to introduce new and often novel technology in order to produce clean, quiet and socially acceptable transport at affordable prices. The combustion process lies at the heart of the engine and the quality of the combustion determines the acceptability of the product to a very large extent. The fuel injection system plays a large role in the combustion process and in consequence, the fuel system type and capabilities strongly influence the performance of the combustion system. There has never been such a range of fuel injection systems available at one time as there is today. High pressure hydraulically actuated systems /1/ compete with cam driven fuel injection systems /2/ to deliver the injection requirements demanded by the vehicles both of today and in the future.

Spark ignition direct injection (SIDI) engines have the potential to realize significant thermal efficiency improvements compared to conventional port fuel injection engines. The effects of fuel properties on efficiency and emissions have been investigated in a prototype of an Avensis Wagon equipped with a 2.0 liter, 4 cylinder spark ignition, direct injection (SIDI) engine designed to meet US 2000 emission standards. The vehicle employed a close coupled three-way catalyst and a NOx storage and reduction catalyst. Seven matrix fuels were blended to the same RON with varying levels of aromatics, olefins, ethanol, and volatility. Relative thermal efficiency, fuel economy, and tailpipe emissions were measured for the matrix fuels and a base fuel under the FTP LA4 driving cycle. The engine was operated in a lean burn mode in light load condition for approximately half of the driving cycle.

Nitric Oxide (NO) can significantly influence the autoignition reactivity and this can affect knock limits in conventional stoichiometric SI engines. Previous studies also revealed that the role of NO changes with fuel type. Fuels with high RON (Research Octane Number) and high Octane Sensitivity (S = RON - MON (Motor Octane Number)) exhibited monotonically retarding knock-limited combustion phasing (KL-CA50) with increasing NO. In contrast, for a high-RON, low-S fuel, the addition of NO initially resulted in a strongly retarded KL-CA50 but beyond the certain amount of NO, KL-CA50 advanced again. The current study focuses on same high-RON, low-S Alkylate fuel to better understand the mechanisms responsible for the reversal in the effect of NO on KL-CA50 beyond a certain amount of NO.

A new V-6 stoichiometric gasoline direct injection engine was developed for high performance FR (Front Engine Rear Drive) vehicles. High power performance, low fuel consumption and low exhaust emissions were achieved by employing a stoichiometric direct injection system that uses Toyota's unique slit nozzle injector that generates a fan-shaped fuel spray and variable intake and exhaust valve timing systems. Focusing on the power performance, maximum power of 183kW (61kW/L) is achieved at 6200rpm and maximum torque is 312Nm at 3600rpm. This power performance is among the top production 3.0 L gasoline engines in the world. This paper outlines the features of this engine and some special technologies contributing to the achievement of the above-mentioned high performance. Optimizing the intake-port design was done to improve power performance.

It is well known that pilot injection is an effective method of reducing diesel knock noise during idling, but no actual system has as yet been commercially produced. With the objective of developing a practicable pilot injection device, simulations were conducted of various simple mechanisms in order to determine the best specifications and analyze the fuel injection characteristics. Based on these results, a chamber expansion type pilot injection device, which enables the injection pump pressure chamber volume to be increased at a given moment during the fuel compression stroke, has been developed and has been found to remarkably decrease knock noise during cold idling. An investigation into the effects of this device on output power, exhaust emissions, cold startability and durability revealed that it is eminently suitable for practical application.

In order to optimize air-fuel mixture formation in a small DI diesel engine, studies were conducted into the effects of combustion chamber shape and fuel spray impingement. Based on the findings of these studies, the shape of the combustion chamber was modified to induce complex air motion with high turbulence and fuel injection was carefully controlled to achieve optimum impingement intensity. As a result, the mixture formation process was greatly improved with a consequent gain in terms of engine performance. To clarify the reasons for this improvement in combustion, a three-dimensional calculation of the in-cylinder air motion was made. The behaviour of the spray and flame was observed using an endoscope. The new combustion system, named TOYOTA Reflex Burn system (TRB) thus developed has been adopted in production engines since August 1988.