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The latest frequency-conversion system, as typified by inverter power generator, is capable of providing superb fuel economy and NVH characteristics by means of real-time control of the engine speed according to its load condition. The current mechanical governor, however, can difficultly achieve that demand of performance. In order to meet these requirements, we have developed the electronic governor system having high control flexibility and response for small diesel engines for agricultural and industrial use. In developing this electronic governor system, we have adopted a method that can minimize modification of current engines. We have successfully developed the electronic governor system by means of a post-assembly installation, in which dedicated functional devices are installed to complete engine while keeping intact the current highly reliable PFR type fuel-injection pump and the mechanical governor.

Optimization of geometric and operating parameters controlling the fuel injection rate of in-line pump-based fuel injection system for small-sized industrial DI diesel engines can be obtained using computer models simulating simultaneously the flow inside the fuel injection system and the subsequent spray development. Empirical sub-models accounting for the effect of injection hole cavitation both on hole exit velocity and on the atomization of the injected liquid have been included in order to enhance model predictions. Validation of the FIE model s performed by comparing model predictions against experimental data for the pumping chamber pressure, delivery valve lift, line pressure, needle lift and injection rate for various pump designs and for a wide range of pump operating conditions. The results confirm that the FIE simulation model is capable of predicting the flow characteristics inside the fuel injection system for all cases investigated.

It is well known that a high-pressure fuel injection is effective for the reduction in particulates and smoke emissions. Exhaust gas recirculation (EGR) is effective for the reduction in NOX emission. In this study an experiment aiming to understand more comprehensive combustion under the condition of EGR and high-pressure fuel injection was carried out by using gas sampling method for the purpose of understanding what occurred inside the spray before and after combustion. The number of combustion cycles in this engine can be controlled in order to change EGR conditions by adjusting the residual gas concentration in the cylinder. Main results were: (1) Close to the nozzle tip, the sampling gas data showed little reaction which implies that combustion never occurs in this area during the injection period. (2) In the case of high-pressure fuel injection O2 concentration decreased faster and air dilution was more active and earlier.

Ammonia is one of the most useful compounds that react with NOx selectively on a catalyst, such as V2O5-TiO2, under oxygen containing exhaust gas. However ammonia cannot be stored because of its toxicity for the small power generator in populated areas or for the diesel vehicles. A new concept for NOx reduction in diesel engine using ammonia is introduced. This system is constructed from the hydrogen generator by fuel reformer, the ammonia synthesizer, SCR catalyst for NOx reduction and the gas injection system of reformed gas into the cylinder. Experimental results show that, the SCR catalyst provides a very high rate of NOx reduction, reformed gas injection into cylinder is very effective for particulate reduction. WHEN CONSIDERING INTERNAL COMBUSTION ENGINES of the 1990's the question of how to harmonize the engine with the natural environments is one of the greatest problems. The internal combustion engine changes a substance into energy via its explosive combustion.

Two dimensional flame temperature distributions in D.I. diesel engine with high pressure fuel injection were measured by the image analysis of high speed photographs based on two color method. Effects of injection pressure and nozzle hole diameter on flame temperature distribution were examined. The flame temperature in the case of high pressure injection is higher than that in low injection pressure. The higher flame temperature in high pressure injection results from the rapid compression of burned gases. The KL value which is an index of soot density in the combustion chamber decreases as injection pressure increases. The higher oxidation rate of soot at the later period of combustion may contribute to a soot reduction in the case of high pressure injection.

To clarify the detailed structure of high pressure fuel spray, 2-D sectional images of non-evaporating fuel sprays in a high pressure vessel were observed by using the laser light sheet of a copper vapor laser. By this system, many sectional and continuous photographs of the same spray were obtained, and were very effective for the detailed observation of the spray inner structure and its developing process. The spray inner structure was very complicated, and its fuel density distribution was very heterogeneous. And for its developing process, the spray advances straight immediately after injected, then meanders, and deforms into a branch-like structure. Advancing downstream, these branches distribute complicatedly and heterogeneously with low density droplets. The heterogeneity is owing to these branches. And, the developing process is divided into four regions. Further, the effects of some parameters on this process were investigated.

It is well known that increasing the fuel injection pressure is effective for improving the diesel engine combustion. While studying the characteristics of the high pressure fuel spray which is injected in a high pressure vessel, the authors found weak shock waves generating around the fuel spray. To investigate the shock waves effect on the fuel spray the authors measured the propagation speed and pressure amplitude as functions of the injection pressure and ambient pressure. The results indicate that shock waves are generated when the fuel injection speed exceeds the ambient sonic speed. Also it was found that the pressure amplitude of shock wave is approximately 10 % of the ambient pressure and the shock waves spread at a sonic speed. The above results make us think that, isn't it possible to use shock waves for combustion improvement.

The characteristics of diesel combustion with high pressure fuel injection were investigated, using a naturally aspirated single cylinder engine and a high pressure injection equipment which can produce over 250 MPa injection pressure. Observation and analysis of combustion were performed using a high speed shadowgraph technique, with different injection pressures. In the case of high injection pressure in combination with smaller nozzle hole diameter, generation of soot in the combustion field is hardly recognized. Also by increasing injection pressure, ignition points tend to shift to the downstream of spray. Analysis of flame motion and turbulence intensity in the combustion field was performed using high speed direct photographs and image analysis technique by tracing flame luminosity distribution time history. By increasing injection pressure, an increase of turbulence intensity at the early stage of diffusion burning was observed.