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Technical Paper

Analysis of Diesel Smoke Emission at Low Engine Speed

In recent years, diesel engine exhaust gas regulations become more severe due to environmental concerns. Especially, particulate reduction is one of the biggest concern, and the reduction through high injection pressure has been studied.(1), (2) and (3) However, much is not yet known about the influence of changes in fuel flow inside the nozzle tip on atomization and engine performance, and there would exist a lot of room for exhaust gas reduction through the nozzle modification. In this research we found that changing the shape of the nozzle tip showed a remarkable difference in the smoke emission at low engine speed, analysis showed that difference in the flow rate at the nozzle orifice cause difference in the fuel spray droplet size and therefore the difference in the smoke emission.
Technical Paper

Benefits of New Fuel Injection System Technology on Cold Startability of Diesel Engines - Improvement of Cold Startability and White Smoke Reduction by Means of Multi Injection with Common Rail Fuel System (ECD-U2)

In the diesel engine field, increasingly strict emission regulations and customer requirements have necessitated advanced technology. One important subject for diesel engines is cold startability and white smoke under cold conditions. In this paper, the combustion mechanism of a multi cylinder engine under cold conditions is discussed. First, during a starting condition, it is proved that the cold flame, which is caused by previously misfired fuel during intermittent combustion, promotes good combustion on the following cycle. Secondly, following engine starting, it is estimated that there is minimum fuel quantity above which combustion is carried out. The minimum fuel quantity depends upon the temperature of the combustion chamber. Unbalance between the minimum fuel quantity and actual injection quantity results in white smoke emission.
Technical Paper

Contribution of Fuel Flow Improvement in Nozzle to Spray Formation

This paper reports on research conducted at Nippondenso Co., Ltd. and Meiji University on nozzles for heavy duty diesel engines. It focuses on fuel flow analysis in the nozzle, a key component of Fuel Injection Systems (FIS). The optimum design nozzle improves fuel flow and spray characteristics. A newer and tougher emission regulation from the EPA for heavy duty diesel engines will be inevitable from 1998 onward. The goal of every company is to design new FIS in advance which meet the regulations of the future rather than paying for expensive developing costs after new laws have come into effect. To meet the regulation, requirements for FIS are higher injection pressure and injection rate control which create better fuel spray atomization and higher utilization of air. In particular, the nozzle must ensure that high injection pressure is effectively converted to fuel spray without pressure losses.
Technical Paper

Contribution of Optimum Design for Nozzle Configuration to Spray Formation

The purpose of this paper is to discuss spray control of nozzle for heavy duty diesel engines. This paper will focus on fuel flow analysis of nozzle, key component of FIE (Fuel Injection Equipment). The optimum designed nozzle controls fuel flow and improves flow efficiency. FIE is required to produce higher injection pressure which creates better atomization and higher utilization of air. But the higher injection pressure results in increased pump driving torque, larger pump size and higher cost. To improve the fuel flow characteristic of nozzle, we analyzed it and developed a theoretical analysis method with computer model simulation to the optimum design nozzle. We also confirmed its effect by experiments.
Technical Paper

Contribution of Optimum Nozzle Design to Injection Rate Control

The purpose of this paper is to discuss injection rate control of the nozzle for direct injection engines. This paper will focus on fuel flow analysis of the nozzle, a key component of Fuel Injection Systems (FIS). The optimum designed nozzle improves fuel flow efficiency and controls injection rate. To meet emission regulations in 1990's, FIS are required to produce higher injection pressure and injection rate control which creates better fuel spray atomization and higher utilization of air. But the higher injection pressure makes injection rate control difficult. In particular, injection rate control by needle lift traveling control is difficult because fuel flow characteristics in the nozzle change with injection pressure and needle lift. Furthermore, the forced control of needle lift results in poor fuel spray atomization.
Technical Paper

Development of a Mechanical Pilot Injection Device for Automotive Diesel Engines

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.
Technical Paper

Development of a Turbine In-Tank Fuel Pump

Considerations have been made on using turbine pumps as in-tank fuel pumps for electronic fuel injection systems (EFI). Flow channel dimension values, which had not been previously used for these types of pumps, were found to be very suitable for use as a fuel pump. The oil film visualization method was used to observe the flow pattern within the pump, and the results served to improve the flow channel shape. This contributed to designing a compact and efficient high-pressure fuel pump.
Technical Paper

Development of the Module Type Fuel Filter

In recent years, concerns with global environmental problems have become major issues. Environmental regulations such as fuel consumption/economy, for example, have become very stringent. On the other hand, the pursuit of a comfortable and spacious passenger compartment and reduced engine compartment room have become more progressive. Size and weight reduction of automotive components are necessary to cope with these requirements. With regards to the fuel filter, size reduction of the filter element is the key technology to achieve both component size and weight reduction. As to a fuel filter, the reduction of its size and weight can be accomplished by reducing the size of its element. We have studied this subject and have invented a new type of element structure. Additionally, we have developed a new filter paper which features a favorable combination of contaminant holding capacity and micron rating.
Technical Paper

Effect of Fuel Injection System Improvement on White Smoke Reduction in Small Diesel Engines with Swirl Chamber

Performance optimization of small diesel engines is greatly owing to the matched improvements between combustion chamber and fuel injection system. Fuel injection characteristics are especially important to realize optimum engine performance in all speed range. In recent years, lower noise and white smoke reduction during cold temperature operation have been strongly required for agricultural and industrial application, which are the same technical trend as automotive's. As these two requirements are in the trade - off relationship from a combustive point of view, it is very complicated to realize both at the same time. Therefore, fuel injection characteristics are analyzed in detail for important factors such as injection pressure pattern, its behavior and injection timing so that the aimed optimum engine performance is obtained. This paper describes an optimization example of achieving simultaneous reduction of white smoke and noise by fuel injection characteristics' improvements.
Technical Paper

Experimental Analysis on Fuel Flow Characteristics in the Nozzle for Direct Injection Engines

The purpose of this study is to make clear the relationship between flow characteristics in the nozzle and injected spray characteristics. In this paper, we discuss the effect of the sac volume in the standard hole type nozzle on fuel flow and spray. The main object of this paper is to analyze fuel flow characteristics in the nozzle by using the enlarged model nozzles. Spray investigations confirmed that reducing the sac volume causes changes in the fuel injection direction at the initial stage of injection and in the spray penetration over consecutive injection. Flow investigations in the injection hole clarified that meandering the flow in the hole causes changes in the fuel injection direction. Flow investigations in the sac chamber clarified that separating the flow from the sac wall causes meandering the flow in the hole. Furthermore, the methods to restrain the flow in the sac chamber from separating from the sac wall were discussed.
Technical Paper

Injection Rate Shaping Technology with Common Rail Fuel System (ECD-U2)

In the diesel field, innovative technology development has been desired for fuel injection system from the points of severe emission reduction to meet increasingly stringent emission regulation year by year respecting environmental protection and product improvement for various customer requirements including fuel consumption improvement. We have been pursuing the ideal fuel injection system which is called “ECD-U2” to meet above expectations. “ECD-U2” is the injection system of highly pressurized fuel with optimum injection timing by using of the injector controlled by high speed response magnetic valve. This system also has the fuel injection pattern controllability in one injection ( injection rate ) as one of the greatest asset. This report focuses on the new injector structure development to achieve desirable injection rate shaping for diesel engine combustion.
Technical Paper

Recent Technology to Improve Engine Combustion Noise and Exhaust Emission by Optimizing Fuel Injection System

In resent years,lower noise has been in high demand in small diesel engines for agricultural and industrial uses as well as automotive engines. Furthermore,emission regulations becomes more severer due to environmental concerns. In order to satisfy these objects,diesel engine combustion needs to be improved. Especially fuel injection system is the key element to control engine combustion and should be improved dramatically. This research is to pursue the ideal fuel injection system to realize optimized diesel engine combustion which creates low combustion noise and clean exhaust emission. Recent progress will be reported in fuel injection technology including injection pressure pattern, injection rate pattern, injection timing and spray pattern, etc.