Injection System Of Diesel Engine Research Articles

Improvement of Diesel Combustion Using a Fuel-Water-Fuel Injection System.

This paper describes the application of a i.e. fuel water-fuel injection system for diesel engines. This system makes it possible to inject water during fuel injection from the same nozzle hole without mixing the liquids. First, it was confirmed that NOx reduction and improvement of thermal efficiency and smoke density could be achieved using this system. The reason for such improvement of combustion with water was investigated in detail using a special test engine with which burning flames could be visualized by taking high-speed photos. Moreover, the distribution of the water vapor in the fuel spray was estimated through calculations using the KIVA code. Using these studies, this system may soon be put to practical use.

A simulation analysis of a DI diesel engine fuel injection system fitted with a constant pressure valve

In the present work, a theoretical and computational investigation is conducted to examine the performance of a fuel injection system fitted with a constant pressure valve, used to power a high speed direct injection (DI) diesel engine. The delivery valve (conventional layout) in the fuel injection system of diesel engines is used to provide a residual pressure in the fuel pipeline for the next injection. However, this layout often results in secondary injections which have a serious effect on engine performance. This problem is more severe in the cases of maintaining high residual pressure values. The use of a secondary valve placed inside the delivery valve, called the constant pressure valve, eliminates this problem by relieving the fuel pipe from the high pressure fluctuations caused by the pressure waves reflected at the injector end and the delivery valve chamber. A relevant experimental investigation is conducted with such a fuel injection system on a high speed direct injection diesel engine, examining the effect of load and speed on the performance of the fuel injection system. The experimental results compare well with the theoretical results obtained from a comprehensive simulation model developed by the present authors. Also, results are presented using the simulation model for the same fuel injection system without being fitted with the constant pressure valve, revealing the occurrence of secondary injections at a high engine speed. The simulation model offers very useful information concerning the design of such a fuel injection system and may be used during the development procedure providing economy in time and a better understanding of the entire injection process.

Cavitation Erosion in Fuel Injection System of Diesel Engines.

The high-pressure injection system has been installed in small high-speed engines in recent years, in order to improve the atomization process of the spray and to reduce the exhausted particulates from engines. However, cavitation erosion appears to occur in this system. In this study, the formation process of cavitation bubbles was investigated via measurement of the pressure history and that of the power spectrum density, PSD, of the high-frequency component of the pressure in the injection pipe. It is revealed that PSD at the early secondary stage pressure is govemed by the differential pressure, Δp. Then mechanism of the generation of erosion source can thus be explained.It is clear that the characteristic value, f(Δp), controls the erosion level.

Injection characteristics simulation and analysis in diesel engines

By means of a purposely developed numerical code an investigation of injection systems in diesel engines has been carried out. Cavitation at low pressure was simulated. The experimental results obtained were compared with the numerical ones. Data on cavitation waves, in the pipe between pump and injector, were obtained during that simulation. In particular, the influence of the relief volume on cavitation volume and injected fuel rate were computed. Unstable working conditions, characterized by a large variation of the injected fuel, at the same operating point, have been experimentally investigated and simulated.

Hydraulic Pressure Pulse Generation by Means of Spool Acceleration.

This paper presents a new high-pressure generation method which relies on a pump driven by a freely moving spool in a hydraulic manner. A strong acceleration of the spool gives a higher rate of delivery at the pipeline inlet, and thus induces strong pressure waves leading to a higher oil pressure at the closed end of the pipeline. The performance of the proposed system is studied using a method of characteristics. The results show that at a given mass of the spool and the plunger, the highest pressure pulse can be achieved at a combination of an inlet dead volume and an inlet-outlet area ratio of the convergent pipeline. It is also suggested that the present method is applicable to a high-pressure fuel injection system for diesel engines.

On a Design of the Fuel Injection System of Diesel Engine : Industrial Application of Characteristic Method

On a Design of the Fuel Injection System of Diesel Engine : Industrial Application of Characteristic Method

Hydrodynamic modeling and analysis of two-phase non-Newtonian coal/water slurries

The two-phase hydrodynamic theory of fluid/solids flow has been utilized to extend the non-Newtonian power-law model to describe the solids rheology for nonhomogeneous slurry flow. The model developed predicts the two-dimensional spatial and temporal variations of solids and liquid velocities and concentration for non-Newtonian power-law slurries experiencing high shear rates typically found in diesel engine injection systems. Comparisons with analytical solutions and literature data for single-phase Newtonian and non-Newtonian flows are presented. The model has been validated using Newtonian single-phase (pure water and No. 2 diesel fuel) and non-Newtonian two-phase (coal/water slurry) capillary tube viscometer shear rate, viscosity, mass flow rate and pressure drop data. Results applicable for typical diesel engine injection systems are presented. The results from this model can be used to calculate the erosion rates at the injection nozzle boundaries and the solids loading at its exit.

Cavitation in the fuel injection system of diesel engines.

Recently, high pressure injection systems have been widely adopted in diesel engines. However, many problems have arisen. One of them is cavitation erosion in the fuel injection system. This erosion is very harmful to the performance and reliability of the engines. A new approach different from the steady flow approach is employed to study this unsteady cavitation phenomenon. In this study, the cavitation phenomenon is clarified by measurement of the pressure, fuel velocity and cavity, and calculation of the axial distribution of the pressure and cavity volume. The method of predicting the degree of erosion is investigated by the injection characteristics. It is clarified that the degree of erosion is well predicted by the overall value of the high frequency alternation contained in the injection pressure.

A fuel injection system for diesel engines with injection pressure control. 2nd report Investigation into the optimum injection pressure on thermal efficiency in pre-combustion chamber engine.

In the first Report, the authors proposed a new conception of the fuel injection control system which would theoretically make it possible to optimize the injection period and quantity of fuel freely in any operation mode of the engine by adjusting the injection pressure, and reported on the results of the relevant basic experiments. The authors applied the above system to a pre-combustion chamber type engine and carried out some experiments to search for the optimum injection pressure. Further, by means of inserting8 an optical fiber probe into the combustion chamber, the authors investigated the influence of the injection pressure upon the behavior of combustion. The second Report briefly describes the results.

A Fuel Injection System for Diesel Engine by Injection Pressure Control : 1st Report, Theories, Influence upon Theoretical Thermal Efficiency and the Result of Basic Experiments

In order to ensure the efficiency of Diesel engines and to adjust the exhaust gas for environmental requirements, it is desirable to control not only the timing of fuel injection beginning but also the period or duration of the injection positively. With the conventional fuel injection systems however, it has been extremely difficult to carry out especially the latter control in all operation modes. The authors, based on a new idea of controlling the amount of fuel injection by means of injection pressure and thereby regulate the injection period freely and at its optimum value in principle, made some basic experiments and obtained satisfactory results on the whole. The results will be reported briefly in the following.

A fuel injection system for diesel engine by injection pressure control. 1st report. Theories, influence upon theoretical thermal efficiency, and result of basic experimantations.

ディーゼル機関の効率確保,および,低公害化推進のためには燃料噴射始め時期だけでなく噴射機関をも積極的に制御することが望ましいが,従前の噴射方式ですべてのモードについてこれを行うことはきわめて困難である。著者らは噴射量を噴射圧で制御し,これによって噴射機関を原則的には任意,かつ,最適値に制御し得る新しい概念の燃料噴射方式により基礎試験を行った結果おおむね良好な結果を得たので,その要旨を紹介する。

FUEL DROPLET SIZE DISTRIBUTION IN DIESEL COMBUSTION CHAMBER

In order to determine spray droplet size in diesel engine, fuel was injected into high pressure gaseous environments with a diesel engine injection system. Droplet size was measured using the liquid immersion sampling technique with the mixtute of water-methylcellulose solution and ethanol used as an immersion liquid for diesel fuel oil. The volume distribution of diesel spray droplet is well correlated with chi-square distribution with freedom, φ=8 in the range of this investigation. The Sauter mean diameter increased with increasing back pressure, with the amount of fuel in a spray and with decreasing pump speed. An empirical correlation was developed between effective injection pressure, air density, the quantity of the fuel delivery and the Sauter mean diameter of spray droplets.

Influence of Fuel Properties on the Injection Characteristics of Fuel Injection System in Diesel Engines

In Diesel engines, it is known that fuel injection and combustion characteristics when using lighter fuels such as gasoline are quite different from those when gas oil is used. However, various points remain unclarified as to the details of fuel injection and spray characteristics under the variety of fuels. The authors have attempted experimental studies on the effect of fuel properties on fuel injection and spray characteristics using gasoline alone. As a result, it was found that a vapour cavity formation phenomenon appeared in the pump barrel with a decrease of fuel feed pressure and fuel properties e.g. fuel viscosity, compressibility, acoustic velocity, etc. considerably influenced the injection quantity, injection timing, injection rate and spray characteristics. Especially, it was noted that these tendencies are notable in lighter fuel such as gasoline.

Influence of Fuel Properties on the Injection Characteristics of Fuel Injection System in Diesel Engines

Influence of Fuel Properties on the Injection Characteristics of Fuel Injection System in Diesel Engines

Velocity of Compressional Waves in Petroleum Fractions at Atmospheric and Elevated Pressures

The problem of dynamics of liquid columns, particularly in Diesel engine injection systems, requires a knowledge of the velocity of propagation of compressional waves in the system. Approximate values are generally used in the solution of such problems. In an effort to correlate the physical properties of petroleum oils with the velocity of wave propagation and to relate the characteristics determined at atmospheric pressure with those at higher pressures, tests were conducted in the Physical Laboratories of the Standard Oil Company of California on thirty-seven hydrocarbon oils at atmospheric pressure. Five hydrocarbon oils were investigated in the Mechanical Engineering Laboratories at the University of California at four temperatures ranging from 57°F to 210°F, and pressures ranging from 500 lb. per square inch to 6000 lb. per square inch. In this paper the experimental methods are described and results presented.