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Technical Paper

Calculation of Inhomogeneous-Charge Combustion in a Swirl-Assisted Lean-Burn Engine

1991-02-01
910266
A multidimensional computational method is extended to include the methodology for modelling of partially-mixed inhomogeneous charge combustion and is applied to investigation of combustion and simultaneous mixing process of an inhomogeneous mixture in a lean-burn spark-ignition engine. The in-cylinder flow and charge mixture distribution pertain to a helical intake port with manifold fuel injection, and were obtained through complete simulation of the induction and compression processes. The engine compression ratio is 12:1 and the study pertains to the operating condition of 2500 rpm. The results show that the flow and charge distribution at the time of ignition is predominantly characterised by the evolution of the induction flow. The effect of heat release on enhancement of charge mixing is marginal and the pre-ignition charge distribution is preserved throughout the combustion.
Technical Paper

Contribution of Optimum Nozzle Design to Injection Rate Control

1991-02-01
910185
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

Application of a High Flexible Electronic Injection System to a Heavy Duty Diesel Engine

1991-02-01
910184
Future strict emission standards such as US 94 and EEC 96 for heavy duty diesel engines require injection systems more and more flexible. They have to be able to electronically control fueling, timing, and injection pressure as independent parameters. To be optimal this fuel injection equipment (F.I.E.) must be able to allow injection rate flexibility, separated pilot injection and cylinder cut-off. The F.I.E. from Nippondenso designated ECD-U2 offers all these characteristics. This paper deals with the installation and the application of this F.I.E. to a “RENAULT Véhicules Industriels” (R.V.I.) turbocharged and intercooled engine such as the MIDR 06.20.45 engine. Using the flexibility of ECD-U2,the US 91 emission targets for NOX and particulates were easily achieved with good fuel economy and the US 94 legislative standard was approached with limited development.
Technical Paper

A Study on Dynamic Parameters of Fuel Injection Pump

1991-02-01
910186
The authors measured and studied rack displacement pattern and injection advance angle of fuel pump on 6130Q diesel engine at both steady and speed change conditions. By means of injection pattern and indicator diagrams actually measured at the same time, this paper deals with the important roles of fluctuation of rack displacement and injection advance angle at steady condition and their dynamic response to operating stability, accelerability and combustion process of the diesel engine.
Technical Paper

Flow and Combustion in a Hydra Direct-Injection Diesel Engine

1991-02-01
910177
Measurements of flow, spray, combustion and performance characteristics are reported for a Hydra direct-injection diesel, based on the Ford 2.5 L, engine and equipped with a variable-swirl port, a unit fuel injector and optical access through the liner and piston. The results provide links between the pre-combustion and combustion flow and, at the same time, between purpose-built single-cylinder optical engines and multi-cylinder production engines of nearly identical combustion chamber geometry. In particular, the spray penetration was found to depend on engine speed, rather than load, with velocities up to around 260 m/s at atmospheric pressure and temperature which are reduced by a factor of 2.5 under operating conditions and seem to be unaffected by swirl. The duration of combustion was reduced with increasing swirl and ignition delay increased linearly with engine speed.
Technical Paper

Comparisons of Measured Drop Sizes and Velocities in a Transient Fuel Spray with Stability Criteria and Computed PDF's

1991-02-01
910179
Two sets of comparisons were made in an attempt to provide a mechanism for understanding the behavior of transient sprays. First, detailed measurements of drop size and velocity in a transient spray were compared to established stability criteria for different droplet breakup mechanisms, specifically criteria for bag breakup and boundary layer stripping. Then, probability-density-functions were determined from the experimental data and compared, where appropriate, to different computed distributions (such as the Chi-square or log-hyperbolic distributions). Comparison with the stability criteria indicates that the a majority of droplets in the spray are susceptible to both breakup mechanisms near the injector tip. However, downstream, the spray appears to stabilize and any redistribution of droplet size must apparently be a result of collisions. The experimentally-determined PDF's for size and velocity are functions of both position and time in the spray.
Technical Paper

The Propagation of Fuel Sprays in a Research Diesel Engine - A Joint Numerical and Experimental Analysis

1991-02-01
910181
A program of development and experimental validation of a multidimensional spray prediction method, based on the discrete droplet model, has been broadened to include computational investigations of the effects of random perturbations of the injection velocity on the spray characteristics, and further detailed examination of the spray structure and development. The results demonstrate strong dependence of the predicted spray penetration length on the precise start-of-injection time and injection velocity data, and relative insensitivity to subsequent variations of the injection velocity. Specifically, it is found that under imposition of random variations of the injection velocity, the variation of the spray-tip penetration and velocity remain smooth, bearing no correspondence to the instantaneous spray injection velocity.
Technical Paper

A Study of Diesel Cold Starting using both Cycle Analysis and Multidimensional Calculations

1991-02-01
910180
The physical in-cylinder processes and ignition during cold starting have been studied using computational models, with particular attention to the influences of blowby, heat transfer during the compression stroke, spray development, vaporization and fuel/air mixture formation and ignition. Two different modeling approaches were used. A thermodynamic zero dimensional cycle analysis program in which the fuel injection effects were not modeled, was used to determine overall and gas exchange effects. The three-dimensional KIVA-II code was used to determine details of the closed cycle events, with modified atomization, blowby and spray/wall impingement models, and a simplified model for ignition. The calculations were used to obtain an understanding of the cold starting process and to identify practical methods for improving cold starting of direct injection diesel engines.
Technical Paper

Resistance Seam Weldability of Polymer-Coated Steel Sheet

1991-02-01
910195
Methanol represents one of the most attractive alternative fuels intended to replace gasoline, but it is corrosive to the terne-coated steel sheet traditionally used for automobile fuel components. Application of a methanol-resistant polymer coating on a steel substrate was found to be a viable solution for methanol-resistant fuel tanks. One-sided electrogalvanized sheet was coated on the bare side with a nonconductive and adhesive thermoplastic. The present work studied the weldability of this sheet with the thermoplastic at the faying interface. A systematic parametric study was performed. Welds were evaluated using a set of criteria based on the joint integrity and corrosion resistance. It was found that the coating melted and resolidified in a continuous film adjacent to the welds. The resistance seam-welding operational envelopes were shifted toward lower welding travel speeds and welding currents.
Technical Paper

Fast Burning and Reduced Soot Formation via Ultra-High Pressure Diesel Fuel Injection

1991-02-01
910225
The relation between the characteristics of a non-evaporating spray and those of a corresponding frame achieved in a rapid compression machine was investigated experimentally. The fuel injection pressure was changed in a range of 55 to 260 MPa and the other injection parameters such as orifice diameter and injection duration were changed systematically. The characteristics of the non-evaporating spray such as the Sauter mean diameter and the mean excess air ratio of the spray were measured by an image analysis technique. The time required for a pressure rise due to combustion was taken as an index to characterize the flame. It was concluded that the mean excess air ratio of a spray is the major factor which controls the burning rate and that the high injection pressure is effective in shortening the combustion duration and reducing soot formation.
Technical Paper

The Effect of Alternative Fuels on Fluorosilicone Elastomers

1991-02-01
910102
Fluorosilicone elastomers are a material of choice for fuel systems designed for use with alternative fuels, such as methanol-gasoline blends. Fuel-immersion results show that not all fluorosilicones behave alike when immersed in methanol-gasoline blends. Information on the specific fluorosilicone being evaluated must be obtained by the fuel-system engineer to make a correct selection.
Technical Paper

High Temperature Resistance of Fluoropolymers in Automotive Fuels

1991-02-01
910103
Materials used in automotive fuel line constructions must offer dependable and predictable performance when exposed to a variety of fuel compositions at high temperatures. This paper presents data from a comprehensive study which demonstrates the high temperature chemical resistance of fluoropolymer resins after exposure to several fuel compositions at various temperatures. Fuel exposure tests were performed at temperatures ranging from room temperature to 120 C (250 F). The test included six different plastics, exposed to four fuel compositions. The exposed samples were tested for weight change, volume change, and retained physical properties. Tensile property testing was conducted at temperatures ranging from room temperature to 204 C (400 F). This data demonstrates that the superior high temperature properties and outstanding chemical resistance of fluoropolymer resins make them well suited for use in fuel handling systems.
Technical Paper

Digitally Controlled Fuel Metering Pump for Small Gas Turbine Engines

1991-02-01
910057
There is a need in the gas turbine industry for an inexpensive fuel control unit for the new breed of high performance small gas turbine engines. To answer this demand, it is proposed to couple an automotive type fuel pump with a stepper motor driven in microstepping mode. The speed of the motor and the fuel flow rate can be controlled by the frequency signal from the computer. This concept is particularly well suited for the gas turbine engine fuel supply where the fuel pressure at low speed is low and the fuel leakage in the pump is not high. The stepper motor driven by a microstepping driver can reach high speeds of several thousands rpm. The unit can be installed inside the fuel, supply tank, as is the case with electric fuel pumps found in automobiles. Prototypes have been made and tested. Both steady state and transient response are showing an impressive performance of such an electronic fuel metering pump.
Technical Paper

Multizone Modeling of a Fumigated Diesel Engine

1991-02-01
910076
A phenomenological, multizone, transient spray model has been developed to simulate the performance and nitric oxide emission characteristics of a turbocharged diesel engine fumigated with alcohol. The effects of speed, load, alcohol proof, and the fraction of the engine's power supplied by the alcohol have been investigated. The multizone model is designed to account for the heterogeneous composition of the cylinder contents by dividing the cylinder into a number of locally homogeneous zones. The model includes the interactions between the fuel spray and swirling air in the cylinder and the effect of wall impingement on fuel-air mixing and combustion. A complete thermodynamic analysis has been applied to the individual zones to obtain cylinder pressure data.
Technical Paper

Study on Variable Injection Pattern Control System in a Spark Ignition Engine

1991-02-01
910080
Mixture formation technology for multipoint fuel injection systems in spark ignition engines has been reviewed regarding reduced exhaust emissions, fuel consumption and improved engine performance. In conventional systems, under light load conditions, the mixture of fuel to suction air is not uniform due to a short injection pulse width against a long duration of suction stroke. Under heavy load conditions, fuel spray is apt to be deflected by the air flow through the intake port and the injected fuel clings and remains onesidely on the cylinder wall during the combustion cycle. Under cold start conditions, the fuel on the intake manifolds and ports is not evaporated quickly enough so that it is evaporated in the cylinder after the temperature rises due to the compression stroke. A lot of fuel is injected to compensate for the small evaporation rate.
Technical Paper

Theoretical Analysis of Mixture Stoichiometry in Engine Carburetor

1991-02-01
910078
A theoretical analysis of the stoichiometry of the mixture produced in a main fuel system of the engine carburetor is presented. The analysis made it possible to develop a computer code which was applied to the particular Weber type carburetor from a small, two-cylinder car engine. The operation of the carburetor in the regimes of the steady and unsteady flow, including the influence of back flows, was investigated. It is concluded that the air pressure pulsations and, in particular, the existence of the back flows cause the significant enrichment of the mixture produced in the carburetor.
Technical Paper

Requirements and Performance of Engine Management Systems under Transient Conditions

1991-02-01
910083
Because of the big influence on driveability and exhaust emissions one of the most important challenges of modern fuel injection systems is to ensure a very good constancy of the air/fuel ratio. A precise feedforward control especially for dynamic transitions is necessary because a feedback control of the air/fuel ratio based on an oxygen sensor in the exhaust gas is not able to avoid dynamic deviations. Therefore in this paper a new fuel injection technique is presented which is founded on a simultaneous control of air and fuel in connection with algorithms based on mathematical models of the different physical effects.
Technical Paper

Long Life Potentiometric Position Sensor - Its Material and Application

1991-02-01
910269
Recently various kinds of position sensors have been used in automotive subsystems which include Electronic Fuel Injection, Active Suspension and Exhaust Gas Recirculation (EGR). Because a potentiometer has a simple structure in which a brush slides on a resistor surface, it has many advantages such as high temperature applications, low cost, high signal level and almost infinite resolution compared to other kinds of position sensors that are magnetic or optical in nature. The potentiometer is considered to have the highest potential for a position sensor. However, conventional potentiometers sometimes lose their linearity after use under severe conditions such as engine vibration (dither). They can endure only tens of millions of cycles of dither.
Technical Paper

A Study on Shallow W-Type Combustion System for High-Speed Diesel Engine

1991-02-01
910485
The authors of this paper have experimented on four and six-cylinder engines of ϕ 0102 x 125mm with shallow W-type combustion system, showing satisfactory results. In a 1200-2800 r/win speed range the prototype engine showed excellent performance characteristics, moreover, it required less accuracy in making their inlet ports. Based on fuel injection and combustion heat release pattern measured under various matches of combustion chamber, injection system and inlet port, the authors have studied each effect of design parameters on combustion characteristics and put forward the key points for optimum combustion match.
Technical Paper

The Development of a Novel Variable Compression Ratio, Direct Injection Diesel Engine

1991-02-01
910484
A production, direct injection diesel engine was modified to incorporate BP Oil's novel variable compression ratio (VCR) engine concept. The operation of the VCR mechanism was demonstrated and the performance and emissions potential of the concept evaluated. The VCR prototype achieved twice the specific power output of the baseline turbocharged, aftercooled engine. Its exhaust smoke emissions at high load were consistent with conventional direct injection (DI) diesel engines using equivalent fuel injection equipment. Light load particulate emissions and high load fuel consumption indicated a need for further development of the combustion system. Unexpectedly low HC emissions were achieved considering the large crevice volumes in the combustion chamber of the prototype engine. Likewise, exceptionally low NOx emissions were demonstrated. It is believed that the low HC and NOx emissions could be inherent features of the unique combustion system configuration.
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