Refine Your Search

Search Results

Viewing 1 to 10 of 10
Technical Paper

Constraints on Fuel Injection and EGR Strategies for Diesel PCCI-Type Combustion

2008-04-14
2008-01-1327
An experimental study has been carried out to explore what limits fuel injection and EGR strategies when trying to run a PCCI-type mode of combustion on an engine with current generation hardware. The engine is a turbocharged V6 DI diesel with (1600 bar) HPCR fuel injection equipment and a cooled external EGR system. The variables examined have been the split and timings of fuel injections and the level of EGR; the responses investigated have been ignition delay, heat release, combustion noise, engine-out emissions and brake specific fuel consumption. Although PCCI-type combustion strategies can be effective in reducing NOx and soot emissions, it proved difficult to achieve this without either a high noise or a fuel economy penalty.
Technical Paper

Characterisation of DISI Emissions and Fuel Economy in Homogeneous and Stratified Charge Modes of Operation

2001-09-24
2001-01-3671
An experimental study of the performance of a reverse tumble, DISI engine is reported. Specific fuel consumption and engine-out emissions have been investigated for both homogeneous and stratified modes of fuel injection. Trends in performance with varying AFR, EGR, spark and injection timings have been explored. It is shown that neural networks can be trained to describe these trends accurately for even the most complex case of stratified charge operation with exhaust gas recirculation.
Technical Paper

DISI Engine Spark and Fuel Injection Timings. Effects, Compromise and Robustness

2001-09-24
2001-01-3672
DISI engine emissions and fuel economy are strongly dependent upon fuel injection and spark timings, particularly when the engine is operating in stratified charge mode. Experimental studies of the effects of injection and spark timings and the interaction between these are described. The sensitivity of HC and NOx emissions to timings during stratified charge operation, the comparison of performance under stratified and homogeneous charge modes of operation and the rationale for mode switch point settings are investigated. The high sensitivity of emissions to injection and spark timing settings gives rise to potential robustness issues. These are described.
Technical Paper

The Influence of Gas/Fuel Ratio on Combustion Stability and Misfire Limits of Spark Ignition Engines

2000-03-06
2000-01-1208
The deterioration of combustion stability as lean operating limits and misfire conditions are approached has been investigated experimentally. The study has been carried out on spark ignition engines with port fuel injection and four-valves-per-cylinder. Test conditions cover fully-warm and cold operation, and ranges of air/fuel ratio, exhaust gas recirculation rates and spark timing. An approximate method of calculating gas/fuel ratio is described. This is used to show that combustion stability, characterised by the coefficient of variation of i.m.e.p., is a function of calculated gas/fuel ratio and spark timing until near to the limit of stability. A rapid deterioration in stability and the onset of weak, partial burning occurs at a gas/fuel ratio between 24:1 and 26:1 under fully-warm operating conditions, and around one gas/fuel ratio lower under cold operating conditions.
Technical Paper

Exhaust System Heat Transfer and Catalytic Converter Performance

1999-03-01
1999-01-0453
Three-way catalytic converters used on spark ignition engines have performance and durability characteristics which are effected by the thermal environment in which these operate. The design of the exhaust system and the location of the catalyst unit are important in controlling the range of thermal states the catalyst is exposed to. A model of system thermal behaviour has been developed to support studies of these. The exhaust system is modelled as connected pipe and junction elements with lumped thermal capacities. Heat transfer correlations for quasi-steady and transient conditions have been investigated. The catalytic converter is treated as elemental slices in series. Exothermic heat release and heat exchange between the monolith, mat, and shell are described in the model. A similar description is applied to lean NOx trap units.
Technical Paper

Audit of Fuel Utilisation During the Warm-Up of SI Engines

1997-05-01
971656
Experimental studies of fuel utilisation during the early stages of engine warm-up after cold-starts are reported. The investigation has been carried out on a 1.81, 4 cylinder spark-ignition engine with port electronic fuel injection. The relationship between fuel supplied and fuel accounted for by the analysis of exhaust gas composition shows that a significant mass of fuel supplied is temporarily stored or permanently lost. An interpretation of data is made which allows time-dependent variations of these to be separately resolved and estimates of fuel quantities made. The data covers a range of cold-start conditions down to -5°C at which, on a per cylinder basis, fuel stored peaks typically at around 0.75g and a total of 1g is returned over 100 seconds of engine running. Fuel lost past the piston typically accounts for 2g over 200 to 300 seconds of running.
Technical Paper

Intake Port Fuel Transport and Emissions: The Influence of Injector Type and Fuel Composition

1996-10-01
961996
Experimental studies have been carried out on a spark ignition engine with port fuel injection to examine the influence of injector type and to contrast this with the effects of fuel composition. Intake port fuel transport characteristics and engine-out emissions for fully-warm and warm-up engine operating conditions have been examined as indicators of performance. The investigation has encompassed four types of injector and five gasoline blends. Fuel transport has been characterised using the τ and X parameters. The influence of injector type on these is of similar significance as that of changes in gasoline composition between summer and winter grades. The latter will limit the in-service accuracy of open-loop mixture control during transients. Injector type has a small effect on engine-out emissions under fully-warm operating conditions but has a significant influence on emissions during the early stages of warm-up.
Technical Paper

Computer Aided Evaluation of Cold Start Fuelling Strategy and Calibration Details for Spark Ignition Engines

1994-02-01
940085
Spark ignition engines for automotive applications must have good cold start performance characteristics at sub-zero ambient temperatures. Satisfactory performance is most difficult to achieve at the lower end of the temperature range, typically around -30°C. The start characteristics of a particular engine depend on basic design features, starter motor characteristics, and the calibration and strategy used to regulate fuel supply during start up. The paper reports a computational model which enables the investigation of these with the minimum of experimental data. The model has been developed to run on desk-top PC machines, specifically as a CAE development tool. The formulation of the model and the experimental tests were used to generate the input data required for particular applications are described.
Technical Paper

The Use of Vehicle Drive Cycles to Assess Spark Plug Fouling Performance

1994-02-01
940101
Spark plug fouling is a common problem when vehicles are repeatedly operated for very short periods, particularly at low temperatures. This paper describes a test procedure which uses a series of short, high-load drive cycles to assess plug fouling under realistic conditions. The engine is force cooled between drive cycles in order to increase test throughput. Spark plug resistance is shown to be a poor indicator of the effect of fouling on engine performance and the rate of misfiring is given as an alternative measure. An automated technique to detect misfires from engine speed data is described. This has been used to investigate the effect of spark plug type, fuelling level and spark timing on fouling. Spark plugs which are designed to run hotter are found to be more resistant to plug fouling. Isolated adjustments to fuelling level and spark timing calibrations within the range providing acceptable performance have a weak effect on susceptibility to plug fouling.
Technical Paper

A Model for the Investigation of Temperature, Heat Flow and Friction Characteristics During Engine Warm-Up

1993-04-01
931153
A computational model has been developed to support investigations of temperature, heat flow and friction characteristics, particularly in connection with warm-up behaviour. A lumped capacity model of the engine block and head, empirically derived correlations for local heat transfer and friction losses, and oil and coolant circuit descriptions form the core of the model. Validation of the model and illustrative results are reported.
X