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An experimental investigation has been carried out to compare the indicated performance and heat release characteristics of a DI diesel engine at compression ratios of 18.4:1 and 15.4:1. The compression ratio was changed by modifying the piston bowl volume; the bore and stroke were unchanged, and the swept volume was nominally 500cc. The engine is a single cylinder variant of modern design which meets Euro 4 emissions requirements. Work output and heat release characteristics for the two compression ratios have been compared at an engine speed of 300 rev/min and test temperatures of 10, -10 and -20°C. A more limited comparison has also been made for higher speeds representative of cold idle at one test temperature (-20°C). The reduction in compression ratio generally produces an increase in peak specific indicated work output at low speeds; this is attributable to a reduction in blowby and heat transfer losses and lower peak rates of heat release increasing cumulative burn.

The paper reports the design of a model and HIL system produced to support the development and testing of Electronic Control Unit/Engine Management System (ECU/EMS) software for a V6 turbo-charged automotive diesel engine. The engine model, developed in Simulink, is compiled to execute on a dSpace platform and interacts with the ECU/EMS module in real time. The main features of the engine model are outlined. The configuration of the model and HIL components are described, and the performance of the system is illustrated and discussed. Practical decisions on the inclusion of real or virtual sensors and actuators, and other implementation issues, are explained. Recent and potential future applications of the system are described.

Kiva-3v Release 2 has been used to investigate combustion and emissions formation processes in a direct injection diesel engine with a high pressure common rail injection system. The influence of split main ratio and separation on NO and soot emissions have been of particular interest. Model validation has been based on comparisons with experimental data for heat release and engine-out emissions. Simulations have been carried out to explore the temporal development of combustion processes under typical part-load operating conditions. The results presented are for an engine speed and BMEP of 1600 rev/min and 6.76 bar, respectively.

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.

A correlation for total gas-side heat transfer rate has been derived from the analysis of engine data for measured heat rejection rate, frictional dissipation, and published data on exhaust port heat transfer. The correlation is related to the form developed by Taylor and Toong, and the analysis draws on this. However, cylinder and exhaust port contributions are separated. Two empirical constants are fixed to best match predicted to measured results for heat rejection to coolant and oil cooler under steady-state conditions, and also for exhaust port heat transfer rates. The separated contributions also defined a correlation for exhaust port heat transfer rate. The description of gas-side heat transfer is suited to needs for the analysis of global thermal behaviour of engines.

A suite of computer programs for engine thermal analysis and the analysis of thermal interactions with external systems has been developed. Defining an engine design is made particularly simple and the representation generated agrees well with measured data. Engine geometry, mass, and internal coolant volume are determined from a short list of key parameters and the selection of a generic template. Thermal conditions in the engine structure are modelled numerically using the lumped-capacity method. Heat exchange at boundaries with gas, coolant and oil flows are described through sub-models giving good agreement with data for global characteristics of engine behaviour. The effects of spark timing and coolant composition on heat transfer rates are taken into account, as is the effect of frictional dissipation as a heat source. Validation and applications of the model are described.

The cycle-by-cycle variation of heat transferred per cycle (q) to the combustion chamber surfaces of spark ignition engines has been investigated for quasi-steady and transient conditions produced by throttle movements. The heat transfer calculation is by integration of the instantaneous value over the cycle, using the Woschni correlation for the heat transfer coefficient. By examination of the results obtained, a relatively simple correlation has been identified: This holds both for quasi-steady and transient conditions and is on a per cylinder basis. The analysis has been extended to define a heat flux distribution over the surface of the chamber. This is given by: where F(x/L) is a polynomial function, q″ is the heat transfer per cycle per unit area to head and piston crown surfaces and gives the distribution along the liner

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.

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.

Two methods of determining the rate of heat transfer from the combustion chamber have been investigated. A First Law analysis is shown to be ill-conditioned because of sensitivity to heat release and gas property calculations. An alternative approach equates cycle-averaged chamber heat transfer to the difference between heat rejected to the coolant and gas heat transfer to the exhaust port. This has been examined as a basis for calibrating the Woschni correlation.