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Technical Paper

A Simulation Model for Transient Operation of Spark-Ignition Engines

A generalized computer model for analysis of multicylinder spark-ignition engines under transient conditions is presented. The model utilizes a two-zone combustion submodel based on flame propagation. It accounts for heat transfer and uses a chemical-kinetics-based procedure for the prediction of nitric oxide and carbon monoxide concentrations. Non-linear wave interactions in the exhaust and intake manifolds are considered. For the transient analysis, a vehicle model is coupled to the engine via a geartrain. The model was used to predict the behavior of two four-cylinder engines under a variety of transient operating conditions. The simulation enabled systematic analysis of the interaction between various dynamic, thermodynamic, and emission variables under transient operating conditions of the engines.
Technical Paper

A Free-Piston Engine Hydraulic Pump for an Automotive Propulsion System

A free-piston engine hydraulic pump (FPEHP) is considered as a power source in the propulsion system of an automotive vehicle. The propulsion system uses a two-stroke spark-ignited free-piston engine coupled to a hydraulic pump and an accumulator where high pressure hydraulic fluid is stored for transmission of power. The energy in the accumulator is transmitted to hydraulic motors which provide the tractive effort. A mathematical model was developed for the FPEHP and computer simulation studies were performed. A particular free-piston engine hydraulic pump concept was simulated at various operating conditions and compared with a similarly-sized conventional engine. We can conclude that the FPEHP engine has no thermodynamic advantage over a conventional engine, but there are reduced nitric oxide emissions. Also, the FPEHP has a limited range of engine speed and a narrower range of ignition timing than a conventional engine.
Technical Paper

Performance and Emission Predictions for a Multi-Cylinder Spark Ignition Engine with Catalytic Converter

A mathematical model is developed to represent an oxidizing catalytic converter in the exhaust system of a spark ignition engine in which the flow is non steady. By using the basic mass transfer, heat transfer and chemical reaction rate equations on the path lines the heat generated at the catalyst surface and the friction factor are allowed for in the generalized non steady flow relations using the method of characteristics. The model is included in a multi-cylinder engine simulation program. Secondary air injection into the exhaust system is represented by a simple mixing process without chemical reaction. A series of tests were carried out on a four cylinder two litre engine with a carbon monoxide and hydrocarbon oxidizing converter and secondary air injection. Comparison of results between experiments and computer calculations shows excellent agreement when the converter is new, but that if the catalyst surface is poisoned or aged the hydrocarbon prediction deteriorates.
Technical Paper

Performance and Emission Predictions of a Multi-Cylinder Spark Ignition Engine with Exhaust Gas Recirculation

A multi-cylinder four stroke cycle spark ignition engine equipped with an exhaust gas recirculation (EGR) system to reduce nitric oxide emission has been comprehensively simulated in a computer program including intake and exhaust manifolds. The program was tested against experiments performed on a standard production four cylinder four stroke engine equipped with a simple laboratory made EGR system. A nitric oxide emission reduction of about 50% was obtained at the peak NO condition. In spite of simplified assumptions the comparison between prediction and measurement of some major engine variables was good. The simulation program holds promise as a tool for engine development work. An appendix is added giving the outline of the calculation procedure.
Technical Paper

Some Further Tests on a Computer Program to Simulate Internal Combustion Engines

The results are presented of an extensive series of tests on a turbocharged 4-stroke diesel engine in which the test results are compared with predictions using a generalized computer program. An examination is made of the influence of the cylinder heat transfer coefficient, the cylinder wall temperature, the exhaust pipe wall temperature, and the air valve flow areas on the engine and turbocharger performance predictions in order to establish the limits of accuracy required for these data. The effect of including the intake system in the calculation is also examined. Results are presented comparing the actual performance of the turbocharger with the predicted performance using steady flow data.