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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.

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.

An extensive experimental and analytical study of the performance of a Wankel engine is reported, with special emphasis on the combustion process. A one dimensional technique for calculating gas velocities in the combustion chamber under motoring conditions is described and this is then used to evaluate flame travel when combustion occurs. A novel three-zone combustion model is introduced. The effect of the position of the rotor recess is examined and shown to change the engine power output and hydrocarbon emissions.

An extensive amount of research has been carried out by various authors on the entrainment of fuel droplets in a steady air flow, in order to understand the transportation of droplet fuel in the spark-ignition engine intake manifold system. However, the utility of this type of steady state model is very limited when applied to the real engine where the air flow is highly pulsative. The present work develops a theoretical model of the flow of fuel droplets entrained in a non-steady air flow which requires the solution of a set of unsteady one-dimensional two phase flow equations by a numerical technique. This model is then applied to a single-cylinder spark-ignition engine fitted with both intake and exhaust manifold systems and also a carburettor.

A numerical scheme for a Computer Aided Design (CAD) package for the design and development of internal combustion engine intake and exhaust manifold is presented. The program is interactive and uses the graphical and visual display unit (VDU) facilities extensively. The basic concept of such a program was described in a previous SAE paper (Paper No. 790277) by one of the authors (SCL). The present program is written to handle a maximum of 10 cylinders and any imaginable configuration of intake and exhaust manifold. The input data, the preparation of which is usually a time-consuming process, are kept at a possible minimum with automatic generation of data from arbitrary drawings drawn manually on the VDU screen. The program is applied to a commercial 4 cylinder - 4 stroke spark ignition engine.

One of the methods of representing a turbocharger-turbine in the exhaust system of internal combustion engines is by assuming quasi-steady flow at turbine boundaries, while taking into account the generation of pressure waves both upstream and downstream of the turbine due to non-steady flow conditions. This method relies substantially on steady flow turbine characteristics for the generation of boundary conditions. A method is presented to allow for wave action both upstream and downstream of a twin-entry radial inflow turbine. The method also allows for different flow rates in each entry to simulate the partial admission condition. Comparison is made between experimental results and theoretical analysis.

An interactive computer program for predicting the performance of a total engine system is described. The facilities include the basic design of the valve time-area diagrams, starting from various cam profiles, wave action effects in inlet and exhaust manifolds and turbocharger matching. The program is accessed via visual display units (VDUs) and its interactive nature takes many activities from the realm of the research department into that of the design department. The results obtained from the program are validated by comparison with a well-known more sophisticated wave action program.

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.

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.

The problem of highly rated turbocharged diesel engines operating under transient load conditions is now well known, and is due to the inability of the turbocharger to supply sufficient air for good combustion. In Part 1, two methods are discussed for reducing turbocharger lag-air injection onto the compressor rotor and oil injection onto a small pelton wheel mounted on the turbocharger shaft. Results are given showing the benefit of fitting these devices to an engine on a test bed. Engine response is improved in all respects particularly smoke and overall response time. In Part 2, a simulation study of a turbocharged diesel engine installed in a 32 tonne truck is presented to investigate the engine performance during load and speed changes. It is shown that by injecting compressed air on to the turbocharger compressor rotor tip, smoke emissions from the engine during load changes are reduced.

Part 1 describes a gas dynamic model to represent a pulse converter. In this model the pulse converter is represented by a three-way branch with pressure losses. Pressure loss coefficients are determined from steady flow tests and included in the boundary conditions for non-steady flow. Non-steady tests on pulse converters fitted in a four cylinder turbocharged engine showed that using the model, predictions of the influence of pulse converter area ratio on wave form and amplitude give good agreement with experiment. Part 2 gives results of a comprehensive investigation on the application of pulse converters to a four stroke automotive engine. It is shown that using the gas dynamic model presented in Part 1 of the paper in a simulation program the optimum combination of pulse converter and turbocharger size may be determined. This combination was confirmed in the experimental programme.

A method is described for matching turbines and compressors for two-stage turbocharging of 4-stroke diesel engines. The method is illustrated for a series turbocharged engine. Experimental results are presented which show that the method gives good predictions for the respective pressure ratios in the turbines and compressors and the overall engine performance.

The development of instrumentation techniques for research in internal combustion engines is described. A general discussion of instrument classification and requirements is followed by a description of transducer development including calibration techniques, signal processing, and data acquisition. Details are given of two direct on-line digitizing devices for high-speed data acquisition (one purpose made and the other using an on-line computer). An analaysis of instrumentation and data acquisition errors is presented. The integration of the data acquisition equipment into a semiautomatic controlled test bed is described and a proposal for a fully automated test bed presented. Appendices giving details of the basic principles of the operation and design considerations of the on-line computer facility for data acquisition and engine test bed control are included.

Comparison is made between the transient response of a medium-speed, turbocharged diesel engine subjected to sudden load changes on a test bed and the response of a computer simulation model of the engine. Brief details are given of the simulation techniques involved and the data required to set up the model. Despite close agreement of model and engine steady-state results over the whole normal operating range, the transient responses of the model were initially found to be much faster than the test-bed responses. It is shown that the most important factor causing this difference is the lack of knowledge of the combustion at low air-fuel ratios and hence prediction of engine exhaust temperature during transient operation. Good agreement was obtained when this was modified.

One of the methods for improving the transient response of a turbocharged diesel engine is to accelerate the turbocharger by injecting air onto the impeller of the compressor. This paper describes experiments carried out on a turbocharger test rig in which air was injected through nozzles at the rotor tip of the centrifugal compressor; performance characteristics are presented. Results from these tests were then used to modify a digital simulation model of a medium-speed turbocharged diesel engine so that air injection could be applied at the onset of a load. Calculations show the predicted improvement in response of the system to step-load changes.

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.