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A comprehensive race car simulation software package, known as HP-VEHSAP, has been developed. The software is based upon a complete system model of a race car and can be applied to the study of all aspects of race car performance. It features a component model library that allows simulation of any type of race car with different levels of detail. The software can predict lap times, perform transient simulations and calculate steady state vehicle characteristics. Several application studies using HP-VEHSAP demonstrate the usefulness of the software for improving race car design and set-up.

A library of macro modules has been written that represent elements common to powertrains of off-highway equipment with diesel powerplants and powershift transmissions. This library allows users to easily and quickly develop complex models of a wide range of vehicle and transmission configurations. These simulation models can be used to evaluate dynamic loadings on the powertrain components, evaluate shift quality, develop control systems and address other powertrain dynamic problems. The library makes use of EASY5 simulation language features to effectively handle such drivetrain nonlinearities as backlash, coulomb friction and hard stops.

Existing models of combustion for multi-dimensional engine flow calculations have problems that limit their usefulness for investigating combustion dependent engine design issues. An alternative model has been formulated that is applicable to premixed charge combustion in engines. The model is robust enough to treat combustion in the bulk and near wall flow regions, and includes a mechanism for flame quenching at the wall. Combustion is represented in terms of separate entrainment and burn-up processes, which is similar to the two zone models commonly used in engine cycle simulations. Calculations have been performed of one-dimensional radial flame propagation in a cylindrical chamber, which is initially filled with a homogeneous fuel-air mixture. Deficiencies in existing combustion models have been demonstrated for this case. The performance of the new combustion model was assessed by studying flame propagation over a range of initial gas conditions typical of engines.

A computational fluid dynamics (CFD) study was carried out on a two-stroke uni-flow diesel engine adapted to operate on direct-injected natural gas (NG) with a diesel pilot ignition source. A medium pressure injector was used to inject the natural gas through the cylinder wall slightly above the intake ports during the gas exchange period. The CFD study concentrated on the effect of the injector orientation on the loss of fuel during scavenging and on in-cylinder mixing of the NG fuel. A three-dimensional CFD model of the cylinder configuration was created in order to simulate the scavenging, NG injection and mixing periods during the cycle. A parametric study of the orientation of the NG injector was performed in order to find the optimal design, within manufacturing constraints, which would minimize HC emissions. It was found that the amount of NG fuel lost during the scavenging period could be reduced if the NG injector is directed downward, toward the bowl in the piston.

Recently, several theories have been offered as possible explanations for claimed increases in diesel engine heat transfer when combustion chamber surface temperatures are raised through insulation. A multi-dimensional computational fluid dynamics (CFD) analysis, using a recently developed near wall turbulent heat transfer model, has been employed to investigate the validity of two of these theories. The proposed mechanisms for increased heat transfer in the presence of high wall temperatures are: 1 piston-induced compression heating of the near wall gas which increases the near wall temperature gradient when wall temperatures are high; 2 increased penetration of hot, burned gases into the near wall flow during combustion through reduction of the flame quench distance.

An important aspect of calculation of engine combustion chamber heat transfer with a multi-dimensional flow code is the modeling of the near wall flow. Conventional treatments of the wall layer flow employ the use of wall functions which impose the wall boundary conditions on the solution grid points adjacent to solid boundaries. However, the use of wall functions for calculating complex flows such as those which exist in engines has numerous weaknesses, including dependence on grid resolution. An alternative wall modeling approach has been developed which overcomes the limitations of the wall functions and is applicable to the calculation of in-cylinder engine flows. In this approach the wall layer flow is solved dynamically on a grid spanning a very thin boundary layer region adjacent to solid boundaries which is separate from the global grid used to solve the outer flow.

A detailed research program has been initiated to study the modeling aspects of turbulent heat transfer in engine applications using multidimensional codes. The main concerns are the representation of turbulent transport in flow regions that differ significantly from constant-pressure boundary layers for which the currently used models have been developed and validated. Both the treatment of near-wall and bulk-flow transport are being investigated. Models are being tested on several representative test cases. A number of such test cases have been identified, which contain key flow features relevant to engine applications and for which a good experimental data base exists. Calculations of these test cases have been made using a standard k-ε model.

A comprehensive simulation has been developed which describes the dynamic behavior of truck powertrains employing. Detroit Diesel Allison heavy duty diesel engines equipped with the Detroit Diesel Electronic Control System (DDEC). The simulation, was developed to address those issues related to DDEC fuel control that impact upon engine smoke production and upon vehicle driveability and responsiveness, and to identify components in the powertrain which interact with the control system. The simulation contains four major submodels: (1) torque and transient air system model of the 8V-92 turbocharged/inter-cooled two-stroke engine; (2) discrete event, DDEC controller/governor model; (3) tandem rear axle drive, torsionally compliant, manual transmission driveline model; and (4) flexible driver simulator and external event module.