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Vehicle functional requirements, diesel emission regulations, and subsystem thermal limits all have a direct impact on the design of a powertrain cooling airflow system. Severe duty cycles, minimal ram air, fouling, and sometimes unconventional package layouts present unique challenges to the designer. This course introduces many airflow integration issues and vehicle-level trade-offs that effect system performance and drive the design. The goal of this course is to introduce engineers and managers to the basic principles of diesel cooling airflow systems for commercial and off-road vehicles.

This report is a contribution to the understanding of inlet aerodynamics and cooling system resistance. A characterization of the performance capability of a vehicle front-end and underhood, called the ram curve, is introduced. It represents the pressure recovery/loss of the front-end subsystem - the inlet openings, underhood, and underbody. The mathematical representation, derived from several experimental investigations on vehicles and components, has four basic terms: Inlet ram pressure recovery; free-stream energy recovered when the vehicle is moving Basic inlet loss; inlet restriction when the vehicle is stationary Pressure loss of the engine bay Engine bay-exit pressure Not surprisingly, the amount of frontal projection of radiator area through the grille, bumper and front-end structure (called projected inlet area), and flow uniformity play a major role in estimating inlet aerodynamic performance.

There is a recognized need in the industry to improve the quality of our CFD (Computational Fluid Dynamics) processes. One part of that initiative is to measure the accuracy of the current processes and identify opportunities for improvement. This report documents the results of a disciplined calibration process that uses statistical analyses techniques to assess CFD quality. The process is applied to UH3D, a Navier-Stokes solver used at Ford to model vehicle front-end geometry and engine cooling systems. The study is focused on a Taurus under relatively ideal circumstances to address one of the major deliverables from the analytical process, i.e., what is the accuracy of the front-end cooling airflow predictions? To address this question, high quality isothermal experiments and calculations were conducted on twenty-three front-end configurations at four non-idle operating conditions.

A literature search to identify deleterious effects of using re-refined oil did not disclose any validated occurrences. Significant engine testing using re-refined lubricating oil is reported and no cases were discovered in which engine operation was affected negatively by the use of re-refined oil. The American Petroleum Institute (API) allows the use of re-refined base stock oils in the blending of end use lubricants. Based on oil sample testing performed in this research as well as other authoritative sources, it was determined that no significant chemical or physical differences exist between re-refined and virgin oils. Differences noted in this research were related to higher levels of poly-nuclear aromatics (PNA's) in the re-refined oil. PNA's are formed due to the extreme conditions of temperature and pressure during operation of an internal combustion engine.

A single-cylinder, 4-stroke, spark-ignition engine was used to evaluate the effect of oxygen enriched air on engine performance and exhaust emissions. Evaluations were made with both gasoline and natural gas. The oxygen content of the intake air was varied between 20.9% (ambient air) and 25%. The effects of oxygen enrichment were evaluated in terms of power output, specific fuel consumption, fuel conversion efficiency, exhaust gas temperature, and exhaust emissions (carbon monoxide and hydrocarbons). Test results indicate that the use of oxygen enriched air produces a significant increase in power output, improved fuel conversion efficiency, lower specific fuel consumption, higher exhaust gas temperature and a substantial reduction in carbon monoxide and hydrocarbon emissions when the engine is fueled with either gasoline or natural gas.

Mechanical Engineering students at Texas Tech participated in the 1989 SAE Methanol Marathon in which a 1988 Chevrolet Corsica was converted to run on M85, a blend of 85% methanol and 15%hydrocarbon fuel. This report describes modifications to the Corsica accomplished in preparation for the continuation of this program, the 1990 SAE Methanol Challenge. The modified Corsica place second overall. In response to the 1990 program requirements, the Corsica was modified to enhance engine, transmission, and suspension performance. Engine modifications include improving cylinder head flow efficiency, changing cam profiles, modifying the engine bore and stroke, using lighter weight pistons with modified rings, using roller-tip rocker arms, enlarging the exhaust runner ports, and installing a specially developed catalytic converter system. The transmission was modified with a lower ratio fifth gear and the suspension was strengthened.

With the increasing emphasis on and importance of aerodynamics on vehicle fuel economy and handling, conservative approaches to sizing front-end cooling openings based on projected radiator area need to be replaced by a performance-based method. The method would not only allow more flexibility in front-end styling, but would enable the design of the grille, cooling hardware and vehicle heat rejection requirements to be based on the cooling performance of the total vehicle. The reductions in cooling drag and front lift from smaller, but more functional, grille openings would improve vehicle fuel economy and handling. A performance-based front-end design approach is described in the paper along with some selected experimental results. The method is based on an experimental technique for simultaneously measuring the total radiator airflow and vehicle aerodynamic performance in an aerodynamic wind tunnel.

This paper describes the computational technique used to predict flow over and through the front end of vehicles; this scope includes flow over the hood, around air dams, through condensers, radiators, fans, and in the engine compartment. The computational procedure, employed is a finite-difference method for solving time-averaged equations for turbulent flow using the κ-∈ model. A two-dimensional program was modified to add variable-depth cells (in the direction of car width) so that some three-dimensional features could be included. A turbulence model was used which is applicable to rotational and irrotational areas of the flow field. The total system model was calibrated with wind-tunnel data, and various modifications to the vehicle configuration were studied. Results from the predictions were compared with wind-tunnel test data.