Search Results

As part of the evaluation of vehicle simulation models, a vehicle dynamics engineer typically desires to compare simulation results to test data from actual vehicles and/or results from known, or higher fidelity simulations. Depending on the type of model, several types of tests and/or maneuvers may need to be compared. For military vehicles, there is the additional requirement to run specific types of maneuvers for vehicle model evaluations to ensure that the vehicle complies with procurement requirements. A thorough evaluation will run two different categories of tests/maneuvers. The first category consists of laboratory type tests that include weight distribution, kinematics and compliance, steering ratio, and other static measures. The second category consists of dynamic maneuvers that include handling, drive train, braking, ride, and obstacle types. In this paper, a process for proper evaluation of vehicle simulation models is presented.

A Stewart & Stevenson M1084A1 FMTV 5-ton cargo truck was used as the subject of a study to evaluate advanced powertrain thermal management components and subsystems. Funded by the U.S. Army TACOM and the National Automotive Center (NAC) under a Small Business Innovative Research grant (SBIR Phase II), the project focused on improving thermal management of the vehicle while reducing the peak fuel consumption by >10% in a vehicle having limited ram air cooling. The FMTV was used as a surrogate test bed to investigate thermal management technologies that could be applied to vehicles with confined package space, such as light armored vehicles. The vehicle was equipped with a thermal management system featuring distributed system architecture, electric coolant pumps and fans, electronic control valve, multiple air-cooled heat exchangers, and an electronic control system with PID feedback. The entire thermal management system was mounted in a metal enclosure behind the truck cab.

Army's next generation vehicles require more electric and electronic devices with increasing power density for improved multi-functionality. The increasing waste heat from these devices will present great challenges to the capabilities of conventional air/liquid cooling systems in cooling multiple, high heat flux sources dispersed over the entire vehicle. In this paper, a high performance hybrid loop thermal bus technology for vehicle thermal management is presented. The technology combines the robust operation of pumped two-phase flow cooling with the simplicity of capillary flow management. The test results show the hybrid loop thermal bus can manage multiple high heat flux heat sources during the startup and transient heat input operation with no flow control.

High-pressure fuel injection combustion is being applied as an approach to increase the power density of diesel engines. The high-pressure injection enables higher air utilization and thus improved smoke free low air-fuel ratio combustion is obtained. It also greatly increases the injection rate and reduces combustion duration that permits timing retard for lower peak cylinder pressure and improved emissions without a loss in fuel consumption. Optimization of these injection parameters offers increased power density opportunities. The lower air-fuel ratio is also conducive to simpler air-handling and lower pressure ratio turbocharger requirements. This paper includes laboratory data demonstrating a 26 percent increase in power density by optimizing these parameters with injection pressures to 200 mPa.

U.S. Army arctic engine oil, MIL-L-46167B, designated OEA, provides excellent low-temperature operation and is multi functional. It is suitable for crankcase lubrication of reciprocating internal combustion engines and for power-transmission fluid applications in ground equipment. However, this product required 22-percent derated conditions in the two-cycle diesel engine qualifications test. Overall, OEA oil was limited to a maximum ambient temperature use of 5°C for crankcase applications. The technical feasibility of developing an improved, multi functional arctic engine oil for U.S. military ground mobility equipment was investigated. The concept was proven feasible, and the new oil, designated as OEA-30, has exceptional two-cycle diesel engine performance at full engine output and can be operated beyond the 5°C maximum ambient temperature limit of the MIL-L-46167B product.

An advanced low heat rejection engine concept has successfully completed a 100 hour endurance test. The combustion chamber components were insulated with thermal barrier coatings. The engine components included a titanium piston, titanium headface plate, titanium cylinder liner insert, M2 steel valve guides and monolithic zirconia valve seat inserts. The tribological system was composed of a ceramic chrome oxide coated cylinder liner, chrome carbide coated piston rings and an advanced polyolester class lubricant. The top piston compression ring Included a novel design feature to provide self-cleaning of ring groove lubricant deposits to prevent ring face scuffing. The prototype test engine demonstrated 52 percent reduction in radiator heat rejection with reduced intake air aftercooling and strategic forced oil cooling.