Alan Montemayor

42-Volt Electric Air Conditioning System Commissioning and Control for a Class-8 Tractor

The electrification of accessories using a fuel cell as an auxiliary power unit reduces the load on the engine and provides opportunities to increase propulsion performance or reduce engine displacement. The SunLine Class 8 tractor electric accessory integration project is a United States Army National Automotive Center (NAC) initiative in partnership with Cummins Inc., Dynetek Industries Ltd., General Dynamics C4 Systems, Acumentrics Corporation, Michelin North America, Engineered Machine Products (EMP), Peterbilt Motors Company, Modine Manufacturing and Masterflux. Southwest Research Institute is the technical integration contractor to SunLine Services Group. In this paper the SunLine tractor electric Air Conditioning (AC) system is described and the installation of components on the tractor is illustrated. The AC system has been designed to retrofit into an existing automotive system and every effort was made to maintain OEM components whenever modifications were made. Hardware modifications were limited to replacing the engine driven compressor for a 42 volt DC driven one, exchanging the expansion orifice for a thermal expansion valve and positioning the components to minimize the length of refrigerant lines. The thermodynamics and PID control algorithms are discussed. Closed loop test results are presented in controlled ambient conditions. Analysis of reversed Carnot cycle changes due to transient operation and coefficient of performance changes are given. INTRODUCTION The engine driven air conditioning system on the 2002 Peterbilt 385 is used for maintaining a comfortable incab temperature and as a windshield defroster. The Original Equipment Manufacturer (OEM) system includes a Sanden SD7 engine driven compressor that draws approximately 6 kW at full load. One disadvantage of this compressor is that it is the same one that is used on all of their trucks, and therefore it is sized for the trucks with the full size sleeper. Peterbilt and Modine engineers have designed this system to provide up to 25000 BTU/hr of cooling. Other disadvantages of having the engine driven compressor include constant parasitic losses from clutch drag, inability to operate the compressor in its efficient zones, and packaging.

Electric Air Conditioning for Class 8 Tractors

Air conditioning and heating of heavy-duty truck cabs is an important contributor to engine efficiency, fuel economy and driver comfort. The air conditioner condenser coil and engine radiator typically share a common cooling fan, making it necessary to run the large engine cooling fan to provide condenser cooling. Engagement of the radiator cooling fan consumes a large amount of energy, further contributing to engine exhaust and noise emissions. Even under moderate temperature conditions, when the conventional enginedriven air conditioning compressor is not in use, the belt drive system adds a small speed-dependent parasitic load to the engine. Electrically driven air conditioning systems have the potential for lower energy consumption than their mechanical counterparts: Electrically driven air conditioning systems can reduce engine idle time by decoupling the air conditioner system from the engine cooling fan while offering near zero parasitic load when not in use. This paper covers the design, integration, and testing of an electric air conditioning system for a Class 8 tractor for day cab cooling and is a continuation of the efforts initially published in SAE paper 2004-01-1478 [1]. A 42 VDC electric air conditioning system consisting of a variable speed compressor, remote condenser with a variable speed cooling fan, and a thermostatically controlled expansion valve was integrated into an existing Class 8 tractor. The OEM evaporator, in-vehicle ducting, and air speed control were unmodified. The electrical power for the electrified air conditioning system is supplied by a fuel cell auxiliary power unit. The Class 8 tractor has been in-service in the desert of Southern California. Included in the paper is a detailed description of the different control schemes examined and the control scheme implemented. Energy consumption and driver comfort for each scheme is evaluated. Future system improvements and possible system enhancements are also identified. All work has been performed at Southwest Research Institute and SunLine Transit Agency and is funded by the US Army RDECOM TARDEC National Automotive Center (NAC).

Low-Temperature Pumpability of U.S. Army Diesel Engine Oils

Abstract : Borderline oil-pumpability temperatures (BPTs) were determined for U.S. Army diesel engines by cranking experiments conducted in a cold box. The variables investigated included: four different diesel engine types; four different oil viscosity grades; and three different viscosity index improver chemical types. In general, for a given oil, the decreasing order of engine severity (i.e., highest BPT) was: the Continental LDT-465-1C and the Cummins VTA-903T were the most severe, and were approximately equivalent. The GM 6.2L engine was the next least severe with the DDC 6V-53T engine being the overall least severe. The different viscosity index improver chemistries of specially blended test oils included: olefin copolymer (OCP), styrene-isoprene polymer (SI), aNd polymethacrylate (PMA). The PMA-containing 15W-40 oils had superior low-temperature oil pumpability performance in each engine in which they were evaluated.

Laboratory Evaluation of Army Multiviscosity Grade Tactical Engine Oils

Several multiviscosity grade oils were subjected to a special 240-hour endurance test procedure in an Army high-output two-cycle diesel engine, and certain of the oils were laboratory tested in the Armys multifuel, four-cycle compression ignition engine and in the Armys air-cooled four-cycle diesel tank engine. Certain of the lubricants were also subjected to standard hydraulic/power transmission tests because acceptable power transmission performance will now be a formal requirement in the D-revision to the engine lubricant specification MIL-L-2104. Parallel to these laboratory evaluations, pilot field tests were conducted in combat/tactical vehicles (engines and power shift transmissions) at three Army bases. The limited field tests indicated that the use of arctic/conventional multiviscosity grade lubricants at ambient temperatures up to 38 deg C (100 deg F) may be possible, and their introduction under MIL-L-2104 should be pursued. Laboratory test results produced a suitable two-cycle diesel engine lubricants qualification test, and showed that SAE 15W-40 grade oils are acceptable for use in Army diesel-powered combat/tactical engine and power transmission fluid systems. Areas for continued lubricant development are outlined.