Testing a Heavy Duty Class 8 Truck, Green Tech, Page 1
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Page content: Les Rencontres Scientifiques d'IFP Energies nouvelles - Int. Scient. Conf. on hybrid and electric vehicles RHEVE 20116-7 December 2011 Proceedings Copyright 2011, IFPEN Hardware-in-the-loop Testing of a Heavy Duty Class 8 Truck Ashok Nedungadi, John Bishop Southwest Research Institute, San Antonio, TX 78228, USA, anedungadi@swri.org Southwest Research Institute, San Antonio, TX 78228, USA, john.bishop@swri.org Abstract - Hardware-in-the-loop Testing of a Heavy Duty Class 8 Truck - Thispaper describes an engine-in-the-loop test facility to quantify the fuel economy benefits ofelectrified accessories. Engine emissions were not included in this study. The vehicle modeling andsimulation software that is at the core of this component-in-the-loop test is mentioned. The twomain mechanical accessories of the heavy duty Class 8 truck, the engine fan and water pump, wereelectrified. The reasoning for this is also presented in this paper. The configuration of the electricfan and water pump are described in more detail. Two different on-road driving cycles are compared interms of fuel consumption of the engine with mechanical and electrical accessories. Discussionsinclude advantages and disadvantages of electrified accessories, and which drive cycles appearto favor accessory electrification.INTRODUCTION In addition to improved fueleconomy, the literature has reported several advantages for accessoryElectrified accessories continue to be a major focus for electrification, namely: improvedvehicle performance,engine OEMs to gain additional fuel economy. In the accessory performance, and enginecooling andpast, the heavy truck accessories that have been improved emissions due to moreeffective thermaltargeted include (ordered in terms of impact on fuel management with better enginecooling/heatingeconomy): engine cooling fan, air-conditioning distribution [Ref 4, 5]. Thedownside of electrifiedcompressor, brake system air compressor, engine water accessories is the potential needfor a 42 V electricalpump and power steering pump. The motivation for bus that is not standard oncurrent truck chassis.targeting vehicle accessory systems are: (a) themechanical accessory systems are generally designed The truck industry has ampleexamples that quantify theto meet a low engine speed requirement; (b) their design fuel economy benefits ofelectrified accessories overgenerally results in the accessories being oversized transient and highway drivingcycles. It should be notedduring higher engine speed operation; (c) some that the examples and the fuelsavings discussed withinaccessory systems have a constant power draw even this paper are application andduty cycle dependent. Awhen not in use [Ref 1, 2]. Figure 1 shows examples of 1.2% improvement in fuel economywas reported for aaccessory systems that have excessive capacity at Volvo tractor with a CumminsN14-480 Hp (343 kW)higher engine speeds [Ref 3]. engine over the EPA FTP drivecycle [Ref 6]. The repeatability between individualtests was not available 35 in the cited reference. APeterbilt tractor/trailer with a Cummins ISL 246kW engine reportedenergy 30 consumption of an electrical pumpto be from 6% to 19% less than that of the mechanicalpump [Ref 7]. Faster 25 warm-up in an automotive dieselengine reduced FLO W RATE (L/m in) emissions and a Toyota Priusdemonstrated improved 20 fuel economy of 1% to 4% [Ref 8,9]. 15 To further demonstrate this, astudy was conducted of a 10 heavy tractor truck with a 246 kWengine that was driven across the U.S; the results aresummarized in Table 1 5 [Ref 10]. The study was performedduring the summer months and utilized the airconditioner during most of the 0 trip. The vehicle used 836.6Liters of diesel fuel during 0 1 2 3 4 5 the 3952 km trip. It wasestimated that the electric ROTATION SPEED (X 1000 rpm) cooling fans saved 349.7 litersof diesel fuel during this trip [Ref 10]. Much of the fuelsavings is due to a moreFigure 1: Accessory Systems with Excessive Capacity efficient and smallerair-conditioning compressor and | ||||||
