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Title COMPARISON OF DRAG AREA ESTIMATION USING NATURAL COAST DOWN AND CONSTANT SPEED TEST METHODS
URL
Publication Date
Degree MS
Discipline/Department Mechanical and Aerospace Engineering
Degree Level thesis
University/Publisher West Virginia University
Abstract Currently in US, more than 26 percent of the total GHG emissions comes from transportation and mostly from heavy duty vehicles. Similarly, the European Council stated that 25 percent of the emissions comes from heavy duty transportation and they expect it to be further increased in the future. However, with the new coming regulations US EPA and European Council aiming to reduce the emissions by 80 percent in US and 60 percent in EU. In order to keep track and control the emissions, both authorities published new regulations and testing methods for certifying the new vehicles. Aerodynamic testing is one of the most important part of certification since, aerodynamic drag is a major contributor of total road load acting on a vehicle which is highly related with emissions of a vehicle. Besides, simulation tools for certification such as “Vehicle Energy Consumption Calculation Tool (VECTO)” and “Greenhouse Gas Emission Model (GEM)” needs drag area ( ) as an input. Moreover, it is essential to determine the drag area correctly, therefore, emission of a vehicle, to be able to estimate the amount of total emissions from heavy duty vehicles. Two different regulatory testing methods were published by US EPA and European Council to determine the drag area ( ) for certification of heavy duty vehicles. While US regulations requires “coast-down (CD)” test, EU regulations requires “constant speed (CST)” test. The objective of this study is to compare these two different regulatory approaches with their different assumptions. In order to be able to make a comparison of these two testing methods, CD and CST performed with same tractor and trailer combination, which is a Class 8 truck for US market, in same conditions. Results yielded up to 9 percent difference between two methods. Possible cause of this difference can be listed as, the different assumptions of each testing method such as speed dependency of losses, different approaches for tire rolling resistance and some neglected or unaccounted loses. These possible reasons were also investigated individually in this study.
Subjects/Keywords Coast-down; fuel consumption; constant speed test; chassis dynamometer; drag area; drag coefficient; tire rolling resistance; Navigation, Guidance, Control, and Dynamics; Other Mechanical Engineering
Contributors Arvind Thiruvengadam; Marc C. Besch; Marc C. Besch
Country of Publication us
Record ID oai:researchrepository.wvu.edu:etd-4976
Repository wvu
Date Retrieved
Date Indexed 2020-07-20
Created Date 2019-01-01 08:00:00

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…41 vii List of Figures FIGURE 2-1: FORCES ACTING ON A MOVING VEHICLE ............................................................................ 4 FIGURE 2-2: TIRE ROLLING RESISTANCE

…APPLIED DURING COAST DOWN TESTING ................................ 22 TABLE 3-6: WEATHER CONDITIONS DURING COAST DOWN TESTING .................................................. 23 TABLE 3-7: RESULTS OF TIRE ROLLING RESISTANCE TEST…

…conditions and generally it is found experimentally[3]. 5 2.3.Tire Rolling Resistance (𝑭𝑹𝑹 ) Tire rolling resistance can be defined as the energy dissipated by a tire per unit of distance covered due to the visco-elastic effect of…

…the material of tires made (i.e. rubber) [4]. Tire rolling resistance is a function of the load on the tire and the speed of the tire and can be written as; 𝐹 = 𝑛 𝑃∝ 𝐿 𝑛 (𝑎 + 𝑏𝑣̅ + 𝑐𝑣̅ ) (2.3)…

…Where; ∝, 𝛽, 𝑎, 𝑏 and 𝑐 are the tire rolling resistance regression coefficient, 𝑛 is the number of tires, 𝑃 is the cold inflation pressure [kPa], 𝐿 is the load over the axle [N], Figure 2-2: Tire Rolling Resistance (…

…calculated for high and low speed ranges and the difference between high and low speed ranges gives us ∆𝐹 . Another loss which is captured by the coast down test but not relevant with drag area is the tire rolling resistance. For this reason, it must be…

…subtracted from coast down data. In order to determine the tire rolling resistance coefficients, one of the drive axle tires was sent to Smithers Rapra North America’s Ravenna Laboratory. Tire rolling resistance coefficients determined by the “Stepwise Coast…

…Down Methodology for Measuring Tire Rolling Resistance” defined in the SAE J2452 standard. The result of the test provide the regression coefficients required to estimate the tire rolling resistance for different speeds. Tire rolling resistance can be…

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