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Title Investigation of the transient nature of rolling resistance on an operating Heavy Duty Vehicle
Publication Date
Discipline/Department Physics
University/Publisher Umeå University
Abstract An operating vehicle requires energy to oppose the subjected driving resistances. This energy is supplied via the fuel combustion in the engine. Decreasing the opposing driving resistances for an operating vehicle increases its fuel efficiency: an effect which is highly valued in today’s industry, both from an environmental and economical point of view. Therefore a lot of progress has been made during recent years in the area of fuel efficient vehicles, even though some driving resistances still rises perplexity. These resistances are the air drag F<sub>d</sub> generated by the viscous air opposing the vehicles propulsion and the rolling resistance F<sub>rr</sub> generated mainly by the hysteresis caused by the deformation cycle of the viscoelastic pneumatic tires. The energy losses associated with the air drag and rolling resistance account for the majority of the driving resistances facing an operating vehicle, and depends on numerous stochastic and ambient parameters, some of which are highly correlated both within and between the two resistances. To increase the understanding of the driving mechanics behind the energy losses associated with the complexity that is rolling resistance, a set of complete vehicle tests has been carried out. These tests were carried out on the test track Malmby Fairground, using a Scania CV AB developed R440 truck equipped with various sensors connected in one measurement system. Under certain conditions, these parameters can allow for an investigation of the rolling resistance, and a separation of the rolling resistance and air drag via explicit subtraction of the air drag from the measured traction force. This method is possible since the aerodynamic property A<sub>HDV</sub>C<sub>d</sub>(β) to some extent can be generated from wind tunnel tests and CFD simulations. Two measurement series that enable the above formulated method of separation were designed and carried out, using two separate measurement methods. One which enables the investigation of the transient nature of rolling resistance as it strives for stationarity, where the vehicle is operated under constant velocities i.e. no acceleration, and one using the well established method of coastdown, where no driving torque is applied. The drive cycles spanned a range of velocities, which allowed for dynamic and stationary analyses of both the tire temperature- and the velocity dependence of rolling resistance. When analysing the results of the transient analysis, a strong dependence upon tire temperature for given constant low velocity i.e. v ≤ 60 kmh<sup>−1</sup> was clearly visible. The indicated dependency showed that the rolling resistance decreased as the tire temperature increased over time at a given velocity, and vice versa, towards a stationary temperature and thereby rolling resistance. The tire temperature evolution from one constant velocity to another, took place well within 50 min to a somewhat stationary value. However, even though the tire temperature had reached stationarity, rolling…
Subjects/Keywords Rolling resistance; Air drag; Heavy Duty Vehicles; Vehicle dynamics; Complete vehicle test; Coastdown; Effective radius; ACEA; Pneumatic tires; Driving resistances; Energy efficiency; Rullmotstånd; Luftmotstånd; Tunga fordon; Fordonsdynamik; Helfordonstest; Utrullningstest; Effektiv radie; ACEA; Pneumatiska däck; Körmotstånd; Energieffektivitet.
Language en
Country of Publication se
Record ID oai:DiVA.org:umu-93298
Repository diva
Date Indexed 2020-01-03

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