Influence of inflation pressure, speed, load and warm-up phase on rolling resistance of passenger car tyres

Typ
Examensarbete för masterexamen
Program
Automotive engineering (MPAUT), MSc
Publicerad
2021
Författare
Rajopadhye, Chirag
Govardhan Raju, Bharath
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The importance of improving vehicle energy efficiency has risen for modern day automobiles. It’s even more vital for electric vehicles which have limited range. The driving range is an important consideration for any potential customer and is influenced by the vehicle’s energy efficiency. The energy efficiency is governed by the vehicle’s driving resistance forces. In a broad sense, the major contributors to the driving resistance force are the aerodynamic drag, inertial drag and rolling resistance. The rolling resistance accounts for a significant share of the driving resistance and has a direct impact on the fuel consumption and energy efficiency of vehicles. Michelin in their 2003 study ‘The tyre: Rolling resistance and fuel savings’ estimate the average contribution of the tyre’s rolling resistance towards the total resistance to movement varies between 20% and 30%. The present-day industry standard to evaluate a tyre’s rolling resistance is the rolling resistance coefficient (RRc) measured using the ISO 28580 standard in the EU. This method is a single point test and does not account for the variation in the operating parameters such as the tyre’s inflation pressure, speed and the load on the tyre. It also does not include the contribution of the warm-up phase of the rolling resistance which has a significant impact on the energy efficiency of tyres. This impact is especially pronounced for short distance travel during which the tyre does not completely warm up. This thesis work investigated the influence of variation in the inflation pressure, speed and load on the rolling resistance and energy consumption of free rolling passenger car tyres. It also investigated the additional contribution due to the warm-up phase and how this varied with pressure, speed and load for different tyres. The RRc shows a negative correlation with change in inflation pressure and load and a positive correlation with change in speed. The magnitude of change in the RRc due to pressure change serves as a conservative approximation of the corresponding change in the tyre’s energy consumption. The same cannot be applied to the influence of speed and load variation however. This is primarily due to their influence on the contribution of the warm-up phase towards the energy consumption of the tyre. This additional contribution was found to be between 25 - 30 % for short driven distances of 5 km and reduced to 2.5 % at 100 km as compared to the respective steady-state values. This additional contribution was found to correlate positively with an increase in the speed and load levels. Through these findings it was concluded that the consideration of the warm-up phase for estimating the energy efficiency of tires is warranted, especially in the context of short distance travel.
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Rolling resistance , warm-up phase , inflation pressure , speed , load , energy loss
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