Measuring the Influence of Wet Pavement to Energy Consumption: Tests Conducted with Volvo Cars Battery Electric Vehicle EX90
Publicerad
Författare
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The automotive industry has been striving for improved energy efficiency to offer customers
longer range, more sustainable means of transportation and to cut down on CO2
emissions. The introduction of electric driveline greatly improves driveline efficiencies.
However, since battery electric vehicles (BEV) have such high efficiency, other factors
have become more prominent in energy consumption. This includes driving on a wet
road surface which can lead to significantly higher rolling resistance. Since rolling resistance
is one of the two main external energy sinks in BEVs, besides aerodynamic drag, it
is very important to address tire rolling resistance especially when driving on wet pavement.
Some old data is available in the literature on how rain affects rolling resistance
and energy consumption, but the fact that measurement technique and tires have evolved
there is a need to gather new data for modern BEVs and state-of-the-art tires.
The master thesis composed of a 6 month project at Volvo Cars to research and test the impact
wet surfaces have on a BEV’s energy consumption. The tests were done at Hällered
Proving Ground using an all wheel drive (AWD) EX90 as test vehicle driving on different
amount of wet roads. The water film thickness (WFT) were measured as well as power
from the inverter and vehicle dynamics parameters. The two main test categories to assess
the impact were: Coast Down & Constant Speed.
The result concluded that WFT increases the rolling resistance. Often the increase in total
resistance was at least 5% higher. For very wet roads, the resistance is around 6% higher at
low speeds (30 km/h) and around 11% higher at high speeds (120 km/h) indicating some
speed dependence at high WFT. Lastly, a proposed model was introduced where WFT
was it’s own variable meaning that knowing the WFT the road load can be estimated for
that particular vehicle. However, the results for having WFT as it’s own varibale to road
load are not strongly correlated.
Beskrivning
Ämne/nyckelord
Rolling resistance, RRC, water film thickness, wet, wetness, tires, coast down, Battery Electric Vehicle, BEV, Vehicle Energy Efficiency, vehicle, efficiency