In Use Determination of Aerodynamic and Rolling Resistances of Heavy-Duty Vehicles

A vehicle’s air drag coefficient (Cd) and rolling resistance coefficient (RRC) have a significant impact on its fuel consumption. Consequently, these properties are required as input for the certification of the vehicle’s fuel consumption and Carbon Dioxide emissions, regardless of whether the certification is done via simulation or chassis dyno testing. They can be determined through dedicated measurements, such as a drum test for the tire’s rolling resistance coefficient and constant speed test (EU) or coast down test (US) for the body’s air Cd. In this paper, a methodology that allows determining the vehicle’s Cd·A (the product of Cd and frontal area of the vehicle) from on-road tests is presented. The possibility to measure these properties during an on-road test, without the need for a test track, enables third parties to verify the certified vehicle properties in order to preselect vehicle for further regulatory testing. On-road tests were performed with three heavy-duty vehicles, two lorries, and a coach, over different routes. Vehicles were instrumented with wheel torque sensors, wheel speed sensors, a GPS device, and a fuel flow sensor. Cd·A of each vehicle is determined from the test data with the proposed methodology and validated against their certified value. The methodology presents satisfactory repeatability with the error ranging from −21 to 5% and averaging approximately −6.8%. A sensitivity analysis demonstrates the possibility of using the tire energy efficiency label instead of the measured RRC to determine the air drag coefficient. Finally, on-road tests were simulated in the Vehicle Energy Consumption Calculation Tool with the obtained parameters, and the average difference in fuel consumption was found to be 2%.

Rolling Resistance Estimation for PCR Tyre Design Using the Finite Element Method

This study presents rolling resistance estimation in the design process of passenger car radial (PCR) tyre by using finite element method. The rolling resistance coefficient of tyres has been becoming one of main requirements within the regulation in many countries as it is related to the level of allowable exhaust gas emission generated by vehicle. Therefore, the tyre being designed must be digitally simulated using finite element method before the tyre is manufactured to provide a high confident level and avoid unnecessary cost related to failure physical product testing. The simulation firstly computes the deformation of several alternative designs of tyres under certain loading, and then the value of deformation force in each tyre component during deformation took place is calculated. The total force of deformation is considered as energy loss or hysteresis loss resulted in tyre rolling resistance. The experiment was carried out on three different tyre designs: two grooves, three grooves, and four grooves. The four groove tyre design gave the smallest rolling resistance coefficient (RRC). Finally, the simulation was continued to compare different crown radius of the tyres and the result shows that the largest crown radius generates the lowest rolling resistance.

The selection of the tail lift parameters

People moving on wheelchairs overcome the forces of resistance such as: air resistance, resistance of the ascent, inertia force and rolling resistance force. Under certain conditions of use of the wheelchair, the only resistance that must overcome the driving force during the movement is the rolling resistance force. This situation occurs during uniformly rectilinear movement, on a flat level surface at speeds of up to 20 km/h, because at this speed the air resistance is negligible. Rolling resistance is mainly influenced by the mass of the rolling object and the rolling resistance coefficient of the running gear. The value of the rolling resistance coefficient can be influenced, among others, by the surface, type and level of pressure in the tire, and the measurement method. There are test methods that in the resistance of rolling beyond the resistance resulting from the contact of the tire with the surface take into account the resistance to connection of the wheel with the driven object. One of them is the innovative method of measuring the rolling resistance coefficient of objects equipped only with the running gear according to the patent application P.424484 and the developed device for these tests in accordance with the patent application P.424483. The article presents the results of wheelchair rolling resistance test with a classic drive system and wheel attachment. These results show differences in the aspect of rolling resistance of classic wheelchairs with wheelchairs equipped with innovative propulsion solutions, such as a lever drive system or a hybrid drive. The study was financed from the means of the National Centre for Research and Development under LIDER VII programme, re-search project no. LIDER/7/0025/L-7/15/NCBR/2016.

Determination of the rolling resistance coefficient of pneumatic wheel systems

The basic resistance during moving objects that are equipped with a circular system is rolling resistance. In objects powered by muscle power, such as: bicycles, wheelchairs, mobile machines, shelves and storage trolleys, the problem of rolling resistance limitation is more important than in the case of structures powered by engines characterized by a significant excess of driving force relative to the sum of resistance forces. Research is being carried out on limiting the rolling resistance force, however, there is a lack of methods for measuring this parameter in the actual operating conditions of devices with a drive system without a drive unit. In the article for research, an innovative method was used of measuring the rolling resistance coefficient of objects equipped only with the rolling chassis of accordance with the patent application P.424484 and a test device compatible with the patent application P.424483. The study involved a pneumatic wheel commonly used in wheelchairs, the use of which gains popularity with increased interest in the construction of electric or diesel vehicles with low energy demand. Examples of such vehicles are available during the Shell Eco-marathon competition. The study was financed from the means of the National Centre for Research and Development under LIDER VII programme, research project no. LIDER/7/0025/L-7/15/NCBR/2016.