Increasing accuracy and repeatability of fuel consumption measurement in chassis dynamometer testing

Abstract

Made available with publisher permission. Always cite as follows: Brace, C. J., Burke, R., Moffa, J., 2009. Increasing accuracy and repeatability of fuel consumption measurement in chassis dynamometer testing.Abstract: The aim of this paper is to identify and investigate the effect of small changes in test conditions when quantifying fuel consumption. Twelve test set-up variables were identified and intentionally perturbed from a standard condition, including the effect of removing the power-assisted steering pump.Initially a design-of-experiments (DoE) approach was adopted and the results showed that most of the tested parameters had significant effects on fuel consumption. Most of these effects were greater than the effect of typical technology changes assessed on chassis dynamometer facilities. For example, an increase of 8.7 per cent in fuel consumption was observed following a 90 min battery discharge from vehicle headlamps. Similarly an increase of 5.5 per cent was observed when the rig was run 3 km/h faster over a drive cycle, and 2.6 per cent when using tyres deflated by 0.5 bar. As a consequence, statistical tolerancing was used to suggest typical tolerances for test rig set-up variables. For example it was recommended that the tyre pressure be controlled to within 0.1 bar and the test rig speed to 0.3 km/h. Further investigations were conducted into the effect of battery discharge, coast-down time, and engine cooling. These highlighted the need for rigorous battery charge management as the battery voltage was found not to be an appropriate measure of the variation in the alternator loading. Coast-down time was found to be a good control measure for a number of set-up variables affecting the rolling resistance of the vehicle. Finally the variations in the engine cooling were quantified using a cumulative engine temperature over a drive cycle. This was found to correlate well with fuel consumption. For each of these subsequent investigations, results were compared with the DoE predictions and found to agree well when considering the relatively low number of tests compared with the number of factors.

Evaluation on effects of using low biodiesel blends in a EURO 5 passenger vehicle equipped with a common-rail diesel engine

“…Some factors are related with experimental setup and equipment, others are engine and vehicle as well driver skills. A 3 km h À1 vehicle speed over the NEDC target speed produces an increasing of 5.5% on the measured fuel consumption [36].…”

“…This allows the fulfillment of the directive requirements, in terms of vehicle speed and timing and allows establishing a comparable data between the different NEDC tests [30]. The system indicates real instant vehicle speed with a resolution of 0.1 km h À1 and timestamp of 0.2 s. Brace et al [36] show that several factors can affect fuel consumption measured with a gravimetric fuel consumption apparatus on a test ring running the NEDC drive cycle. Some factors are related with experimental setup and equipment, others are engine and vehicle as well driver skills.…”

“…Tire inflate pressure, vehicle alignment, engine lubricant fluid level and battery state of charge can have a significant effect on fuel consumption, up to 8.7% at the NEDC, since they can conduct to variations of engine loading [36]. All factors were carefully checked before the NEDC run and kept according vehicle manufacture specifications.…”

Evaluation of the Effects of Biodiesel on Emission and Performance by Comparing the Results of the NEDC and WLTC

“…The conditions of both test vehicle and laboratory have impacts on the results. Brace et al and Loiselle-Lapointe et al studied the effect of testing factors and found out that the battery state of charge, engine oil level, pedal busyness, speed error, road fan speed, vehicle alignment, tire type, tire pressure, and simulated vehicle mass have significant impacts on the results [23,24]. As the same test vehicle was used for all experiments, tire type and vehicle mass were same for all cases.…”

Evaluation, Generation, and Transformation of Driving Cycles

“…Chassis dynamometer experiments are good alternatives to tests on a dedicated track or on-road tests since they give a higher repeatability, lower cost, and better experimental control and supervision. In the past chassis dynamometers usually meant rolls of different dimensions where the surfaces of the rolls are in direct contact with the tires of the vehicle, see, e.g., (Wang et al, 2000;Brace and Moffa, 2009;Carlson et al, 2009). However, in Paper A, a vehicle propulsion laboratory is presented that uses a different type of chassis dynamometer that is mounted directly to the wheel hubs, with the help of adapter plates.…”