Preliminary investigation towards next generation truck design for aerodynamic efficiency
Par Conseil national de recherches du Canada
Preliminary investigation towards next generation truck design for aerodynamic efficiency
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| DOI | Trouver le DOI : https://doi.org/10.4224/40002956 |
| Auteur | Rechercher : McAuliffe, Brian R.1; Rechercher : Ghorbanishohrat, Faegheh2; Rechercher : Barber, Hali1 |
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| Format | Texte, Rapport technique |
| Description physique | 63 p. |
| Résumé | Emerging zero-emission heavy-duty vehicle (ZEHDV) concepts are exhibiting changes in shape from conventional heavy-duty vehicles (HDVs) that include characteristics associated with improved aerodynamic performance, including smaller front cooling-air inlets, angled wind shields and large corner radii. A project has been initiated under Transport Canada’s ecoTECHNOLOGY for Vehicle program to examine the potential energy savings and range extension of ZEHDVs associated with reduced aerodynamic drag. As a first step towards demonstrating this potential, and to support regulatory-development information requests from a project stakeholder (the U.S. Environmental Protection Agency, EPA), a test campaign was undertaken in the NRC 9 m Wind Tunnel using a 30%-scale tractor-trailer model to examine the aerodynamic-drag benefits of HDVs associated with a ZEHDV shape. Three experimental tasks were carried out to examine changes to the aerodynamic drag of HDV and ZEHDV shapes for: 1) combinations of three different tractor and three different trailer configurations; 2) the addition of fender mirrors to, or the removal of main mirrors from, two tractor shapes; and 3) different flow conditions representing the wakes of various upstream-traffic conditions.
Experiments were undertaken using a 30%-scale tractor trailer model with appropriate groundsimulation conditions (spinning wheels and a moving ground plane). Three tractor models, including a day-cab shape, a sleeper-cab shape, and a zero-emission-cab shape, were each tested with three dry-van-trailer configurations with varying levels of trailer-aerodynamic technologies (no technologies, with side-skirts, and with side-skirts and a boat-tail). The zero-emission-cab shape was a first attempt at an improved shape, based on fundamental aerodynamic-shaping strategies, and was an adaptation of the day-cab model. The day-cab and zero-emission-cab tractor models were each tested with the standard main mirrors, with the addition of fender mirrors, and without any mirrors. These experiments were conducted in uniform-flow conditions with road-representative free-stream turbulence. Additionally, the zero-emission-cab model was tested in some traffic-wake scenarios representing real on-road conditions when following other vehicles, such as a compact sedan, a sport-utility vehicle, and another HDV, or when travelling in an adjacent lane to these vehicles.
Drag-coefficient and drag-area results show that changes to the shape of a day-cab tractor, based on aerodynamic considerations to represent emerging ZEHDV shapes, reduced the aerodynamic drag-area of the vehicle by 7-9%, representing about one EPA bin level (0.5 m²). The results further show that aerodynamic improvements to the ZEHDV shape demonstrated less sensitivity to trailer configuration than did the conventional day-cab and sleeper-cab shapes. Conversely, this demonstrates that trailer-device performance was less sensitive to the ZEHDV shape than to the conventional shapes. These outcomes suggest that, with reasonable efforts to optimize the shape of HDVs based on new drivetrain/chassis architectures,Emerging zero-emission heavy-duty vehicle (ZEHDV) concepts are exhibiting changes in shape from conventional heavy-duty vehicles (HDVs) that include characteristics associated with improved aerodynamic performance, including smaller front cooling-air inlets, angled wind shields and large corner radii. A project has been initiated under Transport Canada’s ecoTECHNOLOGY for Vehicle program to examine the potential energy savings and range extension of ZEHDVs associated with reduced aerodynamic drag. As a first step towards demonstrating this potential, and to support regulatory-development information requests from a project stakeholder (the U.S. Environmental Protection Agency, EPA), a test campaign was undertaken in the NRC 9 m Wind Tunnel using a 30%-scale tractor-trailer model to examine the aerodynamic-drag benefits of HDVs associated with a ZEHDV shape. Three experimental tasks were carried out to examine changes to the aerodynamic drag of HDV and ZEHDV shapes for: 1) combinations of three different tractor and three different trailer configurations; 2) the addition of fender mirrors to, or the removal of main mirrors from, two tractor shapes; and 3) different flow conditions representing the wakes of various upstream-traffic conditions.
Experiments were undertaken using a 30%-scale tractor trailer model with appropriate groundsimulation conditions (spinning wheels and a moving ground plane). Three tractor models, including a day-cab shape, a sleeper-cab shape, and a zero-emission-cab shape, were each tested with three dry-van-trailer configurations with varying levels of trailer-aerodynamic technologies (no technologies, with side-skirts, and with side-skirts and a boat-tail). The zero-emission-cab shape was a first attempt at an improved shape, based on fundamental aerodynamic-shaping strategies, and was an adaptation of the day-cab model. The day-cab and zero-emission-cab tractor models were each tested with the standard main mirrors, with the addition of fender mirrors, and without any mirrors. These experiments were conducted in uniform-flow conditions with road-representative free-stream turbulence. Additionally, the zero-emission-cab model was tested in some traffic-wake scenarios representing real on-road conditions when following other vehicles, such as a compact sedan, a sport-utility vehicle, and another HDV, or when travelling in an adjacent lane to these vehicles. Drag-coefficient and drag-area results show that changes to the shape of a day-cab tractor, based on aerodynamic considerations to represent emerging ZEHDV shapes, reduced the aerodynamic drag-area of the vehicle by 7-9%, representing about one EPA bin level (0.5 m2). The results further show that aerodynamic improvements to the ZEHDV shape demonstrated less sensitivity to trailer configuration than did the conventional day-cab and sleeper-cab shapes. Conversely, this demonstrates that trailer-device performance was less sensitive to the ZEHDV shape than to the conventional shapes. These outcomes suggest that, with reasonable efforts to optimize the shape of HDVs based on new drivetrain/chassis architectures,significant energy savings from aerodynamic improvements are possible over conventional North-American HDV shapes.
The main- and fender-mirror test results showed that drag reductions on the order of 4% are possible with the removal of all mirrors from an HDV tractor. Drag changes of 1-2% were documented for fender mirrors, and 3% for main mirrors. These results suggest that reducing mirror size, changing their location, or replacing mirrors with low-drag camera-based rearview systems, can provide measurable energy savings for long-haul HDV applications.
The wake-effects testing, documented strictly for the ZEHDV model here, showed that the model experienced reduced aerodynamic drag in excess of 10% when exposed to the wakes of the specific forward-traffic conditions examined, which represent safe driving distances, even with traffic in an adjacent lane. These results provide some additional evidence that HDVs are experiencing the aerodynamic platooning effect in everyday traffic. The reduced aerodynamic drag from traffic-wake conditions suggests that current estimates of greenhousegas (GHG) emissions via tools like the EPA Greenhouse-gas Emission Model (GEM) may not consider the lower drag of HDVs when driving in traffic, and may therefore be overestimating GHG reductions from aerodynamic technologies/improvements via CDA values measured or assessed for isolated driving conditions.
The results presented in this report regarding the drag reduction associated with one new concept should be considered a precursory study. The findings provide a basis for next steps in examining the potential benefits of emerging ZEHDV shapes. |
| Date de publication | 2022-07-04 |
| Maison d’édition | National Research Council of Canada. Aerospace |
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| Langue | anglais |
| Publications évaluées par des pairs | Non |
| Exporter la notice | Exporter en format RIS |
| Signaler une correction | Signaler une correction (s'ouvre dans un nouvel onglet) |
| Identificateur de l’enregistrement | 610b10b1-805a-4047-a908-174b18a0ea07 |
| Enregistrement créé | 2022-11-08 |
| Enregistrement modifié | 2022-11-08 |
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