Ducted aerodynamic front section of a vehicle

Details Ducted aerodynamic front section of a vehicle Ducted aerodynamic front section of a vehicle

2002-11-27

2004-05-18

Dayoan, D. Glenn (Department: 3612)

Land vehicles: bodies and tops

Bodies

With distinct wind deflector

C296S193110, C296S091000, C180S903000

Reexamination Certificate

active

06736447

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to truck bodies and, more particularly, to aerodynamic front sections of trucks.
BACKGROUND OF THE INVENTION
Motor vehicles, and in particular trucks, are a critical component of the system for transporting materials, goods and people from place to place. The amount of energy required to move such vehicles depends on many factors. For instance, a substantial amount of energy is expended to overcome the resistance encountered in moving the vehicle through air. The amount of energy expended depends in large part on the aerodynamic drag force exerted on the vehicle by the air. A vehicle moving through air experiences a drag force, which may be divided into two components: frictional drag and pressure drag. Frictional drag comes from friction generated generally through the boundary layer as the vehicle passes through the air. Pressure drag results from the net pressure forces exerted as the air flows around the vehicle. A substantial component of the pressure drag is associated with the formation of a low pressure zone behind the vehicle, as evidenced by the formation of a wake behind the vehicle.
The distinction between frictional drag and pressure drag is useful because the two types of drag are due to different flow phenomena. Frictional drag is typically most important for attached flows—that is, where the flow boundary layer has not separated from the vehicle surfaces, and is related to the surface area exposed to the flow. Pressure drag dominates for separated flows, and is generally related to the cross-sectional area of the vehicle facing the air flow. When the drag on vehicle is dominated by pressure drag forces, it will expend far more energy traveling through air than the same vehicle dominated by friction drag forces. It is therefore advantageous in the design of a vehicle to reduce pressure drag forces; thereby increasing the aerodynamic properties and efficiency of the vehicle.
A bluff body, such as a conventional truck hood or front section, produces significant pressure drag at typical highway speeds. One reason for the large pressure drag is the presence of a sharp angle located at a leading edge of the truck hood. More specifically, typical truck front sections include a substantially vertical front surface or grill that meets, along an upper edge, a substantially horizontal top surface. The air flow passing over the front section, therefore, must negotiate an abrupt change in direction as the edge where the hood structure transitions from a substantially vertical orientation to a substantially horizontal orientation. This abrupt turn causes the flow to ‘separate’ from the top surface of the hood, forming a highly turbulent region of air located directly above the top surface of the hood, between the leading edge and the windshield.
In general, when the drag force experienced by a vehicle is dominated by pressure drag, the vehicle is considered to be bluff, and when the pressure drag is relatively small, the vehicle is considered to be streamlined. For a given truck frontal area at typical highway speeds, the pressure drag can contribute significantly to the total drag force, and therefore to the fuel efficiency (or lack thereof) of the vehicle. For example, it is well known that the drag of a cylinder can be ten times larger than a streamlined shape (such as an airfoil) having the same frontal area. It will be apparent to one skilled in the art that it is advantageous to reduce the total drag force exerted upon a vehicle by reducing pressure drag forces.
The front profile of a conventional truck is typically a bluff body. Referring to
FIG. 1
, a perspective view of a prior art Class 8 truck
10
showing an airstream
12
flowing over a hood
16
is depicted. The depicted air stream
12
encounters the conventionally shaped Class 8 truck
10
at the substantially vertical surface of the front surface or grill
14
of the hood
16
. (It will be appreciated that for purposes of the present aerodynamic discussion, the truck's
10
forward motion at highway speeds is equivalent to an air stream
12
having a similar but opposite velocity flowing over a stationary truck.) The air stream
12
turns upwardly as it negotiates the grill
14
, and separates at a leading edge
15
of the hood
16
, thereby forming a vortex or wake region
22
located aft of the leading edge
15
. The airflow separation at the leading edge
15
causes the formation of a large wake region
22
and pressure losses due to eddy formation in the wake region, thereby increasing drag on the vehicle.
Furthermore, in practical applications, the air stream
12
will include ubiquitous highway particulates, e.g. road grime, which are circulated in the eddies formed in the wake region
22
. The eddy driven recirculation of the grime results in an increased rate of deposition of the particulates contained in the air stream
12
upon the hood
16
and windshield
18
. This results in a high rate of road film build-up—thus impairing the driver's vision, and therefore safety, and increasing the amount of labor and stops required to keep the truck's
10
windshield
18
clear, resulting in inefficiency and increased costs.
One method of reducing the bluff body characteristics of the conventional Class 8 truck and thus the resulting aerodynamic drag, is to streamline the outer contours of the front section of the truck
10
. For example, in order to reduce abrupt changes in air flow over the hood, some modern truck hoods have been made to slope downwardly from the windshield toward the front of the truck, creating a less abrupt transition between the front grill
14
of the front section and the top surface of the hood
16
. This more aerodynamic shape reduces the amount of flow separation, and consequently reduces the pressure drag exhibited upon the vehicle. The resulting vehicle shape, however, is significantly different from the aesthetically pleasing bluff-shape body of a conventional Class 8 vehicle. Therefore, although the resulting streamlined shape may be more aerodynamic and thus efficient, it often results in an unappealing aesthetic appearance to many truck operators and purchasers; causing a corresponding decrease in sales and loss of revenue. Further, such a design may still incorporate discontinuous regions, due to packaging for under hood components such as radiators, air ducting, or coolant tanks, that produce abrupt changes in air flow resulting in the creation of a wake region
22
, again allowing road grime to be recirculated to impact and deposit upon the windshield
18
and an increase in drag.
Thus, there exists a need for an aerodynamically designed front section of a motor vehicle that mitigates drag forces and/or reduces grime build-up on the windshield while retaining the aesthetic appeal of a bluff body shape.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the present invention, a truck front section comprising a grill, a hood, and a bridge assembly is provided. The grill has a substantially vertical front surface and an upper portion. The hood has an upper panel with a sloping front end disposed adjacent the grill upper portion. The bridge assembly is disposed above the front end of the hood upper panel and has a pair of oppositely disposed upright end members attached to the hood upper panel. The bridge assembly also has a substantially horizontal aerodynamically shaped member attached to the end members. The upper portion of the grill, the front end of the hood upper panel and the bridge assembly cooperatively form a duct generally disposed above the grill. The duct may be comprised of a single duct portion or multiple duct portions. The duct may discharge into a longitudinal channel formed in the upper panel. The upper portion of the grill may slope rearward. A horizontal width of an inlet of the duct may extend across substantially the entire length of the upper portion of the grill.
In accordance with aspects of another embodiment formed in accordance with the present invention, a

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