Abstract:
A drag-reduction concept for vehicles with open cavities includes dividing a cavity into smaller adjacent cavities through installation of one or more vertical dividers. The dividers may extend the full depth of the cavity or only partial depth. In either application, the top of the dividers are typically flush with the top of the bed or cargo bay of the vehicle. The dividers may be of any material, but are strong enough for both wind loads and forces encountered during cargo loading/unloading. For partial depth dividers, a structural angle may be desired to increase strength.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority under 35 USC § 119(e) to U.S. Provisional Patent Application No. 60/653,603 titled “Dividers for Reduction of Aerodynamic Drag of Vehicles with Open Cavities”, Filed Feb. 15, 2005, the contents of which are herein incorporated by reference. 
     
    
     STATEMENT OF GOVERNMENT RIGHTS  
       [0002]     This invention was made with Government support under contract number NAS2-03144 awarded by NASA. The Government has certain rights in the invention. 
     
    
     BACKGROUND OF THE INVENTION  
       [0003]     1. Field of the Invention  
         [0004]     The present invention generally relates to the field of transportation vehicles, and more specifically, to devices to reduce aerodynamic drag of vehicles having open cavities.  
         [0005]     2. Description of the Related Art  
         [0006]     Open beds, cargo bays, and cavities are highly inefficient from an aerodynamic perspective. For example, in rail transport systems covering a empty open container car has been shown to reduce drag by as much as 40%. However, covering the bed or cargo bay is seldom practical due the size, the required hardware, and the effort involved. As a result, these vehicles typically operate uncovered on long journeys (up to 1000 miles for coal cars).  
         [0007]     To provide a more detailed example of how inefficient open cargo and bays on transport vehicles, consider an example of transportation in the coal industry. Coal accounts for almost 50% of the total electricity production in the United States alone. Of the total coal consumption, almost two-thirds is carried by rail. By far the most important rail commodity, as of 2002 coal accounted for almost 44% of tonnage, 25% of carloads, and 21% of revenue. In 2002, almost 7.9 million carloads of coal were hauled via rail. Moreover, over 85% of all railroad coal shipments are carried by unit trains of 50 or more carloads. Typically, these shipments transport the coal without interruption from the loading facilities to the power plants.  
         [0008]     Due to the increasing use of low sulfur western coal in power plants throughout the country, the average coal haul has risen significantly in recent years from 558 miles in 1992 to 696 miles in 2001. Over the same period, however, the revenue per ton-mile decreased by 23% due to the competitive environment for coal transportation created by alternate energy sources, transportation modes, and railroads.  
         [0009]     The potential for energy savings by reducing the aerodynamic drag of coal cars is significant. A previous study of aerodynamic drag of coal cars suggests that a 25% reduction in drag of the empty cars would correspond to a 5% fuel savings for a round trip. Since coal transport consumes approximately 1.5 billion gallons of diesel fuel annually, a 5% fuel savings would total 75 million gallons per year. This corresponds to 2% of all Class I railroad fuel consumption.  
         [0010]     Moreover, fuel consumption issues affecting open coal railcars also affects other open container transport vehicles, for example, railroad grain cars, container ships, truck trailers, and even pickups. Reducing aerodynamic drag in each of these transport vehicles would save wear and tear, save energy, and reduce overall fuel consumption.  
         [0011]     Devices to reduce aerodynamic drag do exist, but are either too cumbersome, too costly, or a combination of both. Most prior art deals with cavity coverings. For example, open rail cars can be fitted with a soft or hard covering. However, such coverings must be manually installed resulting in increased manpower and time, which reduces productivity.  
         [0012]     Automated soft covers eliminate or reduce the need for manpower and provide some time savings. However, automated soft covers require machinery to roll the covers over or retract the covers from the cargo bay. This machinery adds extra weight to the vehicle so that fuel savings are significantly reduced or eliminated. Further, soft coverings also are prone to quicker wear and tear so that the frequency of repair and replacement also reduce or eliminate hoped for savings. Moreover, because most open cargo and open bay vehicles are designed for long life with a minimum of moving parts, flexible covers and moving doors end up being very poor options.  
         [0013]     In addition, hard covers also have several drawbacks. Hard covers add weight to the vehicle. The added weight requires an increased need for power to move the transport vehicle so that any fuel savings from reduction of aerodynamic drag are significantly reduced or eliminated due to the increased weight. In most instances, the added weight of a cargo-bay cover will also reduce the amount of cargo that may be transported due to weight restrictions.  
         [0014]     From the above, there is a need for a system and process to reduce aerodynamic drag in open cargo bays and beds of vehicles, which can help energy efficiency and help realize energy savings.  
       SUMMARY OF THE INVENTION  
       [0015]     The present invention includes a system and a method for reducing aerodynamic drag in vehicles with open beds or cargo bays. Examples of such vehicles include train cars, truck trailers, pickup trucks, and any other container with an open cavity. In one embodiment, a drag-reduction concept divides a cavity into smaller adjacent cavities by installing one or more vertical dividers. These dividers may or may not extend the entire height of the cavity depending on the application. The dividers typically run the width of the vehicle. Further, some embodiments may include use of longitudinal dividers.  
         [0016]     In one example embodiment, a coal car includes a long rectangular bay that is divided into four nominally square cavities by installing three dividers. The dividers may extend the full depth of the cavity or only partial depth. In either application, the top of the dividers are typically flush with the top of the bed or cargo bay. The dividers may be of any material, but are configured to be strong enough for both wind loads and forces encountered during cargo loading/unloading. For partial depth dividers, a structural angle may be desired to increase strength.  
         [0017]     Once installed, the dividers are configured to remain rigid. For example, in existing vehicles, the dividers may include metal plates that are retrofitted into the vehicle by welding the plates to opposite walls of the vehicle. In other example embodiments, brackets may be installed into opposite walls of a vehicle to allow a plate to be slid into the brackets and secured through friction or some securing means such as screws, bolts, ties, adhesive, or semi-permanent weldings. Thus, the principles of the present invention are applicable for both permanent and semi-permanent configurations.  
         [0018]     The present invention significantly reduces drag of a coal car at zero yaw angle. Further, the present invention may also significantly reduce drag for crosswind. The drag reduction is due to the fact that the flow over the smaller adjacent cavities is more uniform with reduced down flow and pressure on the back of the cargo bay. A regular recirculating flowfield fills each cavity created by the dividers.  
         [0019]     In addition, the dividers are configured to advantageously allow cargo such as grain, coal, or dirt to be loaded or unloaded with little to no interference. Moroever, the principles and benefits of the present invention are also applicable to other open bed or cargo bay vehicles, for example, cargo trucks, pickup trucks, grain rail cars, container ships, or the like, hence, providing transport systems utilizing the present invention with energy savings and efficiency.  
         [0020]     The features and advantages described in the specification are not all inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]     The invention has other advantages and features which will be more readily apparent from the following detailed description of the invention and the appended claims, when taken in conjunction with the accompanying drawings, in which:  
         [0022]     FIGS. (“FIG.”)  1 A and  1 B illustrate examples of fixed dividers for use in an open air vehicle in accordance with the present invention.  
         [0023]      FIGS. 2A through 2C  illustrate examples of removable dividers for use in an open air vehicle in accordance with the present invention.  
         [0024]      FIG. 3  illustrates an example of triangular dividers for use in an open air vehicle in accordance with the present invention.  
         [0025]      FIG. 4  illustrates an example of flow streamlines in a rail coal car without dividers and with dividers in accordance with the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]     The Figures (“FIG.”) and the following description relate to preferred embodiments of the present invention by way of illustration only. It should be noted that from the following discussion, alternative embodiments of the structures and methods disclosed herein will be readily recognized as viable alternatives that may be employed without departing from the principles of the claimed invention.  
         [0027]     Reference will now be made in detail to several embodiments of the present invention(s), examples of which are illustrated in the accompanying figures. It is noted that wherever practicable similar or like reference numbers may be used in the figures and may indicate similar or like functionality. The figures depict embodiments of the present invention for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the invention described herein.  
         [0028]     The present invention includes incorporating a divider system in an open air vehicle to improve aerodynamic flow. An open air vehicle includes vehicles having an open bed or cargo bay. Examples of open air vehicles include rail coal cars (or other open top rail vehicles such as grain cars), open top truck containers, open top cargo ships, pick up trucks, and the like. For ease of discussion, the present invention will be discussed with reference to rail coal cars, although those skilled in the art will understand that the principles disclosed herein are applicable to other open air vehicles.  
         [0029]     Referring now to FIGS. (“FIGS.”)  1 A and  1 B, they illustrate examples of fixed dividers for use in an open air vehicle in accordance with the present invention. The example embodiments include a cargo bay  110  with a plurality of dividers  130 ,  140 . The cargo bay  110  is structured to include four walls  115   a ,  115   b  and  125   a ,  125   b  and a base (or floor or bottom).  
         [0030]     In the illustrated embodiments, the cargo bay is a cavity created by a rectangular shell of two long length (or elongated) walls  115   a ,  115   b  (generally  115 ) and two short length  125   a ,  125   b  (generally  125 ) walls with the base. Generally, the height of the four walls  115 ,  125  is typically the same (or substantially the same). In rail car, cargo truck trailer, cargo ship, or pickup truck vehicle configurations, the elongated walls (or sidewalls)  115  typically form sides of the vehicle, and the short length walls  125  form a front wall and a back wall of the vehicle. The back wall of the vehicle is typically the wall that is opposite the direction of motion (or direction of propulsion) of the vehicle. Note that vehicles such as pick-up trucks would have dividers that are approximately the height of a bed of the pickup, but could also extend above the top of the bed.  
         [0031]     In the example of  FIG. 1A , two dividers  130  are solid and one divider  140  is perforated. In other embodiments, all the dividers may be solid or all may be perforated. An example of a perforated divider is illustrated in  FIG. 2C  as a rigid member with perforations (e.g., openings, such as holes)  280  as shown in the magnified window view. It is noted that the dividers (both solid and perforated) are configured of a rigid material, for example, a metal (e.g., steel, iron, aluminum), rigid rubber, a plastic (e.g., rigid polycarbonate), wood, or a composite of such materials. Perforated dividers allow the flow of cargo like coal or grain between adjacent compartments resulting in a more even load.  
         [0032]     In the illustrated embodiment, the dividers  130 ,  140  are configured so a top of the dividers  130 ,  140  is substantially flush (e.g., flush or almost flush with) the elongated walls  115   a ,  115   b  of the cargo bay  110  and a bottom of the dividers  130 ,  140  is substantially flush (e.g., flush or almost flush with) with the bottom of the walls  115   a ,  115   b  of the cargo bay  110 . The bottom of the walls  115 ,  125  of the cargo bay  110  typically join (e.g., connected to or molded into) the base or floor of the cargo bay  110 . The illustrated embodiments show the installed dividers  130 ,  140  located equidistant from each other to create four compartments  120  from the cargo bar  110 . It is noted, however, in alternative embodiments that the divider need not be flush with the top (and/or bottom) of the elongated walls  115   a ,  115   b , for example, in configurations such as pick up cargo beds.  
         [0033]     In the example of  FIG. 1B , there are again three dividers  160 ,  170  (in this example also there are two solid dividers  160  and one perforated divider  170 ) spaced equidistant apart. However, in this embodiment, while the top of the dividers  160 ,  170  are substantially flush with the top of the walls  115   a ,  115   b  of the cargo bay  110 , the bottoms of the dividers  160 ,  170  do not reach the bottom of the walls  115   a ,  115   b  or base of the cargo bay  110 . Rather, the dividers are configured to only run a partial length of opposite walls  115   a ,  115   b  of the cargo bay  110 . Here, compartments  180  created by the dividers are “open” along bottom edges of the dividers  160 ,  170 . Hence, as an example, if the cargo bay  110  was loaded with coal, coal from one compartment could push into another compartment by slipping under the divider, e.g.,  170 .  
         [0034]     The embodiments illustrated in  FIGS. 1A and 1B  may be configured so that the dividers are fixedly attached to the elongated walls  115   a ,  115   b , of the cargo bay  110 . The dividers may be welded, bolted, attached with adhesive, molded with the elongated  115   a ,  115   b  walls of the cargo bay  110 , or otherwise substantially permanently fixed in place.  
         [0035]      FIGS. 2A through 2C  illustrate examples of removable dividers for use in an open air vehicle in accordance with the present invention. Again, for these example embodiments, a cargo bay  110  is illustrated with one or more dividers spaced equidistant apart. The embodiments in  FIGS. 2A through 2C  illustrate removably configured dividers for use in the cargo bay  110 . In these embodiments, removable dividers  230 ,  260  are held in place in the cargo bay  110  through divider guides (or supports)  240  on the elongated walls  115   a ,  115   b  of the cargo bay  110 .  
         [0036]     Each divider guide  240  is secured to the elongated walls  115   a ,  115   b  of the cargo bay  110  in pairs, i.e., one on one wall  115   a  and one opposite on the facing wall  115   b . One pair is configured to be along the top edge of the elongated walls  115   a ,  115   b  of the cargo bay  110  and the other pair is located along the bottom edge of the elongated wall  115   a ,  115   b  of the cargo bay  110  or along the elongated wall  115   a ,  115   b  where the bottom of the divider  230 ,  260  would reach, e.g., half way down the wall in the case of the short divider  260 .  
         [0037]     Each divider guide  240  includes an opening that is marginally greater than the thickness of the divider  230 ,  260  so that the divider  230 ,  260  can slide through the divider guide  240  as illustrated in the magnified views of  FIGS. 2A through 2C . In addition, the bottom pair of divider guides  240  may also be configured to have a bottom itself so that the bottom of the divider  230 ,  260  rests along a bottom of the divider guide  240 .  
         [0038]     It is noted that the divider guides  240  can be made of any materials that provides substantial rigidity to ensure that the dividers remain in place when secured by them. The divider guides may be made of a metal, a substantially rigid rubber, a polycarbonate, wood, or a combination of materials. In addition, in alternate embodiments, the divider guides  240  can be configured to so that the dividers  230 ,  260  are secured in place using, for example, a nut and bolt configuration, a tie or strap system, an industrial clip configuration, or removable adhesive. Note that each configuration of  FIGS. 2A through 2C  provides a modular design that allows for use of the cargo bay  110  without the dividers  230 ,  260  if so desired.  
         [0039]      FIG. 3  illustrates an example of triangular dividers for use in an open air vehicle in accordance with the present invention. In this example embodiment, the triangular dividers  360  can be frame structures, e.g., three brace structures assembled in a triangular pattern, to which a triangular plate is coupled (e.g., where the triangular bracing already may be in place within the cargo bay) or a substantially solid component in a triangular configuration. The triangular dividers  360  may be held into place by being welded or bolted onto opposing elongated walls  115   a ,  115   b . Alternatively, the triangular dividers  360  may be held into place with a triangular divider support  340  that functions similar to the divider support  240  described previously.  
         [0040]     Two points of the triangular divider  360  can be fixedly or removably attached as pairs along a substantially top edge of the elongated wall  115   a ,  115   b  of the cargo bay  110  as described in the previous embodiments. The third point of the triangular divide is fixedly or removably attached to the base of the cargo bay  110  or to a brace structure  330 . Triangular dividers may be attached to the existing cargo bay bracing typical of modern coal car construction (i.e, bracing is not part of invention).  
         [0041]     The brace structure  330  may traverse from one elongated wall  115   a  to the other elongated wall  115   b  between the base and top of each elongated wall  115   a ,  115   b , e.g., the middle. As with the other embodiments previously described, the triangular dividers  360  may also be configured of a substantially rigid material. Additionally, the triangular dividers  360  may be spaced equidistant apart within the cargo bay  110 .  
         [0042]      FIG. 4  illustrates an example of flow streamlines in a rail coal car without dividers and with dividers in accordance with the present invention. In the illustration of the rail coal car without dividers (top), air flow is shown to create drag by exerting a high pressure region against a back wall  425   a  of the rail car (i.e., the short wall that is away from the direction of movement). In the illustration of the rail coal car with dividers (bottom), the air flow over the top of the coal car drops significantly less than without dividers, into the cargo bay. As a result, the high pressure region on the back wall  425   a  of the cargo bay is reduced along with overall drag.  
         [0043]     It is noted that the cavity may be of shapes other than a rectangle, e.g., a square, hexagon, or the like, with the principles disclosed herein still applicable. Further, it is noted that the embodiments described herein may be mixed and matched, e.g., triangular dividers  360  with full dividers  130  or  230  and/or with short dividers  160 ,  260 . In each instance, the top of the dividers is illustrated as being substantially flush with a top of the walls of the cargo bay  110 . This configuration beneficially provides for more uniform air flow across the top of the cargo bay  110 , and thus, reduces overall aerodynamic drag. However, it is noted that other configurations may also help reduce drag. For example, having a divider that is ¼ of the cargo bay depth below the top of the cargo bay or ¼ of the cargo bay depth higher than the top of the cargo bay still provides the benefit of reducing aerodynamic drag.  
         [0044]     It is also noted that although the dividers have been illustrated and described as being spaced equidistant apart within the cargo bay, they need not always be spaced in such a configuration. Rather, alternative embodiments need only have the dividers spaced sufficiently apart so that air pressure against the back wall is reduced and overall aerodynamic drag is decreased.  
         [0045]     The present invention significantly reduces drag of a coal car at zero yaw angle. Further, the present invention also significantly reduce drag for crosswind. The drag reduction is due to the fact that the air flow over the smaller adjacent cavities is more uniform with reduced down flow and pressure on the back of the cargo bay. As an example, the dividers direct air flow across the top of the cargo bay out the rear to reduce wind resitance caused by pressure on the back of the cargo bay. Moreover, a regular recirculating flowfield fills each cavity created by the dividers.  
         [0046]     In addition, the dividers are configured to advantageously allow cargo such as grain, coal, or dirt to be loaded or unloaded with little to no interference. Moroever, the principles and benefits of the present invention are also applicable to other open bed or cargo bay vehicles, for example, cargo trucks, pickup trucks, grain rail cars, container ships, or the like, hence, providing transport systems utilizing the present invention with energy savings and efficiency.  
         [0047]     In each embodiment, the cargo bay (or container)  110  is configured to appropriately couple a vehicle that is propelled. For example, a railcar hitch or a trailer hitch for coupling to, respectively, a locomotion engine (or other rail car) or a truck (or pickup). In another example, the cargo bay may be coupled by integrating with a vehicle configured for propulsion such as a cargo bed of a pickup truck or a container ship.  
         [0048]     Upon reading this disclosure, those of skill in the art will appreciate still additional alternative structural and functional designs for a system and a process for reducing aerodynamic flow across vehicles with an open bed, cargo bay or other open cavity through the disclosed principles of the present invention. Thus, while particular embodiments and applications of the present invention have been illustrated and described, it is to be understood that the invention is not limited to the precise construction and components disclosed herein and that various modifications, changes and variations which will be apparent to those skilled in the art may be made in the arrangement, operation and details of the method and apparatus of the present invention disclosed herein without departing from the spirit and scope of the invention as defined in the appended claims.