Patent Application
20060201377
The present invention relates in general to the design and construction of railroad cars, and in particular, to methods for improving the aerodynamic characteristics of railroad cars and railroad cars embodying the same.
The railroad system is one the most efficient means for transporting bulk materials, such as coal, iron ore, coke, rock, cement, and the like. One particular railway-based transportation technique which has evolved for efficiently transporting such bulk materials utilizes open-top gondola railroad cars and rotary car dumpers. In this system, the material being transported is simply directly dumped or poured into the open-top of the required number of gondola cars at the departure point, such as a coal mine, transfer dock, or shipping terminal. The filled gondola cars, which remain open-topped, are then coupled into trains and the material transported via the railway system in a conventional fashion. At the destination, for example a power utility generation plant or steel mill, the gondola cars are individually clamped to the rail by specialized heavy equipment and both the gondola car and the track rolled-over to dump out the material within the gondola car.
Utilizing open-top gondola cars has several significant disadvantages. Among other things, current gondola cars, as well as other open-topped railway cars, are aerodynamically inefficient. The result is the creation of significant aerodynamic drag during movement, particularly when the cars are empty, and therefore an increased burden on the train engines. This increased burden directly translates to increased fuel consumption and increased costs.
To increase the aerodynamic efficiency, normally open-topped gondola cars could be covered; however, covering increases the size and weight of each car. Moreover, the addition of covers makes the process of loading and unloading each car more expensive and time consuming, and potentially more hazardous, if additional human interaction is involved.
While the aerodynamic characteristics of gondola cars are important, at the same time, the problem of structural strength of the car must also be carefully considered. Typically, vertical reinforcement ribs are provided along the exterior surfaces of the gondola sidewalls, primarily for wall support during material during transport, such that the internal surfaces of the sidewalls are free of obstructions which would otherwise impede the dumping of the material. These external ribs only further increase the problem of achieving aerodynamic efficiency by increasing aerodynamic drag during both loaded and empty operations of the railroad car.
It should be noted that the problems of aerodynamic drag and structural strength discussed above are not limited to open-top gondola cars. For example, similar problems are encountered in the design and construction of bottom-dump and hopper railroad cars, which are operated in an open-top configuration.
In sum, a new railway car design, particularly suitable for open-top transport of bulk materials is desirable. Such a design should be aerodynamically efficient, but still allow for the construction of a structurally strong railway car, which can withstand the stresses applied during dumping.
The principles of the present invention reduce aerodynamic drag of a gondola or similar railroad car moving with an open-top configuration. In one particular representative embodiment of these principles, a railroad car is disclosed which is adapted for open-top transport of bulk materials, such as coal. The railroad car includes a receptacle for receiving a selected material, the receptacle defined vertically by a floor, defined laterally by first and second sidewalls having a height and extending at an angle from the floor and defined longitudinally by first and second end-walls having a height and extending at an angle from the floor. At least one lateral baffle, disposed within the receptacle between the first and second sidewalls, laterally partitions the receptacle into a plurality of cavities for reducing aerodynamic drag during open-top motion of the railroad car.
Embodiments of the present principles advantageously provide for the design and construction of aerodynamic railroad cars, such as gondola cars, without resort to a cover. The resulting decrease in aerodynamic drag translates into decreased loading on the associated train engines and hence a corresponding decrease in fuel consumption. Moreover, the use of baffles not only reduces aerodynamic drag, but can also provide sufficient structural strength to the car that external drag generating appendages, such as vertical ribs, can be eliminated or modified to achieve further drag reductions.
For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
The principles of the present invention and their advantages are best understood by referring to the illustrated embodiment depicted in
Gondola car 100 includes an elongated receptacle 101 supported on a pair of conventional railroad car trucks 102a and 102b. Receptacle 101, which is adapted to receive bulk materials, for example coal, includes a pair of elongated sidewalls 103a and 103b, and a pair of end-walls 104a and 104b. An internal floor 105, a portion of which is shown in broken lines, defines the bottom of receptacle 101. In the illustrated embodiment, floor 105 is “bathtub” floor, which slopes downward from end-walls 104a and 104b to the dumper 110 (which may be sealed), although gondola car 100 may have a flat-bottomed configuration in alternate embodiments. External vertical reinforcing ribs 106 provide structural strength to sidewalls 103a and 103b during dumping of materials within receptacle 101, as well as during transport of materials within receptacle 101.
In a conventional moving gondola car, particularly one that is empty, high velocity airflow continuously enters the receptacle. Some of this high velocity air flow strikes inner surface of the receptacle rear wall of the moving car creating substantial air pressure rise in the region surrounding the rear wall. The result is significant “parachute drag.” For purposes of the present discussion, parachute drag is defined as the difference between the overall drag of the car operating empty and open-topped and the overall drag when equipped with a flat cover. Since the parachute drag accumulates with each additional gondola car added to the train, the increase drag directly translates into a higher loading on the train engine and consequently an increase in fuel consumption.
According to the principles of the present invention, partitioning the receptacle 101 of gondola car 100 into a plurality of cavities 107 significantly decreases the parachute drag generated when gondola car 100 is in motion. As those skilled in the art will readily appreciate, when an open gondola car is traveling at high speeds, significant drag is created by the pressures acting on the rear wall of the car. This drag results from the tendency of the flow to enter the interior volume of the car. In the present invention, a considerable reduction in the amount of flow entering the interior volume—and thus a reduction in the drag created—is achieved through the inclusion of lateral baffles 108, within gondola car 100. These baffles 108 essentially divide the volume of the receptacle 101 into a number of smaller cavities 107. The longitudinal spacing of the plurality of baffles 108 is sufficiently small such that the amount of airflow that circulates into the cavities 107 is far less than the airflow that circulates into the receptacle of a traditional gondola car to produce the high parachute drag associated with the traditional car. In this manner, the majority of the high velocity air flows above receptacle 101, rather than strike the major surfaces of lateral baffles 108. Although a small amount of the airflow does strike along the upper edges of lateral baffles 108, the total resulting drag is much smaller than the parachute drag generated when high velocity air flow strikes the rear wall of a conventional gondola car.
Computer models representing gondola car 100 and wind tunnel tests of models of the structure of receptacle 101, including lateral baffles 108 and longitudinal baffle 109, have clearly demonstrated that the addition of lateral baffles 108 alone significantly reduces the drag on gondola car 100 in comparison to prior art gondola cars moving with an open-top configuration. The addition of longitudinal baffle 109 further improved the realized reduction in drag at yaw angles other than zero degrees, for example when operating in a cross-wind. In alternate embodiments, a plurality of longitudinal baffles may be provided for further reducing drag with changes in yaw angle. Moreover, while the drag savings realized by gondola car 100 are less than the drag savings achieved by operating a gondola car in a covered configuration, the savings in drag realized by gondola car 100 are substantial with respect to the open-top configuration.
The computer modeling and wind-tunnel testing revealed that most of the reduction in drag is provided by a configuration of gondola car 100 having at least four (4) cavities 107 defined by at least three (3) lateral baffles 108, along with longitudinal baffle 109, although improvement in drag over the conventional single-cavity configuration was still found with only a single lateral baffle 108 dividing receptacle 101 into two (2) large cavities. It should be noted that to optimize aerodynamic efficiency, the number of lateral baffles 108 may vary depending on the length of the railroad car; for example, longer cars may require more lateral baffles 108, while shorter cars fewer lateral baffles 10.
Additionally, the best performance is found when lateral baffles 108 and/or longitudinal baffle 109 are of full depth (i.e. extending from floor 105 of receptacle 101 to substantially the top of receptacle 101 defined by the heights of sidewalls 103 and end-walls 104. Notwithstanding, significant reductions in drag are still realized with lateral baffles 108 and longitudinal baffle 109 of ⅓ or ⅔ of the depth of receptacle 101, as measured downward from the upper edges of sidewalls 103a and 103b, which are positioned such that top edges of lateral baffles 108 and longitudinal baffle 109 are at substantially the same height as the top edges of sidewalls 103.
Advantageously, the principles of the present invention, as discussed above with respect to gondola car 100, provide for the design and construction of an aerodynamically efficient railroad car operating open-top, especially when empty. Additional advantages are illustrated in the embodiments shown in
In gondola car 200 shown in
Similarly, in gondola car 300 shown in
In sum, the principles of the present invention provide for the design and construction of aerodynamic railroad cars, such as gondola cars, which can be efficiently operated open-top. The resulting decrease in aerodynamic drag translates into decreased loading on the associated train engines and hence a corresponding decrease in fuel consumption. Moreover, the use of baffles not only reduces aerodynamic drag, but can also provide sufficient structural strength to the car that external drag-generating appendages, such as vertical ribs, can be eliminated or modified to achieve further drag reductions.
Although the invention has been described with reference to specific embodiments, these descriptions are not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed might be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.
It is therefore contemplated that the claims will cover any such modifications or embodiments that fall within the true scope of the invention.
