This application claims priority to EP Patent Application No. 22165815.6 (filed 31 Mar. 2022), the entire disclosure of which is incorporated herein by reference.
The invention pertains to a discharge nozzle for discharging grit or lubricant into the gap between a route (e.g., a rail) and a wheel of a vehicle (e.g., a rail vehicle), with the discharge nozzle comprising a base body with at least one connection for being connected to a conveyor line for the grit or lubricant and an outlet that is connected to the connection via a channel.
Discharge nozzles of this type are used for discharging grit or lubricant to improve the contact between a rail and a track wheel of a rail vehicle. This contact between the rail and the track wheel plays a decisive role for the dynamics of a rail vehicle because the driving and braking forces, as well as the tracking forces and weight forces, have to be transmitted via a relatively small contact surface. In this context, the friction ratio between rail and track wheel defines the optimal force transmission. Permanently changing conditions exist at the transition between the rail and the track wheel as soon as the rail vehicle is in motion. In addition to the degree of dirt accumulation, the track profile also plays an important role for the respectively current state in the contact point between rail and track wheel, particularly while driving around curves. Sanding and lubricating systems are used in rail vehicles to minimize the extreme influences and the associated negative effects on the braking distance and the wear (stick-slip effect).
Grit, particularly sand, is used for increasing the friction between the rail and the track wheel and for thereby respectively reducing the braking distance and simplifying the start of the rail vehicle. Lubricants are used for optimizing the coefficient of friction to reduce the wear of the track wheel and the rail, among other things in the region of the wheel flange, and for reducing the noise development, primarily while driving around curves or during pendulum motions of the rail vehicle. Grit and lubricant can be discharged separately of one another or also jointly in the form of a mixture that optimizes the coefficient of friction.
Conventional discharge nozzles usually converge toward the outlet. Such discharge nozzles are described, for example, in WO 2015/044245 A1 or in U.S. Pat. No. 2,451,878 A.
To improve the flow profile, it has been proposed, e.g. in DE 20 2005 017 304 U1, to design the underside of the sanding nozzle in a convex manner to generate a suction effect and to keep the sanding channel and the conveyor hose dry and free of dust. However, the increasing channel cross section toward the outlet of the nozzle does not contribute to an improvement of the purposeful introduction of the sand into the gap between the rail and the track wheel.
The efficiency of the discharged quantity of grit or lubricant or a mixture thereof is highly dependent on the aerodynamic influences that occur in the immediate vicinity in front of the gap between rail and track wheel and tend to deflect the jet of grit or lubricant outward as the speed of the rail vehicle increases. The discharged grit or lubricant tends to be deflected outward due to the aerodynamic flow forces that act in the gap between the rail and the track wheel and are already pronounced at slow speeds of the rail vehicle. This significantly reduces the required effect of the grit, particularly at high vehicle speeds.
Another important factor for the material consumption of grit or lubricant is the shape of the discharge nozzle. Since the discharged jet of grit or lubricant has a pronounced conical shape and a minimum clearance has to be observed in the positioning of the discharge nozzle (normative requirement), the projected surface of the discharged jet is significantly wider than the surface of the rail. This results in a high consumption of grit or lubricant, which in turn leads to additional energy consumption (stockpiling, refilling, cleaning, disposal) and to environmental pollution.
In currently used discharge nozzles, only a small proportion (usually less than 40%) of the discharged mediums for improving the coefficient of friction reaches the effective surface between the rail and the track wheel. The remainder ends up in the surroundings of the rail and, under certain circumstances, even has to be vacuumed off and collected or disposed.
The present invention therefore is based on the objective of creating an aforementioned discharge nozzle for discharging grit or lubricant, by which the highest possible proportion of the discharged medium actually reaches an intended destination, namely the gap between a route (e.g., rail) and vehicle wheel (e.g., track wheel). The proportion of mediums for improving the coefficient of friction, which ends up in the effective surface between the route and wheel, and the degree of efficiency of the discharge should be increased as far as possible and the smallest possible quantity of grit or lubricant should be lost and discharged into the surroundings adjacent to the route. It should be ensured that sufficient grit or lubricant for ensuring the effect of the grit or lubricant is introduced between the route and the wheel, particularly also at high speeds of the vehicle. The disadvantages of hitherto existing discharge nozzles should be avoided or at least reduced.
The above-defined objective of the invention is attained in that the outer contour of the base body of the discharge nozzle is in the longitudinal direction shaped in a convex manner at least in the rear region lying opposite of the outlet such that the air flowing around the base body is accelerated in the direction of the outlet. As a result of the convex shape of the outer contour of at least the rear portion of the discharge nozzle, the air flowing around the base body is constricted and accelerated toward the outlet of the discharge nozzle due to the Coand{hacek over (a)} effect such that the grit or lubricant jet is purposefully transported into the annular gap between the rail and the track wheel in a more concentrated manner. Due to this concentration and acceleration of the jet, the air flow caused by the motion of the rail vehicle, particularly at higher speeds, has less influence on the grit and lubricant jet and the deflection of this jet is reduced. As a result, a higher proportion of grit or lubricant can end up in the effective surface between the rail and the track wheel. The usable proportion of grit and lubricant can be increased to as much as 80%. Such a discharge nozzle can be very easily and cost-effectively manufactured, particularly in the case of a rotationally symmetrical shape. However, a simple and cost-effective manufacture is also possible if the shape of the discharge nozzle deviates from a rotationally symmetrical shape, e.g. by means of 3D printing.
According to a characteristic of the invention, the outer contour of the base body of the discharge nozzle may also be shaped in a convex manner in the longitudinal direction over the entire length. In this way, a particularly high concentration and acceleration of the air surrounding the discharge nozzle toward the outlet of the discharge nozzle can be achieved.
A circumferential attachment is advantageously arranged in the rear region of the base body and an annular gap is formed between the surface of the base body and the inner side of the attachment. Such an attachment makes it possible to additionally improve the Coand{hacek over (a)} effect, i.e. the acceleration of the air flowing through the annular gap past the surface of the base body of the discharge nozzle. Such a two-part design of the discharge nozzle consisting of correspondingly designed base body and attachment allows particularly concentrated grit and lubricant jets, which are also not significantly deflected at high speeds of the rail vehicle. Since the attachment has to be correspondingly fastened on the base body of the discharge nozzle, e.g. by means of webs or the like, the annular gap formed between the surface or outer contour of the base body and the inner side of the attachment is interrupted by the webs or the like, but this does not significantly affect the function of the discharge nozzle.
The acceleration of the air flowing around the surface of the base body of the discharge nozzle can be additionally increased if the annular gap is tapered in the direction of the outlet.
According to another characteristic of the invention, the attachment is arranged to be adjustable relative to the base body in the longitudinal direction. Such an adjustability, which may also be realized automatically, e.g., by means of corresponding servomotors, makes it possible to change the acceleration of the flow. For example, the acceleration of the air flowing around the discharge nozzle can be controlled in dependence on the speed of the rail vehicle such that an optimal transport of the grit or lubricant to the gap between the rail and the track wheel is achieved at all vehicle speeds.
A preferred direction or a twist can be imparted on the grit or lubricant jet if air control elements for conducting the flow of the surrounding air are arranged on the inner side of the attachment and/or on the surface of the base body. In this way, the grit or lubricant jet can be steered in the direction of the wheel flange of the track wheel. This results in an even higher degree of efficiency during the discharge of grit or lubricant. The air control elements may be designed in different ways. The air control elements may be integrally manufactured during the production of the base body or the attachment.
According to an embodiment of the invention, the air control elements may be arranged to be adjustable. In this way, the flow of the surrounding air can be changed, e.g. adapted to the speed of the rail vehicle. If the air control elements are arranged in an adjustable manner, they naturally cannot be manufactured integrally during the production of the base body or the attachment. The adjustability can be achieved mechanically, but also electrically by means of corresponding servomotors.
The air control elements may be realized in the form of blades, where the blades may be arranged obliquely referred to the longitudinal direction. Such obliquely arranged blades in the annular gap between the base body and the attachment of the discharge nozzle make it possible to generate a vortex effect of the surrounding air, where the vortex effect steers the surrounding air and therefore the grit or lubricant jet in the desired direction, particularly to the wheel flange of the track wheel.
In an expanded embodiment of the discharge nozzle, the attachment is closed in the region of the at least one connection and at least one compressed air connection for being connected to a compressed air line is arranged on the attachment. In this embodiment, the compressed air supplied via the compressed air connection replaces the surrounding air. The compressed air is concentrated and accelerated due to the design of the base body and the attachment of the discharge nozzle such that the flow profile of the grit or lubricant can be optimized and the degree of efficiency of the discharge system can be improved. During the transport of the grit or lubricant, the compressed air can be blown in, e.g. with a pressure of 1 to 2 bar, either continuously or in the form of pulses that are separated in time. This embodiment is particularly suitable for instances, in which the discharge nozzle is installed in the rail vehicle in a tightly packed manner and little or no access for the surrounding air exists. This is the case, for example, in streetcars, particularly low-floor streetcars.
The base body and/or the attachment can be manufactured of metal, particularly aluminum or an aluminum alloy, such as in a 3D printing process. Metal is particularly suitable due to its resilience and durability.
The base body and/or the attachment can alternatively also be manufactured of a suitable plastic, such as in a 3D printing process. Certain plastics also have a high durability and usually a lower weight than metals. Furthermore, plastic components frequently can be manufactured easier and more cost-effectively than comparable metal components. Combinations such as a base body of metal and an attachment of plastic are also possible.
A simple installation on and removal from the conveyor line can be realized if the at least one connection of the discharge nozzle is provided with a thread.
Icing of the outlet can be effectively prevented, and a flawless function can also be ensured at low ambient temperatures if a heater is arranged in the base body of the discharge nozzle. In metallic discharge nozzles, electric resistance heaters are particularly suitable for heating at least the region around the outlet.
An additional improvement of the purposeful introduction of the grit and/or lubricant into the gap between the rail and the track wheel of the rail vehicle can be achieved if the outlet of the discharge nozzle is arranged obliquely at an acute angle to the longitudinal axis. The acute angle relative to the longitudinal axis of the discharge nozzle particularly lies in a range between approximately 30° and 60°. An even more purposeful introduction of the grit or lubricant can be achieved due to the oblique arrangement of the outlet and a corresponding orientation of the discharge nozzle with respect to the gap between the rail and the track wheel.
A circular cross-sectional design of the base body and/or the attachment results in a simplified manufacturability. Furthermore, the effect of the discharge nozzle is not dependent on the alignment around the longitudinal axis in this case.
However, an additional improvement of the flow profile can be achieved under certain circumstances if the base body and/or the attachment of the discharge nozzle are designed with an elliptical cross section. The higher manufacturing effort in comparison with a rotationally symmetrical discharge nozzle is also kept within reasonable limits if a 3D printing method is used. The asymmetric grit or lubricant jet can also be changed by correspondingly rotating the discharge nozzle with elliptical cross section about the longitudinal direction.
The invention also pertains to a device for discharging grit or lubricant into the gap between a rail and a track wheel of a rail vehicle with an above-described discharge nozzle that is arranged at the end of the conveyor line. The inventive design of the discharge nozzle makes it possible to significantly increase the proportion of grit or lubricant that ends up in the effective surface between the rail and the track wheel and to save material and energy.
The present invention is described in greater detail below with reference to the attached drawings that show different embodiments of discharge nozzles for discharging grit and/or lubricant into the gap between a rail and a track wheel of a rail vehicle. In these drawings:
The highest possible proportion of a metered quantity of grit G or lubricant O or the mixture for optimizing the coefficient of friction is respectively introduced into the gap between the track wheel R of the rail vehicle Z and the rail S by means of the discharge nozzle 1. Due to the traveling speed of the rail vehicle Z in the driving direction A, the relative wind W, but also crosswinds, cause vorticities Y in the region between the discharge nozzle 1 and the track wheel R such that the jet of grit G and lubricant O is deflected and partially ends up adjacent to the rail S.
A control unit may be provided and connected to the metering and conveying device T. As a result, optimal metering and mixing of the grit G or lubricant O or the mixture for optimizing the coefficient of friction can be achieved at best with consideration of influencing factors and environmental parameters. The control unit may also be connected to a sensor for detecting the speed of the rail vehicle Z, as well as to sensors for detecting environmental parameters such as the temperature, the humidity, or the wind speed. Furthermore, the control unit may also be connected to sensors for detecting the state between the track wheel R and the rail S. Such sensors may be realized, for example, in the form of optical devices. The values acquired by such sensors make it possible to determine the coefficient of friction between the track wheel R and the rail S by means of corresponding algorithms. Furthermore, the control unit may also be connected to a (not-shown) GPS receiver to detect the current geographic position of the rail vehicle Z and to also control the discharge of the grit G or lubricant O in dependence on the position of the rail vehicle Z.
In the inventive embodiment of the discharge nozzle 1 illustrated in
The inventive discharge nozzle 1 makes it possible to increase the degree of efficiency of the discharge system and to reduce the resulting costs.
Number | Date | Country | Kind |
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22165815.6 | Mar 2022 | EP | regional |