Improvements to systems for increasing wheel-rail friction in low adhesion conditions

Abstract

A liquid addition system for mounting on rail vehicles, comprising a liquid outlet 1006 configured to direct liquid towards a rail 112 in use, a pump, and a liquid conduit in fluid communication with

Description

Technical Field

[0001] The present invention relates to systems for increasing wheel-rail friction in low adhesion conditions and improvements thereto. More specifically, the present invention relates to train-mounted systems for dispensing water onto a rail surface and thereby to the wheel-rail interface. Background Art

[0002] Adhesion (or traction) between the wheel of a train and the railhead is required to propel the train forward and to enable the train to stop. The traction between the locomotive wheels and the rails is required to start or accelerate the train, to pull loads up gradients, or simply to maintain the required speed.

[0003] Rails that are located adjacent to trees and woodland may lose adhesion (or friction) and become slippery due to the fallen leaves. In particular, leaves on tracks may be compacted by passing trains and form a smooth coating.

[0004] This coating is hard and reduces traction of the wheels with the rails and significantly reduces the effectiveness of the brakes on the train especially when damp. The coating of compacted leaves thereby presents major problems fortrain operating companies and also presents significant safety issues. In particular, trains may not be able to stop in the required stopping distance and may overshoot platforms or the stopping positions for signals. Signals which when passed indicate danger are a significant hazard, and the inability to stop in a reasonable distance increase the chances of a collision. In addition, the acceleration of trains is affected and hindered, since the wheels tend to slip or spin relative to the tracks. Rails may also be contaminated by other matter as well as vegetative matter for example, water, rust, oil, solid particles etc. Adhesion levels can be worsened in certain weather conditions, for example, light rain, drizzle, mist, low temperatures and high humidity, leading to the formation of dew on the rail surface.

[0005] Another problem connected with stopping trains, in particular when rails are slippery, is the damage caused to the rolling surface of the wheels. Such damage may include the creation of flat areas or crevices. 14 07 25

[0006] Various methods and systems have been used or proposed for cleaning rails and increasing the adhesion between the railhead and a wheel. For example, the film or coating on the rail can be scraped off the rail. Other methods and systems include preventive methods (for example, leaf control through vegetation management), cleaning methods (for example, water jetting, scrubbing, etc.) and / or the use of friction improvers (for example, sand).

[0007] Water delivery systems are already used in the rail industry to clean contaminants from the rail surface. Currently, water jetting systems are fitted to special purpose trains which are deployed when the likelihood of rail contamination from fallen leaves is high. In these systems, water is delivered continuously to the rail at extremely high pressures (15,000 psi / 1 03.42MPa) and relatively large flow rates to dislodge materials stuck to the surface of the rail. Due to the amount of water required, large water storage tanks are needed on board dedicated trains. WO 00 / 44992 describes one such system. The large amount of on-train water storage and high cost prevents the use of this solution on normal service trains.

[0008] Othertrackside water delivery systems have been developed to wet certain sections of track which are known to present low adhesion risk. There are a number of issues with this solution including the need to establish and maintain a trackside water delivery infrastructure when the areas of low adhesion risk may not always be in the same place.

[0009] The delivery of large quantities of water to the wheel rail interface (either from trackside or on-train spraying) may also give rise to other issues on the rail network such as accelerated degradation of the rails through stress corrosion and erosion of the rail ballast.

[0010] Applicant's previous patent GB2548317 discloses a train mounted system for controlled addition of water to one or more wheel-rail contact points. Counterintuitively, the addition of water to the rail in a specific range of volume / unit length of rail serves to increase adhesion under certain conditions. [0011 ] While controlled addition of water has now been shown to deliver greatly improved braking and traction for trains experiencing low adhesion when operating in passenger service, the trial work has also highlighted opportunities for further improvements to maximise the market potential of the solution: 14 07 25 1) Further increasing the effectiveness of water addition in removing contaminants and improving wheel-rail friction. 2) Optimising the characteristics of the water addition system and other on-train adhesion mitigation and measurement systems such as the sanding and wheel slide protection systems to maximise train braking and traction. 3) Configuring and controlling a train fleet to deploy water addition from multiple trains operating on the same lines of route, delivering enhanced and targeted rail head and wheel treatment.

[0012] It is an aim of the present invention to provide improved systems and methods for improving wheel-rail adhesion. Summary of Invention

[0013] The basis for the present invention is a train-borne system to supply water in a controlled way to the wheel-rail contact point or points when low adhesion is detected or train braking is initiated. The purpose of adding water in this way is to ensure reliable braking rates that are largely independent of environmental factors and contamination at the wheel / rail interface. The system consists in general of a water reservoir, pump and nozzle arrangement operated either by a dedicated control system or existing train-based control systems. This patent discloses various enhancements to the basic water addition system described in GB254831 7

[0014] According to a second aspect of the invention there is provided a liquid addition system according to claim 1.

[0015] Advantageously, the applicant has found that provision of pulsation increases the effect that the liquid has on increasing wheel-rail friction on rails having a layer of residue.

[0016] Alternatively, the pulsation device is configured to confer oscillatory pressure at an ultrasonic frequency (i.e. above 20kHz). In this case, the pulsation device is an ultrasonic transducer. Preferably the ultrasonic transducer comprises a horn in contact with the liquid flow to transfer ultrasonic energy thereto. 14 07 25

[0017] The invention also provides a train-mounted liquid addition system, comprising a liquid addition system according to the first aspect, andaliquidtankin fluid communication with the liquid outlet.

[0018] The invention also provides method of applying liquid to a railway rail, the method comprising the steps of: providing a train-mounted liquid addition system according to the first aspect; and, urging liquid from the tankto the outlet, via the pulsation device. Brief Description of Drawings

[0019] An embodiment of the present invention will now be described with reference to the following figure in which: FIGURE 1 is a side view of a train; FIGURE 2 is a schematic view of a first system in accordance with the invention; FIGURE 3 is a cross section through a component of the system of Figure 2, not in accordance with the invention; FIGURE 4 is a schematic view of a second system in accordance with the invention; FIGURE 5 is a schematic view of a third system not in accordance with the invention; FIGURE 6 is a creep plot; FIGURE 7 is a schematic view of a fourth system not in accordance with the invention; FIGURE 8 is a schematic drawing of a railway management system; FIGURE 9 is a flow diagram of a process in accordance with the present invention; FIGURE 1 0 is a schematic view of a sixth system not in accordance with the invention. Detailed description

[0020] Referring to Figure 1, a train 100 comprises a leading carriage 102 and a trailing carriage 104, each moving in a forward transit direction D. The carriages 102, 104 each comprise a pair of bogies 106, each bogie having a leading wheel pair 108 (comprising wheels 108L, 108R) and a trailing wheel pair 110 (comprising wheels 11 0L, 11 OR). The wheels are in contact with a rail pair 112 (comprising rails 112L, 112R). 14 07 25 [0021 ] Referring to Figure 2, a generic system 1000 according to the present invention is shown. The system 1000 is a water delivery system comprising a water storage tank 1002, a pump 1004, a delivery nozzle 1006 and an energy source 1 01 0. A first fluid conduit 1003 is provided from the tank 1002 to the pump 1004. A power delivery line 1 005 is provided between the energy source 1010 and the pump 1004. A second fluid conduit 1007 is provided between the pump 1004 and the nozzle 1006. When an activation signal is received from the train, the pump 1004 is switched on and water is delivered to the rails 112 and / or wheels 108 via the nozzle 1 006 to thereby wet the wheel-rail interface. first embodiment

[0022] The first embodiment can be understood from Figure 3 with reference to Figures 1 and 2.

[0023] A section 1112 of fluid conduit is shown in Figure 3. The section 1112 comprises an outer wall 1114, an annular material region 1116 and a lumen or opening 111 8. The outer wall 1114 is constructed from a water-impervious material. The region 1116 is constructed from a compressible foamed material such as a closed-cell polymeric foam. The section 1112 may be employed in one or both of the conduits 1003, 1 005, but preferably in at least the conduit 1005.

[0024] The section 1112 of the first embodiment provides an improvement in system responsiveness. Second embodiment

[0025] Figure 4 shows a further embodiment in which the system 1 000 is further enhanced by the addition of an ultrasonic generator 1123 between the pump 1 004 and nozzle 1 006. The generator 1123 is configured to confer ultrasonic pressure waves (that is, waves having a frequency above 20kHz) within the liquid from the tank 1 002.

[0026] Ultrasonically energised liquid be particularly effective in increasing the friction of the wheel-rail interface. The additional energy in the liquid helps to increase friction by disrupting the oily layer of organic residue. Variations in the second embodiment 14 07 25

[0027] Although the embodiment of Figure 4 shows the ultrasonic energy being added as the fluid passes through the conduit 1003 (i.e., in-line), the generator may be placed at any point in the flow, upstream of the nozzle or at the nozzle to impart ultrasonic energy as the liquid is expelled.

[0028] In some embodiments, oscillatory pressure waves in the fluid may be generated at frequencies lower than 20kHz. For example, the pump 1 004 may be configured to impart an oscillatory pressure wave onto the liquid as it is propelled to the nozzle. This may be, for example, by controlling the power input to the pump (for example electrical power if the pump is powered by an electric motor) or through the oscillatory characteristics of a pneumatic piston pump. Third embodiment

[0029] Figure 5 shows a further embodiment in which the system 1 000 is further enhanced by the addition of a nanobubble generator 1124. The generator 1124 is configured to produce nanobubbles (that is, gas bubbles in the region of below 200nm in diameter) within the liquid from the tank 1 002.

[0030] Utilising nanobubble enhanced liquids has been shown to be particularly effective in increasing the friction of the wheel-rail interface. As the bubbles contact the material, they collapse, generating a force that helps to increase friction and to disrupt the layer of organic and non-organic residue. Variations in the third embodiment [0031 ] Although the embodiment of Figure 5 shows the nanobubbles being generated on an ad-hoc basis as the fluid passes through the conduit 1 003, the generator may be placed at any point in the flow, upstream of the nozzle or at the nozzle to generate bubbles as the liquid is expelled. The nozzle itself may be formed in such a way as to generate bubbles via hydrodynamic means.

[0032] Nanobubbles are known to exhibit neutral buoyancy and a high degree of stability within a liquid. Therefore, in a further embodiment, the nanobubbles may be generated in thetank 1 002 and the stable bubble-enhanced liquid stored for use. In a further alternative, 14 07 25 the nano-bubble enhanced liquid may be generated off the train, and transferred to the tank 1 002 for later use, thus avoiding the need to install a generator on the train.

[0033] Although nanobubbles are optimal, as an alternative, larger bubbles such as micron-scale bubbles may be employed. Fourth embodiment

[0034] Figure 2 shows a controller 1010 which is configured to activate the water system 1 000 of the present invention.

[0035] Turning to Figure 6, a rail creep curve is shown, which is generally known in the art as a means for assessing the quality of the wheel-rail interface. On the x-axis the degree of creep or slip between the wheel and rail is shown (a measure of relative speed at the interface). On the y axis is a representation of friction at the joint- e.g. the coefficient of friction, p.

[0036] The line 1200 shown is representative of a typical ideal creep curve. At low levels of creep, a high degree of friction is available, however once past a certain level, friction decreases as creep increases, resulting in sustained slip. Many trains in the art possess wheel slip protection (WSP) systems which are akin to anti-lock braking system in cars. Once a certain level of slip or creep is detected by a wheel speed sensor, the WSP system is configured to engage based on the creep curve (such as that in Figure 6). In known systems, this may be e.g. 10% creep, represented by point A on the curve 1200. Once the WSP activates, the relevant brake is released and reapplied.

[0037] According to a fourth embodiment, the water addition system of the present invention is utilised as soon as wheel slip is detected. This may take place instead of, or as well as, activation of the WSP system.

[0038] Referring to Figure 9, a flow diagram of an example operation sequence 4000 of the fourth embodiment is shown. The system provided is per Figure 2, with the controller 101 0 linked to, or integrated with, the brake system of the rail vehicle so as to be capable of activating a brake valve to release a brake. The valve may be a blowdown valve, for example.

[0039] At step 4002, the rail vehicle is moving along a track. At step 4004, the vehicle is braked (by driver demand, or by an automated system) such that the brakes are applied. 14 07 25 During brake application, creep (the degree of relative motion between the wheel and rail) is monitored by the controller 101 0.

[0040] At step 4006, due to slippery track conditions, creep reaches an adhesion system activation level. At this point, the water addition system is activated to wet the rail in front of the wheels (as described herein). The addition of water maximises adhesion while minimising wheel damage. At step 4008, the creep again rises following water addition to a WSP activation level and the controller activates brake valve release (in accordance with the usual WSP procedure).

[0041] Step 4010 shows an alternative branch where the creep remains below the WSP level, and the train simply continues.

[0042] In short, water addition is employed initially to attemptto reduce slip. Ifthis first pass is not successful, the WSP system is activated.

[0043] The controller 101 0 may have other inputs and outputs, for example: • True train speed (based on e.g., GPS) may be an input to more accurately determine creep by comparison with measured wheel speed; • Adhesion may be measured (for example by measurement of the lateral acceleration of bogies, or by Al assisted vision systems); • Ambient temperature may be measured; • The controller may control the amount of water added (i.e., a variable flow rate); • The controller may also be able to control separate water addition systems along the train; • The controller may be configured to control water temperature e.g. by means of a heater.

[0044] The addition of water to the railhead as provided by the present invention changes the creep curve. A modified creep curve is shown at 1202, in which the rail has been wetted. Based on this modified curve, in a further embodiment, when the system 1 000 is active, the slip parameter in the WSP system is also modified such that a higher degree of slip is 14 07 25 tolerated before activation. This is because the use of the system modifies the curve to be more tolerant of slip, and does not enter a negative gradient as quickly.

[0045] The water system 1000 may be initiated based on external factors (as discussed below), or manually by the driver or other on board operator. Once active, the WSP may or may not be necessary (depending on rail conditions affecting the degree of creep experienced)..

[0046] In terms of activation of the water system 1 000 according to the invention, this may be triggered in a number of ways, including, but not limited to one or a combination of: • brake step; • wheel speed; • train speed • gradient • location • deceleration • bogie movement. Fifth embodiment

[0047] A fifth embodiment of the present invention concerns a railway management system. Referring to Figure 8, such a system 3000 comprises a central controller 3002, a railway 3004 comprising a plurality of rails 112, and a plurality of rail vehicles 100.

[0048] At least one portion of the railway 3002 extends through a high slip-risk area 3006 comprising adjacent trees 10. At certain times of year, there is a high likelihood that residual organic matter (leaves) will fall on the rails and produce slippery conditions at the wheelrail interface. Because the present invention is particularly well suited to increasing the friction atthe interface in these conditions, it is useful to be able to activate the system along this particular section of railway. It is also desirable not to have the system running along lengths of rail where the problem does not exist. 14 07 25

[0049] Each rail vehicle 1 00 comprises a wheel slide protection system configured to detect and mitigate rail-wheel slide, and configured to communicate rail data to the controller, the rail data comprising a location and at least one of rail-wheel slide detection and, rail-wheel slide protection system activation (whether that is water-based, sanding and / or traditional WSP).

[0050] The controller 3002 is configured to collect the rail data from the plurality of rail vehicles (wirelessly in this case), and to update one or more railway management parameters based on the rail data. [0051 ] The rail management parameters may be logging a high risk area in orderto instruct the vehicles 1 00 to carry out rail treatment (for example with water or sand). It may also be a reduction in the speed limit for that section of rail. It may also be control of the signals in the area to, for example, increase the spacing between the trains 100.

[0052] Rail data can be generated by on-board sensors. It is envisaged that the activation of the system is dependent on the rail conditions expected at a given location..

[0053] It will be noted that as several trains pass over, and wet, the same area of track, there is a cumulative effect (reduction) on the rail contaminants. The repeated cycle of wetting and compression (in the wheel-rail interface) eventually breaks up and reduces contamination.

[0054] Therefore, activation of the system is based on both location, surroundings (foliage) and the time of year.

[0055] It will be noted that the above-referenced system may be employed as a rail cooling system. In high ambient temperatures (exceeding 30C) it is possible for the expansion of the rails to cause undesirable deformation and buckling. Regular wetting of the rails alleviates this problem, and in addition to increasing friction, the above system maybe used to reduce track temperature.

[0056] The system may also be used to reduce the effects of noise. It is noted that as trains move around corners, noise can be generated due to resonance caused by slippage at the wheel-train interface. The addition of water changes the characteristics of the system such th at this problem is alleviated. Therefore, wetting of the rail at locations of high rail curvature is desirable to reduce noise. 14 07 25

[0057] In one embodiment, the driver is provided with an indication of system operation, for example via an audible and / or visual indicator. Sixth embodiment

[0058] Referring to Figure 10, a system 5000 according to a sixth embodiment is shown. The system 5000 is identical to the generic system 1000, with the exception that an electric field generator 5002 is provided which is configured to produce a potential difference between the rail (in electrical contact with the wheel 1 08) and the nozzle 1 006. As such, the nozzle 1 006 is at least partially constructed from a conductive or semi-conductive material.

[0059] In use, this has the effect of providing an electric potential to the water emanating from the nozzle 1 006 such that when it contacts the rail 112 it has a higher electric potential / field potential.

[0060] This is beneficial in ensuring that the water adheres to the rail, but also the higher electric potential helps to disrupt any contaminants on the railhead. The applied electric potential may be e.g., between 5V and 24V. Variations Decontamination system

[0061] Referring to Figure 7, according to the present invention a system 2000 is shown which may be used in addition to the system 1000 described above. In particular, the system 2000 is suited for use with sanding systems or other systems that deposit a friction material onto the track 112 (other than water). The system 2000 is a water delivery system comprising a water storage tank 2002, a pump 2004, a delivery nozzle 2006 and an energy source 2010. A first fluid conduit 2003 is provided from the tank 2002 to the pump 2004. A power delivery line 2005 is provided between the energy source 2010 and the pump 2004. A second fluid conduit 2007 is provided between the pump 2004 and the nozzle 2006. When an activation signal is received from the train, the pump 2004 is switched on and water is delivered to the rails 112 via the nozzle 2006 to thereby wet the wheel-rail interface. It will be noted that any or all of the above components (apart from the nozzle 2006) may be shared with the system 1 000 if installed.

[0062] The intention of the system 2000 is to decontaminate the rail 112 after the train has passed over it. The water from the nozzle 1 006 may be used to wash off any sand or other 14 07 25 solid residue, or indeed may serve to wash off debris after the train wheels have compacted it. Wheel cleaning system

[0063] In a still further embodiment, which may be combined with any or all of the features above, a system similar to the system 1000 may be employed to clean one, several or all of the train wheels 108, 11 0. A build up of contaminants can often be problematic from a friction perspective, and / or may interrupt the wheel-rail electrical contact of the track circuit. Washing the wheels alleviates this problem. In one embodiment, the system may wash the wheels at regular intervals. Water supply

[0064] The above embodiment utilises the lavatory water tank as a supply source. In one alternative embodiment, the present invention may employ an air-water harvesting system. In such a system, water is extracted from ambient air in ordertofeed thetank. Such systems are known in the art, but may, for example, comprise an air collection system in which water is condensed into liquid form by cooling.

[0065] In an alternative embodiment, for trains that utilise a hydrogen power source (such as a hydrogen fuel cell), the water by-product from the hydrogen-oxygen reaction is collected and provided to the tank.

[0066] In a further alternative, water may be collected from a waste water recycling system such as CLEARTRAK (TM) offered by GBR-Rail.

[0067] In a further alternative, water may be collected from the on-board air conditioning system. Water condensation is a natural by-product of air conditioning.

[0068] In a further alternative, rainwater or condensation may be collected from the train (e.g., with a carriage-mounted collector).

[0069] Any of these systems may be used in isolation, or in combination with each other as required.

Claims

14 07 251. A liquid addition system for mounting on a rail vehicle, the system comprising:a liquid outlet configured to direct liquid towards a rail in use;a pulsation device configured to confer oscillatory pressure within the liquid as it is delivered from the outlet to the rail in use,wherein the pulsation device is configured to confer oscillatory pressure at an ultrasonic frequency.

2. A liquid addition system according to claim 1, wherein the pulsation device is an ultrasonic transducer.

3. A liquid addition system according to claim 2, wherein the ultrasonic transducer comprises a horn in contact with the liquid flow to transfer ultrasonic energy thereto.

4. A train-mounted liquid addition system, comprising a liquid addition system according to of claims 1 to 3, and a liquid tank in fluid communication with the liquid outlet.

5. A method of applying liquid to a railway rail, the method comprising the steps of: providing a train-mounted liquid addition system according to claim 4; and, urging liquid from the tankto the outlet, via the pulsation device.

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