Coparative Studies of the Tread Brake Dynaoeter Between Dry and Wet Conditions Min-Soo Ki, Jeong-Guk Ki, Byeong-Choon Goo, and Na-Po Ki Vehicle Dynaics & Propulsion Syste Research Departent Korea Railroad Research Institute 360-1 Wora-dong, Uiwang-si, Kyonggi-do KOREA s_ki@krri.re.kr jki@krri.re.kr cgoo@krri.re.kr npki@krri.re.kr http://www.krri.re.kr Astract: - This paper discuss coparative strudies of the tread rake dynaoeter etween dry and wet conditions. The rake dynaoeters are widely used to evaluate the perforance of rake systes and test the rake parts under various environents (weight, velocity, rake force, wet-dry conditions). In the process of the rake stops, the friction coefficients etween dry and wet conditions ust not deviate fro each other y ore than 15% under the sae conditions. Experients on the rake dynaoeter for the high speed train are shown to illustrate the coparative studies of the tread rake dynaoeter etween dry and wet conditions with initial vehicle speed at 200 [k/h] considering the 920 [] wheel diaeter. Key-Words: - Tread Brake, Brake Dynaoeter, Railway Vehicle, friction coefficients 1 Introduction Dynaoeter is a device for easuring the torque, force, or power availale fro a rotating shaft. The shaft speed is easured with a tachoeter, while the turning force or torque of the shaft is easured with a scale or y another ethod. The first dynaoeter was designed to easure the rake horsepower of a otor. This invention was the work of an engineer, Gaspard. He invented the Prony Brake Dynaoeter in 1821 in Paris. Variations of this dynaoeter are still in use today[1][2]. Brake dynaoeter is designed to siulate the rake characteristic of the high speed train, and has a function of record the data which can e reproduced and help to analyze and copare the experiental oject, and also is used to develop and test the rake syste. An exaple of such a dynaoeter is shown in Figure 1. There are any variations to this asic forat, ecause of the high speed rotation operation. There is an electric otor inserting and asoring power, an inertia section, and a test section where the rake is ounted. Each size of vehicle will require different aounts of inertia. Since these disks are in discrete steps, there is often a coproise aong the nuer of disks and wheels, the changeale inertia. Many test procedures specify how uch inertia should e used ased on vehicle weight and wheel load. The test procedures perfored on the rake dynaoeters cover a wide range of operational conditions. They ay siulate actual vehicle operations. For instance, in aircraft dynaoeters it is typical to siulate actual operating conditions including taxing, take-offs, and landings. In passenger vehicle testing, standard procedures are often used which do not siulate typical vehicle operations, ut instead, represent critical operational scenarios that test the liits of rake perforance or elicit a specific type of perforance characteristic. Fig.1 Drawings of the rake perforance dynaoeter ISSN: 1792-507X 479 ISBN: 978-960-474-230-1
The friction coefficients etween dry and wet condition ust not deviate fro each other y ore than 15% under the sae conditions[7]. This paper contains the coparative studies of the tread rake dynaoeter etween dry and wet condition in initial vehicle speed at 200 [k/h] considering the 920 [] wheel diaeter. This paper is organized as follows. Section 2 overviews a rake dynaoeter. Section 3 descries the experient environent for the tread rake. Section 4 shows the experient results which contain the coparison of dry and wet condition when the tread rake is applied. The ain conclusions are then suarized in section 5. Max. drive torque 2,527N Max. drive speed 2,500rp(400k/h ) Max. rake torque 25,000N Pressure Brake 6,000 N x 2 Flywheel Inertia Max./Min. 1900kg 2 /400kg 2 Diaeter of the test wheel Φ 700 1120 Acceleration tie (0~1500rp) 2 in. 30 sec 2 Brake Dynaoeter A dynaoeter consists of the following ain eleents. The drive-train consists of the following eleents: otor, interchangeale flywheels and rake disk. The flywheels and rake disk is atched to the part nuer to e tested. The test ed consist of the following eleents: caliper & adapter, power transfer axle, load earing ar and load cell to calculate the reaking force. In general, dynaoeters are widely used to siulate the reak perforance of the railway vehicle. Brake dynaoeter is designed to siulate the rake characteristic of the high speed train, and has a function of record the data which can e reproduced and help to analyze and copare the experiental oject, and also is used to develop and test the rake syste. The expected effect and practical schee of the rake dynaoeter are followings: Developent of the rake, disk-pad, wheel and rake syste of the high-speed & conventional train Test and perforance evaluation of the rake syste of the high-speed & conventional train with the international standard Perforance and certification test of the rake syste of the anufactured high speed train Tale 1 shows the ain features of the rake dynaoeter. Tale 1. Main perforance of the rake dynaoeter Max. drive power 397kW(540HP) Fig.2 Brake perforance dynaoeter for high speed train 3 Experients Environent The friction coefficients etween dry and wet condition ust not deviate fro each other y ore than 15% under the sae conditions according to the requireents of the UIC CODE 541-4. [7] The instantaneous friction coefficient µ, which is a deterined in any oent of raking y the ratio of total raking force F to total contact force F, is t calculated as µ Ft a = F (1) And the ean friction coefficient µ deterined fro reaching 95% of the noinal contact force F of the friction coefficient µ for the raking distance S as Eq. (2). 2 ISSN: 1792-507X 480 ISBN: 978-960-474-230-1
S2 1 µ = ds µ (2) S a 2 0 (a) 180 [k/h] Fig. 3 shows control desk screen to control and onitor the raking perforance tester () 170 [k/h] Fig.5 Trade reaking test at dry condition Fig.3 Control desk screen for controlling and onitoring of the raking perforance tester For the tread raking test, we choose the inertia value as 800 [kg 2 ] ecause the UIC test progra prescried 4 [ton] (ass per rake disc) in case of the high speed train. And cylinder force is accoplished under 5.9 [KN]. 4 Experients The two step tests were perfored to copare raking perforance under dry condition with that of wet condition. Fig.4 Tread rake lock of the raking perforance tester In the tread raking test, the initial test speed is set out at 200 [k/h] with coposite tread rake locks for the high speed train. And the sae initial speed applies for testing the rake test at dry and wet condition. 4.1 Test Results of the Tread Brake The experiental results including the speed curve, instantaneous friction coefficient, raking torque, and cylinder pressure fro 200[k/h] to 0 [k/h] were otained. Fig. 5 shows the surface of the wheel tread when it applied the raking process at initial speed of 200 [k/h]. We can oserve the oveent of the theral and according to the speed variation. Fig.6 Measureent data with the dry condition at the initial rake speed 200 [k/h]. In the tread raking test of dry condition, raking distance was easured 1,213 [] and raking tie was gauged 45.7 [sec] during the raking test with cylinder pressure 22.6[kg/c 2 ] (i.e. cylinder force 5.9 [kn]). ISSN: 1792-507X 481 ISBN: 978-960-474-230-1
Fig.7 Measureent data with the wet condition at the initial rake speed 200 [k/h]. In the raking test of wet condition, raking distance was easured 1,263 [] and raking tie was gauged 48.4 [sec] during the raking test with the sae conditions. Fig.9 Mutual coparison etween dry and wet: raking torque The difference of the raking torque under dry and wet conditions appear in Fig. 9. In wet rake stops, a higher raking torque which is average values 201.1 [kgf ] is easured coparing with raking torque (190.9 [kgf ] )under dry rake stops. 4.2 Mutual Coparison etween Dry and Wet Conditions Two kinds of raking tests were perforend and copared the results of the raking tests at a point of view of easured raking distance, raking tie, raking torque, cylinder pressure, and friction coefficient. Fig. 8 illustrates the utual coparisons etween dry and wet conditions, which are raking distance and raking tie. Fig.10 Mutual coparison etween dry and wet: pressure in rake cylinder Fig. 10 shows the utual coparison of pressure in rake cylinder etween dry and wet conditions. In this case the sae pressure in the rake cylinder is applied continuously during the raking operation. Fig.8 Mutual coparison etween dry and wet: raking distance and raking tie Fig.8 indicates that the raking distance under wetting conditions has ore long (50 []) ecause of decreent of the friction coefficient which is caused y in oisture. Fig.11 Mutual coparison etween dry and wet: friction coefficient Fig. 11 illuinates the instantaneous friction coefficient µ and the ean friction coefficient a ISSN: 1792-507X 482 ISBN: 978-960-474-230-1
µ coparisons etween under dry and under wet conditions. The results tell us that the ean friction coefficient under wet conditions has changed within 15% against that of dry conditions ecause the approval deviation of the wet condition is calculated as 0.4071 (= 0.354*1.15). It is appropriate to verify the UIC CODE 541-4 requireents. 5 Conclusion In this paper, we present a tread rake experients on the dynaoeter for high speed train in order to copare raking distance, raking tie, and ean friction coefficient etween dry and wet conditions in specific vehicle speed at 200 [k/h]. In the process of the rake stops, the friction coefficients etween dry and wet conditions ust not deviate fro each other y ore than 15% under the sae conditions. As a test result we could verify the ean friction coefficient under wet conditions has changed within 15% against that of dry conditions. References: [1 ] Winther, J. B., Dynaoeter Handook of Basic Theory and Applications. Cleveland, Ohio: Eaton Corporation, 1975 [2]Martyr, A, Plint M, Engine Testing - Theory and Practice (Third ed.). Oxford, UK, 2007. [3] Sion Iwnicki, Handook of Railway Vehicle Dynaic, CRC Press, 2006. [4] Garg V. K. and Rukkipati R. V., Dynaics of Railway Vehicle Systes, Acadeic press, 1994. [5] UIC CODE 541-1 Brakes Regulations concerning the design of rake coponents, 6th Eds.Noveer 2003. [6] UIC CODE 541-3 Brakes Disk rakes and their application General conditions for the approval of rake pads, 6th Eds.Noveer 2006. [7] UIC CODE 541-4 Brakes Brakes with coposite rake locks General conditions for certification of coposite rake locks, 3rd Eds. May 2007. ISSN: 1792-507X 483 ISBN: 978-960-474-230-1