The Improvement Research of the Freight Train Braking System Li-wei QIAO

Transcription

1 2017 2nd International Conference on Applied Mechanics and Mechatronics Engineering (AMME 2017) ISBN: The Improvement Research of the Freight Train Braking System Li-wei QIA School of Traffic Transportation and Logistics, Southwest Jiaotong University, No.211, 1st Section, Northern 2nd Ring Road, Chengdu, China Keywords: Freight train, Braking wave, Synchronous braking. Abstract. The train which is made up of 60 cargos (P70 boxcar) was take as the research background, and the synchronous braking system was installed in brake branch pipe, the brake wave and brake time was monitored with the related instruments, and reduction rate of the brake pressure and time-consuming was analyzed. The results indicate that the brake wave transmitted slowly in traditional braking system, in service braking, it was transmitted from the locomotive to the last wagon for 3.621s, and in emergency braking, it took 2.928s, under the condition of the test experiment, the brake wave was transmitted Faster in synchronous braking system, and there is a low braking efficiency in traditional braking system. Introduction In the process of railway transportation, there is a time-delay in decompression process when the train brakes. It is difficult to stop the train synchronously due to the air-pressure in the train braking hose gradually decreases from the front of the train to the tail. In this situation, impaction between the wagons is likely to occur[1], the cargo on the platform lorry could moves, in a state of the wagons loaded with some special goods(awkward cargo, concentrated weight goods or Inflammable fragile goods). There is many studies on how to deal with this type of problem [2, 3], but most of the those studies aimed at theoretical research that cause the related data has a greater difference from the actual situation. There are a lot of problems in a train under traditional braking system, for instance, braking inefficiency, the goods slide in the direction of train running suddenly, there are many collisions between the two neighboring goods. So it is necessary to research the train brake synchronization. Current Situation There is an advanced air brake dispensing valve in the locomotive, the speed of the brake propagation has reached 250m/s [4], but it still cannot exceed speed of sound 340m/s. If the length of a freight train is more than 600m, it requires at least 2.4s that the brake-wave will be transmitted from the locomotive to the last wagon when the driver does emergency braking [5]. A longer time to accomplish the brake for an entire train while the locomotive takes the service braking. In this process, the brake shoes in each wagon can not rub against the wheels simultaneously, the longitudinal impulse between each wagon is increased. From the train braking theory, we can draw a conclusion: the relations between the forces acting on goods is different when the train runs on the railroad. Assume that the goods in the wagon are regular and heavy objects, and the point is the center of gravity, as is shown in Figure

2 F 1 T 1 moving direction T 1 W 3 W T 3 3 F wagon I 2 wagon II 3 wagon III 4 cargo 5 track centerline Figure 1. Force acting on cargo when the train moving on the complex curves. When the train moves on the complex curves, the centrifugal forces F1 and F3 in the opposite direction, the direction of W is influenced by the railway curve radius and the curve direction. Therefore the directions of the total forces T1, T2 and T3 are not in a same straight line. Due to the time-delay of braking wave, the impact among the wagon I, wagon II and wagon III is bound to happen when the working condition of train changed from traction to braking, and the wagons in the rear of train would grind against each other. In this case, the goods will traverse or scurry out from the wagons, even cause the train derailment accident. Freight Train Synchronous Braking System At present, air braking in railway transportation can not to achieve train synchronous braking. Therefore, author puts forward a new braking method which can control air emissions from the brake branch pipe by circuit, In this case, the problem of time-delay of braking wave will certainly be solved. This braking method include braking circuit, brake regulators and electromagnetic relay regulators, as is shown in Figure the wheel 2 brake-shoe 3 brake cylinder 4 auxiliary reservoir 5 three-way valve 6 braking adjuster 7 electromagnetic relay regulator 8 air outle 9 brake branch pipe 10 brake circuit wires Figure 2. Schematic diagram for train synchronous braking system. First, the electrical braking signal is transmitted from locomotive to each wagon through brake circuit wires. Second, the electromagnetic relay regulators are adjusted by braking adjusters in wagons according to the full weight of the wagon. Finally, the electromagnetic relay regulators adjust the air emissions from the brake branch pipe to achieve the purpose of freight train synchronous braking. The Braking Wires Settings The brake circuit wire is set in connector of train brake hose, the braking circuit in every wagon is connected once the coupling and docking are completed. The way that set the brake circuit wire and the train brake hose together avoids cumbersome and ignoring wiring when the staff connects the train, meanwhile, the switch of brake circuit is consistent with the train coupling cock which can simplify the operation process and increase safety. 349

3 The Braking Adjuster and the Electromagnetic Relay Regulator Settings The electromagnetic relay regulators and the braking adjusters are set on brake branch pipe, the braking adjusters receive the electrical braking signal from locomotive and make the electromagnetic relay regulators to open outlet valve through the wires when the braking operations are applied. Different models of brake cylinder different dimension, the diversity of lever system in foundation brake rigging lead to a different braking characteristics, therefore, when the electrical braking signal is sent from locomotive the brake shoe pressure in each wagon should be expressed as equation 1. 2 d p n K b (1) Where d is the brake cylinder diameter, (cm); p is the air pressure in brake cylinder, (kg/cm 2 ); η is the transmission efficiency of foundation brake gear; γ is the braking leverage; and nb is the number of brake cylinders. In order to make the cargos for different load in train come into synchronous braking, the pressure must be the same between the brake shoes and the wheel in each cargo, namely, the braking ratio of cargo should be similar. the braking ratio β should be expressed as: β=k/(t+q), where, K is the brake shoe pressure;t is the wagon deadweight and Q is the weight of goods. Field Experimentation The freight train synchronous braking system was installed in a train which is made up of 60 cargos (P70 boxcar), and this system was monitored in test experiment in Ankang east marshalling yard, Shaanxi province in The main technical parameters of P70 boxcar as is shown in Table 1. Table 1. The main technical parameters of P70 boxcar. model of carrying dead-weight volume equivalent coefficient of brakeing cylinder pressure in boxcar capacity [t] [t] [m 3 ] length [m] dead weight diameter [mm] brake-pipe [Kpa] p The test experiment was broken into two stages, and each 4 boxcars forms a detecting unit. First stage, the test experiment based on traditional braking system. Second stage, the test experiment based on synchronous braking system. The service braking and emergency braking were operated in both two stages, in service braking the air pressure in brake pipe was reduced to 350 Kpa, and the air pressure of braking was fell to 0 Kpa Instantly in emergency braking. The YZS-100 Double-needle/tube piezometer was set on brake branch pipe in each boxcar, the technical parameters of YZS-100 double-needle/tube piezometer as is shown in Table 2. Table 2. The technical parameters of YZS-100 double-needle/tube piezometer boxcar. measurement range Precision condition model of piezometer sensitivity repetitive error storage [Kpa] [Kpa] [ ] YZS-100 0~ % 5~60 manual The type of ZYL09 electronic timer was used in test experiment and associated with the piezometer. According to GBT General specification for electronic measuring instruments [21] to re-calibrate the related instruments in experiment. In order to ensure the accuracy the test of accuracy error was carried out and the measuring data was stored in the instruments directly in case of error by artificial reading. The Monitoring results as is shown in Table

4 parameters boxcar number Table 3. The results of braking system experiment. traditional braking system synchronous braking system service braking emergency braking service braking emergency braking pressure Time pressure Time pressure Time pressure Time value consuming value consuming value consuming value consuming [Kpa] [s] [Kpa] [s] [Kpa] [s] [Kpa] [s] locomotive For a clear description, the experimental data of the time consuming of braking wave in pipe in traditional braking system and synchronous braking system were represented by line chart, as is shown in Figure 3. Figure 3. The time consuming of braking wave in pipe in different braking systems. The test results can be obtained that the brake wave was transmitted from the front to back along the train for 2.928s in emergency braking in traditional braking system. However, in circumstances of synchronous braking system the brake wave was transmitted relatively stable in each cargo, and it just take 0.01s to transmit the brake wave through the whole train in service braking or emergency braking. Summary (1) The brake wave transmitted slowly in traditional braking system, in service braking, it was transmitted from the locomotive to the last wagon for 3.621s, and in emergency braking, it took 2.928s 351

5 (2) Under the condition of the test experiment, the brake wave was transmitted Faster in synchronous braking system, and there is a low braking efficiency in traditional braking system. (3) The application of the synchronous braking system can avoid impaction between each cargo and ensure the safety of the goods transportation. Reference [1] Zhang P.C. Development of locomotive auto-passing neutral section device based on onboard monitoring device. China Railway Science, 2009, 3(20): [2] Fedyaeva G.A. Reducing shock dynamic loads on the asynchronous traction drive of a developed diesel locomotive in emergency modes. Russian Electrical Engineering, 2007, 78(12): [3] Xue F., Yan W.Z. Parametric model-based anomaly detection for locomotive subsystems. Proceedings of the 2007 International Joint Conference on Neural Networks, 2007: [4] Grzechca D., Rutkowski J. Fault diagnosis in analog electronic circuits-the SVM approach. Metrology and Measurement System, 2009, 16(4): [5] Barrow K. Alstom fourth generation ETR600 tilting train. International Railway Journal, 2006, 9: [6] The State Standard of the People's Republic of China. GBT General specification for electronic measuring instruments [S]. Beijing: China Standards Press,