| With the characteristics of huge structure and great supporting resistance, the hydraulic support with large mining height shoulders the commission of supporting the roof and protecting the coal wall as well as supplying safe mining space in the fully mechanized longwall face. The height of hydraulic support has been reached from 7m to 8m in super thick coal seam with the development of design level and actual engineering requirements. The maximum height of such hydraulic support has been already far higher than defined 3.8m, which can be classified into ultrahigh hydraulic support. For the purpose of protecting the coal face and supporting the roof immediately in super thick coal seam, it is required that the whole moving process should be completed within 8~12s so that each sub-step process would be compressed accordingly. The dynamic issues would be more intense for such huge mechanism completing gesture change and movement in a short time. Thus, it is significant to do the dynamic characteristics research on the ultrahigh hydraulic support.The kinematic and dynamic issues for the mechanism of the ultrahigh hydraulic support were discussed in this dissertation, and the characteristics of motion along with the mutual acting force for the key components under the propulsion of multi-level leg cylinder and balancing cylinder were obtained. The dynamic characteristics were analyzed by comparing different time intervals for gesture change in the procedure of lifting up and declining down of the ultrahigh hydraulic support. The primary work of this dissertation on the topic of dynamic characteristics research on the ultrahigh hydraulic support is shown as below.1) The mechanism and geometry parameters were analyzed for the two-leg ultrahigh hydraulic support. The expression method for the displacement and angle variations was proposed. The velocity relationship between leg and balancing cylinder was built for keeping the top beam rising up and down horizontally.2) A mathematical analysis model was built for the two-leg ultrahigh hydraulic support by means of Lagrangian theory, and the model can be applied in the hydraulic support with the same structure with two leg shield one. The ultrahigh hydraulic supports ZY18800/36/80 and ZY17300/32/70 were served as analysis objects. The dynamic equations for the mechanism of the two hydraulic support were established. The numerical solution was calculated and the results including displacement, velocity and the acceleration were obtained for the main components.3) It was shown from the result of dynamic solution that when the forces of leg and balancing cylinder were defined as linear value of 800-1000t(KN) and 100-150t(KN) independently, it took 0.5s from the maximum height 7m to 5.5m for the 7m hydraulic support. The velocity along the y direction of the top beam kept increasing until the top beam was balanced in 0.27 s with the acceleration value of zero during the process of raising up from 5.5m to 7m, and it reached the 7m height in 4.5s with the velocity of zero. With the decreasing of the leg force, the motion direction was changed from raising up to decline down. During the process, the velocity of rear link angle and shield angle seemed linear. The velocity of top beam during raising up and declining down was like the parabolic curve. For the 8m hydraulic support, it took 0.5s from the maximum height 8m to 6.5m. The maximum velocity along in the direction y axis was 3.4m/s in the 0.5s, and the maximum velocity along the x axis was 0.4m/s in the 0.33 s. The acceleration along y axis was changed from the initial value of 4.9 m/s2 to 8.4 m/s2, and the acceleration along x axis was changed from the initial value of-1.6 m/s2 to 0.9 m/s2.4) The dynamic simulation model for 8m ultrahigh hydraulic support was built by using dynamic analysis software of mechanical system. Simulation was executed in the same condition with the parameters of dynamic equation solutions. The simulation results showed that it took 0.7s from the maximum height 8m to 6.5m when the leg force and balancing cylinder were set 300 KN and 200 KN independently. Besides of the velocity and acceleration, the dynamic response characteristics such as joint force was obtained. In the process of simulation, the joints force ranged from 160 KN to 800 KN except the joint between leg and basement with its value of 70 KN. The force value in the joint of top beam and shield beam was 219 KN which was smaller than the joint between the balancing cylinder and top beam with a value of 266 KN. The force value in the joint between front link and base beam was changed from initial value of 758 KN to 596 KN at the end. The force value in the joint between rear link and base beam was changed from initial value of 637 KN to 523 KN at the end. The force value in the joint between front link and shield beam was changed from initial value of 683 KN to 562 KN at the end. The force value in the joint between rear link and base beam was changed from initial value of 690 KN to 535 KN at the end. The force in the joint between top beam and the leg was stable with a value of 289 KN around. The force in the joint between base beam and the leg was stable with a value of 74 KN around.5)The simulation model for ZY20000/36/82 D ultrahigh hydraulic support was built with detailed structure including roof and coal wall face protecting devices. The simulation was done for four different working process 12 s, 10 s, 8s, 6s after completing virtual prototype design. In the simulation process of 12 s, the force in the joint between rear link and base beam was much bigger at the beginning and end of rising up and declining down. The maximum force value was 180.59 KN at the moment of 6s, another peak value was 127.39 KN at the moment of 4.5s and 10 s. The extreme force in joint between front link and base beam occurred at the end of advancing process with the value of 160 KN at the moment of 8.5s. Another three peak values were 142.23 KN in 2.5s, 129.3KN in the end of declining down and 141.56 KN at the end of whole process. The maximum force value in the joint between rear link and shield beam was 146.06 KN at the moment of 6s when was the end of declining down, another five peak forces occurred at the time of 2.5s, 4.5s, 8.5s, 10 s, 12 s with the values less than 100 KN.The maximum force value in the joint between front link and shield beam was 148.8KN at the moment of 6s when was also at the end of declining down, another five peak forces appeared at the time of 2.5s, 4.5s, 8.5s, 10 s, 12 s with the values of 121.47 KN, 94.43 KN, 137.7 KN, 94.62 KN, 120.84 KN. The extreme forces in the joint between top beam and shield beam were 87.49 KN at 2.52 s, 87.41 KN at 11.97 s. The results showed such the joint was influenced by pulling out and back the coal wall face protection device most apparently as well as the joint between balancing cylinder and shield beam. The maximum force value on the joint between top beam and leg was 205.8KN at 6s and 8.5s. The maximum force value on the joint between base beam and leg was 308.8KN. There were four extreme force values on the joint between front beam and the first level wall protection device, they were 2233 KN, 2365.9 KN,2366.3 KN,2234.1 KN at the moment of 4.51 s, 5.976 s, 8.52 s, 9.984 s. At the same time, four extreme force values on the joint between front beam and first level cylinder were 228.2 KN, 241.84 KN, 241.87 KN and 228.31 KN. The force value in the link ab1 and bc1 was very similar with the joint between front beam and the first level wall protection device. The joint between second level and third level protection device along with link ab3 and bc3 was reaching the extreme values of 183.84 KN, 38.66 KN and 65.26 KN at the beginning of pulling back, and the extreme values of 181.26 KN, 37.77 KN and 63.58 KN at the end of pulling out the device of coal wall protection.The extreme force value was increased when the working time was compressed. All the extreme force values were happened at the moment of raising up, declining down, pulling out and back the wall protection device, that was, the dynamic problem around start and stop time was the most severely. When the working time was set to 6s, the maximum value was increased sharply with higher level of number. For example, the maximum force value on the joint between front beam and the first level wall protection device was 14891 KN at the moment of 6s and force on link bc1 was 14889 KN. Based on such result, the strength of the relative pins was calculated.The performance of large flow valve and structure mechanics for realizing working time 8s was proposed for the ZY20000/36/82 D ultrahigh hydraulic support. Furthermore, the requirement for new large flow valve was proposed if the extreme working time was shortened to 6s. The weakness was analyzed by the means of dynamic analysis. The performance of pin strength along with the matched structure was required.6) Acceleration testing system was built up for the two-leg ultrahigh hydraulic support. The experiment of acceleration test for the support type ZY22000/39/85 D was executed. The test results showed that each motion was completed around 12~14s, and the motion process was more stable with inconspicuous acceleration vibration signals. That is because such a pump station with limited rated pressure is served for all hydraulic systems in the whole factory and there is much more pressure loss in the process of hydraulic pipes and valves, so that, the pressure and flow is not enough for driving such huge mechanism moving rapidly. For the purpose of moving rapidly, the hydraulic system was kept feeding for raising the hydraulic pressure in the maximum height 8.5m. The experiment results showed the extreme acceleration appeared at the beginning of starting declining down with the value of 331m/s2. The acceleration value was around 85~125m/s2 in the other two declining experiments which pressure cannot be raised. Vibration signals were weak in the raising up tests with the acceleration value of 20~50m/s2. Thus, the hydraulic support ZY10000/16/32 D was chosen as new test object which has one thirds weight as the former one. Comparatively, such hydraulic pressure and flow can drive the new one moving rapidly. The test results showed that each motion was completed around 7~8s which was reduced nearly 50%. The vibrations at the start and end were the most severely. The extreme values of acceleration appeared at the moment of start and end which was larger than the last test with value ranging from 156 m/s2 to 490m/s2. |
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