Valve block test bench for shield propulsion hydraulic system?

This paper introduces the partition working principle of shield propulsion hydraulic system, designs the valve block test-bed of propulsion hydraulic system, and expounds its testing principle and method in detail. The main parameters of the test-bed system are designed and calculated, and the main components are selected. The test results and field propulsion show that the designed test-bed system can meet the functional test of the integrated valve block of propulsion hydraulic system. At the same time, it also shows that the designed integrated valve block is reliable and can be successfully applied to the propulsion hydraulic system to meet the requirements of field shield construction.

Shield machine is a large-scale engineering equipment which integrates multi-disciplinary technology and is specially used for underground tunnel excavation. It has the characteristics of fast excavation speed, high quality, low labor intensity, high safety and little impact on surface subsidence and environment, and has obvious advantages compared with the traditional drilling and blasting tunnel construction [1, 2].

The propulsion system is responsible for the jacking task of the whole shield machine, which requires the completion of turning, curve marching, attitude control, deviation rectification and synchronous movement of the shield machine, so that the shield machine can advance along the predetermined route, and it is the key system of the shield machine. Considering that the shield machine has the characteristics of high power, variable load and long-distance power transmission and control, its propulsion system adopts hydraulic system to realize power transmission, distribution and control [3].

Due to the harsh working environment and limited working space of the shield propulsion system, the valve block of the control system is required to adopt integrated technology with high reliability. This paper mainly introduces the working principle, design and calculation of the test-bed for the valve block of propulsion system, which provides a test platform for the performance test of the valve block of propulsion system.

1 principle design of valve block test-bed for propulsion hydraulic system

In order to test the performance of the designed valve block of propulsion system, a 1 test bench was designed according to the test requirements of the valve block. The test-bed can realize the following tests: 1) valve block sealing performance test; 2) Pressure regulating performance test of proportional pressure valve; 3) Speed regulation performance test of proportional flow valve; 4) Pressure maintaining performance test of hydraulic control one-way valve; 5) Cartridge valve control test.

Fig. 1 is a schematic diagram of the designed test-bed for valve block of propulsion system. The number 12 ~ 22 in the figure is the schematic diagram of the integrated valve group of the propulsion system to be tested. The propulsion hydraulic system uses a constant pressure variable pump with an electric proportional relief valve as the power source and supplies oil to four zones at the same time. Due to the partition control, the four partitions only have different distribution positions of shielding segments, and their control methods and working principles are exactly the same [4]. As shown in the figure, the proportional relief valve 14 regulates the propulsion pressure of the hydraulic cylinder, and forms pressure closed-loop feedback control with the pressure detected by the pressure sensor to control the propulsion pressure in real time; The proportional speed regulating valve 22 regulates the flow entering the system, and forms speed closed-loop feedback control with the displacement detected by the built-in displacement sensor of the hydraulic cylinder to control the propulsion speed in real time. The cartridge valve 12 and the two-position three-way electromagnetic directional valve 13 can short-circuit the proportional governor valve 22 and realize the rapid movement of the hydraulic cylinder, thus reducing the pressure loss along the way when the hydraulic oil enters the hydraulic cylinder. The cartridge valve 2 1 and the two-position three-way electromagnetic directional valve 15 are used to realize the rapid retreat of the propulsion hydraulic cylinder and reduce the backflow resistance of the hydraulic oil. The three-position four-way electromagnetic directional valve 20 is used to complete the switching of working states, and can realize the forward, backward and stop states of the propulsion hydraulic cylinder. Overflow valve 18 is used to realize system overload protection. At the moment of propulsion, the oil inlet of the hydraulic cylinder will be overloaded instantly. At this time, the overflow valve 18 will open immediately to form a short circuit, and the oil inlet and oil return circuits will circulate automatically, so that the overloaded oil circuit will be buffered. The two-position two-way electromagnetic directional valve 17 is adopted to realize the unloading and maintenance of the hydraulic cylinder when it stops, which can reduce the pressure impact during unloading. The damping hole in front of the two-position two-way electromagnetic directional valve 17 can prevent the pressure impact of the two-position two-way electromagnetic directional valve 17 when it is empty. The damping holes in front of cartridge valves 12 and 2 1 are used to adjust the opening speed of cartridge valves, change the static and dynamic characteristics of cartridge valves and reduce the hydraulic impact. The diameter of the damping hole is generally 0.8~2.5 mm according to the empirical value.

According to the working principle of integrated valve group of propulsion system, the testing principle and method of test bench system are as follows:

(1) First, pressurize the test valve group, check the sealing performance of the valve group, and check whether the valve group circuit is unblocked.

⑵ Put the two-position four-way valve 7 on the left, the three-position four-way valve 20 on the left, the proportional speed regulating valve 22 on the maximum opening, and the throttle valve 1 1 on a certain opening, start the hydraulic pump and adjust the proportional relief valve 14. Whether the regulating function of the valve block proportional relief valve is normal can be checked by reading the pressure gauge.

(3) Place the two-position four-way reversing valve 7 on the left, the three-position four-way reversing valve 20 on the left, adjust the proportional relief valve to the maximum, adjust the loading throttle valve 1 1 to the maximum opening, start the hydraulic pump and adjust the proportional speed control valve 22. Whether the adjustment function of the valve block proportional speed regulating valve is normal can be checked by reading the pressure gauge.

(4) Set the two-position four-way reversing valve 7 at the correct position, start the hydraulic pump, close the proportional speed regulating valve 22, close the loading throttle valve 1 1, pressurize the valve group to a certain value, close the hydraulic pump, and test the pressure holding performance of the hydraulic control check valve 16 and the cartridge valve 2 1. By opening the loading throttle valve 1 1, the tightness of the three-position four-way reversing valve 20 can be simultaneously detected. By adjusting the safety valve 18, the overload and unloading capacity of the safety valve 18 can be detected. Energize the two-position two-way reversing valve 17, and check whether there is pressure impact sound, so as to select appropriate damping holes and reduce pressure impact.

5] Put the two-position four-way reversing valve 7 on the left, the three-position four-way reversing valve 20 on the right, the proportional relief valve 14 at the maximum pressure, the proportional speed regulating valve 22 and the loading throttle valve 1 1 at the opening, start the hydraulic pump, and open and close the two-position three-way reversing valves 13 and 15. You can check the valve by reading the pressure gauge.

2 Calculation of main parameters of test system

According to the requirements of the propulsion system, the test system pressure should be greater than or equal to the design pressure of the propulsion system. The maximum working pressure of the propulsion system is 2 1.5 MPa, so the test system pressure is 22 MPa.

2. 1 system flow measurement

The hydraulic cylinder size of the actuator of the propulsion system is φ200/φ 160× 1 900mm, and the system requires that the maximum speed v of the hydraulic cylinders in each region be 1.4 m/min, among which there are 10 hydraulic cylinders in the lower region, and the required flow rate is.

There are 6 hydraulic cylinders in the upper area, and the required flow rate is 95L/min. There are 8 hydraulic cylinders in the left and right zones, and the required flow is 126.6 L/min.

The test system mainly tests the pressure control performance of the integrated valve group of the propulsion system. The flow control performance can simulate the flow control performance of six propulsion hydraulic cylinders in the upper area, so the system flow is determined to be 95 L/min.

2.2 Parameter calculation and selection of main drive pump

Select the main drive hydraulic pump according to the calculated flow and system pressure. When selecting, the rated flow of the pump should be equivalent to the flow required for calculation and should not exceed too much. However, the rated pressure of the pump may be 25% or higher than the working pressure of the system. According to the pump flow formula, the displacement of the pump is

Where: VG-theoretical displacement of hydraulic pump (mL/r)

Q 1- required flow of the system (liter/minute), Q 1 = 95 liter/minute.

N- motor speed (rpm), n = 1 500 rpm.

η V-volumetric efficiency of hydraulic pump, ηv=0.9.

According to the calculation, the hydraulic pump adopts German Rexroth, and the model is A10VO71DR. The pump is a variable displacement pump, which is used in open system. The rated pressure is 28 MPa, the peak pressure is 35 MPa, and the theoretical displacement is 7 1 mL/r, which can meet the working requirements of the system.

2.3 Motor Power Calculation and Selection

According to the formula, the motor power is

Where: n-required motor power (kW)

Qp- rated flow of pump (liter/minute)

VG- displacement of pump (ml/r mL/r), VG = 71ml/r/r.

N- motor speed (rpm), n = 1 500 rpm.

ηm- mechanical efficiency of the pump, ηm=0.9.

ηV- volumetric efficiency of the pump, ηv=0.9.

Delta p-system pressure difference (MPa), delta △p =22 MPa.

According to the calculation, the motor Y2- 250M- 4- B35 of ABB company is selected with a power of 55 kW, which meets the system requirements.

2.4 Fuel tank design

The fuel tank adopts an open fuel tank, and the liquid level in the tank is communicated with the atmosphere. The top of the fuel tank is equipped with an air filter, which is also used as a fuel filler. The effective volume of the oil tank is generally 3 ~ 7 times of the pump's flow rate per minute, and the pump's flow rate per minute is

The effective volume of the fuel tank should be 95.8× 7 = 670.6L. If the effective volume is 80%, the total volume of the fuel tank is 840 L. It can be preliminarily determined that the three-side dimensions of the fuel tank are1000 mm×1000 mm× 850 mm.

2.5 Calculation and Selection of Auxiliary Components

Filter is an important part in hydraulic system. It can eliminate pollutants in hydraulic oil, keep the cleanliness of oil and ensure the reliability of system components. According to its requirements, the system pressure pipeline filter is ZU- H250× 10DFP of Wenzhou Liming Company.

According to the effective volume of the fuel tank of 670.6 L and the maximum flow rate of the system of 95 L/min, the filter EF7- 100 of Liming Company is selected. The fuel flow rate is 1 10 L/min, and the air flow rate is 1 055 L/min. Determine the inner diameter of the oil suction pipe according to the oil suction pipe velocity V of 0.5 ~ 1.5 m/s;

The standard hose diameter is Ф ф50mm, which can meet the requirements.

Determine the inner diameter of the hydraulic oil pipeline according to the flow velocity v of the hydraulic oil pipeline is 4 ~ 7 m/s;

The standard hose diameter Ф19mm can meet the requirements.

Three-dimensional design and entity diagram of pumping station and test bench

In order to improve the accuracy of the system design and the compactness and compactness of the whole assembly of the test-bed system, the three-dimensional entity established by using the three-dimensional parametric design software Pro/E can completely reproduce the real characteristics of each physical component, so that the virtual assembly and motion analysis of the entity can be carried out conveniently and intuitively. By observing each part of the assembly, we can check the correctness, rationality and accuracy of the design, so as to find and solve various problems in the design stage and improve the design efficiency [5]. Fig. 2 shows the three-dimensional layout of the system pumping station and test bench designed by Pro/E, fig. 3 shows the integrated valve block diagram of the propulsion system to be tested, and fig. 4 shows the integrated valve block test bench of the propulsion system.

4 debugging results and field promotion

Through debugging on the test bench, it is found that the sealing performance between the integrated valve block and various components is good and the circuit is smooth. It can work under the system working pressure of 22 MPa for a long time, and can withstand the maximum peak pressure of 35 MPa, which meets the sealing performance requirements of the system. By adjusting the current of the amplifying plate of the proportional valve, the proportional speed regulating valve and the proportional relief valve can adjust the speed stepless within the calibration range of 0 ~ 100%, and can also meet the working requirements of the system. At the same time, the on-off function of the cartridge valve, the overload unloading ability of the overflow valve and the pressure impact of the reversing valve all meet the design requirements.

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