In order to solve the defect of low head and lower efficiency of submersible pump, the author has analyzed this design. This includes the electric pump motor, hydraulic and component design, adjust the gap between the motor thrust disk and the thrust bearing, reducing the friction of the internal components of the motor. Secondly, the parameters of the electric pump impeller are adjusted to improve the overall head in the hydraulic hierarchy structure. The final technical test data are within the expected range, ensuring the normal operation of the overall structure of the electric pump.
The original submersible pump has some drawbacks in operation, mainly due to the unreasonable structure design and parameter setting. The improvement of the overall structure of the electric pump not only reduces the failure of the submersible pumps, but also improves the overall mechanical efficiency.
I. Problems in design of submersible pump for well
1. Well diameter does not match the outer diameter of the electric pump
The depth of mine is inversely proportional to the diameter of the pipe, but it is in direct proportion to the diameter of the submersible pump. General submersible pump selection of stainless steel material, head flow control in 10m~88m, electric pump wellhead flow in 1m3~2.5m3, discharge caliber in 15mm~25mm. Depending on the power model and size of the existing submersible pump, the optional types are: 7.5qjd1.5-25/9,l (s) with an outer diameter of 40mm,l (a) with a diameter of 100mm;100qj1.5-102/17l (s) od size of 44mm, L (a) the applicable bore diameter is 110mm;100qj8-70/13l (s) with an outer diameter of 46mm,l (a) with a bore diameter of 125mm;100qj10-130/27ll (s) with an outer diameter size of 50mm,l (a) for a bore diameter of 135mm But with the continuous increase of the submersible pump head, it is necessary to increase the outer diameter of the pump, which results in a certain difference between the drilling caliber and the outer diameter of the electric pump.
2. Pump axial force residual large
The larger the pump selection power, the farther away the lift, but as the head increases, the axial force of the submersible pump is also more. According to the actual operation of electric pump, the pressure of submersible electric pump motor bearing unit area is limited, when the pressure rating is exceeded, the bearing cannot balance all the axial balance of the motor. Bearings are generally selected alloy materials, the unit area under the pressure of 13000N, beyond the range, the bearing will increase the residual axial force, the surplus axial forces to the thrust bearing, the motor rotor will continue to wear thrust bearings, resulting in local sinking motor rotor, burning the electromagnetic clutch inside the motor.
3. Insufficient motor power
The power of the submersible pump is directly related to the outside diameter of the borehole, and the larger the diameter of the submersible pump, the smaller the size of the outer orifice, resulting in no effective combination of motor power matching. Power the larger the outer diameter of the pump, the matching power requirements of 200mm OD submersible pump, supporting the operating power of 45000W, this operating power can not guarantee the normal operation of the pump, need to increase 29000W on the power, to reach 74000W, to ensure the normal operation of the motor. Ambient operating pressure of 0.2MPa, the need for submersible pump head in the 60m range, the use of 45kW motor power to meet the work needs.
Second, the design of well submersible electric pump
1. Motor Design
In order to reduce the failure rate of the submersible pump, the author analyzes the motor design structure. The sealing ring used between the ball bearing and the motor shaft is highly susceptible to high-pressure mechanical friction, resulting in the sealing ring losing its original sealing effect. Single-stage pump sealing device to the body inside and outside the pressure and pump head plays a vital role, so in the design of the structure of the motor shaft and ball bearings to optimize, as shown in Figure 1, the motor shaft rate is adjusted to 600rad/min, directional deflection 8 °, see the motor wear, loss reduction 38%, The working head of the submersible pump has not changed. Second, adjust the gap between the thrust plate and push bearing, keep the gap within the 0.36mm~0.55mm range, so that the impeller in the motor is flexible, and there is no damage to its internal cable.
2. Hydraulic Design
The hydraulic design of submersible electric pump includes the design of impeller parameters and blades, increasing the ratio of leaf rotation and increasing the pump head. If equipment normal operation, control pump flow q=32m3/h, impeller speed 1200rad/min, head 25m, leaf rotation number ratio is 77.3, operating mechanical efficiency is 78%. To increase the head will cause large area friction on the side of the impeller disc, causing damage to the plane of the impeller gear. However, without affecting the operation of the equipment, adjust the ratio of leaf rotation to reduce the degree of friction, you can increase the mechanical head of the pump. Vane runner curvature (β) 32°, adjusting β to 35° when the pump mechanical head changes, there is a hump curve, at this time the number of leaf rotation ratio in 83.7%. When other parameters are guaranteed to be constant, the pump lift is improved by changing the bending degree of the blade, which makes the mechanical efficiency reach 88.6%. The principle of blade design is to change the angle between blade and blade, and then change the deviation distance between blade and leaves Cordate.
3. Structural Component Design
The design of the pump parts includes the design of the pipeline and the cable structure, the junction of the transmission line and the flange, the interface is curved, so the reinforcement is applied in the sealing treatment, and then the flow velocity in the tube is lowered. Motor cables generally use a small resistance, to prevent large resistance operation, excessive power, internal overheating concentration, resulting in the burning of internal motor.
Three, technical comparative analysis
Through the adjustment of the Unit and the design parameters, the pump is now tested and compared. The results show that the unit and power are normal, and the specific data are shown in table 1.
The test data is compared with the original pump data, which not only increases the lift distance, but also improves the mechanical efficiency of the pump.
Through the design and research of the submersible pump for well, the author has a deeper cognition to the design of the structure. This design structure not only improves the mechanical efficiency of the electric pump, but also makes the safety and stability more reliable.
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