A large inclined axial flow pump applications
1.1 Overview
Large inclined axial-flow pumps are receiving more and more attentions from different users due to their good hydraulic performance, small excavation depth, low height of the plant and uniform stress of the unit, etc. Especially, the low lift (<3m) Flow (<15m3 / s) operating conditions, the traditional vertical, horizontal unit discomfort to use, under-flow unit is not perfect, the case of inclined units is a better choice. The design lift of Taipuhe Pumping Station is 1.39m, the single pump flow 50m3 / s when the pump is designed to lift, the total flow of the pump station 300m3 / s, the choice of six impeller diameter 4.1m large inclined 15 ° installation axial flow pump, single machine supporting power 1600kw, Installed 9600kw, the host part of the pump through the international tender form to determine the contractor.
1.2 The overall layout of the unit
The entire pump unit system has access to water runner part, the pump part, the gearbox part, the motor part and auxiliary equipment and other components. The pump is 15 ° inclined installation, the blade is semi-adjusted; using medium speed motor, the motor speed is 1000r / min, through the two gear box deceleration drive, the pump speed of 73r / min, inflow channel elbow water, out Water channel for the proliferation of diffusion tube, fast gate off flow.
1.3 flow path part of the fluid numerical calculation
The inlet channel is an elbow pipe, and the outlet channel is a variable-diameter diffuser pipe. Both of them play the guiding role of water flow, and a quick gate is installed outside the outlet channel to stop the flow. The majority of runners use reinforced concrete structures. Inlet runner floor to the center of the impeller height 4.25m, impeller inundation depth 3.5m above the center of the impeller. The traditional runner test is designed according to the control unit size of the prototype pump flow channel device, through the test, the runner or hydraulic trimming until the design requirements. Usually the time, manpower, energy and material resources invested in this process are quite large. The inlet and outlet water flow channel of this project was specially requested by Wuhan University of Water Conservancy and Electric Power to calculate the fluid flow in the runner. The hydraulic loss of the runner was calculated to be 0.5m by fluid numerical calculation. The model device was set up by the Scientific Research Institute of Tianjin Water Resources and Hydropower Design and Research Institute The experimental results show that the loss of fluid numerical calculation basically agrees with the experimental results. This result can provide a theoretical basis for the future of large pumping stations.
Figure 1 shows the flow pattern of the model after fluid numerical calculation.
2 large inclined axial flow pump design
Pump design in strict accordance with the requirements of the tender documents and the implementation of national standards; prototype pump performance parameters based on the model device test to determine the prototyping pump hydraulic components to strict design model device according to a similar law design (see design calculations and drawings).
2.1 pump structure
The pump part is composed of the rotor part, the pump shaft part, the guide bearing part, the pump body part, the pump shaft sealing part and the thrust radial composite bearing part. The motor is connected with the pump through two parallel gear drives. College of industrial design professional landscaping design (see Figure II).
2.2 Wheel parts
Runner is the heart of the pump unit, the rotor body, blades, platen and other components. The blade is made of ZG0Cr13Ni4Mo stainless steel. The blade design is based on the geometric similarity of the blade. After the casting is heat-treated to eliminate the stress, the surface of the blade is polished to remove sand and surface crust, Mark the line and find the center of rotation and the 0o base line.
Blade is to ensure that the performance of the pump key, because the blade is a space surface, the traditional pump blades are not machined, on the one hand by the processing equipment constraints, on the other hand affected by the traditional concepts, therefore, the prototype Pump performance indicators can meet the expectations of the requirements is difficult to guarantee. The project leaves open the machining precedent for large pumps and uses the most advanced five-axis CNC machining today. By comparing the model pump blade numerical control processing with the RBI processing, the blade efficiency index of CNC machining can be increased by 1.5%, and the device efficiency reaches 69% when the designed head lift is 1.39m. Blade processing accuracy greatly improved, so that the blade line deviation (tender requirements for ± 6.15mm, drawing requirements are increased to ± 4mm), surface wave, blade surface roughness and the blade weight difference and other important quality indicators have been So as to provide a good guarantee for efficient and stable operation of the pumping station. The design weight of a single leaf of this project is 1950kg. According to the traditional weight difference between two leaves is not more than 150kg, which has a great impact on the balance weight of runner body. The static balance can not be guaranteed, which will affect the stability of unit operation . Blade NC processing, the weight difference between the two leaves only 6kg, the weight of the runner body is small, static balance accuracy greatly increased, and thus the stability of the unit has a reliable guarantee. The cross section of the blade inlet side of the test; ZG270-500 rotator body cast as a whole, the ball using CNC machining; blades using screws and plate fixed to the rotor body, the blade angle using cylindrical pin positioning, and according to the requirements , Adjust the blade angle (angle range of -4 ° ~ +4 °), so that the blade is fixed at an angle operation, blade factory angle set at +2 °.
2.3 pump shaft components
The pump shaft is a hollow shaft with one end flange. The lower flange of the pump shaft is connected with the rotor body. The pump shaft and the rotor body are connected with transverse pins to transmit the torque. The upper end of the pump shaft is connected with the drum gear coupling by a key, Axle and gearbox shaft associated drum gear coupling there is still a gap between the shaft and gearbox shaft in order to adjust the axial distance and concentricity; pump shaft and pump rotating part of the combination of sliding bearings and thrust roller Bearing axial force and radial force, spherical roller bearings spherical roller thrust bearings. The material of the shaft of the pump is the whole steel forging 35, which is 8085mm in length, which is the longest part of the pump. According to the calculation, the diameter of the shaft of the pump is Φ360mm, the strength and rigidity of the shaft can be guaranteed and the safety factor is sufficient; The pump is inclined installation, the stiffness of the shaft will affect the bearing capacity of the water and the pump running stability, so the design of the pump shaft in order to improve the rigidity of the pump shaft diameter increased to Φ410mm, and in the middle of the shaft hit The holes remove the metal evacuated from the forged shaft and reduce the deflection of the shaft itself. In the guide bearing and packing seal contact parts, the welding of the shaft 3Cr13 hard alloy to improve the pump shaft surface hardness and wear resistance, the surface hardness of HRC50 above; and the use of special equipment for grinding parts of the journal, Guide bearing parts journal surface roughness of less than 0.8μm.
3 water guide bearing parts selection
Water-guided bearings are the key technology of inclined pump unit, and also affect the reliable operation of the unit key components. To this end, the domestic has been built inclined units in the use of water-bearing more or less there have been problems. Taipuhe pumping station with pump water guide bearing on the choice of domestic and foreign manufacturers of bearings related to the technology, products were extensively studied, combined with the relevant domestic bearing experts advice, decided to use Spain Sde Wa company's marine stern shaft Bearing products; the guide bearing thin oil-lubricated bearings; bearing material tin-based white metal bearing material, the use of gravity oil bearing lubrication, lubricating oil from the outside through the guide vane holes into the bearing within the oil bath lubrication, the whole Bearing completely immersed in oil to be fully lubricated, the lower part has a back to the oil hole, the bearing can be regularly replaced inside the lubricating oil, and with two temperature measuring element; bearing body and bearing are axial half structure, bearings and bearings Body with spherical contact, so that the bearing can rotate in the bearing body with self-tuning function, can eliminate the shaft system is not good and run-time imbalance caused by uneven bearing force phenomenon; both ends of the bearing are provided with two Road skeleton seal, seal between the two skeletons are also used gravity oil lubrication. Guide bearing according to the radial load of 27 tons design, according to the calculation, the guide bearing can choose the maximum load of 35 tons.
4 pump body design
4.1 pump body part
The pump body includes front cone, telescopic casing, impeller shell, guide vane body, adjustable bend pipe, extension pipe and other parts, the joint surface is flanged rigid connection rubber asbestos seal; wherein the impeller shell, the guide vane body, Diameter reduction pipe are axial sub-half structure, in order to pump installation, maintenance, the half of the bolt connection, conical pin positioning, rubber asbestos board seal. Impeller shell with ZG270-500 matrix, lined with stainless steel to improve its anti-cavitation performance, at the top and bottom of the impeller shell are provided with observation holes, easy to observe the blade operation and installation, maintenance and measurement of blade clearance and guide bearing wear, The gap between the single side of the blade and the shell is about 4mm; the guide vane body adopts the structural part, the flange of the guide vane body and the barrel are welded by the high quality steel plate Q235-A, which can ensure good appearance quality and surface roughness, The guide vane mold airfoil to be tested, the airfoil meets the drawings requirements, the guide vane to take a single piece of cast, made of ZG270-500 cast steel, guide vane surface grinding process, the surface roughness of not more than 12.5μm ,, and then guide After positioning the leaves welded, so as to ensure that parts and drawings consistent, but also to ensure that the guide vane hydraulic performance. Other parts are used Q235-A structure; the top of the reduction pipe is provided with access holes for installation and maintenance spare; in the pre-cone, impeller shell, guide vane body, adjustable pipe bend, the extension of the pipe With support feet, adjust the horn configuration, easy to adjust the elevation and level when installed; the front cone pipe is the intake runner and pump connections, in order to facilitate pumping station installation, the former conical pipe from a period of concrete buried to phase II Concrete buried, in order to effectively prevent the pouring of concrete after the second period of water seepage phenomenon, the length of the pre-tapered tube from 700mm to 1000mm, the flange diameter Φ4800mm increased to Φ4900mm; before the conical tube, adjustable elbow (down), extension tube After all the installation of the pump, it is necessary to cast two concrete embedded in the foundation.
4.2 Shaft seal components
Pump shaft seal components from the packing box, packing, packing ring, packing gland and other components; packing box for the whole cast iron, packing box to be pre-set in the pump shaft; packing ring, As 35 × 35 PTFE asbestos packing, in order to improve the packing lubrication performance, the use of pressure water lubrication, pressure water from the external supply of specialized water supply device, water demand 2L / S, water pressure of 0.10Mpa; connecting fasteners for stainless steel.
4.3 Thrust Radial Combination Bearing Components
Combined bearing components installed in the tail pipe bend, the main water pump to withstand the thrust of the operation, rotating parts of the radial component of the weight. Mainly include: bearing body, bearing gland, two bushings, thrust bearings, radial bearings and skeleton seal composition; axial semi-axial bearing structure; thrust bearings, radial bearings SKF bearings, the use of thin oil circulation Lubricating Oil No. N220 Extreme Pressure Gear Oil and Gearbox Commonly Used Thin Oil Station with 0.05Mpa Hydraulic Pressure and 0.3L / S Fuel Oil, with Temperature Monitoring, Two Skeleton Seal at Both Ends of Bearing; In addition to bearing all the outer circle parts must be pre-installed on the pump shaft.
5. Auxiliary equipment: There are lubricating water system, lubricating oil system and automatic monitoring system.
5.1 Lubricating water system: It is mainly used for the lubrication and cooling of packing seal, which requires adequate and uninterrupted water supply. Less sediment, generally not more than 0.05 ~ 0.1kg / m3, sand particle size not more than 0.05 ~ 0.10mm, each pump water volume 2L / S, pressure 0.10Mpa, before turning on the lubricating water should be 5 minutes Turn on again.
4.4 lubricating oil system
In addition to the gear box, the motor needs thin oil lubrication; pump thrust radial bearings with thin oil circulating lubrication, gearbox dilute station points out for the pump does not run for a long time, before operation should dilute the oil cycle for 5 minutes before turning it on ; Guide bearing using gravity oil lubrication, oil No. N220 mechanical oil, the operation should always check the oil level is normal and timely refueling, in order to ensure the oil cleanliness and viscosity, the first 72 hours of operation to be replaced after the For every 300 to 500 hours of work, replace the thin oil in the guide bearing and filter it before filling. If the pump is not working for a long time, replace the lubricating oil in the guide bearing first before starting the operation.
4.5 Automatic Monitoring System
Monitoring items include pump impeller inlet vacuum pressure, impeller outlet pressure, guide vane outlet pressure, pump inlet and outlet pressure difference, pump vibration, guide bearing temperature, thrust radial bearing temperature and so on are provided with analog output Test components, the standard analog signal 4 ~ 20mA.
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