Fitting curve of circulating pump and its application

Abstract: Hot water heating system is a complicated system composed of thermal users, heat network, heat source and circulating water pump. In order to enable the circulating water pump put into operation in the high-efficiency area, and make the circulating water volume meet the need, without causing serious water and heat imbalance, we must analyze the circulation pump (single or multiple) operating in the system status . The result is a system that matches the system's circulating water pump to the maximum possible "full load, high efficiency" operation.
Keywords: hot water heating system circulating water pump hot water heating system is a hot user, heat network and heat source and circulating water pump posed by a complex overall system. In order to enable the circulating water pump put into operation in the high-efficiency area, and make the circulating water volume meet the need, without causing serious water and heat imbalance, we must analyze the circulation pump (single or multiple) operating in the system status . The result is a system that matches the system's circulating water pump to the maximum possible "full load, high efficiency" operation.

Using the drawing method and the difference method to determine the pump performance parameters and operating points to select the matching pump, the accuracy is poor, and more troublesome; Therefore, using the principle of least squares method for heating circulating pump performance experimental data curve fitting, Discuss the working condition of circulating pump again.

1 circulating pump curve fitting

In this paper, the least squares method to polynomial curve fitting to find the performance curve of circulating pump equations. The basic idea is to set up the error equation through error analysis, to derive the corresponding normal equations under the condition of the smallest error, to obtain the regression coefficient (least squares estimation) by solving the normal equations (linear algebraic equations) Set up a curve fitting polynomial.

2 Applied Research

Introduced in front of the numerical solution of the pump performance fitting curve equation, knowing that the equation can easily know the operation of the pump. If we give the equation of pipeline characteristic and solve them in series, calculate the working point and get the flow and lift of the working point, then we can compare with the total flow and total resistance of the actual pipeline to analyze the system hydraulic conditions , Come to match the pump to determine the solution to the hydraulic imbalance. The examples given in this section are fully analyzed.

2.1 System Overview

Known a heating system, construction area of ​​90,000 m2. The estimated heat load is 5.2MW, the total system water supply temperature is 95 ℃, the return water temperature is 70 ℃, the network heat dissipation and leakage coefficient K is 1.05, and the flow additional coefficient φ is 1.2. The heating radius L is 500m, the friction resistance R is 70 Pa / m, the percentage of local resistance loss relative to the distance takes a as 0.3, the internal resistance of heat source Hr is 10X104Pa, the user system resistance Hy is 1x104Pa, the margin coefficient K is 1.15.

2.2 System Condition Analysis

Therefore, for a serious hydraulic imbalance in heating systems, especially end users is not hot, can not simply use the method to increase the pump to solve. Since the operating point of a single pump is already in the flat area of ​​the pump performance curve, the total flow increase is limited after the pump is increased. If there are two pumps running in parallel, the synthetic curve is more flat, and then add a pump running in parallel, the total flow increase will be smaller or not increase. Therefore, to solve the problem of hydraulic imbalance in heating system, we should first consider adjusting the pipe network through the hot user inlet valve so that the system flow can be rationally distributed. Of course, if the total flow does not meet the requirements, a single pump that matches the system or a combination of more than one pump that makes the pump work in the high-efficiency area should be selected or calculated.

3 Conclusion

(1) For a certain expansion system, with the increase of heat users year by year, original pump has been small, through the pump performance analysis, the use of multiple pumps parallel operation is possible. However, what we often encounter is that the flow and lift of a single pump far exceed the actual needs of a single pump. Due to the imbalance of the network, there are always some users are not hot, in order to make up for the defects brought by the imbalance, the use of multiple pumps in parallel operation. At this point the system of circulating water has increased, but the added value is very small, the pump efficiency is naturally low.

(2) Due to the serious hydraulic imbalance in the network, the pump can not meet the needs of end users after it is connected in parallel. Even replacing high-power and large-flow pumps is of no avail. In fact, if the hydraulic imbalance in the network is serious, as long as the performance of the pipeline is unchanged, the traffic will maintain the same degree of mismatch after the traffic increases.

(3) The analysis of hydraulic conditions is the key to understand the operation of the entire system, and the establishment of circulating pump performance curve equation for the hydraulic conditions of great convenience. Circulating pump performance curve equation for the computer to choose a circulating water pump laid the theoretical foundation, but also the basis for quantitative management.

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Scenery JD-BP series medium pressure submersible pump dedicated frequency converter application

(A) Overview With the development of China's oil industry and oilfield development needs, in order to improve oil recovery and ultimate recovery rate, the application of mechanical oil recovery method is an important step in the development of the entire oil field. As a relatively new mechanical oil recovery equipment, submersible pump has been widely used in our country in recent ten years and has been continuously improved and developed.
Submersible pump is a multi-stage centrifugal pump working downhole, together with the tubing into the well, the ground power through the transformer, control panel and submersible cables will be delivered to the underground submersible electric motor, the motor driven multi-stage centrifugal pump rotation will be The electrical energy is converted to mechanical energy, lifting the well fluid in the well to the surface.
As the submersible pump unit and the pump is below the ground more than two thousand meters of the bottom of the work, the working environment is very harsh (high temperature, strong corrosion, etc.), the traditional power supply ----- Total pressure, frequency so that it Frequent faults, operating costs greatly increased. Submersible pump damaged ground mentioned to repair, only a construction fee reached 50,000 yuan, the value of one hundred thousand yuan on average put on the cable to be replaced five times, the submersible pump on average every ten months to be Maintenance time, maintenance costs about eighty thousand yuan. The traditional way of supplying electricity is far more detrimental, for example:
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2, the oil field supply voltage often fluctuates, the motor under excitation or over excitation, the motor is burned from time to time.
3, two thousand meters downhole cable brought about 150V line loss, as part of the loss can not be compensated, thus affecting the normal operation of the motor.
(B) the application of submersible pump dedicated inverter Submersible pump in the power frequency start, start current, the larger the voltage drop of the motor cable, making the motor cable in the boot process higher back pressure, so that the insulation performance Lower, each will make the pump life greatly reduced, greatly affecting the life of submersible pump. Submersible pump in normal operation, the prevalence of low motor load conditions, "big car" serious phenomenon. Submersible pump power factor is low, reactive power loss, power consumption and more. According to the requirements of oilfield development program, submersible pump should be based on changes in geological conditions, regulating pumping volume. The traditional way to adjust is to change the nozzle to adjust the output, which not only causes the energy loss but also can not be precisely controlled. Sometimes makes the motor and pump running at high pressure for a long time; sometimes make the well out of the sand serious, shorten the life of the equipment, can not meet the requirements of the development program. To solve the above problems, only the use of frequency control system, adjust the hydraulic pressure, adjust the output. We have over 20 electric pump wells in Shengli Oilfield to transform the frequency conversion operation, played a good effect.
Submersible pump dedicated inverter has the following characteristics:
1, the pump can be soft start, soft stop, extend the life of the pump to protect the motor, cables, saving maintenance costs.
2, improve the power factor of the electric pump system, energy-saving effect is obvious.
3, improve the quality of the pipe network, can realize the closed-loop control of the electric pump system, increase the work safety of the electric pump system.
4, high reliability, easy to operate, you can achieve continuous output voltage and current regulation, in order to achieve the purpose of continuously adjustable output power, the electric pump oil production system in the best working condition.
5, improve production efficiency, facilitate the overall management and dispatch, can realize the pump system of distributed control.
6, oil extraction technology involves multidisciplinary fields, the current submersible pump inverter from the original high --- low --- high way into a direct high-high frequency, smaller, more convenient operation, However, in order to improve the automation level of oil recovery, the following problems need to be solved in application:
(1) Make inverter and bottom hole temperature sensor and pressure sensor form closed-loop control system.
(2) The frequency conversion control system with wireless transmission of operating parameters, can monitor the operation of wells at any time.
(C) Recommended Comments In summary, the use of inverter control panel to improve oil production efficiency, while in line with the development program requirements. The submersible electric pump shaft is transformed by frequency conversion to realize the soft start of the electric pump well and the soft stop, effectively protecting the electric pump well unit and the cable; the hydraulic pressure can be conveniently adjusted by adjusting the frequency, thereby avoiding the problems that the unit, Long-term operation under high pressure; extend the life of electric pump wells, saving oil well maintenance, maintenance costs, so that the pump unit in the best conditions to run. Greatly improve the efficiency of electric pump production system. At the same time, improve the power factor, improve the power supply capacity of the power grid, energy-saving effect is obvious. Large-scale promotion of submersible pump frequency conversion technology, will bring good economic and social benefits.

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Small submersible pump for agriculture is one of the main water-lifting equipment in rural areas to solve the problems of farmers' production and domestic use of water for irrigation and farmland irrigation. However, due to the large number of submersible pump manufacturers and large technical forces, the quality of products is very poor. Therefore, in order to choose a reliable, cheap pump, it must start from the following aspects:

1, the manufacturer's choice

Select the submersible pump, we must first recognize the pump manufacturer, it is recommended to give priority to buy water-filled submersible pump, pump the first to see the grade and product certification, must not buy "three no" products, that is, without the manufacturer , No production date, no production license. Otherwise there is a problem, the user will do nothing.

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3, the pump parameters to determine

Select submersible pump focus is to determine the pump flow and head and other parameters. Pump flow selection, water and water to the water and water consumption and family conditions to adapt to the specific issues to be treated specifically. Users need to lift the best choice for the pump head lift close to the use of economic, efficiency can achieve the highest. However, it is not required to be absolutely equal. Generally, a deviation of no more than 20% can work under more energy-efficient conditions. If you choose the pump head is too small, low-lift pump for high-lift work, that is, "small horse drawn cart", even if pumping water, water will be small; pump head is too high, high lift pump for low lift Work, that is, "big horse car", there will be running flow is too large, the motor overload, if the long run, the motor temperature, the winding insulation will gradually aging, or even burn the motor.

4, pump quality inspection

Submersible pump motor water-filled, oil-filled and shielded structure, the general water-filled applications are the most widely used. The pump before use, you must unscrew the two water injection holes bolt, a water injection (no sand), the other to discharge air, water after the static wait for about 15 minutes, and so on all the motor cavity air after the discharge plus clear water , Until after filling the water and then tighten the two water bolts. The motor is sealed. Motor water, the winding work in the water, the motor insulation can be measured, the measured insulation resistance must be megger that shake table, can not use a multimeter, because the multimeter range is limited, for the insulation resistance between the winding and the earth measured Not clear. Insulation qualified, the pump test run test. Wherever conditions permit, after the motor is filled with water, tighten the water injection bolt, the pump can be energized in the pool test run, but can not operate for a long time, no conditions can be idle in the well, but the time shall not exceed 3 seconds.

5, the choice of purchase location

Should pay attention to the agricultural machinery department approved point of sale or store to buy and request a formal invoice, otherwise there is a problem, the user will not be able to solve.

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