Study On The Parallel Pump Unit With High Efficiency And High Reliability

Power consumption of pumps accounts for about20%of the total consumption in China. Therefore, the improvement of the operation efficiency plays an important roal in energy saving and emission reduction. A certain design margin should be considered due to the loss in the process can not be estimated in system design as well as capacity expansion and process requirement fluctuations. So the best condition of the centrifugal pump and piping system are difficult to match. At off-design conditions, not only the pump efficiency is significantly reduced but also the reliability and the service life of components are declined. Therefore, based on the conception of long-term and efficient operation, it is important to reduce the energy consumption of the system and improve the reliability of the pump by studying the mechanism and technology of pump condition adjustment and control.In this paper, a smart pump unit is carried out with parallel pumps.. Based on pump speed and valve adjustment and optimization method, the flowrate and pressure can meet the real-time requirements of the system in a very wide range and ensure that the operating conditions are near the best efficiency point. So the efficiency, reliability and the operating range of the pump system are increased significiently. The main content includes the following aspects:(1) The operating characteristics of parallel centrifugal pump and speed adjustment were introduced; the method to calculate the operation point of parallel pump system was built up; the internal flow, swirl distribution and evolution were simulated; the characteristics of centrifugal pump running in different operating conditions and the relationship with pump reliability were summarized; pump reliability function curve was carried out by comparing and analyzing the reliability data and the internal flow characteristics of pump.(2) Based on the analysis of pump external characteristics, the mathematical model and objective function for low power consumption and long service life were built up; constraint processing method based on the penalty function was studied and a genetic algorithm was design and improved for solving the optimization problem.(3) The optimal operating condition for double pump parallel system was calculated using the method of the Lagrange multiplier; a pump system with two identical pumps in parallel was calculated using genetic algorithms and compared with the experimental results and the theoretical results. Results show that genetic algorithm, theoretical and experimental achieved good agreement; the genetic algorithm is used for different models of dual-pump parallel operation optimization and comparative analysis of the branch valve in parallel pump system.(4) The structure of the smart pump unit was proposed, which is based on valve-speed joint control and operating condition automatically adjustment. The energy consumption and operating reliability of the traditional pump unit with single variable frequency pump and smart pump unit in this article were compared, and result shows that the smart pump system improved the efficiency and reliability significantly; Based on the study above, the optimization algorithm was extended to more than one pump, and a muti-pump system was calculated; the reliability function of the pump was integrated into the optimization algorithm, and the objective function was simplified so that the calculation program can respond faster to changes in demand.(5) In order to analyze the impact of the piping system during dual-pump parallel system adjustment process, a model with the same performance parameters of the test bench was built up in Flowmaster. The pressure, flowrate and other parameters of the key node were analyzed; the way to improve the reliability during adjustment process was sumrized. The results provide guidances for the actual working conditions.In this paper, a smart pump system was proposed based on valve-speed joint adjustment and operating condition optimizing, and the test bench was constructed; The optimizing calculation was carried out to to increase the efficiency and reliability of the pump unit and the results was verified by experiments. The results show that the smart pump unit studied in this paper can increase the flowrate and pressure range significantly under high efficiency and reliability. So the problem in which the operating condition is deviated from the design condition is solved in a certain extent.