Design And Cavitation Performance Research Of Low Specific Speed Hot Water Circulating Pump

With the continuous development of national economy, the application of large scale central air conditions in commercial and civil buildings is becoming more and more popular, its energy consumption in the proportion of total energy consumption is becoming bigger and bigger. Circulating pump provides power for water circulation in the entire air conditioning system, its energy consumption occupies a large proportion in the energy consumption of entire system. Medium in the hot water circulation pump is hot water, and the operation condition is tougher, which will lead unstable flow. As a result, the reasonable design of low specific speed hot water circulating pump is critical, and it is the key for the entire system to realize smooth running and energy saving.On the basis of the traditional design method of centrifugal pump, through the optimization of the geometric parameters to improve the circulation pump hydraulic efficiency and operation stability, will be an important research subject. This paper combines theoretical analysis, numerical calculation and test method to study the hydraulic performance and cavitation performance of low specific speed hot water circulating pump, aims to build a set of hydraulic design method based on increasing-capacity design method. The main works include:1) The existing research status and results of hot water circulating pump were summarized. Based on the given design conditions, combined with the increasing-capacity design method, a preliminary calculation and design of the critical flow components was completed.2) The 3-d full flow model of circulating pump including impeller, volute, pipeline and clearance was built and the whole flow field was calculated with the RNG k-e turbulence model, in order to analyze the internal flow of centrifugal pump and get the hydraulic performance curve. On this basis, the influence of impeller blade type, the back clearance, import diameter, leaf number on centrifugal pump hydraulic performance was researched.3) Based on the theoretical analysis of cavitation in centrifugal pump and piping system, the basic equations of cavitation was established and the calculation method of NPSH was built. Cavitation on the optimized circulation pump model was calculated with hybrid model and Rayleigh-Plesset full cavitation model, in order to get the critical NPSH of the circulating pump and analyze the process of cavitation expanding. Besides, the influence of temperature on the centrifugal pump cavitation performance was researched by changing the medium temperature.4) According to the centrifugal pump performance testing method, centrifugal pump performance test-bed was established, to complete the circulation pump flow performance test and get the test data, draw the performance curve. The simulation results and the test results were analyzed and contrasted.In this paper, the design method of the hydraulic components and the corresponding three-dimensional flow numerical simulation and performance prediction technology, were successfully applied to the performance optimization of circulating pump model, which effectively improved the efficiency and stability of the circulating pump. The design and analysis method of hot water circulating pump has a certain reference value and significance for new model design and development...