Three-dimensional incompressible Navier-Stokes equations closed by RNG κ - ε turbulent model were adopted to simulate the internal flow of a sump shared by two cooling pumps. Computed results show that the bottom slop of the forbay and asymmetric operation scheme of pump sets will result in unfavorable flow conditions, and swirl angles of flow entering the suction pipe of pump are quantitatively analyzed. Since two pumps share a sump in a column, the auxiliary cooling pump in front will interfere with the flow fields of the sump, which is not favorable to the flow conditions of the main cooling pump. Three operation schemes with or without the auxiliary cooling pump were simulated to compare the influence of the flow fields of sump on the flow conditions of the main cooling pump, and the bias angles of flow entering the suction pipe are quantitatively calculated. The validity and reliability of numerical simulation are verified by a model test. The findings indicate that the computational fluid dynamics can be successfully applied to 3D flow of pump sump and numerical computation can provide reliable references for theoretical analyses, model test and modification of design scheme.
To study the significance of internal pressure pulsation characteristics between prototype and model pump devices, monitoring of computational fluid dynamics and dynamic measurement of a model were carried out under different working conditions and measuring points. The results of computational fluid dynamics calculation and model test are as follows. First, the positions of main frequency and subfrequency are almost the same, whereas the amplitude has a slight deviation. Second, the amplitude of inlet impeller is larger, and the main frequency is three times of rotating frequency. Third, the inlet speaker has mainly low pulsation, which is almost distributed in blade frequency and 1/3 times of rotating frequency. Moreover, the pressure pulsation of symmetrical points in each condition has a good symmetry. As the flow rate decreases, both the mixing and blade frequency amplitudes in the inlet speaker and impeller first decrease and then increase. The minimum mixing amplitude appears in the design condition of 253 L/s, whereas the blade frequencies are 203 and 253 L/s. The numerical calculation results are almost the same as those of prototype and model devices. Therefore, numerical calculations and experimental studies on pressure pulsation can guide the design and stable operation of similar pump stations.
According to the features of very low head in many pumping stations of the project of south to north water Transfer Project , it is analyzed on structure types, hydraulic performances and economic indexes for various tubular pumps. It put forward that standard tube tubular, pit tubular and bulb tubular pumps can all be used for these very low heads stations. It is critical to resolve some problems including the material and lubrication of guide hearing , the life noise of gearbox.
According to different processes of tides and peak‐valley electricity prices, this paper determines the optimal start up time in pumping station's 24 hours operation between the rating state and adjusting blade angle state respectively based on the optimization objective function and optimization model for single‐unit pump's 24 hours operation taking JiangDu No.4 Pumping Station for example. In the meantime, this paper proposes the following regularities between optimal start up time of pumping station and the process of tides and peak‐valley electricity prices each day within a month: (1) In the rating and adjusting blade angle state, the optimal start up time in pumping station's 24 hours operation which depends on the tide generation at the same day varies with the process of tides. There are mainly two kinds of optimal start up time which include the time at tide generation and 12 hours after it. (2) In the rating state, the optimal start up time on each day in a month exhibits a rule of symmetry from 29 to 28 of next month in the lunar calendar. The time of tide generation usually exists in the period of peak electricity price or the valley one. The higher electricity price corresponds to the higher minimum cost of water pumping at unit, which means that the minimum cost of water pumping at unit depends on the peak‐valley electricity price at the time of tide generation on the same day. (3) In the adjusting blade angle state, the minimum cost of water pumping at unit in pumping station's 24 hour operation depends on the process of peak‐valley electricity prices. And in the adjusting blade angle state, 4.85%∼5.37% of the minimum cost of water pumping at unit will be saved than that of in the rating state.
A dynamic planning model for optimizing operation of variable speed pumping system, aiming at minimum power consumption, was proposed to achieve economic operation. The No. 4 Jiangdu Pumping Station, a source pumping station in China's Eastern Route of South‐to‐North Water Diversion Project, is taken as a study case. Since the sump water level of Jiangdu Pumping Station is affected by the tide of Yangtze River, the daily‐average heads of the pumping system varies yearly from 3.8m to 7.8m and the tide level difference in one day up to 1.2m. Comparisons of operation electricity cost between optimized variable speed and fixed speed operations of pumping system were made. When the full load operation mode is adopted, whether or not electricity prices in peak‐valley periods are considered, the benefits of variable speed operation cannot compensate the energy consumption of the VFD. And when the pumping system operates in part load and the peak‐valley electricity prices are considered, the pumping system should cease operation or lower its rotational speed in peak load hours since the electricity price are much higher, and to the contrary the pumping system should raise its rotational speed in valley load hours to pump more water. The computed results show that if the pumping system operates in 80% or 60% loads, the energy consumption cost of specified volume of water will save 14.01% and 26.69% averagely by means of optimal variable speed operation, and the investment on VFD will be paid back in 2 or 3 years. However, if the pumping system operates in 80% or 60% loads and the energy cost is calculated in non peak‐valley electricity price, the repayment will be lengthened up to 18 years. In China's S‐to‐N Water Diversion Project, when the market operation and peak‐valley electricity prices are taken into effect to supply water and regulate water levels in regulation reservoirs as Hongzehu Lake, Luomahu Lake, etc. the economic operation of water‐diversion pumping stations will be vital, and the adoption of VFDs to achieve optimal operation may be a good choice.
Abstract Baoying Pumping Station as the first station built in the East Route of the S-to-N Water Diversion Project in China, due to the importance of water source project and its 5000 hours yearly operating time, a serial of model tests and other measures were taken to secure its safety and high efficiency operation. Through the comparative model tests in the preliminary design stage, it was made clear that mixed-flow pump was the right direction of pump selection. The acceptance model test indicated that all performance requirements were satisfied and the head-weighted efficiency of the pumping system reached 80.5%, which was about 7 percentages higher than that obtained in the preliminary research and a good foundation for its efficient and economical operation was laid. The optimization design of inlet and outlet flow passages was not significant for improve the efficiency of pumping system. The verification test results were very close to the acceptance test results, and have been confirmed each other. The international bidding and mechanism of joint venture in purchasing main equipment for Baoying pumping station proved to be a success in introducing advanced foreign technology, and its construction experience can provide a useful reference for similar pumping stations.
This paper introduced the principle of moving least square(MLS) method and its application in fitting pump performance curves.The error of the MLS method was about one-tenth of that of the conventional least square method after a comparison using case studies between two methods.The results showed that moving least square method had high accuracy when it was used in curve-fitting of pump performance,especially in the unstable areas of axial-flow pumps.It has great significance for the research of four-quadrant pump performance curve-fitting and transition simulation.
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