Abstract: In tap water costs, electricity consumption is the bulk; therefore, saving energy is key to reducing the cost of running water. In this paper, several operation modes (constant speed operation, variable speed constant voltage operation and variable speed operation) of secondary pumping station are analyzed from the perspective of energy consumption, and the applicable situations of each operation mode are pointed out. Meanwhile, Pumps in the pump class some of the energy-saving mode of operation. According to statistics, the current pump electricity consumption accounts for about 20% of the total electricity consumption. In the tap water plant, pumping station operating costs account for more than 50% of the water cost of the waterworks, while at the same time, the second pumping station has enormous energy saving potential. Therefore, properly adjusting the traditional water supply methods and adopting the maximum energy-saving measures can not only bring huge economic benefits, but also generate enormous social benefits. Waterworks pump selection, usually according to the city's highest day. The maximum water demand to determine, but the pipe network is obviously not a constant flow of water, so most of the time in the pump are in low-load operation. Pump characteristic curve equation is: H = HX - SXQ2 and the characteristic curve of the pipeline equation is: H = HST + ΣSQ2 Where H ------ pump actual lift Q ------ the actual water pump HX ------ pump when Q = 0 generated by the total virtual head SX ------ pump body imaginary resistance coefficient HST ------ pump static head S ------ represents the length and diameter of the pipe has been set along the way and the local resistance and the coefficient The operating point of the pump unit refers to the point at which the total specific energy of the water supplied by the pump is equal to the total specific energy required by the pipe, that is, the intersection of the pump characteristic curve and the pipe characteristic curve. When the curve changes, the operating point will be transferred. At present, with the development of science and technology, variable speed operation is becoming the trend of development (among them, frequency conversion speed regulation is the main method). There are two kinds of operation modes of speed regulation: ①constant pressure variable flow operation mode ② variable pressure variable flow operation mode. Next, we analyze the effect of constant speed operation and variable speed operation from the viewpoint of energy consumption. 1 constant speed running Constant speed running curve as shown on the left. As can be seen from the figure, when the flow in the pipe network is reduced from Q1 to Q2, the water supply pressure of the water pump will increase from the design water supply pressure H0 to H1. In theory, the water pump needs to consume Q2 * H1. At this time, Pipe network characteristic curve analysis, when the pipe network consumes Q2 * H2 instantaneous power consumption, the pump consumes more power Q2 * H1-Q2 * H2 is actually pipe network pressure is increased and inefficiently consumed in the pipe network. Commonly used in the actual operation of the water plant is to adjust the flow rate by adjusting the valve opening, which is by increasing the resistance of the pipe to balance the pump condition (the pipe characteristic curve steep). Because the water consumption of the pipe network is changing all the time, and the classification of the two pumping stations is limited, depending on the number of pumps switching is not realistic, it is often used throttle throttling measures. Although the use of gate valve throttling, pump shaft power will decrease with the decrease of flow, and easy to operate, but economically, throttling regulation is obviously to consume excess energy pump to maintain a certain amount of water supply; At the same time, it can be seen from the efficiency curve that when the flow rate decreases from Q1 to Q2, the efficiency of the pump is correspondingly reduced from ηA to ηB. 2 variable speed operation Variable speed operation mainly has the following two modes of operation: Jis Stainless Steel Flange,Jis Plate Flat Flange,Jis Standard Blind Flange,Jis Casting Steel Flange New Century Machinery Co., Ltd , https://www.ncmflange.com
⑴ constant pressure and variable flow operation Constant pressure operation curve as shown on the left, when the flow in the pipe network from the design flow Q1 reduced to Q2, the pressure remains constant (constant for H0), because the pump frequency control , That is, the original full speed n becomes n1, as shown in the red line. Theoretically, the pump needs to consume Q2 * H0 at this time, though it is less than Q2 * H1 when it is running at constant speed, but it is still larger than the consumed power Q2 * H2 required by the pipeline at this time. Therefore, in order to balance the working condition of the pump, only single sluice throttling is required. As with the constant speed operation, the more consumed power (Q2 * H0-Q2 * H2) is still inefficiently consumed in the pipe network. However, according to the efficiency characteristic curve, the efficiency of the pump with variable speed operation is improved (from ηA to ηB and the equivalent point of point D is point D); and this mode of operation is of good quality of water supply and can be satisfied in any case at the same time The whole network of users of the water supply flow and lift the different requirements.
Analysis on Speed ​​Regulation and Energy Saving of Water Pump in Secondary Pumping Station