Special lecture on mechanical equipment: “Pumps” – Learn a little every day (20): Self-priming pumps “Improve yourself””

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This post was last edited by tclz007 on 2014-1-1 at 11:56. It’s the year 2014 now, and I wish everyone a successful Year of the Horse – may you soon have money, a house, a car, and more. Before we know it, I’ve already talked about 20 different types of pumps!! If we start anything else, it will be other mechanical equipment. For those who are having problems with the pumps, I hope we can exchange ideas~~! To encourage everyone to come and participate in discussions more actively, as well as to study more diligently, the top five participants each time will receive a “Motivation Reward for Active Learning.” Some people might think that it’s terrifying to spend their working days doing nothing useful, performing menial tasks without knowing what to do or what to learn; day after day, year after year, with no vision for their future We must start working hard from now on; even if we learn a little knowledge every day, it will add up over time and help us enrich ourselves. We need to set clear goals – only by filling our minds first can we enrich other aspects of our lives as well. . . . . . It only takes a short ten-odd minutes per day, and you will see the future! ! ! (Anyway, I have learned it; whether you learn it or not is up to you. Those who know it include that master Hai Chuan, aside from others. . . ) Enough talk – let’s start with the basics today~~! I’ve been posting special threads for so many days now; I’m sure everyone has benefited a lot from them. Thank you all for your support!! Welcome everyone to listen. I have started broadcasting, and I hope those who, like me, want to gain knowledge every day will listen. Let’s learn together every day and discuss~~! These past few days, many people have asked questions, and I’ll do my best to answer them all. There might be some questions I haven’t encountered before, but there are still plenty of people in our community who can help answer them. @AidaiAmu @hcwang12345 @YiHuXiangMing @tjdxz @YouDianDai @NewbiesPlayingHaiChuan @lovestory @ManTianYun @zhaoqingsheng Recently, rotary pumps have been introduced, and I believe those interested in marine equipment now have a basic understanding of rotary pumps!! From now on, I’ll try to break down the knowledge into smaller portions, in manageable amounts, to make it easier for everyone to learn*~~! Someone has asked me about self-priming pumps these past two days! Today, I’ll explain self-priming pumps to you all~~! It might not cover everything; if you have any questions, please ask on the floor. Thank you~~! Self-priming pump 1. Classification of self-priming pumps: a. Classified by the type of power engine used with the pump: self-priming pumps powered by electric motors; self-priming pumps powered by diesel engines; self-priming pumps powered by gasoline engines. b. Based on the structure and mechanism used to achieve self-priming capability, they are classified into the following categories: gas-liquid mixing type (including internal mixing and external mixing types); water ring pump type; jet type (including liquid jets and gas jets); and other types (accompanied by various positive displacement pumps such as hand pumps, diaphragm pumps, plunger pumps, etc.). Structure and working principle of self-priming pumps: Gas-liquid mixed self-priming pump: It uses the mixing of liquid and gas to expel the gas; after gas-liquid separation, the liquid participates in the gas-liquid mixing again to carry away the gas. External mixing type: The liquid in the gas-liquid separation chamber flows back to the outlet of the pump impeller; air and water mix at the outer edge of the impeller. Internal mixing type: The liquid flows back to the inlet of the impeller, where air and water mix (see diagram for structure). External mixing type self-priming pump: In this type of pump, during normal operation, the return hole is generally not blocked. Later, devices for automatically blocking the backflow ports were also developed, as well as internal mixing self-priming pumps. When such pumps start operating normally, the backflow channel must be completely closed – either through automatic operation using ball valves or manual operation using gate valves. There are also two-stage self-priming pump types used for fuel filling. Factors that affect the self-priming capability: 1. The influence of the wheel’s circumferential speed on self-priming performance; U2 is a necessary condition for promoting the mixing of gas and liquid within the self-priming pump, as well as for facilitating the flow of gas and liquid. An increase in U2 not only leads to an increase in the backflow rate of the self-priming pump but also enhances the gas-liquid mixing, thereby improving its self-priming capability. 2. Clearance between the impeller and the pump body’s baffle: The smaller the clearance between the outer circumference of the impeller and the baffle, the greater the suction lift; this clearance is usually kept within the range of 0.5–1 mm. However, some experimental studies contradict this claim, showing that both pump efficiency and suction performance are optimal at a gap of d=2.5 mm. The self-priming capacity is also related to the gap between the impeller rear cover and the pump cover. This gap is greater than 6 mm. No matter how the geometric parameters of the other structures are adjusted, the self-priming height never exceeds 3 m. After checking the drawings and installing a wooden plate on the pump cover to achieve a gap of d=2.5 mm, the self-priming height exceeded 6 meters within 100 seconds. 3. The volume of the liquid storage chamber, Vc: The liquid storage capacity of a self-priming pump refers to the volume of the pump body below the lowest point of the pump’s suction inlet; in other words, it is the volume of the part of the pump that can hold liquid when the pump is stopped. As the amount of liquid stored increases, the self-priming time gradually decreases. However, if the amount of liquid stored is excessive and the liquid level is higher than the outlet height of the diffuser tube in the water chamber, the water level in the gas-liquid separation chamber becomes too high, which hinders the smooth expulsion of the gas separated from the liquid outside the pump, thereby prolonging the self-priming time as well. Vc/Q=0.5-1.27; it is not favorable if the liquid storage volume of the pump is too large or too small, so an optimal value ns should be selected