Special lecture on mechanical equipment: “Pumps” – Learn a little every day (13): Axial flow pumps “Improve yourself””

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This post was last edited by A Dai A Mu on 2013-12-12 at 12:32. In order to encourage more people to come and discuss as well as to study more actively, the top five users each time will receive a “Reward for Active Learning.” Some people might think that it’s terrifying to spend their working days doing nothing, performing menial tasks, not 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. Besides those experts like Hai Chuan, there are still others who know it.) . . ) 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 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 @NewcomersToHaiChuan @Lovestory @ManTianYun @ZhaoQingsheng Yesterday, we started using jet pumps; I believe the members here now have a basic understanding of them~~! From now on, I’ll try to break down the knowledge into smaller portions, in smaller amounts, to make it easier for everyone to learn*~~! Today, I’d like to explain something: in order to encourage everyone to participate more actively in discussions and 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, performing menial tasks, not 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. Besides those experts like Hai Chuan, there are still others who know it.) . . ) 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 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 Yesterday we started using the car pump, and I believe the members here now have a basic understanding of it~~! A friend from the marine community told me that I talk too much every day; in the future I’ll try to present the information in more detailed forms, in smaller amounts, to make it easier for everyone to learn*~~! Today, I’ll explain axial flow pumps and mixed-flow pumps to you all. Come on, let’s learn~! Axial flow pump. Axial flow pumps (A*al-Flow Pump) are, along with mixed-flow pumps, types of blade-type water pumps that have a high specific speed. Their characteristics are medium to high flow rates, as well as medium to low head pressures. Applications: Circulating water pump stations in large factories, thermal power plants, and heat power stations; urban rainwater flood control pump stations, large-scale sewage pump stations, as well as some large lift pump stations in projects such as the Lan River to Tianjin water diversion project, etc. I. Basic structure of axial flow pumps Axial flow pumps can be installed vertically (upright), horizontally (horizontal), or at an angle (inclined). ZLB(Q) type vertical axial flow pump, ZWB(Q) type horizontal axial flow pump, ZXB(Q) type inclined axial flow pump. Basic components of axial flow pumps: (1) Suction pipe; (2) Impeller. Impellers can be classified into three types based on their degree of adjustability: fixed, semi-adjustable, and fully adjustable; (3) Vanes, which convert the rotational motion of the water flowing upward from the impeller into axial motion. Typically, axial flow pumps have 6-13 vanes. (4) Shaft and bearings (5) Sealing device II. Working principle of axial flow pumps The operation of axial flow pumps is based on the lift theory of wings in aerodynamics. Its blades have a cross-sectional shape similar to that of an airfoil; blades with this type of shape are generally referred to as airfoils. Since the distance traveled along the lower surface of the airfoil is greater than that along its upper surface, the flow velocity of the fluid along the lower surface is higher than that along the upper surface. Consequently, the pressure on the lower surface of the airfoil will be less than that on the upper surface, and the fluid will exert a force P on the airfoil directed from above downward. The same airfoil also exerts a reaction force Pf on the fluid, with Pf = P. When a blade with a Hebei-type cross-section rotates at high speed in water, the water flow experiences rapid swirling around the blade. As mentioned above, the blade exerts a force Pf on the water, and as a result of this force, the water is pushed to a certain height. III. Performance characteristics of axial flow pumps: (1) The head increases sharply as the flow rate decreases; the Q-H curve drops steeply and exhibits a turning point. When the flow rate is low, backflow occurs at the inlet and outlet of the impeller blades; the water gains energy repeatedly, similar to a multi-stage pressurization process, which results in a sharp increase in head. Performance characteristics of axial flow pumps: Backflow increases the flow resistance loss, which in turn leads to an increase in shaft power. Generally, the no-load head H0 is about 1.5 to 2 times the head at the designed operating condition. (2) The Q–N curve is also a steeply descending curve; when Q = 0, its shaft power N0 = (1.2–1.4) Nd, where Nd is the shaft power under design conditions. When starting an axial flow pump, the motor should be started with the gate valve fully open; this is commonly referred to as \"starting with the valve open\". The Q-η curve has a hump shape. The range of efficient operation is very narrow; the efficiency drops rapidly once the flow deviates slightly from the design operating point. Using gate valves to regulate flow is disadvantageous. Generally, only the method of changing the blade device angle β is used to modify its performance curve, hence it is called angle variation control. In large fully-tonal axial flow pumps, in order to reduce the starting power of the pump, the β angle of the blades is usually reduced before starting, and then increased gradually after startup. (4) In pump samples, the suction performance of axial flow pumps is generally expressed by the net positive suction head. Due to the high specific speed ns of axial flow pumps, they have a large flow rate. The net positive suction head is also high, sometimes reaching 12 m; the impeller must be submerged in water in order to function, and the installation height is usually negative. Below are my special series of lectures on mechanical equipment – “Pumps”. Learn something new every day: (16) Pneumatic diaphragm pumps – “Improve your knowledge” http://bbs.hcbbs.com/thread-1257985-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (15) Pneumatic diaphragm pumps – “Improve your knowledge” http://bbs.hcbbs.com/thread-1257433-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (14) Mixed-flow pumps – “Improve your knowledge” http://bbs.hcbbs.com/thread-1257224-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (13) Axial flow pumps – “Improve your knowledge” http://bbs.hcbbs.com/thread-1256970-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (12) Jet vacuum pumps – “Improve your knowledge” http://bbs.hcbbs.com/thread-1256707-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (11) Automotive pumps – “Improve your knowledge” http://bbs.hcbbs.com/thread-1256253-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (10) Pump materials – “Improve your knowledge” http://bbs.hcbbs.com/thread-1255790-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (9) Self-priming pumps and pump materials – “Improve your knowledge” http://bbs.hcbbs.com/thread-1255635-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (8) Oil seals – “Improve your knowledge” http://bbs.hcbbs.com/thread-1255340-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (7) Seals – “Improve your knowledge” http://bbs.hcbbs.com/thread-1255132-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (6) O-rings – “Improve your knowledge” http://bbs.hcbbs.com/thread-1254912-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (5) Pump structure – “Improve your knowledge” http://bbs.hcbbs.com/thread-1254630-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (4) Pump structure – “Improve your knowledge” http://bbs.hcbbs.com/thread-1254625-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (3) – “Improve your knowledge” http://bbs.hcbbs.com/thread-1253809-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (2) Schematic diagram of centrifugal pumps – “Improve your knowledge” http://bbs.hcbbs.com/thread-1253590-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (1) Pump selection – “Improve your knowledge”. These are my special posts; I will continue to update them daily. Please give me your support, listen, and discuss! ； If there’s any direction that needs to be explained, feel free to contact me. If many people ask for it, I’ll create a separate post to go over it~~! :) A series of special lectures on mechanical equipment titled “Pumps” – a summary post featuring new knowledge each day, continuously updated at http://bbs.hcbbs.com/thread-1256318-1-1.html. Everyone is welcome to listen; I’ve already started broadcasting these lectures, and I hope those who, like me, want to gain knowledge every day will listen as well. Let’s learn together every day and discuss~~!