Pump is conveying liquid or liquid pressurized machinery. Transmitting mechanical power or other external energy to the liquid it is the prime mover, the liquid energy increases. Pump is mainly used to transport liquids including water, oil, acid and alkali liquid, emulsion, suspension emulsion and liquid metals, but also transport liquid, gas mixtures and liquids containing suspended solids. Enhance water for human life and production are very important. It has a variety of ancient water lifting devices, such as Egypt's chain pump (17th century BC), China's Jie Gao (17th century BC), gin (11th century BC) and the waterwheel (1st century AD). There are more well-known third century BC, Archimedes screw rod invention can provide a smooth continuous water to several meters high, the principle is still used by modern screw.
Around 200 BC, ancient Greek craftsmen ¿ËÌØÎ÷±ÈÎÚ˹ fire pump invention is one of the most primitive piston pump, already have the main components of a typical piston pumps, piston pumps, but only after the emergence of the rapid development of the steam engine was .
1840 ~ 1850, the United States Worthington invention and steam pump cylinder opposed-cylinder, direct-acting steam piston pump, marking the formation of the modern piston pump. The 19th century was the height of the piston pump development, was already used in hydraulic machines and other machinery. However, with the surge in water demand, from the 1920s, low-speed, the flow is very limited piston pump is gradually being replaced by high-speed centrifugal and rotary pumps. However, in areas of high pressure low flow reciprocating pump still occupies a dominant position, in particular, diaphragm pumps, piston pumps with unique advantages, applications are increasing.
Appear with the requirements of the rotary pump for liquid transportation industry increasingly diverse relevant. As early as 1588 there was recorded on four-leaf sliding vane pump, after another appeared in a variety of other rotary pumps, rotary pumps, but until the 19th century, there are still a large leak, wear big and low efficiency. Early 20th century, people solve the rotor lubrication and seals and other issues, and the use of high-speed motor drive, suitable for high pressure, and a variety of small and medium viscous liquid flow rotary pump was developed rapidly. Rotary pump type and kind of liquid transport as much as less suitable for other types of pumps.
Water using centrifugal force idea first appeared in a sketch made by Leonardo da Vinci in. 1689, French physicist Papin invented the four blade impeller centrifugal pump volute. But closer to the modern centrifugal pump, it is present in the United States in 1818 with radial straight blade, semi-open impeller and volute double-suction pump so-called Massachusetts. 1851 ~ 1875, with a multi-stage centrifugal pump vanes have been invented, making the development of high-lift centrifugal possible.
Although early in 1754 after the Swiss mathematician Euler proposed the basic equations of hydraulic machinery impeller, centrifugal pump designed to lay the theoretical foundation, but until the 19th century, the invention of high-speed centrifugal pump motor to get the ideal power source, it was able to give full play to the superiority. ÆÕ·òÀ³µÂÀ× Renault in the UK and Germany, Haier basic theory and practice of many scholars, the centrifugal pump efficiency is greatly improved its performance range and field use is also growing, has become the most widely used modern, the largest output pump.
Pumps are usually divided according to the principle displacement pumps, power pumps and other types of pumps, such as jet pumps, water hammer pump, electromagnetic pump, gas lift pump. Except classification pump works, but also by other methods classification and nomenclature. For example, according to the driving method can be divided into electric pump and turbine pump, etc.; according to the structure can be divided into single-stage and multi-stage centrifugal pump; use can be divided boiler feed pumps and metering pumps, etc.; divided according to the nature of transmission fluid for water pumps, oil pumps and mud pump and so on.
Positive displacement pumps rely on the operating member in the pump cylinder for reciprocating or rotary motion, so that the working volume is alternately increased and reduced, in order to achieve a suction and discharge of liquid. The operating member to reciprocate the displacement pump known reciprocating pumps, rotary movement of the rotary pump is called. Former alternating suction and discharge processes at the same pump cylinder by the suction and discharge valves to be controlled; latter through the rotation of the gear, screw, vane rotor or leaf work element, forcing the liquid from the suction rotor moves to the discharge side.
Positive displacement pumps and forth at a certain speed or the number of traffic is certain, almost no change with pressure; reciprocating pump flow and pressure pulsations have a greater need to take appropriate measures to abate pulsating; rotary pumps generally no or only a small ripple pulsation; self-absorption capacity, the pump can be started after the pipeline pumping air into the liquid; must start the pump discharge line valve is fully open; reciprocating pump for high pressure and low flow; flow rotary pump is suitable for small and medium and higher pressure; reciprocating pumps suitable for pumping clean liquid or gas-liquid mixture. In general, the efficiency is higher than the volume of the pump power pump.
Pump powered by a rapidly rotating impeller forces the liquid to the mechanical energy transmitted to the liquid, which increases the kinetic and pressure energy, and then through the pump cylinder, the majority of the kinetic energy is converted to pressure energy delivery is achieved. Power pump, also known as a pump or vane impeller pump. Is the most common centrifugal pump power.
Lift pump power generated at a certain speed limit, lift with the flow and change; stable, continuous delivery, flow and pressure pulsation-free; generally no self-absorption capacity, the need to be filled with a liquid pump or pipeline pumping after a vacuum in order to start work; wide application range of performance; suitable for transporting small cleaning liquid viscosity, specially designed pump can deliver mud, sewage or water lost solids. Powered pump is mainly used for water supply, drainage, irrigation, process liquid delivery, power storage, hydraulic and marine jet propulsion.
Other types of pump means in another way a class of energy transfer pump. Jet pump for example, rely on high-speed jet of working fluid, the fluid needs to be delivered to the pump suction and momentum mixing of the two fluids to pass through the exchange of energy; pump water hammer is generated using the water flowing in the sudden braking energy, so that part of the pressure rise to a certain height; electromagnetic pump is energized so that the liquid metal in the electromagnetic force generated transport flow is achieved; gas lift pump compressed air through the conduit to the compressed gas or other fluid at the bottom, so as to form a liquid lighter than the gas-liquid mixed fluid, and then borrow outside pipe pressure liquid mixed fluid pressure will rise up.
Pump performance parameters of the main flow and head, in addition to shaft power, speed and essential cavitation margin. Flow refers to the amount of fluid output per unit of time through the pump outlet, the general volume flow; lift is incremental energy delivered per unit weight of the liquid from the pump inlet to the outlet, for the displacement pump, energy incremental pressure increase mainly reflected in the so usually the pressure increment instead head to represent. Pump efficiency is not an independent performance parameters, it can, for example flow, head and shaft power according to a formula obtained by other performance parameters. Conversely, known flow rate, head and efficiency, but also can be obtained shaft power.
There is some change in the relationship of interdependence between the various performance parameters of the pump, the pump can be tested separately measured and calculated parameter values, and draw a curve that these curves called the characteristic curve of the pump. Each pump has a specific characteristic curve, provided by the pump manufacturer. Plant usually given characteristic curve segment also indicates the recommended performance, known as the working range of the pump.
The actual operating point is determined by means of the pump characteristics of the pump curve and the intersection of the pump curve. Selection and use of the pump, the pump operating point should fall within the scope of work, in order to ensure the functioning of the economy and security. In addition, the same delivery pump liquids of different viscosities, and its characteristics will change. Typically, the pump manufacturer given characteristic curve mostly refers to the characteristic curve when transporting clean cold water. For the pump power, as the viscosity of the liquid increases, the efficiency is lowered and the head, the shaft power increases, so the viscosity of the industrial fluid may be heated so that the viscosity becomes smaller, in order to improve the transmission efficiency. |
