What is the pump?
1. pump is mainly used to transport water, oil, acid and alkali liquid, emulsion, suspension emulsion and liquid metal and other liquid, gear pump can also transport liquid, gas mixture and liquid containing suspended solids.
2. pumps can usually be divided into three types of displacement pumps, power pumps and other types of pumps according to their operating principles. Submersible pump in addition to classification according to the principle of work, but also in accordance with other methods of classification and nomenclature. For example, according to the driving method can be divided into the electric pump and the turbine pump; according to the structure can be divided into single-stage pump and multistage pump; use can be divided into the boiler feed pump and the metering pump; according to the nature of transmission fluid can be divided into water pump, oil pump and mud pump etc..
3., the performance of each parameter of the pump has a certain dependence on the relationship between changes, can be painted as a curve to describe, known as the characteristics of the pump curve, each pump has its own specific characteristics curve. A pump is a machine that transports liquids or pumps liquids. It transfers mechanical energy or other external energy of the prime mover to the liquid, increasing the energy of the liquid.
Two. Definitions and historical sources of pumps
A machine that transports liquids or pumps liquids. A pump in broad sense is a machine that carries fluid or makes it supercharged, including some gases. The pump transfers energy from the mechanical energy of the prime mover or other energy to the liquid, increasing the energy of the liquid.
The promotion of water is very important to human life and production，bathtub pump. There are various ancient water appliances, such as chain pump in Egypt (before seventeenth Century), Chinese shadoof (before seventeenth Century), Burton (before eleventh Century), water (first Century AD), and third Century BC in ancient Greece Archimedes invented the spiral rod. Around 200 BC, the ancient Greek craftsman Kurt Siby Lucius invented the most primitive piston pump - Fire pump. As early as 1588, there was a record of 4 vane pumps, and many other rotary pumps appeared in the future. In 1689, the French D. Papan invented the volute centrifugal pump impeller blade 4. In 1818, a centrifugal pump with radial straight blade, semi open double suction impeller and volute appeared in the United states. 1840~1850 years, the United States H.R. Worthington invented the pump cylinder and steam cylinder opposed to the direct impact of the steam piston pump, marking the formation of modern piston pumps. In 1851~1875 years, multistage centrifugal pumps with guide vanes were invented, which made it possible to develop high lift centrifugal pumps. Subsequently, a variety of pumps have been published. With the application of various advanced technologies, the efficiency of the pump is gradually improved, and the performance range and application are also expanding.
Three, pump classification basis
Pump a wide range, according to the principle of work can be divided into:
The power type pump, also called pump or impeller vane pump, fire pump on dynamic effect of rotation of the impeller on the liquid, the liquid pump to continuous energy transfer to the liquid, the liquid kinetic energy (mainly) and the pressure will increase, then converting kinetic energy into pressure energy through the discharge chamber, and can be divided into centrifugal pump, axial flow pump, partial flow pump and vortex pump etc..
The volume type pump, depending on the periodic change of sealing liquid containing space volume, the energy is periodically transmitted to the liquid, the liquid pressure increased to force the liquid discharge, according to the motion form of work elements can be divided into reciprocating pump and rotary pump.
Other types of pumps transmit energy in other forms. As the jet pump work on high-speed jet of fluid will be required to transport fluid suction pump after mixing for momentum exchange in order to transfer energy; diaphragm pump water hammer pump using part of the water flow of the brake is to rise to a certain height of energy transfer; the electromagnetic pump is made of liquid metal flow in the electric power generated under the action of magnetic force and realize delivery. In addition, the pump can also be classified according to the nature of the transmission fluid, driving methods, structure, use and so on.
Four. Application of pumps in various fields
Performance range from the pump to see giant pump flow up to hundreds of thousands of cubic meters per hour, while the micro metering pump pump flow per hour in a few milliliters; pump from atmospheric pressure up to 19.61Mpa (200kgf/cm2); the lowest temperature of the liquid is transported up to -200 degrees Celsius, up to 800 degrees Celsius above. Pumps carry a wide variety of fluids, such as water (clean water, sewage, etc.), oils, acid and alkaline solutions, suspensions, and liquid metals.
In the chemical and oil sector production, raw materials, semi-finished products and finished products are mostly liquid, fire pump and semi-finished and finished products to raw materials, need to go through a complex process, to pump and provide transportation of liquid chemical reaction of the pressure and flow in the process, in addition, many devices also use a pump to adjust the temperature.
In agricultural production, the pump is the main irrigation and drainage machinery. Rural areas in our country are vast and vast, and a large number of pumps are needed every year in rural areas. Generally speaking, agricultural pumps account for more than half of the total output of pumps.
Pumps are also the most widely used equipment in the mining and metallurgical industries. The mine needs pumping and drainage. In the process of ore dressing, smelting and rolling, the pump needs water to supply water first.
In the power sector, nuclear power plants need nuclear pumps, two pumps, three pumps, thermal power plants, a large number of boiler feed pumps, condensate pumps, circulating pumps and ash pumps.
In national defense construction, aircraft flaps, tail rudder and landing gear adjustment, warships and tanks turret rotation, submarine ups and downs, etc., need to use the pump. High pressure and radioactive liquid, and some have to pump without any leakage, etc..
In the shipbuilding industry, the pumps used on each ocean going ship are usually over 100 sets, and their types are various.
As the city water supply and drainage, water steam locomotive, machine tool lubrication and cooling, the textile industry in the transportation of liquid bleach and dye, self suction pump in the transportation of pulp paper industry, food industry and transportation of milk and sugar foods, we need to have a lot of pump.
In short, whether planes, rockets, tanks, submarines, or drilling, mining, trains, ships, or daily life, pumps are needed everywhere, and pumps are running everywhere. That's right. So pump the pump as a universal machine. It's a kind of product in the mechanical industry.
Five, the basic parameters of the pump
The basic parameters of the main performance of the pump are as follows:
1, flow Q
Flow is the amount of liquid (volume or mass) that is pumped out in unit time.
Volume flow is expressed in Q units: m3/s, m3/h, l/s, etc..
Mass flow is expressed in Qm units: t/h, kg/s, etc..
The relation between mass flow and volume flow is:
Qm= P Q
In the p - type liquid density (kg/m3, t/m3), room temperature water P =1000kg/m3.
2 、 lift H
The head is the unit weight of the liquid pump pumping from the inlet of the pump (pump inlet flange) to the outlet of the pump (pump outlet flange) energy increment. That is, the effective energy obtained by pumping a Newtonian liquid through a pump. The unit is N, m/N=m, the height of liquid column pumping liquid, used for short meters.
3, speed n
The speed is the number of revolutions per unit time of the pump shaft. It is indicated by the symbol n. The unit is r/min.
4, cavitation margin
NPSH cavitation, also known as net positive suction head, is the main parameter for cavitation performance. Cavitation has been used in the domestic delta H said.
5, power and efficiency
The power of the pump usually refers to the input power, that is, the power transferred by the prime mover to the pump shaft, so it is also called shaft power, expressed in P;
The effective power of the pump is also called output power, expressed in Pe. Diaphragm pump is a unit of time in the pump from the pump out of the liquid in the pump to obtain the effective energy.
Because the lift refers to the effective energy, pump output unit of heavy liquid obtained from the pump so that the product of head and the mass flow rate and acceleration of gravity, is the effective energy output from the pump in unit time of liquid -- effective power pump:
Pe= P gQH (W) = QH (W)
In the p - density of liquid pumping (kg/m3);
Gamma - pump heavy liquid delivery (N/m3);
Q - pump flow (m3/s);
H - pump lift (m);
G - gravity acceleration (m/s2).
The difference between the shaft power P and the effective power Pe is the loss power in the pump. The size is measured by the efficiency of the pump. The efficiency of the pump as the effective power and shaft power ratio, with ETA said.
Six, what is traffic? What letter is it? How to convert?
The volume of liquid discharged by pump in a unit time is called flow rate. The flow rate is expressed by Q, and the measuring unit is cubic meter / hour (m3/h) and L / S (l/s), L/s=3.6, m3/h=0.06, m3/min=60L/min
G=Q G refers to the weight - liquid proportion
Example: a pump flow of 50 m3/h, pumping hourly weight? The proportion of Water P is 1000 kg / m3.
Solution: G=Q P =50 * 1000 (m3/h kg/ m3) =50000kg / h=50t/h
Seven, what is the head? What letter is it? What units of measurement are used? And the conversion and formula of pressure?
The energy obtained by pumping a liquid of a unit weight is called a lift. The pump head, including suction stroke, is approximately the difference between the pump outlet and inlet pressure. The lift is expressed in H, and the unit is m. The pressure of the pump by P, unit Mpa (Zhao Pa), H=P/ P. Such as P 1kg/cm2, H= (lkg/ cm2) / (1000kg/ m3) H= (1kg/ cm2) (1000 /m3 / kg) = (10000 kg /m2) /1000 kg /m3=10m
1Mpa=10kg/c M2 H= (P2-P1) / P (P2= P1= inlet pressure outlet pressure)
Eight, what is called cavitation margin? What is the suction stroke? Each unit of measurement represents the letter?
The liquid pump at work in the impeller inlet will produce vapor due to a certain vacuum pressure, bathtub pump,vaporization of the air bubbles in the liquid particle movement under the impact of erosion on the impeller, the metal surface, thus undermining the impeller and other metal, then vacuum pressure is called vaporization pressure, cavitation is more than the surplus energy of vaporization pressure liquid a unit of weight in the pump suction port of. The unit with annotation, (NPSH) r with. The absorption process is necessary NPSH H: pump suction fluid allows the vacuum pump installation height is allowed, in meters.
Suction range = standard atmospheric pressure (10.33 meters) - cavitation margin - Safety (0.5 meters)
Standard atmospheric pressure line, vacuum height 10.33 meters.
For example: a pump must be 4 meters in diameter, and the suction range is h
Solution: Delta h=10.33-4.0-0.5=5.83 meters
Nine, what is the phenomenon of water pump cavitation and its causes?
When a liquid drops at a certain temperature to the vapor pressure at that temperature, the liquid produces a bubble. The phenomenon of producing bubbles is called cavitation.
2, cavitation collapse
When the cavitation bubbles, flow to the high pressure, the volume of reduced, so as to burst. This due to the pressure of rising bubbles disappear in the liquid in the phenomenon called cavitation bubble collapse.
3, the cause of cavitation and harm
The pump is in operation, if the over-current part of the local area (usually the impeller blade inlet somewhere later) for some reason, the absolute pressure of pumping the liquid was reduced to liquid vapor pressure temperature, liquid vaporization began in the area, produce a lot of steam, forming bubbles, when the liquid contains a lot of bubbles forward by high pressure impeller zone, high pressure liquid around the bubbles in the bubble decreases drastically and rupture.
Submersible pump condensation in the bubble burst at the same time, the liquid particle filled hole at a high speed, this moment has a very strong effect of water hammer, and with a high impact frequency against the metal surface impact stress of hundreds to thousands of atmospheric pressure, impact frequency can be up to tens of thousands of times per second, serious breakdown when the wall thickness will be.
4, cavitation process
The process of cavitation in a pump is caused by the bursting of bubbles and bubbles in the water pump and the destruction of the over-current components. Water pump cavitation, in addition to the over-current components will have a destructive effect, but also noise and vibration, and lead to the performance of the pump down, seriously when the pump will be interrupted liquid, can not work properly.
Ten. What is the characteristic curve of the pump?
Usually, the relationship between the main performance parameters curve is called characteristic curve or characteristic curve of centrifugal pump in essence, centrifugal pump performance curve is the movement rule of the liquid in the pump form, obtained by measurement. Characteristics include: (Q-H) flow lift curve, traffic - the efficiency curve (Q-), flow - power curve, flow rate (Q-N) - NPSH curve (Q- (NPSH) r), the performance curve of the pump flow is arbitrary, can find a set of relative to the head, in the the curve of power, efficiency and NPSH value, this set of parameters is called working state or condition, referred to as the point of maximum efficiency centrifugal pump working condition known as the best working condition, the optimum condition for general design point. The rated parameters of the general centrifugal pump, that is, the design conditions and the best working conditions coincide or very close to the point. In practice, it is important to understand the performance parameters of the pump in order to save energy and ensure the normal operation of the pump.
Eleven, what is the efficiency of the pump? Formula?
Refers to the ratio of the effective power to the shaft power of the pump. ETA =Pe/P
The power of a pump usually refers to the input power, that is, the power transmitted by the prime mover to the pump shaft, so it is also called shaft power, expressed in P.
Effective power is the product of pump head and mass flow and gravity acceleration.
Pe= p g QH (W) or Pe= QH/1000 (KW) gamma
P: pump liquid density (kg/m3)
Gamma: severe gamma =&rho for pump delivery of liquids; G (N/, m3)
G: gravitational acceleration (m/s)
The mass flow rate of Qm= P Q (t/h or kg/s)
Twelve 、 what is the whole performance test stand for pumps?
The device that can accurately test all the performance parameters of the pump through the precision instrument is a full performance test stand. The national standard accuracy is B. The flow is measured with a precision worm flowmeter, and the head is measured with a precision pressure meter. Determination of suction range with a precision vacuum meter. The power is measured by a precision shaft power machine. Rotational speed is determined by tachometer. The efficiency is calculated according to the measured value: n=rQ102.