Well-known, pneumatics function effect sees aircrew input compare power, have very big concern than power volume and aircrew power worth. Namely power of axis of identical cubage discharge, press, aircrew power is greater, bigger than power, pneumatics machine exceeds cost can.
Power of box of efficiency of the aircrew power input of pneumatics machine and power of electric machinery axis, electric machinery, report, fan power about, and occupy than the biggest is axial power.
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The axial power of pneumatics machine is to be below certain dimension discharge and actuating pressure, electromotor (or diesel engine) the work that pneumatics aircraft main engine gives the axis inside unit time, call axial power.
Pneumatics crankshaft power, we are OK from pneumatics machine interior (namely the axial power of lead plane) and exterior (electromotor axis power) power comsumption will announce the meaning of axial power. Above all from aircrew power input from outside arrive inside the specific power consumption that will analyse pneumatics machine. (see a picture 1)
By formula (1) , we get the composition of aircrew power is:
Power of electric machinery of =P of P aircrew power + P fan power + power of box of P electric equipment — formulary (1)
Formulary (2) , electric machinery power and power of electric machinery axis and electric machinery efficiency concern:
Power of axis of electric machinery of =P of power of P electric machinery / efficiency of η electric machinery — formulary (2)
Formulary (3) , power of electric machinery axis follows power of axis of pneumatics aircraft main engine and transmission efficiency to concern (see a picture 2) :
Power of axis of lead plane of =P of power of axis of P electric machinery / η drive efficiency — formulary (3)
In pneumatics machine industry, on standard, nameplate, conduct propaganda book and business affairs negotiation machine size is connected commonly used ” drive electromotor power ” (HP/kW) express, electromotor nameplate is: “Rated power ” , it is to point to pneumatics crankshaft power actually. (see a picture 3)
If we will be formulary (2) and (3) generation enters formula (1) can get formula (4) :
= of P aircrew power (power of axis of P lead plane / η drive efficiency) efficiency of * η electric machinery + P fan power + power of box of P electric equipment — formulary (4)
By formula (4) sees aircrew power is medium, axial power (lead plane / electric machinery) , efficiency (transmission / electric machinery) all be in pneumatics machine of 6 old systems in dynamical system, it is aircrew power is occupied than the largest part. (see a picture 4)
Screw empty press moves power system to wait for 3 large parts to comprise by system of lead plane, electric machinery, transmission:
From formula (4) sees, want to know the aircrew power of pneumatics machine, we must know power of lead plane axis first.
2, power of lead plane axis
The computation of power of axis of 1. lead plane
Power of axis of pneumatics aircraft main engine, it is the integrated machine that lead plane uses promotion to compress place of airy pressure potential energy to need (or hot) can. Indicate power and adiabatic efficiency to concern with pneumatics machine, but the drive outside including (like gear or belt-conveyor) losing power (see formula (5) )
Ps=Pad/ η adiabatic efficiency — formulary (5)
Ps gives priority to crankshaft power
Pad indicates power for pneumatics machine
～ of =0.7 of η adiabatic efficiency 0.85
Before personnel of pneumatics machine design is designing pneumatics machine normally, should be calculated or the power of lead plane axis of witting pneumatics machine.
Exemple 1, hypothesis should design machine of pneumatics of a screw, exhaust pressure 0.7MPa (gauge pressure) , cubage discharge is 16.67m3/min, inlet pressure is 0.1MPa (press absolutely) . How much is the axial power of this pneumatics machine? Should match how old electromotor?
Solution:
Conversion of 1) cubage discharge: Q=16.67m3/min=277.78l/s
2) compresses the demonstrative powermeter that air place needs to calculate:
3) assumes the adiabatic efficiency of machine of this screw pneumatics: η =80%
The basis is formulary (1) , power of lead plane axis: =79.34/0.8=99.15kW of Ps=Pad/ η adiabatic efficiency
Should match how old electric machinery? Calculate again from the back.
In the graph 6 in can see, pneumatics machine does isotherm impossibly to compress already in reducing a process (compress process air temperature changeless) , hot pressing of impossible also leave no room for manoeuvre shrinks (compress process and outside to be exchanged without any heat) . Because this should be changeful,reduce a process.
Pass a test, because fuel injection screw is empty the lead plane revolution of press is taller, gas be compressioned lifts in pressure in the process, the hot exchange between the lube that enters with gush is very scant, when compressing a process to end, the temperature with temperature oily outclass of gas, just achieve balance of quantity of heat finally in exhaust process, reach identical exhaust temperature.
Accordingly, mistake is close to isotherm to reduce a process to can come true through fuel injection is inaccurate. The experiment proves, the highest efficiency of machine of pneumatics of screw of actual fuel injection still reduces efficiency than heat insulation a bit lower, it is so in computation of nose axis power, compress connection to rise with heat insulation, is not isotherm is compressed.
The person make tomb figure that the energy that job of pneumatics aircraft main engine is dynamical system power uses up, because this wants pneumatics machine is energy-saving, want leader above all energy-saving. (See a picture 7)
Power of axis of 2. lead plane affects factor
We are when the power of lead plane axis of computational pneumatics machine, revolution of temperature of need input inlet pressure, inlet temperature, environment, actuating pressure, lead plane, fall into atmospheric pressure, parameter of exhaust pressing demote (see a picture 8) . So, these parameter can affect the size of power of lead plane axis.
The influence of ① aircrew inlet pressure
Although national level provides empty press make and check according to ” standard operating mode ” (Px=1.013bar of standard inlet pressure) . But using operating mode actually to differ (height above sea level) , pneumatics machine is in different design and make reach client spot expression to also can differ (into baric caustic difference) , produce an effect to the axial power of pneumatics machine.
Graph the abscissa of 9 is inlet pressure, right green ordinate is axial power. When inlet pressure increases, axial power curve drops; Conversely, rise.
We are understandable for, because create compression ratio into baric caustic,differ bring about axial power different.
Exemple 2: A client uses confidential of a pneumatics to beg 0.7MPa in altitude 3000m place, when tolerance 5.44m3/min. (check data environment pressure to be: 0.7bar) , its compression ratio:
I=P is discharged / Px= (7+0.7) / 0.7=11 — formulary (7)
Mean need identical tolerance, right now axial power compares standard operating mode (compression ratio 8) when should big, must select 10bar pneumatics engine. Because this is reduced when inlet pressure, axial power increases.
Exemple 3: Empty filter of some pneumatics machine reachs a powerful person that decrease carry on one’s shoulder to press fall for 35mbar (see a picture 10) , requirement 0.7MPa, when tolerance 5.44m3/min. Its compression ratio:
I=P is discharged / Px= (7+1) / 0.965=8.3 — formulary (8)
Mean need identical tolerance, right now axial power compares standard operating mode (compression ratio 8) when should big 3.6% . Because this is reduced when inlet pressure, axial power increases.
The influence of ② environment temperature
Although national level provides empty press make and check according to ” standard operating mode ” (℃ of standard temperature T=20) . But the operating mode when be being used actually is different, pneumatics machine also is met in different client spot expression different. Environmental temperature difference is met to the power of pneumatics machine generation influence.
Graph the abscissa of 11 is environmental temperature, right green ordinate is axial power. When environmental temperature increases, axial power curve drops. But because cubage discharge curve drops slope is bigger (blue curve) , rise of aircrew instead than power (gules curve) ; Vice versa. Exemple 4 see a picture 12.
③ the influence of actuating pressure
Below same lead plane and revolution circumstance, exhaust pressure is greater, pneumatics crankshaft power is greater! (see a picture 13)
Here, we can distinguish 3 kinds of circumstances:
A) pneumatics machine is in-house systematic pressing falls: Below same actuating pressure, the to the front of gas outlet gas route system after pneumatics aircraft main engine is pressed fall smaller, pressure of lead plane exhaust is less, the axial power of lead plane is less, unit is smaller than power, pneumatics machine is more energy-saving; Conversely criterion bad news can.
The system after B) pneumatics machine presses fall: Below same actuating pressure, pneumatics system (the pipeline after pneumatics machine, purifying device and complementary wait) because waste finished product to enrage (pipeline is divulged, purifying device air consumption is big, unreasonable wait with gas) or systematic pressing falls big (pipeline pressing falls, purifying device is pressed fall, systematic configuration is unreasonable wait a moment) , aircrew increases than power, pneumatics opportunity cost can; Conversely energy-saving.
After press of high above in the sky works for some time, because empty filter core reachs oil gas segregator,core is affected as working hours and environment, can increase block damage, cause lead plane actuating pressure to rise thereby, before arriving at care and maintenance to ask, power of lead plane axis also can increase. Stem from the safe consideration of electromotor, must want to increase this part surplus, in electromotor cent can have the ministry to be quantified in detail.
The influence of revolution of ④ lead plane
Below same lead plane and actuating pressure, lead plane revolution increases or decrease, axial power increases or decrease! (see a picture 15)
Exemple 5, machine of pneumatics of screw of some brand frequency conversion, can undertake two kinds of pressure control mode:
A. In actuating pressure changeless circumstance falls, the revolution that can carry change main engine along with bear change will achieve energy-saving goal; (see a picture 16 left) .
B. Also can be at the same time below the circumstance with axial changeless power, the revolution that carries change main engine along with the change of actuating pressure realizes capacity of pneumatics machine increase and decrease, achieve machine of frequency conversion pneumatics to use thereby the biggest change. This is why the variable that this pneumatics machine has 100Hz (see a picture 16 right) .
The efficiency of ⑤ lead plane is affected
Without giving thought to what lead plane, every archives lead plane can have its efficiency curve (see a picture 17) , when lead plane revolution is too low, because lead plane is divulged increase cause unit taller than power (so the frequency of machine of frequency conversion pneumatics is in 20Hz above, again low not only bad news can, and the likelihood is hit do not vent his anger) ; When lead plane revolution is exorbitant, the mechanical attrition of lead plane increases cause unit taller than power (market common says: The pony pulls cart) .
Because frequency conversion is empty the computational method that controls cost of functional effect demarcate and aircraft of labour frequency pneumatics are different, because this has used the efficiency curve of lead plane, in machine of labour frequency pneumatics not be 1 class after the lead plane of effect passes air officer, can use on machine of frequency conversion pneumatics, obtain 1 degree can the case of effect cans be found everywhere.
Accordingly, from GB19153-2019 ” cubage type compresses value of functional effect demarcate to reach can effect grade ” can see, below same power, it is 1 class likewise can effect, labour frequency asks to be worth than power than frequency conversion than power worth small. From pneumatics system for energy-saving angle, in be fully loaded with operating mode to fall, labour frequency machine is more energy-saving than frequency changer. This and dot of lead plane efficiency are chosen about, in the 3rd chapter ” demarcate of effect of function of pneumatics of fuel injection screw is worth an analysis ” in have an analysis.
The molded lines of ⑥ lead plane is affected
Screw pneumatics machine has had the history of nearly hundred years, the design of lead plane basically is screw line model evolve.
Line design asks:
A) axial air-tightness and transverse air-tightness are tall
B) contacts line length as far as possible short
C) area utilization factor is big
D) decreases and avoid flat triangle
E) weight is light, tigidity is good
The craft sex with good F)
Among them, the most important is the area utilization rate of molded lines: Cn=F/Dm, watch 1 compare for utilization rate of area of a few kinds of dentiform:
Give priority to the treatment craft of machine next.
So a good leader, what consider above all is safety is mixed durable, just be energy-saving next. Bypass the safety of lead plane and durable and theoretic energy-saving, earn get as compensate much.
The influence of ⑦ compression ratio
Mention in inlet pressure influence in front ” compression ratio ” . The process is reduced in pneumatics aircraft main engine in impossible that 100% air are compressed, the air that can have certain amount is divulged, compression ratio is higher, divulge more serious; At the same time ” compression ratio ” taller, compress airy temperature rise taller also, press of high above in the sky from mechanical energy of electric energy translate into, change again when be air pressure potential energy, air temperature change is less, the power of lead plane axis of pneumatics machine is less, pneumatics machine is more energy-saving. This also is two class are compressed in large type the class that compare sheet is compressed reach 1 level more easily can one of reasons of effect
3, transmission system
The transmission system of pneumatics machine points to electric machinery and component of lead plane join, can divide commonly for straight drive, positive drive and belt-conveyor.
Means of 3 kinds of join has a characteristic each, more visible watch 2.
The basis is formulary (3) can know, transmission system is the bridge that power of electric machinery axis transfers power of lead plane axis, transmission efficiency discretion affects aircrew power directly.
4, electromotor axis power
Motive of 1. pneumatics Electromechanical
Pneumatics machine is will former move (it is electromotor or diesel engine normally) mechanical energy is changed into aeriform potential energy (pressure is behaved) device, electromotor is dot of input of pneumatics machine dynamic.
The commonnest pneumatics machine electromotor is three-phase asynchronous electric machinery and permanent magnetism (frequency conversion) electric machinery.
2. electromotor power input
Great majority of pneumatics aircraft electric machinery is three-phase electric machinery, formula of computation of its power input is:
η of 3UIcos Φ of P ＝ √ — formulary (9)
Among them U is line voltage, I is phase current, cos Φ is factor of electric machinery power, η is electric machinery efficiency. We can inquire from electric machinery nameplate. (see a picture 24, zun Tu is labour frequency electric machinery, right graph is electric machinery of permanent magnetism frequency conversion)
From formula (9) can see, electric machinery power input and electric machinery efficiency and power factor have affinity.
Efficiency of ① electric machinery
Electromotor by mechanical energy of electric energy translate into, in energy changeover does not have a loss impossibly. This is the result of action of a lot of elements, for example resistor loss, ventilated loss, magnetization loss and attrition loss and calorific wait. Energy is changed rate is OK will express with η of electric machinery efficiency. (See formula (9) , p1 is power of electric machinery axis (the rated power that normally electric machinery nameplate tags) , p is) of electric machinery power input.
η = , — formulary (10)
η of P = P1 / — formulary (11)
From formula (10) reachs, below the circumstance with changeless P1 of power of electric machinery axis, η of electric machinery efficiency is taller, p of electric machinery power input is lower, pneumatics machine is more energy-saving! National level GB18613-2012 ” value of demarcate of dynamoelectric function effect and can effect grade ” stipulated grade of dynamoelectric function effect divides a level: 1 class, 2 class, 3 class, part the IE4 of corresponding international standard, IE3, IE2.
GB18613-2020 ” value of demarcate of dynamoelectric function effect and can effect grade ” began to carry out June 1, 2021, can effect index promotes further (see a picture 26) .
Current, major pneumatics machine uses electric machinery on the market according to national level GB18613-2012 ” value of demarcate of dynamoelectric function effect and can effect grade ” , three-phase asynchronous electromotor is IE2 commonly (3 class) , permanent magnetism electric machinery is IE4 above commonly (one class) ; η of efficiency of various electric machinery differs 1 ～ 2% , rated power is greater, efficiency value differs smaller (see a picture 27) .
In the 3rd chapter ” demarcate of effect of function of pneumatics of fuel injection screw is worth an analysis ” in introduced fraction defective of sampling observation of 2020 pneumatics machine to be as high as 22.4% , unqualified discovery rate is next to three-phase asynchronous electric machinery 23.3% , and unqualified project is: “Aircrew input is mixed than power can effect marks ” .
Fraction defective of pneumatics machine sampling observation the fraction defective of very old rate and electromotor is actually relative, be versed in frequency uses three-phase asynchronous electric machinery especially. Because the majority is empty,the three-phase asynchronous electric machinery that press uses is IE2 (3 class) , inputting fountainhead when motivation is not energy-saving electric machinery, is machine of He Lai pneumatics energy-saving?
Electric machinery efficiency is reached by technical level, production cost, voltage extremely the factor influence such as number, pneumatics Electromechanical motive chooses (especially three-phase asynchronous electric machinery) should follow the following principle:
A) falls in same rated power, order and degree of electric function effect is higher, electric machinery efficiency is taller, pneumatics machine is more energy-saving; (the proposal chooses IE3 above)
B) falls in same rated power, number of electric machinery pole is higher, electric machinery efficiency is taller, pneumatics machine is more energy-saving; (can use 4 extremely electric machinery need not 2 extremely electric machinery)
C) is in high-power electric machinery, below same rated power, voltage is taller, electric machinery efficiency is taller, pneumatics machine is more energy-saving; (machine of 250kW above pneumatics, choose in proper sequence conditionally: 10kV>6kV>380V)
D) is the same as first gear electric machinery, be fully loaded with carry efficiency than changing tall (electric machinery is optimal efficiency is in 100% bear) (see a picture 28) ;
E) changes ships goes, electric machinery of permanent magnetism frequency conversion is preferential;
F) falls in the condition of contented safety, electric machinery defends grade is jumped over low better.
Exemple 6, the electromotor of 75kW, one is IE2, one is IE4, how much is difference of its power consumption? Solve see a picture 29.
Factor of power of ② electric machinery
In alternating current road, power allots kind of power: P of power of have rendered great service, mix without result power Q inspect in power S, Φ of power factor Cos is P of power of have rendered great service is mixed inspect the ratio in power S, namely Cos Φ =P/S. Power factor is a coefficient that measures discretion of electric equipment efficiency.
P(W) of power of have rendered great service: In circuit, the power that consumes on resistor component is power of have rendered great service, show the rate that power source power is used.
When φ =0, dc road, p=UI
When φ ≠ 0 when, communicate circuit, p= 3UIcos φ .
We can inquire power factor from electric machinery nameplate. (see a picture 24, zun Tu is labour frequency electric machinery, right graph is electric machinery of permanent magnetism frequency conversion) .
The power factor of asynchronous electric machinery is low, the reason is it needs one part power to produce magnetic field, turn in order to keep electric accident. This part produces the power of magnetic field, won’t be used up, between existence and electric machinery and power source, this does not have result power namely.
The magnetic field of permanent magnetism electric machinery is permanent magnet generation, do not need this not to have result power, need to absorb power of have rendered great service to do work external from inside electrified wire netting only so can, its power factor is very accordingly high.
Exemple 7, with nameplate power the permanent magnetism electric machinery of 75 kilowatt and asynchronous electric machinery are exemple, compare their input electric current, know why efficiency of electric machinery of asynchronous of efficiency of permanent magnetism electric machinery is tall. See a table 3
In machine of frequency conversion pneumatics, asynchronous electric machinery glides in efficiency of 80% laden and the following electric machinery serious, power factor glides more serious. Permanent magnetism electric machinery is between 120% load of 20% ～ the efficiency that keeps basically taller and power factor, when the part is laden permanent magnetism electric machinery compares asynchronous electric machinery to have very large energy-saving dominant position, energy-saving even more than 50% . (see a picture 31, 1 for permanent magnetism electric machinery, 2 for asynchronous electric machinery) .
5, of rated power of pneumatics Electromechanical motive choose
Be in exemple 1 in, power of lead plane axis is 99.15kW, how does electric machinery choose?
Power of axis of 1) computation electric machinery:
The basis is formulary (3) : =99.15/0.98=101.17kW of power of axis of P electric machinery (positive drive of =98% of η drive efficiency)
School nucleus 1: GB 18613-2012 ” value of demarcate of dynamoelectric function effect and can effect grade ” be chosen choose 90kW/4 extremely / the efficiency of IE4 is 96.2% .
The basis is formulary (2) : =101.17/0.962=105.17kW of power of P electric machinery (do not issue first gear 110kW more than)
School nucleus 2: GB 18613-2012 ” value of demarcate of dynamoelectric function effect and can effect grade ” be chosen choose 90kW/2 extremely / the efficiency of IE2 is 94.1% .
The basis is formulary (2) : =101.17/0.941=107.5kW of power of P electric machinery (do not issue first gear 110kW more than)
2) computation electric machinery serves coefficient:
Normally the electromotor of pneumatics machine serves coefficient Sf=1.15; Core of consideration empty filter and internal pressure of cycle of service of energy component core fall influence (the axial power of 8% )
Be in exemple 1 in the service coefficient requirement of electromotor: Sf=101.17 *1.08/90=1.21>1.15, mean, or increases the service coefficient of electromotor to 1.25, or revises lead plane revolution afresh (reduce cubage flow) .
Exemple 8: Class of 10.5m3/min/0.7MPa /55kW/2 of machine of some brand pneumatics can effect / IE3 electric machinery / positive drive / Sf=1.15. Box of hypothesis P report + P fan =0.5kW (see a picture 32)
=10.5*6.4=67.2kW of P aircrew power
=67.2-0.5=66.7kW of power of P electric machinery
=66.7*0.946=63.03kW of power of axis of P electric machinery
=63.03*0.98=61.77kW of power of axis of P lead plane
Sf=62.03/55=1.13
Visible, sf is adjacent 1.15, if the machine uses period of time hind, pneumatics machine interior is pressed when falling to cent core jams and increase as a result of essence of life, electric machinery served coefficient to will be not worth, can cause electric machinery safety to move.
Exemple 9, graph 32, in 2009 edition can effect grade is 2 class, check 2019 edition can effect grade becomes 3 form (it is than power worth because of 2 class 6.2) , if want to alter little, change electromotor into IE5 (96.3% ) .
=61.77kW of power of axis of P lead plane
=61.77/0.98=63.03kW of power of axis of P electric machinery
=63.03/0.963=65.45kW of power of P electric machinery
=65.45+0.5=65.95kW of P aircrew power
ε =65.95/10.5=6.28
Still cannot enter 2 stage can effect, but had been close to very much, the efficiency curve that can see lead plane goes amending cubage discharge, reduce revolution of a bit lead plane, enter new 2 form likely can effect.
Because this development understands ” axial power is energy-saving to machine of pneumatics of fuel injection screw influence ” , can make in pneumatics machine not only foster strengths and circumvent weaknesses in the process, compare pneumatics airplane unit power worth to reduce as far as possible, and still can be in intense market is occupied in competition first machine.
