范文一:液压计算公式
关键词:
液压泵(马达) 选用计算公式
液压泵(马达) 选用计算公式
1、 泵选用计算公式
输出流量
在给定转速n 时, 泵的输出流量Q
q×n
Q=――――×ηV ( L/min )
1000
式中:
q —泵的理论排量( mL/r )
n —转速r/min
ηV—泵的容积效率(一般取0.9-0.95)
驱动功率
在一定压力ΔP时,泵的驱动功率N 随着输出流量Q 的变化而变化
Q×ΔP
N=―――――( kW )
61 .2×ηt
式中:
ΔP—泵的进、出口压力差(Mpa )
ηt—泵的容积效率(一般取0.85)
驱动扭矩
在不同的压力ΔP下,泵的驱动扭矩M
q×ΔP
M=――――――――( Nm )
2.04×π×ηm
式中:
ηm—泵的机械效率(一般取0.9)
注意:双联泵或多联泵为单泵计算值之和
2、 马达选用计算公式:
输入流量
在一定转速n 时,马达的输入流量Q
q×n
Q=―――――( L/min )
1000ηV
q —马达的理论排量 ( mL / r )
n —转速 ( r / min )
ηV—马达的容积效率(一般取0.9-0.95)
输出功率
在一定的压力ΔP时,马达的输出功率N 随着输入流量Q 的变化而变化
Q×ΔP×ηt
N=―――――――( kW )
61.2
ΔP—马达的进、出口压力差
ηt —马达的总效率(一般取0.85)
输出扭矩
在不同的压力ΔP下,马达的输出扭矩M
q×ΔP×ηm
M=―――――――( Nm ) or =0.159×ΔP(P1-P2)×q ×ηm( N.m ) 2.04×π
ηm—马达的机械效率(一般取0.9)
范文二:液压计算公式
项 目 公 式 符 号 意 义
液压缸面积 (cm 2 ) A =πD 2 /4 D :液压缸有效活塞直径 (cm)
液压缸速度 (m/min) V = Q / A Q :流量 (l / min)
V :速度 (m/min)
液压缸需要的流量 (l/min) Q=V×A/10=A×S/10t S :液压缸行程 (m)
t :时间 (min)
F = p × A
液压缸出力 (kgf) F = (p × A) , (p×A) p :压力 (kgf /cm 2 )
( 有背压存在时 )
q :泵或马达的几何排量 (cc/rev) 泵或马达流量 (l/min) Q = q × n / 1000 n :转速( rpm )
泵或马达转速 (rpm) n = Q / q ×1000 Q :流量 (l / min)
泵或马达扭矩 (N.m) T = q × p / 20π
液压所需功率 (kw) P = Q × p / 612
管内流速 (m/s) v = Q ×21.22 / d 2 d :管内径 (mm)
U :油的黏度 (cst)
S :油的比重
管内压力降 (kgf/cm 2 ) ? P=0.000698×USLQ/d 4 L :管的长度 (m)
Q :流量 (l/min)
d :管的内径 (cm)
平衡阀属于调节阀范畴,它的工作原理是通过改变阀芯与阀座的间隙(即开度),改变流体流经阀门的流通阻力,达到调节流量的目的。平衡阀相当于一个局部阻力可以改变的节流元件,对不可压缩流体,由流量方程式可得:
式中:Q--流经平衡阀的流量 ξ--平衡阀的阻力系数 P1--阀前压力
P2--阀后压力 F--平衡阀接管截面积 ρ--流体的密度
由上式可以看出,当F一定(即对某一型号的平衡阀),阀门前后压降P1-P2不变时,流量Q仅受平衡阀阻力影响而变化。ξ增大(阀门关小时),Q减小;反之,ξ减小(阀门开大时),Q增大。平衡阀就是以改变阀芯的开度来改变阻力系数,达到调节流量的目的。
Kv为平衡阀的阀门系数。它的定义是:当平衡阀前后差压为1bar(约1kgf/cm2)时,流经平衡阀的流量值(m3/h)。平衡阀全开时的阀门系数相当于普通阀门的流通能力。如果平衡阀开度不变,则阀门系数Kv不变,也就是说阀门系数Kv由开度而定。通过实测获得不同开度下的阀门系数,平衡阀就可做为定量调节流量的节流元件。
在管网平衡调试时,用软管将被调试的平衡阀的测压小阀与专用智能仪表连接,仪表可显示出流经阀门的流量值(及压降值),经与仪表人机对话,向仪表输入该平衡阀处要求的流量值后,仪表通过计算、分析、得出管路系统达到水力平衡时该阀门的开度值。
范文三:液压计算公式
Fluid Power Formula These Formula Cover All Fluid Power Applications In This Manual
For Computer Programs To Work Problems By Simply Filling In The Blanks
See
Your Local Fluid Power Distributor
Many Companies Web Site Or CD
Also See
The Fluid Power Data Book
Packaged With This Manual
For Charts and Other Fluid Power Information
Fluid Power Formula
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Fluid Power Formula
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Fluid Power Formula
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Fluid Power Formula
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Fluid Power Formula
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Fluid Power Formula
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Fluid Power Formula
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Fluid Power Formula
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Fluid Power Formula
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Fluid Power Formula
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Fluid Power Formula
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Fluid Power Formula
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Fluid Power Formula
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Fluid Power Formula
Fluid Power Formula
SIZING A HYDRAULIC CIRCUIT
On the facing page is an exercise sizing a simple single cylinder hydraulic circuit with straight forward parameters. The example gives basic requirements for sizing a hydraulic cylinder powered machine.
In the real world of circuit design, experience, knowing the process, the environment, the skill of the user, how long will the machine be in service, and other items affect cylinder and power unit choices. Before designing any circuit it is necessary to know several things.
First is force requirement. Usually, the force to do the work is figured with a formula. In instances where there is no known mathematical way to figure force, use a mock up part on a shop press or on a prototype machine for best results. If all else fails, an educated guess may suffice. The sample problem requires a force of 50,000 pounds.
Second, choose a total cylinder stroke. Stroke length is part of machine function and is necessary to figure pump size. Use a stroke of 42 inches in this problem.
Third, how much of the stroke requires full tonnage? If only a small portion of the stroke needs full force, a HI-LO pump circuit and/or a regeneration circuit could reduce first cost and operating cost. This cylinder requires full tonnage for all 42 inches.
Load, unload and dwell are part of the overall cycle time, but should not be included when figuring pump flow. Use a cylinder cycle time of 10 seconds for this problem.
Finally, choose maximum system pressure. This is often a matter of preference of the circuit designer. Standard hydraulic components operate at 3000 PSI maximum, so choose a system pressure at or below this pressure. If a company has operating and maximum pressure specifications, adhere to them. Remember, lower working pressures require larger pumps and valves at high flow to get the desired speed. On the facing page part A, taking the square root of the maximum thrust, times 110%, for fast pressure buildup, divided by the maximum system PSI, divided by .7854. This gives a minimum cylinder bore of 5.244
To figure pump capacity, take the cylinder piston area in square inches, times the cylinder stroke in inches, times 60 seconds, divided by the cycle time in seconds, times 231 cubic inches per gallon. This shows a minimum pump flow of 61.7 GPM. A 65 GPM pump is the closest flow available. Never undersize the pump since this formula figures the cylinder is going maximum speed the whole stroke. The cylinder must accelerate and decelerate for smooth operation, so travel speed after acceleration and before deceleration should actually be higher than this formula allows.
Figure horsepower by taking GPM times PSI times a constant of .000583. This comes out to 75.79 HP, and is close to a standard 75 HP motor. This should be sufficient horsepower since the system pressure does not have to go to 2000 PSI with the cylinder size used.
The tank size should be at least two to three times pump flow, which is three times sixty-five, or 195 gallons, so a 200 gallon tank is satisfactory. When using single acting cylinders or unusually large piston rods, size the tank for enough oil to satisfy cylinder volume without starving the pump.
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Fluid Power Formula
Fluid Power Formula
SIZING A PNEUMATIC CIRCUIT
Sizing air cylinders is similar to sizing hydraulic cylinders. Most air systems operate around 100 to 120 PSI with approximately 80 PSI readily available at the machine site. This gives little or no option for selecting operating pressure.
Since the compressor is part of plant facilities, the amount of cubic feet per minute (CFM) of air available for the air circuit usually is many times that required. It is good practice though, to check for ample CFM flow capabilities at the machine location.
The only items needed to figure an air circuit is maximum force required, cylinder stroke, and cycle time. With this information, sizing cylinders, valves, and piping is simple.
To figure the cylinder bore required, use the formula given at A. Notice the added multiplier on the force line. For an air cylinder to move at a nominal rate, it needs approximately 25% greater thrust than the force required to offset the load. When the cylinder must move fast, figure a force at up to twice that required to balance the load.
The reason for this added force relates to filling an empty tank from a tank at 100 PSI. When air first starts transferring, a high pressure difference allows fast flow. As the two tanks get closer to the same pressure the rate of transfer slows until the gauges almost stop moving. The last five to ten PSI of transfer takes a long time. As the tanks get close to the same pressure, there is less reason for transfer since pressure difference is so low.
If an air cylinder needs 78 PSI to balance the load, then it has only 2 PSI differential to move fluid into the cylinder at a system pressure of 80 PSI. If it moves at all, it is very slow and intermittent. As pressure differential increases, from higher inlet pressure or less load, the cylinder starts to move smoothly and steadily. The greater the differential the faster the cylinder movement. Once cylinder force is twice the load balance, speed increase is minimal.
Using the 1.25 figure in the formula shows a cylinder bore of 1.72
To size the valve use the
The formula shows a valve with 1/8
There are many charts in data books as well as valve manufacturers catalogs that take the drudgery out of sizing valves and pipes. There are several computer programs as well to help in proper sizing of components.
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范文四:液压计算公式
平衡阀属于调节阀范畴,它的工作原理是通过改变阀芯与阀座的间隙(即开度),改变流体流经阀门的流 通阻力,达到调节流量的目的。平衡阀相当于一个局部阻力可以改变的节流元件,对不可压缩流体,由流 量方程式可得:
式中:Q--流经平衡阀的流量 ξ--平衡阀的阻力系数 P1--阀前压力
P2--阀后压力 F--平衡阀接管截面积 ρ--流体的密度
由上式可以看出,当 F 一定(即对某一型号的平衡阀),阀门前后压降 P1-P2不变时,流量 Q 仅受平 衡阀阻力影响而变化。 ξ增大(阀门关小时), Q 减小;反之, ξ减小(阀门开大时), Q 增大。平衡阀 就是以改变阀芯的开度来改变阻力系数,达到调节流量的目的。
Kv为平衡阀的阀门系数。它的定义是:当平衡阀前后差压为 1bar (约 1kgf/cm2)时,流经平衡阀的 流量值(m3/h)。平衡阀全开时的阀门系数相当于普通阀门的流通能力。如果平衡阀开度不变,则阀门系 数 Kv 不变,也就是说阀门系数 Kv 由开度而定。通过实测获得不同开度下的阀门系数,平衡阀就可做为定 量调节流量的节流元件。
在管网平衡调试时,用软管将被调试的平衡阀的测压小阀与专用智能仪表连接,仪表可显示出流经阀 门的流量值(及压降值),经与仪表人机对话,向仪表输入该平衡阀处要求的流量值后,仪表通过计算、 分析、得出管路系统达到水力平衡时该阀门的开度值。
范文五:系统计算公式
独立系统:
组件的计算方法:
P (总功率)=P(负载功率)*H(工作时间)/η(系统效率)/H(每天有效日照小时数)
蓄电池容量计算方法:
C(容量)= P(负载功率)*H(工作时间)*D(备电天数)/η(蓄电池的放点深度)/U(系统电压)
控制器的电流计算方法:
? I= P(组件总功率)/ U(系统电压)
? I= I(组件的短路电流)*N(并联数)
离网系统的计算方法和独立系统一样。
说明:η(系统效率) 独立系统按照0.6计算。
η(系统效率) 离网系统按照0.55~0.58计算。 η( 蓄电池放点深度) 一般按照0.68计算。 并网电站的发电量计算:
W(发电量)=P(装机容量)*H(每天的有效日照小时数)*D(天数365)*η(系统效率)
说明:一般的并网电站系统效率按照78%~82%计算,具体的有专门
的评估软件。
每天的日照小时数有专门的查各地有效日照数的软件。
独立系统组件及蓄电池串并联关系计算
N (组件的串联数目)=U(系统电压)/ U(电池组件的电压) N (组件的并联数目)= N(组件总数)/ N(组件的串联数目) 说明:此时的电池组件的电压按照12V 或24V 计算。
蓄电池并联数目最好不能超过3并
并网电站组件的串并联数目要按照逆变器的MPPT 的追踪电压具体计算。
电池片功率计算:
P (单个电池片功率)=S(单个电池片面积)*1000W/mm2*η(电池片转化效率)=组件功率/片数
组件转换效率=组件功率/长/宽
组件中电池片效率=组件功率/片数/S(单个电池片面积)*1000