Figure 2.4 '

Forced balanced pressure transducer

Pascal's law

The underlying principle of how fluids transmit power is revealed by Pascal's law.

Pascal's law states that the pressure applied to a confined fluid is transcmitted

undiminished in all directions. This law forms the basis.for understanding the relationship

between force,pressure and area, which can be mathematically expressed as:

The transmitted pressure acts with equal force on every unit area of the containing

vessel and in a dirction at right angle to the surface of the vessel exposed to the liquid.

pascal's law can be illustrated by the following example.

图2.4”

Forced balanced pressure transducer

强制平衡式压力传感器

Pascal's law

帕斯卡定律

The underlying principle of how fluids transmit power is revealed by Pascal's law.

如何流体传输功率的基本原理是利用帕斯卡定律揭示。

Pascal's law states that the pressure applied to a confined fluid is transmitted

帕斯卡定律说明，施加压力的密闭流体传输

undiminished in all directions. This law forms the basis.for understanding the relationship

在所有的方向不减。这种法律形式依据理解的关系

between force,pressure and area, which can be mathematically expressed as:

之间的力，压力和面积，数学上可以表示为：

The transmitted pressure acts with equal force on every unit area of the containing

发送的压力作用于容每单位面积相等的力

vessel and in a dirction at right angle to the surface of the vessel exposed to the liquid.

容器和在一个方向在暴露于液体的容器表面的右角。

pascal's law can be illustrated by the following example.

帕斯卡定律可由下面的例子说明。

A bottle is filled with a liquid, which is not compressible. A force of 4 kg is applied to

the stopper whose surface area is 3cm. Let's assume that the area of the bottom is 60cm.If the

stopper is inserted into the bottle mouth ,with a force of 4kg such that it makes contact with

the liquid ,then the pressure exerted by the stopper on the liquid in the bottle is given by:

一个瓶子装满液体，这是不可压缩的。一个4公斤力被施加到

the stopper whose surface area is 3cm. Let's assume that the area of the bottom is 60cm.If the

塞其表面积是3平方厘米。让我们假设的底面积60平方厘米。如果

stopper is inserted into the bottle mouth ,with a force of 4kg such that it makes contact with

塞插入瓶口，用力量4kg，使接触

the liquid ,then the pressure exerted by the stopper on the liquid in the bottle is given by:

液体，然后通过在瓶内液体的压力是由：

This pressure will be transmitted undiminished to every square area of the bottle. the bottom of the having an

area of 60cm will be subjected to an additional force of:

This force could break most bottles. This shows why a glass bottle filled with liquid can break

if the stopper is forced into its mouth.

Figure 2.5 illustrates this example better. It also substantiates the fact that pressure does not depend on the shape and size of the container.

这种压力会传染不减于瓶每平方面积。底部的有

area of 60cm will be subjected to an additional force of:

地区60平方厘米将承受额外的力量：

This force could break most bottles. This shows why a glass bottle filled with liquid can break

这种力量可以打破大多数瓶。这说明了为什么一个装有液体的玻璃瓶可以打破

if the stopper is forced into its mouth.

如果是被迫进入嘴里塞。

Figure 2.5 illustrates this example better. It also substantiates the fact that pressure does not depend on the shape and size of the container.

图2.5说明了这个例子更好。这也证实了这一事实，压力不依赖于容器的形状和尺寸。

Application of Pascal's law

In this section, we shall study two basic applications of Pascal's law, the hydraulic jack

and the air-to-hydraulic booster.

帕斯卡定律的应用

In this section, we shall study two basic applications of Pascal's law, the hydraulic jack

在本节中，我们将研究帕斯卡定律两个基本应用，液压千斤顶

and the air-to-hydraulic booster.

与空气的液压助力器。

Hydraulic jack

This system uses a piston-type hand pump to power a single acting hydraulic cylinder as

illustrated in Figure 2.6.

A hand force is applied at point 'A' of handle 'ABC', which pivots about point 'C'.The

piston rod of the hand pump is pinned to the input handle at point 'B' The hand pump

contains a cylinder for aiding the up and down movement. When the handle is pulled, the

piston moves up, thereby creating a vacuum in the space below it. As a result of this,the

atmospheric pressure forces the oil to leave the oil tank and flow through check valve l.

This is the suction process.

液压千斤顶

This system uses a piston-type hand pump to power a single acting hydraulic cylinder as

本系统采用活塞式手泵功率的单作用液压缸

illustrated in Figure 2.6.

图2.6所示。

A hand force is applied at point 'A' of handle 'ABC', which pivots about point 'C'.The

一只手用力点'的'处理' ABC，枢轴点的“C”。

piston rod of the hand pump is pinned to the input handle at point 'B' The hand pump

的手泵活塞杆固定于输入句柄在点B手泵

contains a cylinder for aiding the up and down movement. When the handle is pulled, the

包含一个辅助的上下运动，气缸。当扳动手柄，所

piston moves up, thereby creating a vacuum in the space below it. As a result of this,the

活塞向上移动，从而在空间中产生以下的真空。由于这一结果，该

atmospheric pressure forces the oil to leave the oil tank and flow through check valve l.

大气压力通过止回阀L.离开油槽和油流

This is the suction process.

这是吸程。

When the handle is pushed down, oil is ejected from the hand pump and flows through

the check valve 2. Oil now enters the bottom of the load cylinder. The load cylinder is

similar in construction to the pump cylinder. Pressure builds up below the load piston as

oil is ejected from the pump. From Pascal's law, we know that the pressure acting on the

load piston is equal to the pressure developed by the pump below its piston. Thus each

time the handle is operated up and down, a specific volume of oil is ejected form the

pump to lift the load cylinder to a given distance against its load resistance. The bleed

valve is a hand-operated valve which when opened, allows the load to be lowered by

bleeding oil from the load cylinder back to the oil tank. This cylinder is referred to as

single acting because it is hydraulically powered in one direction only.

当手柄推下，油从手泵和流经喷射

the check valve 2. Oil now enters the bottom of the load cylinder. The load cylinder is

止回阀2。现在石油进入加载缸底。负荷缸

similar in construction to the pump cylinder. Pressure builds up below the load piston as

在施工中泵缸相似。压力积聚低于负载活塞

oil is ejected from the pump. From Pascal's law, we know that the pressure acting on the

油从泵喷出。从帕斯卡定律，我们知道，压力作用在

load piston is equal to the pressure developed by the pump below its piston. Thus each

负荷柱塞等于压力低于活塞泵研制。因此，每个

time the handle is operated up and down, a specific volume of oil is ejected form the

时间的操作手柄向上和向下，特定量的油喷出形成

pump to lift the load cylinder to a given distance against its load resistance. The bleed

泵提升负荷缸一个给定的距离对其负载电阻。流血

valve is a hand-operated valve which when opened, allows the load to be lowered by

阀是一个手动阀，打开时，允许负载可以降低

bleeding oil from the load cylinder back to the oil tank. This cylinder is referred to as

出血油从负荷缸回油槽。这个圆筒被称为

single acting because it is hydraulically powered in one direction only.

单作用，因为它是液压驱动的只在一个方向。

Figure 2.6

Hand-operated hydraulic jack system

Air-to-hydraulic pressure booster

Air-to-hydraulic pressure booster is a device used to convert workshop air into a higher

hydraulic pressure needed for operating cylinders requiring small to medium volumes of

high-pressure oil (Figure 27(a)).

Figure 2.7(a)

An air-to-hydraulic system

It consists of an air cylinder with a large diameter driving a small diameter hydraulic

cylinder. Any workshop equipped with an airline can easily obtain hydraulic power from.

24 Practical Hydraulic Systems

an air-to-hydraulic booster hooked into the airline. Figure 2.7(b) shows an application of

the air-to-hydraulic booster. Here the booster is seen supplying high-pressure oil to a

hydraulic cylinder used to clamp a work piece to a machine tool table.

图2.6

Hand-operated hydraulic jack system

手动液压千斤顶系统

Air-to-hydraulic pressure booster

空气液压助力器

Air-to-hydraulic pressure booster is a device used to convert workshop air into a higher

空气对液压增压器是用来转换车间的空气进入一个更高的装置

hydraulic pressure needed for operating cylinders requiring small to medium volumes of

液压工作缸需要小到中等体积的需要

high-pressure oil (Figure 27(a)).

高压油（图27（a））。

Figure 2.7(a)

图2.7（一）

An air-to-hydraulic system

空气对液压系统

It consists of an air cylinder with a large diameter driving a small diameter hydraulic

它由一个大直径的驱动一个小直径液压气缸

cylinder. Any workshop equipped with an airline can easily obtain hydraulic power from.

缸。任何车间配备一个航空公司可以很容易地获得液压动力。

24 Practical Hydraulic Systems

24实际的液压系统

an air-to-hydraulic booster hooked into the airline. Figure 2.7(b) shows an application of

空气对液压助力器钩到航空公司。图2.7（b）显示中的应用

the air-to-hydraulic booster. Here the booster is seen supplying high-pressure oil to a

空气液压助力器。这里的助推器是视为一个提供高压油

hydraulic cylinder used to clamp a work piece to a machine tool table.

液压缸用于夹紧工件在机床工作台。

Figure 2.7(b)

Manufacturing application of an air-to-hydraulic booster

Since the workshop air pressure normally operates at around 1OO psi, a pneumatically

operated clamp would require a relatively larger cylinder to hold the work piece while it

is being machined.

Let us assume that the air piston has a 10 sq. in. area and subjected to a pressure of

100 psi. This produces a 1000 lb force on the hydraulic cylinder piston Thus if the area

of the hydraulic piston is l sq．in., the hydraulic discharge oil pressure will be 1000 psi.

As per Pascal's law this produces a 1000 psi oil pressure at the small hydraulic clamping

cylinder mounted on the machine tool table.

The pressure ratio of the pressure booster can be determined as follows:

图2.7(b)

Manufacruring应用air-to-hydraulic助推器

由于车间空气压力通常运行在1 oo psi,pneurnatically

夹操作需要一个相对较大的圆柱体的工件

正在加工。

让我们假设空气活塞lO平方。在。区和受到的压力

厕所psi。这产生一个iOO0磅力液压活塞cylipder因此如果该地区

液压活塞的l sq.in。,出水量油压lOOO psi。

根据帕斯卡定律这产生一个1000 psi油压小液压夹紧

油缸安装在机床表。

增压器的压力比,可以确定如下:

Flow

Pascal's law holds good only for liquids, which are at rest or in the static state. As stated

earlier, the study of this science dealinag with liquids at rest is referred to as Hydrostatics.

The study of liquids in motion can be discussed under two headings, Hydrokinetics and

Hydrodynamics.

Hydrokinetics deals with the motion of fluid without considening the forces

causing the motion. The velocity at any point in the flow field at any time is studied in

this branch of fluid mechanies. Once this velocity is known, the pressure distribution and

the forces acting on the fluid can be determined Hyclrodynamics is the study of fluid

motion that includes the forces causing the flow.

Fluid motion can be described by two methods. They are:

I．Lagrangian method

2．Eulerian method.

流

帕斯卡定律是仅适用于液体,在休息或在静态状态。如上所述

早些时候,这个科学的研究dealinag静止的液体称为流体静力学。

研究液体的运动可以讨论下两个标题,流体动力学和

流体动力学。

流体动力学处理流体的运动没有considening部队

导致运动。流场的速度在任何时候在任何时间进行了研究

这个分支的流体mechanies。一旦这速度是已知的,分布和压力

可以确定流体上的力Hyclrodynamics是流体的研究

运动,包括引起流动的力量。

流体运动可以通过两种方法进行描述。它们是:

I.Lagrangian方法

2.欧拉法。

In the Lagrangian method a single fluid particle is followed during its motion and its

characteristics such as pressure, density, velocity; acceleration, etc. are described.

In the Eulernian method, any point in the space occupied by the fluid is selected and an

observation is made on the changes in parameters such as prerssure, density, velocity, and

acceleration at this point. The Eulerian method is generally followed and is most

preferred, when it comes to analyzing hydraulic systems.

No study of flow is complete without understanding three important principles related

to the phenomenon of flow, which are as follows.

在随后的拉格朗日方法单一流体粒子在运动和

特征如压力、密度、速度,加速度等。

Eulernian方法,任何时候选择流体和占用的空间

观察了prerssure等参数的变化,密度、速度、和

在这一点上加速。随后的欧拉法通常是大多数

时优先考虑,分析液压系统。

流的研究没有完全不了解相关的三个重要原则

流动的现象,如下。

1:Flow makes it go: The actuator must be supplied with flow for anything in a

hydraulic system to move. the cylinder is normally retracted and requires flow

to extend itself.The extension and retraction functions are accomplished with

the help of a direction control valve.

2:Rate of flow determines speed:The rate of flow usually measured in gallons

per minute or gpm is determined by the pump. The speed of the actuator

changes with variation in puinrp outlet flow.

3:Changes in actuator volume displacement will change actuator speed at a

given flow rate: when the cylinder retract, less volume needs to be

displaced because of the space occupied by the cylinder rod. This results in a

faster actuator cycle.Terefore,there is always a difference in actuator speed

between the extend and retract functions.

1:让它去流动:致动器必须提供任何在流动

液压系统。气缸正常收回,需要流

扩展本身。扩展和收缩功能

方向控制阀的帮助。

2:流速确定速度:流量通常以加仑

每分钟或gpm是由泵。致动器的速度

改变puinrp出口流量的变化。

3:致动器体积位移的变化会改变执行机构速度

给定流量:当气缸缩回,卷需要

流离失所,因为活塞杆占用的空间。这导致了一个

更快的执行周期。Terefore,总有不同的执行机构的速度

之间的扩展和收缩功能。

. ..

Meaning of flow

Flow velocity is very important in the design of a hydraulic system. When we speak of

fluid flow down a pipe in a system, the term flow in itself conveys three distinct meaning,

which are:

1. Volumetric flow, which is a measure of the volume of a fluid passing through a

point in unit time

2. Mass flow, which is a measure of the mass of a fluid passing through a point in

unit time

3. lVelocity of. flow, which is a measure of the linear speed of a fluid passing

through the point of measurement.

Types of fluid flow

Fluid flow can be classified as follows:

· Steady and unsteady flows

. Uniform and non-uniform flows

. Laminar and turbulent flows

. Rotational and non-rotational flows.

流的意义

流速在液压系统的设计是非常重要的。当我们说话

流体管道系统中,流这一术语本身传达了三个不同的意义,

这是:

1。体积流量,这是一个衡量的体积的流体通过

在单位时间内

2。质量流量,这是衡量质量的流体通过一个点

单位时间内

3。lVelocity。流,这是一个衡量线性流体的速度传递

通过测量。

类型的流体流动

流体可以分类如下:

稳定和不稳定流动

。均匀和非均匀流

。层流和紊流流动

。旋转和non-rotational流动。

英语翻译