-
Unit 21
Pumps
1. Introduction
Pump,
device
used
to
raise,
transfer,
or
compress
liquids
and
gases.
Four'
general
classes
of
pumps for liquids are
described below t In all of them , steps are taken
to prevent cavitation (the
formation of
a vacuull1), which would reduce the flow and
damage the structure of the pump, -
pumps
used
for
gases
and
vapors
are
usually
known
as
compressors .
The
study
of
fluids
in
motion
is called fluid dynamics.
1
．介绍
泵是提出，
转移或压缩液体和气体的设备。下面介绍四种类型的泵。在所有的这些中，<
/p>
我们
一步步采取措施防止气蚀，
气蚀将减
少流量并且破坏泵的结构。
用来处理气体和蒸汽的泵称
为压缩机
，研究流体的运动的科学成为流体动力学。
Water
Pump,
device
lor
moving
water
from
one
location
to
another,
using
tubes
or
other
machinery. Water pumps operate under
pressures ranging from a fraction of a pound to
more
than
10,000
pounds
per
square
inch.
Everyday
examples
of
water
pumps
range
from
small
electric pumps that
circulate and aerate water in aquariums and
fountains to sump pumps that
remove
'Water from beneath the foundations of homes.
水泵是用管子或其他机械把水从一个地方传到另一个地方。<
/p>
水泵的操作压力从一磅到一万磅
每平方英尺。
日常生活中，
泵是很多的，
有用于在鱼池和喷泉使水循环和
向水中充气的电泵，
还有用于从住宅处把水引走的污水泵。
Two types of modern pumps used to move
water are the positive-displacement pump and the
centrifugal pump. Positive-displacement
pumps use suction created by a vacuum to draw
water
into a closed space. An example
of this type of pump is the lift, or force, pump
used commonly in
the rural United
States until the mid-1900s. The lift pump is
operated by raising a handle that is
attached to a piston encased in a pipe.
Lifting the piston creates a partial vacuum
beneath it in
the pipe, causing water
to be drawn from a well below , through the pipe,
and into a chamber in
the pump. A one-
way valve closes after water is pumped into the
chamber, keeping the water
from flowing
back down into the well. Subsequent pumps of the
piston pull more water into the
chamber,
which
eventually
overflows,
spilling
water
out
of
a
spout.
Centrifugal
pumps
use
motor-
driven propellers that create a flow of water when
they rotate. The blades of the propeller
are immersed in the water to be pumped.
As the propeller turns, water enters the pump near
the
axis
of
the
blades
and
is
swept
out
toward
their
ends
at
high
pressure.
An
alternative,
early
version of the centrifugal pump, the
screw pump, consists of a corkscrew-shaped
mechanism in a
pipe
that.
when
rotated,
pulls
water
upward.
Screw
pumps
are
often
used
in
waste-
water
treatment plants because they can
move large amounts of water without becoming
clogged with
debris. In the ancient
Middle East the need for irrigation of farmland
was a strong induceDlent to
develop a
water pump. Early pumps in this region were simple
devices for lifting buckets of water
from
a
source
to
a
container
or
a
trench.
Greek
mathematician
and
inventor
Archimedes
is
thought
to
have
devised
the
first
screw
pump
in
the
3rd
century
Be.
Later,
Greek
inventor
Ctesibius developed
the first lift pump. During the late 17th and
early 18th centuries AD, British
engineer
Thomas
Savery,
French
physicist
Denis
Papin
..and
British
blacksmith
and
inventor
Thomas Newcornen. contributed to the
development of a water pump that used steam to
power
the pump s piston. The steam-
powered water pump's first wide use was in pumping
water out of
mines. Modern-day examples
of centrifugal pumps are those used at the Grand
Coulee Darn on
the Columbia River. This
pump system has the potential to irrigate over one
million acres of land.
现在，<
/p>
两种典型的排水泵是容积泵和离心泵。
容积泵通过由真空产生的吸
力把水引到一个紧
凑的地方。这种类型泵的一个实例就是提升或压力泵，在
20
世纪中叶美国农村普遍使用。
提升泵的操作是通
过一个与被管子包住的活塞手柄来进行的。
当我们提升活塞时在管子下部
产生一个局部的真空，
这样我们就用管子从下面的取水，
并且送到泵的一个空间。
当水被泵
吸入时，单向阀关闭，阻止
水流回到井下。接着泵的活塞吸入更多的水进入泵的膛体中。这
样最后形成溢流，水从管
口处流出。而离心泵时使用了一种螺旋推进器，旋转时使水流动，
而且推进器的切片是在
泵送水时侵入水中的。
而且，
当推进器旋转时，
水进入位于刃片的轴
部的间隙并且以很高的压力甩向底部。与它类似，
离心泵的早期形式，
螺杆泵，通过一个管
子螺丝
钉的组成，当旋转时，把水提升上去。
螺旋泵经常用在污水处理厂中，因为他们可以
运输大量的水，
而不会因为碎片而堵塞。
在
远古的中东，
因为对农场进行灌溉的需求，
所以
有一种强大的动力去推进水泵的进程。
在这些区域里，
早期的泵是为了将水一桶一桶的从水
源或河渠中提升到容器中。
古希腊的发明家和数学家的阿基米德泵认为是公元前
3
世纪首先
提出螺旋泵的发明家。
之后，
古希腊发
明家发明了第一个提水泵。
在十七世纪末和十八世纪
初，英国的
工程师
Thomas
Savory
，法国的物理学家
Denis
Pa]pin
，和英国的铁匠和发明家
Tomas Newco
men,
它们发明了用蒸汽驱动活塞的水泵。
蒸汽驱动的水泵首
先广泛的被应用在
从煤矿往外输水过程中。
现在离心泵使用的例
子，
可以是在哥伦比亚河上使用的大古利水坝。
这个泵有超过灌
溉一百万英亩的土地能力。
2.
Reciprocating Pumps
Reciprocating pumps
consist of a piston moving back and forth in a
cylinder that has valves to
regulate
the
flow
of
liquid
into
and
out
of
the
cylinder.
These
pumps
may
be
single
or
double
acting. In the single acting pump, the
pumping action takes place on only one side of the
piston,
as in the case of the COD1ll1on
lift PUDlP
, in which the piston is
moved up and down by hand. In
the
double acting pump, the pumping action takes place
on both sides of the piston, as in the
electrical or steam-driven boiler feed
pump, in which water is supplied to a steam boiler
under
high pressure. These pumps can be
single-stage or multistaged, Multistaged
reciprocating pumps
have multiple
cylinders in series.
2.
往复泵
往复泵有一个在圆筒中上下
移动的活塞，
可以使水规则的流入或流出圆筒。
这些泵可以是单
作用的，也可以是双作用的。在单作用的泵中，泵的作用仅仅发生在活塞的一侧，
典型的例
子就是升液泵。
在升液泵中，活塞通
过手上下移动。在双作用的水泵中，泵的作用发生在活
塞的两侧，
比如说电动的或气动的锅炉给水泵，
水以高压通过蒸汽锅炉供给。
这些泵可以是
单级的也可以是多级的。多级的往复泵的泵系列有多个刚体。
3.
Centrifugal Pumps
Also
known as rotary pumps, centrifugal pumps have a
rotating impeller, also known as a blade,
that
is
immersed
in
the
liquid.
Liquid
enters
the
pump
near
the
axis
of
the
impeller
,
and
the
rotating impeller sweeps
the liquid out toward the ends of the impeller
blades at high pressure.
The impeller
also gives the liquid a relatively high velocity
that can be converted into pressure in
a
stationary
part
of
the
pump
,
known
as
the
diffuser.
In
high-pressure
pumps
,
a
number
of
impellers
may
be
used
in
series,
and
the
diffusers
following
each
impeller
may
contain
guide
vanes to gradually reduce the liquid
velocity. For lower-pressure pumps, the diffuser
is generally a
spiral passage, known as
a volute, with its cross-sectional area increasing
gradually to reduce the
velocity
efficiently.
The
impeller
must
be
primed
before
it
can
begin
operation,
that
is,
the
impeller
must be surrounded by liquid when the pump is
started. This can be done by placing a
check valve? in the suction line, which
holds the liquid in the pump w-hen the impeller is
not
rotating. If this valve leaks, the
pumps may need to be primed by the introduction of
liquid from
an outside source such as
the discharge reservoir. A centrifugal pump
generally has a valve in the
discharge
line to control the flow and pressure. For low
flows and high pressures, the action of
the impeller is largely radial. For
higher flows and lower discharge pressures, the
direction of the
flow within the pUD1P
is more nearly parallel to the axis of the shaft,
and the pump is said to
have an axial
flow. The impeller in this case acts as a
propeller. The transition from one set of flow
conditions
to
the
other
is
gradual,
and
for
intermediate
conditions,
the
device
is
called
a
mixed-
flow pump.
3
离心泵
离心泵被认为是旋转泵，<
/p>
它是有一个旋转地叶轮，
也有刃片，
刃片
是侵入液体中。
液体也是
由叶轮轴向进入泵，
< br>并且旋转的叶轮将液体甩向叶片根部。
同时叶轮也给液体一个较高的过
度，这个过度能够使泵的一个固定部件转化成压力。我们一般称为扩压器。
在高压泵里，很
多叶轮可以被系列选用，
并且在一个叶轮后有一
个扩压器，
也可能含有导轮，
可以逐渐的降
低液体的过度。
对于低压泵来说，扩压泵一般就是一个螺旋形的通道，
成为蜗壳，
作用原理
是拦截面逐渐增加可以有效降低
流体的过度。
在泵工作前，
叶轮必须被灌注，
< br>也就是在泵启
动时，
叶轮必须被液体包围。
也可以通过在吸入线上放另一个截止阀来实现，
截止阀在泵停
止工作时是液体保留在泵内。
如果阀泄露了，
泵可以通
过阀的入口，
从外面的水源比如说蓄
水池来取水灌注。
一般离心泵在排水线也有一个阀控制流体和压力。
对于小流量和高压力来
说，
叶轮作用很大部分是放射状的。
对
于高速流体和低压排水压力，
泵中流体的方向可以近
似于与轴的
轴向平行，
这时泵有一个轴流。
这时叶轮就近似于螺旋推进器。
从一种流的状态
转换到另一种流的状态是渐进的，对于中间状态
，设备可称为混流泵。
4. Jet Pumps
Jet pumps use a relatively sznall
stream. of liquid or vapor, moving at high
velocity, to move a
larger flow of
fluid. As the high-velocity stream passes through
the fluid, it carries some of the
fluid
out of the pump; at the same time, the high-
velocity stream creates a vacuum that pulls
fluid into the pump. Jet pumps are
often used to inject water into a steam boiler.
Jet pumps have
also
been
used
to
propel
boats,
particularly
in
shallow
water
where
a
conventional
propeller
might be .
4
射流泵
射流泵是通过一个流量相对
较小的液体或蒸汽，
以较高速度移动到较大的液流。
因为高速流
体要通过液体，
它从泵里带走液体一部分，同时，
高速流产生一个真空，这个真空又把液体
吸入泵内。
射流泵经常给蒸汽锅炉注水。
另外，也应用来推动的船只，
特别
是在正常的推进
器可能被破坏的浅水里。
5. Other pumps
A
variety
of
positive-displacement
pumps
are
also
available,
generally
consisting
of
a
rotating
member with a
number of lobes that move in a close-fitting
casing. The liquid is trapped in the
spaces
between
the
lobes
and
then
discharged
into
a
region
of
higher
pressure.
A
common
device of this type
is the gear pump, which consists of a pair of
meshing gear. The lobes in this
case
are the gear teeth. A simple but inefficient pump
can also be constructed by having a screw
turning in a casing and pushing the
liquid along. A similar pump was first invented by
the Greek
mathematician and physicist
Archimedes sometime after 300 Be. In all these
pumps the liquid is
discharged in a
series of pulses and not continuously, so care
must be taken to avoid resonant
conditions in the discharge lines that
could damage or destroy the installation. For
reciprocating
pumps,
air
chambers
are
frequently
placed
in
the
discharge
line
to
reduce
the
magnitude
of
these pulsations and to make the flow
more uniform.
5
其他类型的泵
仍然存在其他很多类
型的容积泵，
一般用带有很多保密配合的圆形突出的回转件。
液
体被收
集在耳朵之间，
而且被转送到一个压力较高的区域。
这种泵的一个典型设备是齿轮泵，
包含
有一
对网状齿轮，
在齿轮泵里耳朵就是齿牙。
也可通过一个在外壳旋
转的螺杆来构造一个简
单而低效的泵，
螺杆推动也提前进。
一个相似的泵在公元前
3
世纪被希腊数学家
和物理学家
阿基米德发明了。在所有的泵里，液体被一些列脉冲排出，并且不连续。因此
我们必须注意
在排除线上来避免共振，
因为共振可能会损伤或破
坏整个设备。
对往复泵来说，
真空经常放
在排除线上，可以减少振动，并使流动均衡。
Unit 22
Pumping Equipment for Gases
Essentially the same basic
types of mechanical equipment are used for
handling gases and liquids,
though
the
construction
may
be
very
different
in
the
two
cases.
Under
the
normal
range
of
operating pressures, the
density of a gas is considerably less than that of
a liquid so that higher
speeds of
operation can be employed and lighter valves
fitted to the delivery and suction lines.
Because
of
the
lower
viscosity
of
a
gas
there
is
a
greater
tendency
for
leakage
to
occur,
and
therefore
gas
compressors
are
designed
with
smaller
clearances
between
the
moving
parts.
Further
differences
in
construction
are
necessitated
by
the
decrease
in
volume
of
gas
as
it
is
compressed , and this
must be allowed for in the design. 'Since a large
proportion of the energy
of
compression
appears .as
heat
in
the
gas,
there
will
normally
be
a
considerable
increase
in
temperature
which
may
limit
the
operation
of
the
compressor
unless
suitable
cooling
can
be
effected. For this reason, gas
compression is often carried out in a number of
stages and the gas
is
cooled
between
each
stage.
Any
gas
which
is
not
expelled
from
the
cylinder
at
the
end
of
compression (the clearance volume )
must be expanded again to the inlet pressure
before a fresh
charge can be admitted.
This continual 'compression and expansion of the
residual gas results in
loss
of
efficiency'
because
.neither
the
compression
nor
the
expansion
can
be
carried
out
completely reversibly'.
With liquids this factor has no effect on the
efficiency because the residual
fluid
is not compressed.
Unit 22
气体的泵设备
对于处理戒指为气体
或液体来说，
虽然设备在结构上有很大差异，
但这两种设备在本
质上属
于相同基本类型的机械设备。
在正常操作范围内，
因为气体的密度比液体小，
所以对气体的
操作
可达到较高的速度，
而且在吸入线和排出线上可使用较轻的阀。
因为气体的粘度小所以
它们容易发生泄露。
因此气体压缩机的移
动部件之间的间隙被设计的非常小。
因为气体压缩
过程中体积减
小，
因此与液体相比在结构上存在差异，
而且这个差异在设计中
也要考虑。
压
缩机中很大一部分能量要被转换成热能。
因此在没有合适的冷却措施时将会限制压缩机的操
作。也因为这个，气体
压缩机分为多级完成，
而且每一级中可分别冷却。任何在压缩机中没
有被排出缸体的气体，
再重新充入时要膨胀到入口的压力。
残余的气体连续压缩和膨胀导致
效率下降，因为不管是压缩还是膨胀都不能被可逆操作。
The principal
types of compressors for gases are described as
follows.
而对液体，间隙容量不会影响效率的，因为残余液体不可压缩。
Reciprocating piston
compressor'
往复式活塞压缩机
This type of compressor
which may consist of from one to twelve stages is
the only one capable
of
developing
very
high
pressures,
such
as
for
example
over
350
M;N
1m2
as
required
for
polythene
manufacture.
A
single-stage,
two?cylinder
unit,
shown
in
Fig.
5.
4,
at
relatively
slow speed and is being replaced wherever possible
by the centrifugal type 'Which can
now
develop all but the very highest pressures .
这种压缩机可以包含
1
—
12
级，
是唯一可以达到较高压力的设备，
比如在乙烯工业中所需水
的压力达到超过
350
万牛
/
每平方米，图
5.
4
是单级双缸的压缩机，操作速度低，在操作压
力较低时可以用
离心压缩机取代。
Rotary
blowers and compressors
旋转式鼓风机和压缩机
These can be divided into two classes-
those which develop a high compreseion ratio and
those
which have very low ratios. The
former include the sliding-vane type@) in which
the compression
ratio is achieved by
eccentric mounting of the rotor (Fig. 5. 5) and
the Nash Hytor pump (Fig. 5. 6)
in
which the compression ratio is achieved by means
of a specially shaped casing and a liquid seal
which rotates with tile impeller.
这种压缩机可以分为较高压缩和较低压缩两种类型。
前者包含
滑片式，
它的压缩比是通过离心转子来实现的。
Nas
h Hytor
泵是通过特殊形状的刚体和叶轮
同时旋转的液体
密封来实现的。
In
the
sliding-vane
unit
the
rotor
is
slotted
to
take
the
sliding
blades
which
subdivide
the
crescent-shaped space between the rotor
and cylinder. On rotation the blades move out
trapping
the gas which is compressed
during rotation and discharged at the delivery
port as shown.
在滑片式压缩机通过在壳体上开槽夹住叶片，而叶片将转子和缸体之间的月牙空间分成一
片一片的。在旋转时，刃片滑片拦住气体但气体在旋转式被压缩，并且在端口被排出。
The
Nash
Hytor
(Fig.
5.
6)
type,
which
is
also
known
as
the
liquid-ring
pump'
is
a
positive
displacement type
with a specially shaped casing and a liquid seal
which rotates with the impeller.
The
shaft
and
impeller
are
the
only
moving
parts
and
there
is
no
sliding
contact,
so
that
no
lubricants are required
and the gas under compression is riot
contaminated.
Nash Hytor
泵也可以
分为液环泵，
属于容积泵类型而且带有一个特殊形状的壳体和一个与叶
< br>轮同时旋转的液体密封。轴和叶轮是没有移动部件而且没有滑动触点，所以不需要润滑剂，
而且被压缩的气体不会受到污染。
With
this arrangement the liquid leaves and re-enters
the impeller cells in the manner of a piston.
The
service
liquid
is
supplied
at
a
pressure
equal
to
the
discharge
pressure
of
the
gas
and
is
drawn in automatically to compensate
for that discharged Irornt he 'ports. During
compression
the
energy
is
converted
to
heat
so
that
this
is
a
nearly
isothermal .process.
Downstream
the
liquid is separated from the gas and
recirculated with any .necessury make up.
在这种压缩机中，
液体通过活塞离开
和重新进入叶轮单元。
工作液体的进口压力与出口压力
相等，<
/p>
而且工作液体自动被吸入来补偿出口的液体。在压缩中，能量转化成热，因此这个工
艺接近于等温工艺。在下液，液体从气体中分离出来通过必要的构造进行再循环。
A
different
kind
of
unit
is
represented
by
the
cycloidal
or
Rootes
blower@.
In
this
type,
compression
is
achieved
by
the
rotation
of
two
elernents..
These
rotors
turn
in
opposite
directions so that,
as each passes the inlet, it takes in air which is
compressed between impeller
and the
wall and is than expelled outwards.
还有其他类型，
比如摆线型或罗茨鼓风机。
在这种类型的压缩机是通过两个部件的旋转来实
现的。
转子以相
反的方向移动，
它们通过入口时，
带入空气，
< br>并将空气在叶轮和壳体之间受
到压缩和排出。
Centrifugal blowers and compressors'
离心式鼓风机和压缩机，包括涡轮压缩机
These depend on the conversion of
kinetic energy into
pressure energy.
Fans are used for low
pressures,
and
can
be
made
to
handle
very
large
quantities
of
gases.
For
the
higher
pressure
ratios now in demand, multistage
centrifugal compressors are mainly used,
particularly for the
requirements
of
high
capacity
chemical
plants.
Thus
in
catalytic
reforming,
petrochemical
separation plants ( ethylene
manufacture), ammonia plant-s with a production
rate of 12 kg/s,
and
for
the
very
large
capacity
needed
for
natural
gas
fields,
this
type
of
compressor
is
now
supreme. These units now
give flowrates up to 140 m3/s and pressures up to
5. 6 MN 1m2 with
the newes
t
range going to 40 MN 1m2? It is important to
accept that the very large units offer
considerable savings over multiple
units and that their reliability is remarkably
high. The power
required is also very
high; thus a typical compressor operating on the
process gas stream in the
catalytic
production of ethylene from naphtha will take 10
MW for a 6. 5 kg/s plant.
这些设备主要服从动能向压能
转换，
鼓风机用在低压，
可以处理大量的气体。
对于先不要求
较高的压力比的情况，
可以使用多级离心
压缩机，
特别是在要求高产量的化学工厂。
因此在
催化参照下，石油化工分离工厂（乙烯加工厂）
，生产进度在１２ｋｇ／ｓ的
氨工厂，和产
量要求较高的天然气田，
这种类型的压缩机是使用
最广泛的了。
这些流量可达到
140
3m/s
，
压力达到
5.6
MN/2m
，最新的达到
40
MN/2m.
。
使用大压缩机与多个
压缩机相比，
它的经济性和可靠性都很高。
能量要求也是很高。
对于从
粗汽油中，
用催化的方式生产乙
烯所产生的气体的操作，
需要石化厂的流量为
6. 5 kg/
s
压力
为１０
MW
的能量。
Unit 23
Solid
Liquid Separation
It
is
difficult
to
identify
a
large-scale
industrial
process
'Which
does
not
involve
some
form
of
solid-fluid separation. In its
entirety, the latter activity involves a vast
array of techniques
and
machines,
This
book
is
concerned
only
those
parts
of
this
technological
diversity
which
relate to solid-liquid
separation (SLS)
对于大规模的工艺来说，
很难找到不包含一些固液分离的形式。
对于整个工业来说，
近来
一
些工作包含大量的技术和机器。本书主要介绍与与固液分离有关的工艺多样性。
.
Attempts have
been made [Svarovsky, 1981 Jto catalogue the
variety of processes and machines
used
in SLS systems , these are usually based on two
principal modes of separation : (1) Filtration,
in which the solid-liquid mixture is
directed towards a
mermbrane
, etc. ). The liquid phase or filtrate flows
through the latter whilst solids? are
retained,
either on the surface, or
within the medium.
在１９８１年
Svarovsky
做出了努力将在固液分离中不同种类的工艺和机
器装成册。这些基
于两种主要的分离模式。
（
< br>
１）
过滤，
在过滤过程中固液混合物共同流向一个媒介，
（筛子，
滤纸，织布，薄膜，等等）
。液相或滤出液流过媒介，故乡被保留在媒介表面或中间。<
/p>
(2)
Separation
by
sedimentation
or
settling
in
a
force
field
(gravitational,
centrifugal)
wherein
advantage is taken
of differences in. phase densities between the
solid and the liquid?. The solid
is
allowed to sink in the fluid, under controlled
conditions. In the reverse process of flotation,
the
particles rise through the liquid,
by virtue of a natural or induced low .
（２）
在一个力场作用下通过沉降
或沉淀进行分离，
在力场（重力场，离心场）
中的沉降分离是利
用固相和液相的密度差。
固体在人为控制下在液体中下沉。
对于一个浮选相反的工艺，
介质
从液体中上
升，利用固相的一个自然优点或外加的低固相密度优点。
The large range of machinery reflects
the uncertainty which attaches to the processing
of solids,
particularly those in small
particle size ranges.
大部分机械
都反应了与固体处理相关的不确定性，特别是较小颗粒尺寸范围。
The filterability and sedimentation
velocity of such mixtures depend on the state of
dispersion of
the suspension; in turn,
the latter is strongly influenced by solid-liquid
surface conditions 'Which
govern
the
stability
of
the
mixture
and
the
overall
result
of
particle-particle
contact.
The
properties of such
systems may also be time dependent, with
filterability' and settling rate being
a function of the history of the
suspension [Tiller , 1974J.
这种混合物的过滤性和沉
积速度主要取决于悬浮液的浮散状态，
反过来浮散状态很大程度上，
受控制混合物的稳定性和控制质点与质点接触整体状态的固液所影响。
这种系统的特
性也可
满足随时间而定的，他们的过滤性和沉积进度是悬浮液经历的一个函数。
The
dispersive
and
agglomerative
forces
present
in
these
systems
are
function
of
pH
t
temperature,
agitation,
pumping
conditions,
etc@.
all
of
which
complicate
the
situation
and
produce the result that suspension
properties cannot be explained in hydrodynamic
terms alone.
Despite
these
formidable
problems,
modem
filtration
and
separation
technology
continues
to
produce
separations
in
seemingly
intractable
situations,
and
to
eliminate
the'
neck
characteristi
c of the SLS stage in many processes.
这些系统中的分散力与凝聚力是ＰＨ值，
温度，
搅拌状态与泵作用等条件的函数。
所用这些
方面的情况
变得复杂，
并且让我们认识到悬浮液的特性不能用水力间距来解释。
尽管有这些
困难的问题，
现代过滤和分离工艺不断被新的技
术似乎比表面上看起来更加难所取代。
消除
在很多工艺中固液分
离的瓶颈特性。
A first step in the
rationalisation of such problems is to choose the
most appropriate technology
from
filtration,
sedimentation
or
a
combination
of
these
two
operations.
In
general,
sedimentation
techniques are cheaper than those involving
filtration; the use of gravity settling
would be considered first, particularly
where large, continuous liquid flows are involved
[Pierson
1981 J.
对于这个问题，
采取的合理的方法第一步是选择最恰当的技术，或过滤，或沉淀，
或两者的
合并。
通常，沉淀技术比那些含有
过滤的技术要经济。利用重力沉淀是要考虑的，
特别是大
流量和
连续性的工艺中。
A
small
density
difference
between
the
solid
and
fluid
phases
would
probably
eliminate
sedimentation as a
possibility, unless the density difference can be
enhanced, or the force field of
gravity
increased by centrifugal action. Such techniques
for enhancing sedimentation the nature
of
the
particulates
was
such
as
to
make
filtration
The
latter
condition
would
ensue
when
dealing
with
small
,
sub-
micron
material,
or
soft,
compressible
solids
of
the
type
encountered in waste
water and other effluents. Some separations
require combinations of the
processes
of sedimentation and filtration; preconcentration
of the solids will reduce the quantity
of liquid to be filtered and,
therefore, the size of filter needed for the
separation.
在液相和固相之间，
密度查一下哦，
似乎不能用沉降工艺，
除非密度差异
可被扩大或通过离
心作用来增加重力场。
为提升沉降能力这些工
艺为那些不能进行重力分离和因为颗粒的特性
而难于进行过滤的分离提供可能。
后面这种情况在处理小的次微小的材料或软的可压缩的固
体时跟着发生在
污水或流出物中。
一些分离方法需要的沉降和过滤工艺，
将固体
集中，
将减
少流过液体的量，而且过滤器尺寸也减小了。
Having decided upon the
general separation method , the next stage is to
consider the various
separational
techniques available within the two fields. These
operational modes may be listed
as:
在决定一般分离方法后，下面就要考虑在这两个区域所存在的
分离技术。操作方法如下：
(1)
Sedimentation: gravity; centrifugal;
electrostatic; magnetic
（１）
沉降：重力，离心力，静电力，磁力。
(2)
Filtration!
gravity vacuum: pressure: centrifugal.
（２）
过滤：重力，真空，压力，离心力。
Another
serious
consideration
is
whether
the
separation
is
to
be
effected
continuously
or
discontinuously;
the
latter
method
is
known
as
processing.
In
this
case,
the
separator
acts
intermittently between filling and discharge
stages. The concentration of solids in the feed
mixture
and
the
quantities
to
be
separated
per
unit
time
are
also
factors
which
affect
the
selection procedure.
下一个疑问是分离的连续性还是不连续性操作。不连续操作称为批量操作。在这种情况下，
分离设备在填料和排出阶段是间歇作用的。
在原料混合物中固体的浓度和单
位时间所要求的
分离量也是影响选择步骤的因素。
This activity is made more complicated
by the fact that the separation stage rarely
stands alone.
Various
pre-
and
post-treatment
stages
may
be
requ
ired
in
the
overall?
SLS
process.
Thus,
the
settling rate of a
suspension, or its filterability, may require
improvement by pretreatment using
chemical or physical methods. After
filtration, wet solids are produced, and- these
may require
further' processing to
deliquor (dry) the filter cake; in some cases, the
latter, being the principal
product,
requires purification by washing wit h clean
liquid.
因为分离过程很少单独存在，
这就使得情况更
加复杂。
不同种类的预处理和后处理在总体固
液分离中有要求。
因此，
悬浮液的沉淀速度或过滤性可能要求要通过化学或物理方
法进行预
处理来改善。在过滤后，有潮湿的固体，粗要进一步处理，对过滤块进行干燥。
在一些情况
下，滤出物为主要产品，需要用干净的液体净化。
It
will
be
apparent
that
in
the
development
of
a
typical
process
for:
(a)
increasing
the
solids
concentration of a
dilute feed, (b) pretreatment to enhance
separation characteristics, (c) solids
separation,
(d)
deliquoring
and
washing
,
many
combinations
'of
machine
and
technique
are
possible. Some of these combinations
may result in an adequate, if not optimal,
solution to the
problem. Full
optimisation would inevitably be time consuming
and expensive , if not impossible
in
an
industrial
situation.
Certain
aspects
of
filter
selection
are
considered
at
the
end
of
this
chapter, on pressure filter process
calculations ~
很显然在典型的工艺发展中
：
（
a
）对稀释原料增加固体浓度，<
/p>
(b)
通过预处理来提高分离特
性，
（
c
）固体分离，
(d)
干燥和洗涤，进行多种技术和机器的组合是可能的。这些组合的充
足的，
不是最佳的，
也会有适当的方法解决问题。
完全最优的方法难免会浪费时间而且不经
济，如果在工业中不是不可
能的。过滤器的选择部分在章末又考虑，过滤工艺的计算压力。
A
typical
medium
for
the
filtration
of
coarse
materials
is
a
woven wire
mesh
which
will
retain
certain particulates on the surface of
the screen. As the size of the particulates
decreases, other
and
smaller
openings
or
pores.
Flow
through
such
a
system
is
shown
in
Fig.
5.
10.
Where
the
particulates are extremely small and in
low concentration, deposition may occur in the
depths of
the medium , such as in water
clarification by sand fitters.
在粗粒的原始物料的过滤典型的媒介是金属筛网，
它将某些颗粒留在筛网表面。
当颗粒尺寸
减小时，需要其他一些筛子。例如，机织布，薄膜，
等等。这些由越来越小的孔构成。在图
5.10
中显示流过这样
的系统。在颗粒相对小并且浓度低时，沉积作用可能发生在媒介深处，
比如用沙子过滤净
化。
The
filtration
medium
may
be
fitted
to
various
Iorms
of
equipment
which,
in
turn,
can
be
operated
in
several
modes.
Thus,
plant
is
available
which
creates
flow
by
raising
the
fluid
pressure
by
pumping
,
or
some
equivalent
device.
Such
filters
operate
at
pressure
levels
above
atmospheric;
the
pressure
differential
created
across
the
medium
causes
flow
of
fluid
through the equipment. Plant of this type can be
operated at constant pressure differential
or at constant flow rate. In the latter
case the pressure differential will increase with
time whilst
at constant pressure,
liquid ?low rate decrease with time.
过滤
网或过滤媒介需要适合多种设备。
反过来说，
设备也可能进行多
种操作，
因此设备可以
通过泵设备作用提高流体压力，
或化学设备。
这种压力过滤在高于大气压下工作；
压力差异
使流体通过媒介而通过设备。
这种类型设备可以再标
准压力差下操作或稳定流速下操作。
在
最近条件下，压力差在压
力不高条件下增加，流速随时间降低。
24
Valve , a mechanical
device used to control the flow of a gas or
liquid, or-in the case of a check
valveCD-to
ensure
that
flow
travels
in
only
one
direction.
Valves
range
in,
size
from
the
small
valve
of
an
automobile
tire
to
large
valves
used
in
the
control
of
locks
and
dams;
these
large
valves can measure
more than 5 m (16 ft) in diameter. Small and low-
pressure valves are usually
made of
brass, cast iron, or plastic, while large pressure
valves are made of cast or forged steel.
Other alloys, such as stainless steel
may be required if the controlled fluid is
corrosive. Valves may
be actuated
manually, mechanically through a servomechanism,
or by the flow of the controlled
fluid
阀，是一种控制液体或气体流动的机械。
例如截止阀，是保证流
体沿一个方向流动。阀的尺
寸范围很大，
小的用在汽车轮胎的阀
，
大的用在控制水闸和大坝上。
大阀的直径可能超过五
米。小阀和低压阀通常由黄铜，铸铁，塑料制造，而较高压力的阀是用锻钢制造的。其他合
金，
比如不锈钢可能用在控制流体有腐蚀作用的流体上。
阀可以手工操作，
可以由伺服机构
机械操作，或由所
控制液流操作。
Basically
there
are
only
four
types
of
valve+-rotary
,
lift,
slide
and
piston@-and
theirevolution
w-as undoubtedly in this order.
基本上由四种类型的阀，回转阀，提升阀，滑阀，活塞阀。而且毫无疑问它们的发展也是这
个顺序。
There are many
variants, however, of these four basic types, as
may be expected; yet all are alike
in
concept
and,
despite
the
present-day
trend
for
greater
simplification
and
standardization,
it
seems clear that the advent of ne-w
industrial processes and techniques, and the
discovery of
new,
and
sometimes
exotic,
materials
of
construction,
will
promote
these
variations,
perhaps
with
四种基本类型有很多种变体
。
然而所有变体与母体在原理上是相似的。
尽管目前发展趋势越
来越标准化，
越来越简化。
新型工艺和
技术的出现预计新的发现和外来的，
结构材料的发现。
将促进这
些变形，也许速度越来越快。
Four
fundamental designs, and their variants, in common
usage, all reliant on manual operation,
are
dealt
with
in
the
first
four
chapters.
The
alert
designer
should,
however,
have
no
trouble
adapting the
reasoning used to designs having similar
characteristics to those chosen by way of
example
四种基本设计以及变形，
在一般使用中，
都依赖手动操作，在最初的四章中讨论，
对
于警惕
的设计者，他们会毫不犹豫将所有的推理与通过实例选择与相似特性的设计配合起
来。
The sequence of the first
four chapters is in order of evolution of the
valves, but it is 'of interest
to note
that the timescale is somewhat logarithmic. For
example, the earliest valve-the cock was
introduced before the Christian era;
the screw-down valve, circa 1790; the wedge-gate
valve in
1839
and
the
parallel
slide
valve
in
1884.
All
are
basically
stop
valves
arranged
for
manual
operation, and, in more recent times
for operation by some form of motive power.
最初的四章是按阀的发展来安排的，但是我们要注意时间分布稍微有对数的特征，
。例如，
早期的阀，旋塞阀，是在公元前发明的。螺杆阀，大约是在
1790
年，闸阀是在
1839
年，
平行滑阀是在
1884
年。所有
这些堵塞阀都是用手操作的，到了最近它们才通过某些形式的
动力来操作。那些自动工作
的阀，比如安全阀或泄压阀，减压阀，非回流阀，凝气阀和相似
的设备。
另外属于一类，
并且在下面的五章中进行讨论，
这些阀
假如用精确意义上的要求来
表达就是自动机器。
在正确的设计和
安装之后，
每一个阀都很正确的执行相应的功能，
毫不
夸张的说有的是一天到头，有的是一年到头。
Valves which function automatically,
such as safety or relief valves, reducing valves,
non-return
valves, steam traps and
similar devices, are in a class apart and are
dealt with in the remaining
five
chapters.
These valves are
automatons
in
the
strict
sense
of
the
word.
Correctly
designed
and
installed,
each
may
Valves
which
function
automatically,
such
as
safety
or
relief
valves,
reducing valves, non-return valves,
steam traps and similar devices, are in a class
apart and are
dealt with in the
remaining five chapters. These valves are
automatons in the strict sense of the
word.
Correctly
designed
and
installed,
each
may
be
relied
upon
to
perform
its
appointed
function, unostentatiously maybe , day-
in, day-out, likely year-in, year-out.
那些自动工作的阀，比如安全阀或泄压阀，减压阀，非回流阀
，凝气阀和相似的设备。另外
属于一类，
并且在下面的五章中进
行讨论，
这些阀假如用精确意义上的要求来表达就是自动
机器。
在正确的设计和安装之后，
每一个阀都很正确的执行相应的功能
，
毫不夸张的说有的
是一天到头，有的是一年到头。
The
safety
or
relief
valve,
an
essential
adjunct
to
any
piece
of
equipment
which
can
justly
lay
claim to being a
pressure vessel@, is particularly note-worthy by
reason of the essential role it
plays
in the safeguarding of life, limb and property. By
since vessels operating at sub-
atmospheric pressure generally require some means
of automatic
protection
if
they
are
liable
to
collapse
under
the
crushing
effect
ofthe
e
should
a
vacuum
be created inside them from any cause whatsoever.
The other examples, important as
their
respective function might be, 'Would be less
likely to engender such doleful consequences
should they fail in their appointed
functionj but no less care should be lavished on
their design on
this account.
对已认定的压力容器的设备，
安全阀或减压阀是必要的附件。
特别值得注意的，
因为它是我
们生命和财产安全的防护装置。
有压力到绝对压力，
因为容器在大气压力下操作，
如果它们
容易受到大气压力起决定影响的试问情况，
他们需要一些形式上的自动保护，
同时在容器内
部存在真空不管
在任何情况时。
另一个例子，
各自的作用也很重要。
如果它们在工作地点失
效，也不会造成太大的损失。但是由于粗心在设计方
面没有注意会浪费过多的篇幅。
For those
students, engineers, designers and draughtsmen
alike, 'Who are confronted with the
design
or
installation
of
these
devices,
and
who
are
aware
of
their
necessity,
it
is
hoped
this
volume
'Will prove to be a vade mecum.
对于那些面临这
些设备设计和安装的学生，
工程师，
设计者，
< br>起草者来说还有认识他们必要
性的人来说，我们希望通过一篇小记成为一个手册。
With suitable materials of
construction and careful attention to design, a
parallel slide valve is
admirably
suited to the control of steam. at the highest
pressures and temperatures ..
如果有合适的结构材
料，对设计精心考虑，对于高温高压的气体来说平行滑阀是最好的选
择。
这简单并且最有作用的结构形式是一种带有盘片的弹簧装置，圆盘装配体一般
用较小
的的阀。
The
simplest and most effective form of construction
is the one employing 'spring?between-
disk
mechanism. The disk assembly is
adopted in the smaller sizes of valves.
在紧密圆盘的预压缩的螺旋状的弹簧作用下，套管式装配体的两个相对圆盘又分开的趋势。
而对弹簧来说，
为了节省纵向空间，
一般来说将盘制造成矩
形截面，
这个结构将两个圆盘压
缩以适应阀的较小尺寸。大尺寸
阀，两个盘同样压缩并覆盖着一个外接的壳体。
The
two opposed disks in telescopic assembly tend to
be urged apart under the influence of a
close-coiled
precornpressed
helical
spring,
usually
made
of
coils
of
rectangular
section
in
the
interests
of saving space lengthwise, This arrangement of
telescoping the two disks is restricted
to the smaller size of valves. In the
larger sizes the two disks are identical and are
housed in a
ng shell.
在紧密圆盘的
预压缩的螺旋状的弹簧作用下，套管式装配体的两个相对圆盘又分开的趋势。
而对弹簧来
说，
为了节省纵向空间，
一般来说将盘制造成矩形截面，
这个结构将两个圆盘压
缩以适应阀的较小尺寸。大尺寸阀，两个盘同样
压缩并覆盖着一个外接的壳体。
Let it be
understood that the function of the spring is not
to secure two pressure-tight facings as
is so often presumed; a spring of very
much larger proportions would be required for
that, which
is anyway not essential and
secured only at the lower line pressures. Its
function is to prevent
vibration or
'chatter' and under appropriate conditions of line
pressure to sweep clear, during the
transition of the disks, any scale or
other undesirable matter which might tend to
adhere to the
facings and to score
them.
我们应该了解到弹簧的作用并不像我们想象那样用来保护这个压力的贴片的
。
如果需要保护
这个贴片就需要一个很大面积的弹簧。
它不是必须的，
而且只有在较低线性压力下才可以保
护贴片。
它的作用主要是防止振动或颤动。
在适当的线性压
力条件下将阀内壁打扫干净。
在
圆盘运动中，任何尺寸或其他不
需要的情况时，将粘到贴片上并且破坏它。
It
is
inevitable
on
stearn
lines
(or
in
any
other
application
where
appreciable
temperature
variations occur
) for differential expansion to take place due to
.the various materials and varying
sections in the assembly, and this will
give rise to some distortion. With the
spring?between-disk
mechanism this is
taken care of, the disks being free to 'breathe'
as it were, the spring yielding in
sympathy.
在重要管线上，
因为不同区域不同材料的部件的膨胀，
并且将增加变形和扭曲。
对于盘片和
弹簧这种节写结构就要考虑这个。盘片应该能够自由的吸气而且弹簧同时屈服
。
Pressure-tightness
is
secured
on
the
downstream
face
only.
If.
reference
be
directed
to
the
closure mechanism assembly, it will be
seen that the line pressure exerted on the
opposing or
upstream disk forces this
disk off its seating by a very small amount, and
in so doing transmits the
resultant
force
via
the
spring
and,
aided
by
the
line
pressure',
to
the
downstream
disk,
the
working fluid having
access to the inside of the valve casing.
< br>压力密封性只有在下游侧才能获得，
如果将这个闭合机械作为整体考虑时，
就可以发现作用
在相反的或上游的盘片上的线性压力迫使盘片离开阀座
。
将合力通过弹簧来传递，
并在线性
压
力下，传递到下游的盘片，这样工作的六日进入阀的两级。
Simply by sliding the disks into the
low-est possible position the line pressure is
utilized to close
the valve. This is
analogous to the slide valve of a steam engine
with the one difference that in
this
case closure is effected without the aid of a
spring or any other external influence other than
that of the steam pressure acting on
the back of the slide valve.
可以简单的通过滑动的
盘片到最低可能达到的位置，
并利用线性压力来关闭阀，
这与蒸
汽机
的滑动阀有类似之处。
与蒸汽机的差别在于蒸汽机没有弹簧
帮助或任何外部的其他影响只有
作用于滑阀两侧的蒸汽压力。
Size for size and operating under the
same pressure conditions, the parallel slide valve
calls for
less axial force to be
imparted by the stem to secure positive closure
than that of the screw-down
stop valve.
A moment's reflection should reveal 'Why.
如果尺寸相同，并且在相同压力下操作，
平行阀与螺旋阀相比，
所要求的轴向力较小，
而轴向力是由正闭合包围，
只要稍加
考虑就可
以知道原因。
Neglecting
all
secondary
resistances,
the
least
force
to
be
exerted
in
order
to
close
down
a
screw-dow-n valve is represented by the
product of the line pressure and the area of the
seating
orifice. In the parallel slide
valve, the least force is that required to slide
the downstream disk
across
its facing and loaded by a force comprised of the
line pressure acting on the area of the
seating ..
忽略侧面的二次压力，
用来关闭螺旋阀的最小的力就是线性压力与底出口面积的乘积。
对于
平行阀最小的力就是用来将下游盘片滑过贴片的而且也包含作用在底座区域上的线性压
力。
25
Classification of any subject,
technical or nontechnical, serves the purpose of
identifying species,
making it easier
to analyze the problems involved, Accordingly
seals may be classified into two
major
categories, static and dynamic,
任何物件的分类
，
技术的还是非技术的，
目的是确定一些种类，
是更加容易的分析它们所包
含的问题。因此密封可以分为两大类，静态的和动态
的。
Static seals comprise
three major groups
known as
gaskets, sealants, and direct contact seals
静态密封由三个密封物件组成，包括垫片密封，密封胶密封，
和直接接触密封。
Dynamic
seals
can
also
be
subdivided
into
t-wo
basic
groups
designated
as
seals
for
rotating
shafts and seals
for reciprocating shafts. These two groups make up
the bulk of industrial seals by
volume
and
require
specific
consideration
for
predominantly
custom-made
sealing
devices.
Further in this
category trade names must be used to identify the
different devices.
names must be
tolerated, since there is no other system for
designating most specific devices.
动态密封又可以被细分为两个基本的密封，
一种是针对旋转轴密封，<
/p>
另一种是针对往复轴密
封。
在数量上，<
/p>
两种密封占了工业上的绝大多数。
而且对于主要的定做密封的设备
要进行特
殊考虑。在动密封分类时，需要用商标来确定不同分类的设备。这些商标必须使
用，因为没
有任何一种方法更加精确地区分设备。
Rotating shaft seals are given special
and extensive consideration since they are the
dominating
category of major industrial
seals. They comprise two principal groups, the
interfacial seals~~ and
the
interstitial seals?.
因为旋转轴密封在主要工业中有重要地位
，
所以必须给与特别细致的考虑。
被分为两种类型，
界面密封和间隙密封。
The
interfacial seals subdivide into axial seals and
radial. seals. Interfacial seals represent a very
large
family
of
industrial
sealing
devices
that
establish
a
direct
contact
between
the
sealing
component and the
rotating_ shaft.
界面密封别细分为轴密封和径向密封。
截面密封提出了工业密封是一个大家族。
主要是密封
件和旋转轴之间有一个接触。
Interatitial seals categorize a family
of four distinct groups in 'Which the scaling
components have
no
direct
cal
contact
with
the
rotating
shaft.
The
sealing
elements
allow
a
certain
leakage that retards flow by
controlling the clearance gap through which the
fluid flow may pass
using external
forces on the fluid.
间隙密封描绘
了包括四个截然不同的种类的家族。
与旋转轴成比例的部件。
密
封元件允许一
部分泄露来控制外力作用下的流体可以通过的间隙尺寸。
< br>
The function of
interstitial seals is to create a pressure drop of
the fluid to be sealed with the
least
possible flow and simultaneously to permit
unrestricted relative motion between moving
parts. Interstitial seals are capable
of maintaining a pressure differential between the
interior of a
machine
and
its
surrounding
environment
by
distinctly
throttling
the
escaping
fluid ..
Unlike
interfacial seals, no mechanical
contact of moving machine parts is intended. This
reduces friction
to
an
absolute
minimum.
To
throttle
fluid
in
a
controlled
manner,
however,
it
is
necessary
to
allow a nominal flow.
间隙密封的功能是在被密封的流体上产生一个压降，
同时允许在自由的部件运动中存在相对
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