【正文】 ，而吸收和吸附進(jìn)行了在較高的壓力。液位水平控制往往與流量控制。然而，有些情況下，它與正常運(yùn)作的一臺(tái)設(shè)備，如一級(jí)的溶劑中的溶劑萃取塔或液位在溶劑萃取塔或液位的反應(yīng)堆。上面提到的四個(gè)控制參數(shù),大多數(shù)控制應(yīng)用在化學(xué)工業(yè)。但是，控制的變量組成的有關(guān)問題，也經(jīng)常遇到。成分控制根據(jù)物料的性質(zhì)，采用一系列不同的技術(shù)，就可實(shí)現(xiàn)物質(zhì)組成的控制③。大部分的這些技術(shù)是根據(jù)三個(gè)不同類型的分析：成分分析，物理性能分析，或化學(xué)性質(zhì)的分析。大多數(shù)以成分分析為基礎(chǔ)的重要控制回路，都采用色譜分析技術(shù)來確定混個(gè)物的組分④。雖然紅外和其他形式的光譜也可以在某些進(jìn)程?；旌衔锏拇_切成分往往擁有一套獨(dú)特的物理特性。這些屬性實(shí)際上可能的組成部分的產(chǎn)品規(guī)格，或可能被用來作為衡量產(chǎn)品的成分。一些較常見的物理特性是衡量和用于控制目的包括密度，初步和最后沸點(diǎn)，顏色，凝固點(diǎn)和粘度。組成的混合物常常與一套獨(dú)特的化學(xué)性能?；瘜W(xué)特性，往往是監(jiān)測(cè)控制的目的包括pH值，氧化還原電位和電導(dǎo)率。（選：克里斯答：克勞森，原則工業(yè)化學(xué)，John Wiley ＆ Sons出版公司，1978。）第四篇：過程裝備與控制工程專業(yè)英語翻譯4Reading Material4Stresses in Cylindrical Shells due to Internal PressureThe classic equation for determining stress in a thin cylindrical shell subjected to pressure isobtained from of forces perpendicular to plane ABCD gives:PL ．2r =2σqLtorσqq=PrtWhereP=pressure,L=length of cylinder ,σThe strain εε=is defined as_2prr2prr=hoop stress ,r=radius, t=thicknessq2p(r+W)2prrr=qorεq=WrAlsoεdWdrThe radial deflection of a cylindrical shell subjected to internal pressure is obtained by substituting the quantity into Eq.().Hence for thin cylindersW=PrEt2Where W= radial deflection, E= modulus of elasticityEquations()and()give accurate results when r rt decreases,however , a more accurate expression is needed because the stress distribution through the thickness is not is then made to the “thick shell” theory first developed by derived equations are based on the forces and stresses shown in theory assumes that all shearing stresses are zero due to symmetry and a plane that is normal to the longitudinal axes before pressure is applied remains plane other words ,?1 is constant at any cross sectionA relationship between σrand σqcan be obtained by taking a freebody diagram ofring dr as shown in forces in the vertical direction and neglecting higherorde terms ,we then haveσ—σr=dσdrrqA second relationship is written asσ σr=q=E（1+μ）（12μ）E[εq(1μ)+μ（εr+ε）]σ1=（1+μ）（12μ）E[εr(1μ)+μ（ε(1μ)+μ（εq+ε+ε）]）]（1+μ）（12μ）[ε1qrSubstituting Eqs.()and()into the first two expressions ofEq.()and substituting the result into Eq.()results in:dwdr+1dwrdr—wr=0A solution of this equation isW=Ar+BrWhere A and B are constants of integration and are determined by first substituting Eq.()into the first one ofEq.()and applying the boundary conditionsσr= —piatr=riatσr= —poatr=roExpression()then bees: w= — μrε1+1Er(rOri)［r2(1μ2μ)（PiriPOrO）+rirO(1+μ)（PiPO）］2222Once w is obtained, the values of σand expressed for thick cylinders asPiriPOri+(PiPO)（rOriqare determined from Eqs.(),and ,(),and()rirOσq=r)σr= —POriPiri+(PiPO)（rOririrOr)whpressureσr=radial stressσq=hoop stressPi=internal pressurePO=externalri=inside radiusrO=outside radiusr=radius at any pointThe longitudinal stress in a thick cylinder is obtained by substituting Eqs.(),(),and()into the last expression of Eqs.()to giveσ1=Eε+2μ(PiriPOrO）r2OriThis equation indicates that σ1 is constant throughout a cross section because εis constantand r does not appear in the second the expressionσ1 can be obtained from statics Asσ1=PiriPOrOr2OriWith σ1 known, Eq.()for the deflection of a cylinder can be expressed asw=r(PiriPOrO)(12μ)+(PiPO)rirO(1+μ)Er(rOri)閱讀材料4圓柱殼體的應(yīng)力源于內(nèi)部壓力。累積力通過正交于平面ABCD給出：PL ．2r =2σqLtorσqq=Prt說明： P=壓力，L=圓柱體的長度，σ正應(yīng)變?chǔ)纽?由下面式子決定：_2prr=環(huán)繞切應(yīng)力，r=半徑，t=殼體的壁厚q2p(r+W)2prrrq并且：ε=2prrdWdrorεq=Wr圓柱狀殼體的半徑偏差源于內(nèi)部壓力。因此，對(duì)薄殼體有：W=PrEt說明：W=半徑的偏差值，E=彈性橫量當(dāng)rt0時(shí)，方程式（）和（）給出精確的結(jié)果。隨著r的減少，然而，一個(gè)更精確的表述是非常必要的，因?yàn)楹穸鹊膲毫Ψ峙洳⒉皇蔷獾?。接著要求助于Lame首先提出來的“厚殼”理論。該理論假定所有的剪切力都為0是由于對(duì)稱性和一個(gè)正?？v軸的平面，在施壓前仍然是平面壓力。換句話說，?1 是恒在任意橫截面上。σr和σq的關(guān)系可以通過一個(gè)環(huán)dr的自由體示意圖獲得。綜合垂直dσdr方向上的力和不計(jì)高階的項(xiàng)，于是我們得到σEq—σr=r第二種關(guān)系可以表達(dá)為：σq=（1+μ）（12μ）[εq(1μ)+μ（εr+ε）]σr=Eσ1=（1+μ）（12μ）E[εr(1μ)+μ（ε(1μ)+μ（εq+ε+ε）]）]（1+μ）（12μ）[ε1qr.()與及把結(jié)果代入Eq.()得：dwdr+1dwrdr—wr=0Br方程的一個(gè)值為W=Ar+r=riatσ：w= — μrε1+= —pir= —poatr=roOEr(rri)r2(1μ2μ（）PiriPOrO）+rirO(1+2222μ)（PiPO）］ 當(dāng)W被求得，σ、圓柱的厚度可以表達(dá)為：rirOσq=PiriPOri+(PiPO)（rOr)riσr= —POriPiri+(PiPO)（r2OrirOr)riσr=徑向應(yīng)力σq=環(huán)向應(yīng)力Pi=內(nèi)部壓力PO=外部壓力ri=內(nèi)半徑rO=外半徑r=任意點(diǎn)的半徑、。其為： σ1=Eε+2μ(PiriPOrO）r2O2ri這個(gè)表達(dá)式說明了σ1是一個(gè)橫截面的常數(shù)因?yàn)棣诺谋磉_(dá)式可以由靜態(tài)值表示:σ1=PiriPOrOr2O2是常數(shù)和r不會(huì)在第二項(xiàng)出現(xiàn)。因此σri,隨著σ1知道了，表示為：w=r(PiriPOrO)(12μ)+(PiPO)rirO(1+μ)Er(rri)2O22222第五篇：過程裝備與控制工程專業(yè)英語翻譯 17Reading Material 17Stress CategoriesThe various possible modes of failure which confront the pressure vessel designer are:(1)Excessive elastic deformation including elastic instability.(2)Excessive plastic deformation.(3)Brittle fracture.(4)Stress rupture/creep deformation(inelastic).(5)Plastic instabilityincremental collapse.(6)High strainlow cycle fatigue.(7)Stress corrosion.(8)Corrosion dealing with these various modes of failure, we assume that the designer has at his disposal a picture of the state of stress within the part in would be obtained either through calculation or measurements of the both mechanical and thermal stresses which could occur throughout the entire vessel during transient and steady state question one must ask is what do these numbers mean in relation to the adequacy of the design? Will they insure safe and satisfactory performance of a ponent? It is against these various failure modes that the pressure vessel designer must pare and interpret stress example, elastic deformation and elastic instability(buckling)cannot be controlled by imposing upper limits to the calculated stress must consider, in addition, the geometry and stiffness of a ponent as well as properties of the plastic deformation mode of failure can, on the other hand, be controlled by imposing limits on calculated stresses, but unlike the fatigue and stress corrosion modes of failur