機械外文翻譯--被困-容積泵的設(shè)計

1、<p>　　畢業(yè)設(shè)計(論文)外文資料翻譯</p><p>　　系　　部： 機械工程系 </p><p>　　專 業(yè)： 機械工程及自動化 </p><p>　　姓 名： </p><p>　　學 號：

2、 </p><p>　　外文出處： Bull.JSME 9,No.34,305–313 </p><p>　　附 件： 1.外文資料翻譯譯文；2.外文原文。</p><p>　　附件1：外文資料翻譯譯文</p><p><b>　　被困-容積泵的設(shè)計</b><

3、/p><p>　　被困-容積泵的設(shè)計在以往的文獻資料中并不多見。關(guān)于這個問題已經(jīng)發(fā)表的兩份重要文獻中的一份是lin.al.1的成果。在這項成果中，因為涉及到作用在旋轉(zhuǎn)斜盤上的控制扭矩，作者考慮了柱塞泵油液密封的影響。這項工作只是在數(shù)值上做了些研究，并沒有在為利用被困容積使得柱塞泵的容積效率得到提高而積極的去指出其中的優(yōu)勢。在此之前，山口就考慮過被困容積設(shè)計對泵的操作效率的影響。他在分析后得到這樣的結(jié)論，被困容積設(shè)計比

4、標準設(shè)計更有效。他的結(jié)論基于柱塞泵中的單獨一個柱塞的P—V圖表。雖然山口的工作是很有價值的，但是他沒有把被困容積效應像標準泵設(shè)計和被困容積泵設(shè)計的對比那樣做出一個封閉的形式。他的成果也沒有恰當?shù)慕忉尡焕^(qū)域是如何在給定的泵的工況下而設(shè)計的。本文的研究試圖在更多細節(jié)上，尤其是封閉形式帶來的結(jié)果上解釋被困容積柱塞泵設(shè)計的效率。此外，為了證實本文一般性的結(jié)論，這里對標準泵設(shè)計和被困泵設(shè)計的相對應的方面做了一對一的比較。被困體積柱塞泵的設(shè)計中不

5、用為了在最底部和最頂部得到平穩(wěn)的壓力轉(zhuǎn)變而開設(shè)插槽，所以流體中的能量不會以某種耗費能量的方式被儲存和釋放掉。在被困體積的情況下，在最底線部位能量由于柱塞腔體積</p><p>　　封閉區(qū)域的角度尺寸用表示。在這種設(shè)計中，壓力的轉(zhuǎn)變并不是靠配流盤上的卸荷槽來實現(xiàn)的，而是單獨靠受控體積在柱塞腔內(nèi)的體積膨脹來完成的。當穿過封閉區(qū)時，柱塞腔立刻與吸油區(qū)聯(lián)通，流體從泵的吸油區(qū)流入柱塞腔。當柱塞腔靠近最底線時，也會有同樣的狀

6、況。在此區(qū)域內(nèi)柱塞從吸油區(qū)移動到排油區(qū)，其封閉的角度尺寸用.表示。在這個位置，壓力的轉(zhuǎn)變由柱塞腔內(nèi)受控體積的壓縮來完成。圖1也在事實上考慮了柱塞泵中單一個柱塞腔的四個不同的區(qū)域的壓力和流動分析。</p><p>　　在這項研究中，因涉及到流體壓縮損失而檢驗軸向柱塞泵的容積效率。特別是，通過兩種配流盤幾何形狀的對比來說明不同配流盤的選擇對柱塞泵的容積效率產(chǎn)生的區(qū)別。這項報告把帶有插槽的標準配流盤形式和同時去除兩個插

7、槽的被困容積式對比。研究分析結(jié)果顯示，標準配流盤設(shè)計因為有不受控制地膨脹和壓縮的流體發(fā)生經(jīng)過插槽本身而產(chǎn)生一種容積損失。通過去除這些插槽同時采用被困容積式，真正起到改善柱塞泵的容積效率的結(jié)果。雖然目的并不在于研究適合所有柱塞泵的理想配流盤設(shè)計，但是該報告的確在被困容積的應用方面提供了理論依據(jù)，并且也對解決配流盤的整體設(shè)計中的問題進行了進一步的探索。</p><p>　　因為以前的結(jié)果都是隨時間變化的，為了出個方法

8、解決這個問題，我們必須為每次壓力轉(zhuǎn)變的操作而設(shè)計一種新的配流盤的設(shè)計理念。顯示了隨著壓力操縱的改變，柱塞泵配流盤的設(shè)計也跟著改變，同時附表給出了基本柱塞泵參數(shù)的變化。讀者也許會記得，這些插槽分擔了部分流體容積的流動，用來協(xié)調(diào)在最底部和最頂部壓力躍遷的變化的。在最底線那里，當柱塞進入排油口時，流體經(jīng)過配流盤上的插槽進入柱塞腔內(nèi)直到柱塞腔內(nèi)的壓力等于柱塞泵排油區(qū)的壓力。為了使得這些壓力相等，柱塞腔內(nèi)的流體受到了壓縮，結(jié)果，一部分能量加到了柱

9、塞腔的體積上。在最頂部，配流盤上的插槽是用來緩解在最底部被壓縮的流體體積的。這種流體的緩解或者說是流體的膨脹導致通過插槽的流體流動釋放了儲存在流體中的能量。</p><p><b>　　柱塞運動學</b></p><p>　　第n個柱塞在泵中運動的三維空間軌跡可以用幾何學來確定。看圖1第n個柱塞在x周方向的運動可以表示為：</p><p>&l

10、t;b>　　（1）</b></p><p>　　這里r是柱塞的間距半徑，i是旋轉(zhuǎn)斜盤的傾斜角，是第n個柱塞腔對泵中心軸線的角位移。</p><p><b>　　柱塞壓力和流量</b></p><p>　　顯示了一個柱塞在柱塞孔中運轉(zhuǎn)，這里的流體體積就是我們研究的受控體積。柱塞外部壓力Pb沒有注明，但是必須隨時間改變來模擬該壓力

11、從流出壓力Pd到吸入壓力Pi的往復變化。排油區(qū)的柱塞孔也隨時間改變來模擬配流盤過渡區(qū)域，那里的插槽提供了很多可變的開口。有標準壓力梯度方程決定的第n個柱塞腔的流體壓力可以表示為：</p><p><b>　?。?）</b></p><p>　　這里Qn是存在于柱塞腔的容積流速，Vn是柱塞腔自身的瞬時體積以及流體體積模數(shù)。如果假設(shè)流入流出柱塞孔的流體速率很高，也就是說雷

12、諾數(shù)大，流動速率Qn可用基于伯努利方程的經(jīng)典小孔流動方程來模擬。方程可寫成：</p><p><b>　?。?）</b></p><p>　　這里的“符號”取決于正負號的討論，Cd是孔的流動系數(shù)，Pb是控制體外部壓力Pi or Pd兩者之一。第n個柱塞孔的瞬時體積可用（1）式的運動學結(jié)論確定。單個柱塞的面積Ap，柱塞的名義體積Vo，可有以下參數(shù)表達式“</p&g

13、t;<p><b>　　（4）</b></p><p>　　定義了dt(1/)d n，用此定義結(jié)合（2）（3）（4）式，單個柱塞腔內(nèi)的壓力梯度可表示為：</p><p><b>　?。?）</b></p><p>　　方程（5）是個沒有任何分析結(jié)論的非線性微分方程。在以下的章節(jié)中我們將用（3）（5）結(jié)合無限接

14、近的微分方法來得到壓力Pn。</p><p><b>　　標準柱塞泵設(shè)計。</b></p><p>　　從單個柱塞腔引出來的腎臟形狀的流道配合著配流盤上的弓形門狀幾何體。當流道旋轉(zhuǎn)到最高線時，就被在配流盤這一區(qū)域上的門狀幾何體所逐漸截斷。當柱塞腔正好位于頂死點時，柱塞腔是關(guān)閉的沒有流體的流進和流出。當柱塞腔向配流盤吸油槽移動時，配流盤上有一很小的卸荷槽聯(lián)通柱塞腔和吸油

15、槽，從而完成了泵從高壓到低壓的平穩(wěn)的過渡。最底線有同樣的結(jié)構(gòu)，在此區(qū)域柱塞腔漸離開吸油區(qū)而移向排油區(qū)。設(shè)計中，頂死點處的卸荷槽使得吸油區(qū)流動平穩(wěn)，卸荷槽的長度用角度表示；同理，最低點的卸荷槽使得排油區(qū)的流動平穩(wěn)，卸荷槽的長度用角度表示。</p><p>　　事實上考慮了柱塞泵中單一個柱塞腔的四個不同的區(qū)域的壓力和流動分析。在區(qū)域1和3中壓力近似等于Pd 或Pi的一個常數(shù)，容積流動速率可由柱塞腔自身的容積時間的變化

16、率得到。在區(qū)域2和4由于隨著角位置而變化，在區(qū)域中必須做近似的壓力和流動的特性分析。當柱塞接近=2時，普通泵設(shè)計的柱塞腔的容積時間變化率近似等于零。這就意味著此區(qū)域內(nèi)壓力梯度方程可近似看成：</p><p><b>　?。?）</b></p><p>　　這里的Vt 是柱塞在=2位置時流體的體積，用方程（3）的一般形式，流出柱塞腔的流動可表示為：</p>

17、<p><b>　?。?）</b></p><p>　　這里的提醒我們注意在此配流盤設(shè)計中排油面積At是個常數(shù)。</p><p>　　圖1是修飾后的配流盤的圖解，它省去了最頂點和最底點的卸荷槽。</p><p>　　把方程（7）代入（6）加上dt(1/)d n，下面的可積分方程在恰當?shù)姆e分域內(nèi)可寫為：</p><

18、p><b>　?。?）</b></p><p>　　這里。方程（8）對第n個柱塞腔穿過卸荷槽接近頂死點時的壓力的解在區(qū)域2中為：</p><p><b>　?。?）</b></p><p>　　把此解代入方程（7）得到關(guān)于柱塞腔流出流體的解：</p><p><b>　?。?0）&l

19、t;/b></p><p>　　注意：此結(jié)果僅僅證實接近頂死點、柱塞腔于配流盤卸荷槽相聯(lián)通這一情況。為了保證卸荷槽足夠，特別要注意到當時柱塞腔的壓力應該等于吸油區(qū)的壓力Pi。這就是說配流盤卸荷槽有效地促成了從排油壓力Pd到吸油壓力Pi的轉(zhuǎn)變。假定Pn=Pi n=，解出方程（9）就可以得到滿足促成有效壓力轉(zhuǎn)變的卸荷槽的長度。其結(jié)果可以表示為：</p><p><b>　?。?

20、1）</b></p><p>　　讀者應當注意配流盤僅是使泵在某一個工況下有最好的工作效率。同理也可成功分析區(qū)域4中從吸油區(qū)壓力Pi到排油區(qū)壓力Pd的轉(zhuǎn)變。在此區(qū)域中柱塞腔內(nèi)的壓力可以表示為：</p><p><b>　?。?2）</b></p><p>　　這里。最底部卸荷槽的面積Ab是個常數(shù)，同時Vb是時柱塞腔內(nèi)的流體體積。作為

21、此次分析的一部分，流出柱塞腔的流體的流動可以表示為：</p><p><b>　　（13）</b></p><p>　　可以得到最底部卸荷槽的長度的表達式：</p><p><b>　?。?4）</b></p><p>　　總結(jié)本章節(jié)所有的近似壓力結(jié)果，以下方程確定了第n個柱塞腔內(nèi)的瞬時壓力：（15

22、）</p><p>　　總結(jié)本章節(jié)所有的近似流動結(jié)果，以下方程確定了第n個柱塞腔流出流體的瞬時流動方程：</p><p><b>　?。?6）</b></p><p><b>　　附件2：外文原文</b></p><p>　　Trapped-Volume Pump Designs</p>

23、<p>　　Trapped-volume pump designs have not been considered extensively in the literature. One of two significant papers that have been published on this topic is the work done by Lin et al.In this work, the author

24、s consider the effect of oil entrapment in axial piston pumps as it related to the control torque acting on the swash plate. This research was numerical in nature and did not positively identify any advantages of using t

25、rapped-volume designs for improved efficiency. Prior to this work, Yamagu</p><p>　　The research presented in this paper attempts to address the efficiency of the trapped-volume pump design in more detail wit

26、h a greater emphasis on closed-form results. Furthermore, a side-byside comparison of the standard pump design is made with respect to the trapped-volume design for the purposes of proving the general conclusions of the

27、paper.</p><p>　　The angular distance of this closed porting is given by the dimension, z t . With this design, the pressure transition is accomplished, not by valve-plate slotting,but by the controlled volum

28、etric expansion of the piston chamber alone. Once the piston chamber crosses the closed-porting zone, it quickly opens up to the intake port and begins to receive fluid from the intake side of the pump. A similar set of

29、conditions exists when the piston chamber is near bottom dead center when u n53p/2. In th</p><p><b>　　（1）</b></p><p>　　where, r is the piston pitch radius, a is the swash-plate angle

30、, and u n is the angular position of the nth piston chamber about the centerline of the pump shaft. Piston Pressure and Flow General. Figure 2 shows a piston as it operates within its bore where the volume of fluid withi

31、n the bore is taken as the control volume of study. The pressure outside the piston bore, Pb , is not shown but must vary with time to simulate the fact that as the cylinder block rotates about the x-axis, this pressu<

32、;/p><p><b>　?。?）</b></p><p>　　where Qn is the volumetric flow rate of fluid exiting the piston chamber, Vn is the instantaneous volume of the piston chamber itself, and b is the fluid b

33、ulk-modulus. If it is assumed that the flow in and out of the piston bore occurs at a high velocity and thus a high Reynolds-number!, the flow rate Qn may be modeled using the classical orifice equation which is based up

34、on Bernoulli principles. This equation may be adapted to the current situation shown in Fig. 2 and written as</p><p><b>　?。?）</b></p><p>　　Journal of Dynamic Systems, Measurement, an

35、d Control </p><p>　　where the ‘‘sign’’ function takes on the value 61 depending upon the sign of its argument, Cd is the orifice discharge-coefficient, and Pb is the boundary pressure outside the control vol

36、ume ~either Pi or Pd!. The instantaneous volume of the nth piston-bore may be determined using the kinematic results of Eq. ~1!, the area on the face of a single piston, Ap , and the nominal piston volume, Vo . This quan

37、tity is expressed</p><p><b>　?。?）</b></p><p>　　By definition, dt5(1/v)du n . Using this definition with Eqs. ~2!, ~3!, and ~4!, the pressure rise-rate within a single piston chamber

38、may be rewritten as</p><p><b>　?。?）</b></p><p>　　Equation ~5! is a nonlinear, first order, differential equation that does not have an analytical solution. In the following sections,

39、 Eqs. ~3! and ~5! will be investigated using closed-form approximations for the pressure, Pn .</p><p>　　Standard Pump Design.</p><p>　　Shows a schematic of a standard valve-plate design that is

40、typically used within pumps. In this figure, a kidney-shaped flow passage from a single piston chamber is shown to match the arcuate porting geometry of the valve plate. As this flow passage moves toward top-dead-center

41、~i.e., toward u n5p/2! the actual flow passage is gradually cut off due to the terminating port-geometry of the valve plate in this region. When the piston chamber is located exactly at top-deadcenter, the piston chamber

42、 </p><p>　　The valve plate shown in Fig. 4 provides, essentially, four different regions to be considered in the pressure and flow analysis for a single piston-chamber within the pump. These regions may be c

43、haracterized by Table 1. Table 1 Standard value slate regions Region Angular Position Pressure Conditions Flow Conditions The pressure within the piston chamber is at discharge pressure. The discharge flow is equal to th

44、e displacement of the piston. The pressure within the piston chamber is between disc</p><p>　　When the piston is located near u n5p/2, it can be shown for the standard pump design that the volumetric time ra

45、te-of-change for the piston chamber is near zero. This means that the governing pressure-rise-rate equation in this region can be approximated by</p><p><b>　?。?）</b></p><p>　　where V

46、t is the fluid volume in the piston chamber when u n 5p/2. Using the general form of Eq. ~3!, the flow out of the piston chamber may be modeled as</p><p><b>　?。?）</b></p><p>　　where

47、. Recall that the discharge area, At , is a constant for this valve-plate design. Substituting Eq. ~7! into Eq.</p><p>　　~6!, and recognizing that dt5(1/v)du n , the following separable differential-equation

48、 with the appropriate bounds of integration may be written:</p><p><b>　　（8）</b></p><p>　　where. Solving Eq. ~8! yields the following result for the pressure within the nth piston cha

49、mber as it moves across the valve-plate slot near top-dead-center within Region 2:</p><p><b>　?。?）</b></p><p>　　Substituting this result back into Eq. ~7! yields the following result

50、 for the discharge flow out of the piston chamber:</p><p><b>　　（10）</b></p><p>　　Note: these results are only valid near top-dead-center when the piston chamber is connected to the v

51、alve-plate slot. To insure that the valve-plate slot is designed sufficiently, it is important to note that when u n5p/21j t , the pressure within the piston chamber should equal the intake pressure, Pi . This means that

52、 the valveplate slot has effectively facilitated a full pressure transition from the discharge pressure, Pd , to the intake pressure Pi . By setting Pn equal to Pi and u n equal t</p><p><b>　　（11）</

53、b></p><p>　　The reader should note that this valve plate is optimized for only one operating condition of the pump. Similar analysis can be done for Region 4 where the pressure transition being achieved i

54、s between the intake pressure, Pi , and the discharge pressure, Pd . In this region, the pressure within the nth piston chamber is given by</p><p><b>　?。?2）</b></p><p>　　where K1b 5A

55、bCdA2/r and K2b 5b/Vbv. Note: in these expressions, the bottom-dead-center slot area, Ab , is a constant and Vb is the fluid volume in the piston chamber when u n53p/2. As a part of this analysis, it can be shown that th

56、e flow out of the piston chamber may be written as</p><p><b>　?。?3）</b></p><p>　　and that the appropriate slot length at bottom-dead-center is given by</p><p><b>　

57、　（14）</b></p><p>　　To summarize the approximate pressure results of this section, the following piecewise equation is presented for the instantaneous pressure within the nth piston chamber:</p>

58、<p><b>　?。?5）</b></p><p>　　The approximate volumetric flow results of this section may be summarized using the following piecewise equation for the instantaneous discharge-flow from the nth