外文翻譯-內(nèi)燃機冷卻風(fēng)扇設(shè)計的新方法(共12頁)

1、精選優(yōu)質(zhì)文檔-傾情為你奉上New Design Method For Engine Cooling FanHuang Hongbin zheng Shiqin Liu Shuyan Yan Weige(School of Vehicular Engineering, Beijing Institute if Technology, Beijing )Abstract Aim To put forward a type of math model for optimizing fans twisting law.Methods This math model was based on turbo

2、-machinery euler equations and calculus of variation, it was conducted for optimizing the aerodynamic parameters along the blade height of the fan and the math method was produced for the optimization of fans twisting law. Results the type 6102Q engine cooling fan was optimized by use of this model,

3、and the calculation data were contrasted with those of iso-reaction coefficiency flow type and free vortex flow type. Some problems existing in long blade can be solved by use of above method.Conclusion The design paramters neednt be determined artificially, so calculating results are more rational

4、to a high degree than that from other methods.Key words: cooling fan, twisting law, optimum designThe design of fan has been a hard work on the orientation of aerodynamics because of the omplicated flow through the blades, so the fan had been designed by use of kaufman theory. This law believes that

5、 the flow through the fan blades is of one-dimension , the airflow parameters at the mean blade diameter are taken into account, but the flow through the root and tip is negative. After that, fan was projected according to the simply radial balance equation. Numerical precision was enhanced by use o

6、f completely radial equilibrium equation and iso-reaction factor of twisting law to determine the air-flow parameters along the blade radial direction, so the flow losses of tip and root are lessen to certain extent.In this paper ,the authors put forward a math model for optimizing airflow parameter

7、 along blade height by use of euler equations and calculus of variation.1MATH MODELWhile the minute matter G flows around the blade which is formed by two neighboring flow surfaces,according to Euler equation,fans power isP= (v2ur2- v1ur1) G (1)Where is the angular velocity of the fan , v1u is the c

8、ircumferential speed at the fan inlet , v2u is the circumferential speed at fan outlet , r1 is the fan inlet radius, r2 is the fan outlet radius, For the case of non-guide blade, Eq.(1) becomesP=v2ur2G (2)We set up the relations between r1and r2 by use of the flow function based on continuity of flo

9、w. The flow function is constant along the flow surface , and the thoroughfare surface of flow passage region is considered as flow surface. Thus, we have the definition of the flow surfaceG= 2 (3)Substitute Eq.(3) into Eq.(2), and integral Eq.(2),thenP= 2v2ur2d (4)Where P is the effective power of

10、the fan,is the flow function of the blade-tipThe theoretical power P1 is = 2(v/2)d1 (5)Where vp is the theoretical speed corresponding to P1Form Eqs.(4) (5),the fan efficiency is, (6)Where r01 and r02 are internal and out radii respectively at the fans inlet stretching region, q(r0) is flow of strea

11、ms per inlet blade height, G is the flow of matter On the basis of Euler equations, the fans power Ph is (7)Substitute this equation into the first law of thermodynamics (8)Where v1 is the absolute speed of the fan inlet, v2 is the absolute speed of the fan outlet,H1 is the inlet enthalpy of the fan

12、,H2 is the circumferential speed of the fan outlet.According to the speed triangle of cascade , substituting the relations between speeds, we can obtain the energy equation of relative motion while static entropyKeeps constant (9)From above equations, actual outlet speed of heat insulation that fric

13、tion existsIs obtained (10) Where is relative speed of fan outlet as communal entropy course, and are relative speeds of the fan inlet and outlet respectively, is the circumferential speed of the fan inlet, is the static enthalpy of the fan outlet as communal entropy course, is the outlet speed para

14、meter of the fan, According to the triangle of speed in the three-dimension space, we have (11) Huang Hongbin et al./ New Design Merhod for Engine Cooling FanSubstituting Eq.(11) into Eq.(6) yields (12) For the fan of non-guide blade,v1f =v1r , v1r=0According to flow continuity qdr0 = ( (13)qdr0 =(

15、(14)where , / is the inlet speed factor , is the outlet speed factor , is inlet flow matter factors, is outlet flow matter factors, is inlet streamline radius, is outlet streamline radius.Eq.(12) belongs to the extreme value problem with qualifications, it can be solved by use of Lagrangian multipli

16、er, the Lagrangian function is (15)Where and are lagrangian multipliersAccording to the relation of aerodynamics, the relationship of densities between inlet and outlet are (16)Thus (17)Where is inlet sound speed, is outlet sound speed.For the extreme value problem of Eq.(12),we make use of the Eule

17、r-lagrangian equations (18) , (19) (20)Where (21)From Eq.(18) we have = 0,Integrating Eq.(8) and Eq.(19)= (22) Substituting Eq.(13) into Eq.(21) (23)Substituting Eq.(14) into Eq.(22),we get+ (24)So we obtain the extreme equations corresponding to the efficiency,i.eEqs.(13)(14)(16)(17)(20)(23)-(26).T

18、o sum up, we can obtain a conclusion that the streamline dip of the fan outlet section ought to keep zero,it is calculated by use of radial balance equation.2 OPTIMUM DESIGN2.1 Variables, Objective Function and RestraintsThe reaction parameters along radial direction were taken for design variables,

19、 so objective function is (j), (25)Where （j）is reaction parameters, j is the number of streamlines along radial direction of blade .The equation about determined by Eq.(12).Some restraints should be taken into account from designing and experimental courses of fan: That the reaction parameters must

20、keep positive along the radial direction (i.e, >0) would protect separated flow at the root, and the reaction parameters must also be larger than 0.50 for relative speed to keep slow at the root. At the tip, these parameters must be smaller than 0.75,for the sake of little leakage. The geometry e

21、xpanding degree of the fan passageway along the radial direction must keep larger than 1.0,that is sin/sin>1, where andare respectively the flow angles of fan inlet and outlet. Relative inlet and outlet maches must be restrained because they influence fan sound i.e M<0.3 and M<0.3. Axial pa

22、rt of absolute fan outlet speed must be positive along radial direction, otherwise the separated flow would appear.2.2Example and Renew the Old ConstructionThe type 6102Q engine cooling fan was selected to be optimized. Some parameters, such as profile, inlet and outlet radii, blade width, and the n

23、umber of blades are the same as those of original fan. Old fan belong to free-vortex type, its blade is very long and relative speed of blade-tip is large, so its reaction parameter at tip is large and appear negative at root. these majority problems can be solved through amending the flow type. opt

24、imum calculating was based on ratedly operated mode(engine angular mtation n=3000 r/min, drive ratio between fan and crankshaft1.18).under this condition the airflow is 2.5 m/s, directionless pressure of fan is 1500Pa.Results are shown in Figs.14（the dotted lines）,the data about flow type =0.6(soild

25、 lines) and free vortex (long dotted lines) are also in theseFigures. r/ Fig.1 Distribution of pressure factor Fig.2 Distribution of counteraction along Radial direction radial derectionPressure amplification factors change gently along radial direction after twisting parameters are optimized, so th

26、e energy loss is smallest among these three types,and extending degree is larger than that of isoreaction ,so the work from this formation is greatest than that from the latter with the same wasted work(Fig.1).Reaction factors of the three type are shown in Fig.2,on this figure,we can find that the

27、reaction grows gradually from root to tip, and this parameter at root is larger than 0.5,so the amplification factors along radial direction difficulties of over small reaction at root that emerged from free-vortex type are surmounted . In Fig.3,the relative inlet speed after optimization is lowest

28、among these three flow types, so the noise level is the lowest, and flow losses are the smallest, the fans efficiency is the highest because the relative speed at tip is low .Because the axial velocity along the blade height of isoreaction flow type drops gradually, the flow outlet angular drops qui

29、cker than the inlet angular , this causes disadvantageous effect for flow pressure extension because (=-) of tip probably keeps very small for the long blade .Optimization for twisting parameters can remedy this defect. In this flow type , changes slowly along the blade height (Fig.4).According to a

30、bove calculating results , we redesigned this fan. Fig.5 contrasts the new results about static pressure efficiency with the old ones ,and real lines indicate the results of the new fan and the dish-lines expresses the results of the old fan. Fig.3 Distribution of relative speed Fig. 4 Distribution

31、of relative flow angle Along radial direction angle along radial direction Q/() Fig. 5 Experimental curves of fans effciency 3 CONCLUSIONThat type 6102Q engine cooling fan was redesigned indicates that the optimum designing method in this paper can solve some key problems existing in long blade and

32、free-vortex flow types. Sme advantages of this method were not provided by iso-reaction and free- vortex flow types. for examples, the small twisting degree, the larger difference between exit and inlet flow angle, the little flow loss of passageway of fan, the strong capacity of work ,small relativ

33、e speed at tip, the large extending degree at root, and so on .Design parameters neednt be determined artificially by use of this method ,and calculating results are more rational to a high degree than other methods. I this twisting majorization was combined with airfoil optimization, the fans perfo

34、rmance would be improved further, and the radial direction flow would be controlled effectively .內(nèi)燃機冷卻風(fēng)扇設(shè)計的新方法黃虹賓  鄭世琴  劉淑艷  閻為革（北京理工大學(xué)車輛工程學(xué)院,北京 10081）摘 要 目的  提出內(nèi)燃機冷卻風(fēng)扇優(yōu)化設(shè)計的數(shù)學(xué)模型。方法  利用歐拉方程和微積分原理，推導(dǎo)出內(nèi)燃機冷卻風(fēng)扇沿徑向氣流參數(shù)優(yōu)化設(shè)計的數(shù)學(xué)模型，建立了風(fēng)扇葉片扭曲規(guī)律優(yōu)化設(shè)計的數(shù)學(xué)方法。結(jié)果 應(yīng)用該方法對6102Q汽油機冷卻風(fēng)扇進

35、行了優(yōu)化設(shè)計，將計算結(jié)果與等反擊系數(shù)流型和自由渦流型的計算結(jié)果做了比較，并利用優(yōu)化結(jié)果對該風(fēng)扇作了重新設(shè)計，解決了長葉片風(fēng)扇設(shè)計中的一些問題。結(jié)論 不需人為給定設(shè)計參數(shù)，計算結(jié)果更為合理。關(guān)鍵詞 冷卻風(fēng)扇  扭曲規(guī)律  優(yōu)化設(shè)計 設(shè)計的關(guān)鍵在于對空氣經(jīng)過復(fù)雜的葉片以后的流動方向的判斷。所以風(fēng)扇設(shè)計采用考夫曼理論，運用考夫曼理論設(shè)計風(fēng)扇時認為氣流經(jīng)過葉片時參數(shù)在一維空間內(nèi)與頁面直徑正比但是在通過葉面根部是對其產(chǎn)生負作用。之后,風(fēng)機是根據(jù)簡單的直線平衡方程。提高了計算精度完全利用徑向平衡方程和等反擊系數(shù)法確定的參數(shù)，葉片沿著徑向的風(fēng)流損失也一定程度的降低。本文提出了一

36、種數(shù)學(xué)模型,為優(yōu)化的氣流計,沿著葉片高度利用歐拉方程和微積分的變異方程。1 數(shù)學(xué)模型當(dāng)微小物質(zhì)G經(jīng)過風(fēng)扇的兩個相鄰表面時根據(jù)歐拉方程就會求出對其產(chǎn)生的力， P= (v2ur2- v1ur1) G, (1)假設(shè)角速度的風(fēng)扇,是圓周速度,是風(fēng)機進口的圓周速度,r1風(fēng)機進口半徑、r2是風(fēng)機出口的半徑,對這些無導(dǎo)向葉片則根據(jù)下面的公式計算，P=v2ur2G (2) 我們建立r1和 r2連續(xù)的流函數(shù)的方程，在沿葉片表面方向函數(shù)是恒定流。通道表面的區(qū)域被視為流道流動的表面。因此,G= 2, (3) 把公式（3）代入到公式（2）然后得到，P= 2v2ur2d (4)假設(shè)P是作用在風(fēng)扇有效面積上的總功率，那么

37、P1就是有效功率得， = 2(v/2)d1 (5) 如果Vp是當(dāng)功率為P1是風(fēng)扇的理論轉(zhuǎn)速，那么根據(jù)（4）（5）就可以得到風(fēng)扇的有效機械效率， , (6) R01和R02分別是風(fēng)扇進口處內(nèi)外的半徑，R0則是風(fēng)扇與壁面之間的間隙，在利用歐拉方程就可求出風(fēng)機的功， (7)在把這個方程代入熱力學(xué)第二定律有， (8)令，V1是風(fēng)機進口的絕對速度的、v2是風(fēng)機出口的絕對速度,H1與H2分別是風(fēng)機進口和出口的切向速度和法向速度。把速度代入三角函數(shù)關(guān)系式，我們就能獲得此時的相對運動的能量和方程的靜態(tài)熵保持不變， (9)由于摩擦的存在實際出口也不是絕對的隔熱，所以就會有熱量的損失， (10) 在風(fēng)扇出口和進口

38、處函值的變化差值就是外界對風(fēng)機所做的有用功，于是就有下面的公式， 根據(jù)三維空間的三角函數(shù)關(guān)系我們得到，, (11)在發(fā)動冷卻風(fēng)扇新型設(shè)計上，黃鴻斌等人把公式（11）與公式（6）聯(lián)立得到， (12)根據(jù)流體的連續(xù)性，對于無引導(dǎo)的風(fēng)機葉片有，v1f =v1r , v1r=0 qdr0 = (13)qdr0 = (14)公式中, / 是出口流量的速度因子，是進口流量的速度因子。，分別是進出口的流線曲率半徑。對于公式（12）是有關(guān)于拉格朗日函數(shù)的極值問題， , (15)在公式中和是拉格朗日因子，下面方程是進出口處的空氣密度與力之間的關(guān)系， (16)因此 (17)在上面的公式中是出口的聲速，是進口的聲速。利用歐拉方程對公式（12）求出極值， (18) , (19) (20) , (21)從公式（18）我們得到=0,聯(lián)立方程（8）和（19）有，=, (22) 聯(lián)立方程（13）和（21）有， (23)聯(lián)立方程（14）和（22）我們就可以得到，+ (24)因此我們和容易得到各個方程的效率值，例如：（13）（14）（16）（17）（20）（23）（26）?？偨Y(jié)以