外文翻译-内燃机冷却风扇设计的新方法(共12页)

1、精选优质文档-倾情为你奉上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 .内燃机冷却风扇设计的新方法黄虹宾  郑世琴  刘淑艳  阎为革（北京理工大学车辆工程学院,北京 10081）摘 要 目的  提出内燃机冷却风扇优化设计的数学模型。方法  利用欧拉方程和微积分原理，推导出内燃机冷却风扇沿径向气流参数优化设计的数学模型，建立了风扇叶片扭曲规律优化设计的数学方法。结果 应用该方法对6102Q汽油机冷却风扇进

35、行了优化设计，将计算结果与等反击系数流型和自由涡流型的计算结果做了比较，并利用优化结果对该风扇作了重新设计，解决了长叶片风扇设计中的一些问题。结论 不需人为给定设计参数，计算结果更为合理。关键词 冷却风扇  扭曲规律  优化设计 设计的关键在于对空气经过复杂的叶片以后的流动方向的判断。所以风扇设计采用考夫曼理论，运用考夫曼理论设计风扇时认为气流经过叶片时参数在一维空间内与页面直径正比但是在通过叶面根部是对其产生负作用。之后,风机是根据简单的直线平衡方程。提高了计算精度完全利用径向平衡方程和等反击系数法确定的参数，叶片沿着径向的风流损失也一定程度的降低。本文提出了一

36、种数学模型,为优化的气流计,沿着叶片高度利用欧拉方程和微积分的变异方程。1 数学模型当微小物质G经过风扇的两个相邻表面时根据欧拉方程就会求出对其产生的力， P= (v2ur2- v1ur1) G, (1)假设角速度的风扇,是圆周速度,是风机进口的圆周速度,r1风机进口半径、r2是风机出口的半径,对这些无导向叶片则根据下面的公式计算，P=v2ur2G (2) 我们建立r1和 r2连续的流函数的方程，在沿叶片表面方向函数是恒定流。通道表面的区域被视为流道流动的表面。因此,G= 2, (3) 把公式（3）代入到公式（2）然后得到，P= 2v2ur2d (4)假设P是作用在风扇有效面积上的总功率，那么

37、P1就是有效功率得， = 2(v/2)d1 (5) 如果Vp是当功率为P1是风扇的理论转速，那么根据（4）（5）就可以得到风扇的有效机械效率， , (6) R01和R02分别是风扇进口处内外的半径，R0则是风扇与壁面之间的间隙，在利用欧拉方程就可求出风机的功， (7)在把这个方程代入热力学第二定律有， (8)令，V1是风机进口的绝对速度的、v2是风机出口的绝对速度,H1与H2分别是风机进口和出口的切向速度和法向速度。把速度代入三角函数关系式，我们就能获得此时的相对运动的能量和方程的静态熵保持不变， (9)由于摩擦的存在实际出口也不是绝对的隔热，所以就会有热量的损失， (10) 在风扇出口和进口

38、处函值的变化差值就是外界对风机所做的有用功，于是就有下面的公式， 根据三维空间的三角函数关系我们得到，, (11)在发动冷却风扇新型设计上，黄鸿斌等人把公式（11）与公式（6）联立得到， (12)根据流体的连续性，对于无引导的风机叶片有，v1f =v1r , v1r=0 qdr0 = (13)qdr0 = (14)公式中, / 是出口流量的速度因子，是进口流量的速度因子。，分别是进出口的流线曲率半径。对于公式（12）是有关于拉格朗日函数的极值问题， , (15)在公式中和是拉格朗日因子，下面方程是进出口处的空气密度与力之间的关系， (16)因此 (17)在上面的公式中是出口的声速，是进口的声速。利用欧拉方程对公式（12）求出极值， (18) , (19) (20) , (21)从公式（18）我们得到=0,联立方程（8）和（19）有，=, (22) 联立方程（13）和（21）有， (23)联立方程（14）和（22）我们就可以得到，+ (24)因此我们和容易得到各个方程的效率值，例如：（13）（14）（16）（17）（20）（23）（26）。总结以