大連水產學院本科畢業論文(設計) 外文翻譯New Design Method For Engine Cooling FanHuang Hongbin zheng Shiqin Liu Shuyan Yan Weige(School of Vehicular Engineering, Beijing Institute if Technology, Beijing 100081)Abstract Aim To put forward a type of math model for optimizing fans twisting law.Methods This math model was based on turbo-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,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 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 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 of 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 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 circumferential 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 flow. 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 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 streams 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,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 friction 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 parameter 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 =( (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 multiplier, 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 Euler-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).To 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, 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 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 expanding degree of the fan passageway along the radial direction must keep larger than 1.0,that is sin/sin1, 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 M0.3 and M0），于此同時為了減小泄露量風扇邊緣的泄露參數必須小于0.75而且根部的速度要相對小應變參數必須大于0.5.2 沿徑向程幾何擴大的風扇比率必須大于1.0，也就是sin/sin1在公式中和分別是風機進出口處的氣流角度。3 進口和出口的相對速度必須要限制，因為他們影響風扇的聲音例如： M0.3 和 M0.3.4 軸在出口處的絕對速度必須沿著風扇的徑向，否則會出現氣流的分離。2.2 引進和更新原有的結構 以6102Q型發動機冷卻風扇為例優化。一些參數,如型材、進出口半徑、葉片寬度及葉片的相同的原有的風扇。原有的風扇屬于自便皮質類型,其刀刃很長,相對速度較大,所以它葉尖的反擊應變參數又大又出現在大多數根部.這些問題可以通過修改流型解決。優化設計計算是基于間接