Experimental Research On Stress State Of Turbine Blade Root

Electricity, has become almost indispensable in our modern production and dailylife. Now, the electricity is short in supply and conventional energy resources isshapely decreased. To solve these problems, the exploitation of new environmentalprotection energy must be the tendency in the future. But for our country, traditionalcoal-fired power generation takes a great part in the whole electricity, and it cannot bechanged in a short time. How to create more energy with limited resources is the mostdifficult problem we must face to. As an important part of the generator set, theproperty of the steam turbine controls the energy conversion efficiency. High-capacityand high parameter are the direction of the power technique. The higher the powerdensity is, and the larger the capacity is, the bigger the engine displacement, thelonger last stage blade is needed. Blade and rotor are connected with blade roots, andthere will be a great challenge to the roots if the blade is too long because of its highcentrifugal pull, so it is necessary and urgent to understand the stress state of the rootsand the contact status of the roots and the rims.Plane photo elasticity usually be used to give an intuitive expression of the stressstate in the root, the location of maximum stress, and the position of the stressconcentration. But shear difference method should be involved when calculating thestress quantificationally, and it is difficult to ascertain the locate the isoclinals line,and the error generates, unavoidably.Digital image correlation method can be easily used to gain the deformation andstrain field of the roots model, and then maximum stress, stress concentration rate andallocation between the three teeth are got. The lube is added to study the effect oflubrication, the distribution of stress between the three roots get better to some extent.The digital image correlation method is taken up to solve the contact problemsfor the first time, and experiment research is done on the problem of the blade rootsand rims. In general case, contact tress is much higher than the maximum stress in theintertooth space, and contact stress concentrate in a small area near the interface, hightension region is small and stress gradient is big. Contact stress is greatly increased bylubrication, and in piecewise linearity relationship with the load. Effective contact length is put forward in this paper, and the effective contact length of the three teeth iscalculated, the contact status is evaluated.Based on the results above, tooth shape optimization is proposed in this paper.After the optimization, the maximum stress and the rate of stress concentration areboth dropped. The maximum contact stress and stress gradient in contact region aregreatly reduced because of the tooth shape optimization. So, tooth shape optimizationimproves the stress condition of the roots and the contact state with the wheel rims.The optimization is reasonable.