Influence of Turbocharger Turbine Blade Geometry on Vibratory Blade Stresses

Abstract

In this paper, a method to influence the vibratory blade stresses of mixed flow turbocharger turbine blade by varying the local blade thickness in spanwise direction is presented. Such variations have an influence on both the static and the vibratory stresses and therefore can be used for optimizing components with respect to high-cycle fatigue (HCF) tolerance. Two typical cyclic loadings that are of concern to turbocharger manufacturers have been taken into account. These loadings arise from the centrifugal forces and from blade vibrations. The objective of optimization in this study is to minimize combined effects of centrifugal and vibratory stresses on turbine blade HCF and moment of inertia. Here, the conventional turbine blade design with trapezoidal thickness profile is taken as baseline design. The thicknesses are varied at four spanwise equally spaced planes and three streamwise planes to observe their effects on static and vibratory stresses. The summation of both the stresses is referred to as combined stress. In order to ensure comparability among the studied design variants, a generic and constant excitation order-dependent pressure field is used at a specific location on blade. The results show that the locations of static and vibratory stresses, and hence the magnitude of the combined stresses, can be influenced by varying the blade thicknesses while maintaining the same eigenfrequencies. By shifting the maximum vibratory stresses farther away from the maximum static stresses, the combined stresses can be reduced considerably, which leads to improved HCF tolerance.

Experimental and Numerical Vibration Analysis of Octet-Truss-Lattice-Based Gas Turbine Blades

“…Therefore, all parameters of rotor systems, including their material characteristics, vibration characteristics, aerodynamic design, structural integrity and durability, should be investigated to ensure an efficient and durable design [2]. Turbine blades, as a major component of turbine rotor system, undergo vibratory and thermal stresses during their operational life, and the severity of these stresses may affect their performance and durability [3,4]. In gas turbines, the flow is highly unsteady, which can induce high amplitudes of blade vibration under resonant conditions [5].…”

Forced response freeform optimization of a radial turbine using the adjoint method

“…The arising vibrational deflections may damage and destroy the wheel. Some authors, for example Drozdowski [2011] and Naik et al [2018], have studied how geometrical changes to the radial turbine blades affect the vibratory response by using a direct approach: They varied the blade by altering single parameters, such as the blade's thickness, and ran dedicated simulations for each geometry change.…”

Simulation and experimental investigation on vibration of a radial turbine wheel using a two-way FSI approach

“…When the dangerous vibration accumulates to a certain value, it causes high cycle fatigue. 2,3 With increasingly stringent emission regulations on internal combustion engines, high-performance and highly responsive turbochargers need to be designed. Therefore, the turbocharger turbine wheel design needs to be more efficient, with a thinner blade thickness to meet the performance and low-speed response requirements, which makes the turbocharger turbine high-cycle-fatigue failure mode more prominent.…”

“…These investigations have mainly focussed on the interaction between the guide vane of the variable geometry turbocharger or variable nozzle turbine turbocharger and the turbine wheel, namely, the rotor-stator interaction. 3,[6][7][8][9] The main aerodynamic excitation research objects of rotor-stator interaction include the potential field, clearance flow, and shock wave generated by the nozzle. 8,10,11 Investigations of the forced vibration response of the rotor-stator interaction have mainly focussed on blade vibration deformation and vibration stress.…”