Analytical Approach of TMF Prediction for Complex Loading

Abstract

Many critical components in turbocharger are subjected to rapid temperature changes during operations. Thermal gradient within these components produces internal stresses and the repetition of these thermal cycles may cause a component to fail due to Thermal Mechanical Fatigue (TMF). Turbine Wheel, Turbine Housing and Manifold are subjected to TMF; these are the most expensive components of the turbocharger and have very complex geometric shapes. The maximum exhaust gas temperature could reach 1050°C. To assess TMF failure, it is very critical to accurately estimate metal temperature of these components subjected to complex duty cycles where exhaust gas temperatures vary significantly with time. Evaluating metal temperature and stress components from finite element analysis for complex duty cycles is a very time consuming process, particularly for complex geometries and approximately requires more than 3 weeks of time to complete analysis for different field complex duty cycles (driving conditions: city, highway and road). Several of these analysis cases are required to consider the impact of the real driving condition. In the present work we have developed an analytical methodology that is accurate and faster to predict the metal temperature and stresses in turbocharger components for complex duty cycles. This method was applied to evaluate the fatigue damage of turbine housing under actual condition.

Temperaturverteilung eines Radialturbinenrads bei transientem Betrieb

“…In Beschleunigungs-und Verzögerungsphasen treten Laständerungen des Motors auf, die starke Variationen der Abgastemperaturen zur Folge haben und somit Inhomogenitäten in Bauteiltemperaturen bedingen. Wie in [2] und [3] beschrieben, verursachen diese hohen thermischen Belastungen Spannungen in den Bauteilen, die sich den Fliehkraftspannungen überlagern und bei einer nicht anforderungsgerechten Auslegung der Bauteile zum Ausfall des Turboladers, bedingt durch Dauerschwingbruch (Low Cycle Fatigue, LCF), führen können. Zur Untersuchung des Einflusses der thermischen Spannungen auf die Lebensdauer der Turbinenbauteile ist die Kenntnis der inhomogenen instationären Temperaturfelder in den Bauteilen erforderlich.…”

Analytical Correction of Nonlinear Thermal Stresses Under Thermomechanical Cyclic Loadings

“…For a plane stress case the relation becomes energy based approach similar to the one used in Ref. [8]. The nonlinear stress is determined by equating the elastic energy to the elastic-plastic energy as shown in Fig.…”

Experimental and numerical investigation of the thermomechanical load on a turbine housing in a radial turbocharger

“…8,10 The thermomechanical fatigue life of a component can be evaluated by solving the thermomechanical temperature and stress of the part. Thermomechanical temperature and strain (stress) simulations are solved by uncoupled or coupled methods; the uncoupled method requires manual control of iteration errors and the assessment of convergence results; it only focuses on the relationship between the core physical quantities in the physical field 2,8,11 The coupling solution can set the iteration error and automatically obtain the convergence result; we focus on the relationship between multiple or all physical quantities in the physical field. [12][13][14] The temperature field measurement of the turbocharger components requires a thermocouple to acquire the temperature at a point on the measured object.…”