scholarly journals A Numerical Study of the Fatigue Life of a Gas Turbine Blade in Transient Operations

Author(s):  
M. Hohlrieder ◽  
H. Irretier

A numerical study of the dynamical response and the life estimation of a gas turbine blade which is subjected to transient nozzle excitation is presented. The mechanical and mathematical model for the blade, the exciting unsteady aerodynamic forces and the life estimation techniques are described and the solution procedure and its realization in a computer code is discussed. For an axial gas turbine compressor blade subjected to unsteady lift and drag forces during a run-up and run-down process numerical results are presented and the relation between the damping ratios, the speed of the run-up/down and the estimated fatigue life is discussed.

Author(s):  
S. Esakki Muthu ◽  
S. Dileep ◽  
S. Saji Kumar ◽  
D. K. Girish

Life estimation of Directionally Solidified (DS) MARM-247 HPT gas turbine blade used in a turbofan engine of a supersonic aircraft is presented. These blades were drafted into the engine as a replacement for the polycrystal (NIMONIC) blades since a more efficient, reliable and durable material with high strength and temperature resistance was required to further enhance the life of the turbine blade and the efficiency of the power generation process. The supersonic aircraft is having a repeated mission cycle of a fast acceleration from idle, a 1hr cruise at Mach 1.5 and a fast deceleration to idle. The mission cycle which is a repetition of acceleration, cruise and deceleration cycles can produce wide variety of complex loading conditions which can result in HCF, LCF and creep damage of the turbine blade. Empirical equation of the universal slope developed by Manson was used to estimate the damage component due to LCF. The cumulative stresses and strains due to creep as a function of time was determined using Time hardening rule. Creep data for MARM-247 was correlated using LMP to predict the lives to 1% of creep strain at worst possible combination of temperature and stress value. Damage due to creep per mission cycle was determined using Life fraction Rule proposed by Robinson and Taira. The vibration characteristics of the turbine blade were predicted using Modal analysis. Campbell diagram was plotted to ascertain whether any nozzle passing frequency fall within the working range of the blade. Harmonic analysis was carried out to evaluate the magnitude of the alternating stresses resulting from the blade vibrations at resonance during the acceleration and deceleration cycle. HCF life of the turbine blade was assessed using Goodman diagram. The total damage of the turbine blade per mission cycle due to the above loading was assumed as the combination of the individual damage due to fatigue and creep. Time to failure under combined creep and fatigue damage was estimated using linear damage rule. Non linear features of FEA tool ANSYS12.0 was exploited to calculate the stress distribution, creep, plastic and the total strain encountered by the turbine blade as a function of mission cycle time. The loading spectrum associated with the mission cycle which includes the temperature, gas pressure and the speed profiles were obtained from a sophisticated engine ground test facility which was configured to simulate actual engine operating conditions. The proposed method of cyclic life estimation using FEM was validated by performing various component and engine level tests. A good agreement was observed between the calculated and observed blade lives.


2012 ◽  
Vol 15 (2) ◽  
pp. 41-44
Author(s):  
Sang-Gwon Kim ◽  
Jong-Chul Lee ◽  
Youn-Jea Kim

Author(s):  
M M Jafari ◽  
G Atefi ◽  
J Khalesi ◽  
A Soleymani

The erosion of the hot regions in a gas turbine is one of the most important challenges encountered by the power plants. Though several numerical simulations of the problem have been reported so far, little is known to give accurate results. In this article, the thermoelastic behaviour of a gas turbine blade with internal steam-cooled channels positioned within a three-dimensional cascade configuration has been studied. A computer code based on the conjugate heat transfer method using the simultaneous solution of Navier–Stokes and heat transfer equations has been developed. From this study, the temperature distribution along with the stress values at high temperatures has been obtained. The blade parameters such as E, α, and K were considered to be a function of the temperature. In the previous works, usually only one or two of these parameters was considered as temperature dependent and the others constant. In this article, all the blade parameters, though making the equations highly non-linear, were considered as a function of temperature. The results have been compared with the available experimental data and a good agreement is observed. According to these findings, taking the temperature dependency of materials into account increases the estimations accuracy and brings the results closer to the reality.


Author(s):  
R. S. Amano

Numerical study is reported of a turbulent flow and a convective heat transfer rate around a gas turbine blade. In the computation of turbulent flow, a hybrid method of the central and the upwind finite differencing is used with the standard k-e turbulence model. The quasi-linear transformed coordinate is adopted for a grid system. For the computation of wall boundaries, the wall function is based on the idea that, beyond the viscous sublayer, the turbulent length scale is universal, increasing linearly with distance from the wall. The computed results display more effects of free stream turbulence level on the suction side where a strong favorable pressure gradient takes place than on the pressure side. The model illustrated here shows results superior to the analytic solution as a whole.


2020 ◽  
Vol 1706 ◽  
pp. 012183
Author(s):  
Yajnesh M Poojari ◽  
Koustubh S Annigeri ◽  
Nilesh Bandekar ◽  
Kiran U Annigeri ◽  
Vinayak badiger ◽  
...  

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