Two-step approach for pressure oscillations prediction in gas turbine combustion chambers

Abstract

Currently, gas turbine manufacturers frequently face the problem of strong acoustic combustion-driven oscillations inside combustion chambers. These combustion instabilities can cause extensive wear and sometimes even catastrophic damage of combustion hardware. This requires prevention of combustion instabilities, which, in turn, requires reliable and fast predictive tools. We have developed a two-step method to find a set of operating parameters under which gas turbines can be operated without going into self-excited pressure oscillations. As the first step, an unsteady Reynoldsaveraged Navier-Stokes simulation with the flame speed closure model implemented in the OpenFOAM Õ environment is performed to obtain the flame transfer function of the combustion setup. As the second step time-domain simulations employing low-order network model implemented in Simulink Õ are executed. In this work, we apply the proposed method to the Beschaufelter RingSpalt test rig developed at the Technische Universität München. The sensitivity of thermoacoustic stability to the length of a combustion chamber, flame position, gain and phase of flame transfer function and outlet reflection coefficient are studied.

Advances by the Marie Curie project TANGO in thermoacoustics

“…Iurashev et al. 50 studied the BRS burner shown in Figure 13 with a hybrid approach: first, the FTF of the flame was calculated with CFD, giving data points in the frequency range [0,…500 Hz]. This FTF data was approximated by an analytical expression representing a low-pass filter with damping and a time-lag τ.…”

“…Flame modelled by FTF from CFD simulations Iurashev et al 50 studied the BRS burner shown in Figure 13 with a hybrid approach: first, the FTF of the flame was calculated with CFD, giving data points in the frequency range [0,. . .500 Hz].…”

Application of a three-step approach for prediction of combustion instabilities in industrial gas turbine burners

“…When the length of the setup under consideration is much larger than its dimensions in the other directions, it is possible to perform a one-dimensional low-order acoustic analysis (Bellucci et al, 2005;Schuermans et al, 2010;Bothien et al, 2015;Iurashev et al, 2016b).…”

“…In order to connect oscillating variables in different sections (see Figure 2), we need to know the jump conditions. To compute the jump conditions between sections separated by a compact acoustic element, such as sharp cross-sectional area change and a compact swirler, the system of linearised equations of conservation of mass and Bernoulli (Dowling and Stow, 2005;Iurashev et al, 2016b) written in terms of f and g is solved.…”

“…To calculate the jump conditions at the flame, the system of linearised equations of conservation of momentum and energy (product of mass conservation equation and Bernoulli equation) written in terms of f and g is solved (Dowling and Stow, 2005;Iurashev et al, 2016b). (17) where coefficients of matrices J and H can be found in Appendix A. Equations ( 16) and ( 17) are directly used in the network model time-domain simulations.…”