Estimation of the turbulent Schmidt number in a model gas turbine combustor

This article presents the estimation of turbulent Schmidt number in a model gas turbine combustor. Different gases are used as the model fuel while maintaining the mass flow rate. The simplest closure models for Reynolds stress and turbulent flux are considered. The anisotropy of turbulent viscosity is demonstrated.

A novel diagnostic method based on filter bank theory for fast and accurate detection of thermoacoustic instability

This study proposes and analyzes a novel methodology that can effectively detect multi-mode combustion instability (CI) in a gas turbine combustor. The experiment is conducted in a model gas turbine combustor, and dynamic pressure (DP) and flame images are examined during the transition from stable to unstable flame, which is driven by changing fuel compositions. As a powerful technique for early detection of CI in multi-mode as well as in single mode, a new filter bank (FB) method based on spectral analysis of DP is proposed. Sequential processing using a triangular filter with Mel-scaling and a Hamming window is applied to increase the accuracy of the FB method, and the instability criterion is determined by calculating the magnitude of FB components. The performance of the FB method is compared with that of two conventional methods that are based on the root-mean-squared DP and temporal kurtosis. From the results, the FB method shows comparable performance in detection speed, sensitivity, and accuracy with other parameters. In addition, the FB components enable the analysis of various frequencies and multi-mode frequencies. Therefore, the FB method can be considered as an additional prognosis tool to determine the multi-mode CI in a monitoring system for gas turbine combustors.

Analysis of the Heat Transfer within combustor liners Using a Combined Monte Carlo and two-flux method

One consequence of increasing efficiency of gas turbine combustors is higher temperatures within the combustor. Management of larger heat load has been advanced to protect the combustor wall and turbines, and among those are thermal barrier coatings (TBCs). Historically, both the flame and TBCs have received a simplified radiation treatment using effective absorptivities and emissivities. In this study, non-gray radiation is compared to gray and black radiation by combining three-dimensional Monte Carlo Ray Tracing solution of non-gray flames in a model gas turbine combustor to one-dimensional energy balance within combustor liners. A recent large eddy simulation of a gas turbine combustor is analyzed, where both gray and non-gray models are exercised. A two-band spectral model is employed for the TBC, where a translucent band and an opaque band are identified. A line-by-line treatment for gas-phase radiation is adopted, and the incident radiative energy on the combustor wall is collected using the MCRT solver, where the fraction of radiative energy within the translucent band is collected and compared with those obtained from the blackbody assumption. The temperature along the multi-layered combustor wall is computed and parametric comparison is conducted. The effects of the nongray flame radiation are more prominent at elevated pressures than at atmospheric pressure. The gray model is found to over-predict the TBC temperature, which leads to a difference of approximately 150 K in the prediction of peak temperature on the hot side of the TBC.