Impact of the 3D Flow Effects on the Silo Combustor Thermal State

Abstract

Many Alstom heavy-duty gas turbines with a silo combustor are in service and moreover undergoing upgrades for performance augmentation, lifetime extension, and emission reduction. Several structural parts of the combustor are exposed to high gas temperatures, and therefore their lifetime depends mainly on the metal temperatures, which must be kept within the acceptable limits. This paper describes methodology based on the state of the art methods of 3D CFD and finite element (FE) computations, which are combined into the computational process for the reliable silo combustor thermal analyses. In the first part of the paper the computational model of the silo combustor is discussed. The model comprises CFD models simulating the hot gas path and the cooling air supply system, as well as the FE model of the structural parts. The CFD models predict the gas temperatures and heat transfer coefficients that are used by the FE model for calculating the metal temperatures. In the second part of the paper the computational results are presented and several 3D flow phenomena are analysed in details. One effect is the interaction of dilution jets in swirled cross flow. At different operation conditions, pairing of those jets occurs, which generates the periodic metal temperature distribution, as recorded in the field. This analysis also revealed factors, which influence on the temperature distribution. The combustor simulation delivers an insight into non-homogeneous temperature profiles in front of the turbine behind the transition channel of the silo-combustor. Finally, by adding leakages into the flow model, the interesting example of the non-homogeneous leakage of cold air, which can lead to local increase of material temperature, was simulated. All these simulations led to reliable silo-combustor upgrades.

Management of air flows inside steel silo during grain storage

“…Active ventilation affects the grain mass with upward flow of atmospheric air. This installation is used for cooling the grain to increase its shelf life [1], to prevent or eliminate self-heating in the grain mass. The second installation for ventilation the over-grain space is to remove condensate formed during the grain storage and settled on silo structures.…”

Methodology for assessing the grain mass thermal effusivity in a metal silo under the influence of active ventilation

“…The purpose of the developed mathematical model is to provide a tool for the calculation of the trajectory of the grain temperature changes in along the layers of the grain mass during an active ventilation of the grain, including changes happen in conditions of variable values of ambient temperatures and with intermittent implementations of active ventilation mode [1].…”