LES and Experimental Study of Flow Features in Humid-Air Combustion Chamber With Non-Premixed Circular-Disc Stabilized Flames

2008 ◽  
Author(s):  
Peiqing Guo ◽  
Shusheng Zang ◽  
Bing Ge
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
Combustion Chamber ◽  
Gas Turbines ◽  
Bluff Body ◽  
Circular Disc ◽  
Humid Air ◽  
Jet Flame ◽  
Humid Air Combustion ◽  
Flow Features

Sydney/Sandia bluff-body flame series [1] has been world-widely studied based on a simple-geometry bluff-body. This study focuses on a turbulent piloted non-premixed methane jet flame with circular-disc which is used in a humid-air combustion chamber without a swirler. Large eddy simulation has been performed to investigate the flow features. Meanwhile, in order to validate the simulation results, an experimental study is also conducted, where the instantaneous velocity and temperature fields are measured using PIV and high temperature thermocouples, respectively. Compared to Sydney/Sandia flame series, the enlarged simulation area effectively eliminates the boundary effects on flow field. Comparisons with experimental data also show that for high resolution of grids, comparatively good agreement is obtained for the flow field. Unlike Sydney/Sandia flame series, central jet tends to break up early in this case because of the existence of the circular disc. It has also been found that the shear layer between the co-flow and the bluff-body wake is captured by LES as well as by PIV. Because of the difference in geometry between Sydney/Sandia and circular-disc bluff-bodies, it needs to be further studied how to apply the conclusions based on the former to the latter. However, current and future LES and experimental study can help to illustrate the tradeoffs among the degree of swirl and the choice of bluff-body shapes in devices such as industrial burners and gas turbines.

Experimental Study of Humid Air Diffusion Flames in HAT Cycle

2007 ◽  
Author(s):  
Bing Ge ◽  
Shu-Sheng Zang ◽  
Xin Gu
Keyword(s):  
Flow Field ◽  
Flow Region ◽  
Flow Fields ◽  
Temperature Fields ◽  
Reversed Flow ◽  
Humid Air ◽  
Turbulent Diffusion Flame ◽  
Dry Air ◽  
Humid Air Combustion ◽  
Combustion Flow

Combustion with humid air is a key process of humid air turbine (HAT) cycles. Many studies have been undertaken to understand the influence of moisture in air on combustion fields. This study focuses on investigating the differences between the propane/humid air turbulent diffusion flame in a bluff-body burner and the same flame with normal dry air. The moisture levels were achieved by injecting steam into dry air. Particle image velocimetry was used to study the velocity fields experimentally in the humid reactive burner flow and the equivalent non-humid flow. The temperature fields of flames were measured using high temperature thermocouples, and the NO distributions were obtained with gas detection instruments. The results show that although humid air reactive flow fields are similar to the non-humid flow fields in general, there are some differences in the humid air combustion flow field comparing to the same combustion flow field with normal dry air: the center of the reversed-flow region goes forward; the dimension of the reversed-flow region is smaller. An analysis of NO formation revealed NO reduction of humid air flames due to the presence of steam. It is suggested that humid air combustion is helpful to shorten the axial length of combustor, and reduce the formation of pollution.

Experimental study on turbulent structure of humid air flame in a bluff-body burner

2009 ◽  
Vol 18 (2) ◽  
pp. 185-192
Author(s):  
Bing Ge ◽  
Shu-Sheng Zang ◽  
Pei-qing Guo
Keyword(s):  
Experimental Study ◽  
Bluff Body ◽  
Turbulent Structure ◽  
Humid Air

Modelling of the Combustion Process of a Premixed DLE Gas Turbine

2000 ◽  
Author(s):  
R. L. G. M. Eggels
Keyword(s):  
Reaction Mechanism ◽  
Flow Field ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Reaction Mechanisms ◽  
Gas Turbines ◽  
Combustion Process ◽  
Operating Conditions ◽  
Dimensional Manifold ◽  
Global Reaction

To obtain a better understanding of the internal combustion processes of gas turbines, CFD computations of a combustion chamber, based on a Rolls-Royce industrial gas turbine, were performed. Minor simplifications are made to generate a 3-D rotational symmetric geometry. Computations are performed at typical gas turbine conditions and natural gas is used as the fuel. An internal Rolls-Royce CFD code is applied to perform the computations. This paper explains the models used for the CFD computations and describes the advantages and limitations on the applied models. The combustion process has been modelled using a two-step global reaction mechanism and Intrinsic Low Dimensional Manifold (ILDM) reduced reaction mechanisms. The global reaction mechanisms are optimised for the considered operating conditions by modification of the reaction rates so that the same burning velocity and the amplitude CO-peak are obtained as predicted by detailed reaction mechanism (GRI 2.11, Bowman 1995). This optimisation is done considering a one-dimensional laminar flame. Although the global reaction mechanism is optimised for one particular operating condition, it appears that it is suitable for use over the entire range of operating conditions. The ILDM reduced reaction mechanisms are derived from GRI 2.11. Two ILDM tables are used to model two operating conditions, as they are specific for the pressure and inlet temperature. The interaction between turbulence and chemistry is modelled using presumed Probability Density Functions (PDF). The flow field in the combustion chamber is studied at isothermal and combusting conditions. It appeared that the flow field for burning and non-burning circumstances is quite different. There is a lack of experimental data so that it is not possible to verify the CFD results in detail. However, there is knowledge about the mechanisms by which the flame is stabilised and emissions are measured in the exhaust. The predicted flame front position agrees with that which is experimentally observed. The predicted increase of CO at low power is at the same order of magnitude as the measured emissions.

Variations of Anchoring Pattern of a Bluff-Body Stabilized Laminar Premixed Flame as a Function of the Wall Temperature

2016 ◽  
Author(s):  
Sandrine Berger ◽  
Stéphane Richard ◽  
Florent Duchaine ◽  
Laurent Gicquel
Keyword(s):  
Flow Field ◽  
Boundary Conditions ◽  
Combustion Chamber ◽  
Wall Temperature ◽  
Bluff Body ◽  
Flame Stabilization ◽  
Premixed Flame ◽  
Strong Impact ◽  
Flame Holder ◽  
Thermal Boundary Conditions

Aircraft engine components are subject to hostile thermal environments. The solid parts in the hot stages encounter very high temperature levels and gradients that are critical for the engine lifespan. Combustion chamber walls in particular exhibit very heterogeneous thermal fields. The prediction of this specific thermal field is a very complex task as it results from complex interactions between fresh gas injections, cooling flow distributions, combustion, flame stabilization and thermal transfers to the solids. All these phenomena are tightly coupled and do not evolve linearly. Today, the design phase of a combustion chamber is strongly enhanced by the use of high fidelity computations such as Large Eddy Simulations (LES). However, thermal boundary conditions are rarely well known and are thus treated either as adiabatic or as approximated isothermal conditions. Such approximations on thermal boundary conditions can lead to several errors and inaccurate predictions of the combustion chamber flow field. With this in mind and to foresee the potential difficulties of LES based Conjugate Heat Transfer (CHT) predictions, the effect of the wall temperature on a laminar premixed flame stabilization is numerically investigated in this paper for an academic configuration. The considered case consists of a squared cylinder flame holder at a low Reynolds number for which several wall-resolved Direct Numerical Simulations (DNS) are performed varying the bluff-body wall thermal condition. In such a set-up, the reactive flow and the flame holder interact in a complex way with an underlying strong impact of the wall temperature. For a baseline configuration where the flame holder wall temperature is fixed at 700K, the flow field is steady with a flame stabilized thanks to the recirculation zone of the flame holder. As the wall temperature is decreased, the position of the stabilized flame moves further downstream. The flame remains steady until a threshold cold temperature is reached below which an instability appears. For solid temperatures above 700 K, the flame is seen to move further and further upstream. For very hot conditions, the flame even stabilizes ahead of the bluff-body. The various flow solution bifurcations as the flame stabilization evolves are detailed in this paper. Heat flux distribution along the bluff-body walls are observed to be dictated by the flame stabilization process illustrating different mechanisms while integration of these fluxes on the whole flame holder surface confirms that various theoretical equilibrium states may exist for this configuration. This suggests that computation of more realistic cases including thermal conduction in the bluff-body solid part could lead to different converged results depending on the initial thermal state.

Experimental study of the flow field produced by a wall crevice in a combustion chamber

1985 ◽  
Vol 20 (1) ◽  
pp. 209-215 ◽  
Author(s):  
J.F. Driscoll ◽  
W. Mirsky ◽  
S. Palaniswamy ◽  
Weixin Liu
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
Combustion Chamber
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