Effect of Centrifugal Force on the Performance of High-G Ultra Compact Combustor

2015 ◽  
Author(s):  
Alejandro M. Briones ◽  
Dave L. Burrus ◽  
Timothy J. Erdmann ◽  
Dale T. Shouse
Keyword(s):  
Temperature Profile ◽  
Turbulent Flame ◽  
Flame Length ◽  
Swirl Flow ◽  
Flame Speed ◽  
Reacting Flow ◽  
Flow Conditions ◽  
Radial Temperature ◽  
Turbulent Flame Speed ◽  
Progress Variable

A numerical investigation of reacting flows in an advanced high-g cavity (HGC), Ultra-Compact Combustor (UCC) concept is conducted. The high-g cavity UCC (UCC-HGC) design uses high swirl in a circumferential cavity (CC) wrapped around a main stream annular flow. The high swirl is generated through angled CC driver jets. This centrifugal force is varied by changing the CC-to-core air mass flow ratio (ṁcc/ṁcore) and jet inclination angle (αjet) relative to the cavity ring surface, while maintaining the global equivalence ratio (ϕGlobal) constant. Steady, rotational periodic, 3D simulations are performed following a multiphase, Reynolds-averaged Navier-Stokes (RANS), and non-premixed flamelet/progress variable (FPV) approach using a customized FLUENT. Results indicate that under non-reacting flow conditions the driver jets impose a very strong bulk swirl flow within the CC and the mainstream flow does not entrain into the CC. Thus, the maximum g-load is primarily sensitive to ṁcc/ṁcore and secondarily to αjet. However, the g-loads become increasingly more sensitive to the latter at greater ṁcc/ṁcore. Now, under reacting flow conditions, the flame interacts with the flow and the bulk swirl flow is diminished at low ṁcc/ṁcore, while boosted at high ṁcc/ṁcore. The former happens because the flame deflects the incoming driver jet flow, enhancing radial and axial velocity components (through thermal expansion), while diminishing the tangential flow velocity. This, in turn, weakens the g-loads within the CC to below its design g-load operation. On the other hand, at high ṁcc/ṁcore and small αjet the flame is perpendicular to the bulk swirl flow, accelerating the flow tangential velocity and enhancing g-loads above its design operation. Qualitatively, the more and hotter the flame that can be sustained within the CC the shorter the flame length. The converse is also true. Flame length does not appear to be strongly influenced by ṁcc/ṁcore and αjet. Even though g-loads appear to enhance reaction progress variable source (SC) and, consequently, turbulent flame speed, through turbulence this does not necessarily mean that the turbulent flame speed under g-loads is various factors greater than its corresponding turbulent flame speed under 0g’s. As the ṁcc/ṁcore increases the center-peaked radial temperature profile at intermediate αjet starts to deteriorate, whereas the radial temperature profile at low αjet improves. For high αjet, increasing ṁcc/ṁcore has no substantial effect on the exit radial temperature profiles.

Investigation of Flamelet Generated Manifold Reaction Source Term Closure Models Applied to an Industrial Gas Turbine

2019 ◽  
Author(s):  
George Mallouppas ◽  
Graham Goldin ◽  
Yongzhe Zhang ◽  
Piyush Thakre ◽  
Jim Rogerson
Keyword(s):  
Gas Turbine ◽  
Source Term ◽  
Mixture Fraction ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Turbulent Flame Speed ◽  
Progress Variable ◽  
Flamelet Generated Manifold ◽  
Reactor Types ◽  
Industrial Gas Turbine

Abstract Three Flamelet Generated Manifold reaction source term closure options and two different reactor types are examined with Large Eddy Simulation of an industrial gas turbine combustor operating at 3 bar. This work presents the results for the SGT-100 Dry Low Emission (DLE) gas turbine provided by Siemens Industrial Turbomachinery Ltd. The related experimental study was performed at the German Aerospace Centre, DLR, Stuttgart, Germany. The FGM model approximates the thermo-chemistry in a turbulent flame as that in a simple 0D constant pressure ignition reactors and 1D strained opposed-flow premixed reactors, parametrized by mixture fraction, progress variable, enthalpy and pressure. The first objective of this work is to compare the flame shape and position predicted by these two FGM reactor types. The Kinetic Rate (KR) model, studied in this work, uses the chemical rate from the FGM with assumed shapes, which are a Beta function for mixture fraction and delta functions for reaction progress variable and enthalpy. Another model investigated is the Turbulent Flame-Speed Closure (TFC) model with Zimont turbulent flame speed, which propagates premixed flame fronts at specified turbulent flame speeds. The Thickened Flame Model (TFM), which artificially thickens the flame to sufficiently resolve the internal flame structure on the computational grid, is also explored. Therefore, a second objective of this paper is to compare KR, TFC and TFM with the available experimental data.

scholarly journals Numerical Investigation of Pressure Influence on the Confined Turbulent Boundary Layer Flashback Process

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 146 ◽  
Author(s):  
Aaron Endres ◽  
Thomas Sattelmayer
Keyword(s):  
Boundary Layer ◽  
Gas Turbines ◽  
Separation Zone ◽  
Turbulent Flame ◽  
Pressure Rise ◽  
Flame Speed ◽  
Zone Size ◽  
Detailed Chemical Kinetics ◽  
Turbulent Flame Speed ◽  
Quenching Distance

Boundary layer flashback from the combustion chamber into the premixing section is a threat associated with the premixed combustion of hydrogen-containing fuels in gas turbines. In this study, the effect of pressure on the confined flashback behaviour of hydrogen-air flames was investigated numerically. This was done by means of large eddy simulations with finite rate chemistry as well as detailed chemical kinetics and diffusion models at pressures between 0 . 5 and 3 . It was found that the flashback propensity increases with increasing pressure. The separation zone size and the turbulent flame speed at flashback conditions decrease with increasing pressure, which decreases flashback propensity. At the same time the quenching distance decreases with increasing pressure, which increases flashback propensity. It is not possible to predict the occurrence of boundary layer flashback based on the turbulent flame speed or the ratio of separation zone size to quenching distance alone. Instead the interaction of all effects has to be accounted for when modelling boundary layer flashback. It was further found that the pressure rise ahead of the flame cannot be approximated by one-dimensional analyses and that the assumptions of the boundary layer theory are not satisfied during confined boundary layer flashback.

scholarly journals Extension of the turbulent flame speed closure model to ignition in multiphase flows

2013 ◽  
Vol 160 (2) ◽  
pp. 351-365 ◽  
Author(s):  
Jan M. Boyde ◽  
Patrick C. Le Clercq ◽  
Massimiliano Di Domenico ◽  
Manfred Aigner
Keyword(s):  
Multiphase Flows ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Closure Model ◽  
Turbulent Flame Speed

Flame Characteristics and Turbulent Flame Speeds of Turbulent, High-Pressure, Lean Premixed Methane/Air Flames

2005 ◽  
Author(s):  
P. Griebel ◽  
R. Bombach ◽  
A. Inauen ◽  
R. Scha¨ren ◽  
S. Schenker ◽  
...  
Keyword(s):  
Flame Front ◽  
Gas Turbines ◽  
Equivalence Ratio ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Operating Conditions ◽  
Turbulent Flame Speed ◽  
Front Position ◽  
Preheating Temperature ◽  
Lean Premixed

The present experimental study focuses on flame characteristics and turbulent flame speeds of lean premixed flames typical for stationary gas turbines. Measurements were performed in a generic combustor at a preheating temperature of 673 K, pressures up to 14.4 bars (absolute), a bulk velocity of 40 m/s, and an equivalence ratio in the range of 0.43–0.56. Turbulence intensities and integral length scales were measured in an isothermal flow field with Particle Image Velocimetry (PIV). The turbulence intensity (u′) and the integral length scale (LT) at the combustor inlet were varied using turbulence grids with different blockage ratios and different hole diameters. The position, shape, and fluctuation of the flame front were characterized by a statistical analysis of Planar Laser Induced Fluorescence images of the OH radical (OH-PLIF). Turbulent flame speeds were calculated and their dependence on operating conditions (p, φ) and turbulence quantities (u′, LT) are discussed and compared to correlations from literature. No influence of pressure on the most probable flame front position or on the turbulent flame speed was observed. As expected, the equivalence ratio had a strong influence on the most probable flame front position, the spatial flame front fluctuation, and the turbulent flame speed. Decreasing the equivalence ratio results in a shift of the flame front position farther downstream due to the lower fuel concentration and the lower adiabatic flame temperature and subsequently lower turbulent flame speed. Flames operated at leaner equivalence ratios show a broader spatial fluctuation as the lean blow-out limit is approached and therefore are more susceptible to flow disturbances. In addition, because of a lower turbulent flame speed these flames stabilize farther downstream in a region with higher velocity fluctuations. This increases the fluctuation of the flame front. Flames with higher turbulence quantities (u′, LT) in the vicinity of the combustor inlet exhibited a shorter length and a higher calculated flame speed. An enhanced turbulent heat and mass transport from the recirculation zone to the flame root location due to an intensified mixing which might increase the preheating temperature or the radical concentration is believed to be the reason for that.

An Efficient Computational Model for Premixed Turbulent Combustion at High Reynolds Numbers Based on a Turbulent Flame Speed Closure

1997 ◽  
Author(s):  
Vladimir Zimont ◽  
Wolfgang Polifke ◽  
Marco Bettelini ◽  
Wolfgang Weisenstein
Keyword(s):  
Computational Model ◽  
Transport Equation ◽  
Turbulent Combustion ◽  
Turbulent Flame ◽  
Reynolds Numbers ◽  
Flame Speed ◽  
Closed Form Expression ◽  
Turbulent Length Scale ◽  
Premixed Turbulent Combustion ◽  
Turbulent Flame Speed

Theoretical background, details of implementation and validation results of a computational model for turbulent premixed gaseous combustion at high turbulent Reynolds numbers are presented. The model describes the combustion process in terms of a single transport equation for a progress variable; closure of the progress variable’s source term is based on a model for the turbulent flame speed. The latter is identified as a parameter of prime significance in premixed turbulent combustion and is determined from theoretical considerations and scaling arguments, taking into account physico-chemical properties of the combustible mixture and local turbulent parameters. Specifically, phenomena like thickening, wrinkling and straining of the flame front by the turbulent velocity field are considered, yielding a closed form expression for the turbulent flame speed that involves, e.g., speed, thickness and critical gradient of a laminar flame, local turbulent length scale and fluctuation intensity. This closure approach is very efficient and elegant, as it requires only one transport equation more than the non-reacting flow case, and there is no need for costly evaluation of chemical source terms or integration over probability density functions. The model was implemented in a finite-volume based computational fluid dynamics code and validated against detailed experimental data taken from a large scale atmospheric gas turbine burner test stand. The predictions of the model compare well with the available experimental results. It has been observed that the model is significantly more robust and computationally efficient than other combustion models. This attribute makes the model particularly interesting for applications to large 3D problems in complicated geometries.

An Optimized Correlation for Turbulent Flame Speed for C1-C3 Fuels at Engines-Relevant Conditions

2021 ◽  
Author(s):  
Sajjad Yousefian ◽  
Eoin M. Burke ◽  
Felix Guthe ◽  
Rory f.d. Monaghan
Keyword(s):  
Turbulent Flame ◽  
Flame Speed ◽  
Turbulent Flame Speed

Validation of a Turbulent Flame Speed Model across Combustion Regimes

2010 ◽  
Vol 182 (3) ◽  
pp. 284-308 ◽  
Author(s):  
H. Kolla ◽  
J. W. Rogerson ◽  
N. Swaminathan
Keyword(s):  
Turbulent Flame ◽  
Flame Speed ◽  
Turbulent Flame Speed ◽  
Combustion Regimes
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