Bistability analysis of opposed jet combustor under cold and reacting flow conditions

2021 ◽  
Vol 33 (3) ◽  
pp. 034126
Author(s):  
Ariel Sharon ◽  
Yeshayahou Levy
Keyword(s):  
Reacting Flow ◽  
Flow Conditions ◽  
Opposed Jet

Numerical Studies on Trapped-Vortex Concepts for Stable Combustion

1998 ◽  
Vol 120 (1) ◽  
pp. 60-68 ◽  
Author(s):  
V. R. Katta ◽  
W. M. Roquemore
Keyword(s):  
Drag Coefficient ◽  
Reacting Flow ◽  
Flow Conditions ◽  
Third Order ◽  
Cold Flow ◽  
Flow Simulations ◽  
Numerical Studies ◽  
Dynamic Flows ◽  
Experimental Findings ◽  
Trapped Vortex

Spatially locked vortices in the cavities of a combustor aid in stabilizing the flames. On the other hand, these stationary vortices also restrict the entrainment of the main air into the cavity. For obtaining good performance characteristics in a trapped-vortex combustor, a sufficient amount of fuel and air must be injected directly into the cavity. This paper describes a numerical investigation performed to understand better the entrainment and residence-time characteristics of cavity flows for different cavity and spindle sizes. A third-order-accurate time-dependent Computational Fluid Dynamics with Chemistry (CFDC) code was used for simulating the dynamic flows associated with forebody-spindle-disk geometry. It was found from the nonreacting flow simulations that the drag coefficient decreases with cavity length and that an optimum size exists for achieving a minimum value. These observations support the earlier experimental findings of Little and Whipkey (1979). At the optimum disk location, the vortices inside the cavity and behind the disk are spatially locked. It was also found that for cavity sizes slightly larger than the optimum, even though the vortices are spatially locked, the drag coefficient increases significantly. Entrainment of the main flow was observed to be greater into the smaller-than-optimum cavities. The reacting-flow calculations indicate that the dynamic vortices developed inside the cavity with the injection of fuel and air do not shed, even though the cavity size was determined based on cold-flow conditions.

scholarly journals Numerical Studies on Trapped-Vortex Concepts for Stable Combustion

1996 ◽  
Author(s):  
Viswanath R. Katta ◽  
W. M. Roquemore
Keyword(s):  
Drag Coefficient ◽  
Reacting Flow ◽  
Flow Conditions ◽  
Third Order ◽  
Cold Flow ◽  
Flow Simulations ◽  
Numerical Studies ◽  
Dynamic Flows ◽  
Experimental Findings ◽  
Trapped Vortex

Spatially locked vortices in the cavities of a combustor aid in stabilizing the flames. On the other hand, these stationary vortices also restrict the entrainment of the main air into the cavity. For obtaining good performance characteristics in a trapped-vortex combustor, a sufficient amount of fuel and air must be injected directly into the cavity. This paper describes a numerical investigation performed to better understand the entrainment and residence-time characteristics of cavity flows for different cavity and spindle sizes. A third-order-accurate time-dependent Computational Fluid Dynamics with Chemistry (CFDC) code was used for simulating the dynamic flows associated with forebody-spindle-disk geometry. It was found from the non-reacting flow simulations that the drag coefficient decreases with cavity length and that an optimum size exists for achieving a minimum value. These observations support the earlier experimental findings of Little and Whipkey (1979). At the optimum disk location, the vortices inside the cavity and behind the disk are spatially locked. It was also found that for cavity sizes slightly larger than the optimum, even though the vortices are spatially locked, the drag coefficient increases significantly. Entrainment of the main flow was observed to be greater into the smaller-than-optimum cavities. The reacting-flow calculations indicate that the dynamic vortices developed inside the cavity with the injection of fuel and air do not shed, even though the cavity size was determined based on cold-flow conditions.

Effect of Downstream Contraction on Liner Heat Transfer in a Gas Turbine Combustor Swirl Flow

2015 ◽  
Author(s):  
Sandeep Kedukodi ◽  
Srinath Ekkad
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Swirl Flow ◽  
Reacting Flow ◽  
Flow Profile ◽  
Flow Conditions ◽  
Gas Turbine Combustor ◽  
Inlet Flow ◽  
Flow Simulations ◽  
Accelerated Flow

Established numerical approaches for performing detailed flow analysis happens to be an effective tool for industry based applied research. In the present study, computations are performed on multiple gas turbine combustor geometries for turbulent, non-reactive and reactive swirling flow conditions for an industrial swirler. The purpose of this study is to identify the location of peak convective heat transfer along the combustor liner under swirling inlet flow conditions and to investigate the influence of combustor geometry on the flow field. Instead of modeling the actual swirler along with the combustor, an inlet swirl flow profile is applied at the inlet boundary based on previous literature. Initially, the computed results are validated against available experimental data for an inlet Reynolds number flow of 50000 using a 2D axi-symmetric flow domain for non-reacting conditions. A constant heat flux on the liner is applied for the study. Two turbulence models (RNG k-ε and k-ω SST) are utilized for the analysis based on its capability to simulate swirling flows. It is found that both models predict the peak liner heat transfer location similar to experiments. However, k-ε RNG model predicts heat transfer magnitude much closer to the experimental values except displaying an additional peak whereas k-ω model predicts only one peak but tends to over-predict in magnitude. Since the overall characteristic liner heat transfer trend is captured well by the latter one, it is chosen for future computations. A 3D sector (30°) model results also show similar trends as 2D studies. Simulations are then extended to 3 different combustors (Case 1: full cylinder and Case 2 and 3: cylinders with downstream contractions having reduced exit areas) by adopting the same methodology for same inlet flow conditions. Non-reacting simulations predict that the peak heat transfer location is marginally reduced by the downstream contraction of the combustor. However the peak location shifts towards downstream due to the presence of accelerated flow. Reacting flow simulations are performed with Flamelet Generation Manifold (FGM) model for simulating premixed combustion for the same inlet flow conditions as above. It is observed that Case 3 predicts a threefold increase in the exit flow velocity in comparison to non-reacting flow simulations. The liner heat transfer predictions show that both geometries predict similar peak temperatures. However, only one fourth of the initial liner length experiences peak temperature for Case 1 whereas the latter continues to feel the peak till the end. This behavior of Case 3 can be attributed to rapid convection of high temperature products downstream due to the prevailing accelerated flow.

Effect of Holes Array on Effusion Cooling Characteristics of a Three-Nozzle Model Combustor Liner

2017 ◽  
Author(s):  
Yongbin Ji ◽  
Bing Ge ◽  
Shusheng Zang ◽  
Jianhua Xin ◽  
Chun Ye ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
Swirling Flow ◽  
Reacting Flow ◽  
Flow Conditions ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Blowing Ratio ◽  
Annular Combustor ◽  
Swirling Flame ◽  
Cooling Behavior

Effusion cooling performance for a simulated three-nozzle annular combustor under both non-reacting and reacting flow conditions is experimentally investigated. Under this realistic swirling flow, cooling behavior shows the remarkable difference with that under uniform flow case. Mainstream air is electrically heated to a certain temperature level (180 °C) under non-reacting conditions, while methane-air premixed combustion is performed under reacting conditions at the equivalence ratio of 0.7. Especially, the effect of effusion holes array is discussed for the in-line and staggered layouts. Infrared thermography is used to record the temperature distribution on the two bent cooling test panels equipped with the outer and inner liners respectively after individual in-situ calibration process. Local and average overall cooling effectiveness results are then analyzed as a vital parameter to weigh the cooling performance. Results show that no matter under non-reacting or reacting flow conditions, the temperature distribution is skewed, which is closely related to the multi-nozzle swirling flow structure inside the combustor. In addition, an elliptic region area of relatively low cooling effectiveness appears at the downstream the injector outlet due to swirling jets impingement effect when the reaction is activated, however, this is not observed under cold flow cases. The impinging swirling flame on the combustor wall also leads to the local blowing ratio declining, so the effusion film will be not easy to issue through the holes. Influence of holes layout on the cooling characteristics are also different on the outer and inner liners. It is assumed to be caused by the interaction of effusion jets and main swirling flow. This reminds us that in the annular combustor, effusion cooling optimization should be considered according to the curvature. Generally, staggered effusion cooling holes arrangement presents better cooling performance than the in-line arrangement.

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.

Effusion cooling characteristics of a model combustor liner at non-reacting/reacting flow conditions

2017 ◽  
Vol 113 ◽  
pp. 902-911 ◽  
Author(s):  
Bing Ge ◽  
Yongbin Ji ◽  
Zhongran Chi ◽  
Shusheng Zang
Keyword(s):  
Reacting Flow ◽  
Flow Conditions ◽  
Combustor Liner

Velocity Measurements in a Combustor Undergoing Limit-Cycle Pressure Oscillations

2000 ◽  
Author(s):  
J. Li ◽  
S. Acharya
Keyword(s):  
Limit Cycle ◽  
Recirculation Zone ◽  
Cfd Modeling ◽  
Reacting Flow ◽  
Flow Conditions ◽  
Velocity Measurements ◽  
Pressure Oscillations ◽  
Thermoacoustic Instability ◽  
Acoustic Instability ◽  
Velocity Information

Velocity measurements are reported in a swirl-stabilized spray combustor undergoing limit cycle pressure oscillations. The pressure-oscillations are a manifestation of the thermo-acoustic instability in the combustor (at 200Hz), and the goal of the present work is to understand the flow in a combustor with strong pressure oscillations. A second goal of the work is to provide data for the CFD modeling of self-excited combustion. The measurements have been made with a LDV for both the non-reacting case and the reacting flow case, and include velocity information for both the gas phase (with titanium dioxide seeding) and the droplet phase (no seeding). Measurements reveal substantial increases in the axial and tangential velocities under reacting flow conditions. The swirl-induced recirculation zone is much stronger (higher negative velocities) with combustion. Unburnt droplets are observed as far downstream as Z/Ro = 0.72 (nearly 5cm from the injection nozzle). Significant enhancements in the turbulence levels are noted in the presence of combustion, and these are partly attributed to the thermoacoustic instability and strong pressure oscillations.

Flow Field and Wall Temperature Measurements for Reacting Flow in a Lean Premixed Swirl Stabilized Can Combustor

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Suhyeon Park ◽  
David Gomez-Ramirez ◽  
Siddhartha Gadiraju ◽  
Sandeep Kedukodi ◽  
Srinath V. Ekkad ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Gas Turbine ◽  
Swirling Flow ◽  
Single Case ◽  
Operating Conditions ◽  
Reacting Flow ◽  
Flow Conditions ◽  
Gas Turbine Combustor ◽  
Lean Premixed

In this study, we provide detailed wall heat flux measurements and flow details for reacting flow conditions in a model combustor. Heat transfer measurements inside a gas turbine combustor provide one of the most serious challenges for gas turbine researchers. Gas turbine combustor improvements require accurate measurement and prediction of reacting flows. Flow and heat transfer measurements inside combustors under reacting flow conditions remain a challenge. The mechanisms of thermal energy transfer must be investigated by studying the flow characteristics and associated heat load. This paper experimentally investigates the effects of combustor operating conditions on the reacting flow in an optical single can combustor. The swirling flow was generated by an industrial lean premixed, axial swirl fuel nozzle. Planar particle image velocimetry (PIV) data were analyzed to understand the characteristics of the flow field. Liner surface temperatures were measured in reacting condition with an infrared camera for a single case. Experiments were conducted at Reynolds numbers ranging between 50,000 and 110,000 (with respect to the nozzle diameter, DN); equivalence ratios between 0.55 and 0.78; and pilot fuel split ratios of 0 to 6%. Characterizing the impingement location on the liner, and the turbulent kinetic energy (TKE) distribution were a fundamental part of the investigation. Self-similar characteristics were observed at different reacting conditions. Swirling exit flow from the nozzle was found to be unaffected by the operating conditions with little effect on the liner. Comparison between reacting and nonreacting flows (NR) yielded very interesting and striking differences.

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