Impact of Cooling Air Injection on the Primary Combustion Zone of a Swirl Burner

2012 ◽  
Vol 134 (12) ◽  
Author(s):  
A. Marosky ◽  
V. Seidel ◽  
S. Bless ◽  
T. Sattelmayer ◽  
F. Magni
Keyword(s):  
Flow Field ◽  
Heat Release ◽  
High Speed ◽  
Equivalence Ratio ◽  
Swirling Flow ◽  
Water Channel ◽  
Combustion Stability ◽  
Flame Stability ◽  
Primary Zone ◽  
Cooling Air

In most dry, low NOx combustor designs, the front panel impingement cooling air is directly injected into the combustor primary zone. As this air partially mixes with the swirling flow of premixed reactants from the burner prior to completion of heat release, it reduces the effective equivalence ratio in the flame and has a beneficial effect on NOx emissions. However, the fluctuations of the equivalence ratio in the flame potentially increase heat release fluctuations and influence flame stability. Since both effects are not yet fully understood, isothermal experiments are made in a water channel, where high speed planar laser-induced fluorescence (HSPLIF) is applied to study the cooling air distribution and its fluctuations in the primary zone. In addition, the flow field is measured with high speed particle image velocimetry (HSPIV). Both mixing and flow field are also analyzed in numerical studies using isothermal large eddy simulation (LES), and the simulation results are compared with the experimental data. Of particular interest is the influence of the injection configuration and cooling air momentum variation on the cooling air penetration and dispersion. The spatial and temporal quality of mixing is quantified with probability density functions (PDF). Based on the results regarding the equivalence ratio fluctuations, regions with potential negative effects on combustion stability are identified. The strongest fluctuations are observed in the outer shear layer of the swirling flow, which exerts a strong suction effect on the cooling air. Interestingly, the cooling air dilutes the recirculation zone of the swirling flow. In the reacting case, this effect is expected to lead to a decrease of the temperature in the flame-anchoring zone below the adiabatic flame temperature of the premixed reactant, which may have an adverse effect on flame stability.

Impact of Cooling Air Injection on the Primary Combustion Zone of a Swirl Burner

2012 ◽  
Author(s):  
A. Marosky ◽  
V. Seidel ◽  
S. Bless ◽  
T. Sattelmayer ◽  
F. Magni
Keyword(s):  
Flow Field ◽  
Heat Release ◽  
High Speed ◽  
Equivalence Ratio ◽  
Swirling Flow ◽  
Water Channel ◽  
Combustion Stability ◽  
Flame Stability ◽  
Primary Zone ◽  
Cooling Air

In most dry low NOx combustor designs the front panel impingement cooling air is directly injected into the combustor primary zone. As this air partially mixes with the swirling flow of premixed reactants from the burner prior to completion of heat release it reduces the effective equivalence ratio in the flame and has a beneficial effect on NOx emissions. However, the fluctuations of the equivalence ratio in the flame potentially increase heat release fluctuations and influence flame stability. Since both effects are not yet fully understood isothermal experiments are made in a water channel where high speed planar laser induced fluorescence (HSPLIF) is applied to study the cooling air distribution and its fluctuations in the primary zone. In addition the flow field is measured with high speed particle image velocimetry (HSPIV). Both, mixing and flow field are also analyzed in numerical studies using isothermal large eddy simulation (LES) and the simulation results are compared with the experimental data. Of particular interest is the influence of the injection configuration and cooling air momentum variation on the cooling air penetration and dispersion. The spatial and temporal quality of mixing is quantified with probability density functions (PDF). Based on the results regarding the equivalence ratio fluctuations regions with potential negative effects on combustion stability are identified. The strongest fluctuations are observed in the outer shear layer of the swirling flow, which exerts a strong suction effect on the cooling air. Interestingly, the cooling air dilutes the recirculation zone of the swirling flow. In the reacting case this effect is expected to lead to a decrease of the temperature in the flame anchoring zone below the adiabatic flame temperature of the premixed reactant, which may have an adverse effect on flame stability.

Impact of Cooling Air Injection on the Combustion Stability of a Premixed Swirl Burner Near Lean Blowout

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
A. Marosky ◽  
V. Seidel ◽  
T. Sattelmayer ◽  
F. Magni ◽  
W. Geng
Keyword(s):  
Flame Front ◽  
Equivalence Ratio ◽  
Flame Stabilization ◽  
Air Injection ◽  
Combustion Stability ◽  
Nox Emissions ◽  
Test Rig ◽  
Lean Blowout ◽  
Burner Exit ◽  
Cooling Air

In most dry, low-NOx combustor designs of stationary gas turbines, the front panel impingement cooling air is directly injected into the combustor primary zone. This air partially mixes with the swirling flow of premixed reactants from the burner and reduces the effective equivalence ratio in the flame. However, local unmixedness and the lean equivalence ratio are supposed to have a major impact on combustion performance. The overall goal of this investigation is to answer the question of whether the cooling air injection into the primary combustor zone has a beneficial effect on combustion stability and NOx emissions or not. The flame stabilization of a typical swirl burner with and without front panel cooling air injection is studied in detail under atmospheric conditions close to the lean blowout limit (LBO) in a full-scale, single-burner combustion test rig. Based on previous isothermal investigations, a typical injection configuration is implemented for the combustion tests. Isothermal results of experimental studies in a water test rig adopting high-speed planar laser-induced fluorescence (HSPLIF) reveal the spatial and temporal mixing characteristics for the experimental setup studied under atmospheric combustion. This paper focuses on the effects of cooling air injection on both flame dynamics and emissions in the reacting case. To reveal dependencies of cooling air injection on combustion stability and NOx emissions, the amount of injected cooling air is varied. OH*-chemiluminescence measurements are applied to characterize the impact of cooling air injection on the flame front. Emissions are collected for different cooling air concentrations, both global measurements at the chamber exit, and local measurements in the region of the flame front close to the burner exit. The effect of cooling air injection on pulsation level is investigated by evaluating the dynamic pressure in the combustor. The flame stabilization at the burner exit changes with an increasing degree of dilution with cooling air. Depending on the amount of cooling, only a specific share of the additional air participates in the combustion process.

Liftoff behaviors and flame structure of dimethyl ether jet flame in CH4/air vitiated coflow

2019 ◽  
Vol 233 (8) ◽  
pp. 1039-1046 ◽  
Author(s):  
Wei Fu ◽  
Fengyu Li ◽  
Haitao Zhang ◽  
Bolun Yi ◽  
Yanju Liu ◽  
...  
Keyword(s):  
Dimethyl Ether ◽  
High Speed ◽  
Equivalence Ratio ◽  
Flame Structure ◽  
High Speed Photography ◽  
Flame Stability ◽  
Jet Flames ◽  
Jet Flame ◽  
Field Temperature ◽  
Vitiated Coflow

The objective of this paper is to investigate the flame structure and liftoff behaviors of a dimethyl ether central jet in CH4/air vitiated coflow in a coflow burner. The liftoff behaviors of dimethyl ether jet flames in the air flow were studied firstly. The flame stability of the burner was analyzed by measuring the flow field temperature with thermocouples. By changing the coflow rate and CH4 equivalence ratio, the liftoff behaviors of dimethyl ether jet flames under different vitiated coflow environments were discussed. The jet flame structure was also analyzed qualitatively by high-speed photography.

scholarly journals Swirling Flow Field inside a Hollow Turbine Shaft for an Internal Cooling Air System

2000 ◽  
Vol 6 (3) ◽  
pp. 215-226
Author(s):  
Tadaharu Kishibe ◽  
Shojiro Kaji
Keyword(s):  
Flow Field ◽  
Swirling Flow ◽  
Pressure Fluctuations ◽  
Tvd Scheme ◽  
Internal Cooling ◽  
Hollow Shaft ◽  
Spiral Vortex ◽  
Air System ◽  
Turbine Shaft ◽  
Cooling Air

The swirling flow field in an internal cooling air system in which the fluid passes through an inducer, a hollow turbine shaft, and a cavity between two disks (referred to as a wheel space) is solved using computational fluid dynamics and the pressure fluctuations on the hollow shaft wall surface are measured.The three-dimensional compressible Navier-Stokes equations are adopted and discretized by an implicit TVD scheme. The region of the cooling air system is divided into two computational domains: one from the inducer to the hollow shaft, and the other from the hollow shaft to the wheel space. In the analysis of the former computational domain, the roles of components such as inducer blades are shown. In the analysis of the latter, the existence of a rotating spiral vortex at the place where the swirling flow turns radially outward is shown and its characteristics are described.The main part of the internal cooling air system of a gas turbine is used as an experimental apparatus. Pressure sensors are embedded axially and circumferentially in the hollow turbine shaft to measure unsteady wall pressures. The existence and characteristics of the rotating spiral vortex are confirmed experimentally. The pressure fluctuations due to instability in the rotating wall boundary layer, whose waves propagate both in the positive and negative directions of the shaft rotation, are captured.

Influence of an Adaptive Blade System on Unsteady Flow Conditions in a 2D Compressor Cascade

2017 ◽  
Author(s):  
Julija Peter ◽  
David Konstantin Tilcher ◽  
Robert Meyer ◽  
Paul Uwe Thamsen
Keyword(s):  
Phase Shift ◽  
Flow Field ◽  
Unsteady Flow ◽  
High Speed ◽  
Optical Measurement ◽  
Water Channel ◽  
Tip Clearance ◽  
Flow Conditions ◽  
Compressor Cascade ◽  
Flow Angle

The flow field inside a compressor is characterized by highly unsteady flow effects. Consequently, the performance of a compressor is significantly influenced by the complex flow field. Especially at off-design conditions, flow separation and tip clearance flow cause vortex structures and thus increased losses. The objective of this paper is to give an insight into the effect mechanism of the movable stator vanes as an adaptive system to affect unsteady flow conditions. The experiments were conducted in a stator cascade in a water channel at a Reynolds number of Re = 500 000. Inlet guide vanes with movable flaps were used to simulate the periodic variation of the inlet flow angle. As parameters, the mean stagger angle of the stator cascade as well as the phase shift between the sinusoidal movement of the stator and the inlet guide cascade were varied. By using the optical measurement technique High-Speed Particle Image Velocimetry (HS-PIV), the flow fields upstream and downstream of the stator cascade were captured. Overall, the results revealed that the loss coefficient is strongly dependent on the phase shift between the inlet guide cascade and the stator cascade. Using certain phase shifts, a reduction in losses of up to 20% was achieved by the movable stator cascade.

Impact of Cooling Air Injection on the Combustion Stability of a Premixed Swirl Burner Near Lean Blowout

2013 ◽  
Author(s):  
A. Marosky ◽  
V. Seidel ◽  
T. Sattelmayer ◽  
F. Magni ◽  
W. Geng
Keyword(s):  
Flame Front ◽  
Equivalence Ratio ◽  
Flame Stabilization ◽  
Air Injection ◽  
Combustion Stability ◽  
Nox Emissions ◽  
Test Rig ◽  
Lean Blowout ◽  
Burner Exit ◽  
Cooling Air

In most dry low NOx combustor designs of stationary gas turbines the front panel impingement cooling air is directly injected into the combustor primary zone. This air partially mixes with the swirling flow of premixed reactants from the burner and reduces the effective equivalence ratio in the flame. However, local unmixedness and the lean equivalence ratio are supposed to have a major impact on combustion performance. Overall goal of this investigation is to answer the question whether the cooling air injection into the primary combustor zone has a beneficial effect on combustion stability and NOx emissions or not. The flame stabilization of a typical swirl burner with and without front panel cooling air injection is studied in detail under atmospheric conditions close to the lean blowout limit (LBO) in a full scale single burner combustion test rig. Based on previous isothermal investigations a typical injection configuration is implemented for the combustion tests. Isothermal results of experimental studies in a water test rig adopting high speed planar laser-induced fluorescence (HSPLIF) reveal the spatial and temporal mixing characteristics for the experimental setup studied under atmospheric combustion. This paper focuses on the effects of cooling air injection on both flame dynamics and emissions in the reacting case. To reveal dependencies of cooling air injection on combustion stability and NOx emissions, the amount of injected cooling air is varied. OH*-chemiluminescence measurements are applied to characterize the impact of cooling air injection on the flame front. Emissions are collected for different cooling air concentrations, both global measurements at the chamber exit and local measurements in the region of the flame front close to the burner exit. The effect of cooling air injection on pulsation level is investigated by evaluating the dynamic pressure in the combustor. The flame stabilization at the burner exit changes with an increasing degree of dilution with cooling air. Depending on the amount of cooling only a specific share of the additional air participates in the combustion process.

Effects of combustor geometry on the combustion process of an RBCC combustor in high-speed ejector mode

2019 ◽  
Vol 33 (27) ◽  
pp. 1950330
Author(s):  
Taiyu Wang ◽  
Zhenguo Wang ◽  
Zun Cai ◽  
Jian Chen ◽  
Mingbo Sun ◽  
...  
Keyword(s):  
Supersonic Flow ◽  
Flow Field ◽  
Heat Release ◽  
Reaction Mechanisms ◽  
Total Pressure ◽  
High Speed ◽  
Combustion Process ◽  
Numerical Approach ◽  
Combined Cycle ◽  
Chemical Reaction Mechanisms

The combustion characteristics of high-speed ejector mode in a 2-dimensional strut-based RBCC (rocket-based combined cycle) combustor had been investigated numerically in a Mach 2.5 supersonic flow. The numerical approach had been validated by comparing numerical results with available experimental data. Besides, three different hydrogen-air chemical reaction mechanisms had also been compared. The effect of the combustor geometry on the combustion process was then discussed by analyzing the heat release distribution and flow field. It was found that the wall configuration, closeout angle of the converging location and converging ratio all have significant influences on the heat release distribution and flow field structures. It is demonstrated that a converging–diverging wall configuration is beneficial for the combustion process with significant heat release increase compared to the other wall configurations. In addition, the closeout angle of the converging location is also closely related to the combustion performance, and there exists an optimized closeout angle in a specific combustor geometry. It is also revealed that the major heat release region moves upstream obviously with increase in the converging ratio, leading to an enhanced combustion process. However, the converging ratio is still to be optimized to keep a balance between heat release increase and total pressure loss of the supersonic flow.

Numerical investigation on the flow field of a modified vortex spinning system for producing core-spun yarns

2019 ◽  
Vol 89 (19-20) ◽  
pp. 4028-4045
Author(s):  
Zeguang Pei ◽  
Ge Chen
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Swirling Flow ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Secondary Flows ◽  
Wall Region ◽  
The Core ◽  
Spun Yarns ◽  
Bottom Roller

A modified vortex spinning technology, which produces core-spun yarns by means of a tangentially injected swirling airflow, is of great prospect in view of its production rate and yarn structure. In this paper, a numerical study based on computational fluid dynamics is presented to investigate the characteristics of the flow field of this system. In the simulation, the effect of the rotating front rollers on the flow field is taken into consideration. Flow characteristics inside the spinning nozzle, flow field of the front rollers, and streamline patterns have been revealed. The results show that a high-speed swirling flow is generated in the near-wall region in the nozzle chamber due to the ejection of air-jets from the tangential injectors. An asymmetric sub-pressure zone is formed in the core region of the nozzle chamber where the interactions of the high-speed swirling flow and three streams of secondary flows generate three vortices. Airflows in the vicinity of the front rollers generally converge toward the nozzle entrance from all directions except those in the boundary layer of the front roller surfaces, which is helpful for the delivery of fibers into the nozzle. A vortex is formed above the top roller and another beneath the bottom roller. The results of the streamline patterns show that the flow characteristics of the modified vortex spinning can facilitate the formation process of the core-spun yarn, which presents a qualitative explanation to the dynamic behavior of the fibers that was experimentally obtained.

Lean Low NOx Primary Zones Using Radial Swirlers

1988 ◽  
Author(s):  
H. S. Alkabie ◽  
G. E. Andrews ◽  
N. T. Ahmad
Keyword(s):  
Natural Gas ◽  
Recirculation Zone ◽  
Fuel Injection ◽  
Swirling Flow ◽  
Combustion Efficiency ◽  
Flame Stability ◽  
Nox Emissions ◽  
Primary Zone ◽  
Outer Expansion ◽  
Curved Blade

Swirling flow primary zones with between 30% and 60% simulated primary zone air flow were investigated using curved blade radial swirlers. Two radial swirlers were compared with the same open area but different outlet diameters, d, giving different expansion ratios, D/d, from the swirler to the combustor diameter, D. Two combustors were used, 76 mm and 140 mm diameter, the larger one corresponding to the size of several gas turbine can combustors. There was no influence of D/d on the weak extinction. It was demonstrated that an adequate efficiency was not achieved in the weak region until there was a significant outer expansion and associated recirculation zone. It was shown that these systems with central gaseous fuel injection had good flame stability with very low NOx emissions. Propane and natural gas were compared and the NOx emissions were 50% lower with natural gas. The optimum NOx emissions, compatible with a high combustion efficiency, were close to 10 ppm NOx emissions corrected to 15% oxygen.

Experimental and Numerical Investigation of the Flow Field at Radial Holes in High-Speed Rotating Shafts

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Jan Sousek ◽  
Daniel Riedmüller ◽  
Michael Pfitzner
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Discharge Coefficient ◽  
Cross Flow ◽  
Test Rig ◽  
Flow Phenomena ◽  
Rotating Shafts ◽  
Discharge Behavior ◽  
Secondary Air ◽  
Cooling Air

Rotating and stationary orifices are used within the secondary air system to transport sealing/cooling air to its consumers. This paper reports on measurements of the discharge coefficient of rotating radial holes since their aerodynamical behavior is different from that of axial or stationary holes due to the presence of centrifugal and Coriolis forces. A test rig containing two independently rotating shafts was designed in order to investigate the flow phenomena and the discharge behavior of these orifices. The required air mass flow is delivered by a screw compressor and can be independently regulated to supply the inner and outer annular passages of the test rig. It allows for measurements of the discharge coefficient with cross flow and co- and counter-rotating shafts with centrifugal and centripetal flow through the rotating holes. On the outer shaft, absolute and differential pressures and temperatures in the rotating frame of reference are measured via a telemetry system. Measurements of the discharge coefficient for sharp-edged and rounded shaft inserts at a variety of different flow conditions and with swirl added to the air upstream of the orifice are presented. Furthermore, experiments were conducted to quantify the influence of the inner shaft (nonrotating and rotating) on the discharge behavior of orifices in the outer shaft. To complement the data acquired from the experiments and to obtain a better understanding of the flow field near the rotating holes numerical flow simulations were also performed.

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