Vortex Combustor Research Articles

Analyzing the aerodynamic structure of swirl flow in vortex burner models

The article presents the results from experimental and numerical investigations of the parameters characterizing large-scale vortex structures formed in the models of various burners with flow swirling. The experiments included flow visualization and velocity field measurements carried out using a modern contact-less diagnostic system constructed on the basis of a laser Doppler anemometer. In addition, the frequency responses of unsteady vortex flow modes were investigated using dedicated acoustic sensors. The distribution of static pressure induced by an unsteady vortex was obtained using the phase averaging method. Along with experiments, the swirl flow parameters were calculated using an analytic theory and the Star CCM+ commercial software package. The adequacy of the mathematical modeling results was checked by comparing them with the physical experiment data.

Analysis of Acoustics and Vortex Shedding Interactions in Hybrid Rocket Motors

Hybrid rocket engines usually have an aft-mixing chamber to improve combustion efficiency. The presence of a sudden expansion at the exit of the fuel port determines the formation of vortices, whose vigorous burning may drive acoustic waves in the chamber. The shedding of vortices itself is then affected by the flow fluctuations, producing a well-known feedback loop. A reduced-order model is used here to analyze this phenomenon. It is assumed that vortex burning is localized in space and time, and a kicked oscillator model is used. A one-dimensional model proposed by the authors is used to determine the values of the eigenacoustic modes and corresponding damping coefficients. Numerical results are compared with experimental data.

Numerical investigation on flow structures of a laboratory-scale trapped vortex combustor

Flow fields of combustors have been commonly used to help understand combustion characteristics. In this paper, numerical simulations with validated methodology are employed to provide insight of the flow structures of a laboratory-scale trapped vortex combustor (TVC). Turbulence model determination and numerical method validation are accomplished with the help of experimental data from particle image velocimetry (PIV) measurements. A comparison of numerical and experimental results suggests that the standard k–ε turbulence model is able to provide a satisfactory prediction of the flow structures. Both of the two typical cavity flow patterns mentioned are observed: in a plane between two radial struts, the cavity flow features the dual-vortex pattern, however, in a plane along a radial strut, the cavity flow is dominated by the single-vortex pattern. This difference in flow patterns of different planes indicates the difference in cavity stream–mainstream mixing mechanism, which further, is believed to lead to enhanced mixing in spanwise direction.

Trapped Vortex Combustion Chamber: Design and Experimental Investigations Using Hydrogen as Fuel

The design of trapped vortex combustion chamber was undertaken as a part of ongoing research on micro combustion chamber using hydrogen as fuel. The reacting experimental studies were then carried out on the designed chamber. The fuel was injected directly into the cavity. The combustion was first initiated in the cavity with 3 % of the main flow air supplied in reverse direction to the fuel flow. The combustion in cavity was of rich type. Temperature levels in the range of 900 K were encountered in the cavity. Thereafter, diffusion combustion was initiated using the flame generated in the cavity. The temperature levels in this stage were in the range of 1,800 K. The overall pressure drop for a trapped vortex combustor was less than 5 % at all operating parameters.

Numerical study of flame/vortex interactions in 2-D Trapped Vortex Combustor

The interactions between flame and vortex in a 2-D Trapped Vortex Combustor are investigated by simulating the Reynolds Averaged Navier Stokes (RANS) equations, for the following five cases namely (i) non-reacting (base) case, (ii) post-vortex ignition without premixing, (iii) post-vortex ignition with premixing, (iv) pre-vortex ignition without premixing and (v) pre-vortex ignition with premixing. For the post-vortex ignition without premixing case, the reactants are mixed well in the cavity resulting in a stable ?C? shaped flame along the vortex edge. Further, there is insignificant change in the vorticity due to chemical reactions. In contrast, for the pre-vortex ignition case (no premixing); the flame gets stabilized at the interface of two counter rotating vortices resulting in reduced reaction rates. There is a noticeable change in the location and size of the primary vortex as compared to case (ii). When the mainstream air is premixed with fuel, there is a further reduction in the reaction rates and thus structure of cavity flame gets altered significantly for case (v). Pilot flame established for cases (ii) and (iii) are well shielded from main flow and hence the flame structure and reaction rates do not change appreciably. Hence, it is expected that cases (ii) and (iii) can perform well over a wide range of operating conditions.

Effect of cavity-injector/radial-strut relative position on performance of a trapped vortex combustor

Previous works have put forward the key role of radial strut in a trapped vortex combustor (TVC), however, few researches focusing on radial strut can be found in the existing literature so far. The present study is carried out to investigate the effect of the cavity-injector/radial-strut relative position on the performance of a trapped vortex combustor. This effect is directly explored by TVC combustion experiments that are run at atmospheric pressure using RP-3 liquid aircraft fuel. The specific positions include: the inline arrangement, the intermediate arrangement and the staggered arrangement. The staggered arrangement shows remarkable advantages in terms of ignition, lean blow out (LBO) and combustor temperature rise, whereas the inline arrangement performs rather poorly. Numerical simulations with validated methodology of non-reacting flows are then conducted for the purpose to explain the experimental results. The good performance of the staggered arrangement is mainly attributed to the counter-rotating streamwise vortex pair, the high turbulent kinetic energy and turbulent dissipation rate.

I223 小型渦燃焼発電システムに及ぼす未燃混合気予熱の影響

I223 小型渦燃焼発電システムに及ぼす未燃混合気予熱の影響

A comparative study between combustion performances of turbine inter-guide-vane burner and trapped vortex combustor

To improve the performance of aero gas turbine engines, more and more interests have been shown on turbine inter-guide-vane burner based on the ultra-compact combustion concept. To make a universal turbine inter-guide-vane burner, a new concept is proposed using a trapped vortex cavity to replace the high swirling circumferential cavity combustor to address the need to scale the configuration for a larger turbine spool. Three models, including trapped vortex combustor, transition model, and turbine inter-guide-vane burner, are designed. Comparative analysis between combustion performances of three models by using numerical simulation method is carried out. The scale-adaptive simulation turbulence model is used in the simulation process, aiming to reduce the deviation between numerical simulation value and actual value. Finally, the turbine inter-guide-vane burner model is found to be the superior design proposal for turbine inter-guide-vane combustion technology, compared with the other two models.

The Influence of Bluff-Body Structural Parameters and Incoming Velocities on Advanced Vortex Combustor

The influence of bluff-body structural parameters and incoming velocity on the cold flow field of advanced vortex combustor (AVC) has been studied, and the results show that the vortex in cavity can be the most stable and the total pressure loss can be the least when structural parameter is B2/B1=0.7, L/B1=0.8. The incoming velocity should not be too high or too low, it should be combined with specific structural parameters of the combustor, the combustion flame speed, fuel type, and the stoichiometric ratio and other factors. If AVC design is reasonable, the cavity can not only stabilize the flame, but also not be sensitive to the speed changes.

Study of Unsteady Vortical Structures in Axisymmetric Hydrodynamic Chamber

The paper is devoted to experimental and numerical investigation of unsteady vortical processes in the isothermal model of axisymmetric vortex burner. Obtained characteristics of precessing vortex core (PVC) show the dependences of PVC`s frequency on flowrate, swirl number and nozzle`s diameter. Pressure drops inside the chamber also have been measured. Laser Doppler Anemometer (LDA) has been used to explore spatial distribution of mean axial velocity. Numerical simulation has been carried out by using computational fluid dynamic (CFD) program Adapco Star-CCM+. Detached Eddy Simulation approach and Spalart-Allmaras model have been used for calculating the flow. Results of comparison of experimental and numerical data have shown validity of used numerical method. Combination of experimental and mathematical modeling gives the possibility of obtaining detailed information representing comprehensive description of spatially complex unsteady flow with the PVC

Study of Turbulence Characteristics in Different Advanced Vortex Combustor Structure

Based on the idea of single cavity trapped vortex combustor, a advanced vortex combustor which is constitute by three blunt bodies and double concave cavity is proposed. And the interior combustor flow characteristics are analyzed. The results shows that the flow field characteristics changed a lot before and after combustor modification, and D2=20mm, D3=4mm are respectively the best modification scheme on the second and third blunt body.

Retrofitting the operating coal-fired TP-87 and BKZ-320 boilers for vortex fuel combustion technology

Scientific and technical problems concerned with retrofitting the TP-87 boiler installed at the Novokemerovo cogeneration station and operating on Grade 2SS Kuznetsk coal and the BKZ-320 boiler installed at the Novosibirsk TETs-3 cogeneration station and operating on Berezovo coal from the Kansk-Achinsk coal field for vortex combustion technology are addressed. A conclusion is drawn that low-cost retrofitting of obsolete boilers at thermal power stations with retaining the existing boiler unit infrastructure is presently the most reasonable strategy of their further use.

Effects of unstable flame structure and recirculation zones in a swirl-stabilized dump combustor

There has been increased demand in recent years for low NOx gas turbines to meet stringent emission goals by operating in a lean, premixed combustion mode. Unfortunately, detrimental combustion instabilities are often excited within the combustor when it operates under lean conditions, degrading performance and reducing combustor life. To eliminate the onset of these instabilities and develop effective approaches for their control, the mechanisms responsible for their occurrence must be understood. This study addresses structural characteristics of natural gas flames in a lean premixed swirl-stabilized combustor with attention focused on the effect of the formation of recirculation zones and vortex interaction on the combustion instability. To improve our understanding of the role of the recirculation zone and vortex combustion instability, the flame structure was investigated for various mixture velocities, equivalence ratios and swirl numbers. The optically accessible combustor allowed for the laser diagnostics of particle image velocimetry (PIV) measurement, while OH chemiluminescence was used to characterize the flow structure under both cold flow conditions and hot flow combustion conditions. Dynamic pressures were also measured at the same time to investigate characteristics of the combustion phenomenon. We also observed fundamental longitudinal type of combustion instability characteristics related to the instability of thermo-acoustics. The result suggests that the formation of the recirculation zone is strongly related to the occurrence of combustion instabilities.

Mixing Enhancement in a Compact Trapped Vortex Combustor

Previous studies on a single-cavity, compact trapped vortex combustor concept showed good flame stability for a wide range of flow conditions. However, achieving good mixing between cavity products and mainstream flow was still a major challenge. In the present study, a passive mixing enhancement strategy of using inclined struts along with a flow guide vane is presented and experimentally tested at atmospheric pressure conditions. Results show excellent mixing and consequently low values of the combustor exit pattern factor in the range of 0.1 and small flame lengths (5–7 times the main-duct depth). The pressure drop is small in the range of 0.35%, and NOx levels of the order of 1–2 ppm are achieved. The flame stability is excellent, and combustion efficiency is reasonable in the range of 96%. The effectiveness of the proposed strategy is explained on the basis of in-situ OH chemiluminescence images and prior numerical simulations of the resulting complex flow field. The flow guide vane is observed to lead to a counterclockwise cavity vortex, which is conducive to the rise of cavity combustion products along the inclined struts and subsequent mixing with the mainstream flow.

Study on the Flow Characteristics of Transverse Injection in Cavity

The combination of transverse injection and cavity flame stabilizer is a good way to improve the mixing efficiency and flame stability. In order to study the influence of transverse injection on the flow field of cavity in advanced vortex combustor, the turbulence flow and the fuel distribution under the influence of different assignments of jet holes were simulated numerically. The results show that the different assignments of jet holes have a bigger impact on the geometry and center of vortex, but lesser on the total pressure of combustor. The content of fuel reduces quickly in the jet direction, injection can improve the mixing of fuel and air. The phenomenon of mass diffusion and transport is obvious, it is in favor of flame stability.

Experimental Investigation of Airflow Distribution for a Novel Combustor Mode

This paper investigated the airflow distribution performance of the combustor which utilized trapped vortex in the cavity to improve the flame stability. Hole-filling method was used to study trapped vortex combustor airflow distribution at normal temperature and pressure condition. The influence of inlet velocity and mainstream flow-passage height were investigated. The results show that, inlet velocity hardly impacts the airflow distribution of trapped vortex combustor, but chamber height is a key parameter for airflow distribution. The size, number and opening area of the holes in trapped vortex combustor are important to airflow distribution, and increasing cavity back body air flow could bring well lean blowout limit. The research results may serve as a useful reference in further development and engineering application of trapped vortex combustor.

Experimental study of entrainment phenomenon in a trapped vortex combustor

Trapped vortex combustor (TVC) is an advanced low-pollution gas turbine combustor, with the adoption of staged combustion technique. To achieve low-pollutant emission and better combustion performance, the proportion of the air flow in each combustion zone should be precisely determined in the design of the combustor. Due to the presence of entrainment phenomenon, the total air flow in the cavity zone is difficult to estimate. To overcome the measurement difficulty, this study adopts the indirect measurement approach in the experimental research of entrainment phenomenon in the cavity. In accordance with the measurement principle, a TVC model fueled by methane is designed. Under two experimental conditions, i.e. with and without direct air intake in the cavity, the influence of the mainstream air flow velocity, the air intake velocity in the cavity, the height of inlet channel, the structure of holder and the structural proportion of the cavity on entrainment in the cavity is studied, respectively, through experiment at atmospheric temperature and pressure. The results suggest that the air flow velocity of mainstream, the air intake velocity of the cavity and the structure of the holder exert significant influence on the air entrainment, while the influence of structural proportion of the cavity is comparatively insignificant. The square root of momentum ratio of cavity air to mainstream air could be used to analyze the correlation of the entrainment data.

Investigation into the structure of a swirling flow in a model of a vortex combustion chamber by laser doppler anemometry

The structure of an isothermal swirling flow is investigated experimentally in a model of a vortex combustion chamber with a horizontal rotation axis and a distributed input of air-fuel jets. The averaged and pulsation characteristics of the velocity field in various sections of the model are measured using laser Doppler anemometry. The features of internal aerodynamics of a new design of a steam-generator firebox are analyzed.

Dynamic Mode Decomposition for Swirling Jet Flow Undergoing Vortex Breakdown

AbstractSwirling jets undergoing vortex breakdown occur in many technical applications, e.g. vortex burners, turbines and jet engines. At the stage of vortex breakdown the flow is dominated by a conical shear layer and a large recirculation zone around the jet axis. We performed Large‐Eddy Simulations (LES) of compressible swirling jet flows at Re=5000, Ma=0.6 in the high swirl number regime (S=1). A nozzle is included in our computational setup to account for more realistic inflow conditions. The obtained velocity fields are analyzed by means of temporal and spatial dynamic mode decomposition (DMD) to get further insight into the characteristic structures dominating the flow. We present eigenvalue spectra for the case under consideration and discuss the stability behaviour in time and space. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of GOx swirl-injector number in a cold-wall swirl-driven combustion chamber

This paper presents a 3-D numerical study of the innovative cold-wall bidirectional vortex combustion chamber. The aim of the study was to examine the effect of the oxygen gas (GOx) swirl injector number on combustion and wall protection. Firstly, a numerical simulation carried out previously on the same combustion chamber equipped with four GOx swirl injectors was achieved. Then the number of GOx swirl injectors was changed to two and eight, the global oxygen mass flow rate was considered, and its influence was analyzed. Results showed that the GOx swirl injector number of eight improves the combustion process which leads to an increase in the engine-specific impulse. Also, the wall temperature reduction permits more flexibility in material selection that can ensure durability and reduced weight.