Combustor Design Research Articles

A comprehensive study on the design and computational analysis of an air swirl burner

This paper presents a comprehensive study on optimizing the design of a vane-type air swirl burner, along with a computational analysis comparing the combustion of diesel and hydrogen fuel within the same burner. For the combustion simulations, a coupled approach was employed involving a Lagrangian approach with the Discrete Phase Model to track the trajectories of fuel particles providing a comprehensive understanding of the particulate dynamics within the system. This research aimed to analyze hydrogen's potential as a sustainable energy carrier in comparison to its conventional counterparts such as diesel fuel. The results showed that the contours of hydrogen fuel revealed a well-defined and intense flame front whereas it was not the same in the case of diesel fuel which had a less intense flame front.

Pure ammonia flames with high thermal intensities through fuel and air staging under extreme rich-to-lean conditions

Ammonia combustion has gained significant attention due to its high hydrogen content and zero carbon emissions. It poses a challenge for stabilization due to their low energy content and limited flammability range, with the added concern of fuel NOx emissions. In the current study, a novel burner design equipped with four series of reactors is proposed to achieve stable pure ammonia-air flames with reduced NOx emissions. The impact of thermal intensity (∼0.7 MW/m3 to ∼4 MW/m3), number of stages, equivalence ratio (0.5–1.2), and fuel staging on flame stabilization and emissions were investigated in the proposed burner. Comprehensive emissions analysis is performed at various burner levels. Numerical simulations incorporating Large Eddy Simulation (LES) modeling are employed to enhance understanding of the impact of thermal intensity and equivalence ratios on ammonia dissociation, mixedness, and NO emissions. The results indicated that the present burner design improved reactant mixing, and flame stability, reduced NH3 emissions (∼ 0 PPM), and lowered NOx levels in non-premixed ammonia-air flames. The computational and experimental results demonstrated that the implementation of fuel staging is crucial for reducing NOx emissions for the flames with lean global equivalence ratios. Lower NO emissions were identified at a global equivalence ratio of 1.1 for all the considered flames in the range of 0.5–1.2. In the four-stage rich-lean combustion strategy employed in this study; it was observed that higher thermal intensity (4 MW/m3) with fuel staging resulted in lower NOx emissions per kW of energy input compared to lower thermal intensities 0.7 MW/m3. This finding underscores the significance of achieving uniform mixtures and ensuring local flame in rich conditions for achieving low NOx emissions in ammonia combustion. Exhaust gas analysis is conducted at three stages of the burner to enhance the understanding of emissions at various levels of the burner. The proposed combustor design has achieved a substantial reduction in NOx to ∼1 PPM/kW and ∼2.8 PPM/kW with and without fuel staging, respectively. This impressive outcome is attributed to the controlled ammonia consumption facilitated by uniform mixing generated through the use of tangential air inlets.

CARACTERIZACIÓN COMPUTACIONAL DEL USO DE HIDRÓGENO EN UN QUEMADOR DE HORNO, EN EL QUE ACTUALMENTE SE QUEMA GAS NATURAL

The implementation of hydrogen as a fuel in industrial applications is an upward trend, and poses a challenge for the design of furnace burners. This article aims to advance in the knowledge of hydrogen combustion, through numerical simulation using SIEMENS STAR-CCM+ code. Several simulations have been carried out with the geometry of a 2.5 MW burner of the current SIDENOR furnace. The fuel burning there, is natural gas. Using the same geometry and the same mesh, a comparison is made between current temperatures and those that would arise when burning hydrogen, as well as mass fractions of other elements such as NOx. Maintaining the power of 2.5 MW and taking into account the lower heating value of methane and hydrogen, the inlet boundary conditions are calculated for the different fuel compositions. In this way it can be seen, qualitatively, the amount of hydrogen needed to meet the necessary temperatures in the billets, without excessive NOx production. Key Words: Hydrogen, burners, Computational Fluid Dynamics, NOx

Optimization Design of Burner Based on Three-dimensional Simulation of Rotary Kiln Temperature Field

Optimization Design of Burner Based on Three-dimensional Simulation of Rotary Kiln Temperature Field

Ammonia blends for gas-turbines: Preliminary test and CFD-CRN modelling

Ammonia, with its high hydrogen density, cost effectiveness and ease of storage, is emerging as a potential fuel to meet decarbonisation targets in various sectors. However, the combustion of pure ammonia poses challenges due to its low calorific value and reactivity. Existing gas turbine combustion systems, refined over decades with conventional fuels, struggle to maintain comparable flue gas emission concentrations when burning ammonia.Overcoming this challenge requires a paradigm shift in gas turbine combustion, with implications for chemistry and combustor design methodology. Research into the chemical kinetic mechanism for ammonia combustion worldwide reveals differences in flame radical pools compared to methane combustion. The dominant NOx formation mechanism shifts to a "fuel-bound nitrogen" type, which differs from the "thermal" mechanism in hydrocarbon and hydrogen combustion.The integration of chemical reaction rates into Computational Fluid Dynamics (CFD) models with transport equations results in impractical computational times for industrial applications. Therefore, streamlined approaches such as chemical reaction reduction methods are being developed. This involves the construction of lumped parameter models (Chemical Reactor Network - CRN) to identify key parameters that affect species production. A reliable CRN implementation involves the identification of critical volumes using a preliminary CFD approach (CFD-CRN).This paper analyses preliminary experimental tests by Baker Hughes on an industrial burner using different ammonia, hydrogen, and methane fuel mixtures. The NOx results show a different behavior between methane and hydrogen. While the detailed mechanisms behind these results remain open questions, the CFD-CRN modelling approach is adopted. A proposed CRN is investigated for methane, hydrogen, and ammonia blends, providing insight into key parameters and a reasonable physical explanation for the different NOx results. A single calibration parameter (ϕpilot/ϕref) is used to predict accurately NOx emissions using experimental data available from experimental campaign.

국립중앙박물관 소장 청자 투각칠보문뚜껑 향로를 받치는 토끼 조형의 맥락과 함의

This study discusses the symbolism of the rabbit statue on the base of a celadon incense burner with an openwork auspicious-character design lid in the National Museum of Korea. Chapter II analyzes the overall design of the incense burner, pointing out that although the rabbit statue is small in size, it is a three-dimensional figure with detailed carving of each part of the body and inlaid techniques used to express the eyes, making it an important component that embodies artistry beyond a simple base. Chapter III explores the spectrum of perceptions of the rabbit by examining rabbit sculptures from before the Goryeo period. As a symbol of fertility and longevity, thought to be a guide to the quick passage of the souls of the dead to the afterlife, rabbits were attached to funerary urns in the Silla period. They were depicted as moon symbols in Goguryeo tomb paintings and Unified Silla roof-end tiles. In Unified Silla, rabbits were also carved into royal tombs as members of the Twelve Great Deities to show the despotic kingship of the kings guarding the tomb, or were majestically displayed in stupas to represent the authority of Bhaisajyaguru. In Chapter IV, the meaning of the three rabbits supporting the incense burner was derived from three aspects. First, the intention of the rabbit's representation on the incense was inferred from the similarities between the rabbit's self-sacrifice and the offering of incense in The Jataka Tales of the Rabbit's Original Life (Sasa Jataka), which is to burn oneself and offer it to the gods. Since the rabbit was Buddha in the previous life, the life in which he practiced the great act of selflessness, it is believed that the rabbit was chosen to stand alone on the base of the incense burner, even though it does not symbolize absolute physical power. Through this carving of the rabbit, it can be seen that the 12th-century Goryeo people understood the offering of incense and the act of self-sacrifice in the same context. Second, the appearance of rabbits in historical texts and geographical journals from the Three Kingdoms and Goryeo periods was examined. In doing so, the chapter describes who recognized rabbits as auspicious animals in addition to being a symbol in Buddhism. Third, it discusses the internationalization of Goryeo culture, which is reflected in the sculpture of the atlas that supports the top. It is interpreted that the incense burner represents the cosmopolitanism of Goryeo culture because the rabbit statue on the incense burner was arranged in a form similar to the atlas statues popular in ancient Greece, Persia, and India and spread along the Silk Road.

Numerical simulations on the effect of swirler installation angle on outlet temperature distribution in gas turbine combustors

The higher demand for temperature rises and low-pollution combustion methods make it more problematic to regulate the outlet temperature distribution (OTD) of advanced gas turbines. The present investigation tackles the significant challenge of achieving uniform outlet temperature distribution in advanced low-emission gas turbine combustors devoid of dilution holes, a concern that directly impacts the service life of turbine blades. Differing from the reliance on dilution holes characteristic of conventional combustor designs, this study aims to control the OTD by adjusting the installation angles of the swirler blades. To this end, a thorough numerical analysis is conducted to assess the impact of swirler blade angles on the temperature distribution within the combustor. The findings reveal that an elevated swirl number drives the flame front and regions of high temperature toward the downstream section of the combustor. This downstream shift exhibits the dual effect of potentially improving heat exchange due to enhanced mixing and substantially reducing the outlet temperature distribution factor (OTDF). Quantitatively, the obtained results demonstrate that by fine-tuning the swirler blade angles, a reduction in the OTDF by approximately 33.6 % and a decrease in the radial temperature distribution factor (RTDF) by about 20.4 % can be achieved. These reductions represent a substantial improvement in controlling the temperature field inside the combustor, which is crucial for minimizing the thermal load on turbine blades. In summary, the research provides valuable insights into the design of gas turbine combustors, highlighting an innovative approach to achieving more uniform temperature distributions at the outlet without the exploitation of dilution holes. The results of this scrutiny contribute to extending turbine blade life and improving the overall performance of gas turbine systems, thereby advancing the development of environmentally friendly combustion technologies.

Author’s innovative technical solutions in the field of ecology and life safety for use in fuel-burning and ash-collecting devices

The study reviews and recommends fundamentally new technical solutions in the field of ecology and safety in the technosphere, confirmed by patents for inventions and utility models developed by scientists and graduate students of the Department of Technosphere Safety of the Far Eastern State Transport University. Innovative developments that are of practical interest and deserve attention include installations for preparing water-oil emulsions for combustion, energy-saving devices for environmentally friendly combustion of liquid fuels, rational designs of low-toxic gas and oil burners, as well as effective filter-cyclone and group cyclone devices for purification of flue gases from coal and fuel oil boiler and furnace units.

The Structure and Stability of Premixed CH4, H2, and NH3/H2 Flames in an Axially Staged Can Combustor

Abstract An experimental investigation of flame structure, stability, and emissions performance was conducted in a two-stage lab-scale generic combustor design operated with CH4, H2, and NH3/H2 fuel blends. The main flame zone features a premixed bluff body stabilized flame, with a secondary flame zone initiated downstream by injecting premixed air and fuel using two opposing radial jets. The total power and air flowrate are kept constant between the different fueling cases, while the air split between stages and equivalence ratios are varied to explore conditions relevant to gas turbine operation. Given the relative novelty of the configuration, special emphasis is given to analyzing the structure of the opposing jet flames in the secondary stage. In contrast to previous literature on reacting jets in cross flow, these interact significantly due to their proximity, leading to a merged flame zone at the impingement location in the center of the combustion chamber, and some flame propagation upstream of the jet location. As the jet-to-crossflow momentum ratio increases, the merged flame zone changes shape, reaching close to the walls for the methane cases but remaining very compact when operating with almost pure hydrogen. For the hydrogen flames, diverting more air to the second stage allows higher total thermal power conditions to be reached, while avoiding flashback, and eliminates thermoacoustic instabilities. For ammonia-hydrogen flames, air is diverted to the second stage, while a constant fuel flow is sent to the primary stage, resulting in some locally rich conditions in the primary flame. A local minima in terms of NOX occurs when the primary flame is operated at an equivalence ratio of 1.15. Analysis of the flame structure suggests that this state corresponds to almost complete combustion or pyrolysis of NH3 in the main flame, with the remaining hydrogen burned in an inverse diffusion flame in the secondary zone.

Development of a Hydrogen Micro Gas Turbine Combustor: Atmospheric Pressure Testing

Abstract The vision of a carbon-neutral world implies the shift from fossil to clean fuels for combustion-driven processes and machines like gas turbines. Green hydrogen is a promising alternative to substitute natural gas and other fossil fuels. In the H2mGT project, funded by the German BMWK, a microgas turbine (mGT) burner with 100% hydrogen firing is developed and validated. The project is collaboration between Technische Universität Berlin (TUB) and the manufacturer Euro-K GmbH. The project consists of three phases: (1). Atmospheric pressure tests with a fused silica combustion chamber; (2). Atmospheric pressure tests with counterflow-cooled steel combustion chamber and secondary air injection; (3). Validation of the burner in the micro gas turbine at elevated pressure levels. This paper will present the results of Phase 1. The hydrogen burner is based on a swirl-stabilized burner of TUB and was scaled to match the requirements of the mGT with its 130 kW thermal power. The burner design features multiple geometrical parameters to enable the optimization of the flame towards low NOx emissions. Therefore, a variable swirl intensity, additional axial momentum of air in the mixing tube, a movable center-body and different fuel injection locations are implemented. Phase 1 investigates the parameter space in terms of flame stability, operational range, and parameter impact on flame shape and emissions. Therefore, temperature, pressure, and emission measurements as well as OH* imaging are carried out. It is found that the flame can be operated over a large range of equivalence ratios and preheating temperatures up to 500 ∘C for many parameter settings. However, at some configurations, flashback into the mixing tube is triggered. As expected, the NOx emissions are mainly influenced by the equivalence ratio, the fuel distribution, and the swirl intensity. Single-digit emissions are reached up to an equivalence ratio of 0.4 at atmospheric pressure conditions. Furthermore, at low air mass flow, the burner can be operated at 100% natural gas or 100% hydrogen without any geometry changes. The fuel switch, thereby, does not change the NOx emissions significantly if reasonable normalization is used.

Performance of biogas blended with hydrogen in a commercial self-aspirating burner

A natural gas and carbon dioxide fuel mixture was enriched by hydrogen to experimentally measure the performance of a hydrogen and surrogate biogas fuel. The performance of various biogas qualities and hydrogen blend ratios was investigated for use in a commercial self-aspirating burner by quantifying the impact on primary air entrainment, blow-off and flashback limits, NOx emissions, radiant heat transfer and flame appearance. The results showed operating limits of a biogas or hydrogen flame alone could be extended by blending one with the other and by increasing fuel injector size (lowering primary air entrainment), with the latter being more effective. The collateral impact of carbon dioxide and hydrogen addition on radiant heat transfer could be mitigated by increasing injector size, with the carbon dioxide content in biogas maintaining NOx levels at or below the level of natural gas. Overall, there appears to be merit for hydrogen and biogas to operate as a mutually beneficial fuel in a commercial self-aspirating burner design.

Effects of the burner on SiO2 formation and deposition in the OVD process

The burner of outside vapor deposition (OVD) is of great significance for enhancing the yields and quality of the optical fiber preform. This study aims to numerically investigate the effects of the burner on silica particles formation and its corresponding deposition performance in the OVD process. This work is based on our recently developed integrated Eulerian-Eulerian multiphase OVD process model combined with a particle nucleation model. The effects of the distance between the burner and target, the horizontal offset of the target to the burner, the shape of burners, swirl burners as well as double burners are investigated. The results demonstrate that there exists an optimal value for the distance between the burner and target to yield the largest deposition efficiency. However, the deposition efficiency monotonically declines as the horizontal offset of the target to the burner increases. The elliptic burner potentially provides a better match with the target surface for particle deposition. An optimal number of helical vanes installed inside the O2–1 inlet is observed in the counter-swirling burner of O2–1 and H2 inlets, which yields the largest deposition efficiency of 33.4%. Double burners could promote the deposition rate, but could not enhance the particle deposition efficiency. The results provide a deeper understanding of the burner design and OVD process optimization.

Characterisation of turbulent non-premixed hydrogen-blended flames in a scaled industrial low-swirl burner

The performance of a scaled industrial, non-premixed, low-swirl burner design was experimentally investigated for hydrogen addition to natural gas. Two strategies for introducing hydrogen are considered, namely, conserving (i) heat input and (ii) velocity/volumetric flow of the original fuel. This work characterises the effects on key performance metrics of the burner as hydrogen fraction is increased. Compared with natural gas, the results with hydrogen showed a 33 % reduction in the radiant fraction and up to a 380 % increase in NOx emissions. The lift-off height was reduced by a maximum of 23 % and 51 % for addition of 10 and 30 vol% hydrogen addition, respectively, with 100 % cases becoming completely attached to the burner. The influence of hydrogen-addition strategy and air adjustment was shown to be significant with respect to NOx emissions but less significant than the resulting changes in fuel composition and heat input with respect to flame appearance, stability and radiant heat transfer.

Parametric Influence on Rotating Detonation Combustion: Insights from Fast Reactive Euler Simulations

A two-dimensional unsteady reactive Euler solver is employed to model rotating detonation combustion (RDC). A baseline case is chosen, and several combustor geometric and design parameters are varied individually in order to assess their effect on flowfield structure, exhaust flow properties, and performance. The parameters of interest are the perimeter and axial lengths of the combustor annulus, mass flux, outlet throat area, air injector throat area, and equivalence ratio. Quantification of the isentropically available work (IAW) in the exhaust flow is employed as a performance criterion. IAW is primarily affected by mass flux and outlet throat area through the effects of one-dimensional flow and, to a lesser degree, by perimeter and axial length through changes in the fraction of the flow that experiences irreversible shock processing. For all cases in the present study, this fraction appears to be solely determined by the ratio of detonation height to axial length. This ratio is also highly correlated to the angle of the oblique shock and the strength of the flow fluctuations. The predicted wave speed is between 90 and 95% of the Chapman–Jouguet velocity for a range of equivalence ratios between 0.6 and 1.4.

Research on temperature field prediction method in an aero-engine combustor with high generalization ability

Using the inlet flow parameters to get the temperature field of the aero-engine combustor can help researchers quickly learn about the combustion state of the combustor, which is essential to aero-engine combustor design and optimization. This study puts forward a fast-predicting scheme on the temperature distribution of aero-engine combustor by deep learning method. Different networks are trained to gain multiple predicting models, and the prediction performance of temperature field models under different dataset processing methods and different network structures are compared. The results show that both temperature field prediction models constructed by fully-connected networks and fusion convolutional networks have good predictive capabilities. However, when the equivalent ratio conditions deviate significantly from the training dataset, the model performance deteriorates seriously. By introducing reference data to process the dataset, the models’ prediction ability for equivalent ratio conditions far from the training dataset is significantly improved. Further research shows that this data processing method has ability to extrapolate to some extent.

Flow Instability Control in a Model Swirl-Stabilized Combustor with Central Jet Injection

Swirling flows often occur in nature and industrial applications. With an increase in swirl intensity, such rotating flows are known to become unstable and undergo a sudden breakdown of the vortex core, resulting in unsteady flow dynamics with intensive pressure fluctuations. In particular, swirling flows are organized in combustion chambers to stabilize the flame around the central recirculation zone, formed due to the vortex core breakdown. However, the impact of large-scale vortex structures, including the precessing vortex core and secondary helical vortices, on unsteady combustion regimes is still unclear. The present paper demonstrates experimentally that for the swirling flow of a model swirl combustor, the injection of a central jet may be used to alter the configuration of coherent flow structures, including helical vortices. In particular, the asymmetric hydrodynamics mode, associated with the precessing vortex core, is suppressed, whereas the symmetrical one becomes dominant. This effect demonstrates the importance of central jet injection to control the dominant mode of flow instability for the design of swirl combustors.

On the design of a hydrogen micro-rectangular combustor for portable thermoelectric generators

Micro-combustion based thermoelectric generators have been proposed to power micro-electromechanical units. The present study aimed to optimize the thermal design of micro-combustor to best suit the requirement of thermoelectric generators. An equivalent heat transfer coefficient was used to consider the arranged thermoelectric generators and its effect was elucidated. Increasing the coefficient enhances combustor wall heat loss, reducing flame stability and uniformity index of temperature. It is thus impossible to constrain combustor outer wall temperature below the maximum allowable temperature of commercial thermoelectric generators (623K) simply through increasing equivalent heat transfer coefficient. To address this issue, three simple strategies of combustor channel modification, adding copper layer and using flue gas heat recirculation were developed. A notable improvement in uniformity index of temperature over 6.5% is achieved for the latter two strategies. Nevertheless, none of these three strategies can ensure outer wall temperature below 623K. Motivated by the different mechanisms to improve temperature uniformity and reduce wall temperature for the two simple strategies of adding copper layer and using flue gas heat recirculation, a hybrid strategy combining them was proposed. The hybrid strategy can maintain flame stability, improve uniformity index of temperature approach to 100% and control combustor outer wall temperature below 623K, making it a qualified strategy for designing high-performance micro-combustors.

A joint numerical study of multi-regime turbulent combustion

This article presents a joint numerical study on the Multi Regime Burner configuration. The burner design consists of three concentric inlet streams, which can be operated independently with different equivalence ratios, allowing the operation of stratified flames characterized by different combustion regimes, including premixed, non-premixed, and multi-regime flame zones. Simulations were performed on three LES solvers based on different numerical methods. Combustion kinetics were simplified by using tabulated or reduced chemistry methods. Finally, different turbulent combustion modeling strategies were employed, covering geometrical, statistical, and reactor based approaches. Due to this significant scattering of simulation parameters, a conclusion on specific combustion model performance is impossible. However, with ten numerical groups involved in the numerical simulations, a rough statistical analysis is conducted: the average and the standard deviation of the numerical simulation are computed and compared against experiments. This joint numerical study is therefore a partial illustration of the community’s ability to model turbulent combustion. This exercise gives the average performance of current simulations and identifies physical phenomena not well captured today by most modeling strategies. Detailed comparisons between experimental and numerical data along radial profiles taken at different axial positions showed that the temperature field is fairly well captured up to 60 mm from the burner exit. The comparison reveals, however, significant discrepancies regarding CO mass fraction prediction. Three causes may explain this phenomenon. The first reason is the higher sensitivity of carbon monoxide to the simplification of detailed chemistry, especially when multiple combustion regimes are encountered. The second is the bias introduced by artificial thickening, which overestimates the species’ mass production rate. This behavior has been illustrated by manufacturing mean thickened turbulent flame brush from a random displacement of 1-D laminar flame solutions. The last one is the influence of the subgrid-scale flame wrinkling on the filtered chemical flame structure, which may be challenging to model.

Multi-Objective Experimental Combustor Development Using Surrogate Model-Based Optimization

Abstract The majority of premixed industrial gas turbine combustion systems feature two or more separately controlled fuel lines. Every additional fuel line improves the operational flexibility but increases the complexity of the system. When designing such a system, the goals are low emissions of various pollutants and avoiding lean blowout or extinction. Typically, these limitations become critical under different load conditions of the machines. Therefore, it is particularly challenging to develop combustors for stable and clean combustion over a wide operating range. In this study, we apply the Gaussian process regression machine learning method for application to burner development, with the aim of improving the process, which is often driven by a trial-and-error approach. To do so, a special pilot unit is installed into a full-scale industrial swirl combustor. The pilot features 61 positions of fuel injection, each of which is equipped with an individual valve, allowing to modify the fuel–air mixture close to the flame root in various degrees. In fully automatized atmospheric tests, we use the pilot system to train two surrogate models for different design objectives of the combustor, relevant for full load and part load operation, respectively. Once trained, the models allow for prediction for any possible injection scheme. In combination, they can be used to identify pilot injector configurations with an improved operation range in terms of low NOx emissions and part load stability. The adopted multimodel approach enables combustor design specifically for high operational flexibility of gas turbines, but can also be extended to other similar industrial development processes.

A Computational Fluid Dynamics-Based Small-Scale Combustor Design Optimization Utilizing a Many-Objective Evolutionary Algorithm

Abstract This work demonstrates the capability of an open-source autonomous computational fluid dynamics (CFD) metamodeling environment (OpenACME) for optimizing small-scale combustor designs. OpenACME couples several object-oriented programing open-source codes for CFD-assisted design using a decomposition-based many-objective evolutionary algorithm. The CFD is based on steady, incompressible, three-dimensional simulations with k–ω SST RANS and flamelet/progress variable combustion model. There are five unconstrained design variables based on combustor liner dilution hole diameters. The CFD results are compared with existing experimental data in terms of combustion efficiency as a function of severity parameter. The comparison demonstrates that the CFD methods capture combustion efficiency trends. Next, more than 500 combustor designs are evaluated with OpenACME. A Pareto Frontier is generated in terms of combustion efficiency, pattern factor, and total pressure losses. Pseudo-weights are used to select a nondominated Pareto Frontier design point for future fabrication and experimental testing. OpenACME is demonstrated to be a viable tool for small-scale combustor design optimization.