Gas Turbine Combustor Design Research Articles

Comparison of Response Surface Based Preliminary Design Methodologies for a Gas Turbine Combustor

Preliminary design of gas turbine combustor is a multi-objective optimization problem. The methodology to be used at the preliminary design stage depends on the freedom of design choices available. In this article, we explore three preliminary design methodologies for gas turbine combustor - M1: combustion liner design for a given casing; M2: combustion liner design without the casing and M3: coupled design of combustion liner and casing. A workflow for the automated design space exploration of gas turbine combustor using response surface methodology is presented. Computational fluid dynamics studies along with central composite design for design of experiments and genetic aggregation for response surface generation are used to quantify the combustor performance in design space. Comparison of three different design methodologies (M1, M2 and M3) is made to show how the choice of design methodology changes the available design space and limits/expands combustor performance. Candidate optimal designs and associated trade-offs from the optimization study are also presented. This study can aid combustor design engineers choose the most suitable preliminary design methodology for their specific use case.

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.

An FV-EE model to predict lean blowout limits for gas turbine combustors with different structures and sprays

The occurrence of Lean Blowout (LBO) is a disadvantage that endangers a stable operation of gas turbines. A determination of LBO limits is essential in the design of gas turbine combustors. A semiempirical model is one of the most widely used methods to predict LBO limits. Among the existing semiempirical models for predicting LBO limits, Lefebvre’s LBO model and the Flame Volume (FV) model are particularly suitable for gas turbine combustors. On the basis of Lefebvre’s and FV models, the concept of effective evaporation efficiency is introduced in this paper, and a Flame Volume-Evaporation Efficiency (FV-EE) model is derived and validated. LBO experiments are carried out in a model combustor with 23 different structures and 10 different sprays. The prediction uncertainty of the FV-EE model is less than ± 13% for all of these 33 structures and sprays, compared with ± 50% for the FV model and ± 60% for Lefebvre’s model. Furthermore, the prediction uncertainty of the FV-EE model is also less than ± 13% for other combustors from available literature.

The Mathematical Model and Research Progress of the Boundary Layer Flashback in Premixed Combustion

Flashback is a key problem influencing the normal operation of power equipment such as gas turbines. As one of the main mechanisms that cause flashback, the boundary layer flashback has an important effect on the design and operation of gas turbine combustors and other combustion devices. Since the critical gradient model for the boundary layer flashback was put forward by Lewis et al. in 1945, the theoretical models for the boundary layer flashback, such as the Peclet number model, the Damköhler number model and the flame angle theory, were developed one after another. However, these theoretical models still need improvements. Until now, the theoretical models for the boundary layer flashback are still in continuous development and modification. The history of the boundary layer flashback was reviewed, and the background, pertinence and shortcomings of the theoretical models were elucidated in the order of the model establishment time. In addition, the development status and research progress of the theoretical models for the boundary layer flashback in recent years were summarized, especially the progress made with new methods such as numerical simulation and statistical analysis. Further, the theoretical research direction and breakthrough points of the combustion boundary layer flashback at present and in the future were put forward.

Development of an Open-Source Autonomous Computational Fluid Dynamics Meta-Modeling Environment for Small-Scale Combustor Optimization

Abstract This work presents an open-source autonomous computational fluid dynamics (CFD) metamodeling environment (OpenACME) for small-scale combustor design optimization in a deterministic and continuous design space. OpenACME couples several object-oriented programing open-source codes for conjugate-heat transfer, steady-state, multiphase incompressible Reynolds averaged Navier-Stokes CFD-assisted engineering design metamodeling. There are fifteen design variables. Nonparametric rank regression (NPRR), global sensitivity analyses (GSA), and single-objective (SOO) optimization strategies are evaluated. The Euclidean distance (single-objective criterion) between a design point and the utopic point is based on the multi-objective criteria: combustion efficiency (η) maximization and pattern factor (PF), critical liner area factor (Acritical ), and total pressure loss (TPL) minimization. The SOO approach conducts Latin hypercube sampling (LHS) for reacting flow CFD for subsequent local constraint optimization by linear interpolation. The local optimization successfully improves the initial design condition. The SOO approach is useful for guiding the design and development of future gas turbine combustors. NPRR and GSA indicate that there are no leading-order design variables controlling η, pattern factor (PF), Acritical , and TPL. Therefore, interactions between design variables control these output metrics because the output design space is inherently nonsmooth and nonlinear. In summary, OpenACME is developed and demonstrated to be a viable tool for combustor design metamodeling and optimization studies.

Prediction of Thermoacoustic Instability and Fluid–Structure Interactions for Gas Turbine Combustor

Abstract This work simulates a laboratory-scale three-dimensional methane/air burner, which features a bluff body stabilized, lean partially premixed flame experiencing strong limit cycle oscillations. A thin steel liner is installed around the combustion chamber, which heavily interacts with the flow field and produces large amplitude structural deformation via fluid–structure interaction (FSI). An unsteady Reynolds averaged Navier–Stokes (URANS) approach uses the shear stress transport (SST) turbulence model and a flamelet generated manifold (FGM) combustion model to predict the thermoacoustic oscillations in the turbulent reacting flow. The solver also has a built-in finite element structure model, which solves the structural governing equations simultaneously with the computational fluid dynamics (CFD)-computed, finite volume flow equations. This way, a fully coupled, two-way FSI simulation can be performed to predict the thermoacoustic instabilities and the associated solid deformations in the burner. Overall, the predicted strongest pressure oscillation and wall displacement modes (frequency and amplitude) are all in good agreement with the experimental data across different operating conditions. The established workflow may support realistic gas turbine combustor design and prognosis.

Response surface methodology for design of gas turbine combustor

• Automated design space exploration with CFD quantifies combustor performance. • SST - kω turbulence model with partially premixed FGM combustion model used. • Removing blow-off design points improves response surface prediction accuracy by 57.2% • Pareto fronts from multi objective optimization used for trade-off decisions. • Six sigma DOE analysis quantifies uncertainty in combustor performance. Gas turbine combustor design is a complex multi-objective problem. In the present study, parametric design space study and optimization of a gas turbine combustor using computational fluid dynamics (CFD) simulations is presented. Baseline case validation, automated workflow setup for geometry modification, meshing, boundary condition specification, CFD solution and output parameter calculations are discussed. Response surface methodology is used to study combustor performance based on combustion efficiency, pattern factor, total pressure drop, Carbon monoxide (CO) and Nitrogen oxides (NOx) with variations in three design variables: swirl number, secondary hole diameter and dilution hole diameter. We use central composite design for design of experiments (DOE) and genetic aggregation for response surface generation. Design space refinement is carried out to identify the blow-off region and limit the search space for optimal designs to swirl number greater than 0.9. Exclusion of blow-off design points while generating the response surface resulted not only in 57.2% average reduction of root mean square error in the response surface predictions but also smoother trends away from the blow-off region. A candidate optimal design point with swirl number = 1.0, secondary hole diameter = 12.24 mm and dilution hole diameter = 15.26 mm is chosen using multi objective genetic algorithm on the response surface. Finally, uncertainty quantification with six sigma DOE analysis quantifies the confidence intervals for performance parameters based on the variations in geometric design variables. This preliminary design methodology can be used to improve existing combustors and guide the design of novel combustor concepts.

Swirl flow in annular geometry with varying cross-section

Swirling gas flow is an important topic of research that helps in the design of rockets, atomizers,and gas turbine combustors. In the present work, swirl flow inside annular geometries with constant and varying cross-sectional areas are examined using computational fluid dynamics (CFD). Effects of changing the flow and geometric parameters on the swirl behaviour were studied. Reynolds number was found to increase the swirl number in straight and diverging cross-sectional geometries while no significant effect of Reynolds number was observed in converging cross-sectional geometry. Radius ratio, defined as the ratio of the inner to the outer radius of the annular geometry, was found to have a significant effect on the swirl number. Decreasing the radius ratio, in straight and diverging annular geometry decreases the swirl number, however, an opposite trend was observed in the case of converging annular geometry due to significant increase in axial velocity as a result of reduced cross-sectional area. Increasing the swirler vane angle increased the swirl number. At higher vane angles of 60° and 70°, a recirculation zone is developed near the exit of the swirler. Using small cone angles was found to lower the swirl decay rate in converging and diverging nozzles.

On-Design Component-Level Multiple-Objective Optimization of a Small-Scale Cavity-Stabilized Combustor

Abstract This work presents an on-design component-level multiple-objective optimization of a small-scaled uncooled cavity-stabilized combustor. Optimization is performed at the maximum power condition of the engine thermodynamic cycle. The computational fluid dynamics simulations are managed by a supervised machine learning algorithm to divide a continuous and deterministic design space into nondominated Pareto frontier and dominated design points. Steady, compressible three-dimensional simulations are performed using a multiphase realizable k–ε RANS and nonadiabatic flamelet/progress variable combustion model. Conjugate heat transfer through the combustor liner is also considered. There are fifteen geometrical input parameters and four objective functions viz., maximization of combustion efficiency, and minimization of total pressure losses, pattern factor, and critical liner area factor. The baseline combustor design is based on engineering guidelines developed over the past two decades. The small-scale baseline design performs remarkably well. Direct optimization calculations are performed on this baseline design. In terms of Pareto optimality, the baseline design remains in the Pareto frontier throughout the optimization. However, the optimization calculations show improvement from an initial design point population to later iteration design points. The optimization calculations report other nondominated designs in the Pareto frontier. The Euclidean distance from design points to the Utopic point is used to select a “best” and “worst” design point for future fabrication and experimentation. The methodology to perform computational fluid dynamics optimization calculations of a small-scale uncooled combustor is expected to be useful for guiding the design and development of future gas turbine combustors.

On integrated experimentation and simulation of a counter-turning swirling mixer, part I: Experimentation

Success in developing advanced combustor concepts relies significantly on achieving rapid and uniform mixing of fuel with combustion air through a fuel/air preparation device called mixer. To guide the design and development of gas turbine combustor expeditiously, detailed understanding of the flow characteristics and performance of a mixer of interest is essential. Leveraging recent advances in computational fluid dynamics (CFD) and diagnostic techniques, a series of studies have been initiated to develop and calibrate best practices on integrated experimentation and simulation for two generic families of mixers, namely for lean-direct injection and rich-dome combustors. Here, a set of three papers have been prepared to summarize our research activities on a mixer relevant to rich-dome combustors. This Part I paper presents the method by which a high-quality Time-Resolved Particle Image Velocimetry (TR-PIV) two-dimensional velocity dataset is established for a counter-turning multi-swirlers (CTS) mixer. The non-reacting flow field characteristics at 3% pressure drop across this CTS mixer are quantified by collecting more than 10,000 image pairs captured and processed via a high-accuracy sub-pixel adaptive correlation algorithm. Mean and root-mean-square velocity profiles are presented along with quantification of critical flow structure metrics. Proper Orthogonal Deconvolution structure analysis is also presented for the dominant modes. A full description of the uncertainty analysis of the TR-PIV velocity data is further provided, as is a detailed convergence study. The dataset is determined to be of sufficient quality to be used for quantitatively anchoring CFD simulations as summarized in our two companion papers Part II (Reynolds-Averaged Navier-Stokes models) and Part III (Large Eddy Simulation).

Experimental and numerical prediction of lean blowout limits for micro gas turbine combustor

PurposeThe lean blowout (LBO) limit of the combustor is one of the important performance parameters for any gas turbine combustor design. This study aims to predict the LBO limits of an in-house designed swirl stabilized 3kW can-type micro gas turbine combustor.Design/methodology/approachThe experimental prediction of LBO limits was performed on 3kW swirl stabilized combustor fueled with methane for the combustor inlet velocity ranging from 1.70 m/s to 6.80 m/s. The numerical prediction of LBO limits of combustor was performed on two-dimensional axisymmetric model. The blowout limits of combustor were predicted through calculated average exit gas temperature (AEGT) method and compared with experimental predictions.FindingsThe results show that the predicted LBO equivalence ratio decreases gradually with an increase in combustor inlet velocity.Practical implicationsThis LBO limits predictions will use to fix the operating boundary conditions of 3kW can-type micro gas turbine combustor. This methodology will be used in design stage as well as in the testing stage of the combustor.Originality/valueThis is a first effort to predict the LBO limits on micro gas turbine combustor through AEGT method. The maximum uncertainty in LBO limit prediction with AEGT is 6 % in comparison with experimental results.

The Potential of a Multifidelity Approach to Gas Turbine Combustor Design Optimization

Abstract The desire to reduce gas turbine emissions drives the use of design optimization approaches within the combustor design process. However, the relative cost of combustion simulations can prohibit such optimizations from being carried out within an industrial setting. Strategies which can significantly reduce the cost of such studies can enable designers to further improve emissions performance. This paper investigates the application of a multifidelity surrogate modeling approach to the design optimization of a typical gas turbine combustor from a civil airliner engine. Results over three different case studies of varying problem dimensionality indicate that a multifidelity surrogate modeling-based design optimization, whereby the simulation fidelity is varied by adjusting the coarseness of the mesh, can indeed improve optimization performance. These results indicate that such an approach has the potential to significantly reduce design optimization cost while achieving similar, or in some cases superior, design performance.

Ignition Probability and Lean Ignition Behavior of a Swirled Premixed Bluff Body Stabilized Annular Combustor

Abstract An experimental investigation was performed in a premixed annular combustor equipped with multiple swirl, bluff body burners to assess the ignition probability and to provide insights into the mechanisms of failure and of successful flame propagation. The experiments are done at conditions that are close to the lean blow-off (LBO) limit, and hence, the ignition is difficult and close to the limiting condition when ignition is not possible. Two configurations were employed, with 12 and 18 burners, the mixture velocity was varied between 10 and 30 m/s, and the equivalence ratio (ϕ) between 0.58 and 0.68. Ignition was initiated by a sequence of sparks (2 mm gap, 10 sparks of 10 ms each) and “ignition” is defined as successful ignition of the whole annular combustor. The mechanism of success and failure of the ignition process and the flame propagation patterns were investigated via high-speed imaging (10 kHz) of OH* chemiluminescence. The lean ignition limits were evaluated and compared to the LBO limits, finding the 12-burner configuration is more stable than the 18-burner. It was found that failure is linked to the trapping of the initial flame kernel inside the inner recirculation zone (IRZ) of a single burner adjacent to the spark, followed by localized quenching on the bluff body probably due to heat losses. In contrast, for a successful ignition, it was necessary for the flame kernel to propagate to the adjacent burner or for a flame pocket to be convected downstream in the chamber to grow and start propagating upward. Finally, the ignition probability (Pign) was obtained for different spark locations. It was found that sparking inside the recirculation zone resulted in Pign∼0 for most conditions, while Pign increased moving the spark away from the bluff body or placing it between two burners and peaked to Pign∼1 when the spark was located downstream in the combustion chamber, where the velocities are lower and the turbulence less intense. The results provide information on the most favorable conditions for achieving ignition in a complex multiburner geometry and could help the design and optimization of realistic gas turbine combustors.

The design strategy and testing of an efficient microgas turbine combustor for biogas fuel

Nowadays, the design and application of free-carbon emission renewable fuels in micropower generators seem to be interesting to provide decentralized clean, affordable, and resilient energy in developing countries, thereby reaching the 2050 net-zero carbon emission objectives. The operation of micro-scale Closed Cycle Gas Turbine (CCGT) system with these fuels such as biogas without negatively impacting the combustion and micro-turbine performance, should be managed and controlled in the successful design of a micro gas turbine combustor. The application of biogas as a potential fuel due to its low calorific value and impurities, should be made possible in an efficient micro gas turbine combustor design for maintaining NOx emissions, the combustor's ability to light and to tolerate sudden changes in engine load, efficient combustion throughout the engine cycle, and the achievement of the required life. In this work, the efficient design techniques and operation of the 12 [kW] biogas micro-turbine combustor are analyzed and investigated. The designed combustor was manufactured, tested and modeled. Afterward, the emission potential of the designed combustor is discussed and how properly a design scenario for a new fuel should be responded.

Experimental Prediction of Lean Blowout Limits for 3kW Micro Gas Turbine Combustor fuelled with LPG

The Lean Blowout Limit of the combustor is one of the important performance parameters for a gas turbine combustor design. This study aims to predict the total pressure loss and Lean Blowout (LBO) limits of an in-house designed swirl stabilized 3kW can-type micro gas turbine combustor. The experimental prediction of total pressure loss and LBO limits was performed on a designed combustor fuelled with Liquefied Petroleum Gas (LPG) for the combustor inlet velocity ranging from 1.70 m/s to 11 m/s. The results show that the predicted total pressure drop increases with increasing combustor inlet velocity, whereas the LBO equivalence ratio decreases gradually with an increase in combustor inlet velocity. The combustor total pressure drop was found to be negligible; being in the range of 0.002 % to 0.065 % for the measured inlet velocity conditions. These LBO limits predictions will be used to fix the operating boundary conditions of the gas turbine combustor.

Reliable Calculation of Thermoacoustic Instability Risk Using an Imperfect Surrogate Model

Abstract One of the fundamental tasks in performing robust thermoacoustic design of gas turbine combustors is calculating the modal instability risk, i.e., the probability that a thermoacoustic mode is unstable, given various sources of uncertainty (e.g., operation or boundary conditions). To alleviate the high computational cost associated with conventional Monte Carlo simulation, surrogate modeling techniques are usually employed. Unfortunately, in practice, it is not uncommon that only a small number of training samples can be afforded for surrogate model training. As a result, epistemic uncertainty may be introduced by such an “inaccurate” model, provoking a variation of modal instability risk calculation. In the current study, using Gaussian process (GP) as the surrogate model, we address the following two questions: First, how to quantify the variation of modal instability risk induced by the epistemic surrogate model uncertainty? Second, how to reduce the variation of risk calculation given a limited computational budget for the surrogate model training? For the first question, we leverage on the Bayesian characteristic of the GP model and perform correlated sampling of the GP predictions at different inputs to quantify the uncertainty of risk calculation. We show how this uncertainty shrinks when more training samples are available. For the second question, we adopt an active learning strategy to intelligently allocate training samples such that the trained GP model is highly accurate particularly in the vicinity of the zero growth rate contour. As a result, a more accurate and robust modal instability risk calculation is obtained without increasing the computational cost of surrogate model training.

Effects of superheated steam on combustion instability and NOx emissions in a model lean premixed gas turbine combustor

This study experimentally explored the effects of preheated steam on combustion instabilities and NOx emissions in a lean-premixed model gas turbine combustor. Three variables were investigated to confirm the effectiveness of preheated steam injection on combustion instability and NOx emissions—the steam flow rate, the injection heights and the inner diameter of injectors. Experimental results denote that optimal the damping ratio of sound pressure can reach 91.73% with preheated steam dilution, the amplitude of sound pressure reduced from 46 Pa to 3.8 Pa. The optimal damping ratio of NOx emissions can reach 83.74% with preheated steam dilution, concentration of NOx emissions reduced from 24.6 ppm to 4.0 ppm. Mode shifting of thermoacoustic instability is appeared as the inner diameter of the injector varied from 1.5 mm to 4.0 mm. The oscillation frequency of the flame CH* chemiluminescence suddenly drops from 256 Hz to 74 Hz as the inner diameter changes from 2.0 mm to 2.5 mm. The lower the relative height of the superheated steam injectors, the better the control effect of combustion instability and NOx emission. However, unreasonable design of the steam injector will trigger thermoacoustic instability. The flame roots, fronts and recirculation zones are all changed under preheated steam, the whole flame become short and compact. The flame length reduced from 75 mm to 37 mm while the preheated steam flow increases. This study explored the dilution effects of preheated steam on lean premixed combustion instability and NOx emissions, the results could be conducive to the design of clean, safe and high-efficient gas turbine combustors.

Multi-fidelity modelling of an impingement/effusion cooled gas turbine combustor liner

The design of gas turbine combustors is an iterative process which is often limited by the available modelling tools. While high degrees of modelling accuracy have been achieved using high fidelity tools, these are computationally expensive and not appropriate for design space exploration. By contrast, reduced order models carry low computational expense, but cannot fully reconstruct the combustion problem which spans multiple branches of physics and is characterised by 3D phenomena. As a result, empirical correlations are often relied upon, but these limit the designer to a narrow range of validity, preventing the exploration of novel design solutions.To facilitate the design of new low emissions combustors, for which empirical models are not valid, a multi-fidelity design process has been followed. In this process, physics-based low order models are built; calibrated by high fidelity simulations and then used in multi-objective optimisation studies. This provides detailed insight early in the design process, leading to more fruitful optimisation studies and a shorter design cycle. This approach has been successfully demonstrated on other turbomachinary sub-systems, but has not yet been applied to combustors using publicly available methods.In the current work, the multi-fidelity design process is demonstrated on the design and analysis of an impingement/effusion cooling layout for a lean direct injection combustor liner. A novel mutli-fidelity methodology was followed which used only publicly available methods. By following this approach, an indication of liner wall temperature distributions could be obtained very early in the design process, prior to any prototyping or testing. As such, applying a mutli-fidelity design approach to gas turbine combustors was shown to be both feasible and beneficial.The results from the high fidelity simulations were compared to those of the low order model, revealing a number of discrepancies due to physics not captured - most notably a strong interaction between the swirling flow and liner wall. These detailed interactions resulted in failure of the initial cooling layout, leading to the liner exceeding its limit temperature by 10%. Inclusion of models to predict these phenomena have been recommended to improve the low order code fidelity. In doing so, the multi-fidelity modelling loop will be closed, yielding a more capable design code to be used for executing design space exploration.

Research on Simulation and Planning of Combustion Chamber in Gas Turbine

A gas turbine is an internal combustion power machine that drives the impeller to rotate at a high speed with a continuous flow of gas as the working medium, and converts the energy of the fuel into useful work. Nowadays, all developed countries attach great importance to the development of gas turbines, and the combustion chamber of the gas turbine is an important part of it. If the combustion chamber is properly optimized, the combustion efficiency will be greatly improved. The change of the number of blades of the gas turbine will have a great influence on the combustion effect inside the combustion chamber. In this paper, the gas turbine blade values are modified to study its influence on the combustion chamber flow field characteristics and methane mixing characteristics. Finally, when other conditions are constant, the larger the value of the blade, the more conducive to the formation of the return zone of the combustion chamber and the mixing of gas, and the better the combustion effect in the combustion chamber. This study also provides a reference for the design of gas turbine combustor.

Generation characteristics of thermal NOx in a double-swirler annular combustor under various inlet conditions

The NOx emission of gas turbine is a key factor of air pollution. It is still a challenge to realize low-NOx generation for all the gas turbines with diverse types of combustors and operation schemes. In this study, a three-dimensional simulation of the internal flow and combustion in a double-swirler annular combustor of a heavy-duty gas turbine was carried out. The realizable k-ε turbulent model and finite rate/eddy dissipation combustion model were employed for the numerical calculation. The effects of the swirl number and temperature of the inlet premixed gas flow on the thermal performance and the relationship between the velocity-temperature field synergy and the thermal NOx formation were investigated on the basis of field synergy principle. The results indicated that the change of the outer swirl number had a greater impact on thermal NOx generation than the change of the inner swirl number. The velocity-temperature field synergy in the combustor became better as the inlet swirl number or the inlet gas temperature increased. This synergy had a correlation with the thermal NOx generation. The formation rate of thermal NOx in the combustor should be controlled with the optimized velocity-temperature field synergy rather than the sole reduction of inlet gas temperature by considering the required thermal uniformity and capacity. The adopted field synergy is a promising concept to evaluate the thermal related performance of combustor. The obtained results on the generation characteristics under various inlet conditions may guide the design and operation of gas turbine combustors.