Dry Low NOx Research Articles

Power augmentation and Ramp-Up rate improvement through compressed air Injection: A dry low NOx combustor CFD analysis

Gas turbines play a key role in accelerating the transition towards more environmentally friendly power generation. This role includes backup of renewable generation that is intermittent, providing grid inertia as well as other ancillary services for grid stability. For quick backup power, the ramp-up rate of gas turbines can be improved through air injection at the back of the compressor, facilitated by integrating compressed air energy storage. Published works have mostly focused on low-fidelity engine system analysis of air injection overall effects. No study has focused on the detailed combustor performance presented in this study. The work shows the impact of air injection on the emissions, thermoacoustic stability and liner wall durability. These yardsticks in assessing the operability of the combustor have also been used for air power augmentation and ramp-up analysis. ANSYS software was used in the computational fluid dynamics (CFD) analysis of the three-dimensional dry low NOx combustor. Low-order models were used for the thermoacoustic stability and durability analysis. For the power augmentation study, the NO and CO emissions produced at 15 % air injection are below the maximum values of the combustor in design operations. Also, the stability and durability were within limits. The ramp-up investigation indicates up to 10 % air injection is allowed and the emissions are similarly acceptable. However, the thermoacoustic analysis shows a potential for combustion instabilities at high frequencies above 1800 Hz. Generally, there was no unusual wall liner durability in these two studies. When benchmarked against previous engine-level analysis, the ramp-up rate can be potentially improved by 54 % if the small concern on thermoacoustic instability is resolved.

Minimum environmental load extension through compressed air extraction: Numerical analysis of a dry low NOx combustor

The operational flexibility of gas turbine (GT) engines is a key requirement to coexist alongside increasing renewable energy that is often intermittent. One of the GT flexibility criteria is the Minimum Environmental Load (MEL). This is the lowest load the engine can be operated, without infringing on emissions limits (particularly CO) and is relevant to periods when there is a priority to renewable generation or low power demand. This study along with a series of related works of the authors proposes compressor air extraction for MEL extension. Here, a stand-alone three-dimensional numerical dry low NOx combustor demonstrates the technical viability concerning combustor performance and emissions. In addition, supplemented with low-order models for durability and stability evaluations. For the first time, there is evidence to show that the combustor can handle the 18% compressed air extraction to sustain a new MEL. This operation is characterised by a 12.3% reduction in CO through an increase of the fuel split ratio by 2% after design exploration cases. However, at the expense of a smaller overall rise in NO emissions by 5%. The durability analysis focused on the wall liner temperature assessments, which show no unusually high temperature rise for the new MEL. Similarly, the thermoacoustic instability frequencies and gains are around the normal operation mode. When benchmarked against previous related engine-level analysis, the evidence shows that the new MEL is a 7% points reduction of load.

Stability and emission characteristics of ammonia-air flames in a lean-lean fuel staging tangential injection combustor

The present work suggests the stability and emission characteristics of an ammonia-air tubular flame in a fuel staging tangential injection combustor. Owing to the development of a large inner recirculation zone induced by a high swirling motion, the ammonia tubular flame exhibited wide operational flexibility at an ambient temperature condition. With ammonia fuel staging, we confirmed that the Thermal DeNOx process significantly mitigates NO emissions when the exit temperature of the primary region is close to the threshold for active NO reduction. In this study, fuel multi-stage technology was used for pure ammonia-air combustion, and the result effectively challenges the existing paradigm of the NO reduction strategy: Rich-Quench-Lean staging configuration. Thus, our results demonstrate the potential use of ammonia as a fuel in a dry low-NOx system.

Experimental and Numerical Investigation of the Non-Reacting Flow in a High-Fidelity Heavy-Duty Gas Turbine DLN Combustor

A dry, low-NOx (DLN) combustor for a heavy-duty gas turbine using lean premixed technology was studied. A high-fidelity test model was built for the experimental study using particle image velocimetry (PIV). The non-reacting flow in the DLN combustion chamber was investigated experimentally and numerically. The numerical results are in good agreement with the experimental data. The results show that recirculation zones were formed downstream of each swirl nozzle and that the flow pattern in each section was self-similar under different working conditions. For two adjacent swirl nozzles with opposite swirling directions, the entrainment phenomenon was present between their two flows. The two flows gradually mixed with each other and obtained a higher speed. If the two adjacent swirl nozzles had the same swirling direction, then the mixing of the two flows out of the nozzles was not present, resulting in two separate downstream recirculation zones. The interaction of swirling flows out of different nozzles can enhance the turbulent fluctuation inside the combustion chamber. Based on the analysis of the recirculation zones and turbulent kinetic energy (TKE) distribution downstream of each nozzle, it can be found that nozzle coupling results in stronger recirculation and turbulent mixing downstream counterclockwise surrounding nozzles.

Evolution of N2O production at lean combustion condition in NH3/H2/air premixed swirling flames

In the development of ammonia - hydrogen blends as potential substitutes for fossil fuels, the retrofitting of existing devices running at very lean condition is one of the promising solutions for decarbonisation of the power sector. However, little is known about the impact of these conditions on the production of NOX, particularly N2O that is a potent greenhouse gas. Therefore, the influence of varying thermal power and Reynolds numbers on the flame and emission characteristics, especially N2O, of ammonia-hydrogen-air swirling flames has been evaluated for the first time through the use of spatially resolved OH*, NH* and NH2* chemiluminescence, spectrometry analyses and advanced emissions characterisation at a fixed lean equivalence ratio, Φ = 0.65, representative of the Dry Low NOX (DLN) approach in traditional stationary gas turbines. NO and NO2 emissions were found to be decreasing (from ∼ 5000 ppmv to ∼ 1000 ppmv; NO and from ∼ 150 ppmv to ∼ 50 ppmv; NO2) with increasing ammonia content (from 50% to 90%) in the fuel while N2O followed reverse trends (from ∼ 50 ppmv to ∼ 200 ppmv). More than 80% ammonia content in the fuel blends exhibited high amounts of unreacted ammonia fractions (∼ 100 to ∼ 1200 ppmv), which can be potentially linked to flame instability and/or low temperatures. Furthermore, any increasing or decreasing trends in NOX with ammonia fraction were made more extreme by increasing thermal power or Reynolds number due to the differences in relevant radicals (NH, OH, NH2 etc.) formation in the flames. Experimental results suggest the unviability of these blends at the conventional lean conditions utilised at the DLN power applications due to excessive NOX emissions. Detailed sensitivity analyses of N2O concentration at the flame and post flame zone has been carried out utilising Ansys Chemkin-PRO to identify and investigate the reactions responsible for N2O formation/consumption in the experimental flames. Results have identified the reaction NH + NO ↔ N2O + H as the major source of N2O production in the flame, while the reactions N2O + H ↔ N2 + OH and N2O(+M) ↔ N2 + O(+M) are responsible for N2O consumption at the post flame zone, with higher reactivity for the latter reaction at longer residence time and relatively lower temperatures.

Expression of Concern: Modeling of a Dry Low NOx burner with the aid of a three-dimensional computational fluid dynamics simulation

Expression of Concern: Modeling of a Dry Low NOx burner with the aid of a three-dimensional computational fluid dynamics simulation

100% Hydrogen Dry Low NOx Combustor Developments for 2MW Class Gas Turbine and Combined Heat and Power Supply Demonstration

100% Hydrogen Dry Low NOx Combustor Developments for 2MW Class Gas Turbine and Combined Heat and Power Supply Demonstration

Numerical Study of Radiation and Fuel–Air Unmixedness on the Performance of a Dry Low NOx Combustor

Abstract The development of gas turbine combustors is expected to consider the effects of radiation heat transfer in modeling. However, this is not always the case in many studies that neglect this for adiabatic conditions. The effect of radiation is substantiated here, concerning the impact on the performance, mainly the emissions. Also, the fuel–air unmixedness (mixing quality) influenced by the combustor design and operational settings has been investigated with regard to the emissions. The work was conducted with a Mitsubishi-type dry low NOx combustor developed and validated against experimental data. This 3D computational fluid dynamics study was implemented using Reynolds-averaged Navier Stokes simulation and the radiative transfer equation model. It shows that NO, CO, and combustor outlet temperature reduce when the radiative effect is considered. The reductions are 17.6% and below 1% for the others, respectively. Thus, indicating a significant effect on NO. For unmixedness across the combustor in a non-reacting simulation, the mixing quality shows a direct relationship with the turbulence kinetic energy (TKE) in the reacting case. The most significant improvements in unmixedness are shown around the main burner. Also, the baseload shows better mixing, higher TKE, and lower emissions (particularly NO) at the combustor outlet, compared to part-load.

Reacting Flow Characteristics and Multifuel Capabilities of a Multi-Nozzle Dry Low NOx Combustor: A Numerical Analysis

The fluctuating quality of natural gas (NG) in Peninsular Malaysia (PM) makes it challenging for the gas turbine (GT) combustor to meet the combustion performance requirements from the Original Equipment Manufacturer (OEM). Moreover, the gas quality sensitivity is more apparent in modern dry low NOx (DLN) combustors. Many of the prior combustion investigations were conducted on a modest scale in the laboratory. In actuality, combustion characterizations in complicated DLN combustors are more valuable to the power generation sector. Hence, the current numerical analysis utilized the RANS formulation and a detailed chemistry to examine the impact of ethane (C2H6), carbon dioxide (CO2), and nitrogen (N2) proportions in NG on combustion characteristics in a multi-nozzle DLN (MN-DLN) combustor, with the support of Modified Wobbe Index (MWI) calculations. Validations were performed using the combustor outlet temperature (COT) from the power plant where the actual MN-DLN combustor is operated, which revealed less than 10 % discrepancy. Qualitative validations were carried out by comparing the burn trace from the actual combustor wall to the predicted results, revealing an adequate Structural Similarity Index (SSIM) of 0.43. From numerical results of flame fronts and COTs, the addition of 20 % diluents (CO2 and N2) to NG demonstrated the blowoff risk. When MWIs of Kerteh and the JDA (major NG resources) were used as baselines, MWI ranges of all NG compositions under study surpassed the OEM’s ± 5 % limit. The increase in CO2 proportion results in a wide MWI range, especially when Kerteh is used as the baseline. Therefore, any GTs in PM that have previously been calibrated to use Kerteh's NG are more likely to have combustion instabilities if CO2 levels in NG suddenly increase. The higher MWI range backs up the current numerical results that showed the deleterious effects of a high CO2 composition throughout the combustor firing process. However, increasing the amount of C2H6 by up to 20 % is predicted to have minor effects on combustion characteristics. Overall, the validated numerical model of the MN-DLN combustor provided critical information about combustion characteristics and multifuel capabilities in respect to the NG quality in PM.

Stratified and Hydrogen Combustion Techniques for Higher Turndown and Lower Emissions in Gas Turbines

Abstract This review overviews combustion technologies for reduced emissions and better fuel economy in the industrial gas turbine. Lean premixed combustion (LPM) technology is introduced as a low-temperature combustion technique to control NOx emissions. The dry low NOx (DLN) is one of the most promising LPM-based combustors for controlling NOx emissions. However, DLN combustors suffer from limited flame stability, especially under low load (near blowout) operating conditions, in addition to the difficulty of separating CO2 from the exhaust stream for reducing the gas-turbine carbon footprint. Trying to overcome such difficulties, the gas turbine manufacturers developed enhanced-design burners for higher turndown and lower NOx emissions, including the Dual Annular Counter Rotating Swirl (DACRS) and environmental-vortex (EV) burners. The volume of the DACRS combustors is almost twice the conventional burners, which provide ample residence time for complete combustion. The mixing effectiveness is improved in EV-burners resulting in higher flame stability at low load or startup conditions. To widen the operability, control the emissions, and improve the turndown ratio of gas turbine combustors, the concept of flame stratification, i.e., heterogenization of the overall equivalence ratio, was introduced. This technique can widen the stability range of existing LPM flames for industrial applications. Integrating stratified combustion techniques with oxy-fuel combustion technology is a way forward that may result in complete control of gas turbine emissions with a higher operability turndown ratio. The recent developments and challenges toward the application of hydrogen gas turbines are introduced.

Scaling of an Aviation Hydrogen Micromix Injector Design for Industrial GT Combustion Applications

Decarbonising the energy grid through renewable energy requires a grid firming technology to harmonize supply and demand. Hydrogen-fired gas turbine power plants offer a closed loop by burning green hydrogen produced with excess power from renewable energy. Conventional dry low NOx (DLN) combustors have been optimized for strict emission limits. A higher flame temperature of hydrogen drives higher NOx emissions and faster flame speed alters the combustion behavior significantly. Micromix combustion offers potential for low NOx emissions and optimized conditions for hydrogen combustion. Many small channels, so-called airgates, accelerate the airflow followed by a jet-in-crossflow injection of hydrogen. This leads to short-diffusion flames following the principle of maximized mixing intensity and minimized mixing scales. This paper shows the challenges and the potential of an economical micromix application for an aero-derivative industrial gas turbine with a high-pressure ratio. A technology transfer based on the micromix combustion research in the ENABLEH2 project is carried out. The driving parameter for ground use adaption is an increased fuel orifice diameter from 0.3 mm to 1.0 mm to reduce cost and complexity. Increasing the fuel supply mass flow leads to larger flames and higher emissions. The impact was studied through RANS simulation and trends for key design parameters were shown. Increased velocity in the airgates leads to a higher pressure drop and reduced emissions through faster mixing. Altering the penetration depth shows potential for emission reduction without compromising on pressure loss. Two improved designs are found, and their performance is discussed.

100% hydrogen dry low NOx combustor developments for 2MW class gas turbine

100% hydrogen dry low NOx combustor developments for 2MW class gas turbine

An overview on dry low NOx micromix combustor development for hydrogen-rich gas turbine applications

The paper presents a survey of the interactive optimization cycle at Aachen University of Applied Sciences, used for the development of a new low emission Micromix combustor module for application in hydrogen fueled industrial gas turbines. During the development process, experimental and numerical methods are applied to optimize a given baseline combustor with 0.3 mm nozzles with respect to combustion efficiency, combustion stability, higher thermal power output per nozzle and reduced manufacturing complexity.Within the described research cycle combustion and flow simulations are used in the context of parametric studies for generating optimized burner geometries and the phenomenological interpretation of the experimental results. Experimental tests, carried out on an atmospheric combustion chamber test stand provide the basis for validation of simulation results and proof of the predicted combustion characteristics under scaled down gas turbine conditions.In the presented studies, an integration-optimized Micromix combustor with a nozzle diameter of 0.84 mm is tested at atmospheric pressure over a range of gas turbine operating conditions with hydrogen fuel. The combustor module offers an increase in the thermal power output per nozzle by approx. 390% at a significant reduced number of injectors when compared to the baseline design. This greatly benefits manufacturing complexity and the robustness of the combustion process against fuel contamination by particles.During atmospheric testing, the optimized combustor module shows satisfactory operating behavior, combustion efficiency and pollutant emission level. Within the evaluated operating range, which correlates to gas turbine part-, full- and overload conditions, the investigated combustor module exceeds 99% combustion efficiency. The Micromix combustor achieves NOx emissions less than 2.5 ppm corrected to 15 Vol% O2 at the design point.Based on numerical analyses and experimental low pressure testing, a full-scale gas turbine combustion chamber is derived. High pressure testing in the auxiliary power unit Honeywell/Garrett GTCP 36–300 shows stable operation during acceleration of the engine, during IDLE and during load variations between IDLE and Main Engine Start (MES) mode. Throughout the investigated operating range, the combustion chamber generates low NOx emissions under full-scale gas turbine conditions.

Numerical and Experimental Evaluation of a Dual-Fuel Dry-Low-NOx Micromix Combustor for Industrial Gas Turbine Applications

Abstract The dry-low-NOx (DLN) micromix combustion technology has been developed originally as a low emission alternative for industrial gas turbine combustors fueled with hydrogen. Currently, the ongoing research process targets flexible fuel operation with hydrogen and syngas fuel. The nonpremixed combustion process features jet-in-crossflow-mixing of fuel and oxidizer and combustion through multiple miniaturized flames. The miniaturization of the flames leads to a significant reduction of NOx emissions due to the very short residence time of reactants in the flame. The paper presents the results of a numerical and experimental combustor test campaign. It is conducted as part of an integration study for a dual-fuel (H2 and H2/CO 90/10 vol %) micromix (MMX) combustion chamber prototype for application under full scale, pressurized gas turbine conditions in the auxiliary power unit Honeywell Garrett GTCP 36-300. In the presented experimental studies, the integration-optimized dual-fuel MMX combustor geometry is tested at atmospheric pressure over a range of gas turbine operating conditions with hydrogen and syngas fuel. The experimental investigations are supported by numerical combustion and flow simulations. For validation, the results of experimental exhaust gas analyses are applied. Despite the significantly differing fuel characteristics between pure hydrogen and hydrogen-rich syngas, the evaluated dual-fuel MMX prototype shows a significant low NOx performance and high combustion efficiency. The combustor features an increased energy density that benefits manufacturing complexity and costs.

Experimental and Numerical Investigations of Novel Natural Gas Low NOx Burners for Heavy Duty Gas Turbine

A novel dry low-NOx gas turbine technology requires well-balanced assessments since the early development phases. The weak knowledge of often conflicting aspects, such as operability and manufacturability, make any roadmap difficult to be drawn. Introduction of innovative manufacturing technologies such as the direct metal laser sintering (DMLS) process allows rapid manufacturing of components and test them in dedicated facilities to support real-time development of new products. The use of such a manufacturing process allows the adoption of designed experiment-based development strategies, which are still uncommon at industrial level, due to the reduced time from drawings to test.The paper describes a reactive test campaign performed by BHGE in cooperation with University of Florence, aimed at the exploration of capabilities of different innovative burners in terms of pollutant emissions containment and blow-out margin. In particular, the test campaign has been conceived to provide a robust estimate of the effects of key geometrical parameters on principal burner performances. The flame stabilization mechanism of the investigated burners is based on the swirling flow generated by different setup of two internal channels: corotating and counter-rotating radial and axial swirlers. The effect of both the shape and the size of the internal air passages, as well as of the swirler characteristics, has been matter of investigation. Burners were tested in a single-cup test rig operated at moderate pressure conditions (up to 6 bar), with two levels of preheated air temperature (300 °C and 400 °C). Each burner was equipped with two natural gas feeding lines representing the diffusion (pilot) and premixed (main) fuel supplies: both lines were regulated during tests to assess the effect of fuel split on emissions and to identify a stable low-NOx operating window, within which a lean blow-out test was performed. Dynamic pressure probes were used to evaluate the onset of combustion instabilities. The burner development was supported by computational fluid dynamics (CFD) investigations with the purpose to have a detailed understating of the flow-field and flame structure and to perform a preliminary screening to select the most promising solutions for the testing phase. The post process of the experimental results has allowed to correlate the main design parameters to burner performance variables discovering possible twofold optimizations in terms of emissions and operability.

Hybrid Model for on-line Detection of Gas Turbine Lean Blowout Events

Modern dry low NOx combustors can target very low emissions levels by operating at a lean air/gas ratio. However, ultra-lean combustion is extremely susceptible to thermoacoustic combustion instabilities and Lean Blowout (LBO), which can lead to large pressure oscillations in the combustor and decreased durability of components. Conventional on-board diagnostics embedded in the Unit Control Panel (UCP) of a Gas Turbine, continuously check the health status of the combustion section at a high scan rate and raise alarms when abnormal conditions occur. While ensuring protection and control, UCP control logics may not provide precise indications on the nature of the issue and further troubleshooting, also using specific tools, is typically required. In a changing environment where Industrial Internet of Things (IIoT) is offering a chance to drive productivity and growth, online Monitoring and Diagnostic (M&D) software and services on connected units are becoming strategic to increase asset availability and reliability, as well as reducing maintenance costs. In this paper, we present a hybrid analytic, which combines physics-based and data-driven models, for the detection of Lean Blowout conditions on Gas Turbines equipped with Dry Low NOx multi-can combustion system. Regarding the data-driven model, we face a problem of classification and exploit dimensionality reduction to reduce the number of variables under consideration. During the development, different techniques are tested and benchmarked. The analytic is trained on real LBO events and finally is deployed in a production environment to process incoming on-line data acquired from monitored units. Obtained results are presented.

Comparison of Numerical Combustion Models for Hydrogen and Hydrogen-Rich Syngas Applied for Dry-Low-Nox-Micromix-Combustion

The Dry-Low-NOx (DLN) Micromix combustion technology has been developed as low emission combustion principle for industrial gas turbines fueled with hydrogen or syngas. The combustion process is based on the phenomenon of jet-in-crossflow-mixing (JICF). Fuel is injected perpendicular into the air-cross-flow and burned in a multitude of miniaturized, diffusion-like flames. The miniaturization of the flames leads to a significant reduction of NOx emissions due to the very short residence time of reactants in the flame. In the Micromix research approach, computational fluid dynamics (CFD) analyses are validated toward experimental results. The combination of numerical and experimental methods allows an efficient design and optimization of DLN Micromix combustors concerning combustion stability and low NOx emissions. The paper presents a comparison of several numerical combustion models for hydrogen and hydrogen-rich syngas. They differ in the complexity of the underlying reaction mechanism and the associated computational effort. The performance of a hybrid eddy-break-up (EBU) model with a one-step global reaction is compared to a complex chemistry model and a flamelet generated manifolds (FGM) model, both using detailed reaction schemes for hydrogen or syngas combustion. Validation of numerical results is based on exhaust gas compositions available from experimental investigation on DLN Micromix combustors. The conducted evaluation confirms that the applied detailed combustion mechanisms are able to predict the general physics of the DLN-Micromix combustion process accurately. The FGM method proved to be generally suitable to reduce the computational effort while maintaining the accuracy of detailed chemistry.

EMISSION INTENSITY AND ABATEMENT COST OF FOSSIL FUEL POWER PLANTS IN THAILAND

Monitoring of air emission and pollution control cost is a key to improve air quality management of electricity generation industry. This research comprehensively evaluates abatement cost of sulfur dioxide (SO2), nitrogen oxides (NOx), emission intensity and emission inventory of sulfur dioxide (SO2), nitrogen oxides (NOx), particulate matter (PM), and carbon dioxide (CO2) emitted from Thailand s fossil fuel power plants. The research applied bottom-up approach with continuously monitored data from 64 percent of Thailand electricity generation industry. The data was used in an evaluation of emission intensity according to technology, fuel type and pollution control system. The research finding indicates that lignite-fired power plants are the major contributors of air pollution in Thailand. The research results will help in improving performance of emission forecast and monitoring via usage of site-specific emission factors. Air emission factors from power plants were found to be 0.022 1.432 g-SO2/kWh, 0.122 5.229 g-NOx/kWh, 0.031 g-PM/kWh, and 452 1,443 g-CO2/kWh. The cost for SO2 reduction from fossil fuel-based power plants are estimated to be 0.03-0.26 US$/Kg-SO2 while abatement costs of NOx are 0.31-9.63 US$/kg-NOx. Flue gas desulfurization with wet lime and dry low-NOx burner are more efficient and cost-effective in controlling SO2 and NOx than the other techniques. The research results were also benchmarked against available international data sources. The findings can be used in policy planning and decision making process of key stakeholders to help improve air quality in the future.

WITHDRAWN:Experimental and numerical investigations of the dry-low-NOx (DLN) syngas micromix combustion principle

Combined with the storage and use of renewable energy sources and the application of the integrated gasification combined cycle (IGCC) technology, high hydrogen content fuels represent a possible alternative gas turbine fuel within future low emission power generation. Due to the large difference in the physical properties of hydrogen compared to other fuels such as natural gas, well established gas turbine combustion systems cannot be directly applied for dry-low-NOx (DLN) hydrogen and syngas combustion. Thus, the development of DLN combustion technologies is an essential task for the future of hydrogen and syngas fueled gas turbines. The DLN micromix combustion principle for hydrogen fuel has been developed to significantly reduce NOx-emissions. This combustion principle is based on cross-flow mixing of air and gaseous hydrogen which reacts in multiple miniaturized diffusion-type flames. The major advantages of this combustion principle are the inherent safety against flash-back and the low NOx-emissions due to a very short residence time of reactants in the flame region of the micro-flames. The present study aims to investigate the applicability of the micromix principle to the combustion of syngas with a composition of 90%-Vol. hydrogen and 10%-Vol. carbon-monoxide and compare different combustion models for the numerical characterization of the micromix flames. The micromix principle has been applied to design a DLN syngas burner for the application in gas turbine combustors. The designed burner has been successfully tested at atmospheric conditions and has shown a stable and typical micromix flame and low NOx emission. Different combustion models have been applied to simulate the micromix syngas combustion numerically. The numerical study revealed the ability of the applied numerical approach to simulate the micromix combustion and to capture the typical micromix flame anchoring and structure and supported the identification of adequate reaction mechanisms that allow an acceptable prediction of NOx emissions.

CFD based exploration of the dry-low-NOx hydrogen micromix combustion technology at increased energy densities

Combined with the use of renewable energy sources for its production, hydrogen represents a possible alternative gas turbine fuel within future low emission power generation. Due to the large difference in the physical properties of hydrogen compared to other fuels such as natural gas, well established gas turbine combustion systems cannot be directly applied for dry-low-NOx (DLN) hydrogen combustion. Thus, the development of DLN combustion technologies is an essential and challenging task for the future of hydrogen fuelled gas turbines.The DLN micromix combustion principle for hydrogen fuel has been developed to significantly reduce NOx-emissions. This combustion principle is based on cross-flow mixing of air and gaseous hydrogen which reacts in multiple miniaturized diffusion-type flames. The major advantages of this combustion principle are the inherent safety against flash-back and the low NOx-emissions due to a very short residence time of reactants in the flame region of the micro-flames.The micromix combustion technology has been already proven experimentally and numerically for pure hydrogen fuel operation at different energy density levels. The aim of the present study is to analyze the influence of different geometry parameter variations on the flame structure and the NOx emission and to identify the most relevant design parameters, aiming to provide a physical understanding of the micromix flame sensitivity to the burner design and identify further optimization potential of this innovative combustion technology while increasing its energy density and making it mature enough for real gas turbine application.The study reveals great optimization potential of the micromix combustion technology with respect to the DLN characteristics and gives insight into the impact of geometry modifications on flame structure and NOx emission. This allows to further increase the energy density of the micromix burners and to integrate this technology in industrial gas turbines.