Gas Turbine Emissions Research Articles

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.

Experimental Investigation on Nonlinear Response of a Low-Swirl Flame to Acoustic Excitation With Large Amplitude

Abstract Thermoacoustic instability is a major issue in developing high-efficiency low emission gas turbine combustors. In order to predict the amplitude of limit cycle oscillation, an understanding of the amplitude-dependent response of the flame, i.e., the nonlinear response, to large acoustic excitation is needed. In the present study, the nonlinear response of a low-swirl CH4/air premixed flame to acoustic excitation is experimentally studied. Amplitude dependences of flame dynamic at 75 Hz and 195 Hz are discussed in detail over a wide range of excitation levels. Experimental results show the gain of flame describing function of the low-swirl flame has a peak value at 65 Hz and a local minimum at 105 Hz which is caused by the destructive (out of phase) and constructive (in-phase) of the axial and azimuthal velocity fluctuation. At low perturbation level, flame heat release fluctuation is in linear relationship with the normalized velocity driving level. Heat release fluctuation begins to saturate at a certain level which depends on the driving frequency. The low-swirl flame oscillates mainly in the axial direction at 75 Hz while it is in the radial direction at 195 Hz. The nonlinear flame heat release response is a result of combination effect of flame rollup process and harmonic responses.

Effect of Adding Emulsifier to Fuel on Work Efficiency and Gas Turbine Emissions

In an effort to reduce the emissivity of transport and energy, numerous studies are being carried out on the impact of the combustion of alternative fuels on the emission and operating parameters of propulsion and energy units. One of the observed trends is the use of emulsion fuels. The addition of an emulsifier to an emulsion fuel reduces the interfacial tension between two liquids, which allows obtaining an emulsion fuel with the expected stability. The research conducted on self-ignition engines and gas turbines (TG) does not give an unambiguous answer as to the influence of the use of fuel-water emulsion on CO emissions. One of the reasons for the discrepancy in the obtained results may be the type and amount of the emulsifier used in the emulsion fuel. Tests were carried out on the GTM-120 gas turbine to compare the operating parameters and emissions between the cases in which TG was supplied with three fuel mixtures—the standard fuel for TG (DF) and DF with 2% and 5% emulsifier addition. It was shown that the addition of 2% of the emulsifier to DF causes an increase in CO emission, with the remaining measured parameters unchanged. On the other hand, increasing the amount of emulsifier in DF to 5% reduces CO emissions to the level observed in the case in which DF was burned reduces NOx emissions and reduces the thermal efficiency of TG.

Study of the reduced kinetic mechanism of methane/dimethyl ether combustion

The development of methane (CH4)/dimethyl ether (DME) combustion systems can reduce fossil energy consumption and pollutant emissions of gas turbines while enhancing fuel diversity. However, employing detailed kinetic mechanisms in the fluid dynamics calculations for the design and optimization of CH4/DME burner configurations is enormously costly for computational resources and time. Therefore, reduced kinetic mechanisms are essential for widespread implementation. In the current work, 1200 + iterations based on the genetic algorithm were performed with 30 target conditions, which extracted a reduced mechanism from the detailed CH4/DME chemical kinetic mechanism. It contained 35 species and 131 reaction steps that reasonably captured the detailed mechanism's main reaction path. Measurements from a shock tube verified that the reduced mechanism provides reasonable predictions of ignition delay times for pure methane, pure DME, and CH4/DME mixtures at T > 1300 K, 1050 K, and 1100 K, respectively. The addition of CH3O2 reaction schemes and modification CH3OCH2 related reactions extended the temperature range to T > 900 K, 700 K, and 760 K under stoichiometric and fuel-rich conditions. The accuracy of the reduced and optimized mechanism was also confirmed by other results obtained from laminar flames, counter-flow diffusion flames, and flow reactors. Accurate replication of the temperature and species profiles was achieved for the numerical simulation of the turbulent flames by the optimization mechanism, which also decreased nearly half the computational time compared to the detailed mechanism. Overall, there is a suitable balance between accuracy and computational efficiency, as shown by the reduced mechanism, promising potential computational cost savings for large-scale numerical combustion simulations.

Effects of oxy jet in cross-flow on the combustion instability and NOx emissions in lean premixed flame

Combustion instability and NOx emission are crucial factors for modern gas turbine combustors, which seriously hampers the research and development of advanced combustors. To eliminate combustion instability and NOx emissions simultaneously, effects of the oxy (CO2/O2, N2/O2, Ar/O2, and He/O2) jet in cross-flow on combustion instability and NOx emissions are experimentally studied. In this research, the flow rate and oxygen ratio of the combustor are varied to evaluate the control effectiveness. Results denotes that all the four oxyfuel gas: CO2/O2, N2/O2, Ar/O2, and He/O2, could suppress combustion instability and NOx emissions. The CO2/O2 dilution can achieve a better damping results than the other three cases. There are peak values or lowest points of sound pressure amplitude as the parameter of oxy jet in cross-flow changes. Mode transition appears in both acoustic signal and CH* chemiluminescence of the flame. But the turning point of mode transition is different. Under the CO2/O2 cases, the NOx emission decreases from 22.3 ppm to 15.2 ppm, the damping ratio of NOx is 40.39%. The flame shape and length were changed under different jet in cross-flow dilutions. This research could promote the application of jet in cross-flow methods on combustion instability or pollutant emissions in gas turbines.

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.

Selective Exhaust Gas Recycling in Gas Turbines with CO2 capture: A comprehensive technology assessment

Modern gas turbines operate with large amounts of excess air for cooling and dilution of the combustion gases, in order to maintain gas turbine blade integrity. Selective recycling of CO2 into the gas turbine compressor inlet, also referred as Selective Exhaust Gas Recirculation (SEGR), can reduce the large volumetric flow rate through a CO2 capture system caused by the gas turbine excess air requirements, by 70 - 77%. It also increases CO2 concentrations to 14-18 vol% from 3-4% vol, increasing the driving force for post-combustion capture systems. This paper provides a comprehensive assessment of the concept and presents research outcomes from the UK-funded SELECT project, including power plant and process modelling, techno-economic assessments, pilot-scale gas turbine experimental work and experimental combustion tests on a representative combustor. Using an integrated model of turbomachinery, power cycles and a generic post-combustion CO2 capture technology with a 30%wt MEA solvent, we show that a reduction of up to 50% of the absorber of the capture plant – the most capital intensive part of the process – can be achieved. The compressor and gas turbine operate without any significant deviation from their design point, and a marginal increase of 0.5% point in the net electrical efficiency can be achieved. Pilot-scale testing - conducted at the Pilot Scale Advanced Capture Technologies (PACT) facilities at the University of Sheffield - show that CO2 injection at the compressor inlet of a 100 kW micro gas turbine (mGT) connected to a 1 tonne per day CO2 capture plant reduces net electrical efficiency by 1-2 %point. This is caused by lower flame temperatures, and, unlike in larger gas turbines, the control system of the micro gas turbine. Combustion tests at Cardiff University’s Gas Turbine Research Centre (GTRC) in a pilot-scale high-pressure generic premixed swirl burner, representative of modern dry-low emissions (DLR) gas turbine burners, show the effect of CO2 as diluent on the operational premixed CH4/air flame stability, chemical kinetics and measured exhaust gas composition. CO2 acts as a combustor inhibitor, causing downstream migration of the premixed flame zone, leading to eventual blow-off, instability and extinction, requiring a change in the operation equivalence ratio. The effect of adding CO2 leads to a reduction in the adiabatic flame temperature due to thermal quenching, which results in higher CO emissions and smaller thermal NOx emissions. Increasing pressure has a significant reducing effect on CO emissions, yet it results in higher NOx production, which may require mitigation if this trend is found to continue towards pressures approaching that of the F-class gas turbine. Finally, a conceptual design assessment of a regenerative adsorption wheel with structured adsorbents is proposed for the selective recycling of CO2 in combined cycle gas turbine (CCGT) power plants. It has the advantage of a relatively small pressure drop to reduce the derating of the gas turbine compared to selective CO2 membrane systems. An equilibrium model of a rotary adsorber with commercially available activated carbon adsorbents shows that four rotary wheels of 24 m diameter and 2 m length would be required in an 820MW CCGT plant. A reduction of 50% in the mass of adsorbent would be possible with an adsorbent with a higher capacity, such as Zeolite X13, with upstream dehydration of the flue gases.

Numerical Investigations of Pollutant Emissions From Novel Heavy-Duty Gas Turbine Burners Operated With Natural Gas

Abstract A numerical investigation of pollutant emissions of a novel dry low-emissions burner for heavy-duty gas turbine applications is presented. The objective of this work is to develop and assess a robust and cost-efficient numerical setup for the prediction of NOx and CO emissions in industrial gas turbines and to investigate the pollutant formation mechanisms, thus supporting the design process of a novel low-emission burner. To this end, a comparison against experimental data, from a recent experimental campaign performed by BHGE in cooperation with University of Florence, has been exploited. In the first part of this work, a Reynolds-averaged Navier–Stokes (RANS) approach on both a simplified geometry and the complete domain is adopted to characterize the global flame behavior and validate the numerical setup. Then, unsteady simulations exploiting the scale adaptive simulation (SAS) approach have been performed to assess the prediction improvements that can be obtained with the unsteady modeling of the flame. For all simulations, the flamelet generated manifold (FGM) model has been used, allowing the reliable and cost-efficient application of detailed chemistry mechanisms in computational fluid dynamics (CFD) simulation. However, FGM typically faces issues predicting flame emissions, such as NOx and CO, due to the wide range of time scales involved, from turbulent mixing to pollutant species oxidation. Specific models are typically used to predict NOx emissions, starting from the converged flow-field and introducing additional transport equations. Also CO prediction, especially at part-load operating conditions could be an issue for flamelet-based model: in fact, as the load decreases and the extinction limit approaches, a superequilibrium CO concentration, which cannot be accurately predicted by FGM, appears in the exhaust gases. To overcome this issue, a specific CO-burn-out model, following the original idea proposed by Klarmann, has been implemented in ANSYS fluent. The model allows to decouple the effective CO oxidation term from the one computed by FGM, defining a postflame zone where the source term of CO is treated following the Arrhenius formulation. In order to support the design process, an indepth CFD investigation has been carried out, evaluating the impact of an alternative burner geometrical configuration on stability and emissions and providing detailed information about the main regions and mechanisms of pollutants production. The outcomes support the analysis of experimental results, allowing an indepth investigation of the complex flow-field and the flame-related quantities, which have not been measured during the tests.

Commissioning of a Combined Hot-Streak and Swirl Profile Generator in a Transonic Turbine Test Facility

AbstractBy enhancing the premixing of fuel and air prior to combustion, recently developed lean-burn combustor systems have led to reduced NOx and particulate emissions in gas turbines. Lean-burn combustor exit flows are typically characterized by nonuniformities in total temperature, or so-called hot-streaks, swirling velocity profiles, and high turbulence intensity. While these systems improve combustor performance, the exiting flow-field presents significant challenges to the aerothermal performance of the downstream turbine. This paper presents the commissioning of a new fully annular lean-burn combustor simulator for use in the Oxford Turbine Research Facility (OTRF), a transonic rotating facility capable of matching nondimensional engine conditions. The combustor simulator can deliver engine-representative turbine inlet conditions featuring swirl and hot-streaks either separately or simultaneously. To the best of our knowledge, this simulator is the first of its kind to be implemented in a rotating turbine test facility.The combustor simulator was experimentally commissioned in two stages. The first stage of commissioning experiments was conducted using a bespoke facility exhausting to atmospheric conditions (Hall and Povey, 2015, “Experimental Study of Non-Reacting Low NOx Combustor Simulator for Scaled Turbine Experiments,” ASME Paper No. GT2015-43530.) and included area surveys of the generated temperature and swirl profiles. The survey data confirmed that the simulator performed as designed, reproducing the key features of a lean-burn combustor. However, due to the hot and cold air mixing process occurring at lower Reynolds number in the facility, there was uncertainty concerning the degree to which the measured temperature profile represented that in OTRF. The second stage of commissioning experiments was conducted with the simulator installed in the OTRF. Measurements of the total temperature field at turbine inlet and of the high-pressure (HP) nozzle guide vane (NGV) loading distributions were obtained and compared to measurements with uniform inlet conditions. The experimental survey results were compared to unsteady numerical predictions of the simulator at both atmospheric and OTRF conditions. A high level of agreement was demonstrated, indicating that the Reynolds number effects associated with the change to OTRF conditions were small. Finally, data from the atmospheric test facility and the OTRF were combined with the numerical predictions to provide an inlet boundary condition for numerical simulation of the test turbine stage. The NGV loading measurements show good agreement with the numerical predictions, providing validation of the stage inlet boundary condition imposed. The successful commissioning of the simulator in the OTRF will enable future experimental studies of lean-burn combustor–turbine interaction.

Comparative Assessment of the Surface Integrity of AD730® and IN718 Superalloys in High-Speed Turning with a CBN Tool

Nickel-based superalloys are typical materials used in components of aeroengines and gas turbine machinery. The strength properties of these alloys at high temperatures are crucial not only to the performance (e.g., power generation efficiency, energy consumption, and greenhouse gas emissions) of aeroengines and industrial gas turbines, but also to machinability during component manufacturing. This study comparatively evaluated the surface integrity of two superalloys, AD730® and Inconel 718 (IN718), during high-speed finishing turning using cubic boron nitride (CBN) tools. IN718 is a conventional superalloy used for the hot section components of aeroengines and industrial gas turbines, while AD730® is a novel superalloy with enhanced high-temperature mechanical properties and good potential as a next-generation superalloy for these components. High-speed turning tests of two superalloys were conducted using a CBN cutting tool and jet stream cooling. The achieved surface integrity of the AD730® and IN718 superalloys was characterized and analyzed to assess the comparability of these alloys.

Methodology development for the control of NOx emissions in Aerospace Industry

A large number of studies conducted in Russia and abroad have been devoted to the development of low NOx emission gas turbine engines for aircraft and power stations. However, the continual improvement of the environmental requirements of ICAO (International Civil Aviation Organization) forces new research to be carried out to meet the future goals of reduced emissions produced by gas turbine combustors (GTE), a better understanding of the process of formation of various pollutants is required. Both empirical and theoretical approaches will be studied in this present research work to provide the exhaust concentrations of NOx emissions. In recent years different methods are already developed for this problem, one of them is associated with a theoretical approach. It is well known that correct theoretical models are economical (help’s to avoid experimental work) and can be useful for deep examination of NOx emissions generated in the combustion chamber process. The main objective of this study is to predict NOx emissions in GTE based on the mathematical simulations and chemical kinetics approach.To validate the simulation results, dispersion type optical system was developed in the laboratory. This system includes UV LED source (λ=245-280nm), single-pass absorption cell with length (L=500 mm) and spectrometer DFS-452 (spectral dispersion up to Δλ = 0.2nm/mm) equipped photo detector MORS-1 with a detection range Δλ=50nm. It allowed us to measure concentrations of some matters which absorbed light in the UVC range.

Combustion and emission characteristics from biojet fuel blends in a gas turbine combustor

Fossil fuels are non-renewable resources that will be depleted within the next century, leading to an energy crisis in the near future. Furthermore, there has been a global focus on emissions and its effect on the climate. The aviation sector stands out as a unique sector because a substantial amount of its emissions are injected at cruise altitude giving increased effectiveness to the pollutants. Biofuels (BF) derived from Jatropha and Camelina feedstocks are considered as one of the near-term solutions to the fuel crisis. The objective of this research is to study the effect of using different biofuel blends on gas turbine emissions and performance. These are blended in varying concentrations with conventional Jet-A1 and tested in a can type combustor at two different operating conditions. The performance of the combustor for these blends was evaluated by determining the combustion efficiency, temperature rise, and the emission indices. The general trend observed is that with increasing amounts of Camelina in the blends, there is an appreciable decrease in Carbon Monoxide (CO), Unburnt Hydrocarbons (UHC) and soot. However, the Nitrogen Oxides (NOx) emission increases slightly due to the higher combustion temperatures for Camelina based blends. The Jatropha-based fuels show a mixed trend even though they have comparable properties to the Camelina based fuels.

The stochastic fields method applied to a partially premixed swirl flame with wall heat transfer

Large eddy simulations of a partially premixed flame are performed with the purpose of predicting the reacting flow in a swirl-stabilised, low emissions industrial gas turbine combustor. The corresponding sub-grid scale turbulence–chemistry interactions are modelled using a probability density function transport equation, which is solved by the stochastic fields method. A 15-step reduced, but accurate, methane mechanism including 19 species is employed for the description of all chemical reactions. The test case involves a combustor with complex geometry and simulations are carried out for two different combustor operating conditions. Overall, results of the velocity, temperature and species mass fractions (including carbon monoxide) as well as the instantaneous thermochemical properties are shown to be in good agreement with experimental data, demonstrating the capabilities of the applied stochastic fields method. The inclusion of wall heat transfer in the combustion chamber is found to improve temperature and species predictions, especially in the near-wall regions. Comparisons between an oscillating and a ‘stable’ flame case furthermore highlight the influence of experimentally observed thermo-acoustic instabilities on the scalar fluctuations near the combustor centreline. None of the default model parameters were adjusted and the results showcase the accuracy and flexibility of the present large eddy simulation method for an application to complex, partially premixed combustion problems; this being particularly important for the designers of new generation low emission gas turbine combustors.

Comprehensive organic emission profiles for gasoline, diesel, and gas-turbine engines including intermediate and semi-volatile organic compound emissions

Abstract. Emissions from mobile sources are important contributors to both primary and secondary organic aerosols (POA and SOA) in urban environments. We compiled recently published data to create comprehensive model-ready organic emission profiles for on- and off-road gasoline, gas-turbine, and diesel engines. The profiles span the entire volatility range, including volatile organic compounds (VOCs, effective saturation concentration C*=107–1011 µg m−3), intermediate-volatile organic compounds (IVOCs, C*=103–106 µg m−3), semi-volatile organic compounds (SVOCs, C*=1–102 µg m−3), low-volatile organic compounds (LVOCs, C*≤0.1 µg m−3) and non-volatile organic compounds (NVOCs). Although our profiles are comprehensive, this paper focuses on the IVOC and SVOC fractions to improve predictions of SOA formation. Organic emissions from all three source categories feature tri-modal volatility distributions (“by-product” mode, “fuel” mode, and “lubricant oil” mode). Despite wide variations in emission factors for total organics, the mass fractions of IVOCs and SVOCs are relatively consistent across sources using the same fuel type, for example, contributing 4.5 % (2.4 %–9.6 % as 10th to 90th percentiles) and 1.1 % (0.4 %–3.6 %) for a diverse fleet of light duty gasoline vehicles tested over the cold-start unified cycle, respectively. This consistency indicates that a limited number of profiles are needed to construct emissions inventories. We define five distinct profiles: (i) cold-start and off-road gasoline, (ii) hot-operation gasoline, (iii) gas-turbine, (iv) traditional diesel and (v) diesel-particulate-filter equipped diesel. These profiles are designed to be directly implemented into chemical transport models and inventories. We compare emissions to unburned fuel; gasoline and gas-turbine emissions are enriched in IVOCs relative to unburned fuel. The new profiles predict that IVOCs and SVOC vapour will contribute significantly to SOA production. We compare our new profiles to traditional source profiles and various scaling approaches used previously to estimate IVOC emissions. These comparisons reveal large errors in these different approaches, ranging from failure to account for IVOC emissions (traditional source profiles) to assuming source-invariant scaling ratios (most IVOC scaling approaches).

Measurements of Periodic Reynolds Stress Oscillations in a Forced Turbulent Premixed Swirling Flame

This work is motivated by the thermoacoustic instability challenges associated with ultra-low emissions gas turbine (GT) combustors. It demonstrates the first use of high-speed dual-plane orthogonally-polarized stereoscopic-particle image velocimetry (PIV) and synchronized OH planar laser-induced fluorescence in a premixed swirling flame. We use this technique to explore the effects of combustion and longitudinal acoustic forcing on the time- and phase-averaged flow field—particularly focusing on the behavior of the Reynolds stress in the presence of harmonic forcing. We observe significant differences between ensemble-averaged and time-averaged Reynolds stress. This implies that the large-scale motions are nonergodic, due to coherent oscillations in Reynolds stress associated with the convection of periodic vortical structures. This result has important implications on hydrodynamic stability models and reduced-order computational fluid dynamics simulations, which do show the importance of turbulent transport on the problem, but do not capture these coherent oscillations in their models.

Results of Pre-Design Studies on the Development of a New Design of the Exhaust Duct of the Gas Turbine Compressor Package GPA-C-16S Type

This article summarizes the results of pre-design studies to reduce pollutant emissions of gas turbine compressor packages. The amount of pollutant emissions of compressor packages used at the Ukrainian gas transmission system as well as gas turbines manufactured by Ukrainian companies is presented. The main methods for reduction in pollutant emissions of gas turbines were analyzed. It was shown that one of the promising methods is to use special catalyst systems in the exhaust ducts. To select the catalyst location, a series of numerical simulations have been performed in the exhaust system of gas turbine compressor package GPA-C-16S type. It was shown that flow in the exhaust system has a complex structure mostly caused by features of the flow at the exhaust collector outlet. It was also found that swirling of the flow at the turbine outlet causes significant change of the flow at the exhaust system (18 % of the mass flow of exhaust gas moves along one of the wall and 82 % along another one). To prevent the degradation of the flow because of swirling at the turbine outlet the especially designed tongue was used at the exhaust collector. To reduce the overall non-uniformity of the flow the exhaust duct design with tubular straightener has been developed. To produce utility heat compressor packages of GPA-C-16S type can be equipped with heat recovery units, of between 3.5 to 9 MW. Their application allows achievement of thermal efficiencies of 0.36 to 0.46. The heat recovery units can contain several separate heat exchangers. Heat power control of the heat recovery units is carried out by heat exchangers on-off and by controlling the flow rate of exhaust gases through them. The design of the heat recovery units allows filling heat exchangers with water without shut-down of the gas turbine. To avoid high thermal stresses heat exchangers are cooled with atmospheric air supplied by fan of the heat recovery unit cooling system.

Numerical Investigation of Influence of Multi-Line Fuel Injection (Methane) on a Tubular Combustor Emissions of Micro Gas Turbine

This work presents a technique for design optimization of a gas turbine tubular combustor. This technique is based on the use of computational fluid dynamics (CFD) with CFX solver to reduce emission gases by using multi-line of fuel injection in secondary zone. This research relates the mass fraction of the multi-line of fuel injection as well as the equivalence ratio of the tubular combustion chamber designed for methane fuel. By using k-ε as turbulent model and Probability Density Function (PDF) Flamelet as combustion model. The operating casing data of micro size gas turbine are used, the validation of fuel flow mixing and combustion analyses were carried out with a focus on species concentration in the combustor outlet section. With variant fuel mass flow rate fraction in fuel lines (F2/F1), It was found that, with the new design NO reduced about 56% for the mass fraction 3 in high equivalence ratio and about 30%for the mass fraction 1 for a low equivalence ratio, while reduction in outlet temperature profile (pattern factor) is about 45% → 35%.

Determination of the effective density and fractal dimension of PM emissions from an aircraft auxiliary power unit

Gas turbine particulate matter (PM) emissions contribute to air quality degradation and are dangerous to both human health and the environment. Currently, PM mass concentrations determined from gravimetric measurements are the default parameter for gas turbine emissions compliance with PM regulations. The measurement of particle size however, is of significant interest due to its specific effects on health and climate science. The mass concentration can be determined from the number-size distribution measurement but requires the experimental evaluation of effective density of a number of particles to establish the power-law relationship. In this study, the effective density of PM emissions from an aircraft Auxiliary Power Unit (APU) with petroleum diesel, conventional aviation fuel (Jet A-1) and a multicomponent surrogate fuel (Banner NP 1014) as combusting fuels have been compared. An experimental configuration consisting of a Differential Mobility Analyzer, a Centrifugal Particle Mass Analyzer and a Condensation Particle Counter (DMA-CPMA-CPC) was deployed for this purpose. Overall, a decrease in the effective density (220–1900km−3) with an increase in the particle size was observed and found to depend on the engine operating condition and the type of fuel undergoing combustion. There was a change in the trend of the effective densities between the PM emissions generated from the fuels burnt and the engine operating conditions with increasing particle size.

Experimental study on combustion emissions of micro gas turbine

Experimental study on combustion emissions of micro gas turbine

Numerical study of a low emission gas turbine like combustor for turbulent ammonia/air premixed swirl flames with a secondary air injection at high pressure

The present study is dedicated to understand the emission characteristics of turbulent premixed ammonia/air swirl flames in a gas turbine like combustor at high pressure with and without secondary air injection. Ammonia has recently created an attention as a sustainable energy source not only because of its carbon free nature but also owing to its high hydrogen capacity of 17.8% in weight. Thus, in the present study, the effect of pressure on NO, unburnt NH3, and H2 emissions in ammonia/air premixed combustion was discussed by having space and time average emissions (STAE) at the exit of cylindrical combustor for various equivalence ratios and high pressures up to 0.5 MPa. The study found that NO emission decreases with an increase in pressure whereas unburnt NH3 emission in rich flame conditions also decreases with increase in pressure, and the study realizes that, at the equivalence ratio of 1.2, NO and unburnt NH3 emissions are minimal and in the same order of 200 ppm of mole fraction, even though still there is an unburnt H2 emission of 6% volumetric exhaust flow at the operating pressure of 0.5 MPa. Subsequently, secondary air injection system was introduced to the combustor, and eventually, the study realizes a low emission combustor with the STAE of NO in the order of 100 ppm of mole fraction at 16% of O2 concentration and zero NH3 and H2 emissions, at the primary zone equivalence ratio of 1.2.