Low calorific value (LCV) gaseous fuels are generated as by-products in many commercial sectors, e.g. as mine gas or bio-gas. Their efficient exploitation can be a considerable source of primary energy. Typically, product gases from biomass are characterized by low lower heating values (LHV) due to their high concentration of inert gases and steam. At the same time, their composition varies strongly based on the initial feedstock and may contain unwanted components in the form of tars and ammonia. These properties make the design of appropriate combustion systems very challenging and issues such as ignition, flame stability, emission control, and combustion efficiency must be accounted for. By employing a proprietary gas turbine burner at the TU Berlin, the combustion of an artificial LCV gas mixture at stoichiometric conditions has been successfully demonstrated for a broad range of steam content in the fuel. The current work presents the stability maps and emissions measured with the swirl-stabilized burner at premixed conditions. It was shown that the flame location and shape primarily depend on the steam content of the LCV gas. The steam content in the fuel was increased until flame blow-out occurred at LHVs well below the target condition of 2.87 MJ/kg (2.7 MJ / m N 3 ). The exhaust gas is analyzed in terms of the pollutants NO x and CO for different fuel compositions, moisture contents, and thermal powers. Finally, OH* measurements have been carried out in the flame. A simple reactor network simulation was used to confirm the feasibility of the experimental results.

Accurate and robust thermochemical models are required to identify future low-NO x technologies that can meet the increasingly stringent emissions regulations in the gas turbine industry. These mechanisms are generally optimized and validated for specific ranges of operating conditions, which result in an abundance of models offering accurate nominal solutions over different parameter ranges. At atmospheric conditions, and for methane combustion, a relatively good agreement between models and experiments is currently observed. At engine-relevant pressures, however, a large variability in predictions is obtained as the models are often used outside their validation region. The high levels of uncertainty found in chemical kinetic rates enable such discrepancies between models, even as the reactions are within recommended rate values. The current work investigates the effect of such kinetic uncertainties in NO predictions by propagating the uncertainties of 30 reactions, that are both uncertain and important to NO formation, through the combustion model at engine-relevant pressures. Understanding the uncertainty sources in model predictions and their effect on emissions at these pressures is key in developing accurate thermochemical models to design future combustion chambers with any confidence. Lean adiabatic, freely-propagating, laminar flames are therefore chosen to study the effect of parametric kinetic uncertainties. A non-intrusive, level 2, nested sparse-grid approach is used to obtain accurate surrogate models to quantify NO prediction intervals at various pressures. The forward analysis is carried up to 32 atm to quantify the uncertainty in emissions predictions to pressures relevant to the gas turbine community, which reveals that the NO prediction uncertainty decreases with pressure. After performing a Reaction Pathway Analysis, this reduction is attributed to the decreasing contribution of the prompt-NO pathway to total emissions, as the peak CH concentration and the CH layer thickness decrease with pressure. In the studied lean condition, the contribution of the pressure-dependent N 2 O production route increases rapidly up to 10 atm before stabilizing towards engine-relevant pressures. The uncertain prediction ranges provide insight into the accuracy and precision of simulations at high pressures and warrant further research to constrain the uncertainty limits of kinetic rates to capture NO concentrations with confidence in early design phases.

Reducing the uncertainties in the prediction of turbine inlet conditions is a crucial aspect to improve aero engine designs and further increase engine efficiencies. To meet constantly stricter emission regulations, lean burn combustion could play a key role for future engine designs. However, these combustion systems are characterized by significant swirl for flame stabilization and reduced cooling air mass flows. As a result, substantial spatial and transient variations of the turbine inlet conditions are encountered. To investigate the effect of the combustor on the high pressure turbine, a rotating cooled transonic high-pressure configuration has been designed and investigated experimentally at the DLR turbine test facility ‘NG-Turb’ in Göttingen, Germany. It is a rotating full annular 1.5 stage turbine configuration which is coupled to a combustor simulator. The combustor simulator is designed to create turbine inlet conditions which are hydrodynamically representative for a lean-burn aero engine. A detailed description of the test rig and its instrumentation as well as a discussion of the measurement results is presented in part I of this paper. Part II focuses on numerical modeling of the test rig to further extend the understanding of the measurement results. Integrated simulations of the configuration including combustor simulator and nozzle guide vanes are performed for leading edge and passage clocking position and the effect on the hot streak migration is discussed. The simulation and experimental results at the combustor-turbine interface are compared showing a good overall agreement. The relevant flow features are correctly predicted in the simulations, proving the suitability of the numerical model for application to integrated combustor-turbine interaction analysis.

The importance of expanded operating flexibility with reduced emissions on dry low emissions (DLE) gas turbines to lower loads has grown in importance for operators in many applications including natural gas transmission. Solar Turbines has developed an improved emissions control algorithm for Solar’s SoloNOx DLE gas turbines being offered as Enhanced Emissions Control . The new algorithm reduces carbon monoxide (CO) and unburned hydrocarbons (UHC) emissions from idle to 50% load. The corresponding startup and shut down emissions are reduced so that operators can obtain permits for operation over longer periods outside of low emissions mode. The algorithm has been evaluated in field trials at two different compressor stations using different gas turbine engine models. Solar’s Taurus™ 60 was tested at a field site in West Virginia and a Mars ® 100 was tested near Houston, Texas in the United States. The new control scheme reduces emissions from part load down to idle. The new controls extend the bleed valve or variable guide vanes’ operating range where they modulate to control combustor temperature from idle to full load. The pilot fuel schedule is also changed to work more directly with the combustor temperature control. Two field trials were completed to measure emissions continuously for more than 10 months at each site to validate the effectiveness of the new algorithm. Operation of the test units was largely at loads over 50% and the continuous data served to validate that the new algorithm with the modifications to pilot control did not change the emissions signature in the ‘low emissions mode.” In addition, multiple site visits were completed to map emissions from idle to 50% load over a range of engine settings. This mapping fully documented the complete emissions performance of the test units from idle to 100% load over a range of ambient temperatures from below freezing to 38°C. The field trials validate that the improved controls reduce CO and UHC emissions from idle to 50% load when compared to the current production algorithm. The testing also validated that the emissions above 50% load were unchanged compared to the current control algorithm. Specifically, CO and UHC emissions were reduced by 35 to 99% over the idle to 50% load operating range. By optimizing the pilot fuel controls the NOx emissions were also reduced 20 to 75% from idle to 50% load. The algorithm makes it possible to offer 15 ppm NOx warranties for the subject engine models in gas transmission applications down to 40% load that have been restricted to 50% load and higher. Over the wide ambient temperature range experienced during the field trial periods, emissions were consistent and no clear trends were documented with ambient temperature or engine speed (load).

F-class gas turbines comprise a major part of the heavy-duty gas turbine power generation fleet worldwide, despite increasing penetration of H/J class turbines. F-class gas turbines see a wide range of applications, including simple cycle peaking operation, base load combined cycle, demand following in simple or combined cycle, and cogeneration. Because of the different applications, local power market dynamics, and varied emissions regulations by region or jurisdiction, there is a need for operational flexibility of the gas turbine and the combustion system. In 2015, GE introduced a DLN2.6+ combustion system for new and existing 7F gas turbines. Approximately 50 are now in operation on 7F.04 and 7F.05 turbines, combining for nearly 150,000 fired hours. The system has been demonstrated to deliver 5 ppm NOx emissions @ 15% O 2 , and it exhibits a wide window of operation without significant thermoacoustic instabilities, owing the capability to premixed pilot flames on the main swirl fuel-air premixers, low system residence time, and air path improvements. Based on the success on the 7F, this combustion system is being applied to the 6F.03 in 2018. This paper highlights the flexibility of the 7F and 6F.03 DLN2.6+ combustion system and the enabling technology features. The advanced OpFlex* AutoTune control system tightly controls NOx emissions, adjusts fuel splits to stay clear of instabilities, and gives operators the ability to prioritize emissions or peak load output. Because of the low-NOx capability of the system, it is often being pushed to higher combustor exit temperatures, 35°C or more above the original target. The gas turbine is still meeting 9 or 15 ppm NOx emissions while delivering nearly 12% additional output in some cases. Single-can rig test and engine field test results show a relatively gentle NOx increase over the large range of combustor exit temperature because of the careful control of the premixed pilot fuel split. The four fuel legs are staged in several modes during startup and shutdown to provide robust operation with fast loading capability and low starting emissions, which are shown with engine data. The performance of a turndown-only fueling mode is highlighted with engine measurements of CO at low load. In this mode, the center premixer is not fueled, trading the NOx headroom for a CO emissions benefit that improves turndown. The combustion system has also demonstrated wide-Wobbe capability in emissions compliance. 7F.04 engine NOx and dynamics data are presented with the target heated gas fuel and also with cold fuel, producing a 24% increase in Modified Wobbe Index. The ability to run unheated fuel at base load may reduce the start-up time for a combined cycle plant. Lastly, there is a discussion of a new OpFlex* Variable Load Path digital solution in development that will allow operators to customize the start-up of a combined cycle plant.

Reducing the fuel consumption and greenhouse gas emissions of large commercial vehicles is a growing priority as governments around the globe introduce more stringent emissions regulations and as companies work to reduce their carbon footprint. Organic Rankine Cycles (ORC) can be applied to these vehicles to recover power from engine waste heat, thereby increasing efficiency and reducing fuel burn. However, the available waste heat consists of both high and low temperature sources making an efficient and cost-effective utilization of these resources challenging. In order to utilize both waste heat streams effectively, a single rotor, dual-entry turbine expander capable of accepting process flow simultaneously from high and low pressure supplies was developed, manufactured and tested. Test results show that the turbine concept was able to meet performance targets while decreasing the size, cost and complexity of the dual pressure ORC.

The SGT-600 3 rd generation DLE is a 24 MW industrial gas turbine which was recently upgraded from the SGT-600 2 nd generation DLE. The upgraded SGT-600 is an addition to the existing low emissions gas turbine portfolio within Siemens. The objectives of the engine upgrade focused on increasing the lifetime of the components, lowering emissions and improving liquid fuel operation. In order to accomplish these objectives the combustion system was fully replaced, an improved gas fuel distribution was implemented and the first stage of the turbine was replaced. Furthermore, the liquid fuel injection system was enhanced in terms of fuel droplet distribution. Both gas and liquid fuel operation were confirmed in Siemens industrial gas turbine test facility located in Finspong, Sweden. The upgraded combustion system originates from the SGT-700 gas turbine, a 33MW class engine, which consists of 18 “3 rd generation DLE” burners that replaced the original “2 nd generation DLE” ones that are normally incorporated in the SGT-600 DLE gas turbines. The first stage of the turbine has also been improved and less air is needed for cooling purposes. Moreover, an additional update on the compressor air bleed control was implemented. The liquid fuel burner hardware was optimized with new fuel injection lances manufactured by electron erosion techniques in order to improve the droplet distribution. The SGT-600 3 rd generation DLE is capable to operate in single digit conditions both in NO x and CO from 100% to 70% load and it is possible to extend single digit operation on NO x down to 50% load. CO emissions are below 80ppm at 50% load which is in compliance with current European regulation. Concerning liquid fuel operation the SGT-600 3 rd generation DLE does not use water injection for emission control and is capable to reach below 58ppm NO x at full load while keeping CO below 40ppm down to 75% load. The present work describes the main modifications performed during the engine upgrade and the results of the performed engine tests. Finally, it should be noted that the SGT-600 3 rd generation DLE is an excellent example of the development/upgrade efforts within Siemens AG. The commercialization process of the SGT-600 3 rd generation DLE has been initiated and three engines are already in commercial operation up to date, and two units will be installed in the near future.

Regulated two-stage (RTS) turbocharging system is an effective way to enhance power density and reduce pollutant of internal combustion engine for increasingly stringent demands of fuel consumption and emission regulation. Due to achieving high boost pressure with great system efficiency and controllable characteristic in wide working range, the RTS turbocharging system improves output power at low speed condition and reduces pumping loss at high speed condition. Composing of two turbochargers and control valves, the RTS turbocharging system is matched with engine at a design point and regulated by adjusting control valves to meet the engine requirement of intake pressure and flow at other working conditions. Calibration of the control valves under all operating conditions by plentiful experiments is significant for turbocharging system, particularly that matched with diesel engine for vehicle. Moreover, when an automobile run on the plateau, the intake air flow will decrease and combustion in cylinder will deteriorate obviously. Compared with other turbocharging system, two-stage turbocharging system is more suitable to the offset power loss of engine. Regulating boost system under different operation conditions draws more attention to engine performance recovery so that the workload of calibration raises rapidly in consideration of altitude factor. Though much work has been done in calibration at various altitudes, there are few, if any, discussion on open-closed boundary of control valves to simplify the calibration process. In this paper, it aims to present a regulation boundary model of control valve at different altitudes to guide the calibration and a series of experiments for RTS system can be saved. Firstly, a thermodynamics analysis of the RTS turbocharging system is conducted and typical regulation methods are compared in terms of the adjustment capacity and efficiency characteristics of turbocharging system, which indicates that high-stage turbine bypass is the optimum regulation method. Then, a regulation boundary model for the RTS turbocharging system at different altitudes is deduced, according to the relation of equivalent turbine area and engine operating condition. The regulation boundaries of different altitudes are obtained by iterative computation of the model, and the whole working mode of the RTS system is divided into a fully closed area and a regulated area. Experiments are carried out to verify the regulation boundary model at sea level condition. Brake torque, efficiency of the RTS system and temperature before high-stage turbine are primary parameters for verification in this article. The maximum error shows up with a value of 3.65% brake torque at 2200rpm. While a one-dimensional simulation model is built up to validate the regulation boundary model of the plateau. All the errors are smaller than 3% at various altitudes. It results that model is accurate enough to predict the regulation boundary of the RTS system. By the calculation of regulation boundary model, the brake torque at regulation boundary will decrease if the engine speeds up. It also manifests that fully closed area will argument if the automobile climbs up to high operating altitude, especially under high speed condition.

Lean premixed combustion has become state of the art technology in gas turbines for power generation because of its very low emission potential in the context of tightening pollutant emissions regulations. Lean premixed combustion is yet also prone to combustion instabilities, resulting in thermo-acoustically induced acoustic pressure oscillations (pulsations). Understanding pulsation behavior over an enginés lifetime is of interest to accurately monitor the engine status, as wear and degradation typically affect combustion behavior and result in changes of both pulsations and emissions. Such improved understanding can be exploited for optimizing both the engine operation concept and the design of relevant hardware parts. In return, pulsation and hardware optimization may lead to reduced degradation and thus inherently more robust long-term operational behavior. The study presented here is conducted for one specific gas turbine of GE’s GT24/GT26 fleet with sequential annular combustion. Based on operational data of the examined gas turbine, a semi-empirical modeling approach is introduced to describe the pulsations measured in the first (EV) combustion chamber. The target is to reproduce measured pulsation amplitudes as well as their different behaviors with engine load. The modeling presented here has been focused on pulsations in a distinctive frequency range below 1kHz. A model based on a small set of data obtained from initial commissioning is able to represent the pulsation behavior within a normalized root mean square error of 11%. Validation with long-term engine data shows that predicted pulsation levels are reasonably matching the initial operation period but increasingly deviate with engine operating time. By using additional data from later engine commissioning and adjustments, the robustness of the model is sensibly increased. Model accuracy on the training dataset remains similar at around 11%, but validation on the long-term data shows a significant decrease of the normalized root mean square error from over 21% to below 16%. Additional model improvements to further reduce prediction errors on long-term data have been also identified.

Concentrations of particulate matter (PM, PM10, PM2.5) from gas-fired gas turbines typically are near or below the overall method detection and quantitation limits of traditional hot filter/cooled impinger methods used for PM/PM10/PM2.5 emissions measurements (e.g., USEPA reference methods 5, 201A, 202). The test results can be highly variable, and may significantly overstate emissions even with application of best practices optimized to minimize bias and variability. An emerging test protocol for modifying USEPA Conditional Test Method 39 (CTM 39), a dilution sampling method for determining PM10/PM2.5 emissions from stationary sources, was used to accurately measure much lower PM concentrations. The lower concentrations are believed to be more representative of actual PM emissions from gas turbines. The modifications include adding ambient air sample collection and analysis methods for improved method sensitivity. Data from several testing programs are presented to illustrate the limitations of traditional methods for determining PM emissions, including measurement challenges associated with post-combustion emission controls such as SCR. Results from the modified method are presented to demonstrate the potential improvement compared with traditional hot filter/cooled impinger methods.

Stringent emission regulations force the gas turbine combustor community to come up with new designs. Lean Premixed (LPM) combustion is gaining popularity to meet the emission regulations. However, lean combustion process is prone to other issues like combustion instabilities and noise. Self-excited combustion instabilities in a gas turbine play vital role in the life cycle of combustor, noise generation and pollutant formation. If the instabilities in combustor dominate at natural modes, there are risks of resonance which can lead to bursting damage to the combustors. In the present work, modal analysis is carried out to predict the longitudinal and the transverse modes in a swirl-stabilized premixed methane-air combustor. The geometrical details and the boundary conditions used in this work are described in Broda et al. [1]. In addition to the modal analysis, Large Eddy Simulations (LES) with Flamelet Generation Manifold (FGM) combustion model are carried out to find out the instabilities and their sources. In the large eddy simulation, at the inlet of the combustor, a broadband impedance boundary condition is used. This will consider the effect of upstream travelling acoustic waves at the inlet. The outlet of combustor is specified with non-reflecting boundary condition. The inlet mass flow rate and the temperature conditions are consistent with Broda et al. [1]. The longitudinal and transverse modes predicted by the modal analysis and the dominant frequency predicted in the LES case are compared with the experimentally observed values. The predicted first longitudinal mode at ∼1760 Hz compares well with the experimental value of 1760 Hz. Predicted values of first and second tangential modes at 10459 Hz and 17344 Hz are also in good agreement with the experimental measurement. The dominant frequency predicted by the LES simulation is 1940 Hz. After applying the appropriate correction to this value for the wall heat transfer effect, it is in-line with that obtained from the modal analysis and the experiments. The spectral analysis at different probe location in LES simulation shows higher thermo-acoustic coupling at natural frequencies. In this work, the effect of variation in inlet swirl number and the temperature is also studies. The predicted trends in the change in dominant frequency with the increase in inlet swirl number and inlet temperature are captured accurately. For each condition, calculations were performed for about four flow-through times (around 12 ms) after the flow field had reached to its limit cycle to obtain statistically steady condition.

Turbocompounding is a promising waste heat recovery technology to improve fuel economy of internal combustion engines and comply with increasingly stringent emission regulations. The performance of a turbocompound engine is significantly influenced by the matching of the turbocharger turbine and the power turbine. Conventionally, the matching of the turbocharger turbine and power turbine is carried out at a single operating point. Single-point matched turbocompound systems tends to have poor performance at off-design operating conditions, which restrained the fuel-saving potential of turbocompound engines under driving cycle conditions. In the present study, a multipoint matching method for turbocompound systems was developed, which was essentially an optimization process of the swallowing capacities of the turbocharger turbine and the power turbine to achieve best performance at multiple matching points. In order to improve the performance of turbocompound engines under driving cycle conditions, common operating points of a driving cycle were used as matching points in the matching process. Common operating points under a driving cycle were determined by clustering the dynamic profiles of the driving cycle. A simulation study was carried out to examine the effectiveness of the multipoint matching method. The performance of the multipoint matched turbocompound system was compared against two single-point matched turbocompound systems under stationary operating points and driving cycle conditions respectively. According to the simulation results, the multipoint matched turbocompound system could attain satisfactory BSFC benefit under a wider operating range when compared with the two single-point matched turbocompound systems. The multipoint matched turbocompound engine showed the largest reduction in fuel consumption under driving cycle conditions.

Turbochargers are commonly used to boost internal combustion engines for both on and off high way applications to meet current emission regulations and performance requirements. Divider wall turbochargers have two exhaust gas inlets and twin scrolls with the divider cast wall connected. Turbochargers with divider wall feature could conserve an engine’s exhaust pulse kinetic energy for great turbine wheel efficiency. It is widely used in 6-cylinder engine applications. Turbochargers with divider wall configuration operate in very hostile conditions with high temperature and great thermal gradient. Using thinner divider wall feature benefits aerodynamic performance, but with the configuration turbine housing may show cracks and large deformation during thermal cycling. In order to achieve the balance between mechanic and aerodynamic, design study of a reasonable divider wall is required. This paper first presents the initial design with thinner divider wall, which experienced severe cracking problem in the divider wall location during the engine thermal shock testing. In order to capture the failure mode at divider wall region, finite element analysis (FEA) with thermal mechanical fatigue (TMF) and creep interaction is performed. The simulation repeats the failure mode very well which shows this numerical analysis method is convincing and fast for further study. Base on the failure case and successful cases, TMF with creep interaction simulation criteria is proposed. The criteria could be used as the reference for the further design, and the design should be controlled within the criteria limit. Based on the methodology and the criteria, the new design is analyzed and the simulation result shows the risk is low. Engine thermal shock testing is done for the final validation. This design has acceptable cracks and no large deformation at divider wall location under the testing condition. TMF and creep interaction gives a right and fast methodology to capture the failure mode at divider wall. Meanwhile it provides a knowledge base for the turbine housing divider wall design.

The GE Rapid Response plant design is described and compared to conventional combined cycle plant design. Advantages of the Rapid Response improved operational flexibility are explained and compared to conventional combined cycle plants. Improvements include faster power delivery to the grid, more economical plant startup, more profitable plant startup and lower emissions during plant startup. The capability of a drum type HRSG for the Rapid Response cycling service is explored. Joint studies between GE and HRSG suppliers are highlighted supporting the adoption of drum type HRSGs for this cycling service. Necessary modifications to other plant equipment are explained. Quantitative comparisons of Rapid Response and conventional combined cycle plant operability are given for electrical energy production and emissions reduction. An advanced Selective Catalytic Reduction SCR control is shown providing improvements in combined cycle plant transient emissions control. Elements of the new control are explained. Argument is made to designate the new control as a second generation GEN II control compared to all other currently existing controls designated GEN I. A brief outline of the current state of Rapid Response plant deployment is provided.

Stringent environmental emission regulations and continuing efforts to reduce carbon dioxide (CO 2 ) from the energy sector, in the context of global warming, have promoted interest to improve the efficiency of power generation systems whilst reducing emissions. Further, this has led to the development of innovative gas turbine systems which either result in higher electrical efficiency or the reduction of CO 2 emissions. Micro gas turbines are one of the secure, economical and environmentally viable options for power and heat generation. Here, a Turbec T100 micro gas turbine (MGT) is simulated using Aspen HYSYS ® V8.4 and validated through experimental data. Due to the consistency and robustness of the steady state model developed, it is further extended to three different innovative cycles: (i) an exhaust gas recirculated (EGR) cycle, in which part of the exhaust gas is dried and re-circulated to the MGT inlet; (ii) a steam injected (STIG) cycle, and (iii) a humid air turbine (HAT) cycle. The steam and hot water are generated through the exhaust of the recuperator for the STIG and HAT cycle, respectively. Further, the steam is directly injected into the recuperator for power augmentation, while for the HAT cycle; the compressed air is saturated with water in the humid tower before entering the recuperator. This study evaluates the impact of the EGR ratio, steam to air ratio, and water to air ratio on the performance and efficiency of the system. The comparative potential for each innovative cycle is assessed by thermodynamic properties estimation of process parameters through the models developed to better understand the behavior of each cycle. The thermodynamic assessment indicates that CO 2 enrichment occurs for the three innovative cycles. Further, the results indicate that the electrical efficiency increases for the STIG and HAT cycle while it decreases for the EGR cycle. In conclusion, the innovative cycles indicates the possibilities to improve the system performance and efficiency.

Operators of heavy duty gas turbines desire more flexibility of operation in compliance with increasingly stringent emissions regulations. Delivering low NOx at base load operation, while at the same time meeting aggressive startup, shutdown, and part load requirements for NOx, CO, and unburned hydrocarbons is a challenge that requires novel solutions in the framework of lean premixed combustion systems. The DLN2.6+ combustion system, first offered by the General Electric Company (GE) in 2005 on the 9F series gas turbines for the 50 Hz market, has a proven track record of low emissions, flexibility, and reliability. In 2010, GE launched a program to incorporate the DLN2.6+ into the 7F gas turbine model. The primary driver for the introduction of this combustion system into the 60 Hz market was to enable customers to capitalize on opportunities to use shale gas, which may have a greater Wobbe range and higher reactivity than traditional natural gas. The 7F version of the DLN2.6+ features premixed pilot flames on the five outer swirl-stabilized premixing fuel nozzles (“swozzles”). The premixed pilots have their roots in the multitube mixer technology developed by GE in the US Department of Energy Hydrogen Gas Turbine Program. A fraction of air is extracted prior to entering the combustor and sent to small tubes around the tip of the fuel nozzle centerbody. A dedicated pilot fuel circuit delivers the gas fuel to the pilot tubes, where it is injected into the air stream and given sufficient length to mix. Since the pilot flames are premixed, they contribute lower NOx emissions than a diffusion pilot, but can still provide enhanced main circuit flame stability at low-load conditions. The pilot equivalence ratio can be optimized for the specific operating conditions of the gas turbine. This paper presents the development and validation testing of the premixed pilots, which were tested on E-class and F-class gas turbine combustion system rigs at GE Power & Water’s Gas Turbine Technology Lab. A 25% reduction in NOx emissions at nominal firing temperature was demonstrated over a diffusion flame pilot, translating into more than 80% reduction in CO emissions if increased flame temperature is employed to hold constant NOx. On the new 7F DLN2.6+, the premixed pilots have enabled modifications to the system to reduce base load NOx emissions while maintaining similar gas turbine low-load performance and bringing a significant reduction in the combustor exit temperature at which LBO occurs, highlighting the stability the pilot system brings to the combustor without the NOx penalty of a diffusion pilot. The new combustion system is scheduled to enter commercial operation on GE 7F series gas turbines in 2015.

The combustion of viscous ash forming fuels generates soot and ash that collectively form the so called particulate matter (PM). In addition to existing SOx and NOx emission regulations, the World Bank has enacted a 50 mg/Nm 3 limit for the PM emissions of large combustion plants, creating a new challenge to power generators who use heavy fuel oils. LTL Holdings Ltd (Colombo, Sri Lanka) that own and operate a 300MW heavy-fueled gas turbine combined cycle (GTCC) at its Kerawalapitiya (Sri Lanka) power plant and GE Power & Water have embarked on a study intended to investigate the best PM abatement technique for heavy fueled gas turbines. This was done with TEKAT Ltd (London, UK) as the additive suppliers and the IRTES-LERMPS laboratory (Sévenans, France). In recent lab and field tests, the authors have thus evaluated the soot abatement capability of various combustion catalysts at different dosages. The results show that cerium proves an efficient oxidation catalyst in a real gas turbine, irrespective to its chemical form (Ce(III) or Ce(IV)), providing very substantial soot abatement rates. After briefly reviewing the different PM abatement techniques, the paper focuses on the lab and field tests performed and places emphasis on the performances of cerium in gas turbine combustors, along with the complex ash chemistry developed by heavy fuel oils.

This paper describes the development of the Dry Low Emission (DLE) combustor for L30A gas turbine. Kawasaki Heavy Industries, LTD (KHI) has been producing relatively small-size gas turbines (25kW to 30MW class). L30A gas turbine, which has a rated output of 30MW, achieved the thermal efficiency of more than 40%. Most continuous operation models use DLE combustion systems to reduce the harmful emissions and to meet the emission regulation or self-imposed restrictions. KHI’s DLE combustors consist of three burners, a diffusion pilot burner, a lean premix main burner, and supplemental burners. KHI’s proven DLE technologies are also adapted to the L30A combustor design. The development of L30 combustor is divided in four main steps. In the first step, Computational Fluid Dynamics (CFD) analyses were carried out to optimize the detail configuration of the combustor. In a second step, an experimental evaluation using single-can-combustor was conducted in-house intermediate-pressure test facility to evaluate the performances such as ignition, emissions, liner wall temperature, exhaust temperature distribution, and satisfactory results were obtained. In the third step, actual pressure and temperature rig tests were carried out at the Institute for Power Plant Technology, Steam and Gas Turbines (IKDG) of Aachen University, achieving NOx emission value of less than 15ppm (O 2 =15%). Finally, the L30A commercial validation engine was tested in an in-house test facility, NOx emission is achieved less than 15ppm (O 2 =15%) between 50% and 100% load operation point. L30A field validation engine have been operated from September 2012 at a chemical industries in Japan.

Early field tests on 25- and 33-MW combustion turbines indicated that, with modest controls on fuel sulfur content, compliance with strict regulations on particulate emissions, such as the 10 lb (4.5 kg) per hour Rule 67 of the Los Angeles Air Pollution Control District, was feasible. This paper describes the field development program to demonstrate Rule 67 compliance on an 80-MW combustion turbine for which the 10-lb/hr (4.5-kg/hr) limit is approximately 4 psm by weight. Particulate controls were implemented by installing improved-smoke combustors, and using water injection and low sulfur fuel. Meticulous sampling and analytical procedures were developed, using a specially designed and equipped environmental test laboratory trailer, to study the properties of particulate collection filters, and to improve the precision of measurements from each portion of the particulate sampling system: probe, filter, and water impingers. The test results clearly indicate that with proper attention to the details of sample system preconditioning, sample collection and analysis, the large combustion turbine can comply with the stringent 10-lb/hr (4.5-kg/hr) particulate limit of Rule 67.

The EPA aircraft emission regulations were promulgated in 1973 and resulted in urgent investigations of many approaches aimed at reducing gas turbine emissions with minimum penalties to normal combustion performance. The impact of this work on small aircraft gas turbine engines is discussed, and emission reduction techniques and data are presented. Unique problems experienced with smaller gas turbine combustion systems are reviewed as are the potential difficulties of developing higher performance small combustors in the future, without the benefit of the complex and costly mechanical approaches which are applicable to the larger engines. The impact of relaxed fuel specifications and alternate-source gas turbine fuels is discussed in terms of altered fuel properties and development of fuel injection technology.