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One of the most important gas turbine engine components is the combustion chamber, the main source of harmful emissions. The study is devoted to the central issues of designing and testing of an automatic control system of harmful emissions and pressure pulsations in flame tubes of a gas turbine plant with a capacity of 16 MW GTP-16 based on a PI-controller with a built-in neural network mathematical model of a low-emission combustor (LEС). Algorithms for a neural network controller of emission of nitrogen oxides and carbon monoxide into the atmosphere, as well as pressure pulsations in the LEC’s flame tubes were developed. The algorithms are given in a graphical programming environment and integrated into the automatic control system of GTP-16, implemented on the PXI NI hardware and software platform. The performance of the emission controller was checked during bench tests on the GTP-16 simulator with LEС neural network model serving as a virtual emission sensor. The errors in estimating the emission of nitrogen and carbon oxides and pressure pulsations in the flame tubes were determined. The normality of the error distribution of the developed nitrogen oxide emission model was proven. A conclusion about the prospects of using neural networks for the development of an adaptive control system of emissions and flame tube pressure pulsations for LECs of the gas turbine plants was drawn.

As alternative fuels are designated for future energy applications, flexible combustor designs require considerable development to ensure stable operation with reduced NOx emissions. A nonpremixed variable swirl burner was used to experimentally appraise changes in NO production pathways, with CH4 NH3 and H2 flames, alongside intermediate fuel blends. Maintaining an equivalent thermal power and flame temperature between fuels, preheated reactants (500 K) were supplied to the burner, with parametric changes made to pressure (1-6 bara) and swirl number (0.8-2.0). NO production was characterized, alongside variations in flame structure and topology, with a correlation demonstrated for exhaust emissions. NO production was shown to be sensitive to combustor pressure, providing an expected increase for CH4 and H2 flames. Emission profiles from both NH3 and H2 flames are shown to be significantly augmented by a change in swirl number. As NH3 fractions were increased in the H2 blend, a decaying trend in NO emissions was observed with an increase in pressure, and as a function of mixture ratio. However, this behavior was markedly augmented by a change in swirl number and suggests that further reductions may be possible at increased pressure. At the low swirl/high pressure condition, the NH3/H2 blend outperformed pure H2, providing lower NO concentrations. Emissions data were normalized using the traditional dry/O2 correction, alongside mass scaled by thermal power, with a comparison provided. The corresponding differences in emission formation pathways were investigated, alongside high-speed OH* chemiluminescence to further elucidate findings. [ABSTRACT FROM AUTHOR]

An economical method for numerical simulation of self-excitation of gas oscillations in low-emission combustors of gas turbine plants is developed and tested. The method is based on using an SAS SST turbulence model and a turbulent combustion model with a modified equation for a variable degree of combustion completion. Simulating the self-excitation of gas oscillations requires that a factor associated with gas pressure oscillations is introduced into the source term of this equation. Isolation of one of the gas oscillation modes prone to self-excitation is carried out using a resonant filter operating in each cell of the computational domain. The computational results obtained using the proposed method make it possible to study the effect of design measures and operating parameters of self-oscillations and to approach the choice of measures to suppress them. [ABSTRACT FROM AUTHOR]

Abstract A low‐pollution single‐tube microgas turbine combustor using different gas fuels was studied. The combustion performance of two kinds of landfill gas and natural gas was tested in a single‐head combustor. The effects of fuel nozzle position, and the fuel distribution ratio between pilot and main combustion stage on pollutant emission were investigated under rated load condition. The flow field, temperature field, and pollutant generation characteristics with different fuel nozzle diameters and nozzle positions were analyzed by numerical simulation. The results show that: the combustor can form an obvious central recirculation zone, which is convenient for ignition and stable flame propagation; in the case of limited premixed length, the influence of fuel nozzle position on fuel–air mixing uniformity is less obvious than that of fuel nozzle diameter. The fuel–air mixing uniformity plays a decisive role in the temperature field and the generation of pollutants in the combustor. The combustor has good pollutant emission characteristics, and the NOx emission can be reduced to about 10 ppmv (15% O2 concentration) under the appropriate combination of fuel nozzle diameter and position, which provides a reference for the further optimization of low‐emission combustor.

A low‐pollution single‐tube microgas turbine combustor using different gas fuels was studied. The combustion performance of two kinds of landfill gas and natural gas was tested in a single‐head combustor. The effects of fuel nozzle position, and the fuel distribution ratio between pilot and main combustion stage on pollutant emission were investigated under rated load condition. The flow field, temperature field, and pollutant generation characteristics with different fuel nozzle diameters and nozzle positions were analyzed by numerical simulation. The results show that: the combustor can form an obvious central recirculation zone, which is convenient for ignition and stable flame propagation; in the case of limited premixed length, the influence of fuel nozzle position on fuel–air mixing uniformity is less obvious than that of fuel nozzle diameter. The fuel–air mixing uniformity plays a decisive role in the temperature field and the generation of pollutants in the combustor. The combustor has good pollutant emission characteristics, and the NOx emission can be reduced to about 10 ppmv (15% O2 concentration) under the appropriate combination of fuel nozzle diameter and position, which provides a reference for the further optimization of low‐emission combustor. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the hydrodynamic and physicochemical characteristics of flow and combustion in a low-emission combustor (LEC) that differs from other combustors in design and lean fuel–air combustion modes. The influence of the composition and residence time of the mixture in the LEC on NO and CO emissions is considered. A LEC operation concept and demonstrator have been developed that provide NO and CO emissions below 5 ppm, which is 2–5 times lower than that in available LECs. The results of experimental studies of the LEC demonstrator with varying flame temperature, pressure, and residence time in the LEC confirm the validity of the proposed solutions. [ABSTRACT FROM AUTHOR]

The main results of VTI's investigations into low-emission combustors for gas-turbine units (GTU) are presented. In recent years, the combustion of a premixed fuel-air mixture (FAM) in a swirling flow in a limited space has been under development for this purpose to attain more complete combustion, stable fluctuation-free operation of a combustor in a wide range of parameters, and compliance with environmental protection requirements. To solve the problems encountered in this field, a procedure has been developed for assessing the effect of temperature in the combustion zone, flow velocity, combustor pressure, and other factors on the combustion stability. A review is presented of a comprehensive approach employed by VTI's specialists to study the processes in combustors using numerical and experimental methods enabling them to cut down the cost and time of activities on development of low-emission combustors. For example, a relationship is presented between the numerically estimated quality of the produced fuel-air mixture and the experimental nitrogen oxide concentrations. A design parameter relating the process conditions in a flame tube with the vibration combustion amplitude is proposed. The experiments demonstrated a good correlation of the proposed parameter with measured pressure fluctuation amplitude. Of real interest are the presented examples of changes in the velocity and temperature fields with an increase in the working pressure, which should be considered in designing and bench testing the combustor. The low-emission combustors (LEC) developed for large- and medium-power GTUs are presented. The potential for scaling the combustors for other GTUs is examined. [ABSTRACT FROM AUTHOR]

This paper presents the comprehensive test results of gas turbine unit (GTU-16P) experimental low-emission combustor (LEC) investigations at pressures up to 2000 kPa and a wide range of ambient temperatures within the ±25°C. The technical solutions applied provided the transition and operation in low-emission modes with automatic control of the LEC fuel channels without pulsations. The emission test results confirmed the high combustion efficiency of fuel in the entire operating range and low emission of carbon and nitrogen oxides at GTU loads from 70 to 100% in accordance with the technical assignment requirements. A system for automatic control of LEC fuel valves depending on the load was developed and implemented, including the protection with transition to safe modes during pressure pulsations with amplitudes exceeding the permissible level. [ABSTRACT FROM AUTHOR]

The possibilities of influencing combustion stability during changeover to low-emission combustion and ways of extending the stable combustion range are analyzed. The flow velocity, temperature, and pressure in the low-emission combustor (LEC) are considered as influencing factors. A premixed swirl-stabilized combustor is considered. The burner unit consists of main and pilot burners. The main burner has two fuel channels that allow controlling the quality of the air-fuel mixture. The LEC developed for an aeroderivative gas turbine was tested at an inlet air pressure of 2 MPa and an inlet air temperature of 475°C and an exhaust gas temperature of up to 1320°C. [ABSTRACT FROM AUTHOR]

The possibilities are examined of using already-available developed designs for low-emission combustors (LEC) of a GTU [gas turbine unit] with its own understood control algorithm in other GTUs, such as in their remodeling. The experience of JSC VTI [JSC "All-Russia Thermal Engineering Institute"] was shown in the use of the LEC design developed by them, which passed successful test station trials of full parameters, and was recommended for installation onto a motor of significantly lower power as a prototype for LEC development. The principles and similarity criteria and stages necessary for successful implementation of scaling the LEC are examined. Test results of the developed model of the LEC and a prototype are presented, with incomplete pressure at the JSC VTI test station by the algorithms of the prototype. Good likeness in LEC management and in received results was attained. [ABSTRACT FROM AUTHOR]

This paper is the last in the series on the reasearch into the sequential combustion process in a combustor with an outlet gas temperature of 1600 – 1700°C and permissible levels of CO and NOx emissions. The results of experiments on a model sequential combustor with an outlet gas temperature of 1460°C at a rated load are presented. The possibility of increasing the temperature to 1690°C was examined. The goal was to confirm that the combustor can operate in the range from 700 to 1700°C. The combustor has two sequential burners. The values of the velocities and air and fuel flow rates in both stages are taken from the previous studies. The model combustor was tested in the following operating conditions of the gas turbine: idling, transition to low-emission operation, and full load. The emission characteristics are compared for the following three schemes of combustion: (i) the air and fuel are supplied only to the first burner, the second burner being closed; (ii) the air is supplied to both burners while the fuel is supplied only to the first burner, the second burner operating as a combustor mixer; (iii) the air and fuel in optimal ratio are supplied to both burners. [ABSTRACT FROM AUTHOR]

A Lean Premixed Prevaporized (LPP) low-emission combustor which is applied with the combustion technology of staged lean fuel is developed. To study the cold flow dynamics and the combustion performance of the LPP combustor, both experimental tests using the Particle Image Velocimetry (PIV) to quantify the flow dynamics and numerical simulation using the Fluent software are conducted respectively. To investigate the emissions of the LPP combustor, four kinds of inlet conditions (viz. 7%, 30%, 85% and 100% F∞ (Thrust Force)) were conducted using numerical simulation. Numerical results are in good agreement with the experimental data. Results show that:1) a Primary recirculation zone (PRZ), a Corner recirculation zone (CRZ) and a Lip recirculation zone (LRZ) exist in the LPP combustor, and the velocity gradients between pilot swirling flow and primary swirling flow have contributed to the exchanges of mass, momentum and energy. 2) With the decrease of thrust force, NO mass fraction, CO2 mass fraction and total pressure losses at the exit of LPP combustor fall gradually. 3) Thermal NO formation rate closely relate to the zone area where gas temperature overruns 1900K and the maximum temperature in LPP combustor. 4) The combustion performance of the LPP combustor proposed in this paper is very well, and through comparative analysis with four kins of typical gas tubine combustor, the NO emission is very low and is equivalent to the CAEP6 43.87%.

This paper is the last in the series on the reasearch into the sequential combustion process in a combustor with an outlet gas temperature of 1600 – 1700°C and permissible levels of CO and NOx emissions. The results of experiments on a model sequential combustor with an outlet gas temperature of 1460°C at a rated load are presented. The possibility of increasing the temperature to 1690°C was examined. The goal was to confirm that the combustor can operate in the range from 700 to 1700°C. The combustor has two sequential burners. The values of the velocities and air and fuel flow rates in both stages are taken from the previous studies. The model combustor was tested in the following operating conditions of the gas turbine: idling, transition to low-emission operation, and full load. The emission characteristics are compared for the following three schemes of combustion: (i) the air and fuel are supplied only to the first burner, the second burner being closed; (ii) the air is supplied to both burners while the fuel is supplied only to the first burner, the second burner operating as a combustor mixer; (iii) the air and fuel in optimal ratio are supplied to both burners. [ABSTRACT FROM AUTHOR]

Results are presented of the experimental investigation of gaseous fuel combustion in a combustor comprising two zones in series each of which has its own burner unit (BU). The first burner unit (BU1) is a conventional one for low-emission combustors. It contains swirlers, a fuel-air mixing zone, a pilot burner, and a main burner. BU1 is fed with a premixed fuel-air mixture (FAM). The second burner unit (BU2) is located downstream along the flow, behind the first combustion zone. It is supplied with gaseous fuel (i.e., natural gas) without premixing with air. Diffusion combustion occurs in the second zone. The potential was studied for extending the stable operation range of the first combustion zone to the range of low excess air factors by creating radial nonuniformity in the FAM concentration at the BU1 outlet. This is accomplished by feed air in one hole in the fuel tubes above the vanes of the main burner swirler. The best FAM concentration at the first stage minimizing NOx and CO emission during joint operation of two combustion stages installed in series was determined. The results of the experiments with BU2, which is a thick hollow disk with a nozzle-shaped orifice with holes in the bore surface for fuel injection, are presented. The experiments were carried out with a model combustor in the test facility at OAO VTI. [ABSTRACT FROM AUTHOR]

The capabilities of controlling a low-emission combustor (LEC) over a wide range of ambient conditions are analyzed. The LES is intended for a GTU-16P gas turbine that is a derivative of the PS-90A aircraft engine by the UEC Aviadvigatel company. The LEC is of premix swirl stabilized type based on GTE-110 prototype. Its burner consists of pilot and main burners. The main burner has two fuel supply channels that allow controlling the quality of the air-fuel mixture. The low-emission operation range of the LEC can be extended to 70% load at negative ambient temperatures by bleeding air to the compressor inlet. [ABSTRACT FROM AUTHOR]

A Lean Premixed Prevaporized (LPP) low-emission combustor which is applied with the combustion technology of staged lean fuel is developed. To study the cold flow dynamics and the combustion performance of the LPP combustor, both experimental tests using the Particle Image Velocimetry (PIV) to quantify the flow dynamics and numerical simulation using the Fluent software are conducted respectively. To investigate the emissions of the LPP combustor, four kinds of inlet conditions (viz. 7%, 30%, 85% and 100% F∞ (Thrust Force)) were conducted using numerical simulation. Numerical results are in good agreement with the experimental data. Results show that:1) a Primary recirculation zone (PRZ), a Corner recirculation zone (CRZ) and a Lip recirculation zone (LRZ) exist in the LPP combustor, and the velocity gradients between pilot swirling flow and primary swirling flow have contributed to the exchanges of mass, momentum and energy. 2) With the decrease of thrust force, NO mass fraction, CO2 mass fraction and total pressure losses at the exit of LPP combustor fall gradually. 3) Thermal NO formation rate closely relate to the zone area where gas temperature overruns 1900K and the maximum temperature in LPP combustor. 4) The combustion performance of the LPP combustor proposed in this paper is very well, and through comparative analysis with four kins of typical gas tubine combustor, the NO emission is very low and is equivalent to the CAEP6 43.87%. [ABSTRACT FROM AUTHOR]

A Lean Premixed Prevaporised (LPP) low-emission combustor with a staged lean combustion technology was developed. In order to study cold-flow dynamics in the LPP combustor, both experimental tests using the particle image velocimetry (PIV) to quantify the flow dynamics and numerical simulation using the commercial software (FLUENT) were conducted, respectively. Numerical results were in good agreement with the experimental data. It is shown from the observation of the results that: there is a Primary Recirculation Zone (PRZ), a Corner Recirculation Zone (CRZ) and a Lip Recirculation Zone (LRZ) in the LPP combustor, and the exchanges of mass, momentum and energy between pilot swirling flow and primary swirling flow are contributed by the velocity gradients, and the shear flow is transformed into a mixing layer exhibiting the higher Reynolds stresses, which suggests the mixing process is strictly affected by the Reynolds stresses. [ABSTRACT FROM PUBLISHER]

An investigation of the low-emission premixed combustion in a conventional combustor is presented. The main problem encountered is the pressure fluctuations induced under certain operating conditions of the combustor. Low-emission operation of the combustor was studied numerically and experimentally. The effect of the concentration distribution at the outlet from the mixing zone on the position and macrostructure of the flame and the combustion stability was investigated at various excess air factors corresponding various GTU loads. It is demonstrated that, for a given excess air factor, there exists the concentration profile such that the interaction of the flame front with dominating flow structures results in excitation of the low-frequency combustion instability. The factors responsible for high-amplitude pressure fluctuations are examined. It is shown that the combustion stability can be estimated using a calculated criterion. Its direct relationship with pressure fluctuation amplitudes is described. The effect of the air pressure in a combustor on the flame macrostructure and the combustion stability was studied. It is shown that an increase in the combustor pressure has no considerable effect on the processes in the combustor. However, a change in the chemical reaction rates affects the stable combustion boundary. In this case, the combustion stability is achieved with higher nonuniformity of the fuel-air mixture entering the combustion zone. The experimental boundaries of stable combustion envelope at an air pressure of 350 and 1500 kPa are presented. [ABSTRACT FROM AUTHOR]

The results of testing the GTÉ-110 gas-turbine low-emission combustor (LEC) at an operating pressure of 1500 kPa are presented. It is shown that the developed technical solution provides pulsation-free changeover to low-emission operation of the LEC. The measurements confirm low NOx emissions and high combustion efficiency in the 50 - 100% load range. The stages of LEC development, the justification of the technical solution, and the results of testing the pilot LEC at an inlet air pressure of 350 kPa were detailed earlier in [1]. Comparing and analyzing the results of tests at reduced and full air pressures reveal that the combustor wall temperatures, gas temperature profiles, and combustion efficiencies are identical. Moreover, the results confirm the adequate simulation of acoustic boundary conditions at test facilities providing reduced and full operating conditions. [ABSTRACT FROM AUTHOR]

A computational and experimental investigation of the processes occurring in premix combustors with swirl stabilization similar to that used in modern gas-turbine engines is described. The combustor burner consists of main and pilot burners. The combustor operates on a mixture of natural gas and air with excess air coefficient from 10 to 2.6. The influence of the fuel fraction in the pilot burner (PFR) with fixed excess air coefficient á on the macrostructure of the flame - the relation between the shape and position of the flame front and the dominating structures of the flow - is examined. The flame front is investigated by means of three-dimensional numerical modeling. Four ma xxx crostructures are observed in the experimental PFR range from 0 to 100% with fixed excess air coefficient á. It is shown that each form of high-frequency combustion instability corresponds to a definite macrostructure of the flame. It is noted that the fuel fractions in the pilot burner at which changes are observed in the flame configuration are associated with the appearance of thermo-acoustic instability. [ABSTRACT FROM AUTHOR]

The article deals with construction of a simplified model of inhibition of nitric oxides formed in the combustors of the gas-turbine plants (GTPs) operating on natural gas. A combustor in which premixed, lean air-fuel mixtures are burnt is studied theoretically and experimentally. The research was carried out using a full-scale combustor that had parameters characteristic of modern GTPs. The article presents the results computed by the FlowVision software and the results of the experiments carried out on the test bench of the All-Russia Thermal Engineering Institute. The calculations and the tests were conducted under the following conditions: a flow rate of approximately 4.6 kg/s, a pressure to 450 kPa, an air temperature at the combustor inlet of approximately 400°C, the outlet temperature t ≤ 1200°C, and natural gas as the fuel. The comparison of the simulated parameters with the experimental results underlies the constructed correlation dependence of the experimental NO emission on the calculated parameter of nonuniform fuel concentration at the premixing zone outlet. The postulate about a weak dependence of the emission of NO formed upon combustion of a perfectly mixed air-fuel mixture-when the methane concentration in air is constant at any point of the air-fuel mixture, i.e., constant in the mixture bulk-on the pressure in the combustor has been experimentally proven. The correctness and the practicability of the stationary mathematical model of the mixing process used to assess the NO emission by the calculated amount of the air-fuel mixture generated in the premixing zone has been validated. This eliminates some difficulties that arise in the course of calculation of combustion and formation of NO. [ABSTRACT FROM AUTHOR]