Low-emission Combustion Chamber Research Articles

A comparative study of effects of methane and hydrogen on ammonia combustion in air via reactive molecular dynamics

Ammonia (NH3) is a promising substitute for fossil fuels to achieve the net-zero emission targets. To improve the combustion performance of NH3, reactive fuels are added to the NH3 combustion. In the present study, the combustions of NH3, CH4/NH3, and H2/NH3 in air conditions were simulated using a reactive molecular dynamics method. Results suggest that whether the addition of CH4 and H2 could accelerate the consumption of NH3 and reduce NOX emissions depends on the fuel ratio of the reactive gas (CH4/H2) and NH3 molecules. The acceleration of NH3 consumption is significant at low H2/NH3 fuel ratios and high CH4/NH3 fuel ratios, as the addition of H2 and CH4 lowers the activation energy for NH3 combustion. NOX emissions are mitigated at low H2/NH3 and CH4/NH3 fuel ratios but increase at high fuel ratios. The pathways for NOx generation and de-NOx reactions were identified. This study unveiled the mechanism via which the reactive fuels affect the NH3 combustion performance from an atomic perspective. The findings will be useful for the design of high-efficiency and low-emission combustion chambers in ammonia-powered energy systems.

Моделирование работы газотурбинной установки SGT5-4000F с исследованием влияния режимных и климатических факторов на устойчивость горения в камере сгорания

When regulating gas turbine units, it is necessary to be confident in the stable combustion process in the combustion chambers, considering the dynamics of the processes and changes of external climatic factors. Many scientific studies are devoted to the problems of experimental research and mathematical modeling of processes in combustion chambers. The possibilities of flame failure, expansion of the lower limit of combustion, determination of the stable position of the flame front and other issues have been assessed. Even though the problem of design of mathematical models and their use remains relevant. The purpose of this research is to model and study the influence of operation and climatic factors on the stability of combustion in the combustion chamber of the SGT5-4000F gas turbine unit. The subject of the research is the SGT5-4000F gas turbine unit with a low-emission combustion chamber. The simulation model of the gas turbine unit has been developed in the environment of dynamic modeling of technical systems SimInTech. The research is carried out using theoretical methods of calculating fuel combustion, thermodynamic foundations of the theory of gas turbine engines, methods of mathematical and simulation modeling, as well as data from the archive of automated process control systems. A simulation model of SGT5-4000F gas turbine unit has been developed. It is distinguished by the ability to assess the proximity of the compressor operating mode to the stability limit and determine the boundaries of stable combustion procedure in the combustion chamber, considering environmental climatic factors. The authors have studied the stability of the compressor and combustion chamber. The results of the experimental studies of a gas turbine unit in the operating load range from 113 to 282 MW and in the range of outside air temperature from –12 to 30 °C have shown that the combustion process in the combustion chamber is unvarying over the entire operational stress spectrum. The results obtained are verified by comparing model values with technological parameters of a gas turbine unit taken from the archive of the power plant control system. The authors have assessed the influence of electrical load on the performance indicators of a gas turbine unit at outdoor temperatures of +30, +15 and –12 °C. According to the results of simulation modeling, the model of SGT5-4000F gas turbine unit is found to be adequate. The developed model can be used as a tool at the stage of functional and technological design of automated control systems for the development of effective automatic control systems.

Low-Emission Combustion Chambers of GTU: Modern Trends, Diagnostics, and Optimization (Review)

Low-Emission Combustion Chambers of GTU: Modern Trends, Diagnostics, and Optimization (Review)

Analysis of the Numerical Modeling Results of the Associated Petroleum Gas Combustion in the Convertible Chamber in a Micro Gas TPP

When developing prospective gas turbine plants or converting existing ones for burning nonstandard fuel gases, one of the main tasks is creation of low-emission combustion chambers with stable combustion. At the stage of sketch design, the parameters of recycling chambers are usually determined using engineering calculation methods. Methods of numerical modeling of the working process allow to clarify the obtained parameters and significantly reduce the costs of creating a combustion chamber thanks to the numerical experiment. The purpose of this work is to develop recommendations for converting existing combustion chambers of microgas-turbine power plants to utilize nonstandard fuel gases. To achieve the goal, the problem of numerical modeling of the working process with and without a stepwise air supply to the combustion zone was solved. The most significant result of the conducted studies is provision of stable combustion due to the change in the medium speed along the combustion zone with stepwise air supply and due to intensification of the reverse currents zone from the swirler with continuous air supply. The significance of the obtained results is that the proposed recommendations for converting a low-emission combustion chamber from components (kerosene+air) to components (combined petroleum gas+air) while keeping the diameter and length of the chamber unchanged, with changing the location of only the side holes. In this work, a three-dimensional numerical model of turbulent combustion for utilizing associated petroleum gases was developed to take into account the real operational conditions in a two-zone combustion chamber and analyze the performance characteristics.

Experimental and numerical study on heat transfer characteristics of tangential effusion cooling for a combustor liner

A great number of studies have been conducted on effusion cooling, which is based on the flat plate. However, the differences in flow and heat transfer characteristics between a flat plate and a circular combustor restricted the immediate application of the previous studies to the design of combustor cooling. In this study, a new type of effusion cooling with tangential injection based on the cylinder, which was fabricated by electric discharging machining, is employed in the present investigation using infrared imaging technique. With the blowing ratio ranging from 2.2 to 17.9, the results of proposed structure were compared with that of effusion holes based on the flat plate. The compound angles (β) of tangential effusion are 45°, 60°,75°, 95° respectively. Results show that compared to the effusion cooling based on the flat plate, the cooling jets of the tangential effusion based on the cylinder have a large tangential velocity component, which keeps the cooling jets attached to the wall and flowing spiral forward. The overall cooling effectiveness of tangential effusion is about 50% higher than effusion holes based on the flat plate. This also indicates that the existing conclusions of effusion cooling based on the flat plate cannot be directly applied to the combustion chamber. The cooling performance of tangential effusion cooling is greatly influenced by the compound angle and the 75° is optimal among them. In the studied range of blowing ratio, the overall cooling effectiveness of tangential effusion is above 0.8, and there is a significant cooling enhanced with the increase of blowing ratio. This provides a reference and database for the cooling design for low-emission combustion chambers with low cooling consumption.

Разработка математической модели газотурбинной установки с малоэмиссионной камерой сгорания и особенности ее интеграции в среду SimInTech

The results of the development of a mathematical model of a gas turbine plant (GTP) SGT5-4000F with an annular low-emission combustion chamber are presented. This plant has a low NOx emission and a high coefficient of performance (COP). The obtained results of mathematical modeling are integrated into the domestic environment of dynamic modeling of technical systems "SimInTech". The obtained results were verified by comparing the model values with the trends of the real technological parameters of the gas turbine unit taken from the archive of the automated process control system of the power plant. According to the results of the experimental studies carried out on the model with changes in the electrical load from 280 to 160 MW, it is shown that the model allows you to control the combustion process in the combustion chamber, depending on the composition of the fuel, evaluate the change in NOx emissions and provide an analysis of the stability of the gas turbine compressor according to surging in conditions of changing temperature and humidity of the incoming air.

SEMI-EMPIRICAL MATHEMATICAL MODEL OF NITROGEN OXIDES EMISSION FROM LOW-EMISSION COMBUSTION CHAMBER AS A PART OF AUTOMATIC CONTROL SYSTEM OF AN AERO ENGINE

The article is devoted to the problem of automatic control of nitrogen oxide emissions from a low-emission combustion chamber (LECC) of a gas turbine engines' (GTE) new generation. Since the measurement technologies have not reached the required level of availability today, and the reliability of the automatic control system (ACS) depends on the validity of input information about the engine state, it is proposed to use the built - in predictive mathematical model of the LECC. The model equations are functions of the measured parameters. The compact design requirements and significant nonlinearity of combustion determine the stochastic nature of the LECC. Taking into account the strict ICAO standards for the emission of harmful substances, all this leads to a narrow range of stable operating modes, limited, on the one hand, by the normalized level of nitrogen oxide emissions, and, on the other hand, by unacceptable modes of flame blowout or vibration combustion (thermoacoustic vibrations). It is proposed to build into the ACS a hybrid model of the processes of generating harmful emissions in the MEKS GTE, consisting two parts. The first semi-empirical submodel combines the physical equation of Zeldovich and the generalized empirical coefficient calculating as a function of several critical variables. This submodel allows generating training samples for the second submodel in case of insufficient experimental data. The second submodel is based on a neural network. The article discusses the development and testing of the first submodel, which identification algorithm is based on the accepted hypothesis of the possibility of applying the principle of superposition in describing the interaction of diffusion and homogeneous flames. The algorithm is based on the Zeldovich equation, which makes it possible to determine the dependence of the generation of nitrogen oxides on the composition of the air-fuel mixture using the distribution function of the probability density of its pulsations depending on the value of the integral equivalent ratio φ, which characterizes the concentration of fuel in the mixture. A feature of the LECC is the presence in the flame tube of longitudinal acoustic waves, excited by the release of heat during combustion, having a frequency equal to natural frequency of the gas-air column. These acoustic waves are leading to fluctuations of φ and causing the harmonic fluctuations in the mathematical expectation of the mixture composition. In this work the numerical modeling of the distribution of the inhomogeneity and pulsation of the fuel-air mixture concentration over the area of the flames in the CFX package allowed to obtain the characteristics of the mathematical expectations and dispersion, as well as the natural frequencies of the object. The distribution functions of the probability density of pulsations of the mixture concentration for diffusion and homogeneous circuits are calculated analytically, taking into account the acoustics of the combustion chamber. The analysis of the effect of dispersion of acoustic waves on the form of the resulting probability density curves in diffusion and homogeneous plumes is carried out.

Specific features of pressure pulsation control in combustion chambers of land based gas turbine units

LLC SPC Teplofizika, developing low-emission combustion chambers with premixing of fuel for ground application gas turbine installations, investigates the problems associated with the occurrence of pressure pulsations in the combustion chambers, as well as with the methods of their registration and measurement. To date, there is no unified method for assessing and calculating the amplitude-frequency characteristics of these pulsations and their measurement in general. This article is based on many years of experience in measuring and recording pressure pulsations under the conditions of a test bench and operation. Methods for evaluating and accumulating measurement results are presented, criteria for determining the average frequency and amplitude of oscillations are developed, reproducible in the course of experiments and during full-scale measurements. To detect vibrating combustion, an additional criterion of coherence of vibrations is also used with the aid of the entropy coefficient. As a result of the computational and experimental study, we find that the pulsation pressure in the volume of the combustion chamber does not allow the use of probes for measuring pressure pulsations in the air volume of the combustion chamber to reliably prevent the occurrence of vibrating combustion during its operation.

МАЛОЭМИССИОННЫЕ КАМЕРЫ СГОРАНИЯ И СПОСОБЫ ОХЛАЖДЕНИЯ

A modern gas turbine engine must meet a large list of requirements that are included in the parameters, resource and per-formance indicators. To increase the service life of a gas turbine engine at elevated temperatures of the gas flow, it is expendable to use thermal barrier protection on explosive structural materials. Cyclic tests of materials and thermal barrier coatings of gas tur-bine engines at temperatures above 1500 ºС are proposed to be carried out on a stand in which a hot gas flow is generated by an air-methane burner. In order to reduce the emission standards for nitrogen and carbon oxides, it is necessary to develop and use in stationary gas turbine engines fundamentally new technologies for organizing combustion and, as a result, designs of combustion chambers. From a detailed analysis of the current requirements, it follows that the newly designed low-emission combustion chamber for advanced gas turbine engines and installations should be accompanied by an increase in gas temperature by 200–300 K, an increase in the durability of the flame tube by 3–4 times, with a twofold decrease in the proportion of air for cooling the walls, a twofold or more reduction in the emission of harmful substances. In this article, heat-resistant coatings of structural elements of gas turbines are considered. The concepts of low-emission fuel combustion are described by organizing the working process according to the "DLE" - Dry Low Emission scheme. As an alter-native method for organizing low-emission combustion, stoichiometric combustion is proposed, which also makes it possible to provide the required temperature of the gas jet. A review of low-emission combustion chambers has been carried out. The existing methods of cooling the combustion chambers of gas turbine and liquid rocket engines are described. The analysis of the collected information made it possible to determine the concept of designing a high-temperature air-methane burner.

Hydrodynamic Low-Frequency Regimes of Unstable Combustion and Methods of their Suppression in Low-Emission Combustion Chambers of Gas-Turbine Facilities

Hydrodynamic Low-Frequency Regimes of Unstable Combustion and Methods of their Suppression in Low-Emission Combustion Chambers of Gas-Turbine Facilities

Development of a Low-Emission Combustion Chamber of an Industrial Natural Gas Turbine with NO<i>x</i> and CO Emission Less than 5 ppm

Development of a Low-Emission Combustion Chamber of an Industrial Natural Gas Turbine with NO<i>x</i> and CO Emission Less than 5 ppm

Investigation of Low-Temperature Lean Combustion Characteristics in Power Plants with External Heating of Components

An integral part of any open-type gas turbine plant is a low-emission combustion chamber, which is usually two-zone and cooled. One of the ways to reduce emission of harmful substanc-es is organizing low-emission low-temperature lean combustion with external heating of compo-nents. This paper investigates the effect of external heating of air and fuel gas on expansion of the lower combustion limit and stable flame position in a single-zone uncooled combustion chamber of a microgas turbine power plant. Stable position of the flame front in combustion chambers of this type mainly depends on the ratio between the average flow rate of the combus-tible-air mixture and the rate of turbulent combustion. This ratio depends on thermal, gas-dynamic, thermochemical and geometric factors. The purpose of this work is to substantiate the possibility of using the relative flow rate as a generalized characteristic. This goal was achieved in processing a large amount of published experimental data and numerical modeling of low-temperature combustion of lean mixtures. The most significant research result is determination of the range of relative flow rate (gk = 0.3…3.5·10-4 kg⁄s∙N), at which it is possible to ensure sta-ble flame position in a single-zone combustion chamber. Significance of the obtained results lies in the fact that using the relative flow rate makes it possible to quickly determine and analyze the geometric and gas-dynamic parameters and characteristics of turbulent combustion in com-bustion chambers of micro-gas turbine power plants.

Investigations of the Emission Characteristics of a Dual-Fuel Gas Turbine Combustion Chamber Operating Simultaneously on Liquid and Gaseous Fuels

Abstract This study is dedicated to investigations of the working process in a dual-fuel low-emission combustion chamber for a floating vessel’s gas turbine. As the object of the research, a low-emission gas turbine combustion chamber with partial premixing of fuel and air inside the outer and inner radial-axial swirls was chosen. The method of the research is based on the numerical solution of the system of differential equations which represent the physical process of mass and energy conservation and transformations and species transport for a multi-component chemically reactive turbulent system, considering nitrogen oxides formation and a discrete ordinates model of radiation. The chemistry kinetics is presented by the 6-step mechanism of combustion. Seven fuel supply operating modes, varying from 100% gaseous fuel to 100% liquid fuel, have been analysed. This analysis has revealed the possibility of the application of computational fluid dynamics for problems of dual-fuel combustion chambers for the design of a floating vessel’s gas turbine. Moreover, the study has shown the possibility of working in different transitional gaseous and liquid fuel supply modes, as they satisfy modern ecological requirements. The dependencies of the averaged temperature, NO, and CO concentrations along the length of the low-emission gas turbine combustion chamber for different cases of fuel supply are presented. Depending on the different operating modes, the calculated emission of nitrogen oxides NO and carbon monoxide CO at the outlet cross-section of a flame tube are different, but, they lie in the ranges of 31‒50 and 23‒24 mg/nm3 on the peak of 100% liquid fuel supply mode. At operating modes where a gaseous fuel supply prevails, nitrogen oxide NO and carbon monoxide CO emissions lie in the ranges of 1.2‒4.0 and 0.04‒18 mg/nm3 respectively.

Features of commissioning a gas turbine unit with a low-emission combustion chamber

Environmental safety issues are a priority in the modernization development of aviation or ground-based combustion chambers of gas turbine engines. In order to reduce the emission of harmful substances from combustion products, a low-emission combustion system, which is based on the concept of LPP (Lean-premixed and prevaporised), is being used today. This concept implements the principle of burning “ultra-poor” premixed air-fuel mixtures. The operational experience of combustion chambers developed in accordance with the indicated concept shows that one of the implementation problems is the difficulty in ensuring a good start. This paper presents the results of adjusting the operating process of a modern combustion chamber, launching a gas turbine unit, including drawing up a fuel supply control algorithm, experiments with igniting ignition devices and setting the gas turbine on idle mode. A feature of the commissioning work is the debugging of the operating process of the combustion chamber directly as part of the gas turbine unit, bypassing the traditional pilot-testing on the rig.

Studying unsteady combustion processes that occur in an annular combustion chamber of a gas turbine engine

When designing low-emission combustion chambers for gas turbine engines (GTE) and power plants, determining their tolerance to high-amplitude pressure oscillations during combustion is a challenging task. This paper proposes a modified instability criterion of combustion processes, which allows us to assess the influence of design and operating parameters on the amplitude of pressure oscillations. The comparison between the modified criterion and experimental data showed that for the volume-averaged estimation of the criterion, it is necessary to use the flame front region, defined by the value of the Progress Variable parameter of the FGM combustion model in the range of 0.3-0.7.

Influence of the distribution of fuel supply in a double-circuit burner on the concentration of harmful substances in combustion products

The design of a double-circuit burner of a low-emission combustion chamber of a gas turbine engine working on natural gas is considered. The distribution of the fuel supply in the double-circuit burner is investigated and its influence on the emissions of harmful substances is determined. Bench equipment, features of experimental studies of the concentration of gas mixture components in combustion products and calculations of the fuel combustion efficiency are presented. The ratio of fuel consumption along the circuits at a minimum concentration of nitrogen oxides and maximum combustion efficiency of carbon oxide in combustion products is determined. Keywords: double-circuit burner, low-emission combustion chamber, experiment, fuel, combustion efficiency, combustion products, nitrogen oxides. andreybaklanov@bk.ru

Influence of plasma-chemical products on process stability in a low-emission gas turbine combustion chamber

Abstract The article describes the stability of gaseous fuel combustion in gas turbine low-emission combustion chambers with the plasma-chemical assistance. The mathematical model of unsteady processes in a low-emission combustion chamber with a plasma-chemical stabilizer that takes into consideration the impact of low-temperature plasma on aerodynamics flow in a combustion chamber and the characteristics of heat release is developed. A methodology of a numerical experiment concerning the stability of gaseous fuel combustion in a combustion chamber with plasma assistance using computational fluid dynamics, which enhances the efficiency of designing and adjustment, is proposed. Practical recommendations for improvement of stability of a gas turbine combustion chamber with partially premixed lean fuel–air mixtures, working on gaseous fuels, are developed. They allow to reduce pressure fluctuations inside the flame tube by 10–35%, to decrease spectral power of static pressure in the flame tube in 1.5–2.0 times, to reduce nitrogen oxide emission up to 33.6 ppm in the exit section while retaining a carbon monoxide emission level, that corresponds modern international ecological standards.

Influence of plasma-chemical products on process stability in a low-emission gas turbine combustion chamber

Abstract The article describes the stability of gaseous fuel combustion in gas turbine low-emission combustion chambers with the plasma-chemical assistance. The mathematical model of unsteady processes in a low-emission combustion chamber with a plasma-chemical stabilizer that takes into consideration the impact of low-temperature plasma on aerodynamics flow in a combustion chamber and the characteristics of heat release is developed. A methodology of a numerical experiment concerning the stability of gaseous fuel combustion in a combustion chamber with plasma assistance using computational fluid dynamics, which enhances the efficiency of designing and adjustment, is proposed. Practical recommendations for improvement of stability of a gas turbine combustion chamber with partially premixed lean fuel–air mixtures, working on gaseous fuels, are developed. They allow to reduce pressure fluctuations inside the flame tube by 10–35%, to decrease spectral power of static pressure in the flame tube in 1.5–2.0 times, to reduce nitrogen oxide emission up to 33.6 ppm in the exit section while retaining a carbon monoxide emission level, that corresponds modern international ecological standards.

РАСЧЕТНО-ЭКСПЕРИМЕНТАЛЬНЫЕ ИССЛЕДОВАНИЯ ОБЛАСТИ УСТОЙЧИВОГО ГОРЕНИЯ ПРИРОДНОГО ГАЗА С ВОЗДУХОМ

One of the rational ways of creating low-emission combustion chambers is the organization of low-temperature lean combustion with external heating of the components before they are fed into the combustion chamber. When organizing lowtemperature lean combustion with large excess air ratios, problems may arise with ensuring a stable position of the flame front. Combustion stability to a large extent depends on the ratio of the average flow rate and the rate of turbulent combustion. The rate of turbulent combustion depends on the composition, pressure and temperature of the components supply and the degree of turbulence in the combustion chamber. The average flow rate depends on the excess air ratio (oxidizer and fuel consumption) and the geometric dimensions of the chamber. Earlier it was shown that when developing a low-emission combustion chamber with low-temperature lean combustion, it is advantageous to use the relative flow rate as a generalized characteristic of the intra-chamber process, which takes into account the consumption, geometric and thermodynamic parameters in the combustion chamber. This work is devoted to the analysis of stable combustion of a fuel composition natural gas + air based on the experimental data available in the public domain by the authors from the University of Michigan (USA). With the help of the methods developed by the authors, the experimental data on the limiting feed rates of the components into the atmospheric burner were processed. The limiting flow rates of air and natural gas, the limiting values of the excess air ratio, the longitudinal values of the speed of the fuel-air mixture and the limiting values of the relative flow rate are obtained and analyzed. Areas of stable combustion by the listed parameters at different degrees of air swirl are graphically presented.

Analysis of methods and characteristics of control systems for gas turbines with low-emission combustion chambers

Analysis of methods and characteristics of control systems for gas turbines with low-emission combustion chambers