Combustion Chamber Outlet Research Articles

Investigation of the Characteristics of a Gas Turbine Combustion Chamber with Steam Injection Operating on Hydrogen-Containing Mixtures and Hydrogen

The article is devoted to the investigation of the characteristics of a gas turbine combustion chamber with a steam injection when operating on hydrogen-containing mixtures and pure hydrogen. The parameters of a cannular combustion chamber with a separate injection of ecological and energy steam were studied to ensure the stable and ecologically clean chamber’s operation without the formation of flashback zones. The injection of ecological steam in the area of the vane swirler of the flame tube for the diffusion-type combustion chamber makes it possible to provide low emissions of nitrogen oxides at significant concentrations of hydrogen in its mixtures with natural gas, even if the maximum gas temperature in the primary zone of a combustion chamber increases. For the investigated chamber’s operating modes, the calculated carbon monoxide emission does not exceed 18.1 ppm. Emissions of nitrogen oxide when the hydrogen content changes from 0 to 50% initially decrease from 36.1 to 17.8 ppm due to increased steam injection to the combustion zone and then increase to 38 ppm when operating on pure hydrogen. An increase in the nonuniformity of the temperature field at the combustion chamber outlet with an increase in the hydrogen content in the mixture with natural gas was noted.

Economic plantwide control of a hybrid solid oxide fuel cell - gas turbine system

This study presents a novel approach for hybrid solid oxide fuel cell (SOFC) - gas turbine (GT) system control. The approach is based on a plantwide top-down strategy which leads to a proper selection of the control structure. As a result, while maintaining the system stability and dynamic performance during transients, the system operation is also kept at optimal conditions using simple PI controllers. The optimization cost function is defined to be the unit price of the net produced electricity. The system inlet fuel flow and the power drawn from the SOFC are considered as the main system disturbances. The two-dimensional disturbance space is discretized. Rigorous optimization problems are performed in each disturbance node and variation of system efficiency and constraint values are evaluated. Three different operating regions, with different sets of active constraints, are characterized. Equivalent to the identified operating regions, an efficiency map is also provided which illustrates the achievable system efficiencies in presence of disturbances. Based on the optimization outcomes, the identification of appropriate controlled variables is accomplished in each region. It revealed that to keep near-optimal operation under various operating conditions; the combustion chamber outlet temperature should be treated as a key controlled variable. Finally, dynamic simulations are performed and the proficiency of the proposed control structure is justified. According to the results, maximum SOFC temperature transients in all regions would be less than 2 K.min-1 while variations on the hybrid system output power are kept below 3 % and efficiency loss is restricted to 2 %.

Exhaust gas recirculation effects on flame heat release rate distribution and dynamic characteristics in a micro gas turbine

Exhaust gas recirculation (EGR) is an option proposed to augment the CO2 content in the exhaust gas for the efficient removal of CO2. In the field of micro-gas turbine (MGT), EGR is also a feasible solution to improve the part-load performance and fuel flexibility. This research combined EGR with an adjustable fuel feeding combustor to assess the part-load performance of a 300 kW MGT and the flame spatiotemporal characteristics. The radical chemiluminescence intensity of hydroxyl is selected to represent the heat release rate (HRR) in natural gas flames. The influence of EGR on HRR was investigated experimentally under various load ratios (50%–100%) and EGR ratios (0–20%). In addition, the temperature at the combustion chamber outlet is also measured. The results show that EGR can effectively reduce OTDF when the load ratio is high. Both the spatial distribution non-uniformity and fluctuation amplitude of HRR are suppressed after applying EGR. And EGR can also reduce the influence of mixing on HRR spatiotemporal characteristics. At last, the frequency characteristics of HRR are analyzed. The result shows that the flame frequency has a strong correlation with the characteristic frequency of turbulence.

Effects of the exit convergent ratio on the propagation behavior of rotating detonations utilizing liquid kerosene

The effects of the exit convergent ratio on the propagation behavior (i.e., initiation processes and propagation characteristics) of rotating detonations utilizing liquid kerosene have been experimentally investigated by varying the exit convergent ratio from 1 to 10 (i.e., CR = 1, 1.25, 1.67, 2.5, 5 and 10) and the mass flow rate of oxidizer. Oxygen-enriched air with an oxygen volume fraction of 40% and kerosene have been used as oxidizer and fuel, respectively, which are supplied into the combustion chamber through an atomizer-slit configuration. Experimental results indicate that rotating detonation waves can be initiated and propagate with different propagation modes under different exit convergent ratios. Three different propagation modes have been obtained, i.e., a deflagration mode, an ignition failure mode and a stable detonation mode. Moreover, the results show that the convergent ratio significantly influences the propagation modes, and when the combustion chamber outlet with a smaller convergent ratio is employed, stable rotating detonation waves can be obtained easily. In addition, it is observed that the time of establishment of the detonation wave increases with the convergent ratio.

Optimization of a biomass-driven Rankine cycle integrated with multi-effect desalination, and solid oxide electrolyzer for power, hydrogen, and freshwater production

The current work is a study of electricity, hydrogen, and freshwater polygeneration system fueled by biomass fuel. Accordingly, innovative integration of a Rankine cycle, a multi-effect desalination, and a solid oxide electrolyzer cell has been considered utilizing a syngas production biomass combustion chamber. The waste heat and a part of the output electricity of the Rankine cycle have been employed to launch the desalination and electrolyzer units, respectively. The suggested polygeneration is analyzed from the thermodynamic and exergoeconomic viewpoints through developing a code in engineering equation solver software and a multi-criteria optimization via MATLAB software. Hence, the NSGA-II optimization method and decision-making TOPSIS technique have been implemented. The parametric study has been conducted based on the effect of biomass fuel mass flow rate, turbine inlet pressure, combustion chamber outlet temperature, and pinch point temperature difference of the steam generator on the thermodynamic and exergoeconomic variables of the whole system. Considering the total exergy destruction rate, exergy efficiency, and total unit exergy cost of products as objective functions, the suggested system achieved the optimum values of 17.64%, 7658.5 kW, and 26 $/GJ corresponding for these variables.

Analysis of dynamic characteristics and sensitivity of hydrogen-oxygen expansion cycle rocket engine system

The success of the launch mission depends on the dynamic characteristics of the rocket engine system, while the engine development process is based on the parameter sensitivity analysis. However, the dynamic characteristics and parameter sensitivity of the hydrogen-oxygen expansion cycle engine remain unclear. This research built the simulation model of basic components and overall system of the hydrogen-oxygen expansion cycle engine. A 3-factor and 9-level numerical simulation study was carried out based on the structural parameters of the cooling channel. Results show that at 0.1s after the ignition of the engine, the speed of oxygen pump drops by 16.4%, while the torque of the hydrogen turbine drops by 43.6%. The rise of coolant temperature between the inlet of the cooling channel and the outlet of combustion chamber is about 185 K, which is about 4 times of that between the outlet of combustion chamber and the first section outlet of the nozzle. The sensitivity of the response time to the rib height reaches 0.36, while the sensitivity of response time to the rib width and the nozzle wall thickness are 0.15 and 0.12, respectively. These findings contribute to the start-up analysis and design of the hydrogen-oxygen expansion cycle engine.

Research on New Energy Technology in Energy-Saving and Emission-Reduction Low-Pollution Aerospace Engine

Under the national energy technology call for energy saving and emission reduction, the paper uses FLUENT software to simulate three-dimensional, two-phase, turbulent combustion in the combustion chamber of a certain type of aeroengine at the maximum and ground idle state and calculates the generation of CO and UHC. The value of temperature field, velocity field and concentration field. Through simulation, it is found that the maximum temperature of the flame is located at the axial position of the main combustion hole. The flame temperature begins to decrease after reaching the maximum temperature near the main combustion hole. In the temperature field of the combustion chamber outlet, the maximum temperature of the outlet section is 1820K and the average temperature is 1342K.The temperature distribution is relatively uniform overall. CO and UHC are mainly generated under low operating conditions, but the oil-gas ratio has a greater impact on pollutant emissions.

Design, Numerical and Experimental Investigation of High Swirling Flow in an Annular Combustion Chamber

In this study, an annular combustion chamber of a turbojet engine with a net trust of 1650N is designed. Kerosene is considered as fuel in this study. The design consists of evaluation of the reference quantities, calculation of the required dimensions, estimation of air distribution and pressure drop, estimation of the number and diameter of air admission holes, as well as aerodynamic considerations. The design process is accompanied by Computational Fluid Dynamics (CFD) based on RANS simulation. Three-dimensional simulation of the reacting process within the combustion chamber is carried out based on the finite volume method. The RNG turbulent model and the finite rate/eddy dissipation combustion model are considered in the present study. Finally, the (atmospheric test) AT rig of the combustion chamber is explained. The Turbine Inlet Temperature (TIT) of combustion chamber is measured at different operating conditions. The TIT values in the numerical simulation and experimental measurement are 1191.1K and 1227 K, respectively, in the design point. The SN and the angle of the RZ are equal to 0.9955 and 35.26 degree, respectively. The temperature, velocity and pressure fields of RZ, air-fuel mixture, combustion turbulence are then presented in image outputs and graphs. The results indicate that the temperature distribution at the outlet of combustion chamber is relatively uniform.

The regulation effect of methane and hydrogen on the emission characteristics of ammonia/air combustion in a model combustor

Ammonia, made up of 17.8% hydrogen, has attracted a lot of attention in combustion community due to its zero carbon emission as a fuel in gas turbines. However, ammonia combustion still faces some challenges including the weak combustion and sharp NOx emissions which discourage its application. It was demonstrated that the combustion intensity of ammonia/air flame can be enhanced through adding active fuels like methane and hydrogen, while the NOx emission issue will emerge in the meantime. This study investigates regulation effect of methane and hydrogen on the emission characteristics of ammonia/air flame in a gas turbine combustor. The instantaneous OH profile and global emissions at the combustion chamber outlet are measured with Planar Laser Induced Fluorescence (PLIF) technique and the Fourier Transform Infrared (FTIR), respectively. The flames are also simulated by large eddy simulation to further reveal physical and chemical processes of the emissions formation. Results show that for NH3/air flames, the emissions behavior of the gas turbine combustor is similar to the calculated one-dimensional flames. Moreover, the NOx emissions and the unburned NH3 can be simultaneously controlled to a proper value at the equivalence ratio (φ) of approximate 1.1. The variation of NO and NO2 with φ for NH3/H2/air flames and NH3/CH4/air flames at blending ratio (Zf) of 0.1 are similar to the NH3/air flames, with the peak moving towards rich condition. This indicates that the NH3/air flame can be regulated through adding a small amount of active fuels without increasing the NOx emission level. However, when Zf = 0.3, we observe a clear large NOx emission and CO for NH3/CH4/air flames, indicating H2 is a better choice on the emission control. The LES results show that NO and OH radicals exhibit a general positive correlation. And the temperature plays a secondary role in promoting NOx formation comparing with CH4/air flame.

Комплексная эффективность применения древесных гранул в энергоустановках

In advanced countries, the dramatic impact of greenhouse gases on the global climate is reduced by replacing fossil fuels with biofuels. This method is being actively encouraged. However, by-products of logging, processing and conversion of wood are classified as difficult to burn fuels due to their high moisture content, low energy density and extremely heterogeneous granulometric composition. A promising direction to increase the energy density and transportability of the timber industry by-products is their granulation. Wood pellet fuel burning in heat-generating plants results in significant increase in their energy and environmental performance. The purpose of the paper is an experimental and calculation study of the energy and environmental performance of 4 MW hot water boilers produced by Polytechnik Luft- und Feuerungstechnik GmbH in the process of burning pine and spruce wood pellets obtained from by-products woodworking. When performing studies, the components of the boiler’s heat balance, gas release, and particulate emissions were determined. Numerical modeling of thermochemical and aerodynamic processes taking place in the boiler combustion chamber was carried out by using the Ansys Fluent three-dimensional simulation software. Together with industrial-operational tests it showed the possibility to reduce the total share of flue gas recirculation into combustion chambers of boiler units to values not exceeding 0.45, in providing an acceptable temperature of combustion products at the combustion chamber outlet and maintaining minimum emissions of carbon and nitrogen monoxides. At the same time, the share of gases fed by recirculation smoke exhausters to the over-bed area of the burner should have higher values than under the reciprocating grates of boilers. Guidelines for comprehensive improvement of wood pellet combustion efficiency in combustion chamber of 4 MW hot water boilers have been developed and implemented. The priorities are: using the air passed through the cooling channels of the setting as secondary air; reducing the rarefaction in the combustion chambers to 30–70 Pa; optimizing the ratio of primary and secondary air, herewith, the share of primary air in the total flow should be 0.26–0.35. Implementation of the developed guidelines allowed to increase the boiler gross efficiency by 0.5–1.8 %, to reduce the aerodynamic resistance of the gas path by 15–20 % and to ensure consistently low emissions of carbon and nitrogen monoxides and soot particles. When designing boiler units for burning wood pellet fuel it is advisable to place heating surfaces in the combustion chamber, included in the circulation circuit of the boiler. This will increase the efficiency and life cycle of the boiler unit.

Combustion characteristics of ignition processes for lean premixed swirling combustor under visual conditions

The combustion characteristics of ignition processes under different ignition fuel ratios were studied on a natural gas-fueled micro gas turbine combustion chamber. With the changing of air mass flow, the equivalence ratio varied from 0.024 to 0.994 at which the fuel mass flow remained the same. The flue gas compositions were measured at the combustion chamber outlet, and used to calculate the combustion efficiency. To characterize the relative flame stability, optical measurements and digital image processing techniques were applied. The results indicate that the combustor can ignite successfully under the ignition fuel ratio conditions of 10%, 15%, and 20%, in which the corresponding equivalence ratios are 0.082–0.497, 0.082–0.746, and 0.098–0.994, respectively. Moreover, the combustion efficiency decreased with the descending equivalence ratio. However, the amount of CO and unburned CH4 in the combustion products increased as the equivalence ratio decreased. The heat release rate in the reaction zone and the morphological characteristics of the flame were obtained using the gray level of average flame images. Furthermore, the flame fluctuation was analyzed by coefficient of variation of the flame area, and the relative flame stability was analyzed by the probability distribution density of the relative flame area ratio. The appropriate equivalence ratios for ignition are around 0.245, 0.243–0.369, and 0.196–0.326 under the ignition fuel ratio conditions of 10%, 15%, and 20%. The ignition fuel ratio has considerable influence on combustion efficiency, combustion product, and flame stability.

Thermodynamic and thermoeconomic analyses and energetic and exergetic optimization of a turbojet engine

In this study, a thermal model for a turbojet engine is proposed. Besides the engine’s performance, the cost flow rate of each component is evaluated by performing the energetic, exergetic and exergoeconomic analyses. The compressor pressure ratio (πAC), flight Mach number (Ma) and turbine inlet temperature (TIT) are three operating variables, which affect the performance of the whole system. Therefore, a sensitivity analysis is carried out to survey the effect of these variables on objective functions (i.e., energy efficiency, exergy efficiency, and exergy destruction). It is found that there are some contradictions between exergy efficiency and exergy destruction, which by increment in TIT energy efficiency increases, while the exergy destruction decreases. Therefore, an optimization should be applied on the presented system. The results show that the highest exergy destruction, unit exergy cost, and cost rate are 34.96 GJ h−1, 34.85 US$ GJ−1 and 437.37 US$ h−1 occur in the combustion chamber, compressor’s outlet flow and combustion chamber outlet stream, respectively. The energetic and exergetic optimization solution is obtained as the Pareto frontier. Final decision-making methods such as TOPSIS, LINMAP are employed for choosing the optimal solution. Design points of LINMAP and TOPSIS having 65.86%, 66.95% thermal efficiency and 12.51 GJ h−1, 12.65 GJ h−1 exergy destruction, respectively.

Thermodynamic modeling and comparative analysis of a compressed air energy storage system boosted with thermoelectric unit

Current study represents the thermodynamic modeling and exergy analysis of a compressed air energy storage system boosted with thermoelectric generator (CAES/TEG). To evaluate the studied system, a comparative analysis between compressed air energy storage system (CAES) with CAES/TEG has been done. Exergy, a powerful tool for analyzing energy conversion systems, is employed to determine the exergy destruction rate and exergy efficiency of the system as well as different related components. The results of exergy analysis indicates that the wind turbine with 35.28 kW (44.81% of total exergy destruction rate) has the highest exergy destruction rate and after that in the second and third places are combustion chamber and cavern. Findings indicate that with adding thermoelectric modules to the CAES system, the output power of Rankine cycle and organic Rankine cycle increase about 1.16 kW and 0.959 kW in comparison with CAES system, which these changes lead to increasing the net output power of the system in CAES/TEG system from 33.59 kW to 35.71 kW compare with CAES. Moreover, the influences of main parameters such as compressor mass flow rate, compressor pressure ratio, and combustion chamber outlet temperature and wind speed on the CAES/TEG performance are investigated.

Thermodynamic analysis and optimization of an oxy-combustion combined cycle power plant based on a membrane reactor equipped with a high-temperature ion transport membrane ITM

This paper presents an advanced zero emission power plant (AZEP) which is a combined cycle power plant with a membrane reactor equipped with a high-temperature ion transport membrane (ITM). The membrane reactor, which is used as a replacement for a combustor in the gas turbine, combines three functions: combustion of fuel, oxygen separation from the air in the ITM, and heating of the oxygen-depleted air. Due to the membrane reactor, the AZEP does not need an energy-consuming external air separation unit, which is a significant advantage over other types of power plants which utilize oxy-combustion technology. The presented thermodynamic model for AZEP with an advanced numeric model of the ITM allows the user to perform thermodynamic analyses for a wide range of AZEP operating parameters and to select their optimal values, without the need to determine the geometric parameters of the ITM and heat exchangers. The obtained results allow one to indicate the basic features of this carbon capture technology. The selection of AZEP operating parameters is related to the balance between the power plant’s efficiency maximization and the limitation of the ITM and heat exchangers surface areas. This manuscript also presents an analysis of the possible AZEP plant development. The development model of the E-AZEP plant assumes a number of improvements in the parameters of the ITM and the entire membrane reactor, with respect to the AZEP plant basic model. The ITM assumes an improvement in the ionic conductivity (σion) by approx. 45%, by changing the value of the conductivity coefficient (C2) as well as increasing the maximum operating temperature of the membrane from 900 °C to 1000 °C. The work demonstrated the great influence of the membrane surface. In the model of the membrane reactor, a higher flue gas temperature was assumed at the combustion chamber outlet, equal to t1g = 1600 °C, which together with the assumption of temperature approximation ΔThe.HHX = 20 K gives an air temperature t3a = 1580 °C. With the current technological possibilities, AZEP plants are competitive compared to alternative solutions, but they do not have a significant advantage over them. However, overcoming the presented limitations may allow us to achieve an advantage in terms of achieved efficiency compared to alternative CO2 capture technologies. Achieving the air temperature at the inlet to the expander, at a level close to the temperatures used in J-class gas turbines (E-AZEP plant case), allows for a decrease in the efficiency when compared to modern combined cycle power plants, at a level of 3% points.

Effects of different fuel supply types on combustion characteristics behind group of V-gutter flame holders: Experimental and numerical study

Experiments on fuel effects flame stabilization processes, NOx generation and temperature at combustion chamber outlet when using a group of three V-gutter flame holders have been reported. Fuel supply directly to the re-circulation zone on the inside of the V-gutter (type A fuel supply), and alternatively in the second type, fuel was supplied to the V-gutter symmetry axis on the outside (type B fuel supply have been carried out.

Computational Studies of the Operating Conditions of a Combustor with Staged Combustion of Fuel-Air Mixture

The paper is devoted to the computational studies of the combustion chamber (CC) with staged combustion of fuel-air mixture for a high-temperature gas-turbine unit (GTU) with a working medium temperature of up to 1670°C. The analyzed combustion chamber is equipped with two burning devices (BD) arranged in series (BD1 and BD2) and three independent fuel supply channels connected to a pilot (diffusion) burner of BD1 and pre-mixing burners of BD1 and BD2. The paper presents the results of calculating the most thermally stressed operating parameters of the combustion chamber with the outlet temperature of up to 1670°C, and shows how the fuel distribution between the CC zones affects the non-uniformity of the temperature and concentration profiles of harmful emissions at the CC outlet at various fuel distribution ratios between the pre-mixing burners of BD1 and BD2. Based on the results of a series of calculations, an algorithm is proposed for controlling the GTU operation by re-distributing fuel between the fuel channels to minimize the level of harmful emissions.

Propulsion Performance of Cylindrical Rotating Detonation Engine

This study evaluated the propulsion performance of a nozzleless, cylindrical rotating detonation engine (RDE). Using a mixture, the RDE was tested in a low-back-pressure environment at propellant mass flow rates of . In high-speed imaging of the self-luminescence within the combustor, rotating luminous regions were observed at mass flow rates above . Measured pressure distributions suggest that burned gas reached sonic velocity at the combustion chamber outlet. This paper proposes the structure of internal flow in the RDE and confirms that calculated pressure distribution based on the structure was close to the experimental distribution. This study also estimated the RDE’s thrust by pressure and momentum exchange and confirmed it by experimental measurement. Moreover, the theoretical thrust calculated under the assumption that exhaust is a sonic flow agreed with the load cell thrusts, suggesting that RDE combustion is perfectly completed inside the chamber. Specific impulses are 80–90% of specific impulses for ideal correct expanded flow for all mass flow rates, and its value was close to that of an annular RDE. In addition, RDE performance will increase by about 20% if the RDE is equipped with a divergent nozzle and the gas is correctly expanded to back pressure.

Experimental Investigation of NOx Emission from a Sequential Combustor with the Kinetic Second Zone

This is the fourth paper in a series of publications on the experimental investigation of fuel-air mixture combustion in a combustion chamber (CC) with two combustion zones set in a series with an outlet temperature ranging from 1550 to 1700°C and meeting the requirements for NOx and carbon oxide emissions. The results of the experimental investigation into combustion of gaseous fuel CS comprising two combustion zones set it a series, each with its own burner unit, are presented. The first burner unit (BU1) is typical for low-emission combustors. It has swirlers, a premixing zone, and pilot and main burners. The premixed fuel-air mixture (FAM) is fed to the BU1 inlet. The second burner unit (BU2) is located downstream of the first combustion zone and is fed with FAM with a fuel concentration equal to or higher than the fuel concentration in the first combustion zone. The kinetic fuel combustion whose rate depends on the kinetics of the fuel oxidation reaction rather than on the rate of migration of the reacting components to the flame surface by molecular or kinetic diffusion (as in case of diffusion combustion) occurs in the first and second zones. The second burner unit has its own premixer. In the second zone, the fuel burns in a high-temperature environment at a reduced oxygen content. Four CS configurations with different lengths of the first and second combustion zones were investigated experimentally. The first configuration with single-zone fuel burning is the base one. In the other three configurations, the length of the first and the second zone varied (with the total length of the liner being the same). The results of optimization of the FAN between two sequential combustion zones are presented. The best length of the second zone minimizing NOx and CO emissions at a CC outlet temperature from 1550 to 1700°С was found.

Counter-current hydrogen–oxygen vortex combustion chamber. Thermal physics of processing

The expediency is substantiated for the use of a vortex counter-current circulation flow of water steam and the stoichiometric hydrogen-oxygen mixture as a source of heat generation. That flow is essential for the purpose of making efficient models of high-temperature combustion chambers for the cogeneration cycles.An experimental investigation was carried out of hydrogen-oxygen mixture combustion in a counter-current combustion chamber-superheater. Operating range values of heat power were obtained. A maximum temperature of the superheated steam at the combustion chamber outlet was 1350 K. There were determined the optimal modes of hydrogen-oxygen mixture outflow ensuring its steady combustion in the counter-current flow core of the water steam.

Improvement of pellet fuel bed combustion technology in low power boilers

This paper describes different ways of efficiency improvement in pellet fuel bed combustion and proposes methods of pellet fuel combustion, ensuring high environmental and energy performance. The constriction in the form of a convergent-divergent passage in the furnace chamber with simultaneous delivery of the secondary air at the point of maximum dispersal of the exhaust gases has reduced unburned combustible losses by 39%. At the same time, the constriction has reduced heat transfer surface area and residence time of hot gases in the furnace chamber, which increased the exhaust gases temperature at the combustion chamber outlet by 98°C. Ansys CFX software package was actively used for numerical simulation during the development of innovative furnace chamber design. To verify simulation results, the firing test bench was designed.