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Researches have shown that the use of a continuous detonation afterburner can improve the propulsion performance of aero engine. However, backpropagation pressure waves (BPW) generated by the pressure gain of detonation will affect the internal flow and performance of turbine. This article simulates BPW through a custom function, and investigates the effects of BPW amplitude, rotation frequency, and propagation mode on turbine performance through three-dimensional simulation. The results show that as the pressure amplitude of the BPW increases, the pressure oscillation at each section of the turbine increases and a local subcritical flow state will appear, leading to the decrease of turbine flowrate and turbine power, as well as an intensification of instantaneous turbine power fluctuations. As the rotation frequency of the BPW increases, the pressure oscillation at each section of the turbine gradually decreases. The flowrate and power of the turbine do not change much, but turbine efficiency gradually decreases. Compared to the aligned mode, the turbine performs better under the influence of BPW in misaligned mode. Compared to the single-wave mode, the fluctuation of transient turbine power is lower under the influence of BPW in the multiwave mode excluding collision mode. Finally, the constraints of equal flowrate region and equal turbine power line on the peak-to-peak value of the BPW were analyzed when the joint operation of the turbine and compressor was not affected. The rotation frequency and mode of BPW will affect the flowrate region and power line. [ABSTRACT FROM AUTHOR]

As the flight envelopes of turbine-based combined cycle (TBCC) engines expand, ensuring reliable ignition and flame stability under varying conditions becomes increasingly critical. Previous work has shown a significantly changed ignition performance and flow pattern in cavity-based combustors when strut structure parameters were altered, indicating a strong correlation between the ignition process, flame structure, and the strut configuration. This suggests that further investigation is required to determine the optimal strut design. Therefore, this study examines the impact of various strut configurations through numerical simulations, validated by high-speed imaging. Findings show that the tail-groove strut designs improve the flame propagation performance compared to the normal struts, with a critical depth beyond which further increases do not enhance performance. Changes in strut length have a lesser impact than depth. Flow analysis indicates that tail-groove struts create additional recirculation zones that enhance fuel atomization and flame stability. These results suggest that optimizing strut configurations is vital for achieving reliable ignition and flame stability, advancing the development of efficient engines across a wide range of operational conditions. [ABSTRACT FROM AUTHOR]

AbstractIn the present study, a combined experimental and numerical study is conducted to investigate the three-dimensional film cooling using forward and reverse injection over a corrugated surface. The experiments are performed to analyze the fluid flow and heat transfer phenomenon of the film cooling and to validate the numerical model under laboratory conditions (i.e. low temperature). Infrared thermography is used to estimate the temperature distribution and heat transfer coefficient. The numerical study is extended for a wide range of operating parameters at actual operating conditions of the afterburner liner. The outcome of numerical results shows promising results with reverse injection. The issue of kidney vortices with forward injection is mitigated with reverse injection. The reverse injection shows vortices in the plane of corrugation which improves the lateral spreading of coolant. A significant improvement in coolant coverage is reported over conventional forward injection, and the maximum improvement is 146%. Finally, a thermal stress analysis is conducted for film-cooled corrugated liners. The reverse injection shows promising results in terms of coolant coverage which reduces the overall temperature of the corrugated liner, hence thermal stress is significantly reduced. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A new afterburner installation is proposed, fueled with pure hydrogen (100%H2) or hydrogen–methane mixtures (60% H2 + 40% CH4, 80% H2 + 20% CH4) for use in cogeneration applications. Two prototypes (P1 and P2) with the same expansion angle (45 degrees) were developed and tested. P1 was manufactured by the classic method and P2 by additive manufacturing. Both prototypes were manufactured from Inconel 625. During the tests, analysis of flue gas (CO2, CO, and NO concentration), PIV measurements, and noise measurements were conducted. The flue gas analysis emphasizes that the behavior of the two tested prototypes was very similar. For all three fuels used, the CO2 concentration levels were slightly lower in the case of the additive-manufactured prototype P2. The CO concentration levels were significantly higher in the case of the additive-manufactured prototype P2 when 60% H2/40% CH4 and 80% H2/20% CH4 mixtures were used as fuel. When pure H2 was used as fuel, the measured data suggest that no additional CO was produced during the combustion process, and the level of CO was similar to that from the Garrett micro gas turbine in all five measuring points. The NO emissions gradually decreased as the percentage of H2 in the fuel mixture increased. The NO concentration was significantly lower in the case of the additive-manufactured prototype (P2) in comparison with the classic manufactured prototype (P1). Examining the data obtained from the PIV measurements of the flow within the mixing region shows that the highest axial velocity component value on the centerline was measured for the P1 prototype. The acoustic measurements showed that a higher H2 concentration led to a reduction in noise of approximately 1.5 dB for both afterburner prototypes. The outcomes reveal that the examined V-gutter flame holder prototype flow was smooth, without any perpendicular oscillations, without chaotic motions or turbulent oscillations to the flow direction, across all tested conditions, keeping constant thermal power. [ABSTRACT FROM AUTHOR]

The article provides a brief analytical review of mathematical models of the working process used to study the parameters and characteristics of a gas turbine engine at all stages of its creation and operation. It is shown that the first-level mathematical model can be used for the estimation of parameters and characteristics under real operating conditions that differ significantly from the calculated ones. A mathematical model of a mixed-flow turbofan engine with an afterburner is proposed in the article; the construction principle and structure of the mathematical model of the engine are given. The model allows solving various problems associated with calculating the performance of a mixed-flow turbofan engine with an afterburner in a wide range of external conditions and engine operating modes.

Copyright of Journal of Dalian University of Technology / Dalian Ligong Daxue Xuebao is the property of Journal of Dalian University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to improve the backward-facing radar stealth capability of the engine exhaust system, five coating schemes for afterburner, which is radar wave strong scattering source, are formulated. The influence of afterburner coating absorbing materials on the horizontal polarization and vertical polarization RCS distribution pattern of the exhaust system in the range of -30°~+30° azimuth of the typical frequency point in the S-band and X-band is analyzed by using the shooting and bouncing rays, also SAR imaging of typical frequency points in the X-band at an azimuth angle of 0° is simulated.The results show that the distribution of strong scattering sources in S-band and X-band is basically the same, and the influence of different coating schemes of absorbing materials on the RCS reduction effect of two bands is similar. The flame stabilizer is the strongest scattering source of radar characteristic signal, and coating it with radar absorbing materials has the greatest benefit on reducing the radar characteristic signal of the exhaust system. Coating absorbing materials in the four parts of afterburner inner cone, flame stabilizer, lobe mixer and afterburner cylinder is the best absorbing material coating scheme for the reduction effect of RCS in the two wave bands. The average RCS reduction effect of horizontal polarization and vertical polarization in S band is 92.3% and 92.0%, and the average RCS reduction effect of horizontal polarization and vertical polarization in X-band is 90.2% and 88.4%.

As the flight envelopes of turbine-based combined cycle (TBCC) engines expand, ensuring reliable ignition and flame stability under varying conditions becomes increasingly critical. Previous work has shown a significantly changed ignition performance and flow pattern in cavity-based combustors when strut structure parameters were altered, indicating a strong correlation between the ignition process, flame structure, and the strut configuration. This suggests that further investigation is required to determine the optimal strut design. Therefore, this study examines the impact of various strut configurations through numerical simulations, validated by high-speed imaging. Findings show that the tail-groove strut designs improve the flame propagation performance compared to the normal struts, with a critical depth beyond which further increases do not enhance performance. Changes in strut length have a lesser impact than depth. Flow analysis indicates that tail-groove struts create additional recirculation zones that enhance fuel atomization and flame stability. These results suggest that optimizing strut configurations is vital for achieving reliable ignition and flame stability, advancing the development of efficient engines across a wide range of operational conditions.

In this study, design calculations and calculations of afterburner used in jet engines are presented by evaluating the results of analytical and computational analysis. Afterburner inlet values of 1050 K temperature, 300 kPa pressure and 3.6 kg/s mass flow rate are taken as the design conditions. Maximum length and diameter are 500 mm and 200 mm, respectively, for the sections to be designed as length constraints within the scope of the conceptual design. The tworing vee-gutter has 1.33 cm in diameter and 4.25 cm high. Jet A fuel is assumed to be injected into the core flow (90 degrees) from the spray bars. The spray is mounted in line with the veegutter to optimize the mixing of the flow. Analyses are performed for 4 cm between the spray bar and the vee-gutter. For the study, the GE J79 engine was examined from the literature and taken as a basis for the aerodynamic transition section design. Within the scope of TEKNOFEST 2023 Jet Engine Design Competition, a preliminary design of an afterburner module that can produce 700 pounds of thrust and has a life capacity of 25 hours should be realized in line with the design requirements and constraints. In the light of geometric constraints, one-dimensional combustion calculations of the module are made, and the parts are modelled using the relevant SolidWorks CAD program and these modelled parts are then transferred to ANSYS™ environment and the results and analyses are verified. The afterburner module flow analysis software program ANSYS™ is used to analyse the afterburner operation in both cold operating ranges (i.e. without combustion) using compressible, viscous and standard k-epsilon turbulence model. As a result, the effect of afterburner length on combustion performance is found to be significant. As a result of the calculations, afterburner length is found as 28.14 cm. It is found that the combustion efficiency is 81.5% and the temperature can be increased from 1050 K to 2044 K. The total pressure loss is 14.96% as pressure drop due to the geometric parameters and heat addition. The blockage ratio calculated due to the use of vee-gutter geometry is the most important parameter in the pressure drop. It is found that the jet engine producing 670 lbs (2981 N) of thrust when the afterburner is not working whereas it can provide a significant amount of power increment at the expense of a 50% increase in specific fuel consumption when the afterburner is active as well as providing a 738 lbs (3238 N) with a 10.1% thrust increase. The reason of the enhancement is mainly coming from the mixing effect of the vee-gutter on the flow structure. [ABSTRACT FROM AUTHOR]

Copyright of Aero Weaponry is the property of Aero Weaponry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An analysis of the problems that arise when dealing with issues of increasing the efficiency of using an afterburner as part of a current aircraft engine is presented, where the complex problem of reducing its influence in non-afterburning operation and improving the work process when using it is solved. In a number of cases, solving the problem comes down to a compromise which does not allow full realization of all the advantages of the design element in question. The results of a study of the influence of the method of gas-dynamic flame stabilization on the main target indicator – specific fuel consumption in a real engine are presented, which makes it possible to justify conducting this kind of research on a real object. Graphs of changes in specific fuel consumption and thrust of a gas turbine engine when changing the engine rotor speed for non-afterburning operating modes are presented, as well as graphs of changes in specific fuel consumption and thrust of a gas turbine engine when changing the speed of the aircraft for afterburning operating modes. A conclusion is drawn about the expedience of using gas-dynamic flame stabilization in the afterburner from the point of view of its effect on specific fuel consumption.

A new afterburner installation is proposed, fueled with pure hydrogen (100%H2) or hydrogen–methane mixtures (60% H2 + 40% CH4, 80% H2 + 20% CH4) for use in cogeneration applications. Two prototypes (P1 and P2) with the same expansion angle (45 degrees) were developed and tested. P1 was manufactured by the classic method and P2 by additive manufacturing. Both prototypes were manufactured from Inconel 625. During the tests, analysis of flue gas (CO2, CO, and NO concentration), PIV measurements, and noise measurements were conducted. The flue gas analysis emphasizes that the behavior of the two tested prototypes was very similar. For all three fuels used, the CO2 concentration levels were slightly lower in the case of the additive-manufactured prototype P2. The CO concentration levels were significantly higher in the case of the additive-manufactured prototype P2 when 60% H2/40% CH4 and 80% H2/20% CH4 mixtures were used as fuel. When pure H2 was used as fuel, the measured data suggest that no additional CO was produced during the combustion process, and the level of CO was similar to that from the Garrett micro gas turbine in all five measuring points. The NO emissions gradually decreased as the percentage of H2 in the fuel mixture increased. The NO concentration was significantly lower in the case of the additive-manufactured prototype (P2) in comparison with the classic manufactured prototype (P1). Examining the data obtained from the PIV measurements of the flow within the mixing region shows that the highest axial velocity component value on the centerline was measured for the P1 prototype. The acoustic measurements showed that a higher H2 concentration led to a reduction in noise of approximately 1.5 dB for both afterburner prototypes. The outcomes reveal that the examined V-gutter flame holder prototype flow was smooth, without any perpendicular oscillations, without chaotic motions or turbulent oscillations to the flow direction, across all tested conditions, keeping constant thermal power.

The afterburner is essential for military aeroengines, providing rapid thrust increase during critical maneuvers. However, complex failure mechanisms pose challenges for fault diagnosis and troubleshooting. This study investigates a specific aviation engine's afterburner engagement principle and typical faults, using fault tree analysis and computational fluid dynamics (CFD). We propose a hybrid diagnostic fault architecture combining traditional observer fault diagnosis with fault trees for online fault diagnosis of critical faults. Simulations and test bench verification confirm the feasibility and effectiveness of our approach, offering valuable insights and guidance for addressing afterburner engagement issues in aviation engines. [ABSTRACT FROM AUTHOR]

The gas turbine industry strongly committed to develop gas turbines operating with 100% hydrogen till 2030, such fully supporting the transformation of the European natural gas grid into a renewable-based energy system by overcoming technical challenges and ensuring that this transformation takes place swiftly. By extending the fuel capabilities of gas turbines to hydrogen, their role can become predominant in the energy transition period but also in longterm energy strategies. In combined cycle configuration (CCGT), gas turbines are already the cleanest form of thermal power generation. For the same amount of electricity generated, gas turbines running on natural gas emit 50% less CO2 emissions than coal-fired power plants. Mixing renewable gas (e.g., green hydrogen, biogas) with natural gas enables further reduction in net CO2 emissions. In this paper pure hydrogen and blends of hydrogen methane will be studied as fuel in order to predict the behavior of afterburner system with a new designed geometry. [ABSTRACT FROM AUTHOR]

The recent advancement of cooling methodologies for critical components such as turbine blades, combustor liners, and afterburner liners has led to the development of a combination of impingement and film cooling. The present study proposes an efficient cooling technique for a modern aero-engine afterburner liner based on the combination of jet impingement and film cooling. To achieve this, a numerical model is devised to model the film flow over a corrugated liner with several jets impinging over it. The numerical model is validated in a set of in-house experiments as well as against experimental data available in the literature. The experiment is performed for a limited temperature range (i.e., with a low-density ratio). However, the numerical simulations are carried out by varying the blowing ratio from 0.3 to 0.6. The density ratio during the simulations is kept at 3.5. The minimum distance between the impinging plate and the liner is kept at h/D = 1. A detailed analysis of the numerical results indicates a significant drop in the temperature distribution over the liner surface because of the employed cooling technique. The present study also reveals that, under similar operating conditions, the combined jet impingement and film cooling system has the ability to achieve the targeted cooling effect at a lower bleed air flow rate due to its higher effectiveness than that of the standard film cooling arrangement. [ABSTRACT FROM AUTHOR]

The development of a new gas turbine engine requires a lot of time and money spent on the design and testing its compressor, which has been shown as the most complex and time-consuming assembly unit of the engine. This article examines the potential application of the industry-developed engine compressors in the designs of a new turbojet engine and a gas turbine compressor. The comparative analysis of the ideal cycles of an augmented turbojet engine and a turbojet engine with a high-temperature combustor is made. The advantage of the turbojet engine with a high-temperature combustor configuration over the augmented turbojet engine configuration is shown. The high rates of jet-pipe gas velocity make a turbojet engine with a high-temperature combustor suitable for supersonic cruise products.

Future passenger cars must comply with whatever regulations will be created to mitigate greenhouse gas emissions (GHG) and pollution. Regarding the pollutants of an internal combustion (IC) engine, they are dealt with by using an exhaust after-treatment system (EATS). Yet, catalytic converters encounter light-off problems after cold start: their after-treatment efficiency is unsatisfactory until their temperature reaches a threshold, usually called the light-off temperature. Consequently, in this phase, important levels of pollutants are produced, being therefore paramount to achieve the catalyst light-off as fast as possible. Passing to EURO7, which is expected to happen in 2025 means to have the EATS ready for efficient treatment “instantaneously” after cold starting. The solutions usually used to generate more heat at the EATS level are not considered sufficient for the coming EURO7 regulation. Consequently, they must be complemented with other systems, such as the afterburner, which is an extra-combustion device. Accordingly, this paper is focused on the challenges that come with the use of such an afterburner and it presents the following: (1) a proposal for a layout and operation strategy of such a device and (2) an experimental investigation of the effect an afterburner has on the light-off performance of a usual three-way catalyst. On the latter, the cold start exhaust emissions were analyzed with and without using this extra-combustion device, thus being able to conclude on its effectiveness: full light-off of the pre-catalyst thanks to burner’s operation up to 1000 °C and, consequently, an efficient treatment of the pollutants. Equally, the paper presents the impact of the afterburner on fuel consumption and, therefore, on GHG it generates, given the fact that it burns carbon-based fuel as the engine.

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, parametric cycle analysis of a conceptual turbojet engine with an afterburner (TJEAB) was conducted at sea level conditions-zero Mach. Based on this analysis, exergetic sustainability parameters of TJEAB were scrutinized for military mode (MM) and afterburner mode (ABM). Constitutively, several design parameters of TJEAB were chosen so as to optimize performance and exergetic parameters which consist of specific fuel consumption (SFC), overall efficiency, exergy efficiency, environmental effect factor (EEF) and exergetic sustainability index (ESI). In this context, compressor pressure ratio (CPR), turbine inlet temperature (TIT) were preferred due to high effect of these variables on engine performance. CPR ranges from 4 to 11 whereas TIT varies from 1150 K to 1550 K. According to optimization of performance parameters, minimum SFC was achieved as 28.59 g/kN.s at MM and 43.95 g/kN.s at ABM. On the other hand, maximum overall efficiency is determined as to be 13.07 % at MM and to be 8.5 % at ABM. As for exergetic parameters, exergy efficiency was calculated as maximum with 30.85 % at MM and 23.2 % at ABM. Finally, maximum exergetic sustainability index of TJEAB was computed as 0.446 at MM and 0.269 at ABM. It is thought that energetic and exergetic parameters analyzed in this analysis could guide in designing turbojet engines in terms of lower fuel consumption thereby environmental-benign. [ABSTRACT FROM AUTHOR]

Presented herein is a comparative performance analysis of a novel turbofan engine with an auxiliary combustion chamber, nicknamed the TurboAux engine, against a turbojet engine, and a low bypass ratio turbofan engine with an afterburner is presented. The TurboAux engine is an adaption of the low-bypass ratio turbofan engine, but with secondary combustion in an auxiliary bypass annular combustion chamber for thrust augmentation. The TurboAux engine is envisioned with the desire to facilitate clean secondary burning of fuel at temperatures higher than in the main combustion chamber with air exiting the low-pressure compressor. The comparative study starts by analyzing the turbojet engine and its performance with and without an afterburner segment attached. In parallel, the conventional turbofan and its mixing counterpart are analyzed, also with and without an afterburner segment. A simple optimization analysis of a conventional turbofan is performed to identify optimal 'fan' pressure ratios for a series of low-bypass ratios (0.1 to 1.5). The optimal fan pressure ratios and their corresponding bypass ratios are adapted to demonstrate the comparative performance of the varying configurations of the TurboAux engine. The formulation and results are an attempt to make a case for charter aircrafts and efficient close-air-support aircrafts. The results yielded increased performance in thrust augmentation, but at the cost of a spike in fuel consumption. This trade-off requires more in-depth investigation to further ascertain the TurboAux's utility. [ABSTRACT FROM AUTHOR]

In this study, we implement attosecond afterburners in an ultrashort soft X-ray free-electron laser (FEL) to improve the performance of generating attosecond pulses. In this scheme, the FEL pulse produced in the normal radiator section is dumped while the well bunched electron beam is reserved and reused in downstream afterburners. Subsequently, radiation in the afterburners gains rapidly as the bunching factor in the current spike is large, making the radiation pulse much shorter and cleaner than that from a normal radiator. Multi-shot simulations are carried out to demonstrate the performance and stability of the proposed technique. [ABSTRACT FROM AUTHOR]

Particle emissions from aircraft engines are mainly related to the emission of particles with very small diameters. The phenomena of the formation of particles in various operating conditions of turbine engines are known. However, it is difficult to find the results of research on the use of the afterburner in the literature. Increased aviation activity within military airports and situations such as air shows are associated with a very intense emission of particles, and pose a direct threat to human health. This article presents an analysis of particulate matter emissions from a military aircraft engine, with particular emphasis on operation with an afterburner. The parameters of the emission of particles determined were: PM Number Emissions Index (EIN), Particle Number Emissions Intensity (EN), PM Mass Emission Index (EIM), PM Mass Emission Intensity (EM), Differential Particle Number Emission Index, Differential Particle Volume Emission Index, and Differential Particle Mass Emission Index. The value of EIN for the afterburner use was the lowest among the whole operation range of the engine and was equal to 1.3 × 1015 particles per kilogram. The use of an afterburner resulted in a sharp increase in the EIM coefficient, which reached 670 mg/kg. Despite a very large increase in fuel consumption, the EIM coefficient turned out to be over 60 times greater than in the case of 100% engine thrust. [ABSTRACT FROM AUTHOR]

The recent advancement of cooling methodologies for critical components such as turbine blades, combustor liners, and afterburner liners has led to the development of a combination of impingement and film cooling. The present study proposes an efficient cooling technique for a modern aero-engine afterburner liner based on the combination of jet impingement and film cooling. To achieve this, a numerical model is devised to model the film flow over a corrugated liner with several jets impinging over it. The numerical model is validated in a set of in-house experiments as well as against experimental data available in the literature. The experiment is performed for a limited temperature range (i.e., with a low-density ratio). However, the numerical simulations are carried out by varying the blowing ratio from 0.3 to 0.6. The density ratio during the simulations is kept at 3.5. The minimum distance between the impinging plate and the liner is kept at h/D = 1. A detailed analysis of the numerical results indicates a significant drop in the temperature distribution over the liner surface because of the employed cooling technique. The present study also reveals that, under similar operating conditions, the combined jet impingement and film cooling system has the ability to achieve the targeted cooling effect at a lower bleed air flow rate due to its higher effectiveness than that of the standard film cooling arrangement.

The processes of fuel-air mixture formation in the afterburner of a gas-turbine engine are studied. The experiments are performed with an element of the mixer with a two-phase working body having several orifices playing the role of spray injectors. The effect of the liquid-to-gas flow rate ratio, which is proportional to the air-fuel ratio, on the mixer operation is investigated. It is established that the presence of an increasing pressure field along the mixer channel leads to nonuniform flow rates of the liquid and the gas with respect to the injectors and spraying parameters. [ABSTRACT FROM AUTHOR]

• An ammonia fuel processor was developed for ammonia solid oxide fuel cell system. • The ammonia fuel processor consisted of a decomposition reactor and afterburner. • The ammonia decomposition rate varied from 32% to 84% by the decomposition reactor. • Nitrogen oxide emissions at the afterburner exceeded the regulatory limit. • The regulatory limit of nitrogen oxide emissions was met by a post-decomposition. Solid oxide fuel cells can overcome the poor flammability of ammonia by directly converting the chemical energy of ammonia into electricity. However, thermal stress by internal decomposition, nitriding at the solid oxide fuel cells stack and nitrogen oxides emissions must be considered when using ammonia in solid oxide fuel cells. In this study, an ammonia fuel processor was developed for stable operation and low emissions of solid oxide fuel cells using ammonia. The ammonia fuel processor consisting of an ammonia decomposition reactor, an afterburner and a post-decomposition reactor was tested using simulated off-gases of solid oxide fuel cells using ammonia. The ammonia conversion of the decomposition reactor varied from 32 % to 84 % with off-gas temperatures from 360 °C to 670 °C. When ammonia conversion after the solid oxide fuel cell stack was 99.70 %, nitrogen oxides emissions of the afterburner was 1.05 g/kWh, which is higher than the regulatory limit of 0.26 g/kWh. High fuel utilization and excess air ratio made nitrogen oxides emission even worse. The regulatory limit was successfully satisfied by using the post-decomposition reactor even when ammonia conversion after the solid oxide fuel cell stack was 99.10 %. The developed ammonia fuel processor could supply fuel at the optimal hydrogen-to-ammonia ratio and prevent nitrogen oxides emissions in solid oxide fuel cells using ammonia. [ABSTRACT FROM AUTHOR]

A comprehensive performance test is conducted on a diffusion burner designed for a 30 kW-class methane solid oxide fuel cell (SOFC) power generation system. To facilitate this assessment, a test system is established, capable of simulating the gas composition and temperature of the anode and cathode at the outlet of the fuel cell stack under various typical operating conditions. The test results demonstrate the afterburner's exceptional robustness, minimal pressure loss, and low emission characteristics. Notably, the afterburner can be ignited and started at low load (6LPM, 20 % of the rated methane flow rate) and can achieve low-load heating (4LPM, at approximately 13 % of the rated methane flow rate) with a significant excess air coefficient of 46.2. Remarkably, the afterburner maintains its reignition capability under all operating conditions. Operational stability is observed with a water-to-carbon ratio below 3, displaying robust resistance to fluctuations in water vapor and airflow. Under generating condition, the afterburner exhibits self-ignition capabilities without the need for an external igniter following flameout. The pressure losses within both the anode and cathode flows remain well below 200Pa, while NOx and CO emissions are recorded at 1.7mg/kWh and 66.2mg/kWh, respectively, complying with the stringent EU EN676:2020 standards. • Conducted experiments on a 30 kW SOFC diffusion burner. • Established a test system simulating operating parameters from startup to generation. • Verified burner's robustness, low pressure loss, and emissions. [ABSTRACT FROM AUTHOR]

The mixing process of pre-evaporated afterburner fuel at different positions upstream of the mixers and airflow was numerically simulated in a straight channel, with semicircular mixer, rectangular mixer, triangular mixer and chevron mixer respectively. The effects of vortices generated by mixers on fuel distribution and mixing characteristics were studied. The results show that: (1) The scale, strength and breaking speed of the streamwise vortex and the development speed of normal vortex are different downstream of the four mixers, which accelerate the mixing process of fuel and airflow. (2) The fuel distribution at the outlet of mixers, downstream of straight section and downstream of the crest and trough is mainly affected by secondary flow, the streamwise vortex and the normal vortex respectively. (3) The fuel mixing uniformity downstream of the four mixers is increased by about 80% compared with no mixer. In the limited distance, the mixing performance of chevron mixer is the best, while the triangular mixer is the worst Rectangular mixer has the fastest mixing speed and superior comprehensive performance. In addition, the effect of the channel wall on the mixing process downstream of mixers cannot be ignored. [ABSTRACT FROM AUTHOR]

In the context of solving the problem of increasing the efficiency of aircraft with the capability to fly at supersonic speed, an important aspect is to reduce the amount of fuel consumed in this flight mode, since this is the most promising direction in the development of aviation and these modes are accompanied by a number of significant problems that require joint efforts of leading organizations in this field. To solve the problem of expanding the range of use of the afterburner during the flight of the aircraft and reducing the amount of fuel required for this flight, we suggest the angle of inclination of the fuel supply should be adjusted relative to the direction of gas flow. The results of calculating the distribution of the afterburner fuel over the volume of the afterburner, supported by known experimental data, are presented. The analysis of characteristic points on the graphs of the dependence of the main variables is carried out and possible reasons for the peculiar characteristics of the working process in the afterburner in the case of changing the nozzle mounting angle are indicated. Possible options of controlling the working process in the afterburner are suggested.

The main problems of the creation of afterburning turbofan engines, among which the irremovable surge of the compressor, is disclosed by historical analysis. According to the published models, such surge is a hydrodynamic instability in the form of rotating stall mutual transitions to surge with the primary cause of instability in the form of stall or vibration combustion in the afterburner. The Pratt & Whitney F100 serial engine, which based on TF30 is one of the first in which the irremovable surge was detected. As a result, several planes F-15 crashed, so far as the compressor could not be restored to a stable state without stopping and restarting the engine. Dissection of the problem with this phenomenon led to the conclusion that this irremovable surge problem was generated by the engine design. To eliminate it, the company had to refine several systems, such as an electronic engine control system, fuel supply of the afterburner along with the nozzle locations, firing belt, combustion stabilization, an extension of flow separation along the contours, etc. According to the analysis of publications, particular difficulties arose with the recoverable unsurge operation of such engines. It is noteworthy that today, the F-135-PW100 engines have been installed on the F-35 aircraft, the predecessors of which are the F-100 engines with the same problems. The results of experimental studies of a fan are presented in the article to deepen in the stall flow mechanism and the occurrence of rotating stall of the fan blades. The perturbations from vibrational combustion in the afterburner combustion chamber to the fan stall boundary in the afterburning turbofan engine system at bench conditions were simulated by independent throttling of the duct over a wide range of the bypass ratio. Numerous monographs and publications according to vibrational combustion, in particular in afterburner combustion chambers TRDF AL-21F and TRDDF AL-31F, of A. M. Lulka, confirm the possibility of the propagation of perturbations against the flow in the bypass duct and the impossibility of their propagation through the turbines. The propagation of surge perturbations in the afterburning turbofan engine to the compressor of the internal duct behind the fan occurs through the interaction of the duct. The more reliable way to prevent emergencies is to provide stability margin area of compressors. Estimation of the pre-stall state of the flow traditionally is carried out by the diffusivity factor of Lieblein FD, which is applicable in 2D calculations. The integral variational principle of nonequilibrium thermodynamics of the “maximum flow of mechanical energy” of V. N. Yershov was applied.

In this study, we implement attosecond afterburners in an ultrashort soft X-ray free-electron laser (FEL) to improve the performance of generating attosecond pulses. In this scheme, the FEL pulse produced in the normal radiator section is dumped while the well bunched electron beam is reserved and reused in downstream afterburners. Subsequently, radiation in the afterburners gains rapidly as the bunching factor in the current spike is large, making the radiation pulse much shorter and cleaner than that from a normal radiator. Multi-shot simulations are carried out to demonstrate the performance and stability of the proposed technique.

Presented herein is a comparative performance analysis of a novel turbofan engine with an auxiliary combustion chamber, nicknamed the TurboAux engine, against a turbojet engine, and a low bypass ratio turbofan engine with an afterburner is presented. The TurboAux engine is an adaption of the low-bypass ratio turbofan engine, but with secondary combustion in an auxiliary bypass annular combustion chamber for thrust augmentation. The TurboAux engine is envisioned with the desire to facilitate clean secondary burning of fuel at temperatures higher than in the main combustion chamber with air exiting the low-pressure compressor. The comparative study starts by analyzing the turbojet engine and its performance with and without an afterburner segment attached. In parallel, the conventional turbofan and its mixing counterpart are analyzed, also with and without an afterburner segment. A simple optimization analysis of a conventional turbofan is performed to identify optimal ‘fan’ pressure ratios for a series of low-bypass ratios (0.1 to 1.5). The optimal fan pressure ratios and their corresponding bypass ratios are adapted to demonstrate the comparative performance of the varying configurations of the TurboAux engine. The formulation and results are an attempt to make a case for charter aircrafts and efficient close-air-support aircrafts. The results yielded increased performance in thrust augmentation, but at the cost of a spike in fuel consumption. This trade-off requires more in-depth investigation to further ascertain the TurboAux’s utility.

Particle emissions from aircraft engines are mainly related to the emission of particles with very small diameters. The phenomena of the formation of particles in various operating conditions of turbine engines are known. However, it is difficult to find the results of research on the use of the afterburner in the literature. Increased aviation activity within military airports and situations such as air shows are associated with a very intense emission of particles, and pose a direct threat to human health. This article presents an analysis of particulate matter emissions from a military aircraft engine, with particular emphasis on operation with an afterburner. The parameters of the emission of particles determined were: PM Number Emissions Index (EIN), Particle Number Emissions Intensity (EN), PM Mass Emission Index (EIM), PM Mass Emission Intensity (EM), Differential Particle Number Emission Index, Differential Particle Volume Emission Index, and Differential Particle Mass Emission Index. The value of EIN for the afterburner use was the lowest among the whole operation range of the engine and was equal to 1.3 × 1015 particles per kilogram. The use of an afterburner resulted in a sharp increase in the EIM coefficient, which reached 670 mg/kg. Despite a very large increase in fuel consumption, the EIM coefficient turned out to be over 60 times greater than in the case of 100% engine thrust.

In this paper, Finite element thermal analysis has been performed on a gas turbine afterburner jet pipe liner. Burnt air and fuel mixture from the main fuel system and afterburner system flows through the liner before exiting into the atmosphere via nozzle experiences a high variation of temperature across it thorough the engine operation thus susceptible to failure due to thermal stress. Simulations were done considering conduction and convection only. The FE (Finite element) model is first studied under steady-state conditions with constant loading. The analysis is extended to transient boundary conditions which are common in practical afterburner jet pipe liners to investigate the effect of temperature. Each of the parameters had a marked effect on jet pipe liner performance within the range of conditions investigated. The research work has been carried out at Heat Transfer Group, Gas Turbine Research Establishment, DRDO Bengaluru, Karnataka, India. [ABSTRACT FROM AUTHOR]

The use of 3-D simulation programs and in particular NX and ANSYS simulators brought the design and fine tuning of gas turbine engine combustion chambers to the next level, as it allows improving the performance (increased combustion efficiency, reduced radial and circumferential non-uniformity of the total gas temperature), as well as determining the weak points of the structure. The article analyzes the flow of fuel jets from the finger sprayers of the afterburner of the combustion chamber of a gas turbine engine. The problem of optimizing the distribution of fuel is formulated: the fuel at the exit of the flame tube is to be evenly distributed by varying the diameters of the holes in the fuel manifolds. Restrictions are imposed on the optimization problem the supply of fuel to the peripheral zone at the outlet of the afterburner is reduced by a factor of five. The optimization effect is verified by comparing the fuel combustion efficiency in the case of standard fuel distribution with the optimized distribution option using the NX and ANSYS 3-D simulations. As a result, we observe an increase in combustion efficiency in all afterburner modes of engine operation.

Flameholder-stabilized flames are conventional and also commonly used in propulsion and various power generation fields to maintain combustion process. The characteristics of flame expansion were obtained with various blockage ratios, which were observed to be highly sensitive to inlet conditions such as temperatures and velocities. Experiments and simulations combined methodology was performed; also the approach adopted on image processing was calculated automatically through a program written in MATLAB. It was found that the change of flame expansion angle indicated increasing fuel supply could contribute to the growth of flame expansion angle in lean premixed combustion. Besides, the influence of inlet velocity on flame expansion angle varies with different blockage ratios, i.e. under a small blockage ratio (BR = 0.1), flame expansion angle declined with the increase of velocity; however, under a larger blockage ratio (BR = 0.2 or 0.3), flame expansion angle increased firstly and then decreased with the increasing velocity. Likewise, flame expansion angle increased firstly and then decreased with the increasing temperature under BR = 0.2/0.3. In addition, flame expansion angle was almost the same for BR = 0.2 and BR = 0.3 at a higher temperature (900 K), and both of which were bigger than BR = 0.1. Overall, BR = 0.2 is the best for increasing flame expansion angle and reducing total pressure loss. The influence of velocity and temperature on flame expansion angle found from this research are vital for engineering practice and for developing a further image processing method to measure flame boundary. [ABSTRACT FROM AUTHOR]

A method is developed for secondary data processing of the results of simulation of two-phase flow in an afterburner with a complex geometry. This method offers a prediction for mixing process efficiency (quality estimate) and combustion efficiency in an afterburner of a power plant. The opportunities of this method were demonstrated at the example of simulation of mixing the two-phase fuel with air in the afterburner of a model power plant with gas generation outlay. The paper presents a mathematical model for studied processes and the simulation results. The fuel was the gasification products (GP) of a high-energy composition (a mixture of gaseous and condensed phases). An algorithm was applied for processing the mathematical simulation results: the output is the evaluation of mixing between GP condensed phase and air flow. The parametric study offers the dependencies for size distributions of GP particles in the afterburner cross sections. The limiting values for GP combustion efficiency in the afterburner were evaluated from analysis of GP flow (gas and condensed phases) mixing with air flow. Simulation gives the data on the influence of injection configuration and GP condensed phase dispersion profile on the mixing efficiency in the afterburner. The results of study can be useful in recommendations for gaining on the cycle efficiency in novel propulsion plants. [ABSTRACT FROM AUTHOR]

Objective Established the animal model of quiescent periodontitis and observed the changes of alveolar bone microstructure in different afterburning time. Methods 156 cases SD rats of 28 weeks old were randomly divided into control group (P= 50) and experimental group (P= 106) .The experimental group were established animals model of quiescent periodontitis, and were randomly divided into periodontal treatment group (P= 50) and periodontal group with orthodontic treatment (P = 50).The first molar of the right maxillary of latter was applied with a force of 50 g.Ten rats were sacrificed and wasobserved by micro-ct at 0, 7, 14,21 and 28 days. Results (T)For the first molar of the right maxillary in the animal model of experimental group,the alveolar bone mineral density (BMD) ,bone volume fraction (BV/TV) and trabecular thickness(Tb · Th) were lower,and the number of trabecular bone (Tb · N) ,trabecular separation distance ( Tb · Sp) were higher than those of the control group at 0,7,14,21 and 28 days;(2)Compared with periodontal treatment group, BMD. BV/TV and Tb · Th of periodontal group with orthodontic treatment were lower, while Tb · N and Tb · Sp were higher at the 14 days,BV/TV were higher and Tb · N and Tb · Sp were lower at the 28 days;(3)At 14 days, for the first molar of the right maxillary in periodontal group with orthodontic treatment, BMD. BV/TV and Tb · Th were decreased to the lowest level, while Tb · N and Tb · Sp were increased to the highest level.However, all the indicators had been repaired to the state of unstressed at 28 days. Conclusion (J) The alveolar bone of animal models of quiescent periodontitis were osteoporotic, which had a slowed response to mechanical stimulation; (2) In the animal model of quiescent periodontitis, alveolar bone absorption was the main factor after sudden stress, but as the force weakened and the force value stabilized, the alveolar bone returned to the stale before the afterloading gradually;®Small force stimulation was beneficial to the repair of alveolar bone in animal models of quiescent periodontitis. [ABSTRACT FROM AUTHOR]

For the first time, a detonation afterburner (DA) for continuous detonation combustion of TS-1 aviation kerosene was developed, manufactured, and tested. Test fires of the DA in combination with a TJ100S-125 small-sized single-circuit turbojet engine were carried out on a ground test bench. In the test fires, stable modes of continuous detonation combustion of aviation kerosene were registered: a near-limit mode of longitudinally pulsating detonation (LPD) and a spin detonation (SD) mode with one detonation wave. Compared to a conventional afterburner, at the same in-chamber pressure, the specific fuel consumption in the DA was 30% lower and the specific thrust and thrust boosting coefficient were 30% higher. It is shown that, when operating in the LPD mode, the average heat flux to the DA walls is about 0.5 MW/m2 and, in the SD mode, 0.86 MW/m2. These values indicate the high potentiality of the DA when used in advanced jet engines. [ABSTRACT FROM AUTHOR]