Search

The text is a summary of selected papers from the 4th National Aerospace Propulsion Conference (NAPC-2022). The conference aims to bring together professionals from the aerospace propulsion community to showcase research activities and foster collaborations. The selected papers cover various aspects of aerospace propulsion, including airbreathing engine components, rocket propulsion, gas turbine combustor design, MILD combustion, and mixing characteristics of free jets. The papers provide insights into the design, performance, and characteristics of different propulsion technologies. The summary acknowledges the contributions of the authors and reviewers and highlights the importance of conferences in facilitating knowledge sharing and networking in the field of aerospace propulsion. [Extracted from the article]

There are many sets of information in the literature (e.g., papers, books and websites) about the great achievements that are expected for aerospace gas turbine engines by the employment of ceramic matrix composites (CMCs) and thermally sprayed environmental barrier coatings (EBCs) in their hot zones (e.g., combustion chambers, vanes, shrouds, blades and afterburners). Among these achievements, it is typically highlighted (i) turbine weight reduction, (ii) reduced fuel consumption, (iii) higher operation temperatures, (iv) superior thrust-to-weight ratio and (v) lower emission of toxic gases to the atmosphere. Although these achievements are true, they are generally not well-explained to the reader on how together they come to be. In addition, according to "conventional wisdom", some of these engineering feats are in fact opposing each other (e.g., higher operation temperatures versus lower emissions). The objective of this tutorial paper is to present the reader how these feats are achieved by the concomitant combination of imaginative engineering. It will explain the non-stop driving force for increasing combustion temperatures; show the basic concepts of CMCs, the paramount need of EBCs, and the complexity of creating EBC architectures via air plasma spray (APS). Finally, highlights on how EBCs/CMCs are tested at high temperature will be provided. The content of this paper shall be understood by anyone with basic knowledge in materials processing and surface engineering. [ABSTRACT FROM AUTHOR]

This study firstly investigated the species, concentration variation, and emission factors of mercury emitted from the burning of incenses and joss papers in an Asian temple. Both indoor and outdoor speciated mercury (GEM, GOM, and PHg) were sampled by manual samplers, while ambient GEM at an indoor site was in-situ monitored by a continuous GEM monitor. Field measurement results showed that the total atmospheric mercury (TAM) concentrations in indoor and outdoor environments were in the range of 8.03–35.72 and 6.03–31.35 ng/m 3 , respectively. The indoor and outdoor ratios (I/O) of TAM in the daytime and at nighttime were in the range of 0.64–0.90 and 1.50–2.04, respectively. The concentrations of GEM, GOM, and PHg during the holiday periods were approximately 1–4 times higher than those during the non-holiday periods. GEM was the dominant mercury species in the indoor and outdoor environments and accounted for 63–81% of TAM, while the oxidized mercury accounted for 19–37% of TAM. Burning incenses and joss papers in a combustion chamber showed that the concentration of GEM from joss paper burning ranged from 4.07 to 11.62 μg/m 3 , or about 13.97 times higher than that of incense burning, while the concentration of PHg from incense burning ranged from 95.91 to 135.07 ng/m 3 , or about 3.29 times higher than that of joss paper burning. The emission factors of incense burning were 10.39 ng/g of GEM and 1.40 ng/g of PHg, while those of joss paper burning were 12.65 ng/g of GEM and 1.27 ng/g of PHg, respectively. This study revealed that speciated mercury emitted from worship activities had significant influence on the indoor and outdoor mercury concentrations in an Asian temple. Higher intensity of worship activities during holidays resulted in a higher concentration of speciated mercury in indoor and outdoor air, which might cause health threats to worshipers, staffs, and surrounding inhabitants through long-term exposure. [ABSTRACT FROM AUTHOR]

All experiments were carried out in a prototype vortexing fluidized bed combustor (VFBC). The dimension of the combustion chamber is 0.7 x 1.4 x 2 m, and the freeboard section is 1 m i.d. and 4 m in height. Paper sludge was used as the feeding material. Two types of coal particles were employed as the supplementary fuel. In order to understand the characteristics of the VFBC system for paper sludge incineration, the effect of various operating parameters, such as the primary airflow, excess air ratio, and secondary airflow rates, on temperature distribution, ash elutriation, combustion efficiency, and pollutant emissions were investigated. [ABSTRACT FROM AUTHOR]

Detonation combustion represents a significant advancement in efficiency over traditional deflagration methods. This paper presents a Pulsed Detonation Combustor (PDC) model that is designed with an aerodynamic mixing chamber featuring Hartmann–Sprenger resonators and crossflow injection. This design enhances operational cycle frequency and enables sustained detonation over short distances (below 200 mm). The PDC's performance was evaluated through a comprehensive full-factorial experimental campaign, incorporating four factors with four discrete levels each. Testing was conducted using both hydrogen/air and hydrogen/oxygen mixtures, highlighting the PDC's potential as a carbon-free combustion chamber suitable for both air-breathing and space-based propulsion systems. One advantage is the versatility of our PDC breadboard, which lies in its applicability to both terrestrial and in-space applications, such as interplanetary travel or trajectory corrections. Thrust measurements were recorded using a load cell and time-averaged thrust levels were determined over the detonation cycle and are reported herein, together with the specific impulse. The results underscore the PDC's promise as an efficient propulsion technology for future aerospace applications. [ABSTRACT FROM AUTHOR]

Despite considerable research effort in the past 60 years, the occurrence of combustion instabilities in rocket engines is still not fully understood. While the physical mechanisms involved have been studied separately and are well understood in a controlled environment, the exact interaction of fluid dynamics, thermodynamics, chemical reactions, heat-release and acoustics, ultimately leading to instabilities, is not yet known. This paper focuses on the investigation of flame-acoustic interaction in a model combustion chamber using detached-eddy simulation (DES) methods. We present simulation results for a new load point of combustion chamber H from DLR Lampoldshausen and explore the flame response to resonant and non-resonant external excitation. In the first part of the paper, we use time-averaged results from a steady-state flow field without siren excitation to calculate the combustion chamber Helmholtz eigenmodes and compare them to the experimental results. The second part of the paper presents simulation results at a non-resonant excitation frequency. These results agree very well with the experimental results at the same condition, although the numerical simulation systematically overestimates the oscillation amplitudes. In the third part, we show that a simulation with resonant siren excitation can correctly reproduce the shift in eigenmode frequencies that is also seen in the experiments. Additionally, for this new load point, we confirm previous numerical results showing a strong influence of transversal excitation on the shape of the dense LOx cores. This work also proposes a bombing method for determining the resonant eigenmode frequencies based on an unexcited steady-state DES by simulating the decay of a strong artificial pressure pulse inside the combustion chamber. [ABSTRACT FROM AUTHOR]

This article presents the authors' considerations regarding the possibilities of developing fuel equipment for modern compression ignition engines used in special and non-road vehicles. The paper discusses the process of fuel combustion and atomization in the chamber of a piston combustion engine. The paper then presents the concept of modifying the atomizer of a modern fuel injector for operation using hydrogen-containing fuels of plant origin. The authors present a review of tests performed using an engine dynamometer on a modern engine with a Common Rail system running on biofuel. The CI engine operated with standard and modified fuel injectors. During the tests, the external ecological characteristics of the engine were analyzed as a function of rotational speed; the values of injection doses at individual rotational speeds and their effects on the characteristics were read from the current parameters, and the pressure and temperature in the engine's combustion chamber were measured. The research results show that implementing the changes proposed by the authors of this work is a good direction for the development of compression ignition engines. [ABSTRACT FROM AUTHOR]

In recent years, heat release associated with the detonation phenomenon is considered a very efficient process. Pressure gain combustors are being developed with detonation waves as the driving force. In this scenario, study of detonation waves has become very important. Deflagration-to-Detonation transition (DDT) is one of the ways used to initiate detonation in the combustors. An attempt has been made in this paper to study the DDT in a tube with obstacles using OPENFOAM. A 2-dimensional rectangular section of a tube containing obstacles filled with stoichiometric hydrogen-air mixtures at different initial conditions have been studied. The effect of changes in the length of the tube, number of obstacles, blockage ratios and initial pressure of the reactants on the detonation wave properties have been studied using numerical simulation based on ddtfoam software. The motivation for this study is to design a pre-detonator for a rotating detonation engine (RDE). In order to make it compatible with the RDE and the test facility, it has been proposed to carry out simulations using shorter lengths of the DDT tube. The number of obstacles has been selected appropriately to obtain detonation at shorter lengths of the tube of the order of 1.5 m, 1.0 m & 0.5 m. As the objective has been to obtain design data for the prototype, the finer details of DDT are not being discussed in this paper. [ABSTRACT FROM AUTHOR]

Designing advanced combustors that operate at high temperatures and produce little pollution, especially in the absence of primary and dilution holes, is a difficult task that may bring significant challenges. In this regard, this paper introduces a Kriging surrogate model approach to optimize the outlet temperature distribution of the combustor to achieve such advanced low-pollution combustors. Building upon previous research, this study explores the effects of the swirler blade installation angle on the outlet temperature distribution of the combustor without primary or dilution holes. Traditional methods, such as the control variable method using computational fluid dynamics (CFD) for numerical simulation, are limited in application due to the complex coupling of flow, heat transfer, mass transfer, and combustion processes. In contrast, surrogate models, especially the Kriging model, offer a rapid and efficient alternative to extensive CFD simulations that provide accurate predictions and error estimates for the solution of the problem. In summary, this paper details the process of generating sample points through three-dimensional numerical simulations, develops a Kriging surrogate model through Latin hypercube sampling, and optimizes the model to identify the most uniform outlet temperature distribution achievable by adjusting the installation angle of the swirl blade. The optimal design parameters, which are quickly obtained through the Kriging model, showed a significant reduction in the overall temperature distribution function and the radial temperature distribution function by 21% and 27.14%, respectively. [ABSTRACT FROM AUTHOR]

Many alternative fuel technologies have been studied for the transport sector to increase its sustainability while reducing costs, greenhouse gases (GHG), and air pollution emissions. Nevertheless, conventional diesel is still the predominant fuel for heavy-duty trucks. Road freight transport consumes 25% of the world's energy and is responsible for emissions with local health impacts and the global greenhouse effect. In this context, this paper reviewed items from 2015 to 2020 to analyze the technologies available for the road freight transport regarding pollutant and GHG emissions. Results are presented in two parts: first quantitatively, quantitative data was extracted from reviewed papers and statistically treated and, second, qualitatively through a comparative chart, which shows the impact on air pollutants from the use of a different type of fuels. In general, papers are mostly concerned with particulate matter (PM), carbon monoxide (CO), nitrogen oxides (NOx), and hydrocarbons (HC) emissions due to its impact on public health, with a low number of papers covering GHG emissions. The trade-off between different fuels and how this process can impact emissions, sometimes increasing or decreasing specific pollutants, is discussed. According to the analyzed papers, the main characteristics that affect the pollutant emissions are, in general, the fuel oxygen content and the combustion chamber temperature. [ABSTRACT FROM AUTHOR]

The catalytic combustion has the advantage of lower auto-ignition temperature and helps to expand the combustible limit of lean premixed gas. However, the intake needs to be preheated to certain temperature commonly through an independent heat exchanger. Similar to the principles of non-catalytic RTO combustion, this paper presents a similar approach whereby the combustion chamber is replaced by a catalytic combustion bed. A new catalytic reactor integrated with a heat recuperator is designed to enhance the heat recirculation effect. Using a two-dimensional computational fluid dynamics model, the performance of the reactor is studied. The reaction performances of the traditional and compact reactors are compared and analyzed. Under the same conditions, the compact reactor has better reaction performance and heat recirculation effect, which can effectively decrease the ignition temperature of feed gas. The influences of the inlet velocity, the inlet temperature, the methane concentration, and the thermal conductivity of porous media on the reaction performance of integrated catalytic reactor are studied. The results show that the inlet velocity, inlet temperature, methane concentration, and thermal conductivity of porous media materials have important effects on the reactor performance and heat recirculation effect, and the thermal conductivity of porous media materials has the most obvious influence. Moreover, the reaction performance of multiunit integrated catalytic reactor is studied. The results show that the regenerative effect of multiunit integrated catalytic reactor is further enhanced. This paper is of great significance to the recycling of low calorific value gas energy and relieving energy stress in the future. [ABSTRACT FROM AUTHOR]

Purpose: A combustor design is a particularly important and difficult task in the development of gas turbine engines. During studies for accurate and easy combustor design, reasonable design methodologies have been established and used in engine development. The purpose of this paper is to review the design methodology for combustor in development of advanced gas turbine engines. The advanced combustor development task can be successfully achieved in less time and at lower cost by adopting new and superior design methodologies. Design/methodology/approach: The review considers the main technical problems (combustion, cooling, fuel injection and ignition technology) in the development of modern combustor design and deals with combustor design methods by dividing it into preliminary design, performance evaluation, optimization and experiment. The advanced combustion and cooling technologies mainly used in combustor design are mentioned in detail. In accordance with the modern combustor design method, the design mechanisms are considered and the methods used in every stage of the design are reviewed technically. Findings: The improved performances and strict emission limits of gas turbine engines require the application of advanced technologies when designing combustors. The optimized design mechanism and reasonable performance evaluation methods are very important in reducing experiments and increasing the effectiveness of the design. Originality/value: This paper provides a comprehensive review of the design methodology for the advanced gas turbine engine combustor. [ABSTRACT FROM AUTHOR]

Research on engine operation using hydrogen may enable appropriate optimization of thrust, and therefore performance, related to its potential use in aircraft. It is particularly important as the share of hydrogen in combustion affects the reduction of combustion products such as carbon dioxide, carbon monoxide, nitrogen oxide, hydrocarbons, and solid matter. This is in line with the new requirements regarding the increased supply of sustainable aviation fuels (SAFs) and the related changes in emissions, i.e., reducing the harmful impact of exhaust gases on the environment. This paper presents the results of measurements carried out in the GTM400 MOD turbojet engine. Based on the research performed, the impact of hydrogen and aviation kerosene combustion on selected engine parameters is presented. The paper shows changes in the rotational speed and volume flow of JET A-1 fuel as a function of engine operation time. Changes in temperature measured at the edge of the flame tube were also examined. The tests confirmed that the combustion chamber worked correctly in the selected area in the range of the tested fuel mixtures. After incorporating hydrogen into the combustion process, the consumption of traditional JET A-1 fuel was significantly reduced. [ABSTRACT FROM AUTHOR]

Experiments and numerical simulations were conducted across a range of contraction ratio to investigate the detonation combustion characteristics of liquid aviation kerosene/air rotating detonation combustor. The research indicates that extremely low and high contraction ratio adversely affect the stable operation of the two-phase rotating detonation combustors. At a contraction ratio that is too low (19.03 % in the RDC discussed in this paper), the atomization and mixing properties of the two-phase fuel are poor, with a lower reaction pressure in the fresh mixture, hindering the initiation of detonation waves. On the other hand, a contraction ratio (85.7 % in the RDC discussed in this paper) that is too high enhances the energy of the detonation wave; it triggers oblique shockwave feedback, preventing the fresh mixture from entering the combustor and thus leading to the quenching of detonation waves. With an increase in the contraction ratio of outlet configurations, there is a noticeable rise in both the peak pressure and combustion efficiency of detonation waves. In contrast, the wave height gradually decreases, and the wave velocity shows a pattern of initially increasing and then decreasing. Along the axial position inside the two-phase rotating detonation combustor, the upstream detonation wave is caused by the reflected shockwaves increasing the pressure of the upstream fresh mixture. In contrast, the downstream detonation wave results from increased fresh mixture pressure and enhanced fuel atomization and mixing due to the increased contraction ratio of outlet configurations and wave feedback. So, the detonation wave exhibits a strong-weak-strong distribution characteristic. • Three-dimensional numerical simulation and experiment in a RDC with separate feeding of kerosene and air is achieved. • Two atomization and mixing structures ("Kerosene" and "Enhanced Kerosene" region) is found. • An optimal contraction ratio size enables the RDC to achieve the best operational characteristics. [ABSTRACT FROM AUTHOR]

The paper presents conclusions from research conducted at the Warsaw University of Technology in 2019–2023 regarding the combustion of fuel–water emulsions in a miniature gas turbine. The presented conclusions were made taking the current state of knowledge available in the literature into account. Particular emphasis was placed on explaining the discrepancies in the results of the experimental studies available in the literature. The main aspects of the combustion of the fuel–water emulsions that were analyzed were their impact on the emissions of NOx and CO, as well as the impact of the surfactant included in the fuel mixture on the combustion process, emissions and the formation of deposits on the walls of the combustion chamber. The impact of the emulsion fuel on fuel consumption was also discussed. In order to explain the changes occurring in the combustion chamber as a result of adding water to the fuel, numerical methods and methods of fluid mechanics were used. Studies have shown a positive impact of the use of fuel–water emulsions on CO and NOx emissions and fuel consumption. It was also demonstrated that fuel additives used for emulsification can create deposits on the walls of the hot engine section. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical evaluation of the pre-chamber induced HCCI combustion concept (PC-HCCI) in terms of engine performance, emissions, and controllability. In this concept, a spark-initiated combustion in the pre-chamber is utilized to trigger the kinetically controlled combustion of an ultra-lean mixture in the main combustion chamber. The experimental measurements were performed on a single-cylinder engine with a custom-made active pre-chamber. A high compression ratio of 17.5 was used, which limits the maximum achievable engine load due to high knocking tendency but enables both standard PCSI combustion (flame propagation) at very high dilution levels and HCCI combustion at reasonable intake temperatures. The analysis of combustion characteristics and the resulting performance is performed at indicated mean effective pressures (IMEPs) of 3.5 and 3.0 bars, and three different intake temperatures of 80 °C, 90 °C, and 100 °C. The variation in engine load was achieved by adjusting the excess air ratio in the main chamber. On each combination of intake temperature and engine load, a spark sweep and an injected PC fuel mass sweep were performed to obtain the highest indicated efficiency while satisfying the restrictions in terms of combustion stability and knock intensity. It was shown that, unlike in a conventional HCCI engine, the combustion phasing can be directly and reliably controlled by adjusting either spark timing or the reactivity of the pre-chamber mixture, ensuring adequate combustion stability and eliminating potential misfires. A similar indicated efficiency as with conventional HCCI combustion was obtained, while the NOx emissions, although slightly elevated, are still insignificant. Compared to PCSI combustion at the same engine load, a 4-percentage-point increase in indicated efficiency and two times lower NOx emissions were achieved. Compared to the most efficient PCSI operating point, it was 1 percentage point lower, indicating that efficiency was achieved, but the specific NOx emissions are reduced by approximately 70%. Most importantly, very similar performance was obtained with significant variations in intake temperature, proving the reliability and adaptability of this combustion concept. [ABSTRACT FROM AUTHOR]

A design scheme of a static shaft turbofan engine is proposed to meet the requirements of light weight and large thrust weight ratio of small aeroengine. As the core component of stable combustion, the thermal protection problem of the mid-mounted combustion chamber is particularly prominent. This paper designs a mid-mounted combustion chamber configuration that combines gas film cooling and central combustion. The influence of structural parameters on combustion characteristics is explored by numerical simulation, and the theoretical design and numerical simulation is verified based on combustion test results. The results show that the flame shape of the mid-mounted combustion chamber conforms to the characteristics of central combustion. The combustion effect of the nozzle with spray angle of 45° and flow rate of 1.87 kg/h meets the requirements of secondary combustion of the static shaft turbofan engine, and the air inlet of the combustion liner effectively increases the thickness of the cooling gas film. The experimental results are in good agreement with the numerical simulation results, and the temperature of the combustion liner wall can be reduced effectively. The above research provides a theoretical basis for the combustion chamber design of small static shaft turbofan engines and a reference for the thermal protection methods of small aeroengine combustion chambers. [ABSTRACT FROM AUTHOR]

With increasing environmental pollution from ship exhaust emissions and increasingly stringent International Maritime Organization carbon regulations, there is a growing demand for cleaner and lower-carbon fuels and near-zero-emission marine engines worldwide. Liquefied natural gas is a low-carbon fuel, and when liquefied natural gas (LNG) is used on ships, dual-fuel methods are often used. The pre-chamber plays a key role in the working process of dual-fuel engines. In this paper, an effective three-dimensional simulation model based on the actual operating conditions and structural characteristics of a marine low-pressure dual-fuel engine is established. In addition, the effects of changing the Precombustion chamber (PCC) volume ratio and the PCC orifice diameter ratio on the mixture composition, engine combustion performance, and pollutant generation were thoroughly investigated. It was found that a small PPC volume ratio resulted in a higher flame jet velocity, a shorter stagnation period, and an acceleration of the combustion process in the main combustion chamber. When the PCC volume was large, the Nitrogen oxygen (NOx) ratio emission was elevated. Moreover, the angle of the PCC orifice affected the flame propagation direction of the pilot fuel. Optimizing the angle of the PCC orifice can improve combustion efficiency and reduce the generation of NOx. Furthermore, reasonable arrangement of the PCC structure can improve the stability of ignition performance and accelerate the flame jet velocity. [ABSTRACT FROM AUTHOR]

The accuracy of sampling of gas components has a significant impact on the measurement of various performance parameters in the combustion chamber of an aero-engine. In order to investigate the effect of the probe geometry of a six-point gas sampling probe on sampling accuracy in supersonic gas flow, a three-dimensional probe gas flow characteristic solution model is established through numerical simulation methods of components of transport and fluid–solid coupling. Probes with three angles of 28°, 30°, and 32° and an optimized conical probe are constructed. The sampling accuracy of the probes with different geometries is compared and evaluated by the deviation of the component volume fraction before and after sampling and the resulting combustion efficiency error. This paper presents a set of calculation methods for solving the relative deviation of volume fraction by an iterative method based on the ideal gas law and the Redlich–Kwong equation (R-K equation). The method is designed to solve the exact component volume fraction problem in the simulation calculation. The study results demonstrate that the 28° and optimized conical probes improve sampling accuracy more effectively than the original 30° structure. The deviation of the volume fractions of the two structures is less than 1.7%, and the combustion efficiency error is less than 0.09%. The developed iterative calculation method can significantly reduce the theoretical calculation error to less than 0.06%. The experimental data of the test bench are in good agreement with the simulation results, thereby demonstrating the reliability and accuracy of the sampling probe following structural optimization. [ABSTRACT FROM AUTHOR]

The backflow of high-temperature products in an engine's combustion chamber is a key issue which can significantly reduce combustion efficiency. This is particularly problematic for hypergolic propellants, as the high-temperature products may still contain fuel or an oxidizer. If either the fuel or the oxidizer backflows into the manifold of the other, it can easily lead to micro-explosions, thereby creating a threat. To address this problem, this paper proposes a new design of an anti-backflow injector, aimed at effectively preventing the backflow of combustion products to the propellant manifold. A steady-state, non-reactive Computational Fluid Dynamics (CFD) model is employed to evaluate the steady internal flow characteristics of the proposed anti-backflow injector. Additionally, a complementary transient, multiphase fluid dynamics simulation is carried out to assess the response characteristics of the anti-backflow injector. Our analysis focuses on the response characteristics of the concave valve core. The study also explores the impact of different expansion port angles on the injection effect, finding that the vortex diameter at the injector outlet is positively related to the expansion port angle. It is also shown that the injection angle becomes more stable as the expansion angle increases. When the expansion port angles are 10° and 20°, the injection angles show similar trends. In terms of anti-backflow effect, taking the injection stiffness of 150% and a time range of 300 µs as examples, the response time of the anti-backflow models with expansion ports of 10°, 15°, and 20° is increased by 67 µs, 99 µs, and 213 µs, respectively, compared to the base models with the same expansion angles. Meanwhile, when the injection stiffness is 50%, the response time of the anti-backflow models with expansion ports of 10°, 15°, and 20° is increased by 207 µs, 210 µs, and 207 µs, respectively. When the injection stiffness is 20%, the response recovery speed of the anti-backflow models with expansion ports of 10° and 15° is increased by 41 µs and 96 µs, respectively. However, the performance of the anti-backflow model with a 20° expansion port is 216 µs of the base model. The optimized design of the anti-backflow injector has potential applications in solving the propellant backflow problem and contributes to the advancement of combustors. [ABSTRACT FROM AUTHOR]

Energy (including thermal) needs are growing rapidly worldwide thus leading to increased energy production. Considering stricter requirements for the employment of non-renewable energy sources, the use of biofuel in energy facilities appears as one of the best options, having high potential for growth that will increase in the long run both in the Baltic region and the European Union as a whole. This publication investigates the possibilities of using various blends of biofuel containing lignin for heat production and emissions to the air during combustion processes. The paper examines the chemical composition of lignin and bottom ash and explores the impact of a different ratio of lignin in the fuel mixture, the effect of the power of biofuel combustion plants (boilers) and the influence of fuel supply to the combustion chamber on gaseous pollutants (CO, NOx, SO2) and particulate matter emissions. The results of the conducted study demonstrate that, in contrast to pure lignin, the concentrations of alkali metals, boron and, to a lesser extent, nickel and chlorine have increased the most in bottom ash. The use of lignin can effectively reduce the need for conventional biofuel by 30–100% and to increase the temperature of exhaust gases. The lowest emissions have been observed using a mixture of 30% of lignin and biofuel at the lowest range of power (2.5–4 MW). Under the optimal oxygen/temperature mode, carbon monoxide concentrations are approximately 20 mg/Nm3 and those of nitrogen oxides–500 mg/Nm3. Particulate matter emissions reach 150 mg/Nm3, and hence applying air treatment equipment is required. [ABSTRACT FROM AUTHOR]

In this paper, exergy, exergoeconomic, and exergoenvironmental analysis of a gas turbine cycle and its optimization have been carried out by MINI-Reference Fluid Properties (MINI-REFPROP) and Matrix Laboratory (MATLAB) SIMULINK. The parametric study was carried out based on the Specific Exergy Costing approach. The mathematical models were developed and presented regarding mass, energy, and economy. The Excel and MATLAB LIBRARY TOOLS BOX are used to perform thermodynamic properties and research analyses. The analyses lead to valuable economic status benchmarks. The exergoeconomic factor, relative cost, total cost of energy loss, and energy destruction for the combustion chamber and work output were determined. The parametric study was conducted, considering the effects of the gas turbine inlet temperature, air compressor inlet temperature, and compressor pressure ratio. For the considered case study status, the combustion chamber in the plant revealed the highest amount of energy destruction (85%), leading to the recommendation that more attention be paid to boilers in terms of design, selection, operation, and maintenance, while the combustion chamber has a high improvement potential (91%). [ABSTRACT FROM AUTHOR]

Despite the fact that the detonation gas spraying method is a high-tech process that allows high-quality coatings deposition on products, it has some disadvantages that may limit its widespread use in industry, compared to other thermal coating methods. Such disadvantages include increased safety requirements, low productivity and reliability of structures. However, the use of the latest component base, accumulated technological experience, modern research in the field of detonation processes, and new approaches to the design of detonation units allow us to hope that the detonation gas method will become widespread along with such methods as plasma or High Velocity Oxygen Fuel spraying. The paper shows the leading role of Ukrainian scientists and engineers in the development and implementation of detonation gas spraying of coatings. Particular attention is paid to the work carried out at the E.O. Paton Electric Welding Institute of the NAS of Ukraine. The concepts and development stages of design from classic detonation guns to valveless multi-chamber guns operating at high frequencies are shown. Automated industrial complexes have been created on their base with application of modern components and equipment that allow effective use of the advantages of detonation gas spraying. [ABSTRACT FROM AUTHOR]

Diesel engine combustion is dependent mainly on the fuel injection characteristics, particularly the injection pressure and rate, which directly affect the engine efficiency and emissions. Herein, an electrically controlled supercharger is added to a traditional high-pressure common rail system to form an ultrahigh-pressure common rail system. Then, the variations in the spray, combustion, and emission characteristics of a diesel engine with a variable fuel injection rate are analyzed. Moreover, a simulation model for a diesel engine combustion chamber is built and verified by experimental results for numerical analysis. The results reveal that the injection rate can be flexibly adjusted via regulation when the solenoid valves are opened on the electrically controlled supercharger. Specifically, (1) the boot-shaped injection rate has greater potential than the traditional rectangular injection rate in terms of combustion and emission; (2) the main injection advance angle at the boot-shaped injection rate can be properly increased to improve combustion; and (3) the pilot injection quantity and advance angle are strongly coupled with the boot-shaped injection rate, potentially enhancing the mixing efficiency of fuel and air in the cylinder to achieve favorable emission results. This paper provides good guidance for the reliable design and optimization of noble-metal-based diesel engines. [ABSTRACT FROM AUTHOR]

In this article, the authors refer to the measurement of acoustic emission, where they found that this methodology can determine the combustion characteristics in the combustion chamber of the engine and thus it is possible to confirm a better combustion process and overall reduction of engine noise after decarbonization. The formation of diesel exhaust soot is also supported by the authors' paper, in which they describe how such soot is formed and what effect the addition of special mixtures to the combustion process has on the formation of such carbon deposits. The article uses BG technologies for deep engine decarbonization, including intake and exhaust parts. This technology is one of many on the market, but it was only with this technology that the authors managed to achieve the relevant results that this article will introduce to. For the test, we selected vehicles that had a problem to pass at the emission control. [ABSTRACT FROM AUTHOR]

Accurately predicting the thermal characteristics and heat transfer distribution of the rotating detonation engine (RDE) and acquiring a clear understanding of the performance and mechanism of the rotating detonation are of great significance for achieving the safe and reliable long-duration operation of RDEs. Using RP-3 as fuel, a long-duration experimental study is performed on a 220 mm-diameter RDC to investigate the details with respect to the thermal environment. The heat flux at the typical location and the average heat flux of both the inner and outer cylinders are measured, respectively. Meanwhile, the peak pressure of the rotating detonation wave (RDW) and specific thrust are analyzed. When the ER is between 0.5 and 1 (oxidizer 2 kg/s), the stable rotating detonation mode is obtained, and the detonation duration is set as 40 s to accurately calculate the heat released by the detonation combustion. The heat flux in the upstream region of the RDW location ranges from 2.40 × 105 W/m2 to 3.17 × 105 W/m2, and the heat flux in the downstream area of the RDW location ranges from 1.05 × 106 W/m2 to 1.28 × 106 W/m2. The results demonstrate the important role of the detonation combustion zone, and the thrust performance of RDC can be improved by making the RDW move forward along the RDC axis, which is the optimal direction of detonation combustion. Through a comparison of average heat flux under different conditions, it is found that the heat released by the RDC is directly related to its thrust. In addition, the average heat flux of the inner cylinder is about three times that of the outer cylinder for the two-phase RDC with a Tesla valve intake structure, indicating that the high-temperature combustion product is closer to the inner wall. Therefore, more thermal protection should be allocated to the inner cylinder, and a more systematic analysis of the two-phase flow field distribution in the annular combustion chamber should be carried out to improve the thrust performance. In this paper, the average heat flux of the inner and outer cylinders of the RDC as well as the typical local heat flux of the outer cylinders is quantitatively measured by means of experiments, which not only deepens the understanding of RDC flow field distribution, but also provides quantitative boundary conditions for the thermal protection design of RDCs. [ABSTRACT FROM AUTHOR]

To investigate the impact of different vortex structure on the combustion stability in a chamber, this paper evaluates the performance of a vortex combustion chamber coupled with a swirler and a guide ring. The simulated cases include different guide ring angles of 95°, 105°, 115°, 125° and 135°, in addition to a control case without coupling the guide ring. The distributions of velocity, vorticity, temperature, outlet temperature distribution factor (OTDF), reaction rate, turbulent kinetic energy (k), synergy angle (β), and NO emission are numerically analyzed. Results show that the coupling of the swirler and guide ring changes the vortex structure and significantly influences the chamber performance. The increase of the guide ring angles (α) enhances the interaction between the swirl flow and the direct jet, which intensifies heat and mass transfer, as well as turbulence. The application of the guide ring induces external entrainment of the jet, leading to the formation of a large central recirculation zone compared to that without a guide ring. With increasing the α from 95° to 135°, both average outlet velocity and tangential velocity (V t) at the coaxial line position decrease, while the flame length decreases by 286 mm. And the OTDF variation among all cases is less than 0.065. The β of the central section decreases from 76.18° to 70.17°. Furthermore, combustion chamber without the guide ring exhibits higher temperature and OTDF. [ABSTRACT FROM AUTHOR]

When aiming to cut down on the emission of nitric oxides by gas turbine engines, it is advantageous to have them operate at low combustion temperatures. This is achieved by lean premixed combustion. Although lean premixed combustion is a proven and promising technology, it is also very sensitive to thermoacoustic instabilities. These instabilities occur due to a coupling between the unsteady heat release rate of the flame and the acoustic field inside the combustion chamber. In this paper, this coupling is investigated in detail. Two acoustic design parameters of a swirl-stabilized pressurized preheated air (300 °C)/natural gas combustor are varied, and the occurrence of thermoacoustic limit cycle oscillations is explored. The sensitivity of the acoustic field as a function of combustion chamber length (0.9 m to 1.8 m) and reflection coefficient (0.7 and 0.9) at the exit of the combustor is investigated first using a hybrid numerical and analytical approach. ANSYS CFX is used for Unsteady Reynolds Averaged Navier-Stokes (URANS) numerical simulations, and a one-dimensional acoustic network model is used for the analytical investigation. Subsequently, the effects of a change in the reflection coefficient are validated on a pressurized combustor test rig at 125 kW and 1.5 bar. With the change in reflection coefficient, the combustor switched to limit cycle oscillation as predicted, and reached a sound pressure level of 150 dB. [ABSTRACT FROM AUTHOR]

Despite the fact that the detonation-gas spraying method is a high-tech process that allows high-quality coatings deposition on products, it has some disadvantages that may limit its widespread use in industry, compared to other thermal coating methods. Such disadvantages include increased safety requirements, low productivity and reliability of structures. However, the use of the latest component base, accumulated technological experience, modern research in the field of detonation processes, and new approaches to the design of detonation units allow us to hope that the detonation-gas method will become widespread along with such methods as Plasma or High Velocity Oxygen Fuel spraying. The paper shows the leading role of Ukrainian scientists and engineers in the development and implementation of detonation-gas spraying of coatings. Particular attention is paid to the work carried out at the E.O. Paton Electric Welding Institute of the NAS of Ukraine. The concepts and development stages of designs from classic detonation guns to valveless multichamber guns operating at high frequencies, are shown. Automated industrial complexes have been created on their base with application of modern components and equipment that allow effective use of the advantages of detonation-gas spraying. 23 Ref., 2 Tabl., 10 Fig. [ABSTRACT FROM AUTHOR]

With an increased inlet gas temperature and the homogenization of the combustion chamber outlet temperature, the endwalls of gas turbines are exposed to extremely high heat loads. The complex flow structure of turbine endwalls makes it difficult to cool some regions of the endwalls, which can easily cause endwall ablation, reducing turbine aerodynamic performance and threatening the turbine's safe operation. In order to improve the cooling and aerodynamic performance of gas turbines, the flow structure, heat transfer and film cooling characteristics of endwalls are analyzed in depth in this paper. This paper summarizes and analyzes the development of the aerodynamic heat transfer and film cooling of gas turbine endwalls in terms of geometric structures and flow boundary conditions and also presents new research directions. Based on the literature, the development and challenge of turbine endwall film cooling are also discussed. [ABSTRACT FROM AUTHOR]

A variety of tools are used to simulate atmospheric aging, including smog chambers and flow reactors. Traditional, large-scale smog chambers age emissions over the course of hours to days, whereas flow reactors rapidly age emissions using high ox- idant concentrations to reach higher degrees of oxygenation than typically attained in smog chamber experiments. The atmospheric relevance of the products generated under such rapid oxidation warrants further study. However, no previously published studies have compared the yields and chemical composition of products generated in flow reactors and smog chambers from the same starting mixture. The yields and composition of the organic aerosol formed from the photo-oxidation of α-pinene and of wood combustion emissions were determined using aerosol mass spectrometry in a smog chamber (SC) and two flow reactors: a potential aerosol mass reactor (PAM) and a micro-smog chamber (MSC). Reactants were sampled from the SC and aged in the MSC and PAM using a range of hydroxyl radical (OH) concentra15 tions and then photo-chemically aged in the SC. The maximum yields/emission factors and the chemical composition of the products in both the α-pinene and wood combustion systems determined with the PAM and SC agreed reasonably well. High OH exposures have been shown previously to lower yields by breaking carbon-carbon bonds and forming higher volatility species, which reside largely in the gas phase, however, fragmentation in the PAM was not observed. The yields determined using the PAM for the α-pinene system were slightly lower than in the SC, possibly from increased wall losses of gas-phase species due to the higher surface area to volume ratios in the PAM, even when offset with better isolation of the sampled flow from the walls. The α-pinene SOA results for the MSC were not directly comparable, as particles were smaller than the optimal AMS transmission range. For the wood combustion system, emission factors measured by the MSC were typically lower than those from the SC, possibly due to nucleation mode particles not observed by the AMS or the condensational loss of gases to the walls inside or after the MSC. The chemical composition of products in the flow reactors and SC were in reasonable agreement in both systems. The emission factors determined using the flow reactors increased relative to the SC when the wood combustion emissions contained higher fractions of aromatic compounds, suggesting that the performance of the flow reactors may be dependent on the chemical composition of the reactants. [ABSTRACT FROM AUTHOR]

Pulse combustion is an attractive yet still little-known form of combustion that can be successfully used in many industrial applications. Experimental studies show that the course of the combustion process in the valveless pulse combustion chamber is conditioned by the process of creating a well-mixed fuel–air mixture inside the chamber. In the paper, numerical calculations were carried out for selected operating conditions of the pulse chamber and compared with experimental results. This allowed for a better understanding and interpretation of the course of the pulsating combustion process itself. The role and importance of the rate of changes in the volume of the combustible mixture zone in the process of improving the efficiency of the combustion process were determined, and the reasons for changes in the pulsation frequency of the combustion process were also explained. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the impact of diesel and kerosene on the transient processes occurring in a micro-turbojet aviation engine. The experiments were conducted under two distinct ambient temperature conditions, 0 and 20 °C. Specifically, we analyzed the starting phase of the micro-engine while operating with kerosene and diesel at both ambient temperature settings. Comparative graphs were generated, and the starting time was meticulously examined. Subsequently, we constructed performance maps for the engine using both fuels and across the two ambient temperature scenarios. We then executed a transient process, comprising sudden acceleration and deceleration, under the aforementioned ambient temperature conditions and with both fuels. The fluctuations in temperature within the combustion chamber, thrust force, and fuel consumption are presented for both rapid acceleration and deceleration events. Furthermore, we conducted comparisons between the thrust force, fuel flow rate, combustion chamber temperature, and specific fuel consumption for the two fuels tested and under the two ambient temperature conditions, both during idle and at higher engine regimes. In the idle regime at 0 °C, the kerosene flow is about 0.78% higher than diesel, with the kerosene thrust approximately 1.92% greater. At 20 °C, the kerosene consumption rises by roughly 5.56% compared to diesel, while the thrust increases by about 1.38%. It was observed that at the maximum operating regime, at 0 °C, the kerosene flow exceeds diesel by around 6%, with the kerosene thrust slightly higher, by about 0.63%. At 20 °C, the kerosene consumption rises by roughly 13.19% compared to diesel, while the thrust increases by about 5.91%. In higher regimes, the kerosene consumption surpasses diesel, but the thrust increase is not significant. Thus, diesel's use as a fuel for the microturbo engine is justified due to its lower consumption at both 0 °C and 20 °C. [ABSTRACT FROM AUTHOR]

A scramjet engine consisting of several components is a highly coupled system that urgently needs a universal performance metric. Exergy is considered as a potential universal currency to assess the performance of scramjet engines. In this paper, a control-volume-based exergy method for the Reynolds-averaged Navier–Stokes solution of truncated and corrected Busemann inlets was proposed. An exergy postprocessing code was developed to achieve this method. Qualitative and quantitative analyses of exergies in the Busemann inlets were performed. A complete understanding of the evolution process of anergy and the location where anergy occurs in the inlet at various operation conditions was also obtained. The results show that the exergy destroyed in the Busemann inlet can be decomposed into shock wave anergy, viscous anergy and thermal anergy. Shock wave anergy accounts for less than 4% of the total exergy destroyed while thermal anergy and viscous anergy, in a roughly equivalent magnitude, contribute to almost all the remaining. The vast majority of inflow exergy is converted into boundary pressure work and thermal exergy. Some of the thermal exergy excluded by the computation of the total pressure recovery coefficient belongs to the available energy, as this partial energy will be further converted into useful work in combustion chambers. [ABSTRACT FROM AUTHOR]