Combustion Research Articles

COMBUSTION SYNTHESIS OF COMPOSITE IN THE Ti-Al-C POWDERS MIXTURE: MODEL AND NUMERICAL SIMULATION

The work uses the basis of conventional combustion theory to propose and study a model of combustion synthesis of a composite material in a three-component powder mixture Ti-Al-C. The model takes into account the dependence of the properties on the composition and structure of the reaction system. The composition of the composite material was analyzed from the reaction initiation stage and to the product cool down. It was shown that the reaction front propagation along the specimen occurs in a stationary regime (with constant rate) for any of the specimens under study. The main synthesis products in the studied concentration range are titanium carbides, titanium aluminide and ternary phases (MAX-phases) Ti2AlC and Ti3AlC2. It was shown that the preliminary heating of the initial reaction mixture prevents the formation of MAX-phases in obtained composites and facilitates the increase in the fraction of carbide phases. Within the framework of the proposed model, the change in an initial porosity of the compact has very little effect neither on the composition evolution of the product. We have found the ranges of concentrations in the initial reaction mixture that provide the prevalence of either intermetallic (TiAl) or MAX-phase (Ti2AlC, Ti3AlC2) in the matrix. The obtained theoretical results are consistent with the experimental results.

Türkiye’de Doğalgazın Tüketildiği Mahallerde Kullanılan Havalandırma Menfezlerin Optimizasyonu

Doğalgaz kullanılan dairelerde TS 7363 standardına göre sabit kanallı havalandırma sistemi olarak cam menfezi veya 150 cm2’lik havalandırma sistemlerinin kullanılmasının zorunluluğu araştırılmıştır. Türkiye’de kullanılan evsel gaz yakıcı cihazlarda A tipi bacasız cihaz (ocak) ve C tipi denge bacalı cihaz (hermetik kombi) ikilisi kullanıldığı görülmüştür. Hermetik cihazlar temiz havayı dışarıdan alıp kirli havayı dışarıya verdiği için iç hava kalitesine etkisinin olmadığı ancak bacasız gaz yakıcı cihazların (daireler için ev tipi ocakların) iç hava kalitesini etkileyip etkilemediği araştırılmıştır. Örnek il olarak Türkiye’nin en soğuk illerinden biri olan Erzurum seçilmiştir. Menfezden geçen havanın hacimsel debisi ANSYS-Fluent paket programı yardımıyla hesaplanmıştır. Havalandırma menfezinden ortama giren taze hava miktarının yanma için ihtiyaç duyulan taze hava miktarından 90 kat fazla olduğu bulunmuştur. Bu sonuç tüketicilerin 150 cm2’lik havalandırma menfezlerinin önemli miktarda enerji kaybına neden olduğu iddiasının doğru çıkartmaktadır. Dairelerde sabit kesit alanlı havalandırma menfezi yerine kullanılan yakıcı cihazların çeşidine ve mevsim şartlarına bağlı olarak değişken kesitli menfez kullanımı önerilir.

Decarbonizing cement plants via a fully integrated calcium looping-molten carbonate fuel cell process: Assessment of a model for fuel cell performance predictions under different operating conditions

This study is part of a comprehensive research devoted to the integration of a Calcium Looping (CaL) process with a Molten Carbonate Fuel Cell (MCFC) for the decarbonisation of a full-scale cement plant. In the proposed process, where the energy intensive oxy-combustion occurring in the CaL calciner is replaced with a conventional combustion in air. The CO2-rich gas leaving the calciner is injected into the MCFC cathode while the anode side is fuelled by H2-rich gases produced by a sorption-enhanced reforming (SER) process. The high CO2-concentrated gas leaving the anode will be sent to valorisation processes and/or the CO2 final disposal.Here we focus on modelling, simulation and characterization of the MCFC used as a device for CO2 separation as well as electricity production, here considered as a process by-product. Polarization curves (I–V curves) and Electrochemical Impedance Spectroscopy (EIS) were measured to support the development and the calibration of a semi-empirical model obtained by theoretical consideration.The experimental campaign demonstrated that the fitted model is able to reproduce the real cell performance when varying the temperature, H2 concentration, CO2 concentration at anode and cathode respectively as well as CO2 CaL capture rate.Indeed, the average difference between numerical and experimental results is always below 2%.Results also demonstrated that the MCFC can be usefully considered as an efficient CO2 concentrator, with a CO2 fraction at the anode outlet that is greater than 51% on a dry basis.

Piston Crown Profile Modifications for Various Combustion Mode Strategies of Modified GDI Engine towards NOx and PM Reduction

In the current development of automotive engines, the major target is to design a combustion chamber in such a way that the combustion process must provide very less concentrations of emissions. To satisfy current worldwide emission norms, petrol engines also equipped with direct fuel in-jection (gasoline/petrol directly injected into engine cylinder) same as like diesel engines. The main drawback of GDI engine is NOx and PM emissions due to lean burn combustion and rich mixture formation over the combustion chamber surface because of wall wetting. In GDI engines, the gasoline fuel injector is placed at various positions with different angles over an engine cylinder head as per the mode of combustion strategy. Based on the mode of combustion with fuel injection angle, the piston crown shape design in much important that the crown surface must not involved in wall wetting during injection. The piston crown shapes were modified for Spray guided combustion mode, Wall guided combustion mode and Air guided combustion mode by keeping in mind that the position of injector with fuel spray angle and the position of spark plug tip on the cylinder head. The main aim of modifying the crown surface profiles of piston is to impart swirl and squish effects for better mixing of air and injected fuel, maintain combustion chamber surface temperature range within the limits and also to avoid wall wetting results in chances of reducing soot particle/PM emission and NOx emission from combustion process.

ОПТИМІЗАЦІЯ ЕФЕКТИВНОГО ПРОЦЕСУ ГОРІННЯ МАЛОГАБАРИТНИХ ПАЛИВНИХ РУЛОНІВ ІЗ ЗАЛИШКІВ ПІСЛЯ ЗБИРАННЯ ЛЬОНУ ОЛІЙНОГО

Currently, the use of secondary agricultural raw material is a topical issue. There are various applications of agricultural crop residues possible, but they are finance- and energy-consuming. Burning crop residues is very harmful for the environment. One of the ways to solve the problem is the production of solid biofuel that can be used to heat buildings. The authors suggest producing solid biofuel in the form of small-sized fuel rolls / pellets (SFR), which are made of oleaginous flax residues. As a result of the conducted experimental investigations, the authors have proved the efficiency and the environmental safety of SFR consumption. The new fuel can be recommended if the requirement of efficient and ecologically safe combustion is met. Thus, the influence of small-sized fuel rolls’ properties on the process of their combustion as well as quantitative and qualitative analysis of the combustion gases from burning solid fuel made of oleaginous flax residues have been investigated. The paper presents the results proving that SFR combustion is the most efficient on condition of providing reduced moisture (10-12%) and reasonable density (80 kg/m3) in the process of pellet production. In addition, it has been determined that there is a significant reduction of harmful CO emissions and normalization of СО2 concentration. The application of the suggested solid biofuel can make it possible to solve the problem of using oleaginous flax residues and provide cheap fuel for household purposes.

REDUCTION OF POLLUTANTS IN THE RESIDENTIAL SECTOR BY MIXING HYDROGEN INTO THE NATURAL GAS NETWORK IN HUNGARY

According to some forecasts, hydrogen will play a significant role throughout the world by 2030 as an energy source, the biggest benefits of which include not only being able to come from renewable sources, but thus storing the energy produced, which is not currently solved. The combustion of hydrogen does not produce CO2, only negligible amounts of combustion air, unlike methane. This will reduce GHG emissions associated with end-user equipment. In this article, the authors examine the amount of hydrogen that can be fed into the Hungarian natural gas network in accordance with the current gas quality standard, and then carry out a comparative analysis of the methane, the main component that makes up hydrogen and natural gas. The authors will study the exact effect of hydrogen content on natural gas-regulated devices and estimate the theoretical CO2 emissions available in the Hungarian residential sector at different rates of hydrogen.

The Application of an Expansion Turbine in the Production of Expanded Aggregates

The research into the expansion of Cypris clay from the overburden rocks of the Družba brown coal open-pit mine in North Bohemia has proven that targeted expansion enables good use of the thermal energy of hot aggregates, which has not yet been fully exploited. The integration of an electricity production expansion turbine into the production line and the use of residual gas heat in the turbine cycle can reduce production costs. The article assesses two possible solutions for the integration of the expansion turbine into the technological line, namely with an open and closed working cycle using various gaseous media. In both cases, the proportion of the energy usable for electricity generation in the expansion turbine cycle has been calculated along with the possible fuel savings in the rotary kiln by using combustion air preheated to a high temperature by the residual heat of the gas from the turbine gas cycle.

Improving the Reliability of Rotary Furnace Drums By Stabilizing the Temperature Regime By Effect of Electromagnetic Fields


 
 
 The unevenness of the heat flow generated in the furnaces of the drums of rotary kilns leads to damage to the drum casing, which can cause premature failure. The author suggests that by deflecting the flame by applying electromagnetic fields, it is possible to prevent direct contact between the flame and the furnace drum, extending the latter’s service life. In this way, it is possible to regulate the directions of movement of the heated combustion products to realize the uniform distribution of heat fluxes, as well as to regulate local temperature fields in real time. The study took into account 5 main factors of the influence of the electromagnetic field on the flame. Based on the studies, a description of a device partially integrated in the furnace is proposed. In this case, there is no significant constructive modernization of the furnace. This device is an analogue of a high-temperature fan, but has several advantages in comparison with it.
 Keywords: electromagnetic field, furnace, flame, heat exchange
 
 

Improving the performance of the passive pre-chamber ignition concept for spark-ignition engines fueled with natural gas

Passive pre-chamber ignition concept has been proven to be an excellent strategy to increase the ignition energy and enhance the combustion velocity even when spark-ignition engines are operating in diluted conditions. Other benefits of this system are the increased combustion stability and combustion efficiency, reducing hydrocarbons and carbon monoxide emissions. However, these advantages are limited at some operation conditions such as low engine load or diluted conditions since both the energy available in the pre-chamber and the scavenge of combustion products are compromised. In this framework, numerical studies using two different computational tools, based on one-dimensional modeling, are utilized to gain knowledge about the governing parameters and to improve the design of a pre-chamber when the engine operates at these restrictive conditions. In particular, the impact of the pre-chamber volume, the total cross sectional area of the holes and tangential angle of the nozzles have been numerically evaluated. Different pre-chamber designs were proposed and experimentally tested in a single-cylinder, high compression ratio turbocharged spark-ignition engine fueled with compressed natural gas and operating on Miller cycle. Results give valuable insight into the key aspects of the internal geometry and some relevant design paths to follow for a suitable pre-chamber definition.

Design of a Bubble Reactor for Altitude Simulators Used to Humidify a Combustion Air Stream by Means of CFD Multi-Phase Models

In this paper, a procedure for the design of a bubble reactor which allows the control of the humidity of a gas stream used as combustion air is presented. This reactor is designed to be used as a component of an altitude simulator test facility for the optimization, homologation and calibration of new hybrid engines. The design has been carried out by means of Computational Fluid Dynamics (CFD) multi-phase models and validated against the experimental data obtained from the developed prototype. A discussion about the adequate mesh topology and cell size is presented, as well as a comparison between the two available models for the air–water interphase. Lastly, a validation of the CFD results using experimental data shows that the model that should be used is the multi-regime interaction model, from which the final design for the bubble reactor was obtained.

Thermodynamically Equilibrium Compositions of the Products Formed During the Filtration Combustion of the Metal-Containing Mixtures

Thermodynamic calculations for describing the compositions of the products formed in conditions of the filtration combustion of the metal-containing mixtures were carried out. The analysis of the equilibrium compositions of the products was carried out using the TERRA high-temperature thermochemical equilibrium calculation program. According to the results of calculations, the metals were divided into two groups. First one forms both the condensed and gaseous phases and in the second one ‒ metals that are only in the condensed phase. In case of the presence of metal compounds in the gas phase, as a rule, these are the following compounds: metals, oxides, hydroxides, hydrides, sulfides and metal sulfates. Metals of the second group cannot be subjected to mass transfer under conditions of the filtration combustion wave and will remain in solid combustion products (in ash).

БРОНЕБІЙНІ СНАРЯДИ З ПРЯМОТОЧНИМ ПОВІТРЯНО-РЕАКТИВНИМ ДВИГУНОМ

The article analyzes the problems of sub-caliber feathered projectile, offers a variant of equipping such a projectile with an air-jet engine, graphs of air resistance, calculations of the required thrust of the air-jet engine. Features of armor-piercing projectiles with a direct-flow air-jet engine are considered, the main calculations are performed using high-level Python programming language. Currently, as armor-piercing ammunition are widely used armor-piercing sub-caliber feathered shells (BPOS) with high penetrating ability This is achieved due to the high initial velocity of ammunition (1650-1840 m / s) and small cross section (d = 20-30 mm). To compensate for the force of air resistance, the provision of jet propulsion ammunition is used. But the main disadvantage of such shells is the dependence of the ability to pierce armor from a distance to the target. That is, due to the resistance of the air, the speed of the projectile is lost, namely its energy. What they are inferior to cumulative projectiles, for which the ability to pierce armor does not depend on the distance to the target. Modern armored vehicles have significant armor and BPOS lose their importance in the range of cumulative projectiles and anti-RPG. This situation can be corrected if the BPOS is equipped with direct-flow jet engines (PPD). Direct-flow air jet engine (PPD), simple in design, has a high efficiency at large Mach numbers, compact, because it does not require the presence of an oxidant in the fuel, as it uses oxygen from the environment. Compressed air entering the combustion chamber from the inlet device is heated by oxidation of the fuel supplied to it. Created from a mixture of air with combustion products gas mixture – the working fluid in the nozzle reaches the speed of sound, and at its output expanding to supersonic. The working fluid flows at a speed greater than the speed of the oncoming air flow, which creates a jet thrust. When the flight speed is much less than the speed of the jet, the thrust increases. As the speed of flight approaches the speed of the jet, the thrust decreases, passing some maximum corresponding to the optimal speed of flight. With the development of mixed solid fuel technology, it began to be used in PPRD. A fuel checker with a longitudinal Central channel is placed in the combustion chamber. The working fluid passing through the combustion chamber oxidizes the fuel from its surface and heats up. The use of solid fuel further simplifies the design of the PPRD as it does not require a combustion chamber. The main part of the filler of mixed fuel PPRD is a fine powder of aluminum, magnesium or beryllium, the heat of combustion, which is much higher than the heat of combustion of hydrocarbon fuels. With the development of mixed solid fuel technology, it began to be used in PPRD. A fuel checker with a longitudinal Central channel is placed in the combustion chamber. The working fluid passing through the combustion chamber oxidizes the fuel from its surface and heats up. The use of solid fuel further simplifies the design of the PPRD as it does not require a combustion chamber. The main part of the filler of mixed fuel PPRD is a fine powder of aluminum, magnesium or beryllium, the heat of combustion, which is much higher than the heat of combustion of hydrocarbon fuels. An example of a solid propellant PPRD can be the propulsion engine of the anti-ship missile P-270 Mosquito. Depending on the speed of flight PPRD are divided into subsonic, supersonic and hypersonic. This division is due to the design features of each of these groups. In the supersonic range PPRD is much more effective than in the subsonic. For example, at a speed of M = 3, the degree of pressure increase in the PPRD is 37, which can be compared with the most high-pressure compressors of turbojet engines. Keywords: armor-piercing sub-caliber feathered projectile, air-jet engine, external ballistics.

Modeling and Analysis of Energy Efficiency Parameters of Medium Pressure Boilers Using a Mixture of Natural and Blast Furnace Gases Taking into Account Air Intakes

The object of this study are the thermal and energy characteristics of medium pressure boilers CHP-1, four boilers CCTI-75/39F-2-4 and two boilers TP-150-2. All boilers operate on a common steam collector 32 atm, 420 °C. Fuel is a mixture of blast furnace and natural gases in a ratio of 0.7–0.9 by volume. The characteristics of blast furnace gas are not constant: the elemental composition, humidity and dustiness of blast furnace gas change significantly. An algorithm for complex calculation of boiler characteristics and a mathematical model for optimal load distribution were developed. Theoretical volumes of combustion products were calculated, boiler efficiency and fuel consumption were determined, basic elements (furnace chamber, scallops, superheater) were calculated, joint calculation of tail heating surfaces (water economizer and air heater) with specification of exhaust gas temperature was determined and thermal balance was determined. The effect of excess air in the exhaust gases from the load was calculated. As a result of the analysis, the temperature of the exhaust gases was calculated, an indicator that characterizes the reliability and efficiency of the boiler, and the temperature at the outlet of the furnace, which characterizes the reliability of the superheater. The efficiency of the boilers was calculated and the value of the efficiency for the considered boilers was adjusted.

Effect of the bleaching and varnishing process on the flame source combustion light intensity of wood material

Bu calisma, ahsap malzemede renk acma ve vernikleme isleminin alev kaynakli yanmada isik yogunluguna etkilerini belirlemek amaciyla yapilmistir. Bu maksatla, Dogu kayini (Fagus orientalis Lipsky), saricam (Pinus sylvestris Lipsky) ve Sapsiz mese (Querqus petraea Liebl.) odunlarindan ASTM D 358 esaslarina uyularak hazirlanan orneklere sodyum hidroksit (NaOH), hidrojen peroksit (H2O2), kalsiyum hidroksit (Ca(OH)2), sodyum silikat (NaSiO3), asetik asit (CH3COOH), sodyum disulfit (Na2S2O5), oksalik asit (C2H2O4) ve potasyum permanganat (KMnO4)’in % 18’lik cozeltisi ile renk acma islemi yapildiktan sonra, ASTM D3023 esaslarina gore su bazli (Sb), sentetik (Sn), poliuretan (Pu) ve akrilik (Av) vernikler uygulanmis ve isik yogunlugu ASTM E 160–50 esaslarina gore belirlenmistir. Sonuc olarak, isik yogunlugu; ahsap turu, renk acma cozeltisi ve vernik cesidi etkilesimine gore en fazla KMnO4+Na2S2O5+H2O2 (R5) ile rengi acilmis sentetik vernikli kayinda gorulurken, en az Na2S2O5+C2H2O4 (R4) ile rengi acilmis akrilik vernikli saricamda elde edilmistir. Buna gore isik yogunlugu en az olan ornekler, yanginda dumandan bogulma riskini arttirabileceklerinden uygulama alanlarinda bu durumun dikkate alinmasi onerilebilir.

SHS Processing of cyclone ferrosilicium dust

This paper offers a review of waste disposal techniques for disposing of dust generated by ferrosilicium industry. The paper examines the possibility of nitriding cyclone ferrosilicium dust through application of a high-pressure infiltration combustion process. The authors describe the key regularities of the ferrosilicium nitride SH-synthesis and demonstrate the potential applicability of the new technique. The findings show that the high-grade dusts resultant from ferrosilicium crushing and screening operations and identified as FeSi65 and FeSi75 consist of iron and silicon disilicides, whereas the dust coming from a 45 % alloy consists of FeSi2 and FeSi. Interaction of the initial alloys with nitrogen in a high-pressure combustion mode results in the generation of high-nitrogen material with the β-phase of silicon nitride at the basis. Such material can be used as unmolded refractory material for application in blast furnaces. Or it can be used to produce nitrogen containing steels, such as transformer steel. Thus, the dust grade PUD-75 would be optimum for application in refractories, and the dust grade PUD-65 — as an alloying component. The paper demonstrates that the composition of the cyclone ferrosilicium dust combustion products can be changed by changing the nitrogen pressure and the dispersity of the burden. Silicon nitride constitutes the main component in the composition of the combustion products (60–85%). It will be iron that will serve as a binder in this composite at the highest nitrogen saturation degree, whereas in the case of a lower nitrogen saturation degree it will iron silicides. It was found that nitrogen is absorbed in two stages during layer-by-layer combustion of ferrosilicium alloys. Passing of the combustion front is followed by the process of bulk post-reaction, during which the share of absorbed nitrogen can increase by 30%. This phenomenon explains why there exists no dependence between the concentration of nitrogen in the combustion products and the applied pressure.

Correlations between 7Be, 210Pb, dust and PM10 concentrations in relation to meteorological conditions in northern Poland in 1998–2018

Analysis of a twenty-year (1998–2018) data series on 7Be concentrations in weekly collected aerosol samples in northern Poland showed a clear pattern of seasonal changes in 7Be with a maximum in the summer period associated with the most intensive thermal convection and vertical mixing. Activity concentrations of 7Be ranged from 480 μBq m−3 to 9370 μBq m−3. A strong relationship has been shown between 7Be concentrations observed in years and the activity of the Sun related to the sunspot number. Activity concentrations of 210Pb in aerosol ranged from 17 μBq m−3 to 1490 μBq m-3 with maximum occurring in the winter. The difference in the seasonal pattern in 7Be and 210Pb concentrations were directly related to the different sources of both isotopes, as an additional source of 210Pb was the products of combustion during the heating season. Similar pattern with maximum concentrations in winter was observed for PM10, as the main source is the same as in the case 210Pb. A content of PM10 was in the range from 6.5 to 81.7 μg m−3. A statistically significant correlation between both isotopes occurs. At the same time, 7Be, 210Pb and PM10 are visibly related to the dust concentrations ranged from 7.3 μg m−3 in winter to 134.8 μg m−3 in spring. Statistical analysis carried out with simple regression model, stepwise multiple regression, and Random Forest models showed that the sunspots number, air temperature and sunshine duration have the most substantial impact on transport, and hence the concentration of 7Be in the surface layer of the atmosphere. The increase in relative humidity and precipitation and higher wind speed have a statistically significant effect on the reduction of 7Be concentrations in surface air.

Flammability analysis of gaseous emissions from western red cedar and SPF (Spruce, Pine, Fir) sawdust

Western red cedar (WRC) is among the most valuable tree species in British Columbia. Application of WRC for pellet production is uncertain because unlike spruce/pine/douglas fir, WRC tends to combust in rotary drum dryers. The scientific reasons for the reported fire incident are not known. The goal of this research is to assess whether WRC has a higher tendency to emit combustible gases than SPF sawdust when these species of wood are heated. In controlled experiments, the composition of emitted gases during heating of WRC and SPF samples at 140 °C was measured. The GC-measured data showed that WRC released a lower amount of carbon monoxide, methane, and hydrogen than SPF. Flammability analysis showed that the concentration of the emitted gas mixture for WRC and SPF samples did not reach a flammable level. Theoretical calculations showed that the volumetric composition of carbon monoxide at 12%in the presence of ample oxygen is prone to combustion. This means that if the biomass smokes in the drum, the level of carbon monoxide might reach to flammable level.

Sub-multiplicative interaction between polygenic risk score and household coal use in relation to lung adenocarcinoma among never-smoking women in Asia

We previously identified 10 lung adenocarcinoma susceptibility loci in a genome-wide association study (GWAS) conducted in the Female Lung Cancer Consortium in Asia (FLCCA), the largest genomic study of lung cancer among never-smoking women to date. Furthermore, household coal use for cooking and heating has been linked to lung cancer in Asia, especially in Xuanwei, China. We investigated the potential interaction between genetic susceptibility and coal use in FLCCA. We analyzed GWAS-data from Taiwan, Shanghai, and Shenyang (1472 cases; 1497 controls), as well as a separate study conducted in Xuanwei (152 cases; 522 controls) for additional analyses. We summarized genetic susceptibility using a polygenic risk score (PRS), which was the weighted sum of the risk-alleles from the 10 previously identified loci. We estimated associations between a PRS, coal use (ever/never), and lung adenocarcinoma with multivariable logistic regression models, and evaluated potential gene-environment interactions using likelihood ratio tests. There was a strong association between continuous PRS and lung adenocarcinoma among never coal users (Odds Ratio (OR) = 1.69 (95% Confidence Interval (CI) = 1.53, 1.87), p=1 × 10−26). This effect was attenuated among ever coal users (OR = 1.24 (95% CI: 1.03, 1.50), p = 0.02, p-interaction = 6 × 10−3). We observed similar attenuation among coal users from Xuanwei. Our study provides evidence that genetic susceptibility to lung adenocarcinoma among never-smoking Asian women is weaker among coal users. These results suggest that lung cancer pathogenesis may differ, at least partially, depending on exposure to coal combustion products. Notably, these novel findings are among the few instances of sub-multiplicative gene-environment interactions in the cancer literature.

Performance analysis of a novel heat recovery system with hydrogen production designed for the improvement of boiler effectiveness

In this study, a multi-generation system is designed for the waste recovery of a 150 MW coal-fired power plant. The waste heat from the boiler system of the power plant is recycled in the power block with supercritical organic Rankine Cycle to obtain the required energy for the proton exchange membrane electrolyzer block. Then, two different cases are handled to utilize the products of the proton exchange membrane electrolyzer block. In the first case, H2 is stored as an energy carrier to be used for external operations where O2 was used for the enrichment of the combustion air. In the second case, H2 is used for the enrichment of the fuel where O2 is used for the enrichment of the combustion air as in the first case. It is determined that it is available to produce H2 in an amount of 0.0417–0.0433 kmol/s. The energy efficiency of the overall system is determined as 25.37% and 24.05% where the exergy efficiency of the overall system is determined as 31.56% and 29.80% for the first and second cases, respectively.

Preparation of aluminum oxide coating on carbon/carbon composites using a new detonation sprayer

AbstractA new multi‐chamber cumulative detonation sprayer (MCDS) was applied to fabricate an aluminum oxide coating on carbon/carbon composites. MCDS provides heating and acceleration of ceramic micropowders by means of combustible gas mixture detonation products with a frequency of 20 Hz and above. The ceramic aluminum oxide particle kinetic energy ensures the destruction of the weakened areas on the carbon‐carbon composite material surface and the incorporation of these particles into the surface layer. The following powder particles decelerate on the already fixed particles and form a ceramic coating. The formed aluminum oxide coating is characterized by high hardness and low porosity (<1%). MCDS provides the formation of a high‐quality ceramic layer, which can also serve as the basis for the formation of protective heat‐resistant coatings.