Combustion Of Hydrocarbon Fuels Research Articles

О поглощении антропогенного диоксида углерода лесами и степной растительностью Республики Тыва

INTRODUCTION. Currently, a coal mining territory is being formed in the Republic of Tyva, the volume of coal mining, the “carbon intensity” of production, and СО2 emissions into the atmosphere are increasing. Emissions of the man-made СО2 into the atmosphere caused by combustion of hydrocarbon fuels, wildfires, deforestation and land use development change the natural СО2 balance in the atmosphere, which is manifested in the photosynthesis and respiration processes of plants with the formation of natural carbon sinks. OBJECTIVES. The research aims to correlate the calculated data on the degree of atmospheric pollution by carbon dioxide emissions from stationary and mobile sources with the sequestration potential (with respect to СО2) of the forest and steppe ecosystems of the Republic of Tyva. RESULTS. The sequestration potential of the ecosystems of the Republic of Tyva makes it possible to capture both its own carbon dioxide emissions (fuel combustion) and those introduced from other regions. CONCLUSIONS. The total impact of the man-made СО2 on the atmosphere in the city of Kyzyl relative to other regions is low, amounting to 1,41 million t-eq СО2/year; currently, the territory of the Republic of Tyva is characterized by an excess of the sequestration capacity of man-made СО2 (7,46 million t-eq СО2/year).

Experimental studies of air ozonization influence on pollutants emission in vortex ignition-stabilizing modules of gas turbine combustion chambers

Reduction of pollutant emissions into the atmosphere is an urgent task of modern gas turbine engineering development. Such substances that have a negative impact on the environment include nitrogen oxides and carbon monoxide. The article provides a review of the existing methods for reducing the emissions of pollutants used in the combustion of hydrocarbon fuels in the combustion chambers of gas turbine units, as well as indicates promising technologies developed based on these methods. Justification is presented of the necessity to study the method of ozonization of air supplied to the fuel combustion zone to reduce the content of pollutants in its combustion products. The purpose of the study was to develop recommendations for reducing pollutant emissions within a given range of variations regime parameters. To perform the necessary set of experimental studies, a specialized laboratory stand was created, the combined circuit and measurement scheme of which is given in the article. A rather detailed description is given of the structural elements of the stand and, in particular, of the subject of research — a full-scale vortex ignitionstabilizing module of the combustion chamber of a gas turbine unit, an electric ozonator, air and combustible gas supply systems, an exhaust system with a central fan, control and measuring instruments and fittings. The tests were carried out in accordance with specially developed methods of controlling the stand operation in three modes: startup; transfer from one steady-state mode to another; stop. The influence of air ozonization on combustion processes in the vortex ignition-stabilizing module was determined by the content of nitrogen oxides and carbon monoxide in it. The factors that influence the decrease in the concentration of carbon monoxide in the combustion products during the combustion of air in ozonized air have been determined. The methods of calculation determination of combustible gas and air parameters — mass flow rates, flow velocities and dynamic heads — are described. The results of the performed experimental studies are presented in graphical interpretation, their detailed analysis is given, on the basis of which recommendations on practical use of the method of air ozonization are given.

Vostok Bay: interseasonal changes in hydrological, hydrochemical and microbiological properties

Current ecological state of the Vostok Bay (Peter the Great Bay, Japan Sea) in spring, summer, and autumn seasons is described on the data of CTD profiling, chemical analysis of the water sampled at the sea surface and bottom, and microbial indication of the surface water. Strong seasonal variations are revealed for all examined parameters, driven by monsoon cycle. The winter monsoon in autumn with northwestern wind predominance causes the river runoff weakening and off-shore surge with the water removal from the top of the bay and the compensating inflow along the eastern coast distinguished by heightened values of salinity and dissolved oxygen and low values of biochemical oxygen demand (BOD5 < 1 mg/L). The summer monsoon in spring and summer with southeastern winds increases the river runoff and simultaneously the inflow of fresh water from the open sea, so causes a sharp difference in the water properties between parts of the Vostok Bay. Bioproductivity increases in these seasons that is reflected in increasing of BOD5 (up to 2 mg/L and sometimes more) and organic phosphorus concentration (up to 50 μg/L and more). In July, when the river runoff is blocked in the northwestern sector of the bay by onshore surge, the maximum number of bacteria is recorded there (up to 105 CFU/mL), including Escherichia coli group at all coastal stations in concentrations of 10–100 CFU/mL, which are not observed in the central and open parts of the bay. Among the groups of metal-resistant microorganisms, relative abundance of nickel-resistant bacteria is noted (up to 103 CFU/mL) that is a sign of hydrocarbon fuels combustion. The hydrocarbon pollution is confirmed by ubiquitous distribution of oil-oxidizing and diesel-resistant microorganisms detected mostly (up to 2.8 ∙ 104 CFU/mL in summer) in the northern part of the bay. Generally, the internal northern part of the bay is distinguished by high abundance of microorganisms belonged to different ecological and trophic groups, because of mutual impacts of the rivers, the coastal highway, nearby settlements, and sandy beaches occupied by vacationers in summer.

An experimental and kinetic modeling study of the impact of nitric oxide and hydrogen on iso-Octane combustion

The knowledge of the combined effects of exhaust recirculation and hydrogen enrichment on hydrocarbon fuels combustion is limited to the complexity of the ternary interaction. In this work, experimental and kinetic modeling techniques were combined to investigate the chemical effects of high-level NO, H2, or NO/H2 additions on hydrocarbon fuels. A series of jet-stirred reactor experiments were conducted on the oxidation of iso-Octane with NO/H2 additions at atmospheric pressure and over a wide range of equivalence ratios and temperatures. Experimental results reveal that high concentrations of NO improves iso-Octane oxidation in the temperature region of 800−1000 K and promotes its consumption more efficiently under the ultra-lean condition than stoichiometric and rich conditions. The addition of H2 slightly enhances iso-Octane oxidation by facilitating hydrogen abstraction reactions under the ultra-lean condition, but this effect is insignificant in the stoichiometric condition. The addition of combined H2 and NO demonstrates a more significant promoting effect on iso-Octane oxidation under both ultra-lean and stoichiometric conditions, indicating additive effect in the global reactivity. Existing kinetic models from the literature were incapable to capture these effects. We developed a detailed model which better accounts for the competing chain promotion/termination effects involved in NO sensitization on fuel oxidation, by modifying important reaction rate constants and introducing key nitrogen- containing C3 species. NO and combined NO/H2 additions both enhance the fuel initiation process, primarily through the NO+HO2=NO2+OH reaction, which promotes hydrogen abstraction pathways by converting HO2 to more active OH radical. The NO/H2 combination leads to intricate effects on intermediate species, driven by the competition between NO+HO2 and H+NO2 reactions for OH evolution, as well as the competition between H+O2 and H+NO2 for H consumption. This work contributes to the understanding of ternary hydrocarbon/NO/H2 interactions, providing insights into the design of improved fuel systems to optimize engine performance and mitigate emissions. Novelty and significance statementThis study investigates the effects of high-level NO, H2, or NO/H2 additions on iso-Octane oxidation through experiments and kinetic modeling. New JSR experiments were performed on the oxidation of iso-Octane with and without NO, H2, or NO/H2 additions at various equivalence ratios, 1 atm, and temperatures ranging from 600−1100 K. Experimental results reveal that high-level NO enhances iso-Octane oxidation under the ultra-lean condition in 800−1000 K. H2 has a moderate impact under the ultra-lean condition, but its effect is insignificant in the stoichiometric condition. Combined H2 and NO significantly enhance iso-Octane oxidation in ultra-lean and stoichiometric conditions. The developed detailed model outperforms existing ones in predicting these effects on fuel oxidation. This research contributes to understanding hydrocarbon/NO/H2 interactions and optimizing fuel systems.

Elucidating the mechanism of 1,3-butadiene oxidation with O2: A DFT study

1,3-Butadiene (1,3-C4H6) is a ubiquitous pollutant produced during the combustion of hydrocarbon fuels in engine cylinders. In this study, we delved into the potential energy surface (PES) and rate constant of 1,3-C4H6 employing the density theory (DFT) method and transition state theory (TST). This study comprehensively clarifies the process of O2 oxidation 1,3-C4H6 and its significance on the prediction of combustion dynamic models. Our research reveals that the addition of O2 to the terminal carbon atom of 1,3-C4H6 is the dominant path for addition reactions, leading to the formation of peroxyl radicals. Subsequently, these reactions predominantly yield acrolein and aldehyde groups. Moreover, our data indicates a barrierless and exothermic path for the generation of peroxyl radicals by the O2 addition to the C4H5 radical site. The energy barrier for the dominant path, 1,3-C4H6+H → iC4H5+H2, has been calculated to be 57.6 kJ/mol with a rate constant of 7.89×1010 cm3 mol−1 s−1. This study integrates the kinetic and thermochemical data derived from our targeted reaction system into the updated AramcoMech 3.0. An in-depth analysis reveals the capability of this mechanism to simulate combustion characteristics of 1,3-C4H6, emphasizing its temperature-dependent species profiles. Comparatively, the performance evaluation of the proposed 1,3-C4H6 kinetic mechanism demonstrates its improvement over its predecessor, showing good agreement with experimental results.

Optimization of a Tidal–Wind–Solar System to Enhance Supply–Demand Balancing and Security: A Case Study of the Goto Islands, Japan

Due to the expected increase in electric power demand in the coming decades and the economic and environmental issues caused by power generation from the combustion of hydrocarbon fuels, the integration of renewable energy into the grids of remote islands has attracted attention. Among all renewable sources, tidal stream energy shows potential to contribute positively in areas with strong tidal currents due to the predictability and semi-diurnal periodicity of the resource, which makes it compatible with short-term energy storage. However, its performance in areas with lower available power density has not yet been addressed. In this paper, energy systems for the Goto Islands, Japan which combine solar, offshore wind, and tidal energy are evaluated based on whole-system performance indicators such as the annual energy shortage and surplus and the battery load factor. Without energy storage, an energy mix of 31% solar, 47% offshore wind, and 22% tidal energy provides the lowest values for annual energy shortage (29.26% of total power demand) and surplus (29.26%). When batteries are incorporated into the system, tidal stream energy is the main contributor to reducing these two parameters, with values up to 23.58% and 19.60%, respectively, for the solar and tidal scenario with 30 MW of installed storage capacity. These results show the advantages of tidal stream energy exploitation in stand-alone energy systems, even with relatively low capacity factors (0.33).

Investigation of the Efficiency of a Dual-Fuel Gas Turbine Combustion Chamber with a Plasma‒Chemical Element

Abstract The study is devoted to the possibility of increasing the efficiency of the working process in dual-fuel combustion chambers of gas turbine engines for FPSO vessels. For the first time, it is proposed to use the advantages of plasma‒chemical intensification of the combustion of hydrocarbon fuels in the dual-fuel combustion chambers, which can simultaneously operate on gaseous and liquid fuels. A design scheme of a combustion chamber with a plasma‒chemical element is proposed. A continuous type mathematical model of a combustion chamber with a plasma‒chemical element has been developed, which is based on the solution of a system of differential equations describing the processes of chemical reactions in a turbulent system, taking into consideration the initiating effect of the products of plasma‒chemical reactions on the processes of flame propagation. A modified six-stage kinetic scheme of hydrocarbon oxidation was used to simultaneously predict the combustion characteristics of the gaseous and liquid fuels, taking into account the decrease in the activation energy of carbon monoxide oxidation reactions when the products of the plasma‒chemical element are added. The results reveal that the addition of plasma‒chemical products significantly reduces CO emissions in the outlet section of the flame tube (from 25‒28 ppm to 3.9‒4.6 ppm), while the emission of nitrogen oxides remains practically unchanged for the studied combustion chamber. Further research directions are proposed to enhance the working process efficiency of a dual-fuel combustion chamber for gas turbine engines as part of the power plant of FSPO vessels.

Experiments on the effect of temperature on HHO production by Alkaline water electrolysis

Hydrocarbon fuel is the major source in today’s automotive industry. It can be noticed that the environment is facing a major issue called global warming which mainly happens due to the harmful gases emitted by automobiles from the combustion of hydrocarbon fuels. Also, hydrocarbon fuels are on the verge of extinction due to the eradication of fossil fuels. HHO gas serves as an alternative for all the issues and also it serves as a clean fuel. This article represents the experimental study of the production of HHO gas and the impact of temperature on its production rate. The experimentation is done by two electrolyser cells connected in parallel, and by supplying direct current varying from 5 Amps to 40 Amps. Another set of experiments has been done by using different electrolyte concentrations of 90% NaOH and 10% Glycerine. The results showed that temperature has no direct effect on the HHO production rate. On change of electrolyte concentration, a colour change has been observed.

Study of the reaction mechanism based on the formation of the first carbocyclic ring from propargyl and diacetylene

The formation of the first carbon ring is a crucial rate-controlling step in developing polycyclic aromatic hydrocarbons (PAHs). It is vital to investigate the mechanism of the creation of the first carbon ring to inhibit the formation of PAHs. To explore the growth process of the first carbocyclic ring, this work used the average localized ionization energy (ALIE) and electrostatic potential (ESP) to predict the reaction sites. Moreover, the reaction paths and chemical kinetic parameters for the generation of the first carbocyclic ring from propargyl (C3H3) + diacetylene (C4H2) are calculated based on the density functional theory (DFT) method and transition state theory (TST). The results showed that the addition reaction of C3H3 +C4H2 can form five-, six- and seven-membered ring molecules, in which the five-membered ring formation is fastest and the six-membered ring formation is slowest. During the formation of the first carbon ring, the activation energy required for the H transfer and cyclization reactions is large, and the reaction rate is slow, which determines the formation rate of the first carbon ring. The rate of H-transfer reaction on each carbon ring depends on the number of C atoms of the carbon ring, with the five-membered ring being the fastest and the six-membered ring the slowest. This paper improves the reaction kinetics and thermodynamic data of the first carbon ring formation during the combustion of hydrocarbon fuels, which offers a powerful theoretical basis for predicting the generation of PAHs.

On tert-butyl hydroperoxide in ignition intensification of n-heptane under engine-relevant condition

The higher reactivity of hydrocarbon fuels is necessary to match supersonic airflow in scramjet engines and micro-scale effect in micro-internal combustion engines. Tert-butyl hydroperoxide (TBHP) was selected in this study as an additive reactively enhancer to explore its capacity to intensify the auto-ignition of a typical hydrocarbon (n-heptane). Ignition delay times (IDTs) of n-heptane doped with TBHP were thus measured at engine-relevant conditions covering pressure of 20 atm, temperatures of 650 – 1250 K, and equivalence ratios of 0.5 and 1.0. A nonlinear promotion effect of TBHP on the auto-ignition of n-heptane was observed. Detonation caused by TBHP in region 2 has an impact on actual reflected shock temperature and pressure at high beginning temperatures (> 1000 K). With the addition of TBHP, the negative temperature coefficient (NTC) behavior of first-stage ignition eventually vanishes accompanied with a weakened main NTC of IDT. Analyses of exothermic reactions, reaction pathways, and species evolution indicated that the quick production of ȮH and ĊH3 radicals from TBHP enhances the reactivity of n-heptane and affects the main exothermic reaction in the early period. This study reveals the potential of TBHP to be used in the ignition regulation of the combustion of hydrocarbon fuels and provides a methodological approach for the efficient utilization of hydrocarbon fuel in scramjet engines and micro internal combustion engines.

Influence of n‐butanol and isomers on the combustion mechanisms of isooctane and coke formation based on ReaxFF simulation

AbstractFuel additives play a significant role in enhancing the thermal stability of fuel combustion. The effect of additives on the combustion of hydrocarbon fuels and the combustion performances of isooctane with three different isomer additives, (n‐butanol (1‐BuOH), diethyl ether (DEE), and 2‐butanol(2‐BuOH)), and additive‐free isooctane were explored by ReaxFF simulation in this work. The simulation system was heated to 3000 K at a heating rate of 10 K/ps and kept stable at 3000 K. A variety of combustion products (e.g., small gas molecules and C1‐C8 hydrocarbon compounds) in each system were analyzed, and the reaction paths were speculated based on the computed trajectory. The simulation results showed that the CC bond scission reaction dominated the combustion process of the three additives. All three additives promote the formation of toxic carbonyl compounds such as formaldehyde, while the pure DEE additive has the best inhibition effect on the formation of the coke precursor, C2H2, C3H4, and C3H6. The pure 1‐BuOH additive can shorten the initial reaction time of the reactants. The effects of DEE/1‐BuOH additive on the combustion of isooctane were investigated to obtain a desirable additive mixture with good performance. The expansion of the DEE proportion (80%/20% DEF/1‐BuOH) shows a slightly better coke (C3H4 and C3H6) reduction effect, while the inhibition effect is not as obvious as that of a pure DEE additive.

Development and Analysis of Solutions to Improve the Efficiency of Volute Inlet Pipes in Radial Turboexpanders

The annual increase in demand for electrical power is accompanied by a significant combustion of hydrocarbon fuels and, accordingly, significant CO2 emissions into the atmosphere, which, in turn, result in increasing the surface temperature of our planet. In addition, hydrocarbon fuel reserves are also depleted every year, which raises the question of the efficient use of fossil fuels. One of the promising solutions to this problem is introducing a technology that allows using the excess gas pressure at gas distribution points in order to generate additional electrical energy. As a rule, a radial turboexpander is used to convert the kinetic energy of natural gas at low power. In this paper, we study a method to reduce losses in a volute inlet of a radial expander. Based on our research, we could find that the use of two symmetrical fins in the volute inlet pipe makes it possible to decrease the turbulent kinetic energy by 1.29% and to reduce the energy losses in the inlet pipe by 2.18%.

Physical and chemical processes of fuel change during ignition in diesel engine

The combustion of hydrocarbon fuels in the combustion chambers of diesel engines is preceded by processes of both physical and chemical transformations. The nature of the chemical transformations and their effect on the workflow are usually not taken into account. Meanwhile, their role in ensuring the efficiency of the workflow is very large. Chemical transformations in hydrocarbon fuels in combustion chambers cause the appearance of products capable of self-ignition under the influence of temperatures and pressures arising at the end of the compression stroke. The chain of these transformations ends with the formation of soot particles, the burning of which with abundant heat release in the form of radiant energy has a significant effect on the value of the indicator efficiency. The content and ways of influencing chemical transformations in fuel are considered, as well as the use of these transformations in increasing the combustion efficiency of fuels and increasing the indicator efficiency.

Experimental investigation on using adsorbent for post‐combustion carbon dioxide capture from CI engine exhaust

AbstractAn unpredictable rise in greenhouse gas (GHG) emissions is a primary concern to the global scientific community. It is directly related to the rapid expansion of the human population and associated with the immense energy demand. The combustion of hydrocarbon fuels in internal combustion (IC) engines releases a large amount of carbon dioxide (CO2), which is one of the causes of GHG emissions. Mitigation of CO2 emissions is a significant challenge to the world. Although several researchers have focused on capturing CO2 from power plants, some researchers have taken initiatives in recent times to capture CO2 in IC engines. This study particularly explored the possibility of using a biomass based‐adsorbent to capture CO2 in the exhaust of a diesel engine. Initially, activated carbon was obtained from palm shells by adopting the preparation methods such as (i) carbonization and (ii) chemical activation. Then, the produced activated carbon was analyzed to examine its physicochemical characteristics and surface textural properties by adopting characterization techniques. The adsorbent sample was loaded in an in‐house fabricated adsorption chamber which was attached to the exhaust of a single‐cylinder, four‐stroke, naturally aspirated, air‐cooled, direct injection (DI), constant speed diesel test engine. The performance of palm shell‐based activated carbon was evaluated as a potential adsorbent for CO2 capture when the engine was operated with two distinct fuels, (i) 100% diesel (D100) and (ii) an optimum biodiesel‐diesel blend (JME20) comprising 80% D100 and 20% Jatropha Methyl Ester (JME). The experimental results showed that an average of about 30% and 37% of CO2 was captured by using palm shell‐based adsorbent in D100 and JME 20 operations, respectively.

Thermodynamic Analysis on the Fate of Ash Elements in Chemical Looping Combustion of Solid Fuels─Iron-Based Oxygen Carriers

Chemical looping combustion (CLC) enables efficient combustion of hydrocarbon fuels while also producing a gas stream with high CO2 concentrations, suitable for carbon capture and storage (CCS). CLC of biomass in combination with CCS results in efficient removal of carbon dioxide from the atmosphere, i.e., negative emissions. However, biomass and waste-derived fuels can contain significant fractions of aggressive ash precursors, which can affect the operability and functionality of oxygen carriers. In this paper, the fate of common ash elements will be investigated thermodynamically in a system utilizing iron-based oxygen carriers: ilmenite and iron oxide. Multiphase, multicomponent equilibrium calculations were performed using databases from FACT and a user-defined database, with a specific focus on alkali (K and Na) and heavy metals (Cu, Zn, and Pb). A detailed and comprehensive comparison with available literature data from experimental investigations was performed, and compounds not available in the databases were identified. Due to a lack of thermodynamic data in the literature, thermodynamic properties for four compounds, K0.85Fe0.85Ti0.15O2, K0.4Fe0.4Ti0.6O2, KTi8O16, and KTi8O16.5, were obtained from first-principles calculations. The fate of ash elements is studied for CLC of three biomass and waste-derived solid fuels under relevant CLC conditions: 950 °C in the fuel reactor and 1050 °C in the air reactor. Results show that the choice of the oxygen carriers largely influences the behavior of the ash elements. Compared to CLC with iron oxide, ilmenite is more beneficial with respect to high-temperature corrosion since less potassium is released into the gas phase since the titanium content in ilmenite immobilizes both potassium and calcium. For both oxygen carriers, the most corrosive compounds are expected to leave with the gas in the fuel reactor, keeping the air reactor free from chlorides. It was found that the compound KTi8O16 is stable in reducing conditions and low potassium concentrations. This is in conformity with previous experimental data, where this phase has been identified in the interior of ilmenite particles used in oxygen carrier aided combustion of wood chips.

Feasibility study of using biodiesel fuels as a blendstock of commercial diesel fuels

Reducing emissions associated with the combustion of hydrocarbon fuels and increasing the consumption of biofuels represents an urgent economic and environmental task. Biodiesel is an alternative to petroleum diesel fuel and is widely used as a commercial fuel blendstock. In this regard, it is important to study the feasibility of using biodiesel obtained from various raw materials as a blendstock of commercial diesel fuels, as well as to identify optimal ratios of biodiesel fuel/petroleum diesel fuel. The addition of even small amounts of biodiesel has a positive effect on the environmental properties of the fuel. In the present study, we synthesize biodiesel fuel from sunflower, corn, and rapeseed oils by the reaction of interesterification using ethyl alcohol as an interesterifying agent and sodium hydroxide as a catalyst. The composition and properties of the synthesized biodiesel fuels were determined. Blends of biodiesel/petroleum diesel fuel with 5, 10, 15, 20 vol.% biodiesel blend content were prepared followed by determination of their composition and properties. It was found that the addition of biodiesel fuel increases the density, viscosity, and self-ignition of the resulting fuel, at the same time as decreasing the sulfur content and making the fractional composition heavier. This effect is directly proportional to the concentration of biodiesel in the blend. The effect of reducing the limiting filterability temperature of the blend fuel by the addition of biodiesel was revealed, with its maximum achieved at different concentrations of biodiesel synthesized from sunflower, corn, and rapeseed oils. For the production of a summer commercial diesel fuel, we recommend blends of 10vol.% biodiesel fuel, derived from any of the vegetable oils under study, and 90vol.% petroleum diesel fuel.

Reaction of Methylidyne with Ethane: The C–C Insertion Is Unimportant

High-accuracy coupled-cluster calculations in combination with the E,J-resolved master-equation analysis are used to study the reaction mechanism and kinetics of methylidyne with ethane. This reaction plays an important role in the combustion of hydrocarbon fuels and in interstellar chemistry. Two distinct mechanisms, the C-C and the C-H insertions of CH in C2H6, are characterized. The C-C insertion pathway is identified to have a large barrier of 34.5 kcal mol-1 and hence plays no significant role in kinetics. The C-H insertion pathway is found to have no barrier, leading to a highly vibrationally excited n-C3H7 radical, which rapidly dissociates (within 50 ps) to yield CH3 + C2H4 and H + C3H6 in a roughly 7:3 ratio. These findings are in good agreement with an experimental result that indicates that about 20% of the reaction goes to H + C3H6. The reaction of the electronically excited quartet state of the CH radical with C2H6 is examined for the first time and found to proceed as a direct H-abstraction via a small barrier of 0.4 kcal mol-1 to yield triplet CH2 and C2H5. The reaction on the quartet state surface is negligibly slow at low temperatures characteristic of interstellar environments but becomes important at high combustion temperatures.

Simultaneous detection of particle and C<sub>2</sub>H<sub>2</sub> at high temperature using tunable diode laser extinction spectroscopy

Soot particles from the combustion of hydrocarbon fuels are the main source of the air fine particles and they are also an important factor of reducing the combustion efficiency. As one of their major precursor, acetylene (C<sub>2</sub>H<sub>2</sub>) plays an important role in forming soot. So the simultaneous detecting of soot particle and C<sub>2</sub>H<sub>2</sub> is significant in studying the mechanism of the soot formation. In this work, a sensor for the simultaneous detecting of soot particle and C<sub>2</sub>H<sub>2</sub> is developed by using a single DFB diode laser with a wavelength near 1540 nm. The extinction spectrum near the proper C<sub>2</sub>H<sub>2</sub> line at 6490.02 cm<sup>–1</sup> is used to infer the mass concentration of particles and the C<sub>2</sub>H<sub>2</sub> concentration. The performance of the sensor is confirmed in a home-made heated static cell which can provide well controlled gaseous environment and particulate environment. The measured mass concentration of particles and the C<sub>2</sub>H<sub>2</sub> concentration are within 2.73% and 5.17% of the expected values over the full temperature range of 500–1000 K, respectively. All the measurements show the potential application of the sensor in the simultaneous detecting of soot particle and C<sub>2</sub>H<sub>2</sub> at elevated temperature.

The application of supplementary fuels for the control of supersonic reacting air-fuel mix flows in the combustion chamber

Besides gas-dynamic methods, chemical ones are also suitable for the implementation of stable supersonic combustion of hydrocarbon fuels. Organoelemental compounds are known for their high reactivity, so attention was paid to organosilicon liquid during the research on the experimental model. The obtained estimates of the laminar flame speed in a mixture of vapors of this liquid with air were 0.72-0.8 m/s, which is higher than that of ethylene successfully used in supersonic combustion tests. The tested compound can be considered as a candidate for supplementary fuel to control the supersonic reactive flows in the combustion chambers of ramjet engines. Keywords: supersonic combustion, supplementary fuels, laminar flame speed, combustion efficiency

Gasification of Densified Biomass (DB) and Municipal Solid Wastes (MSW) Using HTA/SG Technology

The necessity of economical and rational use of natural energy sources caused a rapid development of research on the possibilities of using non-conventional energy resources. Taking the above into account, a new technological process of thermochemical conversion of biomass and communal waste, commonly known as High Temperature Air/Steam Gasification (HTA/SG) and Multi-Staged Enthalpy Extraction Technology (HTAG-MEET), was developed. In relation to traditional techniques of gasification or combustion of hydrocarbon fuels, the presented concept is characterized by higher thermal efficiency of the process, low emission of harmful compounds of carbon, sulfur, nitrogen, dioxins, furans and heavy metals. The use of a high-temperature gasification factor causes an increased thermochemical decomposition of solid fuels, biomass and municipal waste into gaseous fuel (syngas), also with increased hydrogen content and Lower Calorific Value (LCV). In this study, the possibility of using a batch type reactor (countercurrent gasifier) was analyzed for gasification of biomass and municipal waste in terms of energy recovery and environmental protection. The proposed research topic was aimed at examining the possibility of using the thermal utilization of biomass and municipal waste through their high-temperature decomposition in the presence of air, a mixture of air and steam. The main goals of the research were achieved during the implementation of several parallel stages of the schedule, which included, primarily: (a) study of the possibility of using thermal utilization of biomass and municipal waste through their high-temperature gasification in the presence of air or a mixture of air and steam and, secondary (b) analytical and numerical modeling of high-temperature gasification of biomass and municipal waste with the use of ANSYS CFD Fluent 6.3 software. Selected results of the experimental and numerical studies are properly presented. The higher temperature gasification concept shows the capability of this technology for maximizing the gaseous product yield in an up-draft fixed bed gasifier. It was also observed that at a high temperature, steam addition contributed to the thermal conversion of biofuels to gas with higher production of hydrogen.