Concentrations Of Combustion Products Research Articles

Numerical Investigation of In-Cylinder Combustion Behaviors in a Medium-Speed Diesel Engine

Abstract This study aims to advance understanding of in-cylinder combustion processes in medium-speed diesel engines, which are extensively employed in heavy-duty applications where electrification proves inefficient yet remains insufficiently examined in the literature. By modeling a four-stroke engine with dimensions of 210 mm bore and 310 mm stroke, operating at 900 rpm under full load, this research identifies distinct combustion characteristics that differentiate medium-speed engines from their high-speed counterparts. Key findings illustrate that super turbocharging in medium-speed engines enhances the combustion of the fuel–air mixture under elevated temperatures and pressures. Moreover, an increased stroke length promotes gas velocity and turbulence, facilitating fuel atomization and mixing. Notably, rapid fuel ignition occurs near the nozzle due to the high temperature of compressed air, reducing the ignition delay. As a result, the premixed combustion stage nearly disappears, with diffusion combustion dominating, especially pronounced with long-duration injection, a characteristic of medium-speed engines. The study also reveals a more uniform but elevated distribution of nitrogen oxide emissions in medium-speed engines, attributed to prolonged high-temperature conditions that both facilitate their formation. Early stages of diffusion combustion show high concentrations of incomplete combustion products. However, as the combustion process progresses, the conditions favor the complete oxidation of these products at high temperatures, resulting in decreased carbon-based pollutions. In addition, the larger combustion chamber and enhanced turbulence characteristic of medium-speed engines support efficient fuel and air mixing without necessitating the swirl effect required by high-speed engines, diminishing the dependence on wall impingement dynamics for air utilization. Consequently, efficiency optimization strategies for medium-speed engines, emphasizing adjustable injection parameters, encounter fewer constraints than those inherent to the spatial limitations of high-speed engines.

О расчете неопределенности показателя токсичности продуктов горения полимерных материалов

A testing lab must evaluate and determine the contribution of the uncertainty of measurements for each testing methodology in order to implement the reliability and accuracy of tests. In addition, the uncertainty index must be specified in the test (measurement) protocols. Uncertainty can be calculated by using various methods; however, when the desired value of the output parameter is determined from a graph, the method of least squares should be used. In order to determine the toxicity index of combustion products, a series of tests using white laboratory mice have been conducted. Based on the test results, a graph of the dependence of lab mice lethality on the concentration of toxic combustion products has been built; the dose causing the lethality of 50 % of lab mice has been determined. Using the method of least squares, confidence limits of the estimate of measured value have been calculated and graphically shown. As a result of calculations, the uncertainty of toxicity of combustion products was determined as around 25 %. The wide range of data has been caused by the error of measuring equipment, heterogeneity of the test sample and its composition, as well as the characteristics of lab mice and their biological features. The results of uncertainty calculation provided in the article can be used by laboratories conducting fire safety tests of materials.

Effect of excitation Strouhal number on a backward-inclined jet flame in crossflow

Combustion is often accompanied by environmental pollution due to incomplete reaction. A non-excited flame usually exhibits poor combustion performance with features of diffusion flame such as dual-peak temperature distributions and large combustion product concentrations. Efficient fuel-air mixing has been identified as a key factor in mitigating this issue. The present study investigated the effects of the acoustic excitation Strouhal number on the combustion performance of a backward-inclined jet flame in crossflow. A loudspeaker was used to induce jet pulsations with excitation Strouhal numbers ranging from 0.47 to 1.54 at a pulsation intensity of 0.90. Time-averaged and instantaneous flame images were captured using digital cameras. A customized R-type thermocouple and a commercial gas analyzer were employed to analyze the thermochemical structures. A critical excitation Strouhal number of approximately 0.9, distinguishing two characteristic flame modes: strongly affected flame (SA flame) and weakly affected flame (WA flame), was found. At excitation Strouhal numbers lower than the critical value, the SA flame featured single-peak temperature profiles and low unburned hydrocarbon, carbon monoxide, and nitric oxide emissions. The combustion performance was significantly improved due to the strong mixing effect induced by the acoustic excitation. The WA flame appeared at excitation Strouhal numbers higher than the critical value. It exhibited dual-peak temperature distributions and slightly improved combustion performance. The dynamic behavior and emissions of acoustically excited jet flames offered a fascinating insight into the influence of excitation Strouhal numbers on combustion characteristics. More excitation conditions were expected for future research.

Combustion in a chamber furnace with a tangentially swirling vortex

Relevance. The need to analyze the furnace processes in boiler units with vertical vortex when arranging pulverized coal combustion with the enhancement of environmental parameters through the installation of tertiary blast nozzles. Despite the carbon-free policy in modern power engineering coal remains one of the main sources of energy, so the reconstruction of boiler units in order to reduce harmful emissions is very relevant. Aim. To study aerodynamics and combustion processes of pulverized coal fuel in the furnace chamber of a boiler unit with a tangential arrangement of burner devices using a combustion scheme with tertiary air blowing. Methods. The Eulerian–Lagrangian approach was applied to numerical study of flow characteristics, heat transfer and combustion in a furnace with a tangential burner arrangement. Also, k-ε model of gas turbulence, particle-turbulence interaction, diffusion model of particle dispersion, P-1 radiation modeling method and pulverized coal particle combustion model based on global particle kinetics and experimental data were used for numerical calculations. Results. Based on numerical calculations and analysis, the dependences of combustion product concentrations, temperature, hydrodynamics at combustion of Kuznetsky coal grade D in the furnace chamber with tangential arrangement of burners for brown coal, as well as at installation of tertiary blast nozzles have been obtained. Insufficient redistribution of air between burners and tertiary nozzles is revealed, as for maintenance of stable twist of vertical vortex and accordingly presence of high values of velocities at the outlet of burner devices it is not possible to increase the portion of tertiary air without reconstruction of burners. It is also established that the volume of the furnace chamber below the burners is poorly involved in heat exchange.

Toward Zero Carbon Emissions: Investigating the Combustion Performance of Shaped Microcombustors Using H2/Air and NH3/Air Mixtures

The research effort in the microcombustor field has recently increased due to the demand for high-performance systems in microelectromechanical and micro power generation devices. To address rising concerns about pollutants from fossil sources, zero-carbon fuels such as hydrogen (H2) and ammonia (NH3) have been considered as an alternative in microcombustion processes. In a microcombustor, the surface area-to-volume ratio is much higher compared to conventional combustion systems, resulting in faster heat transfer rates and more intense combustion reactions. However, achieving efficient mixing of fuel and an oxidizer in a microcombustor can be challenging due to its small size, particularly for highly reactive fuels like H2. For NH3, challenges in microcombustion involve a low reactive, high ignition temperature (923 K vs. 793 K of H2) and high concentration of NOx combustion products. Therefore, studying the performance of these fuels in microcombustors is important for developing clean energy technologies. In this paper, to explore features of non-premixed NH3/air and H2/air combustion in micro-scale combustors, an Ansys Fluent numerical investigation was conducted on a Y-shaped microcombustor. Results show that for combustion with H2, stationary flames can be achieved even at lower equivalence ratios. Additionally, the pollutants generated from H2 in the flame are generally twice those of NH3. The overall efficiency of the microcombustor is two times greater for NH3 conditions than for H2 conditions.

Mercury concentration in the snow cover of the city of Khabarovsk

The research reveals results of studies of the total mercury content in the snow cover of Khabarovsk in winter period 2021-2022. Researchers highlight a connection between mercury and non-soluble residue, with minor transition into soluble phase. The total mercury content in the non-soluble residue ranged from 0.3 to 1.4 mg/kg. On the northern border of the Bolshekhekhtsirsky Reserve, area with high content of quicksilver (3 mg/kg) was found, which exceeds the maxi-mum permissible concentration by 1.4 times. Authors consider that high concentration of quicksilver may be a result of short-term local pollution and do not exclude cross-border origin of it. Content of mercury as a part of solid atmospheric precipitation on the Earth’s surface in this area is 37.5 µg/m2, with average values of 10-18 µg/m2. The maximum content of mercury (73.9 µg/m2) was found nearby CHP-3 area. The reason is a high concentration of combustion products in snow cover. The amount of solid atmospheric precipitation in the area of CHP-1 also significantly exceeded the average values, but this did not lead to an increase in the total amount of mercury that reached the surface. The minimum concentration of quicksilver was found in the embankment park area of the city - 3.2 µg/m2.

Расчетная оценка эффективности технических решений по естественному проветриванию обычных лестничных клеток при пожаре в жилых зданиях

Introduction. Natural ventilation of ordinary staircases in case of fire is provided for by the provisions of regulatory documents in the field of fire safety and plays an essential role in ensuring the safety of people. This article analyzes the effectiveness of ventilation of staircases through window openings in the outer walls, as well as through the openings of exits to the roof. The purpose of this article is to develop criteria and mathematical relationships for evaluating the effectiveness of technical solutions for ventilation of staircases, as well as their approbation for residential buildings of various heights. Methods. Mathematical methods are used to predict the concentration of combustion products on different floors of stairwells, depending on the area of open window openings and the possibility of opening roof access hatches, as well as an analytical method for evaluating the effectiveness of technical solutions for ventilation of stairwells. Resu lts. Theoretical provisions have been developed to assess the effect of the area of open window openings and roof hatches on the natural ventilation of ordinary staircases in sectional-type residential buildings with exits from apartments to staircases, and calculations have been made to evaluate the effectiveness of these solutions in buildings of various heights. Conclusions. Based on the research, criteria and mathematical ratios have been developed to evaluate the effectiveness of various technical solutions for the natural ventilation of ordinary staircases. At the same time, the effectiveness of these solutions is determined by the possibility of rescuing people from the apartments of the corresponding floor without the involvement of a significant number of firefighters and without the use of personal respiratory and eye protection equipment.

Analysis on roles of thermal radiation to evaporation and combustion of fuel droplets

Thermal radiation is a significant mode of energy transmission besides conduction and convection in most combustion systems. Accurate treatment of thermal radiation is a crucial element for predicting the flame structure and pollutant formation. However, thermal radiation to fuel droplet evaporation is often neglected in the numerical simulations of two-phase spray combustion systems. In this paper, computational analysis on the thermal radiation to evaporation and combustion of fuel droplets in two-phase spray combustion is conducted. The influence of flame radiation on droplet evaporation and combustion is studied by adding radiation source term to the energy equation describing droplet evaporation process. Radiation transfer equation is solved, in which the radiation of CO2, H2O and soot is imposed to consider radiation effect of the flame. The partially premixed combustion model is employed, in which radiation heat transfer between droplet and ambient gases is taken into account. A reduced chemical reaction mechanism for n-heptane consisting of 76 species and 349 reactions is used. Four different numerical setups have been used and compared, and the simulation results coincide with the experiment data in terms of spray statistics and flame shapes. The peak flame temperature increases by 28 K when the radiative heat source term in the evaporation process is considered. The droplet evaporation is significantly enhanced by thermal radiation, leading to a promotion of 34.8% in C7H16 concentration in the center region of combustor. The concentration of combustion products, such as H2O and CO2, increases by 13.2% in the reaction region.

Influence of military actions on the process of the formation of precipitation

This work concerns the study of the influence of military actions on the development of global ecological processes, in particular, the fall of acid rain from individual single explosions. A mathematical model is proposed, which takes into account the emission of pollutants into the subcloud washout zone and the kinetics of the condensation process. The concentration of combustion products in the atmosphere at the level of three to five diameters of the explosion area (the area of the formed explosion funnel) is found using the theory of a convective jet from a warm source to the environment. At the same time, we determined the speed of warm air that rises above the area of the explosion, the average temperature in the transition section of the convective jet, and the flow rate of polluted air in the upper part of the jet. The paper presents a system of dimensionless non-stationary differential equations for a high unshaded source, which can be used to determine the dispersion of the main acid-forming substances in the Boussinesq approximation with the variables "eddy velocity – current function – temperature – concentration" with appropriate initial and boundary conditions. Sulfuric anhydride was considered as an example of the main acid-forming substances and the most dangerous and toxic compounds of explosion products. The proposed mathematical model can be used to forecast the possible fall of acid rain on the territories adjacent to single explosions, thereby making a forecast of changes in environmental risk as a result of military operations for the environment and the population. and will make it possible to determine the zones of influence and dispersion from the place of the explosion.

Flame characteristics of backward-inclined pulsating combusting jet in crossflow

The flame appearances, thermal characteristics, and combustion product concentrations of a backward-inclined pulsating combusting jet in crossflow were experimentally studied. The time-averaged and streak instantaneous flame images were acquired using a still camera and a high-speed camera, respectively. The flame extinguishment processes were captured and analysed on the basis of streak instantaneous images. The flame temperatures and combustion product concentrations were measured using a homemade fine-wire thermocouple and a gas analyser, respectively. Three characteristic flame modes (crossflow dominated, transitional, and jet-dominated) were found when the backward-inclined jet flame in crossflow was subject to acoustic excitation. These characteristic flame modes were observed in different regimes of pulsation intensity and jet backward inclination angle. Discrete flame puffs with a frequency equal to the acoustic excitation frequency appeared in the jet-dominated flame. Periodic flame puffing became unstable when the pulsation intensity was increased to values near the instability limit. When the pulsation intensity was beyond the instability limit, a strong stretching effect caused the recirculation flame, which played the role of a flame ignitor, to almost vanish (misfire). The flame extinguishment then occurred from the area around the lee side of the burner tube tip. The temperature and gas concentration measurement results showed the significant improvement of combustion performance in low inclination angle even at small pulsation intensity in the regime of the crossflow dominated flame. To enhance combustion performance at a large jet backward inclination angle, the pulsation intensity must be large enough to push the flame in the regime of the jet-dominated flame.

Crown Fire Modeling and Its Effect on Atmospheric Characteristics

The article is concerned with the experimental study of the crown fire effect on atmospheric transport processes: the formation of induced turbulence in the vicinity of the fire source and the transport of aerosol combustion products in the atmosphere surface layer at low altitudes. The studies were carried out in seminatural conditions on the reconstructed forest canopy. It was established that the structural characteristics of fluctuations of some atmosphere physical parameters in the case of a crown fire practically coincide with the obtained earlier values for a steppe fire. The highest concentration of aerosol combustion products was recorded at a height of 10–20 m from the ground surface. It was found that the largest number of aerosol particles formed during a crown fire had a particle diameter of 0.3 to 0.5 µm. As a result of experimental data extrapolation, it is concluded that an excess of aerosol concentration over the background value will be recorded at a distance of up to 2000 m for a given volume of burnt vegetation. It is of interest to further study these factors of the impact of wildfires on atmosphere under the conditions of a real large natural wildfire and determine the limiting distance of aerosol concentration excesses over background values.

Mechanical properties evaluation and microstructural analysis study of ceramic-coated IC engine cylinder liner

In the automotive industry, the primary objectives are to bring down the fuel consumption and boost power. The diesel engine has the best performance of any conventional internal combustion engine because of its extraordinarily high compression ratio. Gasoline engines consume more fuel per unit of power than diesel ones, whilst the two have the same performance. Only 40% of the power generated by an engine is utilized for productive purposes on average. Thirty percent of the remaining heat is lost through the exhaust, and another thirty percent is dissipated as heat losses by the cooling system. Ceramic and YSZ Coatings are applied to the cylinder liners and the piston head to transform the heat generated by the combustion process into meaningful mechanical work. As a result, the engine's heat transmission will be reduced, increasing efficiency. The higher gas temperature is expected to minimize the concentration of incomplete combustion products at the expense of an increase in nitrogen oxides (NOx). Scanning Electron Microscopy (SEM) and optical microscopy studied an engine cylinder liner's top-ring reversal point surface texture. Experiments were done on a single spark ignition engine during the break-in stage and the texture of the cylinder liner is studied.

Fire Characteristics Analysis of On-fire Intercity Train in the Tunnel under Open Side Door

In order to explore the fire characteristics of high-speed intercity trains running in the tunnel when the side door of the carriage is opened in case of emergency, this paper simulates the fire intercity trains in the tunnel based on PyroSim fire simulation software, and studies the fire temperature and smoke distribution characteristics in the carriage of intercity trains at different running speeds and obtained: With the increase of train speed, the temperature and smoke concentration in the carriage gradually decrease, when the speed exceeds 140km/h, the temperature influence range and smoke concentration distribution are roughly the same. When the speed exceeds 80km/h, the concentration of combustion products began to decrease and reached the lowest at 200km/h. According to the distribution of train temperature and smoke and products concentration obtained by numerical simulation, it is suggested that the speed of intercity train with fire should maintain its original speed when the side door of the train is opened.

Investigation on the chemical equilibrium products for CnHmOlNk type fuels using equilibrium constants database

As international concern that regards NOx emissions from the shipping industry increases, it is challenging and urgent to reduce ships’ NOx emissions. According to the extended Zeldovich, the determination of the equilibrium concentration of combustion products is crucial for the prediction of NO formation in internal combustion engines. In the present work, an equilibrium constants database of related chemical reactions is established based on the theory that the total Gibbs energy reaches its minimum when a reaction achieves equilibrium. Afterward, a combustion product equilibrium model with twelve species considered is established based on the equilibrium constants database. The accuracy of the model is significantly improved compared with the commonly used ones which calculate the equilibrium constants through fitting function. The errors of the model are within 2% compared with STANJAN which is widely used for chemical equilibrium analysis. The model results are comparable to STANJAN. Afterward, the effects of the temperature, pressure, fuel–air equivalence ratio, O2 concentration, N2 concentration, Ar concentration and fuel type on the equilibrium mole fractions of the combustion products are investigated. The equilibrium concentration of combustion products is significantly affected by the temperature, O2 concentration and fuel–air equivalence ratio, but slightly influenced by the pressure and Ar concentration. The existence of O and N in the fuel slightly reduces the NO equilibrium mole fraction of the combustion products at the same temperature, pressure and fuel–air equivalence ratio. However, the ratio of molar carbon hydrogen in the fuel and the existence of O and N in the fuel have a significant impact on the CO2 mole fraction of the combustion products.

Evaluation of the effect of high air temperature on the behavioural activity and physical performance of animals (in a rat model)

Introduction. The profession of firefighters belongs to extreme activities. Fire hazards include flames, sparks, heat flow, elevated ambient temperatures, increased concentrations of toxic combustion and thermal decomposition products, decreased oxygen concentrations, and reduced visibility in smoke. High air temperature during fire extinguishing is one of the main adverse physical factors affecting firefighters’ bodies. Material and methods. The study was carried out on 124 outbred white male 3-month rats weighing 250-300 g, divided randomly into two groups: the first group (62 rats) underwent single hyperthermia. The second group (62 rats) experienced daily hyperthermia for 14 days. The study of the behavioural activity of animals was carried out after single and prolonged hyperthermia using the following methods: “Open field”, “Elevated cruciform maze”, Porsolt’s test, running on a treadmill. The tests were performed two times: the first time - before exposure, the second - after, with intervals between tests of at least two weeks. Results. The data obtained indicate that the high ambient temperature causes changes in the behavioural responses in animals, which is expressed by an increase in the level of anxiety, a decrease in motor and research activity, the development of depressive states, and a decrease in physical endurance. Conclusion. An experimental model of extreme heat exposure on animals showed the emergence and persistence of changes in animals’ behavioural activity and physical performance indicators. This experiment can be used to study the long-term effects of high temperatures on firefighters’ bodies.

Multi-objective optimization of a lean premixed laboratory combustor through CFD-CRN approach

In this paper, the effects of geometrical characteristics variations on the pollutant emissions in a laboratory lean premixed combustor are studied numerically and experimentally. For this purpose, the combustion chamber, premixing chamber, and equipment for measuring the flame temperature and combustion product concentrations are designed, fabricated, and assembled for a laboratory atmospheric test stand. An object-oriented optimization algorithm based on computational fluid dynamics (CFD), a chemical reactor network (CRN), and the response surface method (RSM) is presented for optimization of the combustion chamber geometry to obtain minimum pollutant emissions. The numerical approaches for modeling the flow field and predicting the detailed chemistry are validated against the experimental results. Parameters, such as minimizing NOx, CO, and NO emissions, are considered for optimizing the combustion chamber's geometry. Finally, it is shown that the hybrid approach of CFD-CRN can serve as a useful tool in the design process and the optimization of combustion chambers. The optimization process results show that minor changes in the combustor design can minimize the defined objectives to an acceptable level.

Greenhouse gas sources and mitigation strategies from a geosciences perspective

Certain gases that are capable of trapping heat in the Earth’s atmosphere are known as “greenhouse gas” and are important for helping to regulate temperature. Major greenhouse gases include carbon dioxide, methane, water vapor, chlorofluorocarbons, and nitrous oxide. Burning fossil fuels produces carbon dioxide as a combustion product and atmospheric concentrations have increased dramatically over the past two centuries. The heat trapped by this additional greenhouse gas is changing climates, melting ice sheets and glaciers in polar regions, raising sea levels, and affecting ocean currents. Climate change can be mitigated by preventing the emission of additional fossil fuel combustion products to the atmosphere and reducing existing greenhouse gas levels back to pre-industrial revolution concentrations. This requires switching energy production to sustainable, non-fossil sources and applying carbon capture, use, and storage technology on the fossil fuel combustion that remains. The implementation of direct air capture technology to reduce existing carbon dioxide levels in the atmosphere can further remediate climate impacts. Captured carbon dioxide can be stored in plant tissues, soils, deep underground in geological repositories, or as solid materials like concrete or carbonates to keep it from reentering the atmosphere. Although non-carbon energy sources have recently become more cost-competitive with fossil energy, technological advancements and government policies are still needed to overcome the inherent economic advantages of fossil fuels. A global strategy must be developed to convince people that the higher cost of clean, sustainable energy is a price worth paying to replace fossil fuels and prevent a major environmental calamity. Cited as: Soeder, D. J. Greenhouse gas sources and mitigation strategies from a geosciences perspective. Advances in Geo-Energy Research, 2021, 5(3): 274-285, doi: 10.46690/ager.2021.03.04

Optical diagnostics of the temperature field of a hydrogen-air flame

A method for multi-wave optical diagnostics of phase structure and temperature fields in an axisymmetric hydrogen-air flame is discussed. An algorithm for numerical simulation of Hilbert images of phase fields reconstructed from radial temperature profiles and molar concentrations of combustion products using the Abel transform is developed and experimentally justified.

A calibration and sampling technique for quantifying the chemical structure in fires using GC/MSD analysis

SUMMARYThis work presents an approach to measure, calibrate, and verify local concentrations of combustion products in pool fires steadily burning in a quiescent environment. This study describes a method that can be used to measure and verify the chemical species present in a fire. Such information is needed to assist in the development and validation of the chemistry subroutines in computational fluid dynamic fire models. Samples are extracted along the centerline of pool fires using a thermal quenching probe. Gas species volume fractions are analyzed using a custom Agilent 5977E Series gas chromatograph fitted with a permanent gas dual‐column comprised of a Molsieve 5 Å and PoraBOND Q capillary columns in parallel flowing into mass selective and thermal conductivity detector. The system can identify and quantify a variety of stable reactant, intermediate, and product species collected from the fire, including several condensable species (eg, water, methanol, ethanol, and acetone). The time‐weighted average soot mass fraction is determined using a gravimetric sampling method. In order to solidify the legitimacy of the measured gas composition, the results are verified by implementing different techniques, including the determination of the carbon to hydrogen ratio, calculating the argon to nitrogen ratio, and comparing the total moles estimated from the chromatogram peaks to the total moles of the injected sample.

Providing the environmental safety by increasing the efficiency of firefighting in unsheltered timber warehouses

Purpose. To develop a method for reducing the impact of fires in unsheltered timber warehouses on the environmental safety by reducing the duration of free burning of timber, the speed of fire front spread, emissions of combustion products and the duration of the firefighting. Methodology. During the experimental research, the method of fractional factor experiment was used. Theoretical research was performed using optimization mathematical models. The Monte Carlo method is used to solve optimization problems. To implement this method, block diagrams of algorithms was developed, based on written corresponded computer programs. Findings. The method was developed for reducing the impact of fires in unsheltered timber warehouses on the environmental safety by reducing the duration of free development of the fire, the speed of fire front spread, the concentration of combustion products and the duration of the fire. Fire prevention measures to reduce the duration of fire and to reduce emissions of combustion products due to fires in unsheltered timber warehouses was implemented by using an automated system to determine the fire extinguishing means and forces by setting an optimization problem, applying the Monte Carlo method and developing software to solve it. Originality. The scientific novelty is the justification of ways to reduce the duration of the free development of fire and to reduce the amount of toxic emissions using optimization mathematical models. Practical value. It is possible to use the obtained results in the practical activities of fire and rescue units of the SES of Ukraine and provide environmental safety in case of fire in unsheltered timber warehouse due to the practical implementation of administrative, legal and economic methods.