Liquid Combustion Research Articles

Simulation of non-isothermal liquid sprays under large-scale turbulence

Due to the high level of achieved research, there are prospects for the widespread use of the method andspecific physical results in the areas under consideration, as well as ways for more effective applicationof mathematical modeling methods using modern computing technology in various subject areas. For thenumerical study of the combustion of liquid fuels, it is required to consider many complex interrelatedprocesses and phenomena, which are laborious tasks of computational thermal physics. In the theory’s studyof combustion and the development of various technical devices, the actions of which are based on the useof the combustion process, a computational experiment is becoming an increasingly important element.Computational fluid dynamics methods have become widespread in technical physics when it becomespossible to optimize an experiment based on its virtual prototype. This work is devoted to the numericalmodeling of the processes of breakup, dispersion, evaporation and combustion of liquid fuel droplets underhigh turbulence. Fundamental characteristics, methods of liquid fuels atomization, the mathematical modeland basic equations describing the collision, distribution and combustion of liquid fuels at high turbulenceare presented. Results of computational experiments by determination of the optimal conditions for thecombustion of liquid hydrocarbon fuel are presented. Influence of the oxidant’s initial temperature on theprocesses of atomization and dispersion of droplets in the combustion chamber under high turbulence isinvestigated. Optimal combustion parameters for the dodecane have been determined. Key words: numerical modeling, atomization, liquid fuel, dodecane, high turbulence.

Удосконалення управління процесом горіння палива в суднових котлах

Annotation – The article discusses the issues of increasing the efficiency of the combustion of liquid fuel in the furnaces of ship steam boilers using the proposed neural network system for automatic correction of the excess air coefficient. It is indicated that modern systems for automatic flame detection have a number of disadvantages, in particular, low sensitivity to extraneous illumination, etc. hot air or flue gases on the walls of the boiler furnace. Such pulsations reduce the reliability of the combustion monitoring and control system. Therefore, the task of developing and introducing on ships new, economically inexpensive and effective methods of effective control and management of the fuel combustion process in ship boilers using modern means of intelligent control is urgent. On the basis of the experiments carried out on a Mitsubishi MV 50 marine steam boiler and the collected experimental data, the values for training the neural network system of the air flow correction process, taking into account the color of the burner flame and the color of the flue gases, were obtained. The use of a trained neural network in the control system, taking into account the fuzzy expert system for monitoring the color of the flame and smoke, makes it possible to achieve the best excess air ratio depending on the steam load of the SEP units. Simulation modeling of the proposed neural system was carried out in a specialized program Matlab (Neural Networks Toolbox). The simulation results showed that the use of a neural network control system for the combustion of liquid fuel, using the example of a marine boiler, allows maintaining a given thermal regime over the entire range of steam load of the power plant units, and also allows timely correction of the excess air ratio, i.e. avoid excessive consumption of fuel.

DEVELOPMENT OF THE COMBINED RESERVOIR OF MIXTURE OF TECHNICAL COMBUSTIBLE LIQUIDS AS COMPONENT OF ENVIRONMENT PROTECTION TECHNOLOGY

In this study the development, analysis and description of the sche­me of environment protection technology for the oil storage were carried out. The proposed scheme is provided for the utilization of vapors of technical combustible liquids stored at the enterprise, namely diesel fuel, gasoline and motor oil, formed during the manifestation of the phenomena of small and large reservoir breathing in significant quantities. Set of initial data and the mass hour­ly emission of such vapors into the en­vironment were obtained according to an improved approach. Development of a high-pressure storage reser­voir for such vapors as the executive device of environmental protection technology for the oil storage according to an improved approach was carried out. Parameters of the reciprocating compressor, which distills the mixture of such vapors from the low-pressure storage reservoir to the high-pressure sto­rage reservoir, compressing them, was selected. Calculation of the reservoir wall thickness ba­sed on the theory of strength of closed solid shells was carried out taking into account the mechanical properties of the wall material, namely steel 60, and the value of the pressure of the gaseous fluid in it. Magnitudes of weight of the deve­loped reservoir and the cost of materials for its manufacture were determinated. Design of a combined reservoir for the ac­cu­mu­lation of a volley of a mixture of such vapors with a system of intermediate cooling of the mixture after its compression by a reciprocating compressor and the pos­sibility of heating the condensate in the reservoir was de­ve­loped.

Fire Protection of Steel Structures with Epoxy Coatings under Cryogenic Exposure

Cases of fire with highly flammable, combustible liquids and combustible gases with high potential heat emission at oil and gas facilities are assumed to develop as a hydrocarbon fire, which is characterized by the temperature rising rapidly up to 1093 ± 56 °C within five minutes from the test start and staying within the same range throughout the test, as well as by overpressure being generated. Although various fireproof coating systems are commonly used to protect steel structures from high temperatures, a combination of fire protection and cryogenic spillage protection, i.e., protection from liquefied natural gas (LNG), is rather an international practice novelty regulated by standards ISO 20088. Thanks to their outstanding features, i.e., ability to sustain chemical and climatic impact, these epoxy-based materials are able to ensure positive fireproof performance for steel structures in the case of potential cryogenic impact. The article discusses tests on steel structures coated with epoxy fireproof compounds, specifically PREGRAD-EP, OGRAX-SKE and Chartek 2218. The test records show the time from the start of cryogenic exposure to the said sample reaching the limit state, as well as the time from the start of heat impact to the sample reaching the limit state in case of hydrocarbon fire temperature.

Insights into ensemble learning-based data-driven model for safety-related property of chemical substances

Risk assessment relying on characteristics of chemicals in process industries can prevent accidents caused by flammable and combustible liquids and gases. Whereas its application is limited by the lack of safety-related properties for abundant chemicals of interest, which promotes the demand for accurate predictive models to evaluate inherent safety implications of chemicals. In this research, staking-based ensemble learning is comprehensively investigated on safety-related properties to assist the risk assessment. Based on molecular structure-based features, individual and ensemble models are built and compared using heterogeneous machine learning (ML) methods. The systematic ensemble learning workflow is deployed by a case on flash points of chemical substances. Several representative ML methods including multiple linear regression, extreme learning machine, feedforward neural network, and support vector machine are taken into consideration. As it turns out, ensemble models exhibit improved predictive accuracy than standard individual ML models, indicating the effectiveness of ensemble learning on improving model performance. Moreover, extremal evaluations with existing models as well as internal analyses against functional group-based organic compound families and structural feature-based data-driven categories are carried out to identify model reliability. Ensemble learning is demonstrated as an effective approach for high-performance predictive modeling in safety-related risk assessments.

Comparison of different processing approaches by SVM and RF on HS-MS eNose and NIR Spectrometry data for the discrimination of gasoline samples

In the quality control of flammable and combustible liquids, such as gasoline, both rapid analysis and automated data processing are of great importance from an economical viewpoint for the petroleum industry. The present work aims to evaluate the chemometric tools to be applied on the Headspace Mass Spectrometry (HS-MS eNose) and Near-Infrared Spectroscopy (NIRS) results to discriminate gasoline according to their Research Octane Number (RON). For this purpose, data from a total of 50 gasoline samples of two types of RON-95 and 98-analyzed by the two above-mentioned techniques were studied. The HS-MS eNose and NIRS data were combined with non-supervised exploratory techniques, such as Hierarchical Cluster Analysis (HCA), as well as other supervised classification techniques, namely Support Vector Machine (SVM) and Random Forest (RF). For supervised classification, the low-level data fusion was additionally applied to evaluate if the combined use of the data increases the scope of relevant information. The HCA results showed a clear clustering trend of the gasoline samples according to their RON with HS-MS eNose data. SVM in combination with 5-Fold Cross-Validation successfully classified 100% of the samples with the HS-MS eNose data set. The RF algorithm in combination with 5-Fold Cross-Validation achieved the best accuracy rate for the test set with the low-level data fusion system. Furthermore, it allowed us to identify the most important features that could define the differences between RON 95 and RON 98 gasoline. On the other hand, using the HS-MS eNose and NIRS low-level data fusion reached better results than those obtained using NIRS data individually, with accuracy rates of 100% in both SVM and RF performances with the test set. In general, the performance of the SVM and RF algorithms was found to be similar.

The study of the effect of forced air supply on the combustion of liquid fuel dispersed by superheated steam

In the present work, the effect of forced air supply on the combustion process of liquid hydrocarbons was studied using diesel fuel as an example. The content of intermediate components of the flame and the temperature distribution along the flame symmetry axis were studied using an atmospheric burner with liquid fuel atomizing by a steam jet. The gas composition of equilibrium combustion products and the heat release were investigated. The influence of the excess air ratio in the combustion chamber of the burner device on the thermal and environmental characteristics was shown.

Kinetic properties and ignition characteristics of fuel compositions based on oil-free and oil-filled slurries with fine coal particles

A difference in the ignition and combustion mechanisms and characteristics was established for fuel compositions based on petroleum waste (used oils) and coal processing waste (high-moisture low-rank coals) with a binding component (polymer thickener), as well as for the individual combustible liquid and solid components used to produce them. Thus, the paper investigates the kinetic combustion characteristics using the isoconversional Friedman method and the temporal ignition characteristics of droplets (particles) under the conditions corresponding to fuel combustion. The data of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were obtained when heating the experimental samples at the rates of 5, 10 and 15 K per minute. It was established that the kinetic combustion characteristics of multi-component fuel compositions differ significantly from those of individual components in a normal state. Unlike single-component liquid and solid fuels, multi-component fuel mixtures based on insoluble liquid components, including those containing fine solid combustible particles, are ignited under the conditions of micro-explosive dispersion when heated in an air medium with a temperature of 973–1273 K.

Pyrolysis Solves the Issue of Organic Contaminants in Sewage Sludge while Retaining Carbon—Making the Case for Sewage Sludge Treatment via Pyrolysis

Contaminants of emerging concern are a growing burden for sewage sludge recycling. Pyrolysis of sewage sludge could be a solution. Yet, the product of sewage sludge pyrolysis (biochar) is currently not included on the list of eligible fertilizers in the new EU Fertilising Products Regulation. This was justified by insufficient evidence for organic contaminant removal through pyrolysis. Here I summarize the current evidence on this topic covering 20 studies and more than 100 different organic pollutants. The studies demonstrate that pyrolysis reduces the concentration of well-established contaminants, such as PAHs, PCBs, and dioxins, but also emerging ones, i.e., pharmaceuticals, hormones, antibiotics, antibiotic resistance genes, antimicrobials, microplastics, and per- and polyfluoroalkyl substances (PFAS) with very high efficacy (>95 to >99% in most cases). After pyrolysis, the levels of organic contaminant in biochar were typically below the limit of detection. Furthermore, modern pyrolysis units prevent environmental release of contaminants that are only vaporized and not decomposed during pyrolysis by internal combustion of pyrolysis liquids and gases. The evidence for effective organic contaminant removal through pyrolysis is comprehensive, covering all relevant groups of compounds. This and its potential as negative emission technology makes pyrolysis of sewage sludge a great opportunity for sustainable and safe nutrient recycling.

Evaporation and combustion characteristics of an ethanol fuel droplet in a DC electric field

The combustion process of droplet in an electric field is observed experimentally. The deformation and temperature of flame and droplet are obtained, and the combustion rate constant is calculated. The results show that the combustion process of droplet is significantly influenced by the electric field. When an electric field is applied, the initial shape of the droplet is elongated. The flame is brighter, the droplet shape is more stable, the flame height decreases significantly and the flame width increases slightly. When the electric field is applied, the combustion time is reduced by 14.9% compared with the condition without the electric field. With the electric field intensity increasing, the flame temperature increases firstly and then decreases, the droplet temperature decreases and the evaporation temperature decrease. When the electric field is applied, the maximum temperature of the flame measured increases by 17.6%, the maximum temperature of the droplet measured decreases by 12.9% and the evaporation temperature measured is reduced by 4.2% compared with the condition without the electric field. The electric field mainly affects the shape and temperature of flame and droplet, but the effect on the combustion rate is not obvious. The fluid flow is accelerated and the heat transfer is enhanced. The electric field charges the droplet and the directional movement in the droplet is enhanced, which promote the evaporation. At the same time, the droplet evaporates and combusts at a lower temperature, which partially counteracts the promotion caused by the flow acceleration. This study gives an insight into the effect of applied electric field on the combustion of liquid fuel in a new perspective of evaporation.

Method for measuring the active electrical resistance of a diffusion flame when burning liquid combustible substances

The article is devoted to the problem of studying the electrical properties of a flame in a fire. The article discusses a method for measuring the active electrical resistance of a diffusion flame when burning liquid combustible substances. The dependence of the electrical resistance of the flame torch on the geometric dimensions of the combustion zone and on the average volumetric temperature of the flame torch in the mode of the laminar flow of the combustible mixture has been established. An empirical dependence has been obtained, which makes it possible to calculate the value of the electrical resistance of the flame.

Experimental investigation of size of fuel droplets formed by steam jet impact

The process of liquid hydrocarbon fuel disintegration into droplets under the action of a supersonic jet of superheated steam was studied by shadow photography and high-speed visualization. During the measurements operating parameters for the conditions of fuel spraying in a real burner were varied for three types of fuel: diesel, oil, and kerosene. For the first time, the photographs of the process of disintegration of various types of liquid hydrocarbon fuel during interaction with a supersonic gas jet were obtained. When oil flows onto the steam jet, thin threads and films of liquid with a chaotic structure are formed. The regime of droplet disintegration corresponds to the “catastrophic” one. It is shown that the proposed method of fuel spraying provides effective dispersion for high-quality combustion and it can be used in liquid fuel burners, even when burning liquid combustible waste, as well as in low-emission gas turbine engines. Size distributions of fuel droplets in the region of fuel ignition were obtained for different fuel and steam flow rates. The use of a long-focus lens allowed optical magnification of 7:1 and identification of droplets as small as 1 μm. For diesel and oil, the characteristic droplet size is 2 µm, and for kerosene, it is 1 µm.

Ignition temperature of combustible liquids in mixtures of air with nitrous oxide

SummaryWhile ignition temperatures in the air are well known for a large number of flammable substances and to a lesser extent in pure oxygen too, no such values exist for ignition temperatures in nitrous oxide in spite of the fact that nitrous oxide is used as oxidizer in combustion processes or aerosol propellant in industry. The ignition temperatures of some pure compounds have now been investigated in oxidizer mixtures of nitrous oxide and air with varying concentration of nitrous oxide up to 80 vol% using a slightly modified standardized apparatus. The ignition temperature increases with increasing nitrous oxide concentration. Up to 580°C, none of the investigated substances ignited in pure nitrous oxide.

In-situ reforming and combustion of liquid fuel using MnOx/Ce-γAl2O3 oxygen carrier in a chemical looping combustion process

A new MnOx/Ce-γAl2O3 oxygen carrier is developed for liquid fuel based fluidized chemical looping combustion (CLC) process. The developed material serves both as a catalyst and as a source of solid phase oxygen for gasification/reforming of liquid fuel followed by the combustion of the gasified products. The support γAl2O3 is modified with cerium, improved thermal stability and minimized the interaction with the main active component MnOx. In order to validate the desired properties, the prepared MnOx/Ce-γAl2O3 samples are characterized using various physicochemical characterizations, including X-ray fluorescence (XRF), nitrogen adsorption, thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscope (SEM), temperature programmed reduction (TPR), and temperature programmed desorption (TPD). TPR, TGA and XRD analysis confirm that the Ce modification improves the thermal stability of γAl2O3 and hinders the formation of difficult reducing manganese aluminate. TPR profiles show excellent reduction and re-oxidation performances of the Ce modified samples. Based on characterizations, a selected sample is further evaluated in a fluidized CREC Riser Simulator (CREC: Chemical Reactor Engineering Centre) using n-hexane as a liquid fuel surrogate. Under the studied reaction conditions (500–650 C; 10–45 s reaction time), CO2 and CO are the main combustion products. At 650 °C, approximately 92% n-hexane combustion and 60% of CO2 selectivity was achieved, which is very encouraging, given the complexity of the interaction of liquid fuel with the solid metal oxides.

Introduction of a flame suppression pattern into integrated and zone models used to analyze the dynamics of hazardous factors of indoor fires

Introduction. Fire risk calculation is performed to substantiate the compliance of space planning solutions of buildings and structures with fire safety requirements. The calculation of time needed for hazardous factors of fire to block evacuation routes is performed with account for unlimited fire propagation. The only system, whose operation is taken into account if the fire risk value is exceeded, is the smoke ventilation system. The operation of other fire safety systems is disregarded due to the unavailability of reliable engineering methods of analysis of their influence on fire escalation. The problem of development of modified mathematical models, used to analyze the fire escalation pattern, with account to be taken of the process of fire extinguishing and its influence on fire propagation, is relevant. The purpose of this research is to develop common principles that allow to take account of the pattern of fire suppression in solid materials and combustible liquids by fire extinguishing substances having various origins and degrees of dispersion, if the fire extinguishing substances are added to integrated and zone models of development of hazardous factors of fire escalation.Calculation methodology. The calculations are based on the equation compiled in furtherance of principles of conservation of mass and energy in the flame zone above the surface of the combustible material.Research results. The co-authors suggest general principles for the introduction of a flame suppression pattern into integrated and zone models used to analyze the evolution of hazardous factors of indoor fires. The coauthors present the main provisions and parameters needed to modify integrated and zone models in case of different methods of fire extinguishing. The co-authors have analyzed hazardous factors of fire with account for the flame suppression pattern.Conclusions. The co-authors applied the research findings to develop the modified integrated and zone models that allow to analyze the dynamics of hazardous factors of fire with account for the extinguishing of solid materials and combustible fluids by fire extinguishing substances having various origins and degrees of dispersion.

Research on the influence of foaming gas in compressed air/nitrogen foam on extinguishing the n-heptane tank fire

Tank fires threaten the lives of people and pollute the environment for their intense radiant heat, rapid fire spread and explosion hazard. Compressed air/nitrogen foam (CAF/CNF), a cleaner fire extinguishing technique used for the tank fire suppression because halogen-based agents were prohibited for environmental reasons. In this work, the influence of foaming gas in CAF/CNF on extinguishing the n-heptane tank fire was firstly investigated. Firstly, it was found that CNF spreads faster with rapid increase in foam thickness, mainly due to its better stability and less evaporation. Secondly, after foam was discharged, there existed a short increase of the combustion intensity, associated with three monotonous regions and two time delays in the whole extinguishing time. The two time delays were caused by Rayleigh–Taylor instability and flame sheet shift, respectively, and the shift distance was larger for CNF. Finally, the influential factors contributing to flame extinction were exhibited to be mainly related to the decrease in liquid burning rate and gas-phase Damkohler number. Among these factors, foam spreading rate and thickness dominated due to coupled chemical and physical extinguishing effects. Resulted from some competitive effects, CNF was slightly more efficient at extinguishing tank fires than CAF.

Experimental investigation of waste oil processing by partial oxidation in a moving bed reactor

A novel approach for oil sludge processing was proposed. The processing can be realized in the reactor with moving layer of inert solid heat carrier, which will allow operating in a continuous mode. This method can be carried out both with an excess of oxidant with the burning of combustible liquids to CO2 and H2O, and with a lack of oxidant when the initial fuel is being converted to syngas. Experimental investigation of air and air–steam conversion of oil waste in a counterflow moving bed filtration combustion reactor was carried out. The oil supply in the experiments was varied from 6 to 13 ml/min so that the stoichiometric excess ratio of oxygen with respect to oil (α) varied from 0.4 to 1.0. The maximum calorific value of the product gas and the efficiency of the process was observed at α = 0.4. Laboratory scale studies showed a possibility to generate the product gas with calorific value up to 7 MJ/m3 and the chemical efficiency of the process to 94%. At α = 0.6–0.8 the calorific value of the product gas is substantially reduced, however, the resulting gas is free of hydrocarbons and can be used in the chemical industry.

МОДЕЛИРОВАНИЕ ПРОЦЕССА СГОРАНИЯ В ДИЗЕЛЬНОМ ДВИГАТЕЛЕ

The issues of combustion processes and the organization of the combustion workflow in diesel engines are relevant in view of the tightening of economic and environmental requirements for them. The problem of saving liquid fuels remains one of the most acute in the provision of fuel and energy resources. The development of highly efficient methods for organizing work processes when burning natural gas in a compressed or cryogenic state in the cylinders of internal combustion piston engines and determining ways to further reduce toxic emissions, increase fuel efficiency and reliability in promising gas engines is an urgent task. Mathematical modeling of liquid fuel combustion is a complex task, since it requires taking into account a large number of complex interrelated processes and phenomena. The article presents a simple 3-D model of cylinder diesel tractor engine D 144, the re- sults of numerical simulation of combustion of liquid and gaseous fuel in the cylinder of the diesel engine D-144. The article presents the results of modeling, including graphs of the dependence of nitrogen oxides, particles in outgoing gases, depending on the consumption of gaseous fuel in the form of pure methane. Additionally, tempe- rature and velocity contours are shown. The corresponding conclusions are made.

Conventional and cement-catalyzed co-pyrolysis of rice straw and waste polyethylene into liquid and gaseous fuels by using a fixed bed reactor

Rice straw is the main agricultural by-product while polyethylene is among the most widely produced plastics in the world. The bulk of rice straw and discarded polyethylene end up in landfills and pose concerns with waste management. By valorizing these wastes into valuable fuels through a suitable conversion approach, the associated environmental pollution and waste management problems can be reduced. In the reported work, a low-cost cement catalyst was tested for co-pyrolysis of rice straw and waste polyethylene into combustible liquid and gases in a fixed bed pyrolysis reactor. Under optimum conditions, the co-feed rice straw and polyethylene yielded 57.2 wt.% of liquid fuel, 21.3 wt.% of gas, and 21.5 wt.% of bio-char. When compared with rice straw alone, the co-feed feedstock produced 16.60% more liquid fuel and 7.5% less bio-char. The liquid product increased with an increase in plastic content of the blend. The amount of liquid product increased from 57.2 to 74.18 wt.% for rice straw to polyethylene ratio of 1:3. The catalyst showed a noticeable effect on composition of the fuels. With the use of catalyst, the gas yield increased from 21.3 to 28.16 wt.% and hydrogen content of gas increased from 19.33 to 31.18 mL/g.

Manufacturing entities flare systems fire hazard analysis

Industrial enterprises of chemical, petrochemical, energy complexes, in the technological process of which combustible gases, flammable and combustible liquids rotate, have flare systems, which are designed for smokeless combustion of combustible and toxic gases or vapors as a result of their periodic, emergency or permanent venting. The main task of flare systems at enterprises is to prevent gas from atmosphere entering by flaring. Flare systems of a manufacturing entities are a complex of structures of high fire danger. The task of the work is to analyze the parameters of the explosion that may occur during the formation of an emergency situation on flare systems.