Terms Of Operators Research Articles

АНАЛИЗ КЛЮЧЕВЫХ НАПРАВЛЕНИЙ РАЗВИТИЯ МАШИНОСТРОИТЕЛЬНОГО КОМПЛЕКСА РОССИИ И ПРОБЛЕМ РЕАЛИЗАЦИИ КАДРОВОЙ ПОЛИТИКИ НАУКОЕМКИХ ПРЕДПРИЯТИЙ

The article provides an overview of the directions of development of mechanical engineering and personnel policy in the Russian industry, also describes the reasons for the decline in human resources in mechanical engineering and factors influencing the development of personnel policy. Special attention is paid to the issue of strengthening the interaction of educational institutions of higher education (hereinafter referred to as OOVO, universities) countries with machine-building enterprises, the creation of departments and laboratories on their basis for conducting practical classes for students of technical and economic specialties. A key component of the HR policy of knowledge-intensive enterprises is increasing the level of competence of young specialists. For any modern enterprise, a properly structured personnel policy helps to increase its competitiveness and safety of operation in the long term. The main purpose of the personnel management system of high-tech enterprises is to provide the company with highly qualified specialists, their productive use, professional and social development that satisfies the owners and management of the enterprise, as well as the employees themselves. The personnel policy of such enterprises should ensure a balance between maximizing management flexibility and staff efficiency. The requirements for the personnel policy of high-tech machine-building enterprises are that it should be based on a systematic analysis of the external and internal environment, flexible response to changes due to the adjustment of management actions.

Optimizing Control of Waste Incineration Plants Using Reinforcement Learning and Digital Twins

More than 60 waste incineration plants (WIPs) are active across Germany. WIPs have various levels of automation, but they still rely on manual operations by human operators. Human operators tend to rely on a few operational levers and infrequent interventions to manage the complex combustion process. Consequently, the combustion process is managed rather inefficiently, and steam outputs and emission levels are not optimal. This article investigates how reinforcement learning (RL) can help enhance process automation and, thus, optimize the combustion process, e.g., by making more frequent and diverse interventions. An RL agent is trained via trial and error with a reward function that includes the optimization criteria. Since the actual equipment, i.e., the real WIP, cannot be used as the training environment, a digital twin is built using original plant data and a neural network. The RL agent is then trained in this offline environment with the deep Q-network algorithm. First, our work demonstrates that a digital twin of a WIP can be built in a data-driven way. Second, we show that the RL agent outperforms the human operator. Thus, the application of RL might benefit the plant operator in financial terms and the environment in terms of reduced emission levels.

DEVELOPMENT OF PERSPECTIVE STRATEGIES FOR ENSURING INTEGRATED ECONOMIC SUSTAINABILITY OF BUSINESS STRUCTURES IN CRISIS CONDITIONS

The practical implementation of the transition to the domestic market and a sharp reduction in export operations in the short term may be complicated by the lack of sufficient demand from the consumer segment. If the consumer segment is made up of households, the Group may face a decline in demand due to a fall in purchasing power in the context of the crisis and macroeconomic instability (rising regional unemployment, higher inflation) or the presence of existing competitors positioning themselves in this market niche and having a certain stable customer base formed, among other things, through loyalty policies. In the context of sales of inputs on the domestic market, in addition to the above, there may be a problem of inconsistency of technical standards and requirements in terms of different technical regulations and the possibilities of using inputs at domestic and foreign enterprises. Based on the above conclusions, it can be concluded that there is a need for a time lag for reorientation from export to domestic trade operations, and it is advisable to take into account the role of state support in stimulating demand for such products.

Estimation of the Prevalence of Body Integrity Dysphoria (BID) in German-Speaking Countries Based on the Use of an Internet-Forum by Those Affected

Body Integrity Dysphoria (BID, BIID) is a disease of unknown cause, in which those affected have the intense feeling that a part of the body does not belong to them. BID-sufferers can feel and move the corresponding limb, but it is not part of their mental body image. Estimating the prevalence of BID is very difficult due to the fact that most sufferers do not confide their suffering to anyone. However, the situation has changed since the widespread use of various Internet platforms. The basis is that in the three German-speaking countries (Germany, Austria, Switzerland) most adults have access to the Internet and, sooner or later, are looking for information about the strange feeling that parts of the body don’t feel like they belong. It can therefore be assumed that many of those affected will at some point register in such a forum in order to exchange ideas with others. The quantities are estimates from: (a) Number of BID affected people in the German speaking BID-DACH forum, (b) Number of BID affected people registered in BID forums in the German speaking areas, (c) Number of those affected by BID who do not register but inform via social media, (d) Estimation of the total number of people affected by BID from (a), (b) and (c). According to this model, the prevalence is in the range of 1 in 5,500 (0.018%) to 1 in 22,000 (0.0045%), mean value is in the range of 1 in 11,000 (0.01%). According to the data from Fischer et al (2015) and Garbos et al (2022), the severity of BID follows a normal distribution. This means that 16% have a very mild form, they feel relatively little pressure and they are often probably not even aware that they are suffering from BID at all. The middle 68% from a statistical perspective have a moderate form of BID. Most achieve sufficient catharis with occasional pretending and often do not seriously pursue real disability. Serious candidates for an amputation or other forms of disability are those with an above-average level; they include the top 16% of the distribution. Of these 1,500, around half suffer from the need for amputation, the other half have a desire for paraplegia or other forms of disability. Here it is to be expected that they will want an operation in the long term. This value can be justified rationally, because every realization of the need for disabilities is associated with massive restrictions in everyday life. Those affected are well aware of these limitations and even in the group of severe cases, most people delay it for decades before giving in to the need and having an operation (or other options) carried out. If we assume that the 750 people ready for amputation are spread across the age group 20-70 years, after processing the backlog of old cases, then a maximum of 15 new candidates for amputation per year would be expected. This model refers to the German-speaking area because the forum is conducted in German. However, it seems entirely permissible that a similar prevalence value can also be assumed for several other countries.

OPERATING CONDITIONS AND STABILITY FIRE RESISTANT LINING SUBMERGED LANCE

To ensure the reliable and long—term operation of submersible lances used in the processes of bucket desulfurization of cast iron before converter processing, reliable means and appropriate conditions for supplying powdered desulfurizing reagents through nozzles of the lance tip, a rational scheme of refractory lining of the submersible lance and improvement of its operation modes are necessary. The purpose of the work is to study the characteristics of the destruction of the refractory lining of submersible lances, intended for desulfurization of iron—carbon melts by blowing powdery reagents deep into the ladle bath. To realize the goal, we used practical information on the researched question and the method of isothermal modeling of the hydrogas dynamics of a bucket bath using variable designs of the tips of stationary and rotating submersible lances. A comparative analysis and study of the features of the destruction of the lining of submerged stationary and rotating lances in the area of contact with the metal melt (below the "slag—metal" border) during gas injection into the bath was carried out using a 230—t pouring ladle model. During the experiments, T—shaped tips were used (for rotating and stationary lances) and tips with two spray pipe placed at an angle of 45 degrees to the axis of the lance (for stationary lances). Based on the results of data processing, mathematical models were obtained for each of the isolated zones on the lining surface of the submersible lance, and the statistical significance of the sample regression coefficients was checked. The nature and features of the destruction of the lining layer in each of the zones corresponding to the changes in the bath blowing conditions were established. New data were obtained regarding the intensity and depth of wear of the lining of the rotating submersible lance, depending on its speed of rotation and carrier gas consumption. It was established that under the investigated conditions of blowing the bath, the speed of rotation of the lance can be attributed to the factor most influencing the depth and intensity of wear of the lance lining.

Solid Oxide Electrochemical Cells for Nitrogen and Oxygen Production

Nitrogen and oxygen are both very important commodities with a wide variety of applications in industries, such as chemical, food and metallurgical plants as well as in the medical sector. Nowadays most of the nitrogen and oxygen are produced via air separation technologies such as cryogenic distillation (ASU) or pressure swing adsorption (PSA). Both ASU and PSA offer economical and mature ways for nitrogen and oxygen production at large (>100 ton/day) or medium scales (20-100 tons/day). If one can develop a technology for providing these gases in an energy efficient and cost effective way also at small scale, preferably driven by electricity only, this would enable new applications of the gases. Such a technology would match characteristics of the future green electricity system relying on small scale (few MWs) power generation and fluctuating production..In this work we present an efficient electrochemical process for N2 and O2 production based on a solid oxide electrochemical cell technology by oxygen extraction from air. Cells with a 53 × 53 mm2 size were produced by a conventional tape casting method. They consist of a ca.10 μm CGO (Ce0.9Gd0.1O2-δ) electrolyte sandwiched between composite electrodes made from either LSCF (La0.6Sr0.4Co0.2Fe0.8O3-δ) - CGO, or LSF (La0.6Sr0.4FeO3-δ) - CGO. To boost performance at low temperature, the electrodes were infiltrated with Pr-oxide. The electrochemical performance with the different supports were characterized by obtaining current-voltage (iV) characteristics at different temperatures as well as through electrochemical impedance spectroscopy(EIS) with or without infiltration. For characterization, air was used as feed stock to the cathode compartment and air, or oxygen was used as sweep gas to the anode compartment. A voltage below 200 mV is needed to drive a current of 1 A/cm2 through the cell, which can provide a purity of 90% of N2 out at an operation temperature of 650 °C (see Figure 1a). The cells were demonstrated to operate for producing a 98% pure N2 stream without degradation over a 1500 h period (see Figure 1b).Further analysis show that the specific power consumption calculated based on the power input and outlet gas flow rate for 90% N2 production is ca. 0.1 kWh/m3 and the specific power consumption for 96% and 98% N2 production is 0.21 and 0.31 kWh/m3, respectively. A 3-fold increase in required power is observed when going from a N2 purity from 90% to 98%.Detailed electrochemical analysis and the electrochemical performance comparison between LSCF and LSF based mixed ionic electronic conductor (MIEC) electrodes will be presented. Factors limiting cell performance will as well as analysis of optimal point of operation in terms of energy consumption and reliability will also be discussed. Acknowledgment This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 862482. Figure 1

Understanding Performance Fading during CO Electrolysis in Zero Gap Electrolyzers

Electrochemical CO reduction (ECOR) can act as a potential bridge between CO2-to-CO technologies and renewable production of C2+ chemicals. Copper has been the most widely studied cathode catalyst for ECOR because of its unique ability to produce multicarbon products. Iridium and nickel are the most-widely used anode materials for acidic and alkaline electrolysis, respectively. However, recent reports on the instability of Ir in alkaline conditions and Ni in near neutral conditions has made it imperative to understand the anodic processes for achieving stable long term operation at high current densities for CO2/CO electrolysers.In this work, our aim was to investigate anode catalysts for ECOR at high current densities in zero gap electrolyser. Commercial Cu nanoparticles (25 nm) was used as the cathode catalysts with Ir black anode in alkaline conditions. Initially, CORR was studied in a hybrid cell with a catalyst coated anion exchange membrane and recirculated catholyte and anolyte. In this cell configuration we observe stable production of ethylene, acetate and ethanol for a total current density of upto 500 mA cm-2. However, in the zero gap electrolyser the catalytic activity decays rapidly (2-3 minutes) and leads to predominance of hydrogen evolution reaction (HER).Analysis of the cathode and anolyte after electrolysis reveals the dissolution of Ir and subsequent deposition at the cathode. This rapid decay is counter intuitive since the dissolution of Ir in alkaline solutions is very slow and should take a few hours to affect the catalytic activity. More importantly this dissolution of Ir does not happen when Ar is circulated at the cathode instead of CO, which indicates that the Ir dissolution is not entirely due to the alkaline environment. NMR analysis of the anolyte shows the presence of CO reduction products acetate and ethanol. Therefore, it is possible that the presence of CO reduction products could aggravate the Ir dissolution. This study is currently underway to analyse the possible Ir dissolution mechanisms. This is an important observations since Ir is still the most widely used anode catalyst for CO electrolysis. This also stresses on the need to explore alternative anode catalysts and/or design strategies that can circumvent the migration of reduction products to the anode.

(Invited) Long Term Operation of Photoelectrochemical Devices: Experiments and Modeling

Achieving long term operation while maintaining a high energy conversion efficiency and large production rates is one of the main challenges for enhancing the economic competitiveness of solar fuel producing photoelectrochemical devices [1]. I will discuss computational and experimental methods to characterize the degradation of photoelectrochemical devices. The models consider multi-scale approaches and multi-physics phenomena [2]. This is required in order to properly account for all the competing and convoluting effects and to properly extract and quantify the degradation from experimental data. I will present our experimental setup that consists of a multi-PEC cell array in order to obtain sufficient and statistically representative data. Additional experiments under high-flux solar irradiation conditions are presented that allow – in conjunction with the model – for the extraction of degradation characteristics and the development of accelerated age testing procedures. I will also report on the long term operation of our outdoor photo-electrochemical system demonstration operating under concentrated light [3].[1] M. Dumortier, S. Tembhurne, S. Haussener, Energy Environmental Science, 8: 3614-3628, 2015.[2] F. Nandjou, S. Haussener, ACS Applied Materials & Interfaces. 10.1021/acsami.2c08204, 2022.[3] I. Holmes-Gentle, S. Tembhurne, C. Suter, S. Haussener, Nature Energy, 10.1038/s41560-023-01247-2, 2023.

Ti-Al-C Based MAX Phase Coating As Corrosion Protection for Ferritic Bipolar Plates

Metallic bipolar plates in fuel cells have the advantages of high electrical conductivity, low permeability to the reactants and gases, and easy manufacturability. However, resistance to corrosion under long term operation conditions limits their practical use in the fuel cell. Owing to the importance of corrosion stability, materials such as austenitic stainless steels, Ni-based alloys and coated titanium or stainless steel plates are currently being used in bipolar plates, although ferritic steels would be cost effective. A pinhole-free anticorrosion coating can help in application of the ferritic steels in fuel cells. MAX phase materials offer excellent corrosion stability and high electronic conductivity and have been successfully tested for corrosion protection of metallic bipolar plates. In the current work, Ti-Al-C-based MAX phase coatings were prepared using high power impulse magnetron sputtering (HiPIMS). The HiPIMS process was in some cases also combined with plasma immersion ion implantation (PIII) to study the influence of the high energetic ion implantation process on the structure and performance of the resulting MAX phase layer. The deposited samples were annealed at 800 °C for 2 h in Ar atmosphere. The structure and composition of the coatings produced were studied with X-ray photoelectron spectroscopy, atom probe tomography and transmission electron microscopy. The corrosion performance of the layers was studied using a scanning flow cell coupled with inductively coupled plasma mass spectroscopy.

Human-influenced changes in pollution status and potential risk of sediment heavy metals in Xincun Bay, a typical lagoon of Hainan, China

Pollution status and ecological risks associated with sediment heavy metals (Cu, Pb, Zn, Cd, and Cr) were investigated around Xincun Bay, assessing their spatial variations and relationship with sediment physiochemical factors. Higher concentrations and associated risks were observed in the central region, where mariculture activities were concentrated, compared to non-maricultured areas. Despite with overall low concentrations, Cd had a higher ecological risk. Correlation and principal component analyses revealed similar sources for all metals in Xincun Bay. Heavy metal concentrations varied with expansion of mariculture operations in terms of quantity and scale, confirming the influence of mariculture activities. Sediments around mariculture had higher contents of clay, silt, and total organic carbon (TOC), and finer particle sizes. Quantitative analyses through correlation and linear regression indicated that TOC significantly regulated heavy metal concentration and distribution (p < 0.05). Considering its significant association with TOC, the influence of mean grain size should not be overlooked.

Trace formulas for time periodic complex Hamiltonians on lattice

We consider time periodic Hamiltonians with complex potentials on the lattice and determine trace formulas. As a corollary we estimate imaginary parts of eigenvalues of the quasienergy operator in terms of the norm of potentials.

Modeling of thermal processes in vertical heat exchangers of ground-source heat pump

The basic directions for perfection heat supply systems are the tendency of transition to the low-temperature heating systems based at application heat pump installations. We consider heat supply systems with ground-source heat pump. The paper considers modeling the efficiency of ground-source heat pumps with the account of Ukrainian climate conditions. The paper presents the energy performance criteria which show the way to rational implementation of ground-source heat pumps for heating. A computational model based at non-stationary heat exchange processes in elements of ground-source heat pumps is developed. Generalization and analysis of theoretical and experimental dates allow establishing nature of dependence thermophysical properties on temperature insoil around ground heat exchangers during long term operation of the system. Numerical simulation of thermal processes in vertical ground pipes for ground-source heat pump working with low-temperature heating systems has been worked out. The results of numerical modeling demonstrated perfection and technical adaption of ground-source heat pump for low-temperature heating systems with rational using ground energy potential. The novelty of our method is complex usage theoretical and experimental results which enable to prevent freezing in the ground during long term exploitation This provides insights at effects of different resource mixes and may serve as a new approach to analysis of future heat pump systems using ground source energy development.The proposed method contributes to the field of creation and implementation the sustainable heating technologies using renewable energy sources. The ground heat exchange pipes quantities that are necessary for effective operation heat pump installation, capacity and coefficient of performance with the account of climate conditions are calculated.

METHODOLOGY OF THE RATIONALE OF AN AMOUNT OF UNMANNED CARGO DELIVERY SYSTEMS

It is possible to reduce human losses during the cargo delivery to units on the battlefield with the use of unmanned systems (UMSs), including logistical unmanned ground vehicles (UGV) of various groups carrying capacity and unmanned aircraft systems (UAS). The urgent task is to determine the required number of unmanned cargo delivery systems in the interests of the mechanized infantry battalion. The method of determining the number of unmanned cargo delivery systems for the logistical means (LM) transportation to the units of the mechanized infantry battalion is described. The optimality criterion of the selected composition of the system is the maximum efficiency-cost ratio (ECR) under the condition of transporting the maximum weight of LM required for the battle day from the combat supply point to the units of the mechanized infantry battalion. In this case, the efficiency indicator is the share of the total weight of LM that must be delivered to the units. In order to calculate this indicator, it is necessary to estimate the probability of successful delivery of LM to different battalion units for each UMSs. The cost indicator is the product of the masses of the cargo and energy costs on the delivery route, purchase costs and total costs for operating the UMSs during the forecasted average life of operation in terms of 1 kg of cargo. Two transport tables are built based on the results of the calculations. The first table includes probability weighting factors, and the second includes weighting factors of the cost of delivering LM from a combat supply point to units by various UMSs. For each of these transport problems, the optimal solution is obtained by linear programming methods, and for the ECR, by methods of optimization of problems with a nonlinear objective function, which is illustrated by an example using the "Solver" add-on in the Excel spreadsheet processor. Keywords: logistic support, unmanned systems, logistical unmanned ground vehicles, unmanned aircraft systems, load capacity, cargo delivery, efficiency-cost, optimization of an amount.

Determination of the optimal cargo operations strategy of a bulk carrier vessel, with continuous ensuring its seaworthiness

The correct loading of bulk carriers is essential for their maritime safety. Inadequate loading can lead to various risks, including compromised hull strength, reduced stability and violation of the vessel's seaworthiness. Existing shipboard instruments do not allow for timely planning and real-time control of loading operations, which can lead to potential risks. The high intensity of loading operations at dry bulk terminals exacerbates the problem, as there is often insufficient time to adequately prepare and verify loading plans, increasing the risk of overloading cargo holds. To address this problem, the article proposes the development of new methods for bulk carriers cargo operations planning. These methods would optimise the distribution of bulk cargo, taking into account factors such as port facilities, ship design and nautical restrictions of the planned voyage. The aim is to formalise cargo operations in terms of a mathematical model of the vessel and to establish functional relationships between parameters that affect the seaworthiness of the vessel. By analysing the relationships between different parameters, the researchers aim to determine the best strategy for cargo operations that will ensure the continuous seaworthiness of the bulk carriers. This approach would help to improve bulk carrier’s safety and reduce the risks associated with incorrect loading. The development of such methods is seen as a promising area of scientific research that can enhance the safety of those vessels. By determining the best strategy for cargo operations based on the criterion of continuous seaworthiness, it aims to prevent the deterioration of the vessel's structural integrity and ensure that the vessel remains in a seaworthy condition throughout the loading process. The article emphasizes the need for scientific research in this area to enhance the safety of bulk carriers and proposes the development of new methods based on mathematical modeling to optimize cargo operations and maintain the vessel's seaworthiness throughout the process.

Some density results by deep Kantorovich type neural network operators

In this paper, we prove density results by using deep Kantorovich type neural network operators. Firstly, we define a two layer neural network operator and prove the density results in the spaces C(I) and Lp(I) for p≥1, where I:=[−1,1]. Then we extend it to a multi-layer neural network operator and prove the corresponding density results. Our study provides a generalizations of the well known single layer Kantorovich type neural network operator in terms of its deeper version.

Factors Influencing the Airline Decision-Making Process in Planning Pricing Mechanisms in the Nigerian Aviation Industry

The airline industry is faced with a lot of challenges based on their various operations in terms of the carriage of goods and passengers. Part of this challenge is the issue of the best pricing strategies to be adopted. Prior to setting fare, the airline industry considered a number factors before the decision is implemented looking at customer satisfaction and profit making. Therefore, based on that, this study set out to assess the factors that influence airline pricing decisions in the Nigerian airline industry. The scope of the study covers all the domestic airlines operating in Nigeria. A questionnaire was administered to three hundred forty-nine staff consist of three categories of staffers (directorate, managerial, and supervisory) of all the domestic airlines in Nigeria. The collected data were analyzed using multiple regression analysis. Eleven variables (factors) were selected as attributes and tested. These include: demand, cost of inputs and supply, prevailing market airfare price, prices (fares) of alternative modes, route status, period (time) of supply and demand, distance between origin and destination, landing fees, availability of slots in peak periods, security on the origin-destination (O-D) market, and availability of aircraft maintenance. The results revealed that distance between the origin and destination, time of supply, and demand are the most significant factors influencing airline pricing decisions in the Nigerian airline industry. Therefore, based on the findings of the study, the study recommends that the airline industry must ensure that passengers are fully informed if prices are changed and also ensure the security of passengers from origin to destination.

A Bimodal Hydrostatic Actuator for Robotic Legs with Compliant Fast Motion and High Lifting Force

Robotic legs, such as for lower-limb exoskeletons and prostheses, have bimodal operation: (1) within a task, like for walking (high speed and low force for the swing phase and low speed and higher force when the leg bears the weight of the system); (2) between tasks, like between walking and sit–stand motions. Sizing a traditional single-ratio actuation system for such extremum operations leads to oversized heavy electric motor and poor energy efficiency at low speeds. This paper explores a bimodal actuation concept where a hydrostatic transmission is dynamically reconfigured using custom motorized ball valves to suit the requirements of a robotic leg with a smaller and more efficient actuation system. First, this paper presents an analysis of the mass and efficiency advantages of the bimodal solution over a baseline solution, for three operating points: high-speed, high-force, and braking modes. Second, an experimental demonstration with a custom-built actuation system and a robotic leg test bench is presented. Control challenges regarding dynamic transition between modes are discussed and a control scheme solution is proposed and tested. The results show the following findings: (1) The actuator prototype can meet the requirements of a leg bimodal operation in terms of force, speed, and compliance while using smaller motors than a baseline solution. (2) The proposed operating principle and control schemes allow for smooth and fast mode transitions. (3) Motorized ball valves exhibit a good trade-off between size, speed, and flow restriction. (4) Motorized ball valves are a promising way to dynamically reconfigure a hydrostatic transmission while allowing energy to be dissipated.

Bosonic Representation of Matrices and Angular Momentum Probabilistic Representation of Cyclic States.

The Jordan-Schwinger map allows us to go from a matrix representation of any arbitrary Lie algebra to an oscillator (bosonic) representation. We show that any Lie algebra can be considered for this map by expressing the algebra generators in terms of the oscillator creation and annihilation operators acting in the Hilbert space of quantum oscillator states. Then, to describe quantum states in the probability representation of quantum oscillator states, we express their density operators in terms of conditional probability distributions (symplectic tomograms) or Husimi-like probability distributions. We illustrate this general scheme by examples of qubit states (spin-1/2 su(2)-group states) and even and odd Schrödinger cat states related to the other representation of su(2)-algebra (spin-j representation). The two-mode coherent-state superpositions associated with cyclic groups are studied, using the Jordan-Schwinger map. This map allows us to visualize and compare different properties of the mentioned states. For this, the su(2) coherent states for different angular momenta j are used to define a Husimi-like Q representation. Some properties of these states are explicitly presented for the cyclic groups C2 and C3. Also, their use in quantum information and computing is mentioned.

Experimental Investigation on the Effects of Direct Injection Timing on the Combustion, Performance and Emission Characteristics of Methanol/Gasoline Dual-Fuel Spark Turbocharged Ignition (DFSI) Engine with Different Injection Pressures under High Load

The exceptional properties of methanol, such as its high octane number and latent heat of evaporation, make it an advantageous fuel for efficient utilization in dual-fuel combustion techniques. The aim of this study is to investigate the effect of direct methanol injection timing on the combustion, performance and emission characteristics of a dual-fuel spark ignition engine at different injection pressures. We conducted four different direct injection pressure tests ranging from 360° ahead to 30° CA ahead at 30° CA intervals. The experimental results indicate that regardless of the injection pressure, altering the methanol injection timing from −360° to −30° CA ATDC leads to distinct combustion behavior and changes in the combustion phase. Initially, as the injection timing is delayed, the combustion process accelerates, which is followed by a slower combustion phase. Additionally, the combustion phase itself experiences a delay and then advances. Regarding performance characteristics, both the brake thermal efficiency (BTE) and exhaust gas temperature (EGT) exhibit a consistent pattern of first increasing and then decreasing as the injection timing is delayed. This suggests that there is an optimal injection timing window that can enhance both the engine’s efficiency and its ability to manage exhaust temperature. In terms of emissions, there are different trends in this process due to the different conditions under which the individual emissions are produced, with CO and HC showing a decreasing and then increasing trend, and NOx showing the opposite trend. In conclusion, regardless of the injection pressure employed, adopting a thoughtful and well-designed injection strategy can significantly improve the combustion performance and emission characteristics of the engine. The findings of this study shed light on the potential of methanol dual-fuel combustion and provide valuable insights for optimizing engine operation in terms of efficiency and emissions control.

MAIN COMPONENTS OF FOSSIL COALS, THEIR CONSUMER QUALITIES AND HAZARDOUS PROPERTIES OF COAL SEAMS

Purpose: the goal is to more fully disclose the essence of the geological processes of coal formation and improve the regulatory framework for the safe conduct of mining operations to establish correlations or trends in changes in the elemental content of the main components of organic mass and mineral impurities for different states of coal during metamorphic transformations of coal seams. Methodology: the technique involves using carbon content as a criterion for assessing the degree of metamorphism of the transformation of coal seams, since it practically functionally controls the sum of the remaining main components of the organic mass throughout the entire range of coalification. This made it possible to use reliable experimental data from technical and elemental analysis of reference and regulatory documents on the consumer qualities of coal in scientific research, established by standard methods over several decades, to predict the hazardous properties of coal seams. Results: The patterns of changes in the elemental content of the main components of organic mass and mineral impurities for different states of coal samples (analytical, organic, working) during metamorphic transformations of coals have been established. Scientific novelty: Based on the change in the elemental content of the relative organic mass of carbon and hydrogen, as well as the moisture of analytical samples, three characteristic stages of metamorphic transformations of coal seams were established, which determine their dangerous properties. With a carbon content of 79÷89%, the hydrogen content per conventional organic mass remains unchanged, and the transformations at this stage are almost completely associated with the reduction of oxygen in other components of mineral impurities. Individual differences between mine layers at this stage of transformation are associated with the moisture content in analytical samples and the amount of external moisture removed during sample preparation. With a further increase in the influence of metamorphic processes (increase in carbon content to 89÷93%), a decrease in hydrogen content occurs, which indicates the removal of a certain proportion of moisture from the analytical samples together with external moisture from the system. At the third stage of metamorphic transformations of coal seams (carbon content more than 93%), together with external moisture, based on the minimum values of hydrogen and moisture in analytical samples, there was a further reduction in the moisture of analytical samples to their minimum values. Practical value: the research results make it possible to develop proposals for improving the regulatory framework for safe mining operations in terms of predicting the manifestation of hazardous properties of coal seams. Keywords: coal seams, hazardous properties, mining operations, coal, samples, condition, analysis, components, organic mass, mineral impurities, metamorphism, forecast, regulatory framework, safety, improvement.