Aerodynamic Characteristics of the Combustion Process of Sawdust in a Vortex Furnace with Counter-Swirling Flows

The aim of this work is to study the working processes of burning the low-quality fuels, namely, the saw dust in the swirling-type furnaces with an opposite twisted motion of the air. The goal was achieved using the physical and mathematical modeling of the flows interaction. The article presented the results of numerical study of aerodynamic characteristics of burning the saw dust in the swirling-type furnace with the opposite twisted air flows. For the research, the facility was used for the saw dust burning with the air supply into the lower and upper zones of burning. The most essential result of the work was modeling of the working process at the ratio of the flows of the primary air and secondary air without the fuel admixture, equal to 0.2. The tangential rate of the flow changed according to the horizontal sections from 3-5 m/s to 40-42 m/s and with respect to the furnace height from 51 m/s to 30 m/s. The average angular rate of the mixture changed relatively the furnace height in the ranges of 171-500 l/s to 100—300 l/s. The significance of the results obtained consists in determination of the possibility of increasing the efficiency of the work of the furnace facilities at the expense of the introduction of the primary and secondary air flows. In this situation, the optimal ratio of consumptions of primary and secondary air was 0.2. Thus, in this work the consumption of primary air was 1.285 kg/s, the consumption of the secondary air was 0.255 kg/s.

Fill dynamics and sample mixing in the AirCore

The AirCore is a long coiled tube that acts as a “tape recorder” of the composition of air as it is slowly filled or flushed. When launched by balloon with one end of the tube open and the other closed, the initial fill air flows out during ascent as the outside air pressure drops. During descent atmospheric air flows back in. We describe how we can associate the position of an air parcel in the tube with the altitude it came from by modeling the dynamics of the fill process. The conditions that need to be satisfied for the model to be accurate are derived. The extent of mixing of air parcels that enter at different times is calculated, so that we know how many independent samples are in the tube upon landing, and later when the AirCore is analyzed.

ASSESSMENT AND ANALYSIS OF AERODYNAMIC PARAMETERS OF AIR FLOWS FOR EFFECTIVE SELECTION OF AIR SUPPLY SCHEMES IN COAL MINES

The article examines a complex technical system on the example of air supply of coal mines, characterized by: multicomponent, a large number of quantitative and qualitative parameters, nonlinearity of interdependencies between them; incompleteness of information, the complexity of experimental research, the risks of dangerous situations and the catastrophic nature of their consequences; the uniqueness of the modes and conditions of the systems functioning. The aim of the work is to develop a methodology for assessing and analyzing the aerodynamic parameters of air flows for the effective selection of air supply schemes in coal mines using the decomposition method. Research methodology: the solution of the set tasks is based on modern methods of mathematical statistics; graph theory; decision theory; apparatus of mathematical logic; factor analysis; mathematical modeling; set theory; reliability theory and systems analysis. Research results. A method for the analysis and analytical modeling of complex technical systems of variable structure (CTS VS) is developed, focused on the features of these systems and their processes in conditions of incomplete information, different quality data on their state and functioning, which differs from the known ones by a combination of the capabilities of analytical and statistical approaches to the construction of CTS VS models, which allows to adapt to changes in systemic and external factors, improve the accuracy of modeling, and also typify the presentation of fuzzy situational features for effective management of the CTS VS. Conclusion. A method has been developed for assessing the reliability of the parameters of the CTS VS based on the algorithms for analyzing and assessing the reliability of the CTS VS, the algorithm for the formation of the most complete subsets listing in the graph all possible compatible subsets of a given set of vertices differing in that they are based on the analysis of enlarged states and decomposition of the structural diagram, which allows analytical and statistical studies to significantly increase the accuracy of assessing the reliability of CTS VS and reduce the amount of calculations. Result: the proposed methods were used to solve the problems of air distribution control in coal mines.

Thermal and mechanical improvement of the air supply system of a turbocharged piston engine

A method of thermomechanical improvement of pulsating air flows in the intake system of a turbocharged piston engine is described. The main objective of this study is to develop a method for suppressing the rate of heat transfer to improve the reliability of a piston turbocharged engine. A brief review of the literature on improving the reliability of piston engines is given. Scientific and technical results were obtained on the basis of experimental studies on a full-scale model of a piston engine. The hot-wire anemometer method was used to obtain gas-dynamic and heatexchange characteristics of gas flows. Laboratory stands and instrumentation facilities are described in the article. The data on gas dynamics and heat exchange of stationary and pulsating air flows in gas-dynamic systems of various configurations as applied to the air supply system of a turbocharged piston engine are presented. A method of thermomechanical improvement of flows in the intake system of an engine based on a honeycomb is proposed in order to stabilize the pulsating flow and suppress the intensity of heat transfer. Data were obtained on the air flow rate and the local heat transfer coefficient both in the exhaust duct of the turbocharger compressor (i.e., without a piston engine) and in the intake system of a supercharged engine. A comparative analysis of the data has been carried out. It was found that the installation of a leveling grid in the exhaust channel of a turbocharger leads to an intensification of heat transfer by an average of 9%. It was found that the presence of a leveling grid in the intake system of a piston engine causes the suppression of heat transfer within 15% in comparison with the baseline values. It is shown that the use of a modernized intake system in a diesel engine increases its probability of failure-free operation by 0.8%. The data obtained can be extended to other types and designs of air supply systems for heat engines.

Convective instability of air flows in the exhaust shaft above a four-row finned beam

Herein, multidirectional quasiperiodic air flows in an exhaust shaft above a four-order horizontal bundle consisting of bimetallic finned tubes used to remove heat in heat exchangers are considered. Modeling of the air movement is carried out on the basis of equations for thermogravitational convection in the Boussinesq approximation. It takes into account the viscosity of the air and the dependence of the air density on the temperature. An interpretation of quasiperiodic airstreams is proposed on the basis of Rayleigh – Bénard convection, as a result of which regular structures, called Rayleigh – Bénard cells, are formed in a liquid or gas. Rayleigh – Bénard cells are an analytical solution to the problem of the stability of hydrodynamics flows in the linear approximation. The appearance of two-dimensional (convective rolls) and threedimensional (rectangular cells) is possible. To estimate the number of emerging structures, the critical Rayleigh numbers were calculated, which characterizes the transition from an unstable mode of the convective fluid flow to a stable mode. For two experiments, the experimental Rayleigh numbers are compared with their critical values. The differences between the experimental conditions and the ideal boundary conditions used in the calculations and the partial destruction of quasiperiodic structures as a result of this are also discussed.

Mary Wollstonecraft and the Right to Air

Air flows through all Mary Wollstonecraft's writings, from her first novel Mary, through her treatises and letters, and to her last novel Maria. She was attuned to the medical importance of a change of air, but also developed a more philosophical notion of a right to air. Her attention to everyday air and smell unavoidably reaffirmed her key intellectual questions of commonality, individuality, equality and freedom. For Wollstonecraft, air was both a metaphor for freedom and also a literal condition for its development. This article situates her numerous remarks on air alongside medical sources, racialized climatological theory, slavery cases, and the pneumatic chemistry of the 1790s. Such a reading of Wollstonecraft's aerial philosophy, and comparisons with Burke, Rousseau, Godwin and Kant, contributes to an ecological reading of her work and to a forgotten history of air rights, with relevance to current debates on air quality and inequality.