Aerodynamic Processes Research Articles

Aerodynamics and Heat Transfer of Swirling Natural Gas Flow in a Vortex Heat Exchanger of the Heating System of a Gas Control Point

Purpose of research. To obtain a two-parameter model characterizing the aerodynamic and heat exchange processes occurring in a vortex heat exchanger, giving a better agreement between the calculated and experimental values of the heat transfer coefficient taking into account the curvature of the swirling gas flow in a vortex heat exchanger, in which a controlled gas pressure drop is used as a source of thermal energy. This technical solution will make it possible to abandon the installation of autonomous sources of thermal energy, which will reduce the cost of gas as a fuel in the heating system of the industrial premises of the gas distribution point (GDP), as well as provide more comfortable working conditions for the hydraulic fracturing pressure regulator. Methods. Comprehensive analysis of thermal and hydraulic characteristics in a vortex heat exchanger is based on well-known theoretical positions and equations of motion of a swirling gas flow and heat exchange laws. Results. It is obtained a dependence that characterizes the intensification of heat transfer based on the influence of the axial and rotational speed, as well as the path of motion of the swirling gas flow. This dependence is obtained on the basis of a comprehensive analysis of the aerodynamic and heat exchange characteristics of a vortex heat exchanger, in which a controlled gas pressure drop is used as a source of thermal energy. Conclusion. The obtained two-parameter model gives the best agreement of the calculated values of the heat transfer coefficient with the values obtained experimentally, which were used in the thermal engineering calculation of the design parameters of the vortex heat exchanger.

Features of thermomechanics of pulsating gas flows in intake systems with grooves in relation to turbocharged engines

Reciprocating engines (RICE) are widely used as heat engines to convert the chemical energy of fuel into mechanical work on the crankshaft. Aerodynamic and thermophysical processes in gas exchange systems significantly affect the efficiency of internal combustion RICEs. This article explores the possibility of influencing the gas dynamics and heat transfer of pulsating gas flows in the intake system by placing a channel with grooves. It is known that the presence of grooves in the channel leads to the formation of significant secondary vortices, which radically change the physical picture of the gas flow. The studies are carried out on a laboratory bench, which was a single-cylinder model of a turbocharged RICE. The system of measurements of basic physical quantities is described, taking into account their high dynamics in gas exchange systems. The experimental data processing techniques are presented. Primary data on the instantaneous values of the gas-dynamic and heat-exchange characteristics of pulsating flows are reported. It is established that the presence of a channel with grooves in the intake system leads to a decrease in the turbulence number by 40% and the intensification of heat transfer in the range of 5-50% compared with the basic intake system. A positive effect is shown in the form of an increase in engine power by 3% when using an upgraded system.

Urban and ecological prerequisites for the development of the Black Sea cities in the Krasnodar region with consideration of thermal and wind processes

Introduction. Ecology of the atmospheric environment of coastal cities directly depends on the thermal and wind processes, which are formed by irradiation of the active city surface and slope mountain areas adjacent to the city, as well as the sea area. Materials and methods. The study is based on a comprehensive methodology for studying urban and ecological processes of the atmospheric environment at the macro- and mesoecological level of urban planning. Modern computer models ICON, GFS and GEM utilized in applied meteorology were used, as well as the semi-graphical method of modeling daily pollution dome transformation based on thermophysical and aerodynamic laws of atmospheric environment and irradiation of the building’s active surface and of the surrounding landscape. Results. The transformation and movement chart of the air pollution dome formed over the city during the day in the “mountains – city – sea” system is presented. It is proved that in the warm season in the first half of the day, the maximum accumulation zone of negative atmospheric pollutants is located in the mountain foothills facing east, by mid-day it will be shifted to the center of the city, and in the evening the maximum pollution will be observed in the coastal zone. The presented ecological efficiency in urban planning on the example of the Black Sea cities of Novorossiysk and Tuapse allows for the assessment of the thermal and wind process impact on the transformation and movement of atmospheric pollution dome in complex terrain and sea area conditions using the assessment classification of “satisfactory” in the first half of the day, “good” in the day and evening. Conclusions. The research is particularly relevant in southern cities located on the coast and bordering the mountainous territory. The main urban and ecological principle of planning organization in the reconstruction, planning and development of coastal cities and towns is the mechanism of thermodynamic and aerodynamic processes of the atmospheric environment, expressed in the form of sea breeze and mountain-valley circulation, as well as convective flows, the study of which allowed to formulate practical recommendations.

Numerical study of the parameters of a gas turbine combustion chamber with steam injection operating on distillate fuel

Abstract Investigations of the working process in a gas turbine combustion chamber with ecological and energy steam injection operating on liquid fuel are conducted. The mathematical model of the aerodynamic processes and liquid fuel combustion in similar burning devices based on the numerical solution of the system of conservation and transport equations for a multi-component chemically reactive turbulent system is developed. The influence of the relative steam mass flow rate (the ratio of the sum of the mass flow rates of ecological and energy steam to the fuel consumption) on the combustion chamber’s emission characteristics is determined. The obtained results can be used for parameter selection and optimization of promising high-temperature gas turbine combustion chambers with steam injection operating on liquid fuels.

Numerical study of the parameters of a gas turbine combustion chamber with steam injection operating on distillate fuel

Abstract Investigations of the working process in a gas turbine combustion chamber with ecological and energy steam injection operating on liquid fuel are conducted. The mathematical model of the aerodynamic processes and liquid fuel combustion in similar burning devices based on the numerical solution of the system of conservation and transport equations for a multi-component chemically reactive turbulent system is developed. The influence of the relative steam mass flow rate (the ratio of the sum of the mass flow rates of ecological and energy steam to the fuel consumption) on the combustion chamber’s emission characteristics is determined. The obtained results can be used for parameter selection and optimization of promising high-temperature gas turbine combustion chambers with steam injection operating on liquid fuels.

OPTICAL 3D MEASUREMENTS IN HYDRODYNAMIC TUNNEL FOR AIRCRAFT ICING STUDY

Abstract. The study of how aircraft icing influences on aircraft aerodynamic performance is very important for developing measures and recommendation to improve aircraft flight safety. The effective method of aerodynamic processes modeling is experiment in wind (aerodynamic) tunnel or water (hydrodynamic) tunnel. They allow to perform experiments with a scaled model of an aircraft affected by icing and to visualize the wing flow process and changes caused by icing. While visualization of the wing flow yields useful qualitative information about flow, it is more important to retrieve quantitative 3D data of flow, which allows to forecast icing process and to develop anti-icing techniques and recommendations.The presented study addresses to creating an photogrammetric system and 3D measurement techniques for quantitate evaluation of 3D flow parameters in a hydrodynamic tunnel for aircraft icing influence exploration. Being an initial part of a long-term research project, this study is aimed at developing of an accurate calibration technique of the photogrammetric system for 3D measurement in condition of two optical media interfaces. The developed algorithms for imaging process through two optical media interfaces are used in calibration procedure and object 3D coordinates measuring. The results of the photogrammetric system calibration are given in comparison with standard (single media) case. Experimental 3D reconstruction of a typical object demonstrated high accuracy of the developed algorithms.

Evidence that the Dorsal Velvet of Barn Owl Wing Feathers Decreases Rubbing Sounds during Flapping Flight.

Owls have specialized feather features hypothesized to reduce sound produced during flight. One of these features is the velvet, a structure composed of elongated filaments termed pennulae that project dorsally from the upper surface of wing and tail feathers. There are two hypotheses of how the velvet functions to reduce sound. According to the aerodynamic noise hypothesis, the velvet reduces sound produced by aerodynamic processes, such as turbulence development on the surface of the wing. Alternatively, under the structural noise hypothesis, the velvet reduces frictional noise produced when two feathers rub together. The aerodynamic noise hypothesis predicts impairing the velvet will increase aerodynamic flight sounds predominantly at low frequency, since turbulence formation predominantly generates low frequency sound; and that changes in sound levels will occur predominantly during the downstroke, when aerodynamic forces are greatest. Conversely, the frictional noise hypothesis predicts impairing the velvet will cause a broadband (i.e., across all frequencies) increase in flight sounds, since frictional sounds are broadband; and that changes in sound levels will occur during the upstroke, when the wing feathers rub against each other the most. Here, we tested these hypotheses by impairing with hairspray the velvet on inner wing feathers (P1-S4) of 13 live barn owls (Tyto alba) and measuring the sound produced between 0.1 and 16 kHz during flapping flight. Relative to control flights, impairing the velvet increased sound produced across the entire frequency range (i.e., the effect was broadband) and the upstroke increased more than the downstroke, such that the upstroke of manipulated birds was louder than the downstroke, supporting the frictional noise hypothesis. Our results suggest that a substantial amount of bird flight sound is produced by feathers rubbing against feathers during flapping flight.

Enhancing Energy Saving in Air Cooling Devices by Intensifying External Heat Transfer

The aerodynamic processes of heated air in the ventilation shaft installed above the heat transferring bundle of bimetallic finned tubes are studied. The regions of suppressed natural, steady, and unsteady mixed air convection in the bundle depending on the degree of narrowing of the outlet section of the ventilation shaft are determined. The maximum Nusselt numbers for multi-row bundles and their corresponding optimum parameters of the degree of narrowing of the outlet section of the ventilation shaft are determined. A method is proposed for determining the Reynolds numbers and the average air velocity during free convection for contracted smooth and finned tube bundles, which will allow optimization of heat transfer processes. The practical effectiveness of single- and two-row bimetallic finned tube bundles with a finning factor φ = 21 and an intertube spacing of 58 mm in air cooling and similar aircooled heat exchangers having a ventilation shaft is scientifically proved.

VORTEX DEVICES OF THE DIESEL AIR SUPPLY SYSTEM: MATHEMATICAL MODEL OF AERODYNAMIC PROCESSES

Introduction. The calculation of effective indicators of the vortex ejector used in the diesel air supply system is a pressing task as it allows significantly reducing time for determination of rational design parameters at the design stage. One of the modifications of the particle dynamics method is a promising direction, allowing with high physical adequacy, “from the first principles,” to model aerodynamic processes in vortex devices. Therefore, the purpose of the paper is to develop a mathematical model of a vortex ejector.Materials and methods. The paper discussed a method of the mathematical simulation of ejection and ejection flows in a vortex ejector. The proposed modification of the particle dynamics method allowed describing aerodynamic processes with the help of simple laws of classical dynamics, and modeling them with the help of software of the Delphi 7 System. The author presented differential equations, which were solved by the Runge-Kutt method of the second order. As a result of the solution, the authors determined paths of air elements movement in the vortex ejector, which allowed estimating effective parameters of vortex devices.Results. To study the model, the author developed a program with the possibility to set geometric parameters of the vortex ejector in the interface window and to display the current values of the process parameters.Discussion and conclusions. Proposed mathematical model and computer program make it possible to quantify efficiency of vortex devices at their design stage. The advantage of the proposed mathematical model lies in more accurate calculation of vortex flow parameters from the vortex ejector design and physical properties of ejecting and ejecting flows.Financial transparency: the author has no financial interest in the presented materials or methods. There is no conflict of interest.

Mathematical modeling of aerodynamic processes in railway tunnels on high-speed railways

The study of aerodynamic processes in railway tunnels on highspeed railways in the absence of practical experience in operation should be carried out with a sufficient degree of accuracy only by mathematical modeling. A multi-factor experiment was performed, which resulted in solving the optimization task of determining the tunnel cross-sectional area, taking into account aerodynamic processes. Based on the analysis of the results, the conclusion is made about the applicability of the method to the prognosis of aerodynamic effects on prospective tunnel structures of high-speed railways and optimization of geometric parameters of the tunnels.

Numerical Studies of the Aerodynamic Features of Dead-end Entries with Side Junction

Investigations of aerodynamic processes occurring in dead-end short entriesaired by turbulent diffusion have been performed. The numerical simulation of the processes of air movement through the entry, flow stalling at the junction with the dead-end entry (for side junction), and the formation of vortices at the dead end have been carried out. The study has been done for a wide range of air flows submitted for computation of air consumption and for various geometric parameters of the dead-end entry. The sizes of the vortex structures and the flow rates in the dead endshave been determined. Based on the results of processing the simulation data, we obtained graphs of the dependences between the length of the ventilated zone of the dead end and its height and width.

КОНТРОЛЬ СОСТОЯНИЯ АТМОСФЕРНОГО ВОЗДУХА И ВОЗДУХА РАБОЧЕЙ ЗОНЫ КАМЕРЫ ГАШЕНИЯ НАПОРА

Introduction. When sewage is transported along sewer pipes, sewer gases are actively formed and released. Special attention (in terms of desorption capacity) should be paid to surge chambers characterized by changes in the flow and flow arrival conditions, as well as by drop flow. The release of sewage gases has an adverse effect on sanitary and environmental safety. Therefore, it is required to control sewage gases’ release and assess the condition of the ambient air and the air in the surge chamber space. Methods. We selected a surge chamber in Cherepovets for monitoring. The experiment included: 1) measurements of sewer gases’ concentrations in the surge chamber and in the ambient air near the hatch; 2) analysis of dissolved hydrogen sulfide concentration in sewage; 3) recording of climate characteristics. Results. Based on the monitoring results, we determined the concentrations of sewer gases in the surge chamber. It has been found that gases leave the chamber in portions, which is due to aerodynamic processes and airing owing to incomplete air tightness. The relationship between the gas concentrations recorded at the same time in the surge chamber and the ambient air is reversed. The analysis of wastewater samples showed that most part of hydrogen sulfide leaves the water medium before wastewater enters the air space of the surge chamber. This is due to the absence of overpressure in the last headrace section. Besides, the maximum allowable concentrations were exceeded manifold both in the chamber and in the ambient air near it. Conclusion. The monitoring results confirm that it is required to develop: methods for assessing the environmental impact of surge chambers; methods for predicting total and one-time maximum emissions in the facilities; recommendations for setting the boundaries of sanitary protection zones around such facilities.

Теорія і практика використання циклонів на деревообробних підприємствах

Теоретично обґрунтовано доцільність зміни геометричних розмірів циклона та на цій основі розроблено нову конструкцію пиловловлювача. Наведено характеристику основним типам циклонів, що використовуються у деревообробній галузі. Проаналізовано наявні підходи до математичного моделювання аеродинамічних процесів у циклонах. Наведено нову математичну модель руху запиленого повітря всередині сепаратора, яка ґрунтується на сумісному розгляді рівнянь Нав'є-Стокса для в'язкої стисливої рідини (газу), рівняння нерозривності, рівнянь стану і рівнянь балансу тепла. Для циклону типу ЦН-15 записано початкові і граничні умови. Розв'язано отриману повну систему диференціальних рівнянь у частинних похідних та досліджено вплив геометричних розмірів сепаратора на експлуатаційні показники апарату. Числовий аналіз задачі проведено для циклона з фіксованими геометричними параметрами. Досліджено залежність гідравлічного опору циклона від таких параметрів, як висота циліндричної частини, глибина занурення вихлопної труби, висота конічної частини, діаметр вихлопної труби, діаметр пиловипускного патрубка. Досліджено розподіл статичного тиску всередині корпуса циклона. Під час досліджень розглядали різні діаметри пиловипускного отвору, а також різні значення висоти циліндричної частини. Досліджено поле швидкостей запиленого потоку всередині пиловловлювача, зокрема, її тангенціальна та осьова складові. На основі розробленої математичної моделі побудовано ізолінії швидкості потоку у характерних площинах, які проходять через вертикальну вісь циклона. Для підтвердження адекватності запропонованої математичної моделі результати числового аналізу підтверджено експериментальними дослідженнями. Для цього розроблено конструкцію експериментального стенда для проведення досліджень, у якій передбачено можливість зміни висоти циліндричної частини, глибини занурення вихлопної труби, площі поперечного перерізу вихлопної труби та використання різних типів конічної частини бункерів.

Justification of technological parameters for underground mining of gas-bearing coal beds prone to spontaneous combustion

The article presents results of the numerical studies of aerodynamic processes in excavated sections of coal mines. The effect of the ventilation and degassing schemes and their parameters on the oxygen content and a danger of spontaneous coal combustion are described. The influence of geological and mining factors on the endogenous fire hazard of the coal bed prone to spontaneous combustion is analyzed. It is recommended to reduce endogenous fire hazards of mining flat gas-bearing coal beds of the Kuznetsk coal basin.

Advanced infrared thermography data analysis for unsteady boundary layer transition detection

Advanced data processing methods for detecting unsteady boundary layer transition in periodic aerodynamic processes by means of infrared thermography measurements are presented. The thermal radiation emitted from the heated suction surface of a pitching airfoil model in subsonic flow is measured with an infrared camera. The unsteady boundary layer transition location is detected by analyzing the difference in the infrared radiation signal over short periods of time with differential infrared thermography (DIT). The DIT method is optimized and automated in the present study, which facilitates the extension of the part of the motion period where valid DIT transition measurements are produced. Additionally, a new infrared thermography data processing method is introduced in this study. The extraction of the extrema of the measured radiation signal at fixed locations on the model surface yields instants of the motion period that relate to the occurrence of boundary layer transition. The local infrared thermography (LIT) approach can be extended to measuring the two-dimensional unsteady boundary layer transition front.

Recent advances and test processes in automotive and motorsports aerodynamic development

This article highlights the advances in the aerodynamic development and test processes of both road and motorsports cars over the last two decades, including explaining the main driving forces behind this evolution. The relentless and continuous drive to improve efficiency and correlation between computational fluid dynamics, real-time simulation, wind tunnel testing, and the track is explained. Key enabling technologies are described, such as: continuous motion systems; high-speed data acquisition systems; steel moving belt ground planes with under floor load cells; on-demand robotic particle image velocimetry; pneumatic model tyres with integral sidewall and contact patch deflection systems; driver simulators and rapid prototyped rake systems for track cars. Finally, as aerodynamicists attempt to simulate and test within ever more complex and realistic environments potential future directions and emerging trends are outlined, including gusts, aeroelasticity, adaptive cooling, and cornering.

On the Energy Efficiency of Indoor Air Conditioning

The increase of average outdoor temperatures and their fluctuations over the past 20 years (as evidenced by the records of summer temperatures in our country) has significantly increased the need for air conditioning premises where people are present for a long time, especially when they are crowded (shops, entertainment halls, classrooms, etc.). The air conditioning process is quite energy-intensive, but the growth of well-being in many republics of the former USSR, as well as the increasing complexity of the physiological adaptation of the human body to rising outdoor temperatures make it possible (and at the same time necessary) to implement these systems on a large scale. It is important to take into account that electricity prices are currently maintained at a high level for homeowners, and in the coming years the prices will only grow. Therefore, the development of new ways of significant increase of the energy efficiency of the indoor air conditioning process is of a great interest. One of these methods is the use of laminar (or close to them) moving layers of conditioned air in a limited area of work or rest of people. Such a zone, about 1.0‒1.2 m height from a floor in each apartment is, e.g., living rooms (bedroom) in which standard temperature conditions are created by means of simple air supplying and air intake devices. In the case of sedentary work of people, the height of such a zone of conditioned air should be increased to 1.3‒1.5 m. It has already been established that the use of laminar (or close to them) air flows allows to reduce the power consumption by two or more times due to significantly reduced heat exchange with the surrounding heated surfaces. Besides, the simplicity of such systems ought to be noted. In particular, in conditions of modern systems of control and management of air conditioning, the "duties" of consumers include only the installation on the control device of the initial data relating directly to the required parameters of the microclimate. At the same time, it should be noted that there is currently no complete scientific and technical description of aerodynamic and heat exchange processes in the air conditioning zone. Even in modern conditions for countries with a sharply continental climate (Russia, Kazakhstan, etc.), the problem is the choice of the type of air conditioner for its effective use in hot periods of summer. In general, it can be noted that all the problems of energy-efficient use of air conditioners must find a comprehensive solution.

Some Aspects of the Transonic Compressor Tandem Design

For the development of the latest generation of axial compressors, it is necessary to enlarge the design space by using advanced aerodynamic processes. This enables a further increase in efficiency and performance. The use of a tandem blade configuration in a transonic compressor row provides the possibility to enlarge the design space. It is necessary to address the design aspects a bit more in detail in order to efficiently apply this blading concept to turbomachinery. Therefore, in the current study, the known design aspects of tandem blading in compressors will be summed up under the consideration of the aerodynamic effects and construction characteristics of a transonic compressor tandem. Based on this knowledge, a new transonic compressor tandem cascade (DLR TTC) with an inflow Mach number of 0.9 is designed using modern numerical methods and a multi-objective optimization process. Three objective functions as well as three operating points are used in the optimization. Furthermore, both tandem blades and their arrangement are parameterized. From the resulting database of 1246 members, a final best member is chosen as the state-of-the-art design for further detailed investigation. The aim of the ensuing experimental and numerical investigation is to answer the question, whether the tandem cascade resulting from the modern design process fulfills the described design aspects and delivers the requested performance and efficiency criteria. The numerical simulations within the study are carried out with the DLR flow solver TRACE. The experiments are performed at the transonic cascade wind tunnel of DLR in Cologne. The inflow Mach number during the tests is 0.9, and the AVDR is adjusted to 1.3 (design value). Wake measurements with a three-hole probe are carried out in order to determine the cascade performance. The experimental results show an increase in losses and a reduction of the cascade deflection by about 2 deg compared to the design concept. Nevertheless, the experimental and numerical results allow a good understanding of the aerodynamic effects. In addition, planar PIV was applied in a single S1 plane located at midspan to capture the velocity field in the wake of blade 1 in order to analyze the wake flow in detail and describe its influence on the cascade deflection and loss behavior. Finally, an outlook will be given on what future tandem compressor research should be focused.

Numerical simulation of transient aerodynamic processes in the vertical axis wind turbine rotor

This paper describes the steps of elaboration of calculation model for dynamic simulation of a small vertical axis wind turbine rotor. The calculation model is based on the finite element analysis ANSYS CFX software. The CFD model is used to determine the performance of the wind turbine rotor for different settings (tip speed ratio, solidity, mesh size etc.). The verification of the proposed model is done by hand calculation of the rotor performance and comparison of the real wind turbines output.

Use of AquaCrop model for estimating crop evapotranspiration and biomass production in hilly topography

The use of crop models in sloping areas is questionable when relief is not taken into account, as relief affects infiltration, radiation, and aerodynamic processes. The objective of this work is to evaluate the performance of FAO-AquaCrop model in simulating crop evapotranspiration, water balance, and biomass production in hilly areas using in situ measurements. The experiment was conducted in the Cap-Bon region, north-eastern Tunisia, on two wheat fields located on opposite sloping rims (A and B) and one control field (C) on a flat terrain: field A is SE-oriented with 5% slope and B is NW-oriented with 6% slope. Three flux stations were used to monitor automatically actual evapotranspiration (ET) and climatic factors whereas soil moisture and biomass production were measured manually. Model’s outputs were compared to actual measurements using statistical indicators: slope of the regression line, root mean squared error (RMSE), and the coefficient of determination (R2). Actual ET varied between 1 and 2 mm during crop initial stage and 3–4 mm during mid-season stage. The ET/ETo ratio during mid-season was 0.81, 0.74, and 1.03, respectively for fields A, B, and C, well below the commonly used value of 1.15. Comparison between measured and simulated ET shows a substantial overestimation of the model in sloping fields with 6–20% higher averages and a RMSE of 0.47–0.77 mm/day. AquaCrop seems to simulate reasonably well water balance, particularly in flat conditions. RMSE of water content in the top 100 cm soil-layer was in the range 41–67 mm/m, representing a relative error of 11–21%. Simulated and measured biomass values presented similar trends (R2 = 0.86–0.94) with a systematic difference, indicating that AquaCrop outputs could be improved by a correction factor.