Search

The question of the effect of viscosity on the occurrence of a stagnation temperature in a dead-end cavity above the deceleration temperature of the incident gas flow the so-called Hartmann–Sprenger effect is considered. It is shown that the Hartmann–Sprenger effect can be used to create the design of the anti-icing system of the aircraft

The subject of study in the article is approaches to improving the system of protection of structural elements of a military transport helicopter from ice formation. The goal of the work is to develop proposals for improving the most energy-intensive system of the aviation equipment of a military transport helicopter, namely, an anti-icing system based on an analysis of as many of its components as possible. The following tasks are solved in the article: analysis of modern anti-icing systems (primarily those used in industrial plants and foreign helicopters), development of a backup system for heating the cockpit glass, development of a non-contact method of transferring electricity to the heating elements of the propeller blades, development of block diagram automatic control of the anti-icing system. The following methods are used: comparative analysis, methods of applied hydrodynamics and electromechanics. The following results were obtained: specific requirements for helicopter ice protection systems were formulated, a liquid cockpit glass washing system was proposed as a backup system for electric heating, a control system scheme for a 6-section anti-icing system using a combined ice formation warning device was introduced. Conclusions: the introduction of a fully automatic ice removal system as a part of the helicopter’s aviation equipment, which significantly relieves the crew, necessarily involves the use of an integrated sensor (group of meters). This will allow the system to respond not only to the appearance of a certain layer of ice on a sensitive surface, but also to environmental parameters at which such a dangerous phenomenon as icing of helicopter structural elements may occur. Modernization of the anti-ice formation system on the elements of the helicopter structure will be effective only with a comprehensive approach to the improvement of all its components together with the development of duplicate ice removal systems., Предметом исследования в статье являются подходы по совершенствованию системы защиты элементов конструкции военно-транспортного вертолета от образования льда. Цель работы – разработка предложений по совершенствованию наиболее энергоемкой системы из состава авиационного оборудования военно-транспортного вертолета, а именно противообледенительной системы на основе анализа как возможно большего числа ее компонентов. В статье решаются следующие задачи: анализ современных систем борьбы с обледенением (прежде всего тех, что используются в промышленных установках, и на зарубежных вертолетах), разработка дублирующей системы обогрева стекла кабины экипажа, разработка бесконтактного способа передачи электроэнергии на нагревательные элементы лопастей винтов, разработка структурной схемы автоматического управления противообледенительной системой. Используются следующие методы: сравнительный анализ, методы прикладной гидродинамики и электромеханики. Получены следующие результаты: сформулированы специфические требования к вертолетным системам защиты от льда, предложена жидкостная система омывки стекол кабины экипажа в качестве дублирующей системы для электрообогрева, предложенная схема системы управления 6-ти секционной противообледенительной системой с помощью комбинированного сигнализатора лёдообразования. Выводы: внедрение полностью автоматической системы устранения льда в составе авиационного оборудования вертолета, которая значительно разгрузит экипаж, обязательно предполагает использование в своем составе комплексного датчика (группы измерителей). Это позволит системе реагировать не только на появление определенного слоя льда на чувствительной поверхности, но и на параметры окружающей среды, при которых возможно возникновение такого опасного явления как обледенение элементов конструкции вертолета. Модернизация системы борьбы с образованием льда на элементах конструкции вертолета будет эффективной только при комплексном подходе к совершенствованию всех её составных частей вместе с разработкой дублирующих систем устранения льда., Предметом дослідження в статті є підходи щодо вдосконалення системи захисту елементів конструкції військово-транспортного вертольоту від льодоутворення. Мета роботи – розробка пропозицій стосовно вдосконалення найбільш енергоємної системи зі складу авіаційного обладнання військово-транспортного вертольоту, а саме протизледенільної системи на підставі аналізу як можливо більшого числа її компонентів. В статті вирішуються наступні завдання: аналіз сучасних систем боротьби з обледенінням (насамперед тих, що використовуються в промислових установках, та на закордонних вертольотах), розробка дублюючої системи обігріву скла кабіни екіпажу, розробка безконтактного способу передачі електроенергії на нагрівальні елементи лопатей гвинтів, розробка структурної схеми автоматичного управління протизледенільною системою. Використовуються такі методи: порівняльний аналіз, методи прикладної гідродинаміки та електромеханіки. Отримано наступні результати: сформульовані специфічні вимоги до вертолітних систем захисту від льоду, запропонована рідинна система омивання скла кабіни екіпажу у якості дублюючої системи для електрообігріву, запропонована схема системи управління 6-ті секційною протизледенільною системою за допомогою комбінованого сигналізатора льодоутворення. Висновки: впровадження повністю автоматичної системи усунення льоду у складі авіаційного обладнання вертольоту, яка значно розвантажить екіпаж, обов’язково передбачає використання у своєму складі комплексного датчику (групи вимірювачів). Це дасть можливість системі реагувати не тільки на появу певного шару льоду на чутливій поверхні, а ще й на параметри навколишнього середовища, при яких можливо виникнення такого небезпечного явища як обледеніння елементів конструкції вертольоту. Модернізація системи боротьби з льодоутворенням на елементах конструкції вертольоту буде ефективною лише при комплексному підході до вдосконалення усіх її складових частин разом з розробкою дублюючих систем усунення льоду.

Пластинчасті теплообмінники є ефективним видом теплообмінного обладнання та можуть використовуватись у багатьох енергетичних установках. У статті аналізується їх використання у якості маслоохолоджувачів та підігрівачів води паротурбінних установок, підігрівачів повітря системи знеліднення газотурбінних установок, регенераторів понадкритичних СО2 циклів. Наведено оптимальні типорозміри теплообмінників та швидкості середовищ для ряду навантажень, дано рекомендації щодо застосування теплообмінників у залежності від параметрів та конфігурації циклів. Plate heat exchangers are an effective type of heat exchange equipment and can be used in many power plants. The article analyzes the use of corrugated plate heat exchangers in a number of installations. Their optimization was done according to the economic criterion of optimality, taking into account capital investments and operating costs. The analysis of the plate heat exchangers uses as oil coolers (a number of loads with oil mass flow rates 10….250 kg/s) and water heaters (heat power 100…2000 kW) of steam turbine plants. It has been established that plate oil coolers are more economical than shell-and-tube ones. Also, the anti-icing system plate air heaters of gas turbine plants with a power of 1 to 20 MW considered. The air for the anti-icing system was taken after the compressor and was additionally heated by exhaust gases. It has been established that it is necessary to install an additional flue gas smoke exhauster for using plate heat exchangers. Air must be extracted after the compressor, otherwise, low air density leads to high hydraulic losses, which makes it impossible to use plate heaters. Optimum air velocities are in the range of 0.4…0.6 m/s, flue gas velocities are 4…6 m/s. The use of standard plate heat exchangers with corrugated plates is impractical for GTU powers above 5 MW. Optimization of plate regenerators of supercritical CO2 cycles with recompression for powers from 1 to 15 MW has been done. Optimum velocities of hot CO2 are about 0.8 m/s, cold ones 0.3…0.5 m/s. The optimal sizes of plate heat exchangers are recommended for all of the above applications.

Experimental study of the local and average heat transfer characteristics of a single round jet impinging on the concave surfaces was conducted in this work to gain in-depth knowledge of the curvature effects. The experiments were conducted by employing a piccolo tube with one single jet hole over a wide range of parameters: jet Reynolds number from 27000 to 130000, relative nozzle to surface distance from 3.3 to 30, and relative surface curvature from 0.005 to 0.030. Experimental results indicate that the surface curvature has opposite effects on heat transfer characteristics. On one hand, an increase of relative nozzle to surface distance (increasing jet diameter in fact) enhances the average heat transfer around the surface for the same curved surface. On the other hand, the average Nusselt number decreases as relative nozzle to surface distance increases for a fixed jet diameter. Finally, experimental data-based correlations of the average Nusselt number over the curved surface were obtained with consideration of surface curvature effect. This work contributes to a better understanding of the curvature effects on heat transfer of a round jet impingement on concave surfaces, which is of high importance to the design of the aircraft anti-icing system.

В данной работе выполнено проектирование турбовинтового газотурбинного двигателя мощностью 1,2 МВт. В качестве прототипа выбран двигатель ВК-1500С. Выпускная квалификационная работа включает в себя введение, три главы и заключение. Кроме того, в работе была изучена спец часть, посвященная обзору, противообледенительной системы газотурбинных двигателей и расчету параметров двигателя при работе противообледенительной системы. В работе выполнены: тепловой расчет; газодинамические расчеты компрессора, камеры сгорания и турбины; прочностные расчеты., In this work, the design of a turbo-prop aircraft gas turbine engine with capacity of 1,2 MW was performed. VK-1500S chosen as a prototype. Final qualifying work includes an introduction, three chapters and a conclusion. In addition, the work includes a special part devoted to the literature revive and calculation of parameters during work of anti-icing system. Explanatory note include: thermal calculation, gas-dynamic calculation of the compressor, combustion chamber and turbine, strength calculations.

В данной работе была поставлена задача выбрать наиболее рациональный режим работы противообледенительной системы лопасти воздушного винта в зависимости от Ñ Ð°Ñ€Ð°ÐºÑ‚ÐµÑ€Ð¸ÑÑ‚Ð¸Ðº нагревательного элемента (сила тока I и сопротивления R), а также в зависимости от материала, из которого изготовлена лопасть. Было установлено в итоге, что с точки зрения теплового состояния борьба с обледенением актуальна только в случае, если лопасть изготовлена из алюминиевого сплава, поскольку он обладает высоким коэффициентом теплопроводности, ввиду чего ПОС может при Ð¾Ð¿Ñ€ÐµÐ´ÐµÐ»ÐµÐ½Ð½Ñ‹Ñ Ñ€ÐµÐ¶Ð¸Ð¼Ð°Ñ Ð¿Ñ€Ð¾Ð³Ñ€ÐµÑ‚ÑŒ лопасть достаточно, чтобы минимизировать появление льда., In this work the task was to choose the most rational mode of operation of the anti-icing system of the aircrew depending on the characteristics of the heating element (current I and resistance R) also depending on the material from which the screw was made. As a result it was found that in terms of the thermal state icing control is relevant only if the blade is made of aluminum alloy since it has a high thermal conductivity, which is why the anti-icing system can warm up the screw enough to minimize the appearance of ice.

The aircraft electro-thermal anti-icing system that can guarantee flight safety may be affected by periodic heating and cyclic aerodynamic force during long-term flight missions, which seems to be a potential threat to ice protection. This paper aims to investigate the impacts of thermal and mechanical cycles on heating elements of the electro-thermal anti-icing system. Specimens were manufactured with CFRP (carbon fiber reinforced polymer) laminated composite, glass fiber prepreg and copper screen, in which sprayable metal film (SMF) was embedded as the heating element. The study focuses on electric resistance variation of SMF and functional fatigue life under the cycling load. Thermal cycling tests were carried out in an insulated chamber where the specimens were heated up to 80 °C and then cooled down to −55 °C for 1000 cycles. Mechanical cycling tests were conducted on a fatigue testing machine where the specimens were imposed on tension-compression loading for 106 cycles. Results showed that the electric resistance of SMF increased with the number of loading cycles. The resistance was increased by 20% and the heating power was decreased by 16.67% after 1000 thermal cycles. During the mechanical cycling tests, it was found that the heating element was destructed before the structural failure, which indicated that the fatigue life of function was lower than that of the structure.

Submitted by Jairo Amaro (jairo.amaro@sibi.ufrj.br) on 2019-06-11T17:38:41Z No. of bitstreams: 1 DaSilvaEtAl-ThermalAnalysisOfAnti-IcingSystemsInAeronauticalVelocitySensorsAndStructures-min.pdf: 1541100 bytes, checksum: 33ff7aad6af12de29de7836f6853d61a (MD5) Made available in DSpace on 2019-06-11T17:38:41Z (GMT). No. of bitstreams: 1 DaSilvaEtAl-ThermalAnalysisOfAnti-IcingSystemsInAeronauticalVelocitySensorsAndStructures-min.pdf: 1541100 bytes, checksum: 33ff7aad6af12de29de7836f6853d61a (MD5) Previous issue date: 2016-01-12 Indisponível. This work reviews theoretical–experimental studies undertaken at COPPE/UFRJ on conjugated heat transfer problems associated with the transient thermal behavior of heated aeronautical Pitot tubes and wing sections with anti-icing systems. One of the main objectives is to demonstrate the importance of accounting for the conduction–convection conjugation in more complex models that attempt to predict the thermal behavior of the anti-icing system under adverse atmospheric conditions. The experimental analysis includes flight tests validation of a Pitot tube thermal behavior with the military aircraft A4 Skyhawk (Brazilian Navy) and wind tunnel runs (INMETRO and NIDF/COPPE/UFRJ, both in Brazil), including the measurement of spatial and temporal variations of surface temperatures along the probe through infrared thermography. The theoretical analysis first involves the proposition of an improved lumped-differential model for heat conduction along a Pitot probe, approximating the radial temperature gradients within the metallic and ceramic (electrical insulator) walls. The convective heat transfer problem in the external fluid is solved using the boundary layer equations for compressible flow, applying the Illingsworth variables transformation considering a locally similar flow. The nonlinear partial differential equations are solved using the Generalized Integral Transform Technique in the Mathematica platform. In addition, a fully local differential conjugated problem model was proposed, including both the dynamic and thermal boundary layer equations for laminar, transitional, and turbulent flow, coupled to the heat conduction equation at the sensor or wing section walls. With the aid of a single-domain reformulation of the problem, which is rewritten as one set of equations for the whole spatial domain, through space variable physical properties and coefficients, the GITT is again invoked to provide hybrid numerical–analytical solutions to the velocity and temperature fields within both the fluid and solid regions. Then, a modified Messinger model is adopted to predict ice formation on either wing sections or Pitot tubes, which allows for critical comparisons between the simulation and the actual thermal response of the sensor or structure. Finally, an inverse heat transfer problem is formulated aimed at estimating the heat transfer coefficient at the leading edge of Pitot tubes, in order to detect ice accretion, and estimating the relative air speed in the lack of a reliable dynamic pressure reading. Due to the intrinsic dynamical behavior of the present inverse problem, it is solved within the Bayesian framework by using particle filter.

International audience; The aim of the present paper is to propose a general methodology for the numerical modelling of both anti and de-icing systems. A lubrication model is used for dealing with the dynamics of the runback water film. As regards thermal effects, in order to take into account heat conduction and unsteadiness, a parabolic temperature profile is assumed with respect to the normal coordinate for the ice layer. Heat transfers in the airfoil solid structure are described using a dedicated solver based on the unsteady heat conduction equation. The most original contribution of this work is the new technique (herein referred to as the "improved Schwarz method") which is proposed for coupling in a robust way the accretion-runback model and the solid heat conduction model. This new coupling algorithm allows to ensure fast convergence of both temperature and heat flux at the coupling interface (airfoil outer surface) and can be used either for steady state computations (anti-icing mode) or unsteady computations (de-icing mode). Numerical test cases which have been performed so far are very promising and show the relevance of this new approach for real applications and 3D extension.

Ice formation on airplane wing profile is a very dangerous condition because of the change in the profile aerodynamic, so it’s necessary to avoid ice formation on the wings. The hardest condition ice formation are at altitudes between 10.000 and 15.000 ft and at temperature between 0° C and −15° C, because they are particularly suitable for ice formation. In this paper an anti-icing system based on hot air impinging jets on internal wing surface is analyzed in order to check the efficiency of the system. A numerical model is given in order to evaluate the thermal and fluid dynamic behaviors of the impinging jet inside the wing panel. A wing profile with an angle of attack of 4.50° is taken into account with a free stream temperature of 258 K. A piccolo tube with a diameter of 1.00 inch and air temperature of 523 K and at variable distance from the wall of the wing profile, is considered for anti-icing system. A structured mesh is used in the discretization of the computational domain for the two-dimensional and three-dimensional case. A steady state solution with k-ε RNG turbulent model has been found. Numerical simulations of a two and a three dimensional model of an aircraft wing has been carried out taking into account the external convective exchange by means of an average coefficient on the external surface and thermo-fluid dynamic field inside the wing due to the anti-icing system. The analysis is performed by means of the FLUENT code in order to find the optimal geometrical configuration to avoid the ice formation on the external wing surface. Results are presented in terms of temperature fields and wall temperature and air velocity profiles along the wing surfaces.