Academic literature on the topic 'Centrifugal nozzle'

In this paper, the numerical simulation of internal and external flow field of target type impinging stream nozzle by using Fluent software is observed, the effect on nozzle atomization was obtained by simulating the size of nozzle structure（the diameter d of nozzle and distance δ between the target and plate）and pressure P (that is to say the flow velocity). The results show that: the larger the structure size and the pressure of nozzle，the better the effect of nozzle atomization.That it has superiority than the general centrifugal nozzles and can save water quantity.

This study presents a method for the fabrication of ultrafine polymeric nanofibers utilizing centrifugal and electrostatic forces simultaneously. To reduce the diameter and variability of nanofibers produced from solid state polymerized PA66 (SSP PA66), a unique electro-centrifuge spinning device was designed using rotating nozzle and collector, whereas the fabrication process (spinning head) was skillfully sealed from ambient airflow. An electric field is applied between the nozzle containing the polymer solution and cylindrical collector. Due to centrifugal force, polymer solution is ejected from the nozzle tip and extended by centrifugal force as well as electrical force. The diameters of nanofibers were controlled by adjusting the selected affecting parameters such as solution concentration, rotational speed of spinning head, syringe content as well as applied voltage. With this new technique, nanofibers were electrospun from SSP PA66 solutions. Field emission scanning electron microscope (FESEM) results demonstrated that ASCES has the unique ability to produce high quality ultrafine nanofibers from SSP PA66 polymer. Well control of parameters was tended to produce the thinnest fibers with mean diameter of 63 nm.

The article contains the main results of the creation of a nozzle of improved design research work. To improve application efficiency of low-pressure nozzle of water mist in automatic fire-extinguishing system (AFS), the construction of centrifugal nozzles with swirl worm screw inserts was changed. The construction features of this sprayer, methods of its testing and obtained results these tests characteristics are presented.

High-speed centrifugal spinning is a novel method to fabricate nanofiber. It has the potential to fabricate nanofiber on a large scale because its production efficiency is much greater than traditional methods. Nozzle is an important part of high-speed centrifugal spinning equipment because its length, shape, and diameter all will affect the morphology and quality of nanofiber. It is useful to study the movement and forces of spinning solution in the nozzle. In this article, the principle and equipment structure of high-speed centrifugal spinning are briefly introduced at first. Then the movement and forces of spinning solution are analyzed by establishing parametric model at nozzle. It can be found that the spinning solution is ejected from nozzle when the rotating speed reaches a critical value. The critical rotating speed is inversely proportional to the radius of nozzle and directly proportional to the viscosity of spinning solution. There are several nozzle structures proposed and compared for nozzle optimization. Finally, the effects of nozzle parameters, concentration of spinning solution, and rotational speed on the morphology of nanofiber are verified by high-speed centrifugal spinning experiments. It lays the foundation for optimizing spinning equipment.

To study the thermal property and the feasibility about the target type impinging stream nozzles, the thermotechnical parameters have been measured in Xi'an No.3 Textile mill. The equation between quantity of water and pressure, aperture, spacing has been established by regression analysis method. In the same way, the equation and the characteristic curve about efficiency and spacing, air mass velocity has been built. Comparing with the centrifugal nozzle, water distribution system about each nozzle has been calculated. Hydrographic net resistance of each kind of system has been calculated and the economical analysis has been done. It may provide a reference basis for choosing nozzle and designing the water spray chamber.

Centrifugal nozzle is an important part of an areoengine in which fuel atomization has strong influence on engine performance. For investigating the fuel spray characteristics, a promising method named off-axis particle holographic measuring system is used here. Characteristics of the nonevaporating spray ejected from a new type of centrifugal nozzle which would be used in the near future are obtained under various injection conditions. By automatic analysis of the holographic reconstructed droplets images, a hollow-cone shape spray with most droplets concentrated in the surface of the cone is observed, and the spray cone angle, droplet sizes and their spatial locations in concerned region are obtained quantitativly. In the near region of the nozzle exit, droplets show greater SMD value, while at a certain distance from the nozzle, the droplets SMD differences become unconspicuous which shows a better atomization. These informations are helpful to understand characteristics of the centrifugal nozzle and offer a database for validating the spray simulation code.

Abstract The forward bending centrifugal fan features long vanes and narrow passages, and the internal flow is apt to be affected by wall boundary layer of the blade surfaces. An aerodynamic investigation on the forward bending centrifugal fan is presented in this paper. The performances of the unsteady flow field in the centrifugal fan is predicted by solving the incompressible Reynolds-averaged Navier-Stokes (RANS) equations based on the Shear Stress Transport (SST) – Scale Adaptive Simulation (SAS) turbulence model. And three-dimensional (3-D) flow phenomenon of non-uniform fluid flow is discussed through observing the flow separation and vortex distribution in the impeller region. The installation location of inlet nozzle is finally adjusted based on the calculated results, and the centrifugal fan with eccentric inlet nozzle is proposed. From the results, the eccentric inlet nozzle with L=3 mm, θ=120° could improve the internal flow of the forward bending centrifugal fan and enhance its aerodynamic performance.

The authors have developed an improved sprayer for two-way chemical treatment of vineyards and orchards. The research aims to justify the design scheme and parameters of the sprayer. The proposed sprayer is equipped with a centrifugal fan, which directs air flow from the inlet window to two opposite sides. The distributor is designed as a truncated cone with an inlet nozzle on its small base and outlet nozzles equally spaced on its large base and connected to sprayers by flexible hoses of equal length. It is established that the diameter of the centrifugal fan wheel 630 mm, number of fan wheel rotations 1500 r/min, diameters of large and small distributor base as a truncated cone 90 mm and 18 mm respectively, the diameter of each nozzle set on its large base 3 mm, cone height 100 mm, number of atomizers 20 pieces and working liquid pressure in the system 0.40-0.45 MPa is provided a uniform distribution of working liquid.

The influence of the physical, rheological, and process parameters on the cellulose nanocrystal (CNC) drops before and after external gelation in a CaCl2 solution was investigated. The dominant role of the CNC’s colloidal suspension properties, such as the viscous force, inertial, and surface tension forces in the fluid dynamics was quantitatively evaluated in the formation of drops and jellified beads. The similarity and difference between the behavior of carbohydrate polymers and rod-like crystallites such as CNC were enlightened. Pump-driven and centrifugally-driven external gelation approaches were followed to obtain CNC hydrogel beads with tunable size and regular shape. A superior morphological control—that is, a more regular shape and smaller dimension of the beads—were obtained by centrifugal force-driven gelation. These results suggest that even by using a simple set-up and a low-speed centrifuge device, the extrusion of a colloidal solution through a small nozzle under a centrifugal field is an efficient approach for the production of CNC hydrogel beads with good reproducibility, control over the bead morphology and size monodispersion.

This work will be focused on issue of a jet engine. The thesis will be divided into search retrieval part and computational part. In the search retrieval part it will focus on different configurations of jet engines as well as areas of their use. The main part of the thesis will however focus on a calculations where a turbine, compressor and an exhaust nozzle will be designed in order to give a thrust of approximately 1kN. Next step will be determination of an engine charcteristic that will give us a preview on how the engine performance will look like in off-design modes.

Роботу присвячено експериментальним дослідженням, що направлені на підвищення ефективності роботи контактних тепломасообмінних апаратів шляхом збільшення міжфазної поверхні тепломасообміну при розпилені рідини відцентровими форсунками, впровадження яких приводить до суттєвої економії матеріальних та енергетичних ресурсів. Виконано комплексні експериментальні дослідження характеристик факелу розпилу рідини (густини зрошення, кута розкриття факела форсунки, середнього об’ємно-поверхневого діаметра крапель рідини). Встановлено вплив вхідних параметрів на відповідні характеристики та визначено площу поверхні крапель розпиленої рідини. Експериментально встановлено значення граничної температури нагріву води та її залежність від початкового паровмісту, при якій вода нагрівається до граничної температури в залежності від початкового паровмісту й витрати сухого повітря. Визначено параметричні границі ефективного використання відцентрової механічної форсунки без випаровування крапель нагрітої рідини. Експериментально досліджено інтенсивність тепло- і масоовіддачі в контактному апараті газокрапельного типу з відцентровою форсункою в умовах утилізації теплоти відхідних газів енергетичних агрегатів. Вперше отримано емпіричні залежності для розрахунку середніх коефіцієнтів тепловіддачі та масовіддачі, які відносяться до дійсної поверхні крапель розпиленої води. Встановлено особливості процесів переносу в газокрапельній системі та отримано узагальнювальні залежності для процесів тепло- і масовіддачі. На основі експериментальних досліджень характеристик розпилу та процесів тепломасообміну при конденсації пари з парогазової суміші на краплях розпиленої рідини розроблено методику розрахунку крапельного контактного утилізаційного апарату.
Dissertation is devoted to experimental research, aimed at improving the efficiency of contact heat and mass transfer units by increasing the interfacial surface of heat and mass transfer during the liquid spraying by centrifugal nozzles, implementation of which results in significant savings of material and energy resources. Comprehensive experimental study of the characteristics of the liquid spraying torch (irrigation density, expansion angle of nozzle torch, the average volume-surface diameter of liquid droplets) was done. The influence of input parameters to the relevant properties was shown and surface area of the sprayed liquid droplets was defined. The limit temperature of water heating and its dependence on initial vapor content in which water is heated to the limit temperature depending on the initial vapor content and dry air output were experimentally set. The parametric borders of effective use of centrifugal mechanical nozzle without evaporation of heated liquid drops were defined. Intensity of heat and mass transfer in the contact gas-droplet unit with centrifugal nozzle in terms of heat utilization of energy units’ exhaust gases was experimentally researched. The empirical dependences for calculating the average heat transfer and mass transfer coefficients relating to the actual surface of the sprayed liquid droplets are obtained for the first time. The peculiarities of transfer processes in the gas-droplet system were determined and generalized dependence for heat and mass transfer were received. Based on experimental studies of spraying characteristics and heat and mass transfer processes at vapor condensation from vapor-gas mixture on the sprayed liquid droplets, the method of calculating the droplet contact utilization unit was developed.
Диссертация посвящена исследованиям, направленным на повышение эффективности работы контактных аппаратов путем увеличения межфазной поверхности теплообмена путем распыления жидкости, внедрение которых приводит к существенной экономии материальных и энергетических ресурсов. Работа содержит результаты экспериментальных исследований характеристик распыла и процессов тепломассоотдачи при конденсации пара из парогазовой смеси на каплях распыленной жидкости. Исследовано влияние температуры и давления воды на тонкость распыла (величину среднего объемно-поверхностного диаметра капель) для центробежной форсунки в параметрических условиях ее работы и применительно к условиям работы контактного утилизатора теплоты отходящих газов. На основании проведенных опытов получены новые зависимости величины среднего объемно-поверхностного диаметра капель для параметров распыливания жидкости с помощью центробежной форсунки в новом диапазоне изменения избыточного давления и температуры воды перед форсункой. В результате теоретического анализа движения капель жидкости в факеле распыления центробежной форсунки и использования экспериментальных данных по средним объемно-поверхностным диаметрам капель предложена методика определения действительной межфазной поверхности процессов тепломассообмена в контактных газожидкостных аппаратах капельного типа. Экспериментально определена зависимость граничной температуры нагрева воды в контактном аппарате газокапельного типа с центробежной форсункой применительно к условиям утилизации теплоты отходящих газов энергетических агрегатов. Исследования проведены в диапазоне избыточных давлений воды перед форсункой (0,2–0,6) МПа и объемной доли водяных паров парогазовой смеси на входе в аппарат от 0,02 до 0,45. Показано использование полученной зависимости для рас чета предельных значений параметров парогазового потока, ограничивающих область эффективной работы контактного аппарата с конденсацией пара и отсутствием режима испарения капель нагретой жидкости. Экспериментально определена интенсивность тепло- и массоотдачи в контактном аппарате газокапельного типа с центробежной форсункой в условиях утилизации теплоты отходящих газов энергетических агрегатов. Исследование проведены в диапазоне избыточного давления воды перед форсункой (0,2 - 0,6) МПа и объемной долей водяного пара парогазовой смеси на входе в аппарат от 0,08 до 0,35. По результатам экспериментальных исследований определены коэффициенты тепло- и массоотдачи, которые были отнесены к реальной поверхности капель. Полученные в работе результаты экспериментальных исследований коэффициентов тепло- и массоотдачи сравнивались с известными литературными данными для одиночной капли. Установлено, что интенсивность теплоотдачи для капель жидкости с парогазовым потоком выше, чем для одиночной капли, а для массоотдачи, ниже. Установлены особенности процессов переноса в газокапельной системе и получены обобщающие зависимости для процессов тепло- и массообмена для факела капель конуса распыла. В результате указанного комплекса работ предложена методика теплового расчета контактного газокапельного утилизатора теплоты низкотемпературных отходящих газов при распылении жидкости механической центробежной форсункой, которая учитывает реальные условия протекания процессов переноса в рассматриваемой двухфазной системе. Приведенная процедура теплового расчета утилизационной установки позволяет при заданных параметрах отходящих газов и воды на входе получить тип и количество распылителей для генерирования капель воды, выполнить компоновку в штатном коробе для отвода газов, рассчитать параметры теплоносителей на выходе с установки и определить ее теплопроизводительность.

Роботу присвячено експериментальним дослідженням, що направлені на підвищення ефективності роботи контактних тепломасообмінних апаратів шляхом збільшення міжфазної поверхні тепломасообміну при розпилені рідини відцентровими форсунками, впровадження яких приводить до суттєвої економії матеріальних та енергетичних ресурсів. Виконано комплексні експериментальні дослідження характеристик факелу розпилу рідини (густини зрошення, кута розкриття факела форсунки, середнього об’ємно-поверхневого діаметра крапель рідини). Встановлено вплив вхідних параметрів на відповідні характеристики та визначено площу поверхні крапель розпиленої рідини. Експериментально встановлено значення граничної температури нагріву води та її залежність від початкового паровмісту, при якій вода нагрівається до граничної температури в залежності від початкового паровмісту й витрати сухого повітря. Визначено параметричні границі ефективного використання відцентрової механічної форсунки без випаровування крапель нагрітої рідини. Експериментально досліджено інтенсивність тепло- і масоовіддачі в контактному апараті газокрапельного типу з відцентровою форсункою в умовах утилізації теплоти відхідних газів енергетичних агрегатів. Вперше отримано емпіричні залежності для розрахунку середніх коефіцієнтів тепловіддачі та масовіддачі, які відносяться до дійсної поверхні крапель розпиленої води. Встановлено особливості процесів переносу в газокрапельній системі та отримано узагальнювальні залежності для процесів тепло- і масовіддачі. На основі експериментальних досліджень характеристик розпилу та процесів тепломасообміну при конденсації пари з парогазової суміші на краплях розпиленої рідини розроблено методику розрахунку крапельного контактного утилізаційного апарату.

This paper reports on a laboratory experiment conducted more than 30 years ago (Eli, 1974, unpublished), and recent Computational Fluid Dynamics (CFD) investigations, focusing on the properties of a plane tangential jet produced by an apparatus called a “centrifugal nozzle.” The authors believe that the centrifugal nozzle has potential industrial applications in several areas related to fluid mixing and particulate matter suspension in mixing tanks. It is also believed that this experiment, or one similar, may provide data useful for benchmarking CFD models.

Experimental investigations were conducted on a radial and a tangential inlet duct to an industrial centrifugal compressor. The tangential nozzle will replace the conventional radial nozzle if a block foundation is used with no pipes allowed on the upper casing half. Models were air tested with and without suction elbows. The tangential duct was tested with various positions of the shaped flow splitter and with variable intake rib angles with the objective to minimize distortions of axial and circumferential velocity profiles and the moment of momentum in the annular eye opening of the impeller. An optimum configuration for the tangential duct was found with smooth profiles and eliminated global vortex at the exit annulus.

A centrifugal gas turbine is developed based on a straight radial flow design with no axial flow turning. The geometry contains only two major elements — a rotor disk and a stator shroud. The rotor consists of a centrifugal compressor and high impulse radial outward-flow turbine connected to an electric generator. The stator shroud contains the combustor and nozzles. Fuel lines are attached to the shroud, ducted directly into the combustor. The difference between this novel design and conventional radial gas turbine is that the compressor and turbine section are installed on the same side of the rotating wheel, while the combustor and nozzle are mounted on the stationary shroud. Thus, the entire assembly consists of two components. Technical advantages are: • Single Rotating Component; • Short Axial Span; • Compact Two-Piece Construction; • Ease of Maintenance/Repair Access. Aerodynamic design, performance, and structural analysis of this design are discussed.

Significant effort has been spent over the years to improve the accuracy and reduce the Computational Fluid Dynamics (CFD) simulation time required to predict performance for centrifugal compressors. Most of the emphasis has been on modeling the impeller and diffuser components. This paper presents an evaluation of volute modeling targeted at reducing simulation time while increasing the accuracy of the results. Providing accurate predictions of performance and operating range is critical to the equipment users as it allows reduction in design margins for plant equipment dependent on compressor performance (i.e. drivers, intercoolers and other auxiliary equipment). The volute is the component that collects the flow from the diffuser and guides it into the discharge nozzle. Due to the circumferential variation (tongue) in the geometry, this component has to be modeled in its entirety (360 degrees); which results in very large grid sizes. The impeller and diffuser, normally modeled as a sector or pie slice, result in significantly smaller meshes. The volute models require large numbers of computing nodes to be solved and tend to have convergence issues. The investigation, with the objective of reducing the amount of time required to run these simulations and improve the convergence of the runs, evaluated several mesh configurations that focused on grid density (element count), element aspect ratio and use of inflation layers. The domain evaluated consisted of several stationary components and one rotating component. The model started at the inlet guide vane section followed by the impeller, vanned diffuser, volute, and discharge nozzle. Commercial software ANSYS CFX was used to develop the meshes using tetrahedral/prism elements and complete steady-state CFD analyses. Detailed flow field characteristics (total and static pressure, velocity streamlines, etc.) and key performance parameters (loss coefficient, pressure ratio, etc.) were compared for the various configurations evaluated. In addition, experimental measurements were used to validate the CFD results. The configuration that resulted in the shortest cycle time with the best performance accuracy was selected as optimum. Accuracy is paramount for performance prediction and reduction in simulation time will allow more volute iterations to be investigated, which would help improve volute performance in centrifugal compressors.

This paper considers the development of a Linear, Time Invariant (LTI) model for centrifugal compressor systems for robust control design. The objective is to obtain a LTI model of the compressor system so that robust controllers can be designed to control the outlet pressure and mass flow. The control variables are the motor armature voltage and the inlet valve position. The approach taken in this paper is to (1) obtain the non-linear, input-output dynamic reactions of the various components (inlet valve, ducts, compressor, nozzle and DC-motor), (2) identify the model parameters and variables (pressure, mass flow, etc.), (3) obtain a linear model of the system, (4) design a controller based on the LTI model and (5) test the designed controller on the non-linear model of the compressor system.

Results from a series of experiments to investigate whether centrifugal compressor stability could be improved by injecting air through the diffuser hub surface are reported. The research was conducted in a 4:1 pressure ratio centrifugal compressor configured with a vane-island diffuser. Injector nozzles were located just upstream of the leading edge of the diffuser vanes. Nozzle orientations were set to produce injected streams angled at −8, 0 and +8 degrees relative to the vane mean camber line. Several injection flow rates were tested using both an external air supply and recirculation from the diffuser exit. Compressor flow range did not improve at any injection flow rate that was tested and generally diminished as injection rate increased. Compressor flow range did improve slightly at zero injection due to the flow resistance created by injector openings on the hub surface. Resistance and flow range both increased as the injector orientation was turned toward radial. Leading edge loading and semi-vaneless space diffusion show trends that are similar to those reported earlier from shroud surface experiments that did improve compressor range. Opposite trends are seen for hub injection cases where compressor flow range decreased. The hub injection data further explain the range improvement provided by shroud-side injection and suggest that stability factors cited in the discussion of shroud surface techniques are valid. The results also suggest that a different application of hub-side techniques may produce a range improvement in centrifugal compressors.

Improving fuel economy and reducing exhaust emissions of automobile engines have become very important. The direct injection gasoline engine has the advantage of reduced fuel consumption, but it also has disadvantages related to exhaust emissions. Weak mixing of fuel with air due to short mixing time and fuel liquid-film adhering to the engine cylinder walls cause emission problems. To reduce these emissions, injectors need to provide fine atomization, low fuel penetration (length of fuel spray), and spray formation control. In this study, we developed a multi-swirl nozzle that forms a thin liquid-film at the nozzle outlet for fine atomization; the thin liquid-film easily breaks up into small droplets. We investigated the fuel spray characteristics of these nozzles experimentally and numerically. Using a long-distance microscope, we found that a liquid-film formed at the nozzle outlet even if its diameter was small. This is an effect of the centrifugal force from the swirl flow. Experimental results also showed that the multi-swirl nozzle reduced the size of coarse droplets (irregular, large droplets) and shortened fuel penetration. We also simulated numerically the fuel flow of the multi-swirl nozzle. Numerical analysis described the swirling flow that the multi-swirl nozzle generated above the nozzle inlet and the thin liquid-film at the nozzle outlet.