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Dynamics of Hollow Cone Spray in an Unconfined, Isothermal, Co-Annular Swirling Jet EnvironmentSunil, Sanadi Dilip January 2015 (has links) (PDF)
The complex multiphase flow physics of spray-swirl interaction in both reacting and non-reacting environment is of fundamental and applied significance for a wide variety of applications ranging from gas turbine combustors to pharmaceutical drug nebulizers. Understanding the intricate dynamics between this two phase flow field is pivotal for enhancing mixing characteristics, reducing pollutant emissions and increasing the combustion efficiency in next generation combustors. The present work experimentally investigates the near and far-field break-up, dispersion and coalescence characteristics of a hollow cone spray in an unconfined, co¬annular isothermal swirling air jet environment. The experiments were conducted using an axial-flow hollow cone spray nozzle having a 0.5 mm orifice. Nozzle injection pressure (PN = 1 bar) corresponding to a Reynolds number at nozzle exit ReN = 7900 used as the test setting. At this setting, the operating Reynolds number of the co-annular swirling air stream number (Res) was varied in four distinct steps, i.e. Res = 1600, 3200, 4800 and 5600. Swirl was imparted to the co¬axial flow using a guided vane swirler with blade angle of Ф=45° (corresponding geometric swirl number SG = 0.8). Two types of laser diagnostic techniques were utilized: Particle / Droplet imaging analysis (PDIA) and shadowgraph to study the underlying physical mechanisms involved in the primary breakup, dispersion and coalescence dynamics of the spray. Measurements were made in the spray in both axial and radial directions and they indicate that Sauter Mean Diameter (SMD) in radial direction is highly reliant on the intensity of swirl imparted to the spray. The spray is subdivided into two zones as function of swirl in axial and radial direction: (1) near field of the nozzle (ligament regime) where variation in SMD arises predominantly due to primary breakup of liquid films (2) far-field of the nozzle where dispersion and collision induced coalescence of droplets is dominant. Each regime has been analyzed meticulously, by computing probability of primary break-up, probability of coalescence and spatio-temporal distribution of droplets which gives probabilistic estimate of aforementioned governing phenomena. In addition to this, spray global length scale parameters such as spray cone angle, break-up length, wavelength of liquid film has been characterized by varying Res while maintaining constant ReN.
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Influência da pressão e da ponta de pulverização na distribuição de caldas em pulverizadores costais manuais / Influence of working pressure and spray nozzle on the distribution of spray liquid in manual backpack sprayersMarangoni Junior, Alcides 27 April 2018 (has links)
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Previous issue date: 2018-04-27 / Outra / O uso de pulverizadores costais manuais no Brasil é frequente em todas as propriedades rurais. Entretanto, são escassos os trabalhos de pesquisa que avaliem as suas características de trabalho, sobretudo com o modelo de ponta de pulverização que equipa os pulverizadores de fábrica e nas condições de pressão de trabalho predominantes na utilização. Desta forma, o objetivo deste trabalho foi avaliar quanto os modelos de pontas e a pressão de trabalho influenciam na qualidade da distribuição de caldas fitossanitárias com pulverizadores costais manuais. Foram avaliadas em mesa de deposição quatro modelos de pontas de pulverização (jato plano convencional - Magnojet TP 110015; jato plano defletor - Teejet TT 110015; jatos cônicos vazios - TeeJet TXA 80015 e “chapinha” original), a 1, 2, 3 e 4 bar de pressão. As análises do perfil de distribuição dos jatos foram realizadas por simetria e o coeficiente de variação analisado pelo teste de Tukey (p<0,05). Os modelos de pontas de pulverização e pressão de trabalho influenciaram em mais de 100% os valores de uniformidade de distribuição da calda, e cerca de 50% na largura da faixa útil de tratamento fitossanitário. Dentre os modelos avaliados neste trabalho, o de jato defletor é o que apresenta o melhor conjunto de características para ser indicado a equipar os pulverizadores costais manuais para os tratamentos fitossanitários a campo. / Manual backpack sprayers are widely used in rural properties in Brazil. However, studies that assess their working characteristics, especially spray tip models and working pressure conditions, are scarce. Thus, the aim of this study was to assess how much the working pressure and spray tips influence the distribution quality of phytosanitary spray solutions in manual backpack sprayers. Four spray nozzles (standard flat-fan Magnojet TP110015, turbo flat-fan TeeJet TT110015, hollow-cone TeeJet TXA80015, and disc-core) were assessed in a patternator table at 1, 2, 3, and 4 bar. Distribution profile analyses of sprays were performed by symmetry and the coefficient of variation analyzed by the Tukey’s test (p<0.05). Spray tip models and working pressure influenced in more than 100% the distribution uniformity values of spray solution and in about 50% the useful bandwidth of the phytosanitary treatment. Among the models assessed in this study, the turbo flat-fan spray nozzle presents the best set of characteristics to be indicated for manual backpack sprayers aiming at field phytosanitary treatments.
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