Preface 1.General Considerations 2.Basic Processes in Atomization 3.Drop Size Distributions of Sprays 4.Atomizers 5.Flow in Atomizers 6.Atomizer Performance 7.External Spray Charcteristics 8.Drop Evaporation 9.Drop Sizing Methods Index

Atomization and Sprays

Scalar profiles and NO formation in laminar opposed-flow partially premixed methane/air flames

Concentrating solar power (CSP) has received significant attention among researchers, power-producing companies and state policymakers for its bulk electricity generation capability, overcoming the intermittency of solar resources. The parabolic trough collector (PTC) and solar power tower (SPT) are the two dominant CSP systems that are either operational or in the construction stage. The USA and Spain are global leaders in CSP electricity generation, whereas developing countries such as China and India are emerging by aggressive investment. Each year, hundreds of articles have been published on CSP. However, there is a need to observe the overall research development of this field which is missing in the current body of literature. To bridge this gap, this study 1) provides a most up-to-date overview of the CSP technologies implemented across the globe, 2) reviews previously published review articles on this issue to highlight major findings and 3) analyzes future research trends in the CSP research. Text mining approach is utilized to analyze and visualize the scientific landscape of the research. Thermal energy storage, solar collector and policy-level analysis are found as core topics of discussion in the previous studies. With a holistic analysis, it is found that direct steam generation (DSG) is a promising innovation which is reviewed in this study. This paper provides a comprehensive outlook on the CSP technologies and its research which offers practical help to the future researchers who start to research on this topic.

A comprehensive review of state-of-the-art concentrating solar power (CSP) technologies: current status and research trends

Flow physics plays a key role in nearly every facet of the COVID-19 pandemic. This includes the generation and aerosolization of virus-laden respiratory droplets from a host, its airborne dispersion and deposition on surfaces, as well as the subsequent inhalation of these bioaerosols by unsuspecting recipients. Fluid dynamics is also key to preventative measures such as the use of face masks, hand washing, ventilation of indoor environments and even social distancing. This article summarizes what we know and, more importantly, what we need to learn about the science underlying these issues so that we are better prepared to tackle the next outbreak of COVID-19 or a similar disease.

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The flow physics of COVID-19

Numerical models of surface tension play an increasingly important role in our capacity to understand and predict a wide range of multiphase flow problems The accuracy and robustness of these models have improved markedly in the past 20 years, so that they are now applicable to complex, three-dimensional configurations of great theoretical and practical interest In this review, I attempt to summarize the most significant recent developments in Eulerian surface tension models, with an emphasis on well-balanced estimation, curvature estimation, stability, and implicit time stepping, as well as test cases and applications The advantages and limitations of various models are discussed, with a focus on common features rather than differences Several avenues for further progress are suggested

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Numerical Models of Surface Tension

Computational Fluid Dynamics simulations are performed to study mixture preparation in the intake manifold of a small engine with Port Fuel Injection. Data from laser-based experiments on two injectors are used as inputs to the spray sub-model. The results reveal improved in-cylinder fuel distribution when the spray is directed onto the intake valve. The Sauter Mean Diameter of the spray is observed to have an insignificant effect during open valve injection, while the targeting is found to have a large influence. The methodology developed as part of this work can be used to further optimize injection parameters in such engines.

Modelling of mixture preparation in a small engine with port fuel injection

Investigation of novel scaling criteria on a reverse-flow combustor

A study on the extinction condition in counterflow diffusion flames of methane and LPG under the influence of polydisperse water mist

Concentration Measurements in a Mixing Module for Lean, Premixed, Gas-Turbine Combustors

Liquid atomization is a problem with applications in many fields. In the present study, an air-assisted impinging jet atomizer has been utilised and its spray characteristics have been studied at various conditions, using water as the liquid and nitrogen as the atomizing gas. Two configurations were studied: one having a central gas jet above two impinging liquid jets, and another having a central liquid jet targeted by two inclined gas jets. Backlit imaging and particle/droplet imaging and analysis techniques were utilised to characterise the sprays. It was observed that the configuration with a central gas jet and impinging liquid jets resulted in better atomization that the other case. It was observed that both the breakup length of the sheet and the resulting droplet sizes, reduced with an increase in the gas flow rate. The diameter of the gas jet orifice was also found to play an important role in changing the spread of the spray, the droplet sizes, and the radial distribution of droplet sizes. Overall, it is observed that by varying the gas-to-liquid ratio and nozzle orifices, it is possible to obtain a fine atomization of the spray using the air-assisted impinging jet configuration even at low injection pressures of below 0.4 MP a. Introduction Air-assisted atomization, in which kinetic energy of air is used to aid liquid breakup, has been used to atomize various kinds of liquids [ 1], [2], [3]. In most of these studies, either an annular/central liquid sheet is blasted with air jets, or gas is allowed to mix with the liquid inside the atomizer to form a spray. This method requires a large amount of gas to achieve droplet sizes of the order of 50 μm. Beck et al. [ 4] achieved a Sauter mean diameter (SMD) of 75 μm with water at a gas to liquid ratio (GLR) of the order of 1.0. On the other hand, impinging jet atomization has been used in rocket engines due to its good atomization and mixing characteristics [ 5], [6]. Impinging jet experiments with water by Shen et al. [ 7] showed that jet velocities of the order of 12.5 m/s was required to obtain an SMD in the range of 300 μm. In the present study, a liquid sheet is formed using two impinging liquid jets, and an air jet is directed on to this sheet to aid the atomization process. This combined effect of impinging jet and air assisted atomization helps in achieving smaller droplets at low liquid injection velocities. Experimental Setup and Methods The experimental setup consists of two parts, a liquid and gas supply system to the atomizer, and the optical setup to measure spray characteristics. In the supply system, high pressure nitrogen from a gas bottle is regulated to the gas reservoir tank and part of it is used to compress the liquid in the liquid reservoir. Liquid and gas flow rates are controlled using needle valves in their respective lines. The gas flow rate is measured using a thermal mass flow meter, while the liquid flow is measured using a gear flow meter. Digital pressure gages placed close to the atomizer measure the injection pressure. The spray is injected in a quiescent ambient condition. The spray is collected into a tank with a small exhaust fan at the bottom which creates sufficient suction to remove the mist without affecting the spray. The atomizer used in the present study consists of two liquid nozzles with an orifice of 0.76 mm in diameter, and a gas nozzle with an orifice diameter of 1.1 mm. The gas jet is placed over the impinging point of liquid jets at a distance of 7 mm, and making equal angles with them. The liquid jets impinge and form a liquid sheet in the plane perpendicular to that containing the axes of the injectors, and the gas supplied through the gas orifice is used to assist in the break-up of this sheet. The optical setup for spray characteristic measurements is based on the backlit direct imaging method. It uses a pulsed Nd:YAG laser along with a fluorescent diffuser as a light source to back-illuminate the spray, and a CCD camera with a resolution of 2048 X 2048 pixels to record the spray images. A pulse duration of around 10 ns is used. The schematic of the experimental setup is shown in Fig. 1. In the present study, two types of image-based measurements are performed, one to study the spray structure and the other for droplet size measurements. For the spray structure measurements, images are taken from the exit of the orifice to 80 mm downstream. Small portions of the spray are imaged using a long distance microscope for droplet size measurements. ∗Corresponding author: ammohan@mecheng.iisc.ernet.in

RV Ravikrishna

Papers

Modelling of mixture preparation in a small engine with port fuel injection

Investigation of novel scaling criteria on a reverse-flow combustor

A study on the extinction condition in counterflow diffusion flames of methane and LPG under the influence of polydisperse water mist

Concentration Measurements in a Mixing Module for Lean, Premixed, Gas-Turbine Combustors

Experimental spray characterisation of air-assisted impinging jets