Spray Jet Research Articles

Numerical simulation of n-dodecane spray combustion based on OpenFOAM

For the purpose of providing the scientific insights to combustion characteristics of spray jet, numerical calculations of reacting and non-reacting spray cases are performed for ECN (engine combustion network) Spray A (n-dodecane spray combustion) which coupled finite chemistry combustion model PaSR and detailed chemical reaction kinetics based on OpenFOAM. The applicability and accuracy of the spray model is verified in the non-reacting spray case, and it is found that the predicted spray characteristics such as the penetration length of liquid and vapor and the mixture fraction are in good agreement with the test results. The two processes of low-temperature reaction and high-temperature ignition experienced by n-dodecane spray ignition are analyzed in reacting spray case, and it is found that the low-temperature reaction continues to exothermic before high-temperature ignition, and continues to proceed stably after high-temperature ignition, which promotes high-temperature ignition and flame stability. Finally, the effects of different fuel injection pressures on ignition delay time and flame lift-off length are studied.

Modeling of interfacial flows based on an explicit volume diffusion concept

A novel volume of fluid (VoF) model called explicit volume diffusion (EVD) is developed for the simulation of interfacial flows, including those with turbulence and primary spray atomization. It is derived by volume averaging the VoF equations over an explicit, physically-defined length scale. Fluctuations at the sub-volume scales, which can arise due to interface dynamics or turbulence, are attenuated by the volume averaging process and their effects appear in unclosed terms representing sub-volume flux, sub-volume stress, and volume averaged surface tension force. Models are proposed for each of these. The sub-volume flux is closed by a gradient diffusion model and involves an explicit volume diffusion coefficient, that is, linked to the explicit length scale. The sub-volume stress closure introduces an explicit volume viscosity that can be augmented by a turbulent viscosity in turbulent flows. The volume averaged surface tension force closure is based on a fractal representation of the wrinkled sub-volume interface. To test the closures individually and the EVD model overall, a series of two-dimensional laminar and three-dimensional turbulent interfacial shear flows and a laboratory-scale airblast spray jet are considered. Numerical convergence is demonstrated by keeping the explicit volume length scale constant while refining the numerical grid such that the numerical diffusion diminishes and becomes overwhelmed by the explicit volume diffusion. Sensitivity analyses are also conducted for variations in the explicit length scale which may be linked to the boundary layer thickness on the light fluid side of the interface.

Evaluation of liquid-phase thermometry in impinging jet sprays using synchrotron x-ray scattering.

Liquid thermometry during primary and secondary breakup of liquid sprays is challenging due to the presence of highly dynamic, optically complex flow features. This work evaluates the use of x-ray scattering from a focused, monochromatic beam of the Advanced Photon Source at Argonne National Laboratory for the measurement of liquid temperatures within the mixing zone of an impinging jet spray. The measured scattering profiles are converted to temperature through a previously developed two-component partial least squares (PLS) regression model. Transmitive mixing during jet merging is inferred through spatial mapping of temperatures within the impingement region. The technique exhibits uncertainties of ±2K in temperature and 2% in capturing the correct scattering profile, showing its potential utility for probing liquid temperature distributions in multiphase flows.

Effect of Cross-Flow Swirl on the Trajectory of Spray in an Annular Passage

Abstract This paper presents the experimental analysis of the impact of swirl number of cross-flowing air stream on liquid jet spray trajectory at a fixed air flow velocity of 42 m/s with the corresponding Mach number of 0.12. The experiments were conducted for 4 different swirl numbers (0, 0.2, 0.42, and 0.73) using swirl vanes at air inlet having angles of 0 deg, 15 deg, 30 deg, and 45 deg, respectively. Liquid to air momentum flux ratio (q) was varied from 5 to 25. High-speed (at 500 fps) images of the spray were captured, and those images were processed using matlab to obtain the path of the spray at various momentum flux ratios. The results show interesting trends for the spray trajectory in swirling air flow. High swirling flows not only lead to spray with lower radial penetration due to sharp bending and disintegration of liquid jet but also result in spray with large spread and spray area. Based on the results, correlations for the spray path have been proposed, which incorporates the effects of the swirl number of the air flow.

Investigation of turbulent inflow specification in Euler–Lagrange simulations of mid-field spray

The process of atomization of a liquid jet by a parallel high-speed gas stream results in a spray, whose downstream development is of considerable interest to several applications. The round jet spray can be spatially divided into (i) a near-field (near-nozzle) region of liquid atomization and (ii) a downstream mid-field region of fully-dispersed droplets. In order to accurately model mid-field droplet dispersion, this work aims at developing a rigorous and robust injection model for Euler–Lagrange spray simulations. Results from experiments are used to obtain the relevant droplet number density, size distribution, and mean and standard deviation velocity distributions of the injection model, systematically in a step-by-step process. Two-phase large eddy simulations are performed by stochastically generating the Lagrangian droplets at the inlet of the mid-field region. Number flux, diameter distribution, mean velocity, and other time-averaged statistics at several downstream locations are shown to agree well with the corresponding experimental data.

Flame self-interactions in an open turbulent jet spray flame

A three-dimensional direct numerical simulation database of an open turbulent jet spray flame representing a laboratory-scale burner configuration has been analyzed to investigate flame self-interactions (FSIs) in the presence of flow induced shear, to the best of the authors' knowledge, for the first time. The FSI occurrences [i.e., unburned gas mixture pockets (UBGPs), tunnel formations (TFs), tunnel closures (TCs), and burned gas mixture pockets (BGPs)] have been identified across the flame at different axial locations. It has been found that the interplays between turbulence, droplet evaporation, and chemistry have a significant influence on the topological nature of the flame surface. Close to the jet exit, the FSI events are found to occur toward the burned gas side of the flame, but moving further away from the jet exit, there are significant occurrences of FSI events within the flame where increasingly fuel-rich, low Damköhler number conditions occur. In this study, the FSI events have been found to be predominantly TFs and TCs, which is consistent with previous analyses of turbulent premixed flames and combustion of droplet-laden mixtures. However, non-negligible occurrences of UBGPs and BGPs are also observed in this case. The results obtained from this analysis have important implications from a modeling perspective where flame topologies have a significant influence on the nature of the flame surface, which will, in turn, affect the flame-surface based modeling approaches. Accordingly, the findings of the current analysis may need to be accounted for during the development of flame surface-based closures in the context of turbulent spray flames.

Large Eddy Simulation of a Turbulent Spray Burner Using Thickened Flame Model and Adaptive Mesh Refinement

Abstract The accurate simulation of two-phase flow combustion is crucial for the design of aeronautical combustion chambers. In order to gain insight into complex interactions between a flame, a flow, and a liquid phase, the present work addresses the combustion modeling for the large eddy simulation (LES) of a turbulent spray jet flame. The Eulerian–Lagrangian framework is selected to represent the gaseous and liquid phases, respectively. Chemical processes are described by a reduced mechanism, and turbulent combustion is modeled by the thickened flame model (TFM) coupled to the adaptive mesh refinement (AMR). The TFM-AMR extension on the dispersed phase is successfully validated on a laminar spray flame configuration. Then, the modeling approach is evaluated on the academic turbulent spray burner, providing a good agreement with the experimental data.

A new disinfectant technique for Campylobacter jejuni and spoilage bacteria on chicken skin using a high-pressure pulsed jet spray apparatus

Campylobacter jejuni (C. jejuni) is an important cause of human gastroenteritis worldwide and chickens are considered to be a major reservoir of infection. Recently, a novel high-pressure pulsed jet spray (HPPJS) technique has been developed in order to increase the efficiency of surface cleaning using an intermittent spray system. We evaluated the efficacy of this new technique for reducing C. jejuni and spoilage bacteria on chicken skin. Breast and thigh skin samples were inoculated with C. jejuni and then treated with chlorous acid water (CAW) (200 and 400 ppm), sodium hypochlorite (NaOCl) (100 and 200 ppm) or tap water using the HPPJS at 9 MPa for 5 or 15 s. The C. jejuni counts were determined by the most-probable-number (MPN) method. In addition, aerobic plate counts (APCs) and total coliform (TC) levels were measured using Petrifilm™. Treatment with CAW at 400 ppm or NaOCl at 200 ppm for 15 s showed the greatest efficacy, with reductions of 1.26–2.60 log10 MPN/cm2, 0.55–1.51 log10 CFU/cm2, and 0.92–1.78 log10 CFU/cm2 for C. jejuni, APCs, and TCs, respectively. These results suggest that HPPJS with chemicals is a highly effective technique for the reduction of C. jejuni and spoilage bacteria on chicken skin.

MICRO-HARDNESS OF THE PARTICLES OF COATING AT ELECTRIC-ARC SPUTTERING WITH PULSING JET SPRAYING

Intense oxidation of sputtered metal happens to be at electric-arc sputtering, due to oxygen, contained in the air, it leading to drastic reduction of the content of alloying elements in the coating.This work contains a method of evaluation of micro-hardness of the particles of the coating, deposited with pulsating air supply into the area of electrodes melting by introducing an additional element into the spraying head of the electric-arc metallizator Also performed was estimation of the amount of non-metallic inclusion. Also included are the results of alternations in particles micro-hardness, depending upon the frequency of pulsations at EAM with application of a pulsating spraying jet.

Fire Fighting Robot Using IoT

In the present day, there are fire accidents are increasing rapidly, it becomes very hard for a fireman to save someone’s life. We cannot appoint a person on that accidental place to continuously observe for an accidental fire where the robot can do it very easily. Therefore, in such situation robot comes in picture. Fire fighting robot will detect fire remotely. These robots are mostly useful for industries level where the possibility of accidental fire is more. The Fire fighting robot can detect fire and controlling it automatically by using the gas sensor and temperature sensor. It has gear motors and motor drivers for controlling the movement of the robot. A relay circuit is used to control the pump and when the robot will detect fire then the robot will communicate with the microcontroller (Arduino UNO R3) via Bluetooth module. The fire fighting robot has a water jet spray that is used to sprinkling water. The sprinkler will move easily towards the required direction. At that time if some obstacle will detect when the robot will be moving towards the source of fire, then the robot has capable of avoiding an obstacle. It will provide a Graphical User Interface for Arduino operation using android. It detects obstacles by using ultrasonic sensors up to a range of 80 m. Communication between the robot and Mobile phone will take place via Bluetooth, which has a GUI to control the movement of the robot. When mobile gets connected to the Mobile phone through Bluetooth after that it will set the module name, baud rate. It is feasible to implement Bluetooth communication between Mobile phones and microcontrollers. Android controlled robots can be used easily in today’s busy life such as in the market, using for controlling home systems, companies, etc. Nowadays, the development of apps for Android in Android SDK is easy without any cost.

Design and test data analysis of a heating system for a wellhead room in a coal mine

This paper introduces the design and the test data analysis of a heating system for a wellhead room in a coal mine. Combined with the system design, the actual operational data of the water jet spray heat exchange device was analysed to calculate some coefficients, the thermal efficiency and the spray heat resistance. For demonstrating the practical application of this heating system, a field test was conducted where the outdoor environment temperature was -7.4°C. The air outlet temperature of the air heating unit was 27.8°C and the air inlet temperature of a wellhead room after mixing the outdoor air and the hot air supplied from the air heating unit was 11.5°C. This performance data demonstrated that this mine return air heat exchange system well satisfies the heating requirement for the wellhead facilities in coal mines located in cold areas and shows significant advances in the designing and operation of the heating system.

Liquid jet fire: The impact of rainout on the predicted hazard

AbstractAlthough jet fires may pose a major hazard in the chemical processing industry, they are typically modeled with semi‐empirical models that were developed based on experimental results of natural gas. In most semi‐empirical models, it is typically assumed that all liquid is instantly vaporized upon discharge and combusted fully in the jet. In reality, depending on discharge fuel momentum, elevation, temperature, and liquid fuel properties, a significant percentage of liquid fuel may fall to the ground and burn as a pool rather than contribute to the jet fire. As a result, such a model may predict overly conservative results when used to model liquid spray jet fires. In this study, a computational fluid dynamic (CFD) model previously proved to be able to predict a subcooled liquid jet fire flame shape, length, rain out condition, and thermal radiation level was used to investigate how some key factors affect the percentage of liquid fuel that could combust in jet fire. Results were used to adjust semi‐empirical jet fire models to take account of rainout effect. Examples are given for rainout jet fire cases predicted with this revised semi‐empirical model.

Unsteady flamelet modeling for N[formula omitted]H[formula omitted]/N[formula omitted]O[formula omitted] flame accompanied by hypergolic ignition and thermal decomposition

In this study, the applicability of the flamelet approach to numerical simulations of hydrazine (N2H4)/nitrogen tetroxide (NTO, N2O4) combustion, in which hypergolic ignition and thermal decomposition occur, is investigated in terms of two-dimensional numerical simulations of two types of N2H4/NTO jet flames, namely, the gaseous N2H4/NTO jet flame and the N2H4 spray jet flame in the gaseous NTO stream. In case of the gaseous jet flame, the numerical simulation is performed employing the unsteady flamelet/progress variable (UFPV) approach. In case of the spray jet flame, on the other hand, a non-adiabatic unsteady flamelet/progress variable (NAUFPV) approach, which combines the UFPV approach and the non-adiabatic flamelet/progress variable (NAFPV) approach, is proposed. The validity of these and some other existing flamelet approaches is investigated by comparison with the results obtained using the exact approach, in which detailed chemical reactions are directly solved. The results show that the UFPV and NAUFPV approaches drastically improve predictions of the N2H4/NTO gaseous and spray combustion behavior, respectively, including the ignition process, the flame lift-off height, and the distributions of temperature and chemical species concentrations. This indicates that self-decomposition flame of fuel is successfully captured by the UFPV approach, and that the NAUFPV approach can additionally take into account the heat loss effect due to evaporation of droplets.

Effect of angled spray nozzle designs on spray distribution and droplet spectrum

ABSTRACT New technologies have been developed to promote uniform, sustainable, safe and effective application of phytosanitary products. In this scenario, spray nozzles of different designs and jet angles can optimize application. Therefore, we aimed to analyze the effect of angled flat fan spray nozzles on spray pattern uniformity and droplet spectrum formation. The spray volumetric distribution of standard flat fan, double flat fan and the new angled flat fan spray nozzle, using two spray volumes were assessed. For that, the spray pattern distribution and the coefficient of variation (CV) were determined. The droplet spectrum characterization produced by the same treatments was performed in a real-time particle size analyzer. Also the effect of adding a fungicide mixture associated with an adjuvant on droplet formation was evaluated. All spray nozzles, regardless of design and spray volumes evaluated, produced CV values below 7%, considered acceptable by international uniformity standards. There was a difference in spray pattern according to the spray nozzle design and spray volume. It was evidenced that the main differences found in droplet spectrum occurred due to spray nozzle type, spray mixture and nominal flow rate, with little influence of spray jet angled or spray volumes.

Numerical simulation of kerosene jet in crossflow atomization and evaporation under the elevated pressure and oscillating air-flow condition

The liquid jet penetration, breakup, and spray evaporation in crossflows, which find their importance in aeroegines, are investigated in the steady and oscillating air-crossflows using detailed numerical simulation to improve the understanding of the influence of the inflow oscillation that is commonly caused by the combustion instability on this complex process. To clarify the oscillation effects on jet atomization, the crossflow multimode breakup is considered, incorporating its unique characteristics of holding two different breakup behaviors, i.e., shear breakup and bag breakup. The oscillation frequency is set to be 500 Hz according to previous research on combustion instability. The results show that the liquid jet trajectory under steady air-flow condition is in good agreement with the analytical solution and experimental correlation, around which the oscillating cases present a reasonable breakup behavior. The vortex morphology behind the liquid jet is found to largely affect the droplets evaporation and their downstream delivery. Moreover, the oscillating air inflow condition shows an enhanced atomization and evaporation property, producing the smaller Sauter mean diameter (SMD) and higher fuel vapor distribution at the leeward downstream region. This behavior of atomized spray in the oscillating crossflow suggests that the combustion instability could impose a significant effect on the subsequent spray combustion process.

Numerical investigation of natural gas-diesel dual-fuel engine with different piston geometries and radial clearances

Piston crevices are the major source of hydrocarbon emissions for spark ignition engine. It is similar for natural gas-diesel (NG-diesel) dual fuel engine, maybe even worse in high compression ratio and lean burn NG-diesel engine at low load. The aim of this paper is to numerically investigate combustion and methane emissions of YC-6K NG-diesel engine with different radial clearances. Four piston clearances (0.5 mm, 0.76 mm, 1.0 mm and 1.54 mm) and four different piston geometries were employed. Three diesel-spray-orientated (DSO) piston bowls were designed based on diesel injectors of YC-6K with the purpose of supplying more natural gas and air mixture to diesel spray jets, in addition, a protrusion-ring was designed at the bowl rim of DSO pistons to enhance methane flame propagation. The results showed that both in-cylinder pressure and heat release rate (HHR) of all three DSO pistons increased due to higher turbulence kinetic energy comparing to the original piston design (OPD). Methane emissions of pistons with radial clearance of 0.76 mm were lower than that of other radial clearances for DSO pistons.

Effects of particle formation behavior on the properties of fish oil microcapsules fabricated using a micro-fluidic jet spray dryer

Abstract Fish oil was encapsulated with whey protein isolate (WPI) as wall material using a Micro-Fluidic Jet Spray Dryer. The effects of core/wall material ratio, drying temperature and total solids content on the properties of microcapsules were studied. Low core/wall material ratios at 1:5 and 1:3 resulted in high encapsulation efficiency (EE) and excellent oxidative stability of microparticles during storage. Reducing the inlet temperature from 160 to 110 °C remarkably decreased EE from around 99 to 64.8%, associated with substantial increases in peroxide value during storage. The total solids content mainly altered the morphology of microcapsules, showing little influence on EE and oxidative stability. We proposed that the different drying conditions impacted on particle formation behavior during spray drying, which could be a crucial factor responsible for the differences in the quality attributes of microparticles. A low core/wall material ratio and high drying temperature facilitated the formation of a rigid protein skin at droplet surface during drying, whereas a high solids fraction in the droplets could limit possible droplet shrinkage. These factors contributed positively to the encapsulation of the lipophilic core material.

Splashing of liquid droplet on a vibrating substrate

The unsteady axisymmetric problem of a liquid drop impacting onto a rigid vibrating substrate is studied. Initially, the drop is spherical and touches the flat substrate at a single point. Then, the substrate starts to move toward the drop and vibrate with a small amplitude and high frequency. The early stage of the impact is studied by using the potential flow theory and the Wagner approach in dimensionless variables. The effect of the substrate vibration on the drop impact is described by a single parameter. It is shown that the vibration of the substrate leads to oscillations of the pressure in the contact region. The low-pressure zone periodically appears in the wetted part of the substrate. The low-pressure zone can approach the contact line, which may lead to ventilation with separation of the liquid from the substrate. The magnitude of the low pressure grows in time. The acceleration of the contact line oscillates with time, leading to splashing of the droplet with the local increase of the thickness of the spray jet sheet at a distance from the contact line. The phase shift of the substrate vibration with respect to the impact instant is not studied. Splashing can be produced only by a forced vibration of the substrate. The impact onto an elastically supported rigid plate does not produce splashing. The obtained results and the theoretical model of the initial stage of drop impact are valid for certain ranges of parameters of the problem.

Effect of successive sprays on liquid distribution in fluidized beds

In processes such as Fluid Coking™, agglomerate formation should be minimized since it reduces the yield of valuable products, and degrades operability because of the fouling of internals. An experimental model, consisting of an aqueous solution of gum arabic with a dye, has been successfully developed to simulate the formation of agglomerates in the Fluid Coking™ process, where bitumen is sprayed into a fluidized bed of coke particles The particles wetted by a spray could be predicted by assuming that all the particles in the wake of bubbles formed from the tip of the spray jet have been wetted by the injected liquid. The transfer of liquid from particles wetted with the spray to dry bed particles was relatively ineffective, as the number of wet particles increased by only 50%. With successive liquid injections, the proportion of the liquid trapped in agglomerates increases in latter injections: large agglomerates from earlier injections accumulate above the grid and are carried by gas bubbles into the spray jet cavity, where they seed fresh agglomerates.

A device for harvesting and utilization of non-grain part of crop and fertilization

An effective method of harvesting grain crops using straw for fertilization, which can be carried out by installing a device on the harvester for spraying the crushed straw mass with a working liquid using a pneumatic slot sprayer designed in Kuban State Agrarian University. The device and the process of operation of this device with pneumatic slotted sprayers of working fluid are considered. Various parameters of sprayers have been studied: the air pressure supplied to the spray jet and the position of the equalizing tank that regulate the static pressure of fertilizers for setting the specified flow rate.