Spray Cloud Research Articles

Superheated fuel sprays: A comparative study of flash boiling ammonia fuel sprays with methanol, ethanol, and gasoline for multi-hole fuel injection

The rising energy demand creates a huge need to explore and implement sustainable alternative fuels e.g., ammonia, hydrogen, methanol, ethanol, etc. to mitigate emission challenges and significantly lower CO2 emissions. Ammonia has gained much attention as promising alternative fuels for internal combustion engines due to its carbon-neutral nature, which can reduce the carbon footprint in transportation. The advantages of ammonia as a fuel includes carbon-free nature, high volumetric energy density compared to hydrogen, and renewable resource-based production. However, there is lack of the deep understanding of the ammonia spray characteristics and fuel-air mixing process, in particular, the superheated spray, which potentially improve the vaporization and fuel-air mixing. This study focused on investigating the impact of superheating on ammonia, methanol, ethanol, and gasoline fuel sprays by heating the fuel injector tip from non-evaporating to flash boiling temperatures. The fundamental spray parameters were investigated in a constant volume spray chamber using a multihole solenoid driven injector for 150 bar constant injection pressure under 10 bar and 30 bar chamber pressure conditions. To observe flash boiling and the dual-phase flow, a Z-type Schlieren imaging technique, known for its sensitivity to density gradients, was used. The experimental results indicated that ammonia spray behavior significantly differed from other tested fuels for both under cold and superheated conditions. The effect of superheating on methanol, ethanol, and gasoline sprays was very similar, resulting in the shrinkage of spray width and the merging of adjacent plumes into a single thick cloud of spray for elevated tip temperatures. However, ammonia sprays exhibited considerable differences in evaporative conditions, developing a more significant dual phase flow than other fuels upon increment in tip temperature. Overall, the results showed that the spray tip penetration and area for all tested fuels reduced upon heating.

Exposure assessment during paint spraying and drying using PTR-ToF-MS.

Spraying is a common way to distribute occupational products, but it puts worker's health at risk by exposing them to potentially harmful particles and gases. The objective of this study is to use time-resolved measurements to gain an understanding of spray applications at the process level and to compare them to predictions of exposure models. We used proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) at 1-s time resolution to monitor the gas phase concentration of the solvents acetone, ethanol, butyl acetate, xylene and 1-methoxy-2-propy acetate during outdoor spraying and indoor drying of metal plate under various conditions of outdoor air supply. We found that during spraying, gas-phase exposure was dominated by the more volatile solvents acetone and ethanol, which exhibited strong concentration variations due to the outdoor winds. During drying, exposure strongly depended on the strength of ventilation. Under conditions with high supply of outdoor air, our measurements show a near-exponential decay of the solvent concentrations during drying. Conversely, under conditions without outdoor air supply, the drying process required hours, during which the less volatile solvents passed through a concentration maximum in the gas phase, so that the exposure during drying exceeded the exposure during spraying. The concentrations measured during spraying were then compared for each of the substances individually with the predictions of the exposure models ECETOC TRA, Stoffenmanager, and ART using TREXMO. For these conditions, ECETOC TRA and Stoffenmanager predicted exposures in the measured concentration range, albeit not conservative for all solvents and each application. In contrast, ART largely overestimated the exposure for the more volatile solvents acetone and ethanol and slightly underestimated exposure to 1M2PA for one spraying. ECETOC TRA and ART do not have options to predict exposure during drying. Stoffenmanager has the option to predict drying together with spraying, but not to predict the drying phase independently. Our study demonstrates the importance of considering both the spray cloud and solvent evaporation during the drying process. To improve workplace safety, there is a critical need for enhanced exposure models and comprehensive datasets for calibration and validation covering a broader range of exposure situations.

Field Study to Assess UASS Mosquito Adulticiding: Methods and Data

Highlights Mosquito adulticiding over operationally relevant areas is feasible using UASS. Wind speed plays an important role in the spray landing position, as expected based on previous studies using CASA. Results are based on both passive and active collectors, including flat cards, rotary impingers, and bottle brushes. Over 1900 total samples were collected in 8 trials, and elevated samplers allowed analysis of the descent of the droplet cloud. Abstract. A spatially extensive experiment was designed to evaluate the effectiveness of Uncrewed Aerial Spray Systems (UASS) in mosquito adulticiding. The practice of adulticiding uses very fine droplets (DV0.5 <50µm). The objective is to fill a volume of air with fine droplets that a flying adult mosquito will encounter in flight. A field program was designed with samplers as far as 500 m downwind from the UASS flight line. A total of over 1900 samples were collected over the course of eight trials. Both passive and active collectors were deployed. Tests were conducted in the early morning and were generally successful in terms of meteorological conditions and data collection. Elevated samplers successfully tracked the descent of the spray cloud, and spray was collected from the most distant samplers. The known dependence of spray movement on wind speed that has been widely observed and codified into label language for Crewed Aerial Spray Aircraft (CASA) was observed. Very low wind speed conditions are problematic for adulticiding in general, and undesirable near-field deposition of adulticiding spray was observed in the data presented here under low wind speed conditions. It needs to be emphasized that much more data needs to be collected before statistically robust conclusions can be drawn. Generally, these data show that UASS can be used to disperse very fine spray droplets over areas representative of operational adulticiding. This paper presents and discusses spray movement and deposition, a second paper is in preparation comparing these data to existing models of spray dispersion and deposition from UASS spraying. A third paper examining mortality from UASS adulticiding has been published. Keywords: Adulticiding, Pesticide drift, UASS Spraying, UAV.

Effectiveness of water spray in infrared signature suppression of engine plumes

In modern military aircraft, reducing the Infrared (IR) signature is critical for stealth. However, the IR signature from the engine plume is particularly challenging to address due to its link with engine operation and its unique, non-continuous characteristics. In this study, a novel approach using a water spray cloud to attenuate the IR signature from the engine plume was proposed, and it is experimentally verified by employing a micro-turbine engine. Six water nozzles generated the water spray cloud, and IR signature reduction was quantitatively measured using an IR spectrometer. Variations in water injection pressure and observation angles were used as experimental conditions. The results revealed that the IR signature was reduced with higher water injection pressure, attributed to the increased thickness of the water spray cloud. The IR signature from the engine plume was effectively attenuated by the water spray cloud in overall, with a more pronounced effect observed at lower observation angles due to the extended path within the cloud. The potential of water spray clouds for enhancing the IR stealth of military aircraft is underscored by this research.

Artist's Statement: Asthma.

During my pediatrics rotation at a community hospital in Baltimore, I was able to witness the high prevalence of asthma in the youth of the city; I saw patient after patient present to the emergency department in respiratory distress from asthma exacerbations. Upon arrival, they received nebulizer treatments that would envelop them in a cloud of bronchodilator spray seeping out from their masks. My digital painting Asthma, on the cover of this issue, represents a composite of my experiences seeing patients with asthma, or indeed any patient burdened with medical equipment. The girl in my portrait is wearing a nebulizer mask, which I implied to be the source of the mist obscuring her. However, I also wanted to give the sense that she is being suffocated by her environment through my portrayal of her eyes piercing through the mist. The round shapes of her curly hair echo the shimmering clouds, as if they are each an extension of the other. The past few years of near-constant masking due to the COVID-19 pandemic have forced us to become accustomed to seeing faces with the lower half entirely covered, with only the eyes exposed. So much can be communicated through the eyes, yet there is still more left unsaid when they are all we can see.Asthma

Comparative Analysis of Injection of Pyrolysis Oil from Plastics and Gasoline into the Engine Cylinder and Atomization by a Direct High-Pressure Injector

The article discusses the results of experimental studies on the course of pyrolysis oil injection through the high-pressure injector of a direct-injection engine. The pyrolysis oil used for the tests was derived from waste plastics (mainly high-density polyethylene—HDPE). This oil was then distilled. The article also describes the production technology of this pyrolysis oil on a laboratory scale. It presents the results of the chemical composition of the raw pyrolysis oil and the oil after the distillation process using GC-MS analysis. Fuel injection tests were carried out for the distilled pyrolysis oil and a 91 RON gasoline in order to perform a comparative analysis with the tested pyrolysis oil. In this case, the research was focused on the injected spray cloud analysis. The essential tested parameter was the Sauter Mean Diameter (SMD) of fuel droplets measured at the injection pressure of 400 bar. The analysis showed that the oil after distillation contained a significant proportion of light hydrocarbons similar to gasoline, and that the SMDs for distilled pyrolysis oil and gasoline were similar in the 7–9 µm range. In conclusion, it can be considered that distilled pyrolysis oil from HDPE can be used both as an additive for blending with gasoline in a spark-ignition engine or as a single fuel for a gasoline compression-ignition direct injection engine.

Electrostatic fields for the control of evaporating charged fuel sprays

The current socio-economic shift towards electrification of the transport sector and development of hybrid thermal–electric propulsion systems provides new opportunities for the development of ‘clean’ aviation technologies. In this work, the use of electrostatic fields to control the location of electrically charged fuel droplets is proposed as a novel technology to enhance pre-evaporation of liquid sprays in confined spaces. An electrospray in cross-flow is numerically investigated using large-eddy simulations for a range of flow and droplet conditions in order to study the feasibility of the approach. A deterministic model is further introduced to compute the trajectory of single droplets in a steady cross-flow. This enables a separation of the effects of turbulence, droplet repulsion and evaporation through comparison with data obtained from the large-eddy simulations, and at the same time provides a cheap computational tool to explore a wider range of operating conditions. It is shown that external electrostatic fields below the breakdown threshold of air can significantly change the trajectory of charged droplets at moderate flow velocities. Moreover, electrostatic forces acting in the opposite direction of the mean cross-flow can potentially be used to stabilise the spray position within a confined region, hence allowing for an increase of the residence time available for full evaporation. The application and modulation of such electrostatic forces is envisioned as a new paradigm to achieve ‘targeted evaporation’ in next-generation hybrid thermal–electric aero-engines and to improve the fuel-oxidiser mixing quality. The electrical power associated with the external electrostatic field to achieve droplet stabilisation is negligible compared to the thermal power released by complete combustion of the injected fuel. In addition, it is shown that stabilisation of the droplets enhances the evaporation rate (by more than 30%) and mixing quality due to an increase of the relative velocity between the droplets and the gas flow, as well as the turbulence induced by the stagnating spray cloud. The results of this work offer new insights for the development of advanced fuel injection strategies based on electrohydrodynamics.

Analysis of the spatial and temporal distribution of a spray cloud using commercial LiDAR

Pesticide spray drift is an important cause of environmental damage. It can also cause phytotoxicity in non-target areas, and reduce efficacy. Suitable methods for evaluating the spray drift are necessary to reduce these hazards and improve the utilisation of pesticides. However, most conventional spray drift evaluation methods based on sampling patterns that are labour-intensive, expensive, and time-consuming. Moreover, the temporal distribution information of drifting droplets cannot be easily obtained. In this study, a spray cloud evaluation method is investigated based on a common commercially available light detection and ranging (LiDAR) system. Its feasibility was verified in terms of evaluating a spray cloud, and the effect of the wind speed on the relationship between the number of cloud points and deposit volume was experimentally studied. The optimal scanning area of the LiDAR was explored and a simple statistical model developed based on the experimental data developed. The model was validated and had a high coefficient of determination (R 2 = 0.71). The deposit volume predicted by the model also exhibited a high correlation coefficient (r = 0.89) and coefficient of determination (R 2 = 0.79) with respect to the measured deposit volume on the collector, and it satisfies the significance test at the 0.01 level. The LiDAR point cloud facilitated an intuitive analysis of the spatiotemporal distribution of drifting droplets in the air, which is difficult to achieve using passive sampling. • Commercial LiDAR system used to evaluate pesticide spray cloud. • Number of LiDAR cloud points correlated with volume measured on polyethylene lines. • Spatiotemporal distribution of drifting spray can aid suitable buffer zone setting. • Laboratory experiments explore optimal scanning area for LiDAR. • Results validate the feasibility of model to predict spray volume airborne.

Effect of the Airblast Settings on the Vertical Spray Profile: Implementation on an On-Line Decision Aid for Citrus Treatments

Airblast sprayers are widely used for the application of plant protection products (PPP) in citrus. Adaptation of the vertical distribution of the spray cloud to the canopy (density, shape and size), is essential to deposit an adequate amount of PPP on the target and to reduce losses (drift, runoff). Vertical spray profiles of three air-assisted axial fan hydraulic sprayers with different configurations and settings were obtained to evaluate the effect of these settings on the vertical spray profile. From the analysis of the empirical results, the impact of operational settings (nozzle, air volume and flow rate) on treatment efficiency is assessed. The empirical database generated in this work has been employed to feed the Citrus VESPA model, a highly intuitive, web-based decision aid tool that helps farmers to easily estimate the vertical spray profiles generated by their particular sprayers and settings and how these influence deposition and potential drift. The tool can also be used to determine the effect and importance of adequately selecting, orienting and opening/closing nozzles and optimizing volume application rate and fan speed, in order to adjust the application to the actual vegetation, with the aim of saving resources and reducing risks to humans and the environment.

Characterisation of the Tyre Spray Ejected Downstream of a Bluff Automotive Body

<div class="section abstract"><div class="htmlview paragraph">Considerations of surface contamination and airborne spray are becoming increasingly significant throughout the automotive design process. Advanced driver assistance systems, such as autonomous cruise control, are growing in popularity. These systems rely on external sensors, the performance of which may be impaired by both direct obstruction and spray. Existing experimental methods of assessing front-end surface contamination and wiper performance have typically utilised fixed spray-grids positioned upstream of the vehicle. The resulting spray is largely steady in nature, in contrast to the unsteady flow-field and tyre spray that would be produced by preceding vehicles. This paper presents the numerical analysis of the spray ejected downstream of a simplified automotive body. The continuous phase (air) is solved using a DDES-based approach coupled with a Lagrangian representation of the dispersed phase (water). Two configurations are examined, a square-back configuration and a variation employing 20° rear-end side tapers. The inclusion of side tapering results in a significant change in wake topology and the resulting spray cloud. Good agreement is achieved between initial single-phase predictions of the continuous phase and existing experimental data. The spray cloud of both configurations is found to be highly unsteady, driven by vortical structures in the near- and far-wake, and is altered significantly by what are relatively minor changes to the geometry. Proper Orthogonal Decomposition reveals comparable spatial modes in the mass flux field of the dispersed phase and the continuous phase velocity field downstream of the vehicle. However, the correlation between the temporal coefficients of these modes is relatively weak. This highlights the presence of slip effects between the two phases, coming as a result of particle inertia, and the need to consider both phases simultaneously in future studies of spray dynamics.</div></div>

NUMERICAL 3D MODELING OF THE PROCESS OF HIGH-SPEED SPRAYING

The article is devoted to the formation of a spray cloud after the interaction of an ultrajet with an obstacle. Variants of different mutual arrangement of the ultrajet and the surface on which the impact occurs are considered. Evaluation of the effectiveness of the choice of angle is carried out by analyzing the values of the coverage area of the target with a spray, set at a fixed distance from the impact site. It is accepted that a large contact area of the spray with the target surface is the best possible result. The research was carried out within the framework of the RFBR grants 18-29-18081 and 19-38-90228\19, the grant of the President of the Russian Federation for state support of the leading scientific schools of the Russian Federation NSh-3778.2018.8 and grants from the Innovation Promotion Foundation under the UMNIK-18 program in accordance with contract No. 14727GU/2019 and No. 14549GU/2019.

Understanding the collapse of flash-boiling sprays formed by multi-hole injectors operating at low injection pressures

Sprays consisting of initially separated plumes, which are generated by multi-hole injectors in strong flash-boiling conditions, may collapse and form a single spray cloud. It has been shown that for high-pressure injection systems (≥5 MPa), such behaviour is dependent on both the superheat and the geometrical configuration of the injector; while the spray collapse in low-pressure systems (≤1 MPa) is not yet understood. To the best of the author's knowledge, this is the first study aimed at filling this information gap. The principal novelty of this work is related to understanding the collapse in low-pressure systems, in terms of the different numbers of nozzles and the difference in the effects from flash boiling between low- and high-pressure sprays.The results showed that the flash-boiling sprays formed by the two- and six-hole injectors were substantially different, which is similar behaviour as for high-pressure sprays. The major difference from the sprays formed at high pressure is that the flash boiling does not result in an increased penetration (in relation to the subcooled conditions). This distinct behaviour was linked with a different jet break-up regime, and different droplet size reduction due to flash boiling, both depending on the injection pressure. This work discusses that the importance of the aerodynamic drag force due to a stronger droplet size reduction in the case of low-pressure sprays can be increased more than twofold compared to the high-pressure sprays.The lack of increased penetration leads to an important finding in terms of practical applications. In contrast to high-pressure systems, flash boiling will not lead to enhanced wall wetting regardless of the number of nozzles.This study has revealed that the interaction of the spray plumes is not sufficient to cause a strong spray collapse and the formation of the single jet-like spray structure. The necessary additional factor is the flow acceleration in the axis of the injector. The results highlighted the crucial role of the circular pattern, which already in subcooled cases led to the creation of flow conditions promoting axial propagation of a gaseous medium; while in the event of flash boiling, it prevented the surrounding air from entering the centre region of the spray cloud.

Effect of MDI Actuation Timing on Inhalation Dosimetry in a Human Respiratory Tract Model.

Accurate knowledge of the delivery of locally acting drug products, such as metered-dose inhaler (MDI) formulations, to large and small airways is essential to develop reliable in vitro/in vivo correlations (IVIVCs). However, challenges exist in modeling MDI delivery, due to the highly transient multiscale spray formation, the large variability in actuation–inhalation coordination, and the complex lung networks. The objective of this study was to develop/validate a computational MDI-releasing-delivery model and to evaluate the device actuation effects on the dose distribution with the newly developed model. An integrated MDI–mouth–lung (G9) geometry was developed. An albuterol MDI with the chlorofluorocarbon propellant was simulated with polydisperse aerosol size distribution measured by laser light scatter and aerosol discharge velocity derived from measurements taken while using a phase Doppler anemometry. The highly transient, multiscale airflow and droplet dynamics were simulated by using large eddy simulation (LES) and Lagrangian tracking with sufficiently fine computation mesh. A high-speed camera imaging of the MDI plume formation was conducted and compared with LES predictions. The aerosol discharge velocity at the MDI orifice was reversely determined to be 40 m/s based on the phase Doppler anemometry (PDA) measurements at two different locations from the mouthpiece. The LES-predicted instantaneous vortex structures and corresponding spray clouds resembled each other. There are three phases of the MDI plume evolution (discharging, dispersion, and dispensing), each with distinct features regardless of the actuation time. Good agreement was achieved between the predicted and measured doses in both the device, mouth–throat, and lung. Concerning the device–patient coordination, delayed MDI actuation increased drug deposition in the mouth and reduced drug delivery to the lung. Firing MDI before inhalation was found to increase drug loss in the device; however, it also reduced mouth–throat loss and increased lung doses in both the central and peripheral regions.

Numerical simulation of fuel spraying into an industrial object

Numerical simulation of fuel spraying into industrial objects is described in this paper. This spatter may be caused by a vehicle or storage tank accident. Prediction of fuel spill is the main aim of simulations that allow predicting possible sources of secondary fires. Numerical simulations are based on the solution of the system of Navier-Stokes equations complemented by the solution of Lagrangian spray cloud and thin fluid film. The simulation results will help to identify better fire prevention and other preventive measures to minimize fire damage.

Physical characteristics of splash and spray clouds produced by heavy vehicles (trucks and lorries) driven on wet asphalt

Heavy vehicles rolling on wet roads produce splash and spray clouds. These aerosols reduce the visibility of other drivers, contribute to a small, but quantifiable proportion of road traffic accidents and affect the operational capabilities of autonomous vehicles travelling near them. Even though knowing the physical properties of these aerosols is essential for testing and validating sensors for environment perception and recognition of autonomous vehicles, there is little information about them.In this work the physical characteristics of spray clouds produced by heavy vehicles rolling on wet asphalt were measured by optical methods. Time resolved droplet size, mass concentration, number density, light extinction and contrast attenuation parallel and perpendicular to the travelling direction of the vehicle were measured. Vehicle velocity, vehicle configuration and water depth were varied during the tests.Results show that the average droplet diameter ranges between 100 and 400 μm with maximum diameters of almost 4 mm. Mass concentration gamuts between 0,2 and 0,7 kg/m3 with peaks surpassing 1 kg/m3 while number density spans between 20 and 40 cm−3 and occasionally exceeds 100 cm−3. Light extinction can reach levels as high as 0,2 m−1 and contrast, evaluated from images, can reach values under 0,1.

Effect of H2O2 Antiseptic on Dispersal of Cavitation-Induced Microdroplets

The persisting outbreak of SARS-CoV-2 has posed an enormous threat to global health. The sustained human-to-human transmission of SARS-CoV-2 via respiratory droplets makes the medical procedures around the perioral area vulnerable to the spread of the disease. Such procedures include the ultrasonic dental cleaning method, which occurs within the oral cavity and involves cavitation-induced sprays, thus increasing the risk of pathogen transmission via advection. To understand the associated health and safety risks for patients and clinicians, it is critical to understand the flow pattern of the spray cloud around the operating region, the size and velocity distribution of the emitted droplets, and the extent of fluid dispersion until ultimate deposit on surfaces or escape through air vents. In this work, the droplet size and velocity distributions of the spray emerging from the tip of a free-standing common ultrasonic dental cleaning device were characterized via high-speed imaging. Deionized water and 1.5% and 3% aqueous hydrogen peroxide (H2O2) solutions were used as working fluids, with the H2O2—an established oxidizing agent—intended to curb the survival of virus released in aerosols generated from dental procedures. The measurements reveal that the presence of H2O2 in the working fluid increases the mean droplet size and ejection velocity. Detailed computational fluid dynamic simulations with multiphase flow models reveal benefits of adding small amounts of H2O2 in the feed stream of the ultrasonic cleaner; this practice causes larger droplets with shorter residence times inside the clinic before settling down or escaping through air vents. The results suggest optimal benefits (in terms of fluid spread) of adding 1.5% H2O2 in the feed stream during dental procedures involving ultrasonic tools. The present findings are not specific to the COVID-19 pandemic but should also apply to future outbreaks caused by airborne droplet transmission.

Numerical Simulation of the Electrostatic Coating Process: the Effect of Applied Voltage, Droplet Charge and Size on the Coating Efficiency

<div class="section abstract"><div class="htmlview paragraph">Electrostatic Rotary Bell Sprayers (ERBSs) have been widely used in the painting industry, especially in the automotive and aerospace industries, due to their superior performance. The effects of the applied voltage and paint droplet charge values on the spraying pattern and coating Transfer Efficiency (TE) in the ERBS, including a high-voltage ring for spray cloud control, have been studied numerically in a wide range of droplet size distribution. A 3D Eulerian-Lagrangian numerical analysis is implemented under the framework of the OpenFOAM package. The fluid dynamics of turbulence, primary and secondary breakup procedures are modeled using a large eddy simulation (LES) model, Rosin-Rammler distribution, and modified TAB approach, respectively. Compared to the conventional ERBSs, in the current work an exhaustive exhibition of the airflow dynamic and spray pattern characteristics around the ERBS with outer high-voltage control-ring field pattern, i.e., velocity, vorticity, electric potential field, overspray, film thickness are reported. Our findings indicate that the control-ring around the rotary bell rim improves the coating procedure TE and produces a more harmonized and narrower spray plume. Our in-depth investigation clearly shows the importance of the droplet charge values, voltage quantity, and considered droplet size range on the film thickness and its corresponding quality that is obtained from the workpiece.</div></div>

Low-Pressure Injection of Water and Urea-Water Solution in Flash-Boiling Conditions

<div class="section abstract"><div class="htmlview paragraph">The flash-boiling effect in sprays has been shown to have the capability to decrease droplet diameters and spray penetration, as well as improve the vaporization process in gasoline direct injection systems. It has also been shown that in certain conditions, the effect on spray penetration can be the opposite. Under a high degree of overheating the spray collapse effect may appear and lead to increased spray penetration - flare flash boiling. Moreover, when the boiling is already strongly present in the nozzle it may lead to flow choking. Thus, the process is difficult to be controlled. While most studies so far have focused on high-pressure direct injection systems, we investigate the process in a low-pressure system to verify if the effects observed in high-pressure systems will be similar. The study was performed on two liquids, water and a urea-water solution, to limit any individual substance’s effects on the results and to improve the practical importance of the study. The results showed no increased penetration in any of the flash-boiling cases, although at the highest considered temperatures the two plumes tend to form a single spray cloud. Although the characteristics were similar for both studied liquids, in certain measurement conditions the differences in almost all analysed spray parameters were considerable. Moreover, the study has shown that the flash-boiling effect can be considered as an effective way to improve jet and droplet break-up while avoiding a pressure increase in low-pressure injection systems.</div></div>

On the Effectiveness of a “Tractor Mounted Road Sanitizing Unit” Designed to Combat COVID-19 Spread

Under the situation of a dreadful spread of COVID-19 throughout the world, it is an absolute necessity to develop proper strategy for its containment. Toward this end, a novel outdoor disinfection system is designed for effective sanitization of long stretches of highways, market places, shopping malls, etc., where there are large traffic and high chances of spreading of the virus. The disinfection system utilizes available tractor powered road tankers of municipal houses, and it has specific features for maximum sanitization coverage. This is achieved through a distributed spraying nozzle mounted around the tank along with two extendable hand sprayers with flexible hoses. The effectiveness of the spray system is studied using an image processing technique. The spray cloud is illuminated by a double-pulsed Nd:YAG laser, and the images are captured using a Nikon D3300 DSLR camera. The average droplet size of the spray coming out from the nozzle is measured, and finally, the area of influence of the spray is obtained from a statistical analysis.

Numerical analysis of fuel injection configuration on nitrogen oxides formation in a jet engine combustion chamber

Emissions of nitrogen oxides from the aviation sector, contrary to the land-based sources, have doubled compared to 1990. Aircraft unique location in the upper atmosphere and daily growth of air-based traffic require particular attention to the effects of these emissions. One way to cope with this problem is to develop and design more efficient combustion systems. In this research, the numerical modelling of combustion process inside a jet engine combustion chamber is presented. The investigated chamber is a theoretical can type chamber mounted with a double stage radial swirler. The advanced k-zeta-f turbulence model was utilised to model the turbulent behaviour, while the spray process was described by the Euler Lagrangian spray modelling approach. Two different modelling approaches for describing the combustion process were employed: reduced chemical mechanism and the 3-zone extended coherent flame (ECFM-3Z) combustion model. Considering the analysis of relevant physical quantities and taking into account the reduction of computational costs while using the ECFM-3Z combustion model, it was employed for analysis of the influence of spray and emission processes by varying number and positioning of fuel introduction nozzle holes. Increase in the number of nozzle holes and their correct positioning can result in emission reduction up to 60%. Such behaviour could be addressed to the specific spray cloud formation and smaller high-temperature regions. Results showed that the presented model can be used as a modern design tool in the early stage of the combustion chamber development.