Spray Impingement Research Articles

Fusing an agent-based model of mosquito population dynamics with a statistical reconstruction of spatio-temporal abundance patterns.

The mosquito Aedes aegypti is the vector of a number of medically-important viruses, including dengue virus, yellow fever virus, chikungunya virus, and Zika virus, and as such vector control is a key approach to managing the diseases they cause. Understanding the impact of vector control on these diseases is aided by first understanding its impact on Ae. aegypti population dynamics. A number of detail-rich models have been developed to couple the dynamics of the immature and adult stages of Ae. aegypti. The numerous assumptions of these models enable them to realistically characterize impacts of mosquito control, but they also constrain the ability of such models to reproduce empirical patterns that do not conform to the models' behavior. In contrast, statistical models afford sufficient flexibility to extract nuanced signals from noisy data, yet they have limited ability to make predictions about impacts of mosquito control on disease caused by pathogens that the mosquitoes transmit without extensive data on mosquitoes and disease. Here, we demonstrate how the differing strengths of mechanistic realism and statistical flexibility can be fused into a single model. Our analysis utilizes data from 176,352 household-level Ae. aegypti aspirator collections conducted during 1999-2011 in Iquitos, Peru. The key step in our approach is to calibrate a single parameter of the model to spatio-temporal abundance patterns predicted by a generalized additive model (GAM). In effect, this calibrated parameter absorbs residual variation in the abundance time-series not captured by other features of the mechanistic model. We then used this calibrated parameter and the literature-derived parameters in the agent-based model to explore Ae. aegypti population dynamics and the impact of insecticide spraying to kill adult mosquitoes. The baseline abundance predicted by the agent-based model closely matched that predicted by the GAM. Following spraying, the agent-based model predicted that mosquito abundance rebounds within about two months, commensurate with recent experimental data from Iquitos. Our approach was able to accurately reproduce abundance patterns in Iquitos and produce a realistic response to adulticide spraying, while retaining sufficient flexibility to be applied across a range of settings.

Numerical Investigation of the Heat Transfer Characteristics and Wall Film Formation of Spray Impingement in SCR Systems

This work established a numerical model to investigate the heat transfer characteristics and wall film formation of spray impinging on the wall in the selective catalytic reduction (SCR) system. The model is developed by the Eulerian–Lagrangian approach, where the Lagrangian approach is used to represent the spray generated by a commercial non-air-assisted pressure-driven injector and the Eulerian approach is adopted to represent exhaust gas. The Stochastic Kuhnke Model is applied to spray/wall interaction. The model considers relevant processes, which include mass transfer, momentum transfer, heat transfer, droplet phase change, spray/wall interaction, and wall film formation. The numerical results compared with that of the experiment indicate that the model can accurately estimate the heat transfer characteristics of the wall surface during the spray impingement. Based on the numerical results, the causes of the spray local cooling effect and the rapid cooling effect are analyzed. The correlation between the critical transition temperature and the critical heat flux temperature for wall film formation is derived from the trends of wall temperature and heat flux. In this work, the Stochastic Kuhnke Model is applied and compared with the Kuhnke Model, which proves that it can improve the disadvantage of sudden change during the wall film formation. When the wall temperature is below the critical transition temperature, the wall film mass is sensitive to the wall temperature and increases as the wall temperature decreases.

Spray impact onto a hot solid substrate: Film boiling suppression by lubricant addition

Spray cooling of solid substrates is one of the methods used in various industrial processes such as forging, quenching or other metallurgical applications, electronics, pharmaceutical industry, medicine, or for cooling of powerful electrical devices. Spray cooling is governed by various hydrodynamic and thermodynamic processes, like drop impact, heat conduction in the substrate and convection in the spreading drops, and different regimes of boiling. The problem of modeling spray cooling becomes even more challenging if the liquid is multicomponent. The presence of components with various physicochemical properties (surfactants, binders, dispersed particles, etc.) can significantly affect the entire process of spray impact, as well as the outcome of the known cooling regimes and could lead to a formation of a thin deposited layer on the substrate. In this experimental study, spray impact onto a substrate, initially heated to temperatures significantly exceeding the liquid saturation point, is visualized using a high-speed video system. The heat transfer associated with spray impact is characterized using an array of thermocouples installed in a thick metal target. As a working fluid, a mixture of a distilled water and industrial white lubricant was used. It is observed that the presence of very small concentrations of lubricant augments the heat flux dramatically, particularly at high wall temperatures, at which usually film boiling is observed for spray cooling by using distilled water. Three main mechanisms lead to the increase of heat flux and shift of the Leidenfrost point. They are caused by the significant viscosity increase of the evaporating lubricant solutions, by an increase of the substrate wettability and by the emergence of stable liquid sheets between bubbles, preventing their coalescence and percolation of the vapor channels.

Soil Microbial Community Involved in Nitrogen Cycling in Rice Fields Treated with Antiozonant under Ambient Ozone.

Ethylenediurea (EDU) can effectively mitigate the crop yield loss caused by ozone (O3), a major, phytotoxic air pollutant. However, the relevant mechanisms are poorly understood, and the effect of EDU on soil ecosystems has not been comprehensively examined. In this study, a hybrid rice variety (Shenyou 63) was cultivated under ambient O3 and sprayed with 450 ppm EDU or water every 10 days. Real time quantitative polymerase chain reaction (RT-qPCR) showed that EDU had no significant effect on the microbial abundance in either rhizospheric or bulk soils. By applying both metagenomic sequencing and the direct assembly of nitrogen (N)-cycling genes, EDU was found to decrease the abundance of functional genes related to nitrification and denitrification processes. Moreover, EDU increased the abundance of genes involved in N-fixing. Although the abundance of some functional genes did not change significantly, nonmetric multidimensional scaling (NMDS) and a principal coordinates analysis (PCoA) suggested that the microbial community structure involved in N cycling was altered by EDU. The relative abundances of nifH-and norB-harboring microbial genera in the rhizosphere responded differently to EDU, suggesting the existence of functional redundancy, which may play a key role in sustaining microbially mediated N-cycling under ambient O3. IMPORTANCE Ethylenediurea (EDU) is hitherto the most efficient phytoprotectant agent against O3 stress. However, the underlying biological mechanisms of its mode of action are not clear, and the effects of EDU on the environment are still unknown, limiting its large-scale application in agriculture. Due to its sensitivity to environmental changes, the microbial community can be used as an indicator to assess the environmental impacts of agricultural practices on soil quality. This study aimed to unravel the effects of EDU spray on the abundance, community structure, and ecological functions of microbial communities in the rhizosphere of rice plants. Our study provides a deep insight into the impact of EDU spray on microbial-mediated N cycling and the structure of N-cycling microbial communities. Our findings help to elucidate the mode of action of EDU in alleviating O3 stress in crops from the perspective of regulating the structure and function of the rhizospheric soil microbial community.

Sea-State-Dependent Sea Spray and Air–Sea Heat Fluxes in Tropical Cyclones: A New Parameterization for Fully Coupled Atmosphere–Wave–Ocean Models

Abstract Air–sea exchange in high winds is one of the most important but poorly represented processes in tropical cyclone (TC) prediction models. Effects of sea spray on air–sea heat fluxes in TCs are particularly difficult to model due to complex sea states and lack of observations in extreme wind and wave conditions. This study introduces a new sea-state-dependent air–sea heat flux parameterization with spray, which is developed using the Unified Wave Interface–Coupled Model (UWIN-CM). Impacts of spray on air–sea heat fluxes are investigated across a wide range of winds, waves, and atmospheric and ocean conditions in five TCs of various sizes and intensities. Spray generation with variable size distribution is explicitly represented by surface wave properties such as wave dissipation, significant wave height, and dominant phase speed, which may be uncorrelated with local winds. The sea-state-dependent spray mass flux is substantially different than a wind-dependent flux, especially when wave shoaling occurs with enhanced wave dissipation near the coast during TC landfall. Spray increases the air–sea enthalpy flux near the radius of maximum wind (RMW) by approximately 5%–20% when mean 10-m wind speed at the RMW reaches 40–50 m s−1. These values can be amplified significantly by coastal wave shoaling. Spray latent heat fluxes may be dampened in the eyewall due to high saturation ratio, and they consistently produce a moistening and cooling effect outside the eyewall. Spray strongly modifies the total sensible heat flux and can cause either a warming or cooling effect at the RMW depending on eyewall saturation ratio. Significance Statement Fluxes of heat and moisture from the ocean to the atmosphere are important for hurricane intensification, but the impact of sea spray generated by breaking waves on these fluxes is not well understood. We develop a new model for heat fluxes with spray that accounts for how waves control spray, and we apply this model to a set of five simulated hurricanes to better understand the broad range of ways that spray impacts heat fluxes in high wind conditions. We find that spray significantly affects heat fluxes in hurricanes and that impacts are strongly controlled by waves, which are not always correlated to winds. This research improves our understanding of how spray affects heat fluxes in hurricanes and provides a foundation for future studies investigating sea spray and its impacts on high-impact weather systems.

The Investigation of the Mixture Formation and Combustion Characteristic of the Spray-wall Impingement

In recent years, investigations into the formation of mixture or combustion characteristics of diesel spray-wall impingement have been summarized. On one hand, the air entrainment strength and fuel concentration distribution in the near-wall area during the spray-wall collision process have been studied. On the other hand, the combustion characteristics of the impinged spray, including ignition and combustion characteristics, have also been discussed. Additionally, the effect of impingement between spray and wall on real diesel engines’ operating condition has been analyzed and summarized. Results showed that increasing the pressure of the injection and shortening the collision distance could enhance the air entrainment strength of spray-wall impingement. Moreover, increasing the injection pressure, shortening the impingement distance, decreasing the environmental pressure, increasing the wall temperature, and reducing the nozzle diameter all improved the mixture formation. Conversely, reducing the environmental temperature, decreasing the nozzle diameter, and increasing the impingement distance all reduced the concentration of soot, and even achieved no soot formation. Under real diesel engine operation conditions, some of the soot formed in the spray-wall collision and deposited on the wall. The structure of these deposits was mainly a simple cluster structure composed of several basic particles, and the porous structure of the deposits was conducive to the oxidation of soot and reduced the deposition rate.

Experimental investigation of a post-combustion pool fire phenomenon due to the spray-wall interaction under DI engine-like cold-start conditions

Spray-wall interactions (SWI) have remained nowadays as an active area of research and the complex multi-physical field processes between the spray and the wall are still not well understood. In this study, a post-combustion pool fire phenomenon due to the SWI was found by optical diagnostic techniques: pool fire appeared near the stagnation point after spray combustion. The spray combustion and pool fire are not continuous. This abnormal combustion characteristic under low ambient temperature conditions (680–720 K) was investigated and the effect of ambient temperature on the macroscopic characteristics of pool fires was quantified and analyzed. The results show that the wall-attached fuel film will be re-ignited and continue to combust for a longer period after the impingement spray combustion. The appearance moment, dwell time, fire duration, and macroscopic characteristics of this post-combustion pool fire are non-monotonic as a function of the ambient temperature. When the ambient temperature is 700 K, the post-combustion pool fire appears earliest, the dwell time is the smallest, and the pool fire duration, flame length, and flame height of the pool fire are the largest. This is mainly dominated by the gas temperature around the wall-attached fuel film and fuel film mass.

Impact of Spraying and Dipping Organic Acids on Hatching traits, Chick Quality, Immunity and eggshell bacterial count

Organic Acids (BacterActive) spraying and dipping on hatching eggs were evaluated experimentally for their effect on embryonic mortality, hatchability, chick quality, immunity, and eggshell bacterial count. A total of 6300 hatching eggs of broiler breeder (Ross-308) at age 58 weeks, were collected and divided to 7 treatments as follows: (T1: General Control, T2: Dipping Water, T3: Spray Water, T4: Dipping and spraying water, T5: Dipping organic acid, T6:spray Organic Acid, T7:dipping-spray organic acid ) Results indicated that using Organic acid (BacterActive) a synergetic blend of formic – propionic - lactic acids applied in a spraying manner with a concentration of 1ml/l significantly (p≤0.01) increased hatching traits, chick quality, and chicks’ antibody titer against Newcastle Disease (ND) and Infectious Bronchitis (IB) also organic acid application significantly reduced embryonic mortality and eggshell total bacterial count in all treatments. while T6 showed the best result among all treatments that used organic acid and T5 showed the lowest value. among control group T3 had the best overall result while T1 shows least favorable result of all treatments. A special note to take in consideration is that dipping eggs in water T2 had least impact on embryonic death. In conclusion results showed that organic acids application via spraying, dipping, and dipping-spraying in broiler breeders leads to significant improvement of hatchability, chick quality and immune status while decreasing embryonic mortality and eggshell total bacterial count.

Mixture formation characteristics and feasibility of methanol as an alternative fuel for gasoline in port fuel injection engines: Droplet evaporation and spray visualization

Under the background of energy saving and emission reduction, methanol is considered an ideal alternative fuel for gasoline because of its renewability, high combustion efficiency and low emissions, while an issue is the cold start of methanol port fuel injection engines. To comprehensively understand the underlying mechanisms and the feasibility of methanol as a substitute of gasoline, a suspension method was first used to investigate the evaporation characteristics of methanol and gasoline droplets at low temperatures. Then an optical intake port was constructed based on the outer contour modification strategy and an optical distortion correction algorithm was proposed. The effects of inlet temperature, inlet flow rate and injection pressure on spray characteristics of methanol and gasoline were comparatively investigated. In addition, the influence of valve temperature on the characteristics of spray impingement on a valve was studied. The results showed that the difference between the evaporation rates of methanol and gasoline was small at 60–90 °C. The difference became obvious when the temperature was below 60 °C or above 90 °C. Reducing the ambient humidity may reduce this difference and improve the cold start performance of methanol engines. A higher inlet temperature slightly increased the spray area. A higher inlet flow rate and injection pressure significantly increased the spray area, but also caused serious wet wall problem. From the point of view of spray in the port, methanol was a feasible substitute for gasoline in the presence of inlet flow and at low injection pressure of 6 bar. The valve temperature should exceed 200 and 230 °C for methanol and gasoline, respectively to form vapor films that prevent fuel adhesion onto the valve. However, methanol may not be a suitable alternative fuel for gasoline when spray directly impacted on the valve in port fuel injection engines due to its much smaller spray area.

Correlation of single-phase convective heat transfer on spray cooled plain surfaces with high Prandtl number liquids

Spray cooling with transmission oils is an innovative cooling concept for electrical machines, whereby the coolant wets the end windings directly. The thermal design process of such machines requires reliable correlations of the heat transfer coefficients obtainable. Thereby, the majority of the literature only focuses on low Prandtl number coolants at ideal nozzle distances. The transferability of the existing heat transfer models to highly viscous coolants above and below the optimal nozzle distance has yet to be investigated. Therefore, the heat transfer coefficients of spray cooling on plain surfaces with aqueous glycerol solutions (model fluid) and a transmission oil of type ATF VI was investigated. The model fluid serves the purpose of covering the entire range of material properties of commercial transmission oils with only one liquid. Prandtl numbers ranging from 80 to 340 were investigated. Various cases of spray coverage were researched by varying the nozzle distance (2mm−100mm), the spray angle (20∘−80∘) and the size of the spray cooled surface (6.35×6.35mm2;12.7×12.7mm2). Regarding the case of the optimal nozzle distance, where the spray impact area just inscribes the cooled surface, the experimental data was validated with models from the literature. Large deviations of up to 450% resulted at nozzle distances above and below the optimum. Therefore, a dimensionless correlation of the heat transfer coefficient is proposed which includes all cases of spray coverage investigated, exceeding the applicability range of the existing models. The model describes the experimental data with a mean absolute percentage error of 15%.

Multi-isotope fingerprints of recent environmental samples from the Baltic coast and their implications for bioarchaeological studies

Stable isotopes in coastal regions are influenced by the so-called sea spray effect which masks the actual terrestrial isotope fingerprint with a marine isotope signal. The sea spray impact on plants was investigated by analyzing different stable isotope systems (δ13Ccellulose, δ18Ocellulose, δ18Osulfate, δ34Ssulfate, δ34Stotal S, δ34Sorganic S, 87Sr/86Sr) in recent environmental samples (plants, soil, water) collected close to the Baltic Sea.All these isotopic systems are influenced by the sea spray, either by the uptake of ions (HCO3−, SO42−, Sr2+) of marine origin, thus exhibiting a marine isotopic signature, or by biochemical reactions associated with, e.g., salinity stress. A shift towards seawater values is observed for δ18Osulfate, δ34S, and 87Sr/86Sr. Cellulose becomes enriched in 13C and 18O due to sea spray, further enhanced (δ13Ccellulose) or mitigated (δ18Ocellulose) by salinity stress. The effect differs both regionally and seasonally, probably as a result of, e.g., differences in wind strength or prevailing wind direction, as well as between plants collected only few meters apart, in either the open field or at more wind-protected sites, reflecting samples more or less influenced by sea spray.The stable isotope data of recent environmental samples are compared to previously analyzed archaeological bone samples of animals from the Viking Haithabu and Early Medieval Schleswig sites located close to the Baltic Sea. Potential regions of origin can be predicted based on the magnitude of the (recent) local sea spray effect. This enables the identification of probably non-local individuals.The insights into sea spray mechanisms, biochemical reactions in plants, as well as seasonal, regional, and small-scale differences in stable isotope data will help to interpret multi-isotope fingerprints at coastal sites. Our study demonstrates the usefulness of environmental samples for bioarchaeological studies. Moreover, the detected seasonal and small-scale differences require adjusted sampling strategies for, e.g., isotopic baselines in coastal areas.

To spray or not to spray: Impact of phosphite spraying for Phytophthora cinnamomi control on Proteaceae species in southwestern Australia

AbstractPhosphite has been sprayed on threatened natural plant communities in southwestern Australia for the past 25 years to mitigate the impact of the globally widespread plant pathogen, Phytophthora cinnamomi. Of concern is that this may result in an increase in phosphorus concentrations in naturally nutrient deficient soils, causing the loss of plant species that are sensitive to increased phosphorus levels. The impact of aerial spraying phosphite on soil and Proteaceae species richness and abundance was measured at three sites within the Southeast Coastal Province of Western Australia. Healthy and diseased vegetation which had been sprayed with phosphite for 14–26 years was compared with nonsprayed healthy and diseased vegetation. Contrary to expectations, there was no evidence that spraying is doing harm to Proteaceae species at the three sites studied. Healthy‐nonsprayed and Healthy‐sprayed areas had generally similar levels of soil total P, and this was associated with similar values for Proteaceae species richness and abundance in these areas. Phosphite spraying of diseased vegetation benefited Proteaceae plant diversity and abundance by preventing the disappearance of some species. Given these results, it was recommended that phosphite spraying be continued as a management action for controlling Phytophthora cinnamomi while research into alternative solutions continues.

Experimental study and theoretical analysis on the criterion of boiling of wall film for different fuels

In direct-injection engines, the formation and vaporization of wall-attached fuel film after the spray impingement is the main factor affecting the emissions of hydrocarbon (HC), soot, and other pollutants. In response to this situation, the formation and evolution characteristics of the fuel film formed by a high-pressure spray impingement onto a heated wall were investigated. The change in the fuel film thickness during the evolution process was measured with the refractive index matching (RIM) method for three different fuels. This paper also quantitatively studied the boiling criterion of the micrometer-scale wall film at various film temperatures. The results indicate that there exists a critical film thickness to trigger the boiling phenomenon, which is closely related to the film temperature. According to the theoretical analysis, it is concluded that the critical thickness is essential for the fuel film boiling at the corresponding fuel film temperature. At the same fuel superheat degree, the critical thickness of different fuels highly relies on their physical properties, among which surface tension is the dominant factor, while the effect of saturation temperature and enthalpy of vaporization is relatively weak.

Impact of NaCl Spray on the Durability of PEMFC Single Cells and Stacks in Marine Environment

The present work investigates the effects of a salt spray injected into the airflow of Proton Exchange Membrane Fuel Cells (PEMFCs) at various time scales and contamination levels, with the long-term objective of identifying the appropriate protection of fuel cells for maritime applications. A dedicated experimental setup generates a sodium chloride (NaCl) mist in the cathode airflow to contaminate single cells and stacks. Constant current density tests led to lifetime shortening with partial recovery after cathode rinsing. Then, Membrane Electrode Assemblies (MEAs) post-mortem characterizations revealed that NaCl was present in the cathode gas diffusion layer, and chlorine reached the catalyst layer for high concentrations. Furthermore, chlorides enhanced current collectors and bipolar plates (BPs) degradation, as corrosion products were identified in MEAs and stack effluents. A sailboat propulsion stack operated 50 h at sea was meanwhile analyzed. As for the laboratory work, chlorine and stainless steel from BPs were found in MEAs, comforting the idea that the marine environment can damage fuel cells. Overall, this study evidences that NaCl effects on PEMFCs not only depend on the concentration but also on the MEA type, plate material, and startup/shutdown procedure.

Effect of herbicide stress on synchronization of carbon and nitrogen metabolism in lentil (Lens culinaris Medik.)

Weed invasion causes significant yield losses in lentil. Imazethapyr (IM), a broad-spectrum herbicide inhibits the biosynthesis of branched chain amino acids necessary for plant growth. Plant growth depends upon translocation of photo-assimilates and their partitioning regulated by carbon and nitrogen metabolism. This study aimed to investigate the impact of imazethapyr spray on carbon and nitrogen metabolism in tolerant (LL1397 and LL1612) and susceptible (FLIP2004-7L and PL07) lentil genotypes during vegetative and reproductive development. Significantly higher activities of invertases and sucrose synthase (cleavage) in leaves and in podwall and seeds during early phase of development in tolerant genotypes were observed as compared to susceptible genotypes under herbicide stress that might be responsible for providing hexoses required for their growth. Activities of sucrose synthesizing enzymes, sucrose phosphate synthase and sucrose synthase (synthesis) increased significantly in podwalls and seeds of LL1397 and LL1612 genotypes during later phase of development towards maturity while the activities decreased in FLIP2004-7L and PL07 genotypes under herbicide stress. Activities of nitrate and nitrite reductase, glutamine 2-oxoglutarate aminotransferase, glutamine synthetase and glutamate dehydrogenase were increased in leaves, podwalls and seeds of LL1397 and LL1612 under herbicide stress. A proper synchronization of carbon and nitrogen metabolism in tolerant lentil genotypes during vegetative and reproductive phase might be one of the mechanisms for their recovery from herbicide stress. This first ever comprehensive information will provide a basis for future studies on the molecular mechanism of source sink relationship in lentil under herbicide stress and will be utilized in breeding programmes.

Surface durability during high-speed spray impingement onto heat-exchanger materials and modified surfaces

Surface durability was investigated for materials used in electronics and heat exchangers during water spray impingement at ambient conditions. Smooth, rough, and modified copper and aluminium samples were tested with surface hardness, roughness and contact angle ranging from 52–100 HV, 0.53–79.28 μm and 48-153°, respectively. Although material loss and hardness alterations were insignificant after the high-speed droplet collisions, changes in surface morphology were observed. Both smooth and rough surfaces were resistant to 36-hour sprays with droplet velocities from 11–22 m s−1. However, sprays did cause changes in surface roughness and static contact angle, and the water repellent coatings were damaged, losing their low wettability.

Splashing characteristics and dynamics of drops impingement on ultracold surfaces

Drop impingement on low-temperature surfaces is a common phenomenon in various situations, such as the icing process on airplanes and spray impingement in internal combustion engines in an ultracold environment. Numerous literatures have reported the spreading and icing characteristics during the cold surface impingement but the characteristics and dynamics of the splashing process under a similar circumstance have not been comprehensively investigated. In this work, the drop splashing process on low-temperature surfaces is investigated both experimentally and theoretically. By employing high-speed shadowgraphy, we find the drop splashing pattern gradually changes from prompt splash to corona splash as the surface temperature decreases from 20 °C to −39 °C because of the physical property changes of the liquid in the drop. The splashing threshold decreases monotonically with surface temperature. The critical Weber number to trigger splash decreases from 441 to 235 and 288 respectively on aluminium and PMMA surfaces as surface temperature drops from 20 °C to −30 °C. A semi-theoretical model to predict the splashing threshold is established based on Riboux and Gordillo’s theory, while the suction force is found dominating the lift forces that induce the levitation of the liquid film. Temperature characteristics of the surrounding air and drop are simplified based on a simulation analysis. The model shows fair agreement with the experiments on both aluminium and PMMA surface.

Spray and dynamic heat transfer induced by 2-methylfuran transient spray impingement on piston surface

In the face of increasing air pollution and stricter emission requirements, it is very important to reduce particulate matter emissions in engine exhaust. The presence of the attached liquid film in gasoline direct injection engines produced by spray impingement is an important reason for the increase in engine particulate emissions. The dynamic heat transfer induced by the spray impingement is a key factor affecting the evaporation and existence time of liquid film. In this paper, a single-hole injector was used to carry out 2-methylfuran (MF) spray impingement experiments. The macroscopic morphological characteristics and the dynamic heat transfer of transient spray impingement under different conditions were systematically studied. Spray particle size distribution and spray impact force were also measured to assist in explaining the underlying mechanism responsible for the dynamic heat transfer. The results show that the surface heat flux increases with the rise of initial piston surface temperature. Increasing the injection pressure makes the droplets have a stronger impact force and smaller average diameter, which enhances the heat flux and also produces more bounce and splash of droplets on piston surface. Both the number of small-size droplets and impact force are reduced by the intense evaporation caused by increasing the injection temperature, resulting in the decrease of heat flux and surface temperature reduction. Increasing the distance decreases the droplet diameter and impacting force, as a result, the heat transfer intensity is weakened.

Impacts of Elevated Ozone and Ozone Protectants on Plant Growth, Nutrients, Biochemical and Yield Properties of Turnip (Brassica Rapa L.)

ABSTRACT An experiment was conducted at Woodhouse farm, Horticultural Research Station, Ooty, during October 2017 to March 2018 to quantify the impact of elevated ozone and ozone protectant spray on plant growth, nutrients, biochemical and yield properties of turnip crop. The experiment was laid out in a factorial completely randomized block design and was replicated thrice. Elevated ozone exposure on turnip significantly reduced the plant height, tuber size, tuber weight, chlorophyll ‘a,’ chlorophyll ‘b’ and total chlorophyll content as well as the nutrient content of plant, viz., total nitrogen, total potassium, total manganese, iron, zinc and copper, also affected. Elevated ozone exposure significantly increased the antioxidant enzyme activity like catalase and peroxidase activity in addition to increment in total phosphorus content in leaf tissues. However, ozone protectants played a major role in nullifying the tropospheric ozone effect on growth and development, physiological traits and yield of turnip while tested with panchagavya performed better followed by neem oil and ascorbic acid.

Experimental investigation of the effect of duct structure geometry on macroscopic spray characteristics and air entrainment of duct fuel spray

The fuel–air mixing process can be improved via straight (ST) ducted fuel injection, but there is a risk of greater heat transfer loss due to prolonged spray tip penetration (STP) and spray impingement. In this study, we propose a convergent-divergent (CD) duct spray to produce an acceptable STP to improve the spray air entrainment (SAE) and spray cone angle (SCA). Three CD and two ST ducts were designed and installed in a constant-volume chamber. An optical Schlieren visualization system with a high-speed camera was used to examine the effects of duct geometry on the macroscopic spray parameters of SCA, STP, spray area (SA), SAE, and spray morphology. Compared with the free spray, the longest STP was noted for the ST2 duct spray, whereas the shortest STP was observed for the CD4.5 duct spray; the STP decreased by 14.5 %, whereas the SCA increased by at least two times for CD4.5 and CD6 duct sprays. A typical trade-off relationship between SCA and STP was confirmed for larger diameter CD duct sprays. When the injection pressure increased from 120 to 140 to 160 MPa, the STP of the ST2 duct spray increased by 1.7 % and 2.4 %, and that of the CD4.5 duct spray increased by 3.1 % and 7.0 %, respectively. At the late spray stage, the CD4.5 and CD6 duct spray had the better SAE ability, followed by the ST3 and CD3 duct sprays, ST2 duct spray exhibited slightly lower SAE values than the free spray. A typical mushroom-shaped spray head was observed near the outlet of the ST2 and ST3 duct sprays, while a cotton-shaped spray was observed for the CD duct sprays during the initial early spray stage. The development of the CD duct spray showed a left–right swing phenomenon with an S-shaped track, particularly for CD4.5 and CD6 duct sprays, which can promote the fuel–air mixing process with a larger SCA. The CD4.5 duct spray demonstrated considerable potential for improving the fuel–air mixture with a stronger SAE and larger SCA, as well as the ability to reduce the heat transfer loss with a shorter STP and weaker spray impingement.