Vertical Spray Research Articles

Hydrodynamics performance and tray efficiency analysis of the novel vertical spray packing tray

Abstract Column setup has been widely utilized in the petroleum and chemistry industries. However, with the fast progress of industries and the increasingly serious energy shortage, designing a new column setup with better performance and higher capacity becomes more urgent. In order to improve column's capacity and expand operating condition, a new type of column tray named novel vertical spray packing (NVSP) tray was designed and experimented. The performances of the novel tray, including pressure drop, weeping, entrainment and tray efficiency, were tested in a plexiglass column. In addition, performances of the novel tray were compared with that of the sieve tray and the Glitsch V1 valve tray. Based on the experiment data, the mathematical correlations of pressure drop, weeping and entrainment for the novel tray were established by regression analysis method. A fundamental model of dry pressure drop of the novel tray was promoted at the form of sum mode. The results indicate that the novel tray has wider operating condition and better performance.

Numerical simulation and analysis of process parameters of GaN-MOCVD reactor

Commercially, semiconductor thin films for use in electronic devices are typically produced by processes such as chemical vapor deposition. This requires the gas flow, heat distribution, and concentration distribution above the substrate in the reactor to be carefully controlled to ensure that the growth rate and thickness uniformity of the thin film are appropriate. This work involved the simulation of a gallium nitride metal-organic chemical vapor deposition (GaN-MOCVD) reactor with a vertical spray structure. The simulation, which was conducted by using computational fluid dynamics software, enabled us to obtain a numerical solution under steady-flow low-pressure conditions with substrate axisymmetrical rotating. The temperature field, flow field, operating pressure, and rotation speed of the substrate were analyzed, and process conditions were optimized. These conditions make it possible to stabilize the flow field in the reactor to ensure thickness uniformity of the deposited thin film. These results not only provide an effective solution for high-quality epitaxial growth, but also provide a theoretical basis for follow-up experiment and equipment improvement.

Implementation of a low-cost crop detection prototype for selective spraying in greenhouses

During phytosanitary treatments aimed at minimizing product losses, selective spraying systems can be employed. These systems consist of a group of detection–action devices which manage the spraying. In this work, the technical feasibility of a low-cost ultrasound detection system prototype has been assessed for pesticide spray application on greenhouse crops. The prototype is based on a commercially-available car parking assistance system, which has been modified to amplify the signal and activate an electro-valve for spray control. This system was fitted into a self-propelled machine with two vertical spray booms. A laboratory test was carried out to evaluate the system limitations (detection range, response time, optimal sensor location); and once the feasibility of the system was known, a field test was conducted. Inside the greenhouse, the same parameters were determined for canopy presence. The system’s capacity to start and stop spraying at the beginnings and ends of the crop lines was also analysed. In addition, the minimum crop line surface with no plant mass that triggers system activation was determined. The results show that the detection range was 0–0.4 m with an average response time of 1.67 s. Based on these parameters, the optimal sensor location was determined for the different forward velocities. In conclusion, the results show that this system is suitable for plant detection at a forward speed of 0.9 m s−1, allowing growers to stop spraying automatically at the ends of the crop lines and where plant mass absence is greater than 1.0 lineal meter.

Potential for Major Explosions from Crude Oil Pipeline Releases in Varied Terrain

Crude oil is often transported by pipelines from remote production sites to refineries. Sometimes oil releases take place, caused by sabotage, corrosion or external impact. In a safety consequence study the main hazards considered are often pool, jet or flash fire. The integral models applied may give somewhat misleading hazard estimates, as a flat terrain surrounding the pipeline is assumed, and the models lack the ability to predict dense gas dispersion for calm and low wind scenarios. In a varied terrain an unrealistic large pool and following pool/flash fire, is often predicted. A major hazard often ignored is vapour cloud explosion. The fractions of volatile components in crude oil are limited. Still, as demonstrated by cascade flow experiments after the Buncefield accident, certain release mechanisms may lead to an enhanced evaporation and the likely generation of flammable vapour clouds. For an oil release it can be assumed that a pressurized oil release generating a vertical oil spray into the air, can lead to the evaporation of significant fractions of flammable vapours of propane, butane and pentane. For major pipeline releses during calm wind conditions (0-0.5 m/s) in a varied terrain, a CFD simulation study demonstrated that very large flammable vapour clouds could be generated and could fill lower lying areas of the terrain. The simulated clouds could be 5-10m deep with likely ignition sources as homes, farm houses and roads inside for 20-30 minutes. Areas with trees and dense vegetation were also inside the gas cloud, and could have led to significant flame acceleration, potentially deflagration to detonation transition (DDT) and severe consequences as seen for the Buncefield accident. For pipelines buried below the ground one possible way to prevent such a scenario will be to avoid the possibility for oil sprays upwards, for instance by covering the pipeline with plates which will remain in place during a major release. If this is not possible, vapour fences may be used to limit the gas cloud migration towards likely ignition sources or areas with dense vegetation. While such scenarios may be rare for unintended releases, the severity of the potential consequences should justify their evaluation as part of a safety study.

One-dimensional model on fuel penetration in diesel sprays with gas flow

In diesel engine, spray penetration is usually changed by in-cylinder gas flow. Accurate prediction on diesel spray with gas flow is important to the optimal design of diesel fuel injection system. This paper presents a theory investigation focusing on the penetration of diesel spray with gas flow. In order to understand the effect of gas flow on the penetration of diesel spray, a one-dimensional spray model is developed from an idealized diesel spray, which is able to predict the spray behavior under different gas flow conditions. The ambient gas flow is simplified as ideal flow that has only constant flow velocity along x-axial and y-axial directions of spray. The x-axial and y-axial directions are respectively defined as along and vertical spray directions. The main assumption is that the y-axial direction gas flow has no effect on the penetration of spray along x-axial direction. The principles of conservation of mass and momentum are used in the derivation. Momentum of in-cylinder air flow is also taken into consideration. Validation of the model at stable condition is achieved by comparing model predictions with experimental measurements of diesel spray without gas flow from Naber's experiments. Furthermore, CFD simulations on penetration of diesel spray with gas flow were performed with the commercial code AVL-fire. The onedimensional model is validated by the penetration results with gas flow from CFD calculation. Results show that a reasonable estimation of the spray evolution can be obtained for both with and without ambient gas flow conditions.

Numerical modeling of self-pressurization and pressure control by a thermodynamic vent system in a cryogenic tank

This paper presents a numerical model of a system-level test bed—the multipurpose hydrogen test bed (MHTB) using the Generalized Fluid System Simulation Program (GFSSP). MHTB is representative in size and shape of a space transportation vehicle liquid hydrogen propellant tank, and ground-based testing was performed at NASA Marshall Space Flight Center (MSFC) to generate data for cryogenic storage. GFSSP is a finite volume-based network flow analysis software developed at MSFC and used for thermofluid analysis of propulsion systems. GFSSP has been used to model the self-pressurization and ullage pressure control by the Thermodynamic Vent System (TVS). A TVS typically includes a Joule–Thompson (J–T) expansion device, a two-phase heat exchanger (HEX), and a mixing pump and liquid injector to extract thermal energy from the tank without significant loss of liquid propellant. For the MHTB tank, the HEX and liquid injector are combined into a vertical spray bar assembly. Two GFSSP models (Self-Pressurization and TVS) were separately developed and tested and then integrated to simulate the entire system. The Self-Pressurization model consists of multiple ullage nodes, a propellant node, and solid nodes; it computes the heat transfer through multilayer insulation blankets and calculates heat and mass transfer between the ullage and liquid propellant and the ullage and tank wall. A TVS model calculates the flow through a J–T valve, HEX, and spray and vent systems. Two models are integrated by exchanging data through User Subroutines of both models. Results of the integrated models have been compared with MHTB test data at a 50% fill level. Satisfactory comparison was observed between tests and numerical predictions.

Perfformances evaluation of different vertical patternators

Assessment of vertical spray profile is one of the main steps to adjust sprayers for bush and tree crops, as it allows to verify that the spray plume matches the target canopy profile. The equipment used for assessing the vertical spray profile is typically a vertical test bench or patternator. Even if the sprayer adjustment is recommended in EU Directive 128/2009/EC, the use of vertical test benches is only optional in the procedures for the inspection of air-assisted sprayers in use currently adopted in the EU Member States, that mainly refer to EN 13790-2 and to new ENISO FDIS 16122-3. At present, in the International Standards, there is not any indication of the minimum requirements that the vertical test benches have to fulfill, neither in terms of constructive characteristics or of functional parameters. For this reason, the types of vertical test benches used in the test stations, even if are based on the same principle of functioning (presence of a vertical surface to collect the whole liquid sprayed and of graduated tubes for measuring it), present some differences in terms of structure, mainly related to collectors types and their disposal along the test bench. Two main categories of vertical test benches can be identified: 1) equipped with a continuous collecting wall; 2) equipped with a discrete number of separated collectors. In each category it is then possible to have different models, depending on the size, materials, number and position of the collectors. With the main purpose to define methodology and criteria for the vertical patternator evaluation, specific performance tests were carried out in laboratory using four different types of vertical test benches and a horizontal test bench complying with ISO 5682-1 requirements. Spray recovery capacity and reproducibility of results, both in terms of recovery and of spray profile were assessed using different droplet sizes, air speeds and air directions. Results of these first experimental trials pointed out that the criteria applied to assess the performance of the vertical test benches seemed able to discriminate the differences between the models tested. Amount of spray recovery was mostly affected by droplets size rather than by air velocity. Spray profile detected on the different vertical patternator types examined resulted generally similar. These first experimental results could constitute a basis for the development of a SPISE advice about test methodology and requirements for vertical test benches.

Deposition of heavy oil droplets onto a circular disk at elevated temperatures

Fouling of equipment surfaces affects the efficient processing of heavy hydrocarbons. An experimental study is reported on the deposition of bitumen‐containing droplets from a gas‐vapour mixture at temperatures up to incipient coking conditions. A heavy oil‐diluent feed mixture was atomized with nitrogen in a vertical spray chamber, and flowed upwards normal to a circular disk. The disk was attached to a load cell to measure total deposited mass with time, and at the end of each experiment the amount deposited was determined gravimetrically. The effects on deposition rate of heavy oil concentration in the feed mixture, temperature, and flow‐rates of feed mixture and nitrogen were determined. Different surfaces and coatings were tested. The deposition rate was found to depend most strongly on the droplet concentration, which was predicted with HYSYS, using an isothermal flash calculation. As temperature was increased, deposit H/C atomic ratio decreased and ash content increased.

ASSESSMENT OF DERMAL PESTICIDE EXPOSURE INSIDE GREENHOUSES USING FLUORESCENT TRACER METHOD

The main object of the search work is to assess the dermal pesticide exposure inside greenhouses during its application and to compare pesticide pollution resulted from handgun sprayer with its values of a vertical boom sprayer prototype. Fluorescent tracer, is semi-quantitative dermal exposure assessment method based on visual observations of fluorescence images, had been used to demonstrate the extent to which dermal exposure can occur under inadequate protective conditions. 22 body segments (˃ 90% of the total body surface area) scored for all workers. Prototype is superior to handgun sprayer, contaminated area ratio of glasses was 0.28% - no pollution for the mask versus 8.11% and 9.15% respectively. Trunk, buttock, chest and shoulder contaminated area with handgun sprayer were 1.75, 1.60, 0.60 and 6.69 % (front view) and were 1.79, 9.51, 0.73 and 0.00 at back view versus no pollution (0.00 %) in all previous cases with vertical boom sprayer prototype. No pollution in any area of worker’s arms compared to polluted area ranged between 0.00 and 8.17% for handgun sprayer. Contaminated area of gloves (​​5% of total body area) ranged between 0.00 and 0.92 % for vertical spray boom prototype versus 11.72 % - 19.50 % for handgun sprayer. Worker’s legs exposed to some pollution (0.42 % and 0.82%) against more detected exposure extended to 13.36 % for handgun sprayer. Regrettably, workers did not wear safety boots, though no data for feet area, which form about 7 % of total body area, was taken. Tested prototype maintained more working safety conditions when compared to handgun sprayer.

Hydrodynamic effects of use of eductors (Jet-Mixing Eductor) for water inlet on circular tank fish culture

Trials were conducted in circular tanks used in aquaculture (1.2m diameter and 0.4 of useful depth) in order to evaluate the effect of different water injection devices on the tangential velocity of the water, its uniformity pattern, the mixing time and the removal of solids through the bottom drain. Two injection devices, without fishes, were evaluated at the tank: a Vertical Spray, considered as standard in aquaculture and an eductor (Jet-Mixing Eductor) which is used in chemical and petrochemical industry to homogenize and keep in movement great volumes of water. The devices were evaluated under the same operating conditions: inlet flow of 4, 6 and 8l/min and water injection angle of 0° and 45°. In each trial, the water velocity inside the tank was measured, also the mixing time and the time in which the 100% of pellets of fish food were eliminated from the tank through the bottom drain. The results indicate that, for all inlet flows, the eductor operating at 45° presents significantly (p<0.001) better result in terms of hydraulic variables such as tangential velocity, uniformity, mixing time and solids removal time from the tank (self-cleaning effect). In the case of eductors, although an increase of inlet flow produces improvements of hydraulic variables, a change of water injection angle, from 0° to 45°, produces significantly better results (p<0.001). Differences of hydraulic performance between the eductor and Vertical Spray are mainly owing to the multiplicative effect of the outlet flow that is generated by the eductor. This means that, for similar values of impulse force and water velocity at the exit of the nozzle injection (V2), the eductors generate significantly higher tangential velocity and uniformity, lower mixing times and secondary flow patterns, which ensure the self-cleaning of solid waste. In terms of power consumption, eductors overcome Vertical Spray in the trial performed. However, when comparing them under equal requirements of hydraulic performances (velocity, mix and/or self-cleaning), eductors present the same or lower energy consumption. Comparatively eductors would generate, under similar operating conditions, clear benefits for produced species in aquaculture, by generating hydraulic conditions that ensure a better quality of water and patterns and uniformity of velocity, which are more suitable for their health and normal growth.

An Experimental Study on the Interaction of Water Mist with Vertical/Horizontal Spray Flame

Spray fire is a major disaster for gas turbines and aero-engine test facilities. Previous studies demonstrated that small spray fires were difficult to extinguish with water mist. An experimental study of the process of water mist interacting with the small size spray fire was conducted in an open space. Studies on suppression of vertical spray fire and horizontal spray fire were carried out, respectively. Experiment discovered that a horizontal fame was more difficult to extinguish compared with the vertical using the same scenario, and implied that the coupling the dilution of fuel in the gas phase with the reduction of radiant feedback plays a predominant role in fire extinguishment.

COMPREHENSIVE EVALUATION OF DIFFERENT VERTICAL BOOM SPRAYER NOZZLES FOR

Recent research work deals with using vertical spray booms for the safe and efficient application of crop protection chemicals in greenhouses. Nozzle type and setting significantly affect spray deposition and crop nutrition and should be carefully considered. Six different types of nozzles were tested and calibrated with two operating pressures for each and different spacing between nozzles. Wetted radius, precipitation rate, discharge were measured and calculated. Nozzle types included: Copper nozzle, Plastic nozzle with four exits, Single fogger (naandan®), Oblique nozzle, Rondo flow-regulated mini sprinkler (green) (RFR) and Rondo mist sprayer (violet). Copper nozzle was recommended for further aspects of selection and technical evaluation. It is demonstrated the best delivery of pest and the best distribution in the lap and inside the greenhouse after testing.

Numerical and experimental analysis of vertical spray control patternators

The experimental vertical spray control walls have the purpose of picking up the liquid delivered by trained sprayer for providing the liquid distribution profile in height. Theoretically this should correspond to the ideal profile, which consists in a uniform distribution on the vegetation. If the profile is different from the ideal, a parameter setup is required on the sprayer. Nonetheless, some problems are hidden in the aforementioned statements: i) no wall measures exactly the distribution profile (i.e. the flow through the sections in the vertical plane, parallel to the direction of advancement of the sprayer). Compared to real profile, sensitive errors are introduced: the evaporation of the drops, the deviation of the air flows caused by the sensors panel themselves; by the possibility that the drops bounce on the wall panels, also due to the current of air that can push the liquid veil laterally or upwards, Moreover, everything varies depending on the geometry of the sensors, air velocity, air humidity; ii) no one knows what exactly is the optimal distribution profile. It is often considered as optimal a profile that reflects the amount of leaf area subtended by each section absorber: however, it is evident that the path of the droplets changes according to the sprayer typology (eg. radial-flow or horizontal flows). In this work a combined numerical-experimental approach is adopted, in order to assess some of the aforementioned issues: numerical data obtained by using computational fluid dynamics models are compared and validated with experimental data, in order to assess the reliability of numerical simulations in configurations which are difficult to analyze using an experimental setup.

Numerical and experimental analysis of vertical spray control patternators

The experimental vertical spray control walls have the purpose of picking up the liquid delivered by trained sprayer for providing the liquid distribution profile in height. Theoretically this should correspond to the ideal profile, which consists in a uniform distribution on the vegetation. If the profile is different from the ideal, a parameter setup is required on the sprayer. Nonetheless, some problems are hidden in the aforementioned statements: i) no wall measures exactly the distribution profile (i.e. the flow through the sections in the vertical plane, parallel to the direction of advancement of the sprayer). Compared to real profile, sensitive errors are introduced: the evaporation of the drops, the deviation of the air flows caused by the sensors panel themselves; by the possibility that the drops bounce on the wall panels, also due to the current of air that can push the liquid veil laterally or upwards, Moreover, everything varies depending on the geometry of the sensors, air velocity, air humidity; ii) no one knows what exactly is the optimal distribution profile. It is often considered as optimal a profile that reflects the amount of leaf area subtended by each section absorber: however, it is evident that the path of the droplets changes according to the sprayer typology (eg. radial-flow or horizontal flows). In this work a combined numerical-experimental approach is adopted, in order to assess some of the aforementioned issues: numerical data obtained by using computational fluid dynamics models are compared and validated with experimental data, in order to assess the reliability of numerical simulations in configurations which are difficult to analyze using an experimental setup.

A Research on Improvement of Vertical Power Centrifugal Spraying Gun with High Speed Based-On ARIZ

The power centrifugal spraying gun is a key facility to treat waste gas yielded in the process of garbage power. Serious wear of bearing that supports the high speed motor shorten its life greatly. To solve the problem, a new tool ARIZ which is initial letters of algorithm for inventive-problem solving is put forward in the paper. After ARIZ’s analysis, a suggested solution is given for the situation. The process of analysis shows us how to use ARIZ and lays foundations for applying knowledge base and patents with thorough analysis.

A vertical spray boom application technique for conical bay laurel (Laurus nobilis) plants

Bay laurel, a commercially grown evergreen ornamental plant and economically important for Flanders (Belgium), is very susceptible to pests. Pest management usually consists of spraying pesticides using handheld application techniques which are labour-intensive, involve a high risk for operator exposure, and provide only suboptimal biological control. One alternative, a vertical spray boom, was evaluated in a bay laurel crop pruned into a conical shape. Different spray boom configurations were by attaching water-sensitive papers to a model that emulated the size and shape of the trees. The optimal nozzle type was determined by deposition measurements in an actual laurel crop. Three application rates were tested, 2450, 4900 and 7200 L ha−1 of ground surface. The most efficient spray application technique was found to be an extended range flat fan, an air included flat fan or a hollow cone nozzle, all at 4900 L ha−1 resulting in the highest relative spray deposits and the most uniform spray distribution in the canopy.

Numerical and experimental analysis of vertical spray control patternators

Numerical and experimental analysis of vertical spray control patternators

Layer by Layer coatings assembled through dipping, vertical or horizontal spray for cotton flame retardancy

Silica-based assemblies have been deposited on cotton fibres through Layer by Layer technique in order to enhance their flame retardant properties. To this aim, three different deposition procedures (namely, dipping, vertical and horizontal sprays) have been considered and compared. The resulting morphologies of the deposited assemblies have been thoroughly investigated by scanning electron microscopy (SEM) and elemental analysis. SEM observations have demonstrated that only the horizontal spray allows obtaining the deposition of a very homogeneous silica coating when compared to vertical spray or dipping. As a consequence, horizontal spray has proved to ensure the best flame resistance, promoting a substantial increase of the total burning time and final residue, as assessed by flammability tests. Furthermore, cone calorimetry measurements have shown a remarkable increase of the time to ignition, and a significant decrease of heat release rate and total heat release for the fabrics treated by horizontal spray.

Spray deposition and distribution in a bay laurel crop as affected by nozzle type, air assistance and spray direction when using vertical spray booms

In Flanders, greenhouse growers predominantly use handheld sprayers instead of spray boom equipment. Nevertheless, handheld sprayers have several drawbacks. Growers increasingly recognize the advantages of spray boom equipment, which has resulted in increasing adoption of spray boom systems. Some growers still doubt the efficacy of spray boom systems, however, while others have questions about their use. In this study, we aimed to address both doubts and questions by optimizing a vertical spray boom application for a bay laurel crop using air support and spray angling. Spray deposition on the stem and the upper and lower side of the leaves was measured using mineral chelates as tracers at twenty collector positions in the top and bottom as well as in the front, back, left and right zone of the plant. Four plant repetitions were used for every spray event. Nine different application techniques were tested in three repetitions in laboratory conditions using a fully automated spray system. The effect of nozzle type, angled nozzles, air support and spraying in two passes with an opposite direction was evaluated. The experiments showed that collector position and application technique had a significant effect on deposition. However, angling the spray, using air support or spraying in two consecutive passes with an opposite direction did not result in a higher deposition or penetration capacity compared with the standard vertical spray boom. Nevertheless, some techniques might still result in a higher bio-efficacy due to a more homogenous liquid distribution. The use of a vertical spray boom is a promising technique for safe and efficient application of plant protection products in a vertical crop. Nozzle choice, spray boom setting, spray distance and the air speed of air assisted sprayers require careful consideration, however. Of the tested techniques, the applications made with an extended range standard flat fan nozzle without air support, directed straight toward the crop and used with a fixed spray distance of 30 cm to the stem generally produced the best spray results in the considered, conically pruned bay laurel crop.

A Numerical study of the Fire-extinguishing Performance of Water Mist in an Opening Machinery Space

Spray fire is a primary disaster in machinery space. Previous studies demonstrated that small spray fires were difficult to extinguish with water mist. A numerical and experimental study of the process of water mist interacting with the small size spray fire was conducted. Studies on suppression of vertical spray fire and horizontal spray fire were carried out, respectively. Three-dimensional physical model was developed based on the experiments. The adopted numerical model is FLUENT. The Large eddy simulation (LES) method, laminar finite-rate model, and Discrete Phase Model were selected to solve the turbulent flame, turbulence-chemistry interaction and particles, respectively. There are qualitative agreements of simulation with the experiment. It was confirmed that water mist can suppress spray fires rapidly, and that the extinguishing time for vertical spray fires were relatively shorter.