Spray Jet Research Articles

Comparative study on Al-SBA-15 prepared by spray drying and traditional methods for bulky hydrocarbon cracking: Properties, performance and influencing factors

Mesoporous aluminosilicates Al-SBA-15 with large pore sizes and suitable acid properties are promising substitutes to zeolites for catalytic cracking of bulky hydrocarbons without molecular diffusion limitation. The conventional processes to synthesize Al-SBA-15 are time-consuming and often suffer from low “framework” Al contents. Herein, Al-SBA-15 microspheres are synthesized using the rapid and scalable microfluidic jet spray drying technique. They possess uniform particle sizes (45–60 μm), variable surface morphologies, high surface areas (264–340 m2/g), uniform mesopores (3.8–4.9 nm) and rich acid sites (126–812 μmol/g) and high acid strength. Their physicochemical properties are compared with the counterparts synthesized using traditional hydrothermal and evaporation-induced self-assembly methods. The spray drying technique results in a higher incorporation of aluminum (Al) atoms into the silica “framework” compared to the other two methods. The catalytic cracking efficiencies of 1,3,5-triisopropylbenzene (TIPB) on the Al-SBA-15 materials synthesized using the three different methods and nanosized ZSM-5 are compared. The optimal spray-dried Al-SBA-15 exhibits the best performance with 100 % TIPB conversion, excellent selectivity (about 75 %) towards the formation of deeply cracked products (benzene and propylene) and high stability. The catalytic performances of the spray-dried Al-SBA-15 with varying Si/Al ratios are also compared. The reasons for the different performances of the different materials are discussed, where the mesopores, high acid density and strength are observed to play the most critical role. This work might provide a basis for the synthesis of mesoporous rich metal-substituted silica materials for different catalytic applications.

Analogous Charging Effect of Surfactant-Pesticide Spray Jet on Droplet Characteristics and Deposition on Hydrophobic Leaf Surfaces

An induction charging principle had been applied to enhance spray droplet characteristics and quantity deposition on hydrophobic abaxial-adaxial leaf surfaces from pesticide EC Glyphosate [C3H8NO5P] and surfactant Silwet L-77 [C13H34O4Si3] formulations. A nozzle cap containing two electrodes (spacing at 9 mm apart) was used to superpose charges to spray droplets under applied voltages of 2–12 kV in an electric field (E) of 8.9 × 105 V/m. From a tee-jet flat fan (TP11004VS) nozzle tip fitted into the electrode cap and positioned at 60 cm high above targeted Brassica campestris leave surfaces, the spray droplets were directed onto the leaves at a liquid flow pressure of 4 bar and travelling speed of 2 m/s. The measurements were done using Keithsley picoammeter to quantify spray chargeability (CMR), droplet sizes by lesser particle size analyzer (LPSA) and deposition on leaf surfaces by high-speed camera. In effect, droplet sizes of EC, L-77 and EC + L-77 decreased with an increasing applied voltage. The CMR of L-77 was lower than EC and highest for EC + L-77 composite solution. Based on Image analysis of droplets density per leaf area, maximum exposure of adaxial leaf surfaces intercepted many charged spray droplets than abaxial surfaces. As regressed, the quantity of charged spray deposition from EC + L-77 formulation was highest at both adaxial (approx. 27.44 Qd/cm2) and abaxial (approx. 5.57 Qd/cm2) hydrophobic leaf surfaces than EC of 26.12: 3.19 Qd/cm2 and L-77 of 24.80: 2.53 Qd/cm2, respectively. Also, contact angle, Theta E, of charged spray droplets was smaller than Theta C on adaxial than abaxial leave surfaces, a phenomenon attributed to high chemo-electrical properties of formulations that aided the direct flight, coiling and deposition of droplets in order of EC > EC + L-77 > L-77. Generally, there was no observable droplet rebound; hence, surfactant-pesticide composite spraying is considered suitable for electrostatic application in plant protection technology. Therefore, for effective application, charged droplets from glyphosate EC in silwet L-77 solution should be recommended, as it provides optimum droplet sizes, chargeability, contact angle and deposition on hydrophobic leave surfaces.

Numerical simulation of spray atomization in crossflow using an empirical primary atomization model

The hybrid Eulerian-Lagrangian approach is used to simulate the atomization process of spray jet in subsonic crossflow. A coupled Volume of Fluid (VOF) - Lagrangian Particle Tracking (LPT) solver is implemented in the open-source platform OpenFOAM to solve the governing equations for the continuous and discrete phase respectively. An empirical model for primary atomization is proposed, in which the aerodynamic effect is taken into account, along with the turbulence effect. Thus, it is suitable for the flow at a low liquid-gas density ratio, i.e., less than 500. The performance of the presented model is evaluated and verified by comparisons of the simulated results with the experimental data. The flow characteristics of flow fields and distribution of droplet diameters are analyzed in detail. It is revealed that the vortex structures have a direct impact on the distribution of the droplets. The effects of the empirical constants in the atomization model are also examined. Finally, it is shown that the model performs better for the flow at a higher Weber number, in which the aerodynamic effect is more significant.

Filter Cleaning System Modification to Improve Dust Colletor

The filter cleaning system is part of the dust collector which functions as a filter between dirty air and clean air. Blockage of the dust collector is due to a lack of maintenance to control the performance of filter cleaning components such as valves, jetspray tubes and bagcloth. Another cause is the less than optimal air pressure from the jetspray to dislodge the dust adhering to the bagcloth. So it is necessary to recondition both the layout of the filter cleaning components and the optimization of jet spray pressure. Determination of the capacity of the jetspray tube is adjusted to the specifications of the compressor and uses the ASME VIII Div I (Pressure Vessel) standard with dimensions of 1400mm x 8inch SCH20. The feasibility test of the jetspray tube is carried out by calculating the allowable thickness and the factor of safety based on the pressure operated on the jetspray tube. Determining the location of the filter cleaning components is based on aspects that make it easier for the operator to carry out the maintenance so that the performance of the filter cleaning components can be controlled properly. Based on the stress simulation using solidworks 2020 for the SCH20 pipe which has a thickness of 6.35mm operated with a pressure of 7 bar it is categorized as safe to use.

ОПРЕДЕЛЕНИЕ СКОРОСТИ И ПРОИЗВОДИТЕЛЬНОСТИ АЭРОЗОЛЬНОЙ СТРУИ ДОЖДЕВАТЕЛЕЙ В КРУГОВЫХ САМОХОДНЫХ ДОЖДЕВАЛЬНЫХ УСТАНОВКАХ

Circular self-propelled sprinkler systems are highly efficient equipment for watering crops by sprinkling. Considering the diameter of irrigation, uniformity and productivity of the installation largely depend on the parameters and relative location of sprinklers on the main pipeline of the sprinkler machine, the assessment of the parameters of artificial rain for compliance with the set values for irrigation conditions requires appropriate theoretical and practical studies. (Research purpose) The research purpose is to theoretically calculate and experimentally confirm the results obtained characterizing the speed and performance of the aerosol jet at the outlet of the sprinkler in the fine sprinkling system, in relation to the main pipeline of the self-propelled sprinkler. (Materials and methods) The ballistic theory of the motion of droplets in the air in the Frene-Serre coordinate system perpendicular to the irrigation plane was used to construct a mathematical model of the motion of an aerosol jet. A set of sprinklers located on the main pipeline of a wide-scope circular sprinkler machine of the T-L Irrigation company was considered as an object of research. (Results and discussion) A mathematical model has been proposed for calculating the movement of an aerosol sprinkler jet in the air, which makes it possible to bring the volume flow rate of the sprinkler to an equivalent diameter and wetting depth in the irrigation plane. It has been shown that the data obtained make it possible to predict for a given set of sprinklers the depth of irrigation per unit of irrigated surface in the plane of the figure formed by two circles determined by the circular motion of two adjacent support trolleys of the machine. (Conclusions) It was determined that in order to bring the uniformity coefficient of circular sprinklers to a normalized value, when compiling appropriate mathematical models of the irrigation process, further adaptation of the movement of a single drop in the air to the parameters of artificial rain formed by the spray jet of the sprinkler is required.

Spray freeze dried uniform mannitol microspheres

Spray freeze drying is an attractive technology for fabricating pharmaceutical powder, but it is still challenging to tailor the microparticle physical and chemical structure. Herein, a series of uniform mannitol microparticles with controllable morphology and crystal properties were successfully fabricated via a self-developed micro-fluidic jet spray freeze tower. The effects of feed solution composition and freezing temperature on microparticle size, morphology, surface architecture and crystal property were investigated to propose the particle formation mechanism. Freezing temperature showed more apparent effect on the microparticle characteristics with higher solid content (10 and 15 w/w%) in aqueous solution; Whereas the addition of ethanol as a co-solvent had a notable impact on microparticle morphology, concurrently perturbing the crystallization tendencies of mannitol. These results provide new insights for producing spray freeze dried pharmaceutical microparticles.

PIV experimental analysis of the escape phenomenon of air spraying jet in factories

Inefficient air spraying can release a large amount of paint particles from a spraying jet, which can seriously endanger the health of operators. The flow field characteristics of air atomizing spray guns have a significant influence on spraying efficiency. To investigate the reasons for the escape of paint particles during air spraying, improve efficiency at the source and curb the escape of pollutants into a factory building, this study measured the whole flow field of an air spray gun via a 2D particle image velocimetry (PIV) system. The results showed that the spraying jet velocity reached a maximum of 28 m/s near the spray nozzle with a Reynolds number of 3000 and subsequently decayed rapidly due to the strong momentum exchange with the surrounding air. The radial velocity at the junction of paint mist and air first increases and then decreases (maximum 0.5 m/s). The turbulence intensity was relatively high at the spraying jet boundary. In addition, the spay flow at the nozzle and the jet boundary showed high intermittency. The turbulence structures were studied by proper orthogonal decomposition (POD). The results indicated that the radial velocity of spray was the major source underlying the development of spraying jet radial diffusion. Finally, the spraying efficiency was calculated to be between 53 % and 58 %. For air spraying, suppressing radial movement can improve spraying efficiency by up to 40 %, which is essential to controlling the escape of paint mist and improving the working environment in spray booths.

Modeling of the spray-induced wall stress acting on the ignition assistance device

This research introduces a novel wall-stress model called the Spray-Induced Wall Stress (SIWS) model, which considers the effects of spray-wall impingement and the resulting formation of wall stress within the Lagrangian spray modeling framework. The primary objective of this paper is to provide a mathematical description of the fundamental physics underlying the model. Subsequently, the proposed model is validated using existing experimental data. The remainder of the study focuses on the practical application of the model to an ignition assistance device. Specifically, this device is installed in a compression ignition engine and designed to enhance ignition in aviation-fueled high-altitude aircraft propulsion systems. The research sheds light on the mechanical impulse caused by the high-speed impact of the spray jet, leading to the accumulation of mechanical stress on the rigid body of the ignition assistance device. Previous studies on fluid–structure interaction have only considered the interaction between the gas phase and the solid wall. However, the SIWS model incorporates the additional impact of the impinging liquid spray jet. Consequently, the simulated stress distribution on the ignition assistance device can be estimated by considering both the gas-phase-induced term and the spray-induced term simultaneously.

Spray Flame Characterization of a Dual Injector for Compact Combustion Systems

ABSTRACT The scalability of liquid fuel operated jet stabilized combustion system toward scales and mixing timescales relevant for corresponding micro gas turbine systems is impeded by the lack of suitable injection concepts. The high momentum of the combustion air jet can deteriorate the spray quality of conventional injection systems. In combustors with reduced mixing timescales (e.g. MGT and compact aero-engines) this results in elevated emissions and a prompt primary atomization is essential. For this purpose, a canonical confined jet spray burner is developed and equipped with a novel in-house dual-pressure swirl/airblast injection concept. An extensive parameter variation on the jet bulk velocity (80 , equivalence ratio (0.6 , combustion air preheat temperature (500 (K) 800) and premixing length (0.0 (mm) ≤ 48) is conducted to delineate the operational range. The spray process originating a partially premixed and a direct injection case is characterized by means of phase Doppler interferometry and shadowgraphy. The combustion process is described via OH*-chemiluminescence, flame photographs and exhaust gas measurements. The results show that the developed injection system yields Sauter mean diameters predominantly below 25 μm over the entire parameter range due to robust and prompt primary atomization. Moreover, the primary atomization process of the dual injector is sufficient under all conditions to confine secondary atomization close-to the combustor nozzle exit. The flame stabilization and reaction progress are more sensitive to the air preheat temperature than the bulk jet velocity variation as the mixture homogenization is limited by the vaporization process. Moreover, with decreasing reactivity (i.e. equivalence ratio and preheat temperature) the flame stabilization is increasingly dominated by the recirculated hot exhaust gas, indicating a transition from conventional turbulent flame propagation to auto-ignition influenced reaction progress. The resulting NOx and CO emissions approximate the values measured previously in related methane powered combustion systems. Consequently, the developed injection system is promising to expand the flexibility of compact gas turbines to liquid fuels while maintaining low emissions.

Effects of in-nozzle liquid fuel vortex cavitation on characteristics of flow and spray: Numerical research

The current work studies the dynamics of vortex cavitation under various conditions, including the pressure and orifice number, and their effects on the nozzle flow and spray characteristics using a modified cavitation model considering the swirling flow. Its validation against experimental data has demonstrated a high precision of the code in terms of vortex cavitation inside the nozzles. The higher the inlet pressure, the higher the mass flow rate and discharge coefficient, but the weaker the vortex cavitation; while the vortex cavitation intensity decreases, the discharge coefficient increases and the mass flow rate is almost constant with increasing back pressure. Moreover, under the influence of vortex cavitation, the primary jet liquid spreading angle, spray penetration, and spray volume coefficient increase first and then decrease with increasing inlet pressure; with an increase of back pressure, however, the primary jet liquid spreading angle increases, the spray penetration vice versa. Additionally, once the inner well-organized large-scale longitudinal vortices are destroyed, the vortex cavitation will not incept, which induces a larger discharge coefficient and spray penetration, but a smaller primary jet liquid spreading angle as a result. The swirling flow in the multi-hole nozzle is inhibited; hence, vortex cavitation is difficult.

The use of high-strength cast iron with a ferritic structure for the reciprocating displacement system of the internal combustion engine pistons and the improvement of its operation parameters

A study of compositions of samples of high‑strength cast iron, the use of which is possible in the development of an internal combustion engine with an improved design of a combined reciprocating conversion system, has been carried out. A number of research methods were carried out, including isothermal hardening. The optimal combination of strength and plastic properties have samples from high‑strength cast iron containing, wt.%: 2.9–3.1 C; 3.2–3.5 Si; 0.28–0.31 Mn; 0.7 Cu; 0.35 % Mo and 0.025B. Also, in the course of the study, the possibility was considered and studies were conducted on quenching cast iron in a spray chamber and jet cooling, as an alternative to traditional quenching in molten salts. The data obtained indicate that during jet‑air isothermal quenching, the structure of cast iron is completely and uniformly formed along the cross‑section, while providing a level of tensile strength up to 950 MPa, hardness up to 360–370 NV while maintaining elongation at tension up to 8 %. The use of such a class of cast iron in improved KSPVPP will both increase the life of the internal combustion engine as a whole, and improve its operational characteristics – reduce noise and reduce the weight of the structure.

Complete Workflow of Internal Nozzle Flow and Engine Simulation Using Multi-Component Fuel at Flash Boiling Conditions

Article Complete Workflow of Internal Nozzle Flow and Engine Simulation Using Multi-Component Fuel at Flash Boiling Conditions Bejoy Mandumpala Devassy 1, Yidan Zhang 2, * , Enyuan Zhang 2, and Long Zhou 2 1 AVL LIST GmbH, Hans-List-Platz 1, Graz 8020, Austria 2 AVL List Technical Center (Shanghai) Co., LTD. Shanghai 201206, China * Correspondence: yidan.zhang@avl.com Received: 17 May 2023 Accepted: 1 September 2023 Published: 14 September 2023 Abstract: At present 3D CFD simulation tools are getting more and more importance for addressing complex physical problems. This article presents a complete virtual analysis of the in-cylinder workflow in gasoline engine at flash boiling condition. Using the standard gasoline surrogate fuel PACE-20, properties of different fuel components was considered both the nozzle and in-cylinder flow. The flow, evaporation, spray jet interaction and spray collapse under flash boiling condition was studied. Molar density fraction was used to describe fuel component distribution for both gas phase and liquid phase. Based on nozzle flow simulation result, in-cylinder simulation has been done, the distribution of different fuel components and the influence on wall film, flame propagation, emission distribution has been studied. It shows that the simulation results have good agreement with testing data, and it proves the model validation for gasoline engine virtual development method under flash boiling conditions.

Comparison of Surface Morphology and Tool Wear in the Machining of Ti-6Al-4V Alloys with Uncoated and TiAlN Tools under Dry, Minimum Quantity Lubrication, Flood Cooling, and Low-Temperature Spray Jet Cooling Conditions.

TiAlN-coated carbide tools have been used to machine Ti-6Al-4V alloys in aviation workshops. However, the effect of TiAlN coating on surface morphology and tool wear in the processing of Ti-6Al-4V alloys under various cooling conditions has not been reported in the public published literature. In our current research, turning experiments of Ti-6Al-4V with uncoated and TiAlN tools under dry, MQL, flood cooling, and cryogenic spray jet cooling conditions were carried out. The machined surface roughness and tool life were selected as the two main quantitative indexes for estimating the effects of TiAlN coating on the cutting performance of Ti-6Al-4V under various cooling conditions. The results showed that TiAlN coating makes it hard to improve the machined surface roughness and tool wear of a cutting titanium alloy at a low speed of 75 m/min compared to that achieved by uncoated tools. The TiAlN tools presented excellent tool life in turning Ti-6Al-4V at a high speed of 150 m/min compared to that achieved by uncoated tools. From the perspective of obtaining finished surface roughness and superior tool life in high-speed turning Ti-6Al-4V, the selection of TiAlN tools is feasible and reasonable under the cryogenic spray jet cooling condition. The dedicative results and conclusions of this research could guide the optimized selection of cutting tools in machining Ti-6Al-4V for the aviation industry.

The influence of needle eccentric motion on injection and spray characteristics of a two-layered eight-hole diesel injector

To meet the increasingly stringent emission regulations nowadays, the quality of injection and spray must be high. The eccentric displacement of an injector needle during injection influences fuel flow characteristics within the nozzle (in-nozzle) and the injection and spray characteristics from the nozzle holes. In this study, the effect of the needle (within a double-layered eight-hole nozzle) on in-nozzle flow, injection and spray was analyzed and characterized. The model was validated by comparing simulation and experimental results from each hole (hole-to-hole). The hole-to-hole internal flow characteristics, injection characteristics, and spray characteristics under various needle eccentricities and radial displacements (needle deflections) were also analyzed. From the results, different asymmetric fuel flow characteristics were noted. Nozzle holes close to the needle deflection formed spray jets with wider cone angles and shorter penetration whereas nozzle holes at the opposite side of the needle deflection, formed spray jets with relatively smaller cone angle and higher penetration. As the needle lift got closer to the maximum lift, the effect of the eccentricity on in-nozzle fuel flow decreased. The direction of the needle eccentricity (needle deflection) dictated the flow dynamics within the holes which then affected the type of cavitation. The holes closer to the needle developed string type cavitation due to the formation of vortex flow in the nozzle. The eccentric effect of the needle was felt more by the lower layer nozzle holes than the upper layer holes.

Numerical study of electrohydrodynamic atomization considering liquid wetting and corona discharge effects

In this paper, the behavior of the cone-jet mode of fluid by electrohydrodynamic atomization (electrospray) is numerically simulated and investigated with the effect of liquid wetting and corona discharge effects. The simulation was performed with contact angle condition to fit the Taylor cone shape by experiments. Experimental data are provided to verify and validate the numerical method, followed by additional analyses on the effects of electrical conductivity, surface tension, flow rate, and fluid viscosity on the electrospray characteristics, including spray current and jet diameter. Numerical results by simulations are in reasonable agreement with experiments and consistent with the literature. Analyses on different contact angles suggest potentially major impacts of this factor on the cone-jet mode in high voltage and low flow rate circumstances. Furthermore, the influence of corona discharge on electrospray is also investigated by both electrospray–corona simulation and experiment using a high-speed camera, yielding a significant improvement in the numerical prediction for Taylor cone formation. Numerical results indicate that liquid wetting on capillary nozzles would be a vital factor for the Taylor cone formation in numerical electrospray–corona discharge studies.

Electric Traction Motor Spray Cooling—Empirical Model Development and Experimental Validation

The growing interest in electric vehicles leads to new developments of efficient electric traction motors with high power density. Since a large part of the losses in an electric motor can occur in the windings, it is important to cool the windings to reduce the temperature and protect the winding insulation from thermal aging. Oil spray cooling systems are becoming more and more relevant for cooling the windings. In this work, an approach for heat transfer modeling of electric traction motors (power classes #2-4 with 60 to 180kW) with hairpin end windings is developed and tested. The model is developed with a testing rig for different flat jet spray nozzle arrangements for a hairpin electric traction motor. The model approach showed a good agreement with the measured temperatures of the end windings in the testing rig. A transient thermal simulation of the testing rig confirms the good agreement. In a second step the model approach is transferred to another electric traction motor with a different spray cooling system. The simulation results of the second electric traction motor also show good agreement with thermal quasi-static operating points and transient measurements at low and medium speed. At high speeds the deviations increased. Possible causes for this behavior are discussed.

Specific power or droplet shear stress: Which is the primary cause of soil erosion under low-pressure sprinklers?

Specific power and droplet shear stress are generally considered to be the most critical indicators of soil erosion in sprinkler irrigation, but there is controversy about which indicator has a greater impact. This creates uncertainty in the optimization design of low-pressure sprinkler irrigation systems. In this study, a commonly used low-pressure sprinkler, i.e., Nelson D3000, was used to carry out in soil box experiments, to study the effects of specific power and average droplet shear stress at the end of a spray jet on soil erosion during sprinkler irrigation under three nozzle diameters (3.97, 5.95, and 7.94 mm), two operating pressures (103 and 138 kPa), and two soil textures (loamy sand and silty loam). Overall, the larger specific power or average droplet shear stress resulted in higher initial and steady runoff rates and a shorter time until runoff occurs and stabilizes. Enlarging the specific power or average droplet shear stress could significantly increase the initial infiltration rate, sediment yield, and surface soil bulk density, but the infiltration depth prior to runoff and surface soil porosity decreased. Furthermore, the specific power was observed to have greater correlations than average droplet shear stress with the surface runoff rate, initial infiltration rate, and increase in the soil bulk density and decrease in the soil porosity after irrigation. However, it was weakly related to the infiltration depth prior to runoff and sediment yield, indicating that the specific power could more accurately reflect the soil erosion with respect to the shear stress. To minimize the risk of soil erosion, a small operating pressure (103 kPa) is recommended in the design of center pivot irrigation systems, especially for the overhang of the system with large nozzle diameters. This research can provide the technical support for soil erosion prevention under low-pressure sprinkler irrigation.

Investigation of the mechanism of global and terminal flame uplifted in subsonic horizontal spray jet flame under sub-atmospheric pressure: From macroscopic to microscopic perspective

This work explored how subsonic horizontal spray flames behave under sub-atmospheric pressure and the mechanisms behind their combustion. For examine a horizontal spray flame with rated air volume flow and equivalence ratio, large eddy simulation (LES) and probability density function (PDF) were employed, based on the discrete phase (DPM) random trajectory model. The simulation results are in good agreement with the previous experiments. Through the micro-analysis of the burning time, burning path, and rate of the burn path of droplets under different atmospheric pressures, the combustion characteristics of the flame have been revealed; as well, a component change analysis was conducted to investigate the combustion mechanisms of the flame. Density distributions in buoyancy plumes can reveal the morphologic mechanisms in the corresponding flame regions. A detailed explanation of the varied mechanisms in horizontal spray flames in low-pressure environments is provided, in conjunction with the results of previous experiments on macroscopic flame morphology. There is also a proposed chain of influence across certain characteristics of horizontal spray flames under low pressure. This improves our understanding of mechanisms governing flame behavior in sub-atmospheric pressure environments by allowing us to theoretically design and regulate flames.

Experimental study on the effect of liquid loading on n-heptane spray jet flame stability

Flame stability significantly influences the performance of a practical combustor. The mechanisms governing the stability limits of spray jet flames are examined here using an annular co-flow spray burner. This study focuses on investigating the impact of liquid loading on spray jet flame stability, represented by flame lift-off height (LOH) and lean blow-out (LBO) limit. This is achieved by utilizing a parametric experimental study in which co-flow temperatures (Tco-flow = 298 K, 350 K, 400 K, and 450 K), spray nozzle sizes (dorifice = 0.209 mm, 0.219 mm, 0.232 mm, and 0.237 mm), fuel/air flow rates, and velocities are independently varied. A single liquid fuel, n-heptane, is used so that the vapor/liquid fractions (droplet lifetime) can be easily predicted via simple vapor–liquid equilibrium calculations to assist in the explanation of the stability mechanisms involved. The results show that the spray flame LOH mechanisms are affected by both chemical flame speed and, to a lesser extent, vaporization. On the other hand, the LBO limit is found to be controlled by the amount of liquid fuel in the presence/entering the flame. When the co-flow temperature is increased, while keeping constant co-flow velocity, the flame stabilizes near the burner lip. However, an opposite trend is noticed for flame blow-out limits, with the flame being more difficult to blow out when lower co-flow temperatures are applied. The variation of nozzle sizes leads to similar conclusions, i.e., when larger nozzle sizes are used, leading to the formation of larger droplets, the flame stabilizes further downstream and becomes more difficult to reach blow-out. The interpretation of the results indicates that delaying the vaporization and generating local enrichment regions near the flame edge enhances the flame LBO performance. Such an approach may be used as an efficient passive control mean to enhance flame stabilization; however, secondary impacts on emissions must be considered.

Optimizing the Auxiliary Air Channels of a Vortex Atomizer by 3D Printing Using the Taguchi Method

In this study, the optimum spraying performance of a pressurized vortex atomizer using water as the working fluid was investigated experimentally by modifying the geometry of auxiliary air holes via the Taguchi method. The experimental results were also examined by CFD simulations. The four control factors of the auxiliary air holes are their numbers, areas, inclination angles, and lengths. With five levels for each control factor, an L25 orthogonal table was selected. Each case of the L25 orthogonal table was test repeatedly three times to obtain key average results. The auxiliary air holes were designed by a KISSlicer CAD tool and fabricated by 3D printing. The 3D printing was carried out by fused deposition of PLA with a resolution of about 30 μm. In the experiments, the spraying jet patterns were recorded, and the water droplet weights were measured. By using the signal to noise ratios and the smaller-the-better quality characteristic, the effect of the control factors of the auxiliary air holes in descending order is the numbers, areas, inclination angles, and hole lengths, respectively. The optimum air hole configuration is the one with six holes, an inclination angle of 20°, an area of 18 mm2, and a length of 8 mm. The optimum condition was confirmed by a signal to noise ratio of 20.5 dB with 95% confidence interval. The resulting smaller jet opening angle is about 42°, close to the simulated angle of 45°. That is, by the novelty of combining 3D printing with the Taguchi method, this study obtains the optimum design with fast prototyping and relatively few experiments.