Nozzle Configuration Research Articles

Production of Monodisperse Oil-in-Water Droplets and Polymeric Microspheres Below 20 μm Using a PDMS-Based Step Emulsification Device

Step emulsification (SE) is renowned for its robustness in generating monodisperse emulsion droplets at arrayed nozzles. However, few studies have explored poly(dimethylsiloxane) (PDMS)-based SE devices for producing monodisperse oil-in-water (O/W) droplets and polymeric microspheres with diameters below 20 µm—materials with broad applicability. In this study, we present a PDMS-based microfluidic SE device designed to achieve this goal. Two devices with 264 nozzles each were fabricated, featuring straight and triangular nozzle configurations, both with a height of 4 µm and a minimum width of 10 µm. The devices were rendered hydrophilic via oxygen plasma treatment. A photocurable acrylate monomer served as the dispersed phase, while an aqueous polyvinyl alcohol solution acted as the continuous phase. The straight nozzles produced polydisperse droplets with diameters exceeding 30 µm and coefficient-of-variation (CV) values above 10%. In contrast, the triangular nozzles, with an opening width of 38 µm, consistently generated monodisperse droplets with diameters below 20 µm, CVs below 4%, and a maximum throughput of 0.5 mL h−1. Off-chip photopolymerization of these droplets yielded monodisperse acrylic microspheres. The low-cost, disposable, and scalable PDMS-based SE device offers significant potential for applications spanning from laboratory-scale research to industrial-scale particle manufacturing.

Parametric study on configuration geometry effect on thrust performance of annular ED nozzles

A numerical investigation is conducted to uncover the parametric influence of configuration geometry on the thrust performance of annular expansion deflection (ED) nozzles. Based on the classic design principle of Taylor’s ED nozzle configuration, the influences of six geometric elements, covering the expansion channel region, the near-pintle region, and the shroud region, including 13 nozzle configurations, are examined in detail. The flow characteristics in each nozzle are demonstrated, according to which the connections between the geometric changes and nozzle thrust performance are elucidated. The present results show that the nozzle flow pattern is closely related to the nozzle configuration geometry. In the open operation mode of the ED nozzle, the wide expansion channel has very little restriction on the axial expansion of the exhaust gas. The high axial velocity brings strong shock strength and total pressure loss, which are unfavorable to the nozzle thrust performance. The large curvature of the shroud expansion section contributes greatly to the exhaust gas deflection, which increases the mass flow rate of the supersonic core flow zone through the nozzle exit plane, and therefore favors the thrust performance. In the closed operation mode, geometric differences in the expansion channel region have little effect on the supersonic gas, which fills almost the entire nozzle. The shroud region still affects the axial deflection of the gas and its large curvature is associated with superior thrust performance. These investigations suggest that the annular ED nozzles with narrow expansion channels and large shroud curvatures are superior in thrust performance.

Effects of nozzle geometry, compression ratio and cerium oxide nanoparticles on algae biodiesel performance in a VCR diesel engine with hydrogen addition

This paper discusses an exploratory analysis of performance and emissions characteristics of a variable compression ratio (VCR) diesel engine using various compression ratios, nozzle hole configurations, and injection timings. Results will be employed to further elucidate interactions among those parameters as well as their influence upon the operation efficiency and environmental output. An engine was tested on the B20 biodiesel blend from the transesterification of algal oil. The sample, which contained nano-additives with cerium oxide (CeO2) at a concentration of 75 ppm, underwent extensive analysis using scanning electron microscopy and energy dispersive X-ray analysis (FTIR). The study included different compression ratios such as 16:1, 17:1, 18:1, and 19:1, utilizing nozzle designs with hole diameters of 2, 3, 4, and 5 mm. Additionally, it also examines the effects of hydrogen injection at time intervals of 3, 4, and 5 ms, aiming to comprehend the interaction between these parameters and their impact on the performance outcome. The presence of CeO2 75 ppm resulted in a significant reduction in emissions, as well as improved combustion efficiency. The configuration resulted in a 6.1% improvement in brake thermal efficiency (BTE), as well as a decrease in brake specific fuel consumption (BSFC) from 250 g/kWh to 200 g/kWh. Improving the number of holes in the nozzle revealed a drop in the temperature of the exhaust gas up to 250°C. Reduced nitrogen oxide (NOX) emissions and improved cylinder pressure accompanied these decreases, thanks to the increased heat release rates generated by hydrogen addition. The addition of CeO2 nanoparticles to the B20 blended fuel, along with modifications to the nozzle hole design and hydrogen injection, not only reduces emission values but also lowers fuel consumption, lowers exhaust gas temperature (EGT), and improves combustion efficiency.

Experimental study on the effect of nozzle configurations on snow quality for outdoor snow-makers

In regions with unfavorable climatic conditions and insufficient natural snowfall, skiing development depends significantly on the support of outdoor snow-makers. The atomized droplets produced by the swirl nozzle of the snow-maker collide with the crystal nucleus produced by the air-assisted atomizer to generate snowflakes. The effects of various configurations of swirl nozzles on snowmaking efficiency and snow quality are notably significant. This study investigates the influence of nozzle number, nozzle diameter, and ambient temperature on snowmaking performance through an outdoor snowmaking experiment. The results indicate that an appropriate nozzle configuration (number and diameter) significantly enhances snow quality. The spatial uniformity of snow density is significantly enhanced when utilizing 24 nozzles with a diameter of 1.9 mm and 72 mixed-diameter nozzles. With a nozzle diameter of 1.7 mm, the snow production of 48 and 80 nozzles is comparable; however, the water consumption of 48 nozzles is lower. Furthermore, at low temperatures, the artificial snow produced by the mixed-diameter nozzles exhibits snow quality characteristics comparable to those produced at high temperatures. Nevertheless, snow production is lower than that of the single-diameter nozzle configuration. Simultaneously, the density of the artificial snow produced at high temperatures is generally greater than that produced at low temperatures. Experimental measurements of the grain size of the artificial snow are concentrated between 0.15 and 0.55 mm. This study provides a basis for regulating snow quality in ski resorts. Additionally, it offers guidance on the design and structuring of efficient snow-makers.

Investigation of steam-diluted hydrogen combustion in a counter-current nozzle configuration using LES

Investigation of steam-diluted hydrogen combustion in a counter-current nozzle configuration using LES

Enhancing thermal performance in power electronic modules through a novel micro-nozzle model and hybrid nanoparticles with varied shape factors

Temperature uniformity in high-heat-flux electronic devices is an important concern in the field of micro-scale heat transfer. The present study recommends four novel configurations of cone-shaped nozzles to reduce the temperature of Si-IGBT electrical modules. Moreover, the thermal characteristics of working fluid (H2O) improved using a 1 % to 5 % volume fraction of Fe3O4 –Ag (50 % -50 %) nanoparticles with Spherical, Blades, and Lamina synthetic shapes. The constant heat flux ranging from 110 W/cm2 to 240 W/cm2 was considered a boundary condition for the top of the module, i.e. IGBT and the Diode. The simulation was conducted by computational fluid dynamic software ANSYS-FLUENT-18.2 which employed the Realizable k-ε model for turbulence flow. The outputs indicated that the spiral nozzles (Case 4) increase the turbulent kinetic energy (TKE) compared to simple cone-shaped nozzles (Case 1). It was also found that the use of hybrid nanoparticles causes an increase in the cooling of the fluid and moves away from the critical point (393.15 K). On the other hand, the synthetic forms of Lamina have caused a reduction of the temperature by almost 2.3 % relative to other forms of nanoparticles because of their higher thermal permeability.

Mixing enhancement with minimal thrust loss for the Mach 1.76 jet issuing from different beveled collar nozzles

The main objective of the present investigation is to enhance the jet mixing by introducing a nozzle collar exit inclination having bevel angles of 30°, 45°, and 60°. In addition to this, the present study also addresses the problem of investigating the jet which attains maximum mixing from beveled collar nozzle with the imposition of a minimal overall thrust loss penalty. The nozzles of the present study have been designed to deliver a uniform Mach 1.76 jet at the nozzle collar exit. The results thus obtained through numerical computations have been compared with that of the reference nozzle which has zero exit inclination. The investigations have been performed under both design and off-design conditions of the jet by varying the nozzle pressure ratio (NPR) from 4.5 to 6.5 with unit step size. It is seen that the rate of jet mixing is augmented with the increase in the bevel angle. Thus, the 60° beveled collar nozzle demonstrated the highest jet mixing in comparison to the reference nozzle, 30° and 45° beveled collar nozzle at each nozzle pressure ratio. However, 60° beveled collar nozzle has been substantially penalized with the highest thrust loss of about 6.5% at nozzle pressure ratio 4.5 and about 3.5% at nozzle pressure ratio 5.5 with respect to the reference nozzle and other nozzles of the present study. The 45° and 30° beveled collar nozzles reported the thrust penalty below 2.3% and 1%, respectively. The overall performance, which includes mixing enhancement along with the minimal thrust loss, has been found in the 45° beveled collar nozzle, which clearly justifies its preference over the other investigated nozzle configurations.

An experimental study on the influence of nozzle hole numbers and patterns of a passive pre-chamber spark ignition system

Pre-chamber spark ignition system enhances the combustion stability and efficiency of lean burn engines. Pre-chamber spark ignition system performance directly relies on the characteristics of the turbulent flame jet, which are governed by the pre-chamber geometrical parameters and nozzle hole configurations. Based on the existing literatures, limited research on nozzle hole numbers and patterns is noted with passive pre-chamber, and thus, the impact of these nozzle hole configurations on the combustion and flame development characteristics for hydrogen-methane-air mixtures is investigated in a constant volume combustion chamber. In the current study, single-layer nozzle hole configurations with three, four, six, and eight nozzle holes and double-layer nozzle hole configurations with six and eight nozzle holes are designed and tested in an optically accessible combustion chamber under various equivalence ratio conditions. The results indicated that the combustion characteristics deteriorated with an increase in nozzle holes, except with the single-layer four nozzle hole configuration. Compared to the single-layer eight nozzle hole configuration, the ignition delay and combustion duration for hydrogen-methane-air mixtures with single-layer four nozzle hole configuration was reduced by 31.9% and 30.7% under lean conditions. A reduction in flame jet penetration length, area and velocity and increased adjacent flame jet interaction was noticed for the single-layer configuration with more nozzle holes, and thus, a different nozzle hole pattern was studied in the current study. The double-layer configurations with more nozzle holes showed better combustion and flame development characteristics than single-layer configurations due to their unique flame structure, uniform and faster flame jet distribution, and reduced adjacent flame jet interaction. The ignition delay and combustion duration for hydrogen-methane-air mixtures with the double layer eight nozzle hole configuration were reduced by 30.5% and 40.7% compared to the single-layer eight nozzle hole configuration.

CFD-DEM simulation and experimental investigations on continuous hydraulic sampling of deep-sea polymetallic nodules

The physical sampling to grasp the distribution of deep-sea polymetallic nodules is essential for efficient mining. A hydraulic sampling scheme is proposed that balances low environmental disturbance, high sampling precision, broad coverage, and statistical data viability to address the limitations of existing methods. This paper utilizes a coupled approach of Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) to explore innovative solutions for precise and continuous hydraulic sampling of deep-sea polymetallic nodules. Focusing on the optimization of the double-row nozzle sampling mechanism design, simulations are conducted to analyze the dynamic characteristics of solid-liquid two-phase flow during the hydraulic sampling process under various nozzle configurations and operational water pressures of the pump. Laboratory experiments with the hydraulic sampling mechanism validate the accuracy of the simulation and the effectiveness of the optimization suggestions. The configuration is finalized with a front nozzle diameter of 10 × φ9 mm, a rear nozzle diameter of 10 × φ7 mm, and an initial working water pressure for the pump of 80 kPa. Subsequently, integrated driving-sampling experiments are conducted using a self-propelled tracked vehicle, validating the feasibility of the proposed configuration.

The formation and post-formation processes of vortex rings discharged from laminar starting jets

Motivated by biological systems, vortex rings can enhance the propulsive efficiency in industrial systems. To study the vortex properties during the formation and post-formation stages, impulsively starting jets are investigated by simulations. The effects of the stroke ratio and nozzle geometry are studied at a fixed jet Reynolds number of 2500. The stroke ratio at the formation number is found to be not enough to produce a vortex ring with maximum circulation. The stroke ratio is suggested to be about twice as large as the formation number. An alternative criterion based on the circulation ratio is proposed to describe the onset of pinch-off. This criterion states that the pinch-off would start when the vortex ring attains about 80% of the total jet circulation. During the formation stage, the scaling laws for vortex trajectories and circulation are proposed for continuous formation. By combining the suggested scaling relations and Saffman's velocity formula, the evolution of non-dimensional energy can be predicted. During the post-formation stage, the scaling laws for vortex properties (e.g., the vortex ring diameter, translational velocity, and circulation) are found to be independent of both the nozzle configuration and the vortex Reynolds number. On the grounds of the invariance of impulse in vortex decay, the scaling laws of vortex motion are derived for the non-dimensional energy, circulation, and diffusivity scale of the vortex core. In consequence, the normalized energy and circulation found in experiments can be successfully derived from the similarity model for both nozzle configurations.

Suppression of Combustion Oscillations in Hydrogen-Enriched Can-Type Combustors Through Fuel Staging

Abstract To achieve decarbonization in power-generating gas turbines, the technology of mixing hydrogen with natural gas is garnering significant attention. However, when blending natural gas with hydrogen, the altered combustion characteristics can lead to combustion instability in gas turbine combustors. Although fuel staging can effectively suppress combustion instability for can-type combustors, further research on mitigation strategies for hydrogen cofiring and their predictive methods is required. This study involves hydrogen cofiring experiments using a full-scale can-type combustor. Moreover, the resulting suppression of combustion instability is analyzed through fuel staging by utilizing three-dimensional (3D) computational fluid dynamics (CFD) and one-dimensional (1D) thermo-acoustic analysis. The experiments used a full-scale industrial can-type combustor with a five-around-one nozzle configuration. Hydrogen was blended with natural gas up to a volume fraction of 30%, maintaining a constant thermal power. Fuel staging was applied by controlling two out of five outer nozzles (ONs) along with the remaining three. Before the 1D thermo-acoustic analysis, the internal flame structure of the combustor was examined through 3D CFD analysis. Based on the results, a multi-input multi-output (MIMO) system was constructed for 1D thermo-acoustic analysis of the can-type combustor. The application of time delays derived from 3D CFD analysis to the 1D model revealed that differences in flame time delays across the nozzles cause combustion instability suppression observed in fuel staging.

A parametric investigation of Dual-throat nozzle bypass channel configurations for advanced Aviation applications

The Bypass Dual-Throat Nozzle (BDTN) has garnered growing attention due to its remarkable thrust vectoring capabilities. This type of nozzle boasts broad application prospects as it achieves deflection control of the jet stream merely through regulating the opening and closing of bypass channels. Our comprehensive study delves deeply into the intricate parameterization of the bypass channel within the BDTN. Research has demonstrated that utilizing Fluent software in conjunction with the Realizable k-epsilon turbulence model, standard wall functions, and the Sutherland formula for viscosity coefficient approximation can yield a relatively accurate representation of the vector flow field structure within the BDTN. Following the validation of the numerical computation methodology employed in this study, we have investigated the influence of factors such as bypass channel radius, precise valve positioning, and actuation direction on the nozzle's vectoring performance. Key findings indicate that, due to the relatively small proportion of secondary flow, the radius of the bypass channel has minimal impact on the thrust vector angle. The positioning of the valve and its opening direction are critical in determining the thrust vector angle, requiring careful consideration during the design and optimization process. Fully opening the bypass channel does not necessarily yield the maximum thrust vector angle. Moreover, the total pressure, velocity, position, and direction of the secondary flow within the bypass channel exert a more profound influence on the nozzle's vector performance compared to the mere presence of the secondary flow itself. Notably, the forward opening method of the valve emerges as the preferred choice, as it facilitates more precise later vector control.

Innovative Metal Powder Production Using CFD with Convergent-Divergent Nozzles in Wire Arc Atomization

This study aims to enhance the production of metal powders using a novel approach that integrates computational fluid dynamics (CFD) with convergent-divergent (C-D) nozzles in wire arc spraying atomization (WASA). The primary objective is to investigate the influence of nozzle design on particle size distribution and production efficiency. Utilizing the ANSYS CFD Fluent program, simulations were conducted to analyze the effects of various parameters, including throat diameter and divergent angles, on gas dynamics and metal droplet behavior. The findings reveal that C-D nozzles facilitate the acceleration of gas flow to supersonic speeds, significantly improving the shear force acting on the molten metal, thereby promoting the fragmentation of droplets into smaller particles. Notably, the optimized nozzle configuration achieved a median particle size (D50) of 44.42 µm, suitable for additive manufacturing applications. The novelty of this work lies in its comprehensive simulation framework that allows for rapid virtual testing, potentially leading to significant improvements in the efficiency and quality of metal powder production processes. This research addresses critical gaps in the existing literature and provides a robust foundation for future studies in the field of metal powder manufacturing. Doi: 10.28991/HIJ-2024-05-03-02 Full Text: PDF

Flow Effects and Propulsion Performance on Various Single Expansion Ramp Nozzle Configurations of Scramjet Engine

This study serves as a research endeavor aiming to explore the behavior of the coupling flow effects of the single expansion ramp nozzle (SERN) in over-expansion conditions during the static start-up process. The open-source program OpenFOAM and its solver “rhoCentralFoam” are employed in the 2D simulation and the two critical geometric variations, the shape of the ramp and the length of the flap beyond the throat, are considered in the geometric variation. The result shows the preferable propulsion performance in the FSS (Free Shockwave Separation) state compared to RSS (Restricted Shockwave Separation). FSS also plays the role of the initial, albeit transient, separation, which originates from the shockwave from the throat and will eventually transform into a stabler RSS state. For the 100% flap length configuration in this study, the axial thrust can achieve a high value of 500 N/m in the FSS state and decrease to around 450 N/m, on average, in the RSS state. The trust angle also shows a preferable performance of around −13° in FSS compared to −30° in RSS. Regarding geometric modifications, both modifications, shorting the flap and bell-shaped ramp adjustments, manifest similar effects. Both conical and bell-shaped short flap configurations demonstrate an axial thrust from around 1750 to 1900 N/m and a thrust angle of around −45°. However, the flap shortening, which may demonstrate an attitude compensation effect, exhibits a more pronounced effect compared to the bell-shaped modification.

Influence of Double-Ducted Serpentine Nozzle Configurations on the Interaction Characteristics between the External and Nozzle Flow of Aircraft

To clarify the influence of the serpentine nozzle configurations on the flow characteristics and aerodynamic performance of aircraft, the flow features and aerodynamic performances of the double-ducted serpentine nozzles with different aspect ratios (AR), length–diameter ratios (LDR) and shielding ratios (SR) are numerically investigated. The results show that the asymmetric nozzle flow occurs due to the curved profile of serpentine nozzles, and a local accelerating effect exists at the S-bend, causing the increase in wall shear stress. The unilateral unsymmetrical expansion of the tail jet in the upward direction interacts with the separated external flow of the afterbody, forming an obvious cross-shock wave and shear layer structure. The surface pressure of the afterbody increases along the external flow direction, and decreases sharply in the separation point of the boundary layer. With the increase in AR and LDR, the local accelerating effect of the nozzle flow weakens, while with the increase in SR, the accelerating effect increases. The total pressure recovery coefficient, flow coefficient and axial thrust coefficient all decrease with the increase in AR, LDR, and SR. The thrust vector angle decreases with the increase in AR but is less affected by LDR and SR.

A numerical study on the influence of multiple nozzles on the infrared radiation signatures of liquid rocket exhaust plumes

A numerical study was conducted to examine the relationship between the infrared radiation characteristics of liquid rocket engine exhaust plumes under the same thrust conditions and the number and expansion degree of nozzles. This study used the Reynolds-averaged computational fluid dynamics method to simulate the flow field of multiple nozzles. A single-line group combined with the G-C approximation was used to calculate the molecular spectral properties, and a three-dimensional radiation transfer calculation model was established based on the line-of-sight method. The infrared radiation characteristics of the exhaust plume were calculated for single, double, three, and four nozzles. The radiation intensity of two typical bands, 2.7 μm and 4.3 μm, was studied, including spectrum, intensity, and radiation intensity distribution. The results show that the integrated infrared radiation intensity of the double-nozzle plume is 51.36 % lower than the average of the other three nozzle configurations under the over-highly under-expansion state. The radiation difference of the double nozzle reaches up to 38.3 % at different detection angles, whereas the differences between the three and four nozzles are below 10.5 % and 6.1 %, respectively, indicating that the radiation difference at each detection angle gradually decreases with the increase in the number of nozzles.

Simulation Analysis on the Characteristics of Aerosol Particles to Inhibit the Infrared Radiation of Exhaust Plumes.

Aerosol infrared stealth technology is a highly effective method to reduce the intensity of infrared radiation by releasing aerosol particles around the hot exhaust plume. This paper uses a Computational Fluid Dynamics (CFD) two-phase flow model to simulate the exhaust plume fields of three kinds of engine nozzles containing aerosol particles. The Planck-weighted narrow spectral band gas model and the Reverse Monte Carlo method are used for infrared radiation transfer calculations to analyze the influencing factors and laws for the suppression of the infrared radiation properties of exhaust plumes by four typical aerosol particles. The simulation calculation results show that the radiation suppression efficiency of aerosol particles on the exhaust plume reaches its maximum value at a detection angle (ϕ) of 0° and decreases with increasing ϕ, reaching its minimum value at 90°. Reducing the aerosol particle size and increasing the aerosol mass flux can enhance the suppression effect. In the exhaust plume studied in this paper, the radiation suppression effect is best when the particle size is 1 μm and the mass flux is 0.08 kg/s. In addition, the inhibition of aerosol particles varies among different materials, with graphite having the best inhibition effect, followed by H2O, MgO, and SiO2. Solid particles will increase the radiation intensity and change the spectral radiation characteristics of the exhaust plume at detection angles close to the vertical nozzle axis due to the scattering effect. Finally, this paper analyzed the suppression effects of three standard nozzle configurations under the same aerosol particle condition and found that the S-bend nozzle provides better suppression.

Computational modeling of the rectangular non-aligned multi-injector for efficient fuel mixing in a supersonic combustion chamber

The present investigation examines the usage of rectangular multi-injectors for fuel injection in a supersonic combustion chamber. To evaluate the fuel jet penetration and distribution, a computational method is applied to model the supersonic compressible flow with cross multi-fuel jets released from annular rectangular nozzles with different nozzle configurations. The main effort of this work is to evaluate the jet interactions in the existence of cross-supersonic flow. Fuel jet penetration and distribution are evaluated for three proposed injector arrangements to attain the more efficient option for better fuel mixing. Our results show that reducing injector space improves fuel mixing inside the combustor via creation of strong vortices. Beside, injection of air from internal nozzle increase fuel interactions and fuel mixing inside combustion chamber.

Increasing the efficiency and stability of fuel supply to the combustion chamber of a liquid rocket engine by spray nozzles

In this paper, various configurations of jet nozzles are analyzed, as well as their design. The effects of the inlet chamfer of jet nozzles on their flow rate and range are considered. It is shown out that today it is expedient to make precision micro-holes of the nozzles using high-precision three-dimensional electric-erosion equipment. The optimal design parameters of jet nozzles are also determined.

Effects of Nozzle Configuration on Efficiency of Direct-Contact Gas-Vapor Mixture Generators

Effects of Nozzle Configuration on Efficiency of Direct-Contact Gas-Vapor Mixture Generators