Nozzle Geometry Research Articles

Adaptation and Validation of Injection Rate Predictive Model for Solenoid Type Injectors with Different Nozzle Geometry

The present research analyses the injection rate of a direct rail injection diesel engine, focusing specifically on the influence of the nozzles and various operating conditions from real road tests on the rate of injection. A diesel injector test bench was used for feedback with real data from the test vehicle under real road conditions. An analysis of the behaviour of the injection rate was carried out using the zero-dimensional model. This model generated a predictive model that incorporated the five variables identified through a developed multivariate analysis of variance, showing a high correlation of dependence between variations in injection pressure, the diameter of the holes, and the number of holes with greater representativeness. The results obtained showed that the nozzle geometry and the physical properties of the fuel had a direct effect on the injection rate. This analysis enriches the understanding of fuel injection and its effects on diesel engine performance by providing an analysis of the system components that influence the injection rate and generating a simple tool to feed thermodynamic diagnostic models. The proposal model may be used as an input in thermodynamics predictive models and reduce the simulation load in computational fluid dynamics predictive models.

Mixing of Hydrogen-Steam Buoyancy Jets Released into the Upper Atmosphere of the Containment Building

This study evaluates the spatial dilution of hydrogen concentration caused by steam-hydrogen buoyancy jets rising through the open top of the steam generator compartment during a loss-of-coolant accident in the OPR1000, the Korean Standard Nuclear Power Plant. The correlation of the concentration decay rate in the plume with relatively high buoyant flux was applied to estimate the hydrogen concentration in the rise distance of the buoyant jet. The MELCOR code was used to calculate the gas composition and discharge flow rate in the ruptured cold leg during the rapid cladding oxidation to determine the volume and buoyant fluxes that affect the mixing behavior. The concentration decay rate at the plume’s center decreases as the steam-hydrogen binary buoyant jet rises. Despite the assumed initial volume flux and simplified jet nozzle geometry, the decay rate correlation can assess conservatively the diluted hydrogen in a severe accident.

Controllable preparation of YSZ-STHS in arc plasma spheroidization: Exploring the plasma flow characteristics' impact on powder quality

Yttria-stabilized zirconia hollow spherical powder (YSZ-HOSP) is a widely utilized ceramic material in thermal barrier coatings (TBCs). Within the category of YSZ-HOSP, yttria-stabilized zirconia spherical thin-walled hollow-shell powder (YSZ-STHS) displays immense potential for producing TBCs with minimal inter-lamellar porosity and cracks. Arc plasma torch equipped with flow-shaping nozzle shows promise for preparing YSZ-STHS. However, there is limited research on the impact of the nozzle geometry on plasma flow field characteristics and the resulting effect on the quality of YSZ-HOSP, particularly in terms of spheroidization ratio, hollow-shell powder ratio, and shell thickness. To achieve controllable preparation of YSZ-STHS in arc plasma spheroidization, this paper proposed a novel model for the formation of YSZ-HOSP under different plasma flow characteristics, including high-speed compressing flow field, intermediate-speed critical flow field, and low-speed expanding flow field. These different plasma flow characteristics were achieved by changing the nozzle diameter and investigated by both numerical simulation and experiments in terms of plasma flow characteristics, electro-thermal characteristics, and the quality of the YSZ-HOSP. Results reveal that YSZ-HOSP prepared with high-speed compressing flow field resulted in a low hollow-shell powder ratio, while low-speed expanding flow field led to an over-thick shell. Conversely, the intermediate-speed critical flow field demonstrates relatively high thermal efficiency and enthalpy, along with moderate jet temperature and velocity, resulting in YSZ-STHS with a spheroidization ratio of 96.6 %, a hollow-shell powder ratio of 92.5 %, and a mean shell thickness of 3.49 μm. Therefore, it is evident that manipulating plasma flow characteristics allows for the controlled preparation of YSZ-STHS.

A nozzle design for mitigating particle slowing in the bow shock region during micro-cold spray of 8 YSZ films

During micro-cold spray deposition, also referred to as the aerosol deposition method or vacuum kinetic spraying, performed with conventional nozzles, the particle impact velocities decrease drastically with particle size for fine particles <500 nm in diameter due to slowing in the stagnation region. A new design for a nozzle that contains pressure relief channels is proposed that allows the pressure in the stagnation region downstream of the bow shock to be reduced. This reduced stagnation pressure results in less particle slowing compared to conventional nozzle geometries, particularly for smaller or less dense particles. The effects of the channel geometry on the particle impact velocity are systematically investigated by independently varying the channel parameters. Calculations show that the impact velocities for 100 and 200 nm yttria stabilized zirconia particles is increased by 111% and 31%, respectively, for a selected pressure relief channel nozzle when compared to a comparable conventional nozzle. Although impact velocities are increased, a tradeoff exists with this nozzle design in that the particle focusing in the nozzle is decreased and some of the particles may be removed from the aerosol by the channels. Experiments using a nitrogen as a carrier gas at ∼40 kPa upstream pressure show that, despite the loss of larger particles into the relief channels, the deposition efficiency is improved by 300% when depositing films from fine 8 YSZ powder with the pressure relief nozzle compared to a conventional nozzle.

Numerical Analysis of Convergent-Divergent Angles and Operating Conditions Impact on Rocket Nozzle Performance Parameters

Comprehensive numerical analysis was conducted to elucidate the exhaust performance of rocket engine nozzles. The study focused on unravelling the intricate relationship between convergence and divergence angles and their impact on the exhaust performance parameters, including velocity coefficient (cv), angularity coefficient (Ca), and gross thrust coefficient (Cfg). In contrast to conventional studies that focus mainly on the divergent section, this research delved into both convergent and divergent aspects of nozzle geometry. For the convergent section, a range of angles from 20° to 45° was systematically examined. For the divergent section, a wide spectrum of angles was explored, ranging from small (10°-13°), medium (14°-19°) and large (20°-25°) divergent angles. Further, we venture beyond geometry, investigating the influence of nozzle pressure ratio (NPR) on these key metrics. Realisable 𝑘𝑘−𝜀𝜀, enhanced wall traitement was used to simulate nozzle flow. The study identified the optimal convergent angle at 37.5°. The 15° diverging angle provides good overall performance, while the 23° angle strikes the ideal compromise: maximizing thrust and efficiency while minimizing weight and maintaining optimal performance.

The impact of the Laval nozzle shape on thrust production, using the method of characteristics

This investigation examines the influence of Laval nozzle geometry on thrust production using the method of characteristics. It explores various divergent section configurations, analyzing their impact on nozzle design and performance. Comparative analysis of software tools, study of supersonic flow phenomena, and application of the method of characteristics form the core of this research. Findings showcase strong agreement between computational tools, emphasizing the Mach number's role in divergent section shape variations and thrust force. Additionally, the study scrutinizes over-expansion and under-expansion phenomena, validated through computational simulations. Future research should be aimed at enhancing computational methodologies and investigating additional parameters affecting nozzle performance, promising advancements in rocket propulsion technology.

Influence of Nozzle Geometry and Scale-Up on Oil Droplet Breakup in the Atomization Step during Spray Drying of Emulsions

Spray drying of oil-in-water emulsions is a widespread encapsulation technique. The oil droplet size (ODS) significantly impacts encapsulation efficiency and other powder properties. The ODS is commonly set to a specific value during homogenization, assuming that it remains unchanged throughout the process, which is often inaccurate. This study investigated the impact of atomizer geometry and nozzle dimensions on oil droplet breakup during atomization using pressure-swirl atomizers. Subject of the investigation were nozzles that differ in the way the liquid is set in motion, as well as different inlet port and outlet orifice dimensions. The results indicate that nozzle inlet port area may have a significant impact on oil droplet breakup, with x90,3 values of the oil droplet size distribution decreasing from 5.29 to 2.30 µm with a decrease of the inlet area from 2.0 to 0.6 mm. Good scalability of the findings from pilot to industrial-scale was shown using larger nozzles. A simplified theoretical model, aiming to predict the ODS as a function of calculated shear rates, showed reasonable agreement to the experimental data for different atomization pressures with coefficients of determination of up to 0.99. However, it was not able to predict the impact of different nozzle dimensions, most likely due to changes in flow characteristics. These results suggest that the stress history of the oil droplets might have a larger influence than expected. Further studies will need to consider other zones of high stress in addition to the outlet orifice.

Study the Performance of Turbofan Engines under the Effect of Changing Chevron Nozzle Geometry

Study the Performance of Turbofan Engines under the Effect of Changing Chevron Nozzle Geometry

Investigation of flame structure and emission production: Combustion modeling of co-flow interaction with spray

Using a validated computational approach, the present study examines the flame structure and emission production by spray combustion in an unconfined, swirl-free lab burner. Some species, such as acetylene, a precursor to the formation of polycyclic aromatic hydrocarbons, are generated within the fuel-rich region. A smaller area of the enclosed region reduces the mass concentration of emissive species. This can be accomplished by modifying the operating conditions, such as the spray characteristics, macro-flow velocity, and nozzle geometry. Increasing the co-flow velocity has a significant effect on transforming the flame structure from a single-reaction regime to a double-structure regime. The fuel-rich area shrinks as the co-flow velocity increases, resulting in a decrease in emissive species but a fall in total heat generation. In terms of air passage design, it appears that altering the air passage area has a noticeable impact on the flame structure, where a reaction zone can be established within the flame core. Depending on the equivalence ratio, the total heat generation and output emissions can be modified through the burner air passage improvement, resulting in a 90% decrease in the production of emissive species and an 18% increase in total heat production.

Effect of Bypass Duct on the Thrust Vectoring Performance of Dual Throat Nozzle in a Supersonic Aircraft

Abstract Due to its ability to maximize thrust vectoring performance, the bypass dual throat nozzle (BDTN) has an advantage over other fluidic vectoring controls. In this study, numerical simulation is performed to analyze the flow characteristics and performance parameters of an aircraft engine with three different nozzle configurations. The nozzle of a representative engine, i.e., an F100 engine was selected as a model geometry to test the efficiency obtained by BDTN. The present investigation has shown that implementing a bypass channel on a real geometry nozzle has no significant effects on thrust vectoring performance in vectored mode. Although the real geometry scheme has a higher thrust and a discharge coefficient, the smaller cavity length resulted in lower vectoring angles. Modifying the real geometry nozzle according to the BDTN configuration significantly improved the thrust vectoring performance. However, the V-shaped bypass passage flow in the modified geometry scheme imposed un-necessary total pressure losses in the nozzle. A geometry scheme that utilized an arc-shaped rather than a V-shaped bypass passage is considered in this research and found to present minimize pressure losses. A total increase of 2% and 3.5% is hereby reported, for thrust and discharge coefficients, respectively. A decrease of 6% is reported in the thrust vectoring angle under an improved geometrical scheme. Out of three geometries, the real geometry scheme reported negligible thrust vectoring performance, while modified and improved geometry schemes indicated improved thrust vectoring performance without substantially changing the engine states.

A Comparative Study of Scarfed Nozzle for Jet-Installation Noise Reduction

AbstractThe experimental investigation of the effects of scarfed nozzles on jet-installation noise was conducted using unheated subsonic jets in an anechoic jet noise facility. Four different types of scarfed nozzles with increasing nozzle lip angles were examined to study the installation effects at various plate distances away from the jet. Mach numbers ranging from 0.3 to 0.8 were investigated in the experiments. The use of scarfed nozzles is known to result in the deflection of flow away from the centre axis, inducing asymmetry in the jet shears, leading to azimuthal variation in the spectra, and ultimately, noise reduction. This study aims to explore the possibility of reducing jet-installation noise using scarfed nozzles at subsonic flow conditions. The characteristics of jet hydrodynamic pressure fluctuations were investigated in the axial direction using far-field measurements. The near-field flow features were studied using surface pressure transducers installed on the flat plate for the installed configurations. Detailed spectral, coherence, and correlation analyses were carried out to determine the noise reduction mechanisms associated with scarfed nozzles in the proximity of a flat plate. The results of the study showed that the use of scarfed nozzles significantly reduced the jet-installation noise. The reduction was attributed to the generation of an asymmetric flow field induced by the nozzle geometry. The reduction in noise levels was also observed to increase with increasing nozzle lip angle. The detailed analyses revealed that the noise reduction mechanism was associated with a decrease in the acoustic power generated by the jet. Overall, the results suggest that scarfed nozzles can be an effective means of reducing jet-installation noise in subsonic flow conditions.

Dynamic Modelling and Simulation of Industrial Plant Fire and Gas Detection Systems; Parametric Analysis of Nozzle Flow

Industrial plant safety is of paramount importance, and the effective operation of Fire and Gas Detection Systems (FGDS) plays a critical role in preventing and mitigating incidents. This study presents a comprehensive parametric computational fluid dynamics (CFD) analysis of nozzle flow, aimed at enhancing our understanding of the complex fluid dynamics within nozzle geometries. Nozzles find wide applications in industries ranging from aerospace propulsion systems to industrial processes. The analysis employs CFD simulations with varying geometric parameters, such as nozzle shape, throat diameter, and expansion ratio, to investigate their influence on flow characteristics, including velocity profiles, pressure distributions, and shock formations. The parametric study involves systematic variations of these geometric parameters, allowing for the identification of optimal configurations for specific applications. The results shed light on the intricate interplay between nozzle geometry and flow behavior, providing valuable insights for nozzle design and optimization.

Polymer Metallization by Cold Spray Deposition of Polyamide-Copper Composite Coatings

Cold spray metallization of polymers is a promising surface engineering technique that enables the deposition of metal coatings onto polymer substrates at low process temperatures, resulting in improved surface properties, thus enhanced functionality of the polymeric material. However, deposition of well-adhering metallic coatings without causing surface damage to the polymer substrate is still a challenge. In this work, copper-polyamide composite coatings with different copper concentrations between 30 and 75 vol.% in the starting powders were deposited on polyamide substrates using a low-pressure cold spray system with two nozzle geometries of short and long diverging sections. The spray parameters were first developed for the deposition of polyamide powder (at gas temperature of 260 °C and gas pressures ranging from 0.41 to 1.37 MPa), and then used to spray the composite powder mixtures where the polyamide particles were acting as a binder for copper particles. Inflight and impact particle characteristics (velocity and temperature) of the polyamide powder were simulated to better understand the deposition properties. Considering that the selected conditions were suboptimal for the deposition of copper particles, no surface damage was caused as no penetration of the copper particles into the polymer substrate occurred. The results show that increasing the copper content in the powder mixtures significantly improved the resulting coating uniformity and the retained copper content. In addition, the coating deposited by spraying the powder mixture with a higher copper content of 75 vol.% and using the longer nozzle yielded the highest cohesion strength. To further improve coatings cohesion, two post-spray processing methods of furnace heating and hot pressing were used, and the effect of each process on coatings properties was investigated.Please confirm if the author names are presented accurately and in the correct sequence (given name, middle name/initial, family name). Given name: [Kintak Raymond] Last name [Yu]. Also, kindly confirm the details in the metadata are correct.The author names are now correct: Kintak Raymond given name and Yu last nameAll other details are corrects

Numerical Study of the Effect of Primary Nozzle Geometry on Supersonic Gas-Solid Jet of Bypass Injected Dry Powder Fire Extinguishing Device

A two-way coupled model between polydisperse particle phases with compressible gases and a density-based coupling implicit solution method, combining the third-order MUSCL with QUICK spatial discretization scheme and the second-order temporal discretization scheme, are constructed based on the discrete-phase model (DPM) and the stochastic wander model (DRWM) in the Eulerian–Lagrangian framework in conjunction with a unitary particulate source (PSIC) approach and the SST k-ω turbulence model. The accuracy of the numerical prediction method is verified using previous supersonic nozzle gas-solid two-phase flow experiments. Numerical simulation of a two-phase jet of dry powder extinguishing agent gas with pilot-type supersonic nozzle was performed to analyze the influence of geometrical parameters, such as the length ratio rL and the area ratio rA of the main nozzle on the two-phase flow field, as well as on the jet performance indexes, such as the particle mean velocity vp,a, velocity inhomogeneity Φvp, particle dispersion Ψp, particle mean acceleration ap,a, etc. By analyzing the parameters, we indicate the requirements for the combination of jet performance metrics for different flame types such as penetrating, spreading, and dispersing.

An Investigation on Uncontrolled and Vortex-Generator Controlled Supersonic Jets

The present study is carried out with a motivation to investigate the axisymmetric supersonic jet both experimentally and computationally. An open jet facility was utilized to carry out the experiments, and the results were compared with computational simulations employing the K-omega SST turbulence model using ANSYS software. It is important to note that, the computational validation has been done incorporating the Rayleigh Pitot formula to match the centerline pressure for the uncontrolled jet, which has not been found in any other validation studies according to the authors’ understanding. Besides, the experimental study is extended with a focus on evaluating the impact of Vortex Generators (VGs) on Mach 1.6 supersonic jets. The aim was to enhance jet mixing, a critical factor for improving engine performance. Various nozzle geometry modifications were explored in the past, but VGs emerged as the most effective method for optimizing jet mixing efficiency. The investigation revealed a substantial decrement in the supersonic jet core length when VGs were introduced at the nozzle exit, especially under favorable pressure gradients. This reduction in the supersonic core emphasized the role of VGs in enhancing mixing efficiency. The study also confirmed that VGs significantly distort wave patterns within the supersonic core, crucial for improved jet mixing. This research signifies the importance of VGs in augmenting the mixing of Mach 1.6 jets, offering the potential for improved jet performance and reduced noise emissions in the aerospace industry.

Oxygen Uptake of Ti6Al4V during Direct Metal Deposition Process

The efficient fabrication of titanium components using laser direct metal deposition (DMD) is gaining significant importance in the aerospace and medical sectors. The DMD process must be appropriately designed to address the issue of oxidation, as titanium exhibits a high affinity for oxygen. The carrier gas flow and shield gas flow, which have been considered secondary factors so far, are shown to exert a substantial influence on the gas dynamics of the DMD process. By varying these parameters, it is possible to identify the influence of the gas volume flows on the oxidation behavior exhibited during the DMD process. To quantify the oxygen uptake in titanium structures during buildup, hot carrier gas extraction is employed. Experiments are conducted using both a three-jet and a coaxial nozzle to assess the influence of nozzle geometry. Additionally, the experiments are conducted within a shielding gas chamber to demonstrate the benefits of such a chamber in mitigating oxidation. Finally, the study reveals that by appropriately combining the parameters of carrier gas volume flow, shield gas volume, and travel speed, it is possible to fabricate titanium components, which fulfill the requirements regarding oxygen content of aerospace and medical applications even without the utilization of a shielding gas chamber.

Multispecies Flow Indirect-Noise Modeling Re-Examined with a Helicopter-Engine Application

Composition noise has recently received increasing attention for its potential to contribute significantly to the indirect noise mechanism. In this study, the importance and definition of composition noise are revisited by proposing a new proper decomposition between entropy and mixture compositional fluctuations. When assuming quasi-one-dimensional, multispecies, isentropic, and nonreactive flow in nozzles, the resulting system of equations shows a new and remarkable one-way coupling between composition waves and both acoustic and entropy waves. Relying on the Magnus-expansion methodology, an exact solution of that system is investigated. The proposed theory is validated by comparing the model predictions with direct numerical simulations of nozzle flows in which compositional fluctuations are pulsed. It is shown that composition transfer functions from the unsteady simulations are in agreement with the analytical model of this paper. Finally, a hybrid approach is investigated consisting of extracting waves from a large-eddy simulation of a real helicopter engine and propagating those through different nozzle geometries. Composition noise is found to be negligible compared to direct or indirect entropy noise since it is at least 20 dB lower than other noise mechanisms for all tested cases.

Influence of materials and nozzle geometry on spray and placement behavior of wet-mix shotcrete

Shotcrete finds extensive applications in civil engineering, from repair and rehabilitation to new constructions. Nevertheless, shotcrete construction frequently suffers from placement issues, such as rebound and overshooting. These challenges can result in reduced operational efficiency, increased material wastage, diminished construction quality, and potential workplace hazards. It is worth noting that these placement issues are intrinsically linked to the spray characteristics of shotcrete. These characteristics are contingent upon various factors, including the material's flowability and viscosity, as well as the nozzle geometry. This research experimentally characterized the spray behavior of wet-mix shotcrete. High-speed cameras and image analysis techniques were utilized to capture and characterize wet-mix shotcrete on a full-scale spraying setup. The study experimentally determined the key placement performance parameters such as placement, rebound, and final build-up thickness and correlates the placement performance of shotcrete with the spray characteristics. The findings reveal that wider spray opening angles, smaller droplet sizes, and higher velocities contribute to improved material deposition, reduced rebound, and increased build-up thickness. The study also assesses the impact of nozzle geometry and rheology of the shotcrete mixture. Increased flowability led to slightly better spray behavior and placement. Higher material viscosity produced a more consistent spray which enhanced shotcrete performance. Multi-air jet guns, where compressed air directly contacts droplets, can enhance shotcrete spray efficiency.

Effect of multi-parameter optimization of water-laser coupling device and nozzle geometry on the stability of water-guided laser beam

The stability of the water jet flow used in water-guided laser processing plays a crucial role in determining the quality of the processing process. The present study aims to investigate the effect of water-laser coupling device and nozzle geometry on the stable length of a water-guided laser beam. A numerical model is developed to analyze the internal flow field within the coupling device. Computational fluid dynamics (CFD) simulations are employed to examine how variations in cone nozzle's length-to-diameter ratio, divergence angle, nozzle aperture, and inlet pressure that affect the flow characteristics of water jet. Subsequently, the Latin Hypercube experimental design method is employed to establish parameter samples and construct a Kriging approximation model for the stable length of water-guided laser beam. The Multiple Island Genetic Algorithm (MIGA) is utilized for global optimization of the approximation model, while CFD methods are employed to analyze and validate the optimization results. Finally, experimental verification was conducted to determine the stable length of water-guided laser beam generated by the optimized cone nozzle structure. The research findings demonstrate that the optimized nozzle structure can compensate for approximately 21 mm in the stable distance of water-guided laser beam under the pressure of 5.0 MPa. This study provides valuable guidance for enhancing the performance and engineering applications of laser micro-jet processing technology.

Optimization Design of Mining Tri-cone Bit Air Nozzle by CFD

Performance of the air nozzle of the mine tri-cone bit directly affects life of bit and rock breaking efficiency. The shape of air nozzle influences performance of mine tri-cone bit. It is necessary to optimize the shape of the air nozzle of tri-cone drill bits. The general specifications of gas mine tri-cone bit were analysed. Working condition and parameters of the air nozzle of the mine tri-cone bit were determined. A three-dimensional model of the air nozzle of the mine tri-cone bit was established. The characteristic geometry and range of air nozzle were determined. The performance index of air nozzle was proposed. An orthogonal experiment table of characteristic geometry of air nozzle was established. The ranking of influence weights of characteristic geometry was obtained. Key characteristic geometry which affects the performance of air nozzle was also obtained. This thesis work helps to improve the working performance of the gas nozzle of the three-cone bit. It can provide some reference ideas for the optimized design of the cone bit