Nozzle Structure Research Articles

Combustion characteristics of methanol engine applying TJI-HPDI with optimized pre-chamber nozzle structure under different injection and spark strategy

Methanol fuel faces challenges in achieving mixing controlled combustion (MCC) due to its low cetane number. This study proposes utilizing turbulent jet ignition to facilitate methanol MCC under high-pressure direct injection mode, namely TJI-HPDI. Three coordination schemes were developed numerically based on the projection angles between hot jets and main methanol spray plumes axis: opposing (Base design), opposing staggered (Design 1), and circumferential staggered interference (Design 2). Varied orifice diameters was employed to regulate jet energy and velocity. The results indicated that Design 2-BSB (Big-Small-Big orifice) scheme exhibited superior combustion and emission performance. Furthermore, the impact of start of main injection timing (SOI) on ignition and combustion characteristics was investigated under this scheme. An SOI of -12 °CA after top dead center (TDC), creating a 7 °CA interval between spark and SOI timing, achieved optimal ITE by minimizing the duration of CA10-CA50 and optimization methanol mixture distribution around hot jets. Additionally, pre-chamber (PC) spark ignition timing (ST) effects were also explored, with the optimal timing at -8 °CA ATDC. ST has minimal impact on heat release rate (HRR), because high-energy jets could ensure rapid and stable combustion. Moreover, the combustion stability of TJI-HPDI was demonstrated, underscoring the importance in understanding and optimizing TJI-HPDI ignition processes.

Design and optimization of annular gap in a nozzle for dyeing machines

The annular nozzle is an important part of the dyeing machine as its impact and traction performance directly affect the quality and efficiency of dyeing. The annular gap forms the core of the nozzle. In this paper, the performance differences between six nozzles with different annular gap shapes were analyzed under various conditions using numerical simulation. The results indicate that the performance of the cone straight nozzle is more stable than other nozzle shapes under various conditions. To further enhance the performance of the nozzle, a multi-objective optimization of the cone straight nozzle structure was performed using a backpropagation neural network and a non-dominated sorting genetic algorithm, thereby obtaining the optimal combination of structural parameters. Finally, the optimization results were verified via experiments and numerical simulations. The results show that the pulling force of the optimized cone straight nozzle is more than 10% higher than that before optimization.

Synergy effect of nozzle structure and pre-chamber reactivity on the combustion characteristics of ammonia engines

Ammonia (NH3) offers an attractive opportunity for internal combustion engines (ICE) to be carbon–neutral. An active pre-chamber fueled with hydrogen might be suitable to overcome the poor combustion characteristics of ammonia engines. The primary goal of this work is to numerically study the combustion characteristics of ammonia engines with a hydrogen-fueled pre-chamber, and the synergy effect of nozzle structure and pre-chamber reactivity (hydrogen quantity) are also considered. The results show that the hydrogen fraction is reduced to a low degree in the pre-chamber because of the scavenging process. Thus, it is better to inject hydrogen into the pre-chamber during the compression stroke. Although high pre-chamber reactivity is effective in improving the main chamber combustion, a multi-hole pre-chamber is needed to get the maximum promoting effect of the high reactivity when compared to the single-nozzle pre-chamber. For multi-hole pre-chamber, 2 mm is the recommended nozzle diameter when considering the promoting effect, and the recommended area-volume ratio (nozzle number) is increased with the pre-chamber reactivity. For nitrogen-based emissions, the distribution strongly depends on the flame characteristics. High pre-chamber reactivity can significantly reduce the NH3 emissions, while NO emissions will increase with the pre-chamber reactivity. The current study can give some insights and be a preface for the development of ammonia engines.

Optimized design of annular ejector primary nozzle based on orthogonal test method

Abstract Annular ejectors are widely used in aerospace and other applications, and their performance has a significant impact on the overall system. In this paper, the effects of main nozzle area ratio, contraction section angle and diffusion section angle on the performance of annular ejector are investigated by using computational fluid dynamics combined with one-factor experiments, on the basis of which the L9(33) orthogonal table is established to optimise the structure of main nozzle and to screen the main influencing factors. The results show that the flow field inside the annular ejector is extremely complex. The influence of the main nozzle area ratio on the performance of the annular ejector is very great, and the change of the area ratio will lead to the change of the position of the second excitation sequence as well as the Mach number at the outlet of the main nozzle. However, as with the results of the one-way analysis, the effect of the angle of the constriction section on the exit Mach number is negligible.

Comparative analysis on pulverized coal combustion preheated by self-sustained purifying burner with coaxial and centrosymmetric air nozzle structures: Purification, combustion and NOx emission characteristics

To optimize secondary air nozzle structure in purifying burner, this study focused on the comparison of purification, combustion and NOx emission characteristics of pulverized coal preheated by a 30 kW purifying burner with coaxial and centrosymmetric structures. Centrosymmetric structure shifted the position of main burning region down in high-temperature reduction unit (HTRU), and the number of branches differently influenced the temperature in different regions with this structure. For reductive gas components, CO concentration with centrosymmetric structure was higher compared to coaxial structure, while the differences in H2 and CH4 concentrations were smaller. Centrosymmetric structure was more disadvantageous to improve physicochemical properties of pulverized coal compared to coaxial structure, and this structure with four branches further deteriorated its properties compared to two branches. In mild combustion unit (MCU), the temperature at top was lower with centrosymmetric structure, while was higher in the rest. Centrosymmetric structure more effectively reduced NOx emission compared to coaxial structure, but with slight sacrifice of combustion efficiency (η). Moreover, both two-branch and four-branch centrosymmetric structures realized ultra-low NOx emission (<50 mg·m–3) with high η of over 98.50%, and the former was more advantageous. With this optimal structure, η and NOx emission were 99.25% and 40.42 mg·m–3.

Enhanced non-equilibrium Peltier cooling through electron gas expansion: A Monte Carlo simulation study

We demonstrate enhanced Peltier cooling at the nanoscale using geometrical constriction. This nozzle structure leads to electron expansion under an applied bias, which in turn results in additional cooling. This extra cooling enhances the overall Peltier effect when the electrons are out of equilibrium with the lattice. An ensemble Monte Carlo simulation is used to demonstrate the non-equilibrium expansion of an electron gas using nanoscale trapezoidal geometric confinement. The proposed device operates under steady-state conditions, providing enhanced cooling compared to a one-dimensional flat geometry. We observe a five-fold increase in both the maximum cooling temperature and cooling power density, reaching more than 5 kW/cm2, when comparing the trapezoidal geometry to the regular flat geometry.

Depressurization strategy of China's advanced pressurized water reactor under typical accidents

Advanced pressurized water reactor was simulated using system analysis program. The depressurization strategy for the automatic depressurization system (ADS) under typical ADS-triggering accidents (2-inch/10-inch cold leg break, inadvertent opening of the ADS, DVI pipeline break) was investigated. The results show that after these accidents, ADS can ensure the operation of the three types of safe injection tanks, with high redundancy and inherent safety. The multi-stage design of ADS aids the sparger in maintaining a stable critical jet state. In 10-inch cold leg break accident, the sparger cannot reached the critical jet state under all of pipeline fault conditions. From a system point of view, adjusting the pipeline design of ADS is necessary to avoid long-term condensation oscillation of the sparger in some accidents. From a design perspective of the local equipment, the nozzle structure of the sparger should attenuate the dynamic load caused by the condensation oscillation and back-attack phenomenon.

Uniformity enhancement of flow field through optimizing nozzle structure for jet electrochemical machining

To improve the processing quality during the Jet electrochemical machining (JECM) process, a single-orifice nozzle and dual-orifice nozzles with different inclination angles were designed, where the fluid dynamic behavior was numerically simulated. Then, through the L49 (74) orthogonal design and error analysis, the influence of nozzle dimension on the flow field characteristics was analyzed. Finally, the nozzle with optimal structure and dimension was obtained and validated by experiment. Results show that the dual-orifice nozzles had better flow field uniformity than the single-orifice nozzle. In the dual-orifice nozzle, the increase of the inlet inclination angle can improve the flow field uniformity. The influence of the nozzle dimension parameters on the flow field uniformity is prioritized as follows: the outlet slit width > upper chamber diameter > the height of the inflow chamber > the height of the transition chamber. After optimization, the optimal dimension parameters were obtained under the upper chamber diameter of 16 mm, the jet outlet slit width of 0.4 mm, the height of the inflow chamber of 7 mm, and the height of the transition chamber of 23 mm. The flow velocity dispersions under the pressures of 0.3, 0.4, and 0.5 MPa can be reduced by 25.41 %, 25.17 %, and 28.16 %. The findings can help understand the flow behavior and guide the structure optimization for improving JECM quality.

Investigation of the correlation between nozzle structure and particle motion during shot peening using the PIV method

Investigation of the correlation between nozzle structure and particle motion during shot peening using the PIV method

Numerical study on heat transfer and pressure performance of different suspension nozzles

The drying process of the lithium battery pole pieces makes extensive use of the suspension nozzle. It is of great significance to study the heat transfer and pressure steady-state characteristics of the suspension nozzle and to select the appropriate nozzle structure for the production of pole pieces. Based on the SSTk-ω\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{SST }}k - \\omega$$\\end{document} turbulence model, this article numerically simulates the impact jet process of suspension nozzles with slits, injection holes, and effusion holes. There is a qualitative and quantitative analysis of the distribution of their velocity field, temperature field, local Nusselt number, average Nusselt number, local pressure coefficient, and average pressure coefficient, and the comprehensive performance index of the nozzle is proposed. The results show that when the weight factor of heat transfer performance α is less than 21.61% and the weight factor of pressure performance β is more than 78.39%, the comprehensive performance of the traditional suspension nozzle with double slits is the best. As the α is increasing, the β is decreasing. The comprehensive performance of the suspension nozzle with effusion holes is the best. The turbulent intermittence, interaction between neighbouring jets, and edge effects affect the heat transfer and pressure uniformity of the suspension nozzle.

The Research on Self-Excited Oscillating Jet Cleaning Technology

Abstract Self-oscillating nozzles have gained wide popularity due to their ability to generate powerful impact forces, long-range projection, and concentrated, stable jets in applications such as water-jet drilling and rust removal. However, the nozzle’s efficient operation relies heavily on specific structural designs and operational parameters, which necessitates further indepth research. By studying the characteristics of self-excited oscillating pulse cavitation jet within the nozzle cavity structure. Analyzing the evolution characteristics of internal flow field. Solving optimization problems in a targeted manner. The purpose of this study is to reveal the resonance principle behind the self-excited oscillation of nozzle. It also explores the regularities of the effects that the cavity diameter has on jet performance, ultimately seeking to find the optimal configuration of nozzle structure and operating conditions.

Exploring Electrochemical Direct Writing Machining of Patterned Microstructures on Zr702 with Polyacrylamide Polymer Electrolyte.

Zirconium alloys possess excellent wear resistance, which ensures the durability and longevity of the components, making them widely used in medical and other fields. To enhance the functionality of these materials, it is often necessary to fabricate functional microstructures on their surfaces. Electrochemical machining (ECM) techniques demonstrate excellent machining performance for these metals, particularly in the processing of microstructures on complex curved surfaces. However, ECM often faces challenges due to the fluid nature of the electrolyte, resulting in low machining accuracy and localization. This paper proposes a novel method for fabricating complex patterned microstructures using a maskless electrochemical direct writing technique with a polyacrylamide (PAM) polymer electrolyte. By leveraging the non-Newtonian properties of PAM, this method effectively confines the electrolyte to specific areas, thus addressing the issue of poor localization in traditional ECM and reducing stray corrosion. To elucidate the electrochemical removal mechanism of Zr702 in the presence of PAM, polarization curves, viscosity characteristics, and current efficiency parameters were analyzed. Additionally, an experimental study was conducted using a custom-designed nozzle structure. The results showed that the PAM electrolyte could effectively reduce the EF, positively impacting machining accuracy and localization. By controlling the nozzle's motion trajectory, complex microstructures were successfully fabricated through direct writing, demonstrating promising application prospects.

Analysis of the Influence of Nozzle Structure of Dry Powder Fire Extinguishing System on Supersonic Jet Characteristics

Analysis of the Influence of Nozzle Structure of Dry Powder Fire Extinguishing System on Supersonic Jet Characteristics

Coaxial air blast atomization of a particulate gel suspension jet

The objective of this study is to experimentally and theoretically explore the impact of particle volume fractions and nozzle thread structure on the coaxial air blast atomization of particulate gel suspension jets through the high-speed flow visualization technology. The four breakup modes of particulate gel suspension jets are confirmed, namely oscillation mode, membrane-type breakup, fiber-type breakup, and superpulsating submode. However, the fiber-type breakup of jets disappears as the particle concentration reaches 40%, primarily attributed to the numerous particles sharply promoting the instability on the free jet surface. The experimental statistical results demonstrate that an increase in particle concentration and the adoption of the threaded nozzle both result in an expansion of the jet spray angle. The breakup length exhibits a reduction trend with the increase of particle concentration. However, it remains nearly the same value as that in the case of volume fraction 20% when the particle concentration continues to increase, contributed by the surge of viscous dissipation counteracting the enhanced instability on the jet interface caused by a large number of particles. The breakup length of a pure gel jet is predicted through the linear instability analysis, which is further modified by the viscosity model of particle suspensions to derive the breakup lengths of particulate gel suspension jets with different concentrations. The theoretical predictions align well with the statistical results in the experiment. The research is poised to have potential implications for numerous industrial processes and engineering applications including gel propellants.

A self-cleaning glue feeding system based on slit coating

Abstract This paper introduces a self-cleaning glue feeding system. Based on the slit coating process, a mid-line adhesive glue feeding system suitable for KDF3E filter rod forming machine has been developed through innovative design of nozzle structure, improvement of coating process flow, optimization of process parameters, and other methods and measures. After the machine test, we can solve the current glue feeding problem and improve the overall efficiency and quality of mid-line glue.

Variable Area Jet Impingement for Enhanced Junction Temperature Control of High-Power Electronics

Abstract Convective heat transfer by jet impingement cooling offers a suitable solution for high heat flux applications. Compared to techniques that rely on bulk conduction in series with convection, direct liquid impingement reduces the thermal resistance between power device hot spots and the coolant. Although capable of highly efficient cooling, static impingement devices must be designed for the worst-case cooling requirements for a transient power profile. This can result in wasted hydraulic performance. Aircraft, highway vehicles, and heavy machinery fall into this category where a substantial factor of safety is required. This work proposes a method for improving power electronics reliability by limiting temperature fluctuations at reduced coolant pressure requirements during transient power cycling using a variable area jet. Single phase jet impingement cooling is implemented in an active control scheme using a variable diameter iris mechanism as the primary nozzle architecture. In addition to pressure drop and temperature control, the active nozzle structure introduces the ability to create pulsating jet flows to further enhance the heat transfer compared to fixed-geometry nozzles. The key underlying fluid mechanics characteristic of pulsating flows is the effect of disrupting the thermal boundary layer on the electrical device surface. By introducing a variable diameter jet, eddy formation can be fine-tuned for optimal boundary layer disruption. Using the definition of the Strouhal number, vortex shedding created by the non-steady jet flows is directly correlated with the resulting Nusselt number as a function of the iris kinematics. An experimental apparatus for jet impingement thermal-fluid testing is used to evaluate the Nusselt number versus Strouhal number for a parametric study of variable diameter iris configurations. The apparatus utilizes a voice coil actuator to achieve sine and square waveforms, to vary the amplitude of actuation, and to vary the mean of actuation. Finally, power cycling with a single emulated hot spot is performed to estimate the reliability increase as a result of maintaining constant junction temperatures with the active jet impingement scheme.

3D Printer Nozzle Structure Form Optimal Structural Analysis

The most representative technology of 3D printing is fused deposition modeling (FDM). To improve the printing accuracy of FDM technology, this paper first takes the outlet diameter, angle of convergence, and rectifier section length of the nozzle as the influencing factors. It takes the melt outlet speed stability, viscosity, and outlet pressure as the indexes to design the orthogonal test. Then, COMSOL Multiphysics fluid–solid coupling simulation was used to simulate and analyze the structural characteristics of the 3D printer nozzle, and the range analysis method was used to analyze the data. Finally, the two-phase flow combination was used to simulate the morphological characteristics of the melt flowing out of the nozzle. The results show that the simulation results of the two materials are similar. As the nozzle diameter decreases, the melt pressure decreases, the velocity increases, and the viscosity decreases. For PLA wire rods, the optimal structure of the nozzle is that the outlet diameter is 0.2 mm, the rectifier section length is 1.5 mm, and the angle of convergence is 60°. For ABS wire, the optimum structure of the nozzle is that the outlet diameter is 0.2 mm, the rectifier section length is 1.5 mm, and the angle of convergence is 30°. The nozzle outlet diameter is inversely proportional to the printing accuracy for ABS and PLA materials. The research results provide a theoretical reference for optimizing the nozzle structure for 3D printing.

Experimental investigation on the effects of complex pressure gradients on the film cooling effectiveness of a serpentine nozzle

Serpentine nozzles more easily deform and damage due to high-temperature airflow because of their multi-bend channel configuration. Therefore, film cooling technologies should be applied to serpentine nozzles. Complex pressure gradients in serpentine nozzles lead to different film cooling characteristics from combustion chambers, turbine blades, and other exhaust systems. This study experimentally investigated the effects of complex pressure gradients and film hole inclination angles on a serpentine nozzle’s film cooling effectiveness (FCE) using pressure-sensitive paint (PSP). The flow mechanisms were obtained via numerical simulations. The experimental nozzle design needs to consider the needs of PSP observations and the normal flow of serpentine nozzles. However, the complex structure of serpentine nozzles makes those increasingly difficult. The studied pressure gradients include the pressure gradient mutation (PGM), strong adverse pressure gradient (SAPG), weak adverse pressure gradient (WAPG), and favorable pressure gradient (FPG). The results show that complex pressure gradients change the coolant coverage and adhesion and may induce a recirculation zone in the SAPG region. This affects the development of the vortex construction and leads to different FCE distributions. The FCE under the effects of the PGM is the largest, followed by the SAPG, WAPG, and FPG. A larger inclination angle weakens the coolant adhesion but may enhance its downstream and lateral flow treads. This is coupled with the effects of complex pressure gradients, where larger inclination angles bring better film cooling effects in some cases. After accounting for the four blowing ratios, the area-averaged FCEs under the effects of the SAPG, WAPG, and FPG are 28.9 %, 42.8 %, and 52.3 % lower than that under the PGM, respectively. The area-averaged FCEs under the conditions α = 45° and 60° are 6.6 % and 10 % lower than that under α = 30°.

Analysis of the effect of jet channel structure on the temperature uniformity of tempered glass

The air jet nozzle structure has a significant impact on the heat transfer uniformity and cooling rate of glass during the glass tempering process, and there is a lack of research on the discrepancy of different jet structures. The effects of double air knife, single air knife structures, and air hole structures on the cooling performance of glass in air-cooled tempering were investigated using numerical simulation and simplified analytical models. The calculated results are in agreement with the experimental results. The results show that the DK structure has a significant effect on improving the overall heat exchange performance of the glass, with lower surface temperatures for the same quenching time. The temperature inhomogeneities of DK, SK, and AH structures in the glass axial direction were 2.09%, 2.53%, and 3.33%, respectively, and the heat transfer uniformity of the DK structure was significantly better than the latter two. In comparison to the AH structure, the average heat transfer coefficients of the DK and SK structures increased by approximately 17.82% and 8.13%, respectively, while the heat transfer rates increased by approximately 7.05% and 4.51%. The study further improves the insufficiency of glass tempering research and provides theoretical guidance for the actual production of tempered glass.

Structure Design of Pressure Swirl Atomizing Nozzle

Based on Solidworks and Fluent, the inner flow field of swirl nozzle is modeled and simulated. The simulation results of the internal flow field of the nozzle show that the change of the internal structural parameters of the nozzle has an importa nt impact on the flow characteristics of the working medium at the outlet of the nozzle. The parameters such as the axial velocity, tangential velocity and atomization angle at the outlet of the nozzle under different structural parameters are comprehensively compared, and finally the nozzle structure with the optimal atomization effect is determined.