Showing papers on "Nozzle published in 2020"
TL;DR: In this article, the influence law of milling cutter speed, helical angle, and cavity shape on the flow field around the milling cutters was studied, and the optimal nozzle profile parameters were obtained.
111 citations
TL;DR: In this paper, five different spray-line distribution nozzles were designed to evaluate the effect of the nozzle spray line distribution on stratified charge combustion of methanol engine.
90 citations
TL;DR: An in-depth examination of the atomizing characteristics and dust suppression performance of a coal cutter external spraying device found the optimal nozzle to be a pressure round-mouth nozzle with an X-shaped core.
86 citations
TL;DR: In this paper, a mathematical model for the supersonic condensation flow of methane gas was established based on the improved Internal Consistent Classical Nucleation Theory (ICCT) model for single component gas.
80 citations
TL;DR: In this paper, the effect of water supply pressure on the atomization characteristics and dust-reduction efficiency of the internal mixing air atomizing nozzle was investigated, where the FLUENT software was used to simulate the flow field inside and outside the nozzle under different water supply pressures.
66 citations
TL;DR: In this article, the authors performed an experimental analysis of base pressure in suddenly expanded compressible flow from nozzles at different Mach numbers and found that microjets are efficient when the flow is under the influence of a favorable pressure gradient.
66 citations
TL;DR: In this paper, the influence of spray chamber flow on the particle morphology is examined and the particle trajectories are calculated to assess the change in particle behavior as well, and the experimental results show that a use of additional coaxial gas leads to an increase in particle circularity up to 10% for relevant particle sizes.
56 citations
TL;DR: In this article, computational fluid dynamics (CFD) simulations of the polymer flow inside the hot-end during material extrusion additive manufacturing are presented, where the free surface of the ABS inside the channel is resolved, melting of the solid filament and filling of an empty liquefier channel are shown in detail.
Abstract: This work presents Computational Fluid Dynamics (CFD) simulations of the polymer flow inside the hot-end during material extrusion additive manufacturing. Two CFD models are investigated: a previously-published one-phase model, where the entire domain is filled with liquid, and a novel model, where the free surface of the polymer inside the channel is resolved. Both models predict a recirculation region between the nozzle wall and the incoming filament. With the free surface resolved, melting of the solid filament and filling of an empty liquefier channel are shown in detail. Moreover, the simulations predict the pressure and temperature distributions inside the channel. The molten polymer (ABS) is simulated as a Generalized Newtonian Fluid with shear- and temperature-dependent viscosity. The numerical results are compared with the experimental measurements of the filament feeding force, which relates to the pressure inside the flow channel. An inverse analysis of the heat transfer coefficient is performed to estimate the thermal resistance at the channel’s wall. It is shown that the model which resolves the free surface is able to predict the feeding force for typical working conditions with a reasonable accuracy. Moreover, it captures the change of the flow regime from stable to unstable extrusion at high feeding rates. A hypothesis that explains the pressure and melt zone oscillations that occur during unstable extrusion is given. The influence of the liquefier temperature, liquefier length and nozzle diameter on the flow are discussed. The predictions of the model become less accurate when different channel geometries are simulated, which is attributed to the simplified material model that does not capture viscoelastic effects and possible buckling of the solid filament.
54 citations
TL;DR: In this paper, a comparison of two modes: multi-material single mixing nozzle and multiple-material multiple nozzles is presented, and the results provide a tool for selection on which type of mode is considered suitable for maximizing efficiency and performance.
Abstract: Multi-material 3D printing and process parameters optimization using multiple extruders are the significant challenges of fused deposition modeling (FDM). This paper focuses on the filament extrusion method and presents a comparison of two modes: multi-material single mixing nozzle and multi-material multiple nozzles, thereby linking technology with the mechanical properties. Tensile testing specimens were printed in two different scenarios to validate the comparison: (1) multi-material multi-layered section printed using a multi in-out single mixing nozzle and (2) multi-material multi-layered section printed using a multiple extrusion nozzle within the same carriage. Both modes followed a rectilinear infill pattern and different material combinations. The material combinations implemented included ABS-HIPS, ABS-PLA, PLA- HIPS, and PLA-HIPS-ABS. A behavioral study was evaluated on the mechanical properties of these materials. The results provide a tool for selection on which type of mode is considered suitable for maximizing efficiency and performance to fabricate a multi-material 3D printed product.
53 citations
TL;DR: In this paper, a modified condensation model is presented to evaluate the steam ejector performance and to optimize the ejector geometry, which is more appropriate than the other three models.
50 citations
TL;DR: In this article, a computational fluid dynamics model is developed to evaluate the potential of the proposed hydrogen fuelling process and a flow behaviour analysis is performed to show the detailed flow structure in the critical and sub-critical processes for the hydrogen ejector.
TL;DR: In this article, the effect of the nozzle pressure ratio n on the flow field of an air jet was investigated to obtain the basis of nozzle design, and it was concluded that n is the primary factor that affects nozzle structure design, n = 1.12 can generate a better flow field structure.
TL;DR: In this paper, a condensing flow model is developed to accurately predict the energy conversion within the supersonic separator, which reduces the energy loss by eliminating the oblique and expansion waves in the newly designed nozzle and improves the energy efficiency for natural gas processing.
TL;DR: In this article, the consequences of geometry alterations in a diesel injector caused by cavitation erosion are investigated with numerical simulations, and the differences in the results between the nominal design geometry and the eroded one are analyzed for the internal injector flow and spray formation.
TL;DR: In this article, the effects of the mixing chamber length on the steam ejector performance under different Mach numbers at the nozzle exit, constant area section length, and diffuser length are studied using three-dimensional (3D) numerical simulations.
TL;DR: In this paper, a single-cylinder research engine with a scavenged prechamber was used to study the early flame propagation phase and its influence on the subsequent main-combustion.
TL;DR: In this article, a multi-nozzle ejector was proposed for hydrogen recirculation in proton exchange membrane fuel cell (PEMFC) systems, which can achieve a wide output power range without a significant change in the primary pressure by simply switching the operating mode of the nozzles.
TL;DR: In this paper, six back-propagation neural network models (BPMs) are developed based on input and output possibilities to predict the pressure in high-speed flows.
Abstract: The experimental analysis of base pressure in a high-speed compressible flow is carried out. The flow is made to expand abruptly from the nozzle into an enlarged duct at fifteen sonic and supersonic Mach numbers. The analysis is made for variation in the nozzle pressure ratio (NPR), length to diameter ratio, and area ratio. The effect of active micro-jets on the base and wall pressure is assessed. The data visualization of the huge experimental data generated is performed using heat maps. For the first time, six back-propagation neural network models (BPMs) are developed based on input and output possibilities to predict the pressure in high-speed flows. The experimental analysis revealed that depending upon the type of expansion, the base pressure changes. A jet of air blown at the base using micro-jets is found to be effective in increasing the base pressure during the under-expansion regime, while the wall pressure remains unaffected. The data visualization provided an insight into the highest impact on the base pressure by the NPR. The six BPMs with two hidden layers having four neurons per layer are found to be most suitable for the regression analysis. BPM 5 and BPM 6 accurately predict the highly non-linear data of the base and wall pressure.
TL;DR: In this article, numerical simulation is used to understand the melting and pressurization mechanism in fused filament fabrication (FFF), and the results show the incoming fiber melts axisymmetrically, forming a cone of unmelted material in the center surrounded by melted polymer.
Abstract: Numerical simulation is used to understand the melting and pressurization mechanism in fused filament fabrication (FFF). The results show the incoming fiber melts axisymmetrically, forming a cone of unmelted material in the center surrounded by melted polymer. Details of the simulation reveal that a recirculating vortex of melted polymer is formed at the fiber entrance to the hot end. The large viscosity within this vortex acts to effectively seal the system against back-pressures of order 1000 psi (10 MPa), which are typical under standard printing conditions. The Generalized Newtonian Fluid (GNF) model was appropriate for simulation within the region that melts the fiber, however, a viscoelastic model, the Phan-Thien-Tanner (PTT) model, was required to capture flow within the nozzle. This is due to the presence of an elongational flow as molten material transitions from the melting region (diameter of 3 mm) to the nozzle at the exit (diameter of 0.5 mm). Remarkably, almost half the pressure drop occurs over the short capillary (0.5 mm in length) attached to the end of the converging flow region. Increased manufacturing rates are limited by high pressures, necessitating more consideration in the nozzle design of future FFF printers.
TL;DR: In order to solve the problem of severe dust pollution in a tunnel during continuous mining effectively, Wang et al. as mentioned in this paper used the external spraying method around a continuous miner and determined the optimal parameter settings via an experimental analysis, numerical simulation and field measurement.
TL;DR: In this paper, the authors present an overview of the various channel wall nozzles manufacturing processes and materials under evaluation including results from the hot-fire testing and future development and technology focus areas relative to channel wall nozzle manufacturing.
TL;DR: In this article, the authors present the results of 3D numerical modeling of an engine with a rotating detonation wave (RDE) fed with hydrogen-oxygen mixture, which is a new approach to increase of thrust characteristics of power facilities.
TL;DR: In this article, the authors investigate the shedding process of cloud cavitation shedding, the reentrant jet and condensation shocks in a scaled-up generic step nozzle with injection into gas using implicit Large-Eddy Simulations.
TL;DR: In this article, the effectiveness of spray injection to achieve near-isothermal compression is investigated experimentally in a liquid piston compressor for a compression ratio of about 2.5, and the results show that water spray injection is highly effective in abating the air temperature rise during the compression process.
TL;DR: In this article, experimental studies on the atomization characteristics and dust reduction performance of six different X-swirl nozzles with different outlet diameters were performed, and the results of the experiments showed that, as the diameter of the nozzle increased, the flow rate of the nozzle gradually increased, while the flow coefficient kept decreasing almost linearly.
TL;DR: In this article, a comprehensive review of recent experimental efforts on using optical diagnostics and/or transparent nozzles is presented and discussed, as well as typical experimental apparatus, multiphase flow characteristics, measurement capacities and limitations.
TL;DR: In this paper, the authors investigated the complex multiphase flow developing inside the micro-orifices of diesel injector nozzles during pilot injection using high speed micro-visualisations of a transparent serial production nozzle tip replica.
TL;DR: In this article, the effect of 3D printer diameter on the surface quality, accuracy, and the strength of the product was investigated experimentally, and it was shown that bigger nozzle hole diameter enhanced the density and tensile strength of products.
Abstract: Abstract Nozzle hole diameter of 3D printer (3DP) can be varied to obtain required product quality as well as to reduce manufacturing times. The use of larger diameter may accelerate manufacturing times of products, yet the product quality, including the mechanical properties, still needs to be investigated profoundly. The purpose of this work is to investigate experimentally the effect of nozzle hole diameter of 3DP to the surface quality, accuracy, and the strength of the product. The specimens were manufactured by fused deposition modelling (FDM) 3D printing using polylactic acid (PLA) as the filaments.Bed temperature, extruder temperature and printing speed were set to be 60∘C, 200∘C and 80 mm/s respectively. The thickness of each layer was set at the ratio of 20% to the nozzle hole diameter. Infill pattern was determined by using line type of 100%. Nozzle hole diameter of 0.3, 0.4, 0.5 and 0.6mmwas compared in thiswork. The results show that bigger nozzle hole diameter enhanced the density and tensile strength of the products thought it was not linearly correlation.
TL;DR: In this paper, a novel quantitative seed feeding system containing a feeding device and a venturi feeding tube is investigated using the coupled CFD and DEM approach, and the effects of different variables related to venturi tube and operations are examined.