Quantitative predictions of cavitation presence and erosion-prone locations in a high-pressure cavitation test rig

Experiments and numerical simulations of cavitating flow inside a single-orifice nozzle are presented. The orifice is part of a closed flow circuit, with diesel fuel as the working fluid, designed to replicate the main flow pattern observed in high-pressure diesel injector nozzles. The focus of the present investigation is on cavitation structures appearing inside the orifice, their interaction with turbulence and the induced material erosion. Experimental investigations include high-speed shadowgraphy visualization, X-ray micro-computed tomography (micro-CT) of time-averaged volumetric cavitation distribution inside the orifice as well as pressure and flow rate measurements. The highly transient flow features that are taking place, such as cavity shedding, collapse and vortex cavitation (also known as ‘string cavitation’), have become evident from high-speed images. Additionally, micro-CT enabled the reconstruction of the orifice surface, which provided locations of cavitation erosion sites developed after sufficient operation time. The measurements are used to validate the presented numerical model, which is based on the numerical solution of the Navier–Stokes equation, taking into account compressibility of both the liquid and liquid–vapour mixture. Phase change is accounted for with a newly developed mass transfer rate model, capable of accurately predicting the collapse of vaporous structures. Turbulence is modelled using detached eddy simulation and unsteady features such as cavitating vortices and cavity shedding are observed and discussed. The numerical results show agreement within validation uncertainty with the obtained measurements.

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Hot-fire testing of liquid oxygen/hydrogen single coaxial injector at high-pressure conditions with optical diagnostics

Progress in Propulsion Physics – Volume 11 ◽

10.1051/eucass/201911391 ◽

2019 ◽

Author(s):

D.I. Suslov ◽

J.S. Hardi ◽

B. Knapp ◽

M. Oschwald

Keyword(s):

High Pressure ◽

High Speed ◽

Optical Diagnostics ◽

Liquid Oxygen ◽

Experimental Investigations ◽

Rocket Engines ◽

Chamber Length ◽

Substantial Progress ◽

Liquid Rocket ◽

Coaxial Injector

Injector behavior is of utmost importance for the performance and stability of liquid rocket engines (LREs). A major problem is getting a highly efficient homogeneous mixture and effective chemical reaction of fuels at minimum chamber length. Despite substantial progress in numerical simulations, a need for experimental data at representative conditions for development and validation of numerical design tools still exists. Therefore, in the framework of the DLR-project “ProTau,” the authors have performed tests to create an extended data base for numerical tool validation for high-pressure liquid oxygen (LOx) / hydrogen combustion. During the experimental investigations, a windowed DLR subscale thrust chamber model “C” (designated BKC) has been operated over a broad range of conditions at reduced pressures of approximately 0.8 (4 MPa), 1 (5 MPa), and 1.2 (6 MPa) with respect to the thermodynamic critical pressure of oxygen. Liquid oxygen and gaseous hydrogen (GH2) have been injected through a single coaxial injector element at temperatures of ~ 120 and ~ 130 K, respectively. High-speed optical diagnostics have been implemented, including imaging of OH* emission and shadowgraph imaging at frequencies from 8 up to 10 kHz to visualize the flow field.

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Approaches for Detailed Investigations on Transient Flow and Spray Characteristics during High Pressure Fuel Injection

Applied Sciences ◽

10.3390/app10124410 ◽

2020 ◽

Vol 10 (12) ◽

pp. 4410 ◽

Cited By ~ 1

Author(s):

Noritsune Kawaharada ◽

Lennart Thimm ◽

Toni Dageförde ◽

Karsten Gröger ◽

Hauke Hansen ◽

...

Keyword(s):

High Pressure ◽

High Speed ◽

Internal Combustion Engines ◽

Fuel Injection ◽

Transient Flow ◽

Numerical Models ◽

Near Field ◽

Transient Nature ◽

Injector Nozzle ◽

Considerable Impact

High pressure injection systems have essential roles in realizing highly controllable fuel injections in internal combustion engines. The primary atomization processes in the near field of the spray, and even inside the injector, determine the subsequent spray development with a considerable impact on the combustion and pollutant formation. Therefore, the processes should be understood as much as possible; for instance, to develop mathematical and numerical models. However, the experimental difficulties are extremely high, especially near the injector nozzle or inside the nozzle, due to the very small geometrical scales, the highly concentrated optical dense spray processes and the high speed and drastic transient nature of the spray. In this study, several unique and partly recently developed techniques are applied for detailed measurements on the flow inside the nozzle and the spray development very near the nozzle. As far as possible, the same three-hole injector for high pressure diesel injection is used to utilize and compare different measurement approaches. In a comprehensive section, the approach is taken to discuss the measurement results in comparison. It is possible to combine the observations within and outside the injector and to discuss the entire spray development processes for high pressure diesel sprays. This allows one to confirm theories and to provide detailed and, in parts, even quantitative data for the validation of numerical models.

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High Speed Transient Flow in Manifolds

Volume 1: Fluid Mechanics ◽

10.1115/ajkfluids2019-5577 ◽

2019 ◽

Author(s):

Nicholas Findanis

Keyword(s):

Aspect Ratio ◽

Flow Field ◽

High Speed ◽

Transient Flow ◽

Flow Distribution ◽

Ideal Gas ◽

Working Fluid ◽

High Speed Flow ◽

Speed Flow ◽

High Speed Flows

Abstract Flows in manifolds is a ubiquitous and important area to implement flow improvements. In almost all applications of industrial pipe flows, there is the requirement to distribute the flow of fluid. There is a deficiency of studies in the area of flow distribution in manifolds with high speed flows. The present work is aimed at providing a further understanding of transient high speed flow distribution in manifolds. The different manifold configurations were analysed computationally. A comparison was focused between through the different aspect ratio manifolds. The velocity field and the eddy viscosity parameters where compared between the simulated flow models to ascertain the key features in the distributed flow field and especially, to determine the areas that showed greater flow recirculation or flow eddies and the separated flow regions. The CFD study was conducted as a high speed flow/ compressible flow regime accounting for the ideal gas dynamic model being air as the working fluid. The study showed that the transient behaviour of flow field can significantly affect distribution of the flow depending on the aspect ratio and number of branches on the manifold. Efficiency gains can be achieved in high speed flows that can be of benefit in industrial and other engineered flow applications.

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INFLUENCE OF WORKING FLUID ON THERMAL PERFORMANCE OF THERMOSYPHONS FOR APPLICATION IN HIGH PRESSURE VACUUM TUBE SOLAR COLLECTORS

10.26678/abcm.encit2020.cit20-0621 ◽

2020 ◽

Author(s):

Guilherme Antonio Bartmeyer ◽

Victor Vaurek Dimbarre ◽

Pedro Leineker Ochoski Machado ◽

PAULO HENRIQUE DIAS DOS SANTOS ◽

Thiago Antonini Alves

Keyword(s):

High Pressure ◽

Thermal Performance ◽

Working Fluid ◽

Solar Collectors ◽

Vacuum Tube

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Cyclone Bomb hits Southern Brazil in 2020

Journal of Atmospheric Science Research ◽

10.30564/jasr.v3i3.2163 ◽

2020 ◽

Vol 3 (3) ◽

Author(s):

Ricardo Gobato ◽

Alireza Heidari

Keyword(s):

High Pressure ◽

Atmospheric Pressure ◽

High Speed ◽

Satellite Images ◽

The State ◽

Southern Brazil ◽

Santa Catarina ◽

High Area ◽

South Of Brazil ◽

Rapid Drop

An “explosive extratropical cyclone” is an atmospheric phenomenon that occurs when there is a very rapid drop in central atmospheric pressure. This phenomenon, with its characteristic of rapidly lowering the pressure in its interior, generates very intense winds and for this reason it is called explosive cyclone, bomb cyclone. With gusts recorded of 116 km/h, atmospheric phenomenon – “cyclone bomb” (CB) hit southern Brazil on June 30, the beginning of winter 2020, causing destruction in its influence over. One of the cities most affected was Chapecó, west of the state of Santa Catarina. The satellite images show that the CB generated a low pressure (976 mbar) inside it, generating two atmospheric currents that moved at high speed. In a northwest-southeast direction, Bolivia and Paraguay, crossing the states of Parana and Santa Catarina, and this draft that hit the south of Brazil, which caused the destruction of the affected states. Another moving to Argentina, southwest-northeast direction, due to high area of high pressure (1022 mbar). Both enhanced the phenomenon.

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YSS YXM4

Alloy Digest ◽

10.31399/asm.ad.ts0780 ◽

2019 ◽

Vol 68 (11) ◽

Keyword(s):

High Pressure ◽

High Temperature ◽

Physical Properties ◽

Tool Steel ◽

High Speed ◽

Temperature Performance

Abstract YSS YXM4 is a cobalt-alloyed molybdenum high-speed tool steel with resistance to abrasion, seizure, and deformation under high pressure. This datasheet provides information on composition, physical properties, and hardness. It also includes information on high temperature performance. Filing Code: TS-780. Producer or source: Hitachi Metals America, Ltd.

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Numerical and Experimental Investigations on Vocal Fold Approximation in Healthy and Simulated Unilateral Vocal Fold Paralysis

Applied Sciences ◽

10.3390/app11041817 ◽

2021 ◽

Vol 11 (4) ◽

pp. 1817

Author(s):

Zheng Li ◽

Azure Wilson ◽

Lea Sayce ◽

Amit Avhad ◽

Bernard Rousseau ◽

...

Keyword(s):

Computational Model ◽

Vocal Fold ◽

High Speed ◽

Computational Models ◽

Ex Vivo ◽

Vocal Fold Paralysis ◽

Future Application ◽

Experimental Investigations ◽

Type I ◽

Mri Scans

We have developed a novel surgical/computational model for the investigation of unilat-eral vocal fold paralysis (UVFP) which will be used to inform future in silico approaches to improve surgical outcomes in type I thyroplasty. Healthy phonation (HP) was achieved using cricothyroid suture approximation on both sides of the larynx to generate symmetrical vocal fold closure. Following high-speed videoendoscopy (HSV) capture, sutures on the right side of the larynx were removed, partially releasing tension unilaterally and generating asymmetric vocal fold closure characteristic of UVFP (sUVFP condition). HSV revealed symmetric vibration in HP, while in sUVFP the sutured side demonstrated a higher frequency (10–11%). For the computational model, ex vivo magnetic resonance imaging (MRI) scans were captured at three configurations: non-approximated (NA), HP, and sUVFP. A finite-element method (FEM) model was built, in which cartilage displacements from the MRI images were used to prescribe the adduction, and the vocal fold deformation was simulated before the eigenmode calculation. The results showed that the frequency comparison between the two sides was consistent with observations from HSV. This alignment between the surgical and computational models supports the future application of these methods for the investigation of treatment for UVFP.

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Particle Size Effects on Selectivity in Confined Bed Comminution

Minerals ◽

10.3390/min11040342 ◽

2021 ◽

Vol 11 (4) ◽

pp. 342

Author(s):

Holger Lieberwirth ◽

Lisa Kühnel

Keyword(s):

Particle Size ◽

High Pressure ◽

Particle Size Distribution ◽

Size Distribution ◽

Size Effects ◽

Experimental Investigations ◽

Ore Processing ◽

Tumbling Mills ◽

Particle Bed ◽

Vertical Roller

Confined bed comminution in high-pressure grinding rollers (HPGRs) and vertical roller mills (VRMs) was previously used preferably for grinding comparably homogeneous materials such as coal or clinker. Meanwhile, it started to complement or even replace tumbling mills in ore beneficiation with ore and gangue particles of rather different breakage behaviors. The selectivity in the comminution of a mixture of particles with different strengths but similar particle size distribution (PSD) of the constituents in a particle bed was investigated earlier. The strength of a material is, however, also a function of particle size. Finer particles tend to be more competent than coarser ones of the same material. In industrial ore processing using confined bed comminution, this effect cannot be neglected but even be exploited to increase efficiency. This paper presents research results on this topic based on experimental investigations with model materials and with natural particles, which were stressed in a piston–die press. It appeared that the comminution result substantially depends on the material characteristics, the composition of the mixture and the PSD of the constituents. Conclusions will be drawn for the future applications of selective comminution in mineral processing.

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Impact of double-diffusive convection and motile gyrotactic microorganisms on magnetohydrodynamics bioconvection tangent hyperbolic nanofluid

Open Physics ◽

10.1515/phys-2020-0009 ◽

2020 ◽

Vol 18 (1) ◽

pp. 74-88 ◽

Cited By ~ 1

Author(s):

Tanveer Sajid ◽

Muhammad Sagheer ◽

Shafqat Hussain ◽

Faisal Shahzad

Keyword(s):

Differential Equations ◽

Ordinary Differential Equations ◽

Transfer Rate ◽

Mass Transfer Rate ◽

Physical Nature ◽

Working Fluid ◽

Nonlinear Ordinary Differential Equations ◽

Gyrotactic Microorganisms ◽

Motile Gyrotactic Microorganisms ◽

Double Diffusive

AbstractThe double-diffusive tangent hyperbolic nanofluid containing motile gyrotactic microorganisms and magnetohydrodynamics past a stretching sheet is examined. By adopting the scaling group of transformation, the governing equations of motion are transformed into a system of nonlinear ordinary differential equations. The Keller box scheme, a finite difference method, has been employed for the solution of the nonlinear ordinary differential equations. The behaviour of the working fluid against various parameters of physical nature has been analyzed through graphs and tables. The behaviour of different physical quantities of interest such as heat transfer rate, density of the motile gyrotactic microorganisms and mass transfer rate is also discussed in the form of tables and graphs. It is found that the modified Dufour parameter has an increasing effect on the temperature profile. The solute profile is observed to decay as a result of an augmentation in the nanofluid Lewis number.

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Experimental investigation of wall heat transfer due to spray combustion in a high-pressure/high-temperature vessel

International Journal of Engine Research ◽

10.1177/14680874211007232 ◽

2021 ◽

pp. 146808742110072

Author(s):

Karri Keskinen ◽

Walter Vera-Tudela ◽

Yuri M Wright ◽

Konstantinos Boulouchos

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

High Pressure ◽

High Temperature ◽

High Speed ◽

Transfer Problem ◽

Wall Heat Transfer ◽

Gas Temperature ◽

Reference Case ◽

High Pressure High Temperature

Combustion chamber wall heat transfer is a major contributor to efficiency losses in diesel engines. In this context, thermal swing materials (adapting to the surrounding gas temperature) have been pinpointed as a promising mitigative solution. In this study, experiments are carried out in a high-pressure/high-temperature vessel to (a) characterise the wall heat transfer process ensuing from wall impingement of a combusting fuel spray, and (b) evaluate insulative improvements provided by a coating that promotes thermal swing. The baseline experimental condition resembles that of Spray A from the Engine Combustion Network, while additional variations are generated by modifying the ambient temperature as well as the injection pressure and duration. Wall heat transfer and wall temperature measurements are time-resolved and accompanied by concurrent high-speed imaging of natural luminosity. An investigation with an uncoated wall is carried out with several sensor locations around the stagnation point, elucidating sensor-to-sensor variability and setup symmetry. Surface heat flux follows three phases: (i) an initial peak, (ii) a slightly lower plateau dependent on the injection duration, and (iii) a slow decline. In addition to the uncoated reference case, the investigation involves a coating made of porous zirconia, an established thermal swing material. With a coated setup, the projection of surface quantities (heat flux and temperature) from the immersed measurement location requires additional numerical analysis of conjugate heat transfer. Starting from the traces measured beneath the coating, the surface quantities are obtained by solving a one-dimensional inverse heat transfer problem. The present measurements are complemented by CFD simulations supplemented with recent rough-wall models. The surface roughness of the coated specimen is indicated to have a significant impact on the wall heat flux, offsetting the expected benefit from the thermal swing material.

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