scholarly journals Analysis of the stress wave effect during coal breakage by a high-pressure abrasive air jet

2018 ◽  
Vol 10 (6) ◽  
pp. 168781401878230 ◽  
Author(s):  
Yong Liu ◽  
Tao Zhang ◽  
Xiaotian Liu
Keyword(s):  
Numerical Simulation ◽  
High Pressure ◽  
Wave Velocity ◽  
Stress Wave ◽  
High Frequency ◽  
Laval Nozzle ◽  
Gas Jet ◽  
Low Permeability ◽  
Hydraulic Permeability ◽  
Potential Core

In view of the defects of borehole collapse, inhibition of gas desorption and migration of gas existing in hydraulic fracturing and other hydraulic permeability–increasing measures for soft coal seams with low-permeability technology is proposed for coal breakage by a high-pressure abrasive gas jet for relieving pressure and increasing permeability. The comparative analysis of gas jet flow field structure between convergent nozzle and Laval nozzle has been given by numerical simulation. For Laval nozzle, the expansion wave and compression wave alternate and move forward steadily in gas jet and vanish when potential core length reaches maximum. So, the Laval nozzle can form more stable flow filed structure of gas jet and avoid shock wave in gas jet. Furthermore, a high-speed camera is adopted to analyze the jet structure and verify the conclusion of numerical simulation. Based on thermodynamic theory, this article calculates and analyzes the critical local sound velocity and pressure generated from the stress wave during the process of coal breakage by the gas jet. Furthermore, experimental coal breakage by a high-pressure abrasive gas jet is carried out. The high-pressure abrasive gas jet impacts the coal body as a quasi-static load and a dynamic load and forms corrosion pits on the surface of the coal body. Penetrating cracks are formed within the coal in the pattern of the loaded stress wave which leads to coal breakage. The effects of porosity and permeability on the propagation of the stress wave in coal are analyzed by establishing the dispersion equation for the spread of the stress wave in coal. The results show that porosity has a significant effect on wave velocity and that the attenuation of the stress wave is intensified with an increase in porosity. Moreover, the stress wave attenuation is more obvious at high frequency. The effect of permeability on the wave velocity is not significant at low frequencies. In contrast, at high frequency and relatively low permeability, the wave velocity increases with the permeability, and the attenuation of the wave velocity initially increases and then decreases. When the permeability is greater than 10−11 m2, the wave velocity is not affected by the permeability. However, the stress wave is not attenuated.

Simulation and Optimize Design for Deflector Plate of the Vehicle Mounted Vertically Thermal Launched Missile

2012 ◽  
Vol 459 ◽  
pp. 579-583
Author(s):  
Shao Zhen Yu ◽  
Yi Jiang ◽  
Yan Li Ma ◽  
Yan Yan Ma ◽  
Bo Wei Liu
Keyword(s):  
Numerical Simulation ◽  
Temperature Field ◽  
Simulation Study ◽  
Three Dimensional ◽  
Gas Jet ◽  
Potential Core ◽  
Structured Grid ◽  
Main Factors ◽  
Deflector Plate ◽  
Volume Method

In this dissertation, academic analysis of the influence to deflector plate in gas jet field of a Vehicle-mounted Vertically Thermal Launched missile as well as simulation study. The finite volume method, a fully structured grid, three-dimensional N-S equation is used for the numerical simulation of the process during the missile launching. The two main factors: temperature and forces on the launcher is the standard we test a launching system. The temperature on the position we test will rise with the decreasing length of the deflector. Especially, when the length is near to the potential core, the temperature changed greatly. Also, the angles of the deflector under the same length have less impacted on the temperature field. However, the force on the deflector would be change greater than the temperature with the change of angles

Experimental Methods for Studying and Characterizing Freely Expanding Supersonic Gaseous Jets

2019 ◽  
Author(s):  
Ryan Holguin ◽  
John Bernardin ◽  
Robert Morgan
Keyword(s):  
High Pressure ◽  
Dimensional Analysis ◽  
High Frequency ◽  
Pressure Ratio ◽  
Experimental System ◽  
Gas Jet ◽  
Hot Wire ◽  
Velocity Measurements ◽  
Gas Entrainment ◽  
Jet Velocity

Abstract This manuscript describes an experimental system that was constructed to observe and scrutinize the transient fluid mechanics of a supersonic gaseous jet freely expanding into ambient air conditions within a steel containment vessel. Measurement parameters included jet expansion angle, peak jet velocity and local velocity profile, shock propagation, vessel gas entrainment, and wall stagnation pressure. Test gases included air and helium at pressure ratios ranging from roughly 2 to 300. The measurement techniques used to characterize the gas jets included hot wire anemometry, high-frequency pressure transducer measurements, and schlieren/shadowgraph imagery. The development of a system capable of capturing the desired data presented many engineering challenges including optical alignment for schlieren imaging, synchronizing the system for consistent and repeatable data collection, development of an experimental vessel capable of incorporating measurement equipment, and accommodation for future measurement capabilities. A vented PVC cylindrical test vessel was utilized in the preliminary stages of experimentation and set up of the gas delivery and diagnostic systems. Upon completion of the preliminary testing, a stainless steel experimental vacuum and pressure vessel, capable of accommodating a variety of diagnostics, was designed and fabricated. The gas jet delivery system consisted of a restrictive flow orifice, high pressure two stage regulator, two isolation valves, and a high pressure relief valve set to 4500 psig. Downstream from the safety manifold was a high pressure AC solenoid. This configuration was able to generate a maximum supply pressure of 4000 psig, corresponding to a maximum gas pressure ratio of 400 for a vessel at atmospheric pressure and 4,000 for vessel under low vacuum. The schlieren/shadowgraph configuration utilized for the imaging is a Z-Type configuration and possesses the advantages of both reducing aliasing effects and decreasing the overall area needed for the schlieren arrangement. Schlieren images taken were captured with a PCO Pixelfly CCD camera. A Photron high speed camera eventually replaced the Pixelfly within the schlieren arrangement expanding the imaging capabilities. A large polycarbonate enclosure was developed to enclose the entire system, shielding both the worker and the optics. Pressure and velocity sensors with high frequency response capability were selected to adequately monitor rapidly changing jet characteristics. PCB Piezotronic pressure sensors were mounted flush to the wall of the vessel opposite the gas jet inlet. A TSI one dimensional hot wire probe was inserted radially along the horizontal axis of the vessel, perpendicular to the jet flow. A NI Compact RIO data acquisition system, run with LabVIEW, was used to record the pressure measurements. For the hot wire anemometry velocity measurements, a standalone TSI IFA 300 was used to capture and process data. A dimensional analysis was performed to define the jet velocity in terms of other jet parameters, characteristic lengths, and fluid properties. The dimensional analysis results did not elucidate the substantiality of the dimensionless groupings; however, some of the missing exponents can theoretically be parameterized through additional future testing. Initial measurements with the experimental system will be presented and discussed. Schlieren and shadowgraph images and velocity measurements of air and helium jets were captured in both the PVC and steel vessel configurations. Pressure ratios of 10 to 300 were examined for helium, while pressure ratios up to 20 were achieved for air. The data shows how the leading edge velocity, average spread angle, and Mach disk height data are all influenced by pressure ratio and gas type. Velocity frequency content, basic jet turbulence structure, and gas entrainment are also evident in the experimental data. Based on these initial measurements, an outline for ongoing experimental studies will be presented.

High-Pressure Gaseous Injection: A Comprehensive Analysis of Gas Dynamics and Mixing Effects

2012 ◽  
Author(s):  
Riccardo Scarcelli ◽  
Alan L. Kastengren ◽  
Christopher F. Powell ◽  
Thomas Wallner ◽  
Nicholas S. Matthias
Keyword(s):  
Numerical Simulation ◽  
High Pressure ◽  
Mass Distribution ◽  
Gas Dynamics ◽  
Internal Combustion Engines ◽  
Direct Injection ◽  
Numerical Results ◽  
Gas Jet ◽  
Computational Time ◽  
X Ray

While the transportation field is mostly characterized by the use of liquid fuels, gaseous fuels like hydrogen and natural gas have shown high thermal efficiency and low exhaust emissions when used in internal combustion engines (ICEs). In particular, high-pressure direct injection of a gaseous fuel within the cylinder overcomes the loss of volumetric efficiency and allows stratifying the mixture around the spark plug at the ignition time. Direct injection and mixture stratification can extend the lean flammability limit and improve efficiency and emissions of ICEs. Compared to liquid sprays, the phenomena involved in the evolution of gaseous jets are less complex to understand and model. Nevertheless, the numerical simulation of a high-pressure gas jet is not a simple task. At high injection pressure, immediately downstream of the nozzle exit the flow is supersonic, the gas is under-expanded, and a large series of shocks occurs due to the effect of compressibility. To simulate and capture these phenomena, grid resolution, computational time-step, discretization scheme, and turbulence model need to be properly set. The research group on hydrogen ICEs at Argonne National Laboratory has been extensively working on validating numerical results on gaseous direct injection and mixture formation against PIV and PLIF data from an optically accessible engine. While a good general agreement was observed, simulations still could not perfectly predict the mixing of fuel with the surrounding air, which sometimes led to significant under-prediction of fuel dispersion. The challenge is to correctly describe the gas dynamic phenomena of under-expanded gas jets. To this aim, x-ray radiography was performed at the Advanced Photon Source (APS) at Argonne to provide high-detail data of the mass distribution within a high-pressure gas jet, with the main focus on the under-expanded region. In this paper, the numerical simulation of high-pressure (100 bar) injection of argon in a cylindrical chamber is performed using the computational fluid dynamic (CFD) solver Fluent. Numerical results of jet penetration and mass distribution are compared with x-ray data. The simplest nozzle geometry, consisting of one hole with a diameter of 1 mm directed along the injector axis, is chosen as a canonical case for modeling validation. A sector (90°) mesh, with high resolution in the under-expanded region, is used and the assumption of symmetry is made. Results show good agreement between CFD and x-ray data. Gas dynamics and mass distribution within the jet are well predicted by numerical simulations.

The gas jet behavior in submerged Laval nozzle flow

2017 ◽  
Vol 29 (6) ◽  
pp. 1035-1043 ◽  
Author(s):  
Zhao-xin Gong ◽  
Chuan-jing Lu ◽  
Jie Li ◽  
Jia-yi Cao
Keyword(s):  
Laval Nozzle ◽  
Gas Jet ◽  
Nozzle Flow ◽  
Jet Behavior
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