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  • A Mixed Radiative-Convective Technique for the Calibration of Heat Flux Sensors in Hypersonic Flow
  • Abstract The ability to measure the very high heat fluxes that typically occur during the hypersonic re-entry phase of space vehicles is generally considered a subject of great importance in the aerospace field. Most of the sensors used for these measurements need to be checked periodically and re-calibrated accordingly. Another bottleneck relates to the need to procure thermal sources that are able to generate reliable reference heat fluxes in the range between 100 and 1000 kW/m2 (as order of magnitude). In the present study, a method is presented by which, starting from a calibration system with a capacity of approximately 500 kW/m2 only,…
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  • Experimental Study on the Erosion of Pipelines under Different Load Conditions
  • Abstract The influence of the material stress state induced by internal and external forces on the erosion rate of pipelines has rarely been investigated in the literature. In order to fill this gap, using a tensile tester machine, a two–phase gas–solid particles jet erosion test was carried out considering a 316L stainless steel under different tensile stresses and different erosion angles. The results show that: 1) In the elastic range, with the increase of stress, the erosion rate manifests a rising trend; 2) In the metal plastic range, the increase of stress leads to a decrease of the erosion rate; 3)…
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  • Experimental Study on the Performance of an Onboard Hollow-Fiber-Membrane Air Separation Module
  • Abstract Onboard air separation devices, based on hollow fiber membranes, are traditionally used for the optimization of aircraft fuel tank inerting systems. In the present study, a set of tests have been designed and executed to assess the air separation performances of these systems for different air inlet temperatures (70°C∼110°C), inlet pressures (0.1∼0.4 MPa), volume flow rates of nitrogen-enriched air (NEA) (30∼120 L/min) and flight altitudes (1.5∼18 km). In particular, the temperature, pressure, volume flow rate, and oxygen concentration of air, NEA and oxygen-enriched air (OEA) have been measured. The experimental results show that the oxygen concentration of NEA, air separation coefficient, and…
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  • Optimization of Process Parameters for Injection Moulding of Nylon6/SiC and Nylon6/B4C Polymer Matrix Composites
  • Abstract In this research study, the mechanical properties of several Polymer matrix composites are investigated. These composites are multi-phase materials in which reinforcing materials are properly mixed with a polymer matrix. More precisely, Nylon 6 reinforced with 5, 15 and 25 wt. % of silicon carbide (SiC) and Nylon 6 reinforced with 5, 15 and 25 wt. % of boron carbide (B4C), prepared by means of an injection moulding process at three different injection pressures are considered. Specific attention is paid to the tensile and impact strength of these composites. The Taguchi technique is used to optimize the process parameters such as reinforcement…
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  • Simulation of the Pressure-Sensitive Seepage Fracture Network in Oil Reservoirs with Multi-Group Fractures
  • Abstract Stress sensitivity is a very important index to understand the seepage characteristics of a reservoir. In this study, dedicated experiments and theoretical arguments based on the visualization of porous media are used to assess the effects of the fracture angle, spacing, and relevant elastic parameters on the principal value of the permeability tensor. The fracture apertures at different angles show different change rates, which influence the relative permeability for different sets of fractures. Furthermore, under the same pressure condition, the fractures with different angles show different degrees of deformation so that the principal value direction of permeability rotates. This phenomenon…
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  • Review of Research Advances in CFD Techniques for the Simulation of Urban Wind Environments
  • Abstract

    Computational fluid dynamics (CFD) has become the main method for the prediction of the properties of the external wind environment in cities and other urban contexts. A review is presented of the existing literature in terms of boundary conditions, building models, computational domains, computational grids, and turbulence models. Some specific issues, such as the accuracy/computational cost ratio and the exploitation of existing empirical correlations, are also examined.

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  • Calculation of the Gas Injection Rate and Pipe String Erosion in Nitrogen Drilling Systems
  • Abstract Detailed information is provided for the design and construction of nitrogen drilling in a coal seam. Two prototype wells are considered. The Guo model is used to calculate the required minimum gas injection rate, while the Finnie, Sommerfeld, and Tulsa models are exploited to estimate the ensuing erosion occurring in pipe strings. The calculated minimum gas injection rates are 67.4 m3/min (with water) and 49.4 m3/min (without water), and the actual field of use is 90–120 m3/min. The difference between the calculated injection pressure and the field value is 6.5%–15.2% (formation with water) and 0.65%–7.32% (formation without water). The results…
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  • Optimization of the Air Deck Blasting Parameters on the Basis of the Holmquist-Johnson-Cook Constitutive Model
  • Abstract The present study considers the so-called air deck blasting, one of the most commonly used techniques for the improvement of blasting efficiency in mining applications. In particular, it aims to improve the operating conditions of large-scale equipment, increase the efficiency of the slope enlarging process, and reduce the mining cost. These objectives are implemented through a two-fold approach where, first, a program for slope enlarging based on the middle air-deck charge blasting-loosening technology is proposed, and second, the physical mechanism responsible for the stress wave attenuation in the rock is analyzed in the framework of a Holmquist–Johnson–Cook constitutive model. Field…
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  • Free Convection of a Viscous Electrically Conducting Fluid Past a Stretching Surface
  • Abstract Free convection of a viscous electrically conducting liquid past a vertical stretching surface is investigated in the presence of a transverse magnetic field. Natural convection is driven by both thermal and solutal buoyancy. The original partial differential equations governing the problem are turned into a set of ordinary differential equations through a similar variables transformation. This alternate set of equations is solved through a Differential Transform Method (DTM) and the Pade approximation. The response of the considered physical system to the non-dimensional parameters accounting for the relative importance of different effects is assessed considering different situations.
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  • Experimental Study on Seepage Characteristics of a Soil-Rock Mixture in a Fault Zone
  • Abstract A mixture of fault gouge and rubble taken out from a fault zone is used to prepare a S-RM (Soil-Rock Mixture) sample with rock block proportions of 20%, 30%, 40%, 50%, 60% and 70%, respectively. A GDS triaxial test system is used accordingly to measure the seepage characteristics of such samples under different loading and unloading confining pressures in order to determine the variation law of the permeability coefficient. The test results show that: (1) The permeability coefficient of the S-RM samples decreases as the pressure increases, and the decrease rate of this coefficient in the initial stage of confining…
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