Laser phase-doppler velocimetry measurements have been used to characterize the particle-gas sprays produced by straight-tube nozzles that simulate idealized fuel injectors for solid fuel combustion systems. Tests were conducted on two nozzle sizes, for two particle sizes, two loading ratios, and two gas velocities. The Reynolds numbers was varied from 9500 to 19000, and the Stokes number from 1.9 to 61.4. It was found that the velocities of the particles in the spray decelerate more slowly, and the velocity profiles are generally more narrow, than for a single-phase free-jet. The turbulence level of the particles in the sprays was found to be less than half the turbulence level of a single-phase free-jet, and the turbulent velocity profiles were not yet fully developed at X = 40D. The hydrodynamic characteristics of the nozzles that are the most important for combustion systems were found to be: (a) the particle spray expands radially at a cone angle of 2° (measured at the radius corresponding to the peak of the particle mass flux distribution); and (b) the nozzle pressure drop and particle mass flow can be related by a correlation that depends on loading ratio, Reynolds number, Stokes number, and the pressure drop coefficient of the nozzle for a single phase flow.
Multi-site damage (MSD) in the form of cracking at rivet holes in lap splice joints has been identified as a serious threat to the integrity of coDJIDe1'Cial aircraft nearing their design life targets. Consequendy, to assure the safety of aircraft that have accumulated large numbers of flights. flight hours and years in service requires inspection procedures that are based on the possibility that MSD may be presenL For inspcc:tions of aircraft components to be properly focused on the defect sizes that are critical for structural integrity, fracture mechanics analyses arenccdcd. Thecmrcntmcthodsareessentiallythoseoflincarelasticfracturemechanics(LEFM) which are sttictly valid only for cracks that extend in a quasi-static manner under small-scale crack tip plasticity conditions. While LEFM is very likely to be appropriate for subcritical crack growth. quantifying the conditions for fracture instability and subsequent propagation may require advanced fracture mechanics techniques. The specific focus in this paper was to identify the conditions in which inelastic-dynamic effects occur in (1) the linking up oflocal damage in a lap splice joint to form a major crack, and (2) large-scale fuselage failure by a rapidly OCCun1ng fluid/structllrC interaction process. InggductionAn:ccntrash of akplanc accidents has drawn considerable public attention to what is now widely known as the aging aircraftissuc. A variety offailure modes has been expcricnccdin the accidents that have focused attention on this issue. However, undoubtedly because of the Aloha Airlines ain:raft canopy scpatation. large-scale fuselage fracture is likely the best known. This failure was abetted by the presence of wide-spread cracking along rows of rivet holes in the lap splice joints in a fuselage skin -a phenomenon generally called multi-site damage (MSD). Of greatest technical concern. the Aloha Airlines incident revealed that the crack arrest capability of the design can be defeated when MSD exists.Considering the great number of older aircraft that are presendy in service -indeed, to determine what "oldcr" really means -some type of quantitative examination is clearly mandated. While details may differ, all such approaches must conform to the "datnage tolerance" philosophy in which periodic proof tests and/or nondesU'UCtive inspections (NDI) are combined with fracture mechanics analyses for the rate of growth to criticality of the most seven: crack that wo~ go undetected. For most situations, ordinary linear elastic fracture mechanics (LEFM) will suffice for this purpose. However, the presence of MSD engenders a number of complications that might lie beyond the limits of LEFM. The objcctive of this paper is to quantify the role of inelastic and dynamic effects that are embodied in an advanced fracture mechanics approach.
Computational simulations of a full-scale, horizontal liquid-liquid gravity separator have been undertaken by Southwest Research Institute (SwRI®) to model the batch separation of oil and water flow in two different software packages. Separator modeling using computational fluid dynamics (CFD) represents a powerful and economical option for design, but caution must be used in the setup and interpretation of data. Many examples are available in literature of poor agreement between simulation results and experimental/field data. Results require interpretation before taking them at face value due to the complexity of the various submodels that can be utilized. This work offers an evaluation of multiphase flow modeling techniques in both ANSYS® Fluent® and in Siemens PLM STAR-CCM+®, and provides a unique comparison between the CFD solvers that cover a broad range of flow rates, water cuts, and viscosities. Verification of the accuracy of each software package to reproduce empirical results while reducing computational resources has been accomplished. The performance of a horizontal gravity separator with perforated baffles has been investigated using CFD. The simulations were carried out using an Eulerian-Eulerian multiphase approach, using monodisperse water droplets in an oil-continuous phase. Separation efficiencies and fluid concentration percentages at several locations throughout the test separator were compared against experimental results for a wide range of inlet flow rates, water cuts, and oil viscosities. Initial computational results indicated that the horizontal liquid-liquid separator can be modeled within 7% accuracy of the local experimental separation efficiency values for the various test conditions in both software packages. An additional simulation with a modification to a known drag model in Fluent showed a significant improvement to the oil-in-water (OiW) concentration in comparison to the same simulation conducted in STAR-CCM+. This effort demonstrates the capability of reliable modeling of multiphase flow fields inside of horizontal gravity separators and offers a viable option for aiding in the design of separation equipment.
Computational simulation of a full-scale, horizontal liquid-liquid gravity separator has been undertaken by Southwest Research Institute® (SwRI®) to model the batch separation of oil and water flow. Separator modeling using Computational Fluid Dynamics (CFD) represents a powerful and economical option for design, but caution must be used in the setup and interpretation of data. Many examples are available in literature of poor agreement between simulation results and experimental/field data. No clear consensus on valid modeling methodology currently exists. Results require interpretation before taking them at face value due to the complexity of the various submodels that can be utilized. This work offers an evaluation of multiphase flow modeling techniques, and provides a unique comparison with experimental data that covers a broad range of flow rates, water cuts, and viscosities. The performance of a horizontal gravity separator with perforated baffles has been investigated using CFD. The simulations have been carried out using an Eulerian-Eulerian multiphase approach. These simulations were conducted using constant dispersed water droplet sizes in an oil-continuous phase. Separation efficiencies and water-cut percentages at several locations throughout the test separator were compared against experimental results for a wide range of inlet flow rates, water cuts, and oil viscosities. Computational results indicated that the horizontal liquid-liquid separator can be modeled within 10% accuracy of the local experimental separation efficiency values for the various test conditions. This effort demonstrates the capability of reliable modeling of multiphase flow fields inside of horizontal gravity separators, and offers an economical option for aiding in the design of separation equipment.
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