Internal Flow Systems Research Articles

Model-based development of a multi-agent system for controlling material flow systems

Abstract The rising number of product variants requires flexible manufacturing systems, including their internal material flow systems (MFSs). An approach to design MFSs reconfigurably is the use of a decentralized control based on software agents. For implementing an agent-based control approach for MFSs this paper presents a meta model describing the knowledge base of individual agents and the overall control task to be fulfilled by the MFS.

Measurement of local heat transfer coefficient during gas–liquid Taylor bubble train flow by infra-red thermography

In mini/micro confined internal flow systems, Taylor bubble train flow takes place within specific range of respective volume flow ratios, wherein the liquid slugs get separated by elongated Taylor bubbles, resulting in an intermittent flow situation. This unique flow characteristic requires understanding of transport phenomena on global, as well as on local spatio-temporal scales. In this context, an experimental design methodology and its validation are presented in this work, with an aim of measuring the local heat transfer coefficient by employing high-resolution InfraRed Thermography. The effect of conjugate heat transfer on the true estimate of local transport coefficients, and subsequent data reduction technique, is discerned. Local heat transfer coefficient for (i) hydrodynamically fully developed and thermally developing single-phase flow in three-side heated channel and, (ii) non-boiling, air–water Taylor bubble train flow is measured and compared in a mini-channel of square cross-section (5mm×5mm; Dh=5mm, Bo≈3.4) machined on a stainless steel substrate (300mm×25mm×11mm). The design of the setup ensures near uniform heat flux condition at the solid–fluid interface; the conjugate effects arising from the axial back conduction in the substrate are thus minimized. For benchmarking, the data from single-phase flow is also compared with three-dimensional computational simulations. Depending on the employed volume flow ratio, it is concluded that enhancement of nearly 1.2–2.0 times in time-averaged local streamwise Nusselt number can be obtained by Taylor bubble train flow, as compared to fully developed single-phase flow. This enhancement is attributed to the intermittent intrusion of Taylor bubbles in the liquid flow which drastically changes the local fluid temperature profiles. It is important to maintain proper boundary conditions during the experiment while estimating local heat transfer coefficient, especially in mini-micro systems.

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J101035 ロケットターボポンプ内部流れの動的設計(〔J101-03〕回転機械のダイナミック設計(3))

Computational fluid dynamics for turbomachinery internal air systems

Considerable progress in development and application of computational fluid dynamics (CFD) for aeroengine internal flow systems has been made in recent years. CFD is regularly used in industry for assessment of air systems, and the performance of CFD for basic axisymmetric rotor/rotor and stator/rotor disc cavities with radial throughflow is largely understood and documented. Incorporation of three-dimensional geometrical features and calculation of unsteady flows are becoming commonplace. Automation of CFD, coupling with thermal models of the solid components, and extension of CFD models to include both air system and main gas path flows are current areas of development. CFD is also being used as a research tool to investigate a number of flow phenomena that are not yet fully understood. These include buoyancy-affected flows in rotating cavities, rim seal flows and mixed air/oil flows. Large eddy simulation has shown considerable promise for the buoyancy-driven flows and its use for air system flows is expected to expand in the future.

New laser based method for non-intrusive measurement of available energy loss and local entropy production

This paper outlines a new experimental technique for measuring the instantaneous entropy production using a non-intrusive, laser based approach. Unlike point-wise methods which yield measured velocities at single points in space, the method of PIV (particle image velocimetry) is used to derive the spatial velocity gradients over the entire problem domain. When combined with local temperatures and thermal irreversibilities, these velocity gradients can be used to determine the energy availability loss due to exergy destruction. This article focuses on frictional effects, which lead to irreversible degradation of mechanical energy into internal energy through viscous dissipation. Frictional effects are significant in various devices, ranging from power turbines, internal flow systems and other turbomachinery. In addition to measured data for validation of predictive models, such data can be used by designers to characterize and improve the energy efficiency of engineering devices.

A novel usage of neural network in optimization and implementation to the internal flow systems

PurposeTo propose a robust and more effective algorithm for aerodynamic design optimization problem by using neural network.Design/methodology/approachNeural network and genetic algorithm (GA) are hybridized in a new way, and quasi one‐dimensional Euler equations are solved for internal flow in the nozzle.FindingsThe results indicate that the nozzle design can be performed successfully and quickly by using the implemented algorithm. It is observed that using the method decreased CFD solver calls about 21 and 46 per cent for transonic and supersonic flow, respectively.Originality/valueIt is the first time that the neural network is used for the candidate solution in the GA.

Low-Reynolds-Number Turbulent Flows in Locally Constricted Conduits: A Comparison Study

In numerous internal flow systems the velocity field can undergo all flow regimes, that is, from laminar, via transitional, to fully turbulent. Considering two test conduits with local constrictions, four turbulence models, with an emphasis on low-Reynolds-number (LRN) turbulence models, were compared and evaluated. The objective was to identify a readily available LRN turbulence model with which incompressible laminar-to-turbulent velocity and pressure fields in complex three-dimensional conduits can be directly computed. The comparison study revealed that the renormalization group (RNG) κ-e and Menter κ-ω models amplify the flow instabilities after tubular constrictions and hence fail to capture the laminar flow behavior at low Reynolds numbers

Aerodynamic Shape Optimization Using Computational Fluid Dynamics and Parallel Simulated Annealing Algorithms

Aerodynamic shape design using stochastic optimization methods, such as simulated annealing method to optimize objective functions evaluated by modern state-of-the-art computational fluid dynamics solvers, normally requires enormous computation time to search for the global optimal design. Aerodynamic shape optimization of internal flow systems is studied using Euler/Navier-Stokes solvers and parallel simulated annealing algorithm, which is implemented on parallel computing platforms. A variety of inverse and direct design of internal flow systems are carried out to examine the efficiency and speedup of the parallel simulated annealing algorithms

Parametric investigation of nonadiabatic compressible flow around airfoils

The compressible flow of a mixture of dry air (an inert carrier gas) and water vapor with nonequilibrium and homogeneous condensation around thin airfoils is examined. The investigation is based on a recent transonic small-disturbance (TSD) theory. The theory provides the governing similarity parameters of the flow and condensation process. The parameters give the relationship between the flow properties, the amount of water vapor mass in the air, and the airfoil’s chord and thickness ratio. The results of varying the similarity parameters are demonstrated by numerical simulations. It is found that heat addition as a result of condensation causes significant changes in the compressible flow behavior and affects the aerodynamic performance of airfoils. Increasing the free-stream frozen Mach number or the airfoil’s chord (with fixed free-stream temperature, pressure, and amount of water vapor) augments the condensation region and the amount of heat transfer to the flow. The heat transfer to the flow also results in the appearance of a compression wave in addition to a regular shock wave. Also, decreasing the free-stream temperature with a fixed amount of water vapor in the air or increasing the free-stream temperature with a fixed free-stream supersaturation ratio enlarges the condensation region and reduces the shock wave strength. These results demonstrate the possible use of condensation phenomena to control aerodynamic characteristics of airfoils operating in internal flow systems.

Developments in Fluid Mechanics and Space Technology. Edited by R. NARASIMHA and A. P. J. ABDUL KALAM. Indian Academy of Sciences, 1988. 454 pp. Advances in Transport Processes, Vol. IV. Edited by A. S. MAJUMDAR and R. A. MASHELKAR. Wiley Eastern, 1986. 617 pp. Particulates and Continuum: Multiphase Fluid Dynamics. By S. L. Soo. Hemisphere, 1989. 400 pp. $49 or

Developments in Fluid Mechanics and Space Technology. Edited by R. NARASIMHA and A. P. J. ABDUL KALAM. Indian Academy of Sciences, 1988. 454 pp. Advances in Transport Processes, Vol. IV. Edited by A. S. MAJUMDAR and R. A. MASHELKAR. Wiley Eastern, 1986. 617 pp. Particulates and Continuum: Multiphase Fluid Dynamics. By S. L. Soo. Hemisphere, 1989. 400 pp. $49 or

A Quasi-Standing-Wave Phenomenon Due to Oscillating Internal Flow

The objective of this investigation is to characterize a quasi-standing-wave pattern having a wavelength two orders of magnitude smaller than the corresponding acoustic wavelength, and relate it to the presence of: a) a downstream travelling wave due to vortical structures generated in a free shear layer, and b) downstream and upstream propagating acoustic waves. In this experiment, the vortical structures were generated by flow past an axisymmetric cavity and their influence extended downstream through the exhaust pipe. The amplitudes of the acoustic waves were associated with Helmholtz resonance of the upstream settling chamber. A linear theory models well the measured amplitude and phase distributions of the fluctuating velocity in the core flow. As system resonance is approached, the ratio of vortex wave amplitude to acoustic wave amplitude decreases. The consequence is an increase in the magnitude and gradient of the phase change across the node, or amplitude minimum, of the resultant standing-wave pattern. In addition, the peak-to-peak amplitude of the quasi-standing-wave increases. A variety of internal (and external) flow systems, including unsteady phenomena in wind tunnels, may be subject to this flow mechanism when the frequency of coherent vortex formation in the test section lies near the Helmholtz resonance frequency of the upstream settling (or plenum) chamber.

Component Interactions and their Influence on the Pressure Losses in Internal Flow Systems

SYNOPSIS The pressure losses arising from the flow through internal flow systems are usually estimated by subdividing the system into elementary components, assigning a loss to each component, and then summing these individual contributions. This approach can lead to appreciable errors when the components are sufficiently close to one another for interactions to occur. As a contribution to the discussion of this complicated subject, this paper is concerned with the steady, turbulent flow through combinations of bends and diffusers. Under some circumstances the combined losses of the interacting components are greater than the sum of the individual losses in interference free flow. In other circumstances the reverse is the case. However, as this paper demonstrates, in all cases it is possible to produce sound physical reasons for the variations and, as a consequence, it is possible to generalise the results to interactions involving other components in combination. The paper concludes with a list of broad design principles which have wide application to systems in which interaction effects are important.

Boundary Layer Influence on the Performance of Submerged Intakes

Submerged intakes are widely used on aircraft as a means of supplying internal flow systems with ambient air. It is the purpose of this note to show by analysis of existing experimental data that the boundary layer at the location of the submerged intake can have an appreciable effect on its performance.Information here relates to the NACA type of divergent submerged intake with a ramp angle, a, of 7° and an aspect ratio, w/d, of 4 because this particular combination of planform and geometry is now almost universally used.

A Radial Diffuser Using Incompressible Flow Between Narrowly Spaced Disks

Owing to the geometric limitations of certain internal flow systems, the use of a conical or rectangular diffuser for the recovery of kinetic energy as static pressure is often impossible. This paper describes a study of swirl-free, incompressible flow in a radial diffuser consisting of two components: A radial channel in which the flow diffusion occurs and an inlet bend which joins the radial channel to the supply pipe outlet. A design for an efficient inlet bend is described and a study made of other geometrical parameters. The experiments showed that the pressure recovery decreased with increasing inlet boundary-layer thickness and decreasing Reynolds number, both for the radial diffuser and a 7-deg conical diffuser of the same area ratio. In addition, the pressure recovery of the radial diffuser was comparable to that of the 7-deg conical diffuser at the high Reynolds numbers generally encountered in internal flow systems. At high Reynolds numbers, it was also possible to predict theoretically the pressure recovery for the radial diffuser.

On chemical reactions in internal flow systems

The basic equations for a non-isothermal homogeneous reaction in an internal flow system with a fully established velocity field are presented. It is shown that the specie concentrations can be found from a single function, i.e. the degree of advancement of the reaction, while the temperature is determined through a generalized enthalpy function which takes into account the thermal exchange with the exterior. Under mildly non-isothermal conditions, to which the analysis applies primarily, the determination of the two basic functions reduces to the solution of two linear parabolic equations and their associated Sturm-Liouville systems. An illustration of the analysis is given and a number of extensions are indicated.