Abstract
Air separators are fitted to helicopter engine intakes to remove potentially harmful dust from the influent air. Their use is necessary in desert environments to eliminate the risk of rapid engine wear and subsequent power deterioration. However, their employment is concomitant with an inherent loss in inlet pressure and, in some cases, auxiliary power. There are three main technologies: vortex tubes, barrier filters, and integrated inlet particle separators. In this work, a vortex tube is investigated numerically. The study was conducted on the number and axial angle of inlet nozzles. Two and three-dimensional models are investigated at a steady state condition then the standard k-ε turbulence model is utilised for determining the flow and temperature fields. The finite volume method base on a Computational Fluid Dynamic (CFD) model is verified through the comparison with experimental data and numerical results of a vortex tube, reported in literature sources. Increasing the number of inlet nozzles, increases the sensitivity of the temperature reduction and the highest possible temperature reduction can be obtained. A vortex tube with an axial angle inlet nozzle of yields better performance. The numerical simulation results indicated that the CFD model is capable of predicting the vortex separation phenomenon inside a Ranque-Hilsch vortex tube with different geometrical parameters.
Highlights
A vortex tube, called a Ranque-Hilsch vortex tube (RHVT), is a simple device with no moving parts that converts a pressurized gas of a homogeneous temperature into two streams of different temperature, one warmer than the inlet and one cooler simultaneously
The number of inlet nozzles changes but the total inlet surface area will remain at a constant value of 8.2 mm2 in line with the Skye et al (2006) model
The temperature separation phenomenon inside the vortex tube is investigated with the help of Ansys Fluent 16.1 software
Summary
A vortex tube, called a Ranque-Hilsch vortex tube (RHVT), is a simple device with no moving parts that converts a pressurized gas of a homogeneous temperature into two streams of different temperature, one warmer than the inlet and one cooler simultaneously. Due to the limitations of the experimental work, some efforts have been made to successfully utilize computational fluid dynamics (CFD) to find numerical simulations to explain the fundamental principle behind the energy separation within the vortex tube. Eiamsa-ard and Promvonge (2007, 2008a) carried out a numerical simulation to examine the phenomena of the flow field and energy separation inside vortex tube flows. (2007) used large eddy simulation to obtain the energy separation inside a vortex tube They compared the predicated results with the published experimental results of Skye et al (2006). (2014) presented a three-dimensional model with the consideration of fluid compressibility and strong swirling characteristics They compared the existing turbulence models and found that RNG k-ε turbulence and standard k-ε models are more suitable for the numerical simulation of the vortex tube. The data for counter-flow vortex tubes with different geometrical parameters has been obtained under similar conditions
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