Numerical Simulation on the Boiling Flow Patterns of Al2O3-Water Nanofluid in Micro/Minichannel under Different Hypergravity Levels and Directions

Due to the influence of hypergravity that has a significant impact on the performance of heat exchanger in aircraft, which is crucial for electronic equipment on the plane and life safeties of pilots and passengers, a numerical study is conducted using Fluent 20R2 software to investigate boiling flow patterns under different gravity levels and directions. In this study, the thermophysical properties of nanofluids are analyzed, and select the most suitable theoretical model of thermal conductivity, viscosity, and surface tension for present simulations. Choose the grid structure of 122,116 after independence check for grid. The VOF approach is employed for present simulation, and the standard κ − ε turbulence model with nonequilibrium wall function is used. The UDFs for mass and energy source terms and thermophysical properties of nanofluid are developed for calculating the HTC of nanofluid. There are three different gravity directions with gravity levels from 1 g to 9 g. The results show that the flow pattern becomes the stratified flow with the gravity levels increasing when the hypergravity direction is perpendicular to the flow direction, and the HTCs decrease with the increment of gravity levels. The vapor-phase transform to circular when the hypergravity direction is the same as the flow direction, and the HTCs of the second half of the tube are decreasing with the increasing gravity levels. On the contrary, the vapor phase is elongated when the hypergravity direction is opposite to the flow direction, and the HTCs show the enhanced tendency.

Study on time delay estimation in boiler acoustic temperature measurement based on third correlation PHAT-β

In order to accurately measure the temperature of power plant boiler, a new algorithm of time delay was proposed based on third correlation and phase transform weighting on the basis of the research of traditional cross-correlation method and generalized cross-correlation. Small peaks can be weakened with the help of phase transform weighting and the addition of exponential coefficient β. The simulation result shows that the PHAT-β algorithm based on third correlation can accurately measure the value of time delay estimation compared with first correlation, second correlation and traditional third correlation, so as to improve the accurancy of temperature of power plant boiler.

Efficient and robust approaches for three-dimensional sound source recognition and localization using humanoid robots sensor arrays

Efficient and robust sound source recognition and localization is one of the basic techniques for humanoid robots in terms of reaction to environments. Due to the fixed sensor arrays and limited computation resources in humanoid robots, there comes challenge for sound source recognition and localization. This article proposes a sound source recognition and localization framework to realize real-time and precise sound source recognition and localization system using humanoid robots’ sensor arrays. The type of the audio is recognized according to the cross-correlation function. And steered response power-phase transform function in discrete angle space is used to search the sound source direction. The sound source recognition and localization framework presents a new multi-robots collaboration system to get the precise three-dimensional sound source position and introduces a distance weighting revision way to optimize the localization performance. Additionally, the experiment results carried out on humanoid robot NAO demonstrate that the proposed approaches can recognize and localize the sound source efficiently and robustly.

Iterative Volumetric Reduction (IVR) Steered Response Power Method for Acoustic Source Localization

Background: Steered Response Power–Phase Transform (SRP-PHAT) approach is a breakthrough in the field of source localization in a high reverberant environment, but the substantial computational cost limits its usage in the practical implementation. Objective: This paper presents an efficient SRP-PHAT based, Iterative Volumetric Reduction (IVR) Steered Response Power method for acoustic source localization in non-ideal surroundings. Methods: Developing the coarse acoustic maps in the preliminary iterations provides a measure of the approximate likelihood of a source lying in the corresponding regions. Subsequently, the search space volume is reduced to the region containing points with significant likelihood. Further, these two steps are iterated to achieve the desired resolution. Results and Conclusion: Conclusively the computational load reduces by 60-80% with considerable upgrading in accuracy as compared to Modified SRP PHAT. The required functional evaluation is adaptable to the environment which makes it an excellent approach over Iterative modified SRP-PHAT in unfavourable circumstances. Experiments conducted in various scenarios demonstrate the method's significance over the other state -of -art methods.