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Jianghao Niu

Civil Aviation University of China, China

Title: CFD Analysis of the Influence of Ionic Liquids on the Performances of a Refrigeration System

The falling film of an ionic liquid ([EMIM] [DMP] + H2O) and its effect on a refrigeration system are numerically simulated in the framework of a Volume of Fluid (VOF) method (as available in the ANSYS Fluent computational platform). The properties of the liquid film and the wall shear stress (WSS) are compared with those obtained for a potassium bromide solution. Different working conditions are considered. It is noted that the ionic liquid demonstrates a better absorption capability, with a coefficient of performance (COP) of 0.55. It is proved that the [EMIM] [DMP] + H2O ionic liquid working substance is superior to the potassium bromide solution in terms of heat and mass transfer.

Xiangxi Du

Xi’an Jiaotong University

Title: Study on the Gas-based Lubrication of Elastic Foil Bearings Using an Over Relaxation Iteration Method

A new type of foil bearings with a specific surface microstructure is studied. First, relevant boundary conditions based on the assumption of rarefied gas flow are proposed, then, the static bearing capacity and friction torque are analyzed in the framework of a numerical technique based on the discretization of the governing equation for rarefied gas-dynamics. It is shown that under the same static load, the difference between the minimum film thickness calculated in this exploration and the results provided by dedicated tests is not obvious; with an increase in the load, the simulation results are closer to the test values; when the bearing rotor speed is 60000r/min, the bearing capacity of the new foil bearing with different foil groove depth is reduced by the effect of the boundary slip. With an increase in the depth of the grooves on the surface of the foil, the influence of the boundary slip effect increases; when the eccentricity of the bearing increases, the gas pressure generated increases and the bearing capacity increases.

Qifei Du

Tiangong University, China

Title: Analysis of the Thermal Behavior of a Lithium Cell Undergoing Thermal Runaway

This study examines the thermal runaway of a lithium ion battery caused by poor heat dissipation performances. The heat transfer process is analyzed on the basis of standard theoretical concepts. Water mist additives are considered as a tool to suppress the thermal runaway process. The ensuing behaviour of the battery in terms of surface temperature and heat generation is analyzed for different charge and discharge rates. It is found that when the remaining charge is 100%, the heat generation rate of the battery is the lowest, and the surface temperature with a 2C charge rate is higher than that obtained for a 0.5C charge rate. The experimental results show that when the additive concentration is 20% NaCl, its ability to inhibit the thermal runaway is the strongest.

Yafei Li

Southwest Petroleum University

Title: A Mathematical Model of Heat Transfer in Problems of Pipeline Plugging Agent Freezing Induced by Liquid Nitrogen

A mathematical model for one-dimensional heat transfer in pipelines undergoing freezing induced by liquid nitrogen is elaborated. The basic premise of this technology is that the content within a pipeline is frozen to form a plug or two plugs at a position upstream and downstream from a location where work a modification or a repair must be executed. Based on the variable separation method, the present model aims to solve the related coupled heat conduction and moving-boundary phase change problem. An experiment with a 219 mm long pipe, where water was taken as the plugging agent, is presented to demonstrate the relevance and reliability of the proposed model (results show that the error is within 18%). Thereafter, the model is applied to predict the cooling and freezing process of pipelines with different inner diameters at different liquid nitrogen refrigeration temperatures when water is used as the plugging agent.

Huali Guo

Guilin University of Aerospace Technology

CFD Analysis and Optimization of an Engine with a Restrictor Valve in the Intake System

In some competitions the rules clearly state that all participating cars must install a restrictor valve structure in the intake system of the engine. The intake air volume of the engine is considerably affected due to the existence of such a valve. Indeed, a small interface diameter through which gas flows can lead to considerable flow resistance and loss. In this study, a four-cylinder engine for FSC racing is analyzed using a combined method based on numerical simulation and experiments. The analysis reveals that the main factors affecting the intake air volume are the intake manifold and the volume of the resonance chamber. The influence of such factors is assessed using a single variable method and an optimal model and parameters are obtained accordingly. Comparison of different results show that the maximum torque for the optimized system is increased from the original 42.6 N·m to 46.9 N·m, thus demonstrating an increase of 10.6%. These findings provide a theoretical basis for the design of the intake system and the improvement of engine performance.

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