Translated Titles

Computational Simulation of Heavy Truck Model with Corner Nozzle Drag Reduction Device



Key Words

計算流體力學 ; 空氣動力 ; 角落噴嘴 ; 轉折角 ; 面積比 ; CFD ; aerodynamics ; corner nozzle ; effusive angle ; area ratio



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Chinese Abstract

重型卡車的油耗代表著能源消耗中很大的比重,它接近火柴盒外型的車體在高速行駛的時候空氣的阻力超過了因重量產生的摩擦阻力,此空氣阻力有很大一部份來自於卡車尾部的貢獻。本研究旨在探討如何利用空氣動力學的原理,來降低重型卡行駛中尾部的空氣阻力,進而降低燃油的消耗。使用的設計稱為角落噴嘴,垂直裝置在卡車尾端的左右兩側角落上,它用來平順的導引經過卡車側面的氣流至卡車尾端,並調整卡車背面的壓力,使達到降低空氣阻力的目的。卡車是採用與NASA Ames 實驗中心風洞試驗同樣的GTS 1/8縮小模型,計算流體力學(CFD)的方法在基本的卡車模型上做計算模擬分析,計算的模型是以CATIA建立外型,以軟體ICEM-CFD進行流場網格生成,再用ANSYS-CFX以有限單元法做流場的計算分析, 分別計算未裝置角落噴嘴及裝上角落噴嘴後的阻力,並據以判定角落噴嘴在降低空氣阻力的功效。角落噴嘴由兩片彎曲薄板構成,其性能由兩個重要參數控制:轉折角(α)和面積比(AR)。本研究討論的轉折角從20度到70度,面積比則從1.0到2.0,增量為0.2改變。計算結果顯示,角落噴嘴確實能降低空氣的阻力,不同的α角及AR有不同的空氣阻力降低效果,每個AR都有其相對的最佳α值使其空氣阻力最低,而此α值隨著AR的變大也跟著變大。在本研究中,最大的空氣阻力降低發生在α=60度及AR=2.0的時候,空氣阻力降低了7.609%。

English Abstract

Heavy truck fuel consumption represents a high percentage in overall energy consumption. Its matchbox-like configuration makes its aerodynamic drag exceed the frictional drag due to its weight. A large portion of the aerodynamic drag is attributed to the drag in the rear end of the truck. The purpose of this research is to study numerically the design of corner nozzles, installed vertically at two corners of the truck’s rear end, for the aerodynamic drag reduction to save fuel consumption. The model of heavy truck in the present study was an 1/8-scale Ground Transportation System (GTS), which was studied experimentally in the 7-by 10-foot NASA Ames wind tunnel facility. Computational fluid dynamics (CFD) method was used to do the numerical simulation. The computational model was created using CATIA CAD file. The numerical method adopted was CFX software for numerical simulation and ICEM-CFD for mesh generation. The simulations were performed on a baseline GTS truck model with and without the add-on corner nozzles. Comparisons were made to see the effectiveness of the corner nozzles. The nozzles in design considerations were made of two curved sheet metals. The performances were determined based on two configuration parameters: the effusive angles from 20 degrees to 70 degrees, and the nozzle outlet to inlet area ratios (AR) from 1.0 to 2.0 at 0.2 intervals. Calculations showed good aerodynamic drag reductions at different percentages. The results indicated that the larger AR has better drag reduction effect. The optimal effective angle for a given AR is proportional to the value of AR. The larger AR has the larger optimal effusive angle. The best design in the present study was found to be 7.609% in drag reduction when AR equals 2.0 and effusive angle is 60 degrees.

Topic Category 工學院 > 航空太空工程學系
工程學 > 交通運輸工程
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