Development of Air Jet Retrieval System of Gravel Scattered on Frozen Road Surface for Slip Prevention

利用回流式喷气技术研制了路面碎石防滑回收系统。本研究的目的是明确用于碎石回收的喷吹喷嘴和吸力喷嘴的最佳安装条件。喷嘴出口高度为h=5 mm，宽度为50 mm。吸嘴入口高度为h=13 mm，宽度为90 mm，吸嘴后面安装有密封射流喷嘴，用于将通过路面缝隙的碎石推后。在改变喷吹角度θ和与路面的距离y0的情况下，用热线风速仪拍摄了碎石的剥离区域，并用热线风速仪测量了路面上的速度分布，得出了喷吹喷嘴的最佳安装条件为y0/h=3，θ=15°，此时碎石的剥离距离增大。其他结果如下：1)从距路面1.5 mm处测得的10m/S的射流速度等高线，可以估算出路面上干砾石的剥落范围。2)天花板安装防尘对剥落距离的影响很小。3)在喷流水动力的作用下，碎石在路面上作滚动和俯冲运动。4)当吸嘴与路面之间的距离小于4 mm时，封闭式射流可以将碎石的抗结块率抑制在3%以下。

Development of retrieval system of the gravel scattered on the road surface for slip prevention by means of recirculation type air jet is conducted. The purpose of this study is to clarify the optimum installation condition of the blow off jet nozzle and the suction nozzle for the gravel retrieval. The height of the blow off jet nozzle exit was h=5mm, and the width was 50mm. The inlet height of the suction nozzle was h=13mm, and the width was 90mm.The sealing jet nozzle which push back the gravel going through the gap between the road surface has been installed behind the suction nozzle. In changing blowing angle θ of the jet and standoff distance from the road surface y_0, the blow off regions of the gravel were photographed and velocity distributions over the road surface were measured by hot-wire anemometer.As the result, optimum installation condition of the blow off jet nozzle were found to be y_0/h=3 and θ=15°, where the blow off distance of gravel is increased. The other results areas follows.1) It is possible to estimate the blow off region of the dry gravel on the road surface from the jet velocity contour line of 10m/s measured at 1.5mm above the road surface.2) The effect of ceiling installation for dustproof on the blow off distance was found to be small. How ever the blow off distance of the gravel is increased, when the sidewall was installed parallel to the centerline of the jet.3) By the hydrodynamic force of the blow off jet, the gravel moves in rolling and saltation over the road surface.4) The sealing jet can suppress the anti-acquisition rate of the gravel below 3%, when the gap between suction nozzle and road surface is less than 4mm.