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

研制了利用再循环式射流回收路面抛撒防滑碎石的系统。本研究的目的是明确砾石回收中吹出喷嘴和吸出喷嘴的最佳安装条件。吹出喷嘴出口高度h=5mm，宽度50mm。吸嘴入口高度h=13mm，宽度90mm。在吸嘴后方安装密封喷射喷嘴，将穿过路面缝隙的碎石推回。通过改变射流的吹风角度θ和离路面的距离y_0，对碎石的吹风区域进行了拍摄，并用热线风速仪测量了碎石在路面上的速度分布。结果表明，吹散射流喷嘴的最佳安装条件为y_0/h=3, θ=15°，可增大砾石的吹散距离。其他结果如下。1)根据在路面上方1.5mm处测得的10m/s射流速度等高线，可以估算出干砾石在路面上的吹落区域。2)吊顶安装防尘对吹离距离的影响较小。然而，当侧壁与射流中心线平行安装时，砾石的吹出距离增加了。在射流的水动力作用下，砾石在路面上以滚动和跳跃的方式移动。4)当吸嘴与路面间隙小于4mm时，密封射流可将碎石反采率抑制在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.