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

研制了一种利用回流式空气射流回收路面碎石防滑料的系统。本研究的目的是为了明确吹除喷嘴和吸嘴的砾石回收的最佳安装条件。吹出喷嘴出口的高度为h= 5 mm，宽度为50 mm。吸嘴进口高度h= 13 mm，宽度90 mm，吸嘴后装有密封喷嘴，用于将通过路面差距的碎石推回。通过改变射流的吹风角θ和射流与路面的距离y_0，拍摄了碎石的吹落区域，并利用热线风速仪测量了碎石在路面上的速度分布，得出了射流喷嘴的最佳安装条件为y_0/h=3，θ=15°，此时碎石的吹落距离增大。试验结果表明：1）在距路面1.5mm处测得的10 m/s的射流速度等值线，可以估算出干砾石在路面上的吹落范围; 2）安装顶棚对干砾石吹落距离的影响较小。当侧墙平行于射流中心线安装时，随着射流距离的增加，碎石的抛撒距离逐渐增大; 3）在抛撒射流的水动力作用下，碎石在路面上以滚动和跳跃的方式运动; 4）当吸嘴与路面之间的差距小于4 mm时，密封射流可以将碎石的反收购率抑制在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.