1. Existing problems
During the operation of the boring machine, the fog spray dust removal process mainly captures dust, so that the dust particles are wet after water, the weight increases, the speed slows down and the settlement. The factors that affect the dust removal effect include: the air content of the fog spray nozzle jet, the form and installation position of the nozzle and the water pressure at the nozzle.
The problems existing in the fog spray nozzle during use are mainly as follows:
(1) The external fog spray water supply is provided by the cutting motor cooling water single way. Limited by the cutting motor water jacket design pressure, external fog spray water supply pressure < 1MPa, flow rate < 25L/min, insufficient capacity.
(2) The nozzle is homemade, the structure is backward, the effect is poor, and the ejector nozzle used by the coal mine shearer is not interchangeable at present.
(3) The installation Angle of the three nozzles at the end of the fog spray shelf is not ideal, so that about 40% of the fog spray fog is hit on the cutting head, and there is no direct effect on the fog spray object.
(4) The appearance of the fog spray frame is abrupt, silly, thin, and its own protection ability is low, and it is easy to be damaged by large coal rocks. Many coal mine users in the machine to the mine, with the mine's thick homemade fog spray rack instead.
(5) Each pipe joint adopts the form of sleeve, which is inconvenient for installation, maintenance and replacement.
(6) The air content of the fog spray nozzle jet is not high, causing the dust removal effect is not obvious.
2 fog spray nozzle improved design
2.1 Improved design of shape structure
(1) The external fog spray water supply is designed in two ways: one low pressure water is supplied to the cutting motor for cooling, and then the cooling water is completely supplied to the three nozzles at the end of the fog spray frame to increase the flow through the three nozzles; Another high pressure water supply, supply the left and right nozzle seat of the 8 nozzles, the road high pressure water can be provided by the surface water or by the pump, the water pressure can reach 3 ~ 5MPa, the flow rate is also greatly increased.
(2) The nozzle adopts the PAA~2/60 ejector nozzle widely used by the shearer, which is not only easy to interchange, but also the center aperture is expanded from 1mm to 2mm, which increases the flow rate. The working principle and advantages of the ejector nozzle: the high-speed water flow from the center hole of the nozzle, the air around the nozzle through the suction hole into the nozzle, the result of air and water mixing makes the atomization effect improved, but also can catch dust from the air, so the dust removal effect is greatly improved. The nozzle outlet is effectively protected and is not easy to clog and wear.
(3) The installation Angle of the three nozzles at the end of the fog spray rack is raised to 5o, so that most of the fog spray fog avoids the cutting head and directly acts on the cutting object.
(4) When designing the appearance of the fog spray rack, the two ends are designed to be excessively circular, and the cover plate thickness is increased (the plate thickness is increased from 16mm to 25mm), which greatly improves its own protection ability.
(5) Each pipe joint adopts the form of quick joint, which is convenient for underground maintenance and replacement.
2.2 Internal structure improvement design
Another main factor affecting the effect of fog spray method is the air content of fog spray nozzle jet, and the air content is directly related to the jet impact Angle of nozzle. Obviously, it is very important to design a suitable jet impact Angle for the fog spray nozzle.