First, you should understand the working principle of a pneumatic rock drill. Pneumatic rock drill is composed of three parts: slewing mechanism, operating mechanism and outrigger. Pneumatic rock drills use compressed air as power, and control the rotation of the motor and the expansion and contraction of the outrigger through the motor control valve and the outrigger control valve. The compressed air enters the upper cavity of the air leg through the quick exhaust valve, and the air leg is extended. When the air leg control valve is closed, the remaining air in the upper cavity of the air leg is vented from the quick exhaust valve, and the air leg falls back by the gravity of the rig. Turn the knob to open the water control valve, and the flushing water enters the drill pipe through the filter screen, the water valve, the water jacket, and the inner hole of the spindle to flush the drill hole.
Changing the rotation angle of the joystick can change the flow of flushing water. According to the working principle of the pneumatic rock drill, one of the sources of noise is the strong noise generated by the compressed air in the drill from the exhaust port of the rotary mechanism and the exhaust port of the propulsion mechanism. The second is the vibration of the drill during drilling operations. The powerful noise and the noise generated by the rock vibration caused by the bit cutting the rock.
Exhaust noise is caused by the interaction of the exhausted high-speed airflow and relatively stable air. The pneumatic bolting rig mainly produces jet noise. The size of the noise has a great relationship with the exhaust speed of the airflow, the geometry and size of the exhaust port. We can take measures to prevent noise from the three aspects of noise source, transmission route and receiver. In order to reduce the exhaust noise, it is necessary to design a new type of muffler. Therefore, it is particularly important to understand the exhaust process of a pneumatic rock drill.
The exhaust gas enters the relatively static atmosphere through the exhaust port at a high speed. In the mixed zone of exhaust gas and atmosphere, the sudden decrease of exhaust velocity causes irregular vortex, and the vortex also circulates irregularly, causing many frequency bands of irregular noise. In addition, the exhausted gas itself is also the propagation medium of mechanical noise inside the pneumatic rock drill. However, there is no way to eliminate these aerodynamic noises. The only way to reduce the noise is to limit the exhaust speed.