impactor, which are uniformly distributed in the circumference. When the groove is
machined, increasing the depth of the groove and increasing the flow area from
1:76 Â 10
À3 to 3:34 Â 10
À3 m
2 will increase the air intake of the rear chamber at
low piston speed, which will play a role in stabilizing the pressure of the rear
chamber. Figure 11.25 shows the pressure of rear chamber at the end of return the
beginning of stroke after increasing the flow area. The amplitude of pressure
fluctuation decreases from 4 Â 10
4 to 1:5 Â 10
4 Pa, which achieves a better results.
11.4.4 Summary
(1) The dynamic model of pneumatic DTH hammer needs to consider the influence
of thermodynamic process on gas state. The numerical simulation of dynamic
process of large diameter DTH hammer and the design of key structural
parameters can be carried out through mathematical modeling and
programming.
(2) For the designed large diameter pneumatic DTH hammer, excessive air pressure will cause the piston to move beyond the maximum stroke, and too small
Inlet passage
Fig. 11.24 Inlet passage of
rear chamber on cylinder
inner surface of prototype
Time t/s
Pressure p/Pa
Fig. 11.25 Rear chamber
pressure fluctuation after
increasing flow area
11.4 Dynamic Process and Theoretical Model of Large Diameter …
239
machined, increasing the depth of the groove and increasing the flow area from
1:76 Â 10
À3 to 3:34 Â 10
À3 m
2 will increase the air intake of the rear chamber at
low piston speed, which will play a role in stabilizing the pressure of the rear
chamber. Figure 11.25 shows the pressure of rear chamber at the end of return the
beginning of stroke after increasing the flow area. The amplitude of pressure
fluctuation decreases from 4 Â 10
4 to 1:5 Â 10
4 Pa, which achieves a better results.
11.4.4 Summary
(1) The dynamic model of pneumatic DTH hammer needs to consider the influence
of thermodynamic process on gas state. The numerical simulation of dynamic
process of large diameter DTH hammer and the design of key structural
parameters can be carried out through mathematical modeling and
programming.
(2) For the designed large diameter pneumatic DTH hammer, excessive air pressure will cause the piston to move beyond the maximum stroke, and too small
Inlet passage
Fig. 11.24 Inlet passage of
rear chamber on cylinder
inner surface of prototype
Time t/s
Pressure p/Pa
Fig. 11.25 Rear chamber
pressure fluctuation after
increasing flow area
11.4 Dynamic Process and Theoretical Model of Large Diameter …
239