chamber has experienced exhaust stroke (L 5 ), compression stroke (L 3 À L 5 ) and
intake stroke (L 1 À L 3 ), in which L max is the maximum return displacement of
piston actual motion and L 1 is the structural stroke. In stroke motion, the front
chamber experiences exhaust stroke (L max À L 2 ), compression stroke (L 2 À L 4 ) and
intake stroke (L 4 ), and the rear chamber experiences intake stroke (L 1 À L 3 ),
expansion stroke (L 3 À L 5 ) and exhaust stroke (L 5 ). Table 11.11 lists the gas distribution process of the front and rear chambers. The single cycle of DTH hammer
Rear
chamber
Front
chamber
Compress
Stage 1:
Front-chamber
intake and
rear-chamber
exhaust
Stage 2:
Front-chamber
intake and
rear-chamber
compression
Front
chamber
exhaust
Front
chamber
expansion
Rear air
chamber
intake
Stage 3:
Front chamber expansion and
rear chamber compression
Stage 4:
Front chamber expansion and
rear chamber intake
Stage 5:
Exhaust from front chamber
and inlet from rear chamber
Fig. 11.14 Return stroke five cycles of DTH hammer single cycle
11.4 Dynamic Process and Theoretical Model of Large Diameter …
225