Page 17 - Air and Gas Drilling Manual

xviii List of Symbols
.
w m
.
= weight rate of flow of rock cuttings solids, lb/sec
w s = weight rate of flow of drilling mud, lb/sec
.
w t = total weigh rate of flow, lb/sec
.
w w = weight rate of flow of the incompressible fluid, lb/sec
.
W as = actual shaft power, hp
.
W asb = actual shaft horsepower required by each compressor, hp
.
W asp = actual shaft horsepower, hp
.
W ast = total actual shaft horsepower needed by the combined primary and booster
compressor system, hp
.
W i = derated input horsepower available, hp
.
W s = time rate of shaft work done, ft-lb/sec
.
W sb = theoretical shaft horsepower required by this compressor, hp
.
W sp = theoretical shaft horsepower required by the primary compressor, hp
.
W t = total actual shaft horsepower by both the compressor and the hydraulic
pump, hp
.
W td = horsepower required at the top drive system, hp
= total shaft work, ft-lb/lb
Ws
β = geothermal gradient constant, °F/ft
∆L c = distance the air flow is compressed inside the drill collars above the

hammer, ft
∆P b = pressure change through the drill bit, lb/ft 2
∆P Tee = approximate pressure change through two valves and Tee, lb/ft 2

= mechanical efficiency
ε m
ε v = volumetric efficiency