Page 36 - Mechatronics with Experiments

JWST499-Cetinkunt
JWST499-c01
22 MECHATRONICS Printer: Yet to Come October 9, 2014 7:39 254mm×178mm

T

Intake stroke Compression stroke Power stroke Exhaust stroke

Pc Pressure

Cylinder pressure Atmospheric Torque
Ignition point

pressure

0 180 360 540 720 deg
TDC BDC TDC BDC TDC
The gas pressure curve
Pressure

Expansion
Compression

Exhaust

Palm

Volume
TDC BDC
FIGURE 1.20: Basic four-stroke cycle operation of a diesel engine: intake, compression,
expansion, exhaust stroke. The pressure in a cylinder is a function of crankshaft position. Other
cylinders have identical pressures as a function of crankshaft angle except with a phase angle.
Compression ratio is the ratio of the cylinder volume at BDC (V BDC ) to the cylinder volume at
TDC (V TDC ). Notice that during the compression stroke, the cylinder pressure opposes the crank
motion, hence the effective torque is negative. During the expansion stoke, the cylinder
pressure supports the crank motion, hence the effective torque is positive.