Design and Simulation of Two Stroke Engines

temperature vs. crankshaft angle (chainsaw engine
simulation)
cylinder (closed cycle two-zone chainsaw
model), 349-350
cylinder temperature, pressure, 392, 393
exhaust system, 390
intake system temperature, pressure, 390-392
internal, 386
scavenge model gases, 388-389
volumetric scavenging model (in engine simulation)
introduction, 241
exit charge temperature, determination of,
241-242
temperature differential factor, 241-242
Testing, engine. See Exhaust emissions/exhaust
gas analysis; Performance measurement
Thermal efficiency
brake thermal efficiency (defined), 37
of Otto cycle, 32
Thermodynamic (Otto) cycle
measured vs. theoretical values, 31-33
thermal efficiency of, 32
work per cycle, 33
Thermodynamic terms, defined
air-fuel ratio, 29-30
charging efficiency, 29, 213
delivery ratio (DR), 27
heat release (combustion, QR), 31, 309
scavenge ratio (SR), 27
scavenging efficiency, 28, 212-213
scavenging purity, 28
trapped charge mass, 30-31
trapped fuel quantity, 30-31
trapping efficiency, 28-29, 213
Thermodynamics of cylinders/plenums. See under
GPB engine simulation model
Three port engine
Day's original design, 1
Throttle area ratio, 371
Torque
Brake torque (defined), 36
indicated torque (defined), 35
Trapping
definitions
charging efficiency (CE) as function of TE
and SR, 213
trapped charge mass, 30-31
621
Index
trapped compression ratio, 8
trapped fuel mass (at trapping point), 31
trapped mass (total, at trapping point), 31
trapping efficiency (basic), 28-29, 213
exhaust closure
basic two-stroke engine, 6, 8
trapped compression ratio
vs. squished kinetic energy (diesel engines),
334, 335
trapping efficiency
defined (basic), 28-29, 213
from exhaust gas analysis, 41-42
measured performance (QUB 400 research
engine), 472-473
in perfect displacement scavenging, 213-214
in perfect mixing scavenging, 215
QUB single-cycle gas scavenging apparatus,
224-226
of simulated chainsaw engine, 479-481
TE plots (CFD vs. experimental values),
248-250
vs. AFR (low emissions engine), 487-489
vs. scavenge ratio (Benson-Brandham
model), 216-219
trapping point
in basic two-stroke engine, 8
trapping pressure
and active-radical combustion, 491
see also Exhaust emissions/exhaust gas analysis;
Scavenging
Turbocharged/supercharged engines
blower scavenging, effect of (three-cylinder engine)
introduction, 400
exhaust tuning, 405-407
open-cycle pressures and charging (cylinders
1-2), 404-405
temperature and purity in scavenging ports,
405, 406
compression ignition
bmep and emissions of (discussion), 531
Detroit Diesel Allison Series 92 diesel engine,
14
in European four-stroke on-road engines, 531
four-cylinder DI diesel, loop scavenging design
for, 272-273
configuration of, typical, 15
exhaust emissions of, 14