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Design and Simulation of Two Stroke Engines

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local acoustic velocity, 60<br />

local Mach number, 60<br />

mass flow rate, 60<br />

particle velocity, 59<br />

pressure amplitude ratio, 59<br />

propagation velocity, 59<br />

the expansion wave<br />

absolute pressure, 60<br />

density, 60<br />

local acoustic velocity, 60<br />

local Mach number, 61<br />

mass flow rate, 61-62<br />

particle velocity, 61<br />

pressure amplitude ratio, 61<br />

propagation velocity, 61<br />

shock formation (wave pr<strong>of</strong>ile distortion)<br />

introduction, 62<br />

compression waves (discussion), 62, 64<br />

expansion waves (discussion), 63-64<br />

flow diagram <strong>of</strong>, 63<br />

particle velocity (shock wave), 62, 64<br />

propagation velocity (shock wave), 62, 63<br />

steep-fronting, 62<br />

Pumping mean effective pressure<br />

determination <strong>of</strong> (in engine testing), 37-38<br />

see also Friction/friction losses<br />

Purity<br />

charge purity<br />

CFD plots (Yamaha DT250 cylinders),<br />

246-248<br />

vs. crankshaft angle (chainsaw engine simulation),<br />

386<br />

in closed cycle combustion model (single-zone),<br />

321<br />

exhaust port purity<br />

correlated theoretical model (Yamaha DT250<br />

cylinders), 239-240<br />

theoretical calculation <strong>of</strong>, 238-239<br />

theoretical curves (eight test cylinders),<br />

239-240<br />

idealized incoming scavenge flow, defined, 212<br />

importance <strong>of</strong> (in Benson-Br<strong>and</strong>ham model),<br />

217-218<br />

in mesh space J (during time step in GPB<br />

model), 161<br />

scavenging purity, defined, 28<br />

613<br />

Index<br />

QUB (Queen's University <strong>of</strong> Belfast)<br />

air-assisted fuel injection system spray pattern,<br />

519<br />

Jante method, experience with, 222-223<br />

laminar flow type silencer design, 565<br />

QUB cross scavenging<br />

deflection ratio, importance <strong>of</strong>, 262<br />

<strong>and</strong> homogeneous charge combustion, 338<br />

piston design for (typical), 10, 11, 12<br />

QUB CROSS ENGINE DRAW ((computer<br />

program)), 25-26<br />

QUB CROSS PORTS ((computer program)),<br />

260, 261-263<br />

scavenging efficiency <strong>of</strong>, 11<br />

squish action in, 262, 325, 338<br />

SR vs. SE (QUBCR cylinder), 230<br />

SR vs. TE (QUBCR cylinder), 231<br />

QUB single-cycle scavenging test apparatus<br />

functional description, 224-227<br />

see also Scavenging<br />

QUB SP single-pulse experimental apparatus<br />

introduction, 170<br />

coefficient <strong>of</strong> discharge for, 172<br />

convergent exhaust taper, 183-185<br />

design criteria <strong>of</strong>, 171<br />

divergent exhaust taper (long megaphone),<br />

185-187<br />

divergent exhaust taper (short), 181-183<br />

effect <strong>of</strong> friction on outflow (straight pipe),<br />

176<br />

exhaust pipe with discontinuity, 188-191<br />

functional description, 171-172<br />

reference gas properties (CO2 <strong>and</strong> air, discontinuous<br />

exhaust), 188-189<br />

straight pipe (inflow process), 175-177<br />

straight pipe (outflow process), 173-175<br />

sudden exhaust expansion, 177-179<br />

QUB stratified charging engine<br />

air-fuel paths in (diagram), 498<br />

bmep (at optimized fuel consumption levels),<br />

499, 500<br />

fuel consumption, optimized, 499<br />

functional description, 498-499<br />

QUB 250-cc racing-model engine, 1, 2<br />

QUB 270 cross-scavenged airhead-stratified<br />

engine<br />

advantages <strong>of</strong>, 512<br />

bmep vs. rpm, 510-511

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