Design and Simulation of Two Stroke Engines

More documents

Recommendations

Info

Design and Simulation of Two-Stroke Engines ciency is seen here, for the charging efficiency drops from a peak of 0.47 to 0.40, which will deteriorate the ensuing power and torque, bsfc and bsHC, by at least that amount, i.e., 15%. The design question is, as written above: What can be done about it? In Fig. 5.17 it is discovered where this spilled charge goes. After 190° atdc, the purity at the cylinder end of the scavenge duct decreases from unity to a value of about 0.90, and, apart from some localized mixing within the transfer duct, remains at that value when the port shuts until the next time it is opened, at which point the aforementioned blowdown backflow takes place and reduces it even further. At the exhaust port, and in the exhaust pipe, spillage causes the purity there to rise from 190° atdc until exhaust closure. You should note the subtlety of the point being made: scavenging has ceased but spillage takes over. The other apparent contradiction is that, during this same period, the cylinder scavenging efficiency, i.e., purity, continues to rise. The explanation is that the spilled charge, i.e., that at the exhaust port, is of lesser purity than the cylinder mean and while mass is lost from the cylinder, the average purity of the cylinder charge is improved. The scavenge model from the theory given Sec. 3.3.2, and shown graphically in Fig. 3.19 for the "loopsaw" test cylinder, is seen in operation in Fig. 5.17, in that the purity at the exhaust port tracks the cylinder purity and lagging behind it as dictated by Eq. 3.3.12. The temperatures of the gas during scavenging, in various locations beside or within the cylinder, are shown in Figs. 5.18 and 5.21. In Fig. 5.18, at the cylinder end of the scavenge duct, the blowdown backflow causes an initial rise to 240°C, and then flow from the crankcase drops it down to about 100°C by bdc, whence cylinder spillage, with gas at a lesser purity and at some 300°C, increases it to nearly 200°C by transfer port closure. After that, with mixing caused by internal pressure wave motion in the transfer duct, and by expansion during the induction phase, the temperature decays to about 130°C by the port opening point. The cylinder temperature shows more dramatic behavior, falling from over 1000°C at the onset of scavenging, to a minimum at about 250°C with the influx of colder air from the crankcase, and then it rises toward the beginning of compression. In Fig. 5.18, the temperature in the exhaust pipe at the exhaust port has an interesting profile. It tracks cylinder temperature but is always higher, as the gas which is leaving the cylinder has a lesser purity and therefore a higher temperature than the mean of the cylinder contents. This follows the discussion in Sec. 3.3.3 regarding the temperature differential model for air and exhaust gas at this very juncture. The behavior of this model is shown in Fig. 5.21, and the apparently inexplicable flat in the exhaust gas temperature profile in Fig. 5.18 is now clarified. At the beginning of scavenging, the entering air is rapidly heated to nearly 600°C, but falls as more enters and cools the entire cylinder contents. On the other hand, the exhaust gas, during this early period of "perfect displacement" scavenging up to 160° atdc, is leaving the cylinder without benefit of this cooling through mixing, which explains the "flat" on the profile. The temperature differential model, as defined in Eqs. 3.3.13 to 3.3.18, is seen to control the average in-cylinder air and exhaust gas profiles in a logical manner. The word logical is employed as there is no means of ever confirming this statement with experimental data. The apparently instantaneous equalization of temperatures at the trapping point is merely the computer program informing the cylinder contents that they will be theoretically treated as a homogeneous gas from that point onward in the compression process. 388
O 1200 -, 1000 - ^ 800 g 600 - LU 0- UJ 400 - 200 - 0 100 CYLINDER MEAN OF BOTH GASES / Chapter 5 - Computer Modeling of Engines EXHAUST GAS IN CYLINDER - — I 200 CRANKSHAFT ANGLE, deg. atdc Fig. 5.21 Temperatures within scavenge model for a chainsaw at 9600 rpm. The exhaust system behavior, Figs. 5.22 and 5.23 The silencer (muffler) is a compact two-box design with considerable restriction to flow so as to achieve an adequate silencing effect. In Fig. 5.22, the pressures at the cylinder outlet, in boxes A and B, and in the final outlet pipe are plotted over the engine cycle at 9600 rpm. As debated above, it is seen that the basic behavior is, during the entire open cycle, to raise the "back-pressure" on the cylinder to above 1.1 atm, and to restrict the scavenge flow. The addition to that debate is that this graph shows the origin of that resistance; it is the final outlet pipe backing up first box B and then box A. Noise, as is discussed more fully in Chapter 8 in terms of this exhaust system geometry on this engine, is caused by a combination of mass 1.3 n EXHAUST PORT CRANKSHAFT ANGLE, deg. atdc BOXB 300 EC IN FINAL OUTLET PIPE Fig. 5.22 Pressures in exhaust system of a chainsaw at 9600 rpm. 389
Page 2 and 3:
Design and Simulation of Two-Stroke
Page 4 and 5:
A Second Mulled Toast When as a stu
Page 6 and 7:
Page 8 and 9:
Acknowledgments As explained in the
Page 10 and 11:
Table of Contents Nomenclature xv C
Page 12 and 13:
Table of Contents 2.10.1 Flow at pi
Page 14 and 15:
Table of Contents 3.5.3.1 The use o
Page 16 and 17:
Table of Contents 6.1.3 The effect
Page 18 and 19:
Nomenclature NAME SYMBOL UNIT (SI)
Page 20 and 21:
speed of rotation speed of rotation
Page 22 and 23:
attenuation or transmission loss wa
Page 24 and 25:
Page 26 and 27:
Page 28 and 29:
Page 30 and 31:
Page 32 and 33:
Page 34 and 35:
Page 36 and 37:
Page 38 and 39:
Page 40 and 41:
Page 42 and 43:
Page 44 and 45:
Page 46 and 47:
Page 48 and 49:
Page 50 and 51:
Page 52 and 53:
Page 54 and 55:
Page 56 and 57:
Page 58 and 59:
Page 60 and 61:
Page 62 and 63:
Page 64 and 65:
Page 66 and 67:
Page 68 and 69:
Page 70 and 71:
Page 72 and 73:
Page 74 and 75:
Page 76 and 77:
Page 78 and 79:
Page 80 and 81:
Page 82 and 83:
Page 84 and 85:
Page 86 and 87:
Page 88 and 89:
Page 90 and 91:
Page 92 and 93:
Page 94 and 95:
Page 96 and 97:
Page 98 and 99:
Page 100 and 101:
Page 102 and 103:
Page 104 and 105:
Page 106 and 107:
Page 108 and 109:
Page 110 and 111:
Page 112 and 113:
Page 114 and 115:
Page 116 and 117:
Page 118 and 119:
Page 120 and 121:
Page 122 and 123:
Page 124 and 125:
Page 126 and 127:
Page 128 and 129:
Page 130 and 131:
Page 132 and 133:
Page 134 and 135:
Page 136 and 137:
Page 138 and 139:
Page 140 and 141:
Page 142 and 143:
Page 144 and 145:
Page 146 and 147:
Page 148 and 149:
Page 150 and 151:
Page 152 and 153:
Page 154 and 155:
Page 156 and 157:
Page 158 and 159:
Page 160 and 161:
Page 162 and 163:
Page 164 and 165:
Page 166 and 167:
Page 168 and 169:
Page 170 and 171:
Page 172 and 173:
Page 174 and 175:
Page 176 and 177:
Page 178 and 179:
Page 180 and 181:
Page 182 and 183:
Page 184 and 185:
Page 186 and 187:
Page 188 and 189:
Page 190 and 191:
Page 192 and 193:
Page 194 and 195:
Page 196 and 197:
Page 198 and 199:
Page 200 and 201:
Page 202 and 203:
Page 204 and 205:
Page 206 and 207:
Page 208 and 209:
Page 210 and 211:
Page 212 and 213:
Page 214 and 215:
Page 216 and 217:
Page 218 and 219:
Page 220 and 221:
Design and Simulation ofTwo-Stroke
Page 222 and 223:
Page 224 and 225:
Page 226 and 227:
Page 228 and 229:
Page 230 and 231:
Page 232 and 233:
Page 234 and 235:
Page 236 and 237:
Page 238 and 239:
Page 240 and 241:
Page 242 and 243:
Page 244 and 245:
Page 246 and 247:
Page 248 and 249:
Page 250 and 251:
Page 252 and 253:
Page 254 and 255:
Page 256 and 257:
Page 258 and 259:
Page 260 and 261:
Page 262 and 263:
Page 264 and 265:
Page 266 and 267:
Page 268 and 269:
Design and Simulation ofTwo'Stroke
Page 270 and 271:
Page 272 and 273:
Page 274 and 275:
Page 276 and 277:
Page 278 and 279:
Page 280 and 281:
Page 282 and 283:
Page 284 and 285:
Page 286 and 287:
Page 288 and 289:
Page 290 and 291:
Page 292 and 293:
Page 294 and 295:
Page 296 and 297:
Page 298 and 299:
Page 300 and 301:
Page 302 and 303:
Chapter 4 Combustion in Two-Stroke
Page 304 and 305:
Chapter 4 - Combustion in Two-Strok
Page 306 and 307:
Page 308 and 309:
Page 310 and 311:
a stratilpl o tions to ivior. If m
Page 312 and 313:
Page 314 and 315:
Page 316 and 317:
CD 30 -, W 20 - LU CO iS _J LU OC 1
Page 318 and 319:
Page 320 and 321:
Page 322 and 323:
181 also x3 = — = 0.905 x6 = 2.17
Page 324 and 325:
to be cur .3.20) .3.21) .3.22) for
Page 326 and 327:
3.23) com- :on is hhas has a /eng-
Page 328 and 329:
stroke .3.29) mean me to 3land ssio
Page 330 and 331:
Page 332 and 333:
a LU z: en 3 CO a LU z EC D m O ho
Page 334 and 335:
CD 1.2 -i 1.0 - di „„ LU 0.8 cc
Page 336 and 337:
CO —> 111" cc LU < LU _J LU CC £
Page 338 and 339:
Page 340 and 341:
Page 342 and 343:
Combustion in compression-ignition
Page 344 and 345:
Page 346 and 347:
Page 348 and 349:
stroke ari more often lseful lental
Page 350 and 351:
lat the ssi ;tribu- ELEVATION VIEWS
Page 352 and 353:
CYLINDER HEAD TYPE IS CENTRAL BORE,
Page 354 and 355:
Page 356 and 357:
CO E 50 40 - O O _i Hi > I CO 30 Z)
Page 358 and 359: CURRENT INPUT DATA FOR 2-STROKE 'SP
Page 360 and 361: Chapter 4 - Combustion in Two-Strok
Page 362 and 363: Cylin- PP £ Pa- tics of Paper Chap
Page 364 and 365: vfitro- ;titi >tants 1970. i(In- Ch
Page 370 and 371: £2 = Pi P2 I Pi J Chapter 4 - Comb
Page 372 and 373: CHAINSAW AT 9600 rpm. Chapter 4- Co
Page 374 and 375: LLI •z. O N -z. 0.21 -, 0.20 DC 0
Page 378 and 379: Design and Simulation of Two-Stroke
Page 458 and 459:
Page 460 and 461:
Page 462 and 463:
Page 464 and 465:
Page 466 and 467:
Page 468 and 469:
Page 470 and 471:
Page 472 and 473:
Page 474 and 475:
Page 476 and 477:
Page 478 and 479:
Page 480 and 481:
Page 482 and 483:
Chapter 7 Reduction of Fuel Consump
Page 484 and 485:
Chapter 7 • Reduction of Fuel Con
Page 486 and 487:
Chapter 7 - Reduction of Fuel Consu
Page 488 and 489:
Page 490 and 491:
Page 492 and 493:
^ s C£ Q 2^ E Q. Q_ z' o ISSI HCEM
Page 494 and 495:
o > z~ Q w CO UJ w g x O z o z o m
Page 496 and 497:
S.S.F.C. , C./SHP-HS Chapter 7 - Re
Page 498 and 499:
Page 500 and 501:
Page 502 and 503:
Page 504 and 505:
Page 506 and 507:
Page 508 and 509:
0.35 • 0.34 LU ° 0.33 - c 03 DC
Page 510 and 511:
Page 512 and 513:
§ 2000
Page 514 and 515:
y, ,6 Chapter 7 - Reduction of Fuel
Page 516 and 517:
Page 518 and 519:
Page 520 and 521:
Chapter 7- Reduction of Fuel Consum
Page 522 and 523:
Page 524 and 525:
INLET FOR r AIR AND FUEL Chapter 7
Page 526 and 527:
Page 528 and 529:
o Q_ Ld < CD 15-, 10- Chapter 7 - R
Page 530 and 531:
6. £ -Q 500 n | "I) 400 -Q 300 100
Page 532 and 533:
Page 534 and 535:
Page 536 and 537:
Page 538 and 539:
Page 540 and 541:
Page 542 and 543:
Page 544 and 545:
JZ x" O Z CO J3 20 i 10 - 10 Chapte
Page 546 and 547:
$ 2 - x O z 2 1 Chapter 7 - Reducti
Page 548 and 549:
Page 550 and 551:
Page 552 and 553:
Page 554 and 555:
Page 556 and 557:
Page 558 and 559:
O 01 III cr cc LU Q. LU h- LU Z o N
Page 560 and 561:
Chapter 8 Reduction of Noise Emissi
Page 562 and 563:
Chapter 8 • Reduction of Noise Em
Page 564 and 565:
Chapter 8 - Reduction of Noise Emis
Page 566 and 567:
Page 568 and 569:
Page 570 and 571:
1 28.6 ^ i d>2£ 1.6 \ f > < 4)28.6
Page 572 and 573:
Page 574 and 575:
Page 576 and 577:
Page 578 and 579:
Page 580 and 581:
Page 582 and 583:
Page 584 and 585:
Page 586 and 587:
Page 588 and 589:
Page 590 and 591:
Page 592 and 593:
Page 594 and 595:
Page 596 and 597:
H Chapter 8 - Reduction of Noise Em
Page 598 and 599:
Name F R Chapter 8 • Reduction of
Page 600 and 601:
Page 602 and 603:
1 Chapter 8 - Reduction of Noise Em
Page 604 and 605:
Page 606 and 607:
• • / . • Appendix Listing of
Page 608 and 609:
Active radical (AR) combustion and
Page 610 and 611:
initial conditions, assumptions reg
Page 612 and 613:
in two-stroke engine (schematic dia
Page 614 and 615:
exhaust timing control valve, effec
Page 616 and 617:
I Exhaust emissions/exhaust gas ana
Page 618 and 619:
Exhaust systems (continued) untuned
Page 620 and 621:
gas constant/universal gas constant
Page 622 and 623:
in crankcase heat transfer analysis
Page 624 and 625:
Mercury Marine air-assisted fuel in
Page 626 and 627:
I PISTON POSITION (computer program
Page 628 and 629:
Pressure wave reflection (in pipes)
Page 630 and 631:
local acoustic velocity, 60 local M
Page 632 and 633:
Roots blower in turbocharged/superc
Page 634 and 635:
Scavenging (continued) scavenging e
Page 636 and 637:
Simulation, engine See Computer mod
Page 638 and 639:
temperature vs. crankshaft angle (c
Page 640 and 641:
work per thermodynamic (Otto) cycle
show all

Design and Simulation of Two Stroke Engines

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?