Design and Simulation of Two Stroke Engines

More documents

Recommendations

Info

Design and Simulation of Two-Stroke Engines The terms for bore, stroke, con-rod length and engine speed, i.e., BO, ST, CRL and RPM are self-explanatory and, as with all of the units in the programs, they are in mm dimensions unless otherwise stated. The trapped compression ratio is TCR; the number of cylinders of the engine is NC Y; the bmep expected at the RPM is BMEP in bar units. The exhaust ports and transfer ports open at EPO and TPO °atdc, respectively; the subtended port angles, 9p, of the exhaust ports is EXANG; the radial thickness of the cylinder liner in the scavenge port belt is LINER. The chordal values of the bars of the exhaust and scavenge (transfer) ports, Xb, are EBAR and TB AR, while that for the bar between the last exhaust port and the first scavenge port is coded as ETBAR, respectively. The value of FOCUS is the proportion of the cylinder radius, from the cylinder center to the edge of the bore on the scavenge side, where the guiding edges of the main scavenge ports index the centerline. The guiding edges in question are the trailing edges of the first port, and the leading edge of the second backswept port. This is shown even more clearly in Fig. 3.40, where they are reproduced in the same manner as the screen display of the computer program. The side port is at right angles to the line of symmetry and the back ports are aligned with it, facing the exhaust port. Naturally, it is essential in this design configuration to elevate the back ports, usually by 50-60°. To allow the designer this flexibility, both the side and the back ports can be elevated by setting angles SUP and BUP between 0 and (a maximum of) 60°. The plan radius of a recessed cylinder bowl in the fashion of a DI diesel engine is RBOWL; the corner radius of that bowl is RCV; the squish clearance, the piston lengths to crown and skirt, and the gudgeon pin offset (+ in direction of rotation) are shown coded as SQCL, GPC, GPS and GPOFF, respectively. The port corner radii, rc, are presented as RTE, RBE, RTT and RBT, the top and bottom corner radii of the exhaust and scavenge (transfer) ports, respectively. The output data are also fairly self-explanatory. However, each line shows: the engine total swept volume (cm 3 ) and power (kW); the mean widths of all of the exhaust and scavenge ports; the port width ratio CA; the areas Axp and Asp of the exhaust ports and scavenge ports, respectively; the exhaust pipe area and its diameter; the blowdown, exhaust and transfer port time areas of those ports (vide Sec. 6.1); the blowdown, exhaust and transfer port time areas of those ports (vide Sec. 6.1); the combustion chamber clearance volume (cm 3 ) and the depth of that chamber; the heights, hx and hs, of the exhaust ports and scavenge ports, respectively; the subtended port angles, 6p, of each of the scavenge ports for they are specifically designed to be identical; the subtended angles, 0b, of each of the bars of the exhaust ports, between the exhaust and the scavenge ports, and between each of the scavenge ports, respectively; the slopes (deg) of each of the focusing edges of the main scavenge ports with respect to the "horizontal" centerline of scavenge symmetry. A change of data is invited by the program for any or all of the input data, as is their recomputation. The code for that data change is the name of that particular input data parameter, to be typed in by the user. A hard copy, i.e., a printout, is available of the entire screen display, and this is drawn to scale from the input and output data. The "by eye" design process is aided by the computer program immediately drawing the sketch of the piston and the porting to scale on the computer screen as a function of the input data. 272
Chapter 3 - Scavenging the Two-Stroke Engine The input and output data in Fig. 3.41 detail the geometry of a four-cylinder DI diesel engine. Those dedicated to the design of the spark-ignition engine should note that the expected power output of this two-liter diesel automobile engine is 104.9 kW at 4500 rpm, which is well up to the performance levels of any gasoline engine of the same swept volume. The design has been conducted so that the maximum port angle, 6p, of any one port does not exceed 25°, permitting the use of unpegged rings on the piston. Even though the back ports are elevated at 60°, while the side ports are at 0°, the effective port width ratio, Cpb, for the scavenge ports is high at 1.23 and reflects the design criterion of maximized port area for the given bore circumference. The equivalent Cpb number for the exhaust ports is (4 times 18.6 divided by 86) 0.865, also a high number by loop-scavenging design standards. The exhaust and scavenge port timings are low at opening values of 113° and 129° atdc, which mild timing still gives acceptably high values of time-areas (see Sec. 6.1) in order to pass the requisite exhaust and scavenge flows in the allotted time span at 4500 rpm. The low port timings are required to give good cylinder trapping conditions for a four-cylinder engine from both a scavenging standpoint and from that of the exhaust system gas dynamics. A fuller debate on the latter topic is in Chapter 5, Sec. 5.5.3, where this program is used to provide the porting data for the simulation of a four-cylinder, externally scavenged, sparkignition, direct-injection engine for automobile applications. 3.6 Scavenging design and development The development of good scavenging is essential for the two-stroke engine to provide the ever more sophisticated performance characteristics required of engines to meet international legislation for exhaust emissions and fuel consumption levels. In Fig. 3.42 is a tiny sample of the range of scavenging characteristics found experimentally from some 1300 differing geometries tested in recent times. They are for uniflow engines (triangle symbol), cross-scav- DISPLACEMENT LINE T ' 1 1 2 SCAVENGE RATIO BY VOLUME Fig. 3.42 Scatter of experimental SEV-SRV characteristics. 273
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: Design and Simulation of Two-Stroke
Page 268 and 269: Design and Simulation ofTwo'Stroke
Page 302 and 303: Chapter 4 Combustion in Two-Stroke
Page 304 and 305: Chapter 4 - Combustion in Two-Strok
Page 310 and 311: a stratilpl o tions to ivior. If m
Page 316 and 317: CD 30 -, W 20 - LU CO iS _J LU OC 1
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 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 342 and 343: Combustion in compression-ignition
Page 344 and 345:
Chapter 4 - Combustion in Two-Strok
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:
Page 362 and 363:
Cylin- PP £ Pa- tics of Paper Chap
Page 364 and 365:
vfitro- ;titi >tants 1970. i(In- Ch
Page 366 and 367:
Page 368 and 369:
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 376 and 377:
Page 378 and 379:
Page 380 and 381:
Page 382 and 383:
Page 384 and 385:
Page 386 and 387:
Page 388 and 389:
Page 390 and 391:
Page 392 and 393:
Page 394 and 395:
Page 396 and 397:
Page 398 and 399:
Page 400 and 401:
Page 402 and 403:
Page 404 and 405:
Page 406 and 407:
Page 408 and 409:
Page 410 and 411:
Page 412 and 413:
Page 414 and 415:
Page 416 and 417:
Page 418 and 419:
Page 420 and 421:
Page 422 and 423:
Page 424 and 425:
Page 426 and 427:
Page 428 and 429:
Page 430 and 431:
Page 432 and 433:
Page 434 and 435:
Page 436 and 437:
Page 438 and 439:
Page 440 and 441:
Page 442 and 443:
Page 444 and 445:
Page 446 and 447:
Page 448 and 449:
Page 450 and 451:
Page 452 and 453:
Page 454 and 455:
Page 456 and 457:
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?