buletinul institutului politehnic din iaşi - Universitatea Tehnică ...

More documents

Recommendations

Info

136 Adrian Sabău et al. No experiments were conducted with either methanol (CH3OH) or methane (CH4) injection, since this would involve re-design of the employed hardware well beyond the scope of this work. The above analysis, though, shows that the total value of each of the terms of this balance at the end of the closed cycle is mainly a function of the total quantity of the injected fuel and not of the detailed preparation and reaction rates. If we substitute CH3OH and CH4 in the employed code as injected fuels and keep the equivalence ratio equal to 0.6 as in the diesel fuel case, we can compute “availability balances” like the ones shown in Figs. 4 and 5. The mass flow rate of air is also kept the same for all three fuels. This is one simple baseline that can be used for the comparison. However the methodology to be presented here can be used for more complicated reference criteria. The detailed time evolution of each of the terms of the presented balances of Figs. 4 and 5 is a function of the precise preparation and reaction rates of CH3OH and CH4 which can only be determined from experimental data. However, the exhaust gas availability (available for heat recovery devices) and the total combustion irreversibility can be approximated without the knowledge of this data, provided that reaction has been completed reasonably early relative to the exhaust valve opening timing. Figs. 6–8 show the comparison between injected fuel availability, exhaust gas availability and combustion irreversibility, for injection with the same equivalence ratio. Diesel Metan Metanol Diesel Metan Metanol Fig. 7 –Exhaust gas availability. Fig. 8 – Combustion irreversibility. It can be seen that the injected fuel availability is significantly higher for the methanol case. Because of the oxygen content of the fuel, higher molar quantity of fuel is necessary for combustion with the same equivalence ratio. Comparing the results for methane and diesel fuel, we observe a significant decrease of combustion irreversibility for methane combustion.
Bul. Inst. Polit. Iaşi, t. LVIII (LXII), f. 4, 2012 137 This is in agreement with the theoretical expectation that the decomposition of the larger hydrocarbon molecules from diesel fuel during chemical reaction should create higher entropy increase than the decomposition of a lighter methane molecule. The decrease of combustion irreversibility is even higher for the case of oxygenated fuel. An “second-law efficiency” can be defined as the ratio of extracted work over injected fuel availability. It should be stressed that this ratio is only calculated here for the closed part of the cycle and is not the second-law efficiency of the full cycle. Comparison of the efficiency for the three cases is presented in Fig. 9. It seems that the use of alternative fuels leads to better second-law efficiency. However, Diesel Metan Metanol especially as far as the comparison Fig. 9 – Second-law efficiency. between methane and methanol is concerned, the difference is small so that conclusions should be drawn with caution given the assumptions of the current analysis. Methanol vapor, for instance, was assumed to be an ideal gas but this is only a coarse approximation. More accurate modelling of the thermodynamic properties of methanol may alter the injected fuel availability. Moreover, for the accurate calculation of the irreversibility created during combustion, an accurate computation of methanol combustion kinetics is necessary. It would also be interesting to investigate the effect of the fact that this is a single-zone analysis by incorporating the current arguments in multizone codes. Revisiting the above assumptions may yield more accurate information about the advantages Figs. 6–9 imply for oxygenated fuels. However, the main point remains that entropy increase during combustion is smaller for such fuels because of the lower mixing entropy of the mixture of reactants. 5. Conclusions 1. A method for the analytic calculation of irreversibility and exhaust gas availability is generalized and used to evaluate alternative fuels in a directinjection, naturally-aspirated, four-stroke diesel engine. 2. Combustion irreversibility is shown to be the main source of irreversibility during the engine operation and its differential variation is
Page 1:
BULETINUL INSTITUTULUI POLITEHNIC D
Page 5 and 6:
Page 7:
VICTOR COTOROS şi EMIL BUDESCU, As
Page 10 and 11:
ALEXANDRU RADU, CONSTANTIN PANĂ an
Page 13 and 14:
Page 15 and 16:
Bul. Inst. Polit. Iaşi, t. LVIII (
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39:
Page 42 and 43:
30 Daniel Dragomir-Stanciu and Mari
Page 44 and 45:
32 Daniel Dragomir-Stanciu and Mari
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61:
Page 64 and 65:
52 Ionel Oprea and low viscosity ar
Page 66 and 67:
54 Ionel Oprea COP PT Puterea speci
Page 68 and 69:
56 Ionel Oprea 8. GWP - global warm
Page 70 and 71:
58 Ionel Oprea suplimentari, cum ar
Page 72 and 73:
60 Răzvan Florin Barzic et al. Cur
Page 74 and 75:
62 Răzvan Florin Barzic et al. 3-
Page 76 and 77:
64 Răzvan Florin Barzic et al. 3.
Page 78 and 79:
66 Ionel Ivancu et al. the second s
Page 80 and 81:
68 Ionel Ivancu et al. a b Fig. 4 -
Page 82 and 83:
70 Ionel Ivancu et al. Gut J.A.W.,
Page 84 and 85:
72 Ion Zabet and Graţiela-Maria Ţ
Page 86 and 87:
Page 88 and 89:
Page 90 and 91:
Page 92 and 93:
Page 94 and 95:
82 Victor Pantilie et al. many rese
Page 96 and 97:
84 Victor Pantilie et al. industria
Page 98 and 99: 86 Victor Pantilie et al. Another i
Page 100 and 101: 88 Victor Pantilie et al. At the en
Page 102 and 103: 90 Victor Pantilie et al. Tang X.,
Page 104 and 105: 92 Alexandru Radu et al. Furthermor
Page 106 and 107: 94 Alexandru Radu et al. Spark timi
Page 108 and 109: 96 Alexandru Radu et al. Fig. 3 - B
Page 110 and 111: 98 Alexandru Radu et al. 4. The bes
Page 113 and 114: BULETINUL INSTITUTULUI POLITEHNIC D
Page 115 and 116: Bul. Inst. Polit. Iaşi, t. LVIII (
Page 127: Bul. Inst. Polit. Iaşi, t. LVIII (
Page 130 and 131: 118 Eugen Rusu et al. in PM emissio
Page 132 and 133: 120 Eugen Rusu et al. also be used
Page 134 and 135: 122 Eugen Rusu et al. Fig. 3 - Maxi
Page 136 and 137: 124 Eugen Rusu et al. Fig. 6 - HC e
Page 138 and 139: 126 Eugen Rusu et al. Pe lângă ce
Page 140 and 141: 128 Adrian Sabău et al. arguments
Page 142 and 143: 130 Adrian Sabău et al. The energy
Page 144 and 145: 132 Adrian Sabău et al. during fue
Page 146 and 147: 134 Adrian Sabău et al. 11 T ⎛ 0
Page 150 and 151: 138 Adrian Sabău et al. calculated
Page 166 and 167: 154 Marius Receanu et al. where: qr
Page 168 and 169: 156 Marius Receanu et al. In Fig. 2
Page 170 and 171: 158 Marius Receanu et al. the ambie
Page 184 and 185: 172 Mariana Lupchian Propulsion eng
Page 186 and 187: 174 Mariana Lupchian Fig. 1 - The p
Page 200 and 201:
188 Costică Atanasiu et al. comput
Page 202 and 203:
190 Costică Atanasiu et al. γ= ε
Page 204 and 205:
192 Costică Atanasiu et al. The sa
Page 206 and 207:
194 Costică Atanasiu et al. Fig. 1
Page 208 and 209:
196 Costică Atanasiu et al. elasti
Page 210 and 211:
198 Ovidiu Niţă et al. rejection
Page 212 and 213:
200 Ovidiu Niţă et al. aluminium
Page 214 and 215:
202 Ovidiu Niţă et al. a b Fig. 5
Page 216 and 217:
204 Ovidiu Niţă et al. căreia ac
Page 218 and 219:
206 Ovidiu Niţă and Vasile Braha
Page 220 and 221:
Page 222 and 223:
Page 224 and 225:
Page 226 and 227:
214 Marian Teodor Popescu et al. 2.
Page 228 and 229:
216 Marian Teodor Popescu et al. Sp
Page 230 and 231:
218 Marian Teodor Popescu et al. Th
Page 233 and 234:
Page 235 and 236:
Page 237 and 238:
Page 239:
Page 242 and 243:
230 Victor Cotoros and Emil Budescu
Page 244 and 245:
Page 246 and 247:
Page 248 and 249:
Page 250 and 251:
Page 252 and 253:
Page 255 and 256:
Page 257 and 258:
Page 259 and 260:
Page 261 and 262:
Page 263 and 264:
Page 265 and 266:
Page 267 and 268:
Page 269 and 270:
Page 271 and 272:
Page 273 and 274:
Page 275 and 276:
Page 277 and 278:
Page 279 and 280:
Page 281 and 282:
Page 283 and 284:
Page 285 and 286:
Page 287 and 288:
Page 289 and 290:
Page 291 and 292:
Page 293 and 294:
Page 295 and 296:
Page 297 and 298:
PC Cell calibration Bul. Inst. Poli
Page 299 and 300:
Page 301 and 302:
Page 303 and 304:
Page 305 and 306:
Page 307 and 308:
Page 309 and 310:
Page 311 and 312:
Page 313 and 314:
Page 315 and 316:
Page 317:
show all

buletinul institutului politehnic din iaşi - Universitatea Tehnică ...

Create successful ePaper yourself

Delete template?

Save as template?