Experimental and Numerical Study of Swirling ... - Solid Mechanics

More documents

Recommendations

Info

Experimental and Numerical Study of Swirling Flow in Scavenging Process for 2-Stroke Marine Diesel Engines Chapter 3 the cylinder and the flow is incompressible. The piston can slide to a position where it completely covers/ closes the cylinder intake port. Moreover, the piston is shifted manually from one position to another and it is not in continuous motion like in real engine. Thus the variation in in-cylinder flow characteristics is not a function of time. Chemical Species: A mixture of air and very small concentration (in ppm) of glycerol droplets as seeding is used as the working fluid. There is no fuel injection, chemical reaction and exhaust products/ gases. Combustion: The measurement is conducted with flowing fluid and experimental setup to be at room temperature. No combustion, heat sources and temperature gradients (in fluid and solid walls, piston and cylinder head) are involved. Stratified Flow: Contrary to real engine scavenging process, no fluid density variations occur inside the test cylinder. Therefore, there is no in-cylinder stratified flow regime where the incoming air interacts with exhaust gases which are lower in density than air. Also the test cylinder is mounted horizontally instead of being vertical in real engines. This factor can be significant if there exists a stratified flow. 3.4 Smoke Visualization A qualitative analysis of the test model is performed by conducting visualization using glycerin smoke from a smoke generator. The smoke is blown in to the setup and pictures are taken using a digital camera. The smoke generator cannot produce a constant jet of smoke and instead injects intermittent puffs of smoke which gradually reduces in concentration at the end of each puff (smoke generator here is one used in Disco/ concerts etc that produces smoke by heating and evaporating glycerin). The smoke enters the experimental setup from one side and the distance is kept in a way that the smoke jet has minimum effect on the actual flow pattern at the inlet to the experimental setup. Figure 3.5 shows the smoke entering the inlet section and being diverted at an angle by the guide vanes thus helping in checking the general performance of the design. The flow then enters the cylinder with an angle to the radius and bends in the axial direction (Figures 3.6). The pictures presented in figures 3.7-3.11 are taken using a 13W (blue color) energy saver light bulb as light source and pictures are taken using a webcam, Microsoft LifeCam Cinema ® . The idea was to attempt to visualize flow patterns by making the blue light giving a fluorescence-like effect after being reflected from the smoke particles. The visualization was carried out by first keeping the experimental setup in darkness and then using blue light as the only light source. The light reflection from glycerin smoke particles 36 Experimental Setup
Experimental and Numerical Study of Swirling Flow in Scavenging Process for 2-Stroke Marine Diesel Engines Chapter 3 appeared to be the major source of light entering the camera compared to other objects. This made the flow patterns, to some extent, visible inside the test model. Here it must be mentioned that the camera is not perfectly aligned with the experimental setup. For all the pictures the position of the smoke generator was kept the same. Figures 3.7-3.10 show the visualization of in-cylinder swirling flow observed from piston window i.e. the flow direction is into the picture plane (see Figure 3.4). Figure 3.11 shows observations taken from one side of the test setup. For a given piston position, the figures are not in a time sequence. It can be seen that in case of fully open cylinder intake port, the in-cylinder flow has a well-defined vortex core region (Figures 3.7 & 3.11a). The smoke after entering the cylinder remains confined mostly in the core region and does not mix to a large extent with the region surrounding the vortex. The core size increases in a conical shape downstream the flow. As the port is closed by 25%, the vortex core region becomes comparatively less defined and more mixing of the smoke is observed along the cylinder length (Figures 3.8&3.11b). However, at 50% closed port, the vortex core is no more visible. The smoke stream enters the cylinder and mixes with the surrounding air very quickly (Figures 3.9 & 3.11c). Similar pattern can be seen in case of 75% closed port (Figures 3.10&3.11d). During the smoke visualization experiment, the author observed that for fully open port the smoke stream, after entering the cylinder, entered in the center vortex core at regions adjacent to piston surface. Observing from the side of cylinder in Figure 3.11a, the smoke in the core region along the cylinder had a shape of expanding hollow cone with cone top side to be at the piston surface. However, with the gradual increase in blockage of intake port, the welldefined conical smoke pattern started to disappear. Instead the smoke pattern resembled to a jet (Figure 3.11 c & d). Viewing from the piston side in figures 3.7-3.10, the Smoke stream entered the cylinder center region after travelling some axial distance from the piston surface. This is probably due to piston wall favoring the flow to enter the cylinder with an axial component. The smoke stream was having a flapping behavior after entering the cylinder, just like a thread connected at one end with a fixed object in air stream. This indicates increased turbulence at the cylinder entrance and consequently an increases in the mixing of smoke with the surrounding air as can be seen in (Figure 3.11 c & d). 37 Experimental Setup
Page 1:
Experimental and Numerical Study of
Page 5 and 6: Experimental and Numerical Study of
Page 23 and 24: Experi imental and Numerical N Stud
Page 55: Experimental and Numerical Study of
Page 107 and 108:
Experi imental and Numerical N Stud
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Page 161 and 162:
Page 163 and 164:
Page 165 and 166:
Page 167 and 168:
Page 169 and 170:
Page 171 and 172:
Page 173 and 174:
Page 175 and 176:
Page 177 and 178:
Page 179 and 180:
Page 181 and 182:
Page 183 and 184:
Page 185 and 186:
Page 187 and 188:
Page 189 and 190:
Page 191 and 192:
Page 193 and 194:
Page 195 and 196:
Page 197 and 198:
Page 199 and 200:
Page 201 and 202:
Page 203 and 204:
Page 205 and 206:
Page 207 and 208:
Page 209 and 210:
Page 211 and 212:
Page 213 and 214:
Page 215 and 216:
Page 217 and 218:
Page 219 and 220:
Page 221 and 222:
Page 223 and 224:
Page 225 and 226:
Page 227 and 228:
Page 229 and 230:
Page 231 and 232:
Page 233 and 234:
Page 235 and 236:
Page 237 and 238:
Page 239 and 240:
Page 241 and 242:
Page 243 and 244:
Page 245 and 246:
Manuscript J Mar Sci Technol manus
Page 247 and 248:
00000000 11111111 piston screen con
Page 249 and 250:
50 % and 75 % partially closed inta
Page 251 and 252:
V θ / V b V θ / V b V θ / V b 1.
Page 253 and 254:
V θ / V b V θ / V b V θ / V b 1.
Page 256:
DTU Mechanical Engineering Section
show all

Experimental and Numerical Study of Swirling ... - Solid Mechanics

Create successful ePaper yourself

Delete template?

Save as template?