University of Wisconsin Engine Research Center Experimental Facilities Objective Injection Timing Effects Conclusions Effects at Varied Equivalence Ratios Effects at Varied Fueling RatesLevel of Fuel Unmixedness Engine Test Cell Setup Fuel Unmixedness Effects in a Gasoline HCCI Engine Students: R.E. Herold, R.J. Iverson (MS, 2004) Faculty: D.E. Foster, J.B. Ghandhi Quantify the effect fuel unmixedness has on gasoline HCCI combustion. Surge Tank 2 Surge Tank 1 Inline Heater EGR AIR Port Fuel Injection Point Exhaust Premixed Fuel Injection Point Engine To Engine Dichroic Mirror Pellin-Broca Prism f = 1000 mm Plano-Convex Spherical Lens f = -500 mm Plano-Concave Cylindrical Lens 90° Turning Prism Beam Stop UG5 Schott Glass Filter Engine Properties CR10.95 Bore86 mm Stroke94.6 mm EVO 131  aTDC IVO 350  aTDC EVC 375  aTDC IVC 595  aTDC Vaporized Fuel 2.3 mm ID Tube Intake Valve Heated Air + EGR Port, Prevaporized Fuel Injector Cylinder Head Quartz Cylinder Window Optical Engine Sapphire Piston Window Bowditch Piston Extention Drop-down Liner Imaging Mirror Optical Setup for PLIF Experiments Nd:YAG Laser Level of fuel unmixedness created when using the port, prevaporized fuel injection was investigated optically using fuel tracer planar laser-induced fluorescence (PLIF). Injection crank angle locations (detailed below) corresponded to those detailed in metal engine experiments. 829°724° 469°364° 361°256° 196° 140° 301° 245° IVC (855°) IVO (358°) IVC (135°) = Intake Valve Open 720° (TDC – Previous Cycle) 360° (TDC Exhaust) 180° (BDC) 0° (TDC – Cycle of Interest) Crank Angle (° bTDC) A significant level of unmixedness is created with prevaporized port fueling. Fuel unmixedness increases with retarded injection timings except for the EoPI = 256° bTDC injection timing, which is less unmixed than the EoPI = 364° bTDC injection timing. For the most retarded injection timing, regions exist in the cylinder with equivalence ratios that differ from the mean by +/- 50%. Variations with respect to intake charge temperature due to heat transfer in intake port. All combustion metrics investigation (i.e., peak pressure, combustion efficiency) show that at a given combustion phasing (CA50) premixed and prevaporized port injection are indistinguishable. NO x emissions increase with fuel unmixedness, resulting from regions richer than the mean which burn hotter after autoignition. CO emissions show a slight increase with fuel unmixedness, possibly a result of regions richer than stoichiometric or quenching in regions leaner than the mean. No changes in combustion observed between premixed and port fueling. Significant NO x emissions increases only observed in 10 mg/cycle fueling. NO x emissions were near zero for the 7 and 5 mg/cycle fueling conditions due to high EGR. The difference in CO emissions between premixed and port fueling increases with decreasing fueling rate. No changes in combustion observed between premixed and port fueling. NO x emissions were near zero for all conditions because of high EGR rate at the 5 mg/cycle fueling condition Decreasing the equivalence ratio (increasing air flow, decreasing EGR at constant fueling rate) leads to an increase in CO emissions but a decrease in the difference in CO emissions between premixed and port fueling. Fuel unmixedness in the absence of thermal and residual unmixedness had no effect on the HCCI combustion. Small changes in CO and NO x emissions were observed for the port fueling, which were attributed to the regions in the charge that were either locally richer or leaner than the mean equivalence ratio. At a given operating condition the CO and NO x emissions are the lowest for a fully homogeneous fuel distribution. Regions locally richer and leaner than the mean equivalence ratio lead to increases in NO x and CO and therefore should be avoiding in an HCCI engine. Fuel unmixedness in the absence of thermal and residual unmixedness does not appear to be a viable method for gasoline HCCI combustion control.