1. A COMPARATIVE ANALYSIS ON THE SPRAY PENETRATION OF ETHANOL, GASOLINE AND ISO-OCTANE FUEL IN A SPARK-IGNITION DIRECT-INJECTION ENGINE Yongming Bao, Shaun Chan, Shawn Kook, Evatt Hawkes, UNSW Australia, Sydney, Australia

2. SAE INTERNATIONAL Down-sized engines using spark-ignition direct injection (SIDI) system: Improved fuel economy. Better transient response. Higher potential for system optimisation. Successful implementation of SIDI system requires good understandings of the development of spray plumes. Earlier SIDI systems that utilized swirl-type nozzles relied on piston bowls to achieve stratification. This approach suffers from: Increased unburnt hydrocarbon. Increased soot emissions. Background Paper # 2014-01-1413 2 UNSW Optical SIDI Engine 3. SAE INTERNATIONAL Multi-hole nozzle has benefits over swirl-type nozzle due to better atomization, droplet breakup & directionality. One key control parameters for multi-hole nozzle is the injection pressure. Increasing injection pressure leads to: A decrease in droplet size. An increase in spray tip penetration. Ethanol can be better utilized in SIDI engines: Higher heat of vaporisation: Maximise charge cooling effect. Increased volumetric efficiency. Higher octane number: Increased knock resistance. Higher compression ratio & therefore improved fuel conversion efficiency. . Background Paper # 2014-01-1413 3 4. SAE INTERNATIONAL Existing literature provides no consensus on spray tip penetration for ethanol and gasoline. Some studies reported a higher spray tip penetration of ethanol sprays than that of gasoline in SIDI fueling system. Attributed to the higher density, boiling point, latent heat & surface tension of ethanol. Others presented reversed trends despite the use of similar SIDI fueling systems. Attributed to the heavier components present within gasoline. Effect of Ethanol on Fuel Spray Paper # 2014-01-1413 4 5. SAE INTERNATIONAL Aim: Clarify the potential causes of mixed conclusions on spray tip penetration of ethanol & gasoline. Methodologies: High-speed Mie-scattering imaging to visualize the spray tip penetration of ethanol, gasoline & iso-octane. Injection pressures: 4, 7, 11 and 15MPa. Two optical facilities were used A constant volume, constant flow optical chamber at room-temperature conditions A single-cylinder optical SIDI engine operated at fully warmed up conditions Aim & Methodologies Paper # 2014-01-1413 5 6. SAE INTERNATIONAL Constant Flow, Constant Volume Spray Chamber Setup Paper # 2014-01-1413 6 7. SAE INTERNATIONAL Injector Paper # (if applicable) 7 Injector Continental DI XL 2 Number of holes 6 Hole diameter 0.204 mm Injector pressure 4, 7, 11 & 15 MPa Injection duration 0.5 ms Chamber ambient pressure 0.2 MPa (abs) Chamber ambient temperature 293 K Fuel temperature 293 K Nozzle configuration (Front view) 8. SAE INTERNATIONAL Optical SIDI Engine Setup Paper # 2014-01-1413 8 Engine specifications Displacement 500 cm3 Bore/Stroke 86 mm/86 mm Compression ratio 10.5 Valve system Double overhead camshaft Operating conditions Engine speed 1200 rpm Intake pressure 0.1 MPa (abs) Temperature in intake manifold 320 K Coolant temperature 363 K Injection timing 270oCA aTDC Injection duration 0.5 ms 9. SAE INTERNATIONAL Mie-scattering Imaging Setup Paper # 2014-01-1413 9 Light source Multiblitz Profilux Plus 400 flash lamp Flash duration 1 ms High-speed CMOS camera Vision Research Phantom v7.3 Frame rate 10,000 fps Spray chamber Optical engine Pixel resolution (mm per pixel) 0.15 (side view) 0.25 (bottom view) 0.33 Exposure time (ms) 0.01 0.001 f-number 2.8 (side view) 16 (bottom view) 16 10. SAE INTERNATIONAL Gasoline sprays at 0.9 ms aSOI from (a) side-view & (b) bottom view Spray Chamber Measurements Paper # 2014-01-1413 10 11. SAE INTERNATIONAL Selected Properties of the Investigated Fuels at 293 K and 1 atm Paper # 2014-01-1413 11 Properties/Fuel Gasoline Ethanol Iso- octane Density (kg m-3) 748 789 692 Surface tension (mN.m-1) 21.58 22.66 19.35 Latent heat at 298 K (kJ.kg-1) 364 902 305 Viscosity (mPa.s) 0.55 (mean) 1.20 0.50 Boiling point (K) 303-473 351.5 372.8 12. SAE INTERNATIONAL Correlation was developed for diesel spray, but predicted values agreed well with measured values in previous SIDI spray studies Droplet size decreases with increasing injection pressure Droplet size: ethanol > gasoline > iso-octane SMD = 0.38dRe0.25WeL -0.32(L/G)0.37(L/G)-0.47 Estimation of Sauter Mean Diameter (SMD) using Empirical Correlation Paper # 2014-01-1413 12 13. SAE INTERNATIONAL Naber & Siebers correlations: Before breakup transition time: S =Ujett Ujet=Cv(2P/l)0.5 After breakup transition time: S (P/a)0.25 t0.5 Temporal Evolution of Spray Tip Penetration at Different Injection Pressures (Chamber) Paper # 2014-01-1413 13 14. SAE INTERNATIONAL Rate of Change of Spray Tip Penetration at Different Injection Pressures (Chamber) Paper # 2014-01-1413 14 15. SAE INTERNATIONAL Bottom-view images of the gasoline, ethanol & iso-octane sprays at various time aSOI in optical SIDI engine. Optical SIDI Engine Measurements Paper # 2014-01-1413 15 16. SAE INTERNATIONAL Rate of Change of Spray Tip Penetration at Different Injection Pressures (Engine) Paper # 2014-01-1413 16 17. SAE INTERNATIONAL Spray tip penetration of ethanol is lower than gasoline at low injection pressure conditions. Attributed to the higher density & nozzle loss from greater viscosity of ethanol. Spray tip penetration of ethanol is higher than gasoline at higher injection pressure conditions. Attributed to higher aerodynamic drag acting on smaller gasoline droplets. Similar observations are found in fully warmed optical SIDI engine. Slight difference in quantitative value due to decreased air density & higher fuel temperature. Conclusions Paper # 2014-01-1413 17 18. SAE INTERNATIONAL Questions? Paper # 2014-01-1413 18