Lubricant Formulations to Enhance Engine Efficiency in Modern Internal Combustion Engines
https://www.osti.gov/servlets/purl/1351980
This was a three year long effort and they did some great work. Some things I thought were particularly neat were:
- Separate oil for the valvetrain from the oil in the rest of the engine. Thicker for the valvetrain since in that engine, it reduced total friction. The thinner oil in the rest of the engine reduced friction due to the more prevalent hydrodynamic lubrication regime there. The fuel leak into the valvetrain oil was unfortunate, considerably reducing the viscosity, and messing up the intent of having higher viscosity there.
- Testing viscosity at 10e-6/s and 10e-7/s shear rates. The higher shear rate reduced the viscosity even more than the lower shear rate did. They also tested viscosity at 100 C and 150 C at 1e-6/s shear rate. Newtonian and non-Newtonian oils were tested. The supposedly Newtonian oil still showed shear thinning, so it wasn’t truly Newtonian, but it was much closer to it than the 15W-40 oils were.
- Tested friction and viscosity modifiers. In the cylinders, it would be ideal for reducing total friction by reducing viscosity below 150 C and increasing it above 150 C. The latter is true because of boundary regime caused by the oil temperatures in the upper part of the cylinder being near 200 C, combined with low piston speed, and high pressure (during expansion). This should also reduce wear.
- A dumbbell base oil blend (mix of thin and thick) caused the more volatile part evaporate quickly enough in the very hot upper cylinder area to significantly increase the oil viscosity, right where that extra viscosity is needed.
- Increasing flow rate to the valvetrain decreased total friction, apparently by decreasing asperity contact...moving the regime to the right on the Stribeck curve, where total friction is lower. That surprised me.
- Fuel dilution effects were tested
https://www.osti.gov/servlets/purl/1351980
This was a three year long effort and they did some great work. Some things I thought were particularly neat were:
- Separate oil for the valvetrain from the oil in the rest of the engine. Thicker for the valvetrain since in that engine, it reduced total friction. The thinner oil in the rest of the engine reduced friction due to the more prevalent hydrodynamic lubrication regime there. The fuel leak into the valvetrain oil was unfortunate, considerably reducing the viscosity, and messing up the intent of having higher viscosity there.
- Testing viscosity at 10e-6/s and 10e-7/s shear rates. The higher shear rate reduced the viscosity even more than the lower shear rate did. They also tested viscosity at 100 C and 150 C at 1e-6/s shear rate. Newtonian and non-Newtonian oils were tested. The supposedly Newtonian oil still showed shear thinning, so it wasn’t truly Newtonian, but it was much closer to it than the 15W-40 oils were.
- Tested friction and viscosity modifiers. In the cylinders, it would be ideal for reducing total friction by reducing viscosity below 150 C and increasing it above 150 C. The latter is true because of boundary regime caused by the oil temperatures in the upper part of the cylinder being near 200 C, combined with low piston speed, and high pressure (during expansion). This should also reduce wear.
- A dumbbell base oil blend (mix of thin and thick) caused the more volatile part evaporate quickly enough in the very hot upper cylinder area to significantly increase the oil viscosity, right where that extra viscosity is needed.
- Increasing flow rate to the valvetrain decreased total friction, apparently by decreasing asperity contact...moving the regime to the right on the Stribeck curve, where total friction is lower. That surprised me.
- Fuel dilution effects were tested
