Adjusting a fuel on-board a vehicle

An on-board fuel separation system, comprising:

• a liquid-liquid extraction unit configured to separate a mixture of an input fuel stream and a fluid solvent into a first liquid fuel stream and a second liquid fuel stream, the first liquid fuel stream comprising a first portion of the input fuel stream defined by a first auto-ignition characteristic value and the fluid solvent, the second liquid fuel stream comprising a second portion of the input fuel stream defined by a second auto-ignition characteristic value that is different than the first auto-ignition characteristic value;
• a separator fluidly coupled to the liquid-liquid extraction unit and configured to receive the first liquid fuel stream and separate the first liquid fuel stream into the fluid solvent and the first portion of the input fuel stream;
• a first heat exchanger positioned to receive the first liquid fuel stream from the liquid-liquid extraction unit and heat the first liquid fuel stream with the fluid solvent from the separator;
• a second heat-exchanger positioned to receive the first liquid fuel stream from the first heat exchanger and heat the first liquid fuel stream with the first portion of the input fuel stream from the separator;
• a third heat exchanger positioned to receive the first liquid fuel stream from the second heat exchanger and heat the first liquid fuel stream with an engine exhaust stream;
• a first fuel tank fluidly coupled to receive the first portion of the input fuel stream from the separator;
• and
• a second fuel tank fluidly coupled to receive the second portion of the input fuel stream from the liquid-liquid extraction unit.

A vehicle system, comprising

• a vehicle;
• a fuel-powered internal combustion engine mounted in the vehicle;
• an on-board fuel separation system, comprising:
• a liquid-liquid extraction unit configured to separate a mixture of an input fuel stream and a fluid solvent into a first liquid fuel stream and a second liquid fuel stream, the first liquid fuel stream comprising a first portion of the input fuel stream defined by a first auto-ignition characteristic value and the fluid solvent, the second liquid fuel stream comprising a second portion of the input fuel stream defined by a second auto-ignition characteristic value that is different than the first auto-ignition characteristic value;
• a separator fluidly coupled to the liquid-liquid extraction unit and configured to receive the first liquid fuel stream and separate the first liquid fuel stream into the fluid solvent and the first portion of the input fuel stream;
• a first heat exchanger positioned to receive the first liquid fuel stream from the liquid-liquid extraction unit and heat the first liquid fuel stream with the fluid solvent from the separator;
• a second heat-exchanger positioned to receive the separated fluid solvent from the first heat exchanger and heat the first liquid fuel stream with the first portion of the input fuel stream from the separator;
• and
• a third heat exchanger positioned to receive the first liquid fuel stream from the second heat exchanger and heat the first liquid fuel stream with an engine exhaust stream;
• a first fuel tank fluidly coupled between the engine and the separator to store the first portion of the input fuel stream from the separator;
• and
• a second fuel tank fluidly coupled between the engine and the liquid-liquid extraction unit to store the second portion of the input fuel stream from the liquid-liquid extraction unit.