Adjusting a fuel on-board a vehicle

A method for separating a fuel on-board a vehicle, comprising:

• receiving, at a control system of an on-board fuel separation system of a vehicle that comprises an engine, an engine operating condition;
• operating the fuel separator of the on-board fuel separator at an operating parameter to separate a fuel stream into a vapor stream and a first liquid stream based on a volatility of the fuel stream, the vapor stream defined by a first auto-ignition characteristic value and the first liquid stream defined by a second auto-ignition characteristic value, the second auto-ignition characteristic value greater than the first auto-ignition characteristic value;
• adjusting, based at least in part on the engine operating condition, the operating parameter of the fuel separator to vary at least one of the first or second auto-ignition characteristic values;
• operating the fuel separator of the on-board fuel separator at the adjusted operating parameter;
• supplying the vapor stream from the fuel separator to a power generator at a first fluid pressure;
• generating electrical power with the power generator based at least in part on a reduction of the vapor stream from the first fluid pressure to a second fluid pressure less than the first fluid pressure in the power generator;
• supplying the fuel stream and the vapor stream at the second fluid pressure from the power generator to a heat exchanger;
• and
• transferring heat from the vapor stream at the second fluid pressure to the fuel stream to heat the fuel stream prior to a heated fuel stream entering the fuel separator.

A vehicle system, comprising

• a vehicle;
• a fuel-powered internal combustion engine mounted in the vehicle;
• an on-board fuel separation system, comprising:
• a fuel separator configured to receive a fuel stream and separate the fuel stream, based on a volatility of the fuel stream, into a vapor stream defined by a first auto-ignition characteristic value and a first liquid stream defined by a second auto-ignition characteristic value, the second auto-ignition characteristic value greater than the first auto-ignition characteristic value;
• and
• a control system communicably coupled to the fuel separator and operable to receive an input from the engine, the input comprising an engine operating condition, the control system configured to adjust an operating parameter of the fuel separator, based at least in part on the engine operating condition, to vary at least one of the first or second auto-ignition characteristic values;
• a first fuel tank fluidly coupled between the engine and the fuel separator to store the first liquid stream output from the fuel separator;
• a second fuel tank fluidly coupled between the engine and a heat exchanger that is fluidly coupled between the fuel separator and an input of the fuel stream to store the second liquid stream output from the heat exchanger;
• and
• a turbine that comprises an input fluidly coupled to the fuel separator and output fluidly coupled to the heat exchanger and configured to receive the vapor stream from the fuel separator and generate electrical power based on a pressure difference of the vapor stream between the input and the output.