Fuel supply system

A fuel supply system configured to supply a first fuel which is separated from a raw fuel and containing components with a higher octane number compared to the raw fuel, and the raw fuel or a second fuel which is separated from the raw fuel and containing components with a lower octane number compared to the raw fuel, selectively or by a specified mixing ratio to an internal combustion engine simultaneously, comprising:

• a separation device which is sectioned to a high pressure chamber and a low pressure chamber via a separation membrane, and configured to separate the raw fuel into the first fuel and the second fuel by the separation membrane in a state the low pressure chamber is maintained in a lower pressure than the high pressure chamber, and then to recover the first fuel from the low pressure chamber side, and to recover the second fuel from the high pressure chamber side;
• a condenser which is connected to the low pressure chamber of the separation device;
• a first fuel tank connected to the condenser and configured to store the first fuel;
• an atmospheric pressure adjustment mechanism configured to adjust an internal atmospheric pressure of the condenser;
• and
• a controller configured to repeatedly execute a negative pressure control processing by controlling an operation of the atmospheric pressure adjustment mechanism, in which, in a first state where the condenser is interrupted from the separation device and the first fuel tank, the condenser is decompressed to a first negative pressure and then the decompression of the condenser is stopped, and subsequently in a second state where the condenser is communicated to the separation device while interrupted from the first fuel tank, the internal atmospheric pressure of the condenser is raised to a second negative pressure, and then in a third state where the condenser is interrupted from the separation device while communicated to the first fuel tank, the decompression of the condenser is also stopped,
• wherein the controller is configured to adjust at least one of the first negative pressure and the second negative pressure so as to make a difference between the first negative pressure and the second negative pressure smaller as a concentration of the high-octane number components of the raw fuel is lower.