Fuel cell system, mobile object, and exhaust gas discharge control method

A fuel cell system mounted in a mobile object, comprising:

• an air compressor;
• a fuel cell that is supplied with air from the air compressor;
• an exhaust gas flow passage that discharges exhaust gas from the fuel cell;
• a bypass flow passage that establishes communication between the air compressor and the exhaust gas flow passage;
• a bypass flow passage adjusting valve that adjusts an amount of air supplied to the bypass flow passage;
• an outside air temperature sensor that acquires an outside air temperature;
• a speed sensor that acquires a speed of the mobile object;
• and
• a control unit that is configured to perform control of the fuel cell system including operation of the fuel cell, wherein
• the control unit is configured to perform a mist formation suppression process for increasing a flow rate of air caused to flow through the bypass flow passage, by controlling a drive amount of the air compressor and an opening degree of the bypass flow passage adjusting valve, when the outside air temperature is equal to or lower than an outside air temperature determination threshold and the speed of the mobile object is equal to or lower than a determination speed, and
• a first flow rate of air flowing through the bypass flow passage at a first temperature that is lower than a second temperature that is equal to or lower than the outside air temperature determination threshold is larger than a second flow rate of air flowing through the bypass flow passage at the second temperature, in the mist formation suppression process.