System and method for monitoring fuel additives

A system for monitoring fuel additives on board a vehicle comprising;

• a fuel line carrying fuel from a fuel source to an engine;
• a fuel additive sensor configured to measure a concentration of fuel additives in the fuel at a point along the fuel line;
• a fuel additive dispenser connected in parallel to the fuel line;
• at least one flow control device for controlling an amount of a first fuel flow from the fuel line into the fuel additive dispenser;
• and
• a controller configured to receive input from the fuel additive sensor and to control the at least one flow control device to adjust the amount of the first fuel flow from the fuel line into the fuel additive dispenser and thereby adjust a fuel flow rate of the first fuel flow through the fuel additive dispenser,
• wherein the fuel additive dispenser is a passive fuel additive dosing system, and wherein the passive fuel additive dosing system comprises:
• a cartridge;
• a membrane-based contactor within the cartridge;
• a fuel inlet to the cartridge connected to receive the first fuel flow from the flow control device;
• a fuel outlet from the cartridge connected to return the first fuel flow back to the fuel line;
• and
• an additive within the membrane-based contactor, the membrane-based contactor being arranged in the cartridge such that, with the first fuel flow in the cartridge, a fuel contact area with the membrane-based contactor is dependent on the fuel flow rate of the first fuel flow to passively dispense an amount of the additive proportional to the fuel contact area.