Method and apparatus for simultaneous controlling of fuel concentration and temperature of liquid fuel by sensor-less and temperature-control based feed-back control, liquid fuel cell apparatus using the same

A method for simultaneously controlling a fuel concentration and a temperature of liquid fuel cell by using a temperature-control based feed-back control without using a concentration sensor, comprising:

• obtaining a database by measuring a fuel consumption rate or speed according to an operating condition of a liquid fuel cell, and preparing a fuel consumption equation according to operating conditions based on the database (S1);
• determining a fuel consumption rate or speed in a given operating condition based on the fuel consumption equation determined in Step S1, and determining an undiluted fuel feed amount or speed corresponding to the determined fuel consumption rate or speed (S2);
• setting a target temperature (Tf) and selecting either a target-condition control mode or a present-condition control mode, and supplying an undiluted fuel to a fuel mixer in an undiluted fuel feed amount or speed determined according to the selected mode, and then supplying thus made diluted fuel in the fuel mixer to a stack of the fuel cell to start an operation of the fuel cell (S3);
• fixing the target-condition control mode so that the undiluted fuel is supplied accordingly if the temperature of the stack reaches a predetermined intermediate temperature (Ti) lower than the target temperature (Tf), and performing a feed-back control to a heat removal rate of the heat exchanger comparing the present temperature of the fuel cell stack with the target temperature so that the temperature of the fuel cell stack is maintained in a normal state where the temperature of the fuel cell stack is within a preset error bound from the target temperature (Tf) (S4);
• and
• increasing or decreasing the undiluted fuel flux or flow rate fixed according to the target-condition control mode in S4, if the fuel cell is in an abnormal state where the temperature (T) of the fuel cell stack deviates from the preset error bound from the target temperature (Tf) although the heat exchanger operates in a maximum manner or in a minimum manner, by feed-back control comparing the present temperature of the fuel cell stack with the target temperature so that the temperature of the fuel cell stack comes back to the normal state where the temperature (T) of the fuel cell stack is within a preset error bound from the target temperature (Tf).