METHOD FOR ADJUSTING THE FUEL CONCENTRATION OF A FUEL MIXTURE CONTAINING ALCOHOL OR ETHER AS FUEL AND WATER, USED BY A FUEL CELL AND A FUEL CELL SYSTEM

摘要

The invention relates to a method for adjusting the fuel concentration of a fuel mixture of a fuel cell using alcohol or ether as fuel and a fuel cell system suitable for said method. Fuel cells in which an alcohol or ether as fuel is directly reacted are operated with a fuel mixture of fuel and water in which the fuel usually has a concentration of between 1 vol.- % and 5 vol.- %. The aim of the invention is to provide a fuel concentration which is as constant as possible. For the above-mentioned concentration range, however, a sufficiently exact and/or fast method for directly measuring the fuel concentration has not been known. According to the invention, the fuel concentration is adjusted to a constant value by means of a specific probe (13). Said probe (13) has a measuring chamber (16) and a membrane (14) closing the measuring chamber (16). Fuel and water permeate the membrane (14). The membrane (14) is selectively permeable in such a way that a measuring mixture is formed in the measuring chamber (16) in which the alcohol concentration is less than 1 vol.- % or more than 5 vol.- %. Suitable fuel sensors (17) can be used for said concentration ranges. The invention also relates to the operation of fuel cells using alcohol or ether as fuels, and water.