Abstract: A fuel cell system includes an ejector for pumping steam and fuel into a steam reformer. Steam is the primary flow through the ejector and fuel is the secondary flow. The rate of steam flow is metered by a variable area orifice in the ejector. The fuel passes through a fuel control valve before reaching the ejector. A pressure regulator maintains a constant pressure drop across a variable area orifice in the valve. The fuel flow is thus metered by the valve orifice area and not by the ejector pumping characteristics. Ejector back pressure is also eliminated as a factor affecting the amount of fuel pumped by the ejector. Means are provided to simultaneously control the orifice areas of the ejector and the fuel valve in order to maintain a desired ratio of steam to fuel for the steam reformer for each operational mode of the fuel cell. In a preferred embodiment this means is a mechanical linkage connecting the ejector and fuel valve to a common actuator.

Abstract: A fuel cell system includes an ejector for pumping steam and fuel into a steam reformer. Steam is the primary flow through the ejector and fuel is the secondary flow. The rate of steam flow is metered by a variable area orifice in the ejector. The fuel passes through a laminar restrictor in the conduit carrying the fuel to the ejector. A pressure regulator increases and decreases the pressure of the fuel supplied to the laminar restrictor by amounts equal to increases and decreases in the ejector back pressure thereby eliminating the ejector back pressure as a factor affecting the rate of fuel flow into the ejector. The laminar restrictor is designed to match the fuel flow to the ejector pumping characteristics so as to provide the desired steam to fuel ratio for the steam reformer for each operational mode of the fuel cell.