Fuel Cell System with Variable Coanda Amplifiers for Gas Recirculation and System Pressure Regulation

A method for operating a Coanda flow amplifier having a suction intake, an outlet, a fluid channel extending between the suction intake and the outlet, and a drive flow inlet that is in fluid flow communication with the fluid channel via a drive-flow discharge slit, wherein the flow cross section of the drive-flow discharge slit is variably adjustable;

• said method comprising:
• feeding a fluid flow that is to be amplified to a suction intake;
• feeding a drive-flow to the drive-flow inlet;
• adjusting a variable flow cross section of the drive-flow discharge slit such that a pressure ratio between the output pressure of the drive flow when it leaves the drive-flow discharge slit and an intake pressure of the drive flow when it enters the drive-flow discharge slit does not exceed a critical pressure ratio.

A fuel cell system comprising:

• at least one fuel cell;
• a fluid source;
• a fluid line;
• a Coanda flow amplifier arranged in the fluid line, with whereby both a suction intake and an outlet of the Coanda flow amplifier being fluid-connected to the fluid line, and whereby a drive-flow inlet of the Coanda flow amplifier being fluid-connected to the fluid source;
• wherein the Coanda flow amplifier includes,
• a suction intake:
• an outlet,
• a fluid channel extending between the suction intake and the outlet;
• and
• a drive flow inlet that is in fluid flow communication with the fluid channel via a drive-flow discharge slit;
• wherein the flow cross section of the drive-flow discharge slit is variably adjustable.