NOVELTY - The device has a metering device (16) for a propulsion gas stream (H2) and comprising valves (15.1-15.4) arranged parallel to an inflow of the propulsion gas stream. The valves are designed as unmetered switching valves. The valves exhibit same flow cross-sections, where the flow cross-sections are doubled from one valve to the other valves. Each valve is connected with nozzle orifices (17.1-17.4) for the propulsion gas stream. The nozzle orifices are adapted to the flow cross-sections of the switching valves. Line elements are led into a region of a nozzle in the nozzle orifices.    USE - Flow-driven device e.g. gas jet pump, turbine such as Pelton turbine, Tesla turbine and radial-flow turbine, for a fuel cell system (all claimed) in a vehicle.    ADVANTAGE - The valves are arranged parallel to the inflow of the propulsion gas stream and designed as the unmetered switching valves, thus switching the valves in a closed position or an open position if required, and avoiding problem of noise emissions from the device, and producing continuous flow propulsion gas stream. The nozzle orifices exhibit high flow rate to realize the optimum energy input into flow of gas. The flow-driven device ensures better conversion of introduced energy with high dosing precision of the propulsion gas stream. The valves exhibit same flow cross-sections, thus ensuring that structure of the flow-driven device is simple and efficient manner, and increasing dosing volumetric flow of the device. The device uses the propulsion gas stream within the fuel cell system without supplementary energy expenditure, so that the fuel cell system works in an energy-efficient manner.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a fuel cell system.    DESCRIPTION OF DRAWING(S) - The drawing shows a principle sectional view of a gas jet pump as a flow-driven device.    Propulsion gas stream (H2)    Valves (15. 1-15.4)    Metering device (16)    Nozzle orifices (17.1-17.4)    Recirculation line (20)