HYDROGEN FUEL PRESSURE ENERGY RECOVERY FOR HYDROGEN ENGINE VEHICLES

A fuel system for a vehicle having a fuel tank (12) for storing hydrogen fuel and an internal combustion engine (11). The internal combustion engine (11) has a fuel delivery system for injecting the hydrogen fuel into at least one combustion cylinder, comprising: a compressor/expander (13) in fluid connection between the fuel tank (12) and the engine's fuel delivery system, the compressor/expander (13) configured to: receive the hydrogen fuel from the fuel tank (12), deliver the hydrogen fuel at a desired fuel pressure to the fuel delivery system, operate in compressor mode when the hydrogen fuel in the fuel tank (12) is below the desired pressure, and operate in expander mode when the hydrogen fuel in the fuel tank (12) is above the desired pressure. The fuel delivery system further comprises a fuel tank pressure sensor (36) for measuring the pressure of the hydrogen fuel at the outlet of the fuel tank (12); a fuel tank temperature sensor (37) for measuring the temperature of the hydrogen fuel at the outlet of the fuel tank (12); an inlet metering valve (31) at the inlet to the compressor/expander (13) for metering flow timing and amount from the fuel tank (12) to the compressor/expander (13); an outlet metering valve (32) at the outlet from the compressor/expander (13) for metering flow timing and amount from the compressor /expander (13) to the fuel delivery system; and a controller (14) for receiving pressure and temperature measurements from the pressure sensor (36) and from the temperature sensor (37), for storing data representing the desired pressure, and for calculating timing of the opening and closing of the inlet metering valve (31) and the outlet metering valve (32) to maintain the desired pressure at a delivery point to the fuel delivery system.