Method for a fuel cell air system leakage diagnostic

摘要

A system and method for identifying leaks in a cathode sub-system of a fuel cell system. An air flow meter is provided up-stream of a compressor and monitors the air flowing into the compressor. When an air leakage diagnostic is commanded, a fuel cell stack by-pass valve and back-pressure valve are closed so that no air flows through or around the stack, and the recirculation valve is opened so that the air flows around the compressor. By knowing the leakage through the by-pass valve and the back-pressure valve, any flow above those values measured by the air flow meter gives an indication of air leakage out of the cathode sub-system components.

主权项

1. A method for determining overboard leakage of cathode air that is provided to a cathode side of a fuel cell stack in a fuel cell system, said method comprising:
setting a compressor that provides the cathode air to the stack to a predetermined compressor speed; closing a back-pressure valve positioned within a cathode exhaust line to prevent cathode air flow through the fuel cell stack; closing a by-pass valve to prevent air flow around the fuel cell stack; opening a recirculation valve to allow the cathode air to flow around the compressor and be sent back to a compressor input; measuring a flow of air into the compressor upstream of a location where the recirculated cathode air is sent to the compressor; and determining whether the measured air flow indicates leakage of the cathode air from the system.