Fuel cell purging method

Abstract

The invention discloses a fuel cell purging method, which comprises the following steps of: purging water in a cell stack after the cell stack is shut down, and monitoring the impedance of the cell stack in the purging process: in a first purging stage, introducing airflow into the cell stack in a constant-pressure and constant-flow manner for purging until the monitored impedance of the cell stack reaches a first impedance threshold value, the setting range is 50%-70% of the target impedance value Rdry; in the second purging stage, the airflow is introduced into the cell stack for purging in a mode of boosting the pressure and increasing the flow until it is monitored that the impedance of the stack reaches a second impedance threshold value, and the setting range is 85%-100% of Rdry; and in the third purging stage, the air flow is introduced into the cell stack for purging in a manner of firstly increasing the pressure and increasing the flow, then decreasing the pressure and decreasing the flow and then increasing the pressure and increasing the flow until the impedance of the cell stack is monitored to reach a third impedance threshold value, and the setting range is 98%-100% of Rdry. The test proves that the battery purging method disclosed by the invention is low in gas consumption and short in purging time.

Description

technical field [0001] The invention relates to the field of fuel cell control, in particular to a fuel cell purging method. Background technique [0002] During the operation of the fuel cell stack, the cathode and anode need to pass gas with a certain humidity, and the cathode will produce a large amount of water. The stack failed to start cold or flooded when the stack started. [0003] The focus of the relevant patents is on the detection methods for controlling the start and stop of purging, such as the use of high-frequency impedance detection methods to determine whether the remaining water content in the stack reaches the standard: continuous ventilation and purging of the stack with constant current and constant pressure, when the real-time high-frequency impedance Above the set threshold, the purging is stopped. [0004] For example, in the Chinese patent application with the publication number CN111029623A, the disclosed purging strategy takes a long time, and t...

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Problems solved by technology

[0004] For example, the Chinese patent application whose publication number is CN111029623A, the purging strategy disclosed in it takes a long time, and the required purging air flow is large, so that the purging efficiency is low and exhaust gas is not economical; and the patent application does not consider the influence of the steady state process , that is, the internal resistance value reaches the requirement after one purge is completed, but after standing for a period of time, the internal resistance value shows a slow decrease until it becomes stable. electrode, but in the porous capillary structure of the gas diffusion layer, after a period of steady-state process (due to the influence of the concentration gradient, the local residual water diffuses from the high-concentration area to the low-concentration area until equilibrium), the local residual water re- The distribution remains in the membrane electrode, the purging is not complete, and the purging requirements are actually not met

[0005] Another example is the Chinese patent application whose publication number is CN113839068A, which discloses the strategy of intermittent multiple purging, but the system is too complicated, and the purging efficiency of the constant current and constant pressure strategy is still low, which is not economical.

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