The customized design of an anode recirculation system that uses an ejector based on the humidified hydrogen is proposed for a submarine PEMFC. Generally, the ejector is useful to enhance its system performance and to easily be operated and maintained since it does not require any parasitic power and has very simple structure. However, the existing commercial ejectors do not meet the practical operating requirements of the PEMFC system with the humidified hydrogen recirculation since the included water raises the ejector performance reduction and accompanying operating limits. The subsonic flow ejector designed by the proposed approach has met the desired entrainment ratio through the whole operating range of the target system as well as it allows the additional advantages to improve the system efficiency and simplicity and to overcome the conventional operating limits. (c) 2007 Elsevier B.V. All rights reserved.