Open system is the pump suction from the tank, the oil through a variety of control valves, the drive hydraulic actuators, valve oil return back for another fuel tank.

开式系统是指液压泵从油箱吸油，油经各种控制阀后，驱动液压执行元件，回油再经过换向阀回油箱。

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On Tuesday, the U.S. Coast Guard said the fire started with a leak in a fuel-oil return line running from one of the ship's engines.

CNN: STORY HIGHLIGHTS

KEDO, the organisation responsible for building two nuclear reactors and making interim deliveries of fuel oil in return for a freeze on the North's production of plutonium, from which nuclear bombs can be made.

ECONOMIST: Europe in the world

This week's accord could result in little more than a return to a 1994 pact between America and North Korea, by which North Korea froze its operations at Yongbyon in return for fuel oil shipments and an agreement eventually to provide replacement nuclear reactors that could less easily be used to make weapons material.

ECONOMIST: Some cheer over North Korea