正确答案: C

Excessive air in the cylinder

题目：第一组： The Wartsila 50DF operates on the lean-bum principle: the mixture of air and gas in the cylinder has more air than is needed for complete combustion. Lean combustion reduces peak temperatures and therefore NOx emissions. Efficiency is increased and higher output is reached while avoiding knocking. Combustion of the lean air-fuel mixture is initiated by injecting a small amount of LFO (pilot fuel) into the cylinder. The pilot fuel is ignited in a conventional diesel process, providing a high-energy ignition source for the main engine. To obtain the best efficiency and lowest emissions, every cylinder is individually controlled to ensure operation at the correct air-fuel ratio and with the correct amount and timing of pilot fuel rejection. Wartsila has developed a special electronic control system to cope with the demanding task of controlling the combustion in each cylinder, and to ensure optimal performance in terms of efficiency and emissions under all conditions by keeping each cylinder within the operating window. Stable and well-controlled combustion also contributes to less mechanical and thermal load on the engine components. Current stringent emission regulations demand the reduction of NOx emissions. In an internal combustion engine this means controlling peak temperature and residence time, which are the main parameters governing NOx formations. In the Wartsila 50DF engine, the air-fuel ratio is very high (typically 2.2). Since the same specific heat quantity released by combustion is used to heat up a larger mass of air, the maximum temperature and consequently NOx formation are lower. The mixture is uniform. throughout the cylinder since the fuel and air are premixed before introduction into the cylinders, which helps to avoid local NOx formation points within the cylinder. Benefiting from this unique feature, NOx emissions from the Wartsila 50DF are extremely and comply with the most stringent existing legislation.What is the combustion feature of the Wartsila 50DF?

解析：C

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举一反三的答案和解析：

[单选题]你船是机动船在试航，从左舷60度驶来一艘挂有尖端向下圆锥体的帆船，致有构成碰撞危险，你船应________。

保向保速

[单选题]下列人员不属于管理级是_______。

管事

[单选题]对使用分道通航制的船舶下列哪种说法是正确的？________。

并不解除任何船舶遵守《国际海上避碰规则》其他各条规定的责任

[单选题]吊艇架的种类有：

旋转式、摇倒式、重力式、自由落水式

[单选题]下列说法错误的是：

闪点是划分可燃液体危险等级的依据，当达到闪点，遇火便可产生持续燃烧现象。

[单选题]泵的有效功率大小取决于( )。

A×B

[单选题]如果遇大面积烧伤病人时，应()。

用干净床单包裹

[单选题]纵横强度合理，大中型船普遍使用的船体骨架形式是( )。

纵横混合骨架式

[单选题]quarantine officer

检疫官员

解析：：A