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Which of the following conditions is realized by the turbo-charging of a previously naturally aspirated diesel engine？

A. Ignition lag increases.
B. Lube oil system pressure increases.
C. Brake specific fuel consumption increases.
D. Mechanical efficiency increases.

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Older loop scavenged engines may have a single injector mounted centrally in the cylinder head. Because the exhaust valve is in the center of the cylinder head on modern uniflow scavenged engines the fuel valves (2 or 3) are arranged around the periphery of the head. The pressure at which the injector operates can be adjusted by adjusting the loading on the spring. The pressures at which the injectors operate vary depending on the engine, but can be as high as 540 bar. Some injectors have internal cooling passages in them extending into the nozzle through which cooling water is circulated. This is to prevent overheating and burning of the nozzle tip. Injectors on modern engines do not have internal cooling passages. They are cooled by a combination of the intensive bore cooling in the cylinder head being close to the valve pockets and by the fuel which is re-circulated through the injector when the follower is on the base of the cam or when the engine is stopped. As well as cooling the injector, re-circulating the fuel when the engine is stopped keeps the fuel at the correct viscosity for injection by preventing it from cooling down. Fuel injectors must be kept in good condition to maintain optimum efficiency, and to prevent conditions arising which could lead to damage within the cylinder. Injectors should be changed in line with manufacturers&39; recommendations, overhauled and tested. Springs can weaken with repeated operation leading to the injector opening at a lower pressure than designed. The needle valve and seat can wear which together with worn nozzle holes will lead to incorrect atomization and dribbling.
Modern uniflow scavenged engines have______.

A. a single injector mounted in the center of the cylinder head
B. several injectors mounted around the external boundary of the cylinder head
C. a single injector mounted at the external boundary of the cylinder head
D. several injectors mounted in the center of the cylinder head

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美联储的政策工具包括________。

A. 法定准备金率、贴现率和公开市场业务
B. 为美国政府保存存款、准备金要求以及贴现率
C. 管制借贷标准、批准或者禁止银行对大型企业的贷款
D. 监管银行系统、买卖商业银行
E. 法定准备金率、收入税率以及公开市场业务

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Which of the following problems can occur if you continually fail to drain off condensate

A. Corrosion and eventual failure of the tank
B. Gumming of the tank relief valves
C. Immediate failure of components downstream of the compressed air system
D. Boiling of the water oil mixture as pressure is reduced

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美国有(2；6；1：2)个地区的联邦储备银行。美联储的主要制定政策委员会是(理事会；联邦公开市场委员会)。美联储设定的最低保留存款百分比被称为(贴现率；法定准备金率)。美联储将准备金贷给商业银行的利率称为(贴现率；法定准备金率)。美联储买卖政府有价证券的活动被称为。

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Which of the following conditions is realized by the turbo-charging of a previously naturally aspirated diesel engine？

A. Ignition lag increases. B. Lube oil system pressure increases. C. Brake specific fuel consumption increases. D. Mechanical efficiency increases.

美联储的政策工具包括________。

Which of the following problems can occur if you continually fail to drain off condensate

A. Ignition lag increases.
B. Lube oil system pressure increases.
C. Brake specific fuel consumption increases.
D. Mechanical efficiency increases.