轮机英语【轮机长】题库

问答题 6分

Product description NALFLEET "SEA SHIELD" DISC/FILTER CLEAN is a mixture of solvents, proprietary su...

Product description
NALFLEET "SEA SHIELD" DISC/FILTER CLEAN is a mixture of solvents, proprietary surfactants
and an organic acid. It is designed specifically for the removal of oily residues and lacquers found in fuel
oil and lube oil purifiers and filters.
NALFLEET "SEA SHIELD" DISC/FILTER CLEAN does not contain any phenols, cresylic acid,
chlorinated hydrocarbons and less than 10% aromatics. The formulation meets the latest regulations from
MARPOL 73/78 as recommended by the Bulk Liquids and Gases (BLG) working group of the Marine
Environmental Protection Committee (MEPC) of the International Marine Organization (IMO), and is
approved by that committee on behalf of IMO. These regulations, effective 1st July 1996, state that
additives used for cleaning ship's tanks must contain less than 10% of a Pollution Category A product.
(Annex II of MARPOL 73/78 now states that petrochemical complex mixtures of hydrocarbons
containing more than 10 wt % of C3-C8 alkylbenzenes (i.e. C9-C14 aromatics) and/or poly (C2 and above)
cyclic aromatics, are assigned to Pollution Category A.)
The formulation also meets the latest OSPARCOM regulations which ban the use of surfactants based
on Alkyl Phenol Ethoxylates in cleaning products.
(The reason for this ban is that Alkyl Phenol Ethoxylates degrade in the environment to Alkyl Phenol
which is persistent and slightly oestrogenic-affects the reproduction cycle of organisms)

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参考解析:
1. The product is most suitable for removing _______. A. solvents B. proprietary surfactants C. organic acids D. oily residues and lacquers 2. Which of the following statements is NOT correct? A. The product can be used not only in fuel oil purifiers and filters but also in lube oil purifiers and filters. B. The product is a mixture of a number of substances. C. There is not any cresylic acid in the product. D. The product does not contain any aromatics. 3. From the passage, we can learn that Annex II of MARPOL 73/78 concerns on the discharging rules of _______. A. oily water B. poisonous liquid C. solid garbage D. sanitary sewage 4. The word “ban” in the passage can be replaced by ________. A. permit B. warn C. forbid D. prevent

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1 问答题 6分

The lubrication system of an engine provides a supply of lubricating oil to the various moving parts in
an engine. Its main function is to enable the formation of a film of oil between the moving parts, which
reduces friction and wear. The lubricating oil is also used as a cleaner and in some engines as a coolant. The
usual method of bearing lubrication is by forced feed system, which supplies oil to all bearings, so that a
film of oil is maintained on the journal and bearing surfaces.
(The following 2 questions are based on the passage above.)

2 问答题 6分

This sequence of events is made possible by substituting ports in the bottom of the cylinder wall for
the inlet and exhaust valves. There are two groups of these ports, one for exhaust and the other for
scavenging air, usually on the opposite sides of the cylinder, but in some designs both groups are arranged
on the same side. The exhaust ports connect with the exhaust manifold, while the scavenging ports
communicate with the scavenging air receiver in which low-pressure air is stored. The exhaust ports are
slightly higher than the scavenging ports, so that they are uncovered by the piston while the scavenging
ports are still closed.
(The following 2 questions are based on the passage above.)

3 问答题 6分

Spark erosion is caused by a voltage discharge between the main bearing and journal surface. The
cause of the potential is the development of a galvanic element between the ship’s hull, sea water,
and the propeller shaft/crankshaft.

The oil film acts as a dielectric. The puncture voltage in the bearing depends on the thickness of the oil
film. With increasing engine ratings, the specific load in the main bearing is increased. This will reduce the
oil film thickness, and enable the discharge to take place at a lower voltage level.

Since the hydrodynamic oil film thickness varies through a rotation cycle, the discharge will take place at
roughly the same instant during each rotation cycle, i.e. when the film thickness is at its minimum. The
roughening will accordingly be concentrated in certain areas on the journal surface. In the early stages, the
roughened areas can resemble pitting erosion. but later, as the roughness increases, the small craters will
scrape off and pick up white metal-hence the silvery white appearance.

Therefore, to ensure protection against spark erosion, the potential level must be kept at maximum 80
mV, which is feasible today with a high efficiency earthing device. If an earthing device is installed, its
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4 问答题 6分

Pressurized oil atomization is used for smaller capacity burners. The nozzle is located at the end of the
oil gun. In the nozzle a number of small holes are oriented to assure the rotating flow for atomizing and
spraying the oil in the most efficient way.

As the geometry of the nozzle is fixed the velocity in the small holes and slits in the nozzle depends
upon the load on the burner. The higher load the higher velocity and thereby the better atomization. On the
other hand this means that the lower load the lower velocity and thereby the poorer atomization. Typically
pressurized jet atomization is efficient for a turndown ratio 1:2, i.e. 50 % load. At lower load, the
atomization will not be satisfying and this means non-satisfying combustion quality eventually causing soot
formations. The oil pressure varies between 0.5 and 2.0 MPa. As mentioned ensuring the correct
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affects the combustion of the oil heavily is the angle of atomization that is a characteristic parameter for the
specific nozzle. For the pressurized jet burners the swirl of the combustion air is created by means of a
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5 问答题 6分

For a certain provision cooling plant, the capacity regulator is generally controlled depending on
pressure, temperature or relative humidity. The pulse emitter is therefore either a pressostat(压力继电器),
thermostat or hygrostat. The switching difference of the control units should be rated as large as possible.
This applies in particular to control by means of the pressure, because change to the load in the
refrigeration circuit results in relatively quick pressure changes compared to temperature, which can in turn
lead to inadmissible oscillation of the regulator.

Under partial load, the suction volume and thus the gas speed can undergo marked changes depending on the
regulation stage. For this reason, the rating and routing of the suction line must be given particular attention.
In order to guarantee sufficient oil return, neither full load nor partial load operation may allow the gas speed
to fall below a minimum level: 4 m/s in horizontal pipe sections; 8 m/s in vertical pipes.

For this reason we recommend that vertical pipes bestaggered into two separate sections (as illustration).
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blocked by an accumulation of oil. This increases the gas velocity in pipe section A. In order to guarantee adequate
oil return, both cross sections must be rated so large that the velocity does not fall below the minimum level
in full and partial load operation. In plants with extensive pipe systems it is recommended at least for R22 and NH3
to install an additional oil separator. This reduces the oil circulation period and can have positive effects above
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第一章船舶主推进装置

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第三章船舶电气和自动化

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