轮机长

考试试题

[问答题]The separation efficiency of the ALCAP separation system has been thoroughly tested with respect to removal of water, catalyst fines and other inorganic solid particles. A detailed review and report on results from the laboratory and shipboard tests are presented in Enclosure 2. These tests were made together with Shell International and Sulzer. The densities of the tested oils were 991,993 and 1013 kg/ m 3 at 15℃. The test results are summarized as follows: --seawater contamination is efficiently reduced in heavy fuel oil with densities up to 1013 kg/m 3 at 15 ℃. --catalyst fines and other inorganic solid particles are efficiently removed from heavy fuel oil with densities up to 1013 kg/ m 3 at 15℃. --freshwater contamination is efficiently reduced in heavy fuel oil with a density of 993 kg/ m 3 at 15 ℃. Example: 3 % freshwater was reduced to 0.5 %-0.6 %. However, the upper density limit for satisfactory reduction of freshwater is probably higher, up to 1010 kg/m 3 . Additional tests are planned to confirm this. --the separation efficiency of the ALCAP separation system is as good as or better than a well adjusted purifier (applicable for heavy fuel oil with density up to 991 kg/m 3 at 15℃ ). --laboratory and shipboard tests conducted to date confirm that the ALCAP separation system delivers optimum separation efficiency, continuously. Based on these findings, the recommended maximum density of heavy fuel oil cleaned with the ALCAP separation system is lO10kg/m 3 at 15℃ measured at 50℃ .The recommended maximum viscosity is 700 cst at 50℃.
[问答题]A two-ram hydraulic gear consists of a hydraulic ram situated on the port side of the tiller and another ram on the starboard side, linked at their outer ends to the tiller arm by a crosshead and swivel block, the other ends of the rams working inside their own hydraulic cylinders and pipes connect these cylinders to a hydraulic pump. The tiller is firmly keyed to the rudder stock. The pump is of special construction and may be axial or radial design. The pump runs continuously in the same direction driven by an electric motor, and the position of a movable plate or a floating ring inside the pump controls the suction and discharge of the oil. When the plate or ring is in mid position, no oil is drawn; when the plate or ring is moved in one direction from mid position, oil is drawn from one cylinder and discharged into the other; when the plate or ring is moved in the opposite direction, the suction and discharge of the oil is reversed in direction. The plate or ring is actuated by a control rod which is attached at its outer end o the hunting gear. A four-ram hydraulic steering gear may be fitted in large ships for greater steering power, instead of the tow-ram type. It is simply a double tow-ram unit, so that the force of tow diagonally opposite rams can act on the tiller to produce double the turning effect. The pump control is moved by the telemotor through a floating lever. The other end of this lever is connected through a safety spring link to the rudder stock or tiller. The telemotor is the receiver of the hydraulic remote control system from wheel on the bridge. The linkage through the floating lever of telemotor, pump and rudder stock forms the hunting gear.
[问答题]Supercharging and Scavenging Air supply is very important to the perfect combustion of fuel oil in the diesel engine. As the air density determines the maximum weight of fuel that can be burned per working stroke in the cylinder, it also determines the maximum power that can be developed by the engine. If the charge-air density is increased by a compressor before it enters the cylinder, a greater amount of fuel can be burned, resulting in an increase of power output. This is the main principle of exhaust turbo-charging. In today’s practice, the compressor, i. e. a blower, is driven by the heat energy obtained from the engine exhaust gases. The turbo-blower comprises a gas-turbine, driven by the engine exhaust gases and directly coupled to the blower, which draws fresh air from the engine-room and discharges it into the air inlet manifold on the engine. The power produced in the turbine must be equal to that required by the compressor. The air is pumped into the cylinder through the inlet ports. The turbo-blower is provided with a filter-silencer. It is usually desirable to fit charge-air coolers to turbo-charged two-stroke engines. As the charge-air density increases, the amount of air flowing into the cylinders is increased and as the charge-air temperature lowers, the exhaust temperature and the engine thermal load are reduced. It is very important that each cylinder should be well scavenged before the charged air is com- pressed, otherwise this fresh air charge will be fouled by the residual exhaust gases from the last cycle. The necessary scavenging is obtained by providing a satisfactory pressure difference between the air manifold and the exhaust manifold.