轮机长

考试试题

[问答题]Hand control of excitation is difficult so use is made of an automatic voltage regulator (AVR) . The AVR consists basically of a circuit fed from the alternator output voltage which detects small changes in voltage and feed a signal to an amplifier which changes the excitation to correct the voltage. Stabilizing features are also incorporated in the circuits to avoid ‘hunting’ (constant voltage fluctuations) or overcorrecting. The statically excited alternator has a static excitation system instead of a d.c. exciter. This type of alternator will more accept the sudden loading by direct online starting of large squirrel cage motors. The static excitation system uses transformers and rectifiers to provide series and shunt components for the alternator field, that is, it is compounded. Brushes and sliprings are used to transfer the current to the field coils which are mounted on the rotor. The terminal voltage from the alternator thus gives the no-load voltage and the load current provides the extra excitation to give a steady voltage under any load condition. The compensation necessary for speed variation requires that a voltage regulator be also built into the system. The brushless high speed alternator was also developed to eliminate d.c. exciters with their associated commutators and brushgear. The alternator and exciter rotors are on a common shaft, which also carries the rectifiers. The exciter output is fed to the rectifiers and then through conductors in the hollow shaft to the alternator field coils. An automatic voltage regulator is used with this type of alternator.
[问答题]Watch requirements (a) Every member of the watch shall be familiar with his assigned watchkeeping duties. In addition, every member shall have with respect to that ship; (i) knowledge of the use of appropriate internal communication systems; (ii) knowledge of escape routes from machinery spaces; (iii) knowledge of engine room alarm systems and the ability to distinguish between the various alarms with special reference to the CO2 alarm; (iv) knowledge of the positions and use of the fire-fighting equipment in the machinery spaces. (b)The composition of an underway watch shall, at all times, be adequate to ensure the safe operation of all machinery affecting the operation of the ship, in either automated or manual mode and be appropriate to the prevailing circumstances and conditions. To achieve this, the following, inter alia, shall be taken into account: (i) Adequate supervision, at all times of machinery affecting the safe operation of the ship; (ii) condition and reliability of any remotely operated propulsion and steering equipment, their controls , control location and the procedures involved in placing them in a manual mode of operation in the event of break-down or emergency; (iii) location and operation of fixed fire detection, fire extinction or fire containment devices and apparatus; (iv)use and operational condition of auxiliary, standby and emergency equipment affecting the safe navigation, mooring or docking operations of the ship; (v) steps and procedures necessary to maintain the condition of machinery installations in order to ensure their efficient operation during all modes of ship operation; (vi)any other demands on the watch which may arise as a result of special operating circumstance, (c)At an unsheltered anchorage the chief engineer officer shall consult with the master whether or not to maintain an underway watch. Fitness for duty The watch system shall be such that the efficiency of the watch is not impaired by fatigue. Duties shall be so organized by the chief engineer officer that first watch at the commencement of a voyage and the subsequent relieving watches are sufficiently rested and otherwise fit for duty. Protection of the marine environment All engineer officers and engine room ratings shall be aware of the serious effects of operational or accidental pollution of the marine environment and shall take all possible precautions to prevent such pollution, particularly within the framework of relevant international and port regulations. (The following questions are based on the passage above)
[问答题]High sulphur content increases the risk for corrosion and wear, particularly at low loads, and may contribute to high- temperature deposit formation. The lubricating oil specification must be matched to this. High vanadium content causes hot corrosion on exhaust valves particularly in combination with high sodium content. The corrosion increases with increased temperatures (increased engine output). High Conradson carbon may cause deposit formation in combustion chamber and exhaust system, particularly at low engine output. High content of asphaltenes may contribute to deposit formation in combustion chamber and exhaust systems ( at low loads). Asphaltenes may under certain circumstances, precipitate from the fuel and block filters and/or cause deposits in the fuel system. Precipitating asphaltenes may also cause excessive centrifuge sludge. Heavy fuels may contain up to 1% water at delivery. Water may also originate from the installation bunker tanks. To avoid difficulties in the engine fuel injection system water must be removed. Although low ignition quality produces long ignition delay, advancing the ignition timing makes things only worse; fuel is injected at a lower compression temperature and this will produce even longer ignition delay. Aluminum + Silicon. Fuels may contain highly abrasive particles composed of aluminum and silicon oxides known as "catalytic fines" from certain refining processes. If not removed by efficient fuel treatment, wear down of high pressure fuel pumps, nozzles and cylinder liners in a few hours may expected.