Методичка по английскому языку для ИТС (пр. С.С.Иванов)

The original design had the gas turbine exhaust through a 6 - ft. dia. pipe to a 9 ft. by 6 ft. vertical duct leading to and through the stack. The governing design parameter for the exhaust system centered on the P & WA desire to limit the exhaust back pressure to 6 in. of water gage. The exhaust system was designed to provide a cushion to enable the turbine rating to be increased in the future. Trouble developed immediately when the turbine commenced smoking. The smoking problem was compounded with the low exhaust gas velocity resulting from the generous stack design. This allowed the smoke to waft out of the stack and down onto the deck. It became necessary to reduce the exhaust stack diameter in order to increase the exhaust gas velocity. Into the initial 9 ft. by 6 ft. duct was inserted 6 - ft. - dia. steel exhaust pipe, which resulted in the desired increase in velocity with an increase in the back pressure level to approximately 7 in. H2 O.

Fuel additives ( combustion improvers ) were investigated together with the possibility of modifying the combustion can design to eliminate the smoke. The prospect of having the CG Cutters produce an over - the horizon signature when in turbine mode was not acceptable. P & WA developed an improved burner can configuration together with new burner nozzles and nuts. The burner cans have re - distributed air inlet holes to allow additional air in the primary zone. The new burner cans and burners were installed on one CG cutter with remarkable results; the smoke emitted was now less when cruising in the gas turbine mode than in the diesel mode. It is planned to retrofit the other cutters with this modification.

Notes

stack – дымовая труба

back pressure - противодавление

cushion – воздушная подушка

velocity = speed - скорость

waft out - стелиться

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additives - присадки

combustion can – камера сгорания

over - the - horizon signature – запредельная характеристика

burner can – камера сгорания.

nozzle - сопло

nut - гайка

Gas Turbine Enclosure

Each gas generator is provided with an insulated enclosure, the purpose of which is to attenuate noise and insulate against heat. The enclosure consists of a demountable frame fitted with removable insulated panels with a hinged door on each side for access. The bottom of the enclosure is fitted with adjustable louvers for cooling air intake and the top with two openings connected through dampers via a duct to the engine room exhaust ventilation system. Air at the rate of 12,000 cfm is drawn from the engine room through the bottom louvers and exits through the top openings. The specification limited the outer surface temperature of the enclosure to a maximum of 1500 F.

The enclosure was not originally equipped with a built-in fire-fighting system. Reliance was placed on the engine room fire-fighting equipment consisting of CO2 and water. In addition, the relatively small quantities of oil in the lube and hydraulic oil system were originally thought to be insufficient to require a built-in fire-fighting capability. However, we reconsidered and decided that the large fuel rate (1500 gph) could feed a large fire if a F.O. line were ruptured and ignition occurred.

The coast Guard investigated various fire fighting systems for the enclosure. Foam and water were ruled out because of thermal shock to the turbine casing (up to 10000 F). Dry chemical (purple ―K‖) was ruled out because of the cleaning chore involved after use and the thermal shock of the water required to prevent re-flash. CO2 was found to be the ideal agent for the 500 cu.ft enclosed space resulting from closing the louvers and dampers.

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The enclosures were retrofitted with a CO2 smothering system complete with fire detector and CO2 -actuated inlet and outlet damper shutoff and fuel shutdown valve. The CO2 release is manual and located in the engine room control booth. The follow-on ships have enclosures with a fire wall to separate the turbine hot section from the oil piping as an added precaution.

Notes

enclosure - кожух

demountable frame – разборный каркас

hinged door – шарнирная дверь.

adjustable louvers – регулируемые жалюзи

dampers - амортизаторы

built - in fire - fighting system – встроенная система пожаротушения

lube – зд. смазка

ignition – зд. возгорание.

chore = work

smothering system – система объѐмного пожаротушения

shutoff – выключение, отключение

shutdown – выключение, остановка

valve – клапан

The Clutch

Each gas turbine drives a reduction gear pinion through a flexible coupling and an air - actuated friction - dental type clutch. This clutch incorporates

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friction disks to synchronize, the free turbine shaft with the pinion gear shaft. When synchronized, the dental portion automatically engages to ensure a solid mechanical lockup, relatively free from the danger of a sudden, unexpected disengagement and capable of absorbing maximum load torque.

The Coast Guard has a more stringent clutch plate ( friction disk ) torque requirement than is customary. The specifications required the turbine clutch to have the capacity to engage a stationary propeller shaft with the turbine idling. The torque required for this far exceeds that needed to synchronize the two rotating shafts. This requirement exposed a weak link in the clutch design installed on the first cutter. Repeated casualties due to overheating and warping of the clutch plates were a continuing problem. Once the plates warped, operation in the diesel mode ( turbine clutch disengaged ) caused the plates to rub, thus generating heat and further warping.

The turbine clutches were finally removed and shipped back to the factory to correct design deficiencies. Detailed examination at the factory revealed that some clutch plates were not being adequately lubricated and cooled. Furthermore, the geometry of the plates made them susceptible to warping when heated. Additional oil passages were provided to ensure adequate flow of lube oil to all clutch plates. The plates were also stress - relieved by cutting notches on the id and od edges. Lastly, the internal air tube assembly was redesigned to prevent leakage. A modified clutch was then assembled and, when tested successfully, the assembled unit was scribemarked for optimum indexing of component parts. To further decrease the possibility of over - heating, the time required to engage was increased by adjusting the reducing valve in the supply air line. The clutches were then installed on our first ship and have operated successfully since.

The gas turbine clutches on the eight follow - on ships were of a different manufacture but they also required similar re -design in the area of the clutch plates and the actuating control system.

As a normal operating procedure, the gas turbine clutches will be engaged only with both the turbine and the pinion shaft operating or stopped. However, in an emergency, the clutches have the capability to clutch in a stationary propeller shaft to an idling gas turbine.

Notes

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reduction gear - редуктор

pinion - шестерня

flexible coupling – гибкая муфта

torque – крутящий момент

clutch - сцепление

stationary - неподвижный

idling - холостой ход

warping – коробление, искривление

shipотгружать

stress - relieve – снимать напряжение.

notch – паз, канавка

assembly – зд. в сборе

leakage - утечка

scribe-mark - размечать

result in – приводить в результате к

Gas Turbine Alignment

The alignment of the gas turbine presents special problems because of large thermal growth. The power turbine axial growth, measured at the output coupling is 1/2 in. The gas generator axial growth, measured at the compressor inlet, is 1 1/2 in. The unique feature of the turbine alignment procedure is that, in the uncoupled condition, the power turbine output shaft is unsupported at the coupling end. The nearest supporting bearing is at the

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after end of the last stage turbine rotor. The output shaft extends forward from the coupling into and through the exhaust elbow for a distance of approximately 8 ft. and connects to a flexible diaphragm coupling located adjacent to the last stage turbine rotor. When aligning the gas turbine, the output coupling is supported by a cradle suspended by a spring scale. Experimentation by P & WA has determined that approximately 300 lb. of upward force is required to position the coupling on the axial center line. The alignment of the gas turbine output to the reduction gear input coupling is predicated on a hot (normal running condition) misalignment tolerance of 0.002 in. The large turbine growth might lead one to expect a substantial cold offset misalignment. However, the compensating effects of the reduction gear growth result in essentially zero cold offset. This simplified the alignment procedure; however, after delivery of the first cutter, it was found that, despite careful shipyard efforts, misalignment of approximately 0.010 in., was found to exist. Fortunately, this was within the flexible coupling design capabilities. Though P & WA stipulates a misalignment tolerance not to exceed 0.002 in., the true misalignment tolerance is 0.05 in. because of the presence of the internal diaphragm-type coupling. In the course of examining what would be required to re-align if necessary, we conclude that the large turbine sub-base would have to be repositioned to allow re-alignment. It would be far more convenient to build an alignment adjustment capability into the power turbine trunnion mounts and this should be considered in future designs.

Notes

alignment - центровка

thermal growth – термическое расширение

output coupling – выходная муфта

compressor inlet – входное устройство компрессора

uncoupled condition – в разъединѐнном положении

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unsupported – без опоры

supporting bearing – опорный подшипник

stage - ступень

output shaft – выходной вал

exhaust elbow – выхлопной патрубок

flexible diaphragm coupling – гибкая диафрагмовая муфта

cradle - опора

scale - шкала

misalignment tolerance – допуск на децентровку

cold offset – смещение при охлаждении

re -align – повторная центровка

sub -base – подложка, основание

trunnion – ось качания или поворота

mount - установка

high - speed dash capabilities – высокоскоростные стартовые характеристики

maintenance – техническое обслуживание

C o n c l u s i o n

The large aircrafttype gas turbine lends itself to the requirements of the CODOG configuration. Its high power - toweight ratio and rapid start up capability make it an uncommonly favourable choice for vessels requiring high-speed dash capabilities. Many of the problems encountered with gas turbines and associated systems are a result of adapting to a marine propulsion environment. It is expected that our follow-on ships with the

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modifications described above will be provided with reliable, lowmaintenance gas turbine propulsion.

BRITAIN‘S LARGEST TRAWLER –―LORD NELSON‖

A 238-ft. Stern Trawler Arranged for Part-freezing of the Catch

To meet the challenge brought about by dwindling catches and narrowing fishery limits British distant water trawler owners are investing in vessels of an entirely new design concept with more efficient methods of fishing and equipped with freezing equipment to preserve the catch. In this way the trawler can remain on the grounds until the holds are full. Though initially costly, it is felt that this type of vessel must be introduced if fish prices are to remain at an acceptable level while, at the same time, preserving or improving the quality.

Last month we were able to inspect one of the first trawlers of this type, the ―Lord Nelson‖, recently completed by Rickmers Werft, one of the

Associated Fisheries companies. Although three larger vessels arranged for stern trawling are in service with the British fleet they are also arranged as factory ships and stay on the grounds for up to three months, so that the

―Lord Nelson‖ is the largest British-owned purely fishing trawler now in service. She is also the first distant-water trawler especially designed to freeze part of her catch at sea and is the first British distant-water trawler to be built for stern fishing. There are both wet and refrigerated fish holds and the vessel will be able to remain at sea for longer periods than the normal 21 days for other distant-water vessels.

Propulsion is by a Mirrless Monarch engine driving a bridge-controlled Liaaen variable-pitch propeller and electrical requirements at sea are met by a double generator unit built on to the main propeller shaft.

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2. Early Design Modifications

When the vessel was originally designed and during the early building stages, the main emphasis was still on the wet-fish side. Consequently a trials speed of 15 knots was necessary and this figure determined the minimum waterline length, the speed/length ratio being just under unity. A fishmeal plant was also incorporated in the original design, this being arranged abaft the engine-room. However, while the vessel was still on the stocks, overproduction in Peru caused a collapse in world fishmeal prices. To this factor was coupled the extension of the territorial limits around Iceland and other countries making it clear that the more distant fishing grounds would have to be used with consequently longer trips. Therefore, it was decided to dispense with the fishmeal plant and increase the freezing equipment and cold store capacity. The space occupied by the proposed fishmeal plant and store was converted into a wet-fish hold with a section for liver boilers and an engine store. In addition, the forward wet-fish hold was shortened and the cold store enlarged.

Stern trawling had already been chosen by the owners for the original design as they felt it would provide a more efficient system of fishing and would incorporate a sheltered working space in which to gut and prepare the fish.

The vessel is constructed of mild steel in accordance with, and under the special survey of Lloyd‘s Register of Shipping for their classification 100A1 ―stern trawler‖. It is a two-deck vessel, the second being the freeboard deck.. Consequently, the rules for open shelter decks were adhered to in respect of strength, and trawler rules elsewhere .

Following the builders‘ standard practice since 1950 , the hull is allwelded and was erected on the berth in sections of up to 35 tons in weight .

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Due to the vessel‘s relatively high speed , the shell plating forward of the fish rooms from the bottom up to the upper deck is increased in thickness. A cellular double bottom is arranged below the forward fish room , cold store and forward part of the engine room.

The stern trawling arrangement is of Rickmers Werft‘s usual pattern , developed and improved since 1956, the ―Lord Nelson‖ being the 10th stern trawler built by this yard.

The electric trawl winch, which is powered by a 350-h.p Siemens electric motor, has two large drums with a capacity of 1200 fathoms of 3 in. circ. trawl warp and two small drums for the bridles.

On emptying the cod-end, the catch is fed down to the working deck through a pneumatically operated hatch at the head of the ramp, which opens or closes in about five seconds. After gutting, the fish are taken forward by a system of conveyer belts through an automatic fish washing machine either into the fish receiving troughs for the freezers , or into the forward wet-fish hold. When the catch is large, the after wet-fish hold is used as a buffer store from which the fish can afterwards be removed by a second conveyer and fed back into the normal system. The conveyer belts and fish-washing machine were supplied by Walker and Co., stainless steel being used in the construction of the troughs and drum.

Notes

Stocks – стапель

Trawl warp –вайер рыболовного трала

Bridles - стропы

Trough-лоток

Fishmeal plant-установка для изготовления рыбной муки

Fish groundрайон рыбного промысла

To dispense with –обходиться без

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