Engineering Abstracts 1959
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Engineering Abstracts from 1959
Project for the Machinery of a 65,000-ton Nuclear Tanker
A first design of a nuclear powered ship was made at Gotaverken Shipyard during the autumn and winter of 1956. The purpose was primarily to obtain a subject for further discussions, detailed investigations and calculations. The project was intended for a tanker of 65,000 tons d.w. with a machinery power of 30,000 s.h.p., and the reactor was of the boiling water type with the steam formed in the core and fed directly to the turbines.
The main propulsion machinery should at normal load produce 30,000 s.h.p. divided between two propellers. This gives a trial speed of 18,25 knots, and a corresponding speed in service of about 17,75 knots. The power transmission from the turbine to the propeller shaft should be electrical via two independent turbogenerators with 11,7 MW coupling power each and two propeller motors with a shaft power of 15,000 s.h.p. each. For propulsion in passages, where the reactor is forbidden to operate, there are two high speed Diesel alternators of 2,000 kW, which are expected to give the ship a speed of about 9 knots.
For production of all auxiliary power needed there are 6 Diesel alternators, each of 400 kW. These are running the pumps of the reactor, the pumps and exciters of the turbogenerators and the rest of the auxiliary machinery on the ship. Two oil fired header type boilers, with a total capacity of 34 tons of steam per hr. of 1701b. per sq. in. gauge are supplying heat to the heating coils, etc. The machinery is located in two engine rooms, one amidship and one aft. In the midship space the reactor with its pumps and the main turbogenerators with their condensers, pumps, etc., are placed. In the aft room are located the propeller motors, the auxiliary Diesel engine, the emergency Diesel engines, the steam boilers and all other conventional equipment. The reactor control room is situated in connexion with the aft engine room. The equipment for water purification, etc., for the primary system is located in a deck house above the midship engine room. With the arrangement described above, several advantages are obtained. Thus, there will be a complete separation of those spaces which are containing radioactive material or might be filled with radioactive material in connexion with a failure or an accident, and those spaces which people normally occupy, i.e. cabins, bridge and the remaining part of the machinery.
In the first mentioned spaces admittance will not be allowed during reactor operation. The reactor is normally producing 132 tons of saturated steam per hour at a pressure of 5851b. per sq. in. gauge, corresponding to a thermal power of 100 MW. Four circulating pumps, located inside the primary shield, provided a 30-fold circulation of the reactor water. The fuel elements are made up of plates of uranium metal canned in Zircaloy. The large cooling area means that the demands upon the purity of the water need not be exaggerated and the materials in the plant might be of normal quality.
As nobody is allowed to enter the midship space where the reactor is located during operation, the primary shield around the reactor can be of relatively small weight, about 750 tons, instead of normally 1,000 tons. However, 20 minutes after shut down the reactor space might be occupied for an unlimited time without any risk of over exposure. In respect of weight a boiling water reactor is particularly favourable; as the pressure vessel is relatively light, a “pressurizer” is not needed, and there are no heat exchangers. The total machinery weight will therefore not exceed that of a Diesel or turbine plant with more than 500-1,500 tons. The nuclear ship has accordingly a greater real loading capacity even on the Suez route, and on the Cape route the loading capacity is 10 per cent greater than that of a conventional steamship. In this case the cost per ton loading capacity is almost the same as that of a steamship. A comparison with a Diesel ship, however, turns out more unfavourable.
—L. Nordstrom and J. Thunell, International Shipbuilding Progress, August 1958; Vol. 5, pp. 365-376.
German Multi-engine Propulsion Proposal
An unusual design for ship propelling machinery developing 24,500 s.h.p. on a single shaft has been prepared by Maschinenfabrik Augsburg-Nurnberg A.G. in close cooperation with shipyards and tanker owners. The use of multiple engine propulsion has been advocated for a number of years, and examples of this form of propulsion will be found in a large number of ships. As an alternative to the direct coupled engine, the geared Diesel engine is the most satisfactory form of indirect drive, for it offers several advantages to the prospective user. These include: a saving in space; increased reliability, as there is very little chance of all engines breaking down at once; the ability to overhaul the engines while at sea; and the advantage that for economical reasons one or more of the engines can be shut down when the ship is light.
The project prepared by M.A.N. is unusual because it is a combination of geared Diesel and Diesel-electric drive. The weight of the complete installation including Diesel engines, gears and couplings, electric generators and motors, without the auxiliary equipment, is about 1,240 tons. The entire machinery can be accommodated in the same amount of space as that required for a turbine installation of similar capacity, without having to extend the hull. The installation consists of two M.A.N. engines, each of 7,000 b.h.p., coupled to the shaft through electro-magnetic couplings or hydraulic couplings and gearing; and two 6,000-b.h.p. engines on flats above and to the side, each driving an alternator which supplies current to electric motors coupled to the main gearbox. With this system, various combinations of drive may be obtained, each having different economic advantages, depending on the amount of cargo being carried, and other circumstances. It must be admitted, however, that the fuel consumption of this proposed scheme would be about 0 0211b. per h.p. higher than that of a slow running engine. For one reason the fuel consumption of the high speed engine is higher because of its slightly lower efficiency, and for another the gearing losses and electrical transmission losses must be taken into consideration. The M.A.N. engines used for the scheme would be suitable for operation on heavy fuel, and would be of the crosshead design with complete separation of cylinder block and crankcase.
—The Shipping World, 24th September 1958; Vol. 139, p. 283.
Pielstick-engined Passenger Vessel with Alternative Speeds
The keel was laid last month at the Forges et Ch. de la Mediterranee, La Seyne, of an unusual passenger vessel being built for the Cie. Generale Transatlantique, to be operated, according to season, either on the Nice-Corsica or the Marseilles-Corsica service.
She is a ship of 4,500 gross tons, to be equipped with 8,000 b.h.p. Pielstick machinery and will have a service speed of 18 knots or 14½ knots, according to the requirements, namely, whether on the Nice or Marseilles run. The four 2,000-b.h.p. SEMT-Pielstick engines are coupled to two shafts through an ASEA electro-magnetic clutch, and with two engines in operation the lower speed of 14½ knots will be easily maintained. The length b.p. is 326ft. 5in., the moulded breadth 51 ft. 10 in. and the maximum draught 15ft. 7in. The deadweight is 1,000 tons and in addition to accommodation for 114 first class, 224 second class and 700 third class passengers, 80 motor cars can be carried, of which 44 will be accommodated in a closed garage. The name of the ship will be Napoleon.
—The Motor Ship, November 1958; Vol. 39, p. 374.
15,000-s.h.p. 26,700-ton Soviet Whale Factory Ship
Details are now available of the first large whale factory ship to be built in Russia. She is under construction at the Nikolaiev yard and is named Sovietskaya Ukraina. The displacement will be 44,000 tons, the length overall 217,8 m., the breadth 27,8 m. and the loaded draught 10,6 m. She is propelled by two 7,500-b.h.p. Burmeister and Wain six-cylinder turbocharged units running at 115 r.p.m. and the speed will be 16 knots. For the supply of current, four 750-kW Diesel engined generators are installed. The crew and factory workers will total 487 men. A helicopter will be carried on deck.
To operate with the factory ship there will be a number of 18-knot whalers constructed, also at Nikolaiev, each 63-6 m. in overall length with a breadth of 9-5 m. and a draught of 4-41 m. Diesel electric machinery of 3,100 b.h.p. is to be installed in each ship and they could operate for 25 days without refuelling.
—The Motor Ship, November 1958; Vol. 39, p. 374.
Notes on the Jerk System of Fuel Injection
The paper aims at drawing attention to certain features of the injection of fuel into the cylinders of compression ignition engines. It is in effect a continuation of that contributed to the Institution of Mechanical Engineers by one of the authors in 1940. Since then data have been accumulated and certain new facts have come to light. As in that paper, attention is confined to the jerk system of fuel injection employing independent pumps and injectors. The authors refer therefore in the first place to the effect on the injection process of details of the design of the nozzle valve (differential needle).
They deal secondly with the effect of the elasticity of the fuel trapped between the pump delivery valve and the nozzle needle valve. From this they build up calculated indicator diagrams for the fuel delivery pipe and then arrive at figures for calculated injection period under various conditions. In these calculations consideration of pipe surges is omitted. They then go on to recommend a procedure for determining the most favourable particulars and dimensions of the fuel injection equipment in any particular engine. In the course of the paper a number of numerical calculations are made to illustrate the influence of the several variables on the injection process.
They are based on certain simplifying assumptions made to reduce the calculations to manageable proportions. It is stressed therefore that the numerical results derived are indicative of trends and cannot be accepted as representing actual facts.
—Paper by W. A. Green and G. R. Green, read at the General Meeting of the Diesel Engineers and Users Association, 20th November
Direct Bridge Control of Ships’ Engines
Direct bridge control of ships’ engines has been in operation in the United States of America, as well as several other countries, for some time. In order to obtain the maximum benefit from such a system, of course, two or more operational positions are required on the bridge or superstructure.
The tug Flying Dipper, owned by the Clyde Shipping Co., Ltd., of Glasgow, and powered by a British Polar Diesel engine, is the first vessel to work in United Kingdom waters using a full application of pneumatic control equipment, and she has four operational positions on the bridge.
The vessel can also be controlled direct from the engine room. Single lever control is provided at the four bridge positions and the interlock features of the controls prevent any mishandling of the engines. Westinghouse type-2A2A Controlair valves are installed at all these single lever control points. Selection of direction is made in the first movement from the neutral position and effected by passing an air signal down the ahead or astern signal line, as required.
This operates a three-position cylinder mounted on the gearbox, and a pneumatic interlock connects the throttle signal line from the Controlair valve to the control port of a Pneudyne positioner mounted on the main engine. This unit is of the servo pattern and provides accurate positioning of the engine throttle in response to the signal given from the bridge. By means of a time delay feature, the engine may be opened up at a .maximum predetermined speed. A pneumatic time delay unit is built into the gearbox control system to ensure that when going from ahead to astern, or vice versa, there is a short pause in the neutral position before the new drive position is selected. To change from one control position on the bridge to another is simple.
The only action required is to depress the changeover button at the new position until the air supply is registered on the air pressure gauge, mounted locally. Full control is then available at the new position. To change control between the engine room and any bridge position, the engineer operates his locally mounted Rotair valve.
While the Flying Dipper is fitted with special control desks incorporating the pneumatic valves, it is claimed that the equipment is suitable for operation by a conventional ship’s telegraph head. Whaling ships, Great Lakes ore carriers, spirit tankers, bulk sugar carriers, a Canadian Shell tanker and Admiralty frigates and tugs are among the ships fitted, or being fitted, with pneumatic control equipment.
—The Shipbuilder and Marine Engine-Builder, November 1958; Vol. 65, p. 630.
Engine Noise Investigation
The demand for higher operating speed and power, combined with light weight construction, has resulted in a considerable increase in the noise level of modern naval Diesel engines. To safeguard the health of crews and to ensure that orders can be heard and understood, the Admiralty Engineering Laboratory at West Drayton, Middlesex, is devoting considerable attention to the design of efficient silencer systems.
Since trials and tests of actual Diesel engines would be expensive, slow and very noisy, special laboratory techniques have been developed. One method which has given excellent results involves the use of an unusual means of noise simulation. Instead of attempting to reproduce the noise frequency spectrum of a given engine, “white” noise (of equal loudness at all frequencies) is fed into an experimental silencer, whose “exhaust” terminates in an anechoic chamber.
A microphone in the chamber feeds an a.f. analyser by means of which the output noise spectrum is plotted. The extent and characteristics of the attenuation given by the model under test can thus be established, in comparison with a datum spectrum obtained by replacing the silencer with a straight pipe.
—British Communications and Electronics, December 1958; Vol. 5, p. 954.
Buchi Telescope-valve System on Four-cycle Diesel Engines
The telescope valve engine is an improved four-stroke cycle internal combustion engine, built with or without pressure charging, preferably combined with scavenging to sweep out the exhaust gases from and to cool the combustion space. A swirl is generated in this space for a simple and perfect fuel distribution and combustion. Such an engine design may be adopted for internal combustion engines of any size and use, and of any cylinder arrangement. The telescope valve system and its special design of the cylinder head, combustion chambers, valves, fuel injection system and valve control mechanism are also favourable for other than Diesel engines, such as gas, gasoline or heavy fuel engines.
Two valves are provided, one coaxially arranged within the other; one of them serving for admitting the charge and the other for discharging the exhaust gases. This system, the so-called telescope or concentric valve system, by means of its concentric valves in conjunction with the form of the upper part of the piston closing the combustion chamber, in its outer dead centre position gives the combustion chamber the shape of a relatively deep disc while the valves are closed.
To obtain ample flow areas relatively adjacent to the valve openings or seats, a corresponding form of the combustion space is chosen in the cylinder head and/or in the piston top. Thus, a circumferential wall is formed around the combustion chamber which conducts the intake air flowing from the inlet valve opening to that of the exhaust valve. Furthermore, the combustion chamber and the cylinder head on its inner side may be so shaped that when the piston is in T.D.C. position and both valves are open, the inner valve disc extends to a corresponding complementary portion of the piston head and an annular passage is formed between the valve disc and the adjacent walls.
The valves and its discs are so shaped that the charge entering through one of the valves is led to the other valve by flowing around the outer valve disc, thereby sweeping through the whole combustion chamber. The valve bodies, the inner wall of the combustion chamber and the surface of the piston head may be given such a shape that, with both valves open, passages of smooth configuration for the scavenging air are formed which provide approximately constant stream areas.
The seat of the inner valve may be recessed so deeply into the outer valve body, and the part of the inner valve body projecting into the combustion chamber is rounded to such an extent, that the scavenging air is deviated gradually and regularly from one valve opening to the other. The surface of the piston head may be advantageously so shaped as to surround, in the T.D.C. position, the surface of the projection on the exhaust valve disc in the open position of this disc. The charge either can be admitted around the outer valve and discharged through the inner annular space between the two valves or vice versa.
Moreover, to the entering charge may be imparted advantageously a rotatory movement about the valve axis, by means of tangential or spiral entrance-surface portions or separate guide surfaces. Alternatively, for effecting this whirling movement the connecting ribs between the stem and the sleeve of the outer valve can be utilized, which may be provided with helical surfaces. Because of this design, the insides of the cylinder head and of the piston top surrounding the combustion space are absolutely symmetrical to the cylinder axis and have a minimum of relatively plain and regular surfaces.
For a sufficient opening of both valves, even during the scavenging period, no cuts or the like are necessary in the piston head or in the cylinder liner for these valves when the piston is near or in its T.D.C. position. The fuel injector or injectors are located in such a manner that the injected fuel arrives uniformly distributed in the combustion space. The fuel injection device or devices inject the fuel in a direction which is transverse and, if necessary, also oblique to the cylinder axis.
—A. J. Buchi: paper contributed to the Oil and Gas Power Division Conference, 1958, of the American Society of Mechanical Engineers, Gas and Oil Power, December 1958; Vol. 53, pp. 325-328.
Cylinder Wear in Marine Diesel Engines
If in a marine Diesel engine chromium plated liners are used and if this engine runs on a fuel with a high sulphur content, a difference in potential between the cylinder wall and the piston can be measured. This potential difference is due to the existence of a galvanic cell formed by the chromium plated wall and the cast iron piston rings with an acid oil film on the wall as electrolyte.
From the results on a test engine it could be calculated that an important part of the corrosive wear of the chromium plated liners is due to the action of this cell. The test engine used for these measurements was a stationary two-cylinder, single acting, two-stroke crosshead Bolnes engine with a bore of 190 mm. This medium speed engine (430 r.p.m.) with 50 h.p. per cylinder is very suitable for experiments on cylinder wear because of insensitivity to fuel quality and the completely separated cylinder lubrication.
As the composition of the oil film on the cylinder wall is important in the study of cylinder wear, drip trays were fixed to the bottom of the liners with drainpipes leading outside the engine. In this way the cylinder oil that runs down from the wall could be collected at regular intervals.
The samples were analysed at once on their water and sulphuric acid content. Another modification in the construction of the engine was necessary to make sure that the measured differences in potential originated indeed from the system piston cylinder. Therefore the piston has to be electrically insulated from the piston rod. It was found that as soon as the engine runs under normal conditions of speed, load and cooling water temperature, the cylinder wall is about 300-400 mV negative relative to the piston near T.D.C. and becomes positive at about 100 mm. from the top. Somewhat farther than halfway down the expansion stroke the difference in potential is negligible.
—W. A. Schultze, International Building Progress, December 1958; Vol. 5, pp. 566-576.
The Stork Marine Diesel Engine
The Stork marine Diesel engine is a single acting two-stroke engine, with uniflow scavenging by means of scavenging ports in the cylinder liner, and four poppet exhaust valves in the cylinder cover. This type of engine is particularly suitable for turbocharging by means of exhaust gas driven turboblowers and so the majority of these engines are now ordered turbocharged. The last normally aspirated engine ordered was delivered last year. There are now three standard sizes of this engine, namely: —
| Bore
mm |
Stroke
mm |
Output per cylinder | |
|---|---|---|---|
| Small | 540 | 1150 | 500 - 520 b.h.p. at 135 - 145 r.p.m. |
| Medium | 630 | 1350 | 800 bhp. at 132 rpm |
| Large | 750 | 1500 - 1600 | 1200 - 1300 bhp at 115 - 118 rpm |
This range thus covers outputs from 2,500 b.h.p. in five cylinders of 540-mm. bore up to about 15,000 b.h.p. in 12 cylinders of 750-mm. bore, all turbocharged. Normally aspirated engines of the small bore, but with a stroke of 900 mm. have been delivered for an output of 375 b.h.p. per cylinder at 155 r.p.m., whereas for ratings above 15,000 b.h.p. a new size of 850-mm. bore is being developed for an output of 20,000 b.h.p. in 12 cylinders.
The engine frame is a rigid assembly of bedplate, columns and cylinder blocks, vertically connected by long tie bolts from the top of the cylinder block to the lower part of the bedplate. The tie bolts are tightened hydraulically and arranged to take the combustion forces and thus relieve the frame of tensile stresses. The jerk type fuel pumps, one for each cylinder, are mounted over the camshaft as near as possible to their relative cylinder covers, thus allowing high pressure fuel lines of minimum length, which is important for the use of residual fuel. The fuel pump is operated from the fuel cam in the normal way by means of a roller cam follower in a roller holder.
The pump plunger is lapped in a case hardened steel barrel, both easily renewable. The pump is provided with a suction and delivery valve; fuel delivery is controlled at the end of the pump stroke by mechanical lifting of the suction valve by means of a gear with levers and push rods, actuated by the roller holder. The fuel delivery is regulated by one of these levers pivoting on an eccentric control shaft. As the suction valve has to be opened against injection pressure, it is provided with a small pilot valve, opening 0'5 mm. prior to the main valve and thus efficiently releasing the pump pressure and so decreasing the load on the control gear. The delivery valve is provided with a built-in release valve, opening at a pressure difference of 100 kg. per sq. cm. between the h.p. fuel line and pump chamber, thus ensuring immediate pressure release in the h.p. fuel line at the end of the pump delivery and so preventing any risk of after-dripping of the fuel valve.
The fuel valve is of the normal needle valve type, which is spring loaded and opened by the fuel pressure. The engine is reversed by means of starting air, operating a reversing piston. The reversing piston effects the turning of a reversing shaft, running parallel to the camshaft, which moves the cam followers free from the cams prior to the axial displacement of the camshaft, which is also effected by the reversing piston.
The engine is turbocharged by means of exhaust driven turboblowers (of the gas entry type); they are entirely self-regulating. The pulse system of turbocharging is used, which means that the turbine energy is derived from the kinetic energy of the exhaust gases (speed) in addition to their static energy (pressure and temperature). Maximum perfection of this system has been attained by the use of one turbocharger for two adjacent cylinders and by arranging them at cylinder head level to achieve the smallest possible volume of exhaust piping between the cylinder cover and exhaust turbine.
As, moreover, a rapid release of the exhaust gases is of paramount importance for this system, four exhaust valves have been provided for each cylinder. The exhaust pulse diagram, Fig. 12, clearly demonstrates the importance of the exhaust pulse energy in comparison with the static energy and also the possibility of a high exhaust peak pressure during pre-exhaustion in combination with a sufficiently low exhaust pressure to ensure efficient scavenging of the cylinder.
The diagram also shows the requirement of a crank angle difference of at least 120 degrees between the cylinders which are connected to a common turbocharger in order to avoid the exhaust pulse of one cylinder disturbing the scavenging process of the other. This requirement can be satisfied by a crank sequence combining satisfactory engine balance with normal torsional vibration characteristics.
—Paper by A. Hootsen and E. A. van der Molen, read at a meeting of the Institution of Engineers and Shipbuilders in Scotland on 24th February 1959.
Oil Motor Pump Drive
A set of engine cooling and lubricating pumps driven hydraulically from the main engine are to be installed in the oil tanker Regent Eagle, 19,000 tons d.w., now under construction by the Blythswood Shipbuilding Co., Ltd. The Regent Eagle will be powered by a six-cylinder Doxford type Diesel engine and the hydraulic installation is being supplied and has been developed by Stothert and Pitt, Ltd.
The use of hydraulically driven salt and fresh water cooling pumps has previously been largely confined to Danish-built vessels, and the system has been installed in a number of vessels fitted with Burmeister and Wain main engines. The installation, which has been built by Stothert and Pitt, Ltd., consists of a generator pump, a motor pump, a salt water pump and a fresh water pump. The generator pump will be located alongside the propeller shaft and will be driven by Renold’s chains through a step-up gearbox. The direct drive arrangement offers a considerable saving in fuel by taking the load off the ship’s generators. The additional fuel consumed by the main engine is a good deal less than what would have been used in the auxiliary set, due to the higher efficiency.
There is also the benefit of simplicity with the direct drive arrangement. The arrangement of the installation is shown on the accompanying drawing. The generator unit consists of a Stothert and Pitt horizontal, positive acting, screw displacement pump of their unidirectional flow design, having internal bearings and timing gears, and fitted with mechanical seals. The pump body is split and a pilot operated pressure relief valve with an external exhaust flange is fitted. The speed of the pump is 745 r.p.m. with a discharge pressure of about 3001b. per sq. in., the output being 250 tons per hr.
The motor pump is an S. and P. horizontal, positive acting, screw displacement pump having internal bearings and timing gears, with shafts extended at each end for coupling to the water pumps. The suction and delivery branches are in the bottom half of the body, which is split through its centre line, the pump covers being designed to withstand 601b. per sq. in. working pressure.
Two mechanical seals are fitted and the pump is equipped with a relief valve having an external flange for returning oil back to source. This pump receives oil from the generator at approximately 300 lb. per sq. in. and delivers it at 1,450 r.p.m. at 601b. per sq. in. at a rate of 250 tons per hr.
—The Shipping World, 29th April 1959; Vol. 140, p. 437.
Dutch V-Type Two-stroke Diesel Engine
The N.V. Machinefabriek “Bolnes” v.h. J. H. van Capellen has developed a V-built two-stroke Diesel engine available in both naturally-aspirated and turbocharged types and in units from six to twenty cylinders. The first engine, a 1,000-h.p. unit, will be placed in the suction dredger Vlaardingen, under construction for Adriaan Volker, N.V., where it will drive the sand pump. The new V-built Bolnes engine is constructed in accordance with the standardized system adopted by the builders after the war and which makes use of welded construction on a large scale and of 50-h.p. units enabling the construction of in-line engines ranging between 100 and 500 h.p., that is, two to ten cylinders. For larger outputs twin sets are available. The V-built engine is available in six to twenty cylinder units up to a maximum output of 1,500 e.h.p. at 475 r.p.m., when supercharged. Twin arrangement enables outputs of up to 3,000 h.p. Like the in-line type of engine, the V-built version is of the crosshead type which uses the cylindrical crosshead and guide as a reciprocating scavenge pump. Uniflow scavenging is employed and circulation cooling is achieved by a pipe cooler. The fuel consumption is 170 grammes per h.p. per hr. and lubricating oil consumption 0’8 grammes per h.p. per hr. The bore is 190 mm. and the stroke 350 mm. The engine has an all-welded single-piece frame with box-type girders. The front columns are of steel and can be taken away for the removal of the built-up crankshaft.
—Holland Shipbuilding, January 1959; Vol. 7, p. 30.
Location of Temperature Rise in Engine Crankcases
A sensitive instrument for detecting temperature rise in any of the main bearing and main working surfaces within the crankcases of Diesel or petrol engines has been developed by the Graviner Manufacturing Co., Ltd.
The apparatus is suitable for installation on all types of Diesel and petrol engines up to 500 h.p. per cylinder, either supercharged or normally aspirated, whether direct or remote-controlled, up to a maximum of 3,000 h.p. The detector is highly suitable for use on auxiliary generators or on the main propulsion engines of smaller vessels. An advantage is that a warning signal may be located, if necessary, away from the apparatus in the engine room, so that it can be ranged alongside other remote control equipment, for example in the wheelhouse.
The Graviner detector operates on the principle of measuring the density of oil mist drawn continuously through two separate tubes of precisely similar dimensions. A beam of light projected down the axis of both tubes energizes two photo-electric cells located at the ends of the tubes from the common light source. The electrical output from each photo-electric cell is proportional to the density of light falling on the surface of each cell and, as their output is opposed electrically, no current flows when the oil mist column contained in the tubes is of equal density.
However, when a difference occurs in the density of the mist contained in one tube relative to the other, the light beam in that tube becomes more obscured and, consequently, the system becomes electrically out of balance. An electric current then flows and operates a sensitive relay which in turn causes an audible and visible warning to occur when the differential e.m.f. reaches an optimum value. The ability of the detector to measure the extremely small quantity of oil mist associated with a corresponding rise in temperature, provides a continuous safeguard against any mechanical trouble which might arise from oil starvation or dilution; in fact, from any set of circumstances which, if allowed to continue, would utimately lead to a major breakdown. This means that apart from the detection of overheated rotating or reciprocating engine components, the high sensitivity detector will quickly sense a broken piston ring.
Furthermore, the extreme sensitivity of the apparatus provides positive protection against crankcase explosion by warning against generation of a dangerous concentration of oil mist within the crankcase.
—The Shipping World, 8th April 1959; Vol. 140, p. 362.
Pressure-charged Engines
Two medium speed Diesel engines in the VCB range manufactured by Messrs. Ruston and Hornsby, Ltd., of Lincoln, have recently been pressure charged and are now known as class VCBX engines. Available in five and six-cylinder sizes, these 5 and 6VCBX engines have a bore of 8in. and a stroke of 10in., providing a power range of 255 to 330 b.h.p. (B.S. rating) at speeds of 600/650 r.p.m. Based on the well proved VCB engine, and incorporating an exhaust turbocharger, the up-rated engines extend the overall power range of the VCB class to 350 b.h.p., giving a total coverage of 102 to 330 b.h.p. in six engine sizes of the same cylinder dimensions, with a wide measure of interchangeability of components between the normally aspirated and pressure charged engines.
The pressure charger employed consists of a single-stage centrifugal blower driven by an exhaust gas turbine and is air cooled. Mounted on the exhaust side of the engine, the pressure charger is lubricated from the main engine lubricating oil system. Apart from embodying a turbocharger, and the arrangement of the piston and camshaft to suit the timing of a pressure charged engine, the VCBX class is the same as the VCB engines, which enables complete component interchangeability to be maintained. As well as providing an extended power range in six engine sizes, with interchangeable components, the pressure charged units enable a lighter power unit to be installed where weight is an important factor. The pressure charged engine weighs little more than the equivalent size normally aspirated engine, giving a most favourable power/weight ratio for an engine of its type. The 5VCBX weighs 6 tons, and the 6VCBX, 7 tons. The class VCBX pressure charged engines are also suitable for marine propulsion or for auxiliary duties and are designated VCBXM and VCBXZ. The basic details of these types are given in Tables I and II.
| Engine | RPM | 5VCBXM | 6VCBXM |
|---|---|---|---|
| Maximum service HP at gearbox
output coupling |
650 | 256 | 307 |
| 600 | 238 | 285 | |
| Maximum continous HP at gearbox
output coupling |
650 | 230 | 277 |
| 600 | 213 | 256 |
| Engine | RPM | 5VCBXZ | 6VCBXZ |
|---|---|---|---|
| Continous Service HP | 650 | 276 | 330 |
| 600 | 255 | 306 |
—The Shipbuilder and Marine Engine-Builder, February 1959; Vol. 66, p. 113.
Propulsion System for Boats
This invention relates to an engine mounted inboard of the boat which drives a screw propeller so mounted on a support that the axis of the propeller is movable relative to the fore and aft axis of the boat for steering, the support itself being pivotable about a horizontal axis to lift the screw propeller clear of the water. In Fig. 1 the engine shaft extends in a fore and aft direction into the lower part of the chain case (36) to carry a chain sprocket (44). The shaft (29) which extends through the arm (15) of the L-shaped member carries another chain sprocket (45); this sprocket, when the L-shaped member lies within the chain case in the same plane as the sprocket (44) being adjacent with the upper end of the chain case. A sprocket chain (46) runs over the two sprockets. Two arms (47), pivotally mounted in the chain case and extending downwardly from their pivotal mountings, carry at their free ends sprockets (48) which engage the chain (46) inside its loop between the sprockets (44 and 45), the arms (47) being acted on by springs (49). The latter tend to urge the arms upwardly and outwardly. The upward and outward movement of the arms (47) is limited by stops (50) so as to ensure that they move through equal distances. It will be apparent that the propeller (26) can be lifted out of the water by rocking the L-shaped member (15, 16) rearwardly and upwardly about the trunnions (17) and such rocking movement will cause the sprocket (45) to swing downwardly and rearwardly. The upper part of the chain loop will tend to move downwardly with the sprocket (45) introducing slack in the chain (46) which will be taken up by upward movement of the idler sprockets (48). Ultimately, when the upper part of the chain (46) extends in a substantially straight line between the sprockets (48), as indidated in dotted lines in Fig. 2, the sprocket (45) will move away from the chain and the driving connexion between the engine and the propeller will be broken.
—British Patent No. 815,182, issued to E. J. Clerk. Complete specification published 17th June 1959.
Development of Borsig-Fiat Engine
The Buries Markes motor ship La Selva, is equipped with a Borsig-Fiat engine with six cylinders, 680 mm. in diameter, having a piston stroke of 1,200 mm. and a normal output of 4,750 b.h.p. at 130 r.p.m. The fuel used is Bunker C, up to 3,500 sec. Redwood I at 100 deg. F. During the shop trials, an output of 3,550 b.h.p. was attained at 118 r.p.m., with a mean effective pressure of 5-2 kg./sq. cm., when the turbochargers were out of action and air was drawn in directly from the engine room to the piston scavenge pumps.
This output corresponds to 75 per cent of the full load power according to the propeller curve, whilst the m.e.p. value is similar to that with the unsupercharged engine. The exhaust temperature before the turbines did not exceed the normal value of 320 deg. C. and the change over from non-turbocharged operation to turbocharging could be made in a very short time.
Thus, all that was needed to attain 75 per cent output without turbocharging was to lock the turbocharger rotors and remove two manhole covers. Further developments have been made in this model, the speed being raised to 140 r.p.m. and the mean pressure to 6-86 kg./sq. cm. Under these conditions the engine has an output of 5,580 b.h.p. The maximum output of 6,300 b.h.p. or 1,050 b.h.p. per cylinder at about 146 r.p.m. is attained with an m.e.p. of 7-4 kg./sq. cm., corresponding to a mean piston speed of 5-8 m./sec. This is the load which the engine is capable of delivering on the test bed and sea trials for a period of three hours. The rated cylinder output of 930 b.h.p. at 140 r.p.m. with an m.e.p. of 6-86 kg./sq. cm., is that for which the engine is designed on the basis of the prevailing rules of the classification societies. The recommended output for continuous service is 80 per cent to 95 per cent of the rated output, according to the actual service conditions, namely, length and severity of the voyages, the frequency and duration of harbour stops, the ambient conditions of the engine room, the quality of fuel and the state of maintenance of the engine. The Borsig-Fiat engine is exhaust turbocharged on the constant pressure series principle, the two exhaust turbochargers being of the BBC.VTR 500 type with voluted gas intakes. They are arranged ahead of the crosshead driven double acting piston scavenge pumps, the total volume of which is about 1-3 times that of the power cylinders. During the trials at the works, it was ascertained that the proportion of the compression work of the turbochargers increases with increasing engine load, while the proportion of the compression work of the engine driven scavenge pumps decreases. This characteristic is desirable from the standpoint of engine efficiency. At full load the turbochargers provide about 75 per cent of the total work required for the compression of the charging and scavenge air. Upon starting, when accelerating and in the low speed range, the piston scavenge pumps provide most of the air supply because the turbochargers do not then deliver their full capacity. In the lower speed ranges, as well as at higher speeds, the engine is readily responsive, with a smoke free exhaust. Detailed results of the tests of the 4,750-b.h.p. engine in the La Selva are shown in Fig. 2, whilst in Fig. 3 the results achieved with the engine after the further development are indicated. They show a total increase of 17-5 per cent, from 4,750 to 5,580 b.h.p., with a simultaneous rise of 130 r.p.m. to 140 r.p.m., or 7-8 per cent and a boost in b.m.e.p. from 6-3 kg. per sq. cm. to 6-86 kg. per sq. cm., or 9 per cent. The exhaust temperatures of the stepped-up 5,580-b.h.p. engine are 10 per cent higher whilst the charging air temperature after the blowers and before the scavenge ports, as well as the air pressure before the latter, have fallen slightly in spite of the increased boost. The ignition pressure of 65 kg. per sq. cm. when running on Diesel oil (60 kg. per sq. cm. when burning heavy fuel) remains the same. These improvements were rendered possible through higher efficiencies of the turbochargers, and improved adaptation of these blowers to the engine’s operating conditions. This also explains, for the most part, the reduction in specific fuel consumption from 164 gr. per b.h.p. per hr. to 156 gr. per b.h.p. per hr. or 4-7 per cent.
—The Motor Ship, May 1959; Vol. 40, pp. 86-87.
24,000-b.H.p. Diesel Plant for Supertanker
In conjunction with a shipbuilding concern and a shipping company, the M.A.N. have put forward plans for the propulsion machinery of 24,000 b.h.p. for a supertanker. The four engines are of standard M.A.N. two-stroke type with 25 per cent turbocharging, the cylinders having a diameter of 570 mm. and a piston stroke of 800 mm. The speed is 225 r.p.m. The installation comprises two engines each of 7,300 b.h.p. driving a single shaft through hydraulic or electromagnetic couplings, and two engines of 6,000 b.h.p. in the wings and on a platform above the engine room floor, each driving an alternator supplying current to two 5,400-b.h.p. electric motors driving the same shaft through gearing.
The total service output is 24,000 b.h.p. Current for the auxiliaries and for other ship requirements at sea is taken from the Diesel alternators so that no other Diesel generating plant is needed when under way. The four vertical cargo pumps are electrically driven, the electric motors being installed in the engine room. There are two Diesel generating sets for harbour and emergency duties and one gas turbine driven generator. The plant is installed in an engine room of the same size as that required for steam turbine and boiler plant. The fuel consumption is not as favourable as with the slower running, direct coupled units, the additional expenditure being about 10 gr./b.h.p.-hr., but it is considered that the saving compared with steam turbine plant is so great that this factor is not of importance.
—The Motor Ship, April 1959; Vol. 40, p. 51.
Torque Transfer Coupling
An interesting feature of the new range of Ruston high pressure turbocharged four-stroke engines is the new type flexible coupling with which they are fitted. These torque transfer couplings, developed by Metalastik, Ltd., are designed expressly to provide an effective and economical solution to the problem of resonant torsional vibration and the serious consequencies arising from it in marine and other installations.
The Metalastik coupling is said to provide initially a very low stiffness with a much higher value for a predetermined torque. The ratio of initial and final stiffness can be varied as required, this being enabled by the fact that for low torques, rubber, loaded in torsional shear, is employed, while for higher torques separate rubber buffers, loaded in compression, provide the greater degree of stiffness required. There is a rather rapid change from low to high stiffness but the characteristics of the coupling can be modified to give a more gradual charge. In addition to its capacity to damp torsional vibrations the coupling is stated to be able to accommodate some malalignment. Basically the coupling consists of two sets of three rocker arms. These are connected at their extremities by means of special shackle pins. Each arm pivots centrally on a Metalastik bush. Rubber-bonded buffers are bolted to flats formed on three of the rocker arms. These come into contact with flats on the other set of rockers when a certain torque has been reached and the initial clearance has been taken up. One set of rockers is connected by three tapered pins to the flywheel and the other set by three pins to the gearbox flange, the inner sleeves of the centre pivot bushes being keyed to the pins.
—The Motor Ship, April 1959; Vol. 40, p. 35.