BMV Maskin A.S. Introduces New Engine

BMV Maskin A.S. has introduced a new heavy fuel burning diesel engine for marine propulsion and auxiliary use as well as for shore side power generation. This new engine, designated the B type, has been undergoing intensive testing at the Bergen Diesel factory since September 1984. The engine has met all design and operational expectations.

Development of the B type engine was a result of an extensive market research program undertaken by BMV Maskin which clearly indicated the need for a modern medium- speed engine with an output of approximately 500 hp per cylinder.

The B type engine is intended to augment the company's product line by offering an engine with twice the per cylinder output of its K type, the company's most popular production engine. The market research further identified the need for the new engine to use fuels which could be expected to be available to the marine market in the foreseeable future. As a result of the research it was decided to base the engine design on fuels with a viscosity of 700 cSt/50°C and a specific weight of 1.010 g/ml assuming the fuel treatment system is compatible.

The company was able to use the experience it had gained during its 20 years delivering the heavy fuel burning K type engine. Corporate design criteria gave low operating costs higher priority than lowest possible initial costs. The governing design criteria included: — high reliability and long overhaul intervals on lower quality heavy fuels — low fuel consumption — low wear rates — good component access and easy servicing of components The B type engine design achieved the stated criteria. As a result of experience to date high reliability and long overhaul intervals are expected. Piston overhaul periods of 20,000 hours and exhaust value overhauls of up to 10,000 hours are expected on the lower quality heavy fuels. With further refinement and optimization of the fuel injection system, combustion chamber shape, and valve timing, the specific fuel consumption is expected to be reduced to 185g/kwh (136g/mph) under ISO-conditions with engine-driven lubricating and cooling water pumps. Low wear is achieved through sound design of pistons, piston rings and cylinders and the close attention to critical component surface temperatures.

Great emphasis was placed on component access and serviceability of the B type engine as exemplified by: — large crankcase covers for easy access to the running gear, bearings, etc.

— large camshaft—compartment covers for good access to camshaft, bearings, and value and fuel pumps actuating mechanisms.

— the camshaft is divided into sections which can be removed sideways and the cams can be exchanged when required — large fuel pumps compartment covers for exceptionally good access to the fuel pumps, their regulating mechanism and to fuel oil and lubricating oil pipes — slanted flanges for cylinder head exhaust and inlet ducts, with good access to all bolt connections and fittings, ensures easy fitting/removal of the cylinder head — hydraulically tightened bolts extensively used The B type engines are conservatively designed 4-stroke cycle diesel engines fitted with turbocharges and intercoolers. Principal engine technical data are: bore—320 mm; stroke 360 mm; engine speed—720/ 750 rpm; brake mean effective pressure— 18-20.3 bar; maximum continuous rating—312-360 kw/cyl., 425-500 hp/cyl.; no. of cylinders— 6-8-9 (in-line), 12-16-18 "(V-types); output range—1,870-6,625 kw, 2,550-9,000 hp; maximum firing pressure—150 bar.

Individual components were designed and are built for extended engine longevity and serviceability.

Noteworthy design and construction features of specific engine components and systems are summarized in the following paragraphs.

Cylinder Block: The cylinder block is made of modular cast iron incorporating a one-piece design with an underslung crank- shaft. Lubricating oil and cooling water passages as well as the charge air receiver are integral elements of the cylinder block casting.

Crankshaft: Heavily dimensioned pins, journals and webs are used in order to create a very stiff shaft with moderate average bearing loads. Counterweights are fitted to every crankweb to balance the rotating inertia forces, thereby reducing the main bearing loads and contributing to the smooth running of the engine.

Bearings: Main and crankpin bearings are of the precision trimetal type (thin-wall steel shell lined with a copper/lead intermediate layer and a tin/lead outer overlay). The main bearings utilize the modern design practice of not using an oil groove in the bottom half in order to improve loadcarrying capacity.

Connecting Rods: The fully forged connecting rods are machined "all over" and have an obliquely split foot with serrated mating surfaces. Comprehensive finite element analyses as well as many years of good experience with similar design K type engine connecting rods were the basis for the B type engine connecting rod design.

Pistons: The pistons utilize a composite built-up design. Piston cooling is accomplished by oil flowing up through the drilled connecting rod. The cooling oil flow rate is set to ensure adequate cooling at full load and yet prevent excessively low metal temperatures at low loads and the resulting low temperature corrosion.

Three compression rings, each with its own carefully selected geometry, and one spring loaded oil control ring are used.

Cylinder Liners: Cylinder liners are centrifugally cast and the running surfaces are both nitrided to improve wear resistance. Bore cooling is used to ensure that the upper part of the liner metal temperatures and thermal stresses are properly controlled. Extensive finite element analysis was undertaken during design to arrive at the appropriate bore configuration.

Cylinder Heads: The four-valve cylinder head utilizes shrunk-in, replaceable valve seats. Exhaust valve seats are stellite armored and water cooled. By using multimaterial exhaust valves—Nimonic valve head material with welded Deloro Alloy 60 seat facing and chomium plated conventional valve steel spindle—heavy fuel associated exhaust valve problems are eliminated, thereby precluding the need for exhaust valve cages. Consequently the exhaust valve ducts are designed for minimum losses and maximum gas throughputs.

Turbochargers: The latest generation turbochargers such as VTR series 4 from BBC are used in conjunction with a turbocharging systems based on the impulse principle. Bergen Diesel has chosen the impulse principle turbocharging system because of its ability to cope with shock loading and its ability to give greater air flow rates at part load than constant pressure systems. For the 8- and 16-cylinder engines, pulse converters are also employed.

Fuel Injection System: Satisfactory combustion of poor heavy fuels and the desire for low fuel consumption requires high injection pressures and short injection periods. To accomplish this very high pressure monoelement fuel pumps with constant pressure unloading valves are used. The pumps being used are operating with upper pressure limits of 1,400 bar. Special precautions are taken to prevent fuel leakage from the fuel pumps and high pressure piping from contaminating the lubricating oil.

For additional detailed information on the new BMV-Maskin engine, including test results and specifications, Circle 2 on Reader Service Card