This paper considers further possibilities of recovering the waste heat dissipated by two stroke diesel engines of the type employed for marine propulsion. A dual-pressure steam cycle is proposed as an effective means of converting this unutilised energy into electricity. Improvements in the specific fuel consumption of diesel engines have lead to a reduction in the available energy of the exhaust gases. The trend towards higher brake mean effective pressures brings a corresponding rise in boost pressure and more heat to reject in the charge cooler. Recently a major engine manufacturer has shown interest in operating a low speed engine with elevated temperature jacket water. In order to best utilise the reject heat of this new breed of engine, a dual pressure steam turbine has been designed. A scheme has been devised which generates steam simultaneously at 8 bar from exhaust gas heat, and at atmospheric pressure using the heat released from the jacket water and the intercooler. The steam turbine is briefly described in the paper. As fuel costs continue to rise and quality to decline, it becomes more important to be able to use the poorer grades of oil for auxiliary power generation, in these circumstances, a steam turbine auxiliary engine, while having a lower thermal efficiency than the equivalent diesel, may show an overall economic advantage. This can be achieved by the ability of the external combustion cycle to consume the worst grades of fuel available, coupled with the possibility of generating free kilowatts whilst the main engine is running. A typical marine installation is analysed and a suggested plant schematic displayed. The relative economic and technical merits of auxiliary power generation by medium speed diesel engines, main engine driven generator, and turbo-alternator are compared. A research and development exercise is currently being undertaken by the author's company to investigate the performance of a dual pressure bottoming plant. In this installation, a 6000 HP medium speed four stroke diesel, employing elevated temperature jacket water cooling and a special intercooler, will be used as a heat source to drive a 500 kW turbo-alternator. A superheated oil fired boiler will be incorporated into the plant. It is hoped to simulate the system performance mathematically, and to devise a computer programme to predict thermodynamic behaviour at full and part load. A brief description of the method of analysis is given. A description of the test plant is also included.
A dual pressure steam cycle for diesel engine waste heat recovery
Ein Zwei-Druck-Dampfzyklus für die Wärmerückgewinnung bei Dieselmotoren
1981
24 Seiten, 7 Bilder, 2 Tabellen, 6 Quellen
Conference paper
Storage medium
English
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