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Contenido archivado el 2019-03-15

DEVELOPMENT AND TESTING OF AN OPERATING METHOD USING EXHAUST HEAT (BOTTOMING CYCLE) AND CAPABLE OF REDUCING THE FUEL CONSUMPTION OF A DIESEL ENGINE

Objetivo



THE PROPORTION OF EXERGY IN THE COOLANT HEAT OF INTERNAL COMBUSTION ENGINES IS TOO SMALL (APPROX. 4 % OF THE PRIMARY ENERGY) BECAUSE THE COOLANT TEMPERATURE IS QUITE LOW (ABOUT 80 DEGREES C). BY CONTRAST, THE EXERGY IN THE EXHAUST GASES AMOUNTS, (WHEN THEY ARE COOLED FROM 560 DEGREES C TO 180 DEGREES C), TO SOME 12 % OF THE PRIMARY ENERGY.

THE AIM OF THIS STUDY IS TO CONVERT EXHAUST HEAT OF INTERNAL COMBUSTION ENGINES INTO MECHANICAL ENERGY AND TO TRANSFER IT TO THE CRANKSHAFT IN ORDER TO IMPROVE THE EFFECTIVE ENGINE EFFICIENCY. FOR DIESEL ENGINES THIS MAY IMPROVE THE OVERALL EFFICIENCY FROM 40 % TO ABOUT 50 %. IN THIS STUDY A BOTTOMING CYCLE UNIT FOR A TURBOCHARGED 6-CYLINDER DIESEL ENGINE INSTALLED IN A LONG-HAUL TRUCK (207 KW AT 2000 RPM) WAS DEVELOPED, CONTRUCTED AND TESTED. TO THIS END, DIFFERENT WORKING FLUIDS WERE COMPARED. A TEST RIG WAS USED TO MEASURE, TEST AND REFINE THE SYSTEM FOR USE.

THE CHOICE OF THE WORKING FLUID FELL ULTIMATELY ON STEAM. (THE ORGANIC RANKINE CYCLE TECHNOLOGY REQUIRES, COMPARED TO A STEAM PROCESS, A HIGHER CAPITAL INVESTMENT DUE TO MUCH GREATER HEAT-EXCHANGER SURFACES, THE EXPENSIVE WORKING FLUID AND THE SAFETY PRECAUTIONS REQUIRED IF THE WORKING MEDIUM HAS AN INFLAMMABLE OR TOXIC BEHAVIOUR). A RADIAL TURBINE WAS CHOSEN, WHILE THE OTHER COMPONENTS OF THE RANKINE ENGINE WERE SELECTED ACCORDING TO CONVENTIONAL PRACTICE. A GEAR BOX WAS USED TO CONNECT THE BOTTOMING ENGINE WITH THE DIESEL ENGINE (LUBRICATION PROBLEMS OF THE GEAR BOX HAVE BEEN SOLVED). AT THE DESIGN POINT, THE SPEED OF THE TURBINE WAS 100,000 RPM AND ITS USEFUL POWER APPROX. 19.4 KW. THE STEAM IS HEATED WITH WASTE HEAT OF 590 DEGREES C, IS EXPANDED AND COOLED DOWN TO 110 DEGREES C.

THE RESULTING HIGH SPEED OF THE TURBINE SHAFT AND THE HIGH TEMPERATURES DID NOT PERMIT THE USE OF CONTACT SEALS. THE AMOUNT OF SEALING AIR DEMANDS A LARGER COMPRESSED AIR TANK FOR THE VEHICLES BRAKE SYSTEM. FURTHERMORE, THE LEAKAGE OF THE SEALING STEAM HAD TO BE SUPPLEMENTED BY TREATED BOILER FEED WATER. THE BOTTOMING CYCLE COMPONENTS (WATER TREATMENT PLANT AND LARGER COMPRESSED AIR TANK) COULD NOT BE ACCOMMODATED ON THE TRUCK WITHOUT SACRIFICING SOME OF THE PAYLOAD CAPACITY. THEREFORE, THIS VERSION OF EXHAUST GAS UTILISATION (GIVEN THE PRESENT PRICE OF DIESEL FUEL AND THE RELATIVELY SMALL DISTANCES TRAVELLED PER YEAR IN EUROPE) IS UNECONOMICAL.

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Coordinador

MAN AG
Aportación de la UE
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Dirección

80001 München
Alemania

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