MARINE DIESEL ENGINES AND GAS TURBINES
THEORY AND GENERAL PRINCIPLES GAS-DIESEL AND DUAL-FUEL ENGINES EXHAUST EMISSIONS AND CONTROL FUELS AND LUBES: CHEMISTRY AND TREATMENT PERFORMANCE ENGINE AND PLANT SELECTION PRESSURE CHARGING FUEL INJECTION LOW SPEED ENGINES—INTRODUCTION MAN B&W LOW SPEED ENGINES MITSUBISHI LOW SPEED ENGINES SULZER LOW SPEED ENGINES BURMEISTER & WAIN LOW SPEED ENGINES DOXFORD LOW SPEED ENGINES MAN LOW SPEED ENGINES CONTENTS MEDIUM SPEED ENGINES—INTRODUCTION ALLEN (ROLLS–ROYCE) ALPHA DIESEL (MAN B&W) CATERPILLAR DEUTZ MAK (CATERPILLAR MOTOREN) MAN B&W DIESEL ROLLS-ROYCE BERGEN RUSTON (MAN B&W) SEMT-PIELSTICK (MAN B&W) SULZER (WÄRTSILÄ) WÄRTSILÄ OTHER MEDIUM SPEED ENGINES ABC, DAIHATSU, GMT, HYUNDAI, MIRRLEES BLACKSTONE, MITSUI, NIIGATA, NOHAB, SKL, STORK-WERKSPOOR DIESEL, WICHMANN, EMD, BOLNES, YANMAR LOW SPEED FOUR-STROKE TRUNK PISTON ENGINES HIGH SPEED ENGINES CATERPILLAR, CUMMINS, DEUTZ, GMT, ISOTTA FRASCHINI, MAN B&W HOLEBY, MITSUBISHI, MTU, NIIGATA, PAXMAN, SEMT-PIELSTICK, WÄRTSILÄ, ZVEZDA, SCANIA, VOLVO PENTA GAS TURBINES FIGURE 1 1 THEORETICAL HEAT CYCLE OF TRUE DIESEL ENGINE THEORETICAL HEAT CYCLE IN THE ORIGINAL PATENT BY RUDOLF DIESEL THE DIESEL ENGINE OPERATED ON THE DIESEL CYCLE IN WHICH THE HEAT WAS ADDED AT CONSTANT PRESSURE THIS WAS ACHIEVED BY THE BLAST INJECTION PRINCIPLE TODAY THE TERM IS UNIVERSALLY USED TO DESCRIBE ANY RECIPROCATING ENGINE IN WHICH THE HEAT INDUCED BY COMPRESSING AIR IN THE CYLINDERS IGNITES A FINELY ATOMIZED SPRAY OF FUEL THIS MEANS THAT THE THEORETICAL CYCLE ON WHICH THE MODERN DIESEL ENGINE WORKS IS BETTER REPRESENTED BY THE DUAL OR MIXED CYCLE, DIAGRAMMATICALLY ILLUSTRATED IN FIGURE 1 1 THE AREA OF THE DIAGRAM, TO A SUITABLE SCALE, REPRESENTS THE WORK DONE ON THE PISTON DURING ONE CYCLE PRESSURE ADIABATIC EXPANSION ADIABATIC COMPRESSION F C P E VOLUME D POUNDER’S MARINE DIESEL ENGINES AND GAS TURBINES STARTING FROM POINT C, THE AIR IS COMPRESSED ADIABATICALLY TO A POINT D FUEL INJECTION BEGINS AT D, AND HEAT IS ADDED TO THE CYCLE PARTLY AT CONSTANT VOLUME AS SHOWN BY VERTICAL LINE DP, AND PARTLY AT CONSTANT PRESSURE, AS SHOWN BY HORIZONTAL LINE PE AT THE POINT E EXPANSION BEGINS THIS PROCEEDS ADIABATICALLY TO POINT F WHEN THE HEAT IS REJECTED TO EXHAUST AT CONSTANT VOLUME AS SHOWN BY VERTICAL LINE FC THE IDEAL EFFICIENCY OF THIS CYCLE (I E OF THE HYPOTHETICAL INDICATOR DIAGRAM) IS ABOUT 55–60 PER CENT: THAT IS TO SAY, ABOUT 40–45 PER CENT OF THE HEAT SUPPLIED IS LOST TO THE EXHAUST SINCE THE COMPRESSION AND EXPANSION STROKES ARE ASSUMED TO BE ADIABATIC, AND FRICTION IS DISREGARDED, THERE IS NO LOSS TO COOLANT OR AMBIENT FOR A FOUR-STROKE ENGINE THE EXHAUST AND SUCTION STROKES ARE SHOWN BY THE HORIZONTAL LINE AT C, AND THIS HAS NO EFFECT ON THE CYCLE PRACTICAL CYCLES WHILE THE THEORETICAL CYCLE FACILITATES SIMPLE CALCULATION, IT DOES NOT EXACTLY REPRESENT THE TRUE STATE OF AFFAIRS THIS IS BECAUSE: 1 THE MANNER IN WHICH, AND THE RATE AT WHICH, HEAT IS ADDED TO THE COMPRESSED AIR (THE HEAT RELEASE RATE) IS A COMPLEX FUNCTION OF THE HYDRAULICS OF THE FUEL INJECTION EQUIPMENT AND THE CHARACTERISTIC OF ITS OPERATING MECHANISM; OF THE WAY THE SPRAY IS ATOMIZED AND DISTRIBUTED IN THE COMBUSTION SPACE; OF THE AIR MOVEMENT AT AND AFTER TOP DEAD CENTRE (TDC); AND TO A DEGREE ALSO OF THE QUALITIES OF THE FUEL 2 THE COMPRESSION AND EXPANSION STROKES ARE NOT TRULY ADIABATIC HEAT IS LOST TO THE CYLINDER WALLS TO AN EXTENT WHICH IS INFLUENCED BY THE COOLANT TEMPERATURE AND BY THE DESIGN OF THE HEAT PATHS TO THE COOLANT 3 THE EXHAUST AND SUCTION STROKES ON A FOUR-STROKE ENGINE (AND THE APPROPRIATE PHASES OF A TWO-STROKE CYCLE) DO CREATE PRESSURE DIFFERENCES WHICH THE CRANKSHAFT FEELS AS ‘PUMPING WORK’ IT IS THE DESIGNER’S OBJECTIVE TO MINIMIZE ALL THESE LOSSES WITHOUT PREJUDICING FIRST COST OR RELIABILITY, AND ALSO TO MINIMISE THE CYCLE LOSS: THAT IS, THE HEAT REJECTED TO EXHAUST IT IS BEYOND THE SCOPE OF THIS BOOK TO DERIVE THE FORMULAE USED IN THE THEORETICAL CYCLE, AND IN PRACTICE DESIGNERS HAVE AT THEIR DISPOSAL SOPHISTICATED COMPUTER TECHNIQUES WHICH ARE CAPABLE OF REPRESENTING THE ACTUAL EVENTS IN THE CYLINDER WITH A HIGH DEGREE OF ACCURACY BUT BROADLY SPEAKING, THE CYCLE EFFICIENCY IS A FUNCTION OF THE COMPRESSION RATIO (OR MORE CORRECTLY THE EFFECTIVE EXPANSION RATIO OF THE GAS/AIR MIXTURE AFTER COMBUSTION) THEORY AND GENERAL PRINCIPLES FIGURE 1 2 TYPICAL INDICATOR DIAGRAM (STROKE BASED) THE THEORETICAL CYCLE (FIGURE 1 1) MAY BE COMPARED WITH A TYPICAL ACTUAL DIESEL INDICATOR DIAGRAM SUCH AS THAT SHOWN IN FIGURE 1 2 NOTE THAT IN HIGHER SPEED ENGINES COMBUSTION EVENTS ARE OFTEN REPRESENTED ON A CRANK ANGLE, RATHER THAN A STROKE BASIS, IN ORDER TO ACHIEVE BETTER ACCURACY IN PORTRAYING EVENTS AT THE TOP DEAD CENTRE (TDC), AS IN FIGURE 1 3 THE ACTUAL INDICATOR DIAGRAM IS DERIVED FROM IT BY TRANSPOSITION THIS FORM OF DIAGRAM IS USEFUL TOO WHEN SETTING INJECTION TIMING IF ELECTRONIC INDICATORS ARE USED IT IS POSSIBLE TO CHOOSE EITHER FORM OF DIAGRAM AN APPROXIMATION TO A CRANK ANGLE BASED DIAGRAM CAN BE MADE WITH MECHANICAL INDICATORS BY DISCONNECTING THE PHASING AND TAKING A CARD QUICKLY, PULLING IT BY HAND: THIS IS TERMED A ‘DRAW CARD’ PRESSURE TDC VOLUME BDC