California Maritime Academy EPO 220 Diesel Engineering I Fuel Injection & Combustion Chamber Design Material Compiled by Robert Jackson
Diesel Engine Combustion Chambers • Combustion chambers are designed to promote air turbulence which helps atomize the fuel in preparation for combustion. • Modern diesel engines typically utilize an open type combustion chamber. • Though not commonly used today, the following chamber designs were utilized in the past to promote complete combustion: • Turbulence Chambers • Precombustion Chambers • Energy Cell or Air Cell Chambers
Air Turbulence in the Combustion ChamberA- Intake Stroke; B-Compression Stroke; C-Power Stroke; Exhaust Stroke
Precombustion Chamber • The precombustion chamber is connected to the piston clearance volume by one or more passages. • This chamber may be located in the head or cylinder wall. • A precombustion chamber will hold 25 to 40 percent of the total clearance volume. • Because of the larger surface area of the combustion chamber, heat losses are increased and thermal efficiency decreases. • The precombustion chamber promotes smooth combustion and improves engine performance at low loads.
Removable Injector plus Precombustion Chamber Combination(Caterpillar Tractor Co.)
Turbulence Chamber • The turbulence chamber is very similar in design to the precombustion chamber. The principal difference between the two designs is the amount of chamber volume compared to the clearance volume of the main combustion chamber. • Engines utilizing turbulence chambers have very small clearance volumes. • When the piston reaches TDC virtually all of the available air has been compressed in the turbulence chamber. • The chambers are usually spherical in shape and are incorporated into either the head or cylinder. • The opening through which the air must pass becomes smaller as the piston reaches the top of the stroke, thereby increasing the velocity of the air in the chamber.
The Lanova Energy Cell • The energy cell is a combination of the precombustion chamber and turbulence chamber designs. • The Lanova system has two rounded combustion spaces shaped like a figure 8. • The fuel is injected in a pencil stream, passing directly across the narrow throat of the combustion chamber so most of the fuel enters the energy cell. • Most of the fuel entering the energy cell is trapped in the small inner cell, but a small portion passes into the outer cell where it meets with a sufficient quantity of super-heated air to explode violently.
Combustion Sequence in the Lanova Energy Cell SystemThe nozzle injects fuel in a pencil stream which penetrates into the energy cell. Partial combustion takes place inside the energy cell radically raising cell pressure. High pressure gasses exiting the energy cell through the venturi throat cause high turbulence levels in the main combustion chamber promoting good combustion.
Fuel Line Pressure (lower line) & Needle Lift Diagrams • At high load • At low load
Port & Helix High-Pressure Fuel PumpIllustration showing pump plunger, barrel, delivery valve, & control rack for adjustment of pump effective stroke
MAN B&W K98MC Slow-Speed Crosshead Diesel EngineBore 980mmStroke 2660mm94 Rpm Maximum6 to 12 Cylinders5,720 kW Per Cylinder 12 Cylinder Engine Produces 68,640 kW(93,360 BHP)
B&W Slow-Speed Diesel Engine High-Pressure Fuel Pump With Variable Injection Timing