Chapter Three - Diesel Engines

Abstract

Publisher Summary This chapter discusses the difference between combustion in diesel engine and combustion in gasoline engine. In the diesel engine, air is compressed by the piston and fuel is injected into the chamber towards the end of the compression stroke. At this point, the temperature of the air is high enough to cause the fuel to ignite spontaneously. The combustion process in the diesel engine is divided into a number of stages. Diesel engines are grouped into two types: (1) direct injection and (2) indirect injection. In the direct injection engine, the combustion chamber is entirely enclosed by the surfaces of the cylinder head and piston and takes the form of a cavity or a bowl in the piston crown. In the indirect injection engine, the combustion chamber is in two parts: one a cavity in the piston of a different shape to that in the direct injection engine and the other a pre-chamber connected to the cylinder by one or more passages. In the direct injection engine, the air movement takes the form of a swirl about the cylinder axis that is generated during the induction stroke by suitable design of the inlet port. The indirect injection engine also relies on rapid air movement that is achieved by causing either the air or the burning gases or both to flow at high velocity through the passage or passages connecting the precombustion chamber with the main cylinder. The main benefits of insulation in the diesel engine are an improvement in thermal efficiency and a reduction in the size of the cooling system.