Paper 1: The Breathing and Combustion Requirements of the Small High-Speed Diesel Engine

Abstract
The use of small diesel engines in light highway vehicles has increased greatly in the last few years, and such engines exhibit some specialized characteristics. The performance requirements of these engines are outlined, and their dependence on the overall air consumption of the engine is emphasized. The latter is defined as the product of the breathing and combustion phases of the engine operation. For the breathing phase, the factors controlling the volumetric efficiency arc examined and the relative importance of heating and pressure effects estimated from the results of tests on a number of engines. The scope for further improvement is discussed in relation to these two factors, and the choice of valve timing. For the combustion phase, the requirements of the high-speed engine are listed and briefly discussed under eight headings, namely, the limiting air utilization; fuel consumption; flexibility of operation over the speed range; ease of starting; intensity of combustion noise; sensitivity to fuel quality; overall reliability; and ease of design and manufacture. The relative merits of direct and indirect injection systems for this duty are then examined with some reference to recent experimental work, and directions in which improvements are possible and desirable are indicated. On considering techniques which are useful in chamber development, a simple method of assessing the airflow pattern within indirect chamber layouts is described and illustrated by reference to test sequences obtained on two different combustion chamber forms. Some general notes on methods of expediting firing tests of new chamber systems are given.

This publication has 3 references indexed in Scilit: