High-Speed C-I Engine Performance; Three Types of Combustion Chamber 350111
MIXING of the fuel and air presents the major problem in maintaining high efficiency at low excess-air percentages in the high-speed compression-ignition engine. The outputs obtained from a single-cylinder 5 by 7-in. test-engine with three types of combustion chamber are compared and their respective characteristics discussed.
Airflow is depended upon for mixing the fuel and air in the pre-chamber engine. Performance is shown to be influenced by clearance distribution, connecting-passage size, pre-chamber shape, location of the fuel spray, and boosting.
The integral, or quiescent combustion chamber depends upon multiple sprays properly proportioned and directed to reach the available air. Results of an extensive series of injection-nozzle variations are shown in tabular form.
The effects of scavenging and boosting and of high coolant-temperatures are discussed. Optimum performance showed either type to be inadequate for use as an aircraft powerplant.
The displacer-piston combustion-chamber combines the advantages of directed multiple fuel-sprays and forced airflow and gave performance definitely superior to either of the other two types, allowing smokeless exhaust to be obtained with only 15 per cent excess air.
Effects of passage width, displacer height, displacer shape, optimum fuel-spray, high-temperature coolant, and boosting are shown. Friction is discussed briefly. Specific outputs are shown to be comparable with those obtainable from boosted gasoline engines. Further improvement in performance is predicted.