Engine: Description and Operation

Fig. 1 Cross sectional view of engine:

Fig. 2 Intake stroke of engine:

Fig. 3 Compression stroke of engine:

Fig. 4 Ignition stroke of engine:

Fig. 5 Power stroke of engine:

Fig. 6 Exhaust stroke of engine:

This engine, Fig. 1, is designed to reduce the amount of hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx) present in the exhaust gases by modifications to the combustion chambers, carburetor and valve train.
The basic principle of the CVCC is progressive ignition of a stratified charge in two chambers which are the main combustion chamber and auxiliary combustion chamber or pre-chamber. These chambers are joined together by a small opening. The auxiliary combustion chamber uses a single small intake valve, and the main combustion chamber uses conventional intake and exhaust valves. All valves are actuated by a single overhead camshaft.
To provide proper intake mixture control under varying operating conditions, the intake air fuel mixture for each cylinder is controlled by three throttle valves in the carburetor, to provide the charge stratification which ensures stable and slow combustion under all operating conditions. This stable and slow combustion provides a low peak temperature which minimizes the formation of NOx and a high average temperature which reduced HC emissions.
During the intake stroke, Fig. 2, a lean mixture is drawn through the main intake valve and into the combustion chamber. At the same time, a rich mixture is drawn through the auxiliary intake valve and into the pre-chamber.
At the end of the compression stroke, Fig. 3, a rich mixture is present in the pre-chamber, a moderate mixture is formed in the main chamber near the pre-chamber outlet, and a very lean mixture is present in the remainder of the main combustion chamber.
During ignition, Fig. 4, the rich mixture in the pre-chamber ignites easily. The flame from the pre-chamber ignites the moderate mixture.
During the power stroke, Fig. 5, the flame area extends further to burn the lean mixture in the main combustion chamber. The formation of CO is minimized because of this lean mixture.
After bottom dead center and during the exhaust stroke, Fig. 6, the air fuel mixture continues to burn. The hot exhaust gasses exit through the exhaust valve and the oxidation process continues in the exhaust system.