Final answer:
A three-valve combustion chamber has two intake valves and one exhaust valve, ensuring efficient entry and exit of gases during the combustion process.
Step-by-step explanation:
A three-valve combustion chamber has two intake valves and one exhaust valve. The primary role of the intake valves is to allow the air-fuel mixture to enter the combustion chamber, while the exhaust valve's purpose is to let the burnt gases (combustion products) escape once the fuel has been combusted. The process of exhaust involves a constant-volume system where the piston movement is minimal, thus creating a scenario where the volume remains constant at VA (= VD) and the exhaust valve opens to release the combustion products.
Then follows the isobaric compression phase where the exhaust valve stays open to expel the remaining combustion gases. This information is crucial for understanding how engines manage air and exhaust gases to maximize efficiency and power output.