What type of combustion chamber is predominantly used in medium- and heavy-duty diesel engines?

The predominant type of combustion chamber used in medium- and heavy-duty diesel engines is direct injection. This method allows for more efficient fuel delivery directly into the combustion chamber under high pressure. By injecting the fuel directly into a turbulent charge of air, direct injection enhances the mixing of the fuel and air, leading to improved combustion efficiency and performance. This setup is particularly beneficial in larger engines, where optimizing power output and fuel economy is essential for operational efficiency.

In medium- and heavy-duty applications, factors such as torque, fuel efficiency, and emissions control are critical. Direct injection helps achieve lower emissions due to better atomization and combustion characteristics, thereby complying with stringent environmental regulations. Additionally, it enables engines to operate at higher compression ratios, which contributes to increased thermal efficiency.

Other types like the swirl chamber and pre-combustion chamber are generally used in older or less efficient engine designs, and pilot injection pertains to a technique for reducing noise and emissions but is not a type of combustion chamber itself. Thus, direct injection has become the preferred choice in contemporary diesel engine design for medium- and heavy-duty applications.