Auto questions: how diesel two-stroke engines work

Hot compressed air combusts with injected diesel in a closed cylinder to drive a piston and produce extraordinary torque for displacement volume.

The principle of a 2-stroke diesel engine is to ignite a combination of compressed air and fuel, to drive a piston that in turn rotates a crankshaft. Valves control the intake of air as well as the outlet of exhaust. A turbocharger compresses air before it is fed in to the cylinder. An injector sprays diesel on to the compressed air. Combustion results in the motion of the piston in a massive power stroke. Each cylinder has between 2 and 4 exhaust valves at the top. All the exhaust valves open at the same time. The piston in each cylinder opens the air intake ports as it completes each downward stroke. The air intake drives out the remaining exhaust and the outlet valves close to allow the piston to move upwards with the force of the compressed air.

2 stroke engines work better on diesel because fuel combustion is more efficient than with a petrol-based system. A diesel 2-stroke engine is able to accommodate more air in the cylinder as compared to a comparable displacement in a 4- stroke petrol engine. This produces a relatively high amount of power as compared to a petrol engine of comparable size. 2-stroke diesel engines are used in heavy equipment and machinery such as locomotives, ships and generators. A 2-stroke diesel locomotive engine will typically have 16 cylinders, each with a displacement of over 600 cubic inches. Such an engine may produce more than 4 thousand horsepower. 2-stroke diesel engines are very reliable and relatively fuel-efficient as well. They have simple design but offer rugged and extremely powerful performance. These engines have relatively few parts and are therefore comparatively easy to maintain.

The turbocharger is at the heart of a 2-stroke diesel engine, for it is primarily responsible for the relatively enormous amount of power the engine can produce for its weight and size. The turbocharger gets a greater volume of air into the cylinder. This increased air volume with additional diesel from the injection system makes for a more potent explosion inside each cylinder. The torque generated is consequently very high compared to a petrol engine with the same displacement. This system is especially productive in high altitudes where the air becomes rare.

The volume of air available for combustion in the cylinder reduces at high altitudes. This effect is partially mitigated in an engine with a turbocharger. A turbocharger in a 2-stroke diesel engine uses hot exhaust to drive a turbine. The latter is connected to an air pump. This system produces a differential pressure that results in a great gush of hot air entering the cylinder. A heat exchange system cools the hot exhaust before it is packed in to the cylinder. More air can be accommodated as a result of such cooling. This ensures more efficient and powerful combustion when diesel is introduced in the chamber. A supercharger may also perform the role of a turbocharger. A supercharger runs on a belt rather than on exhaust gas. The principle of accommodating more air in the cylinder remains the same whether a turbocharger or a supercharger is used.