Diesel engines are the hard working, industirious engines used in larger applications. They can stand up to larger work loads than their gasoline cousins. Diesel engines run cooler and run slower to produce the same power as a gasoline engine.
Diesel engines run on the same basic principle as a gas engine except the air is pre-heated in the combustion chamber. Diesel engines are extremely hard to start in cold weather. Diesel, unlike gasoline, when temperatures are low can become gel-like.
Diesel engines are more efficient than those burning other fuels. Gasoline engines run on a compression ratio of 8:1 to 12:1 while diesel runs on ratios from 14:1 to as high as 25:1.
Diesel engines do not require a spark plug. The fuel is injected directly into the combustion chamber just prior to combustion. The fuel is ignited by the heat.
As in gasoline engines, there are two and four stroke cycle engines, however, the diesel engine does not let out unburned fuel into the atmosphere. The diesel is injected at the top of the compression stroke instead of the bottom in gasoline engines.
Future Diesel engines will be nearly the same as the engines that are used today. We are at the peak of diesel capability. We have the highest compression ratios and clean burning engines. The future may find new use of diesel, but the engine is being phased out.