What Are Aircraft Diesel Engines and Their Components?
Diesel aircraft engines are those that utilize diesel fuel for operation, and they have served airships and some aircraft since the 20th century. Diesel aero engines feature various advantages such as excellent fuel consumption, low flammability, and high density fuel levels. Nevertheless, they are not as widely implemented in modern aircraft as compared to the turboprop engine or gasoline engines. In this blog, we will discuss the aircraft diesel engine, their various components, and their projected future for aviation moving forward.
Across the many types of aircraft engines, the primary operating principle of operation is very often the conversion of chemical energy into mechanical energy through combustion. Typically, many aircraft engines will mix fuel and air together, and then create force through igniting the mixture with spark plugs. The diesel engine stands apart from these types as they instead choose to heat air to extreme temperatures, often exceeding 1,000 degrees Fahrenheit, before it is mixed with the fuel. With such heat, air becomes very compressed and ignites the fuel as they react together. With higher compression ratios, the diesel engine has a greater thermal efficiency and touts an advantageous fuel economy.
To achieve such a reaction, one of the main focuses of the diesel engine is pressure. Suitable pressure is achieved by a series of mechanical and high pressure pumps within the fuel pump assembly of diesel aircraft engines. Pressure within the fuel pump assembly is denoted by a metric unit called bars, and diesel engines typically have a pressure production capability of around 200 bars. These pumps then work in unison with the high pressure pumps to produce pressure that is around 1,800 bars.
Once the pump assembly increases pressure, fuel and air are then mixed for combustion. Electronic aircraft fuel injectors distribute a mist of fuel, and fuel injection can be modified as needed to inject either before or after an engine cycle. The aircraft fuel injectors are robust components, engineered to withstand the heat and high pressure of the system.
Pistons play an important role within diesel aircraft engines, just as they do with many other types. Pistons govern the volume inside of the cylinder. Crankshaft parts are also present within the engine, moving the piston up and down in a rotary motion. A typical diesel engine crankshaft is made up of a crank pin, crank journal, and a weight balance. To connect the crankshaft and crankshaft rotation, a timing chain assembly is implemented which connects the crankshaft sprocket gear to the camshaft.
While diesel engines have a long history of use for airships and early aircraft, they are not widely used in the present due to the popularity and characteristics of other engine types. This trend is beginning to turn, however, due to multiple factors. For one, avgas prices are continuously increasing, and it can prove harder to obtain avgas as compared to diesel fuels. New manufacturers for general aviation aircraft have also begun to develop new designs for diesel aircraft engines. Lastly, as diesel technology continues to be improved upon, such aircraft may be able to achieve higher strength to weight ratios to fulfill specific applications better.
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