Two-stroke engine: is the four-stroke better?
The two-stroke engine is most effective when not too large maximum power is required. Such a small-size single-cylinder engine has a rather simple design. In shipbuilding, this type of engine is also used, it has already more impressive dimensions and contains a crosshead KSHM. As you know, two-stroke engines have a low speed, due to which it is possible to use them directly to drive ship propellers. In addition, these engines are easier to change the direction of rotation. In automobiles, such engines are used quite rarely, since their fuel consumption is quite high with increased toxicity of exhaust gases.
The principle of operation of the two-stroke engine
In comparison with the four-stroke, it is constructively more simple solution, as already mentioned, so it is cheaper.Such motors operate in the usual Otto cycle, however, one such cycle proceeds in just one revolution of the shaft. The cycles of a two-stroke motor are as follows. The intake (suction of the fuel-air mixture into the crankcase, the piston moves upwards, thereby creating a vacuum), compression (the piston moves downwards, the fuel in the crankcase is compressed), the release (the piston is in mt (bottom dead center), fuel the mixture enters the cylinders, displacing the products of combustion),compression (the piston moves up, the fuel mixture is compressed, it enters the crankcase) and the working stroke (piston in the high-speed dead center), the spark plug produces a spark, the fuel mixture ignites, the piston moves down. The two-stroke engine has several disadvantages. For example, during the production, together with the combustion products, part of the useful fuel is also displaced, which is inefficient from the point of view of the increase in power, since it is only 50-60%, and not 100% (since when the clock is reduced twice, the engine power should increase twice). Also, the exhaust gases are more toxic (due to the content in their composition of small amounts of NOx and CO at low temperature exhaust gases).
Today, the two-stroke engine is less popular than its four-stroke fellow. For example, in motorcycle technology, four-stroke engines have now almost completely replaced two-stroke engines. Manufacturers tend not only to make the engine run more efficiently, but also to make it the least harmful to the environment. Although the two-stroke engine still finds its use in saws, low-power motorcycles, snowmobiles, scooters, jet skis and small aircraft.However, there are some unique motors of their kind. For example, the experimental two-stroke engine "Orion", which was developed in the United States. In its design, the piston generator of hot gases and the turbine, which serves as a source of mechanical energy. A two-stroke piston engine is connected to a large centrifugal supercharger that delivers air to the cylinders. The gas turbine is “fed” with exhaust gases that are mixed with cooling air.