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Why can't gasoline generators be direct compression ignition like diesel generators?
June 23, 2022
Diesel generator start is a certain amount of diesel, in a certain period of time, with a certain pressure to atomize the quality of diesel fuel into the cylinder according to a certain injection pattern, and make it and compressed air quickly and well mixed and combustion, while the gasoline generator start and need to use the spark plug to ignite.
We know that the diesel generator start is a certain amount of diesel, in a certain period of time, with a certain pressure to atomize good quality diesel fuel sprayed into the cylinder according to a certain injection pattern, and make it and compressed air quickly and well mixed and combustion, and the gasoline generator start and need to use spark plugs to ignite, in fact, many gasoline generator sets are equipped with direct injection of gasoline engine, can also be The gasoline can be injected directly into the cylinder, so why can't the gasoline engine like diesel engine direct compression ignition? This top Bo power will provide you with a detailed analysis from the following aspects.
1, whether the gasoline is easier to be ignited?
To answer this question, we must first understand a technical term - "flash point", flash point is in the specified test conditions, the use of some kind of ignition source caused by liquid vaporization and the minimum temperature of fire. The flash point of gasoline can be less than 28 ℃, while the flash point of light diesel fuel in 45-120 ℃, the flash point of less than 61 ℃ oil for flammable products. Take the open flame near the diesel is difficult to ignite it, because the temperature 20 ℃ is far below the flash point of diesel, this time diesel is still very stable, no volatility, so it is difficult to ignite!
Diesel is not as easy to volatilize into gas as gasoline, only the surface layer in contact with the air, while gasoline is very easy to volatilize to produce gasoline vapor and air more fully mixed, so it is easier to be ignited.
2、Low auto-ignition point is easier to compress and ignite
Auto-ignition point refers to the temperature of combustible material in the conditions of oxygen autonomy combustion, diesel fuel auto-ignition point is 220 ℃, while the gasoline auto-ignition point is 427 ℃, the high temperature generated by the piston compressed air can reach the auto-ignition point of diesel fuel but can not reach the auto-ignition point of gasoline, so the diesel engine can be used compression ignition, while the gasoline engine can only be ignited by the spark plug.
3, the combustion characteristics of diesel and gasoline are different
Gasoline engine is the use of "prefabricated mixture" fuel, that is to say, the need to burn the gas mixture in the power stroke has been prepared before the ignition, only to be ignited when the spark plug will ignite it.
Because the timing of ignition basically occurs when the piston reaches the upper stop near the piston will have a change of direction, so it can be seen as a short period of time when the combustion space is constant, the mixture in this moment quickly complete the combustion expansion to do work, which is the "constant volume heating" Otto cycle!
The diesel engine is in the piston near the upper end of the cylinder temperature is higher than its self-ignition point when the cylinder began to spray oil, atomized diesel fuel into the cylinder and air mixture, because the temperature reached the self-ignition point, diesel fuel began to burn, because of the slow speed of diesel fuel combustion, so a work required to burn the diesel fuel will not be instantly sprayed, but will continue to spray to the cylinder, the result is that the cylinder while burning and continuous spraying, sprayed into the oil Continue to mix with air and be ignited combustion, expansion of the air continues to push the piston, this is the constant pressure heating Diesel cycle.
That can't help but ask: why can't the gasoline engine compression ratio to do higher, also like the diesel engine in the compression of the upper stop injection it? Top Bo power professional technician said: This is mainly because the gasoline combustion speed is too fast, the combustion process is not controllable, it is difficult to make the engine smooth and soft. The physical characteristics of the two types of oil decided that they are "treated differently".
Through the above introduction, I believe you already know why gasoline generators can not be as direct compression ignition as diesel generators, right? In addition to the differences in combustion systems, diesel generators and gasoline generators also have many differences, basic differences, the most suitable as a backup power is the diesel generator set, if you are torn between the two do not know which type of generator to buy, you are welcome to call us, we will customize a reasonable backup power program for you according to your requirements.
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