Blow by gas意思
"Blow-by gas" is a term used in the context of internal combustion engines, particularly in reference to diesel engines. It refers to the unburned gases that leak past the piston rings into the crankcase of the engine.
During the combustion process in an engine, the piston travels up and down within the cylinder. The piston rings are designed to seal the gap between the piston and the cylinder wall, preventing the combustion gases from escaping into the crankcase. However, due to normal wear and tear, the piston rings may not seal perfectly, and some gases will leak past them.
The blow-by gas contains a mixture of air, fuel vapor, and combustion byproducts such as carbon dioxide, water vapor, and unburned hydrocarbons. This gas can contain significant amounts of oil vapor as well, due to the lubricating oil film on the cylinder walls.
The presence of blow-by gas in the crankcase can lead to several issues:
- Oil contamination: The blow-by gas can mix with the engine oil, diluting its lubricating properties and potentially causing sludge buildup.
- Pressure buildup: The accumulation of blow-by gas in the crankcase can increase pressure, which can lead to oil leaks or, in severe cases, crankcase explosions.
- Emissions: The blow-by gas can contain unburned hydrocarbons, which can contribute to pollution if not properly managed.
To manage blow-by gas, modern engines often have a PCV (positive crankcase ventilation) system. This system captures the blow-by gas and routes it back into the intake manifold, where it can be burned in the combustion process. This not only reduces pollution but also helps to maintain the cleanliness of the engine oil.
In summary, "blow-by gas" is a term used to describe the unburned gases that escape past the piston rings into the crankcase of an engine. It is a normal byproduct of engine operation but can become problematic if not managed properly.