Crude oil is a mixture of various oil products and residues (bitumen). After being rectified and purified in the refinery, the products are separated from low to high according to the temperature required by the distillation equipment to produce products: overhead gas (similar to natural gas), The product density of gasoline, kerosene, diesel, and residual oil (asphalt) also increases sequentially. In actual production, most refineries mix half of kerosene products with gasoline and half with diesel, instead of producing kerosene products.
Gasoline has a low ignition point and can be ignited by electric pistons. Gasoline engines are small and light. Therefore, small-power cars such as cars, motorcycles, and tricycles all use gasoline engines. Common gasoline labels include 90#, 94#, 98#, etc., which refer to relative combustion stability. The larger the label, the better the quality.
Diesel has a high ignition point and needs to be ignited by compressed high-temperature air, while high-temperature and high-pressure wine determines that diesel engines are relatively heavy, but diesel engines can provide a lot of power, so high-power machinery is basically diesel vehicles such as ships, cranes, and tractors. , Trucks, tanks, etc. all use diesel engines. There are 0# and -10# commonly used for diesel oil, which refers to the freezing point temperature of diesel oil.
The ignition point of kerosene is between the first two, it can be ignited with an electric piston, and the combustion is stable. In the early days of liberation, kerosene was used for lighting in most rural areas of our country. Aviation kerosene needs to be specially purified and then re-modulated, and its combustion stability is very high. After being burned in an aircraft engine, it is ejected quickly and can provide sufficient power for the aircraft.
gasoline characteristics:
1. Gasoline has strong volatility, but diesel is difficult to volatilize, so there are fuel evaporative emissions in gasoline vehicle pollutants, and its component is hydrocarbon (HC).
2. Gasoline has the characteristics of being easy to mix with air and not easy to separate after mixing. Gasoline and air can be mixed very uniformly, and there is basically no local over-concentration or over-lean and liquid oil droplets. The molecule of gasoline is small. The mixing of diesel and air is not uniform, and it is inevitable that there will be local hypoxia or local oxygen enrichment. When oil is in high temperature and oxygen deficiency, it is easy to be carbonized to form soot. After the diesel is burned, some odorous organic gases are generated. Therefore, there is still odor in diesel engine emissions.
3. The difference between the two in terms of chemistry: gasoline contains 8-10 carbon atoms, and diesel is 12-15, so diesel contains higher energy. Diesel does not need to be ignited and spontaneously ignites under higher pressure, so it has a higher efficiency (in fact, the maximum utilization rate is only 30%), but it is very heavy and noisy. Gasoline needs to be ignited, so the gasoline engine is small and quiet (its utilization rate is only 15%).
4. The smell is different, gasoline is pungent, diesel smell is weak. The color is different, gasoline is light, diesel is dark. The capacity is different, gasoline is thinner and diesel is thicker. The way to ignite on vehicles is different, gasoline is ignited by a spark plug, and diesel is compression ignition. Diesel has poor anti-knock properties. Compared with gasoline, diesel has less horsepower, is more polluting, and emits black smoke, but the price is lower.
Gasoline and diesel engines are currently widely used in industrial and agricultural production and transportation sectors. The main difference between them lies in the compression ratio, ignition method, fuel used and purpose. Compression ratio refers to the ratio of the maximum volume and the minimum volume of gas in the cylinder when the piston moves in the cylinder. The gas volume in the cylinder is the largest when the piston is at the lowest point, and the gas volume in the cylinder is the smallest when the piston is at the highest point. The former is called the total cylinder volume and the latter is called the cylinder combustion chamber volume. The compression ratio is defined as compression ratio = total cylinder volume/combustion chamber volume compression ratio is an important indicator of an internal combustion engine. The larger the compression ratio, the greater the pressure and the higher the temperature. The compression ratio of gasoline engines is 4-6. The compression ratio of a diesel engine is 15-18. In theory, the larger the compression ratio, the higher the efficiency. However, because the cylinder is limited by the strength of the material, and the temperature of the working fluid in the cylinder cannot exceed the ignition point of the fuel, the compression ratio cannot be too large.
They have different ignition methods. The gasoline engine mixes and pressurizes the gasoline vapor drawn into the cylinder with air, and then uses a spark plug to ignite. In a diesel engine, misty diesel sprayed from a fuel injector is mixed with air, pressurized, and compressed to increase the temperature of the mixed gas for automatic ignition. Gasoline engines use gasoline as fuel, and diesel engines use diesel as fuel. Their name comes from this.
The gasoline engine is made of aluminum alloy, plastic and other materials. It is small in size, light in weight, easy to start, stable in operation, and fast in speed. It is suitable for vehicles and airplanes that require small size and fast speed. Diesel oilThe compression ratio of the machine is large, and the cylinder is made stronger and heavy because it has to withstand greater pressure. Generally, it is made of steel, iron and other materials. It has high power and is suitable for large trucks, tractors, locomotives and ships with large loads.
Because gasoline vehicles and diesel vehicles use different fuels, their engine structure, mixture formation method and combustion method are different, and their pollutant emission rules are also different. The main differences between the two emissions are manifested in the following aspects:
1, gasoline has strong volatility, while diesel is difficult to volatilize, so there are fuel evaporative emissions in gasoline vehicle pollutants, and its components are hydrocarbons ( hc).
2, gasoline has the characteristics of being easy to mix with air and not easy to separate after mixing. The fuel mixture of gasoline vehicles is formed outside the combustion chamber of the engine (in the carburetor and/or intake pipe), and passes through the intake and compression process before being ignited, with a relatively long mixing time. Therefore, gasoline and air can be mixed very uniformly, and there is basically no local over-rich or over-lean and liquid oil droplets. The small molecule of gasoline determines that there are fewer particulates in gasoline vehicle emissions. The ratio of air to gasoline entering the combustion chamber of the engine is basically controlled near the theoretical air-fuel ratio (the so-called theoretical air-fuel ratio refers to the amount of air required to burn 1 kg of fuel in theoretical calculations, usually around 14.7 for gasoline). The spark plug discharges ignition and combustion, and the combustion speed is very fast; the compression ratio of gasoline engine is low, the maximum combustion pressure is low, and the maximum temperature is high. After combustion, the product has a serious tendency to dissociate at high temperature. Some "dead zones" do not catch fire or under certain working conditions Lower the fire, so that there are more carbon monoxide (co) and hydrocarbons (hc) in the gasoline engine emissions. At the same time, the high temperature in the combustion chamber of the engine leads to the production and emission of nitrogen oxides (NOx). Therefore, gasoline vehicle emissions are characterized by high carbon monoxide (co) and hydrocarbon (hc) emissions, while low particulate matter emissions, and nitrogen oxide (nox) emissions are basically the same as diesel vehicles.
3. The formation of diesel fuel mixture is carried out in the combustion chamber of the engine. Diesel fuel is injected into the combustion chamber at high pressure, and after compression and ignition, the diffusion combustion method is performed while spraying and burning. This way of working determines that the mixture of diesel and air is not uniform, and there is inevitably local hypoxia or local oxygen enrichment. When oil is in high temperature and oxygen deficiency, it is easy to be carbonized to form soot. The adjustment of diesel vehicle load is controlled by changing the fuel injection volume. The mixture of diesel vehicles is always in a relatively lean state, that is to say, there is always surplus air in the combustion chamber of the diesel engine. The surplus air is prone to produce nitrogen oxides (nox) under the action of high temperature, while carbon monoxide (co) and hydrocarbons (hc) are not easily formed. Therefore, diesel vehicle emissions are characterized by high particulate matter and nitrogen oxide (nox) emissions and low carbon monoxide (co) and hydrocarbon (hc) emissions.
In addition, some odorous organic gases are generated after the diesel is burned. Therefore, there is still odor in diesel engine emissions.
So gasoline cars can only use gasoline, diesel cars can only use diesel
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