Update: 2020-07-03 15:38 Source: LUFTMY
With the improvement of people's living standard and the development of urbanization, the number of cars in China is increasing, and the accompanying automobile exhaust pollution is becoming more and more serious. The exhaust pollutants are discharged into the atmosphere, causing air pollution and causing haze and other environmental problems.Therefore, to strictly control the emission of automobile exhaust, the detection of exhaust pollutants is also essential.
Composition analysis of pollutants from automobile emissions
The pollutants emitted by cars are complex.In addition to oxygen and nitrogen are combustion products, the rest are harmful components, mainly including particulate matter, carbon monoxide, nitrogen oxide, sulfur oxide and so on.
1. Suspended particulate matter
Suspended particulate matter is one of the most important sources of pollution.For gasoline engines, the particles that may be produced during operation include low-molecular substances and sulfates;Diesel engines produce much more particulate matter than gasoline engines, and the composition is very complex. The main component is soot. The diameter of soot is between 0.1 ~ 10 μm.
2. Carbon monoxide
Incomplete combustion of fuel produces carbon monoxide.Carbon monoxide can react with the hemoglobin in human body to form hydroxyl hemoglobin, which not only affects the normal combination of hemoglobin and oxygen, but also weakens the oxygen transport capacity of hemoglobin, leading to hypoxia and great harm to human health.
3. Nitrogen oxide
In an engine, the fuel is burned at very high temperatures, when the nitrogen in the mixture reacts with oxygen to form nitrogen oxides, mainly nitric oxide and nitrogen dioxide.Among them, nitric oxide can damage the human nervous system and respiratory system, can also damage the earth's ozone layer;However, nitrogen dioxide is soluble in water, so it produces acid pollution and reacts with the atmosphere to create a large amount of photochemical smog, which severely irritates the human respiratory system.
4. Sulfur oxides
Gasoline contains sulfur, and some car purifiers can convert some of that sulfur into sulfur oxide, the main sulfur oxide that causes acid rain.After leaving the purifier, sulfur dioxide will further react with oxygen in the atmosphere to form sulfuric acid smoke, causing more serious pollution.In addition, sulphur dioxide can severely irritate the respiratory tract and damage human health.
Hydrocarbons come mainly from unburned components of engine exhaust emissions.Some of the fuel will be discharged directly without combustion due to uneven gas mixtures or cold combustor walls.When the concentration reaches a certain level, it will have adverse effects on human health, which indicates that after exposure to sunlight, it will react with nitrogen oxides to form peroxides, which will stimulate the oral cavity and nasal mucosa of human body and cause inflammation.Some hydrocarbons also have a pungent odor and have the ability to drip and vaporize fuel in the oil supply system, resulting in incomplete combustion.
Automobile exhaust pollutant detection method
At present, there are many detection methods for automobile exhaust pollutants, and the mainstream equipment has tail gas PM particle sensor. The following are mainly several common detection methods in China:
1. Detection of working conditions
The working condition method is a method of detecting automobile exhaust emission under different working conditions through special testing equipment.Detection will mainly apply to the chassis dynamometer to simulate the car when the road, through the synchronous rotary drum and the wheels, so as to realize the simulation of different working conditions, the car, and then use the five gas analyzer device such as a car exhaust pollutant analysis and detection of vehicle under different conditions of exhaust pollutants content, so you can more accurately measure the checked the actual exhaust emission level.
2. Free acceleration test
Free acceleration, also known as smoke detection, is a method of measuring the amount of carbon particles in the exhaust gas of diesel vehicles through a filter paper smoke meter or an opaque smoke meter.Because the exhaust pollutants of gasoline engine cars are mainly hydrocarbons, carbon monoxide and nitrogen oxides, while the exhaust pollutants of diesel engine cars are mainly carbon particles, the exhaust pollutant detection methods of different cars are also different.During the test, the exhaust gas is introduced into the smoke meter for measurement, and the quality of the exhaust gas is judged by comparing the smoke value or impermeability to determine whether it conforms to the standard.
3. Idle/double idle detection
The idle speed test is a method to measure vehicle exhaust emissions under idle speed condition, and the double idle speed test is a method to increase the high idle speed speed test on the basis of the idle speed test.Essentially, the principle of the two detection methods is the same, but the double idle method is more accurate.The use of these two methods of detection does not require too much detection equipment, the use of a five-gas analyzer.
During the specific test, the vehicle exhaust pollutant value under idle speed condition is first detected, and then the vehicle is accelerated to 70% of the rated speed. After one or two minutes, when the vehicle speed is stable, the vehicle is decelerated to 50% of the rated speed, and the vehicle exhaust pollutant value is tested again, that is, the test is completed.
4. Remote sensing detection method
It is mainly used in the synthesis method of integrated emission receiver analyzer, infrared and infrared detection camera, integrated infrared instrument analyzer, in the pollutant concentration detection process to detect the principle of vehicle emission, can identify the reverse wave.In the case of vehicle emissions and other pollutants, if the vehicle is detected, whether the emission test exceeds the limit.
5. Vehicle exhaust gas detection method
Vehicle-mounted exhaust gas detection method is a method to detect the exhaust pollutant emission data in the process of vehicle driving by installing exhaust gas detection device and five-gas analyzer on the vehicle.The main pollutants tested include CO, CO2, HC, NOX and PM, and the driving process, location information and speed of the car are recorded through the automobile dashcam.The analyzer USES different gases to analyze the particularity of infrared wavelength electromagnetic wave energy, so as to further detect the degree of pollution.
PM of particulate matter is through the exhaust particulates sensor for testing, for example, using LUFTMY LD12 laser particle sensor, can continuous acquisition per unit volume and calculate the number of different particle sizes of suspended particles in the air, the particle concentration distribution, and conversion into mass concentration, and the output in the form of general digital interface, provide accurate tail gas PM concentrations.