With the rapid progress of the country's science and technology and automobile industry in recent years, and the country's environmental requirements, automobile engines have been directly upgraded from the original emission standards of one country, two country, and three countries to the emission standards of four country, five, and even six countries. (National IV vehicles have been banned from being licensed in many places)
. One of the most effective measures to improve exhaust emission standards is to post-treat the engine's exhaust to neutralize and reduce harmful substances in the exhaust gas emitted by the vehicle! The development of science and technology is too fast. It took less than ten years from National III to National VI. Truck drivers who do not have much culture have kept up with the pace of development at all and are at a loss in daily use and maintenance! Below, based on what I have learned, I will introduce to you what the exhaust gas treatment system is. Hope it can help everyone!
Urea liquid is a liquid used in SCR technology to reduce nitrogen oxide pollution in diesel vehicle exhaust. Its composition is 32.5% high-purity urea and 67.5% deionized water. Automotive urea solution is converted into nitrogen, oxygen, and water by selectively catalyzing the reduction of with NOX product , thereby reducing the emission of nitrogen and oxygen compounds.
Next I will talk about the exhaust gas treatment system, and there are two sensors on the silencer. One is an exhaust temperature sensor, whose main function is to monitor exhaust temperature. Because the temperature is too low, urea and urea liquid cannot produce chemical reactions, injecting urea at this time will only cause crystallization in the exhaust pipe to block the exhaust pipe. Only when the exhaust temperature reaches the specified temperature will the computer issue a command to spray urea. So many cars have installed screws on this. Make it get the wrong data to save urea.
Another one is the nitrogen oxygen sensor. The basic working principle is: under certain conditions, the difference in oxygen concentrations between the inside and outside of zirconium oxide is used to generate a potential difference, and the larger the concentration difference, the greater the potential difference.
Under high temperature and catalyzing of platinum, negatively charged oxygen ions are adsorbed on the inner and outer surfaces of the zirconia sleeve. Since there is more oxygen in the atmosphere than in the exhaust gas, the side on the casing that communicates with the atmosphere absorbs more negative ions than the side on the exhaust gas, and the difference in the concentration of ions on both sides generates an electromotive force. After processing through the processing module, the data signal is provided to the ECU.
Urea pump passes urea pipette (negative pressure,) and then continuously transports urea liquid from the urea box through a pipeline (high pressure, with electrical heating) to the urea nozzle. Similar to our diesel pipeline. One is mechanical pump , and the other is electronic pump. Due to the special properties of urea (low-temperature freezing, Aijing), the urea pump has the function of re-suction and emptimentation pipeline. The urea system can work normally, and the ECU also needs to collect other data, such as a urea level sensor, to measure the amount of urea in the urea box.
urea liquid temperature sensor transmits temperature signals to the ECU to control the flow rate of antifreeze (there is an electromagnetic relay valve on the antifreeze pipeline), and heats up the urea liquid. There is also a ventilation plug on the urea box to balance the pressure inside and outside the urea box. (You should also pay attention to maintenance. When blocked, it will affect the urea pump to absorb urea and generate resistance). In order to ensure that the urea nozzle is not blocked by impurities, there is a filter element on the urea pump and a small filter element in the outlet pipe, which should be cleaned or replaced frequently.
gas-driven urea system uses compressed air to pressurize the urea liquid to replace the urea pump. During normal operation, all pipelines and urea irrigation must be in a closed state and must not leak air or liquid. The ECU obtains appropriate pressure by controlling the intake valve and exhaust valve as the pipeline. When stopping, open the exhaust valve to reduce pressure and empties the residual urea liquid in the pipe. The urea liquid filter element is injected, and the urea head needs to be removed before it can be replaced. There is also an air filter element on the urea gas supply pipeline.
When we use our cars in daily life, we must choose good quality urea liquid. Bad urea liquid Aijing blocks the pipeline, or produces other solidified substances after chemical reaction with the exhaust gas, blocking the silencer. The low concentration of urea affects the exhaust gas treatment effect and increases the injection volume of urea. Low-quality diesel is also one of the reasons for the production of cured substances.So when we are consuming, we must keep our eyes open and calculate the accounts, otherwise the gain will not be worth the loss! If the pipelines can be smooth, the wires are in good contact, and the signal transmission is normal, the failure rate of the urea system can be reduced!
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hopes to help card friends, and I hope everyone can add some shortcomings!
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