carThe exhaust gas emitted is mainly composed of carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOX). After they accumulate in the air to a certain extent, under the action of sunlight, nitrogen compounds and hydrocarbons will play a role. The reaction produces photochemical smog containing nitrogen dioxide (NO2) and ozone (O3). Both of these substances are hardly soluble in water. When they are inhaled into the human body, they will drive straight into the lungs. When the concentration is high, they can cause toxic edema, which can enter the blood. The formation of denatured hemoglobin makes the tissue hypoxia, which is extremely harmful to people's health. In 1955, the city of Los Angeles in the United States was shrouded in photochemical smog for a few days. Thousands of people were victimized and 300 people died. In addition, the oxyhydroxide will form acid rain after entering the atmosphere, which will harm the ecological environment. Therefore, as the number of cars continues to increase, countries around the world are paying more and more attention to the issue of car exhaust emissions. Since the 1970s, European and American countries have successively formulated laws and regulations to control automobile exhaust emissions. This kind of government action has promoted the development and application of automobile exhaust purification devices, and a relatively simple and effective catalytic exhaust purification device has also emerged.
The key of a catalytic exhaust purifier is "catalysis", that is, the use of a catalyst to purify the exhaust gas of a car and convert the harmful substances in the exhaust gas into harmless substances. As early as the mid-1970s, the United States had implemented this method, and it has been widely used by the automobile industry in various countries. It is still the most effective purification method so far. There are many types of catalytic exhaust purifiers, such as oxidation type, double-bed type, three-element type, and the most commonly used one is three-element catalytic purifier. The European Community has stipulated that starting from January 1993, all new gasoline engines sold in the European Community countries must be equipped with three-way catalytic converters.
The appearance of the three-way catalytic converter is an exhaustsilencerIn fact, it also functions as a muffler. The shell is made of high temperature resistant stainless steel. The honeycomb channel inside is coated with a catalyst. The catalyst is composed of rare earth metals such as platinum, palladium and rhodium. When car exhaust gas passes through the channel of the purifier, carbon monoxide and hydrocarbons Under the action of the catalyst platinum and palladium, it reacts with the oxygen in the air to produce harmless water and carbon dioxide, while the nitrogen oxide compound is reduced to harmless oxygen and nitrogen under the action of the catalyst rhodium. The so-called three-way catalytic purifier refers to a high-efficiency purifier that can simultaneously convert the three main harmful substances in the exhaust gas into harmless substances as long as the exhaust gas passes through the purifier itself. In order to give full play to the efficiency of the three-way catalyst, the air-fuel ratio of the automobile engine (the weight ratio of the amount of air charged into the cylinder to the amount of fuel entering the cylinder) must be close to the theoretical ratio, and its air-fuel ratio can only be in a small range Internal changes, otherwise the three harmful substances in the exhaust gas cannot be purified at the same time.Therefore, the three-way catalytic converter should be used in conjunction with the electronic computer control system on the car.Oxygen SensorThe oxygen concentration in the exhaust gas is detected, the information is fed back to the computer, and the computer controls the air-fuel ratio.
The three-way catalytic exhaust purifier is installed on the exhaust device of a car engine. Its purification efficiency is very high, and it can purify more than 90% of harmful substances. It is a new device on modern cars. Of course, the catalytic exhaust purifier is not all-powerful. It can only be applied to cars with unleaded gasoline as fuel. Because leaded gasoline is used, the lead in the exhaust gas will cover the catalyst and stop the purifier from working. Play any role, commonly known as "poisoning." Therefore, there are two prerequisites for the use of three-way catalytic exhaust purifiers in automobiles: one is to use unleaded gasoline, and the other is to use electronically controlled fuel injection devices for the engine. In this way, three-way catalytic exhaust purifiers In order to achieve a purification effect. Moreover, the technology of the three-way catalytic exhaust purifier is relatively high. If the catalyst coating on the honeycomb channel is expanded, it will be as large as two football fields. The manufacturing process is quite strict, but due to the good exhaust gas conversion Effect, so it is widely used. Recently, Beijing has implemented new emission standards for light-duty vehicles. Shanghai and some other large cities will also announce such vehicle emission standards. Three-way catalytic exhaust purifiers will be widely used in China.
Related:
·Three-point repair and seven-point maintenance of the car[汽车修理知识]
·Summer useantifreeze[夏季汽车养护]
·How to maintain the car in summer to let your car spend the summer in peace[夏季汽车保养]
·Be careful when driving and maintaining a car with heavy thunderstorms in summer[夏季汽车保养]
·Do "three preventions" and "four inspections" for the use of vehicles in summer[夏季汽车保养]
·The difference between iron rim and aluminum rim and maintenance method[汽车维修知识]
Email: