When the scavenging port is closed but the exhaust port is not closed, the exhaust system will have a back pressure on the fresh charge to be discharged from the exhaust port, and the fresh charge will be back pressured back to the cylinder. This requires energy in the exhaust pipe. During this period, a high-pressure zone near the exhaust port is formed. The specific measure is to design a contraction tube or catalytic converter after the expansion tube to make the gas generate a positive pressure wave due to the reduction of the pipe section, and design appropriate structural dimensions so that the positive pressure wave reaches the exhaust just when the scavenging port is just closed. Breath. When the structure is properly designed, the negative pressure wave is transmitted back along the exhaust pipe to the exhaust port just after the scavenging port is opened, and the ventilation process is accelerated under the positive and negative pressure difference between the intake port and the exhaust port. According to the above design idea, the best economy and power can be obtained at the tuning speed of the engine.
The road test carried out the development of exhaust catalytic converters based on the results of engine simulation calculations. Its main work is to match the power and economy of the exhaust catalytic converter and the engine, match the power and emission performance, and carry out overtaking acceleration and maximum speed comparison tests with the original car on the road in accordance with national standards. One of the criteria for judging whether the match is successful or not.
Comparative test before and after installation. It can be seen from the test results that the maximum acceleration time of the bus after the addition of the catalytic converter is reduced by 5.8% (that is, the acceleration capability is enhanced), and the maximum speed is reduced by 1.6% compared with the original vehicle, indicating that the catalytic converter has no effect on the original vehicle’s power Adverse effects: The maximum acceleration noise change is within 0.3dB (A), and the driver feels good during the road test.
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Link to this article：Engine simulation calculation results
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