Control method for reducing urea crystallization in engine SCR tank

Abstract

The invention discloses a control method for reducing urea crystallization in an engine SCR tank. By calculating crystallization energy factors and controlling opening and closing of a bypass valve based on the crystallization energy factors and SCR upstream temperature by ECU, the demand of bypass high-temperature exhaust gas on demand is realized, when to open the bypass valve can be accuratelyknown, so as to ensure that exhaust gas derived from an exhaust pipe enters directly into gas flow of the SCR upstream bypassing a turbocharger, and thus the exhaust gas temperature entering the SCR tank can satisfy reduction of the urea crystallization in the SCR tank; and at the same time, when to close the bypass valve can be accurately known, the problem of massive engine pump gas loss causedby too long opening time of the bypass valve is avoided, and optimization of the pump gas loss of engine operation is achieved on the basis of satisfying reduction of the crystallization in the SCR tank,.

Description

technical field [0001] The invention relates to the technical field of engine urea crystallization, in particular to a control method for reducing urea crystallization in an engine SCR box. Background technique [0002] The catalytic reduction reaction of the SCR box requires a certain temperature. When the temperature of the SCR box is low, urea cannot be combined with NO X The reaction is complete, and the unconsumed urea forms crystals in the SCR tank, which affects the engine power and emission results, and will block the exhaust pipe in severe cases. [0003] At present, the throttle valve is mainly used to control the intake air volume of the engine to increase the exhaust temperature, thereby increasing the NO X Conversion efficiency. However, using the throttle valve to increase the exhaust temperature will result in more pumping losses; and if the engine runs in a low-load working area for a long time, the risk of urea crystallization will be higher. Therefore, t...

AI Technical Summary

Problems solved by technology

However, using the throttle valve to increase the exhaust temperature will result in more pumping losses; and if the engine runs in a low-load working area for a long time, the risk of urea crystallization will be higher

Therefore, the common problem at present is that it is difficult to achieve a balance between the engine pumping loss and the reduction of urea crystallization

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