Engine nitrogen oxide model value obtaining method and device, equipment and medium

The invention discloses an engine nitrogen oxide model value obtaining method and device, equipment and a medium. The method comprises the steps of estimating volume flow of engine exhaust gas in realtime; inquiring delay time according to the volume flow; conducting time delay on an original nitrogen oxide value according to the delay time to obtain a delayed nitrogen oxide value; calculating achange rate of the delayed nitrogen oxide value; comparing the change rate with a preset calibration coefficient to obtain a comparison result; selecting a filter coefficient according to the comparison result, and conducting selective filtering on the delayed nitrogen oxide value by utilizing the selected filter coefficient; and conducting PT filtering on the delayed nitrogen oxide value by utilizing a selected time coefficient. According to the method provided by the embodiments of the invention, the nitrogen oxide model value obtained through treatment better conforms to the actual situation, urea injection is more