The effects of variable geometry turbocharger (VGT) opening

retarded intake valve closing timing and post injection strategy on the promotion of SCR temperature were experimentally studied in detail

and the comparative analysis of the above approaches was made with regard to SCR temperature rise

emissions and engine operation economy. Experiment results show that using the post injection

increasing the VGT opening and taking the advantage of RIVCA (retarded intake valve closing auction) can effectively increase the SCR temperature. Compared with the post injection strategy

increasing the VGT opening and using the RIVCA make the engine have lower fuel consumption. Based on the above steady state test results

the post injection strategy and VGT-RIVCA strategy were selected and the further comparison was carried out by cold-start of WHTC test. Results show that both strategies can reduce the SCR light-off time to around the 600th second of the test cycle

and at this point the post injection strategy worsens the fuel economy by 3.5%

while the VGT-RIVCA strategy by only 1.1%. Through the contrast test of different VGT openings

an optimized VGT-RIVCA control strategy was obtained. With this strategy

the SCR temperature can reach 190℃ at the 540th second of the test cycle

NOx emission is reduced to 0.929 g/(kW•h） from 1.78g/(kW•h）

and the engine fuel consumption increases by only 1.4%.