Based on an 1D thermodynamics model set up with the GT-power

the comparative simulation study on the performance of a diesel engine equipped respectively with a two-stage turbocharger(TST) system and a regulated two-stage turbocharger(RTST) system at different altitudes (0 km

2 km and 4 km) was carried out to achieve high efficiency and low emissions of diesel engines in a plateau environment. The results show that

at full load

the high stage boosting rates of both two-stage turbocharger systems increase with the altitude. Compared with TST

RTST guarantees higher intake air flow and air/fuel ratio(AFR) at the plateau of 2 km and 4 km

thus having less restrain in torque and reducing the brake specific fuel consumption(BSFC). The temperature before turbocharger and heat transfer energy of TST and RTST increase similarly with the altitude

but those of RTST increase less. At the low altitude of 2 km

the specific emissions of NOx increase with the altitude. At the altitude of 4 km

when the opening of the variable geometry turbocharger(VGT) decreases and the start of main injection(SOI) delays

both the intake air flow and AFR increase. With the increase of the VGT opening and the delay of SOI

the temperature before turbocharger rises. The heat transfer energy decreases first and then increases with the increase in the VGT opening

and decreases with the delay of SOI. NOx specific emissions decrease with the increase in the VGT opening

and decrease slightly with the delay of SOI. Earlier SOI (-7° to -4° in crank angle after the top dead center) coordinated with reasonable VGT opening (0.3~0.5) is beneficial to reducing the trade off between BSFC and NOx specific emissions.