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Two-stage turbocharging technology is a solution to reduce turbo lag and improve the performance of engine and matching characteristics at high altitudes. In the present study, an engine testing system was established to study combustion performance and matching characteristics of a regulated two-stage turbocharging system (R2S) at different simulated altitudes. An equivalent turbocharger concept was put forward aiming to simplify the R2S with three bypass valves, and the total equivalent turbine flow area and equivalent efficiency of the R2S were obtained based on a theoretical study. Intake characteristics, combustion process, torque, power and fuel economy of the diesel engine matched with R2S were analyzed at different altitudes. The results showed that compared with 0 m, intake pressure, maximum combustion pressure, cumulative heat release, heat release rate decreased by 36.5%, 33.6%, 33.5%, 21.6%, −8.9% at 4000 r/min, and decreased by 12.3%, 2.9%, 16.4%, 8.8%, −5.4% at the speed of 2000 r/min at the altitude of 5000 m. The torque, fuel consumption and fuel consumption rate decreased by 10.1%, 5.1% and 5.4% at engine speed of 2000 r/min and by 35.7%, 27.6% and 8.9% at engine speed of 4000 r/min at 5000 m.

A variable geometry turbocharger in series with a variable geometry turbocharger (Twin-VGT) system was designed to improve engine power at high altitudes. The influence of altitudes on the performance of the Twin-VGT system was investigated in the perspective of available exhaust energy. The interaction between exhaust flow characteristics of Twin-VGT and openings of Twin-VGT vanes was theoretically analyzed at different altitudes. Meanwhile, a model of a diesel engine matched with the Twin-VGT system was built to study the matching performance of the Twin-VGT system with engine at different altitudes. The optimal opening maps of both high-pressure and low-pressure VGT vanes at high altitudes were obtained to achieve the maximum engine power. The results showed that the optimal openings of high-pressure and low-pressure VGT vanes decreased with increase in altitudes. The operating points of the two-stage compressors located at the high efficiency region and the compressor efficiency region both exceeded 62% at different altitudes. The global expansion ratio increased with increase in altitudes and reached 4.9 at 5500 m. Compared with the VGT in series with a fixed geometry turbocharger on testing bed, exhaust energy of Twin-VGT turbines at low speeds was utilized reasonably and global pressure ratio increased by 0.69–0.94, while brake-specific fuel consumption decreased by 11.24–33.62% under low speeds above altitudes of 2500 m.

High-altitude calibration of CA6DL2-35E3R common rail diesel engine was finished on engine high altitude simulating environment test bed. The interactions between injection parameters and its impact on engine high altitude performance were studied. Results show that the fuel delivery per cycle per cylinder increases with the adwance of injection timing and the increase of common rail pressure at the calibration sweep as a whole; fuel delivery per cycle per cylinder increased about 0.1–0.3 mg with advancing 1 ° CA injection timing and it would increase 0.07–0.1 mg with increasing 1 MPa common rail pressure averagely. The fitting error of constructed radial-based function neural network model was below 10−12 and the predictive error of which was between 1.5%, which can fulfill common rail diesel engine characteristics modeling demand. The model can help alleviate the influence of the injection timing and common rail pressure on fuel delivery per cycle per cylinder, and achieve the impact of one single injection parameter on engine performance, which can help increase the understanding of common rail diesel engine injection characteristics.

The performance of CY4102BZLQ turbocharged diesel engine with the HP60 turbocharger at different high altitudes was studied on the engine test bed for simulating high altitude (low air pressure). The conclusion indicated that the engine performance such as power and economy decreases with the increase of altitude, and the temperature of exhaust increases simultaneously. In addition, the rotational speed of the turbocharger and turbocharger ratio increase with the increase of altitude.

In order to improve the plateau adaptability of CY4102BZLQ-A2A turbocharged diesel engine, the matching performances of the diesel engine with TB28 and HP60 turbochargers at different altitudes (0 m, 2,000 m, 3,000 m, 3,500 m, 4,000 m) were investigated on the engine test bed for simulating high altitude (1ow atmosphere pressure). Results show that HP 60 turbocharger is more suitable to match the engine in terms of engine performance, intake air characteristics, turbocharger rotational speed etc. TB28 turbocharger is over speed when the engine runs at 3,500 m altitude and 2,600 r/min rotational speed, while HP60 turbocharger is over speed when the engine runs at 4,000 m altitude and 2,800 r/min rotational speed. No matter which turbocharger is selected to match the engine, the performance of the engine will deteriorate at different extents. The intake air flow mass and the air-fuel ratio decrease by 7.1-10.5% and 7.2-10.3% respectively with altitude increasing every 1,000 m. By contrast with 0 m altitude, engine torque and power at 4,000 m altitude decrease within 1% and the specific fuel consumption increases by 3.2-3.5% at the maximum torque speed, while the engine torque and power decrease by 4.6-5.3% and 4.5-5.2% respectively and the specific fuel consumption increases by 5.3-11.5% at higher and lower engine rotational speed.