Theoretical and experimental investigation of the pressure ratio distribution and the regulation strategy of a two-stage turbocharging system for various altitudes operation

Abstract

Fixed two-stage turbocharging system matched at high altitude leads to engine performance deterioration at low altitudes due to unreasonable pressure ratio distribution between two stages. In this paper, a thermodynamic model of regulated two-stage turbocharging system is established. Theoretical analysis shows the pressure ratio distribution should lean towards a turbocharger with greater efficiency, and the high-altitude operation intensifies the role of HP stage. Experiments are conducted on an environment simulation test bench. Then, the optimal pressure ratio distribution and ETAR at various altitudes are proposed. Experiment results demonstrate that the turbocharging system boosts sufficient intake air with the optimal ETAR. Compared to that with the fixed turbocharging system, the maximum increment of the overall efficiency is 9.3 % at 0 m and attains 1.5 % at 3000 m. Consequently, the output torque is 100 % recovered below 3000 m, and it exceeds 91 % at 4500 m. Moreover, the optimal ETAR reduces the BSFC under low altitude conditions.