Research PaperAnalysis on altitude adaptability of turbocharging systems for a heavy-duty diesel engine

- Method of altitude-adaptability evaluation and turbo-engine matching at altitudes is developed.
- Altitude-adaptability of 4 turbocharging systems is quantified based on the method.
- Operation region at plateau is limited by cylinder pressure, turbo-speed and exhaust tempearture.
- Influence of turbine area on operation region is contrary to that of turbo efficiency.
- Fuel margin is the root of influence of the area and efficiency on operational boundaries.

This paper aims to understand discrepancies of altitude adaptability among several widely applied single-stage turbocharging systems, and to develop a method of performance evaluation and turbocharger-engine matching at different altitudes. The investigation is carried out on a 6-cyclinder V-type turbocharged heavy-duty diesel engine via experimentally validated simulation method. It is concluded that the operational region with engine power recovery at different altitudes is bounded by three limits, which are the maximum cylinder pressure, turbocharger speed and exhaust temperature. The operational region is studied for the evaluation of altitude adaptability and turbocharger-engine matching at different altitudes. The influence of the turbine effective flow area and turbocharger efficiency on the operational boundaries are discussed. It is concluded that the influence on the intake mass flow rate and fuel margin is the root for the influence on the boundaries. At last, comparisons among four turbocharging systems (a fixed geometry, two waste-gate and a variable geometry) are carried out based on the theory of the operational region. Results show that the variable geometry turbocharging (VGT) has the best altitude adaptability with regard to the maximum altitude with power recovery and BSFC. Its superior results from the capability of turbine area variation as well as the potential for higher efficiency. A method of optimized turbocharger-engine matching tailored for altitude adaptability are obtained from the investigation.