 As a critical component of an Internal Combustion Engine (ICE), a turbocharger stands highly pulsatile airflow from exhaust pipe, which determines the turbocharger performance is very different from that under steady and quasi-steady conditions. Faced the theoretical and computational challenges associated with the optimization of the inlet and outlet conditions of the turbocharger, this paper presents an active control methodology (ACM) to improve turbocharger operating conditions and performance based on the redistribution of mass flow and fuel flow. Considering the poor-efficiency constant pressure turbocharging system and high structural-dependent pulse turbocharging system, the ACM proposes 3 essential steps: extract partial compressed air from the outlet of the compressor, then heat the compressed air with appropriate amount of fuel in a combustion chamber and finally supply the gas (with high pressure and high temperature) to the turbine inlet. The first step solves the trouble that compressor works nearby surge boundary caused by the stoppage of fresh air in the cylinder intake pipes. The second and third steps guarantee there is enough entropy contained in the extracted gas to satisfy the requirement of a superior performance turbine with high efficiency, high output power and small speed fluctuation. The presented ACM can not only make full use of energy of pulse exhaust of the engine, but also create relatively stable operating conditions for turbocharger to achieve wider surge margin and better engine performance.

In this paper, a two cylinders 2-stroke turbocharged diesel engine with this active control system (ACS) is modelled using a 1-D modelling software GT-power to validate the effectiveness of the methodology. Exemplifications of compressed gas extraction strategy (determined by the pressure in the exhaust pipe of the cylinders) and fuel injection strategy (determined by the gas extraction strategy) are adopted respectively in the 1-D simulation model. The results obtained from above model show that the ACS demonstrates superior effectiveness in improving turbocharger performance and engine performance, supporting by the 62.5% wider surge margin of compressor than the model without ACS and better instantaneous performance of turbine, including mass flow rate, efficiency, shaft power and speed fluctuation specifically. The ACM and ACS presented in this paper provides a totally new idea for designing and optimizing the high-performance turbocharging system for engines. Apart from this, engine performance estimation (with the system level) under various control strategies of gas extraction and fuel injection is also one of the issues worthying discussion and argument in-depth.


An Active Control Methodology to Improve Pulsatile Turbocharger Operating Conditions and Performance

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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