Equivalent model-based optimal matching for two-stage turbocharging systems with bypass valves

A bypass valve can effectively distribute the energy of a two-stage boosting system and adapt to the demand for air intake regulation in multiple combustion modes. Gradually, it has become the direction of evolution of boosting technology. However, the existing two-stage turbocharging system matching methods do not consider the selection of bypass valves simultaneously. This study proposes an optimal matching method (H-TCB) for the critical parameters of a two-stage turbocharging system with a bypass valve based on the equivalent model of a two-stage turbocharging system. Taking the lowest comprehensive energy consumption as the constraint boundary, the theoretical constraint equations for the optimal distribution principle of the pressure and expansion ratios of the two-stage turbocharger with a bypass valve were obtained. The cooperative optimal relationship between the bypass coefficient and flow area of the high-pressure stage turbine and the similar flow of the high-pressure stage compressor were analyzed. The research results show that, as the bypass coefficient increases, the optimized matching high-pressure stage turbocharger efficiency increases gradually, the effective flow area of the high-pressure stage turbine reduces, and the flow of the high-pressure stage compressor increases. [Display omitted] •An equivalent model of a two-stage turbocharging system with a bypass valve.•Optimization matching method for a two-stage turbocharging system with bypass valve.•The optimal distribution principle of pressure and expansion ratio is proposed.•The influence of the bypass coefficient on the HP stage turbocharger is revealed.•The matched turbocharging system has the lowest comprehensive energy consumption.