Preliminary study on a variable-geometry exhaust manifold turbocharging system

A variable-geometry exhaust manifold (VGEM) turbocharging system can realize a switch between two charging modes by use of a controllable valve, and it can give a good performance at both high-speed operation and low-speed operation. In this paper, a new idea about the VGEM turbocharging system for a six-cylinder diesel engine is proposed, and preliminary experiments on this are carried out. Experiments on the two cases when the controllable valve is closed or is open respectively are performed using two different exhaust manifolds. The steady state experimental results indicate that the turbocharging system works as a pulse turbocharging system and the pulse energy can be utilized fully when the controllable valve is closed at low-speed operation; the turbocharging system works as a semiconstant-pressure turbocharging system and the pumping loss can be reduced fully when the controllable valve is open at high-speed operation. The transient experimental results indicate that the transient performance of the pulse turbocharging system is better than that of the semiconstant-pressure turbocharging system.