Homogeneous lean burn engine combustion system development – Concept study

Abstract

TMG (TOYOTA Motorsport GmbH) and FEV have jointly conducted a concept study on environmentally friendly engine with indicated thermal efficiency (ɳinet) of 46% and low emissions while fulfilling high-performance criteria i.e. specific power of 103 kW/l and low end torque (LET) of 2.3 MPa BMEP at 2000rpm. An ultra lean-burn combustion concept has been designed by means of 1D and 3D MBD (Model Base Development) methods and subsequently validated experimentally by a single cylinder TC GDI engine as a technology demonstrator in order to fulfill the requirements of both environmental sustainability and fun to drive in passenger cars.

FEV has developed the concept with TMG by using FEV’s scatter-bands and Charge Motion Design (CMD) approach. Based on the concept layout, TMG has designed the single cylinder engine (SCE) and conducted the validation tests. Additionally, optical diagnostics of flow, mixture formation as well as combustion have also been carried out. In order to meet contrasting demands of enhanced in-cylinder charge motion necessary for ultra-lean burn and high flow performance for high specific power, a variable charge motion (VCM) system has been implemented.

This feature, in combination with high compression ratio (CR) and adapted gas exchange enabled to demonstrate the achievement of ɳinet = 46% at λ=1.90. Furthermore, the efficiency and nitrogen oxides (NOx) engine-out emission trade-off has been analyzed in details with the underlying mechanisms described.