Fernandes, H., Pimenta, C., Rodrigues, W., de Souza Montemor, R. et al., "Experimental Investigation of Internal Exhaust Gas Recirculation on a Variable Valve Actuation Spark Ignition Engine Operating with Gasoline and Ethanol," SAE Technical Paper 2016-36-0399, 2016.
Exhaust Gas Recirculation - EGR - is a well-known technique to reduce NOx and it’s been applied on Diesel engines for a long time. Later studies and application found that other benefits can be achieved with PFI and GDI gasoline engines, such as pumping loss minimization and efficient knock control. Variable valve actuation valve-trains brought broader application possibilities as it enables full internal EGR control without external paths, high precision and response, as required on transient work modes. Comprehensive investigation on PFI and GDI Spark Ignition engines with external Hot EGR and Cooled EGR are widely available. However, variable valve actuation EGR control review on a flexfuel application is not well explored, and this paper is aimed at doing such. This work involves investigating the effects of internal exhaust gas recirculation - IEGR - on the combustion, fuel economy and emissions of a variable valve actuation engine (FCA Multiair II) operating with gasoline and ethanol in a part-load condition. This technology allows to control and anticipate the intake valve opening angle in a wide range, increasing the overlap angle and consequently the IEGR flow, that is the amount of burned gas mass that has flowed from the cylinder across the intake valve into the intake runner during the exhaust phase. There are three main ways in which IEGR could benefit fuel economy in a Multiair system: reduced throttle losses, reduced valve losses, and increased thermal efficiency. However, EGR can also be detrimental to combustion stability and velocities, so a balance must be established, which requires precise control over the EGR content. It’s interesting to know that variable valve actuation offers a great fuel economy potential at moderate loads and the ability to meet future engine fuel consumption targets.