Advanced combustion strategies including premixed charge compression ignition, homogeneous charge compression ignition, and lifted flame combustion are promising approaches for meeting increasingly stringent emissions regulations and improving fuel efficiency in next generation powertrains. Variable valve actuation and closed-loop control promise to play a key role in the promotion and control of these advanced combustion modes. For example, modulation of intake valve closure timing dictates the effective compression ratio and influences the total amount of charge trapped inside the cylinder, and in so doing allows manipulation of the in-cylinder reactant concentrations and temperature prior to and during the combustion process. The effort described here uses data from, and an experimentallyvalidated simulation model for, a multi-cylinder engine with variable geometry turbocharging, cooled exhaust gas recirculation, and fully flexible variable valve actuation. This effort's intent is to determine the control authority over the gas exchange process and effective compression ratio when intake valve closure timing modulation is included on a modern turbocharged diesel engine, as well as to lay the groundwork for closed-loop control design for the promotion and control of advanced combustion modes. The engine testbed at Purdue provides a unique opportunity to pursue these objectives for turbocharged engines with exhaust gas recirculation, as it is the only such engine system in academia outfitted with multi-cylinder fully-flexible valve actuation. A method to estimate in-cylinder temperature at top dead centre is also described. Candidate control architectures for both steady state and transient operation are introduced.

The majority of commercial off the shelf (COTS) diesel engines rely on EGR to meet increasingly stringent emissions standards, but these EGR systems would be susceptible to corrosion and damage if JP-8 were used as a fuel due to its high sulfur content. Starting with a Cummins 2007 ISL 8.9L production engine, this program demonstrates the modifications necessary to remove EGR and operate on JP-8 fuel with a goal of demonstrating 48% brake thermal efficiency (BTE) at an emissions level consistent with 1998 EPA standards. The effects of injector cup flow, improved turbo match, increased compression ratio with revised piston bowl geometry, increased cylinder pressure, revised intake manifold for improved breathing, and piston, ring and liner designs to reduce friction are all investigated. Testing focused on a single operating point, full load at 1600 RPM. This engine uses a variable geometry turbo and high pressure common rail fuel system, allowing control over air fuel ratio, rail pressure, and start of injection. These parameters were optimized for several component combinations to provide an estimate of the best engine efficiency that could be achieved for various levels of engine modification. While the program goal is to have emissions consistent with 1998 EPA standards, testing was also conducted at higher emissions levels to determine the additional gain in BTE that could be possible if emissions were not a constraint.