At the US Department of Energy (DOE) Annual Merit Review in Washington, DC last week, Cory Weaver from Ford Research and Advanced Engineering reported that Ford has completed the planned build of 12 units of the new engine, and is working on vehicle integration for further testing per the project timeline. The project is scheduled to end 31 December of this year; Ford is likely to request a no-cost extension to 30 September 2015.

The approach. Ford’s approach to the project was to engineer a comprehensive suite of gasoline engine systems technologies, including:

• Aggressive engine downsizing in a mid-sized sedan from a large V-6 to a small I-4.

• Mid- and long-term EcoBoost advanced technologies such as dilute combustion with cooled exhaust gas recycling and advanced ignition; lean combustion with direct fuel injection and advanced ignition; boosting systems with active and compounding components; advanced cooling and aftertreatment systems; and advanced friction-reduction technologies, engine control strategies, and NVH countermeasures.

• Progressively demonstrate the project objectives via concept analysis/modeling, single-cylinder engine, multi-cylinder engine, and vehicle-level demonstration—the point at which the development team is now.

The original envisioned architecture was 1.8L I4 / 25 bar BMEP; during the concept evaluation in 2010 and 2011, the research team revised the architecture to 2.3L I4 / 20 bar BMEP. The attributes of the engine have stayed stable since then, and include:

This works out to about 240 hp and 260 lb-ft of torque, Weaver said. Displacement per cylinder is 565 cm³; bore & stroke is 87.5 & 94.0 mm; compression ratio is 11.5:1, and the engine is designed to run on 98 RON gasoline.

Installed in a 2013 Fusion. Source: Ford. Click to enlarge.

The engine. Features of the engine include:

• Transverse central direct injection + ignition w/ intake biased multi-hole injector
• Twin scroll turbocharger w/ scroll control valve + active wastegate
• Low pressure, cooled EGR system
• Composite intake manifold w/ integrated air-water charge air cooler assembly
• Split, parallel, cross-flow cooling with integrated exhaust manifold
• Integrated variable displacement oil pump / balance shaft module
• Compact RFF valvetrain w/ 12 mm HLA
• Roller bearing cam journals on front, all other locations conventional
• Electric TiVCT system
• Torque converter pendulum damper
• Active powertrain mounts
• Assisted direct start, ADS

Cycle-based CAE analysis of fuel economy contribution of critical technologies. Source: Ford. Click to enlarge.

The engine uses a micro-stratified charge. This entails overall lean homogeneous combustion with early primary injection and an air/fuel ratio of ~20-30:1. To this is brought a locally rich stratified charge with a late secondary injection and micro second pulse width.

Advantages of the micro-stratified charge capability include good fuel economy, low NO_x, low PM, acceptable NVH, good stability, and “practical controls”, Weaver said. The capability extends lean combustion capability to a region of good aftertreatment efficiency, potentially enabling an LNT/SCR or passive SCR system, he said, although lean aftertreatment challenges persist.

Given the DeSO_x challenges of a TWC + LNT / SCR system, and the uncertainty of a TWC + passive SCR system, the team received the go-ahead on lean aftertreatment transitioning to stoichiometric at the vehicle level.

Advantages of the micro-stratified charge shown on the dyno. Source: Ford. Click to enlarge.

Ford has completed the build on the first vehicle (a 2013 Fusion) with the engine, and is starting calibration development. The build of a second vehicle is in progress.

MTU’s role. In the project, MTU is supporting Ford in the R&D of advanced ignition concepts and systems to expand the dilute/lean engine operating limits. MTU has completed all six research tasks associated with the project, and continued three research tasks with Ford funding. The six research areas are:

• Advanced ignition & flame kernel development
• The impact of advanced ignition on dilute combustion
• Air/fuel mixing via planar laser-induced fluorescence (PLIF) for fuel injection optimization
• Combustion sensing & control
• Advanced knock detection & control
• In-cylinder temperatures & heat transfer

The work has resulted in several SAE papers already published, with another in progress, as well as a Ph.D. dissertation.

Resources
(DOE will publish Merit Review presentations on its website.)

• Corey E. Weaver (2014) “Advanced Gasoline Turbocharged Direct Injection (GTDI) Engine Development” DOE 2014 Annual Merit Review, Project ACE065

• DOE Advanced Combustion Engines 2013 Annual Progress Report

• Zhang, A., Cung, K., Lee, S., Naber, J. et al. (2013) “The Impact of Spark Discharge Pattern on Flame Initiation in a Turbulent Lean and Dilute Mixture in a Pressurized Combustion Vessel,” SAE Int. J. Engines 6(1):435-446 doi: 10.4271/2013-01-1627

• Chen, W., Madison, D., Dice, P., Naber, J. et al. (2014) “Impact of Ignition Energy Phasing and Spark Gap on Combustion in a Homogenous Direct Injection Gasoline SI Engine Near the EGR Limit,” SAE Technical Paper 2013-01-1630, doi: 10.4271/2013-01-1630