Direct Injection, Spark-Ignited Engines
Omnivorous Engine Setup
New engine technology has made possible engines that will operate on a wide variety of fuel inputs, from gasoline to naptha to ethanol to methanol, without driver intervention. Although flexible fuel vehicles have been produced in the millions, their engines have always been optimized for gasoline operation while accepting significant performance and efficiency degradations when using the alternative fuel.
This project seeks to combine in-cylinder measurement technology, and advanced controls to optimize spark timing, the quantity and timing of injected fuel, to produce an "omnivorous engine"--one that will be able to run on any liquid spark ignition fuel with optimal efficiency and low emissions. This project will complement other Energy, Environment, and Prosperity projects for the production of biofuels and can be combined with hybridization for even greater reductions in fuel consumption.
With the latest ignition, fuel injection, and boosting technologies, producing an intelligent engine that operates with maximum efficiency on a wide variety of conventional and bio-derived fuels is becoming both feasible and cost effective. Combining a number of near-production technologies in a modern spark ignition engine, the intention is to demonstrate exceptional fuel flexibility without a fuel system sensor and achieve excellent fuel conversion efficiencies.
The project's approach is also simple and cost effective, enabling rapid commercialization of the omnivorous engine concept. The omnivorous engine will run effectively on a wide range of liquid fuels but will provide increased performance on biofuels, providing consumers with an incentive to use nonpetroleum fuels.
New technology has been developed to use in-cylinder ionization sensing, which will allow real-time analysis of fuel burn rates. This "combustion signature analysis" ability enables detection of the kind of fuel used to determine optimal spark timing. In addition, this information enables control of other engine parameters, such as boost to increase effective compression ratio and exhaust gas recirculation rates to control exhaust emissions.
Initial work will focus on baseline operation with gasoline and ethanol at stoichiometric air/fuel ratios. Future efforts will calibrate for other renewable fuels such as ethanol, and expand engine regimes to ultra-lean low temperature combustion operation on various fuel blends.
Recent work on this engine platform has been focused on analyzing the impact of alternative fuels on engine efficiency and emissions. Fuels of interest include ethanol at various blend levels with gasoline, as well as higher alcohols such as butanol.
Investigations include measurement of regulated emissions and air toxins before catalyst, as well as at the tail-pipe in steady-state and transient operation. The area of interest further includes measurement of particulate emissions from SIDI engines fuelled with both gasoline as well as gasoline-alcohol blends.
Spark ignition direct injection internal combustion engines show tremendous fuel economy benefits compared to conventional port-injected gasoline engines. The level of complexity of gasoline Direct Injection Spark Ignition (DISI) engines varies widely depending on the operating strategy. Homogeneous stoichiometric DISI engines allow modest fuel economy improvements due to the potential of operation at higher compression ratios. This benefit comes at a higher system cost but allows the use of conventional after-treatment systems. Further significant efficiency improvements are possible with lean burn direct injection concepts; however, these concepts require advanced after-treatment systems that are only effective at low levels of sulfur in the fuel.
Argonne's research evaluates the fuel economy potential of advanced gasoline direct injection spark ignition engine concepts compared to a homogenous stoichiometric direct injection baseline engine already operating at Argonne. Starting with a homogeneous lean burn concept, the operational limits will be identified and consequently further extended towards lean operation using charge stratification. The potential concepts include wall-guided, air-guided, as well as spray-guided modes. A comparison of the different concepts will be performed based on fuel economy, performance, and emissions behavior.
The results of these studies will contribute to more accurate models that predict the drive-cycle efficiencies of such advanced internal combustion engine concepts in complex powertrain configurations.