GOALI: Modeling & Control of Multi-cylinder Homogenous Charge Compression Ignition (HCCI)

Purdue University, West Lafayette IN

Investigators

Abstract

Motivation: There are currently 200 million vehicles on the road in the United States alone, resulting in the consumption of 600 billion liters of fuel each year. With annual growth rates of vehicle sales and miles driven at 0.8% and 0.5%, our domestic challenges are no less than two-fold: 1. Increasing dependence on foreign sources of transportation fuel. 2. Release of significant amounts of greenhouse & smog-generating chemicals, including CO2 & NOx. There is a solution - by integrating advanced internal combustion engines (ICEs) on hybrid powertrains we will realize a 50% reduction in fuel consumption by 2020 (Heywood et al 2003). A significant step to meeting this goal will be the implementation of a promising combustion methodology, homogeneous charge compression ignition (HCCI). HCCI ICEs exhibit a substantial increase in efficiency, 10-15%, compared to spark-ignited (SI) ICEs, and have NOx levels that are dramatically lower than either diesel or SI ICEs. Unfortunately, to date HCCI has not been practical because it is very difficult to control, for the following reasons: 1. Combustion timing: HCCI has no specific initiator of combustion. Ensuring that combustion occurs with acceptable timing, or at all, is non-trivial, requiring closed-loop control of the process. 2. Cycle-to-cycle & cylinder-to-cylinder coupling: During HCCI, subsequent engine cycles & neighboring cylinders are coupled through the temperature of reinducted exhaust gas. Multicylinder control will require accommodation of these cyclic & cylinder-coupling effects. 3. Part-load restriction: During HCCI, fuel and air are diluted with previously exhausted gasses, reducing peak power, requiring the inclusion of an SI or diesel mode in a multi-mode engine. Due to cyclic coupling, a key issue is how to transition from the conventional mode to HCCI. Technical Description: The proposed project PI has developed the first generalizable, validated and experimentally implemented physics-based control methodology for residual-affected HCCI engines (Shaver et al. 2003a, 2005bc, 2006bc), utilizing modulation of effective compression ratio and inducted gas composition (both via flexible valve actuation) to control combustion timing and work output on a cycle-to-cycle basis. While promising, it is important to note that these results have been applied under single-cylinder, constant engine speed operating conditions. In order to practically implement HCCI the dynamics associated with cylinder-to-cylinder coupling and variable engine speed must also be considered. Furthermore, the availability of direct in-cylinder fuel injection provides the opportunity to vary the amount of fuel delivered on a cylinder-independent, cycle-to-cycle basis, a capability that has yet to be exploited in this framework. The PI has the experience and available resources to address these challenges and opportunities. The goal of the proposed project is to, with additional support from the Cummins Engine company, to formulate, validate, and experimentally implement a generalizable, physics-based control strategy for mutli-cylinder, variable speed HCCI engines using cylinderindependent cycle-to-cycle control of inducted gas composition, fueling rate and effective compression ratio. If awarded, NSF funds will be used to support the modeling and control efforts of the PI and a graduate student over the course of the 3 year project. Broader Significance: Originally conceived in 1979, the HCCI methodology has been revisited several times by industry, but has yet to be implemented because industry continues to grapple with the control challenges. The proposed project represents a final step toward the practical implementation of the process. Project outputs will be directly transferable to Cummins Engine company, a leader in engine development and production. The proposed project work and accompanying multi-cylinder testbed developed during the project will be a magnet for excellent graduate students and industrial collaboration, facilitating the development of talented powertrain engineers with an appreciation for both the technical and business issues associated with the nation's escalating transportation challenges. The PI will work with his Purdue colleagues as an AGEP (Alliances for Graduate Education and the Professoriate) professor to increase the number of domestic (particularly minorities) students obtaining doctorates and pursuing academic careers in STEM areas.