1. Paper title: Fundamental phenomena affecting low temperature combustion and HCCI engines, high load limits and and strategies for extending these limits Paper authors: Samveg Saxena, Ivan D. Bedoya Literature review by Chi-Wei Tsang Date: 3/5/15

2. Introduction This review paper has three major parts: 1. Fundamental phenomena affecting high load HCCI - chemical kinetics and fuel properties, in-cylinder charge, combustion timing, and heat transfer 2. Operating limits and practical considerations for high load HCCI - ringing limits, misfire limits, cyclic variability limits, peak in-cylinder pressure limits, etc. 3. Strategies for avoiding and expanding the operating limits for HCCI and LTC - delayed combustion timing, partial fuel stratification, and spark-assisted HCCI

3. Single-Stage and Two-Stage Ignition Single-stage: fuels with higher octane ratings such as ethanol or iso-octane Two-stage: fuels with lower octane ratings such as n-heptane, diesel, PRF80, and DME Fuel chemistry plays an important role in determining combustion characteristics in a HCCI engine (more than in SI and DI)

4. Heat Release Reactions at Low and High Temperatures Low temperature heat release: With higher temperatures the rate of heat release for these reactions is reduced Intermediated and high temperature heat release: Hydrogen peroxide (H 2 O 2 ) is produced from abstraction of HO 2 Above 1000 K: H 2 O 2 -> OH + OH Above 1200 K: H + O 2 -> O + OH

6. Operating Limits for High Load HCCI

7. Strategies for expanding the operating limits Delayed combustion timing achieved by lowering intake temperature More time is available for the natural development of thermal stratifications, which lowers the peak heat release rate Faster charge expansion allows lower pressure rise rates Peak in-cylinder temperatures are lower Downsides: decrease in combustion efficiency, thermodynamic losses, less stable combustion or complete misfire

8. Strategies for expanding the operating limits Partial fuel stratification

9. Conclusions and Comments This paper systematically identified the fundamental phenomena influencing the operation of HCCI engines Operation limits for high load HCCI were discussed Several strategies for extending load limits for HCCI engines were presented This paper could show more evaluations and quantitative results of the downsides of the load-extending strategies such as decrease in thermo and combustion efficiency or increase in NOx and UHC emissions so that readers can know more about the limits of these strategies