Tailoring HCCI heat-release rates with partial fuel stratification: Comparison of two-stage and single-stage-ignition fuels

Proceedings of the Combustion Institute, Volume 33, Issue 2, 2011, Pages 3047-3055

Tailoring HCCI heat-release rates with partial fuel stratification: Comparison of two-stage and single-stage-ignition fuels

Yi Yang, John E. Dec, Nicolas Dronniou, Magnus Sjöberg

yiyang@sandia.gov

Combustion Research Facility, Sandia National Laboratories, USA

Abstract

One of the major issues restricting the application of homogeneous charge compression-ignition (HCCI) engines is overly rapid combustion at high-load conditions.  This can lead to engine knock and potential engine damage. To overcome this problem, partial fuel stratification was used.

Most fuel was premixed with intake air. The rest of the fuel was directly injected during the compression stroke. To be effective, this technique depends critically on the fuel autoignition chemistry. PRF73, a mixture of 73 vol% isooctane and 27 vol% n-heptane that exhibits two-stage ignition under these conditions, successfully enabled control of the combustion heat-release rate with properly adjusted injection parameters. Differences between single- and two-stage fuels result from the different response of their autoignition rates to the variations in equivalence ratio produced by partial fuel stratification, termed ϕ-sensitivity.

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