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Internal Combustion Engines

Quantifying Cyclic Variability in a Multicylinder HCCI Engine With High Residuals

[+] Author and Article Information
Erik Hellström, Jacob Larimore, Anna Stefanopoulou

 University of Michigan, Ann Arbor, MI

Jeff Sterniak, Li Jiang

 Robert Bosch LLC, Farmington Hills, MI

J. Eng. Gas Turbines Power 134(11), 112803 (Sep 28, 2012) (8 pages) doi:10.1115/1.4007164 History: Received May 31, 2012; Revised June 01, 2012; Published September 28, 2012; Online September 28, 2012

Cyclic variability (CV) in lean homogeneous charge compression ignition (HCCI) combustion at the limits of operation is a known phenomenon, and this work aims at investigating the dominant effects for the cycle evolution at these conditions in a multicylinder engine. Experiments are performed in a four-cylinder engine at the operating limits at late phasing of lean HCCI operation with negative valve overlap (nvo). A combustion analysis method that estimates the unburned fuel mass on a per-cycle basis is applied on both main combustion and the nvo period revealing and quantifying the dominant effects for the cycle evolution at high CV. The interpretation of the results and comparisons with data from a single-cylinder engine indicate that, at high CV, the evolution of combustion phasing is dominated by low-order deterministic couplings similar to the single-cylinder behavior. Variations, such as air flow and wall temperature, between cylinders strongly influence the level of CV but the evolution of the combustion phasing is governed by the interactions between engine cycles of the individual cylinders.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Return maps for combustion phasing θ50m and gross heat release Qm for a single-cylinder research engine (black) and for cylinder 4 of a four-cylinder engine (gray)

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Figure 2

Definition of the engine cycle and important variables for curves of pressure p(θ) (thin line) and heat release Q(θ) (thick line)

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Figure 3

Estimates of the efficiency ηm for 40 cycles from cylinder 4. The symbols (▴, ●, ▪, ♦, ▾) represents initial conditions mu(0) equal to (0, 25, 50, 75, 100)% of the injected fuel mass m¯i.

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Figure 4

Pressure and temperature for low and high CV

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Figure 5

Gross heat release in cylinder 4 for low and high CV. Four consecutive cycles are numbered where all except the second cycle have similar total heat release. These cycles are also shown in Figs.  6789.

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Figure 6

Cylinder 4 heat release during the main combustion Qm(k) versus main combustion phasing θ50m(k), temperature at evo Tevo(k), heat release during the nvo period Qn(k), temperature at ivo Tivo(k), combustion phasing θ50m(k+1), and unburned fuel mu(k+1)

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Figure 7

Combustion efficiency ηm and ringing intensity I versus phasing for low and high CV showing the increased spread of values for high CV. The numbered cycles are also shown in Figs. 5, 6, 8, and 9.

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Figure 8

Return maps for phasing θ50m. The marked sequence for cylinder 4 corresponds to the numbered cycles in Figs.  567, and 9.

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Figure 9

Return maps for total heat release Qm. The marked sequence for cylinder 4 corresponds to the numbered cycles in Figs.  5678.

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Figure 10

Symbol statistics for combustion phasing θ50m

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Figure 11

Symbol statistics for the gross heat release Qm

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Figure 12

Return maps and symbol statistics for single-cylinder experiments reported in [19]

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