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Research Papers: Internal Combustion Engines

Combining Instantaneous Temperature Measurements and CFD for Analysis of Fuel Impingement on the DISI Engine Piston Top

[+] Author and Article Information
Kukwon Cho1

Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109

Ronald O. Grover2

Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109

Dennis Assanis, Zoran Filipi

Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109

Gerald Szekely, Paul Najt, Rod Rask

 General Motors Research and Development, Warren, MI 48090-9055

1

Present address: Oak Ridge National Laboratory, Oak Ridge, TN.

2

Present address: GM R&D Center, Warren, MI 48090-9055.

J. Eng. Gas Turbines Power 132(7), 072805 (Apr 19, 2010) (9 pages) doi:10.1115/1.4000293 History: Received May 21, 2009; Revised September 04, 2009; Published April 19, 2010; Online April 19, 2010

A two-pronged experimental and computational study was conducted to explore the formation, transport, and vaporization of a wall film located at the piston surface within a four-valve, pent-roof, direct-injection spark-ignition engine, with the fuel injector located between the two intake valves. Negative temperature swings were observed at three piston locations during early injection, thus confirming the ability of fast-response thermocouples to capture the effects of impingement and heat loss associated with fuel film evaporation. Computational fluid dynamics (CFD) simulation results indicated that the fuel film evaporation process is extremely fast under conditions present during intake. Hence, the heat loss measured on the surface can be directly tied to the heating of the fuel film and its complete evaporation, with the wetted area estimated based on CFD predictions. This finding is critical for estimating the local fuel film thickness from measured heat loss. The simulated fuel film thickness and transport corroborated well temporally and spatially with measurements at thermocouple locations directly in the path of the spray, thus validating the spray and impingement models. Under the strategies tested, up to 23% of fuel injected impinges upon the piston and creates a fuel film with thickness of up to 1.2μm. In summary, the study demonstrates the usefulness of heat flux measurements to quantitatively characterize the fuel film on the piston top and allows for validation of the CFD code.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Construction of coaxial thermocouple (11)

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Figure 2

Heat flux measurement instrumentation: (a) locations of thermocouple probes, and (b) mechanical telemetry linkage system

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Figure 3

Image of computational mesh used in GMTEC with close-up view of the engine cylinder. The grid consisted of 105,400 cells.

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Figure 4

Comparison of 50-cycle averaged surface temperature histories for EOI 300 and EOI 270 deg CA BTDC cases at 2000 rpm, homogeneous mode

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Figure 5

50-cycle averaged heat flux histories (a) for advanced injection timing (EOI 300 deg CA BTDC) and (b) for retarded injection timing (EOI 270 deg CA BTDC) at 2000 rpm, homogeneous mode

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Figure 6

Schematic view of piston location for both injection timings

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Figure 7

CFD predictions for advanced injection timing case (EOI 300 deg CA BTDC): (a) snap shots of the fuel film thickness and its distribution, and (b) injected fuel history

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Figure 8

CFD predictions for retarded injection timing case (EOI 270 deg CA BTDC): (a) snap shots of the fuel film thickness and its distribution, and (b) injected fuel history

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Figure 9

(a) CFD predictions of vaporization history of injected fuel; (b) measurements of the local heat flux due to fuel film warmup and evaporation for EOI 300 deg CA BTDC

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Figure 10

Predicted crank angle resolved fuel film wetted area for advanced injection timing case (EOI 300 deg CA BTDC case)

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Figure 11

Heat loss per area due to fuel impingement

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