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Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

Impact of a Yttria-Stabilized Zirconia Thermal Barrier Coating on HCCI Engine Combustion, Emissions, and Efficiency

[+] Author and Article Information
Tommy Powell

Department of Automotive Engineering,
Clemson University,
4 Research Drive,
Greenville, SC 29607
e-mail: trpowel@g.clemson.edu

Ryan O'Donnell

Department of Automotive Engineering,
Clemson University,
4 Research Drive,
Greenville, SC 29607
e-mail: rodonne@g.clemson.edu

Mark Hoffman

Department of Automotive Engineering,
Clemson University,
4 Research Drive,
Greenville, SC 29607
e-mail: mhoffm4@clemson.edu

Zoran Filipi

Department of Automotive Engineering,
Clemson University,
4 Research Drive,
Greenville, SC 29607
e-mail: zfilipi@clemson.edu

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received February 22, 2017; final manuscript received March 13, 2017; published online August 1, 2017. Editor: David Wisler.

J. Eng. Gas Turbines Power 139(11), 111504 (Aug 01, 2017) (9 pages) Paper No: GTP-17-1077; doi: 10.1115/1.4036577 History: Received February 22, 2017; Revised March 13, 2017

In-cylinder surface temperature has significant impacts on the thermo-kinetics governing the homogeneous charge compression ignition (HCCI) process. Thermal barrier coatings (TBCs) enable selective manipulation of combustion chamber surface temperature profiles throughout a fired cycle. In this way, TBCs enable a dynamic surface temperature swing, which prevents charge heating during intake while minimizing heat rejection during combustion. This preserves volumetric efficiency while fostering more complete combustion and reducing emissions. This study investigates the effect of a yttria-stabilized zirconia (YSZ) coating on low temperature combustion (LTC), efficiency, and emissions. This is an initial step in a systematic effort to engineer coatings best suited for LTC concepts. A YSZ coating was applied to the top of the aluminum piston using a powder air plasma spray (APS) process; final thickness of the YSZ was approximately 150 μm. The coated piston was subsequently evaluated in the single-cylinder HCCI engine with exhaust re-induction. Engine tests indicated significant advancement of the autoignition point and reduced combustion durations with the YSZ coating. Hydrocarbon and carbon monoxide emissions were reduced, thereby increasing combustion efficiency. The combination of higher combustion efficiency and decreased heat loss during combustion produced tangible improvements in thermal efficiency. When the effects of combustion advance were removed, the overall improvements in emissions and efficiency were lower, but still significant. Overall, the results encourage continued efforts to devise novel coatings for LTC.

Copyright © 2017 by ASME
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References

Figures

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Fig. 1

In-cylinder PLIF images illustrating the influence of wall temperature throughout the combustion chamber near TDC for an (a) ensemble averaged and (b) single cycle. Adapted from Ref. [4].

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Fig. 2

Wall surface temperatures for an uninsulated metal wall, a monolithic TBC, and a thin TBC, showcasing the reduction in temperature difference between the coating surface and the bulk gas during both combustion and gas exchange through the application of temperature swing insulation. Adapted from Ref. [15].

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Fig. 3

HCCI engine test setup

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Fig. 4

YSZ coating measurement locations

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Fig. 5

Heat flux probe mounting locations, H1 and H2 [11]

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Fig. 6

The YSZ–TBC had higher (a) peak cylinder pressure at 2000 RPM and a correspondingly higher (b) rate of heat release due to advanced combustion phasing. Pintake = 104 kPa, 10.3 mg fuel/cycle, 90 °C Tintake, 95 °C Tcoolant, Toil, 20.9–21.1 AFR, 47.7–48.9% RGF, 0% external EGR.

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Fig. 7

Combustion phasing and burn durations measured relative to top dead center firing, showing an advancement of combustion when the YSZ coating is implemented. CA50 is located at the intersection of the two burn durations. See operating conditions in Table 2 for FM cases.

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Fig. 8

Decrease in unburnt HC emissions index when using the YSZ TBC. See operating conditions in Table 2 for FM cases.

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Fig. 9

Decrease in carbon monoxide emission index due to YSZ implementation. See operating conditions in Table 2 for FM cases.

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Fig. 10

Increase in combustion efficiency when using the YSZ TBC. See operating conditions in Table 2 for FM cases.

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Fig. 11

Effect of the YSZ TBC on gross-indicated thermal efficiency. See operating conditions in Table 2 for FM cases.

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Fig. 12

Comparison of the (a) cylinder pressures at 2000 RPM and (b) rates of heat release for the phase-matched points with CA50 at 7 deg CA. Pintake = 104 kPa, 10.3 mg fuel/cycle, 109 °C Tintake, 95 °C Tcoolant, Toil, 21 AFR, 47.5% RGF (metal), 45.6% RGF, and 7.0% external EGR (APS-YSZ).

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Fig. 13

Combustion phasing and burn durations for phase-matched operating points relative to top dead center firing, see operating conditions in Table 2 for cases with CA50 at 7 deg CA

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Fig. 14

Hydrocarbon emissions for phase-matched points illustrating a general decrease in HC emission due to the YSZ coating. See operating conditions in Table 2 for cases with CA50 at 7 deg CA.

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Fig. 15

Change in carbon monoxide emissions for the phase-matched points. See operating conditions in Table 2 for cases with CA50 at 7 deg CA.

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Fig. 16

Combustion efficiency for phase-matched, FM points, showing an increase in combustion efficiency during YSZ operation. See operating conditions in Table 2 for cases with CA50 at 7 deg CA.

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Fig. 17

Change in the indicated thermal efficiency for phase-matched, FM operation with the addition of the YSZ–TBC. See operating conditions in Table 2 for cases with CA50 at 7 deg CA.

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Fig. 18

(Measured) (a) heat flux and (b) (calculated) surface temperatures for the metal surface and the APS-YSZ surface at the 1600 RPM, phase match point. Adapted from Ref. [27].

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Fig. 19

(a) Instantaneous heat loss and (b) cumulative heat loss for the metal surface and APS-YSZ at the 1200 RPM phase match point [27]

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