Title: Experimental investigation of the relationship between thermal barrier coating structured porosity and homogeneous charge compression ignition engine combustion

Abstract

Heat transfer has a monumental influence on homogeneous charge compression ignition combustion. When a thermal barrier coating is applied to the combustion chamber, the insulating effect magnifies the wall temperature swing, decreasing heat transfer during combustion. This enables improvements in both thermal and combustion efficiency without the detrimental impacts of intake charge heating. Increasing the temperature swing requires coatings with lower thermal conductivity and heat capacity. An enticing avenue for simultaneously decreasing both thermal conductivity and capacity is to increase the porosity fraction. A proprietary solution precursor plasma spray process enables discrete organization of the porosity structure, called inter-pass boundaries, which in turn produces a step-reduction in thermal conductivity for a given porosity level. In this investigation, yttria-stabilized zirconia is used to create four different thermal barrier coatings to study the potential of structured porosity as means of improving the “temperature swing” behavior in a homogeneous charge compression ignition engine. The baseline coating is “dense YSZ,” applied using a standard air-plasma spray process. Furthermore, significant reductions of the thermal conductivity are achieved by utilizing the solution precursor plasma spray process to create inter-pass boundaries with a moderate overall porosity. Performance, efficiency, and emissions are compared against both a baseline configurationmore » with a metal piston and an air-plasma spray “dense YSZ” coating. Experiments are carried out in a single-cylinder gasoline homogeneous charge compression ignition engine with exhaust re-induction. Experiments indicate that incorporating structured porosity into thermal barrier coatings produces tangible gains in combustion and thermal efficiencies. However, there is an upper limit to porosity levels acceptable for homogeneous charge compression ignition engine application because an elevated porosity fraction leads to excessive surface roughness and undesirable fuel interactions. Comparison of the coatings showed the best results with coating thickness of up to 150 µm. Thicker coatings led to slower surface temperature response and attenuated swing temperature magnitude.« less

Authors:

Powell, Tommy ^[1]; O’Donnell, Ryan ^[2]; Hoffman, Mark ^[3]; Filipi, Zoran  ^[1];

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Jordan, Eric H. ^[4]; Kumar, Rishi ^[4]; Killingsworth, Nick J. ^[5]

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+ Show Author Affiliations

1. Clemson Univ., Greenville, SC (United States)
2. Clemson Univ., Greenville, SC (United States); Robert Bosch LLC., Detroit, MI (United States)
3. Clemson Univ., Greenville, SC (United States); Auburn Univ., AL (United States)
4. Univ. of Connecticut, Storrs, CT (United States)
5. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Publication Date:

2019-07-29

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division

OSTI Identifier:

1550727

Grant/Contract Number:  

AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

International Journal of Engine Research

Additional Journal Information:

Journal Name: International Journal of Engine Research; Journal ID: ISSN 1468-0874

Publisher:

SAGE

Country of Publication:

United States

Language:

English

Subject:

33 ADVANCED PROPULSION SYSTEMS; Thermal barrier coating; yttria-stabilized zirconia; low temperature combustion; heat transfer; homogeneous charge compression ignition