Partial Transparency of Advanced Compression Ignition Combustion Chamber Deposits, Its Impact on Combustion Chamber Wall Temperatures and Application to Thermal Barrier Coating Design

The proven impact of combustion chamber deposits, CCD, on advanced compression ignition, ACI, combustion strategies has spurred researchers to develop thermal barrier coatings, TBC, which can mimic CCD benefits on combustion efficiency and operational range expansion. However, application of TBCs within multi-mode engines exposes them to non-negligible soot radiation. In the present article, the impact of radiation heat transfer on combustion chamber deposits is studied. The morphological construction of the combustion chamber deposit layer is shown to be partially transparent to radiation heat transfer, drawing corollaries with ceramic-based TBCs. Additional experimentation eliminates the optical transparency of CCD to reveal an “effective radiation penetration depth” facilitated by open surface porosity. The effective radiation penetration depth is then utilized to establish the relative communicating porosity of CCD and a magnesium zirconate TBC. The impacts of CCD/TBC radiation penetration on the time varying surface temperature trend are revealed through an analytical investigation. Results indicate that the surface temperature swing can be either increased or decreased depending on the depth of radiation penetration into the TBC, altering its projected impacts on ACI operation. Enabling shallow penetration of radiation heat flux into a TBC enhances the TBC surface temperature swing, providing an avenue for increased efficiency benefits through combustion heat transfer reduction.