New Selectively Absorbing and Scattering Heat-Insulating Coatings of the Combustion Chamber for Low-Heat-Rejection Diesel

An experimental radiation chamber has been developed to nondestructive^ measure the thermal diffusivity of a combustion chamber deposit (CCD) layer. The accumulation of CCD shifts the operability range of homogeneous charge compression ignition (HCCI) to lower loads where the fuel economy benefit of HCCI over a traditional spark ignition strategy is at a maximum. The formation and burn-off of CCD introduce operational variability, which increases the control system burden of a practical HCCI engine. To fully characterize the impact of CCD on HCCI combustion and develop strategies which limit the CCD imposed variability, the thermal and physical properties of HCCI CCD must be determined without destroying the morphology of the CCD layer. The radiation chamber device provides a controlled, inert atmosphere absent of cyclical pressure oscillations and fuel/air interactions found within an engine. The device exposes temperature probes coated with CCD to controlled heat fiux pulses generated by a graphite emitter and a rotating disk. CCD layer thermal diffusivity is then calculated based on the phase delay of the sub-CCD temperature response relative to the response of the temperature probe when clean. This work validates the accuracy of the radiation chamber's diffusivity determination methodology by testing materials of known properties. Wafers of three different materials, whose thermal diffusivities span two orders of magnitude centered on predicted CCD diffusivity values, are installed over the temperature probes to act as CCD surrogates. Multiple thicknesses of each material are tested over a range of heat flux pulse durations. Diffusivity values determined from radiation chamber testing are independent of sample thickness with each of the three calibration materials. The radiation chamber diffusivity values exhibit a slight, but consistent underprediction for all wafers due to residual contact resistance at the wafer-probe interface. Overall, the validation studies establish the radiation chamber as an effective device for the nondestructive thermal diffusivity determination of thin insulative coatings. The similarity of expected CCD diffusivity values to those of the validation specimens instills confidence that the methodology and device presented herein can be successfully utilized in the characterization of HCCI CCD layers.

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“…13. It should be noted that other researchers have reported on the semitransparent behavior of similar ceramics [32][33][34].…”

Section: Impact Of Radiation Transparency On Ex-situ Dittusivitymentioning

confidence: 99%

Development of a Device for the Nondestructive Thermal Diffusivity Determination of Combustion Chamber Deposits and Thin Coatings

Hoffman

Lawler

Filipi

et al. 2014

Journal of Heat Transfer

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“…Coatings 2020, 10, x FOR PEER REVIEW 4 of 13 optical properties is the determining parameter and classifies ceramics by spectral windows revealing semitransparent and opaque TBM (TBC). Lack of analysis of the influence the materials' optical transparency window on the heat resistance of the CC ceramic walls was the reason caused the suspension of the active development ceramic ICE at the end of the 20th century [2,3] and did not introduce the concept of a semitransparent ceramics wall [4,9,10] for automotive engineers.…”

Section: Physical Modeling Of Combined Radiant Heat Transfer For the mentioning

confidence: 99%

“…The authors have repeatedly noted in their previous works [9,10] in 2007-2017 that despite the legendary developments of CC walls coated by ceramic as a semitransparent substance in their current researches, this factor is not considered. This is strange because there are numerous developments of opaque and semitransparent heat-shield composites for aerospace vehicles of American and Soviet engineers [12][13][14] since the 1960s.…”

Section: Introductionmentioning

confidence: 97%

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Thermal Mode Optimization of Combustion Chamber Walls for Power-Plants Using Semitransparent Porous Ceramics

et al. 2020

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The paper examines control and management by thermal mode of the internal surface of heat-insulated combustion chamber walls for green & efficient diesel and gas turbine engines due to the application of opaque or semitransparent thermal barrier materials (coatings). The authors’ model is devoted to combined radiant heat transfer both inside the heat-insulated combustion chamber and its ceramics walls, which could be scattering and absorbing for penetrating radiant component in the subsurface volume of optically heterogeneous porous material. The influence of thermal conduction, scattering (absorption) and external convective effects on the increase of the internal overheating zone in subsurface layers is simulated under intensive radiation. The unique set of optical, thermal-physical and mechanical properties of structural ceramics, depending on their porosity, were first proposed. The radiation fields of the absorbed energy in the near IR region and the corresponding temperature distributions in the modeled opaque and semitransparent ceramics walls were calculated under a stationary radiant-convective heat load during the active combustion phase at time intervals 0.01…0.1 s (diesel engines) and 10...100 s (turbine ones). In order to control the emission of nitrogen oxides, the authors propose a generation model of NOx, its growth or reduction caused by the management of radiant overheating inside semitransparent heat-insulation in which surface temperature is due to volumetric radiant absorption. It is shown that for semitransparent materials (coatings), the optimal thermal mode is determined first of all by thermal radiant characteristics in near IR at heating small times and it begins to correct at long ones due to the effect of thermal conductivity. This process may be modeled and regulated by the selected microstructural porosity of ceramic heat insulation.

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“…These models are based on studies reported by many authors in different scientific areas [1][2][3][4][5][6]. Pollution on the sea surface is considered as semitransparent water-oil emulsions (WOE) or oil films of heterogeneous particles with various physical and geometrical parameters within a natural water binder.…”

Section: Introductionmentioning

confidence: 99%

Simulation of the ocean’s spectral radiant thermal source and boundary conditions

Merzlikin¹,

Krass²,

Cheranev³

et al. 2013

AIP Conference Proceedings

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Abstract. This article considers the analysis of radiant heat transfer for semitransparent natural and polluted seawaters and its physical interpretations. Technogenic or natural pollutions are considered as ensembles of selective scattering, absorbing and emitting particles with complex refractive indices in difference spectral ranges of external radiation. Simulation of spectral radiant thermal sources within short wavelength of solar penetrating radiation for upper oceanic depth was carried out for deep seawater on regions from ~ 300 to ~ 600 nm and for subsurface layers (not more ~ 1 m) -on one ~ 600 -1200 nm. Model boundary conditions on exposed oceanic surface are defined by (1) emittance of atmosphere and seawater within long wavelength radiation ~ 9000 nm, (2) convection, and (3) thermal losses due to evaporation. Spatial and temporal variability of inherent optical properties, temperature distributions of the upper overheated layer of seawater, the appearance of a subsurface temperature maximum and a cool surface skin layer in response to penetrating solar radiation are explained first of all by the effects of volumetric scattering (absorption) and surface cooling of polluted seawater. The suggested analysis can become an important and useful subject of research for oceanographers and climatologists.

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New Selectively Absorbing and Scattering Heat-Insulating Coatings of the Combustion Chamber for Low-Heat-Rejection Diesel

Cited by 19 publications

References 1 publication

Development of a Device for the Nondestructive Thermal Diffusivity Determination of Combustion Chamber Deposits and Thin Coatings

Development of a Device for the Nondestructive Thermal Diffusivity Determination of Combustion Chamber Deposits and Thin Coatings

Thermal Mode Optimization of Combustion Chamber Walls for Power-Plants Using Semitransparent Porous Ceramics

Simulation of the ocean’s spectral radiant thermal source and boundary conditions

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