scholarly journals Inverse Analysis of In-Cylinder Gas-Wall Boundary Conditions: Investigation of a Yttria-Stabilized Zirconia Thermal Barrier Coating for Homogeneous Charge Compression Ignition

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Ryan O'Donnell ◽  
Tommy Powell ◽  
Mark Hoffman ◽  
Eric Jordan ◽  
Zoran Filipi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Homogeneous Charge Compression Ignition ◽  
Engine Performance ◽  
Ex Situ ◽  
Thermal Barrier ◽  
Compression Ignition ◽  
The Impact ◽  
Homogeneous Charge

Thermal barrier coatings (TBCs) applied to in-cylinder surfaces of a low temperature combustion (LTC) engine provide an opportunity for enhanced efficiency via two mechanisms: (i) positive impact on thermodynamic cycle efficiency due to combustion/expansion heat loss reduction, and (ii) enhanced combustion efficiency. Heat released during combustion increases the temperature gradient within the TBC layer, elevating surface temperature over combustion-relevant crank angles. Thorough characterization of this dynamic temperature “swing” at the TBC–gas interface is required to ensure accurate determination of heat transfer and the associated impact(s) on engine performance, emissions, and efficiencies. This paper employs an inverse heat conduction solver based on the sequential function specification method (SFSM) to estimate TBC surface temperature and heat flux profiles using sub-TBC temperature measurements. The authors first assess the robustness of the solution methodology ex situ, utilizing an inert, quiescent environment and a known heat flux boundary condition. The inverse solver is extended in situ to evaluate surface thermal phenomena within a TBC-treated single-cylinder, gasoline-fueled, homogeneous charge compression ignition (HCCI) engine. The resultant analysis provides crank angle resolved TBC surface temperature and heat flux profiles over a host of operational conditions. Insight derived from this work may be correlated with TBC thermophysical properties to determine the impact(s) of material selection on engine performance, emissions, heat transfer, and efficiencies. These efforts will guide next-generation TBC design.

Homogeneous Charge Compression Ignition Operation With Natural Gas: Fuel Composition Implications

2003 ◽  
Vol 125 (3) ◽  
pp. 837-844 ◽  
Author(s):  
J. Hiltner ◽  
R. Agama ◽  
F. Mauss ◽  
B. Johansson ◽  
M. Christensen
Keyword(s):  
Natural Gas ◽  
Compression Ratio ◽  
Homogeneous Charge Compression Ignition ◽  
Engine Performance ◽  
Fuel Composition ◽  
Primary Concern ◽  
Compression Ignition ◽  
Engine Operation ◽  
The Impact ◽  
Homogeneous Charge

Homogeneous charge compression ignition (HCCI) is a potentially attractive operating mode for stationary natural gas engines. Increasing demand for efficient, clean burning engines for electrical power generation provides an opportunity to utilize HCCI combustion if several inherent difficulties can be overcome. Fuel composition, particularly the higher hydrocarbon content (ethane, propane, and butane) of the fuel is of primary concern. Fuel composition influences HCCI operation both in terms of design, via compression ratio and initial charge temperature, and in terms of engine control. It has been demonstrated that greater concentrations of higher hydrocarbons tend to lower the ignition temperature of the mixture significantly. The purpose of this paper is to demonstrate, through simulation, the effect of fuel composition on combustion in HCCI engines. Engine performance over a range of fuels from pure methane to more typical natural gas blends is investigated. This includes both the impact of various fuels and the sensitivity of engine operation for any given fuel. Results are presented at a fixed equivalence ratio, compression ratio, and engine speed to isolate the effect of fuel composition. Conclusions are drawn as to how the difficulties arising from gas composition variations may affect the future marketability of these engines.

Assessing the Impact of Thermal Barrier Coatings on Charge Temperature Stratification Within a Homogeneous Charge Compression Ignition Engine

2018 ◽  
Author(s):  
Ryan O’Donnell ◽  
Tommy Powell ◽  
Zoran Filipi ◽  
Mark Hoffman
Keyword(s):  
Thermal Barrier Coatings ◽  
Homogeneous Charge Compression Ignition ◽  
Thermal Barrier ◽  
Compression Ignition ◽  
Compression Ignition Engine ◽  
Barrier Coatings ◽  
Charge Mass ◽  
The Impact ◽  
Charge Temperature ◽  
Homogeneous Charge

The application of a Thermal Barrier Coating (TBC) to combustion chamber surfaces within a Low Temperature Combustion (LTC) engine alters conditions at the gas-wall boundary and affects the temperature field of the interior charge. Thin, low-conductivity, TBCs (∼150μm) exhibit elevated surface temperatures during late compression and expansion processes. This temperature ‘swing’ reduces gas-to-wall heat transfer during combustion and expansion, alters reaction rates in the wall affected zones, and improves thermal efficiency. In this paper, Thermal Stratification Analysis (TSA) is employed to quantify the impact of Thermal Barrier Coatings on the charge temperature distribution within a gasoline-fueled Homogeneous Charge Compression Ignition (HCCI) engine. Using an empirically derived ignition delay correlation for HCCI-relevant air-to-fuel ratios, an autoignition integral is tracked across multiple temperature ‘zones’. Charge mass is assigned to each zone by referencing the Mass Fraction Burn (MFB) profile from the corresponding heat release analysis. Closed-cycle temperature distributions are generated for baseline (i.e., ‘metal’) and TBC-treated engine configurations. In general, the TBC-treated engine configurations are shown to maintain a higher percentage of charge mass at temperatures approximating the isentropic limit.

The Effect of Thermal Barrier Coating Surface Temperature on the Adhesion Behavior of CMAS Deposits

2020 ◽  
Author(s):  
Robert A. Clark ◽  
Nicholas Plewacki ◽  
Pritheesh Gnanaselvam ◽  
Jeffrey P. Bons ◽  
Vaishak Viswanathan
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Surface Temperature ◽  
Mass Flow ◽  
Experimental Results ◽  
Thermal Barrier ◽  
Back Side ◽  
Surface Temperatures ◽  
The Impact ◽  
Side Flow

Abstract The interaction of thermal barrier coating’s surface temperature with CMAS (calcium magnesium aluminosilicate) like deposits in gas turbine hot flowpath hardware is investigated. Small Hastelloy X coupons were coated in TBC using the air plasma spray (APS) method and then subjected to a thermal gradient via back-side impingement cooling and front-side impingement heating using the High Temperature Deposition Facility (HTDF) at The Ohio State University (OSU). A 1-D heat transfer model was used to estimate TBC surface temperatures and correlate them to intensity values taken from infrared (IR) images of the TBC surface. TBC frontside surface temperatures were varied by changing back-side mass flow (kept at a constant temperature), while maintaining a constant hot-side gas temperature and jet velocity representative of modern commercial turbofan high-pressure turbine (HPT) inlet conditions (approximately 1600K and 200 m/s, or Mach 0.25). In this study, Arizona Road Dust (ARD) was utilized to mimic the behavior of CMAS attack on TBCs. To identify the minimum temperature at which particles adhere, the back-side cooling mass flow was set to the maximum amount allowed by the test setup, and trace amounts of 0–10 μm ARD particles were injected into the hot-side flow to impinge on the TBC surface. The TBC surface temperature was increased through coolant reduction until noticeable deposits formed, as evaluated through an IR camera. Accelerated deposition tests were then performed where approximately 1 gram of ARD was injected into the hot side flow while the TBC surface temperature was held at various points above the minimum observed deposition temperature. Surface deposition on the TBC coupons was evaluated using an infrared camera and a backside thermocouple. Coupon cross sections were also evaluated under a scanning electron microscope for any potential CMAS ingress into the TBC. Experimental results of the impact of surface temperature on CMAS deposition and deposit evolution and morphology are presented. In addition, an Eulerian-Lagrangian solver was used to model the hot-side impinging jet with particles at four TBC surface temperatures and deposition was predicted using the OSU Deposition model. Comparisons to experimental results highlight the need for more sophisticated modeling of deposit development through conjugate heat transfer and mesh morphing of the target surface. These results can be used to improve physics-based deposition models by providing valuable data relative to CMAS deposition characteristics on TBC surfaces, which modern commercial turbofan high pressure turbines use almost exclusively.

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