Solving of Two-Dimensional Unsteady Inverse Heat Conduction Problems Based on Boundary Element Method and Sequential Function Specification Method

The boundary element method (BEM) and sequential function specification method (SFSM) are used to research the inverse problem of boundary heat flux identification in the two-dimensional heat conduction system. The future time step in the SFSM is optimized by introducing the residual error principles to get the more accurate inversion results. For the forward problems, the BEM is used to calculate the required temperature value of discrete point; for the inverse problems, the impacts of different future time steps, measuring point position, and measuring error on the inversion results are discussed. Furthermore, the comparison is made for the optimal future time step obtained by introducing the residual error principle and the inherent future time step. The example analysis shows that the method proposed still has higher accuracy when the measuring error exists or the measuring point position is far away from the boundary heat flux.

Estimation of Thermal Barrier Coating Surface Temperature and Heat Flux Profiles in a Low Temperature Combustion Engine Using a Modified Sequential Function Specification Approach

A modified form of the sequential function specification method (SFSM) is developed with specific consideration given to multiple time scales in an effort to avoid overregularization of the solution estimates. The authors extend their approach to solve the inverse heat conduction problem (IHCP) associated with the application of thermal barrier coatings (TBC) to in-cylinder surfaces of an internal combustion engine. Subsurface temperature measurements are used to calculate surface heat flux profiles. The modified inverse solver is validated ex situ using a custom fabricated radiation chamber. The solution methodology is extended in situ to evaluate temperature data collected from a single-cylinder research engine operating in homogeneous charge compression ignition (HCCI) mode. Crank angle resolved, thermal barrier coating surface temperature and heat flux profiles are produced—enabling correlation of thermal conditions at the gas-wall boundary with engine performance, emission, and efficiency metrics.

Real-Time Evaluation of Severe Heat Load Over Moving Interface of Decomposing Composites

Decomposing composites undergo both surface removal and in-depth decomposition, when they are subjected to severe heating environments. As a result, the gas phase and the chemical species are injected into the boundary layer, resulting in a reduction of the heat flux entering into the solid structure. Under such conditions that geometry changes, the reconstruction of heat flux at the ablating front is quite complicated. Utilizing a procedure based on the sequential function specification method, an inverse problem is solved to anticipate the front-surface heating condition. Temperature measurements as well as measurement of the position of the ablating surface accompanied with additive noises are used for the implementation of the current procedure. Taking into account a complex set of phenomena, a numerical experiment is employed to examine the accuracy and appropriateness of the proposed technique for such problems. The results obtained demonstrate the usefulness and efficiency of the proposed method for the estimation of heat flux at the moving boundary of decomposing materials.