普惠公司

This work overviews a physics-informed implementation of filtered Rayleigh scattering (FRS) to reconstruct the mean field of turbulent jets, despite the presence of noise in the FRS data. The physics-informed FRS methodology is applied to three different jet flows: a noise-free simulated test case, a Mach 0.8 jet flow with low levels of noise, and a Mach 1.25 jet flow with high levels of spectral noise. Using sparse observations of FRS signals, the physics-informed FRS is able to predict the mean axial velocity fields within 3% accuracy and can reconstruct continuous mean field profiles in high noise scenarios where traditional FRS processing introduces discontinuities. To the best of the authors' knowledge, this is the first implementation of a physics-informed neural network that relies exclusively on measured FRS data and is trained using two key components: (i) the compressible Reynolds-averaged Navier-Stokes residuals, and (ii) the residual between the measured FRS signals and a modeled FRS signal derived from the physics-informed FRS model predictions, where the FRS measurement model is incorporated directly into the training process.

Ingestion of particulate within a gas turbine engine leads to undesirable consequences such as erosion, hot spots, and cooling hole blockages. These concerns are prevalent in the combustor wall region that commonly employs a double wall design made up of impingement and effusion liners. Numerous studies on double wall liners have demonstrated the negative impacts dirt deposition has on cooling performance; however, to this point, little has been reported to have found an effective means to mitigate dirt deposition. In the current study, a novel design was investigated that added an upstream impingement plate to the common double wall design, resulting in a triple wall liner. The purpose of the additional impingement plate is that it allows for a sacrificial middle impingement plate to capture the dirt prior to the flow impacting the effusion plate where heat transfer is most critical. Several parameters such as impingement hole diameter, dirt injection mass, and plate-to-plate spacing were evaluated for different configurations. Using the triple wall design, the data indicates that dirt deposition on the effusion plate is reduced by as much as 87% compared to the effusion plate of a double wall design. Performance comparisons were made whereby the triple wall design maintained the same pressure ratio across all three layers as that of the double wall. Flow blockages of the cooling holes were shown to diminish for a triple wall compared to a double wall design. Additionally, cooling features were integrated on the surface of the middle impingement plate, which further reduced deposition on the effusion plate by 25% compared to a triple wall design without features. Overall, the results in this study show that a triple wall design significantly reduces dirt deposition on the effusion plate surface leading to less flow blockage as compared to a double wall, making them desirable for improved liner durability.

This study systematically investigates the tribological behavior of fine-grained isotropic graphite under synergistic variable conditions, addressing a critical knowledge gap regarding its performance in extreme conditions. While graphite is a promising high-temperature solid lubricant, its utility is limited by environmental dependencies. Our research reveals that the tribological performance of fine-grained isotropic graphite depends on the formation and stability of interfacial tribofilm rather than its bulk properties. Comprehensive reciprocating test against 440C stainless steel counter bodies explores friction and wear across varied temperatures (room temperature, 100 degrees C, and 300 degrees C), load, and velocities. Advanced characterization including X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy, optical profilometry, and Raman spectroscopy explains the underlying wear mechanisms. Performance paradox was identified under high-load conditions, failure at 100 degrees C, while low friction (& micro; approximate to 0.035) and low wear (0.718 mm(3)) performance was observed at 300 degrees C. Raman analysis confirmed that the 100 degrees C failure was due to mechanical refinement of graphite into highly disordered carbon debris following moisture desorption. The low wear and friction performance at 300 degrees C load ramp test was due to the formation of a stable ordered graphitic transfer film. However, under high-velocity conditions, frictional heat, a second distinct failure mechanism, causes tribo-oxidation, which degrades the protective film. These findings underscore that controlling the interfacial temperatures is the most important parameter for the sustained low-friction and wear performance. This work provides insights for optimizing graphite's application in demanding tribological environments.

Abstract A physics-informed filtered Rayleigh scattering (FRS) model is applied to a supersonic jet flow with a core flow at ambient temperature and a heated bypass flow. This model serves as a surrogate for larger-scale flows like turbofan engine exhaust. The limited spatial resolution allows for a high uncertainty test case for the force decomposition methodology. The method is evaluated using a computational fluid dynamics (CFD) simulation and measured FRS data. The simulated jet flow provides a noise-free baseline, while the experimentally measured jet flow demonstrates the reduction in uncertainty even with measurement noise. The net force from all results compares within ±10 N (≈3% of net force value). The net force is decomposed into core and bypass contributions using the maximum of the gradient of axial velocity, static temperature, and static density. All three gradient approaches compare within ±8 N (≈2% of net force value), and the bypass force contribution uncertainty can be reduced by a factor of two relative to previous nonintrusive force decomposition techniques. This demonstrates an advancement of the filtered Rayleigh scattering force decomposition approach through its increased capacity to handle noisy data, enabling its deployment in ground test and on-wing applications.

Abstract This article centers on processes used to reduce residual stresses in manufactured components and structures, including thermal relaxation, microplastic relaxation, and microplastic relaxation under cyclic conditions. These processes fit into two primary means to relieve residual stresses: thermal processing to enable local plasticity and creep mechanisms, and mechanical processing to enable local or global yielding. Computational modeling can be used with each of these mechanisms to assess how effective they are at reducing residual stresses. It describes a progression of different creep models and solution procedures, from a simple analytic model with a closed-form solution to a complex displacement-based finite-element numerical solution that is capable of incorporating both material and geometric nonlinearities. The article discusses the implementation of creep data and models for stress-relief simulation. It describes more advanced techniques, beyond the simplified approaches for approximate solutions, that are applicable to transient creep, advanced constitutive models, and complicated stress and temperature loading histories. An example highlights the difference between a steady-state and transient creep analysis solution using a spinning disk that creeps at elevated temperature. The article also presents an overview of mechanical stress-relief modeling.