Thermal and structural analysis of Chemical Vapor Infiltration and Chemical Vapor Deposition furnace

PROJECT DETAILS

The Chemical Vapor Infiltration (CVI) and Chemical Vapor Deposition (CVD) furnace is a specialized thermo-vacuum facility designed to operate at temperatures of up to 2,500°C. The facility is primarily used for the fabrication of high-temperature composite materials that can withstand extreme thermal and mechanical conditions, making them suitable for demanding applications such as supersonic missile systems. The thermo-vacuum facility was commissioned at the Defence Research and Development Laboratory (DRDL), Hyderabad, which is part of the Defence Research and Development Organisation (DRDO) propulsion complex under the Ministry of Defence, Government of India. An electromagnetic induction heating system is employed to achieve the exceptionally high operating temperatures required for CVI/CVD processes. Niharika Computational Engineering Solutions Pvt. Ltd. (NCES) collaborated with the client to evaluate the thermal performance and structural integrity of the furnace using advanced numerical simulation techniques. Computational Fluid Dynamics (CFD) analysis was performed to investigate temperature distribution, heat transfer characteristics, and the effectiveness of the integrated cooling systems under operating conditions. Both steady-state and transient thermal analyses were carried out to understand the thermal behavior of the furnace. In addition, Finite Element Analysis (FEA) was conducted to assess the structural response of the plunger assembly under thermal loading. The temperature distribution obtained from the CFD simulations was used to evaluate thermal expansion and the resulting stresses in the structural components. These analyses helped identify potential areas of high thermal stress, assess component integrity, and provide engineering insights to support the reliable and safe operation of the high-temperature CVI/CVD furnace.

The primary objective of this CFD analysis is to investigate the temperature distribution throughout the furnace and evaluate the heat transfer characteristics under operating conditions. The study aims to quantify heat retention in individual components, identify regions exposed to elevated temperatures, and assess the thermal behavior of the furnace assembly. Additionally, the analysis focuses on evaluating the performance and effectiveness of the integrated cooling systems to ensure adequate heat removal, maintain component temperatures within acceptable limits, and support the reliable operation of the CVI/CVD furnace at high operating temperatures.

A poly-hexcore mesh was generated for the simplified CAD model to ensure accurate and computationally efficient CFD simulations. The mesh was refined in regions with significant temperature and flow gradients to capture the critical thermal characteristics and resolve localized variations with greater accuracy. The overall mesh consisted of approximately 12 million cells, providing sufficient spatial resolution for the analysis of complex heat transfer phenomena within the furnace. The mesh quality was evaluated using standard CFD quality metrics to ensure compliance with established guidelines and to support numerical stability, convergence, and reliable simulation results.

Both steady-state and transient CFD analyses were performed to evaluate the thermal behavior of the thermo-vacuum system under different operating conditions. The steady-state analysis was conducted to determine the temperature distribution and heat transfer characteristics after the system reached thermal equilibrium, while the transient analysis was used to investigate temperature variations over time during the heating process. Material properties were defined based on the data provided in the relevant manufacturer material specification sheets to ensure accurate representation of the thermal characteristics of the furnace components. This approach helped assess the overall thermal performance of the system and provided insights into its heat transfer behavior under operating conditions.

The results of the CFD analysis demonstrate that the induction heater design meets the specified thermal requirements, achieving the desired operating temperatures for the CVI/CVD furnace. The temperature distribution and heat transfer characteristics were evaluated to assess the overall thermal performance of the system under the defined operating conditions. Furthermore, the integrated cooling systems were found to perform satisfactorily, providing effective heat removal from the designated components and helping maintain their temperatures within acceptable limits. These findings support the thermal performance of the furnace design and its suitability for high-temperature operation.

Finite Element Method (FEM) analysis was performed using the temperature distribution obtained from the Computational Fluid Dynamics (CFD) simulations to evaluate the structural response of the furnace components under thermal loading. The thermal results were mapped onto the structural model to assess the effects of temperature variations, including thermal expansion and the resulting stresses and deformations. Material properties were defined based on the specifications and data provided by the respective manufacturers to ensure an appropriate representation of the structural and thermal characteristics of the components. This analysis helped identify critical regions subjected to elevated thermal stresses and evaluate the structural integrity of the plunger assembly under the specified operating conditions.

The FEM analysis results indicate that the stress levels observed in the steel components are approaching the respective material yield strengths, suggesting a limited margin against the onset of permanent deformation under the analyzed thermal loading conditions. For the graphite components, the maximum principal tensile stress exceeds the specified tensile strength of the material, indicating a potential risk of tensile failure or crack initiation in the affected regions. However, the minimum principal compressive stress remains below the specified compressive strength of graphite, suggesting that the compressive stress levels are within the material strength limits. These findings highlight the importance of evaluating the tensile stress concentrations in graphite components and reviewing the structural design to improve the overall integrity and reliability of the furnace assembly under high-temperature operating conditions.