Combustion Chamber Fatigue Life Analysis for Reusable Liquid Rocket Engines (LREs)

Abstract

To increase liquid rocket engines (LREs) lifetime capability and allow for reusability applications, the efficient evaluation of the most critical subcomponents' remaining useful life plays a vital role. Regeneratively cooled combustion chamber (CC) wall must withstand extremely high loads emerging from a massive temperature gradient between the hot gas and the low temperature of the coolant. The combined loading and unloading operations, together with high temperature and rate dependent inelastic strain, significantly lessen the combustion chamber inner liner life. Within the presented research, the post-processing model was developed for low cycle fatigue (LCF) evaluation of the reusable LRE's combustion chamber walls. The proposed damage accumulation model is based on the amalgamation of Bonora-Gentile-Pirondi ( 2004) and Dufailly-Lemaitre (1995) methods, and it incorporates ductile and brittle damage components which are embedded in the post-processing method. Moreover, the required numerical calculation time is further decreased on account of the proposed routine which allows for analysis of only two initial numerically acquired FE cycles. The obtained results based on the developed method combined with coupled thermal-structural quasi 2D Finite Element Analysis (FEA) of the nozzle throat cross-section, were confirmed to be in good agreement with the validation data acquired from the M51 thermo-mechanical laboratory site at DLR Lampoldshausen. The proposed model can be successfully applied for a quick evaluation of the remaining useful life of the CC wall for various rocket engine architectures.

Turbine Blades for Reusable Liquid Rocket Engines (LRE) - Numerical Fatigue Life Investigation

“…The OTP stresses obtained from the 0D beam theory suggested in section 2 were found to be approximately 26% higher than the stresses received through the 3D Finite Element Analysis. In comparison, the stresses calculated with previously developed methods [7], differs from FEM by 28%. The inaccuracy in calculations between 0D and FEM, could be on account of stresses being calculated in radial direction of the turbine (equaling to the height direction of the turbine blade) for former, in contrast to max.…”

“…The comparison of the numerical and analytical 0D results for OTP is summarized in Table 5. The further comparison of analytical and numerical methods for FTP, presented in Table 6, utilizes a 0D calculation approach introduced in publication [7]. This was conducted for additional accuracy evaluation of the analytical method previously proposed.…”

“…The foreseen improvements of the presented methods will include further developed transient analysis and a damped vibration of the turbine blade in the non-admission sections of the turbine. Furthermore, an extended fatigue life analysis with implementation of a damage accumulation method presented in [23], [24], for improved accuracy of the LCF models is envisage. For the post-processing HCF/LCF evaluation, additional tests are foreseen outside LUMEN demonstrator, where LCF effects at increased operating temperatures can be validated.…”

“…Consequently, a gas bending stress amounts to the tensile stress -in the leading and trailing edge, and compressive stress -on the suction side of the blade. The leading or trailing edge of the root section is often where the highest stress is located [1], [7], [8], [15].…”

“…In the Figure 1, the main geometrical parameters of the LUMEN turbine blade are presented. In the following sub-sections, the analytical approach for calculating TB main loads, including: rotational, gas pressure, mechanical is presented [1], [6], [7], [8], [9], [10], [11], [12], [13], [14].…”