PSI - Issue 71

Anoop Kumar A. et al. / Procedia Structural Integrity 71 (2025) 287–294

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(oxidiser). It consists of two parts: the injector head assembly and combustion chamber assembly. The injector elements atomize the fuel and oxidizer and injects them to the combustion chamber where they get mixed before the combustion starts. Injector head assembly comprises of a gas duct, diffuser, and mixer assembly. The oxidiser rich hot gas, after driving the turbine, is fed into the combustion chamber through the injector head assembly. Mixer assembly is made up of three major parts: a mixer body, fire face plate, and injector elements. Fig. 1 shows the configuration of the injector head assembly.

Fig. 1. Configuration of injector head assembly

During operating condition, the injector head assembly is subjected to high pressure and high temperature loads. Response of the structure under these loads are non-linear. The testing of the injector head can only be done along with the engine during hot tests. Due to this reason, finite element simulations were called upon to understand the behavior of the structure to the expected loads. To clear a particular hardware for integration with the engine, acceptance pressure test is proposed wherein the structure would be subjected to internal pressure. The magnitude of the test pressure is arrived at by multiplying the pressure during operation by an appropriate load factor. This paper presents the details of simulations performed to understand the non-linear behavior of the structure under combined loading of pressure and thermal loads. Design modifications affected based on simulations is also presented. Finite element analysis details Finite element model of the injector head assembly was generated using solid elements. Because of the complex geometry, a mix of eight-noded brick elements, four noded tetrahedral elements, and shell elements were used. The acceptance test condition of the assembly was simulated first. Based on the analysis results, the configuration was modified. The suitability of the modified configuration was then verified for the proof test and operating conditions. Analysis for operating conditions considers thermal loads due to the temperature distribution as well as internal pressure loads. Temperature depended mechanical properties are also accounted for. This simulation was done using two sub-assembly models – (i) modified gas duct -diffuser sub-assembly and (ii) mixer assembly Mechanical properties of materials The body of the mixer assembly is made of High strength steel, the fire face plate and protruding elements are made of copper alloy, nominal elements are made of Stainless steel, diffuser and gas duct are made of Nickel alloy [Narayana-Murty, 2022]. The mechanical properties of the materials are evaluated by means of tensile tests at different temperatures spanning the operating regime. Mechanical properties of materials used in the injector head assembly are given in Table 1. 2. 3.