Effect of Weak Boundary on Thermal Stress of Throat Insert in SRM Nozzle
- Paper number
IAC-08.C2.7.8
- Author
Mr. Shi Hongbin, The 41st Institute of the Fourth Academy of CASC, China
- Coauthor
Mr. Tang Min, China
- Coauthor
Mr. Wang Xuekun, China
- Coauthor
Mr. Li Geng, China
- Coauthor
Mrs. Qu Zhuanli, China
- Year
2008
- Abstract
A theoretical model and fundamental calculation method are developed. Considering weak boundary and modulus change of the insulators behind the throat with the change of temperature, the stress field for the throat insert of a solid rocket motor is calculated thematically by using finite element method. The shape and the load of the throat insert are axisymmetric, as a result, the three-dimensional calculation can be simplified to an axisymmetric problem. Among many research subjects for calculating of the thermal stress, the boundary in the back of the throat insert was considered as fixed boundary in the past, and the thermal stress was greater than the actual stress. Actually, in the firing test of the SRM, the property of the insulators behind the throat changes in time and the material can be divided into three layers with the boost in temperature, which are charring layer, pyrolytic layer, and matrix layer, respectively. For the charring layer, there is no way to get a precision sample, so it’s impossible to test the modulus of the charring layer. In this paper, the charring layer contacting the throat insert is considered as weak boundary, and the area of the boundary is varied from 1/8 to 1/2 of the model. Based on tested results, the modulus of the material in the charring layer decreases from 10.5GPa tested at room temperature to 100MPa or 10MPa in linear way with the change of temperature. In the calculation of the temperature field, the thermal resistance between the different layers in nozzle is ignored. The convection heat transfer coefficient and internal flow field are calculated by using Bartz formula and one dimensional isentropic flow. When calculating the stress field, the boundary of the flange is fixed. The boundary between each part of the nozzle can be considered as contact. The calculation results show that the magnitude of the modulus is 10MPa, and the size of the weak boundary is a quarter of the model after the carbonizations of the insulators behind the throat .Calculated results are basically identical with tested results.
- Abstract document
- Manuscript document
IAC-08.C2.7.8.pdf (🔒 authorized access only).
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