Euler-Lagrange simulation of massive aluminum particles and agglomerates combustion in a realistic solid rocket motor environment

In a solid rocket combustor, the aluminum particles often aggregate into larger agglomerates near the burning surface, which contributes to the distributed combustion of aluminum during the flow. This distributed manner influences the overall core flow and adds complexity to the combustion behavior. Therefore, it is crucial to account for the effects of this distributed combustion and agglomerate formation in computational modeling. In this work, based on the Euler-Lagrange model, the aluminum agglomerate combustion model is established with consideration for the smoke phase and alumina cap, which would provide a precise prediction of the particle distributed combustion. Using a typical motor setup, the multiphase reacting flow field is simulated and the particle distributed combustion is captured as the large agglomerates continue to combust in the whole flow field. With massive particle group, from 10⁸ to 10¹², the aluminum particle group combusting flow is numerically studied and reveals the non-neglected particle collective dynamics, as the reacting flow field shows obvious difference. Three typical agglomerate size distributions are investigated; the comparative results indicate the agglomerate has significant effects on combustion efficiency and motor performance, and the size distribution shows combined effects from the different size agglomerates, which indicates the importance of identifying the predominant sizes in each distribution. This work provides valuable insights into how agglomerate size and distribution influence combustion behavior in real motor conditions, emphasizing the importance of incorporating these factors into combustion modeling for more accurate predictions of motor performance.