An agglomeration model: Influence of proximity of particles on agglomeration

Aluminum is widely used in solid rocket propellants to improve the energy performance of the propellant. However, during propellant combustion, aluminum particles may agglomerate, resulting in slag deposition, incomplete combustion of metal particles, increased two‐phase flow losses, and reduced motor specific impulse. Therefore, it is of great scientific significance and engineering value to understand the agglomeration mechanism of aluminum particles and to explore the method of agglomeration suppression. Based on this, this paper firstly briefly introduced the agglomeration process of aluminum particles during propellant combustion. Subsequently, factors influencing the agglomeration of aluminium particles were analysed. The influencing factors can be roughly divided into two aspects: propellant‘s own formulation and external environment. Immediately afterwards, the existing agglomeration suppression methods were emphasized and summarized and analyzed. Presently, agglomeration suppression methods can be broadly classified into four categories, namely, conventional formulation optimization, use of aluminum nanoparticles, and modification of aluminum particles using fluorine‐containing compounds or alloy particles. Finally, several directions that need to be focused on in the future are proposed to address the problems in the study of aluminum particle agglomeration suppression methods.

Section: Introductionmentioning

confidence: 74%

Aluminum particle agglomeration characteristics and suppression method during the combustion of aluminum‐based solid propellants: A review

Liao,

Pei,

Xie

et al. 2023

“…In recent years and due to advancements in computational capabilities, a major development was achieved in the field of agglomeration modelling [9,10]. Xiao et al [9] were able to define various aluminum cluster parameters and determine, with good agreement with experimental results, the agglomerates particle distribution.…”

Section: Introductionmentioning

confidence: 99%

“…In recent years and due to advancements in computational capabilities, a major development was achieved in the field of agglomeration modelling [9, 10]. Xiao et al.…”

Section: Introductionmentioning

confidence: 99%

Agglomeration in Composite Propellants Containing Different Nano‐Aluminum Powders

Cohen

Michaels

Yavor

2022

In order to improve nano‐aluminized solid propellant properties and performance, different materials are being investigated for coating nano‐aluminum particles. Two of the powders which are considered are V‐ALEX, a fluoropolymer (Viton) coated nano‐aluminum, and L‐ALEX, a stearic acid coated nano‐aluminum. It is believed that a thin layer of coating should protect the aluminum core from premature oxidation, as well as provide an exothermic source which may accelerate particle ignition, resulting in reduction of agglomeration. This paper investigates the effect on the agglomeration phenomenon of replacing 33 % of the micron aluminum powder with ALEX, V‐ALEX and L‐ALEX powders, in solid propellant samples containing 20 % HTPB, 65 % AP and 15 % aluminum. Propellant strands were burned inside a windowed pressure chamber, allowing measurements of the agglomerates size and number using a high‐speed camera. The experimental data showed that propellants in which 33 % of the micron aluminum was replaced with nano‐powders exhibited reduced agglomeration, in terms of number of agglomerates and their total volume. The reason is the lower ignition time and temperature of the nano‐powders that ignite before aggregating to agglomerates. The propellants containing ALEX nano‐powder exhibited a reduction of up to 36 % in agglomerates volume compared to the propellants containing only micron powder, while the propellants containing coated nano‐powders, L‐ALEX and V‐ALEX, showed a higher reduction of up to 60 % in agglomerates volume. V‐ALEX showed slightly better performance than L‐ALEX. It can be concluded that by replacing some of the micron‐aluminum with coated nano‐aluminum in solid propellants, it is possible to significantly reduce the propulsive losses due to agglomeration.

Research progress and prospects on agglomeration models and simulation methods of aluminum particles in aluminum‐based composite propellants

Gao,

Wang,

Liu

et al. 2024

The agglomeration of aluminum during the combustion of solid propellants considerably impacts engine operation and has been widely studied in recent years. The characteristics of aluminum agglomeration in aluminum‐based composite propellants have been studied via experiments and simulations. In this study, the agglomeration process and the characteristics of agglomerated particles are summarized. Agglomeration models and simulation methods have garnered considerable attention because they are not influenced by experimental conditions, are economical, and have minimal restrictions. Therefore, five agglomeration models and four simulation methods are introduced herein to investigate agglom eration in aluminum‐based composite propellants. By analyzing the advantages and disadvantages of these models and methods, deeper agglomeration mechanisms can be explored and new directions for suppressing agglomeration can be identified to mitigate agglomeration issues. These efforts can support and guide the design of solid rocket propellants and the safe operation of rocket engines.