ARTICLE IN PRESS JID: PROCI [mNS;October 16, 2020;10:53] Available online at www.sciencedirect.com Proceedings of the Combustion Institute 000 (2020) 1–8 www.elsevier.com/locate/proci Particle burning behaviors of Al/AP propellant with high-speed digital off-axis holography Yingchun Wu a , Zhiming Lin a , Zhu Zhuo a , Shixi Wu b , Chongyang Zhou b , Longchao Yao a , Wen Ao c , Xuecheng Wu a,∗ , Linghong Chen a , Kefa Cen a a State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China b Science and Technology on Aerospace Chemical Power Laboratory, Hubei Institute of Aerospace Chemotechnology, Xiangyang, Hubei 441003, China c Science and Technology on Combustion, Internal Flow and Thermo-structure Laboratory, Northwestern Polytechnical University, Xi’an 710072, China Received 8 November 2019; accepted 24 July 2020 Available online xxx Abstract The behavior of aluminum particles during Al/AP propellant combustion is studied by 25 kHz high-speed digital off-axis holography and high-speed microscopic imaging. The advantage of off-axis holography is that the effects of the enveloping fame are suppressed, thereby, achieving better burning particle imaging. Three- dimensional dynamics of the aluminum particles from a series of time-resolved holograms are given in order to study the motion behaviors of particles during combustion. Typical processes, e.g., formation and change of the condensed phase products, micro-explosion behavior, and diameter ratio of enveloping fame and Al particle, are analyzed. This work provides a new 3D approach, that is, high-speed digital off-axis holographic imaging, for studying solid propellant combustion. © 2020 Published by Elsevier Inc. on behalf of The Combustion Institute. Keywords: Aluminized propellant; Aluminum combustion; Off-axis holography; Micro-explosion; Oxide cap 1. Introduction The development of high-performance solid propellants has always been a substantial issue for aerospace applications. Composite solid pro- pellants have been utilized as the main power source of rocket propulsion for more than sixty ∗ Corresponding author. E-mail address: wuxch@zju.edu.cn (X. Wu). years [1]. Composite solid propellants consist of hydroxyl-terminated polybutadiene (HTPB) matrix and ammonium perchlorate (AP) grains (dozens to hundreds of microns) embedded in the matrix. A large number of investigations suggest that aluminum (Al) is an excellent additive with numerous advantages. Aluminum has relatively high volumetric combustion enthalpy as much as 81.6 kJ/cm 3 . The use of aluminum in composite solid propellants can yield high combustion tem- perature, improve specifc impulse performance, https://doi.org/10.1016/j.proci.2020.07.135 1540-7489 © 2020 Published by Elsevier Inc. on behalf of The Combustion Institute. Please cite this article as: Y. Wu, Z. Lin, Z. Zhuo et al., Particle burning behaviors of Al/AP propellant with high-speed digital off-axis holography, Proceedings of the Combustion Institute, https://doi.org/10.1016/j.proci.2020.07.135