LHD学术报告会(1月24日14:00主楼312会议室)

Studies on Fluid Mechanics and Chemical Kineticsfor Application in Gelled Hypergolic Propellants

 

Prof. Peng Zhang (张鹏)

（Department of Mechanical Engineering

The Hong Kong Polytechnic University）

 

时间：2013年1月24日（周四）下午2:00-3:30

地点：力学所主楼312会议室

邀请人：姜宗林 研究员

 

报人简介：

Peng Zhang received his BSc in Mechanical Engineering from University of Science and Technology of China in 2000, and a MSc in Aerospace Engineering from Institute of Mechanics, Chinese Academy of Sciences in 2003. He obtained his PhD in Mechanical and Aerospace Engineering from Princeton University in 2010.

Before joining the Hong Kong Polytechnic University as an assistant professor in 2012, Peng Zhang worked as a Combustion Energy Research Fellow at Princeton University from 2010 to 2012. He also served as a research staff at Institute of Mechanics, Chinese Academy of Sciences from 2003 to 2004.

 

报告摘要：

Because of the extremely low vapor pressure associated with gelled hypergolic propellants (GHPs) for reduced vapor toxicity, their ignition delay depends critically on the propensity of the injected colliding jets and droplets to merge, mix, and react. The talk will cover both the physical aspect of mixing and the chemical aspect of reactivity, respectively illustrated by an analysis of droplet collision and a quantum chemistry computation for the decomposition of monomethylhydrazine (MMH, CH3NHNH2).

Specifically, a comprehensive theoretical analysis for the head-on binary droplet collision, with attendant bouncing and coalescence outcomes, will be discussed. The model embodies the essential physics that describes the substantial extent of droplet deformation, the viscous loss through droplet internal motion induced by the deformation, the dynamics and rarefied nature of the gas film between the colliding interfaces, and the subsequent merging of these interfaces through the van der Waals attraction force. The results are shown to agree well with experimental observations on the rheologically distinct fluids of hydrocarbon and water droplets, in terms of the nonmonotonic collision outcome of bouncing versus coalescence, in reduced and elevated environment pressure. Additional observations on the non-Newtonian nature of the gelled fluid and unequal-size droplet collision will also be presented.

For MMH chemistry, ab initiotransition state theory based master equation calculation for the thermal decomposition kinetics of MMH will be presented. The simple NN and CN bond fission to produce the radicals CH3NH + NH2andCH3+ NHNH2dominatesthe decomposition kinetics. The transition state theory calculationdirectly provides high pressure dissociation and recombination rate coefficientsfor these reactions. Predictions ofthe pressure dependence and product branching in the dissociation of MMHare obtained by solving the master equationfor a wide range of temperaturesand pressures relevant to rocketoperations.Astudyon the secondary channels in the thermal decomposition kinetics of MMH will bediscussed for their potential importance in modeling product formationfrom the MMH decomposition.

Auxiliary spin-off projects from these two major themes will be briefly discussed where appropriate.