Executive Summary : | At ISRO, the development of a 2000 kN thrust semi-cryogenic engine as a possible replacement of earlier cryo-engine is in progress so as to increase the payload capability. An in-depth understanding of the ignition and combustion process of the Isrosene fuel along with liquid oxygen is required so that the same can be used in semi-cryogenic engine of GSLV MkIII. To achieve ignition of rocket fuel followed by sustenance of this ignition is a challenging task. Rocket engine cycles comprising of ignition and combustion typically involve the interaction of several non-linear processes such as phase change, diffusion, chemical reactions, heat transfer, and turbine and pump operation etc. A subtle change in one of the factor may lead to serious changes in the combustion process. One such factor relates to proper ignition of ignitor fuel which leads to smooth burning of propellant fuel and eventually smooth build-up of thrust. In the proposed work, molecular dynamics simulations using quantum mechanics based ab-initio methods will be conducted to develop an ignition model for triethyl aluminum (TEA) and tryethyl boron (TEB) along with liquid oxygen.
The Gaussian 16 suite of programs will be utilized to formulate the reaction pathways for TEA and TEB respectively. The decomposition study will be primarily performed by using the B3LYP/6-31G(d) level of theory. The theory will enable prediction of enthalpies of formation of several intermediate species. Molecular structures of intermediate species resulting from the decomposition of igniter fuels (TEA and TEB) will be identified by carrying out ground-state and transition-state optimization calculations. Depending upon the case to be studied and size of molecules, other methods such as CBS-QB3 (complete basis set), MP2 (Moller-Plesset) perturbation theory along with 6-311++G (d,p) basis set and the compound G4(MP2) theory can also be employed. To understand the decomposition pathways for the condensed phase reactions, polarizable continuum model (PCM) will be used. The data obtained will be used to estimate reaction rate coefficients using relevant transition state theory. Existing Gaussian 09 suite of programs at IIT Bombay will be used for this step and eventually detailed chemical reaction mechanism for the ignitor fuels will be formulated. Upon successful formulation of the detailed chemical reaction mechanism, continuum based ignition model will be used to predict the ignition delay and sensitivity analysis will be conducted to identify important chemical reaction pathways. The proposed work will thus shed some light on understanding of igniter fuel quantity required relative to oxidizer for proper and smooth combustion, ignition characteristics such as time delay and peak pressure, combustion modelling of the LPRE fuel w.r.t. ignition using detailed chemical kinetics mechanism (DCKM) and a suitable ignition model. |