LSENS: Multipurpose kinetics and sensitivity analysis code for homogeneous gas-phase reactions

LSENS is a multipurpose chemical kinetics and sensitivity analysis code for the solution of complex, homogeneous, gas-phase reactions. The main features of LSENS are its accuracy, efficiency, flexibility, and convenience for treatment of many different chemical reaction models, including static system; steady, one-dimensional, inviscid flow; incident-shock initiated reaction in a shock tube with corrections for frictional losses; perfectly stirred reactor; and perfectly stirred reactor followed by a plug flow reactor. In addition, equilibrium computations can be performed for several assigned states. An implicit numerical integration method, LSODE, which works accurately and efficiently for the extremes of very fast and very slow reactions, is used to solve the "stiff" ordinary differential equation systems that arise in chemical/combustion kinetics. For static and one-dimensional flow reactions, including those behind an incident shock wave and following a perfectly stirred reactor calculation, LSENS uses the decoupled direct method to calculate the sensitivity coefficients of dependent variables and of their derivatives with respect to the initial values of dependent variables and/or the rate coefficient parameters. Solution methods for the equilibrium and postshock conditions and for perfectly stirred reactor problems are either adapted from or based on procedures built into the chemical equilibrium and applications code CEA.