Junrui Shi

Computer Simulation of Combustion Process in a Piston Engine With a Porous Medium Regenerator

In the regenerative engine, effective heat exchange and recurrence between gas and solid can be achieved by the reciprocating movement of a porous medium regenerator in the cylinder, which considerably promotes the fuel-air mixture formation and a homogeneous and stable combustion. A two-dimensional numerical model for the regenerative engine is presented in this study based on a modified version of the engine computational fluid dynamics (CFD) software KIVA-3V. The engine was fueled with methane and a detailed kinetic mechanism was used to describe its oxidation process. The characteristics of combustion and emission of the engine were computed and analyzed under different equivalence ratios and porosities of the regenerator. Comparisons with the prototype engine without the regenerator were conducted. Results show that the regenerative engine has advantages in both combustion efficiency and pollutant emissions over the prototype engine and that using lower equivalence ratios can reduce emissions significantly, while the effect of the porosity is dependent on the equivalence ratio used. [DOI: 10.1115/1.4023973]

Two-Dimensional Pore-Level Simulation of Low-Velocity Filtration Combustion in a Packed Bed with Staggered Arrangements of Discrete Cylinders

ABSTRACT A pore level numerical simulation of filtration combustion in a 2D porous media made of staggered arrangements of discrete cylinders with a diameter of 6 mm was performed. The reaction of methane is described by a single-step first-order Arrhenius type expression, and solid conduction and surface radiation exchange between particles are considered in the model. Numerical simulations are performed with the CH4/Air mixture velocity of 0.23–0.83 m/s and equivalence ratio of 0.15–0.45. Results show that, for low-velocity filtration combustion, the flame and flow are highly two-dimensional, and that the thickness is the order of magnitude of the cylinder diameter. At the same time, the maximum normalized velocity in the centerline of the burner reaches 11.5–14.5 times the average interstitial gas velocity. Obvious thermal nonequilbrium in the burner for the same phase and interphase are observed except for the inlet and exit zones of the burner, which are far from the reaction zone. The extent of the thermal nonequilbrium varies along the flow direction, and its value is rather small just downstream of the reaction zone. The numerical predictions show qualitative agreements with experimental data available from the literature.