Simulation of turbulent flow in a rapid compression machine: Large Eddy Simulation and computationally efficient alternatives for the design of ignition delay time experiments

Abstract

Rapid compression machines (RCMs) are widely used by the fuel research community to provide engine-relevant conditions to study ignition delay time (IDT), which is a crucial target for validating chemical kinetic mechanisms for fuels. Creviced piston heads are routinely used to ensure temperature homogeneity within the combustion chambers of RCMs. However, due to the exponential dependence of kinetic rate coefficients on temperature, homogeneity of the *

Numerical Study toward Fast Intermediate Species Sampling with High Accuracy in a Rapid Compression Machine

“…For the flow simulations in the RCM, the Reynolds number is estimated around 2000∼4000 in the reaction chamber after EOC, which indicates that the flow pattern resides in the transition region. 7 Yousefian et al 29 compared the 3D large eddy simulation (LES) and 2D laminar results and found that the temperature distributions and velocity fields can be well approximated by 2D laminar simulations, especially at higher pressures. Except for the region in the piston crevice, the flow in the reaction chamber of modern RCMs for chemical kinetic studies is designed to be in laminar condition.…”

CFD Study of the Effect of Initial Temperature Inhomogeneities and Buoyancy on the Autoignition Behavior of Ethanol in an RCM

“…A laminar solver was used since it has been shown to achieve the best agreement with experimental results. 29,31 Furthermore, a laminar CFD model has been proven to adequately predict compression and the postcompression flow field in comparison to the computationally more expensive LES models 4 and the overly dissipative RANS models. 21,22,31 The simulations use the ethanol mechanism by Mittal et al 39 containing 113 species and 710 reactions.…”

“…Momentum, energy, and species equations were solved considering mixture-averaged diffusion coefficients. A laminar solver was used since it has been shown to achieve the best agreement with experimental results. , Furthermore, a laminar CFD model has been proven to adequately predict compression and the postcompression flow field in comparison to the computationally more expensive LES models and the overly dissipative RANS models. ,, …”

“…The review by Sung and Curran emphasizes the significance of an RCM design to minimize the effect of the roll-up vortex, which is needed to validate the adiabatic core hypothesis. Yousefian et al , characterized temperature inhomogeneities that evolve during the RCM operation. The authors also went further to provide approaches to quantify the temperature inhomogeneity.…”

“…The literature review shows that the main emphasis of the past CFD studies has been on optimizing the piston crevice design to suppress the roll-up vortex − and the characterization of the flow field in an RCM. ,− There have been limited to no computational studies on the effect that the cooler piston and buoyancy can have on the initial temperature field due to convective flux. Studies utilizing uniform thermal boundary conditions and focusing on temperature distribution inside the RCM have previously been completed ,,,− using the two-dimensional (2-D) axisymmetric approach.…”