A Comparison of 1D-3D Co-Simulation and Transient 3D Simulation for EGR Distribution Studies

Abstract

Computational modeling, an important task for design, research and development stages, is evolving fast with the increase of computational capabilities over the last decades. One-dimensional (1D) CFD simulation is commonly used to analyze the flow rates and pressures of an entire fluid system of interconnected parts such as pipes, junctions, valves, and pumps. In contrast, three-dimensional (3D) CFD simulation allows detailed modeling of components such as manifolds, heat exchangers, and combustion cylinders where the flow contains significant 3D effects. Coupling a 1D model with a 3D domain potentially offers the benefits of both simulation strategies in one co-simulation approach. The present study provides a deep understanding of the co-simulation approach by listing all necessary steps need to be followed before and during the coupling of the 1D and 3D simulation software. It analyses the simulation and convergence time requirements based on the 3D model mesh quality and compares this approach with the current 1D–3D uncoupled approach followed in the industry. The outputs of both simulation approaches are then compared with experimental results. The co-simulation time mainly depends on the mesh quality of the 3D domain and the number of inner iterations per time-step which is entirely determined by the nature and complexity of the simulation. The co-simulation time per engine cycle is almost identical to the uncoupled approach. However, it was found that the number of cycles required for convergence in the coupled approach is nearly double than the uncoupled approach. The comparison between the two simulation approaches and the experimental results demonstrated the very 3D nature of the flows, the sensitivity of the uncoupled approach to input conditions and the sensitivity of co-simulation to the averaged boundary conditions transferred from the 1D model back to the 3D domain.

Assessment of the numerical and experimental methodology to predict EGR cylinder-to-cylinder dispersion and pollutant emissions

“…Particularly, the literature shows a variety of works providing a good agreement between CFD 3D predictions with URANS approach, employing a k − ε closure model. 24,31–33 Thereby, the URANS approach with the k − ε turbulence submodel has been selected to be the baseline setup of this work. In most of these cited works, the turbulence model is fixed throughout the study.…”

Improving Thermal Efficiency of Internal Combustion Engines: Recent Progress and Remaining Challenges

“…This lead to deteriorating particulate matter(PM) and NO x emissions. Therefore, according to the findings of Pavlos et al [111], the amount of turbulence in the flow that is produced at the place where EGR diffusion occurs is the primary component that determines how well an EGR mixer functions.…”

“…The rate of EGR needed by an engine change with engine speed and load, and proper regulation of the quantity entering the cylinders is essential for achieving optimal engine performance and minimal NO x emissions. Nevertheless, regulating the quantity of EGR entering the intake manifold does not guarantee that the EGR rate will be spread uniformly throughout the engine's cylinders [111]. This lead to deteriorating particulate matter(PM) and NO x emissions.…”

Charge Air Subcooling in a Diesel Engine via Refrigeration Unit – Effects on the Turbocharger Equilibrium

“…peak power at full load and minimum fuel consumption at part load). Moreover, the 1D codes accuracy is a key factor, since they often represent the early stages of a more detailed engine characterization, carried out on 3D simulation platforms for which they provide the numerical input [11,12]. In addition to the areas of application mentioned above, the 1D model approach is highly performing for the investigation of the engine performance enhancement through charge air cooling, an already consolidated technique in present turbocharged diesel engines, in which a dedicated heat exchanger allows to partly recover the issues associated with the air density reduction downstream the compressor (i.e.…”