Investigation of an IC Engine Intake Flow Based on Highly Resolved LES and PIV

Abstract

-To reduce emissions and fuel consumption, the current generation of gasoline engines uses technologies such as direct injection, downsizing and supercharging. All of them require a strong vortical in-cylinder charge motion, usually described as "tumble", to improve fuel-air mixing and enhance flame propagation. The tumble development strongly depends on the flow field during the intake stroke. This flow field is dominated by the intake jet, which has to be captured well in the simulation. This work investigates the intake jet on a steady-state flow bench, especially in the vicinity of the intake valve. At first, the general flow dynamics of the intake jet for three different valve lifts and three different mass flows were investigated experimentally. For the smallest valve lift (3 mm), flow-field measurements using Particle Image Velocimetry (PIV) show that the orientation of the intake jet significantly depends on the air flow rate, attaching to the pent roof for low flow rates. This phenomenon is less pronounced for higher valve lifts. An intermediate valve lift and flow rate were chosen for further investigations by scale-resolving simulations. Three different meshes (coarse, medium and fine) and two turbulence models (Sigma and Detached Eddy Simulation-Shear Stress Transport (DES-SST)) are applied to consider their effect on the numerical results. An ad-hoc postprocessing methodology based on the ensemble-averaged velocity field is presented capturing the jet centerline's mean velocity and velocity fluctuations as well as its orientation, curvature and penetration depth. The simulation results are compared to each other as well as to measurements by PIV.

Review Analysis on CFD Techniques and Numerical Methods for IC Engines Fueled with Diesel and Biofuels

“…For the LES-considered section in the DES model, the refining process for the grid also helped to achieve greater resolutions resulting in the flow structures and turbulence attributes. Inside the flow at the inlet port, the Sigma turbulence model, or LES model, was quantitatively scale-up besides the Detached Eddy Simulation-Shear Stress Transport (DES-SST) [85,86]. The Sigma model with a highly precise meshing had the idealistic resulted concurrence compared to the results from PIV, but the DES model had the most variance in the highest velocity and its profiles.…”

Quantitative metrics for comparison of in-cylinder velocity fields using particle image velocimetry

“…While the above treatment is appropriate for whole-field comparisons, in many cases key local features such as the flow over the intake valves, recirculation zones or flows near surfaces are targeted for CFD validation and detailed studies of flow characteristics (Buhl et al 2017). In such cases, care must be taken to consider the spatially resolved nature of the z , of velocity for each sample size is also shown, normalized by a constant scale factor to the value of the CMRI metric for a sample size of 500 cycles flow field variability as convergence of velocity components has been shown to depend on the location within the cylinder (Baum et al 2014).…”

Evaluation of a Near-Wall-Modeled Large Eddy Lattice Boltzmann Method for the Analysis of Complex Flows Relevant to IC Engines

“…Recent studies examined intake phenomena using magnetic resonance velocimetry (MRV) in a steady water flow bench [1] or low-speed particle image velocimetry (PIV) in a steady air flow bench [14,15]. The data from these experiments have been used as validation for large eddy simulation (LES) approaches [14][15][16][17][18].…”