In-Cylinder Flow Computational Fluid Dynamics Analysis of a Four-Valve Spark Ignition Engine: Comparison Between Steady and Dynamic Tests

Abstract

Numerical and experimental techniques were applied in order to study the in-cylinder flow field in a commercial four-valve per cylinder spark ignition engine. Investigation was aimed at analyzing the generation and evolution of tumble-vortex structures during the intake and compression strokes, and the capacity of this engine to promote turbulence enhancement during tumble degradation at the end of the compression stroke. For these purposes, three different approaches were analyzed. First, steady flow rig tests were experimentally carried out, and then reproduced by computational fluid dynamics (CFD). Once CFD was assessed, cold dynamic simulations of the full engine cycle were performed for several engine speeds (1500 rpm, 3000 rpm, and 4500 rpm). Steady and cold dynamic results were compared in order to assess the feasibility of the former to quantify the in-cylinder flow. After that, combustion was incorporated by means of a homogeneous heat source, and dynamic boundary conditions were introduced in order to approach real engine conditions. The combustion model estimates the burning rate as a function of some averaged in-cylinder flow variables (temperature, pressure, turbulent intensity, and piston position). Results were employed to characterize the in-cylinder flow field of the engine and to establish similarities and differences between the three performed tests that are currently used to estimate the engine mean flow characteristics (steady flow rig, and cold and real dynamic simulations).

Numerical model to study the valve overlap period in the Wärtsilä 6L 46 four-stroke marine engine

“…Although CFD was integrated in 1960s on the aerospace industry, the first simulations of engines appeared in 1980s. In the last few years, examples of numerical works about four-stroke engines are those of [2][3][4][5][6][7][8], however, they were not applied to medium or large marine engines. Examples of large engines are those of Lamas and Rodríguez [9] and Nakagaya [10], both of them two-stroke type.…”

In-cylinder flow control in a four-valve spark ignition engine: numerical and experimental steady rig tests

“…For these reasons, such tests are currently used to estimate the effect of geometric changes on the cylinder head and the inlet port with the aim of comparing and improving engine performance. However, steady rig test conditions are far from the real ones, and, therefore, these results should not be used to predict dynamic engine performance [3]. On the other hand, some techniques like particle image velocity, laser Doppler anemometry, or the intensified charge-coupled device (ICCD) camera are currently employed to study in-cylinder flow under dynamic conditions [1,2].…”

“…In recent works [3,8] CFD was applied to study a four-valveper-cylinder Fiat engine. Dynamic hot engine simulations of the whole engine were compared with steady-state cold simulations in order to identify differences in in-cylinder flow.…”

Electromagnetic Exhaust Valve Event Optimization for Enhancing Gasoline Engine Performance

“…At the engine speed of 2000r/min and BMEP is about 0.3MPa. Only single intake valve per cylinder works for the conditions, which can improve the mixing level of fresh charge [9].…”