Flow Field Investigation of a Single Engine Valve Using PIV, POD, and LES

Abstract

Due to stringent emission regulations, it is of practical significance to understand cycle-to-cycle variations in the combustion of fossil or renewable fuels to reach future emission regulations. The present study aims to conduct a parametric investigation to analyse the influence of the valve lift and different mass flows of an inlet valve of the test engine “Flex-OeCoS” on the flow structures. To gain a deeper understanding of the flow behaviour, an optical test bench for 2D Particle Image Velocimetry (PIV) and a Large Eddy Simulation (LES) are used. Turbulence phenomena are investigated using Proper Orthogonal Decomposition (POD) with a quadruple decomposition and the Reynolds stress transport equation. The results show good agreement between the PIV and LES. Moreover, the main flow structures are primarily affected by valve lift while being unaffected by mass flow variation. The turbulent kinetic energy within the flow field increases quadratically to the mass flow and to the decreasing valve lift, where large high-energetic flow structures are observed in the vicinity of the jet and small low-energetic structures are homogeneously distributed within the flow field. Furthermore, the convective flux, the turbulent diffusive flux, the rate of change, and the production of specific Reynolds stress are the dominant terms within the specific Reynolds stress transport equation.

Investigation of Flow Fields Emanating from Two Parallel Inlet Valves Using LES, PIV, and POD

“…The main objective of this investigation is to understand the effects of valve lift variation and different mass flows in a dual-valve setup with real-engine geometry using a low-speed PIV technique. The aim is to expand and complement the findings presented in a previous investigation [70]. Even though the boundary conditions may not be representative of a real combustion engine with moving internals and transient flow, the results obtained from the new setup will provide insights into the flow characteristics as well as generate reference validation data under steady-state conditions.…”

“…According to Hoffmann et al [70], a novel test rig was designed and commissioned. In this study, the test bench was modified to examine how the flow characteristics around two parallel intake valves are affected by variations in the mass flow rate and valve lift.…”

“…Recent studies have concentrated on PIV investigations to analyse the influences of various engine parameters on the in-cylinder flow. A recent study by Hoffmann et al [70] presented a thorough literature review on the different types of in-cylinder airflow in optical engines and experimental test rigs. It also presented an experimental and numerical study of the air flow through a single valve with simplified engine geometry.…”

“…The relevance index shown in Equation ( 8) proposed by Wu et al 2022 [89] is used to compare the vector fields of the xand the y-velocity components of two neighbouring POD modes regarding their similarity. To identify the cut-off mode between the dominant and the coherent structures, a target value between 0.9 and 1 [89], namely, 0.9935 [70], was chosen.…”

“…For the flow analysis of the interaction phenomena of two parallel intake valves, as well as to prove the feasibility of the LES modelling and PIV measurement techniques, a real engine geometry of Engine B at RWTH Aachen was designed as Optical Test Bench 2.1 (OTB 2.1). The main differences between OTB 2.1 and the previously presented OTB 1 [70] are the dual-intake valve setup instead of a single-valve setup and the real engine geometry instead of a simplified one. As shown in Figure 1, the inlet valve and intake pipe geometry of Engine B were used.…”