Measurement of In-Cylinder Turbulence in An Internal Combustion Engine Using High Speed Particle Image Velocimetry

Abstract

In this study, in-cylinder flow has been measured using high speed PIV to investigate turbulent characteristics of in-cylinder flow and to give a guiding principle for optimization of intake port and combustion chamber for down sized boosted engine. To clarify turbulence characteristics which will affect combustion process in engines, decomposition method of turbulence component from instantaneous velocity are investigated. Since velocity spectrum in 1 cycle from intake to compression stroke has a specific frequency where slope of the spectrum changes, a time filtering method for turbulence decomposition is proposed using this specific frequency as a cutoff. A characteristic of turbulent kinetic energy extracted by the proposed method well represents the expected flow characteristics at each test condition and shows good correlation with combustion characteristics such as burning speed and geometry of flame front. The obtain results show that turbulent intensity is high at a vortex center of tumble flow, which suggests that a control of tumble flow was very important in design of a boosted engine.

Development of cycle-to-cycle variation of the tumble flow motion in a cylinder of a spark ignition internal combustion engine with Miller cycle

“…However, in the engine, the fluctuation component u ′ contains both the CCV and turbulent components. Some studies have attempted to separate the CCV component u ′ CCV and turbulent component u ′ turb using a temporal 25,26 or spatial filter. 14,18 Others have utilized the proper orthogonal decomposition (POD) method.…”

“…The previous studies have also considered the effects of different flow fields by different engine geometries. The basic factors involved in changing the strength of tumble and swirling flow are the intake geometry, 24 a shroud on an intake valve, 18 a butterfly valve in one of the intake valves, 25 piston shape, 26 and a control flap to reduce the anti-tumble intake flow. 27 However, the process by which CCV of the flow field develops and the interaction between the factors inducing the CCV remain to be elucidated.…”

Experimental Investigation of the In-Cylinder Flow of a Compression Ignition Optical Engine for Different Tangential Port Opening Areas

“…SCPs of flows inside engine cylinders do not stay in a fixed position but vary with each CA, which is affected by flows from the intake ports and so forth. Our successive studies developed an evaluation technique for SCPs using PIV measurements, which was based on the algorithms proposed in [29,30]. For any fixed arbitrary lattice point, P i,j , in an in-plane velocity field, the following gamma function, Г(P i,j ), was calculated, which indicates the average sine of the angle, θ l , between the vectors connecting the point to all other interrogation window centers and those to the measured velocities [37]:…”

“…However, since these methods measure only one point in a flow field, it is difficult to measure flow velocities in the entire engine cylinder. Therefore, the particle image velocimetry (PIV) technique has garnered attention in terms of measuring flow velocities simultaneously at multiple points inside the engine cylinders without interfering with the flow fields [12,[24][25][26][27][28][29][30][31][32][33][34][35][36][37]. In [30], the PIV technique was applied during the compression stroke to a light-duty optical diesel engine.…”

Simultaneous In-Cylinder Flow Measurement and Flame Imaging in a Realistic Operating Engine Environment Using High-Speed PIV

“…In recent time, the advances in laser development has made powerful, high frequency laser available for researchers. Hence, PIV can now be applied to not just capture spatial characteristics of the in-cylinder flow but also its temporal evolution and development [6][7][8].…”