Barrel swirl breakdown in spark-ignition engines: Insights from particle image velocimetry measurements

Abstract

Particle image velocimetry (PIV) has been used here to study the formation and breakdown of barrel swirl (‘tumble’) in a production geometry, four-stroke, four-valve, motored, spark-ignition, optically accessed internal combustion (IC) engine. The barrel swirl ratio (BSR) of the cylinder head could be enhanced by means of a port face inducer gasket so that the flow processes taking place at low and high swirl ratios could be investigated conveniently. Double-exposed images from planes both parallel and perpendicular to the cylinder axis were recorded at selected crank angles through the induction and compression strokes at a motored engine speed of 1000 r/min, with a wide open throttle, for both high and low BSR cases. The recorded images were interrogated by digital autocorrelation to give two-dimensional maps of instantaneous velocity. In both high and low BSR cases, a barrel or tumbling vortex motion is generated during induction, which is shown to persist throughout the majority of the compression stroke. The details of barrel swirl formation during induction and its subsequent modification during compression, however, differ strongly between the two cases. These differences can be explained qualitatively in terms of two main events; the first being competition during induction between vortices of unequal strength and the second being competition between the large-scale swirl motion and the local flow field generated by piston motion during compression. In the low barrel swirl case, significant dissipation occurs owing to these interactions and consequently the large-scale motion exhibits lower mean velocities and undergoes significant distortion. In the case of high BSR, the competition effects are minimized and a single ordered vertical vortex exhibiting high velocity magnitudes is observed to avoid piston induced distortion. It then moves into the apex of the pent roof combustion chamber where it survives as a single ordered vortex until at least 40° crank angle (CA) before top dead centre (TDC). Limitations and developments of the PIV technique are discussed.

Particle image velocimetry measurement of in-cylinder flow in internal combustion engines-experiment and flow structure analysis

“…A number of papers have and analysed. been published on the application of PIV to in-cylinder ow measurements in internal combustion engines [12][13][14][15][16][17][18][19][20][21][22]. Reuss et al [12] are among the rst researchers who applied PIV to measure the velocity eld in an engine.…”

“…4f ), the velocities are typically less than 1 m/s, V iÕ 1,j+ 1 +2V iÕ 1,j +V iÕ 1,j+ 1 8 ¢x much lower than the total uctuating velocity values, and hence the eld is more random than the total uctuating velocity eld. However, some smaller vortices can + V i+ 1,jÕ 1 +2V i+ 1,j +V i+ 1,j+ 1 8 ¢x (22) still be seen at positions (11, 1), (21, 10), (0, 10) and (16, 8), etc. The diameter of these vortex structures 0.07/mm is not suitable in this research because of the low values of the uctuating velocity and the relatively is about or less than 8 mm.…”

CFD Modeling of Advanced Swirl Technique at Inlet-Runner for Diesel Engine

“…According to the CI combustion theory, better engine performance may be achieved with HVF by improving the in-cylinder air-fuel mixing by increasing the swirl (rotation of air view from top of the cylinder) and tumble (rotation of air view from front of the cylinder) of in-cylinder air inside the fuel-injected region. Various methods have been used to improve the in-cylinder airflow in diesel engines such as: closing part of the intake port using a butterfly valve [22,23,24,25] modifying intake port/manifold geometry inserting shroud around the intake valve and modifying the piston bowl. Alternatively, in-cylinder airflow may be improved through the use of a guide vane.…”

Analysis of large-scale flow characteristics in a four-valve spark ignition engine

“…PIV is a relatively new technique capable of instantaneous two-dimensional velocity measurements. A number of papers have been published on the application of PIV to in-cylinder ow measurements in internal combustion engines [14][15][16][17][18][19][20][21][22].…”

“…Thus ensemble-averaged and cycleresolved ow parameters can be calculated. Although some researches [17][18][19][20][21] into in-cylinder ow had been carried out using these advanced digital PIV techniques and gave the ensemble-averaged and cycle-resolved ow analysis, only a few of them [19,21] analysed the largescale ow characteristics, including cyclic variation, uctuation intensity, kinetic energy and integral length scale, etc.…”