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

Abstract

Computational fluid dynamic (CFD) simulations and experimental steady flow tests (flow discharge, swirl, and tumble) were carried out to study the in-cylinder flow in a commercial four-valve spark ignition engine. The present investigation was aimed at analysing and controlling the generation of macro-vortex structures (swirl and tumble) during the inlet process. A comparative study of the most commonly employed tumble benches along with in-house design was performed, the last showing some advantages with respect to the others. The outcomes from the simulations were in agreement with experimental results. Mainly, the tumble generation rate was in general proportional to the valve lift. However, tumble was reduced drastically at medium valve lift due to a change in the vortex pattern. A stagnation zone was observed between inlet valves. CFD calculations successfully captured this tumble-fall effect, which was related to characteristic changes in the vortex pattern downstream of the inlet valves at medium valve lift. This affects tumble production without affecting the mass flowrate efficiency. Finally, at high valve lifts the tumble production and the vortex pattern were recovered. The capability of the cylinder head to induce swirl, tumble, or combined swirl-tumble by modifying the valve timing or by introducing adjustable flow deflectors was evaluated using CFD. Several valve timing strategies were analysed: some of them produced significant swirl, but introduced high mass flowrate losses. On the other hand, adjustable flow deflectors were shown to be an interesting alternative to induce swirltumble at low load and to improve tumble at high load.

Influence of swirl, tumble and squish flows on combustion characteristics and emissions in internal combustion engine-review

“…Fig.9. Turbulence intensity variations at different positions for the two intake ports [39] Recently, a combined swirl and tumble flows have been used in both SI and CI engines [22, [41][42][43][44]. Floch et al [22] analyzed the effect of tumble and swirl on turbulence and combustion by means of flow-control baffle placed between the intake manifold and the cylinder head.…”

“…They concluded that adding a shroud to the intake valve helped the generation of large-scale tumbling motion and maintenance of the tumbling flow pattern but the use of bowl-in piston showed no immediate help in the generation and the maintenance of the tumbling flow pattern. Recently, a combined swirl and tumble flows have been used in both SI and CI engines [22,[41][42][43][44]. Floch et al [22] analyzed the effect of tumble and swirl on turbulence and combustion by means of flow-control baffle placed between the intake manifold and the cylinder head.…”

Effects of the variable valve lift difference on in-cylinder gas flow in a four-valve gasoline engine

“…[12][13][14] There are a lot of technologies producing swirl. The existing technology mainly include the swirl deflector (SD), 15 the swirl control valve (SCV), 16 the variable valve lift (VVL) 17 and the VVL combined with variable timing (i.e. a 4VVAS), 18 and so on.…”

Insights into the development of the tumble motion using the direct and indirect steady-flow test methods

“…4 Recently, the in-cylinder tumble motion has been frequently introduced to regulate the gasoline direct-injection combustion system or the homogeneous charge compression ignition combustion system. 5 Thus, it is necessary to characterize quantitatively the tumble motion in order to understand it thoroughly and to utilize it efficiently in the engine cylinders.…”

“…16 Nevertheless, there is still the absence of a standard methodology for steady-flow tests with various configurations of the flow bench, although considerable efforts have been made by researchers to explore the effective evaluation method, especially for the evaluation of tumble flow. 2,5,16 The flow coefficient and the tumble intensity are the fundamental parameters to evaluate the flow capacity and the tumble motion respectively. In comparison with evaluation of the engine flow capacity, it is more difficult to assess the tumble intensity in engine cylinders.…”