Computational Fluid Dynamics of Four Stroke In-Cylinder Charge Behavior at Distinct Valve Lift Opening Clearance in Spark Ignition Reciprocating Internal Combustion Renault Engine

Abstract

In-cylinder flow dynamics in internal combustion Renault engine is complex, expensive and difficult to compute experimentally. The present study attempts to emulate the in-cylinder charge behaviour at distinct valve lift opening clearance in four stroke spark ignition internal combustion engine using computational fluid dynamics. Considering the complexity of the geometry and in-cylinder fluid motion, governing equations for unsteady, three dimensional, compressible turbulent flow were computed with continuity equations (conservation of mass), Navier-Stokes equations (conservation of momentum) and RNG k-ε turbulence model. Assumed to be an inline spark ignition (SI) operating on a four stroke cycle, the engine was modelled with SolidWorks 2019 version while the in-cylinder charge behaviour was simulated using ANSYS Fluent 14.5. Increase in cylinder temperature enhanced the thermal properties of air-fuel mixture during combustion. Increase in valve lift opening clearance led to more charge quantity being ingested through the intake valve opening into the cylinder, thereby causing increase in temperature of in-cylinder charge as well as significant improvement in the volumetric and mechanical efficiency of the cycle. It was also observed that the rate of heat retention in the cylinder may be optimum at lower valve lift which may be characterised by minor or zero loses, while significantly high cylinder charge temperature may be prone to reduction of the intake charge density. Based on Particle Image Velocimetry (PIV), in-cylinder velocity vectors, vorticity magnitudes and distributions of turbulence kinetic energy (TKE) increased with increasing valve lift opening clearance, thereby, improving combustion efficiency, increasing torque and power output for effective engine performance.