An application of tomographic PIV to investigate the spray-induced turbulence in a direct-injection engine

Abstract

Fuel sprays produce high-velocity, jet-like flows that impart turbulence onto the ambient flow field. This spray-induced turbulence augments rapid fuel-air mixing, which has a primary role in controlling pollutant formation and cyclic variability in direct-injection engines. This paper presents tomographic particle image velocimetry (TPIV) measurements to analyse the 3D spray-induced turbulence during the intake stroke of a direct-injection spark-ignition (DISI) engine. The spray produces a strong spray-induced jet (SIJ) in the far field, which travels through the cylinder and imparts turbulence onto the surrounding flow. Planar high-speed PIV measurements at 4.8 kHz are combined with TPIV at 3.3 Hz to evaluate spray particle distributions and validate TPIV measurements in the particle laden flow. A comprehensive uncertainty analysis is performed to assess the uncertainty associated with individual vorticity and strain rate components. TPIV analyses quantify the spatial domain of the turbulence in relation to the SIJ and describe how turbulent flow features such as turbulent kinetic energy (TKE), strain rate (S) and vorticity (Ω) evolve into the surrounding flow field. Access to the full S and Ω tensors facilitate the evaluation of turbulence for individual spray events. TPIV images reveal the presence of strong shear layers (visualized by high S magnitudes) and pockets of elevated vorticity along the immediate boundary of the SIJ. S and Ω values are extracted from spatial domains extending in 1mm increments from the SIJ. Turbulence levels are greatest within the 0-1mm region from the SIJ boarder and dissipate with radial distance. Individual strain rate and vorticity components are analyzed in detail to describe the relationship between local strain rates and 3D vortical structures produced within strong shear layers of the SIJ. Analyses are intended to understand the flow features responsible for rapid fuel-air mixing and provide valuable data for the development of numerical models.

Effect of intake manifold geometry on cylinder-to-cylinder variation and tumble enhancement in gasoline direct injection engine

“…3 . Moreover, preventing the distortion due to the curved glass cylinder, a high-speed camera focused on regions near the cylinder axis 28 , 29 . And the minimized distorted PIV images using camera and lenses operated with a depth focus larger than the image plane thickness to provide focused particles with high signal intensity.…”

A Survey of Flow Field and Combustion Characteristics under Subatmospheric Pressure

“…The study involved measurements of the bubble point temperature of kerosene under various ambient pressures, establishing an empirical relationship between ambient pressure and the bubble point temperature. In recent years, numerous researchers have investigated the fuel atomization characteristics of nozzles under low-pressure conditions using optical measurement techniques such as PIV [17], PDPA [18], high-speed cameras [19], and digital holographic microscopy [20]. These studies extensively examined parameters, including penetration depth, breakup process, particle velocity, and size, as well as the spatial distribution of fuel.…”

The effect of intake port shape on in-cylinder flow field and turbulence distribution in a high-tumble production engine with endoscope accesses

“…Previous studies utilised particle image velocimetry (PIV) performed in an optically accessible research engine to show the tumbling air charging motion and its evolution during the intake and compression strokes as well as computational fluid dynamics (CFD) presented extended and detailed physical parametres. 15,[28][29][30][31][32][33][34] High-speed PIV was also performed in a running production engine using rigid endoscopes (borescopes) for both the laser and camera access. [35][36][37] These studies achieved major new findings about the high-tumble engine flow.…”