Collaborative mechanism of the plume expansion and fluctuations in the near-field under non-flash and flash conditions

Abstract

The objective of this study is to unravel the driving mechanisms behind the plume expansion and fluctuations in the near-field. A collaborative experimental and numerical study was performed under various operating conditions. Spray width in the near-field was quantified using diffused back illumination imaging, and microscopic characteristics were captured by phase Doppler anemometry; the modified models were then used to obtain internal flow patterns. The dominant factors that account for the lateral expanding of the plume are examined, and the thermal factors contribute to the plume expansion under high superheat degree conditions. A new parameter is proposed to describe the lateral spreading variations on various operating conditions for different types of fuel. Aerodynamic and internal flow begins to dominate the spray characteristics when superheat degree is not strong enough. The vortex transport is investigated, functioning as a bridge connecting with the cavitation evolution, gas ingestion, and turbulence characteristics. The connection between distinct spray characteristics and operating parameters, fuel properties, and various internal flow patterns is established, supplementing our knowledge about the optimization of injector geometry and injection strategy.