The spray characteristics of fuels when sprayed under superheated and elevated fuel pressure are markedly different than traditional fuel injection sprays. Studying fuel sprays under these conditions will help us understand the complex behaviors that may provide us with information to optimize future applications of certain technologies like supercritical spray combustion. In this work optical diagnostics are used to study the behavior of Jet A-1 under subcritical, transcritical, and supercritical sprays into open air test chambers. The experimental setup includes a high-pressure air driven pump to create the required high fuel pressure and a special heated injector to increase the temperature of the fuel inside the injector before injection to the required temperatures. Optical techniques like Schlieren and backlit shadowgraph are used to capture and study the sprays from a single hole high pressure diesel injector. A combination of 4 different temperatures and 4 different pressures are tested and the resultant images are processed to obtain quantitative measurements such as spray penetrations, spray cone angle, and spray optical density for each case. Moreover, the spray plume structure transition with changing parameters from subcritical, transcritical, and supercritical states for the fuel are also studied. The results show that with the fuel being in a transcritical state before injection there is a measurable variation in the spray cone formation and penetration for any fixed pressure. At this state the spray cone shows a bimodal spray angle distribution with increasing penetration. An increase in vapor turbulence is also observed indicating the occurrence of flash boiling of the fuel. With the fuels pushed to a supercritical state, the spray shows a thinner spray jet near the injector with a reduced overall penetration and reduced optical density near nozzle. The transition between the three different states as shown in this study gives us an interesting relationship between the spray penetration, spray cone angle and the spray optical density. This can be used as an indicator in understanding spray atomization of the fuels under supercritical spray conditions.
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Investigation of the evaporation and fuel property effect on liquid jets in supersonic crossflow
Due to the longer auto-ignition time with liquid fuels compared with hydrogen, the understanding of interaction of shock waves with sprays and the subsequent vapor mixing is significant to design ramjets/scramjets with liquid fuel sprays. In this study, an Eulerian-Lagrangian framework is developed based on the OpenFOAM platform. In this solver, detailed multi-component transport models for Eulerian gas-phase species properties are included. In addition, Lagrangian spray break-up, atomization and evaporation models are added to simulate liquid phase. In addition, an equilibrium wall function is added to model the near-wall properties. The newly developed solver is used to conduct large eddy simulations (LES) on non-reactive liquid jets in supersonic crossflow (JISCF) with liquid sprays. The liquid penetration length are compared with the experimental data, showing a very good agreement. Effects of evaporation and fuel properties (e.g., heat capacity and enthalpy of evaporation) on penetration length, temperature, Sauter mean diameter (SMD) and volumetric parcel flux are discussed in this study. It is shown that evaporation effects primarily show up in the temperature field. For n-heptane sprays, such impact could be conducted to other properties
of the flow field like spray plume size, particle size distribution and volumetric flux, which is
caused by the smaller enthalpy of evaporation and heat capacity comparing to water. Full version of this paper has been published as a journal article: Shufan Zou, Dezhi Zhou, Suo Yang, “Effects of Evaporation and Fuel Properties on Liquid Jets in Supersonic Crossflow: a Computational study using a compressible Eulerian-Lagrangian solver”, Atomization and Sprays 30 (9) (2020) 675-696. https://doi.org/10.1615/AtomizSpr.2020034860
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- Award ID(s):
- 2023932
- NSF-PAR ID:
- 10282028
- Date Published:
- Journal Name:
- 12th U.S. National Combustion Meeting
- Page Range / eLocation ID:
- usncm12-2H10
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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