Real-gas Effects on Fluid Injection: a Numerical and Experimental study. – REFINE

Numerical and experimental diagnostics will be performed in order to deliver the most suitable information (density, velocity, spreading angle for example). To achieve it and have comparable diagnostics, X-ray measures should provide non-polluted information that will be associated to shadowgraphy, CBOS (Colored Background Oriented Schlieren) and numerical LES.
- Shadowgraphy is a line-of-sight method that is often used to obtain qualitative and quantitative information in injection applications. Using a short exposure time light source, detailed information on the interaction between the jet and the surrounding gas can be obtained.
- The use of X-ray based techniques could offer an alternative solution to conventional optical techniques such as LIF, PIV, LDA, etc. that may be perturbed by an index gradient. The X-ray measurements to be performed for the jet characterization in the REFINE project consist in radiography, i.e. absorption measurement, using a table top soft X-ray source associated with a dedicated X-ray detector to collect digital radiographs.
- Evidence of the CBOS technique has already been done in the case of supersonic flows. The relevance of this technique in the scope of super-critical conditions will be tested. The CBOS method, an extension of the Schlieren method, allows refractive objects to be visualized by their distortion of a colored patterned background.
- Numerical simulations (LES) will be performed as diagnostics with the numerical solver SiTCom-B. It is a structured LES and DNS compressible multi-species Navier- Stokes code with perfect or real gas thermodynamics and immersed boundary methods (IBM).

Ongoing results.

Short time: REFINE test bench running and validation of first results.

An invited conference has been done by G. Ribert during the Vth Int. Combustion Institute Summer School (ICISS) in Brazil (2015). The topic was dedicated to the real-gas injection phenomenon.

The REFINE project focuses on the experimental investigation and numerical simulation of real-fluid injection and mixing processes under sub-, trans- and super-critical conditions. The domain of interest of the present proposal concerns the propulsion with application to the automotive and aerospace science and technology where supercritical fluids may be considered as propellants. Indeed, the need for higher efficiency and lower emission levels leads to increase pressure and temperature levels, i.e. to reach supercritical properties of fluids. The objective of REFINE is to build a simple well-controlled test-bench able to study a fluid injection under sub-, trans- and super-critical conditions and to associate experimental and numerical diagnostics to deliver the finest information. An ethane injection occurs in a 5-liter high-pressure experimental test-bench. The X-ray diagnostics setting-up will be the project keystone, as it allows for delivering a non-polluted density measurement. Indeed, such diagnostics are not disrupted by the index gradient observed in corrugated flows, contrary to laser techniques. Colored background oriented Schlieren visualization is used for backup as well as a more classical shadowgraphy technique. Numerical simulations will be realized in parallel to consolidate physics understanding and for model validation.