Estimation of turbulence characteristics from PIV in a high-pressure fan-stirred constant volume combustion chamber

In this paper, a systematic experimental study was conducted to clarify characteristics of turbulence field generated by two opposite fans in a cubic constant volume combustion bomb (CVCB). The effect of the fan speed (1000-2900 rpm) and ambient pressure (0.1-3.0 MPa) on root-mean-square fluctuations, probability density functions, integral length scales and energy spectra was investigated. To overcome the limitation of the 2D-PIV, three sheet velocity fields were measured to reconstruct the three-dimensional boundary of the homogeneous region. Experimental results showed that a nearly homogeneous turbulence field in a flat region around the center of the CVCB was generated while a slight departure from isotropy was unavoidable in the current configuration. The turbulence intensity was independent of the ambient pressure, but positively proportional to the fan speed. Absence of both fan speed and ambient pressure's effect was observed for the integral length scales. Analysis of the turbulent energy spectra implied that the increase of fan speed and ambient pressure resulted in a smaller critical eddy scale where the viscosity dissipation effect started emerging.