#SPEEDINESS INTENSIFIES WINDOWS#
Cross-correlation interrogation windows of 32x32 pixels with 50% overlap were used, corresponding to a measurement spatial resolution of 3.25 mm and a vector every 1.6 mm. In order to reduce the background noise generated by window pollution from MgO particles deposits, particularly significant in the recirculation zone located downstream of the step, images were systematically pre-processed using a subtract-sliding-background type numerical filter.
#SPEEDINESS INTENSIFIES SOFTWARE#
Image acquisition and data reduction were performed using the Davis 7.1 software from LaVision ®. The field-of-view covered the whole height of the chamber (100 mm) and a 130 mm length (65 mm on either side of the step). The camera was equipped with a 50 mm, f/8 lens and a narrow-band interference filter centered at 532 nm wavelength (3 nm FWHM bandwidth) in order to filter out the flame radiation. 3a, using a CCD camera (LaVision ® Flowmaster 3S), with a frame size of 1280x1024 pixels. Particles images were collected perpendicularly to the laser sheets, through one of the chamber lateral UV-glass windows, as shown in Fig. These particles were slightly diluted with nanometric Aerosil® (fumed silicon dioxide) particles in order to fluidize the seeding particles mixture and reduce the risk for particles agglomeration. The size distribution of the particles is centered on 1 µm.
![speediness intensifies speediness intensifies](https://nothingoffnote.files.wordpress.com/2017/08/nyos.jpg)
Magnesium oxide particles, capable of withstanding the high-temperature reacting environment, were chosen. The flow was seeded upstream of the methane injector with solid tracer particles using a pressurized cyclone generator. The time interval between the two consecutive laser pulses was set to 3 µs for the experiments reported in this paper. Fig 3b shows a photo of the combustion chamber with the flame anchored at the step, illuminated with vertical PIV laser sheet (regions upstream from and downstream of the step are seen).
![speediness intensifies speediness intensifies](https://www.letseatcake.com/wp-content/uploads/2018/06/Strawberry-Trifle-4-200x300.jpg)
The laser sheets were placed vertically along the flow axis by using a 100 mm diameter mirror located above the upper window, as shown in Fig. Two superimposed diverging laser sheets at 532 nm wavelength were formed from a double oscillator, frequency-doubled pulsed Nd:YAG laser system (Quantel Twins CFR, 120 mJ/pulse). 3a shows a photo of the PIV setup and high-speed intensified video camera around the stepped combustor. Photos: a) PIV and high-speed intensified video camera setup around combustor, 1: PIV camera 2: high-speed camera 3: 100 mm diameter mirror for laser sheet 4: combustion chamber b) combustion chamber with flame anchored at the step, illuminated with vertical PIV laser sheet Fig.