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NKS Programme Area:
Single Spray Nozzle Tests
This report summarizes the measurement results of single spray nozzle tests carried out in a testing station specifically built for this purpose at Lappeenranta University of Technology (LUT) in 2015. Water was injected through a spray nozzle and the developed droplet distribution was measured with the shadowgraphy application of the PIV system.
The main objective of the tests was to get experience from the use of the shadowgraphy application in order to be able to evaluate its suitability for demanding measurements of different characteristics of spray nozzles. The need for such measurements in Nuclear Engineering Laboratory at LUT emerged when studies focusing on spray operation in nuclear power plant containments were included in the research plan of the INSTAB project of the SAFIR2018 programme.
Five different measurement positions were selected underneath of the spray jet to be used in the tests. The interest was to find out if it has any effect on the droplet size distribution when the measurement area is shifted vertically and horizontally. The majority of the droplets were in the size range of 0.2-0.8 mm in the centreline positions whereas the droplet distribution was broader in the two other positions, which were 300 mm away of the centreline axis.
There are many user-defined parameters in the shadowgraphy application which are used for processing of the particle images. The selection of these parameters has a strong effect on the measurement results and therefore emphasis should be put to making the experimental arrangement as simple as possible.
The measured droplet size distributions revealed that the scaling factor of the used application was too large for these tests in order to get a full range of different droplet sizes. In future spray nozzle tests the camera of the PIV system should always be placed as close to the measurement area as possible in order to get the scaling factor to be as small as possible.