Abstract
A prototype dust sampler with a changeable inlet diameter nozzle for measuring dust concentrations was developed with the objective of implementing a new method for isokinetic sampling of particulates contained in exhaust gases. This sampling method is based on both the isokinetic samplingby changing the nozzle diameter and a constant flow rate of sampling gas even when the flow of exhaustgases varies during sample collection. Experiments to assess the applicability and reliability of the new dust sampler were carried out, and the results can be summarized as follows:
1. The dimensions for the changeable nozzle diameter type dust sampler (nozzle head section) investigated here were approximately 6 cm in external diameter and 12 cm in length, making it possible to use this as a Type 1 dust sampler.
2. By turning the operation valve, the diameter of the suction nozzle could be adjusted easily in the range of φ5.0-φ11.0mm.
3. As the nozzle head section is made of aluminum, the maximum allowable temperature for the changeable nozzle diameter type dust sampler is approximately 200°C. The surface was covered with a Tafram oxide film, and good corrosion resistance could be verified at the actual combustion temperature of the exhaust gases.
4. A small leakage was detected at the thin seams of the changeable inlet diameter nozzle when it was used in funnel form. However, there was no effect on the measurement with the suction nozzle in its normal open shape.
5. A comparative study using test powder and actual combustion dust shows the changeable nozzle diameter type dust sampler and the regular type (ordinary and balanced type dust sampler) maintained a good equivalent relationship of approximately 1: 1, confirming the applicability of the isokinetic sampling method.
