Degradation mechanism of measuring performance of optical particle counter under temperature-pressure coupling effect

Abstract

To investigate the degradation mechanism of measuring the performance of an optical particle counter (OPC) under temperature-pressure coupling, this study first establishes a theoretical calculation model of gas refractive index and then elucidates the comprehensive influence mechanism of temperature and pressure on gas optical properties. Furthermore, the experimental measurement technique and measuring device for gas refractive index are built. By comparing the theoretical and experimental results in the temperature range of 48 °C–560 °C and the pressure range of 0.9–4.6 MPa, the difference between the two errors is just 0.05%, indicating the accuracy of the theoretical model of the refractive index of gas. Secondly, a dynamic model of optical measurement volume (OMV) under high-temperature and high-pressure conditions was established using geometrical optics theory, and the impacts of gas temperature and pressure variations on OPC measurement performance were investigated. The gas temperature (100 °C–1000 °C) and pressure (1–4.6 MPa) are shown to have opposing effects on the OMV, with gas pressure being more relevant. Finally, in order to eliminate the effect of gas refractive index change on the optical measurement performance of OPC, a parallel light model is proposed to solve the problem of the degradation of OPC measurement performance under temperature and pressure coupling conditions.