Moisture absorption, fogging and entrainment can affect the measurement of aerosol particle size and concentration in wet dedusting systems when using light scattering methods. A dilutor can be applied to increase measurement accuracy by reducing relative humidity and promoting droplet evaporation. The effects of droplet diameter, gas temperature, relative humidity and droplet concentration on droplet evaporation time were discussed based on the dynamic equation for droplet evaporation. The results show that when the relative humidity of outlet gas is lower than 15.7%, and the droplet temperature and gas temperature are 20℃ and 20~40℃ respectively with droplet concentration lower than 2×104 P×cm-3, the droplets with diameter of 0.2~5μm can be completely evaporated in the dilutor. Critical evaporation operating conditions at different gas temperatures, humidity and droplet concentrations were obtained when the droplet diameter is 5μm, and the gas temperature and relative humidity are 20℃ and 18%respectively with critical evaporation droplet concentration of 104 P×cm-3. The results of particle size distribution obtained with the dilutor under critical operation conditions show good agreement with that of experimental design.%采用光散射法测量湿法除尘系统的气相颗粒浓度与粒度分布时，测量结果易受颗粒吸湿、凝雾以及雾沫夹带等影响。为准确测量气溶胶浓度，需对采样气流进行稀释以降低相对湿度，促使液滴蒸发。基于液滴蒸发动力学方程，研究了液滴蒸发时间与液滴粒径、混合气温度、相对湿度和液滴浓度的关系。结果表明，在液滴温度20℃、气相温度20~40℃及液滴浓度不大于2×104 P×cm-3时，出口气相相对湿度不高于15.7%时，粒径0.2~5μm的水滴均可在稀释器内完全蒸发。研究得到了不同气相温、湿度及液滴浓度下的临界蒸发操作条件。以5μm液滴为例，气相温度为20℃，气相相对湿度为18%时，临界蒸发液滴数浓度为104 P×cm-3。实验表明加载稀释器时在临界蒸发操作条件下测得的颗粒物粒径分布与真实粒径分布吻合良好。
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