Abstarct: This study investigates methods for measuring and separating oil droplets in two-phase flows (aerosols), particularly within blow-by gases emitted from internal combustion engines. In the first part, a novel approach is introduced for measuring the size distribution of these droplets. The proposed method offers a fast, cost-effective, and practical alternative to conventional techniques for particle size analysis in engine blow-by gases. Compared to a standard optical particle counter, the method shows a deviation of approximately 1 micron in the geometric mean peak diameter. It achieves high measurement accuracy without the need for bulky equipment. Additionally, zeta potential analysis is employed to assess emulsion stability. The effects of temperature, viscosity, and injection pressure were examined. The results reveal that fluid viscosity and surface tension are the dominant factors influencing droplet size, whereas pressure has a negligible effect due to flow choking conditions. In comparison to traditional cascade and impaction-baxsed methods, this technique reduces measurement time by up to 90%. In the second part of the study, a numerical model is developed to address the lack of dedicated simulation tools for predicting liquid droplet separation in aerosol flows. A hybrid computational frxamework was constructed using Fluand MATLAB to simulate droplet behavior within a six-stage horizontal cascade impactor. The model captures droplet deposition on the target plate of each stage and accounts for reflection to downstream plates. The particle separation criterion was derived through an intermediate-region modeling approach baxsed on fitted absorption and dispersion curves extracted from momentum distribution diagrams in prior studies. Grid convergence was verified using the Grid Convergence Index (GCI), and numerical results were validated through experimental measurements, showing a relative mass error of 4.7%. The gethe impactor was designed baxsed on Marple's theory, and flow dynamics were simulated to optimize collection efficiency and separation performance. To enhance the model, design improvements were implemented in the nozzle and pre-nozzle sections. Pre-nozzles were added upstream of each stage, and the particle accumulation zones were reconfigured to introduce a relaxation region. This modification reduced the re-entrainment of droplets and improved measurement accuracy. Experimental validation was carried out by measuring the mass of separated oil and comparing it to numerical predictions, showing strong agreement between simulation and tests. Overall, this research provides a practical and effective tool for improving aerosol separation systems, particularly in applications related to emission control in combustion engines and aerosol science.