###### Abstract  
Conical diffusers are widely used in technical devices (gasifiers, turbines, combustion chambers) and technological processes (ejectors, mixers, renewable energy). The perfection of flow gas dynamics in a conical diffuser affects the intensity of heat and mass transfer processes, the quality of mixing/separation of working media and the flow characteristics of technical devices. These parameters largely determine the efficiency and productivity of the final product. This article presents an analysis of experimental data on the gas-dynamic characteristics of stationary air flows in a vertical, conical, flat diffuser under different initial boundary conditions. An experimental setup was created, measuring instruments were selected, and an automated data collection system was developed. Basic data on the gas dynamics of air flows were obtained using the thermal anemometry method. Experimental data on instantaneous values of air flow velocity in a diffuser for initial velocities from 0.4 m/s to 2.22 m/s are presented. These data were the basis for calculating and obtaining velocity fields and turbulence intensity fields of the air flow in a vertical diffuser. It is shown that the value of the initial flow velocity at the diffuser inlet has a significant effect on the gas-dynamic characteristics. In addition, a spectral analysis of the change in air flow velocity both by height and along the diffuser axis was performed. The obtained data may be useful for refining engineering calculations, verifying mathematical models, searching for technical solutions and deepening knowledge about the features of gas dynamics of air flows in vertical diffusers. c 2024  
diffuser for various boundary conditions. [PERSON] and [PERSON] proposed a new analytical method for calculating the turbulent boundary layer in diffusers to analyze and predict the flow separation point [7]. The proposed method may be useful for designing devices with conical diffusers. [PERSON] et al. created a mathematical model to estimate the distribution of the flow temperature field inside the diffuser for different geometric dimensions and initial conditions [8]. The main objective of this study was to obtain the most uniform temperature field in the diffuser for use in a drying chamber. [PERSON] et al. developed an original diffuser design for the Francis turbine to smooth out (soften) flow pressure fluctuations [9; 10]. The selection of the optimal shape for the conical diffuser resulted in a decrease in the amplitude of the flow pressure fluctuations by 18.6% compared to the basic design of the gas-dynamic system. Accordingly, the determination and prediction of the parameters of liquid and gas flows is a key factor in the process of creating highly efficient machines and devices with conical diffusers. Scientists and specialists often use methods of swirling or turbulizing the flow in a conical diffuser to intensify heat and mass transfer and to improve the processes of mixing/separating working media in gas-dynamic systems with a diffuser [11; 12; 13; 14]. [PERSON] et al. studied the influence of diffuser geometry on the gas dynamics of swirling air flow (the flow was swirled by an axial swirler) using an optical method (PIV method) [11]. The authors obtained detailed data on the gas-dynamic characteristics of the flow with an emphasis on the evolution of the precessing vortex core. [PERSON] et al. performed a similar study inside a draft diffuser tube in relation to a turbine [12]. The obtained results improve engineering methods for calculating diffusers and create more efficient power devices. Modern approaches based on machine learning algorithms are actively used to analyze and predict flow characteristics in conical diffusers [13; 14]. The authors created tools for predicting the profiles of the average velocity, kinetic energy of turbulence and frequency response of swirling flows in diffusers for different boundary conditions based on experimental data, mathematical modeling and machine learning.