The vibrating hole aerosol generator combines high-pressure liquid injection with periodic mechanical disturbance to achieve uniform droplet fracture and precise particle size control. The core principle can be divided into three stages:
High pressure injection and liquid column formation: The liquid is delivered to the microporous sheet at a constant flow rate (Q) through a precision injection pump, forming a cylindrical liquid column. The diameter of micropores is usually 0.05-0.5mm to ensure the stability of the liquid column. For example, the microporous design of TSI3450 model can avoid liquid column displacement and lay the foundation for subsequent uniform fracture.
Periodic mechanical disturbance: Piezoelectric ceramics provide high-frequency vibration (100-1000Hz), causing the liquid column to break into uniform droplets at a specific frequency. The vibration frequency is strictly matched with the droplet generation rate to ensure that one droplet is generated per disturbance cycle. For example, when the vibration frequency is 500Hz, 500 droplets are generated per second, and the geometric standard deviation of particle size distribution is less than 1.01.
Solvent evaporation and formation of monodisperse particles: During the airflow transport process, volatile solvents (such as ethanol and water) rapidly evaporate to form solid or liquid monodisperse aerosol particles. The particle size can be precisely controlled by adjusting the liquid flow rate (Q), solute concentration (C), and vibration frequency (f). For example, when Q=0.1cm ³/s, C=0.01, and f=500Hz, the calculated particle size is about 2.3 μ m, with an actual error of less than 2%.
Typical application scenarios:
Calibration of optical particle counter: requires aerosols with highly uniform particle size (such as 0.3 μ m and 1 μ m standard particles).
Filter efficiency testing: Simulate specific particle size pollutants (such as 0.5 μ m DEHS particles) to test the performance of HEPA filters.
Human exposure research: Generate simulated inhalation scenarios of pollutants with specific particle sizes (such as 2.5 μ m).
Condensed aerosol generator: particle size control for vapor deposition and condensation
The condensing aerosol generator generates aerosols with strictly controllable particle size through gasification condensation process, and its technical process can be divided into three stages:
Nucleation generation: use a spray generator (such as Laskin nozzle) to atomize liquid (such as DEHS, DOP) into tiny droplets as the condensation core. For example, the ZR-1300A generator can generate crystal nuclei with a concentration of up to 10 ⁶/cm ³ by combining 4-10 Laskin nozzles, providing a uniform core for subsequent condensation.
Vapor deposition: Crystal nuclei enter an evaporator containing aerosol substances (such as paraffin oil), surrounded by gaseous substances. Gaseous molecules adsorb and deposit on the surface of crystal nuclei, forming preliminary particles. For example, the Topas SLG series generator from Germany achieves preliminary particle size control by adjusting the evaporator temperature (such as 150 ℃) to control the deposition rate of gaseous substances.
Condensation control: After the mixed gas enters the condensation device, the temperature drops sharply (such as from 150 ℃ to 20 ℃), and gaseous substances adhere to crystal nuclei and condense to form solid or liquid particles. By adjusting the condensation temperature and flow rate (3.5-4.5L/min), the particle size can be precisely controlled. For example, when the condensation temperature is 10 ℃, 0.5 μ m DEHS particles are generated; When the temperature rises to 30 ℃, the particle size increases to 2 μ m.
Key advantages:
Wide particle size range: can generate solid or liquid particles of 0.1-8 μ m (such as Brazilian palm wax, stearic acid).
Controllable concentration: The particle generation concentration exceeds 10 ⁶/cm ³, with a geometric standard deviation of less than 1.25.
Stable Form: Output spherical, electrically neutral particles, suitable for fluorescence or radioactive labeling experiments.
Typical application scenarios:
Wind tunnel experiment particle generation: simulating atmospheric aerosol behavior (such as studying the diffusion of haze particles).
Calibration of laser Doppler velocimeter: High concentration and uniform particles (such as 1 μ m polystyrene particles) are required.
Performance analysis of smoke detectors: detecting the response of detectors to specific particle sizes (such as 2.5 μ m).
Technical comparison and selection suggestions
Particle size control accuracy:
Vibration hole type: The particle size calculation error is less than 2%, the geometric standard deviation is less than 1.01, and it is suitable for scenarios that require strict particle size control (such as instrument calibration).
Condensation type: The particle size range is wider (0.1-8 μ m), but the geometric standard deviation is 1.10-1.25, which is suitable for experiments with slightly wider particle size distribution requirements (such as wind tunnel simulation).
Operational complexity:
Vibration hole type: requires precise adjustment of vibration frequency and liquid flow rate, with high technical requirements for operators.
Condensation type: By adjusting the condensation temperature and flow rate, the particle size can be controlled, making the operation more intuitive.
Application scenario matching:
If it is necessary to generate nano-sized particles with a particle size less than 1 μ m, the condensation method is chosen (the minimum particle size of the vibrating hole method is usually 0.8 μ m).
If high concentration (>10 ⁶/cm ³) aerosols are required, condensing performance is better; If absolute uniformity of particle size is required (geometric standard deviation<1.05), vibration hole type is more suitable.