Design and experimental verification of a photoacoustic flow sensor using computational fluid dynamics

Area of Science:

• Optics and Photonics
• Chemical Sensing
• Environmental Monitoring

Background:

• Photoacoustic (PA) sensing offers high sensitivity for gas detection.
• Real-time analysis requires robust sensor design to mitigate noise.
• Computational Fluid Dynamics (CFD) can optimize sensor performance.

Purpose of the Study:

• To demonstrate a fast, real-time photoacoustic gas sensor.
• To design a PA cell with flow noise immunity using CFD analysis.
• To evaluate the sensor's sensitivity and detection limits for specific hydrocarbons.

Main Methods:

• A stand-alone PA sensor system controlled by a field-programmable gate array.
• CFD analysis to design a flow noise-immune PA cell.
• Mid-infrared interband cascade laser excitation at 2950 cm⁻¹ for hexane and decane.
• PA measurements at varying flow rates and Allan deviation analysis.

Main Results:

• Sensitivity of 0.4±0.1 ppb for hexane at flow rates up to 1.7 L/min.
• Normalized noise equivalent absorption coefficient of 2.5×10⁻⁹ W·cm⁻¹·Hz⁻¹/².
• Detection limit of 0.25 ppbV for decane at optimum integration time.

Conclusions:

• The developed PA sensor provides fast and highly sensitive real-time gas analysis.
• CFD-optimized design effectively minimizes flow noise, enhancing performance.
• The sensor demonstrates significant potential for trace gas detection in environmental applications.