Improved low concentration water content detection in biodiesel utilizing phase shift-based capacitive method

Azmi Mohamed

Abstract

Biodiesel has become an alternative fuel to substitute conventional fuel, yet challenges remain, particularly concerning water content. The presence of water in biodiesel can negatively impact engine spray and combustion properties and may lead to damage storage tanks. To address this issue, a phase-shift-based capacitive sensor was developed in this study to accurately measure water concentration in biodiesel. The sensor, designed with a semicylindrical electrode on a glass tube, is integrated with a signal conditioning circuit and the Digilent Analog Discovery module, allowing for real-time data analysis and enhanced sensitivity in detecting low concentrations of water concentration in biodiesel. The experimental results demonstrated a direct correlation between capacitance values and phase shift, with higher capacitance leading to more significant phase shifts. A Bode plot and simulation analysis, utilizing the transfer function, validated these experimental conditions, confirming the relationship between capacitance and signal phase shift. Additionally, experiments assessing biodiesel water content revealed a proportional increase in phase-shift angle with rising water concentration, measuring water concentration in biodiesel at levels as low as 800 ppm. These findings underscore that the phase-shift magnitude in the sensor's output reliably detects low-concentration water content in biodiesel. The performance of this sensor is particularly advantageous due to its high sensitivity, enabling the detection of low water concentrations that are crucial for maintaining biodiesel quality. Moreover, the real-time data analysis capability provided by the Digilent Analog Discovery highlights the sensor's practicality and efficiency for on-the-spot monitoring, offering a significant improvement over conventional methods.

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