Development Of Liquid Supply Controlling System For Micro Direct Methanol Fuel Cell

Micro Direct Methanol Fuel Cell (μDMFC) has broad application prospects because ofits high efficiency and cleanness. There are close relationships between various workingconditions and the performance ofμDMFC, thus, the influence onμDMFC by theseconditions is to be determined using theoretical analysis and experiment measurement.In this thesis, a newly developed controlling system to satisfy the needs for micro fluxand accuracy temperature control, as well as long-term fatigue testing of the full cell, wasproposed. A testing platform includes soft and hardware module has been established for thepurpose of accurately controlling of micro flux and wide-range temperature for liquid feedμDMFC.In view of the temperature controlling of micro-flux liquid fuel, a heating block withlabyrinth-like single pass channel inside for heating up the methanol solution was fabricated.A semiconductor-refrigerating chip was utilized to heat and cool the liquid flow during testingprocedures, and the heating power of the controlling system was estimated. The micro-fluxliquid fuel was fed to the fuel cell by a high accuracy double-channel syringe pump combinedwith hydraulic delivery system.According to the characteristic of the system, hardware and software for input/outputchannel of industry control computer was developed. A power actuation and transition circuitaccording to the controlling requirements of the semiconductor-refrigerating chip and thetesting system were also developed. A PID based, closed-loop controller was utilized tomaintain accurate control of the liquid temperature. The communication between computerand controllers is realized through the RS232 COM. The exactly timing logic method wasused to test the long-term performance ofμDMFC. The automatic control was actualized bysoftware module written in Visual C++. A liquid supply-controlling module forμDMFC wasthen constructed completely.Online debugging and the performance validation of the integrated control system werecarried out. After the precision of temperature sensor was calibrated, an experiment oftemperature control for micro-flux liquid and long-term fatigue testing was done.Experimental results show that the precision of temperature controlling of the system is betterthan±1℃, and the flux controlling precision is 0.1ml/h. This system can simulate fatigue-testing conditions to meet specific requirements. This system is perfect in stability andit may provide an important and advanced evaluation apparatus to satisfy the needs for realtime performance testing ofμDMFC.