University of Twente Student Theses


Burner optimisation for a boiler with controlled combustion

Oosterhuis, Joris (2010) Burner optimisation for a boiler with controlled combustion.

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Abstract:A Combustion Management System (CMS) is developed for domestic boilers to be able to increase the modulation range of the appliance and to make the boiler applicable for dierent gas types without the need to do manual adjustments before installing. The major dierence in comparison to a conventional boiler is the replacement of the pneumatic gas valve by an electrical one. This electric gas valve is controlled to maintain stable combustion in the boiler operating at the desired air/fuel-ratio. The concentration of ions inside the ame is a measure for this air/fuel-ratio. Therefore an ionisation sensor is placed inside the ame which measures the electrical conductivity of the ame which can again be related to the ion concentration. For stable system operation, a reliable signal is needed from the ionisation sensor over the whole modulation range. To achieve this, the current burner needs to be adjusted. The burner optimisation for a 30 kW appliance is the main topic of this research. By comparing the performance of previously developed burner designs on ionisation current at dierent power levels and dierent air/fuel-ratios, insight has been gained into relations between burner design and ionisation signal. Several design guidelines have been formulated for the ionisation current, the ow resistance of the burner and the sensor sensitivity; all based on the total open area of the burner. Moreover, the in uence of the burner perforation and local design modications on CO-emissions and sensor sensitivity have been investigated as well as the in uence of the location of the sensor. A burner has been developed which meets the specications on ionisation current and sensor sensitivity and which will most likely meet the environmental requirements.
Item Type:Internship Report (Master)
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
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