Ensuring gas works

The sensor is being developed as part of the Fast Response Temperature Sensors for Gas Turbine Efficiency (FRETSGATE) project, led by Oxsensis, an Oxfordshire-based spin-out from the Rutherford Appleton Laboratory (RAL).

Working with Rolls-Royce and Siemens Industrial Turbomachinery, Oxsensis plans to build a prototype temperature sensor within the next two years for use inside gas-turbine combustion chambers.

According to the company, existing thermocouple temperature sensors are adequate for lab research but lack durability for use in an operational environment. They are also susceptible to electromagnetic interference (EMI) within turbo machinery.

The FRETSGATE sensor is based on optical technology and is immune to EMI. The device has been targeted at monitoring the thermal changes in the hydrogen in order to allow it to burn at a maximum temperature while preventing flash-back, a phenomenon that can occur when the flame speed exceeds the gas velocity within the system.

’One of the problems of hydrogen combustion is that flame velocity is much faster than natural gas,’ explained Stephen Fasham, the group’s technology director. ’You can end up with instabilities that cause significant damage to the burner equipment and huge inefficiencies if the flame is in the wrong location.’

The sensor, which is still at the concept stage, will work by measuring the light-interference pattern between two single-crystal sapphire surfaces. The distance between the two surfaces expands with an increase in temperature, allowing the sensor to accurately record thermal changes within the combustion chamber.

The group claims the technology has the potential to improve the efficiency of a typical large industry gas turbine by two per cent, representing a saving of more than one mega tonne of carbon dioxide each year, while extending the time the UK will be able to rely on fossil fuels.

Fasham said investment in systems such as this will be vital to the country’s future energy needs: ’The technology could save a significant amount of carbon in Britain. I think it will be a long time before we can really move away from traditional fuels and, while we see renewables as an important area, it is also important not to ignore technology developments in fossil fuels.’