Emissions
Accurate emissions measurement is key to creating cleaner, smarter combustion technologies - driving progress toward a healthier planet and sustainable aviation.
Emissions measurements are a vital part in the development cycle of combustion technologies to reduce their impact on the environment and human health. As part of this it is necessary to measure both the gaseous species produced and, for fuels containing carbon, the particulate matter (e.g. non-volatile Particulate matter -nvPM). Trade-offs can then be determined between improved emissions performance, and other important areas such as operability and thermoacoustic stability.
Samples for real-time analysis can be extracted from the main gas path or exhaust. The sample is then processed to ensure the integrity to all instruments following practices that meet or surpass current measurement standards and recommended practices within the international community. Data are synchronised and logged across instruments, together with the operating conditions of the source, for instant analysis to ensure the measurement of high-quality repeatable data.
At NCCAT we have measurement devices capable of measuring species including carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), water (H2O), oxygen (O2), nitric oxide (NO), nitrogen dioxide (NO2), sulphur dioxide (SO2), and unburned hydrocarbons. All species are measured wet eliminating errors from sample drying and utilise techniques such as tuneable diode laser absorption spectroscopy for rapid and repeatable high-quality measurements in real-time. The measurements can then be used to provide insight into the temperature of the sampled mixture, the efficiency of the combustion process, and the concentration of pollutants produced per unit of fuel.
Non-volatile particulate matter, or more broadly soot, can be quantified through two key concentrations that are, for example, legislated upon in the aviation industry: nvPM mass and nvPM number. The mass concentration is the total mass of the nvPM in a volume of sample. We can measure it using techniques such as laser induced incandescence (LII), which also measures the soot volume fraction, from the intensity and temporal decay of the emitted blackbody radiation after particles are heated by a pulsed laser. Number concentration can be measured using, for example, differential mobility spectrometry (DMS). This technique determines the size spectral density, i.e. the size resolved measurement of particle number concentration, based upon the electrical mobility diameters of the particles.
Another possible technique that can be used for characterising particulate matter is cavity attenuated phase shift (CAPS) spectroscopy which can determine the ability of the particulates to absorb and scatter light. It is thus related to the mass concentration of an exhaust sample.
Smoke filter paper analysis is a very well-established technique, wherein a volume of exhaust gas is drawn through a filter paper and then reduction in reflectance is measured and used to quantify a smoke concentration. It also remains an effective tool for the calibration of nvPM mass concentration instruments by providing a method of extracting a soot sample through quartz filters.