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It is well known that volcanic ash clouds emitted from erupting volcanoes pose a considerable threat to the aviation. The volcanic ash particles can damage the turbine blades and their thermal barrier coatings as well as the bearings of the turbine. For a detailed investigation of this damaging effect a testbed was designed and constructed, which allowed to study the damaging effects of real volcanic ash to an especially for these investigations modified microgas turbine.
The use of this microgas turbine had the advantage that it delivers near reality conditions, using kerosene and operating at similar temperatures as big turbines, but at a very cost effective level. The testbed consisted out of a disperser for the real volcanic ash and all the equipment needed to control the micro gas turbine. Moreover, in front and behind the microgas turbine the concentration and the distribution of the volcanic ash were measured online by optical particle counters (OPCs). The particle concentration and size distribution of the volcanic ash particles in the intake in front of the microgas turbine was measured by an optical particle counter (OPC) combined with an isokinetic intake. Behind the microgas turbine in the exhaust gas additionally to the measurement with a second OPC ash particles were caught with an impactor, in order to enable the later analysis with an electron microscope concerning the morphology to verify possible melting processes of the ash particles. This testbed is of high importance as it allows detailed investigations of the impact of volcanic ash to jet turbines and appropriate countermeasures.
Detailed mobile measurement of gases and fine particulate matter has been reported in the literature to be suitable to exhibit the air pollutants concentration in populated areas. This concentration is linked to the increase of number of cars, construction areas, industries and other emission sources. However, fixed measurement stations, mostly operated by environmental agencies, are limited in numbers and cannot cover a large area in monitoring. For this reason, to overcome this drawback, mobile measurements of the variability of gases (such as O3, NO, NO2) and particulate matter concentration were carried out during this study using an instrumented car. This car was able to deliver measurement results of all these compounds in a large area. The experimental results in this work demonstrate a large spatial variability of gases and fine particulate matters mainly depended on the traffic density and the location. These effects are especially obvious in the city core and the high traffic roads. In terms of fine particulate matter, this becomes evident for PM 10 and PM 2.5, where the mass and number concentration increases with arriving these zones.
For this study an octocopter UAV was used for carrying an ultrafine (UFP) particle monitor, an optical particle counter (OPC) and a micro aethalometer. The UFP-monitor, based on electrical charging of UFPs, was able to count the number of UFPs and give an estimated mean diameter of the measured particles. The OPC, based on the particle induced light scattering of a laser beam, was able to detect aerosols in a size range of about 250 nm to 32 μm in 31 bins. The micro aethalometer measured the soot by optical attenuation of a light beam which is caused by carbon particulate matter. The octocopter with a lift off weight by 10.5 kg was especially designed and constructed at the University of Applied Sciences, Duesseldorf, for the measurement of air pollutants. It was equipped with eight 900 W electric engines and a pixhawk flight control. Technically this octocopter was able to climb up to altitudes of up to 2 km AGL. However, during this study an altitude range of several 10 meters was used. During this study about 60 octocopter flights were performed. The flights clearly revealed a plume of UFPs coming from the traffic on the bridge. This result was confirmed by various upwind and downwind measurements with the octocopter in the region of the bridge.
Aircraft measurements compared with ceilometer measurements during a sahara dust period in Germany
(2015)
A significant Sahara dust event took place at the beginning of April 2014 over large areas of Germany and Europe. The German Weather Service (DWD) detected and monitored the expansion and propagation of this dust cloud with a ceilometer network of more than 50 ceilometers. Moreover, these ceilometers were also able to track the altitude of the dust cloud at the positions of the ceilometers.
Additionally, aircraft measurements over Germany and France were performed with two aircraft by the Duesseldorf University of Applied Sciences. These aircraft were equipped with optical particle counters (OPC) and were able to measure the particle size distribution within the Sahara dust cloud and as a result of this to calculate the particle mass concentration of the dust. The ceilometer measurements and the aircraft measurements complemented each other: whereas the ceilometers gave continuous information about the Sahara dust cloud at the ceilometer positions, the aircraft measurements delivered interpolating results between the ceilometer positions.
Moreover, at several ceilometer positions intercomparison flights were performed by spiraling with the aircraft up or down around the ceilometer laser beam. This gave the unique possibility for comparing the remote sensing results of the ceilometers with the in-situ measurements of the aircraft.
This study shows that a significant high amount of Saharan dust particles was transported over Germany during a several days long episode. Furthermore, the intercomparison study between the German ceilometer network and aircraft measurements results shows a good agreement. A combination of these techniques could help to detect the vertical and horizontal distribution of the dust cloud and additionally the particle mass concentration.
Emissions of air pollutants from the road traffic are still a major problem in Germany. It is well known that traffic induced fine particulate matter (PM10, PM2.5, PM1), ultrafine particles (UFPs) and gaseous air pollutants, like e.g. NOx, are adverse to human health. Therefore it is important to monitor these air pollutants in the cities. In this study an octocopter UAV is used as a carrier for measurement systems for UFPs, fine particulate matter and soot. This instrumented octocopter was used for studying the vertical and horizontal variation of the air pollution plume, which originated from the traffic on a river bridge, connecting two parts of Duesseldorf in Germany. This octocopter UAV had been especially designed and built at the Duesseldorf University of Applied Sciences for measurements of air pollutants. It was featuring eight 900 W electric propeller drives and was equipped with a pixhawk flight control. Its lift off weight was about 10.5 kg. About 60 measurement flights were performed by the instrumented octocopter throughout this study. These measurement flights could clearly determine the traffic induced air pollution plume originating from the bridge. Moreover, the dispersion of UFPs within the pollution plume could be monitored with the octocopter flights.
Airborne measurements have proved to be an important tool for the investigation of volcanic emission plumes, industrial pollution plumes, fugitive emissions and urban pollution plumes. In this paper several examples are demonstrated, how these investigations can be performed by light and microlight propeller aircraft. Throughout the last years innovative aircraft were developed in the light and microlight class showing an excellent flight performance. This enables airborne measurements, which were performed in former years normally by big jet engine driven research aircraft. Moreover, these light and microlight aircraft are equipped with piston motors, which are sturdy enough to operate even in adverse and harsh flight conditions, e.g. in volcanic plumes with high ash concentration. Additionally, turbo charged versions of these airborne piston motors are available, which allow flight altitudes of 7000m – 9000m enabling a large variety of research missions. Another advantage of light and microlight research aircraft is that they are quite cost effective and have a comparatively short certification process for the installation of new measurement equipment. This made it possible to respond fast to the eruption of the Icelandic volcano Eyjafjallajökull 2010 and Grimsvötn 2011 with research flights in volcanic ash plumes over Germany and Iceland. In this way it was possible to deliver real airborne measurements additional to the ash plume model calculations of the London Volcanic Ash Advisory Center (VAAC). In this paper examples of airborne measurements in the volcanic plumes of the recent eruptions of Icelandic volcanoes are given. Moreover examples are presented, which highlight the outstanding capabilities of these aircraft for pinpointing industrial emissions and for characterizing urban pollution plumes.