CORDIS provides links to public deliverables and publications of HORIZON projects.
Links to deliverables and publications from FP7 projects, as well as links to some specific result types such as dataset and software, are dynamically retrieved from OpenAIRE .
Deliverables
The potential of Computational Fluid Dynamic technique has been investigated by means of a commercial CFD code coupled with an experimental one, developed for calculating particle trajectories in a given air flow field. Trajectories are calculated under both deterministic and stochastic turbulence conditions. The methodology was applied to calculating the aspiration efficiencies of a number of different inlet geometries, on different scales in more realistic conditions that have been done before. Specifically a disk-like sampler and IOM sampler have been considered at two different wind orientations (facing the wind and at 90 degrees respect to it). The scaling methodology has been proven at a factor of four for both samplers and wind orientations conditions. Finally a comparison between deterministic and turbulence particle dispersion sampling efficiencies is shown. The agreement with the experimental data is quite good and in the near future more realistic simulations could be performed (for example personal samplers on manikin) taking advantage of CFD as a suitable technique in personal aerosol sampler inlet efficiency assessment.
Measurements were conducted on two types of aerosol sampling inlet commonly used in ambient air sampling to monitor levels of pollution, the TSP inlet and the Dichot inlet. Owing to the inlet geometry and losses of particles within these inlets, the results obtained relate to the sampling efficiency of the inlets at the point where the aerosol is normally collected, and not to the aspiration efficiency. Hence the data are of practical interest to those responsible for pollution monitoring with instruments using these types of inlet. The sampling efficiency was generally found to be rather low (less than 50%) for particles exceeding 15µm (micrometers) aerodynamic diameter. This means that while such inlets can be used to determine concentrations of small particles capable of reaching the lungs, they will underestimate the concentrations of large particles (for example particles depositing in the mouth of a person exposed to pollutants, or depositing on plants and buildings). Fortunately such large particles are only rarely present in ambient aerosols, occurring under special atmospheric conditions and in few locations.
The small-scale test systems were found to have limited practical application to certain experimental conditions. Losses of particles between the test inlet and the time-of-flight measuring instrument were very significant, and highly dependent on the geometry of the connecting pipe work. These losses can potentially create systematic errors in the results unless certain conditions are fulfilled. As a forward-facing isokinetic reference probe is used to measure the reference concentration in the wind tunnel, the test inlet must be unidirectional rather than omni directional, so that the connection geometry is similar for both test inlet and reference inlet. Furthermore, losses within the test inlet itself must be negligible in magnitude; this is a condition that is only met for a limited range of inlet designs. The scaling principle was demonstrated to work for the small-scale simulation of inhalation of dust into mouth of a human manikin, both facing and at 90 degrees to the external wind. For this system the practical limitations described here were met. Errors in the small-scale results were comparable to those obtained in full-scale tests of the same system, however the results were obtained very much more rapidly.
Three wind tunnel systems ranging in size from 30 cm to 1 m diameter were developed in order to carry out small-scale tests on aerosol sampling inlets. The small-scale systems can simulate full-scale testing of large air samplers in a large wind tunnel, reducing the dimensional scale by up to one fifth. The small-scale test particles are detected using rapid time-of-flight instruments, enabling simulation of full-scale test particles up to 100 µm (micrometres) aerodynamic diameter. The small-scale wind tunnels were configured to produce test aerosols with good spatial and temporal stability. The upper wind speed operating range of the small wind tunnel systems meant that simulation of full-scale conditions was limited to low external winds (up to 1 m/s). The major benefit in small scale testing is the small amount of time required for obtaining results. Carrying out a test on a single sampling inlet, at a single external wind speed, takes approximately one day in the small-scale system, compared to around 45 days in a full-scale system. Overhead time for setting up and commissioning the test system is similar in each case. Investment costs are similar for both types of facility.
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