Institute of Environment & Energy, Technology & Analytics e.V. (IUTA) Hall 7 / P13

In 2024, IEC 63086-2-1 was published as the first international testing standard for measuring the performance of air cleaners with particulate pollutants. For measuring particles in the size range from 0.1 – 1 µm, the standard requires the use of Optical Particle Size Spectrometers (OPSS), whereas the total number concentration including also ultrafine particles <0.1 µm is measured with Condensation Particles Counters (CPC). However, the standard deliberately refrains from prescribing specific models. Moreover, it allows either cigarette smoke or potassium chloride (KCl) as two interchangeable test aerosols and leaves for the latter the flexibility to neutralize the particles or not. So far, there has been no systematic study on the effect of these flexibilities in the choice of the measurement instrument, test aerosol and neutralization on the measurement results.

To address these questions, they were tackled in a detailed investigation using three different air cleaners. The filter types of the air cleaners were an H13 filter in accordance with EN 1822-1 (negligible particle size dependence), a commonly used electret filter (moderate particle size dependence), and a completely discharged electret filter (pronounced particle size dependence). The air cleaners were tested using the methods of IEC 63086-2-1 with ten different measurement instruments in parallel. Besides a CPC and five different OPSS models, also a Mobility Particle Size Spectrometer (MPSS), a Fast Mobility Particle Sizer (FMPS), and two appliances based on the principle of unipolar diffusion charging were used. The tests were performed with cigarette smoke as well as either neutralized or not neutralized KCl particles. From fitting the exponential decay curves with and without air cleaner, the size-dependent Clean Air Delivery Rate (CADR) was derived and compared between the different instruments, test aerosols, and neutralization stages.

For the integrated size range from 0.3 µm to 1 µm, all OPSS showed

In 2024, IEC 63086-2-1 was published as the first international testing standard for measuring the performance of air cleaners with particulate pollutants. For measuring particles in the size range from 0.1 – 1 µm, the standard requires the use of Optical Particle Size Spectrometers (OPSS), whereas the total number concentration including also ultrafine particles <0.1 µm is measured with Condensation Particles Counters (CPC). However, the standard deliberately refrains from prescribing specific models. Moreover, it allows either cigarette smoke or potassium chloride (KCl) as two interchangeable test aerosols and leaves for the latter the flexibility to neutralize the particles or not. So far, there has been no systematic study on the effect of these flexibilities in the choice of the measurement instrument, test aerosol and neutralization on the measurement results.

To address these questions, they were tackled in a detailed investigation using three different air cleaners. The filter types of the air cleaners were an H13 filter in accordance with EN 1822-1 (negligible particle size dependence), a commonly used electret filter (moderate particle size dependence), and a completely discharged electret filter (pronounced particle size dependence). The air cleaners were tested using the methods of IEC 63086-2-1 with ten different measurement instruments in parallel. Besides a CPC and five different OPSS models, also a Mobility Particle Size Spectrometer (MPSS), a Fast Mobility Particle Sizer (FMPS), and two appliances based on the principle of unipolar diffusion charging were used. The tests were performed with cigarette smoke as well as either neutralized or not neutralized KCl particles. From fitting the exponential decay curves with and without air cleaner, the size-dependent Clean Air Delivery Rate (CADR) was derived and compared between the different instruments, test aerosols, and neutralization stages.

For the integrated size range from 0.3 µm to 1 µm, all OPSS showed ...

Electret filters use electrostatically charged nonwoven layers to enhance particle separation efficiency. However, this positive electret effect decreases as the particle loading increases. The aim of ioniser-assisted filtration is to significantly enhance the separation efficiency of a conventional filter with low pressure loss, or to achieve the same degree of separation with reduced electrical power consumption.

The approach is based on the ionisation of the air and the subsequent electrical charging of the particles in the electric field of an ioniser. A downstream electric field induces the polarisation of the filter and the separation of the particles. This effect is switchable and persists as long as the ioniser and the electric polarisation field are in operation.

For the optimal design of the ionisation and polarisation unit, a comprehensive CFD model was developed as an extension of the open-source software OpenFOAM. The model takes into account the physical processes in detail, including ionisation, particle charging, and separation in the gas phase, as well as, bipolar charge transport within the solid filter medium. These processes are coupled via the spatially resolved calculation of the electric field.

The model is validated using a combined approach of numerical simulations and experimental investigations. For the experiments, a laboratory test rig has been setup, which allows the investigation of particle charging by ionisation and particle separation due to electrostatic effects on dielectric components. For this purpose, both fibre filter media and plastic grid structures are used.

The use of plastic grid structure keeps the numerical effort manageable and makes it possible to calculate the physical relationships at the microscale and verify them experimentally without having to perform the simulation on a real filter structure...