Thesis defence by Mustafa Ishak BENZAZA

Particulate air pollution is a major health and environmental issue directly affecting many industrial sectors. The cyclone separator is a widely used pollution control solution in industrial sectors, thanks to its low maintenance costs and the absence of moving parts. However, its performance remains limited when it comes to capturing particles smaller than 5 µm, and the pressure drop remains high at high flow rates.

This research, carried out in collaboration with Stivent Industrie, aims to simultaneously improve the separation efficiency and reduce the pressure drop of an industrial cyclone separator, through the development of a CFD simulation tool using OpenFOAM and the evaluation of passive control solutions.

The numerical methodology is based on a hybrid S-A DES turbulence model, selected for its ability to capture the vortex structures of the cyclonic flow. An original contribution concerns the imposition of a fixedMean-type pressure boundary condition at the outlet, which allows the confined vortex flow to be globally constrained. Validation is carried out by comparison with LES simulations and experimental laser Doppler anemometry (LDA) data from the literature, with good agreement on velocity profiles and pressure drop.

A series of experimental tests on the industrial-scale separator provided further validation of the model. The test rig comprises a differential micro-manometer, a five-hole probe for three-dimensional aerodynamic characterisation, and an isokinetic probe coupled to an OPS 3330 optical particle counter for particle size analysis upstream and downstream of the cyclone.

Four passive control solutions were then evaluated. The Vortex Breaker reduces the pressure drop by 60 per cent, at the expense of filtration efficiency. Channel recycling increases separation efficiency by 70 per cent for PM1.0 and 89 per cent for PM2.5, at the cost of a 29 per cent increase in pressure drop. The Deswirler simultaneously compromises both criteria, although it produces a uniform flow at the outlet. The Twist maintains efficiency whilst reducing pressure drop by 6 per cent.

These results highlight a fundamental trade-off between separation efficiency and energy performance, with the proposed solutions offering strategies for adapting to specific industrial operating constraints.

Rapporteurs

• François-Xavier DEMOULIN, University Professor, University of Rouen Normandy
• Gontrand LEYSSANS, University Professor, University of Haute-Alsace

Examiners

• Bénédicte CUENOT, Accredited to Supervise Research / Senior Engineer, Safran Aircraft Engines
• Denis PETITPREZ, University Professor, University of Lille

Thesis Supervisor

• Céline MORIN, University Professor, INSA Hauts-de-France

Co-supervisors

• François BEAUBERT, Senior Lecturer, INSA Hauts-de-France
• Damien MÉRESSE, Senior Lecturer (HDR), INSA Hauts-de-France
• David UYSTEPRUYST, Senior Lecturer, INSA Hauts-de-France

Guests

• Philippe BECEL, CEO of STIVENT INDUSTRIE
• Bertrand CANAPLE, Managing Director of VALUTEC

Cyclonic separator, CFD simulation, OpenFOAM, LES/RANS model, turbulent flow, particle transport (DPM), passive control, pressure drop, separation efficiency.