"Gas bearings" Laboratory

Coordinator: Terenziano Raparelli

Goals

The laboratory, started with LAQ IBIS project, deals with gas bearings problems. The competences are relative both to radial and thrust gas bearings for high speed spindles, and to pneumostatic pads for precision linear guides.

Some projects:

Journal bearings
Study of the air feeding systems
Pneumostatic bushing with active control
- Pneumostatic bushing
Spindles with gas supports
Supports and pneumostatic linear guides
- Test bench for pneumostatic pads
- Variable profile sealless pistons
Metrology facility
- Dimensional control of mechanical components
- Air flow measurement and flow meters calibration
Supporti pneumostatici con controllo attivo

	Cilindrical journal bearings Guido Belforte Terenziano Raparelli Vladimir Viktorov Andrea Trivella Federico Colombo Using a software at the purpose developed gas journal bearings are simulated and the pressure distribution in the clearance is calculated. Are considered both pressurized bearings and dynamic bearings. The numerical program helps the design of journal bearings because it allows to calculate the load carrying capacity, the air flow consumption and the radial stiffness. Some prototypes of journal bearings are also tested experimentally.
	Journal bearings with modified geometry Guido Belforte,Terenziano Raparelli, Vladimir Viktorov,Federico Colombo In order to reach very high rotational speeds modified geometry journal bearings have been studied. The clearance changes along the circumferential direction. With the numerical models developed it is possible to calculate the dynamic coefficients of the bearings and verify the stability. Guido Belforte, Federico Colombo, Terenziano Raparelli, Andrea Trivella, Vladimir Viktorov, Rodrigo Villavicencio (2013), High speed rotors with elliptic gas journal bearings. 5th world TRIBOLOGY congress, Palaolimpico - Torino, 8-13 settembre 2013.
	Dynamic simulation of rotor-air bearing system Guido Belforte Terenziano Raparelli Vladimir Viktorov Federico Colombo The time evolution of the rotor-bearings system is calculated with a numerical model. The rotor orbital motion is calculated to verify the stability of the system, given the bearings geometry and the inertial rotor characteristics and unbalance. The 4 dof model of the rotor, considered rigid, is coupled with the fluidodynamic equations of the bearings (Reynolds equations). Colombo F; Raparelli T; Viktorov V. (2009) Externally pressurized gas bearings: A comparison between two supply holes configurations. TRIBOLOGY INTERNATIONAL vol. 42, pp. 303-310.
	Study of the gas bearings for a fuel cell mobile system Guido Belforte Terenziano Raparelli Vladimir Viktorov Federico Colombo The gas bearings for a turbocompressor for fuel cell system were designed. Both dynamic and externally pressurized bearings were studied and their stability verified in different operating conditions.
	Thrust gas bearings Guido Belforte Terenziano Raparelli Vladimir Viktorov Andrea Trivella Federico Colombo, Rodrigo Villavicencio Thrust gas bearings are tested experimentally and simulated with numerical programs at the purpose developed. The influence of circular grooves machined on the surface of the thrust on stiffness, air flow and load capacity is studied. Air hammer is studied. Rodrigo Villavicencio, Federico Colombo, Terenziano Raparelli, Vladimir Viktorov (2013), Development of dynamic gas thrust bearings: design and first experimental results. AIMETA 2013, Torino, 17-20 Settembre. Belforte G., Colombo F., Raparelli T., Trivella A., Viktorov V. (2011) Comparison between grooved and plane aerostatic thrust bearings: static performance. MECCANICA, vol. 46 n. 3, pp. 547-555.
	Pneumostatic pads Guido Belforte Federico Colombo Terenziano Raparelli Andrea Trivella Vladimir Viktorov Circular and rectangular pads are studied. Air flow, stiffness and load capacity are experimentally measured and numerically calculated. The influence on these parameters of the supply pressure and of the geometry is studied. Guido Belforte, Federico Colombo, Terenziano Raparelli, Andrea Trivella, Vladimir Viktorov (2013) Experimental Analysis of Air Pads with Micro-Holes. TRIBOLOGY TRANSACTIONS, vol. 56 n. 2, pp. 169-177.
	Resistances with calibrated holes and feed pockets Guido Belforte Terenziano Raparelli Vladimir Viktorov Andrea Trivella By measuring the pressure distribution under the supply orifices of externally pressurized bearings, the discharge coefficients are experimentally identified for different geometries of simple orifices and orifices with feed pocket. A formula is obtained as a function of the orifice geometry and the Reynolds number, calculated in correspondence of the orifice cross section. Federico Colombo, Terenziano Raparelli, Andrea Trivella, Vladimir Viktorov (2013) Investigation on the discharge coefficient of supply micro holes for gas bearings. 5th world TRIBOLOGY congress, Palaolimpico - Torino, 8-13 Settembre 2013.
	Porous resistances with sintered powders Guido Belforte Terenziano Raparelli Vladimir Viktorov Andrea Trivella Resistances composed of sintered powders are experimentally studied in order to obtain the discharge coefficients and the permeability. Forchheimer law is applied with turbulent flow and the coefficients of the formula are calculated.
	Porous resistances with metal woven wire cloths Guido Belforte Terenziano Raparelli Vladimir Viktorov Andrea Trivella Federico Colombo Theoretical and experimental studies are carried out on fluid restrictors consisting on woven wire cloths, which can be used in air bearings to avoid that feed orifices are clogged. Porous resistances are studied by identifying both the coefficients of ISO 6358 formula, both the coefficients of Forchheimer equation.
	Pneumostatic bushing Guido Belforte Terenziano Raparelli Vladimir Viktorov Andrea Trivella Actively controlled pneumostatic supports in precision slideways were studied to increase stiffness. The bearing control system and sensors are electronic and/or fully pneumatic, with components designed specifically at the purpose.
	Pneumatic spindle Guido Belforte Terenziano Raparelli Vladimir Viktorov Andrea Trivella Federico Colombo A prototype of pneumatic spindle is designed and experimentally tested. The radial stiffness on the tool is measured (30 μN/micron). The spindle is driven by a pneumatic turbine. The current spindle (diameter 50 mm, axial length 460 mm) is designed to rotate up to 100 krpm. A data acquisition system based on LabView is used to determine the rotor orbits in radial bushings. The runout is measured either by capacitive displacement trasducers, or by laser beams.
	Electrospindle with gas bearings Guido Belforte Terenziano Raparelli Vladimir Viktorov Andrea Trivella Federico Colombo An electrospindle for high speed machining is designed and realized. The rotating speed is 75 krpm and the shaft diameter is 50 mm. The nominal power is 2.5 kW and speed is 75000 rpm. A tool can be mounted to test the electrospindle during the machining process. Motor and discharge air temperature is controlled by a closed cooling circuit.
	Supports for textile applications Guido Belforte Terenziano Raparelli Vladimir Viktorov Federico Colombo The system, with a rotor of 37 mm diameter, is designed to reach 150 krpm. In this application high stiffness is not required but stability is important. The bushing is mounted floating on rubber O-rings, that introduce a damping action that increases stability. The test bench allows to determine the whirl instability threshold and to investigate on the ways to increase it. With the compliant supports, it was also possible to investigate the whirl stability threshold experimentally without damaging the rotor and the bushing.
	Mesoscopic spindle Guido Belforte Terenziano Raparelli Vladimir Viktorov Federico Colombo Waved bearings are used to support a shaft with diameter 10 mm. The design speed is 300 krpm. This prototype was designed with an extensive use of a simulating numerical software, used as a virtual test bench, in order to find the best journal geometry.
	Test bench for pneumostatic pads Guido Belforte Terenziano Raparelli Vladimir Viktorov Andrea Trivella Federico Colombo Two test benches allow the determination of the static characteristics of gas bearings (load capacity, stiffness and air consumption vs air gap) as well as the pressure distribution under the pads. It is possible to measure the discharge coefficients at inlet ports
	Variable profile sealless pistons Guido Belforte Terenziano Raparelli Luigi Mazza Andrea Trivella Variable profile sealless cylinders are studied both experimentally and theoretically. The unidimensional Reynolds equation is used to obtain closed form formulations fot radial load capacity and flow leakage.
	Dimensional control of mechanical components Guido Belforte Terenziano Raparelli Vladimir Viktorov Andrea Trivella Federico Colombo Precision measurement facilities are set up to determine tolerances and form errors for the components of the benches and the air pads. Comparators, gage blocks, profile projectors, a linear height, a 200X microscope and a 800X fiberoptic microscope are available. Capacitive and inductive displacement transducers and laser beams are used to measure micrometric displacements.
	Air flow measurement and flow meters calibration Guido Belforte Terenziano Raparelli Vladimir Viktorov Andrea Trivella In order to measure with accuracy the low flow rate consumption of gas bearings, the laboratory is provided with several flow meters and with two volumetric accurate instruments to calibrate the flow meters.
	Dynamic test bench Federico Colombo, Terenziano Raparelli, Andrea Trivella, Vladimir Viktorov The test bench allows to study the step force response of a gas bearing. By means of a shaker it is also possible to apply a sinusoidal force and study the frequency response of the bearing.
	Active pads with pressure control Federico Colombo, Daniela Maffiodo, Terenziano Raparelli In this solution the supply pressure to the pad is controlled by means of digital valves controlled via PWM technique. A back pressure sensor is used to measure the pressure under the pad and give to the regulator the feedback of the air gap. Arduino board is used as controller. The goal is to keep the air gap constant under the pad. Active Gas Thrust Bearing With Embedded Digital Valves and Backpressure Sensors / Colombo, Federico; Maffiodo, Daniela; Raparelli, Terenziano. - In: TRIBOLOGY TRANSACTIONS. - ISSN 1040-2004. - 60:5 (2016), pp. 807-813
	Active pads with PZT actuators Federico Colombo, Luigi Lentini, Terenziano Raparelli, Andrea Trivella, Vladimir Viktorov The goal of this solution is to keep the height of the pad constant during the application of variable loads. The PZT is used to modify the height of the pad in order to compensate the air gap variation. It is possible to obtain a passband of 100 Hz. Federico Colombo, Luigi Lentini, Terenziano Raparelli, Vladimir Viktorov, An active compensated aerostatic thrust bearing with flexure hinges and a piezo actuator, Ecotrib 2015, 3-5 june, Lugano, Switzerland
	Semi-active pads Federico Colombo, Danial Ghodsiyeh, Terenziano Raparelli, Andrea Trivella, Vladimir Viktorov By means of flexible elements the supply resistance is modified. The result is an increased pad stiffness. The method is defined semi-active as there are no actuators, but there is an internal feedback of pressure that enables the regulation Federico Colombo, Danial Ghodsiyeh, Terenziano Raparelli, Andrea Trivella, Vladimir Viktorov, A pneumatic active control for air pads, Ecotrib 2015, 3-5 june, Lugano, Switzerland. Diaphragm valve-controlled air thrust bearing / Ghodsiyeh, Danial; Colombo, Federico; Raparelli, Terenziano; Trivella, Andrea; Viktorov, Vladimir. - In: TRIBOLOGY INTERNATIONAL. - ISSN 0301-679X. - STAMPA. - 109(2017), pp. 328-335.

"Gas bearings" Laboratory

Coordinator: Terenziano Raparelli

Goals

Some projects:

Journal bearings with modified geometry

Guido Belforte, Federico Colombo, Terenziano Raparelli, Andrea Trivella, Vladimir Viktorov, Rodrigo Villavicencio (2013), High speed rotors with elliptic gas journal bearings. 5th world TRIBOLOGY congress, Palaolimpico - Torino, 8-13 settembre 2013.

Colombo F; Raparelli T; Viktorov V. (2009) Externally pressurized gas bearings: A comparison between two supply holes configurations. TRIBOLOGY INTERNATIONAL vol. 42, pp. 303-310.

Rodrigo Villavicencio, Federico Colombo, Terenziano Raparelli, Vladimir Viktorov (2013), Development of dynamic gas thrust bearings: design and first experimental results. AIMETA 2013, Torino, 17-20 Settembre.

Belforte G., Colombo F., Raparelli T., Trivella A., Viktorov V. (2011) Comparison between grooved and plane aerostatic thrust bearings: static performance. MECCANICA, vol. 46 n. 3, pp. 547-555.

Guido Belforte, Federico Colombo, Terenziano Raparelli, Andrea Trivella, Vladimir Viktorov (2013) Experimental Analysis of Air Pads with Micro-Holes. TRIBOLOGY TRANSACTIONS, vol. 56 n. 2, pp. 169-177.

Federico Colombo, Terenziano Raparelli, Andrea Trivella, Vladimir Viktorov (2013) Investigation on the discharge coefficient of supply micro holes for gas bearings. 5th world TRIBOLOGY congress, Palaolimpico - Torino, 8-13 Settembre 2013.

Active Gas Thrust Bearing With Embedded Digital Valves and Backpressure Sensors / Colombo, Federico; Maffiodo, Daniela; Raparelli, Terenziano. - In: TRIBOLOGY TRANSACTIONS. - ISSN 1040-2004. - 60:5 (2016), pp. 807-813

Federico Colombo, Luigi Lentini, Terenziano Raparelli, Vladimir Viktorov, An active compensated aerostatic thrust bearing with flexure hinges and a piezo actuator, Ecotrib 2015, 3-5 june, Lugano, Switzerland

Federico Colombo, Danial Ghodsiyeh, Terenziano Raparelli, Andrea Trivella, Vladimir Viktorov, A pneumatic active control for air pads, Ecotrib 2015, 3-5 june, Lugano, Switzerland.

Diaphragm valve-controlled air thrust bearing / Ghodsiyeh, Danial; Colombo, Federico; Raparelli, Terenziano; Trivella, Andrea; Viktorov, Vladimir. - In: TRIBOLOGY INTERNATIONAL. - ISSN 0301-679X. - STAMPA. - 109(2017), pp. 328-335.