Gas–surface interactions of a Couette–Poiseuille flow in a rectangular channel

Pleskun, Heiko; Brümmer, Andreas

doi:10.1063/5.0099256

Cited by 4 publications

(3 citation statements)

References 59 publications

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“…The shape factors for diffuse wall scattering are derived in a previous work in reference [15]. This has been extended to depict the influence of different wall materials in reference [16].…”

Section: One-dimensional Modelmentioning

confidence: 99%

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Validation of inhomogeneous chamber states in rotary positive displacement vacuum pumps

Pleskun

Jünemann

Brümmer

2022

IOP Conf. Ser.: Mater. Sci. Eng.

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Chamber model simulation is a common approach to simulate rotary positive displacement vacuum pumps. Therefore the pump is abstracted into working chambers and connecting clearances, whereby the clearance leakages can be identified as the major loss mechanism in such machines. The clearance mass flow rates are calculated with respect to the thermodynamic states in the adjacent chambers, which are inhomogeneous for rarefied gases due to the movement of the rotors which causes a pressure gradient within the chamber. This effect increases with higher Knudsen numbers, because of the increasingly dominant friction. These inhomogeneous chamber states are assumed to be quasi-static in case that the chamber volume is constant with time. Therefore the chamber must not have a connection to the suction or discharge port. This can be modelled with a one-dimensional approach for geometrically abstracted chambers. In order to validate the one-dimensional characteristics in circumferential direction three-dimensional steady state simulations of a working chamber are performed using a Computational Fluid Dynamics (CFD) solver. To improve the accuracy for rarefied gases Maxwell velocity slip boundary conditions are applied. It is shown, that the inhomogeneous chamber states can be approximated by a regression analysis of a dimensionless number. Furthermore the housing clearance and the radial clearance mass flow rates for given boundary conditions are geometrically abstracted and calculated using a one-dimensional model. The new clearance models and the inhomogeneous chamber states are implemented in a chamber model simulation software and results of a test machine are compared to measurements and to previous simulations.

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Section: One-dimensional Modelmentioning

confidence: 99%

“…The dimensionless flow rates G P used in this model are described in a previous work [6]. For different wall materials the flow rates of the Poiseuille flow can be taken from reference [16].…”

Section: One-dimensional Modelmentioning

confidence: 99%

Validation of inhomogeneous chamber states in rotary positive displacement vacuum pumps

Pleskun

Jünemann

Brümmer

2022

IOP Conf. Ser.: Mater. Sci. Eng.

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“…This expression for the dimensionless pressure gradient is derived in Reference [9] and is a result of a superposition of Couette flow and Poiseuille flow within the chamber. The values for the reduced flow rates for the Couette flow G C and G P can be taken from References [15] and [16] for any gas rarefaction parameter δ, width to height ratio η and different TMACs for any wall.…”

Section: Strouhal Numbermentioning

confidence: 99%

Transient chamber filling in rotary positive displacement vacuum pumps

Pleskun

Syring

Brümmer

2022

IOP Conf. Ser.: Mater. Sci. Eng.

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Chamber model simulation is a common approach to simulate rotary positive displacement vacuum pumps. Therefore the pump is abstracted into working chambers and connecting clearances, whereby the clearance leakages can be identified as the major loss mechanism in such machines. The clearance mass flow rates are calculated with respect to the thermodynamic states in the adjacent chambers, which are inhomogeneous for rarefied gases due to the movement of the rotors which causes a pressure gradient within the chamber. This effect increases with higher Knudsen numbers, because of the increasingly dominant friction. It is shown that inhomogeneous chamber states cause a non-complete chamber filling. As a result the mass-averaged pressure within the suction chamber is lower than the pressure in the suction port. Due to the non-constant chamber volume over time three-dimensional transient simulations with a Computational Fluid Dynamics (CFD) solver are performed in order to investigate the mass within a geometrically abstracted suction chamber. Based on a dimensionless number, a regression analysis is done to provide a quantitative estimation of this effect by means of analytical calculations. This is implemented in a chamber model simulation software and results of a test machine are compared to measurements and to previous simulations.

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Experimental and simulative investigations of burr formation in planing of AISI 1045

Polus,

Saelzer,

Brock

et al. 2024

Int J Adv Manuf Technol

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The clearance flow in dry-running vacuum pumps is the main loss mechanism. To reduce the clearance mass flow rate in rarefied gas flows, sawtooth structures transversing to the direction of flow can be utilized. However, due to the sawtooth’s structure size, micro-machining is necessary, whereby burr formation is a central challenge. First, the effectiveness of non-idealized sawtooth structures is investigated, demonstrating a high sensibility of the performance regarding the geometry of the tip. Therefore, burr formation in the cutting process must be minimized. For this reason, a 3D finite element (FE) chip formation model capable of predicting the burr formation is developed. An analysis of the burr formation zone showed positive triaxialities; thus, the triaxiality-dependent Johnson–Cook damage model is utilized. To minimize the mesh-induced error, a convergence analysis is conducted, showing no convergence of the maximum burr height. This is caused by the pathological mesh size dependence of local continuum damage models. A comparison of the cutting experiments and simulations revealed a reasonable prediction of cutting forces. In contrast, the passive force is predicted poorly, which is attributed to the underestimation of the ploughing force for non-elastic simulations. The prediction quality regarding the maximum burr height differs for the investigated cutting speeds, which can be explained by a built-up edge and a change in the machine tool compliance. Thereby, an analysis of the burr formation revealed that the burr height is captured by a non-physical remeshing algorithm and that the burr volume might be a more appropriate characteristic.

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Gas–surface interactions of a Couette–Poiseuille flow in a rectangular channel

Cited by 4 publications

References 59 publications

Validation of inhomogeneous chamber states in rotary positive displacement vacuum pumps

Validation of inhomogeneous chamber states in rotary positive displacement vacuum pumps

Transient chamber filling in rotary positive displacement vacuum pumps

Experimental and simulative investigations of burr formation in planing of AISI 1045

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