The influence of interstage channel on efficiency of molecular drag stage in hybrid turbomolecular pump

The interstage channel is one of the factors affecting the efficiency of the molecular drag stage in a hybrid turbomolecular pump (TMP). The influence of parameters of the channel on the pumping performance of the molecular drag stage is investigated. The offered approach allows calculating the pumping performance of a molecular drag stage taking into account the effect of the interstage connecting channel on the pumping process. The comparison of the pumping characteristics of a molecular drag stage obtained in calculation taking into account the effect of the channel and excluding it is given. This article assesses the efficiency of the molecular drag stage in a hybrid TMP depending on geometric and dynamic parameters of the channel. The outcomes and recommendations allow to expand the range of working pressures of a hybrid TMP exclusively by means of parameters of the connecting channel.

Study of interstage channel of hybrid turbomolecular pump

The calculation is based on the use of Monte Carlo method (method of test particle), which consists in the statistical modeling of processes. The article describes an algorithm to construct a mathematical model step by step. The article defines both a probability for gas molecules to pass through the interstage channel of a hybrid turbomolecular pump in forward and backward direction. The effect of the movable walls limiting the channel is taken into account. Results and, accordingly, recommendations, given in the article, can be used in designing a flow passage of the hybrid turbomolecular pumps. The dependencies of a probability for gas molecules to pass through the interstage canal on the relative parameters determining the geometry and dynamics of the channel walls are given

SIMULATION OF GAS RELEASE FLOWS FROM THE FLOW SURFACES OF TURBOMOLECULAR VACUUM PUMPS

An algorithm for modeling and an example of calculating gas release flows from the surfaces of the flow part of a turbomolecular pump by the Monte Carlo method in a three-dimensional setting low-density gas flow is considered.

Numerical simulation of gas flow through the flow part of a multi-stage turbomolecular vacuum pump

The modeling of gas flow through a multi-stage flowing part of a turbomolecular vacuum pump to optimize the parameters of rotor and stator impeller wheels is considered. The developed program of statistical modeling by the Monte Carlo method allows us to determine the influence of the geometric parameters of the stages on the pump performance indicators. Keywords turbomolecular pump, impeller wheels, maximum action speed, maximum pressure ratio, Monte Carlo method. [email protected]

Algorithm for Determining Optimum Runner Number in the Blading Section of a Turbomolecular Pump

The paper considers developing an algorithm for determining the optimum runner number in the blading section of a turbomolecular pump. Such pumps are built into chromatograph mass spectrometers for ensuring vacuum production in the chamber. Turbo-molecular pumps boast a number of advantages over other pumping solutions since it is possible to arrive at the required pumping parameters by means of selecting the optimum blading section configuration. In order to solve this problem, we present an algorithm for calculating the optimum runner number in the blading section of a turbomolecular pump, ensuring the pumping characteristics required: pumping speed and pressure ratio. The algorithm is based on well-known analytical expressions describing processes taking place in pumps of this type, which means it is highly computationally efficient. We determined the respective blading section parameter values, selected the values of empirical coefficients and plotted the pumping performance for the first two runners. The algorithm developed may be used to optimise mass and dimensions of turbomolecular pumps, which could significantly expand their use.

Influence of Blade Flexibility on the Dynamic Response Simulation of a Turbomolecular Pump on Magnetic Bearings

This paper proposes the simulation of a complete mechanical model of a turbomolecular pump rotor, including rotor and blades flexibility, suspended by controlled active magnetic bearings. The mechanical model is composed of an eight stage blisk, attached to a shaft. Magnetic forces are linearized by the first-order Taylor expansion around a given point. Including blades and rotor flexibility makes the mechanical system asymmetric, so the equations of motion for the coupled system have periodic terms. A modal controller was designed to control rigid body modes, since the number of sensors is limited and no state observer is implemented. PID controllers are used for low frequency modes combined with the second order filters to damp high frequency modes. First of all, stability analysis was carried out for the axisymmetric case. Second, blades flexibility was included. Forced response of the whole system to an impulsive force was studied. Divergent responses for the system in rotation were obtained as a second order filter pole possibly interacting with blades modes. Taking the second order filters off the control loop allowed the system to be stable. These results show that the analysis method developed here is efficient to evaluate the performance of a controller in closed loop with the complete flexible system. This method may be used in industrial design processes as computation times for the complete system are very short.