Steam Jet Vacuum Pumps Research Articles

О методе расчета параметров откачки ступени диффузионного вакуумного насоса

At present, steam jet vacuum pumps are widely used in various fields of science and technology due to a number of advantages, e.g., reliability, relative simplicity of design, and manufacturability, over other pumping means. The paper analyzes the existing mathematical models of working processes, methods for calculating the pumping parameters of steam-jet vacuum pumps. The problem of improving these methods, which are used in the design, is still urgent. The study attempts to further develop the models in order to increase their practical significance for the pumps design: in particular, the processes of pumping by the first stages of a diffusion pump are considered, since it is they that determine the efficiency of the pump as a whole. Analytical dependences for calculating the main pumping parameters of widely used diffusion vacuum pumps are presented. The obtained equations are a certain clarifying correction of the known provisions on this topic. Findings of research are of practical importance for the design of modern steam-jet vacuum pumps

Numerical Study on the Flow Structure of a Steam-Jet Vacuum Pump at Different Throat Length

The aim of the study is to reveal the complication of the flow process of a steam-jet by using the simulation software package (FLUENT). The paper is able to analyze the flow phenomena inside the steam-jet when its throat length was varied. It is found that the entrainment ratio remains unchanged when the throat length is varied. It is also found that the shocking position moved closer to the exit of the vacuum pump and the critical back pressure of the steam-jet pump increased with the elongation of the throat.

Numerical Research About the Internal Flow of Steam-jet Vacuum Pump: Evaluation of Turbulence Models and Determination of the Shock-mixing Layer

Steam-jet vacuum pump is widely used in a range of applications. This paper evaluated the performance of four well-known turbulence models for predicting and understanding the internal flow of a steam-jet vacuum pump first. With the help of a commercial computational fluid dynamics (CFD) code ANSYS-Fluent 6.3, the simulation results obtained from the concerned turbulence models were compared with experimental values, the k-omega-SST model was chosen as a tool model for carrying out numerical simulations. Then, based on the simulation results obtained from specific operating conditions, a method for locating the shock-mixing layer was put forward. The shape of the shock-mixing layer shows that the secondary steam does not mix with the primary steam immediately after being induced into the mixing chamber of the pump; actually, they maintain their independence till the shocking position instead. After the shock happens, the shock-mixing layer disappear, the two fluid in the pump begin to mix with each other and discharge to the next stage with almost the same state. Based on the shape of the shock-mixing layer and the supersonic region of the secondary steam, a detailed analysis for the flow duct of the secondary steam was carried out. It is found that the throat of the secondary steam flow duct plays a crucial role in maintaining a stable operating state and the length of the throat reflects the back pressure endurance for the pump.

Numerical analysis of spontaneously condensing phenomena in nozzle of steam-jet vacuum pump

The primary fluid in a steam-jet vacuum pump is not assumed as a perfect gas as general research in the present study. A mathematic model based on the wet steam model for transonic flow is proposed to investigate the flow behaviours of primary fluid in the nozzle of a steam-jet vacuum pump. The simulation based on a wet steam model was carried out to predict the flow characteristics of primary fluid along the nozzle axis by a commercial computational fluid dynamics (CFD) code (FLUENT6.3). The simulation results showed that there was spontaneous condensation as the supersonic flow passing through the nozzle and the simulation results had a good agreement with the experimental data. It is found from the numerical simulation results that the steam flow characteristics in nozzle are quite different from a wet steam model and a perfect gas assumption: the outlet pressure of the nozzle predicted in the present study is higher than that as the primary fluid assumed as perfect gas, the outlet velocity is about 10% lower than that as the primary fluid assumed as a perfect gas, and the temperature at the outlet of the nozzle is much higher than that as the primary fluid assumed as a perfect gas. The simulation results demonstrate that the thermo-positive process due to steam condensation would hinder the supersonic expanding flow process in nozzle and depress the efficiency of the nozzle which would affect the pumping performance of steam-jet pump.

Numerical study on the performances of steam-jet vacuum pump at different operating conditions

A mathematic model based on realizable k- ɛ turbulence model for transonic flow was proposed to investigate the mixing flow behaviours of primary and secondary fluids in steam-jet vacuum pump and the affections to the pumping performances. The simulation was carried out to predict the static pressure distribution among mixing chamber wall by a commercial computational fluid dynamics (CFD) code FLUENT 6.2. Close agreements between the predicted results and experimental data validated the present theoretical model. Using the present approach, the velocity vectors and Mach number profiles in mixing chamber at different back pressures and the secondary fluid pathlines and mass flux profiles at different suction pressures were predicted. It is found that there are swirls separated from secondary fluid near the wall and the velocity of secondary fluid was fallen down obviously when the back pressure was bigger than critical back pressure. The above two factors lead to the entrainment ratio ( E m ) reduced rapidly. It is also found that the mass flux increased with the increasing of suction pressures and made the entrainment ratios increased. The prediction results show that the pressure ratio ( K) is a dominant position in affecting the pump's performances.

Prozeßintegrierter Umweltschutz beim Einsatz von Dampfstrahl-Vakuumpumpen

Integrated environmental protection in the use of steam jet vacuum pumps. At the „cold end” of many processes occurring under vacuum various amounts of water vapour and process steam have to be removed, together with various permanent gases, from the plant at process pressure to atmospheric pressure. The vacuum pump systems required are practically all designed to strictly separate process medium and coolant, to keep the atmospheric burden as low as possible, and also to minimise the work of compression from the point of view of overall operating costs. Thanks to their special features, steam-driven jet pumps used in conjunction with water-cooled condensers still represent a straightforward and reliable form of vacuum system. Reduction of the intermediate condenser pressure, separation of coolant and process steam, and coupling with water-ring vacuum pumps have led to combinations satisfying practically all demands with regard to good energy conversion and best possible environmental protection. In addition, process-steam driven multistage jet pumps in which condensation of working and suction steam is effected directly by cooled process fluid have also proved of value. They operate in essentially closed circulation from which only a modest flow of waste gases and heat enters the environment.

739. Steam-jet vacuum pumps and their use for the vacuum degassing of steel: T Messing, Hutnicke Listy, 19 (12), 1964, 851–857, (in Czech)

739. Steam-jet vacuum pumps and their use for the vacuum degassing of steel: T Messing, Hutnicke Listy, 19 (12), 1964, 851–857, (in Czech)

Characteristics of the Steam-Jet Vacuum Pump

This paper is a discussion and presentation of the theoretical and practical limitations, attainable efficiencies, general performance characteristics, and present-day regions of operation of single and various multistage steam-jet vacuum pumps working at pressures from atmosphere to 10−3 torr.