Prediction of Axial Thrust Load Acting on a Cryogenic Liquid Turbine Impeller

2011 ◽  
Author(s):  
Ke Wang ◽  
Jinju Sun ◽  
Zhilong He ◽  
Peng Song
Keyword(s):  
Cryogenic Liquid ◽  
Empirical Method ◽  
Main Flow ◽  
Back Side ◽  
Turbine Stage ◽  
Axial Thrust ◽  
Gap Flow ◽  
Flow Domain ◽  
Side Gap ◽  
Thrust Load

A single stage cryogenic liquid turbine is developed for replacing the Joule-Thompson valve and recovering energy from the liquefied air during throttling process in the large-scale internal compression air-separation unit, and evaluation of the impeller axial thrust at different conditions is essential for a reliable bearing design and stable operation. To predict the axial thrust load, a numerical model is established to simulate the turbine flow in a turbine stage environment, which includes the main flow domain (an asymmetrical volute, variable geometry nozzle, impeller, and diffuser), impeller front and back side gaps, and shaft seal leakage. Numerical simulation of flow is conducted by using the ANSYS-CFX. Flow characteristics in both main flow domain and impeller side gaps of the turbine stage are captured and analyzed. The axial thrust is then calculated based on the obtained pressure data in the impeller and its front and side gaps by using a direct integration approach. Flow behaviour in both main flow domain and impeller side gaps has been well exhibited by the numerical results. At the impeller back side gap inlet, the back flow is encountered even for design condition and it returns the impeller main flow stream; the impeller side gap flow has much influence on the axial thrust. To investigate influence of turbine operation condition on axial thrust, flow simulation is conducted at different mass flow rates and inlet pressure for the turbine stage, based on which the axial thrust is calculated. It is demonstrated from the obtained numerical results that the axial thrust increases as the inlet pressure increases and decreases as turbine flow rate increases. Geometry parametric study is conducted for the shaft seal clearances, which has demonstrated that the axial thrust is influenced largely by the clearance size and it decreases as the clearance grows. For the purpose of comparison, the empirical method is also used to predict the axial thrust load. The obtained results are compared to the numerical ones and evident deviation of the empirical from the numerical exists and the reason is that axial force components caused by the impeller main flow stream and its side gap flow are approximated very roughly in the empirical method.

Investigating the Influence of Impeller Axial Thrust Balance Holes On the Flow and Overall Performance of a Cryogenic Liquid Turbine Expander

2021 ◽  
Author(s):  
Changjiang Huo ◽  
Jinju Sun ◽  
Peng Song ◽  
Shan Sun
Keyword(s):  
Cryogenic Liquid ◽  
Hole Diameter ◽  
Design Flow ◽  
Radial Position ◽  
Axial Component ◽  
Back Side ◽  
Axial Thrust ◽  
Gap Flow ◽  
Overall Performance ◽  
Overall Efficiency

Abstract An excessive rotor axial thrust in any turbomachine can cause critical operational problems, and rotor axial thrust balancing has always attracted much attention. The present numerical study is focused on axial thrust balancing for a cryogenic liquid turbine expander, whose axial thrust balancing is typically challenging because of its small impeller size and large axial thrust. A computational fluid dynamics (CFD) simulation is conducted in a real turbine expander environment constituted by main and gap flow domains with allowing for the thermodynamic effect of liquefied air. The balance hole influential mechanism on the main and gap flows is explored, and its influence on the expander axial thrust and overall performance is quantified. The results show that the use of balance holes creates a highly swirling gap flow, and the static pressure over the impeller disk back-side surface decreases to produce a small axial component force and axial thrust, but the turbine expander overall efficiency drops by 1.1 and 2.8 points at 100% and 50% design flow, respectively, due to an increased internal leakage loss and distorted impeller flow. In addition, a parametric study is conducted to analyze the effect of balance hole diameter, circumferential position and radial position on expander axial thrust and overall performance. The results indicate that the axial thrust is sensitive to both the balance hole diameter and circumferential position but less sensitive to its radial position, while the overall efficiency is influenced by all three parameters.

Flow Analysis of an Operational Natural Gas Turbo Expander

2018 ◽  
Author(s):  
Changjiang Huo ◽  
Jinju Sun ◽  
Shan Sun ◽  
Peng Song ◽  
Guizheng Zhao ◽  
...  
Keyword(s):  
Natural Gas ◽  
Flow Analysis ◽  
Flow Simulation ◽  
Internal Flow ◽  
Main Flow ◽  
Back Side ◽  
Two Phase ◽  
Flow Rates ◽  
Flow Domain ◽  
Side Gap

The paper focuses on an operational gas expander being used in a natural gas plant for over 10 years, whose recent realtime monitoring shows that the impeller back-side gap pressure is excessively low. To ensure the safe operation, an insight into the complex internal flow of the expander is demanded. The reverse engineering is firstly conducted to reconstruct the flow passage data from the used impeller and nozzle. The physical model includes the main flow domain components (nozzle ring, impeller, and diffuser duct), and the leakages and seal chambers (the impeller front and back-side toothed gaps, shaft seal chamber, and seal gas inlet). Two-phase flow simulation is conducted with the homogeneous multiphase mixture equilibrium model, which is used to allow for the phase change in terms of condensation. Flow analysis is performed based on the obtained numerical results. At the concerned operating point, the expander outlet wetness fraction is about 16.0%, and evident condensation is encountered in the main flow domain and its back-side gap around the pressure tap, which is thought to be responsible for the abnormal pressure reading. The condensed small droplets may grow to block the pressure tap leading to a lower gauge reading. At the operating speed and different flow rates, the flow simulation is conducted for the expander: condensation in the expander is encountered locally at all flow rates and the overall isentropic efficiency closely associated with the overall wetness fraction.

A CFD Method for Axial Thrust Load Prediction of Centrifugal Compressors

2001 ◽  
Author(s):  
Zhen-Xue Han ◽  
Paul G. A. Cizmas
Keyword(s):  
Centrifugal Compressor ◽  
Stokes Equations ◽  
Least Squares Method ◽  
Directional Derivatives ◽  
Computational Domain ◽  
Back Side ◽  
Load Prediction ◽  
Time Step ◽  
Axial Thrust ◽  
Thrust Load

This paper presents the development of a numerical algorithm for the computation of axial thrust load on a centrifugal compressor. An unstructured flow solver has been developed for the computation of a hybrid, structured and unstructured grid. The computational domain of the impeller has been discretized using a structured mesh, while the computational domain on the back side of the wheel has been discretized using an unstructured mesh. The two grids are merged and a median dual-mesh is generated. The Navier-Stokes equations are discretized using a finite volume method. Roe’s flux-difference scheme is used for inviscid fluxes and directional derivatives along edges are used for viscous fluxes. The gradients at the mesh vertices are calculated using the Least-squares method. An explicit scheme is used for time integration. Convergence is accelerated using a local time-step and implicit residual smoothing. The results of the numerical simulation include the axial thrust load of the centrifugal compressor. In addition, details of the leakage flow are presented.

scholarly journals Prediction of Axial Thrust Load under Turbocharger Operating Conditions

2016 ◽  
Vol 24 (6) ◽  
pp. 642-648 ◽  
Author(s):  
Inbeom Lee ◽  
Seongki Hong ◽  
Youngchul Kim ◽  
Boklok Choi
Keyword(s):  
Operating Conditions ◽  
Axial Thrust ◽  
Thrust Load

Investigation of Composite Hydrodynamic Thrust Bearing Operating Temperature Under Varying Axial Loads

2017 ◽  
Author(s):  
Kyle Myers ◽  
Collier Fais ◽  
Matthew Zacharias ◽  
Muhammad Ali ◽  
Khairul Alam
Keyword(s):  
Composite Materials ◽  
Operating Temperature ◽  
Sampling Rate ◽  
Axial Loading ◽  
Axial Loads ◽  
Axial Thrust ◽  
Thrust Bearings ◽  
Average Operating ◽  
Thrust Load ◽  
Proper Movement

The purpose of this experiment was to explore the operational behavior of hydrodynamic thrust bearings machined from various composite materials (PTFE-Filled Delrin Acetal Resin and MDS-Filled Nylon) and general Aluminum under a set of different axial loading conditions. Since thrust bearings allow mechanical components subjected to axial loads to rotate more freely, they must counter a great deal of friction which can cause bearing failure in order to maintain proper movement. In order to reduce friction and weight, this research posits that thrust bearings machined from composite materials of lower friction coefficients and densities to that of conventionally used materials such as aluminum may provide some advantages. This hypothesis was tested by machining three thrust bearings, all to the same geometric specifications (two composites and one Aluminum) and subjecting them to thrust loads of 25, 50, 75, and 100 pounds while rotating them at a constant rotational speed of 3050 RPM for 10 minutes at each load using a customized test rig. A thermocouple implanted into the bearings themselves recorded the operation temperatures at a sampling rate of 20 Hz. Based on the average temperatures recorded at the 100 pound axial/thrust load, the experiments suggest that the PTFE-Filled Delrin Acetal maintains the lowest average operating temperature of 29.5 °C, followed by the MDS-Filled Nylon at 41.6 °C and lastly the Aluminum at 54.4 °C — a trend that is observed at each axial load albeit less pronounced. These results suggest that composite materials such as PTFE-Filled Acetal and MDS-Filled Nylon to be used in lieu of conventional metals and operate at lower temperatures and lower friction.

Investigation of the axial thrust load using numerical and experimental techniques during turbocharger operation

2017 ◽  
Vol 232 (6) ◽  
pp. 755-765 ◽  
Author(s):  
In-Beom Lee ◽  
Seong-Ki Hong ◽  
Bok-Lok Choi
Keyword(s):  
Axial Force ◽  
Thermal Effects ◽  
High Speed ◽  
Operating Conditions ◽  
Axial Thrust ◽  
Turbine Wheel ◽  
Compressor Wheel ◽  
The Relationship ◽  
Thrust Load ◽  
Calibration Equations

Identification of the axial thrust load during the operating conditions of a turbocharger provides useful information to turbocharger designers. The axial force acting on the thrust bearing is mainly caused by the imbalance between the turbine wheel and the compressor wheel. It has a significant influence on the friction losses, which reduce the efficiency and the performance of a high-speed turbocharger. Well-known formulae for calculating the thrust load and the mechanical friction have been given in the literature. However, it is difficult to determine an accurate axial force by an analytical approach. This paper presents a detailed procedure for prediction of the axial thrust load during turbocharger operation. The first step is to identify the relationship between the externally applied load and the strain response using a specially designed test device and a numerical method. Next, if the operating strains and temperatures are measured, the strain signals due to the axial thrust can be adjusted by subtracting the thermal effects from the measured strains. Finally, the thrust loads in particular operating conditions are inversely obtained by inserting the adjusted strains into the calibration equations.

AERODYNAMICS AND HEAT TRANSFER INSIDE A GAS TURBINE MID-PASSAGE GAP

2021 ◽  
pp. 1-13
Author(s):  
Faisal Shaikh ◽  
Budimir Rosic
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Film Cooling ◽  
Heat Load ◽  
Turbine Blades ◽  
Turbine Stage ◽  
Gas Turbine Blades ◽  
Cooling Flows ◽  
Turbine Efficiency ◽  
Gap Flow

Abstract Gas turbine blades and vanes are typically manufactured with small clearances between adjacent vane and blade platforms, termed the midpassage gap. The midpassage gap reduces turbine efficiency and causes additional heat load into the vane platform, as well as changing the distribution of endwall heat transfer and film cooling. This paper presents a low-order analytical analysis to quantify the effects of the midpassage gap on aerodynamics and heat transfer, verified against an experimental campaign and CFD. Using this model, the effects of the gap can be quantified, for a generic turbine stage, based only on geometric features and the passage static pressure field. It is found that at present there are significant losses and a large proportion of heat load caused by the gap, but that with modified design this could be reduced to negligible levels. Cooling flows into the gap to prevent ingression are investigated analytically and with CFD. Recommendations are given for targets that turbine designers should work toward in reducing the adverse effects of the midpassage gap. A method to estimate the effect of gap flow is presented, so that for any machine the significance of the gap may be assessed.

Axial Load Control on High-Speed Turbochargers: Test and Prediction

2008 ◽  
Author(s):  
Kostandin Gjika ◽  
Gerald D. LaRue
Keyword(s):  
Axial Load ◽  
High Speed ◽  
Control Volume ◽  
Fluid Dynamic ◽  
Test Facility ◽  
Load Control ◽  
Lateral Motion ◽  
Radial Vibrations ◽  
Axial Thrust ◽  
Thrust Load

This paper deals with axial thrust load control in high-speed turbochargers. A specific test facility was developed to demonstrate the feasibility of axial load measurement and control. A special turbocharger was developed and instrumented to measure axial load and other test parameters. The axial load was controlled by throttling the compressor inlet and/or outlet flow. Extensive testing and analysis during both steady state and transient behavior conditions were completed on a special test bench. A thrust load map was developed and superimposed on the compressor map, and the relationship between turbocharger aerodynamics performance and axial thrust load was identified. During testing, the interaction between axial load, rotating group lateral motion and radial vibrations on the turbocharger housing was also identified. Running the turbocharger with low axial load shows no major problems on rotating group lateral motion or oil leakage. An analytical approach using a control volume type fluid dynamic model and a prediction code for axial thrust load has been developed. It shows good agreement between measured and predicted thrust load.

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