Vane Tip Research Articles

Novel rotary sliding vane expanders with small eccentricity and guide vane ports: Numerical simulation and structural parameter analysis

Expanders are key equipment in energy storage systems. Traditional sliding vane expanders have many problems, such as severe friction, non-uniform flow fields and limited flow rates. To address these issues, a novel rotating-cylinder sliding vane rotary expander (RC-SVRE) with small eccentricity and guide vane ports is proposed where the rotating-cylinder keeps a distance from the rotor to reduce friction between each other and guiding vanes are added into the intake and exhaust ports to improve flow fields. The friction loss and flow fields are predicted through theoretical analysis and numerical simulations, respectively. Compared with traditional expanders, the friction at sliding vane tips as well as that between the rotor and rotating cylinder of new RC-SVREs can be reduced by more than 98%. Among three optimized port configurations, the scheme #1 with guiding vanes and a 12 mm eccentricity obtains the lowest outlet temperature of 422.35 K and the highest isentropic efficiency of 62.27% because guiding vanes are conducive to intensifying the rotational velocity of working fluid. Among three optimized eccentricities, the scheme #4 with guiding vane and a 9 mm eccentricity obtains the lowest discharge temperature of 418.82 K and the highest flow rate of 2.365×10−2 kg/s. When comprehensively comparing all schemes, scheme #4 performs the most optimal due to the combined effects of port configurations and the smallest eccentricity. This work provides the possibility for designing novel sliding vane rotary expanders.

Effect of thermal barrier coatings and integrated cooling on the conjugate heat transfer and thermal stress distribution of nickel-based superalloy turbine vanes

Based on the comprehensive design of the thermal barrier coatings (TBCs) and advanced integrated cooling systems for the Ni-based superalloy turbine vanes. This study employs a multidisciplinary method to research the aerothermal performance and elastic thermal stress of the first stage Ni-based superalloy (DS GTD 111) turbine guide vane cooled by an integrated cooling system and TBC thickness of 0.5 mm. The results show that the highest temperature and average temperature on the substrate under TBC decreased by 126 K and 110 K, respectively. For the vanes without and with TBC, the thermal stresses are concentrated on the midchord region of the suction side, the upper edge of film holes outflow, and junction regions between the vane root, tip, and endwalls, which bear high-temperature gradient and high temperature. However, TBC reduces stress value by 50%∼95% in thermal stress concentration regions of the substrate, which significantly reduces the slip systems activated regions on the substrate. In addition, the activation of the dominant slip system (DSS) is a further optimization objective for cooling turbine vanes. This study provides macroscopic and microscopic perspectives for improving integrated cooling structures of actual vanes in the design process by comprehensively considering aerothermal and thermomechanical performance.

Theoretical and experimental studies of multi-port RF power feeding in rod-type radio frequency quadrupole (RFQ) linac

An analytical and experimental study of multi-port RF power feeding in a four rod-type radio frequency quadrupole (RFQ) has been discussed. First, we have derived generalized relations for multi-coupler power feeding based on S-parameters for n balanced couplers. Using simulation and measurements on a prototype, the optimum position and orientation of two and four couplers in an 80 MHz extended vane rod type RFQ have been determined. A low power RF test has been carried out to show the phase and power balancing using S parameter analysis for two and four mock-up couplers for the RFQ. As a corroborative study, the vane tip voltage measured with a vector voltmeter showed that voltage corresponding to power fed through a single coupler (β = 1) agrees with the value when the same power is fed using two or four couplers.

Numerical Evaluation in a Scaled Rotor-Less Nozzle Vaned Radial Turbine Model under Variable Geometry Conditions

The widespread trend of pursuing higher efficiencies in radial turbochargers led to the prompting of this work. A 3D-printed model of the static parts of a radial variable geometry turbine, the vaned nozzle, and the volute, was developed. This model was up-scaled from the actual reference turbine to place sensors and characterize the flow around the nozzle vanes, including the tip gap. In this study, a computational model of the scaled-up turbine was carried out to verify the results in two ways. For this model, firstly compared with an already validated CFD turbine model of the real device (which includes a rotor), its operating range was extended to different nozzle positions, and we checked the issues with rotor–stator interactions as well as the influence of elements such as the screws of the turbine stator. After showing results for different nozzle openings, another purpose of the study was to check the effect of varying the clearance over the tip of the stator vanes on the tip leakage flow since the 3D-printed model has variable gap height configurations.

Performance investigation and design optimization of novel rotating-cylinder sliding vane rotary compressors

Novel rotating-cylinder sliding vane rotary compressors (RC-SVRCs) are promising machines in energy conversion systems due to extremely low friction. However, three-dimensional visual investigations on geometrical optimizations of RC-SVRCs are highly limited. Besides, most flow mechanisms and leakage flow affected by geometric structures have not been fully revealed yet. Therefore, the sliding vane number, gap heights at vane tips and length-to-diameter ratio are numerically studied in this work. The results show that more sliding vanes (4∼12) lead to more uniform flow and temperature fields, lower mass flow rates and outlet temperature, less leakage between rotor and rotating cylinder. The mass flow rate, leakage mL1 between rotor and cylinder and leakage mL2 at vane tip of 8-sliding-vane scheme are 2.944 × 10−2, 9.949 × 10−4 and 3.692 × 10−5 kg·s−1, respectively. Gap height at vane tips has vital effects on flow fields. As the gap increases (0.01∼0.05 mm), mass flow rate and isentropic efficiency are decreased by 12.68% and 18.26%, the outlet temperature, leakage mL1 and mL2 are increased by 91.5 K, 69.60% and 22 times, respectively. High-temperature areas and leakage flow increase with the increase of cylinder length, which is recommended no longer than 0.6 diameters. This work allows making recommendations for designing RC-SVRCs.

LES predictions of confinement effect on swirling flow generated by single helical axial swirler

PurposeFor higher swirling flows (swirl > 0.5), flow confinement significantly impacts fluid flow, flame stability, flame length and heat transfer, especially when the confinement ratio is less than 9. Past numerical studies on helical axial swirler type systems are limited to non-reacting or reacting flows type Reynolds averaged Navier Stokes closure models, mostly are non-parametric studies. Effects of parametric studies like swirl angle and confinement on the unsteady flow field, either numerical or experimental, are very minimal. The purpose of this paper is to document modeling practices for a large eddy simulation (LES) type grid, predict the confinement effects of a single swirler lean direct injection (LDI) system and validate with literature data.Design/methodology/approachThe first part of the paper discusses the approach followed for numerical modelling of LES with the minimum number of cells required across critical sections to capture the spectrum of turbulent energy with good accuracy. The numerical model includes all flow developing sections of the LDI swirler, right from the axial setting chamber to the exit of the flame tube, and its length is effectively modelled to match the experimental data. The computational model predicts unsteady features like vortex breakdown bubble, represented by a strong recirculation zone anchored downstream of the fuel nozzle. It is interesting to note that the LES is effective in predicting the secondary recirculation zones in the divergent section as well as at the corners of the tube wall.FindingsThe predictions of a single helical axial swirler with a vane tip angle of 60°, with a duct size of 2 × 2 square inches, are compared with the experimental data at several axial locations as well as with centerline data. Both mean and unsteady turbulent quantities obtained through the numerical simulations are validated with the experimental data (Cai et al., 2005). The methodology is extended to the confinements effect on mean flow characteristics. The time scale and length scale are useful parameters to get the desired results. The results show that with an increase in the confinement ratio, the recirculation length increases proportionally. A sample of three cases has been documented in this paper.Originality/valueThe novelty of the paper is the modelling practices (grid/unsteady models) for a parametric study of LDI are established, and the mean confinement effects are validated with experimental data. The spectrum of turbulent energies is well captured by LES, and trends are aligned with experimental data. The methodology can be extended to reacting flows also to study the effect of swirl angle, fuel injection on aerodynamics, droplet characteristics and emissions.

Research on motion and friction of rolling piston in rotary compressor

Based on the Reynolds equation of mixed lubrication, the dynamic model of rolling piston was established, and the axis locus, rotation velocity, sliding velocity at vane tip, and friction loss of the piston were numerically solved. The analysis results indicated that the numeric results of sliding velocity at vane tip are in good agreement with the experimental results. In addition, the influences of crankshaft rotation speed, working condition, piston density and compression structure parameters on motion and friction were analyzed. Taking the ratio of piston rotation velocity and revolution velocity (λ) as evaluation index, whether λ conforms to cosine curve can judge the motion state between piston and vane. The results show that there is not only sliding state but also rolling state between piston and vane tip, and keeping rolling state is helpful to reduce friction loss. The design schemes of lighter piston, thicker vane and larger height-diameter ratio cylinder are proposed to keep rolling state in a wider rotation speed range and smaller pressure difference condition, thereby improving the annual operating efficiency of R32 rotary compressor.

Dynamic modelling and experimental validation of Coupled Vane Compressor

The newly developed Coupled Vane Compressor (CVC) consists of a unique feature that is a couple of vanes cut through the rotor diametrically. Theoretically, this allows the rotor of any diameter which can accommodate the coupled vanes, to be able to operate CVC. Thus, unlike other rotary compressors, CVC design is mostly free of geometrical constraints imposed on the size of its rotor, making it one of the most compact compressors. Nevertheless, CVC suffers from frictional losses similar to other rotary compressors and therefore, studies of dynamic forces acting in CVC is of great interest. In this paper, dynamic forces acting on its components and frictional losses occurring due to rubbing of various components were studied and analysed. Unlike in other vane compressors, in which frictional losses are mostly due to the rubbing of vane tips against cylinder wall and vane sides against vane slot in the rotor, in CVC, the loss also occurs due to rubbing between the coupled vanes. A CVC prototype of 44 cm3 was developed and the compressor power consumption was experimentally studied in an open-type test circuit using air as an operating fluid. The predicted and measured power consumed by CVC were compared and the predicted results were found to have maximum discrepancy of ±15% with the measured results.

Experimental investigation of internal leakages and effects of lubricating oil on the performance of a four-intersecting-vane rotary expander

In this paper, a four-intersecting-vane-rotary expander prototype is presented, and the performance was measured experimentally in dynamic and static conditions. The mechanism is different from conventional rotary vane machines because it has a non-circular stator with radius of between 35.7 and 40.7 mm. The prototype was designed to be eventually implemented in a refrigeration system. However, for testing compressed air was used as the working fluid. The expander was tested at rotational speeds of up to 1750 rpm, suction pressures up to 5 bar(g) and a discharge pressure of 0 bar(g). The effect of different operating parameters and lubricating oil grades on the expander was experimentally studied under dynamic conditions. Then, the internal leakage characteristics of the prototype was analyzed under static conditions. The maximum volumetric and isentropic efficiencies measured were 31.2 % and 45.6 %, respectively. Generally, higher speed and a more viscous oil improved the volumetric efficiency. The expander's isentropic efficiency was significantly affected by the suction pressure, viscosity of oil and rotational speed. The static leakage test showed that the prototype's housing was properly sealed. The average contributions of internal leakages through the radial clearance, vane tips, rotor slot and end face gaps were 37.2 %, 33.3 %, 16.2 % and 14.1 %, respectively. It was observed that the internal leakage paths were generally independent of each other.

Analysis of vane loads and motion in a hydraulic double vane pump with integrated electrical drive

In this paper, the results of the analysis of the forces acting on vanes in a double-acting vane pump with an integrated electric drive have been presented. In the new motor pump unit, the pump is assembled inside the rotor of the electric motor. A dynamic model representing the vane movement has been developed considering the impact of pressure load distribution, vane support forces and friction forces. The loss of contact between the vane head and the cam ring lead to the noise and reduction of the volumetric pump efficiency. The dynamic model which describes the vane motion and contact between the vane tip and cam ring has been solved using MATLAB software. The influence of load distribution, pump design and operational parameters on the vane dynamics has been analysed.

Lubrication and Fluid Film Study on the Vane Tip in a Vane Pump Hydraulic Transmission Considering a Fluid and Structure Interaction

Abstract A mathematical modeling approach to determine fluid film thickness on the vane tip in a vane pump transmission is developed. The transmission is based on a double-acting vane pump with an additional output shaft coupled to a floating ring. Owing to the floating ring design, the internal viscous friction helps to drive the output shaft, whereas the friction is turned into heat in a conventional vane pump. To study the mechanical efficiency, it is crucial to investigate the fluid film thickness between the vane tip and the ring inner surface. The modeling approach in this study takes the interactions between vane radial motion and chamber pressure dynamics into consideration, without using a computational fluid dynamics approach. The lubrication on the vane tip is considered as elasto-hydrodynamic lubrication and the fluid film thickness calculation is based on the Hooke lubrication diagram. Results show that the developed simulation model is capable of revealing the fluid film thickness change and vane radial motion in different operation regions. Sensitivity studies of several parameters on the minimum fluid film thickness are also presented.

Analysis, modeling and simulations of an innovative sliding vane rotary compressor with a rotating cylinder

A novel sliding vane rotary compressor with a rotating cylinder is proposed in this paper. The sliding vane dynamics analysis reveals that, compared with the traditional compressor, the friction loss at the sliding vane tips and between rotor and cylinder can be reduced to 0.25% and 10.23%. To numerically investigate the internal flow mechanism, a reliable three-dimensional simulation method is developed via Fluent 2020R1. Three pressure ratios are considered. During transient calculations, all parameters begin to fluctuate periodically after the fourth round. Both temperature and pressure for a single chamber reach the maximum near the exhaust port. As the pressure ratio εp increases from 5, 10 to 15, the outlet temperature increases from 496.9, 623.0 to 754.4 K and the mass flow rate decreases from 0.03089, 0.02946 to 0.02764 kg/s, the volumetric efficiency and isentropic compression efficiency decrease, with the maximum values of 97.14% and 90.33%. The gaps between the rotor and the cylinder and at the vane tips are 0.03 and 0.01 mm, but the leakage mass of the former is one order higher than that of the latter. The research can provide guidance for the design and practical application of sliding vane rotary compressors.

Impact of discharge port configurations on the performance of sliding vane rotary compressors with a rotating cylinder

With the increasing requirements of compressed gas energy storage systems for compressors and expanders, sliding vane rotary compressors are worth trying. To study the influence of different configurations of discharge ports on the performance of compressors, numerical simulations are conducted on the innovative sliding vane compressors with a rotating cylinder. The reliable Renormalization Group k-ε turbulent model is adopted in Fluent 2020R1. The results show that as the coverage angle increases, the averaged mass flow rates increase, the averaged exhaust gas temperature decreases and the leakage between the rotor and rotating cylinder and at sliding vane tips decrease. When the coverage angle increases from 15° to 45° at the central position angle of −28°, the volumetric efficiency increases from 89.38% to 92.65% while the isentropic efficiency increases from 76.43% to 86.19%. When the central position angles range from −28°, −23° to −18° at the coverage angle of 30°, the farther the discharge port is to the narrowest gap between the rotor and cylinder, the lower the outlet temperature, the less the leakage flow, and the higher the isentropic efficiency. The scheme with the central angle of −28° and coverage angle of 45° is recommended as the best one.

Simulation-based Vibration Sensor Placement for Centrifugal Pump Impeller Fault Detection

In this paper, a simulation-based method is proposed for optimal placement of vibration sensors for the purpose of fault detection in a centrifugal pump. The centrifugal pump is modeled to investigate the effect of vane tip fault on fluid flow patterns numerically. Pressure pulsations are investigated at different locations at the inner surface of the pump before and after the presence of the fault to determine the best location for installing vibration sensors on the pump casing. Experiments are also conducted by mounting accelerometers at various locations on the pump casing. Simulation and experimental results are then compared and a direct correlation between changes in PSD amplitudes of pressure and acceleration signals was observed. The optimum location for placement of an accelerometer is determined to be near the volute tongue on the casing where the highest level of pressure pulsations in the simulation is also calculated in the presence of vane tip fault.

3D CFD numerical analysis of vane dynamic effects on the pressure ripple in a variable displacement vane pump

A numerical three-dimensional CFD analysis of a variable displacement vane pump has been conducted, investigating the effects on the pressure ripple caused by the vane detaching from the pressure ring. The volume of the fluid over the vane tip has been re-meshed at every time step as a function of the forces acting on the bottom and the top of each vane. The numerical model has been developed using the commercial tool, Simerics MP+, including turbulence and cavitation models. The validation of the model has been done comparing numerical and experimental data. It has been observed that the detachment of the vane occurs during the transition zones when unwanted pressure spikes are generated by a nonoptimized valve plate design. The prediction of vane detachment is crucial for designing a quieter and more durable pump. Vane collision on the stator ring can be a source of noise producing premature wear of both components. Vane detachment from the stator ring has a large effect on pressure ripple even if the volumetric efficiency is only slightly influenced.

On the relation between vane geometry and theoretical flow ripple in balanced vane pumps

Advancements related to the correlation between pump design parameters and the kinematic flow ripple in balanced vane pumps are addressed in the present work. In particular, the study focuses the attention on the influence of the vane geometry on the oscillations of the flow rate produced by the volume variation of both under-vane pockets and displaced chambers, that is known as one of the most relevant sources of noise in hydraulic systems. The working principle of the machine is detailed and used as starting point to deduce analytical correlations describing both vane kinematics and delivery flow rate ripple. The set of results that can be achieved with the obtained formulation is evaluated by means of a nondimensional parametric study including the two main design parameters defining the vane geometry, i.e. thickness and tip radius. The resulting trends demonstrate that the theoretical delivery flow ripple is closely related to the vane design and the cam ring shape profile.

A Theoretical Study on the Novel Structure of Vane Compressor for High Efficiency

Aiming at the problem of excessive mechanical loss of the conventional vane compressor, this paper proposes a novel vane compressor structure. This compressor can significantly reduce the mechanical frictional loss through converting sliding friction between vane tip and cylinder into rolling friction by using a rolling bearing. The structure and operation principle are introduced in this paper, and mechanical friction loss calculation models of these two kinds of compressor are theoretically analyzed. The results show that mechanical loss of the novel vane compressor can be reduced by nearly 38% under the same working conditions. At the same time, the actual tested results indicated that the total power consumption of compressor decreased 160.1W (6.89%), and the COP increased by 11.89%.

Coupled 3D multiphysics analysis of 325 MHz ISNS RFQ structure

Abstract A 325 MHz, 3.0 MeV Radio Frequency Quadrupole (RFQ) is being developed for 1 GeV proton accelerator for proposed Indian Spallation Neutron Source (ISNS) facility at Raja Ramanna Centre for Advanced Technology, Indore. RFQ will be a normal conducting four vane resonating structure made of Oxygen Free Electronic (OFE) copper. During high power operation of RFQ, Radio Frequency (RF) field induced heating results in temperature rise, thermal deformations and shift in resonant frequency from designed values. Therefore thermal stability of RFQ is one of the important design issues. Various RF–thermal–structural coupled multiphysics analysis methodologies for thermal management of RFQ have been attempted in past and reported in literature. However, these efforts are primarily limited to 2D simulations for a thin slice of RFQ cross section and do not addresses for longitudinal temperature rise of cooling water, distribution of frequency tuners, vane tip modulations and vane cut back at the inlet and exit of RFQ structure. This paper proposes a finite element method (FEM) based multiphysics analysis methodology for numerical simulation of RFQ structure. The methodology consists of a complete 3D-RF-fluid–thermal–structural–RF coupled analysis for predicting temperature rise, thermal deformations and frequency shift of RFQ structure due to RF heating. All analysis (electromagnetic, fluid, thermal and structural) and their coupling are carried out using a single code namely ANSYS Mechanical. The simulated results from proposed methodology are compared with published work and a maximum error of less than 7% is obtained. The numerical comparison of described methodology with other multiphysics analysis methodologies (such as importing 2D field maps and using heat transfer coefficient from empirical relations) has been carried out. The described methodology is paving the way for the design and development of ISNS RFQ structure.

CFD Simulation on Cavitation in a Rotary Vane Energy Recovery Device

The rotary vane energy recovery device (RVERD), as a kind of rotary vane machines, has a potential application in seawater reverse osmosis (SWRO) system to decrease the system energy consumption, which can significantly improve the system efficiency and make the production of fresh water economical with low carbon emission. Cavitation can occur in RVERD where local pressure falls below the vapor pressure, which may decrease the device efficiency and erode the internal surface. In this work, the internal flow in working chamber and the vane slot of RVERD is fully simulated by ANSYS Fluent software. The stand k-ɛ turbulence model, together with the Schnerr-Sauer cavitation model, is adopted. A dynamic mesh method coupled with the User Defined Functions (UDF) to control the vane movement is proposed for grid generation in the moving and deforming fluid domain. According to the simulation results, the deforming grid generation can be achieved to perform numerical simulation of RVERD by the proposed method. Cavitation tends to occur in the vane tip gap zone, the downstream zone of vane, and the vane slot bottom zone, corresponding to the local low pressure zones within RVERD. This study presents the implementation of the mesh motion and the obtained cavitation results of RVERD, which can help for optimal design of rotary vane machines.

FLOW MODELLING AND PERFORMANCE ASSESSMENT OF ROTARY SLIDING VANE PUMP USING COMPUTATIONAL FLUID DYNAMICS

A pump is a mechanical device that converts mechanical energy into hydraulic energy. The aim of the current work is to examine the behavior of fluid flow inside a rotary sliding vane pump and assessing the performance by studying the effect of change of the rotational speed, number of vanes and the radial clearance gap size between vane tips and stator surface on the performance of the pump. The commercial finite-volume solver ANSYS Fluent was used to simulate flow behavior in the pump with an additional C source code for the description of the dynamic mesh motion. Pump flow has been studied using lubricating oil, 5W-30, as the working fluid. Several computational configurations were used for the numerical simulation. The numerical results showed that 100% increase of the number vanes decreases the overall efficiency by 46.5%, while increasing the clearance gap size from 0.025 to 0.05 decreases the overall efficiency by 9.72%, and results in a 42.85% increase in the internal leakage within the pump.