Centrifugal Stage Research Articles

Development of an Additively Manufactured Stationary Diffusion System for a Research Aeroengine Centrifugal Compressor

Abstract This paper introduces the next generation of the Centrifugal Stage for Aerodynamic Research (CSTAR) facility at the Purdue University Compressor Research Lab. The research centrifugal compressor is designed with an additively manufactured stationary diffusion system which comprises a vaned diffuser, a turn-to-axial bend, and deswirler vanes. The dimensional accuracy and surface finish of the diffusion system has allowed for rapid prototyping of several iterative diffusion system designs and has allowed for configuration of in situ pressure and temperature measurements to experimentally evaluate the aerodynamics and performance of centrifugal compressor diffusion systems. The diffusion system is manufactured from a commercially available stereolithography (SLA) resin, and the design of the parts is adapted to the constraints imposed by current technological and material limits of resin 3D printing. The implementation of additive manufacturing in the prototyping of the diffusion system has allowed for decreased cost and lead time while allowing rapid turnaround to generate experimental data. Performance data have verified the repeatability and temperature independence of the additively manufactured diffusion system through several design iterations. A survey of candidate materials for additively manufacturing these parts is also presented, and the tradeoffs of their material properties are discussed.

Aerodynamic instability evolution of a multi-stage combined compressor

Unstable operating conditions such as surge could cause damage to both aerodynamic performance and structural integrity of a compression system. This paper addresses the critical issue of aerodynamic instability in compressor design, particularly focusing on an axial-centrifugal combined compressor, a widely used yet underexplored configuration. An experimental investigation was conducted on a three-stage axial and one-stage centrifugal compressor (3A1C), using two pipe systems and employing fast-responding transducers to capture the dynamic instability process from choke condition to deep surge. Results reveal that at the design speed, 3A1C enters deep surge directly, whereas at off-design speeds, it experiences rotating stall and mild surge across a wide mass flow range. Some special instability features in the combined compressor can be found in the steady state map and dynamic process. The characteristic curve of the first axial stage keeps a positive slope during the whole mass flow range at an off-design speed. The first stage could work stably on the stall characteristic curve because the centrifugal stage has stronger pressurization and plays a dominant role in global aerodynamic instability. Besides, rotating instability occurs at the first rotor tip and disappears as the back pressure increases, which is also rarely seen in a single-axial compressor. This is also related to the strong pressurization of the centrifugal stage. The findings of this paper will contribute to the understanding of aerodynamic instabilities in combined compressors.

Investigation of the mild surge in an axial–centrifugal compressor

The performance and structural integrity of compressors are critically impacted by aerodynamic instability. This study examines an unstable phenomenon, known as high-frequency mild surge (HFMS), in axial–centrifugal compressors through an experimental investigation and a low-order model. The results reveal that the pressure signal during HFMS is synchronized along the circumferential and streamwise directions. To elucidate the HFMS mechanism and further explore its influential law, a multi-actuator model is developed, successfully capturing the dynamic instability behavior. As the mass flow decreases, the front axial stage becomes unstable first, while the latter centrifugal stage remains stable with a negative slope near the operating point on the performance curve. The strong pressurization of the centrifugal stage maintains the stability of the entire compression system, increasing the mass flow rate. Subsequently, the pressure ratio of the latter centrifugal stage decreases with increasing mass flow, causing the front axial stage to become unstable again. The axial stage's Helmholtz frequency is consistent with the test HFMS frequency, further proving that it is a local systematic instability dominated by the axial stage. This matching feature is particularly common in combined compressors, making HFMS a typical instability phenomenon in such systems.

Experimental Investigation on the Aerodynamic Instability Process of a High-Speed Axial-Centrifugal Compressor

Abstract Aerodynamic instability plays an important role in compressor design and may cause performance degradation and fatigue damage. In this paper, an experimental study on the evolution of aerodynamic instability is carried out on a compressor that combines the performance benefits of an axial stage and centrifugal stage. The spatiotemporal characteristics of unsteady wall pressure were obtained using fast-responding pressure transducers over a range of operating conditions. The results show that the axial stage works on the positive slope of the performance characteristic curve from choke to stall at low-speed operating conditions, and mainly features rotating instability. Rotating stall is also observed in the impeller (IMP) and diffuser passages. At medium-speed operating conditions, the centrifugal stage suffers a high-frequency mild surge, alternating with rotating stall. With the increase in back pressure, the mild surge diminishes, and rotating stall persists. This behavior is similar to a two-regime-surge, which has been reported for centrifugal compressors. At high-speed operating conditions, the compressor directly reaches surge without other instabilities. Further analysis of the spatial pattern of the rotating stall revealed the existence of a high-pressure region near the volute tongue, resulting in obvious pressure distortion along the circumferential direction at the volute inlet. This induced the amplitude difference of stall cells in corresponding diffuser passages. The disturbance caused by stall cells propagates upstream through the blade passage, and the largest pressure disturbance induced by the stall cell propagation appears in a circumferential position 45 deg downstream of the volute tongue at the impeller inlet and the axial stage inlet.

Multidimensional calcium phosphate coatings for bio activation of titanium implant surfaces using methodological approach

This paper presents the methodological approach for multidimensional coated with calcium phosphate for bio activating surfaces of titanium implants. Dental transplant are a revolt in dentistry, but there is some difficulties are noticed. The objective of this effort was to create a soaking technique that does not have the drawbacks of the concentrated simulated bodily fluid (SBF) soaking approach utilizing a supersaturated CaP (calcium phosphate) solution. Titanium samples were acid etched and sandblasted. The objective of this research was to create a soaking technique without the limitations of the concentrated simulated bodily fluid (SBF) soaking strategy using a supersaturated CaP (calcium phosphate) solution. Bio film formation is assessed by methoxy nitro-sulfophenyl-tetrazolium carboxanilide (XTT) assay and it is controlled by anti-adhesive coating. Bacterial adhesion is assessed by Lipid per oxidation and controlled by antibacterial properties. Sand blasting is treat the surface and the sandblasting particles that were imbedded and the surface now has a roughness of around 1.2micrometers, Micro-porosities and high surface moist ability. Our study has demonstrated the importance of the centrifugation stage, which influences coating formation, thickness, and coverage. A thin coating (∼1.5 µm) composed of apatite analogous to bone mineral was deposited.

High-performance aerodynamic design of supercritical CO2 centrifugal compressor for the Megawatt-class nuclear microreactor (MSC-GFR)

Design of the SCO2 centrifugal compressor is critical for the fuel economy and power output of the nuclear microreactors. In this study, we developed a high-performance aerodynamic design & analysis platform (XJHPCCD) for real-gas centrifugal compressors. Based on the single-zone method, the platform realizes efficient and fast solution to the direct and inverse problems of centrifugal stages in real gases. Using the XJHPCCD platform, we performed a principal component analysis on the performance prediction errors in different combinations of the multiply expressed loss mechanisms. On the results of composite analysis, an optimal loss model was proposed regarding the hundred-kW SCO2 compressor in Megawatt-class microreactors. By coupling the optimal loss model in performance prediction, the errors of pressure rises were reduced from 5–10% to 3% for the Sandia’s verified model, greatly promoting the reliability of aerodynamic analyses. To demonstrate the engineering values of the specifically optimized toolkit, we numerically conducted a design research on the main compressor of a 1 MWt SCO2-cooled fast breeder microreactor (MSC-GFR). Results showed the XJHPCCD platform (coupled with the optimal loss model) has well satisfied the technical demands with high-performance aerodynamic design and low prediction errors. Thereby, it is proved that we have successfully proposed a specifically optimized aerodynamic toolkit for the component design of Megawatt-class microreactors.

Magnetic Nanoparticles Molecularly Imprinted Polymers: A Review

Abstract: The molecularly imprinted polymers (MIPs) technology, which has been around since the 1970s, has grown in popularity in recent decades. MIPs have shown to be a useful approach for determining target molecules in complicated matrices containing other structurally similar and related chemicals. Despite MIPs have intrinsic polymer features such as stability, robustness, and low-cost production, traditional MIPs have a number of drawbacks. Surface molecular imprinting appears to be an alternative approach that can address some of the drawbacks of traditional MIP by anchoring shells to the surface of matrix carriers such as nanoparticles. The incorporation of nanoparticles into the polymeric structure of MIPs can improve their properties or provide novel capabilities. Magnetic nanoparticles have been widely explored for their separation and extraction capability. Magnetic components in MIP can help develop a regulated rebinding process, allowing magnetic separation to substitute centrifugation and filtration stages in a simple and cost-effective strategy. Polymers are created directly on the surface of a magnetic substrate to create a unique material termed magnetic molecularly imprinted polymer (MMIP). These materials have been widely used to extract molecules from complex matrices in a variety of applications, especially in environmental, food, and biological studies. This paper seeks to summarize and discuss the nanoparticle synthesis and magnetic nanoparticle combination in the MIP preparation. The novel applications of MMIP in environmental, food, and biological analysis are also discussed in this paper.

Development of an electrochemical membrane bioreactor for succinic acid production and in situ separation with engineered Yarrowia lipolytica cultivated on municipal biowaste hydrolysate

A novel electrochemical membrane bioreactor (EMB) integrating succinic acid (SA) production and in situ separation in the anode compartment through an anion exchange membrane was employed in fed-batch fermentations with Y. lipolytica PSA02004 using hydrolysates from the organic fraction of municipal solid waste (OFMSW) as feedstock. The initiation of electrolysis cell operation and the reduction of pH from 6 to 5.5 at 30 h in a 6.7 L bioreactor improved the SA production efficiency, resulting in 66.7 gSA/L, 0.51 g/g yield, 0.78 g/(L·h) productivity, high coulombic efficiency (66.2%) and relatively low electricity consumption for SA separation (2.6 kWh/kgSA). The recirculation of the fermentation broth in the cathode compartment and the OH– produced by water reduction reduced NaOH consumption (35.4%) for pH control during fermentation. The fermentation was efficiently replicated in a 30 L bioreactor with a low membrane surface area (100 cm2) electrolysis cell, but it failed with a higher membrane surface area (702 cm2) electrolysis cell indicating that yeast cell viability, cell design and EMB configuration are important aspects for process scale-up. SA crystals were purified, at 99.95% purity and 95% yield, from the anolyte solution via activated carbon treatment, evaporation, crystallization and drying. Cell removal via centrifugation and acidification stages were not required as in conventional SA purification processes. The produced SA crystals were suitable for the production of polyester polyols for polyurethane urea dispersions applications.

On axisymmetric dynamic spin coating with a single drop of ethanol

We carried out experimental and numerical investigations on the axisymmetric spreading evolution of dynamic spin coating with a single drop of ethanol. The results show that the dynamic spreading process consists of two stages: inertial spreading stage and centrifugal thinning stage. These two stages are connected by a transient state in between characterized by the minimum contact line moving velocity. The Weber number determines the spreading in the first stage, similar to the case of the impact of a drop on a static substrate. The rotational Bond number has a marginal effect on the inertia spreading and the radius at the transient state. In the centrifugal thinning stage, the rotational Bond number dominates the flow while the effect of the Weber number is negligible.

Manufacturing of Complex-Shape PM Products Consisting of Several Powder Elements

The article’s primary purpose is to give a technological assessment of manufacturing complex-shaped parts using powder metallurgy. The process is considered in the example of a complex-shaped product consisting of several elements manufactured separately from the Fe-C-Cu powder mixture and then combined into a single structure. The joining was carried out by impregnation of porous structural elements with the fusion of copper-containing material. It has been demonstrated that the infiltration process is affected by many factors: porosity of structural elements, wettability of their pore channels, fluid flowability of the infiltrating material, and other factors. The research was carried out on the mass products - centrifugal pump stages for oil production. The elements compaction was carried out on hydraulic press at a pressure of 500 MPa, which ensured the average density of the parts after sintering up to 7.8-8.4 g/cm3. During sintering and impregnation, various types of defects of the pieces were detected, which were caused by the excessive thickness of the infiltrating material, different densities of the walls, and insufficient wettability in the connection zones of the elements.The investigations have shown that manufacturing complex components by prefabricating single elements and their subsequent sintering combined with infiltration is feasible. It can be done in a chamber furnace as well as with belt sintering. However, it is necessary to carefully prepare the mold before sintering, choose the infiltrating agent, and analyse possible disadvantages.

Verification and Validation of CFD Modeling for Low-Flow-Coefficient Centrifugal Compressor Stages

In this paper, the numerical model of a centrifugal compressor low-flow stage is verified. The gaps and labyrinth seals were simulated in the numerical model. The task was to determine the optimal settings for high-quality modeling of the low-flow stages. The intergrid interface application issues, turbulence and roughness models are considered. The obtained numerical model settings are used to validate seven model stages for the range of the optimal conditional flow coefficient with Φopt = 0.008–0.018 and the conditional Mach number Mu = 0.785–0.804. The simulation results are compared with the experimental data. The high pressure stage-7 (HPS-7) stage with Φopt = 0.010 and Mu = 0.60 at different inlet pressure of 4, 10 and 40 atm is considered separately. Acceptable validation results are obtained with the recommended numerical model settings; the modeling uncertainty for the polytropic pressure coefficient δη*pol < 4% for the efficiency coefficient δη*pol exceeds the limit of 4% only in the two most low-flow stages, U and V.

On the Correlation Between Spanwise Inducer Incidence and Impeller Diffusion for Ruled Surface and Barreled Sweep-Bow Impeller Design at Inlet Guide Vane-Off-Design

AbstractIn the present paper, three centrifugal stages of high volume flow coefficient are compared to each-other regarding their aerodynamic performance in design point and off-design point conditions at different speed and inlet guide vane (IGV)-setting angle: two stages with full-blade design (no splitter blades) have been numerically designed with different design geometry methodology. One geometry is based on a classical ruling surface design with a linear leading edge, the second geometry based on a fully-three-dimensional surface including a blade bow at the trailing edge and a barreled sweep at the leading edge. According to impeller test rig measurements and computational fluid dynamics (CFD) calculation, the classical ruling surface designed impeller outperforms the more sophisticated centrifugal stage with fully 3D-blade at fully axially guided IGV-flow. In the contrary, at closing IGV-off-design setting angles, toward surge operation, the fully 3D-blade impeller performs with higher efficiency and steeper negative pressure slope. On the search of the geometrical causes for the different aerodynamic performance (especially at IGV-off-design conditions), focus is set on the analysis of IGV-flow-interaction with the inducer flow and impeller diffusion. The one-dimensional analysis of the spanwise flow at the impeller leading edge reveals that, compared with the ruling surface impeller, the fully 3D-blade performs with lower flow incidence losses in favor to IGV-off-design operation than at IGV-neutral position. The streamwise flow analysis confirms the improved flow incidence characteristics of the 3D-blade impeller due to reduction of aerodynamic blockage and entropy production in the vicinity of the impeller leading edge. Based on CFD calculations, a new correlation of secondary flow and flow incidence is proposed, to be used for one-dimensional modeling.

Effect of front impeller seal leakages on centrifugal stage characteristics

One of the main criteria in designing a pump unit is its economic efficiency and reliability. The efficiency of the pump is impacted by losses which appear in the pump and can be classified into three categories: hydraulic, mechanical and volumetric. Volumetric losses in centrifugal pumps appear in impeller annular seals and throttling gaps of hydraulic balancing devices. Decreasing clearance in annular seals could, undoubtedly, reduce the volumetric losses and lead to an increase in pumps efficiency. In duties close to optimal, a volume of leakages is almost negligible for the main flow passing through the hydraulic passage. On the contrary, impact of leakages becomes significant at underloaded duties. This article deals with effect of leakages in impeller front seal on efficiency and head-capacity curve.

Creation a universal technique of predicting performance curves for small-sized centrifugal stages of well oil pump units

The work provided is a continuation the development of research work on the process of pumping high-viscosity liquids and is aimed at creating a universal technique of recalculating the performance curves of dynamic small-sized pumps from water to high-viscosity liquid. The practical need to develop such a technique became relevant after obtaining different results when using existing methods of predicting performance curves for hydrodynamic oil well pumps. The expediency of carrying out studies aimed at clarifying the scope of the technique for calculating the work parameters of a well oil centrifugal pump, which is being developed, is substantiated, and more thorough analysis of the structure of conversion coefficients taking into account the scale factor and flow regime in the hydraulic flow parts of the studied pumps.

The flow research in vane diffusers of centrifugal compressors transonic stages

. Computational fluid and gas dynamics methods are used at all stages of design, including blade machine design: from the creation of a schematic design to a detailed study of all the main units [1, 2]. The industries using refrigeration centrifugal compressors (oil refining, chemical, food) development requires the machines unit capacity, efficiency and reliability increase, the weight and size characteristics and metal consumption decrease. Since this machine type production often has a small-scale or individual character, and the needs for machine specified characteristics maintain during the entire service life exists, design remains an important stage in the creation process. This article is devoted to the possibility of validating the calculations using the numerical gas dynamics methods research. The centrifugal compressor end stage numerical and a full-scale research were made during the investigation; refrigeration centrifugal compressor end stage full-scale investigation carried out by D.A. Kapelkin was chosen as a base of the research [3]. As a result, the diffuser flow numerical simulation results were analyzed and the calculated and full-scale characteristics comparison was carried out. Recommendations for the numerical gas dynamics methods application are given in a particular case, applied to refrigeration centrifugal compressors vane diffusers gas-dynamic calculations.

Numerical study of the equivalent roughness effect on the low-flow centrifugal compressor impeller characteristics

The article presents the results of a numerical study of the effect of equivalent sandgrain roughness on the characteristics of a low-flow centrifugal compressor stage. Low-flow stages are widely used in high-pressure compressors as the last stages. These compressors are used for natural gas booster compressor stations, as well as in technological processes for the production of methanol, ammonia, high - pressure polyethylene, etc. The efficiency of the low-flow stages is lower than that of medium-and high-flow centrifugal compressors stages. Stages operate at high pressure and have low gas volume flow rates. For this reason they have narrow channels of the flow part, significant friction and leakage losses. The study was conducted in the Ansys CFX 19.2 software package. In the first part of the study, the low-flow stage numerical model is validated with the test results. Full-scale tests of the stage were carried out at the LPI-SPbPU earlie. In the second part of the study, impeller equivalent sand-grain roughness numerical study carried out. As a result, the characteristics of the stage were obtained at four different values of equivalent sand-grain roughness ks. The impeller losses were estimated. It is established that when the ks values increase, the polytropic head and efficiency values do not decrease equally over the entire characteristic. Characteristics are significantly reduced in areas of high expenditure and change slightly with minimal expenditure. The internal head coefficient varies slightly depending on ks.

Про вплив форми меридіонального контуру на енергетичні характеристики відцентрового колеса компресора

This work is concerned with the development of approaches to the optimal aerodynamic design of centrifugal compressor wheels, which is due to the use of centrifugal stages in compressors of modern aircraft gas turbine engines and power plants. The aim of this work is a computational study of the effect of the meridional contour shape of a centrifugal compressor wheel on its power characteristics. The basic method is a numerical simulation of 3D turbulent gas flows in centrifugal wheels on the basis of the complete averaged Navier¬–Stokes equations and a two-parameter turbulence model. The computational study features: varying the shape of the hub and tip part of the meridional contour over a wide range, formulating quality criteria as the mean integral values of the wheel power characteristics over the operating range of the air flow rate through the wheel, and a systematic scan of the independent variable range at points that form a uniformly distributed sequence. As a result of multiparameter calculations, it was shown that in the case of a flow without separation in the blade channels of a wheel with a given starting shape of the meridional contour, varying that shape has an insignificant effect on the wheel power characteristics. It is pointed out that in similar cases it seems to be advisable to aerodynamically improve centrifugal wheels by varying the shape of their blades in the circumferential direction rather than in the meridional plane. This conclusion was made using rather a “coarse” computational grid, which, however, retains the sensitivity of the computed results to a variation in the centrifugal wheel geometry. On the whole, this work clarifies ways of further aerodynamic improvement of centrifugal compressor impellers in cases where the starting centrifugal wheel is a well-designed wheel with a flow without separation in the blade channels. The results obtained may be used in the aerodynamic optimization of centrifugal stages of aircraft gas turbine engines.

Design of 1 + 1 / 2 counter rotating centrifugal turbine and performance comparison with two-stage centrifugal turbine

The counter-rotating turbine technology is one of the potential technical measures to improve the performance of aero-engine. Inspired by axial-flow counter-rotating turbine, this paper applied the counter-rotating turbine technology to the centrifugal turbine and carried out the aerodynamic design of the 1 + 1/2 counter-rotating centrifugal turbine stage by theoretical analysis using the air ideal gas as the working fluid. Then the blade profile of 1 + 1/2 counter-rotating centrifugal turbine was designed based on the velocity triangle obtained from theoretical analysis. At last, 1 + 1/2 counter-rotating centrifugal turbine was numerically analyzed and compared with the two-stage co-rotating centrifugal turbine under the same thermal parameters. The results show that the 1 + 1/2 counter-rotating centrifugal turbine has 12.0% less maximum diameter and 1.57% higher efficiency than the two-stage co-rotating centrifugal turbine.

X-sperm Enrichment of Bovine Semen by Percoll Density Gradient Method and Its Effect on Semen Quality, Sex Ratio and Conception Rate

In cattle, sex selection has a significant economic impact when it improves herd capacity of milk or meat production and is commonly used for the production of calves of the desired gender. New separation techniques which present both better accuracy and low costs are necessary. Density gradient centrifugation might be an approach to sexing spermatozoa because of the additional DNA content and volume of X-bearing sperm head. The present study was designed to apply the modified percoll discontinuous density gradient for X-sperm enrichment in cross bred bovine semen. We attempted to amplify the level of X-sperm enrichment by using double centrifugation in percoll gradient. In addition, effect of percoll density gradient on fertility of semen was also evaluated at three stages; before centrifugation (stage I), after 1st centrifugation (stage II) and after 2nd centrifugation (stage III) respectively and ultrasonography was carried out to confirm the sex of fetus at 60-90 days post AI. Semen was collected from two cross bred bovine bulls and 34 cows were inseminated with liquid X-sperm enriched semen after double centrifugation in percoll gradient. 22 cows were inseminated with non-sexed fresh liquid semen (control). Results showed that the volume, progressive motility, live sperms, concentration and HOST reactive sperms significantly (P is less than 0.05) decreased at stage II and stage III compared to stage I. However, no significant (P is greater than 0.05) change was observed in pH and mass motility of semen at all three stages. There was non-significant effect on per cent spermatozoa with intact acrosomal membrane and fully damaged acrosomal membrane at all three stages however, partially damaged acrosomal membrane sperms were significantly (P is less than 0.05) decreased at Stage II and Stage III compared to Stage I. The conception rate significantly (P is less than 0.05) decreased with X-enriched semen (41.17%) compared to non-sexed liquid semen (59.09%). The female sex ratio of calves significantly (P is less than 0.05) increased to 66.66% with X- sperm enriched semen compared to the male percentage of 33.33% with sexed semen and female percentage of 46.15% with non-sexed semen.

Exfoliated graphitic carbon nitride nanosheets for on-line vortex-assisted dispersive micro-solid phase extraction of indium prior to determination by ICP-OES

ABSTRACT A new online vortex-assisted dispersive micro-solid phase extraction method was developed for the preconcentration of trace amounts of indium as a prior step to its determination by inductively coupled plasma-optical emission spectrometry. The methodology is based on the direct adsorption of In(III) ions by the graphitic carbon nitride nanosheets without using any chelating agent. In this method, after dispersion of sorbent particles into the sample solution, the resulting suspension was passed through a membrane filter and subsequently, the adsorbed In(III) ions were eluted from the membrane and directly introduced into the ICP-OES spectrometer. The developed on-line technique facilitates the conventional D-µSPE method by eliminating the centrifugation stage. Under the optimum conditions, the detection limit for the determination of In(III) was found to be 0.32 µg L−1. The developed method was employed for the preconcentration and quantitation of indium in various water samples.