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Aerodynamics of a Tandem-Bladed Axial Compressor Rotor under Circumferential Distortion at Different Rotational Speeds

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Journal of Thermal Science 2024年第4期33卷 1340-1356页

作者： Amit KUMAR Jerry T.JOHN A.M.PRADEEP R.A.D.AKKERMANS Dragan KOZULOVIC Department of Aerospace Engineering Indian Institute of Technology Bombay Department of Automotive and Aeronautical Engineering Hamburg University of Applied Sciences Institute of jet propulsion Bundeswehr University Munich

For most aircraft engines,inflow distortion is inevitable.Inflow distortion is known to degrade the aerodynamic performance and stable operating limits of a compressor.Tandem rotor configuration is an arrangement that effectively controls the growth of the boundary layer over the suction surface of the blade.Therefore,a higher total pressure rise can be achieved through this unconventional design approach involving the splitting of the blade into forward and aft sections.It is expected that the effect of inlet flow distortion would be more severe for a tandem-rotor design due to the greater flow turning inherent in such designs.However,this aspect needs to be thoroughly examined.The present study discusses the effect of circumferential distortion on the tandem-rotor at different rotational speeds.Full-annulus RANS simulations using ANSYS CFX are used in the present study.The performance of the rotor at a particular flow coefficient and different rotational speeds is compared.The total pressure and efficiency are observed to drop at lower mass flow rates under the influence of circumferential distortion.The loss region in each blade passage is mainly associated with the blade wake,tip leakage vortex,secondary flow,and boundary layer.However,their contribution varies from passage to passage,particularly in the distorted sector.At the lower span,the wake width is found to be higher than that at a higher span.Due to the redistribution of the mass flow,the circumferential extent reduces at a higher span.In the undistorted sector,the strength of the tip leakage vortex is significantly higher at the design rotational speed than at lower speeds.The distortion near the tip region promotes an early vortex breakdown even at the design operating condition.This adversely affects the total pressure,efficiency,and stall margin.Under clean flow conditions,this phenomenon is only observed near the stall point.At the design operating condition,the breakdown of the forward rotor tip leakage vortex is detected in four blade passages

关键词： tandem rotor circumferential distortion loss tip leakage vortex vortex breakdown diffusion factor aerodynamics of compressor blade

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Long-term Integration Ability of the Submillimeter Wave Astronomy Satellite (SWAS) Spectral Line Receivers

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Research in Astronomy and Astrophysics 2024年第6期24卷 317-324页

作者： Bing-Ru Wang Di Li Paul F.Goldsmith Jingwen Wu Chao-Wei Tsai Rudolf Schieder Gary J.Melnick National Astronomical Observatories Chinese Academy of Sciences University of Chinese Academy of Sciences Research Center for Astronomical Computing Zhejiang Laboratory jet propulsion laboratory California Institute of Technology Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University KOSMA I.Physik.Institut Universit?t zu K?ln Center for Astrophysics | Harvard & Smithsonian

The Submillimeter Wave Astronomy Satellite（SWAS） was the first space telescope capable of high spectral resolution observations of terahertz spectral lines. We have investigated the integration ability of its two receivers and spectrometer during five and a half years of on-orbit operation. The CI, O2, H2O, and13CO spectra taken toward all observed Galactic sources were analyzed. The present results are based on spectra with a total integration time of up to 2.72 × 10～4hr（■10～8s）. The noise in the spectra is generally consistent with that expected from the radiometer equation, without any sign of approaching a noise floor. This noise performance reflects the extremely stable performance of the passively cooled front end as well as other relevant components in the SWAS instrument throughout its mission lifetime.

关键词： instrumentation: miscellaneous ISM: lines and bands space vehicles: instruments telescopes

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旋转带肋通道流阻特性研究

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风机技术 2024年第2期66卷 51-61页

作者：由儒全许云腾李海旺 National Key laboratory of Science and Technology on Aero Engines Aero-thermodynamics Beihang University Research Institute of Aero-Engine Beihang University Advanced jet propulsion Innovation Center AEAC Tianmushan laboratory

With the development of aero-engines, the turbine inlet temperature continues to rise. In order to ensure the safety and reliability of the turbine blades, cooling structures must be set inside turbine blades to cool them. Heat transfer coefficient and flow resistance are the key parameters to measure the cooling characteristics of internal cooling structures. In this paper, the characteristics of flow resistance in a rotating ribbed channel is presented numerical simulation under different rib spacings, rib angles, and thermal boundary conditions. The results show that, separation and reattachment of fluid between ribs is the key effect of rib spacing on flow resistance. The flow resistance is small when the rib spacing is small, because it's difficult for the fluid to form reattachment between the ribs. With the increase of rib spacing, the reattachment phenomenon is more obvious and the flow resistance increases accordingly. In general,p: e=10 channel has the maximum flow resistance. Secondary flow caused by the ribs is the key factor affecting the flow resistance characteristics with different rib angles. The secondary flow interacts with the main flow and causes flow loss through mixing, thus affecting the flow resistance of the channel. Under static condition, the flow resistance of 60°ribbed channel is the largest. The flow resistance of channel was affected by the temperature rise ratio also. And with the increase of the Ro, the temperature rise ratio has a more obvious effect on the flow resistance of the ribbed channel.When Ro=0.45, the flow resistance of the channel with a temperature rise ratio of 0.4 is 2.4 times that of the channel without temperature rise, while when Ro=0.3, it is 1.6 times, and when Ro=0.15, it is 1.2 times.

关键词： Blade Cooling Ribbed Passage Rotation Flow Resistance Characteristics

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Risk assessment of erosive aggressiveness due to the condensation shock by numerical simulation

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Journal of Hydrodynamics 2022年第2期34卷 200-206页

作者： Wei Zhang Bing Zhu Science and Technology on Water jet propulsion laboratory Marine Design and Research Institute of ChinaShanghai200011China School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai200093China

Cavitation is,for the engineering areas such as fluid machinery and ship propulsion,a known source of erosion.The erosion damage due to cavitation bubble collapse can lead to extreme failure events,implying the replacement of a ship propeller or a turbine in a hydropower plant,all of which are very costly operations.The dynamics of cavitation hydraulic structure is of great importance for cavitation erosion.As a result,the blade surface endures some extremely high stresses,which lead to the cause of wear.Two major mechanisms,re-entrant jet as well as condensation shock,are known to such transient cavitating flow.In the present work we study the latter since less has been reported for the erosion caused by such an unsteady cavitating flow.We adopted an energy transportation equation based method,combined with a collapse event detection strategy,to carry out numerical erosion risk assessment for erosive aggressiveness due to the condensation shock.Comparing with the paint test,our result shows good agreement in the erosive pattern.We further discussed the hydrodynamics of the related flow structures.

关键词： Condensation shock numerical simulation cavitation erosion

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Air Pollution or Global Warming:Attribution of Extreme Precipitation Changes in Eastern China—Comments on “Trends of Extreme Precipitation in Eastern China and Their Possible Causes”

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Advances in Atmospheric Sciences 2015年第10期32卷 1444-1446页

作者： Yuan WANG jet propulsion laboratory California Institute of Technology

The recent study ＂Trends of Extreme Precipitation in Eastern China and Their Possible Causes＂ attributed the observed decrease/increase of light/heavy precipitation in eastern China to global warming rather than the regional aerosol effects. However, there exist compelling evidence from previous long-term observations and numerical modeling studies, suggesting that anthropogenic pollution is closely linked to the recent changes in precipitation intensity because of considerably modulated cloud physical properties by aerosols in eastern China. Clearly, a quantitative assessment of the aerosol and greenhouse effects on the regional scale is required to identify the primary cause for the extreme precipitation changes.

关键词： aerosol effects global warming extreme precipitation

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Microbiome-liver crosstalk:A multihit therapeutic target for liver disease

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World Journal of Gastroenterology 2023年第11期29卷 1651-1668页

作者： Jorum Kirundi Sheida Moghadamrad Camilla Urbaniak Department of Biomedical Research University of BernBern 3014Switzerland Department of Gastroenterology/Hepatology Laboratories for Translational ResearchEnte Ospedaliero CantonaleBellinzona and Faculty of Biomedical SciencesUniversitàdella Svizzera italianaLugano 6900Switzerland Biotechnology and Planetary Protection Group NASA Jet Propulsion LaboratoryPasadenaCA 91011United States ZIN Technologies Middleburg HeightsOH 44130United States

Liver disease has become a leading cause of death,particularly in the West,where it is attributed to more than two million deaths annually.The correlation between gut microbiota and liver disease is still not fully understood.However,it is well known that gut dysbiosis accompanied by a leaky gut causes an increase in lipopolysaccharides in circulation,which in turn evoke massive hepatic inflammation promoting liver cirrhosis.Microbial dysbiosis also leads to poor bile acid metabolism and low short-chain fatty acids,all of which exacerbate the inflammatory response of liver cells.Gut microbial homeostasis is maintained through intricate processes that ensure that commensal microbes adapt to the low oxygen potential of the gut and that they rapidly occupy all the intestinal niches,thus outcompeting any potential pathogens for available nutrients.The crosstalk between the gut microbiota and its metabolites also guarantee an intact gut barrier.These processes that protect against destabilization of gut microbes by potential entry of pathogenic bacteria are collectively called colonization resistance and are equally essential for liver health.In this review,we shall investigate how the mechanisms of colonization resistance influence the liver in health and disease and the microbial-liver crosstalk potential as therapeutic target areas.

关键词： Microbiome Nonalcoholic fatty liver disease Nonalcoholic steatohepatitis Liver disease Microbiome-host crosstalk Gut homeostasis Microbial metabolites

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Identification of partial differential equations from noisy data with integrated knowledge discovery and embedding using evolutionary neural networks

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Theoretical & Applied Mechanics Letters 2024年第2期14卷 90-97页

作者： Hanyu Zhou Haochen Li Yaomin Zhao HEDPS Center for Applied Physics and Technologyand College of EngineeringPeking UniversityBeijing 100871China State Key laboratory for Turbulence and Complex Systems College of EngineeringPeking UniversityBeijing 100871China

Identification of underlying partial differential equations(PDEs)for complex systems remains a formidable challenge.In the present study,a robust PDE identification method is proposed,demonstrating the ability to extract accurate governing equations under noisy conditions without prior knowledge.Specifically,the proposed method combines gene expression programming,one type of evolutionary algorithm capable of generating unseen terms based solely on basic operators and functional terms,with symbolic regression neural networks.These networks are designed to represent explicit functional expressions and optimize them with data gradients.In particular,the specifically designed neural networks can be easily transformed to physical constraints for the training data,embedding the discovered PDEs to further optimize the metadata used for iterative PDE identification.The proposed method has been tested in four canonical PDE cases,validating its effectiveness without preliminary information and confirming its suitability for practical applications across various noise levels.

关键词： PDE discovery Gene Expression Programming Deep Learning Knowledge embedding

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Analysis of an Evaporator-condenser-separated Mechanical Vapor Compression System

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Journal of Thermal Science 2013年第2期22卷 152-158页

作者： Wu Hong Li Yulong Chen Jiang School of jet propulsion Beihang University

An evaporator-condenser-separated mechanical vapor compression (MVC) system was presented. The better effect of descaling and antiscaling was obtained by the new system. This study focused on the method of thermodynamic analysis, and the energy and exergy flow diagrams were established by using the first and second law of thermodynamics analysis. The results show that the energy utilization rate is very high and the specific power consumption is low. Exergy analysis indicates that the exergy efficiency is low, and the largest exergy loss occurs within the evaporator-condenser and the compressor.

关键词：压缩系统分离机械蒸汽压缩冷凝器蒸发器能源利用率除垢防垢第二定律

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Why did life develop on the surface of the Earth in the Cambrian？

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Geoscience Frontiers 2016年第6期7卷 865-873页

作者： Carlo Doglioni Johannes Pignatti Max Coleman Department of Earth Sciences Sapienza University 00185 Rome Italy nasa jet propulsion laboratory California Institute of Technology Pasadena CA 91109 USA nasa Astrobiology Institute USA

Life was limited for most of Earth＇s history, remaining at a primitive stage and mostly marine until about 0.55 Ga. In the Paleozoic, life eventually exploded and colonized the continental realm. Why had there been such a long period of delayed evolution of life？ Early life was dominated by Archaea and Bacteria, which can survive ionizing radiation better than other organisms. The magnetic field preserves the atmosphere, which is the main shield of UV radiation. We explore the hypothesis that the Cambrian explosion of life could have been enabled by the increase of the magnetic field dipole intensity due to the solidification of the inner core, caused by the cooling of the Earth, and the concomitant decrease with time of the high-energy solar flux since the birth of the solar system. Therefore, the two phenomena could be responsible for the growth and thickening of the atmosphere and the development of land surface life.

关键词： Origin of lifeInner core solidificationSolar ionizing radiations

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Numerical Investigation of Electrohydrodynamic (EHD) Flow Control in an S-Shaped Duct

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Plasma Science and Technology 2012年第10期14卷 897-904页

作者：杨晖李锋宋耀颖孙佰刚 School of jet propulsion Beihang University

An electrohydrodynamic （EHD） method, which is based on glow discharge plasma, is presented for flow control in an S-shaped duct. The research subject is an expanding channel with a constant width and a rectangular cross section. An equivalent divergence angle and basic function are introduced to build the three-dimensional model. Subsequently, the plasma physical models are simplified as the effects of electrical body force and work （done by the force） on the fluid near the wall. With the aid of FLUENT software, the source terms of momentum and energy are added to the Navier-Stokes equation. Finally, the original performance of three models （A, B and C） is studied, in which model A demonstrates better performance. Then EHD control based on model A is discussed. The results show that the EHD method is an effective way of reducing flow loss and improving uniformity at the duct exit. The innovation in this study is the assessment of the EHD control effect on the flow in an S-shaped duct. Both the parametric modeling of the S-shaped duct and the simplified models of plasma provide valuable information for future research on aircraft inlet ducts.

关键词： electro hydrodynamic （EHD） S-shaped duct flow control glow discharge plasma total pressure.

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