检索结果-南通市图书馆

Coexisting Phenomena of Surge and Rotating Stall in an Axial Flow Compressor

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2013年第6期22卷 547-554页

作者： Takuya ABE Hiroaki MITSUI Yutaka OHTA graduate student Graduate School of Science and EngineeringWaseda University Department of Applied Mechanics and Aerospace Engineering Waseda University

The unsteady inner flow structure of a single-stage axial flow compressor under the coexisting conditions of surge and rotating stall was experimentally investigated via detailed measurements of the unsteady characteristics and the internal flow velocity fluctuations. The main relevant feature of the tested compressor is a shock tube with a capacity tank connected in series to the compressor outlet through slits and a concentric duplex pipe: surge and rotating stall can both be generated by connecting the shock tube. Research attention is focused on the unsteady behavior of a rotating stall during the surge cycle. The size of the rotating stall cell during the recovery process of an irregular surge cycle was experimentally determined by the circumferential flow velocity fluctuations ahead of the rotor blade. The results suggested that the size of the rotating stall cell at the switching point of the performance curve between large and small cycles is considered to be the key parameter in determining the following surge cycle. In addition, the surge cycle is largely influenced by the unsteady behavior of the rotating stall cell.

关键词： Axial flow compressor Surge Rotating stall Coexisting state of surge and rotating stall

Genetic Algorithm to Optimize the Design of Main Combustor and Gas Generator in Liquid Rocket Engines

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2014年第3期23卷 259-268页

作者： Min Son Sangho Ko Jaye Koo graduate student Korea Aerospace University School of Aerospace and Mechanical Engineering Korea Aerospace University

A genetic algorithm was used to develop optimal design methods for the regenerative cooled combustor and fuel-rich gas generator of a liquid rocket engine. For the combustor design, a chemical equilibrium analysis was applied, and the profile was calculated using Rao's method. One-dimensional heat transfer was assumed along the profile, and cooling channels were designed. For the gas-generator design, non-equilibrium properties were derived from a counterflow analysis, and a vaporization model for the fuel droplet was adopted to calculate residence time. Finally, a genetic algorithm was adopted to optimize the designs. The combustor and gas generator were optimally designed for 30-tonf, 75-tonf, and 150-tonf engines. The optimized combustors demonstrated superior design characteristics when compared with previous non-optimized results. Wall temperatures at the nozzle throat were optimized to satisfy the requirement of 800 K, and specific impulses were maximized. In addition, the target turbine power and a burned-gas temperature of 1000 K were obtained from the optimized gas-generator design.

关键词： Liquid Rocket Engine Main Combustor Gas Generator Optimization Genetic Algorithm

Break-up Characteristics of Gelled Propellant Simulants with Various Gelling Agent Contents

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2010年第6期19卷 545-552页

作者： Inchul Lee Jaye Koo graduate student Korea Aerospace University School of Aerospace and Mechanical Engineering Korea Aerospace University

Gel propulsion systems have many advantages with respect to high performance, the energy management of liquid propulsion systems, storability, high density impulse, and low leakage of liquid propellants. The atomization process provides sufficient contact surface area between the gelled fuel and oxidizer jets. It is important to study how injection characteristics of gelled propellants are related with break-up and spray distribution. The break-up and mixing processes are very important in achieving maximum efficiency and necessitate the careful study of combustion instability. Gelled propellants are non-Newtonian fluids in which the viscosity is a function of the shear rate, and they have a high dynamic shear viscosity which depends on the amount of gelling agent contents. The present study has focused on the break-up process, wave development of ligament and liquid sheets formed by impinging jets with various gelling agent contents. Especially, the break-up processes of the impinging jets at the initial conditions are studied. The break-up process of like-on-like doublet impinging jets are experimentally characterized using non-Newtonian liquids which are mixed by ionized water 98.5 wt%, Carbopol 941 0.5wt% or 1.0wt%, and NaOH(concentration 10%) 1.0wt%. For the like-on-like doublet injector, the generation of a liquid sheet at the impinging point of two jets was observed. The spray shape with elliptical pattern is distributed in a perpendicular direction to the momentum vectors of the jets. Gelled propellant simulants with high viscosity jets are more stable and produce less pronounced surface waves than low viscosity jets. Generally, the break-up length decreased due to the increasing Reynolds number. However, surface waves and atomized droplets increased. Gelled propellant simulants from like-on-like doublet impinging jets have the spray shape of closed rim patterns at low pressure. Also, the rim patterns of spray have no disturbances on the spray sheet. As the

关键词： gelled propellant simulants storability low leakage impinging injector rimless pattern wave-like structure

Noise Reduction and Surge Margin Improvement Using Tapered Diffuser Vane in a Centrifugal Compressor

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2010年第1期19卷 21-25页

作者： Takashi Goto Eri Ohmoto Yutaka Ohta Eisuke Outa Department of Applied Mechanics and Aerospace Engineering Waseda University graduate student Graduate School of Applied Mechanical EngineeringWaseda University

Improvement of surge margin and reduction of interaction tone noise radiated from a centrifugal compressor with a vaned diffuser is discussed from experiments and CFD *** types of one-side tapered diffuser vanes,which are shroud-and hub-side tapered vanes,were used in the *** height of the leading edge of the tapered vanes varied from 100% to 10%.Both types of tapered vanes are effective for the reduction of the interaction tone noise radiated from the compressor,because of the smaller interaction area between impeller-discharge flow and diffuser vane ***,the hub-side tapered diffuser vane suppresses the evolution of the leading-edge vortex,which causes reverse-flow in the diffuser ***,the hub-side tapered diffuser vane,which has an optimized diffuser leading edge shape,can improve the compressor pressure-rise characteristics at low-flow operation and can enlarge the surge margin.

关键词： Centrifugal compressor tapered diffuser vane interaction tone noise CFD

Breakup Structure of Two-phase Jets with Various Momentum Flux from a Porous Injector

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2014年第1期23卷 60-67页

作者： Inchul Lee Dohun Kim Jaye Koo graduate student Korea Aerospace University School of Aerospace and Mechanical Engineering Korea Aerospace University

Spray structure and atomization characteristics were investigated through a comparison of a porous and a shear coaxial injector. The porous injector shows better atomization performance than the shear coaxial injector. To in- crease atomization performance and mixing efficiency of two-phase jets, a coaxial porous injector which can be applicable to liquid rocket combustors was designed and tested. The characteristics of atomization and spray from a porous and a shear coaxial injector were characterized by the momentum flux ratio. The breakup mechanism of the porous injector is governed by Taylor-Culick flow and axial shear forces. Momentum of injected gas flow through a porous material which is composed of sintered metal is radically transferred to the center of the liquid column, and then liquid column is effectively broken up. Although the shapes of spray from porous and shear co- axial jets were similar for various momentum ratio, spray structures such as spray angle and droplet sizes were different. As increasing the momentum flux ratio, SMD from the porous injector showed smaller value than the shear coaxial injector

关键词： Porous injector Shear coaxial injector Breakup mechanism Momentum flux ratio

Mixing Characteristics of Pulsed Air-assist Liquid Jet into an Internal Subsonic Cross-flow

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2010年第2期19卷 136-140页

作者： Inchul Lee Youngsu Kang Jaye Koo graduate student Korea Aerospace University School of Aerospace and Mechanical Engineering Korea Aerospace University

Penetration depth,spray dispersion angle,droplet sizes in breakup processes and atomization processes are very important parameters in combustor of air-breathing *** processes will enhance air/fuel mixing inside the *** results from the pulsed air-assist liquid jet injected into a cross-flow are *** experiments were conducted to a range of cross-flow velocities from 42～136 m/*** is injected with 0～300kPa,with air-assist pulsation frequency of 0～*** frequency was modulated by solenoid *** Doppler Particle Analyzer(PDPA) was utilized to quantitatively measuring droplet ***-speed CCD camera was used to obtain injected spray *** air-assist liquid jet will offer rapid mixing and good liquid jet ***-assist makes a very fine droplet which generated mist-like *** air-assist liquid jet will introduce additional supplementary turbulent mixing and control of penetration depth into a cross-flow *** results show that pulsation frequency has an effect on penetration,transverse velocities and droplet *** experimental data generated in these studies are used for a development of active control strategies to optimize the liquid jet penetration in subsonic cross-flow conditions and predict combustion low frequency instability.

关键词： cross-flow penetration pulsed air-assist liquid jet pulsation frequency

Quantification of Ride Comfort Using Musculoskeletal Mathematical Model Considering Vehicle Behavior

在线全文

学校读者我要写书评

暂无评论

Computer Modeling in Engineering & Sciences 2023年第6期135卷 2287-2306页

作者： Junya Tanehashi Szuchi Chang Takahiro Hirosei Masaki Izawa Aman Goyal Ayumi Takahashi Kazuhito Misaji graduate student Graduate School of Industrial TechnologyNihon UniversityChiba275-8575Japan Hitachi Astemo Ltd.Tochigi321-3325Japan Former graduate student Graduate School of Industrial TechnologyNihon UniversityChiba275-8575Japan College of Industrial Technology Nihon UniversityChiba275-8575Japan

This research aims to quantify driver ride comfort due to changes in damper characteristics between comfort mode and sport mode,considering the vehicle’s inertial *** comfort of riding in an automobile has been evaluated in recent years on the basis of a subjective sensory evaluation given by the ***,reflecting driving sensations in design work to improve ride comfort is abstract in nature and difficult to express ***,we evaluated the human body’s effects while driving scientifically by quantifying the driver’s behavior while operating the steering wheel and the behavior of the automobile while in motion using physical *** this end,we collected driver and vehicle data using amotion capture system and vehicle CAN and IMU *** also constructed a three-dimensional musculoskeletal mathematical model to simulate driver movements and calculate the power and amount of energy per unit of time used for driving the joints and muscles of the human ***,we used comfort mode and sport mode to compare damper characteristics in terms of *** comfort mode,damper characteristics are soft and steering stability is mild,but vibration from the road is not easily transmitted to the driver making for a lighter load on the *** sport mode,on the other hand,damper characteristics are hard and steering stability is comparatively ***,vibration from the road is easily transmitted to the driver,whichmakes it easy for a load to be placed on the *** a result of this comparison,it was found that a load was most likely to be applied to the driver’s *** result in relation to the neck joint can therefore be treated as an objective measure for quantifying ride comfort.

关键词： Human engineering biomechanics driver’s sense of fatigue double lane change musculoskeletal mathematical model

Repetitive traumatic brain injury–induced complement C1–related inflammation impairs long-term hippocampal neurogenesis

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Neural Regeneration Research 2025年第3期20卷 821-835页

作者： Jing Wang Bing Zhang Lanfang Li Xiaomei Tang Jinyu Zeng Yige Song Chao Xu Kai Zhao Guoqiang Liu Youming Lu Xinyan Li Kai Shu Department of Neurosurgery Tongji HospitalTongji Medical CollegeHuazhong University of Science and TechnologyWuhanHubei ProvinceChina Department of Neurosurgery Shanxi Bethune HospitalShanxi Academy of Medical SciencesTongji Shanxi HospitalThird Hospital of Shanxi Medical UniversityTaiyuanShanxi ProvinceChina Department of Pathophysiology School of Basic Medicine and Tongji Medical CollegeHuazhong University of Science and TechnologyWuhanHubei ProvinceChina Institute for Brain Research Wuhan Center of Brain ScienceHuazhong University of Science and TechnologyWuhanHubei ProvinceChina Department of graduate student Chongqing Medical UniversityChongqingChina Department of Basic Medicine School of Medical ScienceHubei University for NationalitiesEnshiHubei ProvinceChina Department of Anatomy School of Basic Medicine and Tongji Medical CollegeHuazhong University of Science and TechnologyWuhanHubei ProvinceChina

Repetitive traumatic brain injury impacts adult neurogenesis in the hippocampal dentate gyrus,leading to long-term cognitive ***,the mechanism underlying this neurogenesis impairment remains *** this study,we established a male mouse model of repetitive traumatic brain injury and performed long-term evaluation of neurogenesis of the hippocampal dentate gyrus after repetitive traumatic brain *** results showed that repetitive traumatic brain injury inhibited neural stem cell proliferation and development,delayed neuronal maturation,and reduced the complexity of neuronal dendrites and *** with repetitive traumatic brain injuryalso showed deficits in spatial memory ***,following repetitive traumatic brain injury,neuroinflammation was enhanced in the neurogenesis microenvironment where C1q levels were increased,C1q binding protein levels were decreased,and canonical Wnt/β-catenin signaling was *** inhibitor of C1 reversed the long-term impairment of neurogenesis induced by repetitive traumatic brain injury and improved neurological *** findings suggest that repetitive traumatic brain injury–induced C1-related inflammation impairs long-term neurogenesis in the dentate gyrus and contributes to spatial memory retrieval dysfunction.

关键词： complement C1 dendrite dentate gyrus hippocampus neural stem cell neurogenesis neuroinflammation neurological function neuron traumatic brain injury

Unsteady Behavior of Surge and Rotating Stall in an Axial Flow Compressor

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2012年第4期21卷 302-310页

作者： Yutaka OHTA Yutaka FUJITA Daisuke MORITA Department of Applied Mechanics and Aerospace Engineering Waseda University 3-4-1 Okubo Shinjuku graduate student Graduate School of Science and Engineering Waseda University 3-4-1 Okubo Shinjuku

Unsteady behaviors as well as unsteady cascade flow fields of a single-stage axial flow compressor were experi- mentally investigated by detail measurements of unsteady performance characteristics and casing wall pressure and internal flow velocity fluctuations. The main feature of the test compressor is a capacity tank connected di- rectly to the compressor outlet in series through slits and a concentric duplex pipe, and also jet nozzles in order to inject compressed air toward the rotor tip region. Research attention is focused on the post-stall characteristics of surge and rotating stall which occur simultaneously. When the compressor was connected to the capacity tank, surge was generated with rotating stall in accordance with the capacitance increment of whole compressor system The surge behavior changed irregularly with throttling valve installed behind the compressor, and several types of surge cycles were observed. In addition, the surge cycle changed by jet injection to the rotor tip region. The re- suits suggested that the blockages of the cascade flow which were generated by a stall cell play an important role in deciding the surge behaviors.

关键词： Axial flow compressor Surge Rotating stall Stall cell Jet injection