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Thermodynamics-Acoustics Coupling Studies on Self-Excited Combustion Oscillations Maximum Growth Rate

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Journal of Thermal Science 2022年第5期31卷 1591-1603页

作者： zhao dan Department of Mechanical Engineering College of EngineeringUniversity of CanterburyPrivate Bag 4800Christchurch8041New Zealand

Unlike electric vehicles and electric aircrafts,hydrocarbon-fuelled(fossil)engine systems are much *** conducting one-step chemical reaction-thermodynamics-acoustics coupling studies and experimental measurements,we explore the universal physics of how hydrocarbon-fuelled combustion is a noise *** also explain that how combustion-sustained noise at a particular frequencyωis intrinsically *** frequencies correspond to the acoustic resonance nature of the *** find that a reacting gas in which the rate of chemical reacting increases with temperature is intrinsically and naturally unstable with respect to acoustic wave motion,since its modal growth rateαis greater than *** disturbances tend to exponentially ***(αt)increase first and then are limited by nonlinear effects and finally grow into limit cycle *** growth rateαis found to increase first and then decrease with the gradient of the heat release rate with respect to the temperature change,*** *** maximum(α/ω)_(max)depends on the specific heat ratioγ,which is related to the speed of *** unstable nature could be changed by introducing some acoustic dissipative/damping mechanisms,such as the boundary layer viscous drag and boundary *** is shown that such losses could lead to increased critical heat capacity,below which stable combustors can be ***,the acoustical energy consisting of both potential and kinetic energy is found to grow exponentially faster by 100%than the acoustic disturbance amplitude.

关键词： thermodynamics acoustics hydrocarbon chemical reaction energy conversion thermo-acoustics

Temperature Dependence of Laminar Burning Velocity in Ammonia/Dimethyl Ether-air Premixed Flames

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Journal of Thermal Science 2022年第1期31卷 189-197页

作者： CAI Tao zhao dan Department of Mechanical Engineering College of EngineeringUniversity of CanterburyChristchurch 8041New Zealand

The combustion of ammonia(NH3)has attracted wide interest in fuel vehicle engines,marine engines,and power generators to mitigate carbon dioxide ***,the relatively low laminar flame speed presents a technical barrier for this renewable fuel to be used in *** work is concerned with numerical examining the effects of elevating inlet temperature on the laminar burning velocity of NH3/air flames with various contents of dimethyl ether(DME)using ID freely propagating flame calculations,and to shed light on the flame enhancement *** this,the mechanism is first validated by comparing the numerical predictions with experimental *** show that increasing the inlet temperature has a positive effect on the laminar burning velocity of pure NH3/DME/air *** is revealed that elevating inlet temperature contributes to a higher adiabatic flame temperature,which is beneficial to the overall chemical reaction ***,the thermal diffusivity of the binary mixture is observed to increase substantially as *** kinetic and sensitivities analyses reveal that the inlet temperature has a minimal effect on the reaction pathway,leading to the relative importance of the dominant chain branching over terminating reaction steps to be varied *** present work confirms that the flame speed enhancement with increasing inlet temperature is primarily the synergetic result of the thermal and diffusion effects,rather than the chemical effect.

关键词： ammonia dimethyl ether laminar burning velocity temperature dependence kinetic analyses

Temperature Difference and Stack Plate Spacing Effects on Thermodynamic Performances of Standing-Wave Thermoacoustic Engines Driven by Cryogenic Liquids and Waste Heat

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Journal of Thermal Science 2022年第5期31卷 1434-1451页

作者： GUO Lixian zhao dan BECKER Sid Department of Mechanical Engineering College of EngineeringUniversity of CanterburyPrivate Bag 4800Christchurch8041New Zealand

The standing-wave thermoacoustic engines(TAE)are applied in practice to convert thermal power into acoustic one to generate electricity or to drive cooling *** there is a number of existing numerical researches that provides a design tool for predicting standing-wave TAE performances,few existing works that compare TAE driven by cryogenic liquids and waste heat,and optimize its performance by varying the stack plate *** present work is primarily concerned with the numerical investigation of the performance of TAEs driven by cryogenic liquids and waste *** this,three-dimensional(3-D)standing-wave TAE models are ***-and time-independence studies are conducted *** validations are then performed by comparing with the numerical results available in the *** validated model is then applied to simulate the standing-wave TAEs driven by the cryogenic liquids and the waste heat,as the temperature gradientΔT is *** is found that limit cycle oscillations in both systems are successfully generated and the oscillations amplitude is increased with increasedΔ*** is identified with acoustic streaming and the flow reversal occurring through the *** studied are then conducted between the cryogenic liquid-driven TAE and that driven by waste heat in the presence of the same temperature gradientΔ*** is shown that the limit cycle frequency of the cryogenic liquid system is 4.72%smaller and the critical temperatureΔT_(cri)=131 K is lower than that of the waste heat system(ΔT_(cri)=187 K).Furthermore,the acoustic power is increased by 31%and the energy conversion efficiency is found to increase by 0.42%.Finally,optimization studies on the stack plate spacing are conducted in TAE system driven by cryogenic *** is found that the limit cycle oscillation frequency is increased with the decreased ratio between the stack plate spacing and the heat penetration *** the ratio is set to between 2 and

关键词： thermoacoustic engine standing-wave cryogenic thermodynamics acoustical energy plate spacing heat transfer acoustic streaming

Non-fragile guaranteed cost control for uncertain neutral large-scale interconnected systems

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Journal of Systems Engineering and Electronics 2010年第4期21卷 635-642页

作者： dan zhao Qingling Zhang Heli Hu Chunyuan zhao Department of Fundamental Teaching Shenyang Institute of Engineering Shenyang 110136 P. R. China Institute of Systems Science Northeastern University Shenyang 110004 P. R. China Key Laboratory of Manufacturing Industrial Integrated Automation Shenyang University Shenyang 110044 P. R. China

This paper focuses on the problem of non-fragile decentralized guaranteed cost control for uncertain neutral large-scale interconnected systems with time-varying delays in state,control input and interconnections.A novel scheme,viewing the interconnections with time-varying delays as effective information but not disturbances,is *** on Lyapunov stability theory,using various techniques of decomposing and magnifying matrices,a design method of the non-fragile decentralized guaranteed cost controller for unperturbed neutral large-scale interconnected systems is proposed and the guaranteed cost is *** further results are derived for the uncertain case from the criterion of unperturbed neutral large-scale interconnected ***,an illustrative example shows that the results are significantly better than the existing results in the literatures.

关键词： neutral large-scale interconnected systems nonfragile decentralized guaranteed cost control time-varying delay linear matrix inequality(LMI).

Identification of differentially expressed metastatic genes and their signatures to predict the overall survival of uveal melanoma patients by bioinformatics analysis

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International Journal of Ophthalmology(English edition) 2020年第7期13卷 1046-1053页

作者： dan-dan zhao Xin zhao Wen-Tao Li Shanxi Eye Hospital Taiyuan 030001Shanxi ProvinceChina Datong Second People’s Hospital Datong 037006Shanxi ProvinceChina Taiyuan University of Science and Technology Taiyuan 030051Shanxi ProvinceChina

AIM:To identify metastatic genes and mi RNAs and to investigate the metastatic mechanism of uveal melanoma(UVM).METHODS:GSE27831,GSE39717,and GSE73652 gene expression profiles were downloaded from the Gene Expression Omnibus(GEO)database,and the limma R package was used to identify differentially expressed genes(DEGs).Gene Ontology(GO)term enrichment analysis and Kyoto Encyclopedia of Genes and Genomes(KEGG)pathway analysis were performed using the DAVID online tool.A comprehensive list of interacting DEGs was constructed using the Search Tool for the Retrieval of Interacting Genes(STRING)database and Cytoscape *** Cytoscape MCODE plug-in was used to identify clustered sub-networks and modules of hub genes from the proteinprotein interaction *** online software was used for survival analysis of UVM patients(n=80)from the The Cancer Genome Atlas(TCGA)*** R online software was used to find that the mi RNAs were associated with UVM prognosis from the TCGA *** Scan Human 7.2 software was then used to identify the mi RNAs targeting the ***:There were 1600 up-regulated genes and 1399 down-regulated *** up-regulated genes were mainly involved in protein translation in the cytosol,whereas the down-regulated genes were correlated with extracellular matrix organization and cell adhesion in the extracellular *** the 2999 DEGs,five genes,Znf391,Mrps11,Htra3,Sulf2,and Smarcd3 were potential predictors of UVM ***,three mi RNAs,hsa-mi R-509-3-5 p,hsa-mi R-513 a-5 p,and hsa-mi R-1269 a were associated with UVM ***:After analyzing the metastasis-related enriched terms and signaling pathways,the up-regulated DEGs are mainly involved in protein synthesis and cell proliferation by ribosome and mitogen-activated protein kinase(MAPK)***,the down-regulated DEGs are mainly involved in processes that reduced cell-cell adhesion and promoted cell migration in the extracellular matrix t

关键词： gene ontology bioinformatics uveal melanoma protein-protein interactions network survival analysis

Mitigating self-excited flame pulsating and thermoacoustic oscillations using perforated liners

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Science Bulletin 2019年第13期64卷 941-952页

作者： dan zhao Ephraim Gutmark Arne Reinecke Department of Mechanical Engineering College of EngineeringUniversity of CanterburyChristchurch 8140New Zealand Department of Aerospace Engineering and Engineering Mechanics University of CincinnatiCincinnatiOH 45221-0070USA School of Mechanical and Aerospace Engineering Nanyang Technological UniversitySingapore 639798Singapore

Open-loop control of self-excited flame pulsating oscillations and thermo-acoustic instability is considered in this *** performance of the control strategy is numerically evaluated in a 2 D Rij ke-type combustor with a perfo rated pipe *** is found that approximately 38 dB sound pressure level(SPL)reduction can be achieved by actively tuning the cooling flow through the perforated ***,the vorticity-induced damping performance is contributing to the breaking up of flame-acoustics ***,the shedding of vortices is not uniformly distributed along the perforated *** apply the control strategy in practice and to validate the findings,experimental studies are performed on a customerdesigned Rij ke-type combustor with a perfo rated liner *** mimic practical engines,a cooling flow generated by a centrifugal pump is provided to pass through the perforated *** tuning the cooling flow rate is found to lead to the unstable combustor being successfully *** is red uced by approximately 35 dB at ω1/2π≈245 Hz,and harmonic thermoacoustic modes are completely *** study is conducted by suddenly re moving the perforated pipe *** combustion system is found to be associated with not only classical thermo-acoustic limit cycle oscillations with a dominant mode at 2.45 × 102 Hz,but also beating oscillations at 1.4 × 1 00 *** is revealed that increasing acoustic losses by implementing the perforated pipe is another critical mechanism contributing to attenuating flame pulsating *** present work opens up an applicable means to attenuate both selfexcited high-frequency thermoacoustic and low-frequency flame pulsating oscillations.

关键词： Flame beating Combustion instability Thermo-acoustic instability Thermal-diffusive instability Perforated pipe Acoustic losses

Ionic thermoelectric materials and devices

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Journal of Energy Chemistry 2021年第10期30卷 88-103,I0003页

作者： dan zhao Alois Würger Xavier Crispin Laboratory of Organic Electronics Linkoping UniversityNorrkoping 60247Sweden Univ.Bordeaux&CNRS LOMA(UMR 5798)F-33405 TalenceFrance Wallenberg Wood Science Center ITNLinköping UniversityNorrköpingSweden

The tremendous amount of wasted heat from solar radiation and industry dissipation has motivated the development of thermoelectric concepts that directly convert heat into *** main challenge in practical applications for thermoelectrics is the high cost from both materials and ***,breakthrough progresses in ionic thermoelectrics open up new possibilities to charge energy storage devices when submitted to a temperature *** charging voltage is internally from the ionic Seebeck effect of the electrolyte between two *** electrolytes with high thermoelectric figure of merit are classified as ionic thermoelectric *** ionic thermoelectric materials are composed of abundant elements,and they can generate hundreds of times larger thermal voltage than that of electronic *** emerging thermoelectric category brings new hope to fabricate low cost and large area heat-to-energy conversion devices,and triggers a renewed interest for ionic *** this review,we summarize the state of the art in the new field of ionic thermoelectrics,from the driving force of the ionic thermodiffusion to material and application *** present a general map of ionic thermoelectric materials,discuss the unique characters of each type of the reported electrolytes,and propose potential optimization and future topics of ionic thermoelectrics.

关键词： Electrolytes Soret effect Thermodiffusion Thermal energy conversion

Large eddy simulations of a turbulent mixing layer periodically excited with fundamental and third harmonic frequency

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Chinese Journal of Aeronautics 2023年第5期36卷 33-40页

作者： Jörg SCHLÜTER dan zhao Abhishek SARKAR School of Engineering Deakin UniversityWaurn Ponds 3216Australia College of Engineering University of CanterburyChristchurch 8041New Zealand School of Mechanical and Aerospace Engineering Nanyang Technological UniversitySingapore

A better understanding of the mixing behavior of excited turbulent mixing layers is critical to a number of aerospace *** studies of excited turbulent mixing layers focused on single frequency excitation or the excitation with fundamental and its second harmonic *** is a lack of detailed studies on applying low and higher frequency *** this study,we have performed large-eddy simulations of periodically excited turbulent mixing *** excitation consists of a fundamental frequency and its third *** have used phase-averaging to identify the vortex structure and strength in the mixing layer,and we have studied the vortex *** different vortex paring mechanisms are observed depending on the phase shift between the two excitation *** influence of these two mechanisms on the mixing of a passive scalar is also *** is found that exciting the mixing layer with these low and high frequencies has initially an adverse influence on the mixing process;however,it improves the mixing further downstream of the splitter plate with the excitation using a phase shift ofΔφ=πshowing the best mixing *** present works shed lights on the fundamental vortex dynamics,and has great potential for aeronautical,automotive and combustion engineering applications.

关键词： Flow control Flow excitation Large eddy simulations Turbulent mixing layer Vortex dynamics

Softening micromechanical constitutive model of stress induced martensite transformation for NiTi single crystal shape memory alloy

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Science China(Physics,Mechanics & Astronomy) 2014年第10期57卷 1946-1958页

作者： ZHU YiGuo ZHANG Yang zhao dan State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering Mechanics Dalian University of Technology

Based on the assumption of laminated microstructure, a micromechanical model of stress induced martensite transformation for NiTi shape memory alloys single crystal is proposed. Elasticity anisotropy and different proper-ties for two phases are considered. Martensite volume fraction is chosen as the internal variable that controls the phase transformation quantitatively. An effective macroscopic elasticity matrix based on the different elasticity characteristics of each phase and the martensite volume fraction are obtained with the help of the perfect interfa-cial relationships. A phase transformation driving force is derived to construct the transformation criterion. The model corresponds to a non-convexity free energy function during phase transformation, so softening behavior can be well simulated by the model. A numerical simulation is implemented for the uniaxial loading of NiTi single crystal alloy according to the model, and simulation results are proved by experimental results of polycrystal with strong {111} texture. Superelasticity, Anisotropy, the evolution of microstructure and softening behavior can be well simulated.

关键词： shape memory alloys softening model laminated microstructures phase transformation