Attenuation effects of perforated plates with heterogeneously distributed holes on combustion instability in a spray flame combustor

Hao Zhou,Zihua Liu,Hao Fang,Chengfei Tao,Mingxi Zhou,Liubin Hu 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.11

Perforated plates have been widely used in combustors to attenuate harmful sounds. In this study, the acoustic absorption capability of plates with heterogeneously distributed holes under bias flow was evaluated in an impedance tube, and the sound attenuation effect of each plate located in the liquid fuel combustor inlet section was experimentally studied. The perforated plate with heterogeneously distributed large holes showed the best control effect under the designed experimental conditions. After control, the peak dynamic pressure in the chamber and plenum decreased by 90 % and 75 %, respectively, and the reduction in the heat release fluctuation was 60 %. When the primary air flow rate deviated from the optimal value, the plate with large holes still reduced the pressure amplitude in the chamber by approximately 70 %. It was also found that installing the perforated plate with a back cavity had the dual effect of gaining and damping combustion instability.

Seismic Response Analysis Method for Lining Structure in Underground Cavern of Hydropower Station

Hao Zhou,Ming Xiao,Yang Yang,Guoqing Liu 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.3

Based on the analysis of joint shear test, the complex shear strength model of the interface between surrounding rock and lining structure, considering the interfacial bonding characteristics, shear failure mechanism and seismic dynamic deterioration effect, is established. And based on the dynamic contact force method, the dynamic calculation method of contact surface is presented, which is suitable for the dynamic analysis of the contact system between surrounding rock and lining of underground powerhouse. Then the dynamic numerical simulation method for the lining structure of underground powerhouse is formed by coupling the complex shear strength model with the dynamic calculation method of the contact surface. By using this method and based on the independently developed dynamic calculation platform of underground powerhouse, the evolution process and characteristics of seismic damage of lining structure of Yingxiuwan underground powerhouse are studied. At the same time, the numerical simulation analysis is carried out on the vibration damping measures of the lining structure. The results shows that the dynamic numerical simulation method for lining structure is effective and reasonable. In addition, the idea on the aseismic design of lining structure of underground powerhouse is put forward.

Waypoints Following Guidance for Surface-to-Surface Missiles

Zhou, Hao,Khalil, Elsayed M.,Rahman, Tawfiqur,Chen, Wanchun The Korean Society for Aeronautical Space Sciences 2018 International Journal of Aeronautical and Space Sc Vol.19 No.1

The paper proposes waypoints following guidance law. In this method an optimal trajectory is first generated which is then represented through a set of waypoints that are distributed from the starting point up to the final target point using a polynomial. The guidance system then works by issuing guidance command needed to move from one waypoint to the next one. Here the method is applied for a surface-to-surface missile. The results show that the method is feasible for on-board application.

Energy absorption investigation of square CFRP honeycomb reinforced by PMI foam fillers under quasi-static compressive load

Hao Zhou,Rui Guo,Kuo Bao,Haiyang Wei,Rongzhong Liu 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.33 No.6

A type of hybrid core made up of thin-walled square carbon fiber reinforced polymer (CFRP) honeycomb and Polymethacrylimide (PMI) foam fillers was proposed and prepared. Numerical model of the core under quasi static compression was established and validated by corresponding experimental results. The compressive properties of the core with different configurations were analyzed through numerical simulations. The effect of the geometrical parameters and foam fillers on the compressive response and energy absorption of the core were analyzed. The results show that the PMI foam fillers can significantly improve the compressive strength and energy absorption capacity of the square CFRP honeycomb. The geometrical parameters have marked effects on the compressive properties of the core. The research can give a reference for the application of PMI foam materials in energy absorbing structures and guide the design and optimization of lightweight and energy efficient cores of sandwiches.

Crystal elasticity analysis of contact fatigue behavior of a wind turbine gear

Hao Zhou,Peitang Wei,Huaiju Liu,Caichao Zhu,Wei Wang 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.10

Rolling contact fatigue is the main factor limiting the service performance of wind turbine gears. The inherent microstructure of the gear material has a significant impact on its contact fatigue behavior and service life. In this research, a two-dimensional contact fatigue model considering the gear material microstructure and the elasticity anisotropy characteristics of the crystals is established. The predicted results reveal a pronounced scatter phenomena of the stress distribution in the subsurface and the localized stress concentration at the grain boundaries caused by crystal elasticity anisotropy. Changes of initial grain orientations can cause a certain fluctuation in the critical stress and its depth in the subsurface. Under the same load level, the gear contact fatigue life calculated by the crystal elasticity anisotropy model is lower compared to isotropic material. Considering the anisotropic properties of the crystal elasticity, an S-N curve based on the maximum contact pressure for the wind turbine gear is drawn.

Control of thermoacoustic instability of liquid-spray flame with porous sound absorber

Hao Zhou,Hao Fang,Dongliang Wei,Zihua Liu,Zhaowen Wang,Hanxiao Meng 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.8

A kind of porous sound absorber was studied to control the thermoacoustic oscillation of liquid mist flame, which combined natural fibrous materials and perforated plate. It could optimize the sound absorption characteristics of fibrous materials by adding perforated plate and air cavity. The influences of the interlayer and back cavity depth of two kinds of fibrous materials with the mass of 20, 30, 40 g were investigated experimentally in an impedance tube and applied to control the oscillating ethanol flame. The results showed that the best depth of interlayer and back cavity were 20 cm and 30 cm, respectively. The addition of two kinds of fiber sandwich structures could reduce the amplitude of the sound pressure oscillation in the combustion chamber by 89.2 % and 92.6 %, as well as 88.0 % and 91.2 % in the plenum chamber, meanwhile, restrained the flame heat release fluctuation by 73 %. It was proved that the porous sound absorber could act as a damp in the acoustic transmission path and suppress the sound source.

Waypoints Following Guidance for Surface-to-Surface Missiles

Hao Zhou,Elsayed M. Khalil,Tawfiqur Rahman,Wanchun Chen 한국항공우주학회 2018 International Journal of Aeronautical and Space Sc Vol.19 No.1

The paper proposes waypoints following guidance law. In this method an optimal trajectory is first generated which is then represented through a set ofwaypoints that are distributed from the starting point up to the final target point using a polynomial. The guidance system then works by issuing guidance command needed to move from one waypoint to the next one. Here the method is applied for a surface-to-surface missile. The results show that the method is feasible for on-board application.

Sol-Gel Encapsulation as Matrix for Potentiometric Nitrite-Selective Membranes Doped with Chloro (5, 10, 15, 20-Tetraphenylporphyrinato) Cobalt (III)

Hao Zhou,Mark E. Meyerhoff,Kai-shun Bi,Sung Bae Park 한국전기화학회 2009 한국전기화학회지 Vol.12 No.4

Organic-inorganic hybrid sol-gel matrices were used as hosts for chloro (5, 10, 15, 20-tetraphenylporphyrinato) cobalt (III) (Co[TPP]Cl), a known ionophore for nitrite. The sol-gel precursor was prepared by the reaction of (3-isocyanopropyl) triethoxysilane with 1,4-butanediol. An appropriate amount of the anion-exchanger, tridodecylmethylammonium chloride (TDMAC) and the plasticizer, tributylphosphate (DBP) were used as membrane additives. On mixing with an acidic catalyst, the sol-state precursors slowly gelled, yielding a membrane in which the active components, Co[TPP]Cl and TDMAC, were encapsulated. The performances of the sol-gel membrane-based electrodes were compared to those of Co[TPP]Cl-based poly(vinyl chloride) (PVC) membrane electrodes. Membranes with a molar ratio of Co[TPP]Cl: TDMAC (1 : 0.1) showed reasonable response slopes toward nitrite. The response slopes were typically 53 mV/ decade between 10−5.4 and 10−1.0 M. Selectivities toward nitrite over hydrophilic and small anions such as chloride were somewhat inferior to those observed with PVC-based membranes, but selectivities over lipophilic anions were quite similar. Reduced asymmetry potentials due to protein adsorption were found to occur with the sol-gel matrix relative to PVC-based films when the sensors were employed as a detector in flow-through configuration.

Multi-objective geometry optimization of composite sandwich shielding structure subjected to underwater shock waves

Hao Zhou,Rui Guo,Wei Jiang,Rongzhong Liu,Pu Song 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.44 No.2

Multi-objective optimization was conducted to obtain the optimal configuration of a composite sandwich structure with honeycomb-foam hybrid core subjected to underwater shock waves, which can fulfill the demand for light weight and energy efficient design of structures against underwater blast. Effects of structural parameters on the dynamic response of the sandwich structures subjected to underwater shock waves were analyzed numerically, from which the correlations of different parameters to the dynamic response were determined. Multi-objective optimization of the structure subjected to underwater shock waves of which the initial pressure is 30 MPa was conducted based on surrogate modelling method and genetic algorithm. Moreover, optimization results of the sandwich structure subjected to underwater shock waves with different initial pressures were compared. The research can guide the optimal design of composite sandwich structures subjected to underwater shock waves.

Analysis of thermal performance and thermal stress using two-dimensional thermoelastic model for a 50 MWe external cylindrical solar receiver

Hao Zhou,Yuhang Zuo,Yawei Li,Mingxi Zhou 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.10

The thermal stress arisen from highly inhomogeneous solar radiation and temperature distribution during operation is mainly responsible for the failure of the central receiver. In the present study, the analytical approximation method, finite volume method and 2D thermoelastic analytical approach were used in combination to obtain the thermal characteristics of a 50 MWe external cylindrical receiver. The results demonstrated that the direct normal irradiance and tube surface absorptivity significantly affected the thermal stress. The axial distribution of the equivalent thermal stress at θ = 0° consisted with the surface solar flux distribution, and the maximum equivalent stress was underestimated by 30.0 % with the homogeneous surface solar flux distribution. Compared with molten salt flowing into the receiver from the south, the maximum equivalent stress and maximum wall temperature of molten salt flowing from the north are 16.3 % higher and 8.1 % lower, respectively.