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Influenced by the local angle of attack of the air rudder, a complex separation and reattachment flow will form at the position of the full-motion rudder shaft thermal-protection ring during a hypersonic flight, accompanied by severe aerodynamic heating loads, which is the weak link in the thermal protection design of the air rudder. Taking the flat plate/air rudder shaft thermal-protection ring as the research object, the numerical calculation method was used to study the influence rule of different rudder deflection angles and geometric parameters of the thermal-protection ring′s annular gap on the flow and aerodynamic heating. The numerical calculation was based on the unstructured hybird gird finite volume method. The calculation results and analysis show that the rudder deflection has the greatest effect on the heat flux distribution in the thermal-protection ring. Under the condition of rudder deflection, a reattached flow and high flux region will form at the chamfer of the thermal-protection ring. The area of the high flux region and the flux peak are proportional to the rudder deflection angle. When the rudder deflection angle equals 0°, the airflow at the Z=0 mm cross-section of the annular gap will flow upward into the gap at the bottom of the rudder surface. When the rudder deflection angle is greater than 0°, the incoming flow in the gap at the bottom of the rudder surface will form a vortex in front of the chamfer of the thermal-protection ring, and at the same time the airflow on the flat plate enters the annular gap downward and forms a vortex in the direction of the gap depth. When the rudder deflection angle and the gap width are fixed, the gap depth mainly affects the heat flux at the chamfer of the thermal-protection ring and the annular gap windward side. As the gap depth increases, the flow structure at the Z=0 mm cross-section of the annular gap develps from 2 vortices to 3 vortices. When the rudder deflection angle and the gap depth are fixed, the gap width mainly affects the heat flux at the annular gap windward side. As the gap width increases, the vortex at the Z=0 mm cross-section of the annular gap develops more fully, and the flow structure in the depth direction develops from 3 vortices to 2 main vortices and 2 small vortices at the bottom of the annual gap.

The gas injection effect is the main heat dissipation mechanism of ablative materials, which would significantly affect the thermal insulation characteristics of ablative thermal protection systems. Based on the shock tube wind tunnel, the experimental study on the influence of gas injection on downstream aero-heating was conducted. The influence of factors such as gas injection, mainstream Mach number, Reynolds number was obtained. Combined with numerical simulation results, the correlations of the influence of gas injection on aero-heating were obtained under laminar and turbulent boundary layer flow conditions. The cooling efficiency of gas injection for laminar boundary layer is remarkable. The maximum cooling efficiency for laminar boundary layer is close to 100% when the blowing ratio F=0.483%. The cooling efficiency would decrease sharply when the boundary layer transition occurs because of the strong mixing effect of turbulent boundary layer. The larger the specific heat capacity of cooling gas, the better the cooling effect.

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to prolong the service life of ZrO2 thermal barrier coatings,HS188 alloy was used as the substrate,and NiCrAlY powder (base layer, d50=106 μm) and yttria stabilized zirconia (YSZ,d50=50 μm) were employed as sprayed feeder to prepare NiCrAlY+YSZ thermal barrier coatings using high-energy plasma spraying equipment with a progressive exploration method.The microstructure of the coatings was controlled by adjusting the stand-off distance (85,95,105 and 115 mm) and air-cooling manner (rear air cooling,rear air cooling+gun cooling,front air cooling,and front air cooling+gun cooling). The bonding strength of the coatings was evaluated by the drawing method.The results indicate that under the conditions of long stand-off distance and low cooling rate, it is difficult for the coatings to form a vertical crack structure due to the low instantaneous heating temperature and insufficient quenching on the sample surface.However, when the instantaneous heating temperature reaches the critical value and the air cooling rate is excessive,un-melted spray particles exist.When the stand-off distance is 85 mm and the cooling method is front air cooling, a thermal barrier ceramic coating with vertical crack morphology was obtained on HS188 alloy. Simultaneously,it has a moderate density of vertical cracks, the highest bonding strength and the best toughness. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ballistics / Dandao Xuebao is the property of Journal of Ballistics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the future, high-speed vehicles will develop towards the integration of aviation and aerospace technologies, such as longer range and faster speed, and constantly break through the boundary of flight speed and cruising space. With the continuous increase of flight speed, the thermal load is becoming more and more severe. Meanwhile, the requirements of multi-function integrated design of thermal protection structures and strong constraints on structural quality have put forward new requirements and challenges for thermal protection. In response to these, new features and needs of thermal protection are emerged, and the demand for thermal protection has undergone significant changes. There are obvious gaps in existing technologies, design methods, and recognition of relevant scientific issues, so revolutionary technologies are urgently needed. Therefore, the concept of new thermal barrier was proposed in this paper. It analysed the research status of long time heating, non-ablative heat protection and refined thermal environment prediction, pointed out the specific connotation and important development direction of new thermal barrier, reviewed the new direction and new methods being explored in thermal protection technology, including low ablative/non-ablative technology, system genome material design method, channel-based innovative thermal protection technology, etc. It is believed that solving the new thermal barrier is a scientific and technological problem to break through the limit of existing thermal protection technology, and it is necessary to break through the bottleneck problem of thermal protection of high-speed aircraft with multi-approach combination, multi-method synthesis and multidiscipline crossing. It explores innovative solutions to the problem of new thermal barrier from the aspects of refined thermal environment prediction and control, multi-scale performance prediction of thermal protection materials, new design approach of thermal protection materials, innovative thermal structure, etc. The progress of related research was summarized.

Numerical simulation and related experimental research on supersonic aerodynamic heating are important contents in the development of hypersonic vehicles. The boundary layer flow and heat transfer process in the supersonic aerodynamic heating phenomenon are analyzed, and the effects of the engineering model, gas model, turbulence model, grid scale, calculation scheme, and boundary conditions in aerodynamic heating simulation on the numerical simulation are discussed from the physical point of view. This paper introduces the test equipments commonly used in the research of aerodynamic heating, such as oxygebacetylene flame ablation, radiation heater and high enthalpy wind tunnel, and their advantages and disadvantages, also discusses the similar parameters in the ground simulation test, and points out the reasons for the over high heat flow of the cold wall.

In order to reduce the rain zone noise of wet cooling towers and enhance the heat transfer and ventilation, the influence of sound barriers on the thermal performance of wet cooling towers with synergistic optimization of fillers and water distribution was studied based on threedimensional numerical calculations. It is found that under the working conditions of this research, the sound barrier and the two zone synergistic efficiency scheme can uniformly distribute the temperature field, air flow velocity distribution, and water vapor mass fraction distribution inside the cooling tower;The two zone synergistic efficiency enhancement scheme can to some extent counteract the adverse effect of the noise barrier on the heat transfer performance of the cooling tower, resulting in an average increase of 0. 06℃ and 3. 8% in the circulating water temperature drop and cooling number compared to the original tower, respectively;Although the ventilation capacity of the entire tower has been reduced after the renovation, the distribution of the aerodynamic field is more reasonable, which is more conducive to the heat exchange of the cooling tower. This study can provide reference for the design of a two zone synergistic cooling tower with sound barriers. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Polymer Materials Science & Engineering is the property of Sichuan University, Polymer Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Aero Weaponry is the property of Aero Weaponry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Smart Rail Transit is the property of Smart Rail Transit Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Refractories / Naihuo Cailiao is the property of Naihuo Cailia (Refractories) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Objectives] In order to compare the effects of different plant fibers on the properties of polylactic acid (PLA) composites, three kinds of plant fibers with better properties: rice husk, reed straw and bamboo were used to prepare high content plant fiber/PLA composites (50% plant fiber content). [Methods] The composition of the plant fiber was analyzed. The functional groups and micromorphology of the plant fiber/PLA composite were observed. The mechanical properties, water barrier property and thermal stability of the PLA composites were determined. [Results]Bamboo fiber/PLA composite had the best comprehensive mechanical properties, its flexural strength was 91.37 MPa, which was 17.18% and 40.33% higher than rice husk and reed straw fiber/PLA composite, and its impact strength was 5.06 kJ·m-2, which was 9.49% and 53.56% higher than rice husk and reed straw fiber/PLA composite. The microstructure of bamboo fiber/PLA composite was the densest, and the combination of fiber and PLA was the best. The results showed that the water resistance and thermal stability of the PLA composites were reduced by filling with plant fiber, while the bamboo fiber/PLA composites had better water resistance and heat resistance. [Conclusions] Among the three kinds of high content plant fiber composites, bamboo fiber composite has the best comprehensive performance, which lays a foundation for further expanding the application of PLA composite. [ABSTRACT FROM AUTHOR]

For conventional missile-borne infrared imaging system is affected by the aerodynamic heating problems, the infrared lateral window imaging method is studied. The aerodynamic heating of the spherical blunt body warhead under different flight conditions is calculated by numerical simulation method. And the analysis shows that the high temperature effect in the non-stagnation point area of the head and side is much smaller than that in the stagnation point area of the front, the incoming Mach number affects the generation of the high temperature area, and the flight angle of attack does not change the extreme value of the high temperature area but affects its spatial distribution. A set of infrared lateral window imaging system is proposed and designed, and the imaging effect with high quality is verified by experiments, which provides a new idea for reducing the adverse effect of aerothermal on missile-borne infrared detection. [ABSTRACT FROM AUTHOR]

A finite-difference unsteady coupled heat transfer solver was developed. This solver was utilized to simulate the hypersonic flow over a backward-facing step with a transverse gap, and the unsteady thermal conduction in an infinite circular pipe. The backward-facing step leads to local dramatically changing distributions of aerodynamic parameters and wall heat fluxes. The gas flow in the gap decelerates rapidly along with the increase of the gap depth, and there is rather weak convective heat transfer at the bottom of the gap. In the case of hypersonic flow around the infinitely long circular pipe, there exists large temperature gradient in the boundary layer, and the wall temperature increases with time, otherwise the aerodynamic parameters outside the boundary layer change quite slightly. The predicted results are in good agreement with the tested data. The comparison between numerical simulation results and tested data verifies the calculation ability of the developed solver. [ABSTRACT FROM AUTHOR]

Due to the large flutter boundary variation and the difficulty of conducting flutter tests on the ground of hyper-sonic vehicles, the thermal flutter test technology of wing surface structure on the ground is studied. Firstly, the aerodynamic heating of the structure is analyzed based on the engineering method, and then the thermal flutter characteristics of the structure are evaluated. Considering the influence of structure temperature rise on the actual flight, an aerodynamic force comprehensive optimization order reduction algorithm based on multi-condition points is established to ensure the accuracy of aerodynamic force simulation during the whole temperature rise process. By establishing a multi-point coordinated control system based on the fuzzy logic proportional integral derivative (PID) control, the excitation force controller of the time-varying system in the process of temperature rise is designed. Finally, the ground flutter test system is built, and the thermal flutter characteristics of the structure are tested according to the typical flight conditions. The relative error between the test results and the simulation results is about 10%. [ABSTRACT FROM AUTHOR]

Thermoplastic composites have excellent mechanical properties and are ideal structure materials for reusable launch vehicles. The research of mechanical behavior has attracted tremendous attention in the fields of solid mechanics and material sciences worldwide. In this paper, the prediction methods of macro-mechanical properties, plastic constitutive relations, damage and fracture mechanical behavior, and analysis of mechanical behavior of typical structures of thermoplastic composite are reviewed. At present, many important key problems need to be solved, such as accurate prediction of macroscopic mechanical properties of thermoplastic composites, reasonable characterization of elastoplastic damage mechanical behavior of thermoplastic composites, and simulation of mechanical behavior of thermoplastic composite structures in complex multi-field coupling environment such as aerodynamic heating, overload and impact. Future research can be carried out from the following aspects: (1) to establish a unified macro and micro mechanical property prediction model of thermoplastic composites, (2) carry out macro and meso-mechanical analysis of carbon nanotubes reinforced thermoplastic composites, (3) study the mechanical behavior of thermoplastic composites under typical multifield coupling environment such as thermodynamic coupling, (4) carry out structure-level experimental research on thermoplastic composites. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The calculation of aerodynamic force and aerodynamic heating for flight vehicles round trip to Earth􀆳s atmosphere （over different flow regimes） is one of the challenges and hotspots in computational fluid dynamics. Since the flow scenarios faced by such vehicles are no longer purely continuous flow or rarefied flow， neither the Navier-Stokes equations’ solver nor the direct simulation Monte Carlo （DSMC） method can obtain accurate results. In recent years ，based on the Boltzmann model equation， which is independent of the continuity hypothesis， various numerical approaches have been developed to simulate fluid flow problems in all flow regimes by discretizing this equation in both physical space and velocity space. This paper reviews and analyzes the research progress of this kind of algorithm， including the gas kinetic unified algorithm （GKUA），the unified gas kinetic scheme （UGKS） and the improved discrete velocity method （IDVM）. It focuses on the basic ideas and the implementation of these methods and pays attention to their current progress and applications. At the same time， the IDVM is further extended to simulate the unsteady flows in all flow regimes. Finally， some problems existing in this kind of algorithm are discussed and the prospect for work in the future is proposed. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Aeronautical Materials is the property of Editorial Board of Journal of Aeronautical Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aerodynamic heating effect of the aircraft during supersonic flight has a great impact on the structural strength and thermal protection design. The aerodynamic thermal environment in the real state needs to consider the coupling of the external flow field and the structure and the influence of the boundary conditions of the inner wall surface. The S-A turbulence model is used to solve the Navier-Stokes equation. The coupling of the flow field and the solid wall is used to realize the coupled numerical analysis of the external flow field and the structural field. The coupling numerical study of the supersonic flow aerodynamic heating of three different airfoils is carried out, and the aerodynamic thermal effects of the inner wall surface of the airfoil under different thermal boundary conditions are compared. The results show that different airfoils have aerodynamic thermal effects similar to aerodynamic forces. The boundary condition of the inner wall considering convective heat transfer is the closest to reality; considering the fuel tank of the wing is full, the heat flux at the leading edge of the 3D wing can be up to 4 200 W/m2.

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of National University of Defense Technology / Guofang Keji Daxue Xuebao is the property of NUDT Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To study the impact of low speed ejection on aerodynamic heating of hypersonic aircrafts，the flat injecting of large area under hypersonic flow condition is numerical simulated in this paper. The influence of ejecting pore structure，incidence angle and injecting inlet velocity on boundary layer flow field are discussed. Wall heat flux under different ejecting pore structures variation of ejecting factors and flow parameters with inlet velocity are obtained. The results show that low speed gas ejecting can relieve the aerodynamic heating situation of injecting regional wall and the downstream wall to some extent. The bigger the inlet velocity，the better the thermal reduction will be. As for four ejecting pore structures the wall heat flux is the lowest in ejecting pore structure 4（surface ejecting pore structure），the other three ejecting cooling effect are basically quite. The thermal reduction of angle of attack α = 10° is obviously better than the state of α =0° . When injecting inlet velocity is 20 m/s，the injecting factor of injecting area is about 0.23，which means the averaged wall heat flux decreases about 23% under α =0°. And the injecting factor of injecting area is about 0.45 which is about double of the value of α=0°. [ABSTRACT FROM AUTHOR]

The division iterative marching method on aerodynamic heating and structural heat transfer for the thermal environment of the cone body is presented. The flow field is calculated by the finite volume method. Spatial discretization scheme uses AUSM + . Explicit multi - step Runge - Kutta is used to calculate time iteration scheme. However，the structural heat transfer is calculated by the finite element method. Besides， the data exchange on the coupled wall is conducted by the interpolation method based on the virtual space. The verification example on the circular tube is analyzed，and the relative errors between the calculated values and corresponding test values for the heat flux and temperature of the stagnation point are 1.34% and 4.95% respectively at 2 s. Finally，the analysis on thermal environment of the straight biconic body is conducted. The initial wall heat flux is well matched with the experimental result，and the relative error between calculated value and experimental value at stagnation point is 3.1%. The temperature at the stagnation point increases with the time，and the upward trend slows down gradually. Finally it tends to the steady-state value. The time almost has no influence on the wall pressure，but the wall heat flux decreases with the increase of the time. [ABSTRACT FROM AUTHOR]

Pre-pressurization rise process of the liquid oxygen stored in a tank is simulated through 3D CFD simulations. The phase transformation rate and temperature stratification of liquid oxygen are specified. The results suggest that evaporation rate of the liquid oxygen is fluctuating around 0.012 6 kg/s under the aerodynamic heating boundary condition. The liquid oxygen boiling rate near the wall is also investigated and averagely reaches 0.086 kg/s in the whole process, which is consistent with the tank heat leakage. The temperature stratification is observed when the high-temperature gas pressurization enters the tank by a diffuser. The liquid oxygen temperature in the gas-liquid interface increases from 89.51 K to 93.61 K. The average increasing rate of the liquid temperature is 0.022 K/s for 183 s after the pre-pressurization. [ABSTRACT FROM AUTHOR]

Aero-engine is increasingly to face the trend of higher load， efficiency and reliability， so that multi-field coupling problems are taken more and more attention. This research took the semal system of an aero-engine compressor as the research object， 3D flow field in the single sector and structural models were established by the method of cyclic symmetric. Considering the influence of former stator wakes， compressor flow field was simulated. Based on the Kriging model， load transfer of aerodynamic pressure and temperature achieved from flow field to blade structure. Then the coupling effects of aerodynamic pressure， temperature and centrifugal stress on compressor fatigue life were discussed. The results show that the load transfer with the Kriging model can meet the requirement of multi-field coupling dynamic calculation. In the low pressure compressor， centrifugal force plays a major role on deformation and stress of semal system， and bending stress induced by aerodynamic pressure and temperature can counteract part of bending stress induced by centrifugal force. However， temperature load makes the maximal deformation of blade-disc system increase. [ABSTRACT FROM AUTHOR]

Thermal barrier coatings (TBC) are crucial materials of high-temperature components in aero-engine. Its quality and performance is therefore significant for nondestructive testing (NDT). This paper systematically reviews the history and research state of NDT techniques in the field of TBC. Moreover, it mainly introduces the development direction of NDT techniques which apply to the inspection of thermal grown oxide (TGO) and residual stress in thermal barrier coating. [ABSTRACT FROM AUTHOR]

Through the analysis of properties of unsteady thermal response of ceramic thermal protection structure: Low thermal conductivity and Bi>100, the coupling effect between air and solid is assumed to be ignored. Besides, the surface temperature of solid is considered to be the same with the fluid temperature, and then according to these conditions, an uncoupled approach is brought forward to solve the unsteady thermal response of structure by using the first kind boundary condition. Compared with the results of tight coupled method for the problem of a two-dimensional cylinder with hypersonic flow, this new uncoupled approach not only has high accuracy in the results of thermal response and temperature distribution, but also saves much computing time and meets the practical demand for the design of structure thickness and prediction of aerodynamic heating, which show this method has a great value in the engineering application. [ABSTRACT FROM AUTHOR]

To get the surface temperature characteristics of projectile flying at high rotational speed, based on the six degree of freedom (6-DOF) rigid body trajectory model, the heat balance equations were established by using node thermal network method. With the heat exchange theory of flow around a cylinder, the influence of rotation was considered for the calculation of aerodynamic heating. The temperature field distribution under the control of trajectory data and airflow properties was obtained by solving the trajectory equations and the heat balance equations simultaneously. Finally, the factors which have impact on the surface average temperature field, including launching velocity, initial rotational speed, launching angle and airflow temperature, were also studied. The results show that the surface temperature increases with launching velocity non-linearly. The temperature gradient is inversely proportional to the distance from the warhead. The bigger the initial rotational speed is, the higher the peak temperature and the rate of temperature change are. The higher the airflow temperature is, and the smaller the launching angle is, the higher the average temperature is. [ABSTRACT FROM AUTHOR]

An axial cooling fan on multiple units was designed based on one-dimensional calculation and three-dimensional numerical simulation. The influence of constant circulation exponent on aerodynamic performance of axial cooling fan was analyzed. Three-dimensional model was presented based-on the one-dimensional calculation. Numerical simulation and thorough analysis were carried out on the blower with software NUMECA. The optimized projects were presented. The model machine was based on geometry parameter of the best project. The performance experiment of the improved blower was studied. The model machine testing results show that the performance of the optimized axial cooling fan is better than that of the original one. Especially the efficiency is improved by 3%. The inlet and outlet flow field is much steady. The optimized blower is better than that of the same style of the imported one in performance. [ABSTRACT FROM AUTHOR]