In order to reduce the complexity of machine construction and improve the mechanical efficiency, high speed rotation machineries usually implement self-acting gas bearings to substitute the traditional oil-lubricated ...
详细信息
In order to reduce the complexity of machine construction and improve the mechanical efficiency, high speed rotation machineries usually implement self-acting gas bearings to substitute the traditional oil-lubricated bearings. This paper presents test results of a gas thrust bearing with viscoelastic support which is designed for high speed turbo-machinery. The gas bearing, which belongs to compliant foil bearings, consists of a top thin metal foil and a bottom thin rubber foil. Static and stability experiments are conducted on a high speed gas turbine test rig. The static results indicate that the structural stiffness of test bearing generally increases with the increase in axial load and the decrease in thickness of bottom foil. In the rotation tests, rotor runs stably with small vibration amplitude, which is dominant in waterfall plot during whole speed up procedure. It shows that test bearing has preferable stability characteristics for high speed gas turbines.
There are many ways of describing a solid,porous or fluid region of the computational domain when solving the Navier-Stokes equations(NSE)for flow *** these the porous cell method is one of the most flexible *** this ...
详细信息
There are many ways of describing a solid,porous or fluid region of the computational domain when solving the Navier-Stokes equations(NSE)for flow *** these the porous cell method is one of the most flexible *** this method,a parameter is defined as a ratio of the volume open to water and air in a calculation cell to its cell *** the calculation,the same numerical procedure is applied to every cell and no explicit boundary conditions are needed at solid *** method is used to simulate flow through porous media,around solid bodies and over a moving *** results compare well with experimental data and other numerical *** our future work the porous cell method will be applied to more complex fluid-solid interaction situations.
In this paper, the experimental study on the off-design performance and dynamic response of an aircraft environmental control system (ECS) was presented. A bootstrap air cycle refrigeration system with high-pressure w...
详细信息
In this paper, the experimental study on the off-design performance and dynamic response of an aircraft environmental control system (ECS) was presented. A bootstrap air cycle refrigeration system with high-pressure water separation was employed in the ECS. Both the static test and the dynamic test were conducted on the ECS. The performance of the key components including precooler, recuperator, compressor, and turbine was investigated. The test results show the performance of the tested ECS can meet the requirements of design. However, some parameters including outlet pressure, turbine efficiency, and rotational speed might vary obviously when the operation conditions changed. The outlet humidity ratio and outlet temperature might also fluctuate largely during the start-up process. It is necessary to take into account the off-design performance and the transient performance in the design of ECS.
Experiments were carried out to study the characteristics of heat transfer on a downward-facing heated surface with porous media in narrow horizontal gap at atmosphere pressure using water as working fluid. The boilin...
详细信息
Experiments were carried out to study the characteristics of heat transfer on a downward-facing heated surface with porous media in narrow horizontal gap at atmosphere pressure using water as working fluid. The boiling curves were obtained under different conditions. The heat transfer increases significantly with porous media in the gap especially under boiling condition. The heat transfer in narrow horizontal gap can be enhanced by increasing the gap size and by using porous media with high thermal conductivity and appropriate porosity. Based on the mechanism of heat transfer in porous media, the correlations for natural convection and nucleate boiling were proposed to predict the heat transfer under the present condition.
A kind of phosphonium family based IL, [PC6C6C6C14][Tf2N]under several conditions was studied and the nano-structures (Fig.1) were observed using molecular dynamics simulation based on both all-atom and united-atom fo...
A kind of phosphonium family based IL, [PC6C6C6C14][Tf2N]under several conditions was studied and the nano-structures (Fig.1) were observed using molecular dynamics simulation based on both all-atom and united-atom force ***, little uniform and explicit standards for judging the nano-structure, or in another way, the aggregation in ILs have been reported.
A series of chemical reactions happen in the coal gasifier and as a result, high temperature syngas is obtained which contains a lot of solid granules. The high-temperature syngas must be cooled, because it can not be...
详细信息
A series of chemical reactions happen in the coal gasifier and as a result, high temperature syngas is obtained which contains a lot of solid granules. The high-temperature syngas must be cooled, because it can not be utilized directly. The opposed water spray cooling is not only effective, but also could dedust the syngas. In the present study, the CFD technique is used to investigate the effect of the opposed spray cooling in a gasifier. The Euler-Lagrange method is applied to deal with the syngas and the water droplets respectively. A non-dimensional parameter Temperature Non-uniform Factor (TNF) is defined to confirm the height of the cooling section. The simulated results match the designed data well. If water droplets with small diameters are used, the single-stage water spray cooling is more economic than the two-stage water spray cooling.
An artificial neural network (ANN) for predicting Nusselt number was trained successfully based on the data of transition boiling experiment, which was conducted in confined space with downward facing surface at atmos...
详细信息
An artificial neural network (ANN) for predicting Nusselt number was trained successfully based on the data of transition boiling experiment, which was conducted in confined space with downward facing surface at atmospheric pressure. The effects of wall superheat, Δtw, the ratio of the gap size to the diameter of heated surface, δ/D, Prandtl number and Rayleigh number on Nusselt number under transition boiling condition were analyzed based on the trained ANN. A correlation used to accurately predict the natural convection heat transfer under the present condition was obtained and it provides a reasonable agreement against the experimental data.
Turbulent mixing layer flow with 200 mg/kg polymer additives was measured by PIV and compared with pure water cause. The velocity ratio between high and low speed is 4:1 and the velocity difference ranges from 0.25 m/...
详细信息
Turbulent mixing layer flow with 200 mg/kg polymer additives was measured by PIV and compared with pure water cause. The velocity ratio between high and low speed is 4:1 and the velocity difference ranges from 0.25 m/s to 1.25 m/s. It is showed that large vortex structures exist in flow field with/without polymer addictives, but the coherent structure is much clearer and the large eddy will roll up earlier when polymer is added. Similar with pure water case, the Reynolds stress is decreasing and the vorticity is increasing with increasing the velocity difference. However, the width and range of Reynolds shear stress and vorticity are wider and larger.
暂无评论