Blockage effect on the flow around a cylinder probe in calibration

Flow around a 2-D cylinder pressure probe placed in uniform flow,free jet flow,and wind tunnel flow was analyzed with potential flow theory and simulated with numerical method.Blockage effect was investigated under several typical flow Mach numbers.The result from numerical simulation shows a similar trend to the one from potential flow method while varies in quantity.Wind tunnel walls accelerate the flow near the probe and thus produce a blockage effect;Boundary of free jet flow,however,decelerates the flow and thus produces a 'negative' blockage effect.A maximum incoming Mach number exists when the probe is calibrated in wind tunnel in high subsonic condition due to choking caused by shocks and shock induced separation.The critical Mach number varies with blockage ratio,which makes high Mach number impossible to achieve in large blockage ratio condition.The blockage effect itself is unavoidable for calibration or measurement although a sufficiently small blockage ratio brings minor effect.Correction can be implemented based on the numerical simulation result presented in this paper and further works.

Numerical analysis and optimization of the inlet stage of a multi-stage high pressure compressor

An opti mization process is used to redesign blades of a high-pressure compressor.An artificial neural network (ANN) method is coupled to Navier-Stokes solvers and is applied to three different redesigns.A newrotor blade of a transonic compressor is designed by modifying thick,stacking line andinlet angle using a 3Dapproach,with a significant efficiencyi mprovement at the design point.The off-design behavior of this new compressor is also checked afterwards,which shows that the whole performance of the inlet stage is improved over a wide range of mass flow.The losses are reduced,proving the good performance of the opti mum.The whole results indicate that the opti mization method can find i mproved design and can be integrated in a design procedure.

Development of a micro gas turbine combustor with T-type vaporizers

The study includes the experimental investigation of the evaporation performance of T-type vaporizer,mainly studied the relationship of the inlet air temperature and vaporizer wall temperature with the evaporation ratio.Then,it studied the LBO(lean blow out) and combustion efficiency of the micro aero-engine combustor with T-type vaporizer on the normal pressure test rig.The inlet air condition is environmental pressure and temperature.The gas analysis method is used to study the combustion efficiency,and the inlet air temperature is 300 K,400 K and 500 K.It could be concluded that the evaporation performance is improved with the increasing of the inlet air temperature and vaporizer wall temperature;the average LBO is 0.003;the combustion efficiency rises with the inlet air temperature,and it remain constant when the fuel/air ratio changed in the range from 0.008 to 0.02.The vaporization ratio is the key factor to determine the combustion performance.

Effects of Axial Non-uniform Tip Clearances on Aerodynamic Performance of a Transonic Axial Compressor

这篇论文在一个接近音速的轴的压缩机转子(NASA 转子 37 ) 的空气动力学的表演上论述轴的不一致的尖端清理的效果的数字调查。在转子经过以内的三维的稳定的流动地以 17188.7 rpm 的设计车轮速度与 0.356 公里的资料尖端清理被模仿。模拟结果与测量结果很好一致，它验证了数字方法。然后，在转子经过以内的三维的稳定的流动地与不同轴的不一致的尖端清理分别地被模仿。计算结果证明最佳的轴的不一致的尖端清理能改进压缩机表演，当效率和压缩机的压力比率被增加时。流动机制是轴的不一致的尖端清理能削弱尖端漏旋涡，在界面层刮倒低精力的液体并且减少流动阻塞和尖端损失。

Streamwise-body-force-model for rapid simulation combining internal and external flow fields

A streamwise-body-force-model （SBFM） is developed and applied in the overall flow simulation for the distributed propulsion system, combining internal and external flow fields. In view of axial stage effects, fan or compressor effects could be simplified as body forces along the streamline. These body forces which are functions of local parameters could be added as source terms in Navier-Stokes equations to replace solid boundary conditions of blades and hubs. The val- idation of SBFM with uniform inlet and distortion inlet of compressors shows that pressure performance characteristics agree well with experimental data. A three-dimensional simulation of the integration configuration, via a blended wing body aircraft with a distributed propulsion system using the SBFM, has been completed. Lift coefficient and drag coefficient agree well with wind tunnel test results. Results show that to reach the goal of rapid integrated simulation combining internal and external flow fields, the computational fluid dynamics method based on SBFM is reasonable.

Flow Field Measurements in the Cavity of a Trapped Vortex Combustor Using PIV

The experimental research on cavity flow field plays an important part in the structural design and optimization study of trapped vortex combustor (TVC). Many of the previous flow field experiments were conducted in the cold condition instead of during combustion. This paper adopting PIV system and Lambda-2 vortex criterion in-vestigates the influence of various factors, such as equivalent ratio in the cavity, air intake parameter in the cavity, mainstream air intake parameter and mainstream holder structure, on cavity flow field for a TVC using methane as the fuel. The experimental research showed that cold-condition flow field differed from the combustion flow field, in terms of either vortex core position or vortex structure. Mainstream air intake velocity and cavity air intake velocity affected the flow field structure. U-type and V-type mainstream holders had significant influence on cavity flow field.

Large eddy simulation of compressible turbulent channel flow with spanwise wall oscillation

The influences of the modification of turbulent coherent structures on temperature field and heat transfer in turbulent channel flow are studied using large eddy simulation(LES) of compressible turbulent channel flows with spanwise wall oscillation(SWO).The reliability of the LES on such problems is proved by the comparisons of the drag reduction data with those of other researches.The high consistency of coherent velocity structures and temperature structures is found based on the analyses of the turbulent flow field.When the coherent velocity structures are suppressed,the transportations of momentum and heat are reduced simultaneously,demonstrating the same trend.This shows that the turbulent coherent structures have the same effects on the transportations of momentum and heat.The averaged wall heat flux can be reduced with appropriate oscillating parameters.

The Design and Performance of a High Temperature Rise Combustor for Wind Tunnel

A high-temperature-rise combustor that can be used in high-temperature wind tunnel is introduced in this study.Aviation kerosene is used in this type of combustor,with division combustion scheme and evaporator fuel-supply device adopted.In the performance test under atmospheric pressure,when the inlet temperature is 500K and air flow is within the range of 1.5-3.0 kg/s,the outlet temperature can be precisely regulated within the range of 1050K-2100K.Moreover,higher uniformity of outlet temperature distribution and higher combustion efficiency can be achieved.After the long-time working in the wind tunnel,various components of the combustor,especially the combustor liners are checked without finding any anomaly such as thermal deformation.

Effects of a Kind of Non-smooth Blade on the Performance of an Axial Fan

这份报纸在一把轴流动的扇子的表演上论述一种投出 streamwise 的片的效果的试验性的调查。在从在中心的后面的边下游的 25% 弦的流动地以不同集体流动的条件用一根 5 洞压力探针被测量。沟片的扇子表演与光滑的片的相比。测量结果显示那：(1 ) 非光滑的片在一样增加扇子的集体流动除了一个近的货摊条件，扼杀条件；(2 ) 非光滑的片在转子经过减少相对全部的压力损失并且在除了近的货摊的集体流动的条件调节的测试增加扇子总数压力上升；(3 ) 当光滑的片被非光滑的代替时，否定好处以一个近的货摊条件被获得。扇子团流动减少 0.9% 当全部压力的上升减少时， 2.4% 在近的货摊调节。

Boundary Vorticity Flux and Engineering Flow Management

To improve the performance of complex viscous engineering flows,the focus should be on local dynamics(local processes and structures)measured by the space-time derivatives of the primary-variable fields,rather than these fields themselves.In the context of optimal flow management such as optimal configuration design and flow control,the local fluid dynamics on solid wall is of most direct relevance.For large Reynolds-number flows,we show that the on-wall local dynamics is highlighted by the balance between tangential pressure gradient and vorticity creation rate at the wall(boundary vorticity flux,BVF),namely the on-wall coupling of the compressing and shearing processes.This basic concept is demonstrated by previously unpublished and newly obtained numerical examples for external and internal flows,including the role of BVF as a faithful marker of the local appearance of boundary-layer separation and wall curvature discontinuity,and the use of BVF-based formulas to optimize the integrated performance of airfoil and compressor rotor blade.

Effects of a Kind of Non-smooth Blade on the Unsteady Flow Field at the Exit of an Axial Fan

在一个轴流动的迷的一个出口的不稳定的流动地上的一种投出 streamwise 的片的效果的试验性的调查被执行。在从在中心的后面的边的 25% 弦 downstream 的流动领域以不同集体流动的条件用一根快反应的五洞的压力探针被测量。投出的片的不稳定的流动与光滑的片的相比。测量结果显示那：(1 ) 投出的片由 modulating 制止速度变化和压力变化片界面层，它在中心区域并且在转子贡献流动损失减小以设计条件弄醒区域；(2 ) 溪流明智的沟在在片界面层制止光线的迁居并且消除混合的尖端流动起一个重要作用，它以设计条件在尖端区域贡献流动损失减小；(3 ) 在近的货摊调节，投出的表面不能减少流动损失，当分离发生在片界面层时，甚至附近增加损失。