DADOS:A Cloud-based Data-driven Design Optimization System

This paper presents a cloud-based data-driven design optimization system,named DADOS,to help engineers and researchers improve a design or product easily and efficiently.DADOS has nearly 30 key algorithms,including the design of experiments,surrogate models,model validation and selection,prediction,optimization,and sensitivity analysis.Moreover,it also includes an exclusive ensemble surrogate modeling technique,the extended hybrid adaptive function,which can make use of the advantages of each surrogate and eliminate the effort of selecting the appropriate individual surrogate.To improve ease of use,DADOS provides a user-friendly graphical user interface and employed flow-based programming so that users can conduct design optimization just by dragging,dropping,and connecting algorithm blocks into a workflow instead of writing massive code.In addition,DADOS allows users to visualize the results to gain more insights into the design problems,allows multi-person collaborating on a project at the same time,and supports multi-disciplinary optimization.This paper also details the architecture and the user interface of DADOS.Two examples were employed to demonstrate how to use DADOS to conduct data-driven design optimization.Since DADOS is a cloud-based system,anyone can access DADOS at www.dados.com.cn using their web browser without the need for installation or powerful hardware.

基于多系统集成仿真方法的燃气轮机动态特性仿真研究

In order to simulate the actual operation process of gas turbine more accurately,this paper uses multi system integration simulation technology to study the dynamic characteristics of gas turbine.Firstly,considering the factors such as variable stator vanes,air extraction,cooling mixing and multiple inertias,a refined model of gas turbine is established.Then,AMESim is used to establish the model of the VSV actuator of the gas turbine,and Flowmaster is used to establish the model of the secondary air system of the gas turbine.Finally,the multi-system integration simulation model of gas turbine is established by using interface technology to study the dynamic characteristics of gas turbine under load mutation.The simulation results show that the established multisystem simulation model of gas turbine can effectively simulate the dynamic operation process of gas turbine under the condition of load mutation,which is of great significance to the simulation research of gas turbine.

Knowledge and data jointly driven aeroengine gas path performance assessment method

Aeroengines,as the sole power source for aircraft,play a vital role in ensuring flight safety.The gas path,which represents the fundamental pathway for airflow within an aeroengine,directly impacts the aeroengine's performance,fuel efficiency,and safety.Therefore,timely and accurate evaluation of gas path performance is of paramount importance.This paper proposes a knowledge and data jointly driven aeroengine gas path performance assessment method,combining Fingerprint and gas path parameter deviation values.Firstly,Fingerprint is used to correct gas path parameter deviation values,eliminating parameter shifts caused by non-component performance degradation.Secondly,coarse errors are removed using the Romanovsky criterion for short-term data divided by an equal-length overlapping sliding window.Thirdly,an Ensemble Empirical Mode Decomposition and Non-Local Means(EEMD-NLM)filtering method is designed to“clean”data noise,completing the preprocessing for gas path parameter deviation values.Afterward,based on the characteristics of gas path parameter deviation values,a Dynamic Temporary Blended Network(DTBN)model is built to extract its temporal features,cascaded with Multi-Layer Perceptron(MLP),and combined with Fingerprint to construct a Dynamic Temporary Blended AutoEncoder(DTB-AutoEncoder).Eventually,by training this improved autoencoder,the aeroengine gas path multi-component performance assessment model is formed,which can sufficiently decouple the nonlinear mapping relationship between aeroengine gas path multi-component performance degradation and gas path parameter deviation values,thereby achieving the performance assessment of engine gas path components.Through practical application cases,the effectiveness of this model in assessing the aeroengine gas path multi-component performance is verified.

Design Optimization of Outlet Temperature Distribution of Hydrogen Micromixing Diffusion Combustor Based on Micro-turbojet Engine Engine

This paper focuses on the optimization of the outlet temperature field of a hydrogen micromixing diffusion combustor for a micro-turbojet engine with a thrust of 20kgf.The joint simulation optimization platform was established combiningWorkbench and UG and the multi-parameter driven optimization design process was developed.The surrogate models and genetic algorithms were employed to investigate the influences of key parameters on the hotspot temperature at the combustor exit.It was found that smaller diameters of the dilution holes and positions further from the exit lead to lower hotspot temperatures.Additionally,an optimal solution for achieving a uniform temperature distribution at the combustor outlet was obtained.This solution involves a single row of dilution holes on both the inner and outer walls of the flame tube,arranged in an alternating axial and angular pattern.Through aerothermal process analysis,it was determined that the outlet temperature distribution coefficient(OTDF)of the combustion chamber is below 0.2.Meanwhile,the axial dimension of the flame is short,approximately one-third of the flame tube length.The conclusions derived from this study provide important guidance for the design of hydrogen micromix diffusion combustor.

扇形气膜孔冷却效果的数值模拟研究（英文）

扇形气膜孔是一种先进的气膜冷却结构,其冷却效果相对于常规的圆形气膜孔显著提高。本文在多种流动进口条件下,对扇形气膜孔的冷却效果开展了数值模拟研究,研究中使用的流动进口条件包括:三种吹风比(0.5,1.0,1.5),四种主流道马赫数(0.3,0.45,0.6,0.75)。研究中使用了三种不同的RANS湍流模型(可实现的k-ε,SSTk-ω,标准k-ε)进行了CFD计算分析,以中心线绝热冷却效果为观测对象,对数值模拟和试验结果进行了对比分析。对比试验结果,可实现的k-ε模型相对另外两种模型在计算冷却效果时有较高的温和度,但是另一方面,上述三种湍流模型计算得到的冷却效果相对试验结果都是偏高。

Development of a deviation package method for low-cost robust optimization in compressor blade design

Manufacture variations can greatly increase the performance variability of compressor blades. Current robust design optimization methods have a critical role in reducing the adverse impact of the variations, but can be affected by errors if the assumptions of the deviation models and distribution parameters are inaccurate. A new approach for robust design optimization without the employment of the deviation models is proposed. The deviation package method and the interval estimation method are exploited in this new approach. Simultaneously, a stratified strategy is used to reduce the computational cost and assure the optimization accuracy. The test case employed for this study is a typical transonic compressor blade profile, which resembles most of the manufacture features of modern compressor blades. A set of 96 newly manufactured blades was measured using a coordinate measurement machine to obtain the manufacture variations and produce a deviation package. The optimization results show that the scatter of the aerodynamic performance for the optimal robust design is 20% less than the baseline value. By comparing the optimization results obtained from the deviation package method with those obtained from widely-used methods employing the deviation model, the efficiency and accuracy of the deviation package method are demonstrated. Finally, the physical mechanisms that control the robustness of different designs were further investigated, and some statistical laws of robust design were extracted.

Experimental investigation of junction growth of rough contacts using X-ray computed tomography

The real contact area(RCA)of randomly rough contacts has received a great deal of attention because it correlates strongly with friction,lubrication,sealing,and conductivity.Simulations have revealed that the RCA associated with deterministic normal squeezing loads increases when tangential loads are also applied,in a phenomenon called junction growth.However,experimental investigations of the junction growth of randomly rough contacts are rare.Here,we used X-ray computed tomography(CT)to measure junction growth when two aluminum alloy surfaces were in contact.A high-resolution experimental setup was used to apply loads and observe contact behaviors at a resolution of 4μm.The RCA and average contact gaps were computed using a three-dimensional(3D)geometric model constructed from gray CT images using the Otsu thresholding method.The results showed that the RCA increased as the normal load increased.The RCA increased by 22.67%after a tangential load was applied(junction growth),and the average gap decreased by 14.01%after a tangential load was applied.Thus,X-ray CT accurately measured the junction growth as a novel quantitative method.

Breaking the geometry-performance tradeoff in compressor deviation modeling:Nested principal component analysis

Uncertainties in the aerodynamic performance of compressors,introduced by manufacturing variations,have received more and more attentions in recent years.The deviation model plays a crucial role in evaluating this uncertainty and facilitating robust design.However,current deviation models with a few variables cannot simultaneously achieve a precise geometric approximation of deviation and provide an accurate assessment of performance uncertainty.This paper introduces a novel deviation modeling method named Nested Principal Component Analysis(NPCA)to break this tradeoff.In this method,both geometry-based and performance-based modes are utilized to describe manufacturing variations.By considering aerodynamic sensitivity,surface deformations that significantly impact aerodynamic performance can be extracted for deviation modeling.To demonstrate the superiority of this newly proposed method,ninety-eight newly manufactured compressor rotor blades were measured using a coordinate measurement machine,and both NPCA and Principal Component Analysis(PCA)were employed to model the real manufacturing variations.The results indicate that,in comparison to the PCA method,the NPCA method achieves an equivalent level of accuracy in geometric reconstruction and evaluation of mean performance.Furthermore,the same level of accuracy can be obtained with eight NPCA modes and fifty PCA modes when assessing the scatter in aerodynamic performance.Finally,the working mechanism of the NPCA method for accurate uncertainty quantification was further investigated.

Failure mechanisms of bolted flanges in aero-engine casings subjected to impact loading

In this paper,a failure evaluation criterion was proposed for the bolted casing-flange structure under impact loading.Subsequently,ballistic tests with eighteen bolted casing-flange structure specimens were conducted to validate the failure evaluation criterion.Parameter studies were then carried out using the validated FE models.Both the experimental and numerical results demonstrated the accuracy of the failure evaluation criterion.The failure evaluation criterion provided a quick and easy way to determine the failure mode of the casing connection area by using the materials and dimensions of the structure.Based on the failure evaluation criterion,designing the structural failure mode of the bolted casing-flange structure to be between flange failure and bolt failure can improve the impact resistance of the connection area of the aero-engine casings.This investigation revealed that the impact failure is not the unique criterion in evaluating the containment of the casing connection area,structural failure should also be involved in the evaluation criteria.

Aerodynamic Characteristic Research on Final Stage Stator of a Highly Loaded Fan

Due to corner separation and other complex three-dimensional flows existing in the highly loaded stator, which influences the fan performance significantly, highly loaded stator blades of a transonic fan with a maximum camber angle of 57° were studied in this paper and sector cascade experiment was adopted. In order to get the stator aerodynamic parameters as realistic as possible and conduct the experiment without the existence of rotor, an adjustable guide vane was designed to simulate the velocity magnitude and direction of the stator inlet flow. Results show that the adjustable guide vane can simulate the rotor outlet velocity direction and magnitude in most span range. The deviation angle is positive and the maximum value is nearly 21° because the severe separation is at 27% span. Corner separation exists on both pressure side and suction side and the location of separation initiation is determined. Finally, the stator blades were redesigned with some suction slots on the suction side. Experiment results show that the suction slots change the flow field structure, increase the capability of flow turning, and decrease the flow loss.

Experimental investigation on separation characteristics of axial cyclone separator

Axial cyclone separator has been widely applied in chemical production as an efficient gas-liquid separation device.In this study,a new axial cyclone separator with integrated swirler and exhaust pipe is designed to achieve the development goal of compact structure for advanced engine,and the distribution characteristics of swirling flow patterns as well as the variation in separation characteristics are investigated under slug flow pattern.Based on flow visualizations and fluctuation characteristics of pressure signals,three typical flow patterns,namely,slug flow,swirling intermittent flow,and swirling annular flow,in the horizontal swirling separation flow are characterized.It is investigated how the inlet conditions affect the separation characteristic parameters.The separation purity and extreme points of the air separation efficiency are independent of the inlet liquid flow rate.The separation pressure drop is quadratically related to the inlet air flow rate.Based on the drift-flux model and other methods,the prediction methods for the air separation efficiency and pressure drop are proposed,and the prediction accuracy is within±20%,which may provide instructions for the practical application of axial cyclone separator.

Blade bowing effects on radial equilibrium of inlet flow in axial compressor cascades

The circumferentially averaged equation of the inlet flow radial equilibrium in axial compressor was deduced. It indicates that the blade inlet radial pressure gradient is closely related to the radial component of the circumferential fluctuation（CF） source item. Several simplified cascades with/without aerodynamic loading were numerically studied to investigate the effects of blade bowing on the inlet flow radial equilibrium. A data reduction program was conducted to obtain the CF source from three-dimensional（3D） simulation results. Flow parameters at the passage inlet were focused on and each term in the radial equilibrium equation was discussed quantitatively. Results indicate that the inviscid blade force is the inducement of the inlet CF due to geometrical asymmetry. Blade bowing induces variation of the inlet CF, thus changes the radial pressure gradient and leads to flow migration before leading edge（LE） in the cascades. Positive bowing drives the inlet flow to migrate from end walls to mid-span and negative bowing turns it to the reverse direction to build a new equilibrium. In addition, comparative studies indicate that the inlet Mach number and blade loading can efficiently impact the effectiveness of blade bowing on radial equilibrium in compressor design.

A forced ignition probability analysis method using kernel formation analysis with turbulent transport and Lagrangian flame particle tracking

A forced ignition probability analysis method is developed for turbulent combustion,in which kernel formation is analyzed with local kernel formation criteria,and flame propagation and stabilization are simulated with Lagrangian flame particle tracking.For kernel formation,the effect of turbulent scalar transport on flammability is modelled through the incorporation of turbulenceinduced diffusion in a spherically outwardly propagating flame kernel model.The dependence of flammability limits on turbulent intensities is tabulated and serves as the flammability criterion for kernel formation.For Lagrangian flame particle tracking,flame particles are tracked in a structured grid with flow fields being interpolated from a Computational Fluid Dynamics(CFD)solution.The particle velocity follows a Langevin model consisting of a linear drift and an isotropic diffusion term.The Karlovitz number is employed for the extinction criterion,which compares chemical and turbulent timescales.The integration of the above two-step analysis approach with non-reacting CFD is achieved through a general interpolation interface suitable for general unstructured CFD grids.The method is demonstrated for a methane/air bluff-body flame,in which flow and fuel/air mixing characteristics are extracted from a non-reacting simulation.Results show that the computed ignition probability map agrees qualitatively with experimental results.A reduction of the ignition probability in the recirculation zone and a high ignition probability on the shear layer of the recirculation zone near the mean stoichiometric surface are well captured.The tools can facilitate optimization of spark placement and offer insights into ignition processes.