查看更多>>摘要：The efficiency of the aircraft Ice Protection Systems(IPSs)needs to be verified through icing wind tunnel tests.However,the scaling method for testing the IPSs has not been systematically established yet,and further research is needed.In the present study,a scaling method specifically designed for thermal IPSs was derived from the governing equation of thin water film.Five scaling parameters were adopted to address the heat and mass transfer involved in the thermal anti-icing process.For method validation,icing wind tunnel tests were conducted using a jet engine nacelle model equipped with a bleed air IPS.The non-dimensional surface temperature and runback ice closely matched for both the reference and scaled conditions.The validation confirms that the scal-ing method is capable of achieving the similarity of surface temperature and the runback ice cov-erage.The anti-icing scaling method can serve as an important supplement to the existing icing similarity theory.
查看更多>>摘要：To numerically study the impact of total temperature distortion on a transonic compres-sor with reduced computational costs,a Body-Force Model(BFM)is developed.Firstly,the inter-actions between the distorted flow and the compressor are analyzed using full-annulus Unsteady Reynolds-Averaged Navier-Stokes(URANS)results and the orbit method.It is found that the induced swirl distortion and the mass flux nonuniformity are intensified in the compressor upstream flow field.A correction factor is thus added to the BFM to account for the effect of the induced swirl,which is crucial for the accurate representation of distortion transfer in the intake.Then,steady simulations with large-amplitude 180° circumferential total temperature distortion are per-formed using the developed BFM.It is shown that the distorted compressor map simulated with the BFM matches well with URANS results.The circumferential phase shift of total temperature and the generation of the additional total pressure distortion across the rotor are in line with the time-averaged URANS flow field.The compressor upstream effects on the distorted inflow can also be exactly captured.All above-mentioned results demonstrate the BFM developed in this paper can effectively capture the distorted flow features inside the compressor,and significantly reduce the computational costs by five orders of magnitude compared with URANS.
查看更多>>摘要：The mid-passage gap is an inevitable structure in a vane passage due to turbine vanes being manufactured individually.The coolant from this gap is able to prevent hot mainstream ingression and provide cooling protection for the endwall.A novel idea of enlarging the endwall's coverage area and reducing the endwall's thermal load by applying the mid-passage gap with vari-able surface angles is carried out in this paper.The endwall's aerothermal and film cooling perfor-mances under four mid-passage gap modes at three typical mass flow ratio conditions are numerically investigated.Results indicate that under the traditional mid-passage mode,the coolant flows into the mainstream with a perpendicular incidence angle and can't stick to the endwall.Thus,cooling failure occurs,and the endwall's thermal load is badly increased.The film cooling level at the suction-side endwall is improved when applying the mid-passage gap of a 45° surface angle due to the secondary vortex being suppressed.In addition,when applying the mid-passage gap of a 135° surface angle,the horseshoe vortex is pushed away,and the coverage area at the pressure-side end-wall is enlarged significantly.The best film cooling performance is achieved when the upstream sur-face angle is 135° and the downstream surface angle is 45° due to the adiabatic film cooling effectiveness being increased at both the pressure-and suction-side endwall.When the mass flow ratio is 1.5％,the coverage area is enlarged by 43％,and the area-averaged adiabatic film cooling effectiveness is increased by 37％,when compared with those under the traditional mid-passage mode.
查看更多>>摘要：Ground lifetime test is the most crucial experiment to assess the performance,reliability,and flight qualification of electric propulsion,and it can bring new insights for understanding the operation characteristics.This work demonstrates a full lifetime test of 140000 cycles on a Micro-Cathode-Arc Thruster(μCAT)with 160 μs charging time and 86 mJ charging energy.A four-probe resistivity measurement method is utilized to investigate variations in the conductive film thickness and resistivity throughout the thruster lifespan.Direct film parameters show that the lifetime of the μCAT can be divided into three stages.In the initial stage,the film thickness decreases by 1.2 μm and the resistivity increases significantly due to the high discharge intensity and intense film ablation;In the steady stage,the change of the film thickness is within 5％,and the resistivity of the film increases slowly from 0.050 Ω·mm to 0.223 Ω·mm.In the end stage,the resistivity exponentially increases from 0.223 Ω·mm to 1.176 Ω·mm,with the increase accounting for 81％,ultimately resulting in the failure of the thruster open circuit.Additionally,the evolution of discharge parameters,and the variation of plume parameters are measured throughout the life-time.The discharge characteristics also show significant differences in the duration of voltage and current in these three stages.The results of plume shape and plasma parameters are also well con-sistent with the discharge parameters and film state.These results suggest that,for evaluating the steady stage lifetime of thrusters,the film thickness is the best indicator compared to the variations in resistivity and voltage-current characteristics.For the end stage,the plasma plume morphology,discharge duration,and plume parameters can conveniently and clearly characterize the thruster failures and irregularity.
查看更多>>摘要：Piezoelectric resonant de-icing systems are attracting great interest.This paper aims to assess the implementation of these systems at the aircraft level.The article begins with the model to compute the power requirement of a piezoelectric resonant de-icing system sized from the pro-totype detailed in Part 1/2 of this article.Then the mass,drag,and fuel consumption of this system and the subcomponents needed for its implementation are assessed.The features of a piezoelectric resonant de-icing system are finally computed for aircraft similar to Airbus A320 aircraft and air-craft of different categories(Boeing 787,ATR 72 and TBM 900)and compared with the existing thermal and mechanical ice protection systems.A sensitivity analysis of the main key sizing param-eters of the piezoelectric de-icing system is also performed to identify the main axes of improvement for this technology.The study shows the potential of such ice protection systems.In particular,for the realistic input parameters chosen in this work,the electro-mechanical solution can provide a 54％reduction in terms of mass and a 92％reduction in terms of power consumption for an A320 aircraft architecture,leading to a 74％decrease in the associated fuel consumption compared to the actual air bleed system.
查看更多>>摘要：The modern aircraft Thermal Management System(TMS)faces significant challenges due to increasing thermal loads and limited heat dissipation pathways.To optimize TMS during the con-ceptual design stage,the development of a modeling and simulation tool is crucial.In this study,a TMS simulation model library was created using MATLAB/SIMULINK.To simplify the complex-ity of the Vapor Cycle System(VCS)model,a Response Surface Model(RSM)was constructed using the Monte Carlo method and validated through simulation experiments.Taking the F-22 fighter TMS as an example,a thermal dynamic simulation model was constructed to analyze the vari-ation of thermal response parameters in key subsystems and elucidate their coupling relationships.Furthermore,the impact of total fuel flow and ram air flow on the TMS was investigated.The find-ings demonstrate the existence of an optimal total fuel flow that achieves a balance between maxi-mizing fuel heat sink utilization and minimizing bleed air demand.The adaptive distribution of fuel and ram air flow was found to enhance aircraft thermal management performance.This study contributes to improving modeling efficiency and enhancing the understanding of the thermal dynamic characteristics of TMS,thereby facilitating further optimization in aircraft TMS design.
查看更多>>摘要：Blended-Wing-Body(BWB)aircraft is promoted as one of the most possible layouts to achieve more sustainable civil aviation.Due to the non-circular cross-section of the center-body,a bulge deformation forms over the upper surface of the body under the coupled loads of the internal pressurization of the cabin and the aerodynamic bending moments of the wing,which reduces the lift-to-drag ratio of BWB aircraft.Under a limited deformation,the relationship between the aero-dynamic performance and the structural weight needs to be studied.In this work,the effects of stiff-ness constraints on the center-body deformation,structural weight of the airframe and aerodynamic performance were investigated by using an analytical model of the Pultruded Rod Stitched Efficient Unitized Structure(PRSEUS)for the airframe and the computational fluid dynamics method,respectively.The results show that as the stiffness constraint increases,the spacings between the rod stringers and the frame stiffeners decrease,and the structural weight increases inversely.A 5.2％reduction of the lift-to-drag ratio is encountered at cruise for a medium deformation design of 42.8 mm/m.A higher aerodynamic penalty is suffered when the stiffness constraint is further released.The final deformation criterion is different when the weight vector of the aerodynamic per-formance and structural weight is different.
查看更多>>摘要：Polynomial Chaos Expansion(PCE)has gained significant popularity among engineers across various engineering disciplines for uncertainty analysis.However,traditional PCE suffers from two major drawbacks.First,the orthogonality of polynomial basis functions holds only for independent input variables,limiting the model's ability to propagate uncertainty in dependent vari-ables.Second,PCE encounters the"curse of dimensionality"due to the high computational cost of training the model with numerous polynomial coefficients.In practical manufacturing,compressor blades are subject to machining precision limitations,leading to deviations from their ideal geomet-ric shapes.These deviations require a large number of geometric parameters to describe,and exhibit significant correlations.To efficiently quantify the impact of high-dimensional dependent geometric deviations on the aerodynamic performance of compressor blades,this paper firstly introduces a novel approach called Data-driven Sparse PCE(DSPCE).The proposed method addresses the aforementioned challenges by employing a decorrelation algorithm to directly create multivariate basis functions,accommodating both independent and dependent random variables.Furthermore,the method utilizes an iterative Diffeomorphic Modulation under Observable Response Preserving Homotopy regression algorithm to solve the unknown coefficients,achieving model sparsity while maintaining fitting accuracy.Then,the study investigates the simultaneous effects of seven depen-dent geometric deviations on the aerodynamics of a high subsonic compressor cascade by using the DSPCE method proposed and sensitivity analysis of covariance.The joint distribution of the depen-dent geometric deviations is determined using Quantile-Quantile plots and normal copula functions based on finite measurement data.The results demonstrate that the correlations between geometric deviations significantly impact the variance of aerodynamic performance and the flow field.There-fore,it is crucial to consider these correlations for accurately assessing the aerodynamic uncertainty.
查看更多>>摘要：To overcome the limitations posed by three-dimensional corner separation,this paper proposes a novel flow control technology known as passive End-Wall(EW)self-adaptive jet.Two single EW slotted schemes(EWS1 and EWS2),alongside a combined(COM)scheme featuring double EW slots,were investigated.The results reveal that the EW slot,driven by pressure differ-entials between the pressure and suction sides,can generate an adaptive jet with escalating velocity as the operational load increases.This high-speed jet effectively re-excites the local low-energy fluid,thereby mitigating the corner separation.Notably,the EWS1 slot,positioned near the blade leading edge,exhibits relatively low jet velocities at negative incidence angles,causing jet separation and exacerbating the corner separation.Besides,the EWS2 slot is close to the blade trailing edge,result-ing in massive low-energy fluid accumulating and separating before the slot outlet at positive inci-dence angles.In contrast,the COM scheme emerges as the most effective solution for comprehensive corner separation control.It can significantly reduce the total pressure loss and improve the static pressure coefficient for the ORI blade at 0°-4° incidence angles,while causing minimal negative impact on the aerodynamic performance at negative incidence angles.Therefore,the corner stall is delayed,and the available incidence angle range is broadened from-10°--2° to-10°-4°.This holds substantial promise for advancing the aerodynamic performance,operational stability,and load capacity of future highly loaded compressors.
查看更多>>摘要：Micro aerial platforms face significant challenges in achieving long controlled endurance as most of the energy is consumed to overcome the weight of the body.In this study,we present a controllable micro blimp that addresses this issue through the use of a helium-filled balloon.The micro blimp has a long axis of 23 cm and is propelled by four insect-sized flapping-wing thrusters,each weighing 80 mg and with a wingspan of 3.5 cm.These distributed thrusters enable controlled motions and provide the micro blimp with an advantage in flight endurance compared to multi-rotors or flapping-wing micro aerial vehicles at the same size scale.To enhance the performance of the controlled flight,we propose a wireless control module that enables manipulation from a dis-tance of up to 100 m.Additionally,a smartphone application is developed to send instructions to the circuit board,allowing the blimp to turn left and right,ascend and descend,and achieve a com-bination of these movements separately.Our findings demonstrate that this micro blimp is one of the smallest controlled self-powered micro blimps to date.
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