As a key subsystem for flight safety and stability, the aircraft Environmental Control System typically employs an air-cycle refrigeration system with high-pressure water separation. The water separator removes water from moist air, severely affecting the effective cooling capacity of the environmental control systems. To reduce the escape of free liquid droplets and prevent water films from entering the turbine, this study established a simulation model for the water separator. Using simulation data, a Kriging surrogate model was constructed, followed by a multi-objective optimization framework aimed at simultaneously improving separation efficiency, reducing pressure drop, and minimizing liquid film. A genetic algorithm was employed to optimize key structure parameters, including the number of vanes, wrap angle, outlet angle, axial length, and core diameter. The results showed that when the flow field exhibits distinct characteristics, i.e., the tangential velocity shows a “valley-shaped” distribution in the radial direction and the axial velocity shows a “peak-shaped” distribution, the cyclone could achieve high separation efficiency and lower pressure drop. Furthermore, the increase in the number of wall rivulets results in a more uniform circumferential liquid film distribution and a reduced maximum film thickness, which is beneficial for water separation. Under typical operating conditions, the optimized design improves separation efficiency by 17.1% and decreases liquid film thickness by 48.7%, at the cost of only a 6.3% increase in pressure drop. The findings can provide a reference for the design optimization of water separators, thereby enabling high-quality regulation of the aircraft environment.

The accurate characterization of ice crystal motion and impact behavior lies at the core of numerical simulations for aircraft icing. In current non-spherical ice crystal studies, rotation is generally neglected, an unvalidated hypothesis inherited from research on spherical supercooled droplets, which may lead to prediction inaccuracies for small precision components. This study examines the rationality of the hypothesis and proposes a refined six-degree-of-freedom (6-DOF) numerical framework. Through the coupling of Navier-Stokes equations with 6-DOF rigid-body dynamics, a two-way fluid-solid interaction model is developed to precisely capture the coupled translational-rotational motion of non-spherical ice crystals. The framework is validated against the NACA0020 airfoil under representative aircraft icing conditions. Results demonstrate excellent trajectory consistency between the 6-DOF and traditional Lagrangian methods: 97 % of impact position errors are within 4 mm, and 93.5 % of collection efficiency differences are maintained within +/- 0.06. These findings confirm both the rationality of the rotation-neglected hypothesis and its engineering applicability for large-scale aircraft components. Three classical Lagrangian drag coefficient models are quantitatively evaluated using 6-DOF results as the benchmark, confirming the Ganser Model's optimal trajectory prediction accuracy. Furthermore, the 6-DOF method captures self-excited motion and rotational oscillations of non-spherical ice crystals. These phenomena originate from the dynamic coupling between unsteady aerodynamic torque and particle inertia, and are undetectable by traditional Eulerian or Lagrangian methods due to their inherent simplifying assumptions. This study delivers an advanced computational approach and robust theoretical support for the precise dynamic characterization of non-spherical ice crystals, while offering clear guidance for drag coefficient model selection in engineering ice accretion simulations.

Thermal network method is employed to predict the temperature distribution of equipment within a UAV compartment. Through node discretization, construction of thermal network diagram, and simultaneous solution of nodal equations, temperature values at each node in equipment are obtained and systematically analyzed. The results are experimentally validated, demonstrating the feasibility and accuracy of applying thermal network method to temperature prediction in UAV equipment compartments. Compared with CFD simulations, this method significantly reduces computational time requirements, suggesting its preferential adoption during preliminary thermal design phases of UAV compartments.

A flow condensation experiment was performed in a 300 mm long mini channel with a diamond pin fin array. The working fluid is R134a and four pin fin arrays were tested, including different channel widths of 1.0, 1.2, and 1.4 mm, as well as fin angles of 60 degrees and 90 degrees. The experimental system used in previous studies was adopted to obtain the local heat transfer coefficient. The measurements were done within the saturation pressure range of 600-1500 kPa with mass flux ranging from 160 to 450 kg/m(2)s. The experimental results indicated that the local heat transfer coefficient increases with an increase in vapor quality, mass flux, and heat flux whereas it decreases with an increase in saturation pressure. The influence of heat flux and pin fin array structure on heat transfer coefficient was more significant in the high vapor quality region relative to that of the low vapor quality region. Higher fin density and larger fin angles contribute to improved condensation. With a diamond fin angle of 60 degrees, the heat transfer coefficient of the pin fin array with a fin density of 0.22 is 24 %similar to 56 % higher than that of the pin fin array with a fin density of 0.16. For the pin fin array with the same fin density, the heat transfer coefficient at fin angle 90 degrees is 1.1-1.4 times that at fin angle 60 degrees.Additionally, the performance evaluation criteria named Penalty Factor was applied to evaluate the performance of the pin fin array, and SG60_3 outperforms the other channel, corresponding to a fin angle of 60 degrees and channel widths of 1.4 mm. The Penalty Factor value of SG60_3 is 70 %similar to 80 % of that of the other three pin fin array. The existing correlations fail to give a reasonable prediction for the heat transfer coefficient of the present experimental data. Therefore, a new correlation accounting for the effects of geometric sizes of pin fin array and heat flux was developed with the maximum mean absolute deviation of 7.48 % on four test channels. The present study can provide valuable knowledge on the design optimization of mini channel condensers with pin fin array.

The anti-ice system is a crucial subsystem for ensuring aircraft safety. Water droplet evaporation on its surface is a frequent occurrence during flight. Investigating the characteristics of water droplet evaporation is essential for designing effective active or passive aircraft anti-ice systems. Previous research has primarily focused on the evaporation of small droplets under constant wall temperature conditions. The emergence of more electric aircraft has led to the adoption of electrical heating anti-ice systems, which typically operate under conditions of constant wall heat flux. Despite this shift, the quantitative characteristics of evaporation under different surface properties and constant wall heat flux conditions have not been thoroughly investigated. In this paper, an experimental test site was built to study the evaporation characteristics of water droplets on heating surfaces with various coatings and under different wall thermal conditions. The experimental results showed that the evaporation time for droplets on hydrophobic surfaces was longer than that on hydrophilic surfaces. The increase in evaporation time ranged from 5 to 13 times as the surface temperature was raised from 40 degrees C to 80 degrees C. Furthermore, the difference in evaporation time between small and large droplets was more pronounced under constant temperature conditions than that of constant heat flux conditions. For droplets on polished aluminum and hydrophilic surfaces, the evaporation rate was linearly related to the evaporation surface area. The findings of this study can inform future optimizations of anti-ice systems.

Flow boiling in mini-channel is a pivotal technique for airborne vapor compression cycles. This study conducts experimental tests to examine the flow boiling characteristics in mini-channel having four distinct pin fin configurations: diamond, square, circle, and sinusoidal. All channels maintain a uniform hydraulic diameter of 0.67 mm, with only a 2.3% variation in total heat transfer area. The experiments cover a range of operating conditions, including mass fluxes of 150 - 300 kg/(m²·s) and heat fluxes of 10 - 25 kW/m². The results reveal that the pin fin shapes have a significant impact on the pressure drop during flow boiling in mini-channel. Notably, the diamond fins exhibit the least flow resistance. In conditions of identical operation, the pressure drop in channels with square, circular, and sinusoidal fins increases by 303.6%, 120.0%, and 71.6% in meanly, respectively, compared to that of the diamond fins. However, the impact of fins on heat transfer property is less pronounced. Upon analyzing both the pressure drop and heat transfer property, the diamond fins emerge as the superior choice in terms of overall property. The insights gained from this research can inform future optimization efforts for airborne evaporator design.

In this paper, an experimental study of flow condensation was carried out of R134a in a multiport mini channel and a mini channel with pin fin array. The former comprised 20 parallel rectangular channels with an equivalent diameter of 0.64 mm. The latter is a narrow rectangular mini channel containing 10 rows of diamond pin fins with a staggered configuration, and height and longitudinal/transverse pitch of 0.5 mm and 2 mm respectively. To acquire the local value of heat flux and heat transfer coefficient, air jet impingement cooling devices were adopted to condense the vapor of refrigerants. The effects of vapor quality, mass flux, heat flux, and saturation pressure on flow condensation heat transfer coefficient were investigated with the operating conditions: vapor quality from 1 to 0, mass flux from 160 to 450 kg/(m2s), heat flux from 10.0 to 39.8 kW/m2, and saturation pressure from 600 to 1500 kPa. The experimental results indicated that the pin fin array significantly improves the condensation heat transfer coefficient up to nearly 186 % compared to the multiport mini channel in the high vapor quality region. For both channels, the local heat transfer coefficient increases with an increase in vapor quality, mass flux, and heat flux whereas decreases with increase in saturation pressure. The influence of heat flux and mass flux on heat transfer coefficient was more pronounced in the high vapor quality region than in the low vapor quality region. A sensitivity analysis was performed at different vapor quality levels. The most influential parameters in the smooth channel and the pin fin array are saturation pressure and mass flux, respectively. The relative contribution of heat flux is more obvious in the high vapor quality region. Some of the existing correlations have good prediction performance for the smooth channel experimental data in this paper, and the corresponding MAD is within 20 %. However, their deviations are much greater for the applications of pin fin array.

Anti-icing systems are crucial subsystems for ensuring aircraft safety. The movement of water droplets on protective surfaces and evaporation are common phenomena during flight. Understanding water droplets' movement and evaporation characteristics is critical to designing an effective active or passive anti-icing system. Experimental setups were conducted to investigate water droplets' motion characteristics and evaporation performance on heating surfaces with various coatings. The results indicated that the critical diameter for droplet motion was affected by surface hydrophilicity. A water droplet of th e same size could move more readily on hydrophobic surfaces. The results also revealed that the evaporation time of water droplets decreased with increasing surface hydrophilicity. This effect was more pronounced with the droplet size increase, as larger droplets exhibited higher temperature gradients than smaller droplets. The evaporation time of 6 µL water droplets on superhydrophobic coating surfaces was more than 3.5 times longer than that on hydrophilic coating surfaces. The findings of this paper reveal the mechanisms of water droplet motion and evaporation, which can benefit future anti-icing system design.

Ice crystal icing occurs in jet engine compressors, which can severely degrade jet engine performance. In this paper, two different numerical calculation methods, the Eulerian method and the Lagrangian method, were used to evaluate the dynamics, mass transfer, heat transfer, phase transition and trajectory of ice crystals. Then, we studied the effects of initial diameter, initial sphericity, initial temperature of ice crystal, and relative humidity of airflow on the phase transition and collection characteristics of ice crystal particles. Results indicate that the non-spherical characteristics of ice crystals have a significant impact on their impingement limits and collection characteristics. The collection coefficient of unmelted ice crystals is positively correlated with the initial particle diameter and sphericity, and negatively correlated with the initial particle temperature and the relative humidity of airflow. The melting rate of ice crystal particles on the impact surface increases exponentially with the initial diameter of the particles, linearly increases with the relative humidity of the airflow and initial temperature of the particles, and exponentially decreases with the sphericity of the particles.

The heat dissipation characteristics of fuel tank skins are critical for fuel thermal management. The overall heat transfer coefficient of the fuel tank skin mainly depends on the heat transfer coefficients inside and outside the bottom plate of the fuel tank, as well as the skin’s thermal conductivity and thickness. In this paper, a three-dimensional model is established based on the fluid-volume method to analyze the heat dissipation characteristics of composite fuel tank skins. The developed model was validated through various experimental tests. The results show that the air-side heat transfer coefficient has a significant effect on the total heat transfer coefficient of the skin, especially when the airplane is at a higher altitude or lower flight speed. The utilization of composite materials for the fuel tank skin reduces the overall heat transfer coefficient, and this reduction is more pronounced as the air-side convective heat transfer coefficient increases and the skin thickness increases. When the remaining fuel level is less than 20%, the overall heat transfer coefficient can increase by as much as 21. 1% compared to that of under full fuel conditions. The insights from this investigation are expected to benefit future fuel tank thermal management.

Abstract Composite material, supercritical aircraft wings, and multi-electrical technology represent the future development trend of civil aircraft. However, domestically, the use of electrical heating for anti-icing on civil aircraft made of composite materials has not yet been implemented. In this study, focusing on the anti-icing technology of a specific aircraft wing leading edge, the article initially designs a metal thermal spraying circuit based on the thermal load distribution on the surface of the anti-icing area. Next, the research explores the resistive properties of the electrical heating film on the composite material wing leading edge, examining how the porosity and oxide content of the coating affect its resistivity. Finally, the metal thermal spray test is completed on the leading edge of the composite material aircraft wing. The test results indicate that the adherence and deposition rate of the coating on the leading edge of the aircraft wing are reliable. The resistivity of the heating film meets the performance specifications. The article develops an integrated metal thermal spray control method based on high-curvature composite materials, resulting in an electrical heating film with excellent shape adaptability, varying power density, and strong bonding, providing support for the domestic advancement of wing electrical heating anti-icing technology.

In this paper, two key components of thermal management system are modeled by the underlying logic operation of SIMULINK. Simulink-PS signal conversion module is used to connect the electric grid and the calculation part of the heat grid to build the fuel tank heat grid model. The temperature transient simulation model of phase-change heat exchanger was established by using the integral module in Simulink library. Experimental verification and literature data verification are provided for these two components. The results show that the error between simulation results and experimental data is between 0.1% and 3%, which proves the accuracy and feasibility of the system modeling in this paper. It lays a foundation for the simulation of the overall thermal management scheme.

The supercooled water droplets in the air will form a water film on the aircraft during flight, which will then form icing, which will have an impact on the aerodynamic performance of the aircraft and even endanger the flight safety. In this paper, based on the Eulerian Wall Films model, the partial wetting effect is introduced, and the water film flow on flat plates driven by airflow shear force is investigated. The flow behaviours of water film with different contact angles under different flow rates were explored through water film test. The effectiveness of the calculation method for water film flow characteristics in this paper was verified by comparison between numerical simulation and test records, which laid a foundation for the anti-icing calculation in subsequent studies.

Concentration distribution of air pollutants in commercial aircraft cabins are important for providing passengers and crew wi th a healthy and comfortable environment. To verify whether the concentration of air pollutants meets airworthiness standards, this article focuses on the cabin of a specific aircraft and employs numerical simulation to analyze the CO2concentration distribution during single-engine drift. The MCT single-engine drift calculations reveal that pollutants initially increase and then decrease as the aircraft descends from 7620m to the emergency ventilation altitude, the concentrations of pollutants in the x section, y section and z section increasing by 66.87%, 55.61%, and 61.08% respectively, maintaining pollutant concentrations within acceptable limits throughout the drift.

Flow boiling in mini channels with micro pin fins is a promising heat sink technique to achieve high-efficient aircraft thermal management. The accurate prediction of its heat transfer coefficient is critical for the practical design of two-phase heat exchanger based on mini channels with micro pin fins. Previous investigation shows that heat transfer coefficient prediction accuracy of the machine learning method is generally better than that of conventional empirical correlations. However, the machine learning method cannot guarantee its prediction accuracy among different data domains. To extend the application region of the conventional machine learning method, a transfer learning framework was proposed in present study. First of all, an experimental system was built to acquire test data from different sample domains (i.e., the diamond pin fins with different geometries). Then a conventional machine learning model was developed based on the deep learning method. Furthermore, the developed deep learning model was adjusted with transfer learning process, and the performance of these two kinds of models (i.e., conventional machine learning model and transfer learning model) was comprehensively evaluated. Results showed that the conventional machine learning model had a good prediction accuracy with an overall deviation of 4.11 % but was only confined in the same data domain as training data. Differently, the transfer learning model with 70 % data set from the new domain can achieve appropriate prediction in the new domains with deviation of 4.28 %. The results of this paper demonstrated that the conventional machine learning model can extend into different domains with reasonable prediction accuracy through transfer learning frameworks. It will benefit the practical design of high-efficiency heat exchangers for aircraft thermal management.

2023年12月14日是祁英涛先生诞辰一百周年纪念日.祁英涛先生是新中国成立初期至20世纪80年代我国古建筑保护的见证者和践行者,是中国营造学社建筑遗产保护东方之路的传灯人.本文汇集了来自高等院校、地方古建筑保护研究机构及中国文化遗产研究院的专家学者,以点滴事例回顾了祁英涛先生对于中国文物保护事业的突出贡献.正如朱光亚先生所说,祁英涛先生是新中国成立后建筑遗产保护领域的先锋、主将和中坚,是构建中国的建筑遗产保护学的巨匠和开拓者,他不仅是一位学者和工程师,还是一位引导文物界众多后学的诲人不倦的老师.也正是在山西等省的古建筑修缮工程中,祁英涛先生不仅掌舵为各工程的技术方案决策做出了决定性的贡献,同时还推动了参与这些工程并在实践中不断学习总结提高的一批自学成才的技术人员的成长,包括地方上的一批英才的成长.朱光亚先生指出,热爱祖国,瞄准中国文物保护的问题,开放式学习,勿问西东,以经世致用的态度去回应现实,是祁英涛先生留给我们后学的一份宝贵的精神遗产.党的二十大提出的中国式现代化道路为我们指明了廓清文化遗产保护事业中各种迷雾的任务.回顾祁英涛先生那一代先贤走过的路和做出的思考,将为我们完成这一任务提供启示.

Flow boiling in micro pin fin arrays is an effective way to solve the heat dissipation problem. However, studies on the flow boiling performance of pin fin arrays with different structural parameters are still insufficient, especially for the application of long channels for practical evaporators in aircraft environmental control systems. In this paper, the flow boiling performance of R134a was experimentally investigated in a 300 mm long mini channel with micro pin fin arrays. The mass fluxes, heat fluxes, inlet saturation pressures and vapor qualities were in ranges of 200 -500 kg/(m2s), 15–30 kW/m2, 500–700 kPa and 0.05–0.90, respectively. The local heat transfer coefficient and pressure drop of staggered diamond pin fin arrays with different channel widths of 1.0, 1.2 and 1.4 mm were comprehensively studied. Subsequently, the performance analysis of the above channels was carried out. Results indicate that the nucleate boiling and convective boiling together govern the two-phase flow boiling heat transfer in the pin fin array. In particular, the increase in channel width delays the transition to convective boiling dominated flow. The local heat transfer coefficient increases with mass flux. However, in the high vapor quality region, the flow disturbance caused by a large mass flux may suppress the heat transfer, as high-speed gas destroys the continuous thin liquid film on the walls. Furthermore, the influence of saturation pressure on the heat transfer coefficient is reversed with the increase in vapor quality. Additionally, the performance analysis indicated better performance of the pin fin array at low vapor quality regions and small mass flux. Significantly, the best performance was obtained in pin fin array with a channel width of 1.4 mm, due to a drastic increase in two-phase pressure drop compared to heat transfer. Finally, a new correlation with the consideration of pin fin array structure parameters was proposed with an overall mean absolute deviation of 16.2

In a chiller plant, primary or critical sensors are used to control the system operation while secondary sensors are installed to monitor the performance/health of individual equipment. Current sensor fault detection and diagnosis (SFDD) approaches are not applicable to secondary sensors which usually are not involved in the system control. Consequently, a hybrid multiple sensor fault detection, diagnosis and reconstruction (HMSFDDR) algorithm for chiller plants was developed. Machine learning and pattern recognition were used to predict the primary sensor faults through the comparison of the weekly performance curves. With the primary sensor signals reconstructed, the secondary sensor faults were estimated based on mass and energy balance. By applying the algorithm with various logged plant data and comparison with site checking results, a maximum of 75% effectiveness could be achieved. The merits of the present approach were further justified through off-site sensor testing which reinforced the usefulness of proposed HMSFDDR algorithm.

研究了制冷剂R134a在角度分别为30°、60°和90°的菱形离散肋微小通道内的流动沸腾换热特性.微小通道内菱形离散肋分布区域长300 mm、宽20 mm,进口处饱和压力为(700±5)kPa,其他工况范围为:干度0～1,质量流率200～500 kg/(m2·s),热通量10～30 kW/m2.实验结果表明:离散肋中的流动沸腾换热受到核态沸腾和对流沸腾的共同作用,传热系数随质量流率和热通量的增加而增加,但随着干度的升高,热通量的作用减弱并趋于消失.此外,离散肋结构对流动沸腾换热有显著影响,相同工况下,90°菱形离散肋的传热系数高于30°和60°,且在高干度更显著.最后,基于实验数据和分析结论,提出了一个适用于预测不同结构离散肋微小通道中流动沸腾传热系数的计算关联式.