Glaze Icing Research Articles

Improved composite network via bismuth iodide for efficient ice-nucleating application

The urgent demand for electricity requires more safe energy transportation. AgI-based weather modification agents are commonly employed to facilitate ice nucleation and remove the undesirable glaze icing to suppress the negative effects of natural disasters. However, the intrinsic nucleation potency of AgI strictly limits its further improvement. Here, a hexagonal BiI3 was added in AgI-based agents. The chemical interactions of BiI3 and precursors optimize the crystallization of the polymer composite, leading to an oriented composite network. In addition, BiI3 could alter the structure and morphology of the combustion products, therefore creating more possible heterogeneous nuclei sites. The resultant BiI3-modified AgI-based weather modification agent exhibits an ice nucleation ∼1014, which is nearly ten times higher than the sample without AgI-BiI3, leading to a 71.21% enhancement of deicing efficiency compared to AgI sample. Our results indicate the effectiveness of BiI3 dopant to improve both nucleation and deicing performance for weather modification applications.

Anti-icing performance and influencing factors of super-lubricated surface in simulated glaze icing

Abstract The icing of the overhead aluminum conductor has caused the conductor load to be too heavy or uneven, which results in huge accidents. The super-lubricated surface (SLIPS) shows great potential in anti-icing. Glaze ice is a common type of icing, and its damage to transmission lines is the most serious. However, the properties and influencing factors of anti-icing lubricated surfaces at glaze ice surroundings are rarely reported. In this study, the super-lubricated surface was prepared by the anodic oxidation method, and the anti-icing properties and influencing factors of surfaces were investigated in glaze ice surroundings. The results demonstrate that the SLIPS can decrease the icing amount, which is only 41% of the original aluminum surface. SLIPS exhibits excellent anti-icing performance in different environments temperatures and rainfalls. This study provides experimental guidance for the practice application of SLIPS in anti-icing aluminum conductors.

Ice accretion simulation incorporating roughness effects and separation correction through a transition model

In the simulations of ice accretion, accurately modeling the impact of surface roughness and calculating the separated flow are crucial aspects. A modified laminar–turbulent transition model that incorporates both separation and roughness-induced transition correction is employed for icing simulations. An iced airfoil was selected to validate the modified model's predictive capability for large separation, and a rough airfoil was utilized to assess the modified model's capability in simulating roughness effects. Icing simulations under different conditions are conducted for an airfoil. The results indicate that roughness induces an earlier laminar–turbulent transition, thereby influencing the heat transfer coefficients. The effects of separation and roughness correction on rime icing simulation are minimal, but they are significant for glaze icing simulation, resulting in more accurate predictions of maximum ice thickness and ice horn orientation. The simulated glaze ice causes more pronounced separation and more substantial reductions in lift compared to simulated rime ice. The modified model can accurately predict the separation bubble and reduce the prediction error of lift over 60%.

Ice accretion characteristics on rotating aeroengine fan blades

An experimental study was conducted to characterize the dynamic ice accretion process on rotating aero-engine fan blades to evaluate the icing-induced detrimental effects on the fan rotor performance. A scaled spinner-fan model was installed in an Icing Research Tunnel and exposed to typical rime and glaze icing conditions. It was found that, while ice structures accreted on both the suction and pressure surfaces of the fan blades, more ice accumulated in the region near the blade roots than those near the blade tips. The ice structures accreted on the fan blades not only deteriorated the shapes of the deliberately designed blades greatly but also blocked the airflow passages through the fan rotor substantially, regardless of the icing type. More specifically, the thickness of the fan blades was found to increase up to 40 % after undergoing 480 s of the rime icing experiment, the airflow passages were blocked by up to 14 % due to the rime ice accretion near the blade roots, resulting in about 70 % reduction of the air pressure increment across the fan rotor. Due to the combined effects of the aerodynamic shear forces and centrifugal forces associated with the rotating motion, substantial water runback was observed over the rotating blade surfaces under the glaze icing condition, resulting in the rapid growth of more complex “needle-like” icicles along the blade leading edges. Glaze ice accretion was found to cause more serious and faster performance degradation to the fan rotor than the rime icing scenario. While the airflow passages between the neighbouring blades were blocked by up to 18 % after undergoing 120 s of the glaze icing experiment, the airflow was found to be depressurized, instead of pressurized, after passing the iced fan rotor.

A novel superhydrophobic Al conductor with excellent anti-icing performance and its mechanism

Overhead conductor icing is one of the main factors causing transmission line failures. Superhydrophobic surface (SHS) with composite pore structure exhibits excellent anti-icing effectiveness and durability. Herein, this novel SHS was prepared on complex aluminum conductors by two-step anodic oxidation technology, and the motion behavior of droplets on the SHS conductor in the glaze icing environment was studied experimentally to analyze the anti-icing mechanism. The simulated glaze icing experiment results show that the SHS conductor significantly reduces the ice accumulation, and the icing weight is only 23 % of the untreated conductor. Compared with the flat surface, the groove structure of the SHS conductor enhances the ability of millimeter-sized droplets to bounce, and the contact time is less than 9 ms. Also, micron-sized spraying droplets exhibit excellent mobility on the SHS conductor surface, and the contact time is further reduced. Moreover, the SHS conductor has a good ability to delay the freezing of spraying droplets. The above factors endow the SHS conductor excellent anti-icing performance. This work lays a foundation for the anti-icing application of SHS on transmission lines.

Anti-icing application of superhydrophobic coating on glass insulator

Insulators, as important components in transmission lines, are prone to disturb the safe running of the power system by the ice accumulation on surfaces. Traditional anti-icing coatings are difficult to practically apply to insulators. Here, superhydrophobic (SHP) coatings were fabricated on the glass insulator surface by spraying. We studied microstructure, wettability, water droplet bouncing behavior, and anti-glaze icing properties of SHP coating. The results demonstrated that SHP coatings had micro-nano rough structures. The excellent superhydrophobicity (contact angle of 165.2° and sliding angle of 3.7°) was achieved. The water droplet was easily adhered to the surface of the glass insulators. At the same time, individual water droplets could bounce away from the surface after impacting the SHP coating. In the glaze environment, water droplets sprayed onto the SHP coating merged with each other and slid off the surface. These significantly reduce the likelihood of freezing. Furthermore, the SHP coating could dramatically delay the glaze icing and decrease the icing area. The icing weight and icicle length were smaller than glass insulators. The SHP coatings prepared in this work display great potential for the anti-icing of glass insulators.

Effects of the Second Anodization Parameters on the Hydrophobicity and Anti-Icing Properties of Al Surface with Composite Nanopore Structure

Icing on transmission lines often causes potential electric damage in power systems. Superhydrophobic anodized Al conductors have been proposed to have good anti-icing properties. In this study, superhydrophobic anodized Al conductors with composite nanopore structures were prepared by a two-step anodization. The microstructure, hydrophobicity, and anti-icing properties of composite nanopore structures were compared and studied. The optimal preparation parameter was determined as a current density of 0.04375 A/cm2 and anodization time of 15 min. Compared with the bare substrate, the optimal anodized Al surface of the composite nanopore structures show excellent hydrophobic and anti-icing properties, including a contact angle of 173°, a contact angle hysteresis of 0.122°, an ice adhesion strength of 0.71 kPa, and a glaze icing weight of 0.1 g after the 8 h. Therefore, the prepared anodized Al surface of composite nanopore structures with good anti-icing properties has profound application potential for overhead transmission lines.

Fabrication of Superhydrophobic Coatings by Using Spraying and Analysis of Their Anti-Icing Properties

Ice accumulation on glass insulators is likely to cause faults such as flashover, tripping and power failure, which interfere with the normal operation of the power grid. Accordingly, superhydrophobic coatings with great anti-icing potential have received much attention. In this study, three superhydrophobic coatings (PTFE, Al2O3 and SiO2) were successfully prepared on glass surfaces by using one-step spraying. The microscopic morphology, wettability, anti-icing and anti-glaze icing properties of the superhydrophobic coatings were comparatively analyzed. The results indicated that the PTFE coating had a densely distributed rough structure, showing a contact angle of 165.5° and a sliding angle of 3.1°. The water droplets on the surface could rebound five times. Compared with the Al2O3 and SiO2 coatings, the anti-icing performance of the PTFE coating was significantly improved. The freezing time was far more than 16 times that of glass (4898.7 s), and the ice adhesion strength was 9 times lower than that of glass (27.5 kPa). The glaze icing test in the artificial climate chamber showed that the icing weight of the PTFE coating was 1.38 g, which was about 32% lower than that of the glass. In addition, the icing/melting and abrasion cycles destroyed the low-surface-energy substances and nanostructures on the surface, leading to the degradation of the anti-icing durability of the PTFE coatings. However, the PTFE coating still maintained excellent hydrophobicity and anti-icing properties after UV irradiation for up to 624 h. The superhydrophobic coatings prepared in this work have promising development prospects and offer experimental guidance for the application of anti-icing coatings on glass insulators.

The Glaze Icing Performance of a Robust Superhydrophobic Film Composed of Epoxy Resin and Polydimethylsiloxane

Ice accretion on transmission lines can cause operational difficulties and disastrous events. In this study, a micro/nano-structured epoxy resin/polydimethylsiloxane (EP/PDMS) film on glass, with water droplet contact angles (CA) observed as high as 160° and the water droplet sliding angle (SA) < 1° was fabricated by aerosol-assisted chemical vapor deposition (AACVD). The glaze icing performance of the superhydrophobic EP/PDMS films have been investigated by comparing the bare glass and room temperature vulcanized (RTV) silicon rubber-coated glass substrate representing the glass insulators and silicone rubber insulators, respectively. Compared with the bare glass and the RTV silicon rubber coating, the EP/PDMS superhydrophobic coating showed excellent performance in delaying glaze icing, especially in the early stages of icing. After 20 min of glaze icing with tilting angle of 90° at −5 and −10 °C, 38.9% and 85.7% of the RTV silicon rubber coating were covered, respectively, and less than 3% of the EP/PDMS coating was covered by ice when the blank glass sheet was completely covered. The EP/PDMS films also showed good mechanical robustness and long-term stability, which are important considerations in their widespread real-world adoption.

Anti-Icing Mechanism for a Novel Slippery Aluminum Stranded Conductor.

The icing of transmission conductor seriously threatens the safe operation of power grids. Slippery lubricant-infused porous surface (SLIPS) has shown great potential for anti-icing applications. However, aluminum stranded conductors have complex surfaces, and the current SLIPSs are almost prepared and studied on small flat plates. Herein, the construction of SLIPS on the conductor was realized through anodic oxidation and the anti-icing mechanism of the slippery conductor was studied. Compared to the untreated conductor, the SLIPS-conductor reduces the icing weight by 77% in the glaze icing test and shows very low ice-adhesion strength (7.0 kPa). The excellent anti-icing performance of the slippery conductor is attributed to the droplet impact dynamics, icing delay, and lubricant stability. The dynamic behavior of water droplets is most affected by the complex shape of the conductor surface. Specifically, the impact of the droplet on the conductor surface is asymmetric and the droplet can slide along the depression in low-temperature and high-humidity environments. The stable lubricant of SLIPS increases both the nucleation energy barriers and the heat transfer resistance, which greatly delays the freezing time of droplets. Besides, the nanoporous substrate, the compatibility of the substrate with the lubricant, and the lubricant characteristics contribute to the lubricant stability. This work provides theoretical and experimental guidance on anti-icing strategies for transmission lines.

Evaluating Practical Performance of Weather Modification Aerosol Catalysts via 12000 m3 Artificial Climate Chamber

The lack of experimental tools to evaluate the deicing performance of newly developed weather modification agents hinders their further development. Here, for the first attempt, the largest artificial climate chamber in Asia (volume = 12000 m3) was employed and successfully generated freezing rains. As a result, deicing properties of modified aerosol catalysts could be revealed both qualitatively and quantitatively. It was found that 96.98% of the formed glaze icing was inhibited and transformed to snow after applying the catalyst. Such an artificial climate chamber may be applicable for evaluating new weather modification agents without the need for field experiments.

Experimental Study of Dynamic Icing Process on a Pitot Probe Model

An experimental study was conducted to characterize the dynamic ice accretion process over the surface of a typical aeronautic Pitot probe model under different icing conditions. The experimental study was conducted in the Icing Research Tunnel available at Iowa State University. While a high-speed imaging system was used to record the dynamic ice accretion process, a three-dimensional (3D) scanning system was also used to measure the 3D shapes of the ice layers accreted on the test model. While opaque and grainy ice structures were found to accrete mainly along the wedge-shaped lip of the front port and over the front surface of the probe holder under a dry rime icing condition, much more complicated ice structures with transparent and glazy appearance were observed to cover almost entire surface of the Pitot probe under a wet glaze icing condition. While a flower-like ice structure was found to grow rapidly along the front port lip, multiple irregular-shaped ice structures accreted over the probe holder under a mixed icing condition. The characteristics of the icing process under different icing conditions were compared in terms of 3D shapes of the ice structures, the profiles of the accreted ice layers, the ice blockage to the front port, and the total ice mass on the Pitot probe model. The acquired ice accretion images were correlated with the 3D ice shape measurements to elucidate the underlying icing physics.

Extended scaling approach for droplet flow and glaze ice accretion on a rotating wind turbine blade

This paper presents and analyzes a non-dimensional model of the flow field and droplet trajectories with glaze ice accretion on a rotating wind turbine blade. The formulation leads to similitude relationships for glaze ice accretion to evaluate new scaling parameters corresponding to the rotation of the blade. New scaling parameters are developed to determine ice scaling conditions based on the geometry scale factor of a wind turbine blade. The scaling methodology can be used to determine alternative test conditions and predict glaze icing conditions on a full-scale wind turbine blade. Numerical CFD icing simulations are performed using ANSYS FENSAP ICE software. A wind blade model is developed using blade element momentum theory (BEM). Each blade size is tested at specific flow conditions using the scaling equations. Scaled conditions for velocity (streamwise and rotational), droplet size, and icing time are tested. CFD solutions for the flow field are obtained for comparisons of the velocity, droplet trajectories, pressure coefficient distributions, ice thickness, and ice shapes. Recommended parameters to be used for glaze ice scaling on a rotating blade are presented and numerical results are reported to support these recommendations. The paper provides new insights into modeling of glaze ice accretion on large wind turbine blades based on smaller scaled blade sections tested in a laboratory setting.

Proper matching of lubricants and modifiers: Another key factor for durable anti-icing performance of lubricated surfaces

Slippery liquid-infused porous surfaces (SLIPSs) with anti-icing properties are challenged by the lubricant loss. Many strategies (such as structure optimization, lubricant improvement) are used to retain the lubricant in the porous structure. However, the matching of modifier and lubricant is rarely studied, which is another key factor for durable anti-icing performance of lubricated surfaces. Herein, proper matching of different lubricants and modifiers were investigated. Perfluoropolyether oil (PFPE) and silicone oil (SO) are chosen as lubricants. Linear alkane (OTS) and fluorinated alkane (FAS) are chosen as modifiers. A series of SLIPSs were prepared by infusing lubricants into unmodified and modified anodized aluminum oxide (AAO) surfaces. The suitable matches (OTS with SO, FAS with PFPE) make the prepared SLIPS have high water mobility and enable high affinity between the lubricant and modified AAO surface. The former contributes to improving the anti-icing performance in the simulated glaze icing test, and the latter is beneficial to improving the durability during the icing/deicing cycles. This work provides useful information to determine the suitable pairs of lubricant-modifier for durable anti-icing lubricated surfaces.

Influence of key parameters of ice accretion model under coexisting rain and fog weather

Based on 30 complete wire icing processes lasted longer than 24 h observed from the Enshi, Jinsha, Dacaoping and Shennongding of Shennongjia in mountainous areas of Hubei province during the winter of 2008–2016, the macroscopic effects of rain–fog weather on the ice accretion process were analyzed. Furthermore, the distribution characteristics of key simulation parameters in supercooled fog (SF) and freezing rain (FR) were discussed according to the physical model of icing process. Finally, the evolution characteristics of the simulated ice thickness in rain–fog weather were proposed. Results showed that the duration of ice accretion in mountainous areas is the key factor affecting the maximum ice thickness; the freezing rain is most frequent during the glaze icing process, which leads to the substantial growth of ice thickness. The average growth rates of ice thickness with and without freezing rain are 1.26 mm h−1 and -0.11 mm h−1, respectively. Collision rate is the main parameter for inhibiting ice accretion of SF, with an average value of ∼ 0.1, while freezing rate is the main parameter for inhibiting ice accretion of FR, with an average value of ∼ 0.6. The ice accretion of SF shows the characteristics of periodic growth, while the ice accretion of FR shows the explosive growth of ice thickness, which makes the simulated values of icing closer to the observations. The ice formation efficiency of FR was more than twice that of SF, with a negative feedback mechanism to the ice accumulation of SF.

An experimental study of dynamic icing process on an Aluminum-Conductor-Steel-Reinforced power cable with twisted outer strands

An experimental campaign was conducted to investigate the dynamic icing process on an Aluminum-Conductor-Steel-Reinforced (ACSR) power cable with twisted outer strands and characterize the resultant wind loads experienced by the power cable under both dry rime and wet glaze icing conditions. In addition to recording the dynamic icing process over the cable surface with a high-resolution imaging system, the three-dimensional (3D) shapes of the ice layers accreted on the cable model were also quantified by using a novel 3D profile scanning system. While the evolution of the wake flow behind the iced ACSR cable was quantified with a Particle Image Velocimetry (PIV) system, the variation of the wind loads experienced by the cable model was also examined based on the measurements of force/moment transducers. Under the dry rime icing condition, opaque, grainy ice was found to accrete only within the impinging zone of airborne water droplets over the cable frontal surface without any noticeable water runback flow over the cable surface. In comparison, substantial unfrozen water was observed to run back over the cable surface under the wet glaze icing condition, causing the formation of transparent, glazy ice layer over a much wider area over the cable surface. Correlating with the formation of more complicated glazy ice humps/horns over the ACSR cable surface, the accumulated ice mass was found to grow much faster during glaze icing process, in comparison to that of rime icing case. While the resultant wind loads acting on the iced ACSR cable was found to decrease gradually with the increasing icing time under the rime icing condition, the corresponding values were found to increase continuously under the glaze icing condition.

Experimental Study of Dynamic Ice Accretion Process over Rotating Aeroengine Fan Blades

An experimental campaign was conducted to study dynamic ice accretion on rotating aeroengine fan blades and evaluate the icing-induced performance degradation to the fan rotor. The experiments were performed in an icing research tunnel with a scaled spinner-fan model exposed to typical dry rime and wet glaze icing conditions. Although the accreted ice layers were found to conform well with the shapes of the fan blades under the rime icing condition, the performance of the fan rotor was found to degrade substantially due to the much rougher blade surfaces, causing up to 60% reduction in the pressure increment after 360 s of the rime icing experiment. More complicated, needlelike icicles were found to grow rapidly over the rotating spinner and fan blades under the glaze icing condition due to the combined effects of the aerodynamic forces and the centrifugal forces associated with the rotation motion. The irregular-shaped glaze ice structures were found to induce tremendous detrimental effects on the fan rotor, making the airflow depressurized, instead of pressurized, after passing the iced fan rotor. The iced spinner-fan model was always found to consume more power, regardless of rime or glaze ice structures accreted on the fan blades.

Interface quasi‐distributed fibre Bragg grating positioning detection of glaze icing load on composite insulators

The electrical performance of transmission line insulators will decrease dramatically under ice-covered conditions, and ice flashover may occur under operating voltage. There is no direct and effective monitoring method for ice cover on insulators of transmission lines. In this paper, the interface quasi-distributed fibre Bragg grating (FBG) is used to study the positioning detection of glaze icing loads on composite insulators, and a mechanical lever model of single glaze icing load on single umbrella detection with three FBGs is established. Based on this model, a multi-glaze location detection method on multiple umbrella skirts is proposed. Six optical fibres with 13 quasi-distributed FBGs each are implanted into the interface of a 110 kV composite insulator. The minimum load test of FBG for detecting glaze icing load, the FBG axial/circumferential sensing rule test for the glaze, and the weight simulation test and laboratory icing verification test for multi-glazes on multi-umbrellas location detection method are carried out. The results show that the positioning of glaze simulated by weights is accurate, and the positioning of icing in the laboratory is basically correct.

Preventive Scheduling for Reducing the Impact of Glaze Icing on Transmission Lines

The icing on transmission lines threatens the power system security while the heat caused by power transmission losses can prevent icing growth. This paper proposes a preventive scheduling model for mitigating the glaze icing by optimizing the distribution of power losses on ice-coated transmission lines. An analytical glaze icing growth model is established based on the heat balance theory, which builds a direct relationship between icing growth and power transmission losses. Accordingly, the analytical glaze icing model is embedded into the proposed scheduling model to quantify the impact of power system schedules on transmission line icing and reduce the glaze icing of transmission lines. The scheduling model co-optimizes active power dispatch, demand response, and reactive power optimization for promoting the de-icing effect. To overcome the computational difficulties, the analytical glaze icing growth model is further linearized, and the Lagrangian relaxation method is adopted for identifying a practical solution. Case studies are conducted on different icing scenarios in the IEEE RTS-79 test system to verify the validity of the proposed model. Results show that the proposed preventing scheduling model can avoid the icing on transmission lines for mild ice disasters, while efficiently restraining the icing growth on transmission lines when they cannot be completely de-iced in severe storms.

An experimental study on mitigating dynamic ice accretion process on bridge cables with a superhydrophobic coating

An experimental study is conducted to evaluate the effectiveness of utilizing a superhydrophobic surface (SHS) coating to mitigate ice accretion on bridge cables and to characterize the resultant aerodynamic forces acting on bridge cables under different icing conditions. Two bridge cable models (i.e., a model with untreated hydrophilic surface and a model with SHS coated surface) were used for a comparative study. The dynamic ice accretion process and the resultant aerodynamic forces acting on the bridge models were found to change significantly after applying the SHS coating to treat the cable surface. Under glaze icing condition, the SHS coated cable model was found to have much narrower ice coverage, less amount of accreted ice mass, and smaller aerodynamic drag forces, in comparison to that with untreated cable surface. While the SHS coating was found to be less effective for icing mitigation under rime icing condition, the much rougher rime ice grains accumulated within the droplet direct impinging zone on the SHS coated cable surface caused a greater reduction of the aerodynamic drag forces acting on the cable model at the initial stage of the rime icing process. The acquired ice accretion images were correlated with aerodynamic force measurements for a better understanding of the underlying physics in the context of bridge cable icing mitigation.