Piccolo Tube Research Articles

Experimental validation and tightly coupled numerical simulation of hot air anti-icing system based on an extended mass and heat transfer model

When an aircraft flies through a cloud containing supercooled liquid water droplets, ice accretion may deposit, posing a threat to flight safety. Hot air anti-icing is one of the most widely used anti-icing techniques. An extended mass and heat transfer model for runback water on a hot air anti-icing surface is developed. The model is based on the mass conservation and energy conservation of continuous water film and rivulet water film, considering the conditions under which continuous water film may break up into rivulet water film. Additionally, the effect of water vapor resulting from liquid water evaporation is also taken into account. Then, a three-dimensional tightly coupled numerical method for hot air anti-icing systems is constructed based on the developed model. The method includes modules for the calculation of external cold air flow, solid skin heat conduction and internal hot air flow, the calculation of water droplet impingement, and the calculation of anti-icing thermodynamics. The accuracy of the method is validated against experimental studies on an enhanced heat transfer piccolo tube anti-icing system in the icing wind tunnel of China Aerodynamics Research and Development Center (CARDC). The temperature results obtained from the three-dimensional numerical simulations showed good agreement with the experimental results, indicating that this method can be utilized in preliminary and detailed designs to evaluate the thermal performance of hot air anti-icing systems.

Influence of confinement on pressure and heat transfer distribution by impinging an air jet from a piccolo tube on a concave surface

Experimental work is carried out to understand the effect of longitudinal confinement on wall static pressure and heat transfer distribution on a concave surface by impingement of an air jet from a piccolo tube (orifice). The experiments are conducted for different parameters such as orifice diameter (d = 10–16 mm), curvature ratio (D/d = 2–5), circumferential angle (θ = 0°−40°), orifice to target surface distance (Z/d = 1–4), confinement distance to the orifice diameter ratio (l/d = 15–9.375) and the Reynolds number of flow (Re = 5000–50,000). It is observed that the maximum wall static pressure and the Nusselt number occur at a stagnation point (X/d = 0 and θ = 0°) for all Z/d and l/d ratios. For confined flow, the value of wall static pressure (Cp and Cpo ) and the Nusselt number (Nu and Nuo ) distribution are higher when compared to unconfined flow conditions. The results of the study can be used in optimising the cooling system design.

Single- and multi-objective optimization of an aircraft hot-air anti-icing system based on Reduced Order Method

Geometric optimization of piccolo tube provides a cost-effective approach to shorten the design circle of hot-air anti-icing system and maximize the utilization efficiency of bleed air. An optimization methodology for aircraft hot-air anti-icing systems based on Reduced Order Method (ROM) is developed. ROM based on Proper Orthogonal Decomposition (POD) and Radial Basis Function neural network (RBF) is constructed to evaluate objective and constraint functions of single- and multi-objective optimizations. POD is adopted for data compression and characteristics extraction for the anti-icing performance snapshot matrix. Then, a lower-dimensional approximation for the snapshot matrix is derived from the projection subspace consisting of a set of basis modes. RBF neural network is introduced to construct the mapping between the design variables of piccolo tube geometric configuration samples and the linear combination coefficients of basis modes. The piccolo tube is parameterized by five design variables and is optimized by the developed methodology. The predicted results indicate that the constructed ROM can provide the distributions of surface temperature and runback water with high accuracy and computational efficiency. The optimal results indicate that the developed optimization methodology is efficient and reliable for handling single- and multi-objective design problems of aircraft piccolo tube hot-air anti-icing systems.

CFD Impingement Flow Study on Temperature Profile of Concave Plate

All the aircraft are equipped with an anti-icing system to prevent ice accretion on the body of the aircraft. The anti-icing system is important because ice accretion degrades the performance of the aircraft and may cause aircraft crashes. Piccolo tube Anti-icing system uses the impingement hot air and creates hotspot on nacelle lip-skin and edges of wings. The temperature distribution caused by the impingement of hot air must be studied to get a better design of the anti-icing system. The skin geometry shape affects hot airflow behavior in the impingement vicinity, hence influences temperature distribution on wing skin and nacelle lip-skin. Thus, the CFD simulation of the hot air impingement air various concave curvature radius was conducted by using ANSYS Fluent 19.2. The result shows the temperature contour has been plotted from the software. Correlation between Nusselt number on impingement point and Reynolds number was successfully done as the validation. Increasing the Reynolds number increases the dimensionless temperature of the concave plate. Temperature is 0.147125 has been recorded as the highest dimensionless temperature under the set of an air temperature of 43°C, Reynolds number of 4070, and 300mm curvature radius. Besides that, increases in heat dissipation decrease the dimensionless temperature of the plate with the curvature radius also decreases. The dimensionless temperature increases from 0.138747 to 0.142316 when the curvature radius increases from 150mm to 300mm.

Optimization of Parameters Affecting Anti-Icing Performance on Wing Leading Edge of Aircraft

In this article, one of the hazardous trouble in-flight situations called ice accumulation on wing leading edge of aircraft has been numerically investigated. While the target surface is kept constant temperature at Tw=263.15 K, the inlet temperature is taken constant at Tin=473.15 K and it enters to the system with m ̇=0.004 kg/s. The investigation starts with validation of numerical study utilizing airfoil type of NACA 0015 using constant piccolo tube dimensions, jet angle, distance among jets and distance between jet-to-target positions. The second and third stages are to analyze the anti-icing performance of changing positions of piccolo tube on X (4≤H/d≤8) and Y (-1.25≤L/d≤1.25) directions under different jet angles (30°≤≤150°). The fourth stage is to determine the optimum H/d, L/d, and ratios to increase anti-icing performance with maximum convective heat transfer and minimum pressure drop condition. The optimization study has been done using Response Surface Methodology (RSM). Finally, while the best anti-icing performance proposed design is achieved using° L/d=0.0, and H/d=4.0, the optimization results show that the L/d, and H/d values should be 55.45°, 0.0, and 4.0, respectively to achieve maximum heat transfer rate with minimum pressure drop value.

Investigation of fluid flow and heat transfer characteristics for a thermal anti-icing system of a high-altitude and long-endurance UAV

ABSTRACT This research performs a three-dimensional simulation to investigate the fluid flow and heat transfer characteristics for hot-air jets impinging on the wing leading-edge surface. Both the periodic model and the whole model are proposed to examine the thermal anti-icing performance for hot air ejecting from a piccolo tube onto the impinging surface. The results show that, for the periodic model, the enhancement of the average Nusselt number can be up to 94.4%, and the enhancement of the average heat flux is up to 29.7% for 100 ≦ uj ≦ 350 m/s and 300 ≦ Tj ≦ 550 K when compared with the results of the basic case of uj = 200 m/s and Tj = 450 K. The maximum enhancement of the $\overline {Nu} $ is 62.3% as the spacing decreases from Sn = 8 to Sn = 4 and the optimum Numax and $\overline {Nu} $ occur at Si = 5 and Si = 6 for the single-array holes with 3 ≦ Si ≦ 7 and 4 ≦ Sn ≦ 8. In addition, the θh for maximum $\overline {{{Nu}}} $ is 10° and the maximum enhancement of the $\overline {{{Nu}}} $ is ∼15.7% for double-array holes and staggered-array holes as compared with single-array holes. In addition, the nonuniformity of Nusselt number and heat flux distributions are significantly improved. For the whole model, the maximum enhancement of the average Nusselt number is ∼7.5% and the optimum configuration is θh = 40°, for cases with La = 60, Dp = 8, $\dot{m}$ = 0.15 kg/s, Si = 6, 1 ≦ Nh ≦ 5, 10 ≦ Sn ≦ 30 and 10° ≦ θh ≦ 60°.

Turbulent multi-jet impingement cooling of a heated circular cylinder

The experimental and numerical studies of eight circular air jets emerging from a piccolo tube and impinging over a long heated target cylinder of diameter (D), have been presented for both the inline and staggered layouts of holes. The ratio of the diameter of the heated cylinder (D) to the inner diameter of piccolo tube (dpic), D/dpic is taken as 2.4. The jet Reynolds number, calculated based on the average mass flow rate of a single jet and the diameter (d) of jet holes on a piccolo tube, Red=Mind/(nAjetμ), is varied in the range of 5000 – 20000. The dimensionless distance from the piccolo tube to the target cylinder, H/d is varied from 2 to 12. The dimensionless spacing between two adjacent holes, Pc/dpic and the D/d are considered in the range of 1.4 ≤ Pc/dpic ≤ 2.9 and 5.5 ≤ D/d ≤ 17, respectively. The experimental results show that the configuration of multi-jet impingement with D/d = 5.5 cools the circular cylinder more effectively due to higher mass flow rate of jet fluid for the fixed values of Red and H/d and Pc/dpic. Correlations for the average Nusselt numbers are also presented for both the inline and staggered layouts of jets using the experimental results.

Heat transfer enhancement of a heated cylinder with synthetic jet impingement from multiple orifices

This study proposed and investigated a method to enhance the heat transfer performance of a heated cylinder with synthetic jet impingement from multiple orifices. A synthetic jet has a flow with alternately changing orientations at its exit and eventually generates a periodic flow in constant orientation in the area far from the exit. First, the flow characteristics of synthetic jets generated from the multiple orifices on a piccolo tube were investigated in detail with a hot-wire anemometer. Next, the heat transfer of a heated cylinder was enhanced with multiple synthetic jets. The Nusselt number of the heated cylinder was calculated using the temperature variation of the cylinder with time. The heat transfer rate enhanced with multiple synthetic jets was 2–3 times higher than that without jets. The results also showed that the heat transfer rate with upward-oriented jets from the piccolo tube located below the heated cylinder was higher than that with downward-oriented jets from the tube located above the cylinder. We also compared synthetic jets to continuous jets generated with a high-pressure air source. The results showed that the effects of the synthetic jets were valid at greater distances than those of the continuous jets.

Turbulent impingement jet heat transfer on concave surfaces for aeronautical applications

Turbulent impingement jet heat transfer on concave surfaces has been employed in different engineering applications, e.g., aviation industry. In the aircraft anti-icing systems, hot air from the engine compressor impinges on the inside surface of the leading edge through small drilled holes, configuring the so-called piccolo tube system. A critical aspect in the design of such system is the prediction of heat transfer impinging jets from the piccolo tube. The correct evaluation of the heat transfer rate in such devices is of great interest to optimize both the anti-icing performance and the hot-air bleeding from the high-pressure compressor. Therefore, the present study develops a parametric study of the impingement jet flow on concave surfaces employing the CFD tool. The main goal is to determine the effect of the jet Mach number on this heat transfer mechanism. The present results also showed that at lower H/d conditions, i.e., lower jet-to-impinging surface distances, the temperature field exhibits a more efficient heating process inside the domain, resulting in greater Nusselt number values. A correlation taking into account geometric parameters such as the jet-to-jet spacing and the jet-to-impinging surface distance and jet Mach number is also proposed.

Effect of nozzle rotation angles and sizes on thermal characteristic of swirl anti-icing

The Federal Aviation Administration requires all aircraft manufacturers to adhere to maximum noise level standards. Thus, a bias acoustic liner is introduced, to intensify the noise equipment system, as well as prevent ice accumulation on the nacelle D-chamber. The hotspot phenomenon, by the Piccolo tube anti-icing system, could damage the bias acoustic liner. Therefore, a swirl anti-icing system is further investigated, to reduce the hotspot effect on the bias acoustic liner. The present work investigates the effect of nozzle rotation angles at various mass-flow-rates of hot-air supplied on the nacelle lip-skin temperature distribution, in order to enhance the swirl antiicing system’s performance. The effect of the nozzle ratio area on the swirl anti-icing system’s performance to be discussed in the present work. The simulation results show that the hotspot temperature decreases by 26 % and the cold spot temperature increases by 18 %, as the nozzle to be rotated from 0o to 13o towards the inner skin. However, the nozzle ratio area shows a negative effect on the swirl antiicing performance, where the hotspot temperature increases by 6.7 % and the cold spot temperature decreases by 30.2 % with the ratio nozzle area increasing from 0.1083 to 0.8354. According to swirl anti-icing empirical values, the average Nusselt number is directly proportional to the average Reynolds number. In conclusion, the temperature distribution on the nacelle lip-skin and the swirl anti-icing system’s performance improves as the angle of nozzle direction increases, rotating towards the inner skin. Swirl anti-icing does not generate hotspot on the inner skin, thus making it suitable for use in a bias acoustic liner system.

Simulation Study of the Effect of Anti-Icing on the Nacelle Lip-skin Material

One of the key concerns in aircraft flight is the accumulation of ice on the wing leading edge and nacelle lip-skin. It is well known that ice accretion may dangerous to the aircraft since it severely degrades the aerodynamic performance of aircraft. As a consequence, the piccolo tube anti-icing system is installed by the aircraft manufacturer inside wing leading edge and nacelle lip-skin in order to prevent ice accumulation. However, the hotspots from piccolo tube anti-icing system potentially defect or destroy material of nacelle lip-skin. Therefore, in present work, the numerical investigation with one-way fluid-structure interaction (FSI) has been carried out to study the effect of Reynolds number based on effective-impingement-surface of piccolo tube anti-icing system on the maximum thermal stress and strain of nacelle lip-skin for several aluminum series. The simulation results reveal that the maximum strain increases with the Reynolds number. For the stress analysis, the maximum stress increases to the peak value, then it gradually decreases with Reynolds number. Among the materials have been studied, aluminium 7 series shows the highest maximum stress and maximum strain for all Reynolds number and hotspot temperature, however, aluminium 1 series produces the lowest maximum stress and maximum strain.

Experimental study of curvature effects on jet impingement heat transfer on concave surfaces

Experimental study of the local and average heat transfer characteristics of a single round jet impinging on the concave surfaces was conducted in this work to gain in-depth knowledge of the curvature effects. The experiments were conducted by employing a piccolo tube with one single jet hole over a wide range of parameters: jet Reynolds number from 27000 to 130000, relative nozzle to surface distance from 3.3 to 30, and relative surface curvature from 0.005 to 0.030. Experimental results indicate that the surface curvature has opposite effects on heat transfer characteristics. On one hand, an increase of relative nozzle to surface distance (increasing jet diameter in fact) enhances the average heat transfer around the surface for the same curved surface. On the other hand, the average Nusselt number decreases as relative nozzle to surface distance increases for a fixed jet diameter. Finally, experimental data-based correlations of the average Nusselt number over the curved surface were obtained with consideration of surface curvature effect. This work contributes to a better understanding of the curvature effects on heat transfer of a round jet impingement on concave surfaces, which is of high importance to the design of the aircraft anti-icing system.

Jet impingement heat transfer on a concave surface in a wing leading edge: Experimental study and correlation development

Extensive experimental studies of the heat transfer characteristics of jet impingement on a variable-curvature concave surface in a wing leading edge were conducted for aircraft anti-icing applications. The experiments were performed using a piccolo tube with three rows of aligned jet holes over a wide range of parameters: the jet Reynolds number (Rej) from 50,000 to 90,000, the relative tube-to-surface distance (H/d) from 1.74 to 20.0, the jet impingement angle (α) from 66° to 90°, and the relative chordwise arc length in the jet impingement zone (r/d) from 13.2 to 34.8. Experimental results indicated that the heat transfer performance at the stagnation point was enhanced with increasing Rej and α, and an optimal H/d existed to achieve the best heat transfer performance at the stagnation point corresponding to specific operating parameters. It was found that the attenuation coefficient curve of jet impingement heat transfer in the chordwise direction exhibited an approximate bell shape with the peak located at the stagnation point, affected only by r/d in the peak zone. In the non-peak zone, however it was affected significantly by a variety of factors including Rej, H/d and r/d. Experimental data-based correlations of the Nusselt number at the stagnation point and the distribution of the attenuation coefficient in the chordwise direction were developed and validated, which contributes significantly to the future design of a wing anti-icing system with three rows of aligned jet holes.

Applying Computational Fluid Dynamic to Predict the Thermal Performance of the Nacelle Anti-Icing System in Real Flight Scenarios

Ice accumulation on the inner surface of a nacelle lip-skin can be hazardous. Therefore, it is necessary that the aircraft be protected against the effect of ice accumulation. The Piccolo Tube Anti-Icing (PTAI) is one of the most reliable ice protection systems for nacelle lip-skins and aircraft wings, and is commonly used in commercial aviation. Thus, many researchers studied and developed the empirical correlation of the PTAI system, including Jeffry Brown of Queens University Belfast. He focused on the nacelle lip-skin PTAI system. However, the Brown correlation was developed at room temperature. In present study, on the other hand, the Brown correlation was modified with the help of CFD, in order to make it suitable at different ambient temperatures. CFD analysis can help to save time and effort, as well lower the cost of the nacelle design, by reducing the number of experiments required during the development. The present research executed CFD in 5 different conditions, i.e. Laboratory, Taxi, Climb, Hold, and Descent. Laboratory data closely agree with the Brown correlation, having been run in similar conditions. The average Nusselt number increases as the Reynolds number increases. In conclusion, the research demonstrated that CFD is not only capable of predicting the thermal performance of the PTAI, but it can also be used to investigate some parameters/characteristics that are difficult to obtain from experiments, e.g. the ambient temperature effects and the hot air velocity inside the D-chamber. Keywords: Anti-Icing, CFD, Lip-Skin and Aircraft Crash, Nacelle, Piccolo Tube Anti-Icing

Experimental study of jet impingement heat transfer on a variable-curvature concave surface in a wing leading edge

In this paper, extensive experimental investigation of the heat transfer characteristics of jet impingement on a variable-curvature concave surface in a wing leading edge was conducted for aircraft anti-icing applications. The experiments were carried out over a wide range of parameters: the jet Reynolds number, Rej, from 51,021 to 85,340, the relative tube-to-surface distance, H/d, from 1.736 to 19.76, and the circumferential angle of jet holes on the piccolo tube, θ, from −60° to 60°. In addition, jet impingements with single one, two and three rows of aligned jet holes were all investigated. Experimental results revealed the effects of various parameters on the performance and characteristics of jet impingement heat transfer in the specific structure adopted here, and our insufficient understanding on the corresponding physical mechanism was presented. It was found that the jet impingement heat transfer performance was enhanced with the increase of jet Reynolds number. For single one row of jet holes, an optimal H/d of 4.5 was determined under Rej=51,021 and d=2mm, for which the jet impingement achieved the best heat transfer performance. For two and three rows of aligned jet holes, the Nux curves in the chordwise direction exhibited much different shapes due to different intensity of the interference between adjacent air jets. This work contributes to a better understanding of the jet impingement heat transfer on a concave surface in a wing leading edge, which can lead to optimal design of the aircraft anti-icing system.

Structural Robust Optimal Design based on Orthogonal Experimental and Parametric Finite Element Analysis

In this paper, based on orthogonal experiment, piccolo tube dynamic optimization was performed to achieve the purposes of reducing the time of sample, identifying the key parameters and optimizing design. Firstly, parameterized finite element model of the piccolo tube was built. After that, the orthogonal experiment under four design variables covering three levels was performed. After 10 times dynamics simulation analysis (9 times simulation for orthogonal experiment and 1 time simulation for optimal design verification experiment), the optimal design of the piccolo tube was quickly determined. The first order natural frequency of the piccolo tube was improved to 1771HZ from initial design 1496.3HZ. The trend and sensitivity between the design variables and structural performance were obtained. The analyze process shows that the proposed method is simple and efficient. It can provide technical reference for piccolo tube optimization design and other complex structures.

Mach Number Effect on The Heat Transfer Mechanism of Aircraft Anti-Icing Systems

The primary means of preventing ice formation on wings and engine inlets for modern commercial transport aircraft is by extracting hot air from the compressor and blowing it on the inside surface of the leading edge through small holes drilled in the so-called piccolo tube system. A critical aspect in the design of such system is the prediction of heat transfer impinging jets from the piccolo tube. The correct evaluation of the heat transfer rate in such devices is of great interest to optimize both the anti-icing performance and the hot air bleeding from the high-pressure compressor. A review of the literature reveals that there are some experimental and numerical studies that developed correlations for the average Nusselt number. However, most of the research was performed using a single jet or a group of jets impinging on a flat slat, which is different from the jet impingement on concave surfaces, as the inside surface of a wing. Therefore, the objective of the present work is to perform a parametric study of the impingement jet flow on concave surfaces employing CFD tool. The main goal is determine the effect of the Mach number on this heat transfer process

Numerical Validation of Conjugate Heat Transfer Method for Anti-/De-Icing Piccolo System

An anti-/de-icing conjugate heat transfer method based on a ANSYS-CFX flow solver and FENSAP-ICE software is presented. The ANSYS-CFX flow solver is used as the flow solver module with the shear stress transport turbulence model. DROP3D is used as the droplet impingement module. ICE3D is used as the ice accretion and water film runback module. CHT3D/CFX is used for the thermal coupling of all modules. Before solving for the temperature distribution in a three-dimensional antiicing system geometry based on a piccolo tube with three jet rows, a test case consisting of a two-stream parallel gas-to-gas microheat exchanger will validate the CHT3D/CFX procedure. For the antiicing system in wet air mode, the temperature results at corresponding experimental locations are presented and compared to results from the literature.

NUMERICAL STUDY OF A HOT-AIR-BASED AIRCRAFT WING ANTI-ICING SYSTEM USING THE BOX-BEHNKEN DoE APPROACH

This article proposes the use of the Box-Behnken design of experiment (DoE) methodology to study an aircraft anti-icing system. The anti-icing system consisted of a piccolo tube with round apertures for producing air jets inside a wing. Mass flow, jet to wall distance, and jet impact angle were varied, starting from an initial design, in order to maximize heat transfer effectiveness. A conjugate heat transfer procedure from commercial CFD software was used to solve for cold air external flow, compressible internal flow, and thermal conduction in the airfoil skin. The DoE methodology was validated using a single impinging jet. A quadratic model of the heat transfer effectiveness of the anti-icing system was then built using the methodology and the maximal value was sought.

Optimization via FENSAP-ICE of Aircraft Hot-Air Anti-Icing Systems

This paper presents a methodology for the optimization of hot-bleed-air anti-icing systems, known as Piccolo tubes. Such systems are widely used to anti-ice the wings of many commercial aircrafts, ranging from regional to wide-body jet aircrafts. Having identified the most critical in-flight icing conditions, as well as any anti-icing system constraints as inputs, the ideal aim is to achieve fully-evaporative conditions over the heated surfaces. To do so, an optimization method based on three-dimensional computational fluid dynamics, reduced-order models, and genetic algorithms was constructed to determine the optimal geometric configuration of the Piccolo tube (jet angles, spacing of jets, and distance from leading edge). The external and internal airflows are computed using the finite element Navier–Stokes applications package (FENSAP-ICE). The methodology leads to significantly-improved configurations for threeto five-dimensional design spaces.