TAN LAI 2019a - Revision history

Rimni at 11:56, 28 May 2021

2021-05-28T11:56:51Z

Rimni at 11:51, 28 May 2021

2021-05-28T11:51:23Z

Rimni: /* 3.2 Effect of pressure on icing */

2021-05-28T11:50:38Z

‎3.2 Effect of pressure on icing

Rimni at 11:45, 28 May 2021

2021-05-28T11:45:58Z

Rimni at 11:38, 28 May 2021

2021-05-28T11:38:34Z

Rimni at 11:37, 28 May 2021

2021-05-28T11:37:53Z

Rimni at 10:23, 19 March 2020

2020-03-19T10:23:18Z

Rimni at 10:21, 19 March 2020

2020-03-19T10:21:24Z

Rimni at 12:09, 13 September 2019

2019-09-13T12:09:11Z

Rimni at 12:08, 13 September 2019

2019-09-13T12:08:35Z

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 <div class="auto" style="text-align: left;width: auto; margin-left: auto; margin-right: auto;font-size: 85%;">
-. Yuan, Q.H., Fan, J., Bai, G.C. Review of ice crystal icing in aero-engines. J. Propul. Technol. 39:2641-2650, 2018.
+[1] Yuan Q.H., Fan J., Bai G.C. Review of ice crystal icing in aero-engines. J. Propul. Technol., 39:2641-2650, 2018.
-. Mason, J.G., Strapp, J.W., Chow, P. The ice particle threat to engines in flight. AIAA Aerospace Sciences Meeting and Exhibit, January 2006-206.
+[2] Mason J.G., Strapp J.W., Chow P. The ice particle threat to engines in flight. AIAA Aerospace Sciences Meeting and Exhibit, January 2006-206.
-. Pasztor, A. Airline regulators grapple with engine-shutdown peril. Wall Street Journal, 251, 2008.
+[3] Pasztor A. Airline regulators grapple with engine-shutdown peril. Wall Street Journal, 251, 2008.
-. Grzych, M.L., Mason, J. Weather conditions associated with jet engine power-loss and damage due to ingestion of ice particles: what we’ ve learned through 2009. 14th Conference on Aviation, Range and Aerospace Meteorology, Washington, DC, U.S., 2010.
+[4] Grzych M.L., Mason J. Weather conditions associated with jet engine power-loss and damage due to ingestion of ice particles: what we’ ve learned through 2009. 14th Conference on Aviation, Range and Aerospace Meteorology, Washington, DC, U.S., 2010.
-. Currie, T.C., Struk, P.M., Tsao, J.C., Fuleki, D., Knezevici, D.C. Fundamental study of mixed-phase icing with application to ice crystal accretion in aircraft jet engines. AIAA Aerospace Sciences Meeting and Exhibit, 2012-3035.
+[5] Currie T.C., Struk P.M., Tsao J.C., Fuleki D., Knezevici D.C. Fundamental study of mixed-phase icing with application to ice crystal accretion in aircraft jet engines. AIAA Aerospace Sciences Meeting and Exhibit, 2012-3035.
-. Fuleki, D.M., Macleod, J.D. Ice crystal accretion test rig development for a compressor transition duct. AIAA Aerospace Sciences Meeting and Exhibit, 2010-7529.
+[6] Fuleki D.M., Macleod J.D. Ice crystal accretion test rig development for a compressor transition duct. AIAA Aerospace Sciences Meeting and Exhibit, 2010-7529.
-. Mason, J.G., Chow, P., Dan, M.F. Understanding ice crystal accretion and shedding phenomenon in jet engines using a rig test. ASME rep. ASME GT, 2010-22550.
+[7] Mason J.G., Chow P., Dan M.F. Understanding ice crystal accretion and shedding phenomenon in jet engines using a rig test. ASME rep. ASME GT, 2010-22550.
-. Struk, P.M., Tsao, J.C., Bartkus, T.P. Plans and preliminary results of fundamental studies of ice crystal icing physics in the NASA propulsion systems laboratory. AIAA Aerospace Sciences Meeting and Exhibit, 2016-3738.
+[8] Struk P.M., Tsao J.C., Bartkus T.P. Plans and preliminary results of fundamental studies of ice crystal icing physics in the NASA propulsion systems laboratory. AIAA Aerospace Sciences Meeting and Exhibit, 2016-3738.
-. Villedieu, P., Trontin, P., Chauvin, R. Glaciated and mixed-phase ice accretion modeling using ONERA 2D icing suite. AIAA Aerospace Sciences Meeting and Exhibit, 2014-2199.
+[9] Villedieu P., Trontin P., Chauvin R. Glaciated and mixed-phase ice accretion modeling using ONERA 2D icing suite. AIAA Aerospace Sciences Meeting and Exhibit, 2014-2199.
-. Zhang, L.F., Liu, Z.X., Zhang, M.H. Numerical simulation of ice accretion under mixed-phase conditions. P I Mech. Eng. G. J. Aer., 230:2473-2483, 2016.
+[10] Zhang L.F., Liu Z.X., Zhang M.H. Numerical simulation of ice accretion under mixed-phase conditions. P I Mech. Eng. G. J. Aer., 230:2473-2483, 2016.
-. Norde, E., Weide, E.T.A., Hoeijmakers, H.W.M. Eulerian method for ice crystal icing. AIAA J. 1-13, 2017.
+[11] Norde E., Weide E.T.A., Hoeijmakers H.W.M. Eulerian method for ice crystal icing. AIAA J., 1-13, 2017.
-. Nilamdeen, S., Habashi, W.G. FENSAP-ICE: Modeling of water droplets and ice crystals. AIAA Aerospace Sciences Meeting and Exhibit, 2009-4128.
+[12] Nilamdeen S., Habashi W.G. FENSAP-ICE: Modeling of water droplets and ice crystals. AIAA Aerospace Sciences Meeting and Exhibit, 2009-4128.
-. Spalart, P.R., Allmaras, S.R. A one-equation turbulence model for aerodynamic Flows. AIAA Aerospace Sciences Meeting and Exhibit, 1992-0439.
+[13] Spalart P.R., Allmaras S.R. A one-equation turbulence model for aerodynamic Flows. AIAA Aerospace Sciences Meeting and Exhibit, 1992-0439.
-. Bourgault, Y., Boutanios, Z., Habashi, W.G. Three-dimensional Eulerian approach to droplet impingement simulation using FENSAP-ICE. Part 1: Model, algorithm, and validation. J. Aircraft, 37:95-103, 2000.
+[14] Bourgault Y., Boutanios Z., Habashi W.G. Three-dimensional Eulerian approach to droplet impingement simulation using FENSAP-ICE. Part 1: Model, algorithm, and validation. J. Aircraft, 37:95-103, 2000.
-. Hughes, T.J.R., Brooks, A. A theoretical framework for Petrov-Galerkin methods with discontinuous weighting functions: Application to the streamline-upwind procedure. Wiley press, pp. 647, 1982.
+[15] Hughes T.J.R., Brooks A. A theoretical framework for Petrov-Galerkin methods with discontinuous weighting functions: Application to the streamline-upwind procedure. Wiley press, pp. 647, 1982.
-. Struk, P., Currie, T., Wright, W.B., Knezevici, D.C., Fuleki, D., Broeren, A., Vargas, M., Tsao. J.C. Fundamental ice crystal accretion physics studies. SAE rep., 2011-38-0018.
+[16] Struk P., Currie T., Wright W.B., Knezevici D.C., Fuleki D., Broeren A., Vargas M., Tsao J.C. Fundamental ice crystal accretion physics studies. SAE rep., 2011-38-0018.
 </div>

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 ===3.3 Effect of the ratio of LWC/ TWC on icing===
-The calculation of working conditions shown in Table 3 is also carried out. The web bulb temperature is -3℃, the angle of attack are 0°, the MMD of ice crystal is 150 μm, the MVD of droplet is 40 μm, and the ice accretion time is 120 s. Here, the total water content TWC is 4 g/m<sup>3 </sup>(TWC=IWC+LWC).
+The calculation of working conditions shown in [[#tab-3|Table 3]] is also carried out. The web bulb temperature is -3℃, the angle of attack are 0°, the MMD of ice crystal is 150 μm, the MVD of droplet is 40 μm, and the ice accretion time is 120 s. Here, the total water content TWC is 4 g/m<sup>3 </sup>(TWC=IWC+LWC).
 <div class="center" style="font-size: 75%;">'''Table 3. '''Calculation conditions IІ
 </div>
+<div id='tab-3'></div>
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 ===3.2 Effect of pressure on icing===
-In order to study the effect of pressure on icing, the calculations of the following conditions are carried out (Table 2, the conditions of Model A is the same as that of run 543 of NRC’s experiment [16]). In all models, the angle of attack are 0°, the MMD of ice crystal is 150 μm, the MVD of droplet is 40 μm, and the ice accretion time is 60 s.
+In order to study the effect of pressure on icing, the calculations of the following conditions are carried out ([[#tab-2|Table 2]], the conditions of Model A is the same as that of run 543 of NRC’s experiment [16]). In all models, the angle of attack are 0°, the MMD of ice crystal is 150 μm, the MVD of droplet is 40 μm, and the ice accretion time is 60 s.
 <div class="center" style="font-size: 75%;">'''Table 2. '''Calculation conditions І
 </div>
+<div id='tab-2'></div>
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 |-

@@ Line 414: / Line 414: @@
 ==3. Case study==
-In this paper, a symmetrical wedge airfoil in NRC’s experiment [5,16] is taken as the research object. The front angel of this airfoil is 40°, and the rear angel is 20°. The chord length is 220.92 mm (Figure 2a). The grinder used in NRC’s experiment could produce ice crystals with an estimated median mass diameter (MMD) of between 100-200 μm, and the air-assist atomization nozzles could produce droplets with a median volume diameter (MVD) of 40 μm. Here, the ice crystal size is set as 150 μm in calculation. The whole flow field model (154, 064 hexahedral grids) is shown in Figure 3, and the inlet is about 1.27 m away from the leading edge of the wedge airfoil.
+In this paper, a symmetrical wedge airfoil in NRC’s experiment [5,16] is taken as the research object. The front angel of this airfoil is 40°, and the rear angel is 20°. The chord length is 220.92 mm ([[#img-2|Figure 2]]a). The grinder used in NRC’s experiment could produce ice crystals with an estimated median mass diameter (MMD) of between 100-200 μm, and the air-assist atomization nozzles could produce droplets with a median volume diameter (MVD) of 40 μm. Here, the ice crystal size is set as 150 μm in calculation. The whole flow field model (154, 064 hexahedral grids) is shown in [[#img-3|Figure 3]], and the inlet is about 1.27 m away from the leading edge of the wedge airfoil.
+<div id='img-2'></div>
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+<div id='img-3'></div>
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 ===3.1 Experiment verification===
-In order to verify the accuracy of the numerical method in this paper, the run 139 of NRC experiment is used to compare with the numerical results. The operating conditions are shown in Table 1.
+In order to verify the accuracy of the numerical method in this paper, the run 139 of NRC experiment is used to compare with the numerical results. The operating conditions are shown in [[#tab-1|Table 1]].
 <div class="center" style="font-size: 75%;">'''Table 1. '''Run 139 operating conditions [16]
 </div>
+<div id='tab-1'></div>
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-The abundant flow field data are obtained by the above numerical method. It could be found that the numerical results are basically the same as the experimental results (Figure 4).
+The abundant flow field data are obtained by the above numerical method. It could be found that the numerical results are basically the same as the experimental results ([[#img-4|Figure 4]]).
+<div id='img-4'></div>
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-Although the total temperature is 12.5 ℃, the wet bulb temperature is negative. The intense evaporation process absorbs a large amount of heat, which results in the droplets temperature decreasing gradually. When the droplets reach the stagnation point, the temperature of droplets decrease from the initial temperature of 10℃ to -8℃ (Figure 5a), and the diameter decrease from 40 μm to 39.3 μm (Figure 5b). After 402 s exposure under this condition, the numerical results are basically consistent with the experimental results (Figure 6).
+Although the total temperature is 12.5 ℃, the wet bulb temperature is negative. The intense evaporation process absorbs a large amount of heat, which results in the droplets temperature decreasing gradually. When the droplets reach the stagnation point, the temperature of droplets decrease from the initial temperature of 10℃ to -8℃ ([[#img-5|Figure 5]]a), and the diameter decrease from 40 μm to 39.3 μm ([[#img-5|Figure 5]]b). After 402 s exposure under this condition, the numerical results are basically consistent with the experimental results ([[#img-6|Figure 6]]).
+<div id='img-5'></div>
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+<div id='img-6'></div>
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-Figure 7 shows the comparison of droplet (Figure 7a) and ice crystal (Figure 7b) diameters on the airfoil surface. It could be found that the droplet and ice crystal diameters of Model A are obviously smaller than the other two models. The results show that the decrease of total pressure will lead to the increase of evaporation rate and the further decrease of wet bulb temperature under the same conditions. Therefore, under the influence of evaporation rate, the mass loss of ice crystal or droplet is the greatest under low pressure (Model A).
+[[#img-7|Figure 7]] shows the comparison of droplet ([[#img-7|Figure 7]]a) and ice crystal ([[#img-7|Figure 7]]b) diameters on the airfoil surface. It could be found that the droplet and ice crystal diameters of Model A are obviously smaller than the other two models. The results show that the decrease of total pressure will lead to the increase of evaporation rate and the further decrease of wet bulb temperature under the same conditions. Therefore, under the influence of evaporation rate, the mass loss of ice crystal or droplet is the greatest under low pressure (Model A).
+<div id='img-7'></div>
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 |-
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-Figure 8 shows the comparison of mass collection rate (Figure 8a) and ice thickness (Figure 8b) on the airfoil surface. It could be found that droplets (or ice crystal) are most likely to impact the leading edge of the airfoil (<math> z=\pm 2 mm</math>), and there is little difference in particle collection between the three models (Figure 8a). However, in the other parts of the airfoil windward, the mass collection rate under low pressure condition (Model A) is higher than that under high pressure conditions (Mode B and Model C). Because the larger the particle size, the higher the probability of rebound or breakup after impacting on the surface. From the comparison of ice thickness (Figure 8b), it could be found that the pressure has a great influence on icing. It is easier to freeze under low pressure condition (the ice thickness of Model A at stagnation point is 4.6 mm, while that of experiment is 4.5 mm). On the one hand, the mass collection rate is higher under the lower pressure condition (Figure 8a). On the other hand, the wet bulb temperature is lower under the lower pressure condition (the wet bulb temperature of Model A, B and C are -3℃, -1℃, and 1℃ respectively), which is more conductive to freeze.
+[[#img-8|Figure 8]] shows the comparison of mass collection rate ([[#img-8|Figure 8]]a) and ice thickness (Figure 8b) on the airfoil surface. It could be found that droplets (or ice crystal) are most likely to impact the leading edge of the airfoil (<math> z=\pm 2 mm</math>), and there is little difference in particle collection between the three models ([[#img-8|Figure 8]]a). However, in the other parts of the airfoil windward, the mass collection rate under low pressure condition (Model A) is higher than that under high pressure conditions (Mode B and Model C). Because the larger the particle size, the higher the probability of rebound or breakup after impacting on the surface. From the comparison of ice thickness ([[#img-8|Figure 8]]b), it could be found that the pressure has a great influence on icing. It is easier to freeze under low pressure condition (the ice thickness of Model A at stagnation point is 4.6 mm, while that of experiment is 4.5 mm). On the one hand, the mass collection rate is higher under the lower pressure condition ([[#img-8|Figure 8]]a). On the other hand, the wet bulb temperature is lower under the lower pressure condition (the wet bulb temperature of Model A, B and C are -3℃, -1℃, and 1℃ respectively), which is more conductive to freeze.
 In summary, the lower the pressure, the lower the wet bulb temperature and the stronger the evaporation, the easier the formation of icing conditions, which also explains why the engine internal icing usually occurs at high altitude.
+<div id='img-8'></div>
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-Figure 9 shows the comparison of ice accretion, and Figure 10 shows the velocity magnitude contour of different models. The Model D has no liquid water (LWC=0 g/m<sup>3</sup>), and doesn’t form mixed phase. The dry airfoil surface can’t stick any ice crystals to form ice layer. Model E contains less liquid water, and only liquid film and ice layer appear on the windward side of airfoil. However, with the increase the LWC, the liquid film on the surface begin to flow to the leeward side (Model F, Model G and Model H) and form ice layer on the leeward side. When the ratio of LWC/TWC is 0.5, the ice layer at stagnation point is the thickest (Figure 9). When there is less liquid water, the ice layer is thinner and the sticking ability of film is weaker. When there is less ice crystal, it is not conducive to the formation of icing conditions.
+[[#img-9|Figure 9]] shows the comparison of ice accretion, and [[#img-10|Figure 10]] shows the velocity magnitude contour of different models. The Model D has no liquid water (LWC=0 g/m<sup>3</sup>), and doesn’t form mixed phase. The dry airfoil surface can’t stick any ice crystals to form ice layer. Model E contains less liquid water, and only liquid film and ice layer appear on the windward side of airfoil. However, with the increase the LWC, the liquid film on the surface begin to flow to the leeward side (Model F, Model G and Model H) and form ice layer on the leeward side. When the ratio of LWC/TWC is 0.5, the ice layer at stagnation point is the thickest ([[#img-9|Figure 9]]). When there is less liquid water, the ice layer is thinner and the sticking ability of film is weaker. When there is less ice crystal, it is not conducive to the formation of icing conditions.
+<div id='img-9'></div>
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+<div id='img-10'></div>
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@@ Line 286: / Line 286: @@
 The above governing equations are solved by Streamline-Upwind Petrov- Galerkin method [15].
+<div id='img-1'></div>
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@@ Line 303: / Line 303: @@
 ===2.2 Model of ice accretion ===
-In this paper, the classical Messinger model is used to calculate the icing process. The mass and energy conservation equations are established based on a control volume in this model [11]. The masses enter into the control volume are the melted part of ice crystal <math>{\dot{m}}_{c,ic,w}</math>, droplet <math>{\dot{m}}_{c,d}</math> and runback water <math>{\dot{m}}_{in}</math> from theneighboring upstream control volume. The outgoing masses are evaporating water <math>{\dot{m}}_{ev}</math>, icing mass <math>{\dot{m}}_f</math> and runback water  <math>{\dot{m}}_{out}</math> (Figure 1). Therefore the mass conservation equation of control volume is shown as:
+In this paper, the classical Messinger model is used to calculate the icing process. The mass and energy conservation equations are established based on a control volume in this model [11]. The masses enter into the control volume are the melted part of ice crystal <math>{\dot{m}}_{c,ic,w}</math>, droplet <math>{\dot{m}}_{c,d}</math> and runback water <math>{\dot{m}}_{in}</math> from theneighboring upstream control volume. The outgoing masses are evaporating water <math>{\dot{m}}_{ev}</math>, icing mass <math>{\dot{m}}_f</math> and runback water  <math>{\dot{m}}_{out}</math> ([[#img-1|Figure 1]]). Therefore the mass conservation equation of control volume is shown as:
 {| class="formulaSCP" style="width: 100%; text-align: left;"

@@ Line 133: / Line 133: @@
 In this paper, the icing process of symmetrical wedge airfoil was calculated based on Eulerian method. The phase transformation and particle rebound were taken into account. The numerical results also were compared with the NRC’s experimental results. The effects of pressure and the ratio LWC/TWC on icing also were analyzed.
-==2. Numerical Methods ==
+==2. Numerical methods ==
 It could be considered that the effect of carrier phase on the dispersed phase is unidirectional, because the value of particle loading (<math>PL={\alpha }_d{\rho }_d/{\alpha }_c{\rho }_c</math>) is less than 0.1. Here, the flow field is simulated based on Palart-Allmaras turbulence model [13]. Then the above results are used to calculate the particle trajectory. At last, the Messinger model is used to obtain the results of icing process.
-===2.1. Model of Particle Motion and Phase Change===
+===2.1. Model of particle motion and phase change===
 Since the mixed phase is a necessary condition for ice crystal icing. The volume fraction of dispersed phase  <math>\alpha </math> should be divided into solid phase  <math>{\alpha }_i</math> and liquid phase <math>{\alpha }_w</math>. The momentum conservation equation is extended from one to two
@@ Line 301: / Line 301: @@
-===2.2 Model of Ice Accretion ===
+===2.2 Model of ice accretion ===
 In this paper, the classical Messinger model is used to calculate the icing process. The mass and energy conservation equations are established based on a control volume in this model [11]. The masses enter into the control volume are the melted part of ice crystal <math>{\dot{m}}_{c,ic,w}</math>, droplet <math>{\dot{m}}_{c,d}</math> and runback water <math>{\dot{m}}_{in}</math> from theneighboring upstream control volume. The outgoing masses are evaporating water <math>{\dot{m}}_{ev}</math>, icing mass <math>{\dot{m}}_f</math> and runback water  <math>{\dot{m}}_{out}</math> (Figure 1). Therefore the mass conservation equation of control volume is shown as:

← Older revision		Revision as of 12:09, 13 September 2019
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−	Figure 8 shows the comparison of mass collection rate (Figure 8a) and ice thickness (Figure 8b) on the airfoil surface. It could be found that droplets (or ice crystal) are most likely to impact the leading edge of the airfoil (<math> z=\pm 2 mm</math> ), and there is little difference in particle collection between the three models (Figure 8a). However, in the other parts of the airfoil windward, the mass collection rate under low pressure condition (Model A) is higher than that under high pressure conditions (Mode B and Model C). Because the larger the particle size, the higher the probability of rebound or breakup after impacting on the surface. From the comparison of ice thickness (Figure 8b), it could be found that the pressure has a great influence on icing. It is easier to freeze under low pressure condition (the ice thickness of Model A at stagnation point is 4.6 mm, while that of experiment is 4.5 mm). On the one hand, the mass collection rate is higher under the lower pressure condition (Figure 8a). On the other hand, the wet bulb temperature is lower under the lower pressure condition (the wet bulb temperature of Model A, B and C are -3℃, -1℃, and 1℃ respectively), which is more conductive to freeze.	+	Figure 8 shows the comparison of mass collection rate (Figure 8a) and ice thickness (Figure 8b) on the airfoil surface. It could be found that droplets (or ice crystal) are most likely to impact the leading edge of the airfoil (<math> z=\pm 2 mm</math>), and there is little difference in particle collection between the three models (Figure 8a). However, in the other parts of the airfoil windward, the mass collection rate under low pressure condition (Model A) is higher than that under high pressure conditions (Mode B and Model C). Because the larger the particle size, the higher the probability of rebound or breakup after impacting on the surface. From the comparison of ice thickness (Figure 8b), it could be found that the pressure has a great influence on icing. It is easier to freeze under low pressure condition (the ice thickness of Model A at stagnation point is 4.6 mm, while that of experiment is 4.5 mm). On the one hand, the mass collection rate is higher under the lower pressure condition (Figure 8a). On the other hand, the wet bulb temperature is lower under the lower pressure condition (the wet bulb temperature of Model A, B and C are -3℃, -1℃, and 1℃ respectively), which is more conductive to freeze.

	In summary, the lower the pressure, the lower the wet bulb temperature and the stronger the evaporation, the easier the formation of icing conditions, which also explains why the engine internal icing usually occurs at high altitude.		In summary, the lower the pressure, the lower the wet bulb temperature and the stronger the evaporation, the easier the formation of icing conditions, which also explains why the engine internal icing usually occurs at high altitude.

← Older revision		Revision as of 12:08, 13 September 2019
Line 607:		Line 607:


−	Figure 8 shows the comparison of mass collection rate (Figure 8a) and ice thickness (Figure 8b) on the airfoil surface. It could be found that droplets (or ice crystal) are most likely to impact the leading edge of the airfoil (z=±2 mm), and there is little difference in particle collection between the three models (Figure 8a). However, in the other parts of the airfoil windward, the mass collection rate under low pressure condition (Model A) is higher than that under high pressure conditions (Mode B and Model C). Because the larger the particle size, the higher the probability of rebound or breakup after impacting on the surface. From the comparison of ice thickness (Figure 8b), it could be found that the pressure has a great influence on icing. It is easier to freeze under low pressure condition (the ice thickness of Model A at stagnation point is 4.6 mm, while that of experiment is 4.5 mm). On the one hand, the mass collection rate is higher under the lower pressure condition (Figure 8a). On the other hand, the wet bulb temperature is lower under the lower pressure condition (the wet bulb temperature of Model A, B and C are -3℃, -1℃, and 1℃ respectively), which is more conductive to freeze.	+	Figure 8 shows the comparison of mass collection rate (Figure 8a) and ice thickness (Figure 8b) on the airfoil surface. It could be found that droplets (or ice crystal) are most likely to impact the leading edge of the airfoil (<math> z=\pm 2 mm</math> ), and there is little difference in particle collection between the three models (Figure 8a). However, in the other parts of the airfoil windward, the mass collection rate under low pressure condition (Model A) is higher than that under high pressure conditions (Mode B and Model C). Because the larger the particle size, the higher the probability of rebound or breakup after impacting on the surface. From the comparison of ice thickness (Figure 8b), it could be found that the pressure has a great influence on icing. It is easier to freeze under low pressure condition (the ice thickness of Model A at stagnation point is 4.6 mm, while that of experiment is 4.5 mm). On the one hand, the mass collection rate is higher under the lower pressure condition (Figure 8a). On the other hand, the wet bulb temperature is lower under the lower pressure condition (the wet bulb temperature of Model A, B and C are -3℃, -1℃, and 1℃ respectively), which is more conductive to freeze.

	In summary, the lower the pressure, the lower the wet bulb temperature and the stronger the evaporation, the easier the formation of icing conditions, which also explains why the engine internal icing usually occurs at high altitude.		In summary, the lower the pressure, the lower the wet bulb temperature and the stronger the evaporation, the easier the formation of icing conditions, which also explains why the engine internal icing usually occurs at high altitude.