CN107132278B - Multi-cylinder array icing detection method - Google Patents
Multi-cylinder array icing detection method Download PDFInfo
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Abstract
The invention discloses a multi-cylinder array icing detection device which comprises a cylinder array arranged on a test surface, wherein the cylinder array comprises three cylinders with different diameters which are sequentially arranged along the same axis, the diameters of the cylinders are gradually increased from one end to the other end, the surfaces of the two adjacent cylinders are not in contact, a cavity structure is arranged in each cylinder, a vibrating piece is arranged in each cavity structure, an acceleration sensor is arranged on the surface of each cylinder, and a signal acquisition system is connected with the vibrating piece and the acceleration sensor; the invention combines the traditional mechanical icing detection method, overcomes the defect that large and small-scale supercooled water drops cannot be distinguished, fully exerts the advantages of the traditional mechanical icing detection, better coordinates the two contradictions of the icing detection of the large-scale supercooled water drops and the small-scale supercooled water drops, better solves the icing detection problem on the surface of the airplane, and has practical significance for solving the design of an anti-icing and anti-icing system of an aircraft and guaranteeing the flight safety.
Description
Technical Field
The invention relates to the field of aerodynamics, in particular to a method and a device for detecting icing of various objects easy to freeze under high-altitude icing meteorological conditions.
Background
Icing is a physical phenomenon widely existing in flight practice and is one of the main hidden dangers of causing flight safety accidents. When an airplane flies under the icing meteorological condition that the environmental temperature is lower than the freezing point or is near the freezing point, supercooled water drops in the atmosphere impact the surface of the airplane, and the icing phenomenon is easy to occur on the surfaces of components such as wings, empennages, rotors, air inlet channels, windshield glass, antenna covers, instrument sensors and the like. The icing of the airplane not only increases the weight of the airplane, but also destroys the aerodynamic appearance of the surface of the airplane, changes the streaming flow field, destroys the aerodynamic performance, causes the descending of the maximum lift force of the airplane, the ascending of the flight resistance, the descending of the operating performance and the reduction of the stability performance, and causes great threat to the flight safety, the flight accidents caused by the icing are rare, and the serious icing can even lead to the death of the airplane.
In 1994, air accidents of ATR-72 commuter aircrafts in the United states occur, and after long-time research and analysis, an accident research team finds that the icing of large-scale supercooled water drops is the main cause of the flight accidents, so that researchers pay more and more attention to the research and detection of the icing of the large-scale supercooled water drops. Large scale supercooled water droplet freezing (SLD) is supercooled water droplets having an average droplet diameter of more than 50 microns in FAR25 appendix C. The supercooled water drops with the size are large in size, heavy in mass, large in inertia and poor in airflow following performance, dynamic phenomena such as deformation and breakage are prone to occurring, the motion track of the supercooled water drops is greatly different from that of small-sized supercooled water drops, meanwhile, the heat release speed is slow in the freezing process, so that the supercooled water drops cannot be immediately frozen on the surface of an aircraft, and a part of liquid water overflows to the downstream of an anti-icing surface, so that an ice ridge phenomenon which cannot be prevented and removed is formed outside an anti-icing area is formed. Under the complex icing meteorological condition that large and small-scale supercooled water drops are mixed with each other, an icing detection method and a related device capable of distinguishing the large and small-scale supercooled water drops are designed and developed, and the method is the key for providing a reasonable trigger signal for an aircraft anti-icing system.
The existing icing detection device is mainly designed according to the principles of optics, mechanics, electricity and the like. The initial optical ice detection devices relied on the eyes of the pilot, and later increasingly employed cameras or video cameras with highly sensitive CCD components. Because the flying environment of the aircraft is severe and is often in a cloud-penetrating flying state, the icing detection device based on the principle has large limitation and is easy to misjudge in the environment with large cloud mist. At present, the optical fiber icing detection device can overcome the influence on the surrounding cloud and mist environment, and becomes a research hotspot of non-contact icing detection. The icing detection is a method for detecting icing through the principles of light reflection, scattering, transmission and the like. However, this detection method has disadvantages that the emitting end of the optical fiber is not a point light source, but a surface light source with a large diameter, and a large part of the emitted light is caused by loss and deflection phenomena when passing through a special porous medium material such as ice, which causes a large dependence on the shape, size and area of the emitting end of the optical fiber in measurement accuracy and accuracy, and is greatly influenced by the internal structural characteristics of ice, which is a key reason that the conventional ice detection device often reports a false alarm or has a large measurement error. The icing detection device of the electrical method is designed by utilizing the rule that the resistance of the conductive wire is changed in an icing state, but the icing detection device is too sensitive, so that even raindrops or dust on the surface of the conductive wire can generate signal change, thereby influencing the accuracy of icing detection.
The icing detection device of the mechanical method is still the mainstream icing detection device at present, is widely applied to aircrafts of various models, and has the characteristic of high reliability. The icing detecting device of the mechanical method is a method for estimating the icing quality on the surface of an aircraft by vibrating an icing detecting rod arranged on the surface of the aircraft by means of various components or devices generating vibration and measuring the natural vibration frequency of the icing detecting rod. However, this method has many problems, and the most important defect is that the icing conditions of large and small-scale supercooled water drops cannot be distinguished, so that the method has the defect of insufficient accuracy of icing detection. The icing protection of large and small-scale supercooled water drops has large difference on the design of an anti-icing system and the energy consumption demand, and is an important reason for influencing flight safety. At present, SLD icing detector appearance design methods proposed by researchers lack basis of appearance design, and are designed by means of experience and intuitive guesses. The SLD icing detector invented by Yixian and the like in China aerodynamic research and development center is very similar and close to the SLD icing detector invented by Gejunfeng and the like in China university of science and technology in design method, and the final appearance is almost the same and is a diamond-shaped structure with one expansion and one contraction. Moreover, the icing detector may play a certain role in distinguishing large and small supercooled water drops under the flight condition of zero flight angle of attack or very small flight angle of attack, but under the condition of larger flight angle of attack, the icing detector has larger measurement error and even cannot distinguish the large supercooled water drop from the small supercooled water drop.
Disclosure of Invention
The invention aims to provide a novel icing detection method and a novel icing detection device capable of distinguishing large-scale and small-scale supercooled water drops, which are supplemented and improved aiming at the defects of the traditional mechanical icing detection device.
In order to achieve the purpose, the invention adopts the following technical scheme:
a multi-cylinder array icing detection device comprises a cylinder array arranged on a test surface, wherein the cylinder array comprises three cylinders with different diameters which are sequentially arranged along the same axis, the diameters of the cylinders are gradually increased from one end to the other end, and the surfaces of the two adjacent cylinders are not in contact with each other;
the cylinder is internally provided with a cavity structure, a vibrating piece is arranged in the cavity structure, the surface of the cylinder is provided with an acceleration sensor, and a signal acquisition system is connected with the vibrating piece and the acceleration sensor.
In the above technical solution, the cylinder array is divided into a first cylinder, a second cylinder and a third cylinder along the incoming flow direction of air, the upper impact limit streamline and the lower impact limit streamline of the air flow are critical air streamlines bypassing the upper surface and the lower surface of the leading edge of the first cylinder, and the second cylinder and the third cylinder are arranged in the range between the upper impact limit streamline and the lower impact limit streamline.
In the above technical solution, the diameter of the second cylinder is equal to the distance between the upper impact streamline and the lower impact streamline of the area where the diameter of the second cylinder is located.
In the above technical scheme, the diameter of the third cylinder is equal to the distance between the upper impact streamline and the lower impact streamline of the area where the diameter of the third cylinder is located.
In the above technical solution, the signal acquisition system includes a dynamic analysis module, and signal input ends of the dynamic analysis module are respectively connected to the acceleration sensors on the cylinder.
In the above technical solution, the signal acquisition system includes a power amplifier, and the power amplifier is connected to the vibrating element in each cylinder through a respective switch.
A multi-cylinder array icing detection method comprises the steps that when air flow flows to a multi-cylinder array from a far field, the cylinder array is provided with three cylinders which are located on the same axis and have the axis direction consistent with the direction of an air flow field, supercooled water drops impact the surface of a first cylinder along with the air flow, splashing phenomenon is generated after the supercooled water drops impact the surface of the first cylinder, and the splashed supercooled water drops continue to impact the surface of a second cylinder or a third cylinder along with the air flow to be iced;
the cylinders are driven to vibrate through the external drive, the vibration frequency, amplitude and phase parameters of the surfaces of the cylinders are acquired through cylinder surface data acquisition, and the cylinder surface parameters acquired after icing and the cylinder surface parameters of the icing are used for calculating to obtain the volume of the supercooled water drops.
In the above technical solution, the cylinder array includes three cylinders with different diameters sequentially arranged along the same axis, the diameters of the cylinders are gradually increased from one end to the other end, and the surfaces of two adjacent cylinders are not in contact.
In the above technical solution, the upper impact limit streamline and the lower impact limit streamline of the air flow are critical air streamlines that bypass the upper surface and the lower surface of the leading edge of the first cylinder, and the second cylinder and the third cylinder are disposed in a range between the upper impact limit streamline and the lower impact limit streamline.
In the technical scheme, the diameter of the second cylinder is equal to the distance between the upper impact streamline and the lower impact streamline of the area where the diameter of the second cylinder is located.
In the above technical scheme, the diameter of the third cylinder is equal to the distance between the upper impact streamline and the lower impact streamline of the area where the diameter of the third cylinder is located.
In the above solution, the air stream comprises supercooled water droplets of two sizes, one of which has an average diameter of not more than 50 microns and the other of which has an average diameter of more than 50 microns.
In the technical scheme, in the impact process of the supercooled water drops with the average diameter not more than 50 micrometers, the motion streamline of the supercooled water drops is the same as that of the air streamline, the supercooled water drops collide with the first cylinder to be frozen on the surface of the first cylinder, and the second cylinder and the third cylinder are not frozen.
In the above technical solution, the second cylinder and the third cylinder are located in the upper and lower impact limit streamline of the first cylinder, that is, in the water drop shielding region of the first cylinder.
In the technical scheme, in the impact process of the supercooled water drops with the average diameter of more than 50 microns, the motion streamline of the supercooled water drops is different from the air streamline, the deviation of the upper impact limit streamline and the lower impact limit streamline of the supercooled water drops is small, and after the supercooled water drops impact the first cylinder, splashed water drops impact two sides of the front edge area of the second cylinder or the third cylinder along with the air flow to freeze.
In the technical scheme, when the supercooled water drops with the average diameter exceeding 50 micrometers impact the surface of the first cylinder, the water drops cannot be immediately frozen, part of unfrozen liquid water overflows towards the downstream of the cylinder, if the circumference of the surface of the first cylinder is not enough to be frozen, the unfrozen liquid water is blown to the surface of the front edge area of the second cylinder by the airflow, and at the front edge of the second cylinder, part of the unfrozen liquid water also overflows towards the downstream of the cylinder and then is blown to the front edge area of the third cylinder by the airflow to be frozen.
In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:
the invention adopts the simplest cylinder shape from another vision, utilizes the characteristic that the cylinder shape has little influence on the surrounding flow field, realizes the purpose of detecting large and small-scale supercooled water drops by arranging and combining a plurality of cylinders, and has the characteristics of easy implementation, simplicity, practicability and suitability for various attack angle flight conditions.
The invention combines the traditional mechanical icing detection method, overcomes the defect that the large and small-scale supercooled water drops cannot be distinguished on the basis, fully exerts the advantages of the traditional mechanical icing detection, better coordinates the two contradictions of the icing detection of the large-scale supercooled water drops and the small-scale supercooled water drops, better solves the problem of the icing detection on the surface of the airplane, and has practical significance for solving the design of an anti-icing and anti-icing system of an aircraft and guaranteeing the flight safety.
The invention adopts a multi-cylinder array icing detection method aiming at icing meteorological conditions (including icing meteorological conditions in an experimental simulation environment and a real atmospheric environment), and is directly used for the process and the purpose of icing detection on parts which are easy to be iced, such as aircrafts, wind turbines, power transmission lines and the like.
Drawings
The invention will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a schematic diagram of a multi-cylinder array icing detection method under small-scale supercooled water droplet conditions;
FIG. 2 is a schematic diagram of a multi-cylinder array icing detection method under large-scale supercooled water droplet conditions;
FIG. 3 is a schematic view of a multi-cylinder array icing detection apparatus.
Detailed Description
All of the features disclosed in this specification, or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations of features and/or steps that are mutually exclusive.
The supercooled water droplets in the far field are divided into two types, namely large-scale supercooled water droplets (the average diameter exceeds 50 micrometers), and small-scale supercooled water droplets (the average diameter does not exceed 50 micrometers). The air flow 1 in the air flow of fig. 1 and 2 flows from a far field to the multi-cylinder array, the supercooled water drops 2 impact or bypass the surface of the multi-cylinder array along with the air flow, small-scale supercooled water drops (water drops with the average diameter smaller than 50 micrometers) have good air flow following performance due to low mass and low inertia, the motion streamline of the water drops is almost the same as that of the air streamline, the upper impact limit streamline 3 and the lower impact limit streamline 4 of the air flow are respectively critical air streamlines which bypass the upper surface and the lower surface of the front edge of the first cylinder 6, and correspondingly, the upper impact limit streamline and the lower impact limit streamline of the small-scale supercooled water drops are consistent with the upper impact limit streamline 3 and the lower impact limit streamline 4 of the first cylinder 6. The diameter of the second cylinder 7 is designed, by numerical calculation, to be exactly equal to the distance between the upper and lower impingement streamlines, so that small-scale supercooled water droplets 2 will typically only freeze 5 in the region of the leading edge of the cylinder. Accordingly, from theoretical and numerical calculations, the icing phenomenon does not occur on the surfaces of the second cylinder 7 and the third cylinder 8, and because the latter two cylinders are positioned in the upper and lower impact limit streamlines of the first cylinder, namely in the water drop shielding area of the first cylinder, supercooled water drops do not generally impact on the surfaces of the second cylinder and the third cylinder. If the large-scale supercooled water drops 2 flow into the air flow from the far field, the mass of the large-scale supercooled water drops is high, the inertia of the large-scale supercooled water drops is large, the following performance of the air flow is poor, and therefore the difference between the motion streamline of the large-scale supercooled water drops and the air streamline is large, and deflection is not easy to occur. Therefore, the respective upper and lower impact limiting streamlines are less offset, and thus icing phenomena 9, 10 are more likely to occur on the surfaces on both sides of the leading edge region of the second cylinder 7 and the third cylinder 8. Moreover, due to the large volume and size of the large-scale super-cooled water drops, the large-scale super-cooled water drops are easy to break in the process of flowing along with air, and are also easy to splash when impacting the surface of the solid wall of the cylinder, and the like, and part of the water drops splashed out of the surface of the solid wall are easy to impact two sides of the front edge area of the cylinder behind along with the air flow. Meanwhile, large-scale supercooled water drops impact the surface part of the cylinder, due to the fact that the large-scale supercooled water drops are large in size, the large-scale supercooled water drops are not easy to freeze immediately, part of unfrozen liquid water also easily overflows towards the downstream of the cylinder, and if the circumference of the surface of the first cylinder is not enough to freeze, the unfrozen liquid water is blown to the surface of the front edge area of the second cylinder by air flow. Therefore, icing of the surfaces on both sides of the leading edge region of the second cylinder will easily occur. Similarly, similar icing will occur on the surfaces on either side of the leading edge region of the third cylinder, based on previous analysis.
Utilize the law of conservation of mass, to the small-scale super-cooled water droplet, the condition is comparatively simple, the volume of freezing W1 on first cylinder surface equals the super-cooled water droplet quality in the upper and lower striking limit streamline of small-scale super-cooled water droplet, and to the large-scale super-cooled water droplet, most icing phenomenon takes place for first cylinder leading edge surface, the total mass (W) of first cylinder icing volume (W1), second cylinder icing volume (W2), third cylinder icing volume (W3), equals the super-cooled water droplet quality sum in the upper and lower striking limit streamline. And with the assistance of numerical calculation and theoretical analysis, the liquid water content and the average water drop diameter of the large and small-scale supercooled water drops can be reversely deduced through the icing quantity of each cylindrical surface. The spacing and diameter between each cylinder may also be determined by computational fluid dynamics.
The icing detection device is composed as shown in fig. 3.
In the figure:
6 is a first cylinder: the first cylinder of the multi-cylinder array of the present invention is the cylinder with the smallest diameter in the multi-cylinder array, and is mainly used for collecting the small-scale supercooled water droplets and the vast majority of the large-scale supercooled water droplets.
7 is a second cylinder: the diameter of the second cylinder of the multi-cylinder array is slightly larger than that of the first cylinder, the distance between the diameter D1 of the second cylinder and the upper and lower impact limit streamline of the air flow is equal to or close to that of the first cylinder, the second cylinder is mainly used for collecting a small amount of supercooled water drops which are not collected by the first cylinder, and the supercooled water drops have larger possibility of generating dynamic phenomena such as crushing, splashing and the like due to large volume and heavy mass and are easy to impact the surfaces of the front edge areas of the second cylinder and the third cylinder under the action of the air flow, so that angular icing shapes are formed at the upper side and the lower side of the front edge areas of the second cylinder and the third cylinder.
8 is a third cylinder: this is the third cylinder of the multi-cylinder array of the present invention, which is slightly larger in diameter than the second cylinder, and functions as a supplement to the second cylinder for collecting small amounts of large scale supercooled water droplets and unfrozen overflow water that were not collected by the first two cylinders, thereby forming small amounts of ice on either side of the leading edge region of the third cylinder.
14 is a power line: the power supply is connected with the power amplifier, and the vibration component is connected with the power supply through the power amplifier.
15 is a switch: the electronic component is used for controlling the on-off function between a power supply and the vibration component.
16 is a power amplifier: the instrument is connected with an arbitrary function generator, and different types of signals generated by the function generator are subjected to bias, filtering and gain, so that the vibrating signals meet the requirements of damaging or stripping an ice layer.
And 17 is a power supply: the power supply component is used for supplying power to various instruments and sensors, and can rectify, transform and the like the conventional 220V industrial voltage so as to generate the power supply component required by the various instruments and sensors.
18 is an acceleration sensor: the method is used for measuring the acceleration characteristic represented by the vibration generated on the surface of the anti-icing component, and therefore the parameters such as the vibration frequency, the amplitude and the phase position are calculated and analyzed.
And 19 is a signal acquisition line: the cable is used for transmitting various measurement signals, is used for connecting various instruments, sensors and a data acquisition module, and inputs acquired electric signals into the data acquisition module.
20 is a dynamic analysis module: the device is used for collecting and analyzing vibration signals measured by the acceleration sensor, and can obtain the natural frequency generated by the surface vibration of the anti-icing component before and after icing. By measuring the natural frequency of the vibration of the piezoelectric fiber film, whether the anti-icing surface is iced or not can be judged. If the anti-icing surface is iced, the natural frequency of the piezoelectric fiber film is greatly changed, and if the surface is not iced, the natural frequency of the piezoelectric fiber film is kept unchanged. The natural frequency is related to the thickness of the ice on the vibration surface, the type of the ice and the like, and can be calibrated through a large number of experiments, the natural frequency of the vibration surface is related to the thickness of the ice and the type of the ice, a quantitative relation is established, and judgment and reference are provided for adjusting parameters such as vibration frequency, amplitude and phase in the vibration deicing process.
21 is an icing detection surface: the invention can be applied to the surfaces of a nose, a fuselage, wings and an empennage of an airplane, the surfaces of blades of a wind turbine and a transmission conductor, or the surfaces of other components of national economy related equipment such as a high-speed train and the like which need to be frozen for detection.
The invention relates to an icing detection method and device based on a multi-cylinder array, which is designed by utilizing the most common and simplest cylinder appearance according to the airflow following characteristic of large-scale and small-scale supercooled water drops, the dynamic characteristics of crushing, splashing and the like of the large-scale supercooled water drops and the collection characteristic of cylinders to different-scale supercooled water drops.
Firstly, calculating and measuring the natural vibration frequency of each clean cylinder to obtain parameters such as vibration frequency and the like under the condition of no icing as reference values for calculating the icing thickness and the icing mass of the surface of the cylinder;
a mechanical vibration cam arranged in the cylinder or an electric control piezoelectric ceramic or other vibration components are periodically started, and the periodic vibration strategy can greatly reduce the energy consumption required by the icing detection, so that the periodic vibration strategy can intermittently generate vibration with certain frequency, amplitude and phase;
measuring the vibration frequency of the cylinder by using an accelerometer or a strain gauge and other sensors arranged on the surface of the cylinder, inputting the obtained signal into a dynamic analysis module, and calculating and analyzing the natural frequency;
if the cylinder is not frozen, the natural frequency of the cylinder is not changed, the function generator and the power amplifier keep the original vibration parameters, the gain, the offset and the like of the vibration parameters, and the periodic vibration strategy of the step a is kept;
if the cylinder is frozen in the vibration process, parameters such as the vibration frequency of the frozen cylinder and the like are changed, the frozen vibration signal is measured by adopting sensors such as an accelerometer or a strain gauge and the like, and the measured vibration signal is input into a dynamic analysis module for analysis and calculation to obtain the natural vibration frequency of the frozen cylinder;
according to the relationship between the pre-calibrated icing quality and icing thickness and the natural frequency of the cylinder, the natural vibration frequency after icing is calculated through a data acquisition module and fed back to an airplane deicing system to serve as a trigger signal for starting deicing.
The method for determining the distance and the diameter between the circular columns comprises the following steps:
1) And performing corresponding numerical simulation on the flow field around the multi-cylinder array by using a computational fluid mechanics method and adopting a Navier-Stokes equation when the low speed is not compressible to obtain the air flow field around the multi-cylinder array.
2) On the basis of numerical calculation of a flow field around the multi-cylinder array, numerical simulation is carried out on supercooled water drops at the entrance of the flow field by utilizing a Lagrange method according to a Newton's second law, a fixed upper impact limit streamline (3) and a fixed lower impact limit streamline (4) of the supercooled water drops are obtained and are used as tangents for determining the diameters of the second cylinder and the third cylinder, and an upper impact limit streamline and a lower impact limit streamline with the critical average water drop diameter of 50 micrometers are obtained in a key mode. Accordingly, the second (D2) and third (D3) cylinder diameters are equal to the distance between the upper and lower impact limit streamlines. Meanwhile, the distance H1 between the first cylinder and the second cylinder and the distance H2 between the second cylinder and the third cylinder cannot be too large or too small, and the principle of medium distance is followed, after the diameters of the second cylinder and the third cylinder are determined, because the upper and lower impact limit streamlines are determined aiming at supercooled water drops with different sizes, the distances H1 and H2 can also be determined. Or the distances H1 and H2 are determined, and then the diameters (D2 and D3) of the second cylinder and the third cylinder are determined through the fixed upper and lower impact limit streamline.
H1≈(D2-D1)/2(1)
H2≈(D3-D2)/2(2)
3) Because the invention relates to large-scale supercooled water drops, the dynamic phenomena such as deformation, crushing and the like are easy to occur in the process of flowing along with air, and the resistance can also change along with the change of the relative Reynolds number, the resistance of small-scale supercooled water drops selects a classical spherical resistance formula, and the resistance of large-scale supercooled water drops increases the influence of the dynamic characteristics such as deformation, crushing and the like on the basis of the spherical resistance formula, so that the capture of the motion track of the large-scale supercooled water drops is more accurate.
4) When the supercooled water drops are close to the surface of an object, the motion trail of the supercooled water drops does not change violently like the motion trail of air particles because the inertia of the supercooled water drops is larger than that of the air particles, and the original motion trail and direction are kept as far as possible. For large scale super-cooled water droplets, due to their larger mass and inertia, they are more likely to deviate from the air streamlines, thereby forming a more slowly changing motion trajectory, and therefore, they are also more likely to impinge on both sides of the leading edges of the second and third cylinders, thereby forming overflow ice.
5) In all the super-cooled water drop motion track clusters, two motion tracks tangent to the upper surface and the lower surface of the front edge of the cylinder are an upper impact limit streamline and a lower impact limit streamline. All supercooled water droplets within these two paths of motion will impinge on the cylindrical surface. Supercooled water droplets outside the two tangential paths of motion will bypass the cylinder and will not impinge on the surface of the cylinder. Within the two tangential motion trajectories, the number of supercooled water droplets impinging on the cylindrical surface is the amount of supercooled water droplets impinging on the cylindrical surface.
The method for determining the average diameter of the small-scale super-cooled water drops comprises the following steps:
for simplicity, it is assumed that the diameter of supercooled water droplets is uniform.
(1) The natural vibration frequency F of the clean cylinder is obtained by calculation and experiment.
(2) Attaching different additional masses Wi to the surface of the clean cylinder, combining calculation and experiments to obtain new natural vibration frequency Fn of the cylinder under different additional masses, and establishing a calibration relational expression of related frequency and additional mass to provide calibration data reference for icing detection.
(3) The multi-cylinder array icing detection system is placed in an icing wind tunnel, icing experiments under different icing meteorological conditions are carried out, the natural vibration frequency of the icing cylinder on the surface is measured and compared with a calibration relation, and the calibration relation between the natural frequency Fn and the icing additional mass Wi is further corrected.
Wi＝f(Fn)(3)
(4) Supposing that supercooled water droplets in the incoming flow are small-scale supercooled water droplets, the average diameter is Dw, and the density is ρ, therefore, the mass Dw1 of a single supercooled water droplet satisfies the following relationship:
dW＝ρ·4/3·π·(Dw/2)3(4)
(5) According to the vibration ice detection principle and by combining the calibration relation, the mass W1 of ice formed on the first cylindrical surface and the average density ρ 1 of an ice layer can be obtained, and the icing volume V1 and the average thickness h1 of the cylindrical surface can be obtained:
V1＝W1/ρ1(5)
h1＝W1/(ρ1·A1)(6)
where A1 is the icing area of the first cylindrical surface.
(6) The number NW1 of supercooled water droplets whose cylindrical surface is frozen can also be obtained by the following formula:
NW1＝W1/dW(7)
in addition, the average icing thickness h1 of the cylindrical surface can also be calculated according to the following relation:
h1＝NW1·4/3·π·(Dw/2)3/A1(8)
(7) Assuming that the liquid water content of supercooled water droplets in an incoming flow is LWC, the area of an incoming flow inlet sandwiched between an upper impact limit streamline and a lower impact limit streamline is a, the incoming flow velocity is V, and the freezing coefficient of the supercooled water droplets is θ (for example, when small-scale supercooled water droplets are instantly frozen, θ =1, and when large-scale supercooled water droplets cannot be instantly frozen, θ < 1), in a unit time t, supercooled water droplets in the upper impact limit streamline and the lower impact limit streamline satisfy the following relational expression:
W1＝LWC·V·A·t·θ(9)
thus, the liquid water content LWC of supercooled water droplets in the incoming flow can also be obtained:
LWC＝W1/(V·A·t·θ)(10)
alternatively, the liquid water content LWC can also be calculated as follows:
in the formula: eb-the water collection coefficient of the cylindrical surface, obtained by computational fluid dynamics calculation methods;
v is far-field incoming flow velocity, m/s;
t-icing time, s.
(8) From the liquid water content LWC that has been obtained previously, the mass of supercooled water droplets per unit area or per unit volume can be obtained. The fixed upper and lower impact limit streamlines are obtained through numerical calculation, supercooled water drops clamped between the two limit streamlines can impact the surface of the cylinder, and other supercooled water drops can follow the air flow to be far away from the cylinder.
The method for determining the average diameter of the large-scale supercooled water droplets is similar to that of the small water droplets, and satisfies the steps (1) to (4) and the corresponding formulas, except that the icing phenomenon occurs in the second cylinder.
(9) According to the vibration ice detection principle and by combining the calibration relation, the mass W1 of ice formed on the first cylindrical surface and the average density ρ 1 of an ice layer can be obtained, and the icing volume V1 and the average thickness h1 of the cylindrical surface can be obtained:
V1＝W1/ρ1(12)
h1＝W1/(ρ1·A1)(13)
where A1 is the icing area of the first cylindrical surface.
The mass of ice formed on the second cylindrical surface is W2, the average density of the ice layer is rho 2, and the icing volume V2 of the cylindrical surface and the average thickness h2 thereof can be obtained:
V2＝W2/ρ2(14)
h2＝W2/(ρ2·A2)(15)
(10) The number NW1 of supercooled water droplets frozen on the first cylindrical surface can also be obtained by the following formula:
NW1＝W1/dW(16)
the number NW2 of supercooled water droplets whose second cylindrical surface is frozen can also be obtained by the following formula:
NW2＝W2/dW(17)
NW3＝W3/dW(18)
NW＝NW1+NW2+NW3(19)
(11) Supercooled water droplet liquid water content LWC in the incoming stream:
LWC＝(W1+W2+W3)/(V·A·t·θ)(20)
alternatively, the liquid water content LWC can also be calculated as follows:
the invention is not limited to the foregoing embodiments. The invention extends to any novel feature or any novel combination of features disclosed in this specification and any novel method or process steps or any novel combination of features disclosed.
Claims (3)
1. A multi-cylinder array icing detection method is characterized in that: when the air flow flows to the multi-cylinder array from a far field, the cylinder array is provided with three cylinders which are positioned on the same axis and the direction of the axis is consistent with the direction of an air flow field, supercooled water drops impact the surface of the first cylinder along with the air flow, a splashing phenomenon is generated after the supercooled water drops impact the surface of the first cylinder, and the splashed supercooled water drops continue to impact the surface of the second cylinder or the third cylinder along with the air flow to be frozen;
each cylinder is driven to vibrate through the outside, vibration frequency, amplitude and phase parameters of the surface of the cylinder are acquired through cylinder surface data acquisition, the volume of the supercooled water drops is obtained through calculation by using the cylinder surface parameters acquired after icing and the cylinder surface parameters before icing, and then the mass of the supercooled water drops in unit area or unit volume is calculated;
the parameters of the cylindrical surface are obtained as follows:
the method comprises the following steps: firstly, calculating and measuring the natural vibration frequency of each clean cylinder to obtain the vibration frequency parameter of the cylinder under the condition of no icing as a reference value for calculating the icing thickness and the icing mass of the surface of the cylinder;
step two: a mechanical vibration cam arranged in the cylinder or an electric control piezoelectric ceramic or other vibration components are periodically started, and the periodic vibration strategy can greatly reduce the energy consumption required by the icing detection, so that the periodic vibration strategy can intermittently generate vibration with certain frequency, amplitude and phase;
step three: measuring the vibration frequency of the cylinder by using an accelerometer or a strain gauge sensor arranged on the surface of the cylinder, inputting the obtained signal into a dynamic analysis module, and calculating and analyzing the natural frequency;
step four: if the cylinder is not frozen, the natural frequency of the cylinder is not changed, the function generator and the power amplifier keep the original vibration parameters, the gain and the offset of the vibration parameters and the periodic vibration strategy in the step a;
step five: if the cylinder is frozen in the vibration process, the vibration frequency parameter of the frozen cylinder changes, an accelerometer or a strain gauge sensor is adopted to measure the vibration signal after freezing, and the vibration signal is input into a dynamic analysis module for analysis and calculation to obtain the natural vibration frequency of the frozen cylinder;
step six: calculating the natural vibration frequency after icing through a data acquisition module according to the relationship between the icing quality and the icing thickness calibrated in advance and the natural frequency of the cylinder, and feeding the natural vibration frequency back to an airplane deicing system to serve as a trigger signal for starting deicing;
the air stream comprises supercooled water droplets of two sizes, one of which has an average diameter of no more than 50 microns and the other of which has an average diameter of more than 50 microns;
in the collision process of the supercooled water drops with the average diameter not more than 50 microns, the motion streamline of the supercooled water drops is the same as that of the air streamline, the supercooled water drops collide with the first cylinder and are frozen on the surface of the first cylinder, and the freezing phenomenon does not occur on the surfaces of the second cylinder and the third cylinder;
the method for calculating the mass of the supercooled water drops in unit area or unit volume comprises the following steps:
the method comprises the following steps: obtaining the natural vibration frequency of the clean cylinder through calculation and experiments;
step two: attaching different additional masses Wi to the surface of a clean cylinder, combining calculation and experiments to obtain new natural vibration frequencies Fn of the cylinder under different additional masses, establishing a calibration relational expression of related frequencies and the additional masses, and providing calibration data reference for icing detection;
step three: placing the multi-cylinder array icing detection system into an icing wind tunnel, carrying out icing experiments under different icing meteorological conditions, measuring the natural vibration frequency of the icing cylinder on the surface, comparing the natural vibration frequency with a calibration relation, and further correcting the calibration relation between the natural vibration frequency and the icing additional mass: wi = f (Fn);
step four: supposing that supercooled water droplets in the incoming flow have a diameter of less than 50 μm, an average diameter Dw and a density ρ, the mass Dw1 of the individual supercooled water droplets satisfies the following relationship:
dW1＝ρ·4/3·π·(Dw/2)3；
step five: according to the vibration ice detection principle and by combining the calibration relational expression, the mass W1 of ice formed on the surface of the first cylinder and the average density ρ 1 of an ice layer can be obtained, and the icing volume V1 and the average icing thickness h1 of the surface of the first cylinder can be obtained:
V1＝W1/ρ1
h1＝W1/(ρ1·A1)
wherein A1 is the icing area of the first cylindrical surface;
step six: assuming that the liquid water content of supercooled water drops in an incoming flow is LWC, the area of an incoming flow inlet clamped between an upper impact limit streamline and a lower impact limit streamline is A, the incoming flow speed is V, the freezing coefficient of the supercooled water drops is theta, and the supercooled water drops in the upper impact limit streamline and the lower impact limit streamline meet the following relational expression in unit time t:
W1＝LWC·V·A·t·θ
thus, the liquid water content LWC of supercooled water droplets in the incoming stream can also be obtained:
LWC＝W1/(V·A·t·θ)；
the number NW1 of supercooled water droplets frozen on the first cylindrical surface can also be obtained by the following formula:
NW1＝W1/dW1
in addition, the average icing thickness h1 of the first cylindrical surface can also be calculated according to the following relation:
h1＝NW1·4/3·π·(Dw/2)3/A1；
step seven: according to the obtained liquid water content LWC, the mass of the supercooled water drops in unit area or unit volume can be obtained, fixed upper and lower impact limit flow lines are obtained through numerical calculation, the supercooled water drops clamped between the two limit flow lines can impact the surface of the cylinder, and other supercooled water drops can follow the air flow to be far away from the cylinder;
when cold water drops with the diameter smaller than 50 micrometers are instantly frozen, the freezing coefficient theta =1, and when cold water drops with the diameter larger than 50 micrometers cannot be instantly frozen, the freezing coefficient theta is smaller than 1;
when the average diameter of the supercooled water droplets exceeds 50 micrometers, the mass W1 of ice accreted on the first cylindrical surface and the average density ρ 1 of the ice layer can be obtained on the basis of steps 1 to 4, and the icing volume V1 of the cylindrical surface and the average thickness h1 thereof can be obtained:
wherein A1 is the icing area of the first cylindrical surface,
the mass of ice formed on the second cylindrical surface is W2, the average density of the ice layer is rho 2, and the icing volume V2 and the average icing thickness h2 of the second cylindrical surface can be obtained:
V2＝W2/ρ2
h2＝W2/(ρ2·A2)
the number NW1 of supercooled water droplets in which the first cylindrical surface is frozen can also be obtained by the following formula:
NW1＝W1/dW
the number NW2 of supercooled water droplets frozen on the second cylindrical surface can also be obtained by the following equation:
NW2＝W2/dW
the number NW3 of supercooled water droplets frozen on the third cylindrical surface can also be obtained by the following equation:
NW3＝W3/dW
supercooled water droplet liquid water content LWC in the incoming stream:
LWC＝(W1+W2+W3)/(V·A·t·θ)。
2. the method of claim 1, wherein the second and third cylinders are located within the upper and lower impact limit streamlines of the first cylinder, i.e., within the water drop shadow of the first cylinder.
3. The method of claim 1, wherein the distances and diameters between three cylinders in the cylindrical array are determined by:
the method comprises the following steps: performing corresponding numerical simulation on the flow field around the multi-cylinder array by using a computational fluid mechanics method and adopting a low-speed incompressible time average Navier-Stokes equation to obtain an air flow field around the multi-cylinder array;
step two: on the basis of numerical calculation of a flow field around the multi-cylinder array, carrying out numerical simulation on a movement track of supercooled water drops at an inlet of the flow field along with the flowing of air by using a Lagrange method according to a Newton's second law to obtain a fixed upper impact limit streamline and a fixed lower impact limit streamline of the supercooled water drops, wherein the fixed upper impact limit streamline and the fixed lower impact limit streamline are used as tangents for determining the diameters of a second cylinder and a third cylinder to obtain an upper impact limit streamline and a lower impact limit streamline of a critical average water drop diameter of 50 micrometers;
step three: the diameter of the second cylinder and the diameter of the third cylinder are equal to the distance between the upper impact limit streamline and the lower impact limit streamline, meanwhile, the distance between the first cylinder and the second cylinder and the distance between the second cylinder and the third cylinder follow the principle of medium distance, and after the diameters of the second cylinder and the third cylinder are determined, the distances can also be determined because the upper impact limit streamline and the lower impact limit streamline are already determined for supercooled water drops with different sizes.
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| CN108169819B (en) * | 2017-12-06 | 2020-10-16 | 太原航空仪表有限公司 | Supercooled water content measuring method based on resonant icing detector |
| CN109490352B (en) * | 2018-12-28 | 2021-07-09 | 中山大学 | Multi-factor low-temperature freezing rain icing environment simulation test system |
| CN111307405B (en) * | 2020-04-28 | 2020-08-11 | 中国空气动力研究与发展中心低速空气动力研究所 | Air flow pulse shear type single micro water drop generating device |
| CN112345196B (en) * | 2021-01-11 | 2021-03-23 | 中国空气动力研究与发展中心低速空气动力研究所 | Super-cooled large water drop splash simulation test device and method |
| CN112798213B (en) * | 2021-04-08 | 2021-07-02 | 中国空气动力研究与发展中心低速空气动力研究所 | Hot air supply rapid adjusting system and air supply method for icing wind tunnel |
| CN114136623A (en) * | 2021-10-20 | 2022-03-04 | 中国航发四川燃气涡轮研究院 | Cloud and mist water drop volume and liquid water content measuring device and system |
| CN113899784B (en) * | 2021-12-08 | 2022-02-18 | 中国空气动力研究与发展中心低速空气动力研究所 | Method for measuring content of complex icing cloud mist water in large icing wind tunnel |
| CN114162331B (en) * | 2022-02-14 | 2022-04-29 | 中国空气动力研究与发展中心低速空气动力研究所 | Icing detection device and icing detection method |
| CN114180072B (en) * | 2022-02-16 | 2022-04-12 | 中国空气动力研究与发展中心低速空气动力研究所 | Icing thickness detection method |
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