Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a mechanism for realizing uniform air stretching vibration of the surface of a vehicle based on a plasma generator so as to finish the resistance reduction of the vehicle.
The purpose of the invention is realized by the following technical scheme:
a wall surface drag reduction mechanism based on a plasma generator at least comprises a plurality of drag reduction units which are arranged on the surface part of a vehicle side by side and are composed of the plasma generator and a power supply part connected with the drag reduction units; the resistance reducing unit consists of a plurality of groups of plasma generators which are arranged side by side along the air flow direction and are composed of an upper electrode plate, a lower electrode plate and an insulating layer between the upper electrode plate and the lower electrode plate; when the air close to the surface part is driven, the plasma generators in the resistance reducing units are sequentially driven according to a given rule, and the corresponding plasma generators among the resistance reducing units are simultaneously driven.
After high voltage electricity (usually thousands of volts) is applied to two adjacent upper and lower electrodes in a plasma generator arranged on a surface part, nearby air is broken down by glow discharge to be dissociated into electrons and ions, and the electrons and the ions move to two electrode plates under the action of an electric field, so that a jet flow parallel to a wall surface is formed. The span-wise vibration effect of the wall surface is approximately realized by controlling each jet flow according to a certain rule, so that the drag reduction effect on vehicles is good.
According to a preferred embodiment, the upper electrode plates and the lower electrode plates of the resistance reducing unit are arranged in a staggered mode.
According to a preferred embodiment, the upper electrode plate is disposed outside the insulating layer of the watch portion, the lower electrode plate is disposed inside the insulating layer, and the upper electrode plate and the lower electrode plate are disposed along the air flow direction.
According to a preferred embodiment, each upper electrode plate in the resistance reducing units is electrically connected with one pole of the power supply part through a circuit, each lower electrode plate is electrically connected with the other pole of the power supply part through a circuit, and the connecting circuits of the upper electrode plates and the lower electrode plates at corresponding positions among the resistance reducing units are simultaneously conducted.
According to a preferred embodiment, the drag reduction unit has a width S in the spanwise direction at the surface portion, and S satisfies S>c×ldWherein c is a set safety factor and is more than 1; ldThe electrode plate arc discharge distance.
According to a preferred embodiment, N groups of upper electrode plates and lower electrode plates are arranged in the resistance reducing unit.
According to a preferred embodiment, the plasma generators of the drag reduction units correspond to 2N excitation states,
according to a preferred embodiment, when N is 3, the plasma generator of the drag reduction unit corresponds to 6 excitation states, respectively: the resistance-reducing unit comprises an M1 excitation state, wherein when the M1 excitation state is adopted, a first upper electrode plate and a first lower electrode plate in the resistance-reducing unit are conducted with a power supply part and are in an excitation state; the resistance-reducing unit is in an M2 excited state, and when the resistance-reducing unit is in the M2 excited state, the second upper electrode plate and the second lower electrode plate are conducted with the power supply part and are in an excited state; the resistance-reducing unit is in an M3 excited state, and when the resistance-reducing unit is in the M3 excited state, the third upper electrode plate and the third lower electrode plate are conducted with the power supply part and are in an excited state; the resistance-reducing unit is in an M4 excited state, and when the resistance-reducing unit is in the M4 excited state, the third upper electrode plate and the second lower electrode plate are conducted with the power supply part and are in an excited state; the resistance-reducing unit is in an M5 excited state, and when the resistance-reducing unit is in the M5 excited state, the second upper electrode plate and the first lower electrode plate in the resistance-reducing unit are conducted with the power supply part and are in an excited state; and in the M6 excitation state, when the M6 excitation state is adopted, the first upper electrode plate and the third lower electrode plate in the resistance reduction unit are conducted with the power supply part and are in an excitation state.
According to a preferred embodiment, when N is 3, the plasma generators of the drag reduction units are sequentially driven from M1 excited state to M6 excited state, forming a period T.
According to a preferred embodiment, the pulse ratio B of the drag reduction unit is set to a value as small as possible. Preferably, the pulse oscillation ratio in this test example is 2%.
The main scheme and the further selection schemes can be freely combined to form a plurality of schemes which are all adopted and claimed by the invention; and the invention can also freely combine (non-conflicting) choices with each other and with other choices. The skilled person in the art can understand that there are many combinations, which are all the technical solutions to be protected by the present invention, according to the prior art and the common general knowledge after understanding the scheme of the present invention, and the technical solutions are not exhaustive herein.
The invention has the beneficial effects that: the drag reduction mechanism provided by the invention skillfully designs a layout structure under the limit frame of the existing plasma processing technology, and realizes the uniform vibration of the air near the wall surface in the spanwise direction. Thereby realizing the control effect of the vibration of the spreading wall surface, and reducing the flow friction resistance of the vehicle. Because the plasma generator is light and cheap, compared with a mechanical actuator, the plasma generator has great advantages and is convenient for engineering popularization and application. And considering that about half of the surface resistance of vehicles such as automobiles, high-speed rails, civil aircrafts and the like is caused by frictional resistance, the resistance reduction through the device means that the energy consumption is greatly reduced, and the device has very strong economic and environmental benefits.
Detailed Description
The following non-limiting examples serve to illustrate the invention.
Referring to fig. 1 and 2, a wall surface resistance reducing mechanism based on a plasma generator is disclosed, and the resistance reducing mechanism at least comprises a plurality of resistance reducing units which are arranged on a surface part 101 of a vehicle side by side and are formed by the plasma generator, and a power supply part 105 connected with the resistance reducing units.
After applying high voltage (usually thousands of volts) to two adjacent upper and lower electrodes in a plasma generator arranged in the meter part 101, nearby air is broken down by glow discharge to be dissociated into electrons and ions, and the electrons and the ions move to two electrode plates under the action of an electric field, so that a jet flow parallel to the wall surface is formed. Macroscopically, the plasma generator has the excitation effect as a near-wall volume force fzThe flow control is similar to zero mass jet flow, and the near-wall air is driven by a proper rule to realize the span-wise vibration effect of the wall surface, so that the vehicle obtains a good drag reduction effect.
Preferably, the drag reduction unit comprises a plurality of groups of plasma generators which are formed by an upper electrode plate 103 and a lower electrode plate 104 and are arranged side by side along the air flow direction. The driving of the near-wall air is achieved by a plasma generator.
Further, the upper electrode plates 103 and the lower electrode plates 104 in the drag reduction unit are arranged in a staggered manner. The upper electrode plate 103 and the lower electrode plate 104 are connected according to a given rule, so that the near-wall air is driven in the expansion direction.
Further, the upper electrode plate 103 is disposed outside the insulating layer 102 of the watch portion 101, the lower electrode plate 104 is disposed inside the insulating layer 102, and the upper electrode plate 103 and the lower electrode plate 104 are disposed along the air flow direction. By providing the lower electrode sheet 104 inside the insulating layer 102, generation of an arc between the electrode sheets is prevented.
Preferably, when the air close to the surface is driven, the plasma generators in the resistance reducing units are sequentially driven according to a given rule, and the corresponding plasma generators among the resistance reducing units are simultaneously driven. That is, the electrode plate groups consisting of the upper electrode plate 103 and the lower electrode plate 104 are sequentially electrified in the drag reduction unit to drive the near-wall air. And the electrode plate groups at corresponding positions among the resistance reducing units are simultaneously electrified to complete the driving of the air near the wall surface.
And the width of the drag reduction unit in the unfolding direction of the surface part 101 is S, and S satisfies S>c×ldWherein c is a set safety factor and is more than 1; ldThe electrode plate arc discharge distance. By arranging the resistance reducing units on the surface part 101 in the width direction in the spreading direction, the phenomenon of arc discharge between the adjacent resistance reducing units is avoided, and thus the plasma generators of the resistance reducing units are protected.
Further, in order to sequentially drive each upper electrode plate 103 and each lower electrode plate 104 group in the resistance reducing unit according to a given rule, each upper electrode plate 103 in the resistance reducing unit can be electrically connected with one electrode of the power supply part 105 through a line, each lower electrode plate 104 is electrically connected with the other electrode of the power supply part through a line, and the power supply part 105 sequentially energizes each line according to the given rule, that is, sequential energization of the electrode plate groups in the resistance reducing unit is realized.
Furthermore, the connecting lines of the upper electrode plates 103 and the lower electrode plates 104 at the corresponding positions among the resistance reducing units are conducted, so that the upper electrode plates 103 and the lower electrode plates 104 corresponding to the resistance reducing units are driven simultaneously.
Preferably, as shown in fig. 2, each of the drag reduction units in the drag reduction mechanism of the present invention may be configured to be composed of N sets (3 sets in this example) of the upper electrode plates 103 and the lower electrode plates 104. The figure shows 3 drag reducing units, and 3 upper electrode plates 103 for each drag reducing unit. The upper electrode plate 103 is disposed in the same direction as the relative movement of air when the vehicle is moving. The first upper electrode plate of each resistance reduction unit is in a power-on state in the figure. In a coordinate system in the figure, the x direction is the relative movement direction of air when the vehicle moves; the y direction is a direction away from the watch part 101; the z direction is the span direction of the watch portion 101.
Preferably, the upper electrode plate 103 is usually tens of microns thick according to the current processing technology, is much smaller than the thickness of the local boundary layer, has little influence on the air flow, and can be conveniently adhered to the surface of the vehicle by solid glue. The lower electrode sheet 104 is placed in an insulating coating (not shown in fig. 2), and the upper electrode sheet 103 is exposed to air (shown in a long bar).
Further, each upper electrode plate 103 in each drag reduction unit can be divided into a first upper electrode plate 103, a second upper electrode plate 103 and a third upper electrode plate 103 according to position. Each lower electrode plate 104 in each drag reduction unit can be divided into a first lower electrode plate 104, a second lower electrode plate 104 and a third lower electrode plate 104 according to positions.
Preferably, as shown in fig. 1, the first upper electrode tab 103, the second upper electrode tab 103, and the third upper electrode tab 103 are connected to one pole of the power supply section 105 through a line 3, a line 2, and a line 1, respectively. The first, second, and third lower electrode sheets 104, 104 are connected to the other pole of the power supply unit 105 via lines c, b, and a, respectively.
Thus, the adjacent upper electrode plate 103 and lower electrode plate 104 in each drag reduction unit in the drag reduction mechanism and the insulating layer (102) therebetween constitute a plasma generator, and the plasma generators of the drag reduction units in the drag reduction mechanism correspond to 2N (6 in this example) excitation states, which are respectively: an M1 excited state, wherein when the M1 excited state is adopted, the first upper electrode plate 103 and the first lower electrode plate 104 in the drag reduction unit are conducted with the power supply part and are in an excited state; an M2 excited state, wherein when the M2 excited state is adopted, the second upper electrode plate 103 and the second lower electrode plate 104 in the drag reduction unit are conducted with the power supply part and are in an excited state; an M3 excited state, wherein when the M3 excited state is adopted, the third upper electrode plate 103 and the third lower electrode plate 104 in the drag reduction unit are conducted with the power supply part and are in an excited state; an M4 excited state, wherein when the M4 excited state is adopted, the third upper electrode plate 103 and the second lower electrode plate 104 in the drag reduction unit are conducted with the power supply part and are in an excited state; an M5 excited state, wherein when the M5 excited state is adopted, the second upper electrode plate 103 and the first lower electrode plate 104 in the drag reduction unit are conducted with the power supply part and are in an excited state; and in the M6 excited state, when the M6 excited state is adopted, the first upper electrode plate 103 and the third lower electrode plate 104 in the drag reduction unit are conducted with the power supply part and are in an excited state.
Preferably, the spatial layout and the temporal firing sequence of the electrode slices in the drag reduction mechanism are shown in fig. 3. In the figure, the plasma generators of the drag reduction units are sequentially driven from an M1 excitation state to an M6 excitation state according to a given rule to form a period T.
Wherein the three states M1-M3 generate right jet flow, and push near-wall air to move to the right. The three states M4-M6 produce leftward jets that push the near-wall air to the left. The firing time series for the 6 states are shown on the right side of the figure for each state: the high potential indicates that the plasma generators of the corresponding group are in a power-on excitation state; a low potential indicates that the corresponding group of plasma generators is in a de-energized, unexcited state. T is the period of air expansion vibration generated by a plasma generator in the drag reduction mechanism, TonPulse on time, T, for a single stateoffPulse off time for a single state. Assuming that the pulse on time for each excited state is the same, for this example, there is Toff=2Ton. To weaken the starting vortex formed by sudden excitation of the plasma generator, TonShould be taken to a suitably small value where the power supply equipment allows to ensure uniformity of the flow in the spanwise direction.
Meanwhile, a pulse time to oscillation period ratio (abbreviated as pulse oscillation ratio) B may be defined, where B is Ton/T。
The plasma generator layout of the drag reduction mechanism proposed by the present invention ensures sufficient uniformity of excitation of near-wall air motion, which is critical to many flow controls. Aiming at the layout, relevant numerical experiments are carried out in low Reynolds number channel turbulence, and the optimal spanwise vibration period T is investigatedoptThe following effects prove that the plasma generator layout of the drag reduction mechanism can be realized when B is 2%The air near the wall can be promoted to form uniform vibration in the spanwise direction, the control effect equivalent to the spanwise wall vibration is achieved, and the drag reduction rate can reach 30%.
The drag reduction mechanism provided by the invention skillfully designs a layout structure under the limit frame of the existing plasma processing technology, and can realize uniform vibration of near-wall air of a vehicle in the spanwise direction. And the effect of vibration to the wall surface is realized through the layout, so that the flow friction resistance of the surface of the vehicle is reduced. Because the plasma generator is light and cheap, compared with a mechanical actuator, the plasma generator has great advantages and is convenient for engineering popularization and application. At present, numerical experiments show that the novel layout of the plasma generator adopting the resistance reducing mechanism can achieve 30% of resistance reducing effect under low Reynolds number. Considering that about half of the surface resistance of vehicles such as automobiles, high-speed rails, civil aircrafts and the like is caused by friction resistance, even 10 percent of resistance reduction means great reduction of energy consumption, and the method has strong economic and environmental benefits.
The foregoing basic embodiments of the invention and their various further alternatives can be freely combined to form multiple embodiments, all of which are contemplated and claimed herein. In the scheme of the invention, each selection example can be combined with any other basic example and selection example at will. Numerous combinations will be known to those skilled in the art.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.