A multi-electrode continuous-discharge spark discharge generating device

Abstract

The application discloses a multi-electrode continuous discharge spark discharge generating device, and relates to the field of aero-engine ignition. The spark discharge generating device comprises an ignition circuit and a multi-electrode spark plug. The multi-electrode spark plug comprises a metal shell and a plurality of central high-voltage electrodes arranged in the metal shell. The application matches the design parameters of the multi-electrode spark plug with the non-uniformity coefficient of the electric field in the ignition end face, and designs the ignition circuit, so that the maximum value of the delay difference between the breakdown time of two adjacent discharges is less than the arc duration time, the continuous discharge of the multiple electrodes is realized, the arc flame energy is higher, the contact area of the ignition arc and the mixed fuel is larger, the combustion in the combustion chamber is more uniform, the misfire rate of the spark plug is effectively reduced, and the operation reliability of the engine is improved.

Description

Technical Field

[0001] This application relates to the field of aero-engine ignition, and in particular to a spark discharge generating device for continuous multi-electrode discharge. Background Technology

[0002] The combustion chamber is one of the core components of an aero-engine, and its ignition reliability is a fundamental performance requirement in combustion chamber design, crucial for engine start-up and safe flight. In actual operation, aero-engine ignition often involves various extreme situations (in-flight restart after engine shutdown, continuous ignition operations, and start-up under high-altitude and frigid conditions), posing new challenges to the stability and reliability of aero-engine ignition. Currently, most civil aircraft engines use semiconductor spark plugs as igniters in the combustion chamber. Semiconductor spark plugs have advantages such as simple structure, strong controllability, and low cost. Equipped with corresponding ignition circuits, they together form the aero-engine ignition device. This device generates a high-temperature flame of sufficient temperature and size, allowing the flame to fill the entire combustion chamber, thereby ensuring the reliable completion of electric ignition in the aero-engine.

[0003] Most existing semiconductor spark plugs use a single-electrode structure, which is easy to operate but has disadvantages such as low spark discharge energy conversion rate and high misfire rate. Summary of the Invention

[0004] In response to the aforementioned technical problems and needs regarding the low energy conversion rate and high misfire rate of existing single-electrode spark plug ignition devices, the applicant proposes a multi-electrode continuous discharge spark discharge generating device. The technical solution of this application is as follows:

[0005] The spark discharge generating device includes an ignition circuit and a multi-electrode spark plug. The multi-electrode spark plug includes a metal shell and n central high-voltage electrodes disposed inside the metal shell. The metal shell is grounded and serves as the grounding electrode; n is an integer parameter and n≥2.

[0006] The metal shell has a hollow cylindrical cavity inside, and multiple central high-voltage electrodes are symmetrically arranged inside the cavity of the metal shell. Semiconductor material is filled between the central high-voltage electrodes and the metal shell. Each central high-voltage electrode has the same specifications and the distance d between each central high-voltage electrode and the metal shell is equal.

[0007] The electric field non-uniformity coefficient f inside the ignition end face of the multi-electrode spark plug is matched with the design parameters of the multi-electrode spark plug, and the electric field non-uniformity coefficient inside the ignition end face of the multi-electrode spark plug is less than a predetermined threshold. The design parameters of the multi-electrode spark plug include the radius r0 of each central high-voltage electrode and the distance d between each central high-voltage electrode and the metal shell.

[0008] The ignition circuit is used to power the multi-electrode spark plug, so that each center high-voltage electrode and the ground electrode can have a discharge channel to cause discharge breakdown, and the maximum value of the delay difference between the breakdown times of two adjacent discharge breakdowns is less than the duration of the electric arc.

[0009] The further technical solution involves determining the design parameters for multi-electrode spark plugs, including:

[0010] Based on the design objective that the electric field non-uniformity coefficient inside the ignition end face of the multi-electrode spark plug is less than a predetermined threshold, the range of values ​​for b / r0 is determined, and the radius r0 of each central high-voltage electrode and the distance d between each central high-voltage electrode and the metal shell are determined according to the radius R0 of the metal shell and the number n of the central high-voltage electrodes.

[0011] The expression for the electric field non-uniformity coefficient inside the ignition end face of a multi-electrode spark plug is: E max This represents the maximum electric field strength inside the ignition end face of a multi-electrode spark plug. E av This represents the average electric field strength inside the ignition end face of a multi-electrode spark plug. U represents the electric field strength at any position j inside the ignition end face of the multi-electrode spark plug for any i-th central high-voltage electrode, 1≤j≤m, where m is the total number of positions inside the ignition end face of the multi-electrode spark plug and is an integer parameter; i q represents the voltage of the i-th central high-voltage electrode; q represents the number of central high-voltage electrodes undergoing discharge breakdown.

[0012] The electric field strength of any i-th central high-voltage electrode at any position j inside the ignition end face of a multi-electrode spark plug Where x is the straight-line distance between the i-th central high-voltage electrode and position j, and b is the offset distance between the i-th central high-voltage electrode and the metal casing along the ray direction from the i-th central high-voltage electrode to position j.

[0013] The further technical solution is that the ignition circuit includes a DC power supply, several parallel and independent RC circuits and several gas discharge tubes. Each RC circuit corresponds to a central high-voltage electrode. Each RC circuit includes a series voltage divider resistor and an energy storage capacitor. One end of the voltage divider resistor of each RC circuit is connected to the positive terminal of the DC power supply. One end of the energy storage capacitor of each RC circuit is connected to a metal shell and grounded. The common terminal of the voltage divider resistor and the energy storage capacitor in each RC circuit is led out and connected to one end of a gas discharge tube. The other end of each gas discharge tube is connected to a corresponding central high-voltage electrode.

[0014] The DC power supply charges the energy storage capacitors in each RC circuit. The voltage across each gas discharge tube increases synchronously with the voltage across the energy storage capacitor in the connected RC circuit. When the voltage difference across the gas discharge tube does not reach the breakdown voltage of the gas discharge tube, the gas discharge tube is in the open state. When the voltage difference across the gas discharge tube reaches the breakdown voltage of the gas discharge tube, the gas discharge tube breaks down and conducts to supply power to the connected central high-voltage electrode.

[0015] A further technical solution is that each RC circuit also includes a protection diode, with the anode of the protection diode connected to the positive terminal of the DC power supply and the cathode of the protection diode connected to a voltage divider resistor.

[0016] A further technical solution involves determining the resistance value of the voltage divider resistor and the capacitance value of the energy storage capacitor in each RC circuit, including:

[0017] Based on the design objective that the maximum delay difference between the breakdown times of two adjacent discharge breakdowns is less than the duration of the arc, the range of values ​​for the product of the voltage divider resistor R and the energy storage capacitor C in each RC circuit is determined, and the resistance R and capacitance C that satisfy the range of values ​​for the product are determined.

[0018] The expression for the maximum time delay difference between two adjacent discharge breakdowns is as follows: Where, Δt max U represents the maximum time delay difference between the breakdown times of two adjacent discharge breakdowns. n-1 x is the breakdown voltage of the (n-1)th breakdown electrode. n-1 b is the straight-line distance between the (n-1)th breakdown electrode and the nth breakdown electrode. n-1 U is the offset distance between the (n-1)th breakdown electrode and the metal casing along the ray direction from the (n-1)th breakdown electrode to the nth breakdown electrode. A The voltage of the DC power supply;

[0019] The (n-1)th breakdown electrode is the central high-voltage electrode corresponding to the discharge channel where the (n-1)th discharge breakdown occurs in the spark discharge generator, and the nth breakdown electrode is the central high-voltage electrode corresponding to the discharge channel where the nth discharge breakdown occurs in the spark discharge generator.

[0020] A further technical solution involves determining the expression for the maximum value of the delay difference between two adjacent discharge breakdown times, including:

[0021] The expression for the breakdown voltage U1 at the first discharge breakdown of the spark discharge generator is: Where p is the gas pressure inside the gas discharge tube where the first discharge breakdown connection occurs, γ is the secondary electron emission coefficient, and A and B are experimental constants related to the type of gas inside the gas discharge tube where the first discharge breakdown connection occurs.

[0022] The electric field strength at any (k+1)th breakdown electrode decreases after discharge breakdown occurs at any kth breakdown electrode. Determine the breakdown voltage U at which the (k+1)th breakdown electrode experiences discharge breakdown. k+1 =U k +ΔU k , The time delay difference between the breakdown time of the (k+1)th breakdown electrode and the breakdown time of the kth breakdown electrode, determined according to the capacitor boost formula, is: And proportional to U k The integer parameter is 1 ≤ k ≤ n-1;

[0023] Determine U when k = n-1 k The maximum value is reached, and the corresponding delay difference reaches its maximum value. The expression for the maximum time delay difference between two adjacent discharge breakdowns is obtained by rearranging the expression:

[0024] Among them, U k U is the breakdown voltage of the k-th breakdown electrode. k+1 Let x be the breakdown voltage of the (k+1)th breakdown electrode. k Let b be the straight-line distance between the k-th breakdown electrode and the (k+1)-th breakdown electrode. k The offset distance between the k-th breakdown electrode and the metal casing along the ray direction from the k-th breakdown electrode to the (k+1)-th breakdown electrode;

[0025] The k-th breakdown electrode is the central high-voltage electrode corresponding to the discharge channel where the spark discharge generator experiences its k-th discharge breakdown, and the (k+1)-th breakdown electrode is the central high-voltage electrode corresponding to the discharge channel where the spark discharge generator experiences its (k+1)-th discharge breakdown.

[0026] The further technical solution is as follows: the offset distance of any central high-voltage electrode is d≤b≤R+δ, where δ is the electrode eccentricity distance between the center of each central high-voltage electrode and the center of the metal shell. The radius R0 of the metal shell ranges from 6.5mm to 9mm, the electrode eccentricity distance δ ranges from 2mm to 4mm, and R0 / δ ranges from 3 to 4. The distance d between each central high-voltage electrode and the metal shell ranges from 4mm to 7mm, the radius r0 of each central high-voltage electrode ranges from 0.5mm to 1.5mm, the d / r0 ranges from 6 to 10, the b / r0 ranges from 6 to 12, and the distance between the centers of any two central high-voltage electrodes is greater than 3mm.

[0027] A further technical solution involves filling the space between the central high-voltage electrode and the metal casing with a semiconductor material having a depth ranging from 1mm to 3mm and a conductivity ranging from 10. -6 S / m~10 5 S / m, resistance value range is 0.3Ω~0.75Ω, capacitance value range is 20pF~4-pF.

[0028] A further technical solution is that the resistance R of the voltage divider resistor in each RC circuit ranges from 1kΩ to 3kΩ, the capacitance C of the energy storage capacitor ranges from 0.1μF to 5.5μF, and the product of the resistance R of the voltage divider resistor and the capacitance C of the energy storage capacitor ranges from 2.5×10⁻⁶. -4 kΩ·μF~2×10 -3 kΩ·μF.

[0029] The further technical solution is that the breakdown voltage of each gas discharge tube is in the range of 150V to 4000V, the maximum withstand current is greater than 15kA, and the capacitance value is in the range of 1pF to 10pF; the reverse withstand voltage of each protection diode is greater than 1.5kV, and the maximum withstand current is greater than 10A.

[0030] The beneficial technical effects of this application are:

[0031] The multi-electrode spark plug structure designed in this application has multiple central high-voltage electrodes and ignition circuits on the ignition end face, which can realize continuous discharge of multiple electrodes, resulting in higher energy of the electric arc, a larger contact area between the ignition arc and the mixed fuel, and more uniform ignition in the combustion chamber. This can effectively reduce the spark plug misfire rate and improve the reliability of engine operation.

[0032] This application matches the electric field non-uniformity coefficient inside the ignition end face of the multi-electrode spark plug with the design parameters of the multi-electrode spark plug, thereby reducing the influence of the irregular generation and transmission of particles in the ionization region on the electric field uniformity. This makes the electric field non-uniformity coefficient less than a predetermined threshold, reducing the influence of the non-uniform transmission of ions on the current density of the spark plug's ignition end face, and making each central high-voltage electrode have higher uniformity, thus better realizing continuous discharge of the multi-electrode.

[0033] This application also includes an ignition circuit. By controlling the parameters of the ignition circuit components, a discharge channel is created between each central high-voltage electrode and the ground electrode, resulting in discharge breakdown. Furthermore, the maximum delay difference between the breakdown times of two adjacent discharge breakdowns is less than the arc duration, further ensuring the continuity of multi-channel discharge in the spark discharge generator. Through the regulation of the ignition circuit, each central high-voltage electrode is kept at the same potential, making it less likely for discharge breakdown to occur between them.

[0034] The ignition circuit of this application includes multiple parallel independent RC circuits. Compared with the traditional single-energy-storage circuit structure of spark plugs, with the same total energy of the capacitor, the individual capacitors in this application store less energy, resulting in smaller capacitor size, faster charging rate, reduced voltage requirements, and simplified circuit structure complexity. Furthermore, when powered by a small-capacity capacitor, the proportion of residual energy in its components to the total energy stored in the capacitor is smaller, reducing energy loss and effectively improving the utilization efficiency of spark plug energy. Simultaneously, the ignition circuit of this application incorporates a unidirectional diode protection device to effectively prevent short circuits. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the overall structure of a spark discharge generating device in one embodiment of this application.

[0036] Figure 2 This is a radial cross-sectional schematic diagram of a spark discharge generating device in one embodiment of this application.

[0037] Figure 3 This is a circuit diagram of a spark discharge generating device in one embodiment of this application.

[0038] Figure 4 This is a schematic diagram of the ignition end face of a spark discharge generating device in one embodiment of this application.

[0039] Figure 5 This is a schematic diagram of the parameters of a spark discharge generating device in one embodiment of this application.

[0040] Reference numerals: 1. First central high-voltage electrode; 2. Second central high-voltage electrode; 3. Metal casing; 4. Semiconductor material; 5. Wiring port. Detailed Implementation

[0041] The specific embodiments of this application will be further described below with reference to the accompanying drawings.

[0042] like Figure 1 and Figure 2 As shown, a multi-electrode continuous discharge spark discharge generating device of this application includes an ignition circuit and a multi-electrode spark plug. The multi-electrode spark plug includes a metal shell 3 and n central high-voltage electrodes disposed inside the metal shell 3. The metal shell 3 is grounded and serves as a grounding electrode; n is an integer parameter and n≥2. A hollow cylindrical cavity is formed inside the metal shell 3. The multiple central high-voltage electrodes are symmetrically arranged inside the cavity of the metal shell, and a semiconductor material 4 is filled between the central high-voltage electrodes and the metal shell. Each central high-voltage electrode has the same specifications, and the distance d between each central high-voltage electrode and the metal shell 3 is equal. One end of each central high-voltage electrode is exposed at the ignition end face of the multi-electrode spark plug, and the other end is connected to the ignition circuit through a terminal 5. In one embodiment, there are two central high-voltage electrodes, namely a first central high-voltage electrode 1 and a second central high-voltage electrode 2, which are symmetrically distributed inside the cavity of the metal shell.

[0043] In this embodiment, the central high-voltage electrode is needle-shaped or rod-shaped, and both the central high-voltage electrode and the metal shell are made of tungsten-based stainless steel alloy. Optionally, the semiconductor material is a ceramic semiconductor with titanium dioxide as the main component.

[0044] The role of semiconductor materials is that when current passes through the central high-voltage electrode and through the semiconductor material, electrons are emitted. Under the influence of the electric field, the electrons accelerate, promoting the formation of electron avalanches, which in turn promotes the discharge breakdown of the central high-voltage electrode.

[0045] The ignition circuit includes a DC power supply, several parallel and independent RC circuits, and several gas discharge tubes. Each RC circuit corresponds to a central high-voltage electrode. Each RC circuit includes a series voltage divider resistor and an energy storage capacitor. One end of the voltage divider resistor in each RC circuit is connected to the positive terminal of the DC power supply. One end of the energy storage capacitor in each RC circuit is connected to a metal casing and grounded. The common terminal of the voltage divider resistor and the energy storage capacitor in each RC circuit is led out and connected to one end of a gas discharge tube. The other end of each gas discharge tube is connected to the terminal of the corresponding central high-voltage electrode.

[0046] The function of a gas discharge tube is to act as a circuit switch. When the voltage across the gas discharge tube is less than the breakdown voltage, the gas discharge tube does not work and the switch is open. When the voltage across the gas discharge tube is greater than or equal to the breakdown voltage, the gas discharge tube works and the switch is closed.

[0047] In one embodiment, each RC circuit also includes a protection diode, with its anode connected to the positive terminal of the DC power supply and its cathode connected to a voltage divider resistor. The function of the protection diode is to prevent short circuits in the RC branches corresponding to other central high-voltage electrodes from further discharging and breaking down when a single central high-voltage electrode experiences discharge breakdown. Optionally, the protection diode has a reverse withstand voltage greater than 1.5kV and a maximum withstand current greater than 10A.

[0048] In one embodiment, such as Figure 3 As shown, when the multi-electrode spark plug M has two center high-voltage electrodes, there are two corresponding RC circuits and DC power supply S. One RC circuit includes a protection diode D1, a voltage divider resistor R1, and an energy storage capacitor C1 connected in series, as well as a gas discharge tube K1 connected to the common terminal of the voltage divider resistor R1 and the energy storage capacitor C1. The other RC circuit includes a protection diode D2, a voltage divider resistor R2, and an energy storage capacitor C2 connected in series, as well as a gas discharge tube K2 connected to the common terminal of the voltage divider resistor R2 and the energy storage capacitor C2.

[0049] The ignition circuit is used to power the multi-electrode spark plug, so that each center high-voltage electrode and the ground electrode can have a discharge channel to cause discharge breakdown, and the maximum value of the delay difference between the breakdown times of two adjacent discharge breakdowns is less than the duration of the electric arc.

[0050] The DC power supply charges the energy storage capacitors in each RC circuit. The voltage across each gas discharge tube increases synchronously with the voltage across the energy storage capacitor in the connected RC circuit. When the voltage difference across the gas discharge tube does not reach the breakdown voltage of the gas discharge tube, the gas discharge tube is in the open state. When the voltage difference across the gas discharge tube reaches the breakdown voltage of the gas discharge tube, the gas discharge tube breaks down and conducts to supply power to the connected central high-voltage electrode.

[0051] The working principle of the spark discharge generating device of this application is as follows: the DC power supply continuously charges the energy storage capacitor until the voltage across the energy storage capacitor reaches the breakdown voltage, the gas discharge tube works, the ignition circuit is turned on, and a discharge channel is formed between the central high-voltage electrode corresponding to the energy storage capacitor and the metal shell, generating an electric spark.

[0052] Because the spark discharge generating device of this application has multiple central high-voltage electrodes that are offset from the central axis of the metal casing, the electric field intensity distribution at each central high-voltage electrode inside the spark plug ignition end face is uneven. This results in the spark plug with the strongest electric field intensity being the first to discharge and break down, causing a discharge delay difference among the multiple central high-voltage electrodes.

[0053] In order to achieve continuous discharge and improve ignition efficiency of the spark discharge generating device of this application, the parameters of the device need to be designed to achieve two set objectives, including:

[0054] 1. The electric field non-uniformity coefficient inside the ignition end face of the multi-electrode spark plug is less than a predetermined threshold.

[0055] like Figure 4 The diagram shows an ignition end face with two central high-voltage electrodes in one embodiment. Based on the design goal that the electric field non-uniformity coefficient inside the ignition end face of the multi-electrode spark plug is less than a predetermined threshold, the range of values ​​for b / r0 is determined. The radius r0 of each central high-voltage electrode and the distance d between each central high-voltage electrode and the metal shell are determined according to the radius R of the metal shell and the number n of the central high-voltage electrodes.

[0056] The offset distance b of any central high-voltage electrode is in the range of d ≤ b ≤ R + δ, where δ is the electrode eccentricity distance between the center of each central high-voltage electrode and the center of the metal casing. For example, the predetermined threshold is 2.

[0057] The expression for the electric field non-uniformity coefficient inside the ignition end face of a multi-electrode spark plug is: E max This represents the maximum electric field strength inside the ignition end face of a multi-electrode spark plug. E av This represents the average electric field strength inside the ignition end face of a multi-electrode spark plug. U represents the electric field strength at any position j inside the ignition end face of the multi-electrode spark plug for any i-th central high-voltage electrode, 1≤j≤m, where m is the total number of positions inside the ignition end face of the multi-electrode spark plug and is an integer parameter. i q represents the voltage of the i-th central high-voltage electrode; q represents the number of central high-voltage electrodes undergoing discharge breakdown.

[0058] In one embodiment, most of the time only one central high-voltage electrode experiences discharge breakdown, q = 1; occasionally two central high-voltage electrodes experience discharge breakdown simultaneously, q = 2; and the simultaneous discharge breakdown of three or more central high-voltage electrodes is rare. The value of q can be obtained by calculating the time delay difference between the breakdown times of two adjacent discharge breakdowns.

[0059] The electric field strength of any i-th central high-voltage electrode at any position j inside the ignition end face of a multi-electrode spark plug Where x is the straight-line distance between the i-th central high-voltage electrode and position j, and b is the offset distance between the i-th central high-voltage electrode and the metal casing along the ray direction from the i-th central high-voltage electrode to position j. Figure 5 The diagram shows parameters b and x.

[0060] This application reduces the impact of non-uniform ion transport on the current density at the spark plug's ignition end face by controlling the electric field non-uniformity coefficient to be less than a predetermined threshold, thereby enabling each central high-voltage electrode to have higher uniformity and better achieve multi-electrode continuous discharge.

[0061] 2. The maximum time delay difference between two adjacent discharge breakdowns is less than the duration of the electric arc.

[0062] The expression for the breakdown voltage U1 at the first discharge breakdown of the spark discharge generator is: Where p is the gas pressure inside the gas discharge tube where the first discharge breakdown connection occurs, γ is the secondary electron emission coefficient, and A and B are experimental constants related to the types of gas inside the gas discharge tube where the first discharge breakdown connection occurs.

[0063] In one embodiment, since the electric field non-uniformity coefficient is less than 2, there is no visible corona before discharge breakdown. The corona initiation condition is the gap breakdown condition. The electric field strength inside the ignition end face of the multi-electrode spark plug is determined to be the corona initiation field strength at the first discharge breakdown. Furthermore, since the nth breakdown electrode weakens the electric field of the first breakdown electrode, the decrease in electric field strength of the nth breakdown electrode after the (n-1)th breakdown electrode undergoes discharge breakdown is equal to the increase in electric field strength after the (n-1)th breakdown electrode undergoes discharge breakdown. The (n-1)th breakdown electrode is the central high-voltage electrode corresponding to the discharge channel of the (n-1)th discharge breakdown in the spark discharge generator, and the nth breakdown electrode is the central high-voltage electrode corresponding to the discharge channel of the nth discharge breakdown in the spark discharge generator.

[0064] Because the discharge breakdown of the (n-1)th breakdown electrode alters the electric field distribution at the spark plug ignition end face, reducing the electric field strength at the nth breakdown electrode, the nth breakdown electrode cannot reach the corona initiation field strength E0, requiring a higher voltage to achieve discharge breakdown. In this embodiment, it is determined that the electric field strength at any (k+1)th breakdown electrode decreases after the discharge breakdown of any (k)th breakdown electrode. Determine the breakdown voltage U at which the (k+1)th breakdown electrode experiences discharge breakdown. k+1 =U k +ΔU k ,

[0065] The known formula for capacitor boost is: Where U(t) is the voltage of the energy storage capacitor at time t, U A This is the voltage of the DC power supply. The breakdown voltage U is the voltage at which the energy storage capacitor reaches the k-th breakdown electrode and discharges. k hour, When the energy storage capacitor reaches the breakdown voltage U at the (k+1)th breakdown electrode, it will cause discharge breakdown.k+1 hour, The time delay difference between the breakdown time of the (k+1)th breakdown electrode and the breakdown time of the kth breakdown electrode, determined according to the capacitor boost formula, is: And proportional to U k The integer parameter is 1≤k≤n-1.

[0066] Determine U when k = n-1 k The maximum value is reached, and the corresponding delay difference reaches its maximum value. The expression for the maximum time delay difference between two adjacent discharge breakdowns is obtained by rearranging the expression:

[0067] Among them, U k U is the breakdown voltage of the k-th breakdown electrode. k+1 Let x be the breakdown voltage of the (k+1)th breakdown electrode. k Let b be the straight-line distance between the k-th breakdown electrode and the (k+1)-th breakdown electrode. k Let Δt be the offset distance between the k-th breakdown electrode and the metal casing along the ray direction from the k-th breakdown electrode to the (k+1)-th breakdown electrode. max U represents the maximum time delay difference between the breakdown times of two adjacent discharge breakdowns. n-1 x is the breakdown voltage of the (n-1)th breakdown electrode. n-1 b is the straight-line distance between the (n-1)th breakdown electrode and the nth breakdown electrode. n-1 The offset distance between the (n-1)th breakdown electrode and the metal casing along the ray direction from the (n-1)th breakdown electrode to the nth breakdown electrode.

[0068] The k-th breakdown electrode is the central high-voltage electrode corresponding to the discharge channel where the spark discharge generator experiences its k-th discharge breakdown, and the (k+1)-th breakdown electrode is the central high-voltage electrode corresponding to the discharge channel where the spark discharge generator experiences its (k+1)-th discharge breakdown.

[0069] In actual operation of a spark discharge generator, the electric field strength of each central high-voltage electrode decreases with increasing distance. Therefore, when a central high-voltage electrode experiences discharge breakdown, the central high-voltage electrodes furthest from it are most likely to reach the discharge breakdown condition. This can be analyzed by examining the formula x... k and b k For delay difference Δt k The effect can also be derived, x k and b k The larger the value, the greater the delay difference Δt. k The smaller.

[0070] By analyzing the delay difference Δt kAs can be seen from the formula, the breakdown voltage increases continuously with each discharge breakdown, and the time delay difference Δt between two adjacent discharge breakdowns... k With breakdown voltage U k It is directly proportional. Therefore, when the device design parameters are fixed, the time difference between two adjacent discharge breakdowns increases with time. Thus, the maximum time difference between two adjacent discharge breakdowns is the time difference between the last two discharge breakdowns.

[0071] Based on the design objective that the maximum delay difference between the breakdown times of two adjacent discharge breakdowns is less than the arc duration, the range of values ​​for the product of the voltage divider resistor R and the energy storage capacitor C in each RC circuit is determined, and the resistance R and capacitance C values ​​that satisfy this range are also determined. In one example, if the spark plug arc duration is 10 microseconds, then the maximum delay difference Δt between the breakdown times of two adjacent discharge breakdowns must be guaranteed in this application. max Less than 10 microseconds.

[0072] In one embodiment, the product of the resistance R of the voltage divider resistor and the capacitance C of the energy storage capacitor in each RC circuit ranges from 2.5 × 10⁻⁶. -4 kΩ·μF~2×10 -3 kΩ·μF. Optionally, the resistance R of the voltage divider resistor in each RC circuit ranges from 1kΩ to 3kΩ, and the capacitance C of the energy storage capacitor ranges from 0.1μF to 5.5μF.

[0073] This application improves the continuity of multi-channel discharge and greatly enhances ignition efficiency by rationally designing the parameters of the voltage divider resistor and the energy storage capacitor and controlling the voltage rise rate of the energy storage capacitor. This makes the maximum delay difference between the breakdown times of two adjacent discharges less than the duration of the arc.

[0074] In one embodiment, a spark discharge generating device is designed to meet the above two set objectives. For example, the radius R0 of the metal casing ranges from 6.5mm to 9mm, the electrode eccentricity distance δ ranges from 2mm to 4mm, and R0 / δ ranges from 3 to 4; the distance d between each central high-voltage electrode and the metal casing ranges from 4mm to 7mm, the radius r0 of each central high-voltage electrode ranges from 0.5mm to 1.5mm, and d / r0 ranges from 6 to 10, b / r0 ranges from 6 to 12, and the distance between the centers of any two central high-voltage electrodes is greater than 3mm. For example, the semiconductor material has a depth range of 1mm to 3mm and a conductivity range of 10. -6 S / m~10 5The resistance value ranges from 0.3Ω to 0.75Ω, and the capacitance value ranges from 20pF to 40pF. For example, the breakdown voltage range of the gas discharge tube is 150V to 4000V, the maximum withstand current is greater than 15kA, and the capacitance value ranges from 1pF to 10pF.

[0075] In one example, the radius R0 of the metal casing is 9 mm, the electrode eccentricity δ is 3 mm, R0 / δ is 3, the radius r0 of each central high-voltage electrode is 1 mm, the distance d between each central high-voltage electrode and the metal casing is 6 mm, d / r0 is 6, and the distance between the centers of any two central high-voltage electrodes is 4 mm.

[0076] The above descriptions are merely preferred embodiments of this application, and this application is not limited to the above embodiments. It is understood that other improvements and variations that can be directly derived or conceived by those skilled in the art without departing from the spirit and concept of this application should be considered to be included within the protection scope of this application.

Claims

1. A spark discharge generating device for continuous multi-electrode discharge, characterized in that, The spark discharge generating device includes an ignition circuit and a multi-electrode spark plug. The multi-electrode spark plug includes a metal shell and n central high-voltage electrodes disposed inside the metal shell. The metal shell is grounded and serves as a grounding electrode. n is an integer parameter and n≥2. The metal shell has a hollow cylindrical cavity inside, and multiple central high-voltage electrodes are symmetrically arranged inside the cavity of the metal shell. Semiconductor material is filled between the central high-voltage electrodes and the metal shell. Each central high-voltage electrode has the same specifications and the distance d between each central high-voltage electrode and the metal shell is the same. The electric field non-uniformity coefficient f inside the ignition end face of the multi-electrode spark plug matches the design parameters of the multi-electrode spark plug, and the electric field non-uniformity coefficient inside the ignition end face of the multi-electrode spark plug is less than a predetermined threshold. The design parameters of the multi-electrode spark plug include the radius r0 of each central high-voltage electrode and the distance d between each central high-voltage electrode and the metal shell. The ignition circuit is used to supply power to the multi-electrode spark plug, so that a discharge channel is obtained between each center high-voltage electrode and the ground electrode to cause discharge breakdown, and the maximum value of the delay difference between the breakdown times of two adjacent discharge breakdowns is less than the duration of the electric arc.

2. The spark discharge generating device according to claim 1, characterized in that, Determining the design parameters of the multi-electrode spark plug includes: Based on the design goal that the electric field non-uniformity coefficient inside the ignition end face of the multi-electrode spark plug is less than a predetermined threshold, the range of values ​​for b / r0 is determined, and the radius r0 of each central high-voltage electrode and the distance d between each central high-voltage electrode and the metal shell are determined according to the radius R0 of the metal shell and the number n of the central high-voltage electrodes. The expression for the electric field non-uniformity coefficient inside the ignition end face of the multi-electrode spark plug is as follows: E max This represents the maximum electric field strength inside the ignition end face of the multi-electrode spark plug. E av This represents the average electric field strength inside the ignition end face of the multi-electrode spark plug. U represents the electric field strength of any i-th central high-voltage electrode at any position j inside the ignition end face of the multi-electrode spark plug, 1≤j≤m, where m is the total number of positions inside the ignition end face of the multi-electrode spark plug and is an integer parameter; i q represents the voltage of the i-th central high-voltage electrode; q represents the number of central high-voltage electrodes undergoing discharge breakdown. The electric field strength of any i-th central high-voltage electrode at any position j inside the ignition end face of the multi-electrode spark plug Where x is the straight-line distance between the i-th central high-voltage electrode and position j, and b is the offset distance between the i-th central high-voltage electrode and the metal casing in the ray direction along the i-th central high-voltage electrode to position j.

3. The spark discharge generating device according to claim 1, characterized in that, The ignition circuit includes a DC power supply, several parallel and independent RC circuits, and several gas discharge tubes. Each RC circuit corresponds to a central high-voltage electrode. Each RC circuit includes a series voltage divider resistor and an energy storage capacitor. One end of the voltage divider resistor in each RC circuit is connected to the positive terminal of the DC power supply. One end of the energy storage capacitor in each RC circuit is connected to the metal casing and grounded. The common terminal of the voltage divider resistor and the energy storage capacitor in each RC circuit is led out and connected to one end of a gas discharge tube. The other end of each gas discharge tube is connected to a corresponding central high-voltage electrode. The DC power supply charges the energy storage capacitors in each RC circuit. The voltage across each gas discharge tube increases synchronously with the voltage across the energy storage capacitor in the connected RC circuit. When the voltage difference across the gas discharge tube does not reach the breakdown voltage of the gas discharge tube, the gas discharge tube is in the open state. When the voltage difference across the gas discharge tube reaches the breakdown voltage of the gas discharge tube, the gas discharge tube breaks down and conducts to supply power to the connected central high-voltage electrode.

4. The spark discharge generating device according to claim 3, characterized in that, Each RC circuit also includes a protection diode, the anode of which is connected to the positive terminal of the DC power supply, and the cathode of which is connected to the voltage divider resistor.

5. The spark discharge generating device according to claim 3, characterized in that, Determining the resistance values ​​of the voltage divider resistors and the capacitance values ​​of the energy storage capacitors in each RC circuit includes: Based on the design objective that the maximum delay difference between the breakdown times of two adjacent discharge breakdowns is less than the duration of the arc, the range of values ​​for the product of the voltage divider resistor R and the energy storage capacitor C in each RC circuit is determined, and the resistance R and capacitance C that satisfy the range of values ​​for the product are determined. The expression for the maximum time delay difference between two adjacent discharge breakdowns is as follows: Where, Δt max U represents the maximum time delay difference between the breakdown times of two adjacent discharge breakdowns. i-1 x is the breakdown voltage of the (n-1)th breakdown electrode. n-1 b is the straight-line distance between the (n-1)th breakdown electrode and the nth breakdown electrode. n-1 U is the offset distance between the (n-1)th breakdown electrode and the metal casing along the ray direction from the (n-1)th breakdown electrode to the nth breakdown electrode. A The voltage of the DC power supply; The (n-1)th breakdown electrode is the central high-voltage electrode corresponding to the discharge channel of the (n-1)th discharge breakdown of the spark discharge generator, and the nth breakdown electrode is the central high-voltage electrode corresponding to the discharge channel of the nth discharge breakdown of the spark discharge generator.

6. The spark discharge generating device according to claim 5, characterized in that, The expression for determining the maximum value of the time delay difference between two adjacent discharge breakdowns includes: The expression for the breakdown voltage U1 at the first discharge breakdown of the spark discharge generator is determined as follows: Where p is the gas pressure inside the gas discharge tube where the first discharge breakdown connection occurs, γ is the secondary electron emission coefficient, and A and B are experimental constants related to the type of gas inside the gas discharge tube where the first discharge breakdown connection occurs. The electric field strength at any (k+1)th breakdown electrode decreases after discharge breakdown occurs at any kth breakdown electrode. Determine the breakdown voltage U when the (k+1)th breakdown electrode experiences discharge breakdown. k+1 =U k +ΔU k , The time delay difference between the breakdown time of the (k+1)th breakdown electrode and the breakdown time of the kth breakdown electrode, determined according to the capacitor boost formula, is: And proportional to U k The integer parameter is 1 ≤ k ≤ n-1; Determine U when k = n-1 k The maximum value is reached, and the corresponding delay difference reaches its maximum value. The expression for the maximum time delay difference between two adjacent discharge breakdowns is obtained by rearranging the expression: Among them, U k U is the breakdown voltage of the k-th breakdown electrode. k+1 Let x be the breakdown voltage of the (k+1)th breakdown electrode. k Let b be the straight-line distance between the k-th breakdown electrode and the (k+1)-th breakdown electrode. k The offset distance between the k-th breakdown electrode and the metal casing along the ray direction from the k-th breakdown electrode to the (k+1)-th breakdown electrode; The k-th breakdown electrode is the central high-voltage electrode corresponding to the discharge channel where the spark discharge generator experiences its k-th discharge breakdown, and the (k+1)-th breakdown electrode is the central high-voltage electrode corresponding to the discharge channel where the spark discharge generator experiences its (k+1)-th discharge breakdown.

7. The spark discharge generating device according to claim 2, characterized in that, The offset distance of any central high-voltage electrode is d ≤ b ≤ R + δ, where δ is the electrode eccentricity distance between the center of each central high-voltage electrode and the center of the metal shell. The radius R0 of the metal shell ranges from 6.5 mm to 9 mm, the electrode eccentricity distance δ ranges from 2 mm to 4 mm, and R0 / δ ranges from 3 to 4. The distance d between each central high-voltage electrode and the metal shell ranges from 4 mm to 7 mm, the radius r0 of each central high-voltage electrode ranges from 0.5 mm to 1.5 mm, the d / r0 ranges from 6 to 10, the b / r0 ranges from 6 to 12, and the distance between the centers of any two central high-voltage electrodes is greater than 3 mm.

8. The spark discharge generating device according to claim 7, characterized in that, The semiconductor material filling the space between the central high-voltage electrode and the metal casing has a depth ranging from 1 mm to 3 mm and a conductivity ranging from 10. -6 S / m~10 5 S / m, resistance value range is 0.3Ω~0.75Ω, capacitance value range is 20pF~4-pF.

9. The spark discharge generating device according to claim 4, characterized in that, In each RC circuit, the resistance R of the voltage divider resistor ranges from 1kΩ to 3kΩ, and the capacitance C of the energy storage capacitor ranges from 0.1μF to 5.5μF. The product of the resistance R of the voltage divider resistor and the capacitance C of the energy storage capacitor ranges from 2.5 × 10⁻⁶. -4 kΩ·μF~2×10 -3 kΩ·μF.

10. The spark discharge generating device according to claim 9, characterized in that, The breakdown voltage of each gas discharge tube is in the range of 150V to 4000V, the maximum withstand current is greater than 15kA, and the capacitance value is in the range of 1pF to 10pF; the reverse withstand voltage of each protection diode is greater than 1.5kV, and the maximum withstand current is greater than 10A.

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