Plasma ignition and combustion head excited by central sliding arc discharge

Abstract

A plasma ignition and combustion-supporting head excited by a central sliding arc discharge is disclosed. A fuel nozzle is located within a combustion head mounting base, maintaining a discharge distance between the fuel nozzle outlet discharge end face and the inner ring end face of the combustion head mounting base. A high-voltage electrode is located on a ceramic electrode mounting base, maintaining a discharge distance between the high-voltage electrode inlet end face and the fuel nozzle outlet end face. This invention achieves plasma discharge through the inner ring of the combustion head mounting base and the high-voltage electrode. A rotating sliding arc is formed by a first-stage strong swirling current. Under the action of a convergence segment at a specific angle, the arc is elongated towards the central region of fuel atomization, defining the discharge area. The arc development and breakdown are achieved by the incoming flow, placing the arc in the optimal ignition and combustion-supporting position, which is beneficial for the contact and combustion of the arc and fuel. The densely distributed discharge arc in the fuel atomization area improves combustion efficiency, reduces pollutant emissions, better achieves ignition and combustion-supporting effects, increases combustion stability, and widens the combustion range of the combustion chamber.

Description

Technical Field

[0001] This invention relates to plasma ignition and combustion technology in the field of aerospace propulsion, specifically a plasma ignition and combustion head excited by a central sliding arc discharge. Background Technology

[0002] To meet the development needs of future advanced aero-engine propulsion systems, it is urgent to overcome numerous technical bottlenecks that restrict the efficient, stable, reliable, and safe operation of aero-engine combustors. Plasma-assisted combustion technology, as a promising new combustor technology, compared with other traditional enhanced combustion technologies, uses electrical discharge to cause high-energy electrons to collide with fuel molecules, breaking down the large carbon chains of fuel molecules into lower-carbon chains and generating a large number of free-excited particles, ions, electrons, and other active particles. This reduces the activation energy required for the combustion chemical reaction, increases the chemical reaction rate, and widens the flameout boundary. Furthermore, it improves the uniformity of fuel-air mixing and the flame propagation speed, contributing to flame stability and reducing pollutant emissions in the exhaust gas.

[0003] Plasma ignition and combustion have significant advantages and promising prospects, and related research has been carried out both domestically and internationally. For example, in 2015, Murisev Andrei Nikolayevich et al. disclosed a patent for a plasma spark ignition device for a gas turbine engine in invention publication number RU2015109229U (e.g., Figure 1 As shown, the device generates an electric arc between the central electrode and the annular grounding electrode. Air is drawn in from the outside of the tangential groove to ensure a stable discharge range for the plasma jet and improve the spark plug's ignition capability. However, the central electrode contacts of this plasma spark invention are prone to erosion. Furthermore, because the igniter is mounted in the combustion zone, carbon buildup and leakage at the central electrode result in low secondary voltage and a limited number of active particles formed during ionization, making reliable ignition impossible. This makes it unsuitable for direct use in the harsh working environment of aero-engine combustion chambers.

[0004] In 2022, Mark Harris et al. disclosed a pulsed plasma igniter with a driver unit (such as...) in invention patent application US202217676992A. Figure 2 , 3 As shown, it uses nanosecond pulse power supply, which is beneficial for the discharge structure between multiple electrodes and the inner wall of the igniter housing, generating multiple plasma arcs to improve the ignition and combustion effect. It is used in gas turbine engines that operate in low air density conditions. However, the igniter still has problems such as complex structure, need for self-priming air, easy carbon buildup on electrodes and insufficient excitation.

[0005] In 2022, Shenyang Aerospace University disclosed a structure for generating a sliding arc and a plasma igniter having the same structure in its invention patent application CN113915005A. Figure 4As shown, the introduced airflow drives the central shaft to rotate through a cyclone separator. The grounding electrode on the central shaft and the high-voltage electrode of the high-voltage electrode holder are arranged in multiple rows in a ring, forming a sliding arc discharge. This increases the contact between the arc and the air, which is more conducive to the generation of active particles. The incoming airflow passes through the front-end discharge area, and the temperature in this area rises sharply under the action of a large number of arcs, which helps to reach the ignition limit. However, this invention adds a rotating electrode structure, making the igniter structure more complex. Since the temperature rise caused by plasma discharge is relatively weak, it is difficult for the front-end discharge arc to be blown away from the igniter outlet to achieve the ignition effect. Moreover, the increase in electrodes increases the power output, affecting engineering applications.

[0006] In 2022, the Aerospace Engineering University of the Strategic Support Force of the Chinese People's Liberation Army disclosed an invention with the publication number CN114340131A, which describes a three-dimensional sliding arc plasma generator (such as...). Figure 5 As shown, its cathode is spiraling upwards, forming an electric arc between the anode electrode rod and the reactor cathode. Air is drawn in through the inlet to achieve a three-dimensional sliding arc discharge. This structure is simpler and facilitates contact with the fuel, promoting combustion. However, this invention requires control of the self-drawn air flow rate to achieve sliding arc discharge. A high flow rate causes the arc to break prematurely, while a low flow rate is insufficient for the arc to reach the predetermined ignition and combustion-supporting position, presenting a problem in controlling the sliding arc. Furthermore, when the arc reaches the end of the cathode, it may cause the casing to break down and become electrified, posing a safety hazard.

[0007] The above inventions all suffer from limitations in discharge structure, installation location, and the generation of limited active particles, failing to overcome their limitations in ignition and combustion. However, some scholars have innovated by combining the combustion chamber head with plasma discharge. In 2019, the Air Force Engineering University of the Chinese People's Liberation Army disclosed a plasma jet-based ignition combustion system for aero-engines in its invention patent announcement CN106438158B (e.g., a plasma jet-based ignition combustion system for aero-engines). Figure 6 As shown, this device integrates the igniter and nozzle, thereby reducing the size of the igniter and combustion chamber, mitigating electrode erosion, and simplifying the structure. It employs plasma jet ignition technology, allowing the active particles generated by the plasma to contact and burn with the fuel-air mixture immediately, improving the ignition reliability of the aero-engine combustion chamber and possessing certain application value. However, this invention still requires separate bleed air, increasing structural complexity. While eliminating the swirler at the combustion chamber inlet reduces airflow losses, the igniter's swirling effect is poor, reducing fuel-air mixing. Furthermore, the angled fuel inlet severely affects fuel atomization, leading to a significant reduction in combustion efficiency.

[0008] In 2020, Harbin Engineering University disclosed an invention, CN111006241A, of a plasma ignition and combustion chamber (such as...) that burns low-calorific-value gaseous fuels. Figure 7As shown, based on the combination of the igniter and the combustion chamber head, a secondary swirl is added, which is more conducive to fuel mixing and makes the combustion reaction easier. However, this is combined with the gas pipe, which requires a separate gas priming structure and pre-atomization, making the structure more complex and difficult to disassemble and maintain. Furthermore, the atomized fuel easily comes into contact with the generator and the inner wall of the gas pipe, affecting its atomization effect and reducing the combustion reaction rate. In addition, the limited contact between the plasma generator arc and the fuel reduces the plasma utilization rate and significantly reduces the combustion-supporting effect.

[0009] The integration of sliding arc plasma discharge with the head solves the problem of requiring external air evacuation. In 2020, the Air Force Engineering University of the Chinese People's Liberation Army disclosed a filamentary arc plasma exciter based on a swirling orifice (e.g., in invention patent ZL2020105699588) in its invention patent ZL2020105699588. Figure 8 As shown, this invention combines a sliding plasma exciter with the combustion chamber head of an aero-engine, eliminating the need for external bleed air. It can replace the original combustion chamber head, resulting in a simpler structure and integrated ignition and combustion assistance, thus improving combustion efficiency. However, the distance between the two electrodes within the swirling orifice is relatively large, requiring a high-power supply. Increasing the number of electrodes can also affect the swirling effect and lengthen the arc, reducing the ignition and combustion assistance effect. Furthermore, both the inner and outer plasma swirlers are made of ceramic, a fragile material that is difficult to apply in practical engineering.

[0010] In 2021, the Hunan Power Machinery Research Institute of China Aero Engine Corporation disclosed an vortex generator structure for rotary sliding arc ignition in invention patent application CN113623685A (e.g., Figure 9 As shown in the diagram, this invention utilizes a built-in cone and a vortex generator body for discharge, thus optimizing the discharge structure. However, the nozzle of this invention is located behind the built-in cone, which severely affects the contact between the fuel-air mixture entering the combustion zone and the electric arc, and reduces the ignition effect.

[0011] In 2020, Shenyang Aerospace University published a paper (CN111765032A) for a fuel atomizing nozzle with a sliding arc plasma-high disturbance cross structure (e.g., Figure 10 As shown in the diagram, this invention combines sliding arc discharge and a dual-swirling high-disturbance cross structure on the combustion chamber head. The discharge structure is simple and can continuously and stably provide highly active plasma groups, promoting more complete combustion, improving combustion efficiency, and reducing pollution emissions. However, the cross nozzle is positioned behind the electrode, which is detrimental to fuel-sliding arc contact. Under large inflow conditions, fuel atomization and the discharge region are significantly affected by the flow field; the fuel atomization region detaches from the nozzle, and the sliding arc plasma cannot make good contact with the fuel. This cross nozzle placement easily causes atomized fuel to re-contact and condense, resulting in unsatisfactory fuel pyrolysis.

[0012] In 2022, the Air Force Engineering University of the Chinese People's Liberation Army disclosed a rotating sliding arc plasma enhanced combustion swirling device (such as...) in its invention patent application CN115218222A. Figure 11 As shown, this device promotes fuel atomization and cracking, and ensures thorough mixing of active components with the atomized fuel through a fuel nozzle and anode cyclone discharge structure. It simplifies the structure of plasma-excited combustion chamber cyclones and enhances the strength of the cyclone. However, the large discharge breakdown area of ​​this design leads to unstable discharge. Furthermore, the initial breakdown point is at the end face of the first-stage cyclone sleeve, resulting in a discontinuity with the venturi tube, which is detrimental to arc development. The cyclone carries high voltage, requiring proper insulation and posing a safety hazard.

[0013] In 2022, the Air Force Engineering University of the Chinese People's Liberation Army disclosed a sliding arc plasma duty flame head (such as...) in its invention patent application CN113898974A. Figure 12 As shown, this device requires no external bleed air; the two-stage cyclone separator at the outlet generates counter-current swirling. An electric arc is generated between the cathode sleeve and the anode venturi tube, and under the action of the swirling current, the arc develops and breaks down, thereby promoting fuel atomization and ensuring thorough mixing of the atomized and pyrolyzed fuel-air mixture with the active particles generated by plasma discharge, thus improving the combustion rate. It has a simple structure and significant combustion-supporting effect, and can replace the original combustion chamber head of an aero-engine. However, the arc development in this design proceeds from the near end to the far end of the anode venturi tube. Under strong incoming current, the arc may break down before reaching the far end of the anode venturi tube, resulting in a large breakdown range and failing to achieve optimal combustion-supporting effect, while also causing unnecessary energy waste.

[0014] The plasma igniters or combustion boosters proposed in the above-mentioned inventions have problems such as producing few active particles and low utilization rate during operation, weak adaptability to different incoming flows, unsatisfactory pyrolysis effect, unstable discharge breakdown, large breakdown range and energy waste. They cannot meet the high requirements of the new generation of aero-engine combustion chambers for widening the ignition boundary and stable combustion range. Summary of the Invention

[0015] To overcome the shortcomings of existing technologies, such as the discharge region being greatly affected by the flow field, poor adaptability to strong and weak incoming flow conditions, low generation of active particles, unsatisfactory fuel pyrolysis effect, unstable discharge breakdown, large breakdown range, complex discharge device, and the need for external bleed air, this invention proposes a plasma ignition and combustion aid head excited by a central sliding arc discharge.

[0016] This invention includes a fuel nozzle, a combustion head mounting base, a ceramic electrode mounting base, a ceramic insulating tube, a cable, and a high-voltage electrode. The fuel nozzle is fitted inside the combustion head mounting base, with its outlet face axially protruding beyond the outlet face of the inner ring of the combustion head mounting base, and the axial length of the protrusion is d1, ensuring that the high-voltage electrode preferentially discharges with the fuel nozzle. The ceramic electrode mounting base is located at the outlet end of the combustion head mounting base, and the high-voltage electrode is mounted on the conical outlet face of the ceramic electrode mounting base. The discharge distance between the inlet end of the high-voltage electrode and the outlet face of the fuel nozzle is d2. The cable is connected to the high-voltage electrode through the ceramic electrode mounting base.

[0017] The combustion head mounting base has a three-layer coaxial rotating structure consisting of an inner ring, a middle ring, and an outer ring. The inner ring has an inner diameter that fits tightly with the outer diameter of the fuel nozzle. The inner ring diameter D1 = 16mm~22mm, wall thickness L1 = 8mm~16mm, and axial height H1 = 30mm~45mm. The middle ring has an inner diameter D2 = 80mm~100mm, wall thickness L2 = 14mm~22mm, and axial height H1. Swirl blades are machined between the inner and middle rings to form an axial swirler. There are 10~16 swirl blades with an installation angle α1 of 30°~60°. The outer ring has an inner diameter D3 = 130mm~150mm, wall thickness L3 = 12mm~18mm, and axial height H2 = 80mm~90mm. There are 6~12 connecting bosses that axially penetrate the outer circumference of the middle ring between the middle and outer rings. The radial height H3 = 3mm~9mm, and the circumferential width d3 = 2mm~6mm.

[0018] The combustion head mounting base has an axial through hole with an inner diameter D4 of 8mm to 12mm machined on its bottom ring for mounting a ceramic insulating tube. The inner surface of the inner ring of the combustion head mounting base fits tightly with the outer surface of the fuel nozzle; the outlet end face of the fuel nozzle protrudes from the end face of the inner ring; the protrusion length is d1, where d1 = 2mm to 5mm.

[0019] The ceramic electrode mounting base has a coaxial rotating body that first converges and then expands. The inner diameter at the inlet of the convergence section is D5 = 80mm to 100mm; the outer diameter at the outlet of the expansion section is the same as the outer diameter of the outer ring of the head mounting base, which is D6 = 109mm to 149mm; the inner surface of the convergence section forms a convergence angle α2 with the horizontal plane, and the inner surface of the expansion section of the ceramic electrode mounting base forms an expansion section α3 with the horizontal plane, where α2 is 30° to 50° and α3 is 40° to 60°.

[0020] The converging section of the ceramic electrode mounting base is machined with a cable mounting hole with a diameter D7 of 2mm to 5mm. The converging end face of the cable mounting hole is machined with a groove with a diameter D8 of 8mm to 12mm, and a projection depth H4 of 1mm to 3mm on the horizontal plane. The bottom surface of this groove mates with the end face of the ceramic insulating tube, and the wall surface of the groove mates with the outer surface of the ceramic insulating tube. This groove allows the ceramic mounting tube to be embedded within the ceramic electrode mounting base, preventing discharge between the cable and the combustion head mounting base. The inner surface of the converging section of the ceramic electrode mounting base is machined with a high-voltage electrode mounting groove, the projection of which on the horizontal plane is H5 = 6mm~10mm. The depth from the inner surface of the converging section to the bottom surface of the electrode mounting groove is H6 = 0.6mm~1mm. The bottom end is located at the connection between the converging section and the expanding section of the ceramic electrode mounting base, and the top surface of the groove is parallel to the end face of the converging section. The expanding section of the ceramic electrode mounting base is machined with guide holes D9 = 1.5mm~2.5mm parallel to the horizontal plane, evenly distributed in 2~4 circles on the conical surface at the outlet end, with 12~36 holes per circle. The vertical distance d4 between the first circle of guide holes and the outer diameter of the electrode mounting groove is 4mm~6mm, and the distance d5 between each circle of guide holes is 2mm~6mm. The end face of the converging section of the ceramic electrode mounting base mates with the middle ring end face of the combustion head mounting base; the outer surface of the expanding section of the ceramic electrode mounting base mates with the outer ring end face of the combustion head mounting base.

[0021] The outer diameter D of the boss on the ceramic insulating tube 10 =14mm~16mm, the boss end face fits with the middle ring end face of the combustion head mounting seat, the outer surface of the tube fits with the axial through hole of the combustion head mounting seat, and the tube end face fits with the groove of the converging section end face.

[0022] The high-voltage electrode is installed in the conical groove of the expanded section of the ceramic electrode mounting base, and the gap is fixed by ceramic adhesive. The thickness of the circular high-voltage electrode is H6 = 0.4~0.8 mm. The discharge distance d2 between the end face of the annular high-voltage electrode and the outlet end face of the fuel nozzle is 15 mm~25 mm.

[0023] This invention is highly versatile and can completely replace the original combustion chamber head of an aero-engine without altering the original combustion chamber's structural characteristics. All inlet gases for the combustion chamber must pass through the original combustion chamber head. Similarly, the swirling flow generated by the combustion chamber mounting base and the direct current gas generated by the guide channel both originate from the combustion chamber inlet gas, eliminating the need for additional gas intake from outside the combustion chamber to the exciter for arc development and breakdown. This invention features a simple structure, reducing the complexity and failure rate of the combustion chamber structure. Furthermore, the swirling flow generated by the design of the swirling blades on the combustion chamber mounting base promotes fuel atomization and ensures thorough mixing of the atomized and pyrolyzed fuel, air, and active particles generated by plasma discharge. Secondly, a portion of the incoming air passes through the swirling blades and then through the convergent and expander sections of the high-voltage electrode mounting base, forming swirling gas. Another portion of the incoming air passes through the gaps between the middle ring, outer ring, and various connecting bosses of the combustion chamber mounting base, entering the pressure-stabilizing cavity formed by the outer surface of the convergent and expander sections and the inner surface of the outer ring, and then passes through the guide holes to form direct current gas. Figure 20 The diagram shows the airflow motion of this invention. This aerodynamic structure of direct-flow and swirling air can improve flame propagation and fuel-air mixing, further increasing the combustion rate and improving the quality of the outlet temperature field. Figure 21 The temperature field distribution at the combustion chamber outlet is shown for an airflow of 250 L / min. It can be seen that the combustion chamber outlet temperature distribution is uniform under the action of the combustion head mounting base, which can improve the service life of components such as the turbine of the aero-engine.

[0024] The present invention has good discharge stability and good arc motion stability due to the driving force of the sliding arc discharge by the first-stage strong swirling current and the directional DC, as well as the stable discharge structure of the fuel nozzle and the high-voltage electrode. Figure 22 The waveform diagram shows the arc development cycle under the conditions of an input power of 800W and an air flow of 250L / min. The arc movement is relatively stable, and the current does not show obvious pulse peaks. Within 40-49ms of the sliding arc discharge, the peak voltage and current are approximately 1kV and 1.3A, respectively. The voltage waveform changes periodically, while the current waveform is relatively smooth for most of the time, with almost no pulse peaks. This invention has good discharge stability, making it less demanding on discharge power supply parameters, adaptable to a wide range of incoming currents, and conducive to engineering applications.

[0025] This invention utilizes the inner ring of the combustion head mounting base and a high-voltage electrode to achieve plasma discharge. A rotating sliding arc is formed through a primary strong swirling current, and simultaneously, under the action of a convergent segment at a specific angle, the arc is elongated towards the central region of fuel atomization. It should be noted that this discharge region is precisely defined, and the arc development and breakdown rely solely on the incoming flow. Therefore, the arc can be positioned at the optimal ignition and combustion-supporting position, and the sliding arc is more concentrated, which is beneficial for the contact between the arc and the fuel and for combustion. Figure 23Figures a and 23b show the discharge and combustion diagrams of this invention at an airflow rate of 250 L / min, respectively. The discharge arc is densely distributed in the fuel atomization area, ensuring good contact between the arc and the fuel. This helps improve combustion efficiency and completeness, reduce pollutant emissions in the exhaust gas, and better achieve ignition and combustion-aiding effects. Furthermore, this invention directly generates a large number of active particles through plasma discharge within the combustion chamber, effectively improving the reaction between these particles and the fuel, thereby enhancing combustion stability and widening the stable combustion range of the combustion chamber. Figure 24 The diagram shows the flameout boundary and widening ratio of this invention under different intake flow rates. The flameout fuel-air ratio under plasma-assisted combustion is significantly higher than that under plasma-assisted combustion conditions. The widening becomes more pronounced with increasing intake flow rate, reaching its maximum of 14.8% at an intake flow rate of 350 L / min.

[0026] The discharge section (high voltage electrode) of this invention is simple to disassemble and process, and can be easily replaced in time after it is corroded, without having to replace the entire head. Attached Figure Description

[0027] Figure 1 It is a plasma spark ignition device for gas turbine engines developed by Mulysev Andrei Nikolayevich and others; among them, Figure 1 'a' is the main view. Figure 1 b is Figure 1 A view of section AA in section a.

[0028] Figure 2 This is a cross-sectional view of a pulsed plasma igniter with a driver unit developed by Mark Harris and others.

[0029] Figure 3 This is an isometric view of a pulsed plasma igniter with a driver unit developed by Mark Harris and others.

[0030] Figure 4 It is a structure for generating a sliding arc and a plasma igniter with the structure developed by Shenyang Aerospace University.

[0031] Figure 5 It is a three-dimensional sliding arc plasma generator developed by the Aerospace Engineering University.

[0032] Figure 6 It is a main combustion chamber for aero-engines developed by the Air Force Engineering University based on plasma jet ignition and combustion.

[0033] Figure 7 It is a plasma ignition and combustion chamber for burning low-calorific-value gaseous fuels, developed by Harbin Engineering University.

[0034] Figure 8It is a filamentary arc plasma exciter based on a swirling orifice, developed by the Air Force Engineering University;

[0035] Figure 9 It is a vortex generator structure for rotary sliding arc ignition developed by Hunan Power Machinery Research Institute of China Aero Engine Corporation.

[0036] Figure 10 It is a fuel atomizing nozzle with a sliding arc plasma-high disturbance cross structure developed by Shenyang Aerospace University.

[0037] Figure 11 It is a rotating sliding arc plasma enhanced combustion swirling device developed by the Air Force Engineering University.

[0038] Figure 12 It is a structure of the sliding arc plasma duty flame head of an aero-engine combustion chamber.

[0039] Figure 13 This is a schematic diagram of the structure of the present invention.

[0040] Figure 14 This is a schematic diagram of the combustion head mounting bracket; in which, Figure 14 'a' is the main view. Figure 14 b is Figure 14 Left view of a Figure 14 c is Figure 14 AA section view in b.

[0041] Figure 15 Schematic diagram of the installation distance between fuel injector and high-voltage electrode.

[0042] Figure 16 This is a schematic diagram of the electrode mounting base; in which, Figure 16 'a' is the left view. Figure 16 b is the front view. Figure 16 c is Figure 16 BB section view in b.

[0043] Figure 17 This is a schematic diagram of the structure of a ceramic insulating tube.

[0044] Figure 18 This is a schematic diagram of the cable structure.

[0045] Figure 19 This is a schematic diagram of the high-voltage electrode structure; in which, Figure 19 'a' is the left view. Figure 19 b is the front view.

[0046] Figure 20 This is a schematic diagram of airflow motion according to the present invention.

[0047] Figure 21This is a temperature field distribution diagram of the combustion chamber outlet under an air flow rate of 250 L / min according to the present invention.

[0048] Figure 22 This invention presents a discharge waveform diagram of one cycle of arc development under a power input of 800W and an air flow of 250L / min.

[0049] Figure 23 This is a discharge and combustion diagram of the present invention at an airflow rate of 250 L / min; wherein, Figure 23 a is the discharge diagram. Figure 23 b is the combustion diagram.

[0050] Figure 24 This is a diagram showing the flameout boundary and widening ratio of the present invention at an intake flow rate of 250 L / min.

[0051] In the figure: 1. Fuel nozzle; 2. Combustion head mounting base; 3. Electrode mounting base; 4. Ceramic insulating tube; 5. Cable; 6. High-voltage electrode; 7. Sliding arc discharge; 8. Atomized fuel; 9. Inner ring; 10. Middle ring; 11. Outer ring; 12. Swirl blade; 13. Connecting boss; 14. Axial through hole; 15. Inner surface of the converging section; 16. Inner surface of the expanding section; 17. Cable mounting hole; 18. End face of the converging section; 19. Groove; 20. Groove wall; 21. Groove wall; 22. Electrode mounting groove; 23. Vertical guide hole; 24. End face of the middle ring; 25. Outer surface of the expanding section; 26. End face of the outer ring; 27. End face of the boss; 28. Bottom end of the middle ring; 29. ​​Outer surface of the tube; 30. End face of the tube; 31. Inner surface of the high-voltage electrode; 32. Incoming air of the present invention; 33. Swirl air formed by the present invention; 34. Direct air formed by the present invention. 35. Current curve with a power input of 800W and an air flow of 250L / min; 36. Voltage curve with a power input of 800W and an air flow of 250L / min; 37. Lean fuel-air ratio for flameout under conventional combustion conditions; 38. Lean fuel-air ratio for flameout under plasma application conditions; 39. Flameout ratio widening ratio of the present invention. Detailed Implementation

[0052] This invention is a plasma ignition and combustion aid head excited by a central sliding arc discharge, and its technical features will be described in detail through three embodiments.

[0053] The present invention includes a fuel nozzle 1, a combustion head mounting base 2, an electrode mounting base 3, a ceramic insulating tube 4, a cable 5, and a high-voltage electrode 6.

[0054] The fuel nozzle 1 is installed in the inner ring of the combustion head mounting base 2, with the inner circumferential surface of the inner ring 9 tightly fitted to the outer circumferential surface of the fuel nozzle. The outlet end face of the fuel nozzle 1 axially protrudes from the end face of the inner ring; the protrusion length is d1, where d1 = 2mm to 5mm, facilitating the formation of a sliding arc 7 discharge between the fuel nozzle and the high-voltage electrode, and ensuring sufficient contact between the sliding arc and the atomized fuel 8. The inlet end of the fuel nozzle 1 is connected to the engine fuel compartment.

[0055] The ceramic insulating tube 4 is installed in the axial through hole 14 located on the combustion head mounting base 2. The electrode mounting base 3 is located at the outlet end of the combustion head mounting base. One end of the cable 5 passes through the ceramic insulating tube and the electrode mounting base, and is connected to the high-voltage electrode 6; the other end of the cable is connected to the high-voltage power supply. The high-voltage electrode is annular and is installed in the groove on the inner surface 16 of the expansion section of the electrode mounting base. The discharge distance d2 between the end face of the high-voltage electrode and the outlet end face of the fuel nozzle is 15mm to 25mm. This invention achieves plasma discharge through the fuel nozzle and the high-voltage electrode, forming a rotating sliding arc through the incoming flow generated by the combustion head mounting base, while simultaneously elongating the arc towards the central region of fuel atomization. Since the discharge region is defined, the arc develops and breaks down under the action of the incoming flow, placing the arc in the optimal ignition and combustion-supporting position, effectively increasing the probability of fuel passing through the discharge region.

[0056] The fuel nozzle 1, combustion head mounting base 2, electrode mounting base 3, and high-voltage electrode 6 are all coaxial.

[0057] The fuel nozzle 1 uses existing technology.

[0058] The combustion head mounting base 2 has an inlet diameter equal to its outlet diameter and is a hollow rotating body made of high-temperature alloy material. The combustion head mounting base includes an inner ring 9, a middle ring 10, an outer ring 11, and swirl blades 12. The inner ring 9, middle ring 10, and outer ring 11 are coaxially mounted. Swirl blades 12 are located between the inner ring 9 and the middle ring 10, forming an axial swirler. The swirl blades 12 utilize existing technology, are parallelogram-shaped plates, and number 10 to 16. The installation angle between the inlet and outlet ends of the swirl blades is α1, forming a swirl angle; α1 = 30° to 60°.

[0059] The inner ring 9, middle ring 10, and outer ring 11 are all cylindrical, wherein: the inner ring has an inner diameter D1 = 16mm~22mm, a wall thickness L1 = 8mm~16mm, and an axial length H1 = 30mm~45mm; the middle ring 10 has an inner diameter D2 = 80mm~100mm, an axial length the same as the inner ring's axial length H1, and a wall thickness L2 = 14mm~22mm; the outer ring 11 has an inner diameter D3 = 97mm~131mm, an axial height H2 = 80mm~90mm, and a wall thickness L3 = 12mm~18mm.

[0060] The outer circumferential surface of the middle ring is evenly distributed with 6 to 12 connecting bosses 13 that axially penetrate the outer circumferential surface of the middle ring. The radial height H3 of the connecting boss is 3 mm to 9 mm, and the circumferential width d3 is 2 mm to 6 mm. The axial through hole 14 is located on the middle ring; the inner diameter of the axial through hole is 8 mm to 12 mm.

[0061] The electrode mounting base 3 is made of ceramic. The longitudinal section of the electrode mounting base is V-shaped, consisting of a converging section and an expanding section. The converging section is connected to the outlet of the combustion head mounting base 2, forming a hollow rotating body that first converges and then expands through the converging and expanding sections.

[0062] The wall thickness of the electrode mounting base is the same as the wall thickness of the inner ring of the combustion head mounting base, L4 = 14mm~22mm. The inner diameter at the inlet of the converging section is D5 = 80mm~100mm; the outer diameter at the outlet of the expanding section is the same as the outer diameter of the outer ring of the head mounting base, D6 = 109mm~149mm; the inner surface 15 of the converging section forms a converging angle α2 with the horizontal plane; α2 = 30°~50°. The inner surface 16 of the expanding section of the electrode mounting base forms an expanding angle α3 with the horizontal plane; α3 = 40°~60°.

[0063] The converging section of the electrode mounting base has a cable mounting hole 17 machined on its housing, and the cable mounting hole extends axially through the converging section, with its inlet located on the end face of the converging section and its outlet located on the inner surface of the expanding section. The diameter of the cable mounting hole is D7 = 2mm to 5mm.

[0064] The converging end face 18 of the cable mounting hole is machined with a groove 19 for embedding a ceramic insulating tube, with a diameter D8 of 8mm to 12mm and a depth projection of 1mm to 3mm on the horizontal plane. The groove wall 20 mates with the outer surface 29 of the ceramic insulating tube, and the groove bottom 21 mates with the end face 30 of the ceramic insulating tube. This groove design can isolate the cable and prevent the cable 5 from discharging with the combustion head mounting seat 2. The inner surface 15 of the converging section of the electrode mounting seat is machined with an electrode mounting groove 22, the height H5 of which is projected on the horizontal plane is 6mm to 10mm, the depth H6 from the inner surface of the converging section to the bottom surface of the electrode mounting groove is 0.4mm to 0.8mm, the bottom end is at the connection between the converging section and the expansion section of the high-voltage electrode mounting seat, and the top surface of the groove is parallel to the end face of the converging section. The inner surface 16 of the expansion section of the high-voltage electrode mounting base is machined with guide holes 23 parallel to the horizontal plane, with a diameter D9 of 1.5mm to 2.5mm. These guide holes are evenly distributed in 2 to 4 circles on the conical surface at the outlet end. The vertical distance d4 between the first circle of guide holes and the outer diameter of the electrode mounting groove 22 is 4mm to 6mm. The vertical spacing d5 between guide holes 23 of different circles is 2 to 6mm, with 12 to 36 guide holes per circle.

[0065] The ceramic insulating tube 4 is a tubular coaxial rotating body structure with a boss, made of ceramic, with a bore diameter of D5, an outer diameter of D4, and a boss outer diameter of D. 10 =14mm~16mm. The boss end face 27 mates with the bottom end 28 of the middle ring of the combustion head mounting seat. The outer surface 27 of the ceramic insulating tube mates with the axial through hole 14 of the combustion head mounting seat, and the end face 30 of the ceramic insulating tube mates with the groove 19 of the converging section of the electrode mounting seat. The gap is fixed by ceramic adhesive.

[0066] The cable 5 is existing technology and is connected to the circular high-voltage electrode 6 through the ceramic insulating tube 4 and the electrode mounting base 3.

[0067] The circular high-voltage electrode 6 is annular and made of a thin metal sheet with good ductility and conductivity. The high-voltage electrode 6 is installed in the conical groove 19 of the expansion section of the electrode mounting base 3. The thickness of the circular high-voltage electrode is H7 = 0.4 to 0.8. The gap is fixed by ceramic adhesive, so that the inner surface 31 of the high-voltage electrode is flush with the inner surface 16 of the expansion section of the ceramic electrode mounting base.

[0068] The converging end face 18 of the electrode mounting base mates with the middle ring end face 24 of the combustion head mounting base; the outer surface 25 of the expanding section of the electrode mounting base mates with the outer ring end face 26 of the combustion head mounting base. Figure 20As shown, a portion of the incoming air 32 passes through the swirl vanes 12, and then through the converging and expanding sections of the high-voltage electrode mounting base to form swirling air 33. Another portion of the incoming air 32 passes through the gap between the middle ring 10, the outer ring 11, and each connecting boss 13 of the combustion head mounting base, enters the pressure stabilizing cavity formed by the outer surface of the converging and expanding sections of the electrode mounting base and the inner surface of the outer ring, and then passes through the guide hole 23 to form direct current air 34.

[0069] The waveform diagram of one cycle of arc development when the power input is 800W and the air flow is 250L / min is shown below. Figure 22 As shown, this invention exhibits good discharge stability. No significant pulse peaks are observed in current 35 within the 40-49 ms of the sliding arc discharge; the peak values ​​of current 35 and voltage 36 are approximately 1 kV and 1.3 A, respectively. The voltage 36 waveform exhibits periodic variations, while the current 35 waveform remains relatively smooth for most of the time, with almost no pulse peaks. It has low requirements for discharge power supply parameters and is adaptable to a wide range of incoming currents.

[0070] like Figure 24 The diagram shows the flameout boundary and widening ratio of this invention under different air intake flow rates. The flameout oil-gas ratio (37) under plasma-assisted combustion is significantly higher than that under plasma-assisted combustion conditions (38). The larger the air intake, the more pronounced the widening. At an air intake flow rate of 350 L / min, the flameout oil-gas ratio widening ratio (39) is the largest, reaching 14.8%.

[0071] This invention illustrates its technical solution through three embodiments. The structures of each embodiment are the same; the differences lie in the technical parameters. See Table 1 for details.

[0072] Table 1

[0073]

[0074]

Claims

1. A plasma ignition and combustion aid head excited by a central sliding arc discharge, characterized in that, The device includes a fuel injector, a combustion head mounting base, a ceramic electrode mounting base, a ceramic insulating tube, a cable, and a circular high-voltage electrode. The fuel injector is fitted inside the combustion head mounting base, with its outlet end face protruding beyond the end face of the inner ring. The axial length of the protrusion is d1 to ensure that the high-voltage electrode preferentially discharges with the fuel injector. The ceramic electrode mounting base is located at the outlet end of the combustion head mounting base, and the circular high-voltage electrode is mounted on the conical outlet end face of the ceramic electrode mounting base. A good discharge distance d2 is maintained between the inlet end of the circular high-voltage electrode and the outlet end face of the fuel injector. The cable is connected to the circular high-voltage electrode through the ceramic electrode mounting base. The combustion head mounting base has a three-layer coaxial rotating structure consisting of an inner ring, a middle ring, and an outer ring. The inner ring's inner diameter fits tightly against the fuel nozzle's outer diameter. The inner ring's inner diameter D1 = 16mm–22mm, wall thickness L1 = 8mm–16mm, and axial height H1 = 30mm–45mm. The middle ring's inner diameter D2 = 80mm–100mm, wall thickness L2 = 14mm–22mm, and axial height H1. Swirl blades are machined between the inner and middle rings to form a shaft. The cyclone separator has 10 to 16 cyclone blades with an installation angle α1 of 30° to 60°. The outer ring has an inner diameter D3 of 130 mm to 150 mm, a wall thickness L3 of 12 mm to 18 mm, and an axial height H2 of 80 mm to 90 mm. There are 6 to 12 connecting bosses that axially penetrate the outer circumference of the middle ring between the middle ring and the outer ring. The radial height H3 is 3 mm to 9 mm, and the circumferential width d3 is 2 mm to 6 mm.

2. The plasma ignition and combustion aid head excited by a central sliding arc discharge as described in claim 1, characterized in that, The ceramic electrode mounting base consists of a converging section and an expanding section; the inner diameter at the inlet of the converging section is D5 = 80mm~100mm; the outer diameter at the outlet of the expanding section is the same as the outer diameter of the outer ring of the head mounting base, which is D6 = 109mm~149mm; the inner surface of the converging section forms a converging angle α2 with the horizontal plane, and the inner surface of the expanding section of the ceramic electrode mounting base forms an expanding angle α3 with the horizontal plane, where α2 is 30°~50° and α3 is 40°~60°.

3. The plasma ignition and combustion aid head excited by a central sliding arc discharge as described in claim 1, characterized in that, The ceramic electrode mounting base has a converging section with a cable mounting hole having a diameter of D7 = 2mm to 5mm. The converging end face of the cable mounting hole has a groove with a diameter of D8 = 8mm to 12mm. The depth H4 of this groove's projection on the horizontal plane is 1mm to 3mm. The groove wall mates with the outer surface of the ceramic insulating tube, and the bottom surface of the groove mates with the end face of the ceramic insulating tube. This groove design isolates the cable, preventing discharge between the cable and the combustion head mounting base. The inner surface of the converging section of the ceramic electrode mounting base has an electrode mounting groove with a projection height H5 = 6mm to 10mm on the horizontal plane, and a depth H6 = 0.6m from the inner surface of the converging section to the bottom of the electrode mounting groove. The groove is approximately 1 mm long and its bottom end is located at the connection between the converging and expanding sections of the ceramic electrode mounting base. The top surface of the groove is parallel to the end face of the converging section. The expanding section of the ceramic electrode mounting base is machined with guide holes D9 = 1.5 mm to 2.5 mm parallel to the horizontal plane. These guide holes are evenly distributed in 2 to 4 circles on the conical surface at the outlet end, with 12 to 36 holes per circle. The vertical distance d4 between the first circle of guide holes and the outer diameter of the electrode mounting groove is 4 mm to 6 mm. The vertical spacing d5 between guide holes of different circles is 2 mm to 6 mm. The end face of the converging section of the ceramic electrode mounting base mates with the middle ring end face of the combustion head mounting base. The outer surface of the expanding section of the ceramic electrode mounting base mates with the outer ring end face of the combustion head mounting base.

4. The plasma ignition and combustion aid head excited by a central sliding arc discharge as described in claim 1, characterized in that, The outer diameter D of the boss on the ceramic insulating tube 10 =14mm~16mm; the boss end face mates with the middle ring end face of the combustion head mounting seat, the outer surface of the ceramic insulating tube mates with the axial through hole of the combustion head mounting seat, and the end face of the ceramic insulating tube mates with the groove of the converging section end face of the ceramic electrode mounting seat.

5. The plasma ignition and combustion aid head excited by a central sliding arc discharge as described in claim 1, characterized in that, The thickness of the annular high-voltage electrode is H7 = 0.4 mm to 0.8 mm. The electrode is installed in the conical groove of the expansion section of the ceramic electrode mounting base, and the gap is fixed by ceramic adhesive so that the inner surface of the high-voltage electrode is flush with the inner surface of the expansion section of the ceramic electrode mounting base. The thickness of the circular high-voltage electrode is H6 = 0.4 to 0.8 mm. The good discharge distance d2 between the end face of the annular high-voltage electrode and the end face of the fuel nozzle outlet is 15 mm to 25 mm.

Images