CN102913365B - Annular discharge based transient state plasma igniter - Google Patents

Abstract

A transient plasma igniter based on an annular discharge. The insulating sleeve is located in the insulating protective sleeve, and one end of the insulating sleeve is located in the cathode. The anode conducting rod is located in the insulating sleeve, and one end of the anode conducting rod is fitted into the central hole of the anode. One end of the insulating protective sheath is installed in the fixing seat. The anode is located within the cathode. There is a gas mixture channel on the transient plasma igniter. The invention utilizes high-energy nanosecond pulse discharge to form a local high-temperature area, and stimulates a large number of active particles to ignite combustible mixture in a very short time. The invention has a large ignition area and can ignite the mixed gas at multiple points; the ignition time is extremely short and has a shorter ignition delay time; the ignition energy can be better coupled with the gas mixture, and the macromolecular hydrocarbon fuel in the ignition area is ionized into activation energy Small active particles make the chemical reaction rate of the mixture faster, the reaction time is shorter, and the ignition success rate is high.

Description

A Transient Plasma Igniter Based on Ring Discharge

technical field

The invention relates to the field of engines, in particular to a transient plasma igniter based on annular discharge.

Background technique

At present, the spark plug ignition method is widely used in the combustion chambers of various power plants. Spark plug ignition is based on the thermal theory of ignition. At the moment of ignition (the moment of spark plug discharge), the temperature of the mixed gas around it rises rapidly, so that the exothermic reaction in this small volume begins.

The ignition energy utilization rate of the spark plug ignition process is low, only about 5% to 20% of the energy is used to heat the mixture, most of the energy is used to heat the electrode, the ignition delay time is long, and it can only be used in a small area Realize single point ignition. Currently, the use of lean premixed combustion can improve the fuel economy of internal combustion engines while significantly reducing NO _x , HC and CO emissions. It is difficult to ignite the fuel-lean premixed combustible mixture in the combustion chamber reliably and quickly by using the traditional spark plug ignition, and the mixture near the lean lower limit is prone to flameout phenomenon, which is caused by the inherent limitations of the spark plug itself. of.

In 2007, the U.S. Naval Postgraduate Institute developed a Transient Plasma Ignition (TPI) for Pulse Detonation Engine (PDE). The structure of the Transient Plasma Ignition is shown in the attached Figure 1 shows. The transient plasma igniter is composed of high-voltage electrodes, ceramics, annular porous sleeves and mounting supports. When the transient plasma igniter is working, the high-voltage electrode is connected to a high-voltage power supply, and the high-voltage electrode exposed in the mixed gas is discharged between the high-voltage electrode and the annular porous sleeve, ionizes and heats the combustible mixture in the annular porous sleeve, and finally ignites the annular porous Gas mixture in the casing.

With the continuous reduction of fossil fuel reserves and the increasingly stringent emission regulations in various countries, modern power plants are faced with the dual challenges of improving thermal efficiency and reducing pollutant emissions. At present, the use of lean premixed combustion can improve the fuel economy of internal combustion engines, while significantly reducing NOx, HC and CO emissions. It is difficult to ignite the fuel-lean premixed combustible mixture in the combustion chamber reliably and quickly by using the traditional spark plug ignition, and the mixture near the lean lower limit is prone to flameout phenomenon, which is caused by the inherent limitations of the spark plug itself. of.

The ignition energy utilization rate of the spark plug ignition process is low, only about 5% to 20% of the energy is used to heat the mixture, most of the energy is used to heat the electrode, the ignition delay time is long, and it can only be used in a small area Realize single point ignition.

Transient plasma ignition uses high-energy pulse discharge to form a local high-temperature area, and excites a large number of active particles to achieve rapid ignition of combustible gas mixture. Transient plasma ignition can overcome many shortcomings of traditional spark plug ignition. Its advantages are: the ignition area is large, and the mixture can be ignited at multiple points; the ignition time is extremely short; the ignition energy can be better coupled with the gas mixture, and the ignition area is large. Molecular hydrocarbon fuel is ionized into active particles with small activation energy, which makes the chemical reaction rate of the mixture faster, the reaction time is shorter, and the ignition success rate is high.

In 2007, the U.S. Naval Postgraduate School developed a transient plasma igniter, and its schematic structure diagram and photos are shown in Figure 1. The transient plasma igniter is composed of high-voltage electrodes, ceramics, porous sleeves and mounting supports. When the transient plasma igniter is working, the high-voltage electrode is connected to a high-voltage power supply, and the high-voltage electrode exposed in the mixed gas is discharged between the high-voltage electrode and the annular porous sleeve, ionizes and heats the combustible mixture in the annular porous sleeve, and finally ignites the annular porous Gas mixture in the casing. The transient plasma igniter can quickly ignite the combustible mixture, and has a shorter ignition delay time, ignites the combustible mixture at multiple points, and has a high ignition success rate.

The high-voltage electrode of the igniter developed by the U.S. Naval Postgraduate Institute is a solid cylinder, which is suitable for high-voltage discharge and has high requirements for power supply. Under low-voltage conditions, it is not conducive to discharge.

Contents of the invention

In order to overcome the deficiency that the transient plasma igniter in the prior art is not conducive to discharge at low voltage, reduce the requirements for power supply, and increase the ignition area, the present invention proposes a transient plasma ignition based on annular discharge device.

One of the technical schemes of the present invention comprises an anode, a cathode, an insulating sleeve, an anode conducting rod, a fixing base, an insulating protective sleeve and a cathode connecting rod; the insulating sleeve is located in the insulating protective sleeve, and one end of the insulating sleeve extends into the cathode Between the two cathode connecting rods; the anode conducting rod is located in the insulating sleeve, and one end of the anode conducting rod is installed in the center hole of the anode; one end of the insulating protective sleeve is installed in the fixing seat; the two cathode connecting rods of the cathode One end of the anode is fixed on the outer circular surface of the fixed seat; the anode is located in the cathode; there is a cross rib inside the anode, and a mixed gas channel is formed between the cross rib and the outer ring of the anode. The inner diameter of the cathode is greater than the outer diameter of the anode, so that after the anode is loaded into the cathode, a discharge ignition zone is formed between the outer surface of the anode and the inner surface of the cathode.

Another technical scheme of the present invention includes anode, insulating sleeve, anode lead-through rod, insulating protective sleeve, cathode, detonation tube, air intake hole and fixing base; the insulating sleeve is located in the insulating protective sleeve, and one end of the insulating sleeve extends Inserted between the two cathode connecting rods of the cathode; the anode conducting rod is located in the insulating sleeve, and one end of the anode conducting rod is inserted into the center hole of the anode; one end of the insulating protective sleeve is installed in the fixed seat; The detonation tube is used as the cathode, and a pair of air inlet holes are symmetrically distributed on the shell of the detonation tube to form a mixture gas channel.

In the above two technical solutions: the centerline of the anode conducting rod coincides with the centerline of the anode 1 . The inner diameter of the insulating sleeve is the same as the outer diameter of the anode lead-through rod; there is a radially protruding anti-backflow platform on one end face. The outer surface of the anode is threaded.

The cathode and anode of the invention are processed by metal or alloy with high temperature resistance and strong electrical conductivity. When working, a high-voltage pulse is input to the anode, and the cathode is grounded. The high-voltage pulse breaks down and ionizes the mixture between the cathode and the anode, and quickly ignites the combustible mixture. Change the diameter of the anode to adjust the distance between the cathode and the anode, or change the input voltage and current of the transient plasma igniter to control the breakdown strength and the ionization degree of the working gas, so as to achieve the purpose of adjusting the ignition intensity of the igniter.

The anode in the present invention has a hollow tubular thin-walled structure, and the thin-walled structure makes the charge concentrate on the surface of the anode, which is more conducive to discharge. The inside of the anode is hollow, and the hollow internal channel can circulate the mixed gas. The outside is a threaded surface, which is easier to form a tip discharge. The anode and the anode connection section are connected by threads, and the inside of the anode can be connected by cross ribs or porous structures. .

The cathode and anode are coaxial hollow tubes. The inner diameter of the cathode is greater than the outer diameter of the anode, and the gap between the cathode and the anode is the discharge ignition area. The cathode can be fixed on the mounting seat by two or more cathode connecting rods, so that the mixed gas enters the ignition area. The cathode connecting rod and the cathode can be fixed by means of welding or threading.

The insulating sleeve is made of high-temperature-resistant insulating material, covering the surface of the anode, which is both insulating and high-temperature resistant, and is used to isolate the cathode and anode, thereby improving energy utilization; the outside of the insulating sleeve is protected by an insulating protective sleeve. There is an anti-backflow boss inside the insulating protective cover, which is used to prevent the gas backflow in the combustion chamber; one end of the insulating protective cover with the anti-backflow boss is fixed to the fixing seat through the external thread, and the other end is connected to the high-voltage power supply through the external thread, and the high-voltage Piezoelectric input anode connection section.

Compared with the anode developed by the U.S. Naval Postgraduate Institute as a solid cylindrical transient plasma igniter, the igniter of the present invention has the following advantages:

When the discharge distance between the anode and the cathode of the two igniters is equal, the transient plasma igniter based on annular discharge has a larger ignition area.

When the two igniters input the same breakdown voltage, the transient plasma igniter based on annular discharge has more breakdown streamers, which is more conducive to igniting the mixture.

When the ignition areas of the two igniters are equal, the discharge distance between the anode and the cathode of the transient plasma igniter based on annular discharge is smaller, and the breakdown voltage is smaller, which is more conducive to the discharge breakdown of the mixture.

Description of drawings

Accompanying drawing 1 is that the anode developed by U.S. Naval Postgraduate Institute is a schematic diagram of a solid cylindrical transient plasma igniter;

Accompanying drawing 2 is the front cross-sectional view of the transient plasma igniter based on annular discharge of the present invention, wherein Fig. 2 a is the front view of the present invention, and Fig. 2 b is the A-direction cross-sectional view of the front view of the present invention;

Accompanying drawing 3 is the side sectional view of cathode and cathode connecting section;

Accompanying drawing 4 is the side sectional view of anode;

Accompanying drawing 5 is the anode side sectional view changed into porous structure;

Accompanying drawing 6 is the right side view of holder;

Accompanying drawing 7 is the application example in pulse detonation engine. In the picture:

1. Anode 2. Cathode 3. Insulation sleeve 4. Anode lead 5. Fixing seat

6. Insulation protective sleeve 7. Cathode connecting rod 8. Rib 9. Detonation tube 10. Air intake hole

Detailed ways

Implementation example one

This embodiment is a transient plasma igniter based on annular discharge, which is used for ignition of internal combustion engines, including anode 1, cathode 2, insulating sleeve 3, anode conducting rod 4, fixing seat 5, insulating protective sleeve 6 and cathode connection pole 7. As shown in Figure 2. A pair of cathode connecting rods 7 protruding axially are symmetrically distributed on the end surface of one end of the cathode 2 , and the other ends of the two cathode connecting rods 7 are fixed on the outer circular surface of the fixing seat 5 . The anode 1 is located inside the cathode 2 . One end of the insulating protective sheath 6 is located in the inner hole of the fixing seat 5 . The insulating sleeve 3 is installed in the inner hole of the insulating protective sleeve 6 , and one end of the insulating sleeve 3 extends between the two cathode connecting rods 7 of the cathode 2 .

The anode 1 is annular and made of high temperature resistant alloy material GH3039. There is a cross-shaped reinforcing rib 8 on the inner surface of one end of the anode 1, and there is an anode conducting rod through hole in the center of the cross of the reinforcing rib 8; the center line of the anode conducting rod through hole is connected with the anode The centerlines of 1 coincide.

The anode conducting rod 4 is a rod made of high temperature resistant alloy material. The shape of the anode conducting rod 4 is stepped. The diameter of the large-diameter section at one end of the anode lead-through rod 4 cooperates with the large-diameter section in the inner hole of the insulating sleeve 3; One end of the anode lead-through rod 4 is matched with the central hole of the anode 1 .

The cathode 2 is in the shape of an annular sleeve. The inner diameter of the cathode 2 is greater than the outer diameter of the anode 1, so that after the anode 1 is packed into the cathode 2, the distance between the inner surface of the anode 1 and the outer surface of the cathode 2 is 6mm, forming a discharge ignition zone. A pair of cathode connecting rods 7 extending in the axial direction are symmetrically distributed on the end surface of one end of the cathode 2 , and the distance between the pair of cathode connecting rods is the same as the inner diameter of the cathode 2 . There is a through connecting hole at the ends of the pair of cathode connecting rods, through which the cathode connecting rod is fixed to the outer peripheral surface of the fixing base 5 with screws.

The insulating sleeve 3 is hollow tubular and made of ceramic material. The inner hole of the insulating sleeve 3 is stepped, and one end of the insulating sleeve 3 is a section with a large diameter. The diameter of the large-diameter section of the insulating sleeve 3 is the same as the diameter of the large-diameter section of the anode lead-through rod 4; The step at the junction of the large aperture section and the small aperture section of the insulating sleeve 3 forms the positioning surface of the anode lead-through rod 4 . The outer surface of the insulating sheath 3 is also stepped, and the stepped outer surface of the insulating sheath 3 matches the stepped inner surface of the insulating protective sheath 6 . During assembly, the insulating sleeve 3 is wrapped on the outer surface of the anode conducting rod 4 , the protective sleeve 6 is set on one end of the insulating sleeve 3 , and one end of the anode conducting rod 4 is inserted into the through hole of the anode conducting rod located at the center of the anode 1 .

The inner diameter of the insulating sleeve 3 is the same as the outer diameter of the anode conducting rod 4 ; there is a radially protruding anti-reflux platform on one end surface; the insulating sleeve 3 is wrapped on the outer surface of the anode conducting rod 4 . The insulating sleeve 3 is made of ceramics, which is both insulating and high temperature resistant, and is used to isolate the cathode 2 and the anode conducting rod 4, thereby improving energy utilization. The outside of the insulating sheath 3 is wrapped and protected by an insulating protective sheath 6 .

The fixed seat 5 is a hollow body of revolution. The aperture of the inner hole of the fixing seat 5 is the same as the outer diameter of the protective cover 6; Distributed with screw holes. On the outer peripheral surface of one end of the fixing seat 5 there is a radially protruding flange, and 8 connection holes are evenly distributed on the flange.

In this embodiment, the inside of the anode 1 is fixed by cross ribs 8 , the anode 1 and the anode lead-through rod 4 are connected by threads, and the cross section of the outer end of the anode 1 is flush with the outer end cross section of the cathode. The holes between the cross ribs 8 inside the anode 1 and the outer ring of the anode 1 are used to circulate the mixed gas. The outer surface of the anode 1 is threaded, and the surface of the thread is more likely to form a tip discharge.

The cathode 2 is fixed with two countersunk screws between the two cathode connecting rods 7 and the holder 5, and the width of the cathode 2 is slightly larger than that of the anode 1. The cathode 2 is coaxial with the anode 1, and the inner diameter of the cathode 2 is larger than the outer diameter of the anode 1, and the gap between the outer surface of the anode 1 and the inner surface of the cathode 2 is a discharge ignition area.

There is an anti-backflow boss inside the insulating protective sheath 6 , and the size of the anti-backflow boss matches the size of the insulating sheath 3 . The backflow of gas in the combustion chamber is prevented by the anti-backflow boss; the end of the insulating protective sleeve 6 with the anti-backflow boss is fixed to the fixing seat 5 through an external thread. The anode connecting section, the insulating sleeve and the insulating protective sleeve are connected to the high-voltage power supply through the external thread of the insulating protective sleeve. The fixed seat 5 is fixed with the combustion chamber of the engine using a flange.

When working, a high-voltage pulse is input to the anode lead 4 and transmitted to the anode 1, and the cathode 2 is grounded. The high-voltage pulse breaks down and ionizes the mixture between the anode 1 and the cathode 2, and quickly ignites the combustible mixture. Change the diameter of the anode 1 to adjust the distance between the anode 1 and the cathode 2, or change the input voltage and current of the transient plasma igniter to control the breakdown strength and the ionization degree of the working gas, so as to adjust the ignition intensity of the igniter the goal of.

Embodiment two

This embodiment is a transient plasma igniter based on annular discharge applied to a pulse detonation engine, including an anode 1, an insulating sleeve 3, an anode conducting rod 4, an insulating protective sleeve 6, a cross rib 8, and a detonation tube 9. The air intake hole 10 and the fixing seat 5. The structure is shown in Figure 7.

In this embodiment, the detonation tube 9 is used as the cathode, and the anode 1 is discharged and ignited. The inlet end of the detonation tube 9 is fixed on the end face of one end of the fixing base 5 by screws. One end of the insulating sheath 6 is put into the central hole of the fixing seat 5, one end of the insulating sheath 3 is put into the said insulating sheath 6, and the other end of the insulating sheath 3 penetrates into the inner hole of the detonation tube 9 middle. The anode conducting rod 4 is loaded into the insulating sleeve 3 , and the anode 1 is installed at the end of the anode conducting rod 4 located at one end of the inner hole of the insulating sleeve 3 .

In this embodiment, both the anode 1 and the anode conducting rod 4 are made of high temperature resistant alloy materials. The anode 1 is ring-shaped, and its interior is fixed by cross ribs 8 . There is an anode conducting rod through hole in the center of the cross of the reinforcing rib 8; the anode conducting rod through hole is a threaded hole. The centerline of the through hole of the anode conducting rod coincides with the centerline of the anode 1 . The outer surface of the anode 1 is threaded, and the surface of the thread is more likely to form a tip discharge.

The anode conducting rod 4 is a rod made of high temperature resistant alloy material. The shape of the anode conducting rod 4 is stepped. The diameter of the large-diameter section at one end of the anode lead-through rod 4 cooperates with the large-diameter section in the inner hole of the insulating sleeve 3;

A pair of air intake holes 10 are symmetrically distributed on the outer circumference of the inlet section of the detonation tube 9 , through which the mixed gas enters the detonation tube 9 .

The insulating sleeve 3 is hollow tubular and made of ceramic material. The inner hole of the insulating sleeve 3 is stepped, and one end of the insulating sleeve 3 is a section with a large diameter. The diameter of the large-diameter section of the insulating sleeve 3 is the same as the diameter of the large-diameter section of the anode lead-through rod 4; The step at the junction of the large aperture section and the small aperture section of the insulating sleeve 3 forms the positioning surface of the anode lead-through rod 4 . The outer surface of the insulating sheath 3 is also stepped, and the stepped outer surface of the insulating sheath 3 matches the stepped inner surface of the insulating protective sheath 6 . During assembly, the insulating sleeve 3 is wrapped on the outer surface of the anode conducting rod 4 , the protective sleeve 6 is set on one end of the insulating sleeve 3 , and one end of the anode conducting rod 4 is inserted into the through hole of the anode conducting rod located at the center of the anode 1 .

The inner diameter of the insulating sleeve 3 is the same as the outer diameter of the anode conducting rod 4 ; there is a radially protruding anti-reflux platform on one end surface; the insulating sleeve 3 is wrapped on the outer surface of the anode conducting rod 4 . The insulating sleeve 3 is made of ceramics, which is both insulating and high temperature resistant, and is used to isolate the cathode 2 and the anode conducting rod 4, thereby improving energy utilization. The outside of the insulating sheath 3 is wrapped and protected by an insulating protective sheath 6 .

The fixed seat 5 is a hollow body of revolution. The aperture of the inner hole of the fixing seat 5 is the same as the outer diameter of the protective cover 6; Distributed with screw holes. On the outer peripheral surface of one end of the fixing seat 5 there is a radially protruding flange, and 8 connection holes are evenly distributed on the flange.

The insulating protective sheath 6 is made of heat-resistant steel. The outer diameter of the insulating protective sheath 6 is the same as the inner diameter of the center hole of the fixing seat 5 . There is a radially protruding step in the inner hole at one end of the insulating protective cover 6, forming an anti-backflow boss, which cooperates with the steps on the outer surface of the insulating cover 3 to prevent gas backflow in the combustion chamber. One end of the insulating protective sheath 6 with the anti-backflow boss is fixed to the fixing seat 5 through an external thread.

The anode connecting section, the insulating sleeve and the insulating protective sleeve are connected to the high-voltage power supply through the external thread of the insulating protective sleeve. The fixed seat 5 is fixed with the combustion chamber of the engine using a flange.

When working, a high-voltage pulse is input into the anode lead 4 and transmitted to the anode 1, the detonation tube 9 is grounded, the high-voltage pulse breaks down and ionizes the mixture between the anode 1 and the detonation tube 9, and quickly ignites the combustible mixture. Change the diameter of the anode 1 to adjust the distance between the anode 1 and the detonation tube 9, or change the input voltage and current of the transient plasma igniter to control the breakdown strength and the ionization degree of the working gas, so as to adjust the igniter The purpose of ignition strength.

Claims (5)

1. A transient plasma igniter based on annular discharge, characterized in that, comprises anode, cathode, insulating cover, anode lead-through rod, fixed seat, insulating protective cover and cathode connecting rod; insulating cover is positioned in insulating protective cover , and one end of the insulating sleeve extends between the two cathode connecting rods of the cathode; the anode conducting rod is located in the insulating sleeve, and one end of the anode conducting rod is inserted into the center hole of the anode; one end of the insulating protective sleeve is installed In the fixed seat; one end of the two cathode connecting rods of the cathode is fixed on the outer circular surface of the fixed seat; the anode is located in the cathode; there is a cross rib inside the anode, and a mixture is formed between the cross rib and the outer ring of the anode Gas channel; the anode is annular, the cathode is annular sleeve-shaped, and the inner diameter of the cathode is greater than the outer diameter of the anode, the anode is packed into the cathode, and the distance between the outer surface of the anode and the inner surface of the cathode forms The discharge ignition area. 2. A transient plasma igniter based on annular discharge, characterized in that it comprises an anode, an insulating sleeve, an anode lead-through rod, an insulating protective sleeve, a detonation tube, an air inlet and a fixed seat; the detonation tube serves as Cathode, a pair of air intake holes are symmetrically distributed on the shell of the detonation tube to form a gas mixture channel; the anode is annular; A discharge ignition area is formed between them; the inlet end of the detonation tube is fixed on the end surface of one end of the fixed seat; one end of the insulating protective sleeve is inserted into the center hole of the fixed seat, and one end of the insulating sleeve is inserted into the insulating protective sleeve , and the other end of the insulating sleeve penetrates into the inner hole of the detonation tube; the anode conducting rod is loaded into the insulating sleeve, and the anode conducting rod is installed at the end of the inner hole of the insulating sleeve. There are anodes. 3. The transient plasma igniter based on annular discharge according to claim 1 or 2, wherein the centerline of the anode conducting rod coincides with the centerline of the anode. 4. The transient plasma igniter based on annular discharge as claimed in claim 1 or 2, wherein the inner diameter of the insulating sleeve is the same as the outer diameter of the anode lead-through rod; there is a radial protrusion at the end face of the insulating sleeve anti-reflux table. 5. The transient plasma igniter based on annular discharge according to claim 1 or 2, wherein the outer surface of the anode is threaded.