A full-bridge high-energy ignition device

Abstract

The present invention discloses a full-bridge high-energy ignition device, which includes an igniter, an ignition cable and an ignition gun; the igniter, the ignition cable and the ignition gun are connected by threads to directly ignite a gas mixed with natural gas, liquefied petroleum gas, kerosene, diesel, heavy oil, residual oil and air. The present invention adopts a capacitor low-voltage high-energy ignition system, the ignition voltage is only about 2000V, and the maximum ignition power can reach 500W. It is mainly used in the ignition system of the heater of the hypersonic air test wind tunnel, and has the advantages of high ignition frequency, large single ignition energy, low heat generation of components and can be used for a long time, etc., which can well meet the requirements of the wind tunnel air heater for real-time ignition.

Description

Technical Field

[0001] The invention belongs to the technical field of electric energy ignition test of a hypersonic air test heater and relates to a full-bridge high-energy ignition device. Background Art

[0002] With the development of modern science and technology and modern industry, safe ignition is required in many occasions, such as gas kilns in petrochemical and metallurgical industries, boiler ignition in power plants, and air heating in aviation high enthalpy wind tunnels. Under normal circumstances, electric ignition is the most widely used and studied system because it can reliably ignite the fuel mixture, accurately ignite the ignition time, and adjust the ignition time within a wide range. For electric ignition systems, the main form of discharge is inductive discharge. The inductive discharge voltage is high, the single energy is low, generally less than 50mJ, and the discharge form is surface discharge, that is, discharge along the interface between the conductor and the contact air. When the discharge ignites, the current breaks through the air gap between the positive and negative poles, which belongs to the surface discharge phenomenon. The breakdown voltage is generally at least 10kv or more, otherwise it cannot break through the spark gap between the two plates. For high-voltage surface nozzles, although the ignition frequency is high, according to the basic principle of Thomson discharge, as the air pressure increases, its breakdown voltage also increases. Since the power supply voltage of the igniter is high (the system output voltage is above 10kV at this time), the insulation (voltage resistance strength) requirements for other accessories of the entire system are also high. Moreover, under such high voltage conditions, when there is contamination on the device, the possibility of breakdown increases due to the reduction of electrical resistance, and too high voltage produces strong electromagnetic interference to the surrounding system. It can be said that the high ignition voltage is a defect of the inductive ignition system, which hinders the application of the ignition system in large energy (greater than 100W) and burners with precise measurement and control systems. Summary of the invention

[0003] (I) Purpose of the invention

[0004] The object of the present invention is to provide a full-bridge high-energy ignition device to reduce the ignition voltage.

[0005] (II) Technical solution

[0006] In order to solve the above technical problems, the present invention provides a full-bridge high-energy ignition device, which includes an igniter, an ignition cable and an ignition gun; the igniter, the ignition cable and the ignition gun are connected by threads to directly ignite a mixture of natural gas, liquefied petroleum gas, kerosene, diesel, heavy oil, residual oil and air.

[0007] Among them, the ignition device is encapsulated with an ignition circuit, which includes a high-power CD-type step-up transformer, a full-bridge high-voltage rectifier bridge, a high-voltage energy storage capacitor, a vacuum discharge tube, a brake resistor and a high-voltage insulating joint; the main coil of the high-power CD-type step-up transformer is connected to an AC power supply, one end of the secondary coil is grounded, and the other end is connected to one end of the brake resistor, the other end of the brake resistor is connected to the I end of the full-bridge high-voltage rectifier bridge, the II end and the IV end of the full-bridge high-voltage rectifier bridge are grounded, the III end of the full-bridge high-voltage rectifier bridge is connected to the positive electrode of the high-voltage energy storage capacitor, the negative electrode of the high-voltage energy storage capacitor is connected to one end of the vacuum discharge tube, and the other end of the vacuum discharge tube is connected to the ignition gun.

[0008] Among them, the full-bridge high-voltage rectifier bridge includes four diodes, diode I and diode II are connected in series, diode III and diode IV are connected in series, two groups of series diodes are connected in parallel, the positive poles of diode I and diode IV are grounded, and the negative poles of diode II and diode III are connected to the positive pole of the high-voltage energy storage capacitor.

[0009] Wherein, the diode is a gallium nitride PN junction diode.

[0010] Wherein, a heat sink is installed on the full-bridge high-voltage rectifier bridge.

[0011] The vacuum discharge tube comprises two discharge electrodes with lead-out ends, a gap is left between the discharge electrodes, and the discharge electrodes are sealed by a glass insulating shell, and a low-pressure nitrogen-hydrogen mixed gas is filled inside.

[0012] Wherein, the ignition cable is a 5KV high-voltage insulated cable with an outer metal braided layer to shield the electromagnetic interference of the ignition energy.

[0013] Among them, the ignition gun adopts a semiconductor voltage-resistant ignition electric gun, including an ignition gun shell, semiconductor alumina ceramic, insulating ceramic, a front electrode, a copper pad and a rear electrode. The front electrode is covered with a semiconductor alumina ceramic, and the rear electrode is covered with an insulating ceramic. The front electrode and the rear electrode are separated by a copper pad. The front electrode, the copper pad and the rear electrode constitute the power generation core of the ignition gun, and the power generation core is installed in the ignition gun shell; the structural gaps of the semiconductor voltage-resistant ignition electric gun are sealed with silicone rubber.

[0014] The semiconductor alumina ceramic is doped with conductive impurities in the 3 mm thick alumina on the ignition end face side to make it conductive.

[0015] When the ignition gun is used, a threaded hole is punched on the combustion chamber, the thread at the front end of the ignition gun housing is connected to the combustion chamber, and the rear thread of the ignition gun housing is connected to the ignition cable to input the high voltage current required for ignition.

[0016] (III) Beneficial effects

[0017] The full-bridge high-energy ignition device provided by the above technical solution adopts a capacitor low-voltage high-energy ignition system. The ignition voltage is only about 2000V, and the maximum ignition power can reach 500W. It is mainly used in the ignition system of the heater of the hypersonic air test wind tunnel. It has the advantages of high ignition frequency, large single ignition energy, low heat generation of components and long-term use. It can well meet the requirements of wind tunnel air heaters for real-time ignition; in terms of structure, it has the advantages of advanced performance, reasonable structure, flexible movement, smooth and reliable operation, and easy to realize automatic control operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is an appearance diagram of a full-bridge high-energy ignition device according to an embodiment of the present invention.

[0019] Figure 2 The figure is a working principle diagram of the ignition circuit of the full-bridge high-energy ignition device according to an embodiment of the present invention.

[0020] Figure 3 This is a structural diagram of a vacuum discharge tube.

[0021] Figure 4 This is a cross-sectional view of a high-energy ignition gun.

[0022] Figure 5 This is the charge and discharge characteristic diagram of the igniter. DETAILED DESCRIPTION

[0023] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below in conjunction with the drawings and examples.

[0024] like Figure 1 As shown, the full-bridge high-energy ignition device of this embodiment includes an igniter, an ignition cable and an ignition gun; the igniter, the ignition cable and the ignition gun are connected by M18×1 threads, and can directly ignite natural gas, liquefied petroleum gas, kerosene, diesel, heavy oil, residual oil and other gases mixed with air. The ignition device has strong anti-pollution ability and can ignite in water, ether and alcohol. It can also ignite even if the ignition end is coked. In recent years, it has been widely used in energy and power systems, and its performance is better than the commonly used inductive high-voltage gap ignition.

[0025] An ignition circuit is encapsulated in the igniter, and the ignition circuit includes a high-power CD-type step-up transformer, a full-bridge high-voltage rectifier bridge, a high-voltage energy storage capacitor, a vacuum discharge tube, a brake resistor and a high-voltage insulating joint; the main coil of the high-power CD-type step-up transformer is connected to the AC power supply, one end of the secondary coil is grounded, and the other end is connected to one end of the brake resistor, the other end of the brake resistor is connected to the I end of the full-bridge high-voltage rectifier bridge, the II end and the IV end of the full-bridge high-voltage rectifier bridge are grounded, the III end of the full-bridge high-voltage rectifier bridge is connected to the positive electrode of the high-voltage energy storage capacitor, the negative electrode of the high-voltage energy storage capacitor is connected to one end of the vacuum discharge tube, and the other end of the vacuum discharge tube is connected to the ignition gun.

[0026] The full-bridge high-voltage rectifier bridge includes four diodes, diode I and diode II are connected in series, diode III and diode IV are connected in series, two groups of series diodes are connected in parallel, the positive poles of diode I and diode IV are grounded, and the negative poles of diode II and diode III are connected to the positive pole of the high-voltage energy storage capacitor.

[0027] like Figure 3 As shown, the vacuum discharge tube includes two discharge electrodes with lead-out ends, a gap is left between the discharge electrodes, and they are sealed by a glass insulating shell, and the interior is filled with a low-pressure nitrogen-hydrogen mixture.

[0028] The ignition cable is a commonly used 5KV high-voltage insulated cable with a metal braided layer on the outside to shield the electromagnetic interference of the ignition energy.

[0029] The ignition gun is made of a composite of metal, insulating ceramics and semiconductor materials.

[0030] The working principle of the full-bridge high-energy ignition device is as follows: the AC power frequency 220V or 110V is boosted by a high-power CD-type transformer, and converted into high-voltage pulsating DC by a high-voltage rectifier bridge to charge the high-voltage energy storage capacitor. When the voltage on the capacitor rises to the breakdown voltage of the vacuum discharge tube, the discharge current passes through the discharge tube and the shielded cable until it reaches the semiconductor nozzle. After the current passes through the inner core of the nozzle, it breaks through the semiconductor alumina ceramic between the inner core and the outer shell, generating an arc spark. When the igniter stops working, the residual charge on the capacitor is discharged through the brake resistor, such as Figure 2 .

[0031] The ignition of the full-bridge high-energy ignition device of this embodiment is completed by charging and discharging the high-voltage and large-capacity capacitor in the device at a constant voltage.

[0032] This device realizes low-voltage and high-energy ignition. Its key technologies are as follows: 1. Vacuum discharge tube opened at a lower voltage; 2. Application of high-voltage full-bridge rectifier bridge with high-speed switching; 3. Semiconductor ignition gun with lower breakdown voltage.

[0033] 1. Vacuum discharge tube opened with lower voltage: The vacuum discharge tube in the igniter circuit is composed of two discharge electrodes with lead-out terminals, with a gap between the electrodes, and sealed by a glass insulating shell, and filled with a certain proportion of low-pressure nitrogen-hydrogen mixture. When the voltage at both ends of the discharge tube is not high, the discharge tube presents high impedance (about 650MΩ). When the voltage at both ends is increased to the breakdown voltage, discharge begins between the two electrodes in the discharge tube, and quickly turns from glow discharge to high-energy arc discharge. The discharge tube presents extremely low impedance. When the voltage of the high-voltage energy storage capacitor drops below the arc discharge maintenance voltage, the discharge stops, and the tube returns to a high impedance state. After repeated experiments, the nitrogen-hydrogen filling ratio and gas pressure in the vacuum power generation tube are adjusted, so that the voltage required for the breakdown of the vacuum discharge tube of this device can reach a minimum of 1800V. Its role in the circuit is equivalent to a switch, controlling the charging and discharging of the capacitor.

[0034] 2. Application of high-speed switching high-voltage full-bridge rectifier bridge: The power supply of the ignition device is AC power supply, while the ignition gun needs DC power. After the AC power of the power supply is boosted to reach the predetermined ignition voltage, the high-voltage AC power needs to be rectified. The rectification of the general mains voltage uses a diode or a rectifier bridge composed of diodes, but for medium current and high voltage circuits, a single diode cannot reach the required withstand voltage value, so it is generally necessary to connect a series of diodes in series (several to dozens) to achieve the purpose of rectifying the high-voltage alternating current. This component composed of multiple diodes in series is called a high-voltage silicon stack. Although the high-voltage silicon stack rectifier can withstand high voltage, each diode inside it has a turn-on and turn-off time, and the overall turn-on and turn-off time of the high-voltage silicon stack is much higher than the algebraic sum of the switching time of each diode, making the turn-on and turn-off time of the high-voltage silicon stack on the order of ms. In addition, the excessive switching time also makes it impossible for the high-voltage silicon stack to build a full-bridge rectifier circuit. If a high-voltage silicon stack is used to build a rectifier bridge, due to its slow switching time, in one cycle of the AC signal, the positive cycle cannot be effectively closed when the negative cycle is turned on, which will result in a short circuit and burn the rectifier bridge. In order to solve the above problems, a rectifier bridge composed of a diode and a diode using a gallium nitride PN junction suitable for high voltage is specially customized. The switching speed can be the same as that of an ordinary diode, and the maximum withstand voltage can reach 4000V. A heat sink is installed on it to reduce the heat generated by the rectifier bridge switch, achieving the purpose of taking into account both high voltage and full-bridge efficient rectification.

[0035] 3. Semiconductor ignition gun with lower breakdown voltage: This device uses capacitors to store energy, vacuum generator switches to control charging and discharging, and the ignition gun is electrically ignited. The commonly used ignition nozzles today are semiconductor nozzles and spark plug nozzles, and these two ignition methods each have inevitable advantages and disadvantages: The advantage of semiconductors is that they have high energy, can be used in harsh environments, have good discharge ignition functions, and have advantages such as heat resistance and anti-coking. However, there are also areas where the needs cannot be met under specific pressure resistance and installation conditions. Spark plugs have perfect characteristics for pressure resistance and installation in any position, but they cannot be used for ignition in harsh environments and with large coking. In response to the above situations and lower voltage ignition requirements, a new type of semiconductor pressure-resistant ignition electric gun has been developed, such as Figure 4 As shown, it is composed of an ignition gun shell 1, a semiconductor alumina ceramic 2, an insulating ceramic 3, a front electrode 4, a copper pad 5 and a rear electrode 6. The front electrode 4 is covered with a semiconductor alumina ceramic 2, and the rear electrode 6 is covered with an insulating ceramic 3. The front electrode 4 and the rear electrode 6 are separated by a copper pad 5. The front electrode 4, the copper pad 5 and the rear electrode 6 constitute the power generation core of the ignition gun, and the power generation core is installed in the ignition gun shell 1; the structural gaps of the semiconductor pressure-resistant ignition electric gun are sealed with silicone rubber. When in use, a threaded hole is drilled on the combustion chamber, and the thread at the front end of the ignition gun shell 1 is responsible for connecting it. The rear thread of the ignition gun shell 1 is connected to the ignition cable to input the high-voltage current required for ignition. The copper pad 5, as the softest part of the entire structure, also plays a role in deformation coordination and pressure resistance. The insulating ceramic 3 plays a role in blocking the insulating ignition gun shell 1 and the rear electrode 6. The semiconductor alumina ceramic 2 is doped with conductive impurities in the alumina of about 3 mm thick on the ignition end face, which can make it conductive. The current is directly conducted along the semiconductor alumina from the center electrode without breaking through the air, so the conduction voltage is smaller than that of the spark plug nozzle. Since only a very thin layer near the head has semiconductor alumina ceramic, the current density is larger, it is easier to generate sparks, and the conduction voltage is smaller than that of ordinary semiconductor ceramics. In addition, this ignition gun has high energy, high pressure and high sealing, has high corrosion resistance and anti-coking properties, and can be used in harsh environments. This nozzle can work under a pressure of 10MPa and is completely sealed without leakage.

[0036] The device inputs the working voltage, and obtains the DC pulsating high voltage through boosting and rectification, and charges the high-voltage energy storage capacitor. After the energy storage element reaches the opening voltage of the vacuum discharge tube, the electric energy passes through the discharge element, and the ignition cable and the high-voltage ignition gun concentrate the electric energy on the semiconductor alumina ceramic on it, breaking down the semiconductor, and generating high-temperature pulse electric sparks at the same time, igniting gas, light oil, heavy oil or residual oil, etc. The dynamic characteristics of charging and discharging of the igniter can be characterized by the voltage value changes at both ends of the high-voltage energy storage capacitor, such as Figure 5The data displayed on the oscilloscope shows the dynamic charge and discharge characteristics of a full-bridge high-energy igniter with a discharge frequency of 18.333Hz, a storage capacitor of 6uF, and a vacuum discharge tube breakdown voltage of 2000V. It can be seen that the amplitude of each discharge voltage is very stable, and the discharge frequency displayed on the oscilloscope does not change, meeting the design and use requirements of lower voltage and higher frequency.

[0037] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A full-bridge high-energy ignition device, characterized in that: Including igniter, ignition cable and ignition gun; igniter, ignition cable and ignition gun are connected by threads to directly ignite the gas mixed with natural gas, liquefied petroleum gas, kerosene, diesel, heavy oil, residual oil and air; The igniter is encapsulated with an ignition circuit, which includes a high-power CD-type step-up transformer, a full-bridge high-voltage rectifier bridge, a high-voltage energy storage capacitor, a vacuum discharge tube, a brake resistor and a high-voltage insulating joint; the main coil of the high-power CD-type step-up transformer is connected to an AC power supply, one end of the secondary coil is grounded, and the other end is connected to one end of the brake resistor, the other end of the brake resistor is connected to the I end of the full-bridge high-voltage rectifier bridge, the II end and the IV end of the full-bridge high-voltage rectifier bridge are grounded, the III end of the full-bridge high-voltage rectifier bridge is connected to the positive electrode of the high-voltage energy storage capacitor, the negative electrode of the high-voltage energy storage capacitor is connected to one end of the vacuum discharge tube, and the other end of the vacuum discharge tube is connected to the ignition gun; The ignition gun adopts a semiconductor withstand voltage ignition electric gun, including an ignition gun shell, semiconductor alumina ceramic, insulating ceramic, a front electrode, a copper pad and a rear electrode. The front electrode is covered with a semiconductor alumina ceramic, the rear electrode is covered with an insulating ceramic, the front electrode and the rear electrode are separated by a copper pad, and the front electrode, the copper pad and the rear electrode constitute a power generation core of the ignition gun, and the power generation core is installed in the ignition gun shell; The gaps between the structures of the semiconductor withstand voltage ignition electric gun are sealed with silicone rubber; The semiconductor alumina ceramic is doped with conductive impurities in the 3 mm thick alumina on the ignition end face side to make it conductive; When the ignition gun is used, a threaded hole is punched on the combustion chamber, the thread at the front end of the ignition gun shell is connected with the combustion chamber, and the rear thread of the ignition gun shell is connected with the ignition cable to input the high voltage current required for ignition.

2. The full-bridge high-energy ignition device according to claim 1, characterized in that: The full-bridge high-voltage rectifier bridge includes four diodes, diode I and diode II are connected in series, diode III and diode IV are connected in series, two groups of series diodes are connected in parallel, the positive poles of diode I and diode IV are grounded, and the negative poles of diode II and diode III are connected to the positive pole of the high-voltage energy storage capacitor.

3. The full-bridge high-energy ignition device according to claim 2, characterized in that: The diode is a gallium nitride PN junction diode.

4. The full-bridge high-energy ignition device according to claim 3, characterized in that: A heat sink is installed on the full-bridge high-voltage rectifier bridge.

5. The full-bridge high-energy ignition device according to claim 4, characterized in that: The vacuum discharge tube comprises two discharge electrodes with lead-out ends, a gap is left between the discharge electrodes, and the discharge electrodes are sealed by a glass insulating shell, and the interior is filled with low-pressure nitrogen-hydrogen mixed gas.

6. The full-bridge high-energy ignition device according to claim 5, characterized in that: The ignition cable is a 5KV high-voltage insulated cable with a metal braided layer on the outside to shield the electromagnetic interference of the ignition energy.

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