JP2009047149A - Composite discharge method and composite discharge apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize pulse discharge, which can maximize the generation of active species by pulse discharge in a period of the service life of the active species, for efficiently performing ignition with a main discharge arc by generating a large amount of active species, for example, in previous glow or streamer discharge. <P>SOLUTION: Pulse waveforms and repetition frequency, for example, in glow or streamer discharge prior to arc discharge are optimized to generate a large amount of active species and thus to increase the active species concentration immediately before the arc discharge. To this end, the pulses optimally have a pulse width of 10 to 500 ns, that is, are neither very short pulses having a pulse width of 10 ns or less nor wide pulses having a pulse width on the order of μs or more. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for igniting an internal combustion engine by an arc discharge that is continued after a high voltage burst short pulse discharge generated from a pulse generation circuit.

  An internal combustion engine is a machine that takes out power by burning fuel in a combustion chamber, and is classified as a type of heat engine that converts thermal energy into mechanical energy. Piston engines (reciprocating and rotary engines) are the examples. The piston engine is “intermittent combustion”. In the case of a piston engine, fuel is combusted inside a cylinder (cylinder), and the pressure generated by the combustion utilizes the force pushing the piston.

  A type of piston engine, a gasoline engine, also called a gasoline engine, is an internal combustion engine that compresses a mixture of fuel (gasoline) and air with a piston and then ignites, burns, and expands to reciprocate the piston. Most are Otto cycle institutions.

  Normally, it is output to the rotating shaft by a crank mechanism. Combustion is performed at once in a short period of time near the volume of the air-fuel mixture, so that the combustion is performed with a substantially constant volume. For this reason, it is also called a fixed volume combustion cycle engine. Otto is the name of the developer of this combustion cycle.

  Gasoline engines have a large output per displacement, are easy to drive at high speeds, are quiet with little vibration and noise, and have become mainstream in passenger cars, small commercial vehicles, and motorcycles.

  The combustion of the gasoline engine is started by a spark plug. The spark plug is a component that plays a role of igniting a mixed gas containing fuel by being electrically discharged. In an internal combustion engine called a spark ignition engine, a spark plug is placed in a cylinder head and ignited by an electric discharge to create a trigger for combustion. The spark plug is used for igniting the air-fuel mixture in both combustion engines such as heating appliances as well as internal combustion engines. The engine is repeatedly ignited several hundred to several thousand times per minute, and the heating device or the like operates only at the start of combustion.

  Recently, as global environmental problems become more serious, the energy efficiency of gasoline engines has been improved to reduce CO2 emissions, the exhaust gas has been cleaned to reduce air pollutants, and the use of rare resources such as precious metals used as catalysts has been reduced. For this purpose, lean-burn engines have attracted attention again.

  A mixed gas of fuel and air needs a certain ratio to the ratio of fuel and air in the phenomenon of ignition → combustion → explosion. The limit at which ignition → combustion → explosion occurs when the ratio of fuel to air is small is called the lower explosion limit.

  The lean combustion method that has been actively implemented was a development method for reducing the amount of NOx discharged from high-concentration fuel, but the problem of the position of the ignition plug, the problem of the ignition timing, and the space of the mixed gas concentration・ Development of lean-burn engines has been driven out of the market due to the fact that a state close to the flammability limit occurs at the time of ignition due to time distribution, ignition failure and flame propagation are often interrupted, and expensive catalysts are required. .

  Conventionally, plasma discharge has often been used independently for each of arc discharge, glow discharge and streamer discharge. In some cases, plasma display panels (PDP) and excimer lasers use a discharge that is generated before the main discharge. However, this is a glow discharge by DC or high frequency, which is useful for increasing the main discharge uniformly and strongly.

  Furthermore, arc discharge has been mainly used for ignition of combustible gas. Arc discharge can be ignited with a simple discharge circuit, but since the discharge region is limited to the vicinity of the arc, misfire often occurs during flame propagation after ignition. In order to prevent this in automobile gasoline engines, the use of a highly durable material such as iridium as the discharge electrode minimizes the electrode volume, reduces heat absorption and heat dissipation by the electrode, and prevents flame cooling. Successful.

  The conventional discharge that occurs before the main discharge is performed under reduced pressure. Under atmospheric pressure or under pressure, the gas temperature rises, it is difficult to maintain the discharge, and it is difficult to discharge stably. The conventional discharge that occurs before the main discharge is established under a certain condition, and the discharge condition cannot be changed according to the pressure change, temperature change, or composition change. The conventional discharge that occurs before the main discharge is a preliminary weak discharge and cannot be replaced by the role of the main discharge. Therefore, it is often necessary to prepare a separate power source for each discharge.

  A conventional gasoline engine has an air-to-fuel mass ratio of approximately 14.7, which is close to the stoichiometric air-fuel ratio at which oxygen and fuel burn without excess or deficiency. In conventional gasoline engines, oxygen-rich lean combustion is difficult because a three-way catalyst that removes three types of harmful gases, hydrocarbons, carbon monoxide, and nitrogen oxides, is generated. In order to prevent global warming, “improvement of fuel consumption = reduction of CO 2” is required for automobiles, and lean combustion is required again. In conventional ignition devices, it has been difficult to completely burn a lean air-fuel mixture at a flame temperature that does not discharge nitrogen oxides.

  Conventional arc discharge ignition promotes flame propagation and burns the mixed airflow by strong turbulence. Therefore, the temperature of the air-fuel mixture is increased to prevent the combustion from disappearing, and since the temperature becomes high, a large amount of nitrogen oxide is generated.

In the conventional discharge, the gas is activated by a slightly capacitive discharge just before the arc, but the rise of the pulse is slow, so the effect is almost negligible.
The following attempts have been made as methods for improving the ignition performance of a lean mixed gas.

(1) Widen the ignition area.
There is a method of expanding the discharge region for the purpose of increasing the probability that a mixed gas having a high concentration reaches the ignition region. An example in which ignition is promoted by a pulse power ignition method in which ignition is performed in combination with pulse streamer discharge. Patent Document 1 is a method corresponding to a concentration distribution of an air-fuel mixture by expanding an ignition region between discharge electrodes. There is a rail plug method as an ignition method with the same aim of expanding the discharge ignition region. The rail plug system is an ignition system using a discharge plug having a rail-shaped discharge electrode developed at the University of Texas, USA (Non-Patent Document 1). When an arc current flows between the rail-like discharge electrodes, the discharge site moves on the rail-like discharge electrode by Lorentz force that is caused by the interaction between the magnetic field generated by the current and the current. Since the arc discharge site moves, it can be discharged over a wide range, and since it does not discharge at the same location, the electrode surface is hardly damaged.

(2) Increase the number of ignitions per hour.
Ignition discharge was repeated in the vicinity of the ignition timing to increase the probability that a high-concentration gas mixture would reach the ignition position (Patent Document 2).

(3) Increase the concentration of active species that promote the combustion reaction.
As one of the active species excitation methods, there is excitation by a laser beam linked with the ignition timing (Patent Document 3). The laser excitation method can realize stable ignition conditions without causing the ignition part to deteriorate like an ignition plug. On the other hand, it can be applied to a large system with a large installation space such as an aircraft engine.

In general, it is known that the process from ignition to flame propagation goes through two stages of inductive discharge following capacitive discharge. It is known that the capacitive discharge in the high impedance state in the initial stage activates oxygen or combustion components and contributes to the flame generation by the subsequent inductive discharge (Non-Patent Document 2). However, little effort has been made to promote their activation at this stage of capacitive discharge, rather an approach has been taken from the direction of how to ensure inductive discharge following capacitive discharge (Non-Patent Documents). 3). In recent years, attempts have been made to reinforce capacitive discharge, focusing on the fact that capacitive discharge activates oxygen or combustion components (Non-Patent Documents 4 and 5). In addition, in order to stably perform capacitive discharge, studies have been conducted to clarify the relationship between the pulse width and the electric field strength that shifts to arc discharge (Non-Patent Document 6, FIG. 1).
JP 2000-110697 A JP, 2004-0779458, A Multipoint ignition Japanese National Patent Publication No. 8-505676 Matthews, R.A. D. Hall, M .; J. et al. Faidley, R .; W. Chiu, J .; P. , Zhao, X, W. Annezer, I .; Koenig, M .; H. Harber, J .; F. Darden, M .; H. , Weldon, W.M. F. , And Nichols, S .; P. "Further Analysis of Railplugs as a New Type of Ignitor," Journal of Engines 101 (3), pp. 1851-1862, 1993. Kanako Mitsuo “Spark Plug” Sankaido (1999/12) “3S Class Marine Engine Mechanic Instruction Manual”, Chapter 2, Section 2.8, Japan Marine Engine Maintenance Coordination Sergey V.M. Pancheshnyi et. Al, “Propane-Air mixture ignition by a sequence of nanosecond pulses” XXVII IGPIG, Eindhoven, the Netherlands, 18-22, Juy, 2005 Sergey V.M. Pancheshnyi et. Al, “Ignition of Propane-Air Mixtures by a Repeatable Pulsed Nanosecond Discharge”, IEEE Transactions on plasma science, 34 (6), p. 2478-2487, December 2006 J. et al. Lowke, et. al, IEEE Transactions on Plasma Science, 23 (4), 661 (1995).

  As described above, various methods for improving the ignition performance of a lean mixed gas have been conventionally performed, but each has the following problems. The rail plug system that expands the ignition region has a problem that a large amount of electric power is required for discharging. The method of repeating the ignition discharge for increasing the number of ignitions per hour near the ignition timing has a problem of plug deterioration due to discharge more than necessary and discharge at high temperature. Excitation with a laser beam that increases the concentration of active species that promote the combustion reaction is difficult to install in systems with limited space and cost, such as automobiles. There is a problem that sufficient reliability is not obtained. Management of gas in a gas laser, reliability of an excitation light source discharge tube or a semiconductor laser in a solid-state laser are problems. Focusing on the fact that capacitive discharge activates oxygen or combustion components, conventional attempts to enhance capacitive discharge use extremely short pulses that are extremely suppressed in the transition to arc discharge. There are problems such as the limit of the total amount of energy required to excite and activate a large number of molecules, and the fact that it is difficult to reduce the size of the power source and its application is limited.

  In the present invention, attention is paid to capacitive discharge, which is a solution means for the purpose of activating oxygen and combustion components in capacitive discharge. Since this method can reduce the probability of misfire, reducing the activation energy required for the oxidation-reduction reaction in the combustion system is effective in promoting flame propagation in inductive discharge. This is achieved by increasing the internal energy of gas and fuel molecules and exciting them into dissociated or active complexes.

  The composite discharge method and the composite discharge apparatus characterized in that the pulse discharge is generated at least once before the main discharge under the negative pressure or the positive pressure according to claim 1 of the present invention. Realized by the principle of When plasma is generated by glow or streamer discharge before arc discharge, a part of the mixed gas is excited and becomes active species. Active species include radicals, ions, electrons, luminescent species, etc. Among them, radicals are the most common. However, active species have a lifetime, and if the concentration of charged particles increases, capacitive discharge does not occur when an electric field is applied, and inductive arc discharge tends to occur, so active species accumulate in the ignition space. There are limits to what you can do. In such a limit, in order to perform ignition with the main discharge arc more efficiently, a large number of active species are generated by prior glow or streamer discharge, and the active species concentration immediately before the arc discharge is increased. This is very important. That is, the number of pulse discharges set before the main discharge as described in claim 2 and the interval between the pulse discharges set before the main discharge as described in claim 3 are arbitrarily controlled. The composite discharge method and the composite discharge device according to claim 1 are provided, and a pulse discharge that maximizes generation of active species by pulse discharge within a time within the active species life is realized.

  4. The composite discharge method and composite as claimed in claim 1, wherein the means for generating active species is a stream discharge or a glow discharge, wherein the pulse discharge set up before the main discharge is as described in claim 4. A discharge device is provided. The relationship between the pulse width and the electric field intensity that shifts to arc discharge has a negative correlation (FIG. 1). The narrower the pulse width, the higher the electric field strength that shifts to arc discharge. Therefore, the narrower the pulse width, the more stable the glow or streamer discharge can be made. However, since the lifetime of active species is finite, there is a limit to the accumulation amount and accumulation time. Therefore, if the pulse energy is made too small, the active species must be discharged many times to increase the number of active species, which requires a longer time, resulting in the end of the life of the active species generated at the beginning, resulting in a decrease in the total amount of active species. It will be a situation. On the other hand, the repetition frequency has a limit in order to prevent damage to the element due to heat generation due to loss of an electric circuit called a switching circuit that applies or cancels the pulse voltage. If the pulse width is too narrow, the number of repetitions required for injecting the predetermined energy cannot be obtained.

  If the energy per single pulse discharge is Esp, the maximum repetition frequency is F, the average life of active species is Tlt, and the energy efficiency contributing to the generation of active species is Rpw, the effective active species concentration Neff before the ignition arc discharge is (Equation 1). The composite discharge method and the composite discharge device according to any one of claims 1 to 4, wherein the main discharge according to claim 5 is an arc discharge as ignition means.

Neff ∝ Esp × F × Tlt × Rpw (Formula 1)
Thus, pulse discharge that maximizes the value of Esp × F × Rpw is required. Among active species, ions and electrons are 3-4 orders of magnitude less than radicals and have a short lifetime. Luminescent species are 3-4 orders of magnitude less than ions. Therefore, the comparison of the active species concentration is approximated by the radical concentration.

  On the other hand, according to Non-Patent Document 6, the energy efficiency that contributes to the generation of active species changes depending on the pulse width as shown in the left vertical axis of FIG. When the pulse width is narrow and the peak voltage is high, that is, when the voltage rise rate (dV / dt) is high, the spontaneously generated incident electrons are sufficiently accelerated and the energy at the time of collision with the gas molecules increases, resulting in inelastic collision. Increases internal energy and increases the probability of generating active species. The voltage increase rate (dV / dt) is a voltage change of the discharge electrode, and has a positive correlation with the current injection speed to the electrode. Therefore, the greater the current increase rate (di / dt), the higher the energy efficiency that contributes to the generation of active species. However, as shown in FIG. 1, when the pulse width falls below 0.1 [ns], the efficiency decreases. This is thought to be due to the fact that the energy gained by the electrons increases, but the velocity increases so much that the cross-sectional area of collision with the molecules decreases. In addition, when the pulse width is wide, the voltage increase rate (dV / dt) and current increase rate (di / dt) are small, and the collision of electrons with electrons before they are accelerated sufficiently increases the internal energy of the molecules. It is mainly an elastic collision that cannot be done. Molecules are excited to a low energy state and discharged without generating much excited species, and current injection into a low impedance plasma is performed. The added energy is used for Joule heat, reducing the probability of generating active species. That is, the active species generation efficiency decreases rapidly.

  However, even if only the energy efficiency is high, the total amount of active species actually generated does not increase unless the applied energy is increased. When the discharge voltages are equal, the injection energy is approximately proportional to the input charge amount, so the product of the current density and the energy efficiency is proportional to the active species concentration mainly composed of radicals (Formula 1).

In the examples described in Non-Patent Document 4 and Non-Patent Document 5, an ultra-short pulse having a current value of 40 [A] and a pulse width of 1 to 2 [ns] is discharged after 4 to 5 times, and then shifts to arc discharge ignition. . When the number of times of glow or streamer discharge before transition to arc discharge ignition described in Non-Patent Document 4 is m, the input charge amount Q1 per glow or streamer discharge with a pulse interval of about 33 [μs] is Q1 = 40 [A]. × 2 × 10 ⁻⁹ [s] × m [pulse] = 8.0 × m × 10 ⁻⁸ [C]
It becomes.

On the other hand, in the case of the present invention, assuming that the transition to arc discharge ignition is performed after n discharges, the input charge amount Q2 per glow or streamer discharge with a pulse interval of about 13 [μs] is a current value 2 slightly estimated from FIG. From [A] and the pulse half width of 100 [ns], Q2 = 2 [A] × 100 · 10 ⁻⁹ [s] × n [pulse] = 2.0 × n × 10 ⁻⁷ [C]
It becomes.

When the product of these values and the active species generation efficiency Rpw corresponding to each pulse width is obtained, the case of the ultrashort pulse discharge with a pulse width of about 2 [ns] or less and the pulse width of about 100 [ns] of the present invention are obtained. The energy efficiency ratio in the case of short pulse discharge is as follows.

(Q1 × Rpw1) / (Q2 × Rpw2) = (8.0 × m × 10 ⁻⁸ × 0.54) / (2.0 × n × 10 ⁻⁷ × 0.30) = 7.2 × 10 ^{− 1} x (m / n)
If m is not 1.4n or more, Q1 does not exceed Q2, and the capacitive discharge of an extremely short pulse performing pulse compression cannot increase the repetition frequency (pulse interval 13 [μs of the present invention). ] Is higher than the pulse interval 33 [μs] in the example described in Non-Patent Document 4, and it is expected that the generation efficiency of active species will not be improved.

  The current values in the present invention are both an order of magnitude smaller than those described in Non-Patent Document 4 for both glow discharge and arc discharge, which is considered to be due to the difference in electrode structure. When the same electrode structure is used, it is considered that (Q1 × Rpw1) / (Q2 × Rpw2) is further greatly different. Therefore, it can be said that the net energy conversion efficiency in the generation of active species in the present invention is more effective than the example described in Non-Patent Document 4.

  Developments have been made to smoothly ignite a lean mixed gas mainly by these methods. The present invention belongs to the category (3). In other words, after introducing the gas mixture, glow or streamer discharge with short pulses is repeatedly performed before ignition, and the active species generated from the gas mixture are diffused and accumulated in the system, and when the ignition discharge is established, it is in an excited state. The active species causes an oxidation reaction in a chain with less energy, promotes flame propagation, and causes combustion and explosion.

  The concentration of the active species is determined by how effectively the glow or streamer discharge occurs before the transition to the main discharge. As described above, there are “increased input energy efficiency dependent on pulse width” and “increased active species generation efficiency dependent on pulse width” as requirements for effectively causing glow or streamer discharge. These requirements are in a trade-off relationship. The shorter the pulse width, the higher the generation efficiency of active species. However, if the pulse width is too short, the reflected wave increases and the energy input efficiency decreases. The active species generation efficiency reaches 40% near 30 [ns] and saturates at 50% at 1 [ns] (FIG. 21). On the other hand, when the pulse width is narrow, a steep rise in current voltage makes it difficult to achieve impedance matching with the reactor, resulting in an increase in reflected waves and a decrease in energy input (FIG. 20). The pulse width that maximizes the generation of active species when the two requirements of active species generation efficiency and energy input efficiency are taken into consideration was obtained. The product of “active species generation efficiency” and “input energy efficiency” is an arbitrary unit [a. u. ] Is plotted on the vertical axis and plotted against the pulse width (FIG. 22). A convex characteristic was obtained that maximized the pulse width of 0.1 to 0.2 [μs]. From these, the half width of the desirable pulse voltage waveform is 0.01 μs or more and 1 μs or less, more preferably 0.05 μs or more and 0.5 μs or less, and further preferably 0.1 μs or more and 0.2 μs or less. Then, active species can be efficiently accumulated by glow or streamer discharge.

  The optimum pulse width is described in claim 6 as a means for efficiently accumulating the active species. That is, the composite discharge method and the composite discharge apparatus according to any one of claims 1 to 5, wherein a half-value width of a pulse voltage waveform of a pulse discharge set up before the main discharge is set to 0.01 μs or more and 1 μs or less. . Desirably within that range, as shown in FIG. 22, the voltage waveform according to claim 7 is set up by a pulse electric field having a half-value width of 0.05 μs or more and 0.5 μs or less. The composite discharge method and the composite discharge apparatus according to claim 6, and more preferably, as shown in FIG. 22, the pulse voltage waveform according to claim 8 is set up by a pulse electric field having a full width at half maximum of 0.1 μs to 0.2 μs. The combined discharge method and the combined discharge device according to claim 1, wherein the combined discharge method and the combined discharge apparatus are provided.

The energy entering the system can be roughly calculated by the above pulse width, but whether the energy can be efficiently input to the system depends on the voltage increase rate (dV / dt) or current increase rate (characteristic of the pulse waveform). di / dt) needs to be optimized. If these are large, the amount of active species generated when the same energy is applied increases, but on the other hand, impedance matching with the discharge load is difficult to achieve, reflection increases, energy input decreases, and active species decreases. To do. In the pulse discharge set up before the main discharge, the voltage increase rate (dV / dt) is 3 × 10 ¹¹ [V / s] or less, or the current increase rate (di / dt) is 3 × 10 ⁷ [A / s] or less. In a certain pulse characteristic, the electrical energy conversion rate converted from the power source to the plasma is 10% or more (energy reflection is 90% or less) by using the glow before ignition or streamer discharge (FIGS. 23 and 24). .

On the other hand, the dependency of the active species generation efficiency on the voltage increase rate (dV / dt) or current increase rate (di / dt) is opposite. Pulses with a voltage rise rate (dV / dt) of 1 × 10 ⁸ [V / s] or more, or a current rise rate (di / dt) of 1 × 10 ⁶ [A / s] or more are converted to active species. The efficiency is 20% or more (FIGS. 25 and 26).
As a result, if the voltage increase rate (dV / dt) or the current increase rate (di / dt) is too low, the energy conversion efficiency to the active species decreases, and if it is too high, the electrical compatibility with the reactor is poor. It turns out that energy becomes difficult to enter. The product of “input energy efficiency” and “active species generation efficiency” is arbitrarily set in the same way as when the product of “input energy efficiency” and “active species generation efficiency” is plotted on the vertical axis in an arbitrary unit system and the pulse width dependency is plotted. By plotting the voltage rise rate (dV / dt) or current rise rate (di / dt) dependency on the vertical axis in the unit system, the optimum active species generation range is 1 × 10 ⁸ [V / s] of the present invention. <Voltage increase rate (dV / dt) <3 × 10 ¹¹ [V / s], or 10 ⁶ [A / s] <Current increase rate (di / dt) <3 × 10 ⁷ [A / s] ( FIG. 27, FIG. 28).

Thus, as means for realizing the optimization of the voltage increase rate (dV / dt) or the current increase rate (di / dt), as described in claim 9, from the power source to the plasma in the pulse discharge standing before the main discharge. The rate of voltage increase (dV / dt) is 1 × 10 ⁸ [V / s] or more and 3 × 10 ¹¹ [V / s] so that the converted electric energy conversion rate is 10% or more or energy reflection 90% or less. Or a pulse characteristic such that the current increase rate (di / dt) is 1 × 10 ⁶ [A / s] or more and 3 × 10 ⁷ [A / s] or less. A composite discharge method and a composite discharge device according to claim 1 are provided.

  In the glow or streamer discharge caused by the short pulse electric field, the interval and number of bursts are variable by the control circuit, and the burst of short pulse glow or streamer discharge can be controlled according to the driving state of the internal combustion engine. At the time of high rotation or high load, the temperature of the mixed gas rises and the life of the active species is shortened, so that the active species that promote ignition are easily generated by narrowing the pulse interval and increasing the number of times. On the contrary, at the time of low rotation or low load, the temperature of the mixed gas decreases and the life of the active species is extended, so that the pulse interval is widened and the number of times is reduced.

  Active species are generated in an avalanche due to inelastic collisions with mixed gas molecules as the surviving electrons are accelerated by a pulsed electric field with a high voltage rise rate. The higher the pressure of the diluted gas mixture, the shorter the mean free path, so the energy given to electrons by a single pulse electric field becomes smaller. Therefore, it becomes important how much energy is given to the glow or streamer discharge within the lifetime of the active species.

  In Non-Patent Document 4 and Non-Patent Document 5, active species are generated with a pulse width 1-2 orders of magnitude shorter than the present invention. In the reference, the energy per pulse is smaller than that of the present invention, and the generated amount of active species effective for ignition is smaller than that of the pulse discharge having a half width of 10 to 200 ns.

  As described above, the burst of the glow or streamer discharge having an appropriate pulse width according to the present invention can be applied to the stable ignition of a lean mixed gas. Moreover, according to the stable combustion of the lean mixed gas according to the present invention, in addition to the above-described effects, the generation suppression of fine particulate matter resulting from incomplete combustion of nitrogen oxides or fuel in the exhaust gas and the energy efficiency are improved. be able to. The effects obtained in the present invention are summarized in the following clauses.

(1) By generating a pulse voltage by a high-speed switching element, high-energy electrons can be efficiently generated, and the mixture is excited and the generation of active species is promoted. Glow or streamer discharge can be established stably over a wide pressure range, creating an atmosphere rich in active species that is easily transferred to arc discharge.

(2) By changing the pulse waveform and pulse frequency, the discharge conditions can be optimized according to the pressure change, temperature change or composition change. As a result, the active species concentration in the reactor can be brought to a substantially desired value before the arc discharge, and the arc discharge as the ignition discharge can be stabilized. In particular, in order to shift the active species having a finite lifetime to arc discharge with a concentration as high as possible, the pulse width in the present invention is characterized by giving an optimum range of values.

(3) Glow or streamer discharge is a non-equilibrium discharge and does not raise the gas temperature to the conventional ignition temperature, but by controlling the number of repetitions, the active species concentration can be increased and the ignition temperature can be lowered, with the same pulse waveform. It is possible to ignite with less energy than the conventional arc discharge for ignition after ignition, and stable ignition can be achieved even when the fuel concentration is leaner.

(4) A single power source can perform glow or streamer discharge to main discharge.

(5) The number of glows or streamer discharges before the main discharge can be changed according to the discharge conditions, and the discharge before the main discharge can be established with the optimum number of repetitions according to the operating conditions according to a preprogrammed algorithm. .

(6) By arranging the discharge region and the discharge electrode that maximize the effect of glow or streamer discharge, ignition and flame propagation can be assisted uniformly and most effectively. Not only gaseous substances at normal temperature and normal pressure such as methane and propane, but also liquid substances at normal temperature and normal pressure such as hexane, gasoline, ethanol and light oil are vaporized and the same mechanism as ignition, combustion, and explosion The same effect can be expected in a system where the chemical reaction proceeds in a chain reaction.

(7) Since the DC power supplied from the storage battery is once converted into pulse power power of several kV by the ignition timing control signal sent from the engine control device, the step-up ratio in the ignition coil can be lowered. As means for realizing this, a pulse power generation circuit for reducing the boost ratio and reactor component of the secondary coil on the primary side of the boost coil for supplying high voltage power to the spark plug compatible electrode as described in claim 10. And a pulse generation circuit for generating a high voltage pulse outside the internal combustion engine, wherein the pulse generation circuit is applied to the ignition of an internal combustion engine that burns and explodes the combustible gas according to claim 11, The composite discharge method and composite discharge device according to claim 1, further comprising a discharge electrode that is connected in an internal combustion engine and generates active species of combustible gas. In addition, as described in claim 12, a spark plug compatible electrode and a booster coil are disposed in a cylinder of the internal combustion engine, and a pulse voltage generation circuit is directly connected to the booster coil in the vicinity of the coil. A spark plug-compatible electrode and a booster coil are disposed in a cylinder of the internal combustion engine according to claim 11 and the composite discharge method and composite discharge device according to claim 13, and a common pulse voltage installed in the internal combustion engine is provided in the booster coil. 13. The composite discharge method and the composite discharge apparatus according to claim 1, wherein the high-voltage pulse is distributed from the generation circuit. Thereby, the stray reactance and stray capacitance in the ignition coil are reduced, the amount of active species generated by glow before ignition or streamer discharge can be increased, and a more lean mixed gas can be ignited stably.
In addition, the reduction of the boost ratio of the ignition coil is also effective in increasing the reliability of the ignition coil. Furthermore, since an ignition coil is provided in each cylinder, fine cylinder control can be performed, whereby an integrated ignition system that does not use a distributor useful for exhaust gas purification or fuel efficiency improvement can be achieved.

  Embodiments of the plasma reactor according to the present invention will be described below with reference to FIGS.

First, the internal combustion engine ignition method according to the first embodiment is a system that performs arc discharge ignition after n times of glow or streamer discharge. As shown in FIG. 2, this system includes a pulse signal generator 22 that generates a signal that indicates a pulse waveform and a pulse interval, and a high voltage pulse that is connected to the pulse signal generator 22 and instructed from the signal generator. A pulse generation circuit 21 for generating (high voltage pulse train 24) and connected to the pulse generation circuit 21 and installed in the reaction vessel 23 by the pulse high voltage (or high voltage pulse train 24) generated by the pulse generation circuit 21 The device configuration is such that the active species are generated in the plasma space by discharging between the electrodes. FIG. 3 is an enlarged schematic view of the reaction vessel 23 in FIG. 2, and includes a perforated plate 31 for introducing and discharging a mixed gas, a fan 32 for stirring the introduced gas, a window 33 for observing a discharge / combustion state, and a discharge electrode 34. Have. FIG. 4 shows the discharge electrode shape dependence of the minimum ignition energy at each equivalence ratio with the equivalence ratio of the methane (CH ₄ ) -air mixture according to the exemplary embodiment of the present invention on the horizontal axis. FIG. 5 shows the discharge electrode shape dependence of the minimum ignition energy at each equivalence ratio with the equivalence ratio of methane (C ₃ H ₈ ) -air mixture as the horizontal axis according to an exemplary embodiment of the present invention. In FIG. 6, both electrodes are rod-shaped electrodes, and the legends in FIGS. 4 and 5 are labeled as counter electrode plugs. In FIG. 7, the high voltage side is a rod-shaped electrode and the low voltage side is a mesh electrode, and the aim is to prevent heat generated during ignition from being dissipated through the electrode. In FIG. 8, the high voltage side is a rod-shaped electrode and the low voltage side is a plate electrode. In the lean equivalence ratio region, in the case of methane (CH ₄ ), the plate electrode 43 resulted in having a higher minimum ignition energy compared to the other counter electrode plug 41 and the mesh electrode 42. Propane (C ₃ H ₈ ) was almost equivalent. From these results, it was clarified that the ignition phenomenon in this system is hardly affected by the electrode shape.

Discharge electrodes are arranged as shown in FIGS. 2 to 3 in a simulated internal combustion container in which a predetermined amount of propane (C ₃ H ₈ ) or methane (CH ₄ ) and dry air are mixed under atmospheric pressure, and the pulse interval is about 13 [ 9 and 10 show waveform data in a state from application of a pulse train 24 of μs] to generating capacitive glow or streamer discharge to transition to inductive arc discharge and ignition. Here, arc discharge by a pulse train after glow or streamer discharge or the like occurs six times and active species are generated in the space continues to ignite and propagate the flame.

Compared with the case of only arc discharge, the air-fuel equivalent ratio of methane (CH ₄ ) and propane (C ₃ H ₈ ) was able to expand the ignition region to a leaner region (FIGS. 11 and 12). Here, the solid line represents the limit of flammable gas explosion in the air by Lewis and Elbe, the black circle represents the ignition only of the conventional arc discharge, and the white circle represents the 10 discharges before ignition. It is a figure which shows the expansion of the ignition region of the lean mixed gas to a leaner region. In the methane (CH ₄ ) / air mixed gas, the flame limit equivalent ratio was 0.575 only with the conventional arc discharge, but it decreased to 0.525 when the discharge before ignition was performed 10 times. It is shown that. In the propane (C ₃ H ₈ ) / air mixed gas, the flame limit equivalent ratio was 0.65 only with the conventional arc discharge, but when the pre-ignition discharge was performed 10 times, it decreased to 0.60. It shows that.

  The ignition delay time is defined as the time from the time when the pressure in the reaction vessel reaches 10% of the maximum value until it reaches 90%. The short ignition delay time means that the pressure increase speed after ignition is large and flame propagation is large. It shows that it is in a state where it proceeds quickly and promotes combustion. The activated species accumulated by the short pulse discharge accelerates the combustion of the fuel gas, so that the pressure increase rate after ignition increases. In the pressure rise curve, the ignition delay time was improved by 20% at an equivalence ratio of 0.6 for methane (FIG. 13), improved by 10% at an equivalence ratio of 0.65 for propane (FIG. 14), and 10 for an equivalent ratio of 0.70 for gasoline. % Improvement (Figure 15). Both have the effect of promoting flame propagation.

  Schematic diagrams of an internal combustion engine in which a predetermined amount of fuel and air are mixed and ignited and exploded are shown in FIGS. 16 and 17 (only two cylinders are shown). FIG. 16 shows a system in which the pulse generation circuit 21 is provided for each cylinder, and FIG. 17 shows a system in which the pulse generation circuit 21 is provided in one place and distributes power to each cylinder. An ignition timing signal from the engine control device 82 is introduced into the pulse generation circuit 21. The DC power of the storage battery 81 is converted into pulse power power by the pulse generation circuit 21 and sent to the ignition coil 85. The ignition coil 85 boosts the voltage to the discharge voltage, and controls the discharge of the spark plug compatible electrode 83. The arrangement | positioning schematic diagram of these components is shown in FIG.18 and FIG.19. Capacitive glow or streamer discharge generated by this system shifts to inductive arc discharge, and proceeds to ignition, flame propagation, and explosion.

  FIG. 18 shows an example of the present invention in which the pulse generation circuit 21 and the ignition coil 85, which are shaded portions in the system of FIG. In FIG. 18, the ignition timing signal sent from the engine control device 82 through the ignition signal line 105 is converted and amplified by the pulse generation circuit 21 from the DC power supplied from the storage battery 81 through the power supply line 106 to the pulse power power. 85 is supplied to the primary winding 107. It takes several kV for the primary winding, and when this is taken out by the secondary winding 104 of the ignition coil, it is boosted to a voltage required for discharge by the spark plug compatible electrode 83.

  For comparison, FIG. 19 shows an integrated ignition system that does not use a conventional distributor corresponding to the hatched portion and spark plug in the system of FIG. In FIG. 19, the DC power supplied from the storage battery 81 through the power supply line 116 is controlled by the ignition timing signal sent from the engine control device 82 through the ignition signal line 105 and supplied to the primary winding 107 of the ignition coil 85. The primary winding takes 10 tens V, and this is boosted to a voltage necessary for the discharge of the spark plug 118 by the secondary winding 104 of the ignition coil.

  The conventional integrated ignition device has a reactor component value of about 10 [mH], on the order of mH (Millihenry), and the pulse waveform cannot be made steep. On the other hand, in the system shown in FIGS. 2, 3, 16, 17, and 18 of the present invention, about 5 [μH], the order of μH (microhenry), and about 3 orders of magnitude smaller than the conventional circuit. Therefore, a steep pulse waveform can be obtained, and one or more repetitive pulse glows or streamer discharges that are effective for generating active species and do not shift to arc discharge can be stably obtained.

  The ignition method and the ignition device of the present invention are characterized in that the fuel / air mixed gas before combustion and explosion occurs is activated in advance to promote flame propagation, and the active species contributing to the reaction are increased before ignition. Because of its simple principle, it can be applied to the promotion of various phenomena caused by chemical reactions such as external combustion engines, gas decomposition, discharge plasma, gas lasers, etc. in addition to internal combustion engines.

FIG. 1 is a diagram showing a negative correlation between the electric field strength and the pulse width described in Non-Patent Document 6, which shows that it is advantageous that a smaller pulse width is advantageous in suppressing the transition to arc discharge. . FIG. 2 is a schematic diagram showing an entire system used for principle confirmation according to an exemplary embodiment of the present invention. FIG. 3 is a schematic diagram of the reaction vessel 23 of FIG. 2 according to an exemplary embodiment of the present invention. FIG. 4 illustrates the equivalence ratio dependence of the methane (CH ₄ ) -air mixture of the minimum ignition energy by discharge electrode shape according to an exemplary embodiment of the present invention. FIG. 5 illustrates the equivalence ratio dependence of the propane (C ₃ H ₈ ) -air mixture of the minimum ignition energy by discharge electrode shape according to an exemplary embodiment of the present invention. FIG. 6 is a schematic diagram of the rod structure of both the low voltage side and high voltage side discharge electrodes 34 of FIG. 3 according to an exemplary embodiment of the present invention. FIG. 7 is a schematic diagram of the mesh structure of the low-voltage side discharge electrode 34 shown in FIG. 3 according to an exemplary embodiment of the present invention. FIG. 8 is a schematic diagram of the plate structure of the low-voltage side discharge electrode 34 shown in FIG. 3 according to an exemplary embodiment of the present invention. FIG. 9 is a time change of voltage waveform data from a capacitive glow or streamer discharge to an inductive arc discharge according to an exemplary embodiment of the present invention. FIG. 10 is a time variation of current waveform data from a capacitive glow or streamer discharge to an inductive arc discharge according to an exemplary embodiment of the present invention. FIG. 11 is a diagram illustrating an expansion of the ignition region to a lean region in a methane (CH ₄ ) -air mixture, according to an exemplary embodiment of the present invention. FIG. 12 is a diagram illustrating an expansion of the ignition region to a lean region in a propane (C ₃ H ₈ ) -air mixture, according to an exemplary embodiment of the present invention. FIG. 13 is a diagram illustrating an improvement in ignition delay time in a pressure rise curve after ignition in a methane (CH ₄ ) -air mixture, according to an exemplary embodiment of the present invention. FIG. 14 is a diagram illustrating an improvement in ignition delay time in a pressure rise curve after ignition in a propane (C ₃ H ₈ ) -air mixture, according to an exemplary embodiment of the present invention. FIG. 15 is an estimation diagram showing an improvement in the ignition delay time in the pressure rise curve after ignition in a gasoline-air mixture, according to an exemplary embodiment of the present invention. FIG. 16 is a schematic diagram showing an overall system of a system in which a pulse voltage generation circuit is loaded for each cylinder applied to an actual internal combustion engine according to an exemplary embodiment of the present invention. FIG. 17 is a schematic diagram showing an overall system of a system for distributing a high voltage pulse from a common pulse voltage generation circuit applied to an actual internal combustion engine according to an exemplary embodiment of the present invention. FIG. 18 is a schematic diagram showing an entire system according to an exemplary embodiment of the present invention. FIG. 19 is a schematic diagram showing an entire system according to an exemplary embodiment of a conventional integrated ignition system. FIG. 20 is a graph showing the pre-ignition discharge pulse width dependence of the input energy according to an exemplary embodiment of the present invention. FIG. 21 illustrates a non-patent document J.A. Lowke, et. al, IEEE Transactions on Plasma Science, 23 (4), 661 (1995), is a graph showing the pulse width dependence of the input energy conversion efficiency used for generating active species. FIG. 22 shows the net active species generation energy efficiency (= the product of “energy input efficiency” in FIG. 20 and “input energy conversion efficiency used for generation of active species” in FIG. 21) according to an exemplary embodiment of the present invention. It is a graph which shows pulse width dependence. FIG. 23 is a graph showing the voltage rise rate (dV / dt) dependence of energy efficiency according to an exemplary embodiment of the present invention. FIG. 24 is a graph showing the current rise rate (di / dt) dependence of energy efficiency according to an exemplary embodiment of the present invention. FIG. 25 shows active species generation shown in FIG. 1 (Non-Patent Document 6 J. Lowke, et.al, IEEE Transactions on Plasma Science, 23 (4), 661 (1995)), according to an exemplary embodiment of the present invention. The dependence of the energy conversion efficiency on the pulse voltage increase rate (dV / dt) is shown. FIG. 26 shows active species generation energy shown in FIG. 1 (Non-Patent Document 6 J. Lowke, et.al, IEEE Transactions on Plasma Science, 23 (4), 661 (1995)), according to an exemplary embodiment of the present invention. The dependence of the conversion efficiency on the pulse current increase rate (di / dt) is shown. FIG. 27 shows a net efficiency proportional to the product of the net energy used to generate the active species and the energy introduced into the reactor, according to an exemplary embodiment of the present invention (the energy input efficiency of FIG. 25 is a graph showing the dependence of the product of active species conversion efficiency on 25) on the pulse voltage increase rate (dV / dt). FIG. 28 shows a net efficiency proportional to the product of the net energy used to generate the active species and the energy introduced into the reactor, according to an exemplary embodiment of the present invention (the energy input efficiency of FIG. 26 is a graph showing the dependence of the product of the active species conversion efficiency at 26 on the pulse current increase rate (di / dt).

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 ... Pulse generation circuit 22 ... Pulse signal generator 23 ... Reaction container 24 ... High voltage pulse train Pc 31 ... Hole plate 32 ... Fan 33 ... Observation window 34 ... Discharge electrode 41 ... Rod counter electrode plug 42 ... Mesh electrode 43 ... Plate electrode DESCRIPTION OF SYMBOLS 81 ... Storage battery 82 ... Engine control device 83 ... Spark plug compatible electrode 84 ... Piston 85 ... Ignition coil 86 ... Cylinder 87 ... Cylinder block 104 ... Secondary winding 105 ... Ignition signal line 106 ... Feed line 107 from storage battery ... Primary Winding 118 ... Spark plug

Claims (13)

  A composite discharge method and a composite discharge apparatus characterized in that a pulse discharge is generated at least once before a main discharge under a negative pressure or a positive pressure.   The combined discharge method and the combined discharge apparatus according to claim 1, wherein the number of pulse discharges set up before the main discharge is arbitrarily controlled.   3. The composite discharge method and the composite discharge apparatus according to claim 1, wherein an interval between pulse discharges set up before the main discharge is arbitrarily controlled.   4. The composite discharge method and composite discharge apparatus according to claim 1, wherein the pulse discharge that is generated before the main discharge is a streamer or a glow discharge.   The composite discharge method and composite discharge apparatus according to claim 1, wherein the main discharge is an arc discharge.   6. The composite discharge method and the composite discharge apparatus according to claim 1, wherein the pulse discharge set up before the main discharge is set up by a pulse electric field having a full width at half maximum of 0.01 μs to 1 μs in the pulse voltage waveform. .   7. The composite discharge method and composite according to claim 1, wherein the pulse discharge that is generated before the main discharge is generated by a pulse electric field having a half-value width of 0.05 μs or more and 0.5 μs or less of a pulse voltage waveform. Discharge device.   8. The composite discharge method and composite according to claim 1, wherein the pulse discharge generated before the main discharge is generated by a pulse electric field having a full width at half maximum of 0.1 μs to 0.2 μs. Discharge device. The voltage increase rate (dV / dt) is 1 × 10 ⁸ [V so that the electrical energy conversion rate converted from the power source to the plasma in the pulse discharge set up before the main discharge is 10% or more or the energy reflection is 90% or less. / S] and 3 × 10 ¹¹ [V / s] or less, or the current increase rate (di / dt) is 1 × 10 ⁶ [A / s] and 3 × 10 ⁷ [A / s] or less. 6. The composite discharge method and the composite discharge apparatus according to claim 1, wherein the plasma is generated with an excellent pulse characteristic.   In the discharge method and the discharge device, a pulse power generation circuit for lowering the step-up ratio of the secondary coil and the reactor component is electrically coupled to the primary side of the step-up coil that supplies high voltage power to the spark plug compatible electrode. The composite discharge method and composite discharge apparatus according to claim 1.   In the discharge method and discharge apparatus, a pulse generation circuit that generates high voltage pulses outside the internal combustion engine by applying it to ignition of an internal combustion engine that burns and explodes combustible gas, and the pulse generation circuit is connected in the internal combustion engine The composite discharge method and the composite discharge apparatus according to claim 1, further comprising a discharge electrode that generates active species of combustible gas.   In the discharge method and the discharge device, a spark plug compatible electrode and a booster coil are arranged in a cylinder of an internal combustion engine that burns and explodes a combustible gas, and a pulse voltage generation circuit is directly connected to the booster coil in the immediate vicinity of the coil. The composite discharge method and composite discharge apparatus according to claim 1.   In the discharge method and the discharge device, a spark plug compatible electrode and a booster coil are disposed in a cylinder of an internal combustion engine that burns and explodes combustible gas, and the booster coil has a high voltage from a common pulse voltage generation circuit installed in the internal combustion engine. 13. The composite discharge method and composite discharge apparatus according to claim 1, wherein pulses are distributed.

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