CN110905688B

CN110905688B - Device for improving working frequency of pulse detonation engine by using non-combustible liquid

Info

Publication number: CN110905688B
Application number: CN201910982176.4A
Authority: CN
Inventors: 范玮; 孙田雨; 赵明皓; 王可; 宋尔壮
Original assignee: Northwestern Polytechnical University
Current assignee: Northwestern Polytechnical University
Priority date: 2019-10-16
Filing date: 2019-10-16
Publication date: 2021-06-11
Anticipated expiration: 2039-10-16
Also published as: CN110905688A

Abstract

The invention provides a device for improving the working frequency of a pulse detonation engine by using non-flammable liquid, which comprises a liquid injection system, a fuel and oxidant supply system, a detonation tube, an ignition device and a system control method. The liquid jetting control system and the pressure atomizing nozzle are respectively positioned at the outer side and the geometric center of the thrust wall of the detonation tube, and the spraying half cone angle of the nozzle is equal to the included angle between the valveless fuel and oxidant supply channel and the positive direction of the detonation tube shaft; the liquid injection pressure must be higher than the pressure of the detonation platform area in the engine and the reactant supply pressure; the liquid injection amount required by each cycle is calculated by the equivalent steam layer thickness required under different pressure working conditions. The invention realizes the isolation between the high-temperature burned product and the next circulating reactant when the pulse detonation engine works at high frequency by means of the evaporation heat absorption and the expansion of the non-flammable liquid, avoids the problem of the reduction of the detonation performance caused by the dilution of the reactants by the traditional nitrogen isolation, and improves the working frequency and the performance of the engine.

Description

Device for improving working frequency of pulse detonation engine by using non-combustible liquid

Technical Field

The invention relates to the technical field of pulse detonation engines, in particular to a device for improving the working frequency of a pulse detonation engine by using non-flammable liquid.

Background

A Pulse Detonation Engine (PDE) is a power device which obtains thrust by using high-temperature and high-pressure gas generated by Pulse Detonation waves. The average thrust of the PDE per unit time is approximately proportional to the operating frequency, and therefore achieving high frequency operation of the PDE is important to improve the thrust of the engine.

The filling of the explosive mixture takes a significant amount of time during one operating cycle of the PDE. Currently, methods for increasing the operating frequency of a PDE by speeding up the filling can be divided into two categories: firstly, the rotary valve and the pneumatic valve which can realize large-flow high-frequency stable filling are developed, secondly, reactants are supplied without the valve, and the stable work of PDE is realized only by controlling the ignition time sequence. The second method can realize higher working frequency, but the high-frequency PDE adopting the second method can only work under the dilution of isolation gas (such as nitrogen, argon, helium and the like). The introduction of the inert diluent gas reduces the Detonation performance of the explosive mixture, so that the time and distance for Transition from slow combustion to Detonation Transition (DDT) are increased, and the improvement of PDE performance and frequency are seriously influenced.

Disclosure of Invention

Technical problem to be solved

Stable operation at higher frequencies can be achieved with a PDE with a valveless feed scheme, but under currently available technology conditions, PDEs employing this scheme must operate under dilution with barrier gases (e.g., nitrogen, argon, helium, etc.). The detonation performance of the diluted explosive mixture is reduced, and the DDT time and distance are increased, so that the working frequency and the propulsion performance of the PDE are influenced. To overcome these deficiencies, the present invention proposes a device for increasing the operating frequency of a pulse detonation engine using a non-combustible liquid. The device isolates high-temperature burned products and unburned explosive reactants by injecting non-combustible liquid drops into the PDE, accelerates the discharge of the high-temperature burned products in the last detonation working cycle by utilizing the characteristics of heat absorption and volume expansion when the liquid is vaporized at high temperature, and enables the temperature of the head of the PDE to be quickly reduced to the temperature required by the reactant filling process, so that the circulating working period of the PDE is shortened, and the working frequency of the PDE is improved. At the same time, this method avoids the engine performance degradation caused by dilution of the unburned explosive mixture with the insulating gas.

Technical scheme

The technical scheme of the invention is as follows:

the device for improving the working frequency of the pulse detonation engine by using the non-flammable liquid is shown in figure 1, and is characterized in that: the device consists of a liquid injection system, a fuel and oxidant supply system, a detonation tube and an ignition device. The liquid injection system consists of a liquid injection control system (1) and a high-performance pressure atomizing nozzle (2); the fuel and oxidant supply system consists of a fuel valveless supply channel (3) and an oxidant valveless supply channel (4); one end of the detonation tube (5) is closed, and the other end of the detonation tube is open, wherein the closed end is an upstream end, and the open end is a downstream end; the liquid injection control system (1) is positioned on the outer side of a thrust wall of the detonation tube (5); the high-performance pressure atomizing nozzle (2) is positioned at the geometric center of a thrust wall of the detonation tube, and the non-flammable liquid passes through a flow channel of the upstream liquid injection control system (1) and is sprayed into the detonation tube (5) through the high-performance pressure atomizing nozzle (2); the fuel valveless supply channel (3) and the oxidant valveless supply channel (4) are communicated with the detonation tube (5), and are symmetrically distributed about the central axis of the detonation tube (5), and the included angle between the fuel valveless supply channel and the oxidant valveless supply channel and the positive direction (from upstream to downstream) of the central axis of the detonation tube (5) is 30-45 degrees; the inner diameters of the fuel valveless supply channel (3) and the oxidant valveless supply channel (4) are half of the inner diameter of the detonation tube (5), the inner side walls of the two channels are virtually extended towards the interior of the detonation tube (5), so that an intersection surface can be obtained, and the intersection point of the intersection surface and the central axis of the detonation tube (5), which is close to the upstream, is superposed with the outlet position of the high-performance pressure atomizing nozzle (2); the ignition device (6) is located at the downstream of the fuel and oxidant valveless supply channel and is fastened on the wall surface of the detonation tube (5) through a thread structure.

The device for improving the working frequency of the pulse detonation engine by using the non-flammable liquid is shown in figure 1, and is characterized in that: the spray half cone angle of the high-performance pressure atomizing nozzle (2) is equal to the included angle between the fuel valveless supply channel (3) and the positive direction (from upstream to downstream) of the central axis of the detonation tube (5); the average evaporation time of liquid drops sprayed by the liquid spraying system when the engine works is less than 0.4 ms; the single injection quantity of the high-performance pressure atomizing nozzle (2) under different working frequencies is kept unchanged.

The device for improving the working frequency of the pulse detonation engine by using the non-flammable liquid is shown in figure 1, and is characterized in that: injecting normal-temperature non-combustible liquid drops into the head of the pulse detonation engine through a high-performance pressure atomizing nozzle (2), and mutually isolating a high-temperature burned product of the previous detonation working cycle and an unburned and combustible reactant of the next detonation working cycle; the characteristics of heat absorption and volume expansion of liquid during high-temperature vaporization are utilized to accelerate the discharge of high-temperature burned products in the previous detonation working cycle, so that the temperature of the head of the pulse detonation engine is more quickly reduced to the temperature required by the reactant filling process in the next detonation working cycle, the cycle working period of the pulse detonation engine is shortened, and the working frequency of the engine is improved.

The control method of the device for improving the working frequency of the pulse detonation engine by using the non-combustible liquid is characterized in that as shown in figures 1 and 2: firstly, filling fuel and oxidant into a detonation tube (5) through a fuel valveless supply channel (3) and an oxidant valveless supply channel (4); when the filling process is close to the end, the liquid injection control system (1) controls the nozzle (2) to start injecting normal-temperature non-combustible liquid drops into the detonation tube (5); after a certain amount of liquid drops are injected, carrying out ignition by using an ignition device (6) for one time, and continuously injecting the liquid drops; the detonation wave and the detonation wave are respectively propagated downstream and upstream in the detonation tube (5), when the detonation wave is propagated to the inlet positions of the fuel valveless supply channel (3) and the oxidant valveless supply channel (4), a high-temperature high-pressure region with pressure higher than the supply pressure of the fuel and the oxidant is formed, the valveless filling process of the fuel and the oxidant is stopped, and meanwhile, the liquid injection control system (1) controls the nozzle (2) to stop injecting; after the detonation wave and the detonation wave sweep through the incombustible liquid, the liquid is evaporated into gas and expanded by the high temperature after the detonation wave and the detonation wave, and high-temperature burnt products are pushed to be discharged to a downstream open end; because the evaporation process absorbs heat, the temperature of the combustion products close to the upstream closed end of the detonation tube (5) is reduced, and the gas after the non-flammable liquid is evaporated forms a relatively low-temperature region, and the region isolates the high-temperature combustion products of the previous detonation working cycle from the explosive reactants of the next detonation working cycle; as the exhaust process progresses, the pressure at the upstream closed end of the detonation tube (5) is gradually reduced, when the pressure is reduced to be lower than the supply pressure of the fuel and the oxidant, the fuel valveless supply channel (3) and the oxidant valveless supply channel (4) start to fill the detonation tube (5) with the fuel and the oxidant, and the engine enters the next cycle.

The control method of the device for improving the working frequency of the pulse detonation engine by using the non-combustible liquid is characterized in that as shown in figure 2: the non-flammable liquid injection pressure of the liquid injection system must be higher than the detonation platform area pressure and the fuel and oxidant supply pressure in the engine, while also meeting the above requirements for average droplet evaporation time.

The control method of the device for improving the working frequency of the pulse detonation engine by using the non-combustible liquid is characterized by comprising the following steps of: the liquid amount required to be injected in each cycle of the detonation tube (5) is calculated by the equivalent steam layer thickness required under different pressure working conditions; the time for starting the droplet injection can be calculated by using the amount of liquid to be injected per cycle, in combination with the flow rate of the liquid injection system and the time for ending the non-combustible droplet injection.

The device for improving the working frequency of the pulse detonation engine by using the non-flammable liquid is characterized in that: the upper limit of the working frequency of the pulse detonation engine adopting the device only depends on the lower limit of three conditions of the size of the detonation tube (5), the working frequency of the ignition device (6) and the working frequency of the liquid injection system which are independent of each other.

Advantageous effects

Compared with the traditional pulse detonation engine, the invention has the advantages that high-pressure nitrogen and a precise rotary valve are not used, incombustible liquid drops are injected into the PDE to isolate high-temperature burned products and unburned explosive reactants, the discharge of the high-temperature burned products in the previous detonation working cycle is accelerated by utilizing the characteristics of heat absorption and volume expansion during high-temperature vaporization of liquid, the temperature of the head of the PDE is quickly reduced to the temperature required in the reactant filling process, the cycle working period of the PDE is shortened, and the working frequency of the PDE is improved. Meanwhile, the method avoids the problems of decreased detonation performance, increased DDT time and distance and the like caused by dilution of unburned explosive mixture by the isolation gas, and reduces the volume and complexity of a PDE supply system.

Drawings

FIG. 1: detonation tube structure schematic diagram with non-flammable liquid injection device

FIG. 2 is a drawing: control sequence diagram of pulse detonation engine with non-combustible liquid injection device

FIG. 3: detonation tube pressure time-dependent curve in pulse detonation engine with non-combustible liquid injection device

The aboveIn the figure, (1) is a liquid injection control system, (2) is a high-performance pressure atomizing nozzle, (3) is a fuel valveless supply channel, (4) is an oxidant valveless supply channel, (5) is a detonation tube, (6) is an ignition device, (t) is a fuel-free valve supply channel, (3) is a fuel-free valve supply channel, and_start) Is the start time of the non-flammable droplet injection, (t)_stop) At the end of the injection of the non-combustible droplet (Δ t)_inj) Duration of non-combustible droplet injection, (p)_f) Is the supply pressure of the fuel, (p)_o) Is the supply pressure of the oxidizing agent, (p)_CJ) C-J knock pressure for this condition.

Detailed Description

The invention will now be further described with reference to specific embodiments and drawings in which:

a device for improving the working frequency of a pulse detonation engine by using non-combustible liquid is shown in figure 1 and comprises a liquid injection system, a fuel and oxidant supply system, a detonation tube and an ignition device. The liquid injection system consists of a liquid injection control system (1) and a high-performance pressure atomizing nozzle (2); the fuel and oxidant supply system consists of a fuel valveless supply channel (3) and an oxidant valveless supply channel (4); one end of the detonation tube (5) is closed, and the other end of the detonation tube is open, wherein the closed end is an upstream end, and the open end is a downstream end; the liquid injection control system (1) is positioned on the outer side of a thrust wall of the detonation tube (5); the high-performance pressure atomizing nozzle (2) is positioned at the geometric center of a thrust wall of the detonation tube, and the non-flammable liquid passes through a flow channel of the upstream liquid injection control system (1) and is sprayed into the detonation tube (5) through the high-performance pressure atomizing nozzle (2); the fuel valveless supply channel (3) and the oxidant valveless supply channel (4) are communicated with the detonation tube (5), and are symmetrically distributed about the central axis of the detonation tube (5), and the included angle between the fuel valveless supply channel and the oxidant valveless supply channel and the positive direction (from upstream to downstream) of the central axis of the detonation tube (5) is 30-45 degrees; the inner diameters of the fuel valveless supply channel (3) and the oxidant valveless supply channel (4) are half of the inner diameter of the detonation tube (5), the inner side walls of the two channels are virtually extended towards the interior of the detonation tube (5), so that an intersection surface can be obtained, and the intersection point of the intersection surface and the central axis of the detonation tube (5), which is close to the upstream, is superposed with the outlet position of the high-performance pressure atomizing nozzle (2); the ignition device (6) is located at the downstream of the fuel and oxidant valveless supply channel and is fastened on the wall surface of the detonation tube (5) through a thread structure. The spray half cone angle of the high-performance pressure atomizing nozzle (2) is equal to the included angle between the fuel valveless supply channel (3) and the positive direction (from upstream to downstream) of the central axis of the detonation tube (5); the average evaporation time of liquid drops sprayed by the liquid spraying system when the engine works is less than 0.4 ms; the single injection quantity of the high-performance pressure atomizing nozzle (2) under different working frequencies is kept unchanged.

A method for controlling a device for increasing the operating frequency of a pulse detonation engine by using a non-flammable liquid, as shown in fig. 1 and 2, can be specifically expressed as follows: using ethylene as fuel, oxygen as oxidant, water as liquid barrier medium, ignition with a spark plug, using the control sequence shown in fig. 2; after the device is checked to be correct, firstly, filling fuel and oxidant into a detonation tube (5) through a fuel valveless supply channel (3) and an oxidant valveless supply channel (4) at the pressure of 0.3-0.5 MPa, wherein the equivalence ratio of a combustible mixture is 1.0; towards the end of the filling process, i.e. (t)_start) At the moment, the liquid injection control system (1) controls the nozzle (2) to start injecting water in a liquid drop shape to the detonation tube (5) at high pressure, and the injection pressure is set to be 7MPa and is far higher than the pressure (about 1.14MPa) of a detonation platform area and the supply pressure of fuel and oxidant; after about 0.9ms of droplet injection, carrying out primary ignition by using an ignition device (6), and continuing to inject the droplet; the detonation wave and the detonation wave are respectively propagated to the downstream and the upstream in the detonation tube (5), about 0.08-0.1 ms after ignition, the detonation wave is propagated to the inlet positions of the fuel valveless supply channel (3) and the oxidant valveless supply channel (4) to form a high-temperature high-pressure area with the pressure higher than the supply pressure of the fuel and the oxidant, so that the valveless filling process of the fuel and the oxidant is stopped, and the moment is (t) the moment is_stop) At the moment, the liquid injection control system (1) controls the nozzle (2) to stop injecting, and the duration (delta t) of the injection of the incombustible liquid drops_inj) About 1 ms; liquid water in the area where the detonation wave and the detonation wave pass is evaporated into vapor with larger volume due to high temperature, and high-temperature burned products are pushed to be discharged to the downstream open end; as a result of the heat absorption of the evaporation process, the temperature of the burnt products near the upstream closed end of the detonation tube (5) is reduced, where a phase is formedFor a low temperature region, the equivalent saturated water vapor layer thickness calculated by the pressure of the detonation platform region is about 40mm, and the region isolates high-temperature burned products of the previous detonation work cycle from unburned explosive reactants of the next detonation work cycle; the pressure at the upstream closed end of the detonation tube (5) is gradually reduced along with the progress of the exhaust process, when the pressure is reduced to be lower than the supply pressure of the fuel and the oxidant, the fuel valveless supply channel (3) and the oxidant valveless supply channel (4) start to fill the detonation tube (5) with the fuel and the oxidant, and the engine enters the next cycle period. The liquid amount required to be injected in each cycle of the detonation tube (5) is calculated by the equivalent steam layer thickness required under different pressure working conditions; using the quantity of liquid injected per cycle, combining the flow rate of the liquid injection system with the time (t) at which the injection of said non-combustible drops ends_stop) The time (t) at which droplet ejection begins can be calculated_start). The upper limit of the working frequency of the pulse detonation engine adopting the method only depends on the lower limit of three conditions of the size of the detonation tube (5), the working frequency of the ignition device (6) and the working frequency of the liquid injection system which are independent of each other.

FIG. 3 is a graph of detonation tube pressure versus time in a pulse detonation engine with a non-combustible liquid injection device operating at a frequency of 300Hz which is much higher than the operating frequency of current conventional PDEs; in fig. 3, the x axis uses the thrust wall of the detonation tube (5) as an origin, the direction pointing to the downstream along the central axis of the tube is used as a positive direction, and piezoelectric pressure sensors corresponding to the upper curve and the lower curve are respectively placed on the wall surfaces at the positions where x is 230mm and 260 mm. In the figure (p)_CJ) C-J detonation pressure (3.27MPa) at atmospheric ambient conditions for an undiluted ethylene-oxygen mixture. After the influence of the temperature drift of the piezoelectric pressure sensor is eliminated, the pressure measured by the experiment is consistent with the C-J detonation pressure, which shows that the device successfully avoids the detonation performance reduction caused by dilution of unburned explosive mixture by the isolation gas, and improves the working frequency and the performance of the PDE.

Claims

1. A device for improving the working frequency of a pulse detonation engine by utilizing non-combustible liquid is characterized in that: the device consists of a liquid injection system, a fuel and oxidant supply system, a detonation tube and an ignition device; the liquid injection system consists of a liquid injection control system (1) and a high-performance pressure atomizing nozzle (2); the fuel and oxidant supply system consists of a fuel valveless supply channel (3) and an oxidant valveless supply channel (4); one end of the detonation tube (5) is closed, and the other end of the detonation tube is open, wherein the closed end is an upstream end, and the open end is a downstream end; the liquid injection control system (1) is positioned on the outer side of a thrust wall of the detonation tube (5); the high-performance pressure atomizing nozzle (2) is positioned at the geometric center of a thrust wall of the detonation tube (5), and the non-flammable liquid is sprayed into the detonation tube (5) through the high-performance pressure atomizing nozzle (2) through a flow channel of the upstream liquid injection control system (1); the fuel valveless supply channel (3) and the oxidant valveless supply channel (4) are communicated with the detonation tube (5), and are symmetrically distributed about the central axis of the detonation tube (5), and the included angle between the fuel valveless supply channel and the oxidant valveless supply channel and the positive direction (from upstream to downstream) of the central axis of the detonation tube (5) is 30-45 degrees; the inner diameters of the fuel valveless supply channel (3) and the oxidant valveless supply channel (4) are half of the inner diameter of the detonation tube (5), the inner side walls of the two channels are virtually extended towards the interior of the detonation tube (5), so that an intersection surface can be obtained, and the intersection point of the intersection surface and the central axis of the detonation tube (5), which is close to the upstream, is superposed with the outlet position of the high-performance pressure atomizing nozzle (2); the ignition device (6) is located at the downstream of the fuel and oxidant valveless supply channel and is fastened on the wall surface of the detonation tube (5) through a thread structure.

2. The apparatus of claim 1, wherein the means for increasing the frequency of operation of the pulse detonation engine comprises means for increasing the frequency of operation of the pulse detonation engine with a non-combustible liquid, wherein: the spray half cone angle of the high-performance pressure atomizing nozzle (2) is equal to the included angle between the fuel valveless supply channel (3) and the positive direction (from upstream to downstream) of the central axis of the detonation tube (5); the average evaporation time of liquid drops sprayed by the liquid spraying system when the engine works is less than 0.4 ms; the single injection quantity of the high-performance pressure atomizing nozzle (2) under different working frequencies is kept unchanged; the injection pressure of the liquid injection system must be higher than the pressure of the detonation platform region and the supply pressure of the fuel and oxidant in the engine.

3. The apparatus of claim 1, wherein the means for increasing the frequency of operation of the pulse detonation engine comprises means for increasing the frequency of operation of the pulse detonation engine with a non-combustible liquid, wherein: injecting normal-temperature non-combustible liquid drops into the head of the pulse detonation engine through a high-performance pressure atomizing nozzle (2), and mutually isolating a high-temperature burned product of the previous detonation working cycle and an unburned and combustible reactant of the next detonation working cycle; the characteristics of heat absorption and volume expansion of liquid during high-temperature vaporization are utilized to accelerate the discharge of high-temperature burned products in the previous detonation working cycle, so that the temperature of the head of the pulse detonation engine is more quickly reduced to the temperature required by the reactant filling process in the next detonation working cycle, the cycle working period of the pulse detonation engine is shortened, and the working frequency of the engine is improved.

4. The apparatus of claim 1, wherein the means for increasing the frequency of operation of the pulse detonation engine comprises means for increasing the frequency of operation of the pulse detonation engine with a non-combustible liquid, wherein: firstly, filling fuel and oxidant into a detonation tube (5) through a fuel valveless supply channel (3) and an oxidant valveless supply channel (4); when the filling process is close to the end, the liquid injection control system (1) controls the nozzle to start injecting normal-temperature non-combustible liquid drops into the detonation tube (5); after a certain amount of liquid drops are injected, carrying out ignition by using an ignition device (6) for one time, and continuously injecting the liquid drops; the detonation wave and the detonation wave are respectively propagated downstream and upstream in the detonation tube (5), when the detonation wave is propagated to the inlet positions of the fuel valveless supply channel (3) and the oxidant valveless supply channel (4), a high-temperature high-pressure area with pressure higher than the supply pressure of the fuel and the oxidant is formed, the valveless filling process of the fuel and the oxidant is stopped, and meanwhile, the liquid injection control system (1) controls the nozzle to stop injecting; after the detonation wave and the detonation wave sweep through the incombustible liquid, the liquid is evaporated into gas and expanded by the high temperature after the detonation wave and the detonation wave, and high-temperature burnt products are pushed to be discharged to a downstream open end; because the evaporation process absorbs heat, the temperature of the combustion products close to the upstream closed end of the detonation tube (5) is reduced, and the gas after the non-flammable liquid is evaporated forms a relatively low-temperature region, and the region isolates the high-temperature combustion products of the previous detonation working cycle from the explosive reactants of the next detonation working cycle; the pressure of the upstream closed end of the detonation tube (5) is gradually reduced along with the progress of the exhaust process, when the pressure is reduced to be lower than the supply pressure of the fuel and the oxidant, the fuel valveless supply channel (3) and the oxidant valveless supply channel (4) start to fill the detonation tube (5) with the fuel and the oxidant, and the engine enters the next cycle period; the liquid amount required to be injected in each cycle of the detonation tube (5) is calculated by the equivalent steam layer thickness required under different pressure working conditions; the duration of droplet jetting in each cycle is calculated by the liquid amount required to be jetted and the flow of a liquid jetting system; the moment at which droplet ejection starts is calculated from the duration of the ejection and the end of the ejection.

5. The apparatus of claim 1, wherein the means for increasing the frequency of operation of the pulse detonation engine comprises means for increasing the frequency of operation of the pulse detonation engine with a non-combustible liquid, wherein: the upper limit of the working frequency of the pulse detonation engine adopting the device only depends on the lower limit of three conditions of the size of the detonation tube (5), the working frequency of the ignition device (6) and the working frequency of the liquid injection system which are independent of each other.