Real-time ultrasonic atomization system for nanofluid fuel based on shock tube test platform

Abstract

The invention relates to combustion experiment technology, and aims to provide a real-time ultrasonic atomization system for nanofluid fuel based on a shock tube test platform. The system includes a shock tube, and a blind flange with an axial through hole is arranged at the end of the low-pressure section of the shock tube; the ultrasonic atomization head has a conical nozzle part and a cylindrical tail section, and its nozzle part is docked with the through hole; a high-frequency line plug and a liquid inlet are arranged on the end face of the tail section of the ultrasonic atomization head, the former is connected to a driving power supply through a cable, and the latter is located at the end of the atomization channel and connected to a liquid feed pump through a liquid infusion tube. The present invention can save atomization energy consumption and ensure that there are always suspended nanofluid fuel atomized droplets; a common liquid feed pump can be used to complete fuel injection and rate control, and the structure is simple and the versatility is strong. It can be applied to shock tube ignition experiments of different sizes and different requirements, and has strong versatility. It can be applied to most working conditions in shock tube ignition and combustion experiments, and is reliable, efficient and repeatable.

Description

Technical Field

[0001] The patent of this invention relates to the field of combustion experiment technology, and aims to provide a real-time ultrasonic atomization system for nanofluid fuel based on a shock tube test platform. Background Art

[0002] Nanofluid fuels are composed of solid nanometals (aluminum, boron, etc.) and liquid hydrocarbon fuels. They have the advantages of high energy density, low ignition temperature, and high combustion efficiency. They are potential substitutes for liquid engine fuels and have attracted extensive attention from researchers at home and abroad. The study of the ignition and combustion characteristics of nanofluid fuels is related to the energy release and combustion kinetics of the fuel, and is one of the hot topics in the field of aerospace engineering. The ignition delay time is an important representation of the combustion characteristics of nanofluid fuels, and is also an important basis for verifying the chemical kinetic model and simplified model of the combustion reaction. In the field of aerospace engineering applications, the ignition delay of the fuel is an important parameter and basis for the design of aeroengines, and has an important influence on the combustion performance and combustion stability of the combustion chamber of the aeroengine. Therefore, accurate testing of the fuel ignition time is an important prerequisite for conducting fuel combustion research and an important condition for theoretical research on combustion kinetics. Fuel combustion is generally divided into three stages: ignition, flame propagation, and stable combustion. The nanoparticles in nanofluid fuels can shorten the ignition delay of such fuels, making the ignition delay time of nanofluid fuels lower than that of hydrocarbon liquid fuels. However, due to the presence of solid-liquid two-phase substances in such fuels, it also increases the difficulty of measuring the ignition delay time of such fuels.

[0003] The shock tube is one of the main equipment used in the laboratory to measure the ignition delay characteristics of fuels. The pressure difference between the high-pressure section and the low-pressure section breaks the diaphragm to generate incident shock waves and reflected shock waves to uniformly adiabatically heat the fuel non-isentropically, thereby achieving the purpose of heating and igniting the fuel. Because the shock tube has a wide range of measurement parameters, the ignition and combustion characteristic parameters in the required measurement range can be obtained by changing the pressure difference between the high-pressure section and the low-pressure section. Therefore, it is widely used in the experimental study of fuel ignition characteristics in the fields of aerodynamics, chemical reaction kinetics, combustion, and aeroacoustics.

[0004] For hydrocarbon liquid fuels, the ignition and combustion experiments in the shock tube are generally carried out by gasification or atomization, and the liquid is sent into the shock tube. However, for nanofluid fuels, gasification will directly separate the liquid hydrocarbon fuel and the solid nanoparticles, which fundamentally changes the characteristics of the nanofluid, and is obviously not suitable. Therefore, choosing a reasonable atomization method is a prerequisite for the ignition and combustion experiments of nanofluid fuels in the shock tube. Most of the existing technologies use a pressure difference atomization method, and the fuel is first atomized into the shock tube before starting the ignition operation. However, once the atomized mist torch enters the shock tube, the atomized droplets contain a large number of solid nanoparticles. Most of these solid particles have a large density and will quickly settle due to gravity, causing the liquid-solid separation of the nanofluid fuel, which will directly affect the test results of the ignition and combustion characteristics experiment. Since the pressure in the shock tube needs to be stable during the ignition period, it cannot be sprayed in real time and continuously during the ignition experiment (because the differential pressure fluctuation will have an impact). Therefore, how to ensure the existence of stable suspension and uniform particle size distribution of atomized droplets in the shock tube test section and determine the amount of droplet suspension entering the shock tube are key issues in measuring the ignition characteristics of nanofluid fuel shock tubes.

[0005] The problems with current atomization methods are: (1) Differential pressure atomization is not only complex in structure, but also difficult to achieve real-time atomization, and has many errors in shock tube ignition experiments. (2) The premixing method uses a premixing tank to premix the atomized droplets with air, but nanofluid fuel is a solid-liquid two-phase flow fuel and cannot form a stable aerosol like a single-phase hydrocarbon fuel. If it is delivered before the ignition operation, the solid will still settle quickly due to the gravity effect. (3) Other efficient atomization methods, such as electrostatic atomization, can be delivered in real time and have little effect on pressure, but this method consumes a lot of energy. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a nanofluid fuel real-time ultrasonic atomization system based on a shock tube test platform.

[0007] To solve the technical problem, the solution of the present invention is:

[0008] Provided is a nanofluid fuel real-time ultrasonic atomization system based on a shock tube test platform, comprising a shock tube consisting of a high-pressure section, a low-pressure section and a diaphragm; a blind flange is arranged at the end of the low-pressure section, and an axial through hole is provided on the blind flange for installing an ultrasonic atomization head and communicating with the inner cavity of the low-pressure section; the ultrasonic atomization head has a conical nozzle portion and a cylindrical tail section, and a through atomization channel is arranged on its symmetrical central axis, and the radial dimension of the atomization channel has a trend of gradually shrinking from the tail section to the nozzle portion; the ultrasonic atomization head is fixedly mounted on the blind flange, and its nozzle portion is butted with the through hole; a high-frequency line plug and a liquid inlet are arranged on the terminal end face of the tail section of the ultrasonic atomization head, the former is connected to a driving power supply through a cable, and the latter is located at the end of the atomization channel and connected to a liquid feeding pump through a liquid infusion tube.

[0009] In the present invention, the ultrasonic atomizing head is an integrated structure.

[0010] In the present invention, the liquid inlet at the end of the atomization channel is a tubular structure protruding from the surface of the blind flange, and the ultrasonic atomization head is docked in the tubular structure with its nozzle portion.

[0011] In the present invention, the symmetrical central axis of the ultrasonic atomization head is arranged parallel to the central axis of the shock tube, and the ultrasonic atomization head is located above the central axis of the shock tube; assuming that the distance between the two central axes is h and the radius of the radial section of the shock tube is R, then R / 4<h<R / 2.

[0012] In the present invention, a radially contracted connection portion is provided between the nozzle portion and the tail section of the ultrasonic atomizing head; a clamp is provided on the blind flange, and the clamp is embedded in and clamped to fix the ultrasonic atomizing head at the liquid inlet.

[0013] In the present invention, the cable connecting the high-frequency line plug and the driving power supply is a coaxial cable.

[0014] In the present invention, a sealing rubber ring is arranged between the liquid inlet and the nozzle portion of the ultrasonic atomizing head.

[0015] In the present invention, a valve is provided on the infusion tube (to improve the stability of liquid feeding).

[0016] In the present invention, the blind flange is fixed to the flange at the end of the low-pressure section by bolts, and a gasket is arranged between the two (to ensure the sealing effect).

[0017] In the present invention, a plurality of gaskets are arranged between the blind flange and the flange surface at the end of the low-pressure section, and the plane where the blind flange and the flange surface at the end of the low-pressure section are located is tangent (reducing the interference of the nozzle on the flow field in the pipe).

[0018] Compared with the prior art, the technical effects of the present invention are:

[0019] (1) Apply ultrasonic atomization technology to the atomization of nanofluid fuel in the shock tube to save atomization energy.

[0020] (2) Real-time continuous liquid inlet and ultrasonic atomization are used to ensure that there are always suspended nanofluid fuel atomized droplets in the shock tube test section. At the same time, due to the use of ultrasonic atomization, the pressure in the low-pressure section of the shock tube will not change during the continuous flow of the mist torch, and can be synchronized with the ignition operation in real time to ensure the accuracy of the test.

[0021] (3) Because the low-pressure section of the shock tube is generally negative pressure, an ordinary liquid feed pump can be used to complete fuel injection and rate control, which has a simple structure and strong versatility.

[0022] (4) By measuring the settling rate of the atomized droplets in advance and controlling the sampling rate and time by the valve on the liquid delivery tube, the actual suspended amount of the atomized droplets of the nanofluid fuel in the test section in the tube can be determined.

[0023] (5) By changing the blind flange and opening size of the shock tube, it can be applied to shock tube ignition experiments of different sizes and requirements, and has strong versatility.

[0024] (6) It can be well adapted to most working conditions in shock tube ignition and combustion experiments, and is reliable, efficient and repeatable. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a front view of a blind flange;

[0026] FIG2 is a side cross-sectional view of the blind flange in FIG1 ;

[0027] Figure 3 is a cross-sectional view of an ultrasonic atomization head;

[0028] Figure 4 Schematic diagram of the real-time ultrasonic atomization system for the nanofluid fuel.

[0029] Reference numerals in the figure: liquid inlet 1, high-frequency line plug 2, shock tube 3, gasket 4, ultrasonic atomization head 5, blind flange 6, clamp 7, driving power supply 8, liquid feed pump 9, valve 10. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings.

[0031] The real-time ultrasonic atomization system of nanofluid fuel based on the shock tube test platform of the present invention comprises a shock tube 3 composed of a high-pressure section, a low-pressure section and a diaphragm. A blind flange 6 is arranged at the end of the low-pressure section of the shock tube 3, and a through hole is arranged on the blind flange 6, one end of which is connected to the inner cavity of the low-pressure section and the other end is connected to the liquid inlet 1.

[0032] The ultrasonic atomizing head 5 has a conical nozzle part and a cylindrical tail section, with a radially contracted connection part in the middle. An axial atomizing channel is provided on the symmetrical central axis of the ultrasonic atomizing head 5, and its radial dimension has a trend of gradually contracting from the tail section to the nozzle part. A high-frequency line plug 2 and a liquid inlet 1 are provided on the end face of the tail section of the ultrasonic atomizing head 5. The former is connected to the driving power supply 8 through a coaxial cable, and the latter is located at the end of the atomizing channel and connected to the liquid pump 9 through an infusion tube, and a valve 10 is provided on the infusion tube. A clamp 7 (optionally made of stainless steel) is provided on the blind flange 6, and the clamp 7 is embedded and clamped to fix the ultrasonic atomizing head 5 in a manner that the connection part is embedded and clamped; at this time, its nozzle part is docked at the liquid inlet 1. The liquid inlet 1 is a tubular structure protruding from the surface of the blind flange 6, and its orifice shape is consistent with the conical shape of the nozzle part of the ultrasonic atomizing head 5. A sealing rubber ring is provided between the two to reduce wear and increase air tightness. The symmetrical central axis of the ultrasonic atomizing head 5 is arranged parallel to the central axis of the shock tube 3 and is located above the central axis of the shock tube 3. Assuming that the distance between the two central axes is h and the cross-sectional radius of the shock tube 3 is R, then R / 4<h<R / 2. Such a design can ensure that the atomized fuel droplets are suspended for a longer time.

[0033] During processing, the ultrasonic atomizing head 5 preferably adopts an integrated structure, that is, the conical nozzle part and the cylindrical tail section are an integral whole. Figure 3 As shown. Because the ultrasonic atomization device used in the shock tube experiment is very small, the entire ultrasonic atomization head 5 directly has the function of "energy conversion + atomization", and does not need to be separately designed, manufactured and assembled like the ultrasonic atomization device used in industry (larger in size). Normally, the length of the atomization channel is controlled in the range of 10 to 15 cm, and the radial size gradually shrinks from 6 to 8 mm at the tail end to 0.5 to 1.5 mm at the nozzle. Under this size condition, by controlling the power of the driving power supply 8, the size range of the atomized droplets of the nanofluid fuel can be controlled to be 50 to 100 μm.

[0034] During installation, the blind flange is fixed to the flange at the end of the low-pressure section with bolts, and a gasket 4 is arranged between the two to increase air tightness and reduce wear. The optional material of the gasket 4 is graphite or polytetrafluoroethylene. By setting a suitable number of gaskets 4, the top of the nozzle part of the ultrasonic atomizing head 5 is tangent to the plane where the flange surface at the end of the low-pressure section is located to reduce the impact on the flow field in the tube. The driving power supply 8 is used to convert 50Hz alternating current into high-frequency power supply, which is provided to the ultrasonic atomizing head 5 to realize fuel atomization; the liquid supply pump 9 is connected to the ultrasonic atomizing head 5 through a liquid delivery tube with a valve 10, which can control the liquid supply amount and rate.

[0035] Before use, first set the liquid feeding rate of the liquid feeding pump 9, open the valve 10 on the liquid infusion tube while turning on the liquid feeding pump 9, and close the liquid feeding pump 9 and the valve 10 at the same time when the liquid infusion tube is filled with the fuel to be tested; after the low-pressure section of the shock tube 3 is evacuated, first turn on the driving power supply 8 and adjust the appropriate power, then start the liquid feeding pump 9 and open the valve 10 to control the introduction of the atomized fuel. Record the sedimentation time of the atomized droplets with the help of the observation window of the low-pressure section of the shock tube 3, and calibrate the droplet sedimentation rate under different liquid feeding rates.

[0036] During the test, first set the liquid feeding rate of the liquid feeding pump 9, open the valve 10 on the liquid infusion tube while turning on the liquid feeding pump 9, and when the liquid infusion tube is full of the fuel to be tested, close the liquid feeding pump 9 and the valve 10 at the same time; after adjusting the high-pressure section and the low-pressure section of the shock tube 3 to the set working conditions, turn on the driving power supply 8 and adjust it to the specified power; then start the liquid feeding pump 9 and open the valve 10, and the fuel enters the shock tube 3 continuously in real time after ultrasonic atomization, and the shock tube 3 is controlled to break the membrane to complete an ignition characteristic test.

[0037] The driving power supply 8 and the liquid feeding pump 9 in the present invention are available in various models of conventional commercial products. After repeated verification, the ultrasonic atomizing head 5 of the present invention can convert high-frequency electrical energy into mechanical vibration energy, the atomization effect is stable and energy-saving, and the ignition success rate is high and the effect is ideal under various test conditions.

[0038] Although this application has shown and described the embodiments of the patent of the present invention, it is understood by those skilled in the art that various changes, modifications, substitutions and deformations may be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the patent of the present invention is defined by the appended claims and their equivalents.

Claims

1. A nanofluid fuel real-time ultrasonic atomization system based on a shock tube test platform, comprising a shock tube consisting of a high-pressure section, a low-pressure section and a diaphragm; characterized in that: A blind flange is provided at the end of the low-pressure section, and an axial through hole is provided on the blind flange for installing an ultrasonic atomization head and communicating with the inner cavity of the low-pressure section; the ultrasonic atomization head has a conical nozzle portion and a cylindrical tail section, and a through atomization channel is provided on its symmetrical central axis, and the radial dimension of the atomization channel has a trend of gradually shrinking from the tail section to the nozzle portion; the ultrasonic atomization head is fixedly mounted on the blind flange, and its nozzle portion is butt-jointed with the through hole; a high-frequency line plug and a liquid inlet are provided on the terminal end face of the tail section of the ultrasonic atomization head, and the high-frequency line plug is connected to a driving power supply through a coaxial cable, and the liquid inlet is located at the end of the atomization channel and connected to a liquid feeding pump through an infusion tube; The liquid inlet at the end of the atomization channel is a tubular structure protruding from the surface of the blind flange, and the ultrasonic atomization head is docked in the tubular structure with its nozzle portion; A radially contracted connecting portion is provided between the nozzle portion and the tail section of the ultrasonic atomizing head; a clamp is provided on the blind flange, and the clamp is embedded in and clamped to fix the ultrasonic atomizing head at the liquid inlet.

2. The nanofluid fuel real-time ultrasonic atomization system according to claim 1, characterized in that: The ultrasonic atomizing head is an integrated structure.

3. The nanofluid fuel real-time ultrasonic atomization system according to claim 1, characterized in that: The symmetrical central axis of the ultrasonic atomization head is arranged parallel to the central axis of the shock tube, and the ultrasonic atomization head is located above the central axis of the shock tube; assuming that the distance between the two central axes is h and the radius of the radial section of the shock tube is R, then R / 4<h<R / 2.

4. The nanofluid fuel real-time ultrasonic atomization system according to claim 1, characterized in that: A sealing rubber ring is arranged between the liquid inlet and the nozzle portion of the ultrasonic atomizing head.

5. The nanofluid fuel real-time ultrasonic atomization system according to claim 1, characterized in that: Set a valve on the infusion tube.

6. The nanofluid fuel real-time ultrasonic atomization system according to any one of claims 1 to 5, characterized in that: The blind flange is fixed to the flange at the end of the low-pressure section by bolts, with a gasket arranged between the two.

7. The nanofluid fuel real-time ultrasonic atomization system according to claim 6, characterized in that: A plurality of gaskets are arranged between the blind flange and the flange surface at the end of the low-pressure section, and the top of the nozzle of the ultrasonic atomizing head is tangent to the plane where the flange surface at the end of the low-pressure section is located.

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