CN110274801B - Isokinetic sampling pipe, sampling method and fuel concentration measuring system - Google Patents
Isokinetic sampling pipe, sampling method and fuel concentration measuring system Download PDFInfo
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- CN110274801B CN110274801B CN201910624764.0A CN201910624764A CN110274801B CN 110274801 B CN110274801 B CN 110274801B CN 201910624764 A CN201910624764 A CN 201910624764A CN 110274801 B CN110274801 B CN 110274801B
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- G01—MEASURING; TESTING
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- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/02—Devices for withdrawing samples
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- G01N1/2247—Sampling from a flowing stream of gas
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N25/20—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity
- G01N25/22—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity on combustion or catalytic oxidation, e.g. of components of gas mixtures
- G01N25/40—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity on combustion or catalytic oxidation, e.g. of components of gas mixtures the heat developed being transferred to a flowing fluid
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Abstract
The utility model relates to an isokinetic sampling pipe for to the gas sampling in the aeroengine combustion chamber, include: a sampling head; the first end of the gas guide pipe is used for mounting the sampling head, the second end of the gas guide pipe is connected to a gas collecting device, and a bending part is arranged in the area of the gas guide pipe close to the first end so that the first end and the second end form a set angle; the outer tube is sleeved outside the air guide tube; the conical head is sleeved on the sampling head and close to one end of the air guide pipe, and is detachably connected with the outer pipe; and the middle layer is arranged between the air guide tube and the outer tube and can support and heat the air guide tube. According to the isokinetic sampling pipe provided by the embodiment of the disclosure, the fuel concentration in the combustion chamber of the aircraft engine can be measured at least conveniently and accurately.
Description
Technical Field
The present disclosure belongs to the field of gas component analysis of an aircraft engine combustor, and particularly relates to an isokinetic sampling tube according to the preamble of claim 1, a sampling method according to the preamble of claim 9, and a fuel concentration measuring system according to the preamble of claim 11.
Background
The method for measuring the fuel concentration distribution in the combustion chamber of the aero-engine has important significance for further analyzing the combustion performance. At present, two methods, namely a spectroscopic measurement method and a sampling method, are mainly used for measuring the fuel concentration distribution.
The measurement of the fuel concentration distribution by the photometry has two main problems, one of which is that it is difficult to obtain the concentration distribution of the gas phase and the liquid phase at the same time, and usually only the concentration of the gas phase or the liquid phase can be measured; secondly, it is difficult to determine the corresponding relationship between the optical signal and the concentration distribution quantitatively, and the concentration distribution is usually characterized qualitatively according to the intensity of the optical signal.
Compared with the optical method, the sampling method can simultaneously collect gasified fuel oil and liquid oil mist, and the fuel oil concentration in the sampled gas can be quantitatively measured by using the corresponding gas analyzer, so that the two short plates of the optical method are effectively compensated. The sampling method has the key points that: not only needs to accurately collect local gas-liquid two-phase fuel oil, but also needs to reduce the interference of a sampling system to a flow field as much as possible.
The isokinetic sampling pipe basically maintains the idea that the original streamline enters a sampling area based on the gaseous fuel oil and the liquid oil mist, guarantees the authenticity of a sampling result by enabling the sampling speed to be equal to the local flow speed of a sampling point, reduces the flow field interference on the upstream of a sampling probe by virtue of the reasonable design of the sampling gas flow and the sampling pipe structure, and better deals with two main points of the sampling method.
However, for an aircraft engine combustor, the related isokinetic sampling tube is limited by the following defects, and is difficult to be applied to a high-speed and high-temperature working environment:
(1) sampling speed: the existing isokinetic sampling pipe is mainly designed aiming at environmental protection and industrial control, is only suitable for sampling smoke under the working conditions of low speed and normal temperature, and has the allowed maximum sampling speed of about 1m/s, while the flow velocity magnitude in the environment of an aeroengine combustion chamber can reach 10-100 m/s;
(2) interference with the flow field: the minimum inner diameter of the head part of a sampling probe of the existing isokinetic sampling tube is 4mm, the cross section area can generate larger interference to a flow field for an aeroengine combustion chamber flowing at a high speed, and the strength problem can be caused by the impact of high-speed incoming flow by simply scaling the existing isokinetic sampling tube to reduce the cross section area of the head part of the probe;
(3) temperature of the pipeline: the existing pipeline heating design of the equipower sampling pipe mainly aims at preventing water vapor in flue gas from condensing, adopts a heat tracing pipe for heating, and the maximum bearing temperature is generally 200 ℃. The boiling range of the aviation kerosene can reach about 300 ℃.
Disclosure of Invention
In view of this, the embodiments of the present disclosure provide an isokinetic sampling tube and a fuel concentration measurement system, thereby facilitating accurate measurement of fuel concentration in an aircraft engine combustion chamber.
In one aspect of the present disclosure, an isokinetic sampling tube is provided for sampling gas in a combustion chamber of an aircraft engine, comprising:
a sampling head;
the first end of the gas guide pipe is used for mounting the sampling head, the second end of the gas guide pipe is connected to a gas collecting device, and a bending part is arranged in the area of the gas guide pipe close to the first end so that the first end and the second end form a set angle;
the outer tube is sleeved outside the air guide tube;
the conical head is sleeved on the sampling head and close to one end of the air guide pipe, and is detachably connected with the outer pipe; and
the middle layer is arranged between the air guide tube and the outer tube and can support and heat the air guide tube.
In some embodiments, the intermediate layer comprises:
at least one heating wire; and
the corundum support sheet is provided with a central hole and at least one outer hole along the thickness direction, the central hole is used for penetrating through the air guide pipe, and the at least one outer hole is used for penetrating through the at least one electric heating wire.
In some embodiments, the corundum support plate has a cylindrical structure, and the upper bottom surface and the lower bottom surface of the cylindrical structure are parallel to each other;
the multiple corundum supporting sheets are arranged at the bending part of the air duct, any two adjacent corundum supporting sheets in the multiple corundum supporting sheets are arranged between the air duct and the outer tube in an abutting mode of adjacent end surfaces, and are fastened and limited by pressing devices respectively arranged at the first end and the second end of the air duct.
In some embodiments, the intermediate layer further comprises:
the corundum insulating sheet is provided with a center hole along the thickness direction and used for penetrating through the air guide pipe, and the corundum insulating sheet is arranged between the pressing device and the corundum supporting sheet and used for preventing the electric heating wire from conducting outwards.
In some embodiments, the outer tube has an internal thread on its inner surface near the second end of the airway tube, and a guide groove is formed along the length direction of the outer tube, and the compressing device disposed at the second end of the airway tube includes:
the compression bolt is detachably assembled with the internal thread and is provided with a central hole for leading out the air guide pipe;
the guide gasket is arranged at one end of the compression bolt close to the corundum support sheet, is provided with a central hole for penetrating the air guide pipe and an outer hole for penetrating the electric heating wire, and can be matched with the guide groove through a guide pin arranged along the radial direction to provide circumferential positioning for the outer hole; and
the first fastening screw is arranged at the nut part of the compression bolt along the radial direction and can be used for jacking and limiting the air guide pipe arranged in the central hole of the compression bolt by screwing in the compression bolt.
In some embodiments, the tapered head is connected to the airway tube by a thread seal, and the compressing device disposed at the first end of the airway tube includes:
and the second fastening screw is used for fastening the conical head and the outer pipe after the conical head and the bent part of the outer pipe are sleeved.
In some embodiments, the inner diameter of the sampling head is 1mm, the sampling head is welded to the conical head, and the sampling head extends out of the range of the conical head.
In some embodiments, the isokinetic sampling tube further comprises:
the static pressure pipe is composed of a radial hole arranged on the conical head and a wall surface hole arranged on the gas guide pipe, wherein the wall surface hole and the radial hole have the same diameter and are coaxial; and
the pitot tube is fixedly arranged on one side of the outer tube through a clamp and has the same air inlet direction as the sampling head.
In another aspect of the present disclosure, there is provided a sampling method, wherein the isokinetic sampling tube described in any one of the above is used, the sampling method comprising:
in the sampling process, the static pressure tube is used for measuring the sampling static pressure of the sampling airflow in the air guide tube, the pitot tube is used for measuring the local total pressure and the local static pressure of the sampling head, and the sampling flow of the sampling head is adjusted according to the balance relation between the sampling static pressure and the local static pressure, so that the isokinetic sampling of the sampling tube is realized; and
and in the calibration process, the influence of total pressure loss between the sampling head and the static pressure hole on the balance relation between the sampling static pressure and the local static pressure is considered when the sampling flow of the sampling pipe is adjusted.
In some embodiments, the calibration process comprises:
m1, recording local total pressure, local static pressure and sampling static pressure under different sampling flow rates at a set incoming flow speed, calculating the sampling speed in the air duct according to the flow area of the air duct and the sampling static pressure, and calculating the local speed of the sampling head according to the local total pressure and the local static pressure;
m2, changing the sampling flow of the sampling pipe, and recording the sampling speed and the pressure reduction difference value of the local static pressure and the sampling static pressure when the sampling speed is equal to the local speed; and
m3, changing the set incoming flow speed, repeating the M2 step, and establishing a functional relation between the sampling speed and the static pressure difference value;
the sampling step comprises the following steps:
n1, calculating a local speed according to the local total pressure and the local static pressure measured by the pitot tube, and searching a static pressure difference value corresponding to the sampling speed which is the same as the local speed according to the functional relation in the M3 step on the basis of the local speed;
and N2, incorporating the static pressure difference value obtained in the N1 step into a balance relation calculation process of the sampled static pressure and the local static pressure, and adjusting the sampling flow of the sampling head based on the balance relation.
In another aspect of the present disclosure, there is provided a fuel concentration measurement system comprising an isokinetic sampling tube according to any of the preceding claims, the measurement system further comprising:
an air source;
the inlet of the catalytic combustion device is connected with the outlet of the isokinetic sampling pipe and the air source and is used for enabling the fuel gas to be sampled and combusted with air under the catalytic condition; and
and the tail gas analysis device is connected to the outlet of the catalytic combustion device and is used for analyzing the tail gas combusted under the catalytic condition.
In some embodiments, the measurement system further comprises:
the air pump is used for controlling the flow of the air source;
a vacuum pump for controlling the intake flow rate of the exhaust gas analysis device;
a first flow meter for measuring a flow rate of the air source;
a second flow meter for measuring an intake air flow rate of the exhaust gas analysis device; and
and the controller is in communication connection with the air pump, the vacuum pump, the first flow meter and the second flow meter and can respectively control the opening degrees of the air pump and the vacuum pump based on the measurement values of the first flow meter and the second flow meter.
In some embodiments, the catalytic combustion device comprises a vacuum furnace, the measurement system further comprising:
the first temperature sensor is used for measuring the temperature of the sampling area of the isokinetic sampling pipe; and
a second temperature sensor for measuring a temperature of the vacuum furnace;
the controller is in communication connection with the first temperature sensor, the second temperature sensor, the isokinetic sampling pipe and the vacuum furnace;
the controller is further configured to: the heating power of the isokinetic sampling tube and the combustion power of the vacuum furnace can be controlled according to the measured values based on the first temperature sensor and the second temperature sensor.
Therefore, the isokinetic sampling pipe, the sampling method and the fuel concentration measuring system provided by the embodiment of the disclosure can at least facilitate accurate measurement of the fuel concentration in the combustion chamber of the aircraft engine.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description, serve to explain the principles of the disclosure.
The present disclosure may be more clearly understood from the following detailed description, taken with reference to the accompanying drawings, in which:
FIG. 1 is a schematic cross-sectional structural view of an isokinetic sampling tube according to some embodiments of the present disclosure;
FIG. 2 is a schematic diagram of a connection configuration of a fuel concentration measurement system according to some embodiments of the present disclosure;
FIG. 3 is a schematic view of an installation configuration of an isokinetic sampling tube according to some embodiments of the present disclosure;
FIG. 4 is a schematic representation of an outer tube isometric configuration of an isokinetic sampling tube according to some embodiments of the present disclosure;
FIG. 5 is a schematic cross-sectional structural view of an outer tube of an isokinetic sampling tube according to some embodiments of the present disclosure;
FIG. 6 is a schematic primary perspective structural view of an outer tube of an isokinetic sampling tube according to some embodiments of the present disclosure;
FIG. 7 is a schematic illustration of a main view angle configuration of an outer tube of an isokinetic sampling tube according to some embodiments of the present disclosure;
FIG. 8 is a schematic view of an installation configuration of a hold-down device for an isokinetic sampling tube according to some embodiments of the present disclosure;
FIG. 9 is a schematic view of a mounting structure of a catalytic combustion device according to some embodiments of the present disclosure;
FIG. 10 is a cross-sectional structural schematic of an isokinetic sampling tube according to some embodiments of the present disclosure.
In the figure:
1. cone head, 12, sampling head, 13, static pressure tube, 2, air duct, 3, outer tube, 31, outer tube bending section, 311, second set screw, 32, outer tube straight section, 4, middle layer, 41, heating wire, 42, corundum support sheet, 43, corundum insulation sheet, 5, hold-down device, 51, hold-down bolt, 52, guide gasket, 511, first set screw, 6, pitot tube, 71, air source, 72, catalytic combustion device, 73, tail gas analysis device, 74, air pump, 75, vacuum pump, 761, first flowmeter, 762, second flowmeter, 77, controller, 781, first temperature sensor, 782, second vacuum stable sensor, 79, furnace, 81, displacement cover plate, 82, mounting arm.
It should be understood that the dimensions of the various parts shown in the figures are not drawn to scale. Further, the same or similar reference numerals denote the same or similar components.
Detailed Description
Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. The description of the exemplary embodiments is merely illustrative and is in no way intended to limit the disclosure, its application, or uses. The present disclosure may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. It should be noted that: the relative arrangement of parts and steps, the composition of materials, numerical expressions and numerical values set forth in these embodiments are to be construed as merely illustrative, and not as limitative, unless specifically stated otherwise.
The use of "first," "second," and similar terms in this disclosure is not intended to indicate any order, quantity, or importance, but rather are used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element preceding the word covers the element listed after the word, and does not exclude the possibility that other elements are also covered. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.
In the present disclosure, when a specific device is described as being located between a first device and a second device, there may or may not be intervening devices between the specific device and the first device or the second device. When a particular device is described as being coupled to other devices, that particular device may be directly coupled to the other devices without intervening devices or may be directly coupled to the other devices with intervening devices.
All terms (including technical or scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs unless specifically defined otherwise. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate.
As shown in FIGS. 1 to 10:
in one aspect of the present disclosure, an isokinetic sampling tube is provided for sampling gas in a combustion chamber of an aircraft engine, comprising:
a sampling head 12;
the first end of the gas guide tube 2 is used for installing the sampling head 12, the second end of the gas guide tube is connected to a gas collecting device, and a bending part is arranged in the area, close to the first end, of the gas guide tube 2 so that the first end and the second end form a set angle;
the outer tube 3 is sleeved outside the gas guide tube 2;
the conical head 1 is sleeved at one end of the sampling head 12 close to the air duct 2 and is detachably connected with the outer tube 3; and
and the middle layer 4 is arranged between the air guide tube 2 and the outer tube 3 and can support and heat the air guide tube 2.
For an aircraft engine combustion chamber, the fuel gas in the combustion chamber is in a high-temperature and high-speed state, and the boiling range of the aviation kerosene can reach up to 300 ℃. Therefore, when the gas is sampled and the concentration of the fuel is analyzed, the sampling pipe not only can bear the impact of the gas, but also can prevent the kerosene and gas in the sampled gas from being condensed.
On this basis, this application is through in the air duct 2 with set up heatable intermediate level 4 between the outer tube 3, right when air duct 2 carries out effective support, heat air duct 2, prevent that the aviation in the gas-liquid two-phase flow from not liquefying in advance, and lead to concentration measurement result inaccurate.
The arrangement of the conical head 1 and the outer tube 3 can protect the air duct 2 from the outside, and the air duct 2 is prevented from being directly impacted by high-temperature and high-speed airflow. Especially, the conical head 1 not only plays a role in stabilizing the sampling head 12, but also can effectively reduce the whole windward area of the sampling tube by virtue of the self-inclined conical surface, so that the sampling tube is more stable.
As shown in fig. 6 and 7, the bent portion of the airway tube 2 may also adopt various bent shapes (such as a right-angle bend, a gooseneck bend, etc.) to facilitate the arrangement of the tube and adapt to the incoming flow conditions under different conditions.
Further, as shown in fig. 5, in order to enable the intermediate layer 4 to perform a supporting function and a heating function on the airway tube 2, in some embodiments, the intermediate layer 4 includes:
at least one heating wire 41; and
and the corundum support plate 42 is provided with a central hole and at least one outer hole along the thickness direction, the central hole is used for penetrating through the air duct 2, and the at least one outer hole is used for penetrating through the at least one heating wire 41.
The corundum supporting sheet 42 utilizes the properties of high hardness, good supporting property and high temperature resistance of corundum materials, and can keep the setting position of the gas guide tube 2 under the impact of high-temperature and high-speed airflow of an aeroengine combustion chamber, so that the sampling tube can be positioned in the incoming flow of fuel gas in a set posture, and the setting position requirement of a sampling port in the isokinetic sampling process is ensured.
The at least one external hole of the corundum supporting plate 42 is used to arrange the at least one heating wire 41, so that the external hole is preferably uniformly arranged around the air duct 2 along the circumference of the air duct 2 in order to uniformly heat the air duct 2 by the heating wire 41 arranged therein.
The heating wire 41 may be heated based on an electrothermal principle, and thus, for different sampling conditions, the heating wire 41 may control the heating power by adjusting the current flowing through the heating wire 41 or replacing the heating wire 41 with different resistance values.
Further, in order to make the corundum supporting plate 42 uniformly arranged between the gas-guiding tube 2 and the outer tube 3 along the axial direction of the gas-guiding tube 2, as shown in fig. 1, in some embodiments, the corundum supporting plate 42 has a cylindrical structure, and the upper bottom surface and the lower bottom surface of the cylindrical structure are parallel to each other;
the plurality of corundum supporting sheets 42 are arranged at the bending part of the air duct 2, any two adjacent corundum supporting sheets 42 in the plurality of corundum supporting sheets 42 are overlapped and arranged between the air duct 2 and the outer tube 3 in an abutting mode of adjacent end surfaces, and are fastened and limited by the pressing devices 5 respectively arranged at the first end and the second end of the air duct 2.
The middle layer 4 is heated by the heating wire 41 and is sheathed with a plurality of sections of corundum supporting sheets 42 in an insulating way, so that the maximum design temperature of the sampling tube can reach 1100 ℃ and is far higher than the maximum boiling point of the aviation kerosene by 300 ℃, and the liquid-phase fuel oil mist can be gasified and the gas-phase fuel oil cannot be condensed even if the sampling fuel gas is in the condition of high speed and short heat exchange time.
Of course, as shown in fig. 10, the corundum support plate 42 with a cylindrical structure may also have upper and lower bottom surfaces that are not parallel to each other, so as to adapt to the bending section of the airway tube 2 in a manner that the bottom surfaces are attached to each other, thereby providing a more stable support for the airway tube 2.
Although the cross-section of the corundum supporting plate 42 is circular as shown in fig. 10, it should be understood by those skilled in the art that, no matter whether the corundum supporting plate 42 adopts a structure in which upper and lower surfaces are parallel to each other or a structure in which the upper and lower surfaces are not parallel to each other, the corundum supporting plate 42 is not limited to a cylindrical structure, but may have other cross-sectional shapes such as a square, an oval, etc., and thus can provide better adaptability to the outer tubes 3 having different cross-sectional shapes and the benefit of saving corundum material.
Further, as shown in fig. 1, in some embodiments, the intermediate layer 4 further includes:
the corundum insulation sheet 43 is provided with a central hole along the thickness direction and is used for penetrating the air duct 2, and the corundum insulation sheet 43 is arranged between the pressing device 5 and the corundum support sheet 42 and is used for preventing the electric heating wire 41 from conducting electricity outwards.
As shown in fig. 1 and 8, in some embodiments, the inner surface of the outer tube 3 near the second end of the airway tube 2 has internal threads, and is provided with a guide groove along the length direction of the outer tube 3, and the compressing device 5 disposed at the second end of the airway tube 2 includes:
the compression bolt 51 is detachably assembled with the internal thread and is provided with a central hole for leading out the air guide pipe 2;
a guide washer 52, which is disposed at one end of the pressing bolt 51 close to the corundum support plate 42, has a central hole for passing through the air duct 2 and an outer hole for passing through the electric heating wire 41, and can be matched with the guide groove through a guide pin disposed in a radial direction to provide circumferential positioning for the outer tube 3; and
the first set screw 511 is radially arranged at the nut part of the hold-down bolt 51, and can tightly push and limit the air duct 2 arranged in the central hole of the hold-down bolt 51 by screwing in the hold-down bolt 51.
The guiding spacer 52 can make the air duct 2 and/or the corundum supporting sheet 42 not rotate along with the screwing-in and screwing-out process of the pressing bolt 51 through the matching between the guiding pin and the guiding groove on the outer tube 3, thereby avoiding the possibility that the heating wires are twisted with each other.
In some embodiments, as shown in fig. 1, the conical head 1 is connected to the airway tube 2 by a thread seal, and the compressing device 5 disposed at the first end of the airway tube 2 includes:
and a second fastening screw 311 which fastens the cone 1 and the outer tube 3 after the cone 1 and the bent portion of the outer tube 3 are sleeved.
Further, in some embodiments, the inner diameter of the sampling head 12 is 1mm, the sampling head 12 is welded to the conical head 1, and a portion of the sampling head 12 extends out of the sleeving range of the conical head 1.
The internal diameter of sampling head 12 is 1mm, is less than the internal diameter 2mm of air duct 2 to be less than the sampling probe of current sampling pipe 4mm internal diameter, on the one hand through flow area less sampling head 12 makes the sampling flow continue to keep in setting for the within range under big flow velocity, on the other hand then less internal diameter sampling head 12 with air duct 2 can reduce the windward area of sampling pipe, thereby reduce to the interference of flow field in the combustion chamber. In addition, the sampling head 12 extends forwards for a certain distance relative to the conical head 1, so that the interference of the conical surface to the head inflow of the sampling head can be reduced.
Further, to achieve isokinetic sampling of the sampling tube, in some embodiments, the isokinetic sampling tube further comprises:
the static pressure pipe 13 is composed of a radial hole arranged on the conical head 1 and a wall surface hole arranged on the gas guide pipe 2, wherein the wall surface hole and the radial hole have the same diameter and are coaxial; and
and the pitot tube 6 is fixedly arranged on one side of the outer tube 3 through a clamp and has the same air inlet direction as the sampling head 12.
Compared with simple probe sampling without considering control of sampling flow, the invention can provide local total static pressure by the pitot tube 6, combine the internal flow static pressure fed back by the static pressure tube 13, and combine the balance relation of the internal and external flow static pressures, control of sampling flow can realize isokinetic sampling, and improve sampling accuracy.
Specifically, the core of gas sampling is isokinetic sampling, which is the same concept as isoflow sampling or isovelocity sampling. The assumption on which isokinetic sampling is based is: the particles in the flow field are not entrained by the airflow and move along the original direction even if the direction of the airflow changes. Therefore, the isokinetic sampling has the function of ensuring that the concentration of particulate matters entering the sampling pipe is constant, and for measuring the concentration of fuel oil, namely the concentration of liquid fog in the sampled fuel gas can faithfully reflect the concentration of liquid fog at a measuring point.
Therefore, the key point of isokinetic sampling is not whether the gas velocity is consistent with the local velocity (flow rate) or not, but the gas velocity is consistent with the local velocity, at this time, the movement locus of the oil mist particles and the gas kerosene streamline are not interfered by the sampling head 12, and the sample gas can faithfully reflect the local gas-liquid two-phase distribution state (gas-liquid ratio).
In addition, the assembly process of the invention should pay attention to the sequence, because the sampling tube is an integral J-shaped tube, the outer tube bending section 31 and the outer tube straight section 32 should be respectively sleeved in from the two ends of the gas guide tube 2, and the threaded connection between the outer tube straight section 32 and the outer tube bending section 31 is firstly completed; then, the conical head 1 is rotated to complete the threaded connection with the air duct 2; at the moment, the outer pipe bending section 31 is partially nested on the outer wall of the conical head 1, and a fastening screw on the outer pipe bending section 31 is screwed to finish fastening with the conical head 1; after the electric heating wire 41 and the corundum support sheet 42 of the middle layer 4 are inserted and assembled, the electric heating wire is sleeved into a gap ring between the air duct 2 and the straight section 32 of the outer tube; finally, a guide gasket 52 is placed in the clearance ring, the compression bolt 51 is screwed to complete the fastening of the middle layer 4, and the first fastening screw 511 is screwed to complete the fixing of the compression bolt 51 and the air duct 2.
In another aspect of the present disclosure, there is provided a sampling method, wherein the isokinetic sampling tube described in any one of the above is used, the sampling method comprising:
in the sampling process, the static pressure tube 13 is used for measuring the sampling static pressure of the sampling airflow in the air guide tube 2, the pitot tube 6 is used for measuring the local total pressure and the local static pressure of the sampling head 12, and the sampling flow of the sampling head 12 is adjusted according to the balance relation between the sampling static pressure and the local static pressure, so that the isokinetic sampling of the sampling tube is realized; and
and in the calibration process, the influence of total pressure loss between the sampling head 12 and the static pressure hole on the balance relation between the sampling static pressure and the local static pressure is considered when the sampling flow of the sampling pipe is adjusted.
Further, in some embodiments, the calibration process comprises:
m1, recording local total pressure, local static pressure and sampling static pressure under different sampling flow rates at a set incoming flow speed, calculating the sampling speed in the air duct 2 according to the flow area of the air duct 2 and the sampling static pressure, and calculating the local speed of the sampling head 12 according to the local total pressure and the local static pressure;
m2, changing the sampling flow of the sampling pipe, and recording the sampling speed and the pressure reduction difference value of the local static pressure and the sampling static pressure when the sampling speed is equal to the local speed; and
m3, changing the set incoming flow speed, repeating the M2 step, and establishing a functional relation between the sampling speed and the static pressure difference value;
the sampling step comprises the following steps:
n1, calculating a local speed according to the local total pressure and the local static pressure measured by the pitot tube 6, and searching a static pressure difference value corresponding to the sampling speed which is the same as the local speed according to the functional relation in the M3 step on the basis of the local speed;
and N2, including the static pressure difference value obtained in the N1 step into a balance relation calculation process of the sampled static pressure and the local static pressure, and adjusting the sampling flow of the sampling head 12 based on the balance relation.
Specifically, when the internal and external static pressure balance relationship is used, the total pressure loss of the sampling head 12 from the static pressure pipe 13 should be considered, and before sampling, an equal flow curve should be obtained through experiments for calibration, and the calibration idea and process are as follows:
in the actual sampling process, the isokinetic sampling pipe can measure three pressure values of local total pressure P1, local static pressure P2 and sampling static pressure P3; for calibration experiments, a steady incoming flow with a certain velocity V1 was provided. When one incoming flow velocity V1 is selected, the sampling flow rate is changed under the condition that V1 is maintained, the flow velocity V2 in the sampling probe can be calculated by combining the cross section area of the sampling probe, and when V2 is equal to V1, isodynamic sampling is carried out, and the local total pressure P1, the local static pressure P2 and the sampling static pressure P3 at the moment are recorded.
And then changing the incoming flow speed V1, and repeating the steps to establish the relation between the sampling speed V1 and the static pressure difference delta P (P2-P3), wherein an equal flow curve is obtained if a V2-delta P graph is drawn.
Returning to the sampling operation process, according to the local total pressure P1 and the local static pressure P2, the local flow velocity V1 can be estimated according to the Bernoulli equation, the sampling speed V2 needs to be equal to V1, the static pressure P4 which needs to be reached by the corresponding speed sampling inner tube can be searched by combining an isoflow curve V2-delta P diagram, and the sampling flow is adjusted to enable the actually measured static pressure P4 in the sampling tube to be equal to P3.
In another aspect of the present disclosure, as shown in fig. 2, there is provided a fuel concentration measuring system comprising an isokinetic sampling tube according to any of the preceding claims, the measuring system further comprising:
an air source 71;
a catalytic combustion device 72, the inlet of which is connected to the outlet of the isokinetic sampling pipe and the air source 71, for burning the gas sample and air under catalytic conditions; and
and a tail gas analyzing device 73 connected to an outlet of the catalytic combustion device 72 for analyzing the tail gas combusted under the catalytic condition.
In some embodiments, the measurement system further comprises:
a suction pump 74 for controlling the flow rate of the air source 71;
a vacuum pump 75 for controlling the intake air flow rate of the exhaust gas analyzing device 73;
a first flow meter 761 for measuring a flow rate of the air source 71;
a second flow meter 762 for measuring an intake air flow rate of the exhaust gas analyzing device 73; and
and a controller 77 communicatively connected to the suction pump 74, the vacuum pump 75, the first flow meter 761, and the second flow meter 762, and configured to control opening degrees of the suction pump 74 and the vacuum pump 75 based on measurement values of the first flow meter 761 and the second flow meter 762, respectively.
As shown in fig. 2 and 9, in some embodiments, the catalytic combustion device 72 includes a vacuum furnace 79, and the measurement system further includes:
the first temperature sensor 781 is used for measuring the temperature of the sampling area of the isokinetic sampling pipe; and
a second temperature sensor 782 for measuring the temperature of the vacuum furnace 79;
the controller 77 is communicatively connected to the first temperature sensor 781, the second temperature sensor 782, the isokinetic sampling tube and the vacuum oven 79;
the controller 77 is further configured to: the heating power of the isokinetic sampling tube and the combustion power of the vacuum furnace 79 can be controlled based on the measured values based on the first temperature sensor 781 and the second temperature sensor 782.
As shown in fig. 3, the connection state of the mounting arm 82 and the displacement cover plate 81 in the assembly process of the isokinetic sampling tube provided by the present invention is shown, specifically, the two-dimensional translation of the isokinetic sampling tube relative to the experimental apparatus is realized by the translation of the sliding sheet in the cavity, and the precise adjustment of the position of the isokinetic sampling tube can be further realized by the cooperation of the two-dimensional displacement mechanism. The mounting arm 82 is fixedly provided with the isokinetic sampling tube in a pressing block-pressing bolt 51 mode, and the displacement direction between the pressing block and the pressing bolt 51 is perpendicular to the incoming flow direction in the experimental process, so that the isokinetic sampling tube provided by the invention cannot be loose in connection or greatly shake due to the impact of the incoming flow.
Based on the technical scheme, the isokinetic sampling pipe, the sampling method and the fuel concentration measuring system provided by the embodiment of the disclosure can at least facilitate accurate measurement of the fuel concentration in the combustion chamber of the aircraft engine.
Thus, various embodiments of the present disclosure have been described in detail. Some details that are well known in the art have not been described in order to avoid obscuring the concepts of the present disclosure. It will be fully apparent to those skilled in the art from the foregoing description how to practice the presently disclosed embodiments.
Although some specific embodiments of the present disclosure have been described in detail by way of example, it should be understood by those skilled in the art that the foregoing examples are for purposes of illustration only and are not intended to limit the scope of the present disclosure. It will be understood by those skilled in the art that various changes may be made in the above embodiments or equivalents may be substituted for elements thereof without departing from the scope and spirit of the present disclosure. The scope of the present disclosure is defined by the appended claims.
Claims (11)
1. An isokinetic sampling tube for sampling the gas in an aircraft engine combustion chamber, comprising:
a sampling head;
the first end of the gas guide pipe is used for mounting the sampling head, the second end of the gas guide pipe is connected to a gas collecting device, and a bending part is arranged in the area of the gas guide pipe close to the first end so that the first end and the second end form a set angle;
the outer tube is sleeved outside the air guide tube;
the conical head is sleeved on the sampling head and close to one end of the air guide pipe, and is detachably connected with the outer pipe; and
the middle layer is arranged between the air guide tube and the outer tube and can support and heat the air guide tube;
the intermediate layer includes:
at least one heating wire; and
the corundum support sheet is provided with a central hole and at least one outer hole along the thickness direction, the central hole is used for penetrating through the air duct, and the at least one outer hole is used for penetrating through the at least one electric heating wire;
the corundum supporting sheet is provided with a cylindrical structure, and the upper bottom surface and the lower bottom surface of the cylindrical structure are parallel to each other;
the corundum supporting sheets are arranged at the bending part of the air duct, and any two adjacent corundum supporting sheets in the corundum supporting sheets are overlapped between the air duct and the outer tube in an abutting mode of adjacent end surfaces and are fastened and limited by the pressing devices respectively arranged at the first end and the second end of the air duct.
2. The isokinetic sampling tube of claim 1, wherein the intermediate layer further comprises:
the corundum insulating sheet is provided with a center hole along the thickness direction and used for penetrating through the air guide pipe, and the corundum insulating sheet is arranged between the pressing device and the corundum supporting sheet and used for preventing the electric heating wire from conducting outwards.
3. The isokinetic sampling tube according to claim 1, wherein the outer tube has an inner surface near the second end of the gas-guiding tube with an internal thread and a guiding groove along the length direction of the outer tube, and the compressing device disposed at the second end of the gas-guiding tube comprises:
the compression bolt is detachably assembled with the internal thread and is provided with a central hole for leading out the air guide pipe;
the guide gasket is arranged at one end of the compression bolt close to the corundum support sheet, is provided with a central hole for penetrating the air guide pipe and an outer hole for penetrating the electric heating wire, and can be matched with the guide groove through a guide pin arranged along the radial direction to provide circumferential positioning for the outer pipe; and
the first fastening screw is arranged at the nut part of the compression bolt along the radial direction and can be used for jacking and limiting the air guide pipe arranged in the central hole of the compression bolt by screwing in the compression bolt.
4. The isokinetic sampling tube of claim 1, wherein the conical head is sealingly connected to the airway tube by threads, and the constriction device disposed at the first end of the airway tube comprises:
and the second fastening screw is used for fastening the conical head and the outer pipe after the conical head and the bent part of the outer pipe are sleeved.
5. The isokinetic sampling tube according to claim 1, wherein the sampling head has an inner diameter of 1mm, and is welded to the conical head, and the sampling head extends out of the range of the conical head.
6. The isokinetic sampling tube of claim 1, further comprising:
the static pressure pipe is composed of a radial hole arranged on the conical head and a wall surface hole arranged on the gas guide pipe, wherein the wall surface hole and the radial hole have the same diameter and are coaxial; and
the pitot tube is fixedly arranged on one side of the outer tube through a clamp and has the same air inlet direction as the sampling head.
7. An isokinetic sampling method, characterized in that, by using the isokinetic sampling tube according to claim 6, the sampling method comprises:
in the sampling process, the static pressure tube is used for measuring the sampling static pressure of the sampling airflow in the air guide tube, the pitot tube is used for measuring the local total pressure and the local static pressure of the sampling head, and the sampling flow of the sampling head is adjusted according to the balance relation between the sampling static pressure and the local static pressure, so that the isokinetic sampling of the sampling tube is realized; and
and in the calibration process, the influence of total pressure loss between the sampling head and the static pressure pipe on the balance relation between the sampling static pressure and the local static pressure is considered when the sampling flow of the sampling pipe is adjusted.
8. The sampling method of claim 7, wherein the calibration process comprises:
m1, recording local total pressure, local static pressure and sampling static pressure under different sampling flow rates at a set incoming flow speed, calculating the sampling speed in the air duct according to the flow area of the air duct and the sampling static pressure, and calculating the local speed of the sampling head according to the local total pressure and the local static pressure;
m2, changing the sampling flow of the sampling pipe, and recording the sampling speed and the static pressure difference value of the local static pressure and the sampling static pressure when the sampling speed is equal to the local speed; and
m3, changing the set incoming flow speed, repeating the M2 step, and establishing a functional relation between the sampling speed and the static pressure difference value;
the sampling process comprises the following steps:
n1, calculating a local speed according to the local total pressure and the local static pressure measured by the pitot tube, and searching a static pressure difference value corresponding to the sampling speed which is the same as the local speed according to the functional relation in the M3 step on the basis of the local speed;
and N2, incorporating the static pressure difference value obtained in the N1 step into a balance relation calculation process of the sampled static pressure and the local static pressure, and adjusting the sampling flow of the sampling head based on the balance relation.
9. A fuel concentration measuring system comprising an isokinetic sampling tube according to any one of claims 1 to 6, characterized in that the measuring system further comprises:
an air source;
the inlet of the catalytic combustion device is connected with the outlet of the isokinetic sampling pipe and the air source and is used for enabling the fuel gas to be sampled and combusted with air under the catalytic condition; and
and the tail gas analysis device is connected to the outlet of the catalytic combustion device and is used for analyzing the tail gas combusted under the catalytic condition.
10. The measurement system of claim 9, further comprising:
the air pump is used for controlling the flow of the air source;
a vacuum pump for controlling the intake flow rate of the exhaust gas analysis device;
a first flow meter for measuring a flow rate of the air source;
a second flow meter for measuring an intake air flow rate of the exhaust gas analysis device; and
and the controller is in communication connection with the air pump, the vacuum pump, the first flow meter and the second flow meter and can respectively control the opening degrees of the air pump and the vacuum pump based on the measurement values of the first flow meter and the second flow meter.
11. The measurement system of claim 10, wherein the catalytic combustion device comprises a vacuum furnace, the measurement system further comprising:
the first temperature sensor is used for measuring the temperature of the sampling area of the isokinetic sampling pipe; and
a second temperature sensor for measuring a temperature of the vacuum furnace;
the controller is in communication connection with the first temperature sensor, the second temperature sensor, the isokinetic sampling pipe and the vacuum furnace;
the controller is further configured to: the heating power of the isokinetic sampling tube and the combustion power of the vacuum furnace can be controlled according to the measured values based on the first temperature sensor and the second temperature sensor.
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| CN2183562Y (en) * | 1993-11-04 | 1994-11-23 | 中国航天工业总公司第三研究院第三十一研究所 | Fuel-concentration sampling tube for engine combustion chamber |
| JP3673854B2 (en) * | 2001-05-11 | 2005-07-20 | 独立行政法人産業技術総合研究所 | Dust sampling device with variable aperture suction nozzle |
| CN102445518A (en) * | 2010-10-09 | 2012-05-09 | 胡建华 | Internal combustion engine exhaust on-line measurement and diagnosis method and equipment |
| CN102507268A (en) * | 2011-10-25 | 2012-06-20 | 广东电网公司电力科学研究院 | Air flow sampling device for pulverizing system and sampling method thereof |
| CN203688301U (en) * | 2014-02-18 | 2014-07-02 | 北京盛邦天业科技有限公司 | Intelligent constant-temperature heating fume particle sampling gun |
| CN205607936U (en) * | 2016-03-24 | 2016-09-28 | 西安科技大学 | Burning flue gas analysis experiment monitoring devices |
| CN106248442B (en) * | 2016-09-06 | 2019-07-19 | 山东能工低碳科技有限公司 | SO in a kind of detection flue gas3Method |
| KR102002967B1 (en) * | 2017-09-05 | 2019-10-01 | 주식회사 정엔지니어링 | An exhaust gas continuous isokinetic sampling apparatus with a sectional area adjustment device attached to the suction nozzle |
| CN108693090A (en) * | 2018-06-01 | 2018-10-23 | 浙江大学 | A kind of granule density measuring device for high temperature oil-containing dusty gas |
| CN208399221U (en) * | 2018-07-31 | 2019-01-18 | 国电南京电力试验研究有限公司 | A kind of high smoke temperature flue gas dust concentration Testing gun of thermal power plant |
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