RU2765107C1 - Method for heating the gas flow by aerodynamic braking of jets - Google Patents

Abstract

FIELD: thermal engineering.

SUBSTANCE: proposed method for heating a gas flow by aerodynamic braking of jets relates to gas dynamics and thermal engineering, or rather, to methods for heating high-pressure gas due to its own potential gas energy, which is converted into thermal gas energy when aerodynamic braking effects occur at the intersection and collision of gas jets, and the so-called aerodynamic gas heating. In the claimed method, before dividing the gas flow into two jets, using a gas-dynamic generator of gas pressure fluctuations that have no moving parts, fluctuations of pressure and velocity that does not reach supersonic speed of movement are created, while the gas flow is divided into two jets at least once, and before the collision, the jets are directed into expanding channels forming areas of primary collision and aerodynamic braking of the jets, and then into the zone in front of the exit channel.

EFFECT: expansion of the range of solutions for heating the gas flow by aerodynamic braking of jets.

1 cl, 12 dwg

Description

The technical field to which the invention belongs

The method proposed by me for heating a gas flow by aerodynamic deceleration of jets (hereinafter referred to as the “method”) refers to gas dynamics and heat engineering, and more precisely, to methods and methods for heating high-pressure gas due to its own potential energy of the gas, which is converted into thermal energy of the gas during the implementation of aerodynamic deceleration effects occurring at the intersection and collision of gas jets, and the so-called aerodynamic gas heating.

The method proposed by me can be applied to gas of any type of gas (monatomic gases, polyatomic gases, mixtures of gases - including: nitrogen, hydrogen, argon, carbon dioxide, oxygen, air, natural gas, welding gas mixtures, etc.) .

Possible areas of application of the method proposed by me (not limited to those listed):

- heating of compressed gas before reduction (from the value of storage pressure in the tank/cylinder to the pressure of use) to prevent freezing of the reducer and gas pipelines,

- heating of natural gas in high-pressure main networks and gas control stations to prevent hydrate formation in natural gas,

- gas heating by forced circulation of this gas in a closed circuit.

State of the art

The closest to the method proposed by me in terms of technical principles is the “Method of heating the gas stream” USSR patent SU 1790724 A3 (author V.E. Finko). This known method also uses the principle of heating a gas moving at high speed during its aerodynamic braking and aerodynamic heating.

However, the known method has a number of disadvantages, mainly associated with the use of supersonic gas velocity, which leads to rapid wear and erosion of the heater elements, which leads to the use of high-quality and expensive materials in the manufacture of the heater. However, even when high-quality materials are used in the process of aerodynamic braking and the impact of a supersonic flow directly on structural elements (accelerator, cone-shaped nozzles, braking grid), they still wear out quickly, and the elements change significantly: they wear out, lose their original geometric shape, as a result which cease to perform the necessary function or are completely destroyed.

Disclosure of the essence of the invention

The purpose of my invention is to create a new method, devoid of the disadvantages of the known method mentioned above, while implementing the well-known principle of aerodynamic braking and gas heating.

The method proposed by me uses a subsonic gas flow velocity, and aerodynamic braking and aerodynamic heating of the gas are produced as a result of collision and mutual braking of gas jets without a direct collision of gas with fixed elements of the heater structure. In this case, erosion and abrasion of the surface of the internal elements of the device are insignificant, therefore, high-strength materials are not required for the manufacture of the heater and devices intended for the implementation of the method I propose, and it is possible to use inexpensive grades of steel, ceramic, composite or other materials. At the same time, during long-term operation of such a heater or device with a constant flow of gas flows, a slow gradual abrasion of the surface of the gas channels is still inevitable. The geometry of the gas channels proposed in my method, when worn, does not change significantly, while maintaining the geometric similarity and full performance for a long service life.

To implement the method of heating the gas flow, the available pressure drop of the gas is used. The pressure drop of the gas must be sufficient to form a high-speed gas jet. Depending on the type of gas (its molecular weight, thermal and other characteristics) for the implementation of the proposed method, there is a minimum required gas pressure drop, which is found experimentally. To implement the method, it is possible to use any value of the gas pressure drop above the minimum.

The above known method of gas heating also requires a pressure drop, which is used to accelerate the gas above the speed of sound, while achieving supersonic speed requires a much larger pressure drop than is necessary in my method for subsonic gas movement. Therefore, the method proposed by me can be more widely used in industry, as it is also applicable in those technological processes where the available gas pressure drop is insufficient to achieve supersonic gas velocity and does not allow the implementation of the above known method.

The method proposed by me should not be confused with fundamentally different methods and designs of gas-dynamic shock-wave and resonator-acoustic heaters based on the Hetman-Springer effect, in which the energy of a supersonic gas flow is converted into shock-wave or acoustic gas oscillations in a resonator chamber, leading to to heating the walls of the chamber itself, while the gas is discharged cold.

Also, the method proposed by me should not be confused with methods using vortex tubes with the Ranque-Hilsch effect, which is based on the separation of the main gas flow into a “hot” and “cold” component.

The technical and physical principles of these methods and devices are categorically different from the principles used in the proposed method.

In the method I propose, the following essential features and principles of operation can be distinguished:

1. The gas flow is heated by converting the intrinsic potential energy of the gas (gas pressure) into the thermal energy of the gas (the kinetic energy of the gas molecules). That is, an increase in the gas temperature occurs without additional energy being supplied to the gas from the outside (the total internal energy of the gas remains constant), in the process of energy conversion and increase in the gas temperature under consideration, the gas pressure decreases accordingly (that is, the potential energy of the gas previously received by the gas from mechanical devices for increasing pressure/compressors).

2. The transformation of the internal energy of the gas is carried out when creating two identical jets from a single gas flow using symmetrical gas channels, accelerating these jets in the gas channels due to the difference in gas pressure at the inlet and outlet of these gas channels, bringing the jets to nozzle devices located frontally opposite a friend. When the jets exit from two nozzle devices located frontally opposite each other, the gas jets enter the expanding channels and collide with each other ("head-on"). Since gas jets are not dense bodies, after a collision, gas jets pass into each other ("on a collision course") with a double relative speed, increasing each other's density and mechanically interacting with each other at the molecular level. As a result of collisions and interactions of molecules in the areas of primary collision, aerodynamic braking and stopping of these gas jets is observed, characterized by an increase in the speed and randomness of the movement of individual gas molecules (that is, an increase in the kinetic energy of gas molecules), which is ultimately observed as an increase in gas temperature. The incoming subsequent portions of gas push out the above stopped and heated portions of gas from the areas of primary collision into the zone in front of the outlet channel, in which they are mixed, averaged in temperature and enter the outlet channel as a single flow, having a residual pressure for subsequent movement through the outlet channel.

3. Before the separation of the gas flow into jets, it is planned to create gas pressure fluctuations in the gas flow, which provide an impulse increase (with some periodicity/frequency) of the gas pressure drop, and, accordingly, an increase in the speed of the gas jets and their “shock” interaction. Fluctuations in gas pressure are created in a gas-dynamic generator of gas pressure oscillations, which does not have moving parts, based on the previously known principle of operation of pneumatic devices and jet machines. The oscillation frequency depends on the parameters and dimensions of the elements of the gas-dynamic generator and can be selected experimentally to ensure sufficient fluctuations in gas pressure at a known inlet gas pressure. Without the use of a gas pressure oscillation generator, a gas flow stably flowing to separate it into jets will not create a sufficient pressure drop, will not provide jet acceleration and their “shock” interaction, which will exclude aerodynamic deceleration of the jets and gas heating, but instead a uniform flow will be observed gas through gas channels without any heating.

Brief description of the drawings

On FIG. 1 shows a general view of a gas-dynamic generator of gas pressure fluctuations as part of a device for heating a gas flow by aerodynamic deceleration of jets.

On FIG. 2 shows a general view of the base module as part of the device for heating the gas flow by aerodynamic deceleration of the jets.

On FIG. 3 shows the minimum set of elements in the device for heating the gas flow by aerodynamic deceleration of the jets.

On FIG. 4 shows a possible variant of the set of elements in the device for heating the gas flow by aerodynamic deceleration of the jets.

On FIG. 5 shows a gas-dynamic generator of gas pressure oscillations, in which the following elements can be distinguished: inlet channel with nozzle 1, working cavity 2, profiled wall 3, nozzle 4, chamber 5, outlet channel 6.

On FIG. 6 shows the first stage of operation of the gas-dynamic generator of gas pressure oscillations.

On FIG. 7 shows the second stage of operation of the gas-dynamic generator of gas pressure fluctuations.

On FIG. 8 shows graphs of changes in time of the inlet and outlet gas pressure as a result of the operation of the gas-dynamic generator of gas pressure fluctuations.

On FIG. 9 shows the basic module, in which the following constituent elements can be distinguished: inlet channel 7, two identical symmetrical jet channels 8, two identical symmetrical nozzles 9, two identical symmetrical expanding channels forming regions 10 and zone 11 in front of the outlet channel 12.

On FIG. 10 shows the first stage of operation of the basic module.

On FIG. 11 shows the second stage of the basic module.

On FIG. 12 shows graphs of changes in time of the inlet and outlet gas pressure as a result of the operation of the basic module.

Implementation of the invention

The method I propose can be implemented technically using a device for heating a gas flow by aerodynamic braking of jets (hereinafter referred to as the "device"), consisting of at least a gas-dynamic generator of gas pressure oscillations (see Fig. 1) and a base module (see Fig. 2), in which working cavities and gas channels are made by casting, stamping or milling. The working cavities and gas channels of the gas-dynamic generator form a working gas jet and feed it to the input of the base module. Through the gas channels of the base module, the working gas jet is divided into two accelerating gas jets, which are directed at each other and collide, which provides the effect of aerodynamic heating of the gas during its deceleration in the oncoming gas jets. In this case, there is no direct impact of the jets on the elements of the device.

Cross-sections of gas channels can be both round and oval, and rectangular. The smoothness and roundness of the channel walls reduces vortex formation during the formation and flow of gas jets, which increases their speed and increases the efficiency of gas heating.
The device can be made of various materials (stainless steel, carbon steel, ceramics, glass and other materials) depending on their chemical compatibility with the heated gas and the strength requirements of the device design when working with high pressure gases.

On FIG. 3 shows the minimum set of elements of the device in which the method proposed by me is implemented.

If it is necessary to heat the gas to higher temperatures, it is possible to repeatedly (more than once) sequentially apply the method I propose, which is limited only by the available pressure drop (that is, the potential energy of gas pressure that can be converted into thermal energy) of the heated gas. Figure 4 shows a variant of the set of elements of the device, which implements multiple sequential application of the proposed method.

The gas-dynamic generator of gas pressure fluctuations (see Fig. 1) is based on the well-known principle of pneumatic machines described and used in the USSR (for example, "Pneumonica" L.A. Zalmanzon, Nauka Publishing House, Moscow, 1965). The gas-dynamic generator of gas pressure fluctuations uses the property of a gas jet to “stick” to the wall of the gas channel and spread in a compact jet without significant dispersion even after it enters the working cavity from the gas channel.

On FIG. 5 shows a gas-dynamic generator of gas pressure oscillations, in which the following elements can be distinguished: inlet channel with nozzle 1, working cavity 2, profiled wall 3, nozzle 4, chamber 5, outlet channel 6.

On FIG. 6 shows the first stage of operation of a gas-dynamic generator of gas pressure oscillations, in which, after applying a constant gas pressure to the Inlet, a jet of the source gas is formed using nozzle 1, which enters the working cavity 2 with a profiled wall 3. The gas flow, which is pressed against the profiled wall 3, enters nozzle 4 and enters chamber 5. Chamber 5 is filled with incoming gas, which, accordingly, does not enter the outlet channel at this moment, and the gas pressure at the outlet decreases.

On FIG. 7 shows the second stage of operation of the gas-dynamic generator of gas pressure oscillations, in which, after chamber 5 is filled to operating pressure, back pressure is created in it, and the reverse gas flow from chamber 5 through nozzle 4 repels the source gas jet from the profiled wall 3 and directs it to the outlet channel 6. The jet, without losing its shape and without creating vortices in the working cavity 2, “sticks” to the outlet channel 6. The gas pressure at the outlet rises. For some time, a gas jet passing through the working cavity 2 by means of ejection pumps the gas out of the chamber 5, lowering the pressure in it. At a certain moment, the pressure in chamber 5 will become so low (relative to the pressure of the source gas jet) that the nozzle 4 will suck the main gas flow to the profiled wall 3. The source gas jet will press against the profiled wall 3 and begin to fill the chamber 5, while the gas pressure at the outlet decreases. Thus, the cycle closes - there is a self-oscillatory process of changing the gas pressure at the outlet (see P _out in Fig. 8). The oscillation frequency depends on the volume of the chamber 5 and the properties of the gas, and their amplitude depends on the inlet pressure of the gas and the properties of the gas.

The base module (see Fig. 2) implements the technology of splitting the gas flow into two jets, jet acceleration, bringing jets to nozzle devices located frontally opposite each other, organizing areas of primary collision and aerodynamic deceleration of jets, organizing the area of secondary collision and combining jets, diversion of the combined heated stream for further use.

The principle of increasing the temperature of gases in the direct impact of open gas jets is described in the works of employees of the Department of Thermal Power Plants of the Ural Federal University, for example, the article "Features of the thermomechanical interaction of oncoming gas jets" in the journal "Modern problems of science and education", number 2, 2014. However, this article and similar papers about this study do not consider the conditions for a direct collision of gas jets in a limited space of gas channels (that is, "closed jets"), except for this, no option is announced or claimed anywhere to use such a jet interaction mechanism for heating gas flow.

In addition to the interaction of jets flowing at a constant pressure at a constant speed, the method proposed by me uses the condition of fluctuations in gas pressure, the variability of the velocities of the jets and the collision of the jets under conditions of unsteady impact on each other, which increases the relative velocity of the jets and increases the efficiency of vortex formation, aerodynamic deceleration and aerodynamic gas heating.

Since the base module is installed in series behind the gas-dynamic generator of gas pressure oscillations, then the input of the base module is supplied with a variable output pressure from the gas-dynamic generator of gas pressure oscillations (see _Pout in Fig. 8).

On FIG. 9 shows the basic module, in which the following constituent elements can be distinguished: inlet channel 7, two identical symmetrical jet channels 8, two identical symmetrical nozzles 9, two identical symmetrical expanding channels forming regions 10 and zone 11 in front of the outlet channel 12.

On FIG. 10 shows the stage of applying a pressure pulse of the working gas to the Inlet, passing through the inlet channel 7, splitting into two jets, and accelerating the jets when passing through gas channels 8 and through nozzles 9.

On FIG. 11 shows the stage of reducing the pressure at the Inlet according to the cycle of operation of the gas-dynamic generator of gas pressure fluctuations, at this moment there is a mutual penetration of the jets into each other in zone 11, which at high (but subsonic) speed slip through the opening of the outlet channel 12 and pass in the region 10 - the primary collision and aerodynamic braking of jets. Since in these zones the jets and gas molecules move towards each other, their relative velocity is summed up, the layers of gas rub against each other, vortex formation, deceleration of gas molecules against each other, and their stop, which leads to aerodynamic heating of the gas and the formation of local areas of high gas pressure (due to its complete stop). In this region, the stagnation temperature is reached:

(где Т - температура газа, К; W - скорость газа, м/с; Ср - удельная теплоемкость газа, Дж/кг·К).

(where T is the gas temperature, K; W is the gas velocity, m/s; Cp is the specific heat of the gas, J/kg K).

The heat transferred by the heated gas to the body of the device is also involved in heating the subsequent cold portions of the gas. The body of the device is thermally insulated from the outside to reduce heat loss to the environment.

After stopping the gas jet from areas 11, supported by the pressure of new portions of gas from nozzles 9, they are directed towards zone 10 - a secondary collision occurs, mixing and combining gas jets into a common stream that exits through the outlet channel 12 and further - to the outlet of the device. At this time, a new pressure pulse arrives at the Inlet, and the cycle closes: when the next portion of gas arrives, a portion of the heated gas is discharged to the Outlet of the base module. Thus, the gas pressure at the Outlet is also subject to pulsation, but is somewhat smoothed out by delays and eddies in the gas flow, which are formed during the collision of jets (see Fig. 12).

Since a slight increase in temperature and a drop in pressure of the source gas are expected for one collision cycle in one base module, and gas pressure pulsation is maintained during the passage of the base module, the method proposed by me provides for the possibility of the gas flow passing successively several base modules, that is, several cycles of aerodynamic braking for the purpose of more complete conversion of the potential energy of compressed gas into thermal energy and gas heating. The number of repetitions depends on the type and properties of the gas, and is determined by the residual pressure level and pressure fluctuations, which must be sufficient for the formation of high-speed jets and conditions for aerodynamic braking and heating of the gas. As a result, in the process of sequential passage of the flow through several basic modules, the gas pressure pulses will be averaged and leveled, which were obtained as a result of the operation of the gas-dynamic generator of gas pressure fluctuations - the outgoing heated reduced pressure gas can be used by the consumer without additional pressure fluctuation compensation. On FIG. 4 shows a variant of a set of elements in a device in which the method proposed by me is implemented.

Claims (2)

1. A method for heating a gas flow by converting the self-potential energy of gas pressure into thermal energy of the gas, which consists in dividing the gas flow into two jets, accelerating these jets, bringing these jets to nozzle devices that are frontally placed opposite each other, colliding these jets, their mutual deceleration before exiting and diverting the combined heated flow for further use, characterized in that before the separation of the gas flow into two jets in it, using a gas-dynamic generator of gas pressure fluctuations that does not have moving parts, pressure and speed fluctuations are created that do not reach supersonic speed , wherein the separation of the gas flow into two jets is carried out at least once, and before the collision, the jets are directed into expanding channels forming the areas of primary collision and aerodynamic deceleration of the jets, and then into the zone in front of the outlet channel. 2. The method according to claim 1, characterized in that after the gas-dynamic generator of gas pressure fluctuations, a sequential repetition (more than 1 time) of the separation of the gas flow into two jets is performed with their direction into expanding channels, forming areas of primary collision of these jets and aerodynamic deceleration of the jets, that is, the method according to claim 1 is repeatedly implemented, which ultimately leads to a more complete conversion of the potential energy of gas pressure into thermal energy of the gas and more efficient heating of the gas flow.

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