Reactor for a chemical reaction and method for controlling the chemical reaction

A reactor for a chemical reaction, comprising a housing and a reaction chamber, a nozzle member with an inlet for letting at least one reactant flow into the reaction chamber, wherein the nozzle member is mounted in a movable manner relative to the housing, a sensor device and an adjusting device influencing the movement of the nozzle member can be adjusted, a control unit configured for receiving from the sensor device a measurement signal of the sensor device based on the measuring quantity and generating a control signal for the adjusting device depending on the measurement signal.

A reactor with a reaction chamber and a housing enclosing the reaction chamber is known from DE 10 2016 109 639 A1. A first reactant is fed into the reaction chamber via a nozzle member. Another nozzle member feeds a second reactant into the reaction chamber, wherein the two reactants collide with each other with great kinetic energy. According to DE 10 2016 109 639 A1, the kinetic energy is used in this case for the atomic or molecular restructuring of at least one of the two reactants. The reactants may be water and a liquid hydrocarbon, such as diesel fuel, for instance. One intended product of the chemical reaction taking place in the reaction chamber, i.e. of the atomic or molecular restructuring of at least one of the reactants, is a modified diesel fuel with which a particularly low-emission combustion is possible. Particularly where use in internal combustion engines is concerned, there is a great demand for such fuels because the emission limits for motor vehicles are becoming stricter and stricter.

Generally, atomic or molecular restructuring is accompanied by an energy input or a loss of chemically bound energy so that the above-mentioned chemical reaction of water and diesel fuel for generating a modified diesel fuel with improved properties, for example, may result in high production costs or an unfavorable environmental balance for the modified diesel fuel. Particularly if the chemical reaction has only a small yield, it may be that the advantages of the modified diesel fuel do not justify the increased expenditure for its production.

It is therefore the object of the invention to provide a reactor in which high-yield chemical reactions are made possible with low energy expenditure.

The object on which the invention is based is achieved with the combination of features according to claim1. Exemplary embodiments of the invention are apparent from the claims dependent on claim1.

The nozzle member of the reactor according to the invention has an inlet for letting at least one reactant flow into the reaction chamber of the reactor, wherein the nozzle member is mounted in a movable manner relative to the housing of the reactor. The reactor comprises a sensor device by means of which at least one measuring quantity can be detected during the chemical reaction taking place in the reaction chamber of the reactor. At least one mounting parameter can be adjusted by means of an adjusting device. The manner in which the nozzle member is mounted can be described by means of the mounting parameter and possibly by means of further mounting parameters. How the nozzle member can be moved relative to the housing and which movement or form of movement results during the chemical reaction is then dependent thereon. The movement of the nozzle member can be induced or influenced by the chemical reaction or by process parameters, such as pressures, temperatures, flow velocities etc.

The reactor according to the invention further comprises a control unit configured for receiving from the sensor device a measurement signal of the sensor device based on the measuring quantity. The control unit can then generate a control signal for the adjusting device depending on the measurement signal. As a result, it is possible to adjust the at least one mounting parameter by means of the adjusting device depending on the measuring quantity detected by the sensor device.

The control unit may include a processor in which the function between the input measurement signal and the output control signal is stored in a memory. In this case, the output control signal may depend on further influencing quantities that are detected during the chemical reaction and supplied to the control unit as additional influencing signals.

In an exemplary embodiment, the sensor device has a sensor for detecting a frequency with which the nozzle member oscillates. The sensor for frequency detection, which may be configured as a sound sensor, then transmits a measurement signal corresponding to the detected frequency to the control unit, which defines or computes a control signal on the basis of this measurement signal and transmits the former to the adjusting device. The mounting parameter is readjusted by means of the adjusting device in accordance with the control signal, which affects the movement, in this exemplary embodiment the frequency, of the nozzle member.

Surprisingly, it was found that the yield of degree of efficiency of the chemical reaction can be optimized by adjusting the frequency. It was also found that, by adjusting the frequency with which the nozzle member oscillates, the course of the chemical reaction can be influenced in such a manner that different products are created.

In an exemplary embodiment, a first stop and a second stop for the nozzle member are provided, between which the nozzle member can move. In this case, a distance between the first stop and the second stop constitutes an adjustable mounting parameter. The oscillation amplitude of the nozzle member moving back and forth between the first stop and the second stop can be adjusted by means of the distance between the two stops for the nozzle member, which has an effect on its frequency.

Preferably, only one of the two stops is configured as a movable stop, whereas the other stop is stationary and is incapable of being moved. A movable adjusting member as a part of the adjusting device may include this movable stop. In one exemplary embodiment, the adjusting member is a threaded member whose axial position can be adjusted by rotating it. In this case, the movable stop preferably acts in the axial direction of the threaded member. If the pitch of the thread of the threaded member is very small, the axial position of the threaded member and thus the effective position of the movable stop can be adjusted very accurately.

The distance between the first stop and the second stop for the nozzle member may extend parallel to a main flow direction with which the reactant flows through the nozzle member. In this exemplary embodiment, the nozzle member thus moves parallel to this main flow direction, i.e. either in the main flow direction or in the opposite direction, i.e. shifted by 180° relative to the main flow direction.

The distance between the stops results in a mounting with play of the nozzle member, wherein the play of the mounting leads to the necessary freedom of movement of the nozzle member. The play may have values of 0.01 to 3 mm, preferably 0.2 to 2 mm.

As a result, the nozzle member may be considered a part of a oscillating system comprising an oscillating mass and a spring damping system, wherein the spring damping system is defined by the type of mounting of the nozzle member in the housing and influences the oscillation behavior of the nozzle member. For example, a soft or tight mounting of the nozzle member may be provided, wherein a force with which the nozzle member is clamped into the housing may also be considered a possible mounting parameter, which may be adjusted by means of the adjusting device in order to influence the movement of the nozzle member. Thus, a clamping force may be varied by means of the adjusting device.

The nozzle member may have an outlet, wherein a flow cross-section of the outlet is greater than a flow cross-section of the inlet. In one exemplary embodiment, the flow cross-section of a nozzle duct (flow duct between the entrance and the exit) increases continuously starting from the inlet. It is also possible that the flow cross-section forms a minimum (in the form of a constricted portion, wherein the flow cross-section of this constricted portion is in each case smaller than the flow cross-sections of the inlet and outlet) or a maximum between the inlet and the outlet.

The nozzle duct may have the shape of a truncated cone. An opening angle of the truncated cone may have values of between 20 and 70°, 30 to 60° or preferably 40 to 50°. In this case, the opening angle is the angle between the cone envelope and the central axis of the truncated cone.

For example, the inlet of the nozzle member may be supplied with a pressurized mixture of two reactants, so that the mixture is pressed through the inlet and then flows through the nozzle member at high velocity. For example, the reactants may be water and a liquid hydrocarbon.

Due to the greater flow cross-section of the outlet and the accompanying pressure drop, bubbles may form in at least one reactant, which then collapse (cavitation) in the nozzle member between the inlet and the outlet or, viewed in the flow direction, behind the outlet of the nozzle member. Due to the moving nozzle member, changing, preferably alternating pressure conditions arise particularly between the inlet and the outlet of the nozzle member, wherein, according to the invention, these changing pressure conditions are exploited in such a manner that the phase of the implosion of the bubbles is stretched in time. In the process, the energy released during the collapse of the bubbles which, in the case of cavitation, otherwise remains unused as heat energy, for example, can be used in a targeted manner for the atomic or molecular restructuring of the at least one reactant. Thus, the oscillation of the nozzle member permits the targeted use of the energy released during cavitation for the chemical reaction.

The reaction chamber is to also include the space located between the inlet and outlet within the nozzle member. Thus, the reaction chamber also includes the nozzle duct. Without being bound to this theory, it is assumed that a not inconsiderable part of the chemical reaction already takes place in the nozzle duct, i.e. between the inlet and the outlet of the nozzle member.

The nozzle member may be configured as a preferably circular disk. The disk may have a central opening. The inlet is disposed in the plane of a first base surface of the disk, the outlet is disposed in an opposite second base surface. Preferably, the nozzle member is a substantially rotationally symmetric body, with the central opening being formed coaxially with the central axis.

In one exemplary embodiment, the nozzle member separates the reaction chamber from a pre-chamber. The pre-chamber serves for supplying to the inlet of the nozzle member the at least one reactant for the chemical reaction or the mixture of several reactants. In this case, the reactant or the mixture is under pressure in the pre-chamber and arrives in the reaction chamber through the inlet of the nozzle member. Hereinafter, only the term “reactant” is used for the reactant and for the mixture.

In one exemplary embodiment, the nozzle member not only serves for feeding the reactant into the reaction chamber, but also for providing for alternating pressure conditions in the reaction chamber, with which the course of the cavitation (formation of gas bubbles and their implosion) is influenced and controlled. The design of the nozzle member, whose mass is the oscillating mass of the above-described oscillating system, to a decisive extent depends, as well as on the design of the nozzle duct, also on the outer shape of the nozzle member, for example in order to realize a predetermined value for the mass/oscillating mass of the nozzle member.

The nozzle member may consist of a material whose density is greater than 5 g/cm3, preferably greater than 8 g/cm3. Iron or brass, for example, may be possibilities for the material of the nozzle member. In one embodiment, a ratio of the mass of the nozzle member (measured in g) to the flow cross-section of the inlet (measured in mm2) takes on values between 30 and 100, 40 to 80, or 50 to 70. If, for example, the diameter of a circular flow cross-section of the inlet is 2 mm and the mass of the nozzle member is 150 g, this yields a ratio mass/flow cross-section of 48 g/mm2.

A ratio of a projected total surface area of the flow cross-section of the inlet may have values of between 500 and 3000, preferably between 1000 and 2000, wherein this total surface area is to correspond to the surface area of the nozzle member projected into the plane of the flow cross-section of the inlet. If, for example, the nozzle member is a circular disk with a diameter of 80 mm, with the diameter of the circular inlet of the nozzle member being 2 mm, this yields a ratio of the projected total surface area to the flow cross-section of the inlet of 1600 (802/22).

In one exemplary embodiment, the nozzle member is attached to the housing via a peripherally extending diaphragm. If the nozzle member is configured as a circular disk, the peripherally extending diaphragm may be a ring. The peripherally extending diaphragm may be firmly connected to the housing with an outer portion, whereas it is firmly connected to the nozzle member with an inner portion. Then, the nozzle member is mounted in a movable manner relative to the housing due to the elasticity of the diaphragm. The diaphragm may have the additional function of sealing the reaction chamber with respect to the pre-chamber.

The diaphragm may consist of an elastic material, e.g. of rubber or an elastomer. The assembly consisting of the diaphragm, the housing and the nozzle member may be chosen such that the diaphragm is under a certain mechanical tension in the non-operating state of the reactor. It is possible to readjust or control this tension during the operation of the reactor depending on the measuring quantity detected during the chemical reaction.

The reactor may have an adjusting member with a needle-shaped tip, which is disposed in front of the inlet of the nozzle member or protrudes into the inlet of the nozzle member. The position of the needle-shaped tip relative to the inlet of the nozzle member can be adjusted in one exemplary embodiment. By means of this adjustment, the yield of the chemical reaction or the quality of the products produced by the chemical reaction can be influenced.

The adjusting member may have a duct for supplying another reactant. Thus, another fluid (liquid, gaseous or as a flowable solid in the form of small particles) can be introduced from the adjusting member into the nozzle duct, in addition to the reactant from the pre-chamber.

Surfaces structures may be incorporated in the vicinity of the inlet, for example—in the case of the exemplary embodiment with the circular disk as a nozzle member—on the first base surface facing towards the pre-chamber. In one exemplary embodiment, these surface structures are disposed around the inlet. In this case, the surface structures may be configured in the form of radially extending notches. The notches or furrows may also be disposed around the inlet in a spiral shape. It was found that, due to the surface structures, the flow conditions (increased turbulence) in front of the nozzle member change such that the yield of the chemical reaction can be increased.

Another object of the invention, namely providing a method for controlling a chemical reaction with the goal of a high yield with as small an energy input as possible, is achieved by the combination of features according to claim12. Exemplary embodiments of the method of the invention are apparent from the claims dependent on claim12.

The above-described reactor can be used in the method according to the invention. In the method according to the invention, the nozzle member executes an oscillating movement during the reaction, wherein at least one parameter of the oscillating movement is being detected and wherein the chemical reaction is controlled on the basis of the detected oscillation parameter. In one exemplary embodiment, the oscillation parameter is the frequency of the oscillating movement of the nozzle member. In one exemplary embodiment, a target value for the frequency is between 16 and 20,000 Hz, 100 to 10,000 Hz, or 1000 to 5000 Hz. It is also possible for the frequency to be in the ultrasound range, with frequencies in excess of 20,000 Hz being assumed for this case (e.g. 20,000 Hz to 100 kHz).

The method may provide that the oscillating movement is stopped by the above-described first stop for the nozzle member and the above-described second stop for the nozzle member, wherein the distance between the first stop and the second stop is being varied or adjusted in order to control the reaction.

In one exemplary embodiment, the position of the needle-shaped body relative to the inlet of the nozzle member is changed in order to control the chemical reaction.

By means of the device according to the invention or the method according to the invention, it is possible, in the case of a liquid hydrocarbon (such as diesel fuel, for instance) to bond oxygen to the carbon chains in such a way that the diesel fuel retains oxidation stability. The oxygen is chemically bonded to the hydrocarbon as a hydroxyl or carboxyl.

During combustion in the internal combustion engine, this oxygen drops to a lower oxidation state and forms the usual combustion products H2O and CO2. During the combustion in the internal combustion engine, the H2O formed transitions into the vapor phase, whereby mechanical energy is generated in the cylinder of the internal combustion engine together with the release of thermal energy due to the combustion.

Due to the additional chemically bonded oxygen atoms, the diesel fuel burns with less emission at high degrees of efficiency. In particular, NOxemissions can be reduced already during combustion by means of the diesel fuel modified in this manner.

Without being bound to this theory, a splitting of the water molecules takes place in the method according to the invention, during which radical hydroxyl ions are produced that form new chemical structures together with the hydrocarbon molecules. When the water molecules are split, the gas phase is avoided and the reaction material remains in a liquid state. Thus, this reaction requires relatively little energy input. It was found that, immediately after the process of change, the processed material has a radical character. Due to the further treatment, the radical structures are converted by oxidation into stable structures. The radical chemical state can be stabilized by adding oxygen, hydrogen, CO2, methane and other gases and liquids. This makes it possible to provide the diesel fuel with more favorable properties. Thus, this method is based on the artificial radicalization of the reactants and the stabilization through oxidation.

The method can also be used where emulsions are being used (e.g. in the cosmetics and food industries). Due to the method, the use of otherwise necessary additives, such as surfactants, for example, can be reduced or even avoided.

FIG.1schematically shows a reactor designated in its entirety with1. In this case, the reactor1is to include those components that are located within the chain dotted line. The reactor includes a housing10and a reaction chamber3enclosed by the housing10. A nozzle member is arranged in a movable manner relative to the housing10. This nozzle member is not shown inFIG.1, but inFIGS.2and3, and there is given the reference numeral30. An adjusting device50serves for adjusting a mounting parameter for the movably mounted nozzle member30. In this exemplary embodiment, the mounting parameter is a play which provides for a certain mobility of the nozzle member30, so that it can move back and forth or execute an oscillating movement.

The adjusting device50is connected to a control unit70via a signal line60. The sensor device80detects at least one frequency with which the nozzle member oscillates. The sensor device80feeds the detected frequency or a measurement signal based on the detected frequency to the control unit70via a signal line61. Based on the measurement signal of the sensor device80, the control unit70determines a control signal for the adjusting device50, which is transmitted via the signal line60. Thus, the control unit50controls the frequency of the nozzle member30.

Moreover, the reactor comprises a second adjusting device90with which an axial position of a needle-shaped tip (see reference numeral92in theFIGS.2and3) relative to the nozzle member30can be adjusted. More details in this regard can be gleaned from the description of theFIGS.2and3. The adjusting device90is connected to the control unit70via a signal line62. Thus, an axial position of the needle-shaped tip can also be adjusted by means of the control unit70.

A first reactant100is supplied to the housing10of the reactor1via a pump101. Moreover, a pump103pumps a second reactant102for the chemical reaction taking place in the reactor into the housing10. The reactant100and the reactant101are brought together outside the reactor1, so that a mixture of the reactants100and101reaches the reactor1. A pump104ensures that the part of the mixture that has not taken part in the chemical reaction is resupplied to the housing10in a circuit. The reactant100may be water. The reactant102may be a common diesel fuel.

The further elements depicted outside the chain dotted line serve for post-processing the products of the chemical reaction or collecting leaked material. Post-processing is not part of the invention and is therefore not described in any more detail.

FIG.2shows a longitudinal section parts of the reactor1, whereinFIG.3shows an enlarged portion ofFIG.3. In this case,FIG.3does not show all the features ofFIG.2, or slightly modified components. The housing10comprises a first housing part11and a second housing part12. A nozzle member30is movably mounted in the housing10. In the exemplary embodiment shown inFIGS.2and3, the nozzle member30can be moved back and forth towards the left and the right in the plane of the drawing.

The nozzle member30is configured as a circular disk having a central bore31. The central bore31is disposed coaxially with a central axis5of the reactor1. The central bore31defines an inlet32and an outlet33of the nozzle member30and may also be referred to as a nozzle duct (seeFIG.3). It is discernible that a circular flow cross-section of the inlet32is smaller than a circular flow cross-section of the outlet33. The flow cross-section of the outlet33(calculated in unit areas, independent of the shape of the flow cross-section) may be greater by the factor 4 or more than the flow cross-section of the inlet32. A main flow direction through the nozzle duct31extends parallel to the central axis5.

The mounting of the nozzle member30has a little play which permits the reciprocating movement of the nozzle member30parallel to the central axis5.

The nozzle duct31has the shape of a truncated cone. An opening angle of the truncated cone designated a inFIG.3is about 45°.

The nozzle member30has a first base surface34and a second base surface35spaced apart therefrom. The distance of the first base surface34from the second base surface35in this case corresponds to a thickness of the nozzle member30. The thickness may be 1 to 10 mm, for example.

As can be seen inFIG.2, the first housing part11forms an inlet duct13through which the mixture of the reactants100and102for the chemical reaction is fed into a pre-chamber2(the inlet duct is not shown inFIG.3). In this case, the pre-chamber2is delimited by the first housing part11and the nozzle member30. Through the inlet32, the pressurized mixture of water and diesel fuel arrives in the nozzle duct31, which leads into a reaction chamber3. The nozzle duct31is supposed to be a part of this reaction chamber3so that in the narrower sense, viewed in the flow direction of the mixture, the reaction chamber3already begins at the inlet32of the nozzle member30. The part of the mixture that does not come through the inlet32leaves the pre-chamber2through an outlet opening14and is returned to the pre-chamber via the pump104(seeFIG.1).

The second housing part12enclosing the reaction chamber3has a cylindrical inner sleeve15and an outer sleeve16disposed coaxially therewith, wherein the inner sleeve15forms the actual wall of the reaction chamber3. An annular chamber4between the inner sleeve15and the outer sleeve16serves for collecting water and diesel fuel that may escape because of the pre-chamber being imperfectly sealed. The collected leaked material is discharged from the annular chamber4through a discharge duct17.

Moreover, the reaction chamber3is delimited by a sleeve-shaped attachment36which is placed coaxially on the second base surface35of the nozzle member30. The attachment36, which has a slightly reduced diameter compared to the diameter of the inner sleeve15, serves for delimiting the reaction chamber3even better from the annular chamber4.

An outlet opening18, through which the products of the reaction taking place in the reaction chamber3can exit the reactor1, is provided at an end of the substantially cylindrical reaction chamber3opposite the nozzle member30.

The nozzle member30is held by an annular diaphragm40. An inner portion41of the diaphragm40is clamped between a fastening ring37and a thickness-reduced peripherally extending edge38of the nozzle member30. Threaded bores39are provided for accommodating fastening screws by means of which the inner portion41of the diaphragm40can be clamped between the fastening ring36and the edge37.

An outer portion42is clamped between the first housing part11and an annular fastening flange19. The outer portion42of the diaphragm can be fixed between the first housing part11and the fastening flange19by means of fastening screws that can be screwed into the threaded bores20.

The above-mentioned play required for the reciprocating movement of the nozzle member30relative to the housing10is defined by an annular first stop21and an adjusting member51with a second stop52. The axial position of the second stop52(parallel to the central axis5) is variable due to the axial adjustability of the adjusting member51. The adjusting member51is a part of the adjusting device50and configured as a threaded member. The threaded member has a male thread53that cooperates with a female thread22on the fastening flange19. The adjusting member51has an outer toothing54meshing with a gear55. When the gear55is rotated, this rotary movement is transmitted on to the adjusting member51, resulting, due to the cooperation of the male thread53and the female thread22of the fastening flange19, in an axial displacement of the adjusting member51and thus also in an axial displacement of the second stop52for the nozzle member30. In other words, the play and thus the maximum amplitude for the nozzle member30can be adjusted by rotating the adjusting member51.

In the first housing part11, an axially movable further adjusting member91is provided coaxially with the central axis5as a part of the adjusting device90that comprises a needle-shaped tip92already mentioned above. In this case, the needle-shaped tip92reaches through the inlet32and thus protrudes into the nozzle duct31. The adjusting member91has a duct93through which another reactant can be introduced into the nozzle duct31in addition to the mixture fed into the pre-chamber2. The adjusting member91has an outer toothing94that is in engagement with a gear95. A male thread96of the adjusting member91cooperates with a female thread23incorporated into the first housing part11, so that a rotation of the gear95results in an axial displacement of the adjusting member91. The axial position of the needle-shaped tip92with respect to the nozzle duct31can thus be adjusted by rotating the gear95.

The mixture of water and diesel fuel arrives in the pre-chamber2under high pressure (e.g. 2 to 5 bars). In the process, the mixture is pressed through the inlet32into the nozzle duct31, wherein, caused by the flow and pressure conditions prevailing in the nozzle duct31or the reaction chamber3, gas bubbles are formed that then collapse again (cavitation). The nozzle member30is caused to oscillate by the flow and pressure conditions, wherein the play for the nozzle member30can be adjusted by the adjusting member51. This in turn affects the frequency with which the nozzle member30can oscillate. Preferably, a resonance frequency is aimed at, so that the nozzle member30oscillates with the excitation frequency.

The energy released when the gas bubbles collapse is used for triggering the oscillating movement of the nozzle member30.

The oscillating movement of the nozzle member30is thus triggered by the implosion of the gas bubbles. Since, according to the invention, the nozzle member30is configured to be movable, the oscillation energy of the nozzle member30acts primarily in two directions parallel to the central axis5, that is, in the illustration ofFIG.2, towards the left in the direction of the main flow direction and opposite to the main flow direction, i.e. towards the right (back and forth). Through this process, the course over time of the implosion phase is changed. Since the implosion phase takes place in the microsecond or millisecond range, it is possible, according to the invention, to influence this phase. I.e. the method preferably has to be controlled in such a way that the oscillation goes into resonance. Two phases have to be distinguished:

a) Shortening the duration of the implosion phase: The shortening of the duration of the implosion phase that occurs when the nozzle member moves in the direction of the main flow direction causes the release of a higher energy, which is used for deconstructing molecular structures (breaking up the existing chemical structures). In this phase, the oscillation energy is used for the higher active energy.

b) Extending the duration of the implosion phase: The extension of the duration of the implosion phase, which occurs during a movement of the nozzle member30in the direction opposite to the main flow direction, is used for the (re-)structuring of the molecules because the structuring process requires a longer phase in time.

The oscillation of the nozzle member30may also be artificially (mechanically or electrically) excited (instead of by means of cavitation).

The oscillation amplitude of the nozzle member30may be modulated in such a way that the molecular structures are broken up in a reactor part and these broken-up molecular structures are re-structured in another reactor part.

An electrical potential may be applied between the needle-shaped tip92and the nozzle member30. That may serve for accelerating the deconstruction process.

In the narrower sense, the invention uses cavitation, if at all, only for exciting the nozzle member30. As soon as the intended frequency has been reached and the chemical reaction is adjusted, a cavitation in the sense of a disordered release of energy is no longer at hand. Rather, according to the invention, the release of the energy during the implosion of the gas bubbles is used in a targeted manner for restructuring at least one reactant.

FIG.4shows an exemplary embodiment of the geometry of the nozzle duct31. Starting from the inlet31, the nozzle duct31first has a first portion31awith a constant or approximately constant flow cross-section, wherein an opening angle in this portion is 0° or 0° to 5°. The first portion is followed by a second portion31b, which may also be referred to as a transitional portion. In this transitional portion, the almost non-existent opening angle of the first portion31atransitions into the opening angle α in a third portion31c. In this exemplary embodiment, the opening angle α is about 25°. In the third portion31c, the opening angle α is constant along the length of the portion31c. It is also possible that the opening angle becomes larger and larger towards the outlet33.

InFIG.4, the thickness of the nozzle member is designated by the letter d. The length of the first portion31(parallel to the central axis5) may be 10 to 50% of the thickness d, e.g. 2 mm, with a thickness d of 5 mm. The length of the second portion31bmay be 5 to 30%. The length of the third portion31cmay be 20 to 85% of the thickness d.

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