JPS6339770B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In order to obtain the limit performance of a diesel engine with a turbocharger, especially a diesel engine, the present invention aims to improve the turbine so that the relationship between the boost pressure ratio of the compressor and the air flow rate is as close as possible to the surge limit line. This invention relates to a low compression ratio (hereinafter simply referred to as LCR) diesel engine whose output can be adjusted.

In conventional diesel engines, the turbocharger is designed to match the engine in terms of air flow through the engine and compressor boost pressure ratio required to obtain the desired engine performance. That is, turbochargers are typically designed to operate as close as possible to the compressor's surge limit line in order to achieve critical engine performance.

However, regarding the above-mentioned design,
Special problems are posed when the engine is an LCR engine. Such LCR engines are generally limited to engines with compression ratios of 12:1 or less. Diesel engines require a minimum cylinder pressure for the initiation of combustion in the cylinders, especially during startup and warm-up. In the LCR engine, this requirement is
The relatively low compression ratio in the first place poses special problems. Turbochargers are usually
The compressor is designed to increase the air pressure supplied to the engine cylinders, but the air pressure required at a given engine speed will, of course, be different in practice, to ensure that the compressor operates under surge conditions. In some cases, it may be requested. LCR diesel engines are difficult to start when cold, so they are often configured to preheat the intake air when starting.

The object of the present invention also includes improvements to eliminate the problem of poor combustion during startup and light loads.
Our goal is to provide LCR diesel engines.

The invention will now be described in more detail with reference to the accompanying drawings, which illustrate one embodiment of the invention.

FIG. 1 depicts an engine incorporating aspects of the present invention. Such engines typically include a plurality of engine cylinders and a plurality of associated reciprocating pistons, one cylinder 10 and its piston 11 being shown schematically in FIG. There is. This engine also
A turbocharger 9 includes a compressor 12 and a turbine 13, which are connected to each other by a drive shaft 14. The drive shaft 14 is connected at both ends to rotors of the compressor 12 and the turbine 13, respectively.
An intake manifold 16 communicates the air outlet 17 of the compressor 12 with an intake port 18 of the cylinder 10, while an exhaust manifold 19 connects the air outlet 17 of the compressor 12 with the intake port 18 of the cylinder 10.
The exhaust port 21 of the turbine 13 and the air intake port 22 of the turbine 13 are communicated with each other. As is well known to those skilled in the art, during engine operation, exhaust gas flows out of the engine cylinders and passes through the exhaust manifold 19 to drive the turbine 13. The turbine 13 drives a compressor 12 which supplies intake air at boost pressure to an intake manifold 16.

The engine further includes a bias line 26 with an inlet 27 opening into the intake manifold 16 and an outlet 28 opening into the exhaust manifold 19. Connected to the bypass line 26 between the ports 27 and 28 is a flow control or surge control valve 29 and an air ejector 31, which are shown in more detail in FIG. This ejector 31
is facing toward the exhaust manifold, and the pipe line 26
It includes an air nozzle 32 oriented to emit a jet or flow of air in a direction downstream of the air. This nozzle 32 is connected via a line 33 to a compressed air supply 34, which is also provided with two control valves, designated 36 and 37 and described in more detail below. . Thus, when these two valves 36 and 37 are both open, a stream or jet of air is ejected through the nozzle 32, creating a stream of air through the line 26 and towards the exhaust manifold 26. Normally, air passing through conduit 26 passes through valve 29, but when valve 29 is occluded, a device (not shown) closes the conduit to allow air flow through ejector 31. 26 upstream of the nozzle 32.

The flow rate control valve 29 adjusts the valve 29 to adjust the amount of bypass air.
It is operatively connected to a control mechanism 41 shown in FIGS. 1 and 2. The control mechanism 41 is configured to respond to the output of the compressor 12, as will be explained later.

The exhaust manifold 19 is provided with an exhaust manifold burner 4 which is designed to burn fuel within the exhaust manifold 19 in order to provide an additional amount of heated air to drive the turbine 13.
2 is provided. This exhaust manifold burner 42 is connected to a fuel supply amount control unit 46 (hereinafter simply referred to as a fuel control unit) from a fuel supply device 47.
and a fuel injection nozzle 43 that receives fuel through a fuel line 44. A spark plug 48 is provided within the exhaust manifold burner and is adapted to ignite the fuel injected into the burner combustion chamber by the nozzle 43.
This spark plug 48 is connected to an exciter 49 which provides it with electrical energy.

Further, the engine can be equipped with the following devices for improving engine performance. That is, for example, the intake manifold 16
It is like an air aftercooler 51 provided in front of the intake port 18 of the cylinder 10 within the cylinder 10. Further, an intake manifold burner 52 is installed between the aftercooler 51 and the cylinder intake port 18 to improve combustion performance. Further, another fuel control device 53 is provided between the fuel supply device 47 and the intake manifold burner 52 in order to adjust the amount of fuel supplied to the intake manifold burner 52.

The engine also includes a number of controls for coordinating the operation of the components and protecting them from damage. For example, a system 61 constituting a part of the engine's lubrication system is connected to the turbocharger drive shaft 14 for lubrication, and the presence of lubrication pressure in the lubrication system 61 to control the opening and closing of the valve 36. A control system 62 is arranged to sense. This control system 62 senses the lubrication pressure and controls the lubrication system 61.
A control switch 63 is provided which causes the valve 36 to open only when there is lubricating pressure therein.
This control device prevents the ejector 31 from operating until the engine is rotating during startup and the drive shaft 14 is lubricated. The valve 37 provided in the compressed air supply line 33 is responsive to the respective internal pressures of the intake manifold 16 and the exhaust manifold 19 and is activated only when the pressure in the intake manifold 16 is lower than the pressure in the exhaust manifold 19. This is an air differential pressure responsive valve that opens the valve 37. When the pressure in the intake manifold 16 is higher than the pressure in the exhaust manifold 19, this pressure difference creates an air flow through the bypass line 26 toward the exhaust manifold, so that the ejector 31
activation is normally not required. The fuel control unit 46 senses the pressure in the air supply line 33 downstream of the valve 36 and the air pressure in the aftercooler 51, thereby increasing the pressure to the fuel injection nozzles 43 of the exhaust manifold burner 42. Controls fuel supply amount. On the other hand, the control mechanism 4
1 receives high pressure air via a line 66 communicating with line 33, and a valve 67 provided in line 66 responds to the discharge pressure of compressor 12 via line 68.

The operating principle of the control mechanism 41 and the flow rate control valve 29 is based on the following discovery. That is, with respect to the surge limit line in the typical compressor operating characteristic diagram shown in FIG. This is the discovery of a phenomenon in which the ratio of the aerostatic pressure in the passage 96 to the air dynamic pressure in the total air pressure in the passage 98 approaches a constant value. The goal to be achieved using this heuristic is to operate the compressor near its performance limits and within the non-surge region.

FIG. 2 shows the control mechanism 41 and flow control valve 29 in detail in an enlarged manner. Control mechanism 4
1 includes a spool valve device including a housing 76 and a cover 77, and a diaphragm chamber 78 is formed between the housing 76 and the cover 77. In addition, a flexible diaphragm 79
is provided extending across diaphragm chamber 78 between housing 76 and cover 77 . This diaphragm 79 forms a gas-tight connection between the housing 76 and the cover 77. A spring cap 81 is provided above the diaphragm 79, and a compression spring 82 is inserted between the upper side of the spring cap 81 and the lower side of the cover 77 in a resilient state. That is, the cap 81 and the spring 8
2 is accommodated in the diaphragm chamber 78.
A common hole is drilled in the center of diaphragm 79 and cap 81 through which the threaded upper end of spool 83 extends and is tightened to diaphragm 79 and spring cap 81 by nut 84. Preferably, the diaphragm 7
A flat pressure plate 85 is installed between the lower side of the spool 83 and a step 86 formed at the upper end of the spool 83.

The housing 76 has a spool hole 91 and a plurality of airflow passageways therein. The spool hole 91 has a sleeve 92 that is fitted into the spool hole and slidably receives the spool 83. Said conduit 66 through which the first air flow passage 93 communicates on one side with the compressed air supply device 34
(see FIG. 1), another air flow passage 94 is connected on one side to said passage 96 which communicates with the intake manifold 16, and yet another air flow passage 97 is connected on one side to said passage 96 which also communicates with the intake manifold 16. Manifold 16
It is connected to a passage 98 that communicates with the. The other side of the air flow passage 94 opens into a diaphragm chamber 78 formed above the diaphragm 79, and the other side of the air flow passage 97 opens into a diaphragm chamber 78 formed below the diaphragm 79. ing.

A threaded cap 99 having a through hole 101 in the center is screwed onto the lower end of the spool hole 91 so that the lower end is open to or communicates with the atmosphere.
A compression spring 102 is interposed between the cap 99 and the lower end of the spool 83 in a resilient manner so as to bias the spool 83 upward. Nevertheless, the compression spring 82 provided in the diaphragm chamber 78 is connected to the diaphragm 79 and the spool 83.
It goes without saying that there is a tendency to urge downward.
In addition to each of the aforementioned air flow passages formed in the housing 76, two more air flow passages 103 and 104 are formed in the housing 76, each one side of which is connected to the cylinder chamber of the flow control valve 29. are connected to two passages 106 and 107, respectively, which communicate with the spool hole 9.
It opens at 1.

The sleeve has a communication hole 111 on one side in the radial direction that communicates the other side of the air flow passage 93 with the internal space of the spool hole 91, and the two air flow passages 103 and 111 on the other side in the radial direction. 1
Communication holes 112 and 11 connect the other sides of 04 to the internal space of the spool hole 91, respectively.
It has 3. An annular groove 114 is formed on the outer periphery of the spool 83 at its axial center, and the axial length of the annular groove 114 is slightly shorter than the axial distance between the two communicating holes. . Thus, when the spool 83 is in its neutral position as seen in FIG. 2, the annular groove 114 does not communicate with either of the two communicating holes 112 and 113. On the other hand, the other communication hole 111
In the embodiment of the present invention shown in FIG. 2, the annular groove 114 of the spool 83 and allowed to communicate at all times. As is clear from FIG. 2, when the spool 83 moves upward, the annular groove 114 comes into communication with the communication hole 113, and thus the air flow passage 93 and the air flow passage 104 are connected to the annular groove 114.
placed in communication via. On the other hand, spool 8
3 moves downward, the annular groove 114 comes into communication with the communication hole 112, and thus the air flow passage 93 and the air flow passage 103 are placed in communication via the annular groove 114. As described above, the annular groove 114 cannot communicate with the two communication holes 112 and 113 at once, and as the spool 83 moves, it communicates with only one of the communication holes.

The spool 83 has an open hole 116 formed in its radial center and extending in the axial direction.
The lower end of the open hole 116 opens into the spool hole,
It communicates with a common hole 101 that communicates with the atmosphere. This open hole 116 further includes two narrow annular grooves 117 formed around the outer periphery of the spool 83 on the upper and lower sides separated from the annular groove 114.
and communicates with 118. Upper narrow annular groove 117
, the spool 83 is moved downward and the annular groove 11
4 is arranged so that when the communication hole 112 communicates, the narrow annular groove 117 and the communication hole 113 communicate with each other at the same time. Conversely, when the spool 83 is moved upward and the annular groove 114 communicates with the communication hole 113, the lower narrow annular groove is arranged so that the lower narrow annular groove communicates with the communication hole 112. ing. In the above configuration, when the spool 83 is moved downward from the position shown in FIG.
6 receives high pressure air from the compressed air supply device 34, the air flow passage 103 also receives high pressure air, while the air flow passage 104 communicates with the atmosphere via the narrow annular groove 117 and the open hole 116 in the spool 83. be done. On the other hand, when the spool 83 is moved upward, the air flow passage 104 receives high pressure air from the compressed air supply device 34 through the pipe line 66, the communication hole 111, the annular groove 114, and the communication hole 112 in this order. .

Two passages 96 and 98 communicate with the engine's intake manifold 16, as generally described above in FIG. Passage 96 is provided to respond to static air pressure within intake manifold 16 at outlet 17 of compressor 12, while passageway 98 is provided to respond to static air pressure within intake manifold 16 at outlet 17 of compressor 12. arranged to respond to pressure.

The flow control valve 29 includes a pneumatic cylinder having a cylinder chamber 122. Cylinder chamber 1
A piston 123 is slidably housed in the piston 22, and a piston rod 124 is attached to the piston 123.
and extends through the bottom of the cylinder 121. A pipe line 107 is provided to connect the communication hole 126 opened at the upper end of the cylinder chamber 122 and the air flow passage 104.
A conduit 106 is provided to connect a communication hole 127 that opens at the bottom of the air flow passage 22 and the airflow passage 103 . Thus, conduits 106 and 107 are connected to cylinder chamber 12 on either side of piston 123, respectively.
It will communicate with 2. A seal 128 is provided on the outer peripheral surface of the piston 123 to prevent air from flowing through the piston.

The piston rod 124 projects out of the cylinder 121 through an airtight hole 131 at the bottom of the cylinder, and is connected at its lower end to a bypass valve that opens and closes the bypass line 26. The bypass valve and the piston rod are connected by a "knock-off" connection method. To explain this "from-motion" connection in detail, the piston 123 and piston rod 124 are configured to apply a downward force to the valve member 132, but not to apply an upward force to the valve member 132. It is. That is, this connection is provided with a sleeve 133 attached to the lower end of the piston rod 124, and the sleeve is slidably positioned within a cylindrical hole 134 formed inside the valve member 132.
The lower end of this sleeve can abut against a step 136 formed at the lower end of the cylindrical hole 134. The downward movement of piston rod 124 and sleeve 133 thus causes sleeve 133 to abut step 136 of valve member 132 and pushes valve member 132 downwardly. But on the other hand,
The upward movement of piston rod 124 and sleeve 133 simply causes sleeve 133 to slide upwardly within said cylindrical bore 134 without applying an upward force to valve member 132.

One compression spring 137 contacts a step 138 formed on the outer peripheral surface of the valve member 132 on one side, contacts an inner wall surface 139 of the valve housing on the other side, and is located around the valve member 132. It is deployed in a compressed state. Valve member 1
32 further communicates the lower end of the cylindrical hole 134 with the inside of the bypass conduit 26, and when the sleeve 133 moves up and down within the cylindrical hole 134, air flows inside and outside the lower end of the cylindrical hole 134. A narrow passage 141 serving as a ventilation hole for allowing circulation is formed.

The valve member 132 is located within an air passageway that is part of a bypass line defined by a wall 142. A valve seat 143 is formed in this air passage and comes into contact with a valve seat formed at the lower end of the valve member 132. Valve member 13
2 is pushed downward to the position shown in dotted lines in FIG. However, when the valve member 132 is moved upwardly, as shown in solid lines in FIG. 2, bypass air is forced past the valve member and through the bypass line 26. The valve seat 144 is
Preferably, a substantially cylindrical guide protrusion 146 extending close to the bypass pipe wall surface 147 is provided. It has also been found that the provision of this guide protrusion 146 stabilizes the operation of the bypass valve. The spring 137 holds the valve member 132 on the valve seat 143 when the piston 123 and sleeve 133 are in the upper position. However, when a pressure difference exists between the intake manifold 16 and the exhaust manifold 19 that is sufficient to overcome the elastic force of the spring 137, the valve member 1
32 acts as a check valve and opens to allow air flow from intake manifold 16 to exhaust manifold 19. This check valve device prevents air flow in the opposite direction.

Returning again to FIG. 1, the passages 96 and 98 are connected to the intake manifold 16 as described above, and the control mechanism 41 controls the static air pressure and total air pressure in the intake manifold at the outlet 17 of the compressor 12. A vent lily, preferably formed by a constriction 151, is provided to intensify the two pressure signals, respectively responsive to pressure, but also static pressure and total pressure. Thus, the aerostatic pressure passage 96 connects to a passage 152 that opens into the constriction 151 of the bench lily, while the total pressure passage 98 is located immediately downstream of the constriction 151 and opens at one end in the upstream direction. It is connected to pipe 153. The static air pressure in the constriction 151 of the bench lily will be directed into the passages 152 and 96, and the total air pressure will be directed into the tube 153 and the passage 98. This total air pressure is equal to the static air pressure plus the dynamic air pressure created by the compressor discharge air through the bench lily.

Returning again to FIG. 2, the operation of the control mechanism 41 and flow rate control valve 29 will be explained. An aerostatic pressure P _s exists above the diaphragm 79 and a total air pressure P _t
exists below the diaphragm 79. The static pressure acts on the total area A ₁ of the diaphragm, while the total pressure acts on the total area A ₁ of the diaphragm minus the cross-sectional area A ₂ of the spool 83.

When both of the above pressures produce a pressure balance of [P _s A ₁ =P _t (A ₁ −A ₂ )], the spool 83 is in a position where it does not communicate with any of the communication holes 112 and 113 of the annular groove 114 of the spool. is placed in a neutral position. Therefore, in this case, neither side of the cylinder chamber is pressurized, and the sleeve 133 will stop at the current position regardless of its position.

From the pressure balance described above, when the static pressure becomes higher than the total pressure, the spool 83 is moved downward and the high air pressure in the line 66 is supplied to the lower side of the cylinder chamber 122. Therefore, piston 123 is forced upwardly and air pressure in intake manifold 16 opens check valve 29 to bypass air in the intake manifold. On the other hand, when the dynamic pressure increases, the spool 83 is moved upward, causing the high pressure pipe line 66 to communicate with the upper side of the cylinder chamber 122.
This action forces piston 123 downwardly, causing valve 29 to close so as to reduce the amount of bypass air.

Note that the following two points are added regarding the configuration of the control mechanism 41 of the present invention described above. That is, firstly,
The upper end of the cap 81 serves as a stopper to prevent the spool 83 from moving upwards excessively, and secondly, the control mechanism 41 serves as a pilot valve to amplify the pressure signal in the operation described above. However, this control mechanism 41
can be omitted by configuring the flow control valve 29 to respond directly to air pressure.

With reference to FIG. 3, the operation of the engine system of the present invention will be further explained.

Figure 3 shows changes in three elements, with the horizontal axis representing air flow expressed in weight per second, and the vertical axis representing air pressure converted to boost pressure ratio. . Third
In the illustrated graph, line 161 represents the compressor surge limit line, line 162 represents the compressor output for a non-bypass turbocharger, and line 163 represents the desired compressor operating line. Assuming now that the engine is operating in a non-bypass condition at low speeds, the amount or weight of air drawn into the engine is indicated by point 164 and the intake air pressure at that time is indicated by point 166. The intersection point _C1 between the air weight and the air pressure is located to the left of the surge limit line 161, and the compressor 12 does not operate in this region. However, due to the bypass device of the present invention, the demands of the engine will be met. When the compressor 12 starts with a discharge pressure above the operating line 163, the increased static pressure moves the piston 123 upwardly and a portion of the compressor discharge pressure is bypassed through the bypass line 26. As the bypass line is opened, the compressor 12 begins to generate a large amount of air flow. The compressor air flow rate then increases to point 167 while maintaining its pressure as indicated by point 166. The amount of air bypassed differs between points 164 and 167. As a result, the engine operates at an operating line 1 for the engine's maximum performance (limit performance), which approaches the surge limit line but is located to the right of it.
While the compressor is operating on 63, the engine will receive the desired air pressure and amount. Changes in engine speed cause the air demand to change, but the compressor continues to operate on operating line 163 while the amount of bypass air changes. When the flow rate control valve 29 adjusts the amount of bypass air, the air pressure state in the constricted portion 151 of the bench lily changes, but the operation immediately stabilizes.

From the above discussion, it can be seen that a constant ratio between the static and dynamic pressures at the compressor outlet creates an operating line 163 that is close to and parallel to the surge limit line 161. This ratio is then used to adjust the amount of bypass air in the bypass line 26.

FIG. 4 is a graph of actual test data in the development of the engine system of the present invention. There are
A compressor surge limit line and a number of operating lines on either side of the surge limit line are shown.
For the diaphragm to spool diameter ratios tested, the actuation line is moved to either side of the surge limit line while remaining generally parallel to the surge limit line. If another compressor is used whose surge limit line has a different slope, the ratio of the diaphragm cross-sectional area to the spool cross-sectional area A ₁ /
It would be necessary to make A ₂ equal to a value other than 14.9 as shown on the graph in Figure 4. In addition to adjusting the position of the surge limit line, the two springs 82 and 10 in the control mechanism 41 shown in FIG.
2 contributes to the stabilization of the engine device of the present invention.

On the other hand, when the control mechanism 41 and the flow control valve 29 can also be used as waste gas or anti-surge control devices, it is preferable to use them in combination with the ejector 31 and the exhaust manifold burner 42. As mentioned earlier, LCR (low compression ratio)
Since the engine is difficult to start when the engine is cold, the bypass line 26 is made to cooperate with the burner 42 to improve the starting performance of the engine. When the engine's electrical system is first connected and the starter motor is activated, the engine is turned and the fuel and lube pumps begin operating. Exciter 49 also produces a spark in plug 48. The lubricating pressure actuates switch 63, opening air valve 36. Initially, valve 37 is opened because there is not enough exhaust from the engine to drive turbine 13 and there is no pressure differential between the intake and exhaust manifolds. The compressed air supplied from the compressed air supply 34 thus flows through the nozzle 32 and this relatively small amount of air is combined with the exhaust of the engine and flows into the burner 42 . Then, the fuel from the fuel injection nozzle 43 and the combined gas are mixed and ignited by the ignition plug 48. As a result, the burner exhaust resulting from this ignition easily drives the turbine 13. On the other hand, the compressor 12 is driven in accordance with the drive of this turbine, and supplies a large amount of air into the intake manifold 16. A portion of this air is bypassed and flows through the bypass line 26 by the action of the ejector 31. This increased air flowing to the burner 42 increases the burner exhaust,
The driving performance of the turbine 13 is improved. This boost strap operation thus increases the rotational speed of the turbocharger. The intake air is compressed and heated by the compressor 12. When the energy added to this intake air reaches a certain threshold, combustion occurs within the cylinder and the engine runs.

Ejector 31 and/or burner 42 may also be operated to increase engine power and/or engine performance during other engine conditions. Additionally, the intake manifold burner 52 is used to heat intake air during engine starting and idling. The aftercooler 51 is configured not to normally operate when the engine is started.

[Brief explanation of the drawing]

1 is a schematic diagram of a diesel engine having a turbocharging device and a bypass device according to the invention; FIG. 2 is a sectional view of an air bypass control device of said engine; and FIGS. are diagrams each showing the operating state of the engine. 12... Compressor, 13... Turbine, 1
6... Intake manifold, 17... Compressor discharge port, 19... Exhaust manifold, 22... Turbine intake port, 26... Bypass pipe line, 29... Flow rate control valve, 41... Control device, 42... Exhaust Manifold burner, 46, 53...Fuel control unit, 47...Fuel supply device, 48...Blug, 5
1... Aftercooler, 52... Intake manifold burner, 79... Diaphragm, 132... Valve member, 143, 144... Valve seat, 146... Guide projection, 161... Surge limit line, 162... Non-bypass Turbocharger operating line, 163...
The operating line of the turbocharger of the present invention.

Claims (1)

[Scope of Claims] 1. At least one engine cylinder, a turbine compressor unit, an intake manifold connecting an outlet of the compressor to an inlet of the cylinder, and an exhaust port of the cylinder connecting the outlet of the compressor to an inlet of the cylinder. an exhaust manifold connected to the intake manifold; a valve device disposed within the bypass line to control the flow of bypass air out of the bypass line;
connected to the intake manifold to sense static air pressure and total air pressure within the intake manifold, and to adjust the valve device according to a ratio between the static pressure and the dynamic pressure in the total air pressure. and a control device. 2. The device of claim 1, wherein the control device comprises a spool valve device coupled to the valve device and a pressure sensing device provided in the intake manifold. 3 In addition to what is described in claim 1, the invention further includes a vent lily portion formed within the intake manifold, and the control device includes a vent lily portion formed in the intake manifold for sensing static pressure within the intake manifold. Claim 1, further comprising a first passage connected to the constriction and a second passage extending into the constriction of the bench lily for sensing total combined static and dynamic pressure. The device according to item 1. 4. The apparatus of claim 1, wherein the bypass line is further coupled to the exhaust manifold for supplying bypass air into the exhaust manifold. 5. A one-way valve is further provided in the bypass line to allow bypass air to flow only in the direction from the intake manifold to the exhaust manifold. The device according to item 4. 6. The apparatus of claim 4, further comprising a burner disposed within the exhaust manifold and receiving the bypass line. 7. The device according to claim 6, characterized in that the bypass line is provided with an ejector device for ejecting air into the bypass line and directing the air towards the burner. . 8. The control device comprises a movable member for adjusting the valve arrangement, the movable member having one side responsive to the static pressure and the other side responsive to the dynamic pressure, and 2. Device according to claim 1, characterized in that the position is determined by the ratio of the static pressure to the dynamic pressure.