This invention relates to an exhaust system having a nozzle allowing exhaust gases to be discharged from the engine used in helicopters.

The nozzles enabling exhaust gases to be discharged from helicopter engines also enable the combustion gases coming out of the engine area to be discharged with minimum performance loss and to draw the necessary air to cool the engine area with its venturi effect. The discharge of waste exhaust gases from the nozzles at a low temperature is critical for the survival of helicopters on the battlefield. The discharge of exhaust gases from the exhaust system at high temperatures increases the risk of helicopters of being detected and destructed by missiles that can be locked to high-temperature areas of their targets using an infrared seeker. Therefore, the ability of discharging exhaust gases from nozzles with minimum performance loss at a low temperature provides a great advantage for the survival of military helicopters on the battlefield. Backpressure and thermal trace are some of the substantial parameters to be taken into account in the nozzle design. The effect of the nozzle structure on performance and on the ability to draw outdoor air is generally inversely proportional to each other. Therefore, even if the nozzle provides effective cooling, the backpressure may be higher than allowed. Cone-shaped structures can be used in the design of nozzles providing alternative high outdoor air in the prior art.

The United States patent document US10273018, which is included in the known state of the art, describes an exhaust system for reducing the infrared visibility of exhaust gases, wherein exhaust gases are cooled by mixing exhaust gases with secondary air and are so discharged in an upward direction with respect to the air vehicle. As a result of discharging cooled exhaust gases in an upward direction with respect to the air vehicle, the thermal trace of exhaust gases for infrared guidance systems is reduced.

The United States patent document US6971240, which is included in the known state of the art, describes a system for reducing the infrared trace by passing exhaust gases through flow channels. There is provided a nozzle outlet opening in an exhaust outlet section for mixing the gases prior to discharge, and this opening may have a lobed structure in another embodiment of that invention.

The United States patent document US6606854, which is included in the known state of the art, describes a multilobe nozzle with exhaust mixing geometries that reduce the infrared visibility of hot parts. There are protrusions which enable the internal and external channels to rotate. While inner channels move away from each other in the longitudinal axis direction, the outer channels converge in the longitudinal axis direction, with lobes provided which are bent around the longitudinal axis.

The United States patent document US4487017, which is included in the known state of the art, describes a 5-lobe design comprising convex and concave lobes. A good mixing efficiency, good aerodynamics, short axial length and low weight properties are achieved due to the form of flow surfaces which are bent along the longitudinal axis.

With an exhaust system developed by this invention, an efficient helicopter nozzle design can be realized for discharging exhaust gases from the engines in helicopters, wherein performance loss is lowered, cooling capacity is enhanced and thermal trace is reduced.

Another object of this invention is to realize an effective nozzle design, increasing the cooling performance and reducing the infrared trace without the need for a conical structure in itself by a nozzle design with inner and outer lobes positioned at equal angular intervals.

A further object of the present invention is to realize a helicopter nozzle design, wherein engine performance loss is reduced by virtue of low backpressure values.

The exhaust system realized to achieve the object of the invention, as defined in the first claim and in the claims dependent thereon, comprises at least one engine of the type used in air vehicles; exhaust gas generated by the operation of the engine and removed from the engine; at least one nozzle with an almost entirely cylindrical geometry, positioned on the engine and enabling the exhaust gas (E) to be discharged from the engine as well as the flow of the exhaust gas (E) to be changed; outdoor air taken from the atmosphere and, by enabling it to be mixed with the exhaust gases, cooling the exhaust gases; an ejector on the nozzle, extending in a cylindrical geometry along the axis on which the nozzle extends as well as extending outward from the nozzle so that it almost completely surrounds the nozzle and allowing exhaust gases (E) to be mixed with the outdoor air (H); more than one outer lobe on the nozzle at equal angular intervals, directing the exhaust gases from the engine to the ejector; more than one inner lobe positioned on the nozzle in an alternating fashion with the outer lobes so as to extend into the interior from the nozzle and transferring the outdoor air to exhaust gases through the nozzle to enable the mixing of exhaust gases with outdoor air.

The exhaust system of the invention comprises an inner lobe extending from above the nozzle to the inside of the nozzle so as to face the outer lobe and positioned against the outer lobe, thereby allowing outdoor air to be homogeneously mixed with exhaust gases so as to provide a high cooling capacity and create a low backpressure.

In an embodiment of the invention, the exhaust system comprises more than one outer lobe central axis that radially divides the outer lobes in two, more than one inner lobe central axis that radially divides the inner lobes in two, and a nozzle enabling outdoor air to be efficiently mixed with exhaust gases by placing in an almost entirely co-aligned manner the outer lobe central axis and the inner lobe central axis which are positioned against each other with respect to the radial direction. The expression 'with respect to the circumference of the nozzle' corresponds to the expression 'with respect to the direction of an arc a circle defines along its circumference' or 'with respect to the radial direction'.

In an embodiment of the invention, the exhaust system comprises an outer lobe having a larger diameter value than the motor outlet diameter, and a nozzle enabling outdoor air to be efficiently mixed with exhaust gases by the ratio of the inner lobe diameter value to the outer lobe diameter value being at least one half. In an embodiment of the invention, the exhaust system comprises an inner lobe with a concave surface on the nozzle so as to extend toward the interior of the nozzle in an almost completely U-shape. The U-shape contributes to a homogeneous mixing of outdoor air and exhaust gas with a high cooling capacity.

In an embodiment of the invention, the exhaust system comprises an inner lobe with a concave surface on the nozzle so as to extend toward the interior of the nozzle in an almost completely V-shape. The V-shape contributes to a homogeneous mixing of outdoor air and exhaust gas with a high cooling capacity.

In an embodiment of the invention, the exhaust system comprises 3, 5, 9 or 15 inner lobes positioned at equal intervals along the circumference of the nozzle. The expression 'along the circumference of the nozzle' corresponds to the expression 'along an arc a circle defines along its circumference' or 'along the radial direction'. There are inner lobes positioned at equal intervals of 120°, 72°, 40° or 24° along the circumference of the nozzle. Preferably there are 5 inner lobes.

In an embodiment of the invention, the exhaust system comprises 3, 5, 9 or 15 outer lobes positioned at equal intervals along the circumference of the nozzle. The expression 'along the circumference of the nozzle' corresponds to the expression 'along an arc a circle defines along its circumference' or 'along the radial direction'. There are outer lobes positioned at equal intervals of 120°, 72°, 40° or 24° along the circumference of the nozzle. Preferably there are five outer lobes.

In an embodiment of the invention, the exhaust system comprises an inner lobe enabling outdoor air to be efficiently mixed with exhaust gas by enabling a horseshoe vortex, streamwise vortex, Kelvin-Helmholtz and normal vortex to be created due to the pinch-off effect created by its eccentric and protruding geometry.

In an embodiment of the invention, the exhaust system comprises a nozzle enabling outdoor air to be efficiently mixed with exhaust gases by providing more than one outer lobe angle, which is the angle that the outer lobe sweeps around the nozzle, and more than one inner lobe angle, which is the angle that the inner lobe sweeps around the nozzle, and arranging the ratio of the outer lobe angle to the inner lobe angle to be as three.

In an embodiment of the invention, the exhaust system comprises a nozzle enabling the flow fluctuations of exhaust gas and outdoor air to be reduced by means of the radiused geometry of the surface transitions between the inner lobe and the outer lobe. Thus, a continuous surface integrity without harsh surface transitions between the inner and outer lobes is achieved.

In an embodiment of the invention, the exhaust system comprises an inner lobe which can be produced using a deep drawing method. By producing the concave-surfaced inner lobes by means of a deep drawing method, the possibility of wrinkle formation is enabled to be reduced.

In an embodiment of the invention, the exhaust system comprises a nozzle enabling the inner lobes and outer lobes provided in an alternating manner along the circumference of the nozzle to be produced by welding to each other.

In an embodiment of the invention, the exhaust system comprises a nozzle extending with a conical geometry. The conical geometry is in an expanding form in the direction in which exhaust gases are transferred from the engine to the nozzle.

The exhaust system realized to achieve the object of this invention is shown in the attached figures, wherein from these figures;

Figure 1 is a perspective view of an exhaust system.

Figure 2 is a perspective view of a nozzle.

Figure 3 is a front view of a nozzle.

Figure 4 is a side view of a nozzle.

Figure 5 is a front view of a nozzle.

Figure 6 is a schematic view showing alternative lobe configurations of a nozzle. The parts illustrated in figures are individually assigned a reference numeral and the corresponding terms of these numbers are listed below.

1. Exhaust system

2. Engine

3. Ejector

4. Nozzle

410. Outer lobe

410m. Outer lobe central axis

41 Oy. Outer lobe angle

420. Inner lobe

420m. Inner lobe central axis

420y. Inner lobe angle

(E) Exhaust gas

(H) Outdoor air

The exhaust system (1) comprises at least one engine (2) of the type used in air vehicles; exhaust gas generated by the operation of and removed from the engine (2); at least one nozzle (4) with an almost entirely cylindrical geometry, positioned on the engine (2), enabling exhaust gas (E) to be removed from the engine (2) and the flow of exhaust gas (E) to be manipulated; outdoor air (H) taken from the outer environment and, by enabling it to be mixed with the exhaust gases (E), providing the cooling of exhaust gases (E); an ejector (3) on the nozzle (4), extending in a cylindrical form along the axis on which the nozzle (4) extends as well as extending outward from the nozzle (4) so as to almost completely surround the nozzle (4) and enabling exhaust gases (E) to be mixed with outdoor air (H); more than one outer lobe (410) on the nozzle (4) at equal intervals, transferring exhaust gases (E) from the engine (2) to the ejector (3); more than one inner lobe (420) provided on the nozzle (4) in an alternating fashion with the outer lobes (410) so as to extend inward from the nozzle (4) and directing outdoor air (H) to exhaust gases (E) through the nozzle (4) to enable the mixing of exhaust gases (E) with outdoor air (H) (Figure-1, Figure-2, Figure-3, Figure-4). The exhaust system (1) of the invention comprises an inner lobe (420) extending over the nozzle (4) to the interior of the nozzle (4) so as to face the outer lobe (410) and be placed against the outer lobe (410), thereby enabling outdoor air (H) to be efficiently mixed with exhaust gases (E) (Figure-3, Figure-5, Figure-6).

In helicopters, which are one of the air vehicles, the power required is provided by a turboshaft engine (2). In order for the engine (2) to be able to work, fresh air taken from the external environment by means of an air intake is compressed by a compressor in the engine (2), then mixed with fuel and combusted in the combustion chamber. Thus, the chemical energy of the fuel is converted into kinetic energy by means of turbines and the blades that move the helicopter are driven and the power required for the operation of various components is obtained. Waste exhaust gases (E) are generated as a result of combustion and waste exhaust gases (E) resulting from combustion in the engine (2) and having no function must be discharged from the engine (2) in order to ensure the operational continuity of the engine (2). For this purpose, exhaust gases (E) are discharged from the engine (2) by means of the nozzle (4). Some of the most important parameters that designers should pay attention to in the design of nozzles (4) are backpressure and the cooling performance of the engine (2) zone. The harder the designers design the passage of exhaust gases (E) through the nozzle (4), the higher will be the backpressure of the nozzle (4). This results in lower power being obtained from the engine (2) or more fuel being consumed to obtain the same power. Therefore, it is desired that the design of the nozzle (4) has as little resistance and obstacle as possible for the flow of exhaust gases (E), i.e. low backpressure values. On the other hand, the nozzle (4) must be able to provide sufficient outdoor air (H) for the engine (2), and these two parameters are inversely proportional to each other. If the backpressure is too low, the nozzle (4) cannot provide sufficient outdoor air (H) for the engine (2), and also since it will discharge the exhaust gases (E) from the helicopter without being sufficiently cooled, the infrared trace of the air vehicle will increase. This poses a serious risk of survival, especially for attack helicopters deployed in a battlefield, against the risk of being hit by missiles performing target detection using infrared warheads. In order to reduce this risk, the desired exhaust gas (E) flow can be provided by designing an appropriate nozzle (4), and the exhaust gas (E) temperatures can be further reduced by taking the outdoor air (H), which is colder than the exhaust gas (E), from the atmosphere and mixing it with the exhaust gases (E) in the nozzle (4). Outdoor air (H) can also be named as the secondary air. The way outdoor air (H) interacts with exhaust gas (E) at the outlet of the nozzle (4) is critical in designing the nozzle (4) in that how much the maximum exhaust gas (E) temperature can be reduced and how homogeneous the exhaust gas (E) temperature distribution can be made. Conical structures or lobed structures have been used in the prior art. Although lobed structures are more cost-effective than conical structures, their cooling performance is much more efficient. With its indented structure inward from the nozzle (4), the inner lobe (420) directs the outdoor air (H) toward the exhaust gases (E), allowing the outdoor air (H) to be mixed with the exhaust gas (E). With its expanding geometry relative to the engine (2), the outer lobe (410) directs the exhaust gas (E) from the engine (2) toward the surrounding of the nozzle (4), enabling the exhaust gas (E) to be mixed with the outdoor air (H). The ejector (3) has almost entirely a circular cross-section. The ejector (3) extends outward from the engine (2) and the nozzle (4) so as to at least partially remain out of the nozzle (4) (Figure-1 , Figure-2).

The nozzle (4) can intake more outdoor air (H) for cooling the exhaust gases (E) and the area of the engine (2) and reduce the level of infrared traces. Furthermore, thanks to low backpressure values, the engine (2) keeps the performance loss at a minimum level. Thanks to its expanding structure relative to the engine (2), the exhaust gas (E) expands toward the outer lobe (410) and is discharged from the nozzle (4). Since the cross- sectional area decreases as the exhaust gas (E) passes through the inner lobe (420) with an indented geometry toward the inside of the nozzle (4), the exhaust gas (E) accelerates and a venturi effect is created that forms a local low pressure zone. While the resulting venturi effect increases the generation of low backpressure values, it also creates an effect that enables outdoor air (H) to be directed toward the local low-pressure zone, thereby increasing the mixing of outdoor air (H) with exhaust gas (E) and creating a low backpressure. The outer lobe (410) and the inner lobe (420) mutually positioned on the nozzle (4) almost completely face each other. In this way, the effective cross-sectional area in the front view of the nozzle (4) remains constant. In this way, although the distribution of the exhaust gas (E) toward the periphery of the nozzle (4) takes place much more homogeneously, it is ensured that the outdoor air (H) is efficiently mixed with the exhaust gas (E), so that the maximum exhaust gas (E) temperature can be further reduced and the cooling effect is made more homogeneous. The expression 'toward the circumference of the nozzle (4)' corresponds to the expression 'toward the arc a circle defines outward along its circumference' or 'toward the radial direction' (Figure-1 , Figure- 2, Figure-3, Figure-5, Figure-6).

In an embodiment of the invention, the exhaust system (1) comprises more than one outer lobe central axis (410m) that passes almost entirely through the middle of the outer lobes (410) with respect to the circumference of the nozzle (4), more than one inner lobe central axis (420m) that passes almost entirely through the middle of the inner lobes (420) with respect to the circumference of the nozzle (4), and a nozzle (4) enabling outdoor air (H) to be efficiently mixed with exhaust gases (E) by positioning in an almost entirely coaxial manner the outer lobe central axis (410m) and the inner lobe central axis (420m) which are positioned against each other with respect to the circumference of the nozzle (4). The fact that the outer lobe central axis (420m) and the inner lobe central axis (410m) are coaxial contributes to an effective aerodynamic flow by ensuring that the outer lobes (420) and inner lobes (410) are positioned exactly mutually.

In an embodiment of the invention, the exhaust system (1) comprises an outer lobe (410) having a larger diameter than the outlet diameter of the engine (2), and a nozzle (4) enabling outdoor air (H) to be efficiently mixed with exhaust gases (E) by the ratio of the diameter of the inner lobe (420) to the diameter of the outer lobe (410) being at least one half. The fact that the ratio of the diameter of the inner lobe (420) to the diameter of the outer lobe (410) is one half contributes to an effective mixing of exhaust gases (E) with outdoor air (H) (Figure-5).

In an embodiment of the invention, the exhaust system (1) comprises an inner lobe (420) with a concave surface on the nozzle (4) so as to extend toward the interior of the nozzle (4) in an almost entirely U-shape. The U-shape enables the flow to be manipulated as desired, allowing outdoor air (H) to be efficiently mixed with exhaust gas (E) (Figure-2, Figure-5). In an embodiment of the invention, the exhaust system (1) comprises an inner lobe (420) with a concave surface on the nozzle (4) so as to extend toward the interior of the nozzle (4) in an almost entirely V-shape. The V-shape enables the flow to be manipulated as desired, allowing outdoor air (H) to be efficiently mixed with exhaust gas (E) (Figure-3).

In an embodiment of the invention, the exhaust system (1) comprises 3, 5, 9 or 15 inner lobes (420) that can be positioned at equal intervals along the circumference of the nozzle (4). As a result of previously determining the angular position intervals by the user, the numbers of the inner lobe (420) and outer lobe (410) on the nozzle (4) and therefore the flow characteristic can be altered. There are inner lobes (420) and outer lobes (410) provided which can be positioned at equal intervals of 120°, 72°, 40° or 24° along the circumference of the nozzle (4). There are preferably five inner lobes (420) provided along the circumference of the nozzle (4). In this way, it is possible to realize a design by which the exhaust gas (E) has optimum homogeneity, back pressure and effective cooling properties. The expression 'along the circumference of the nozzle (4)' corresponds to the expression 'along an arc a circle defines along its circumference' or 'along the radial direction' (Figure-2, Figure-6).

In an embodiment of the invention, the exhaust system (1) comprises 3, 5, 9 or 15 outer lobes (410) that can be positioned at equal intervals along the circumference of the nozzle (4). As a result of previously determining the angular position intervals by the user, the numbers of the inner lobe (420) and outer lobe (410) on the nozzle (4) and therefore the flow characteristic can be altered. There are inner lobes (420) and outer lobes (410) provided which can be positioned at equal intervals of 120°, 72°, 40° or 24° along the circumference of the nozzle (4). There are preferably five outer lobes (410) provided along the circumference of the nozzle (4). In this way, it is possible to realize a design by which the exhaust gas (E) has optimum homogeneity, back pressure and effective cooling properties (Figure-2, Figure-6).

In an embodiment of the invention, the exhaust system (1) comprises an inner lobe (420) enabling outdoor air (H) to be efficiently mixed with exhaust gas (E) by generating a horseshoe vortex, streamwise vortex, Kelvin-Helmholtz and normal vortex due to the pinch-off effect created by its eccentric and protruding geometry. Thanks to this effect, the outdoor air (H) is enabled to be efficiently mixed with exhaust gas (E) by turbulences generated by the vortexes (Figure-2, Figure-3).

In an embodiment of the invention, the exhaust system (1) comprises a nozzle (4) enabling outdoor air (H) to be efficiently mixed with exhaust gases (E) by providing more than one outer lobe angle (41 Oy), which is the angle that the outer lobe (410) sweeps around the nozzle (4), and more than one inner lobe angle (420y), which is the angle that the inner lobe (420) sweeps around the nozzle (4), and arranging the ratio of the outer lobe angle (41 Oy) to the inner lobe angle (420y) to be as three. This ratio contributes to an effective mixing of outdoor air (H) with exhaust gas (E).

In an embodiment of the invention, the exhaust system (1) comprises a nozzle (4) that reduces the flow fluctuations of the exhaust gas (E) and outdoor air (H) by means of the radiused form of surface transitions of the inner lobe (420) and outer lobe (410). The radiused form provides an effective cooling performance by reducing the pressure and speed fluctuations of the outdoor air (H) and exhaust gas (E) and enhancing the homogeneous mixing of the outdoor air (H) with exhaust gases (E) (Figure-1 , Figure-2).

In an embodiment of the invention, the exhaust system (1) comprises an inner lobe (420) produced by a deep drawing method. The surfaces of the inner lobe (420) are designed in a surface form that will not allow wrinkles to form and the effect of production parameters on the wrinkle formation is taken into account during the design (Figure-1 , Figure-3).

In an embodiment of the invention, the exhaust system (1) comprises a nozzle (4) produced by welding the inner lobes (420) and outer lobes (410), which are provided in an alternating manner along the circumference of the nozzle (4). The final nozzle (4) geometry is formed by welding the inner lobes (420) and outer lobes (410) produced by a deep drawing method to each other respectively. The production of the nozzle (4) by welding the inner lobes (420) and outer lobes (410) reduces the cost of the final part. In case any part on the nozzle (4) is damaged, only the locally damaged area on the nozzle (4) is replaced and the disposal of the entire nozzle (4) is prevented (Figure-3). In an embodiment of the invention, the exhaust system (1) comprises a nozzle (4) extending in a conical form. The conical form contributes to an improvement of the flow performance of the nozzle (4) (Figure-2).