The present invention relates to the structure of a propeller cap and, more particularly to a combined propeller cap for reducing rotational flow and hub vortex and enhancing propulsive efficiency, whereby the propeller cap reduces noise and vibration in a vessel by decreasing hub vortex cavitation behind a propeller for propelling the vessel, prevents erosion and corrosion of a rudder, and enhances propulsive efficiency to save fuel.
Further, the present invention relates to a combined propeller cap for reducing rotational flow and hub vortex and improving propulsive efficiency, the combined propeller cap being capable of reducing hub vortex cavitation that is generated behind a propeller by using a combined propeller cap structure in which a diffusion type propeller cap is coupled to the end of a contraction type propeller cap in order to solve the problem with a PBCF (Propeller Boss Cap Fin) in the related art, which is difficult to manufacture and is expensive due to precise machining for designing and manufacturing fins caused by a configuration of attaching a plurality of small fins to a propeller cap to reduce hub vortex, and being capable of being easily manufactured with a low cost in a simple structure as compared with the PBCF.
Further, the present invention relates to a combined propeller cap for reducing rotational flow and hub vortex and improving propulsive efficiency, the combined propeller cap being capable of additionally reducing hub vortex cavitation by forming a combined propeller cap structure, in which a diffusion type propeller cap is coupled to the end of a contraction type propeller cap, and by attaching plate-shaped guide fins at a contractive section or between an contractive section and a diffusive section of the propeller cap, whereby it can reduce rotational flow and hub vortex cavitation that are generated behind a propeller and can be easily manufactured at a low cost in a simple configuration, as compared with an existing PBCF.
In general, sea vessels are moved forward by a thruster such as a propeller that generates propulsion and such a propeller type thruster is connected to a rotary shaft of an engine of a vessel and rotated by power from the engine.
In detail, a propeller type thruster is largely includes a propeller cap connected to the rotary shaft of an engine to form the body of a propeller and a plurality of blades formed around the propeller cap, and propulsion and torque is generated by the flows passing the blades, whereby a vessel is moved forward by the propulsion with the torque offset by power from the engine.
In general, the propellers of vessels use only 70% of the power from a main engine as propulsion for moving the vessels forward and the other power from the engine is wasted as friction, a thermal loss, a vortex behind the propeller, and a propeller hub vortex.
In these factors, the rotational flow and the hub vortex behind the propeller consume about 5 ∼ 7% and 1 ∼ 3% of the power. Further, a strong hub vortex generates hub vortex cavitation, which causes problems such as noise, vibration, erosion and corrosion of a rudder. Accordingly, various devices have been developed in the related art to solve problems with restoration of wasted energy and cavitation.
For example, a "Ship propulsion device and ship with same" has been disclosed in Korean Patent Application Publication No.
In detail, Korean Patent Application Publication No.
Further, a "Propeller boss cap of the ship" for improving propulsion and saving fuel by reducing hub vortex cavitation behind a propeller has been disclosed in Korean Patent Application Publication No.
In detail, the propeller boss cap for a ship disclosed in
As described above, there have been various studies for increasing propulsion and saving fuel by decreasing rotational flow and hub vortex cavitation. However, according to these methods of the related art, propeller caps are formed in specific shapes different from those existing before or forming a plurality of fins separate from the blades of propellers, so the configuration is complicated, whereby it is difficult to design and manufacture a propeller, and the manufacturing cost is also increased.
In detail, as for a device for restoring rotational energy behind a propeller, as described above, there are a CRP (Contra-Rotating Propeller), a pre-swirl stator, a postswirl stator, a vane-wheel, and a rudder thrust (bulb) fin). These devices have been known to save energy by about 2 ∼ 5%, but they are relatively large structures, so they are expensive to install and mount and have a structural danger.
Further, for example, there is a PBCF (Propeller Boss Cap Fin) and a rudder bulb that are devices for overcoming the problem with hub vortex cavitation by a propeller. These devices have an energy saving effect of about 1 ∼ 3% and have a small and simple configuration, as compared with the devices for restoring rotational energy behind a propeller, so they can be easily mounted and manufactured at low cost.
The PBCF, which was been developed in the 1970s, improves propeller efficiency about 1 ∼ 3% by absorbing hub vortex energy using small fins on a propeller cap on the hub at the rear portion of a propeller and, reduces noise and erosion and corrosion of a rubber due to hub vortex cavitation by decreasing hub vortex cavitation by the propeller.
However, the fins for the PBCF have to be designed in different ways every time to have appropriate characteristics, depending on the types of vessels and the use environment, require very precise design, and should be manufactured substantially in the same way as a propeller after being designed. Accordingly, a large manufacturing cost is needed, as compared with the rudder bulb.
Therefore, in order to solve the problems with the methods of reducing hub vortex cavitation by a propeller using the PBCF that requires precise design for each vessel, which should be manufactured in the same way as propellers, and thus is not easy to manufacture and which increases the manufacturing cost, it is required to develop a new propeller structure that can be manufactured at a low cost with a simpler configuration, can reduce hub vortex cavitation generated behind the propeller, thereby being able to reduce noise and vibration in a vessel, prevent erosion and corrosion of a rudder, and save fuel by improving propulsive efficiency.
A combined propeller cap according to the preamble of claim 1 is known from
An object of the present invention is to provide a combined propeller cap for reducing rotational flow and hub vortex and improving propulsive efficiency, the combined propeller cap being capable of reducing hub vortex cavitation that is generated behind a propeller by using a combined propeller cap structure in which a diffusion type propeller cap is coupled to the end of a contraction type propeller cap in order to solve the problem with a PBCF (Propeller Boss Cap Fin) in the related art, which is difficult to manufacture and is expensive due to precise machining for designing and manufacturing fins caused by a configuration of attaching a plurality of small fins to a propeller cap to reduce hub vortex cavitation, and being capable of being easily manufactured with a low cost in a simple structure as compared with the PBCF.
Another object of the present invention is to provide a combined propeller cap for reducing rotational flow and hub vortex and improving propulsive efficiency that is configured not only to reduce hub vortex cavitation that is generated behind a propeller through a combined propeller cap structure in which a diffusion type propeller cap is coupled to the end of a contraction type propeller cap, but also to additionally reduce hub vortex cavitation by attaching plate-shaped guide fins to the contractive section or between the contractive section and the diffusive section of the propeller cap, whereby it is possible to reduce rotational flow and hub vortex cavitation that are generated behind a propeller, to easily manufacture the propeller cap at a low cost in a simple configuration, as compared with the existing PBCF, to reduce noise and vibration in a vessel and prevent erosion and corrosion of a rudder, and to save fuel by improving propulsive efficiency.
In order to achieve the objects of the present invention, according to an aspect of the present invention, there is provided a combined propeller cap for reducing rotational flow and hub vortex and improving propulsive efficiency.
According to an aspect of the present invention, there is provide a combined propeller cap for reducing rotational flow and hub vortex and improving propulsive efficiency. The combined propeller cap has: a first diffusive section having a diameter that increases from an end of a propeller as it goes away from the propeller; a straight section horizontally extending from the first diffusive section; a contractive section extending from the straight section and having a diameter that decreases as it goes away from the propeller; and a second diffusive section extending from the contractive section and having a diameter that increases as it goes away from the propeller, in which the combined propeller cap is formed at a front portion by the first diffusive section having the diameter that increases from the end of the propeller as it goes away from the propeller, so pressure at a pressure side of the propeller increases and propulsive efficiency is improved, pressure of a flow passing the propeller cap from the propeller is recovered by the contractive section, so the propulsive efficiency is improved, and rotational flow (vortex) of a flow from the propeller is weakened by the second diffusive section, so hub vortex cavitation is reduced.
The inclination angles of the first diffusive section and the second diffusive section may be set to 0 ∼ 40°.
A side of the contractive section may be formed straight, or the side of the contractive section may be curved to be convex outwardly with a predetermined curvature, or the side of the contractive section may be curved to be convex inwardly with a predetermined curvature.
According to another aspect of the present invention, there is provided a combined propeller cap for reducing rotational flow and hub vortex and improving propulsive efficiency. The combined propeller cap has: a first diffusive section having a diameter that increases from an end of a propeller as it goes away from the propeller; a straight section horizontally extending from the first diffusive section; a contractive section extending from the straight section and having a diameter that decreases as it goes away from the propeller; a second diffusive section extending from the contractive section and having a diameter that increases as it goes away from the propeller; and a plurality of guide fins formed in a thin plate shape having a rectangular or curved cross-section with a predetermined uniform thickness and, disposed with regular intervals at the contractive section or between the contractive section and the diffusive section, in which the combined propeller cap is formed at a front portion by the first diffusive section having the diameter that increases from the end of the propeller as it goes away from the propeller, so pressure at a pressure side of the propeller increases and propulsive efficiency is improved, pressure of a flow passing the propeller cap from the propeller is recovered by the contractive section, so the propulsive efficiency is improved, rotational flow (vortex) of a flow from the propeller is weakened by the second diffusive section, so hub vortex cavitation is reduced, and rotational flow by rotation of the propeller is changed into a straight flow in a rotational axial direction, so the hub vortex cavitation is further reduced.
The inclination angles of the first diffusive section and the contractive section may be set to 0 ∼ 40°.
A side of the contractive section may be formed straight, or the side of the contractive section may be curved to be convex outwardly with a predetermined curvature, or the side of the contractive section may be curved to be convex inwardly with a predetermined curvature.
The guide fins may be formed in a thin rectangular plate shape and attached between the contractive section and the second diffusive section of the propeller cap by simple welding, and a size of the guide fins may be determined to correspond to the diameter of the diffusive section in order to avoid an increase in resistance due to the guide fins.
The guide fins may be formed in a thin pentagonal plate shape and attached between the contractive section and the second diffusive section of the propeller cap by simple welding, and a length of a portion extending from an end of the second diffusive section may be within two times the diameter of the second diffusive section.
The guide fins may be formed in a thin trapezoidal plate shape and attached between the contractive section and the diffusive section of the propeller cap by simple welding, and a length of a shortest portion of portions extending from a side of the contractive section may be within two times the diameter of the second diffusive section.
Two to eight guide fins may be disposed at the contractive section or between the contractive section and the second diffusive section of the propeller cap, and the guide fins may be attached with a tolerance of +10 ∼ -10 degrees or +20 ∼ -20 degrees with respect to 0 degree when seen from vertically above.
According to another aspect of the present invention, there is provided a propeller for a vessel, which uses the combined propeller caps described above, in which as compared with existing propellers, energy loss due to hub vortex cavitation and a propeller cap shape is prevented and propulsive efficiency is improved, vibration and noise are reduced, and erosion and corrosion of a rudder by the hub vortex cavitation are prevented, and in comparison to existing PBCFs, manufacturing cost is reduced.
According to the present invention, there is provided a combined propeller cap for reducing rotational flow and hub vortex and improving propulsive efficiency, the combined propeller cap being capable of reducing hub vortex cavitation that is generated behind a propeller and being capable of being easily manufactured at a low cost in a simple configuration, as compared with the existing PBCF, through a combined propeller cap structure in which a diffusion type propeller cap is coupled to the end of a contraction type propeller cap, whereby it is possible to solve the problem with a PBCF (Propeller Boss Cap Fin) in the related art, whereby manufacturing is difficult and expensive due to precise machining for designing and manufacturing fins caused by a configuration of attaching a plurality of small fins to a propeller cap to reduce hub vortex cavitation.
Further, according to the present invention, as described above, there is provided a combined propeller cap for reducing rotational flow and hub vortex and improving propulsive efficiency that is configured not only to reduce hub vortex cavitation that is generated behind a propeller through the combined propeller cap in which a diffusion type propeller cap is coupled to the end of a contraction type propeller cap, but also to additionally reduce hub vortex cavitation by attaching plate-shaped guide fins to the contractive section or between the contractive section and the diffusive section of the propeller gap. Accordingly, it is possible to reduce rotational flow and hub vortex cavitation that are generated behind a propeller, to easily manufacture the propeller cap at a low cost in a simple configuration, as compared with the existing PBCF, to reduce noise and vibration in a vessel and prevent erosion and corrosion of a rudder, and to save fuel by improving propulsive efficiency.
Hereinafter, detailed embodiments of a combined propeller cap for reducing rotational flow and hub vortex and improving propulsive efficiency according to the present invention are described with reference to accompanying drawings.
It should be understood that the following description is just an example for accomplishing the present invention and the present invention is not limited thereto.
Further, it should be understood that components that is determined as being the same as or similar to those in the related art or as being easily understood and achieved by those skilled in the art are not described in detail for simple description in the following description about embodiments of the present invention.
Further, in the following description about embodiments of the present invention, it should be understood that the same or similar components are given the same reference numerals and are not described in detail for simple description.
Further, as described below, the present invention relates to a combined propeller cap for reducing rotational flow and hub vortex and improving propulsive efficiency, the combined propeller cap being capable of reducing hub vortex cavitation that is generated behind a propeller by using a combined propeller cap structure in which a diffusion type propeller cap is coupled to the end of a contraction type propeller cap in order to solve the problem with a PBCF (Propeller Boss Cap Fin) in the related art, whereby manufacturing is difficult and expensive due to precise machining for designing and manufacturing fins caused by a configuration of attaching a plurality of small fins to a propeller cap to reduce hub vortex cavitation, and being capable of being easily manufactured with a low cost in a simple structure as compared with the PBCF.
Further, as described below, the present invention relates to a combined propeller cap for reducing rotational flow and hub vortex and improving propulsive efficiency that is configured not only to reduce hub vortex cavitation that is generated behind a propeller through a combined propeller cap structure in which a diffusion type propeller cap is coupled to the end of a contraction type propeller cap, but also to additionally reduce hub vortex cavitation by attaching plate-shaped guide fins to the contractive section or between the contractive section and the diffusive section of the propeller cap, whereby it is possible to reduce rotational flow and hub vortex cavitation that are generated behind a propeller, to easily manufacture the propeller cap at a low cost in a simple configuration, as compared with the existing PBCF, to reduce noise and vibration in a vessel and prevent erosion and corrosion of a rudder, and to save fuel by improving propulsive efficiency.
Hereinafter, detailed embodiments of a combined propeller cap for reducing rotational flow and hub vortex and improving propulsive efficiency according to the present invention are described with reference to accompanying drawings.
First, referring to
As shown in
In detail, the contraction type propeller cap has high propulsive efficiency, but large hub vortex cavitation is caused by concentration of motion of the hub in the cap, so noise and vibration are increased and erosion and corrosion of a rudder may become severe.
On the other hand, the diffusion type propeller cap has low propulsive efficiency, but hub vortex cavitation is weakened, so noise and vibration can be reduced and erosion and corrosion of a rudder can be attenuated.
Accordingly, in general, vessels that sail at high speeds such as a container ship are usually equipped with the diffusion type propeller cap due to the problem of corrosion of a rudder due to hub vortex cavitation and are additionally equipped with an additional device such as a PBCF to overcome reduction of propulsive efficiency, thereby improving the propulsive efficiency and coping with hub vortex cavitation.
On the contrary, tank ships that sail low speeds are usually equipped with the contraction type propeller cap because they generate weak hub vortex cavitation.
When a container ship using a diffusion type propeller is equipped with a PBCF that is a device for saving fuel to prevent reduction of propulsive efficiency, the fins of the PBCF are designed and manufactured in the same way as the existing propellers, so the manufacturing cost is high relative to the size.
Therefore, the inventor(s) has proposed a new propeller cap structure that can improve propulsive efficiency with low hub vortex cavitation, similar to the PBCF, and can achieve an effect similar to the PBCF even at a very low manufacturing cost in comparison to the manufacturing cost of the PBCF by simplifying the configuration.
Further, referring to
In detail, as shown in
That is, the combined propeller cap 20 according to the first embodiment of the present invention, as shown in
The inclination angle α of the contractive section 21 may be set, for example, to 0 ∼ 40°.
When the inclination angle of the contractive section 21 exceeds 40 degrees, the performance rapidly drops due to flow separation, that is, when flow separation is generated, pressure is not recovered on the propeller cap, so resistance increases.
In more detail, referring to the following Table 1, Table 1 shows changes in performance due to changes in the inclination angle α of the contractive section 22.
The result in Table 1 shows estimated values of propulsive performance according to changes in the inclination angle α of the contractive section 22, as compared with a propeller equipped with a diffusion type propeller cap of the related art.
Further, referring to
In the following description of the second embodiment of the present invention, the same or similar components as in the first embodiment are not described and only other different components are described for simple description.
That is, as shown in
That is, the combined propeller cap 30 according to the second embodiment of the present invention is characterized in that the contractive section 31 is curved to be convex outwardly with a predetermined curvature, as shown in
The curvature of the contractive section 31 can be appropriately determined, depending on the type or the use of a propeller or a ship, and other parts are the same as those in the first embodiment, so they are not described in detail.
Accordingly, as the propeller cap is formed in a shape of which the diameter decreases and increases again, when a propeller is operated, pressure is recovered and propulsive efficiency is improved by the shape of which the diameter decreases to the contractive sections 21 and 31 at the middle portion of the propeller caps 20 and 30 and a strong rotational flow (vortex) is weakened by the shape of which the diameter increases over the diffusive sections 22 and 32 at the end of the propeller caps 20 and 30, whereby it is possible to reduce hub vortex cavitation.
Further, energy loss due to hub vortex and a cap shape is prevented accordingly, so the propulsive efficiency can be improved in comparison to the existing diffusion type propellers (1 ∼ 3%), vibration and noise due to hub vortex can be reduced, and erosion and corrosion of a rudder can be prevented in comparison to the existing contraction type propeller caps.
In more detail, referring to
That is, it can be seen from
That is, as described above, according to the configuration of the combined propeller caps 20 and 30 of the first and second embodiments of the present invention, the propulsive efficiency is improved by pressure recovery due to the shape from a propeller to the contractive sections 21 and 31 and a strong rotational flow (vortex) is weakened by the diffusive sections 22 and 32 while the flow from the propeller passes over the ends of the caps, whereby hub vortex cavitation can be suppressed. Accordingly, energy loss due to hub vortex and a cap shape is prevented, so the propulsive efficiency of a vessel can be improved by about 1 ∼ 3% in comparison to the existing diffusion type propeller. Further, vibration and noise due to hub vortex cavitation can be reduced, and erosion and corrosion of a rudder can be prevented, as compared with the contraction type propeller caps.
Further, according to the configuration of the combined propeller caps 20 and 30 of the first and second embodiments of the present invention described above, there is an advantage that it is possible to reduce hub vortex cavitation, similar to the existing diffusion type propeller caps used for container ships, and it is possible to improve propulsive efficiency in comparison to the existing diffusion type propeller cap. Further, there is another advantage that it is possible to obtain propulsive efficiency similar to the contraction type propeller caps when it is applied to tank ships, but it is possible to greatly reduce hub vortex cavitation.
Further, since the shapes of the combined propeller caps 20 and 30 of the first and second embodiments of the present invention described above are simple in structure, they can be easily manufactured, so there is also an advantage that it is possible to remarkably decrease the manufacturing cost, which was over one hundred million South Korean won due to precise machining of the fins of the PBCF in the related art, to within thirty million South Korean won similar to the existing propeller caps.
Further, referring to
In detail, the combined propeller cap 50 according to the third embodiment of the present invention has a first diffusive section 51 of which the diameter increases from the end of a propeller, a straight section 52 that horizontally extends from the first diffusive section 51, a contractive section 53 that extends from the straight section 52 and of which the diameter decreases as it goes away from the propeller, and a second diffusive section 54 that extends from the contractive section 53 and of which the diameter increases again as it goes away from the propeller.
That is, the combined propeller cap 50 according to the third embodiment of the present invention, as shown in
In more detail, since the combined propeller cap 50 according to the third embodiment of the present invention is formed at the front portion by the first diffusive section 51 of which the diameter increases from the end of the propeller, as shown in
That is, the propeller cap 50 according to the third embodiment of the present invention for reducing hub vortex cavitation and improving propulsive efficiency is additionally improved in propulsive efficiency by pressure recovery due to the shape from the propeller to the contractive section 53 at the middle portion, as shown in
Further, as hub vortex cavitation is reduced, as described above, it is possible to improve propulsive efficiency in comparison to the existing diffusion type propeller caps and it is also possible to prevent vibration and noise due to hub vortex cavitation and erosion and corrosion of a rudder. Further, it is possible to more efficiently prevent vibration and noise and, erosion and corrosion of a rudder and to improve propulsive efficiency, as compared with the existing contraction type propeller caps.
The inclination angles α and β of the first diffusive section 51 and the contractive section 53, respectively, may be set, for example, to 0 ∼ 40°.
When α and β exceed 40 degrees, the performance rapidly drops due to flow separation, that is, when flow separation is generated, pressure is not recovered on the propeller cap, so resistance increases.
In more detail, referring to the following Table 2, Table 2 shows changes in performance due to changes in the inclination angles α and β of the first diffusive section 51 and the contractive section 53.
In Table 1, when α was changed, β was fixed at 30 degrees, while when β was changed, α was fixed at 30 degrees. Further, the result in Table 2 shows estimated values of propulsive performance according to angle changes, as compared with a propeller equipped with an existing diffusion type propeller cap.
Further, referring to
In the following description of the fourth embodiment of the present invention, the same or similar components as in the third embodiment are not described and only other different components are described for simple description.
That is, as shown in
However, in the combined propeller cap 60 according to the fourth embodiment of the present invention, the contractive section 63 is not straight as in the third embodiment shown in
That is, the combined propeller cap 60 according to the fourth embodiment of the present invention is characterized in that the contractive section 63 is curved to be convex outwardly with a predetermined curvature, as shown in
The curvature of the contractive section 63 can be appropriately determined, depending on the type or the use of a propeller or a ship, and other parts are the same as those in the third embodiment, so they are not described in detail.
Therefore, according to this configuration, it is possible to not only reduce hub vortex cavitation with a simple configuration, but further improve propulsive efficiency in comparison to propeller caps in the related art.
In more detail, referring to
That is, it can be seen from
As described above, according to the combined propeller caps 50 and 60 of the third and fourth embodiments of the present invention, since the first diffusive sections 51 and 61 are formed such that the front potions of the propeller caps are formed with the diameter that is increasing from the end of a propeller, the pressure at the pressure side of a propeller increases and the propulsive efficiency is improved. Further, the propulsive efficiency is further improved by pressure recovery due to the shapes of the contractive sections 53 and 63 at the middle portions.
Further, as a strong rotational flow (vortex) is weakened by the second diffusive sections 54 and 64 while the flow from the propeller passes over the diffusive cap end, hub vortex cavitation can be reduced, the propulsive efficiency of a vessel can be improved about 1 ∼ 3% in comparison to the existing diffusion type propeller, vibration and noise due to hub vortex cavitation can be reduced, and erosion and corrosion of a rudder can be prevented in comparison to the existing contraction type propeller caps.
That is, according to the configuration of the combined propeller caps 50 and 60 of the third and fourth embodiments of the present invention described above, there is an advantage that it is possible to reduce hub vortex cavitation, similar to the existing diffusion type propeller caps used for container ships, and it is possible to improve propulsive efficiency in comparison to the existing diffusion type propeller cap. Further, there is another advantage that it is possible to obtain propulsive efficiency similar to the contraction type propeller caps when it is applied to tank ships, but it is possible to greatly reduce hub vortex cavitation.
Further, since the shapes of the combined propeller caps 50 and 60 of the third and fourth embodiments of the present invention described above are simple in structure, they can be easily manufactured, so there is also an advantage that it is possible to remarkably decrease the manufacturing cost, which was over one hundred million South Korean won due to precise machining of the fins of the PBCF in the related art, to within thirty million South Korean won similar to the existing propeller caps.
Further, referring to
In more detail, as shown in
That is, in the combined propeller cap 80 according to the fifth embodiment of the present invention, as shown in
In this configuration, the inclination angle α of the contractive section 81 may be, for example, set to 0 ∼40°, and when the inclination angle of the contractive section 81 exceeds 40 degrees, the performance rapidly drops due to flow separation. Further, when flow separation is generated, pressure is not recovered on the propeller cap, so resistance increases.
In more detail, referring to the following Table 3, Table 3 shows changes in performance due to changes in the inclination angle α of the contractive section 81.
The result in Table 3 shows estimated values of propulsive performance according to changes in the inclination angle α of the contractive section 81, as compared with a propeller equipped with a diffusion type propeller cap of the related art.
Accordingly, as the propeller cap is formed in a shape of which the diameter decreases and increases again, when a propeller is operated, pressure is recovered and propulsive efficiency is improved by the shape of which the diameter decreases to the contractive section 81 at the middle portion of the propeller cap 80 and a strong rotational flow (vortex) is weakened by the shape of which the diameter increases over the diffusive section 82 at the end of the propeller cap 80, whereby it is possible to reduce hub vortex cavitation.
Further, energy loss due to hub vortex is prevented accordingly, so the propulsive efficiency can be improved in comparison to the existing diffusion type propellers, vibration and noise due to hub vortex cavitation can be reduced, and erosion and corrosion of a rudder can be prevented in comparison to the existing contraction type propeller cap.
Further, the guide fins 83, as shown in
The number of the guide fins 83 may be appropriately changed, for example, within 2 ∼ 8 and the size of the guide fins may be determined in accordance with the diameter of the diffusive section 82 to avoid an increase in resistance due to the guide fins.
Further, the guide fins 83 are attached with a manufacturing tolerance of +20 ∼ -20 degrees, preferably +10 ∼ -10 degrees with respect to 0 degree when seen from vertically above.
In more detail, according to the propeller cap 80 of the fifth embodiment of the present invention, the propulsive efficiency is improved by pressure recovery due to the shape from the propeller to the contractive section 81 at the middle portion and a strong rotational flow (vortex) is weakened by the diffusive section 82 while a flow from the propeller passes over the diffusive cap end, so hub vortex cavitation can be reduced. Further, since the guide fins 83 having a triangular plate shape are attached between the contractive section 81 and the diffusive section 82 of the propeller cap 80, as described above, a vortex induced by rotation of the propeller is weakened by the guide fins 83 before it reaches the diffusive section 82 of the propeller cap 80, so the vortex by the rotation of the propeller is changed into a straight flow in the rotational axial direction, whereby hub vortex cavitation can be further reduced, thus rotational flow and hub vortex cavitation by rotation of the propeller both can be reduced. Accordingly, energy loss due to hub vortex is prevented, so the propulsive efficiency of a vessel can be improved about 1 ∼ 3% in comparison to the existing diffusion type propellers, vibration and noise due to hub vortex cavitation can be reduced, and erosion and corrosion of a rudder can be prevented in comparison to the existing contraction type propeller caps.
That is, according to the principle of the combined propeller cap 80 of the fifth embodiment of the present invention having the configuration described above, the propulsive efficiency is improved by pressure recovery from the propeller to the contractive section 81 at the middle portion by the shape and a strong rotational flow (vortex) is weakened by the diffusive section 82 while the flow generated by the propeller flows over the end of the cap, so hub vortex cavitation is reduced. Further, since the guide fins 83 having a plate shape are attached between the contractive section 81 and the diffusive section 82 of the propeller cap 80, the vortex induced by rotation of the propeller is weakened by the guide fins 83 before reaching the diffusive section 82 of the propeller cap 80, so the vortex by the rotation of the propeller is changed into a straight flow in the rotational axial direction, thus rotational flow and hub vortex cavitation can be reduced.
Therefore, according to the combined propeller cap 80 of the fifth embodiment of the present invention having the configuration described above, not only hub vortex cavitation is reduced by the diffusive section 82 of the propeller cap 80, but the vortex induced by rotation of a propeller is slightly weakened by the guide fins 83 before reaching the diffusive section 82 of the propeller cap 80, thereby changing the vortex by the rotation of the propeller into a straight flow in the rotational axial direction, so hub vortex cavitation can be additionally reduced. Accordingly, it is possible to improve propulsive efficiency by preventing energy loss due to hub vortex, reduce vibration and noise due to hub vortex cavitation, and prevent erosion and corrosion of a rudder.
Further, since the combined propeller cap 80 according to the fifth embodiment of the present invention having the configuration described above has a very simple shape and structure and, the guide fins 83 are formed in a simple plate shape, so they can be easily manufactured and attached by simple welding, it is possible to considerably decrease the high manufacturing cost due to precise machining of the fins of a PBCF in the related art.
In more detail, referring to
That is, it can be seen from
That is, according to the propeller cap 80 of the fifth embodiment of the present invention, the propulsive efficiency is improved by pressure recovery due to the shape from the propeller to the contractive section 81 at the middle portion and a strong rotational flow (vortex) is weakened by the diffusive section 82 while a flow from the propeller flows over the diffusive cap end, so hub vortex cavitation can be reduced. Further, since the guide fins 83 having a triangular plate shape are attached between the contractive section 81 and the diffusive section 82 of the propeller cap 80, as described above, a vortex induced by rotation of the propeller is weakened by the guide fins 23 before it reaches the diffusive section 82 of the propeller cap 80, so the vortex by the rotation of the propeller is changed into a straight flow in the rotational axial direction, whereby hub vortex cavitation can be further reduced, thus rotational flow and hub vortex cavitation by rotation of the propeller both can be reduced. Accordingly, energy loss due to hub vortex is prevented, so the propulsive efficiency of a vessel can be improved about 1 ∼ 3% in comparison to the existing diffusion type propellers, vibration and noise due to hub vortex cavitation can be reduced, and erosion and corrosion of a rudder can be prevented in comparison to the existing contraction type propeller caps.
That is, according to the configuration of the propeller cap 80 of the fifth embodiment of the present invention, similar to diffusion type propeller caps that are used by container ships in the related art, hub vortex cavitation can be reduced and the propulsive efficiency is greatly improved as compared with the diffusion type propeller caps of the related art. Further, the propulsive efficiency is high and hub vortex cavitation can be remarkably reduced in comparison to the existing contraction type propeller caps when the propeller cap 80 is applied to tank ships. Further, as described above, since the guide fins 83 having a triangular plate shape are attached between the contractive section 81 and the diffusive section 82 of the propeller cap 80, rotational flow and hub vortex cavitation are additionally reduced, so vibration and noise due to hub vortex cavitation can be reduced and erosion and corrosion of a rudder can be prevented.
Further, precise machining for manufacturing the fins of a PBCF was a problem because it increased the manufacturing cost, but the propeller cap 80 according to the fifth embodiment of the present invention can be easily manufactured in simple shape and structure, so there is also an advantage that it is possible to remarkably decrease the manufacturing cost, which was over one hundred million South Korean won due to precise machining of the fins of the PBCF in the related art, to within thirty million South Korean won similar to the existing propeller caps.
Further, referring to
In the following description of the sixth embodiment of the present invention, the same or similar components as in the fifth embodiment are not described and only other different components are described for simple description.
That is, as shown in
However, in the combined propeller cap 100 according to the sixth embodiment of the present invention, the contractive section 101 is not straight as in the fifth embodiment shown in
That is, the combined propeller cap 100 according to the sixth embodiment of the present invention is characterized in that the contractive section 101 is curved to be convex outwardly with a predetermined curvature, as shown in
The curvature of the contractive section 101 can be appropriately determined, depending on the type or the use of a propeller or a ship, and other parts are the same as those in the fifth embodiment, so they are not described in detail.
Further, a combined propeller cap according to a seventh embodiment of the present invention is described with reference to
That is, referring to
In detail, as shown in
That is, in the combined propeller cap 110 according to the seventh embodiment of the present invention, as shown in
The inclination angle α and β of the first diffusive section 111 and the contractive section 113 respectively, may be set, for example, to 0 ∼ 40°.
When α and β exceed 40 degrees, the performance rapidly drops due to flow separation, that is, when flow separation is generated, pressure is not recovered on the propeller cap, so resistance increases.
In more detail, referring to the following Table 4, Table 4 shows changes in performance due to changes in the inclination angles α and β of the first diffusive section 111 and the contractive section 113.
In Table 4, when α was changed, β was fixed at 30 degrees, while when β was changed, α was fixed at 30 degrees. Further, the result in Table 4 shows estimated values of propulsive performance according to angle changes, as compared with a propeller equipped with an existing diffusion type propeller cap.
Therefore, according to the combined propeller cap 110 of the seventh embodiment of the present invention, as shown in
Further, the combined propeller cap 110 according to the seventh embodiment of the present invention is additionally improved in propulsive efficiency by pressure recovery due to the shape from the propeller to the contractive section 113 at the middle portion, as shown in
Further, energy loss due to hub vortex is prevented accordingly, so the propulsive efficiency of a vessel can be improved about 1 ∼ 3% in comparison to existing diffusion type propellers, vibration and noise due to hub vortex cavitation can be reduced, and erosion and corrosion of a rudder can be prevented in comparison to the existing contraction type propeller caps.
Further, the guide fins 115, as shown in
The number of the guide fins 115 may be appropriately changed, for example, within 2 ∼ 8 and the size of the guide fins may be determined in accordance with the diameter of the second diffusive section 114 to avoid an increase in resistance due to the guide fins.
Further, the guide fins 115 are attached with a manufacturing tolerance of +20 ∼ -20 degrees, preferably +10 ∼ -10 degrees with respect to 0 degree when seen from vertically above.
In more detail, according to the principle of the propeller cap 110 for reducing a rotational flow and hub vortex and improving propulsive efficiency of the seventh embodiment of the present invention, the propulsive efficiency is improved by pressure recovery due to the shape from the propeller to the contractive section 113 at the middle portion and a strong rotational flow (vortex) is weakened by the second diffusive section 114 while a flow from the propeller passes over the diffusive cap end, so hub vortex can be reduced. Further, since the guide fins 115 having a triangular plate shape are attached between the contractive section 113 and the second diffusive section 114 of the propeller cap 110, as described above, a vortex induced by rotation of the propeller is weakened by the guide fins 115 before it reaches the second diffusive section 114 of the propeller cap 110, so the vortex by the rotation of the propeller is changed into a straight flow in the rotational axial direction, whereby hub vortex cavitation can be further reduced, thus rotational flow and hub vortex cavitation by rotation of the propeller both can be reduced. Accordingly, energy loss due to hub vortex is prevented, so the propulsive efficiency of a vessel can be improved about 1 ∼ 3% in comparison to the existing diffusion type propellers, vibration and noise due to hub vortex cavitation can be reduced, and erosion and corrosion of a rudder can be prevented in comparison to the existing contraction type propeller caps.
That is, according to the principle of the combined propeller cap 110 of the seventh embodiment of the present invention having the configuration described above, the propulsive efficiency is improved by pressure recovery from the propeller to the contractive section 113 at the middle portion by the shape and a strong rotational flow (vortex) is weakened by the second diffusive section 114 while the flow generated by the propeller flows over the end of the cap, so hub vortex is reduced. Further, since the guide fins 115 having a triangular plate shape are attached between the contractive section 113 and the second diffusive section 114 of the propeller cap 110, the vortex induced by rotation of the propeller is weakened by the guide fins 115 before reaching the second diffusive section 114 of the propeller cap 110, so the vortex by the rotation of the propeller is changed into a straight flow in the rotational axial direction, thus rotational flow and hub vortex cavitation can be reduced.
Therefore, according to the combined propeller cap 110 of the seventh embodiment of the present invention having the configuration described above, not only hub vortex cavitation is reduced by the second diffusive section 114 of the propeller cap 110, but the vortex induced by rotation of a propeller is slightly weakened by the guide fins 115 before reaching the second diffusive section 114 of the propeller cap 110, thereby changing the vortex by the rotation of the propeller into a straight flow in the rotational axial direction, so hub vortex cavitation can be additionally reduced. Accordingly, it is possible to improve propulsive efficiency by preventing energy loss due to hub vortex, reduce vibration and noise due to hub vortex cavitation, and prevent erosion and corrosion of a rudder.
Further, since the combined propeller cap 110 according to the seventh embodiment of the present invention having the configuration described above has a very simple shape and structure and, the guide fins 115 are formed in a simple plate shape, so they can be easily manufactured and attached by simple welding, it is possible to considerably decrease the high manufacturing cost due to precise machining of the fins of a PBCF in the related art.
Further, referring to
That is, it can be seen from
That is, according to the combined propeller cap 110 of the seventh embodiment of the present invention, since the first diffusive section 111 is formed such that the front potion of the propeller cap is formed with the diameter that is increasing from the end of a propeller, the pressure at the pressure side of a propeller increases and the propulsive efficiency is improved. Further, the propulsive efficiency is further improved by pressure recovery due to the shapes of the contractive section 113 at the middle portion.
Further, since the strong rotational flow (vortex) is weakened by the second diffusive section 114 while the flow from the propeller passes the diffusive cap end, hub vortex cavitation can be reduced. Further, as described above, since the guide fins 115 having a triangular plate shape are attached between the contractive section 113 and the second diffusive section 114 of the propeller cap 110, as described above, rotational flow and hub vortex cavitation can be additionally reduced. Accordingly, energy loss due to hub vortex is prevented, the propulsive efficiency can be improved about 1 ∼ 3% in comparison to the existing diffusion type propellers, vibration and noise due to hub vortex cavitation can be reduced, and erosion and corrosion of a rudder can be prevented in comparison to the existing contraction type propeller caps.
That is, according to the configuration of the combined propeller cap 110 of the seventh embodiment of the present invention, similar to diffusion type propeller caps that are used container ships in the related art, hub vortex cavitation can be reduced and the propulsive efficiency can be improved as compared with the diffusion type propeller caps of the related art. Further, the propulsive efficiency is similar and hub vortex cavitation can be remarkably reduced in comparison to the existing contraction type propeller caps when the propeller cap 110 is applied to tank ships. Further, as described above, since the guide fins 115 having a triangular plate shape are attached between the contractive section 113 and the second diffusive section 114 of the propeller cap 110, rotational flow and hub vortex cavitation are additionally reduced, so vibration and noise due to hub vortex cavitation can be reduced and erosion and corrosion of a rudder can be prevented.
Further, precise machining for manufacturing the fins of a PBCF was a problem because it increased the manufacturing cost, but the combined propeller cap 110 according to the seventh embodiment of the present invention can be easily manufactured in simple shape and structure, so there is also an advantage that it is possible to remarkably decrease the manufacturing cost, which was over one hundred million South Korean won due to precise machining of the fins of the PBCF in the related art, to within thirty million South Korean won similar to the existing propeller caps.
Further, referring to
That is, as shown in
However, in the combined propeller cap 130 according to the eighth embodiment of the present invention, the contractive section 133 is not straight as in the seventh embodiment shown in
That is, the combined propeller cap 130 according to the eight embodiment of the present invention is characterized in that the contractive section 133 is curved to be convex outwardly with a predetermined curvature, as shown in
The curvature of the contractive section 133 can be appropriately determined, depending on the type or the use of a propeller or a ship, and other parts are the same as those in the seventh embodiment, so they are not described in detail.
Further, referring to
In detail, although the guide fins are formed in a triangular shape and attached in the recession between the contractive section and the diffusive section, and have a size corresponding to the diameter of the diffusive section in order not to protrude at the end of the diffusive section in the fifth to eighth embodiments of the present invention, the present invention is not limited to this configuration, that is, the present invention may be configured, as shown in
In this configuration, the size of the guide fins 143 may be determined such that the length L of the portion extending from the end of the diffusive section 142 is within two times the diameter D of the diffusive section (that is, L ≤ 2D).
Alternatively, the present invention may be configured, as shown in
In this configuration, the size of the guide fins 153 may be determined such that the length L2 of a shorter portion of the portions extending from the side of the contractive section 151 is within two times the diameter of the diffusive section 152 (that is, L2 ≤ 2D), but other factors L1 and W are not specifically limited.
Further, the other configurations except the guide fins 143 and 153 can be achieved in the same way as the fifth to eighth embodiments, so they are not described in detail.
Examples of applying the guide fins 143 and 153 to the propeller cap according to the first embodiment shown in
Further, referring to
That is, it can be seen from
Therefore, according to the configuration, it is possible to achieve a combined propeller cap for reducing rotational flow and hub vortex and improving propulsive efficiency according to the present invention.
Further, according to the present invention, as a combined propeller cap for reducing rotational flow and hub vortex and improving propulsive efficiency according to the present invention is achieved, it is possible to reduce hub vortex cavitation that is generated behind a propeller through a combined propeller cap structure in which a diffusion type propeller cap is coupled to the end of a contraction type propeller cap, so a combined propeller cap that can be easily manufactured at a low cost in a simple configuration, as compared with the existing PBCF, for reducing rotational flow and hub vortex and improving propulsive efficiency. Further, a plurality of small fins is attached to the propeller cap to reduce hub vortex cavitation, so it is possible to solve the problem with the existing PBCF (Propeller Boss Cap Fin) in that manufacturing is difficult and the manufacturing cost is high due to precise machining for designing and manufacturing fins.
Further, according to the present invention, as described above, there is provided a combined propeller cap for reducing rotational flow and hub vortex and improving propulsive efficiency that is configured not only to reduce hub vortex cavitation that is generated behind a propeller through a combined propeller cap structure in which a diffusion type propeller cap is coupled to the end of a contraction type propeller cap, but also to additionally reduce hub vortex cavitation by attaching plate-shaped guide fins to the contractive section or between the contractive section and the diffusive section of the propeller cap. Accordingly, it is possible to reduce rotational flow and hub vortex cavitation that are generated behind a propeller, to easily manufacture the propeller cap at a low cost in a simple configuration, as compared with the existing PBCF, to reduce noise and vibration in a vessel and prevent erosion and corrosion of a rudder, and to save fuel by improving propulsive efficiency
Although combined propeller caps for reducing rotational flow and hub vortex and improving propulsive efficiency according to embodiments of the present invention were described above, the present invention is not limited to the embodiments and may be changed, modified, combined, and replaced in various ways, depending on necessities in design and other various factors by those skilled in the art.
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.