Propeller guard for a propulsion unit

Abstract

To provide a technique capable of improving thrust of a propulsion body.SOLUTION: This propeller guard for the propulsion body is applied to the propulsion body having the propeller and an object positioned on the suction side of the propeller and overlapping with at least a part of the propeller when viewed from the suction side of the propeller. The deviation angle φ from the radial direction of the propeller to the chord of the wing shape satisfies an expression using a length L of a line segment extending to the bottom surface of the object along a rotation axis direction which is the direction of the rotation axis of the propeller with the starting position as a starting point.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a propeller guard for a propellant. [Background technology]

[0002] Economic growth and globalization in newly industrialized countries have led to a growing demand for improved thrust of propulsion devices, such as aircraft, ships, and submarines. When a propeller is used as the thrust of a propulsion device, increasing the propeller thrust generally improves the thrust of the propulsion device. However, improving the propeller thrust requires a great deal of effort and time to optimize the propeller's pitch angle and blade shape.

[0003] Meanwhile, a technology has been proposed in which a component that increases the thrust of a propellant body is attached around the propeller while leaving the settings and structure of the propeller unchanged. For example, Patent Document 1 proposes a technology in which a rotor guide that is L-shaped in cross section (hereinafter referred to as an "L-shaped rotor guide") is attached around the propeller as a component for increasing thrust. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-134696 Summary of the Invention [Problem to be solved by the invention]

[0005] Some propulsion devices have at least a portion of the propeller overlapping an object when viewed from the suction side of the propeller. For example, when a drone is miniaturized to enable flight in a small space, the propeller may be located below the drone body, which is equipped with a camera and control equipment. Also, when a drone flies with a load placed on top of the body, the propeller may be located below the load.

[0006] However, if the L-shaped rotor guide described in Patent Document 1 is attached when the drone body and objects such as the transported goods cover the upper side of the propeller, there is a problem that the thrust of the propellant will actually decrease.

[0007] Therefore, the present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a technology that can improve the thrust of a propellant. [Means for solving the problem]

[0008] The propeller guard for a propellant body according to the present disclosure is a propeller guard for a propellant body that is attached to a propellant body that includes a propeller and an object that is located on the suction side of the propeller and overlaps at least a portion of the propeller when viewed from the suction side of the propeller, and the propeller guard for a propellant body is provided at a distance from the propeller along at least a portion of the rotation direction ... passes through the center of the propeller. When viewed in a cross section including the rotation axis, the object has a blade shape, and a position that is away from the center of the propeller in the radial direction of the propeller by the total length obtained by adding the radius R of the propeller to the chord length l of the blade shape is defined as an origin position, and the deflection angle φ from the radial direction of the propeller to the chord of the blade shape satisfies the following equation (1), which uses the length L of a line segment that starts at the origin position and extends along the rotation axis direction, which is the direction of the rotation axis of the propeller, to the bottom surface of the object.

[0009]

number

[0010] According to the present disclosure, the deflection angle φ from the radial direction of the propeller to the chord of the blade shape satisfies formula (1) using the length L of a line segment extending from the origin position to the bottom surface of the object along the rotation axis direction, which is the direction of the rotation axis of the propeller. With this configuration, the thrust of the propellant can be improved. [Brief explanation of the drawings]

[0011] [Figure 1] 1(a) and 1(b) are a plan view and a cross-sectional view, respectively, showing a propellant according to the first embodiment. [Figure 2] FIG. 10 is a cross-sectional view for explaining the thrust force improving effect. [Figure 3] FIG. 1 is a diagram illustrating a system that is the subject of a computational fluid analysis. [Figure 4] FIG. 10 is a diagram showing the results of a computational fluid analysis. [Figure 5] FIG. 10 is a diagram showing the results of a computational fluid analysis. [Figure 6] FIG. 10 is a diagram showing the numerical values ​​of the symbols in the results of the computational fluid analysis. [Figure 7] 10(a) to 10(c) are contour diagrams showing gauge pressure. [Figure 8] FIG. 10 is a perspective view showing a propellant according to a second embodiment. [Figure 9] 10(a) and 10(b) are a plan view and a cross-sectional view, respectively, showing a propellant according to a second embodiment. [Figure 10] FIG. 11 is a perspective view showing a propellant according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] <First Embodiment> Hereinafter, an example of a propellant body equipped with a propellant propeller guard according to Embodiment 1 will be described. Fig. 1(a) is a plan view of the propellant body according to Embodiment 1 as seen from the discharge side of the propeller 1, and Fig. 1(b) is a cross-sectional view passing through the center of the propeller 1.

[0013] The propulsion body shown in Figures 1(a) and 1(b) includes a propeller 1, an object 2, and a propeller guard 3 for the propulsion body. For convenience in the following explanation, a cylindrical coordinate system o-rθz is introduced, with the origin o being the intersection of the rotation axis of the propeller 1 and the extension direction of the blades 13 of the propeller 1, i.e., the center of the propeller 1. This center of the propeller 1 is also the center of the thickness of the propeller 1. The directions of the +r, +θ, and +z axes are the radial direction of the propeller 1, the rotation direction, and the suction side direction of the propeller 1 parallel to the rotation axis, respectively.

[0014] In this case, the propulsion direction of the propulsion body in Figures 1(a) and 1(b) is the +z-axis direction, and the thrust that is desired to be increased is the resultant force in the +z-axis direction acting on the propulsion body. In this case, Figure 1(b) shows a θ cross section including the rotation axis passing through the origin o of the propeller 1, and in Figure 1(b), the upper side (+z-axis side) of the propeller 1 is the suction side, and the lower side (-z-axis side) of the propeller is the discharge side. Note that the propeller 1 and the object 2, and the object 2 and the propeller guard 3 for the propulsion body are connected and fixed via driving devices, holding members, and the like (not shown).

[0015] <Propeller 1> Propeller 1 includes a shaft 11 connected to a drive unit (not shown), a boss 12 connected to shaft 11, and two blades 13 extending outward from boss 12 in opposite directions. The rotation of the drive unit causes propeller 1 to rotate. The length from origin o to the tip of blade 13 (i.e., the blade tip) is defined as the radius R of propeller 1.

[0016] <Object 2> The object 2 includes, for example, at least one of a propellant body composed of a flight control device, an amplifier, a motor, an airframe, etc., and an object carried by the propellant. For example, if the propellant is a drone, the propellant body is the drone body equipped with a camera and control equipment. In this specification, for example, at least one of A, B, C, ..., and Z means any one of all combinations of one or more types selected from the group A, B, C, ..., and Z.

[0017] The object 2 is located on the +z-axis side of the propeller 1 and overlaps at least a part of the propeller 1 when viewed from the +z-axis side. This condition is sufficient to obtain the thrust improvement effect described later, but in order to simplify the situation, in this first embodiment, an additional condition is imposed that the object 2 overlaps the entire propeller 1 when viewed from the +z-axis side, and that the object 2 has a shape that is rotationally symmetrical with respect to the rotation axis (z-axis) of the propeller 1. The deflection angle from the r-axis to the bottom surface of the object 2 (the surface on the -z-axis side) is Φ c The distance along the z-axis from the origin o to the bottom surface of object 2 is defined as L c It is defined as follows. c When viewed from the θ cross section, the r axis is the starting line, and the +z axis direction is positive and the -z axis direction is negative.

[0018] <Propeller Guard 3 for Propulsion Unit> When viewed from the +z axis side, the propeller guard 3 for the propeller body is provided at a distance from the propeller 1 along at least a portion of the rotation direction of the propeller 1. Note that in Figure 1(a) and other figures, the distance between the propeller guard 3 for the propeller body and the propeller 1 is small, and they are shown as overlapping.

[0019] The propeller guard 3 for a propulsion body has a blade shape including a flat blade shape and an airfoil shape when viewed in the θ cross section. As shown in FIG. 1(b), a position that is away from the center of the propeller 1 in the r-axis direction of the propeller 1 by the total length (R+l) obtained by adding the radius R of the propeller to the chord length l of the blade shape is defined as the starting point position 41. The deflection angle φ from the r-axis to the chord of the blade shape satisfies the following equation (2) using the length L of a line segment that starts from the starting point position 41 and extends along the +z-axis direction (rotation axis direction) to the bottom surface of the object 2. Note that in the configuration of FIG. 1(b), L=L c +(R+l)tanΦ c The argument φ is positive in the +z direction and negative in the -z direction when viewed from the θ cross section, with the r axis as the starting line.

[0020]

number

[0021] The condition of formula (2) is sufficient to obtain the thrust improvement effect described below, but in this embodiment 1, an additional condition is imposed: the propellant body propeller guard 3 has an annular shape when viewed from the +z axis side, is provided spaced apart from the propeller 1 along the entire rotation direction of the propeller 1, and has the same flat plate blade shape when viewed in any θ cross section. This condition ensures safety by preventing the propeller 1 or the propellant body from coming into contact with surrounding structures and being damaged during propulsion, and also reduces manufacturing costs.

[0022] Furthermore, in the first embodiment, an additional condition is imposed that the entire propellant propeller guard 3 overlaps the object 2 when viewed from the +z-axis side. According to this condition, fluid resistance is reduced when the propellant translates in the +z-axis direction, thereby improving energy efficiency.

[0023] Furthermore, in this first embodiment, as shown in FIG. 1(b), an additional condition is imposed that the position of the trailing edge 31 of the flat plate blade in the z-axis direction coincides with the center of the thickness of the propeller 1 in the z-axis direction (i.e., z = 0). This condition makes it possible to suppress backflow that occurs at the blade tip of the propeller 1, thereby enhancing the thrust improvement effect of the propeller body. Note that the trailing edge 31 is defined as the end point on the origin o side (-r axis side) of the chord of the flat plate blade in the θ cross section of the propeller guard 3 for a propeller body (i.e., the long side of the flat plate blade on the +z axis side). The thickness of the propeller 1 in the z-axis direction corresponds to the thickness of the boss 12 or the blade 13 in the z-axis direction, for example.

[0024] <Effects> The effect of rotating the propeller 1 in a propulsion body configured as described above will be described below. Figure 2 is a cross-sectional view showing the flow field. When the propeller 1 is rotated, the surrounding fluid is sucked into the propeller 1 along the bottom surface of the object 2 due to the Coanda effect, as shown in Figure 2. Since the propeller guard 3 for the propellant body is exposed to the flow of this fluid, region 47 on the upper surface side (+z-axis side) and region 46 on the lower surface side (-z-axis side) of the propeller guard 3 for the propellant body become a negative pressure region (M region) and a positive pressure region (P region), respectively, relative to the surroundings which have atmospheric pressure.

[0025] Although details will be described later, when the deflection angle φ satisfies equation (2) using the length L, it is possible to prevent the negative pressure region 47 on the upper surface side of the propellant propeller guard 3 from spreading to the bottom surface of the object 2. This makes it possible to generate thrust in the +z-axis direction on the propellant while minimizing the generation of force in the -z-axis direction on the object 2. This force in the +z-axis direction is added to the thrust generated by the propeller 1, thereby improving the thrust of the propellant.

[0026] The results of the thrust enhancement effect of the propeller guard 3 for the propellant body confirmed by computational fluid analysis are described below. Figure 3 shows a system that was the subject of computational fluid analysis. This system comprises the propellant body, which is composed of the propeller 1, object 2, and propellant propeller guard 3 shown in Figure 1, and a cube 4 that surrounds them. The area inside the cube 4 is a dummy area necessary for performing computational fluid analysis, and is filled with fluid. The center of the cube 4 coincides with the origin o, which is the center of the propeller 1, and the faces that make up the cube 4 include two faces that are perpendicular to the z-axis. In this analysis, the fluid is assumed to be air. However, even if the fluid is a gas other than air or a liquid, the same thrust enhancement effect can be obtained as when the fluid is air. Furthermore, in this analysis, the radius R of the propeller 1 is assumed to be 8 inches (i.e., 203.2 mm), but the thrust enhancement effect is not limited to this radius.

[0027] Unsteady computational fluid analysis was performed on the airflow in the system shown in Figure 3 to calculate the time-averaged thrust F (force in the +z-axis direction) acting on the propulsion body. However, for ease of analysis, the parallel movement of the propulsion body (i.e., movement perpendicular to the +z-axis direction) was not taken into account, and the analysis focused on the case where the propulsion body was in a hovering state. Air was considered a compressible fluid that can be approximated as an ideal gas, and the governing equation was Unsteady Reynolds-Averaged Navier-Stokes (URANS). The turbulence model was assumed to be k-ω SST, and a cylindrical sliding mesh was used to represent the rotation of the propeller 1. The space was discretized using the finite volume method. iconCFD (registered trademark) was used as the calculation software.

[0028] The boundary conditions were that the total pressure on the two faces perpendicular to the z-axis of the cube 4 was equal to atmospheric pressure, and that there was no slip on the other faces. In addition, a velocity equal to the rotational speed was applied to the surface of the propeller 1, and there was no slip between the object 2 and the surface of the propeller propeller guard 3. The initial conditions used were the solution of a steady-state computational fluid analysis obtained with the Reynolds-Averaged Navier-Stokes (RANS) governing equation for the system shown in Figure 3. The settings for this steady-state computational fluid analysis were the same as those for the unsteady computational fluid analysis, except that the rotation of the propeller 1 was modeled using a Multiple Reference Frame (MRF).

[0029] First, we confirmed whether the above-described computational fluid analysis could evaluate the thrust of the propellant with sufficient accuracy. Figure 4 shows the results of a computational fluid analysis on the thrust-improving effect of a rotor guide having an L-shape when viewed in the θ cross section (i.e., an L-shaped rotor guide) described in Patent Document 1. In this computational fluid analysis, the object 2 and the propellant propeller guard 3 were removed from the system shown in Figure 3, and the L-shaped rotor guide was installed.

[0030] The dimensions of the L-shaped rotor guide followed the dimensions optimized in Patent Document 1. Specifically, the center of the hole in the L-shaped rotor guide was aligned with the origin o, and the bottom and side surfaces of the L-shape were positioned parallel to the r-axis and z-axis, respectively. The inner and outer diameters of the bottom surface were 1.03 and 1.3 times the diameter 2R of the propeller 1, respectively, the z coordinate of the bottom surface was 0 [mm], and the thickness in the negative z-axis direction was 1 [mm]. In addition, the height of the side surfaces was 0.12 times the diameter 2R of the propeller 1, and the thickness in the negative r-axis direction was 1 [mm].

[0031] The vertical axis of Fig. 4 is the thrust F and thrust F prop The thrust F is the thrust of the propulsion body when the L-shaped rotor guide is installed, that is, the thrust that is the sum of the forces in the +z axis direction obtained from the propeller 1 and the L-shaped rotor guide. Thrust F prop is the thrust when only the propeller 1 is installed without installing the L-shaped rotor guide. prop As with thrust F, unsteady computational fluid analysis was performed on the air flow in the system with only propeller 1, and the time-averaged value was calculated.

[0032] From Figure 4, at any rotation speed N of propeller 1, F / F prop exceeds 1, confirming an improvement in thrust of approximately 15%. This is quantitatively consistent with the results claimed in Patent Document 1, and it can be said that the computational fluid analysis set out above can evaluate the thrust of a propellant with sufficient accuracy.

[0033] Figures 5 and 6 show the results of the computational fluid analysis using the above settings, where the rotation speed N of the propeller 1 and the deflection angle Φ of the bottom surface of the object 2 are c , the distance L along the z-axis from the center of propeller 1 to the bottom surface of object 2 c 10 is a graph showing the results of investigating the thrust F of the propellant while varying the chord length l of the propellant propeller guard 3.

[0034] The vertical axis of Fig. 5 represents the deflection angle φ, and the horizontal axis of Fig. 5 represents the value obtained by dividing the length L by the sum of the radius R and the chord length l. The symbols (scattered points) in Fig. 5 correspond to the symbols in Fig. 6, and the rotation speed N and deflection angle Φ in Fig. 6 c , distance L c , the value of the chord length l, and the deflection angle φ is changed in increments of π / 18 to calculate the thrust F of the propulsion body. The deflection angle φ at which the thrust F is at its maximum value is max Represents.

[0035] The error bars attached to each symbol in FIG. 5 indicate that the thrust F is the thrust F of the propulsion body (i.e., the propeller 1 and the object 2) to which the propellant propeller guard 3 is not attached. no In other words, the range of the error bar represents the range of the deflection angle φ in which the thrust can be improved by adding the propellant propeller guard 3. The upper and lower limit values ​​of the error bar were calculated by linear interpolation after calculating the thrust F while changing the deflection angle φ in increments of π / 18. Thrust F no As with thrust F, unsteady computational fluid analysis was performed on the air flow in the system consisting of only propeller 1 and object 2, and the time-averaged value was calculated.

[0036] The smaller deflection angle φ of the thin dashed line and the thin dot-dash line in Fig. 5 is less than or equal to the upper limit of the error bar of each symbol. Also, the deflection angle φ of the thin solid line in Fig. 5 is greater than or equal to the lower limit of the error bar of each symbol. The thin dashed line and the thin dot-dash line in Fig. 5 correspond to the right side of equation (2), and the thin solid line in Fig. 5 corresponds to the left side of equation (2). Therefore, when the deflection angle φ satisfies equation (2) using the length L, it can be said that the thrust of a propulsion body to which the propellant propeller guard 3 is attached can be improved.

[0037] Note that each symbol in Figure 6 roughly corresponds to the smaller deflection angle φ of the thick dotted line and the thick dashed line in Figure 5. Therefore, when the deflection angle φ satisfies the following equation (3) using the length L, the thrust of the propellant body to which the propellant propeller guard 3 is attached can be made to approach the maximum thrust value in the computational fluid analysis.

[0038]

number

[0039] Furthermore, in FIG. 5, the black symbols indicate that the thrust F of the propeller body consisting of the propeller 1, the object 2, and the propeller guard 3 for the propeller is smaller than the thrust F of the propeller 1 alone. prop Therefore, it is preferable that L / (R+l)≧0.5 is satisfied, that is, the length L is 0.5 times or more the total length (R+l).

[0040] Figure 7(a) is a contour diagram showing the gauge pressure p around the blade tip of the propeller 1. Figure 7(b) is a contour diagram showing the gauge pressure p around the blade tip of the propeller 1 and the propeller guard 3 for the propeller. Figure 7(c) is a contour diagram showing the gauge pressure p around the blade tip of the propeller 1 and the L-shaped rotor guide whose dimensions are optimized in Patent Document 1. The gauge pressure p increases as the color changes from black to gray, with black indicating p<0 [Pa], i.e., negative pressure, and gray indicating p>0 [Pa], i.e., positive pressure.

[0041] Note that the propeller 1 is not shown in Figures 7(a) to 7(c), and the area of ​​the propeller propeller guard 3 for the propulsion body is shown as a white area in Figure 7(b), and the area of ​​the L-shaped rotor guide is shown as a white area in Figure 7(c). The areas where the gauge pressure p is discontinuous, that is, the area where 100≦r≦200 [mm] and z≒±20 [mm] and the area where r≒200 [mm] and -20≦z≦20 [mm], are the boundary areas between the cylindrical sliding mesh used in the computational fluid analysis and the normal mesh. This boundary area is an unavoidable part of the visualization post-processing and has no physical meaning.

[0042] In addition, the thin white area in Figure 7(b) extending diagonally upward to the right at r ≈ 240 [mm] and 30 ≦ z ≦ 40 [mm] is a software bug that occurred in the post-processing of visualization, and is not the propeller guard 3 for the propulsion body. In addition, the calculations in Figures 7(a) to 7(c) used values ​​for the deflection angle φ that satisfy equation (2). Specifically, the rotation speed N of the propeller 1 is N = 6000 [rpm], the deflection angle Φ of the bottom surface of the object 2 is c = 0, distance L along the z-axis from the center of propeller 1 to the bottom surface of object 2 c = 100 [mm], the chord length of the propeller guard 3 for the propeller body was set to l = 50 [mm], and the deflection angle φ = π / 36.

[0043] 7(a) to 7(c) show that a negative pressure region where p<0 [Pa] spreads on the +z-axis direction side of the propellant propeller guard 3 or the L-shaped rotor guide. Here, in the L-shaped rotor guide of FIG. 7(c), the negative pressure region exists on the bottom surface (z=100 [mm]) of the object 2. Therefore, the L-shaped rotor guide generates a force in the -z-axis direction on the object 2, reducing the thrust of the propellant in the +z-axis direction. On the other hand, in the propellant propeller guard 3 of FIG. 7(b), the negative pressure region does not substantially exist on the bottom surface (z=100 [mm]) of the object 2. Therefore, the propellant propeller guard 3 can generate a thrust in the +z-axis direction on the propellant without generating a force in the -z-axis direction on the object 2, thereby improving the thrust of the propellant.

[0044] <Embodiment 2> Fig. 8 is a perspective view showing a propellant according to the second embodiment, and Fig. 9(a) and Fig. 9(b) are a plan view and a cross-sectional view, respectively, showing the propellant. Hereinafter, among the components according to the second embodiment, components that are the same as or similar to the components described above will be given the same or similar reference numerals, and different components will be mainly described.

[0045] 9(b), in the second embodiment, when viewed in a central axis cross section (θ cross section) of the propeller 1, the blade shape of the propeller guard 3 for the propeller body is airfoil-shaped, and the leading edge 32 of the airfoil shape is located on the opposite side of the propeller 1 from the trailing edge 31 of the airfoil shape. In addition, the position of the trailing edge 31 of the airfoil shape in the direction of the rotation axis of the propeller 1 (z-axis direction) is within the thickness of the propeller 1 in the direction of the rotation axis of the propeller 1 (z-axis direction). With this configuration, a pressure difference is more likely to occur between the upper surface (+z-axis side) and the lower surface (-z-axis side) of the propeller guard 3 for the propeller body, thereby improving the thrust of the propeller body.

[0046] 1, all of the propeller 1 and all of the propeller guard 3 for the propellant body overlap with the object 2 when viewed from the suction side (+z-axis side) of the propeller 1. However, as in the present embodiment 2, even if the propeller 1 and the propeller guard 3 for the propellant body each partially overlap with the object 2 when viewed from the suction side (+z-axis side) of the propeller 1, the propeller guard for the propellant body can improve the thrust of the propellant body.

[0047] Furthermore, in the first embodiment, the object 2 has a shape that is rotationally symmetrical with respect to the rotation axis (z-axis) of the propeller 1, but it does not have to have a shape that is rotationally symmetrical as in the second embodiment. Furthermore, in the first embodiment, the propellant body propeller guard 3 is provided at a distance from the propeller 1 along the entire rotation direction of the propeller 1 when viewed from the +z-axis side, but as in the second embodiment, the propellant body propeller guard 3 may be provided so as to partially surround the propeller 1. With such a configuration, it is expected that the reduction in material costs and the improvement in thrust due to the weight reduction can be achieved.

[0048] Furthermore, in the first embodiment, the propeller guard 3 for a propellant body is configured so that the deflection angle φ is the same regardless of the central axis cross section (θ cross section) of the propeller 1, thereby making it possible to reduce manufacturing and processing costs. However, this is not limited to this, and as in the second embodiment, in a certain θ cross section, the deflection angle φ may be partially changed by, for example, reversing the blade shapes of two portions of the propeller guard 3 for a propellant body that face each other on both sides of the propeller 1. With such a configuration, it is expected that the thrust of the propellant body will be optimized.

[0049] <Third Embodiment> 10 is a perspective view showing a propellant according to the present embodiment 3. Hereinafter, among the components according to the present embodiment 3, components that are the same as or similar to the components described above will be given the same or similar reference numerals, and different components will be mainly described.

[0050] In the first embodiment shown in Fig. 1 and the second embodiment shown in Fig. 8, the propellant body is provided with one propeller 1, but as in the third embodiment shown in Fig. 10, the propellant body may be provided with multiple propellers 1. Furthermore, as shown in Fig. 10, a propeller guard 3 for the propellant body may be provided for each of the multiple propellers 1, or a single propeller guard 3 for the propellant body may be provided to surround the multiple propellers collectively.

[0051] As in the third embodiment, the propeller guard 3 for a propellant body is configured so that at least one of the position of the trailing edge of the propeller guard 3 relative to the propeller 1 and the deflection angle φ can be actively and temporally changed. For example, a motor 5 connected to the propeller guard 3 for a propellant body may actively and temporally change at least one of the position of the trailing edge of the propeller guard 3 relative to the propeller 1 and the deflection angle φ in accordance with the environment around the propellant body. With this configuration, the thrust of the propellant body can be brought as close to the maximum value as possible even if the environment around the propellant body changes.

[0052] <Other> In the above-described first to third embodiments, the propeller is configured with two blades extending in opposite directions, but the shape, arrangement, and number of the blades are not limited to this. Also, the bottom surface of the object 2 is linear, but may be curved.

[0053] The propellant body propeller guard 3 may be installed as standard on the propellant body, or may be retrofitted to an existing propellant body as an optional part. Furthermore, if the propellant body already has another propeller guard attached, the propellant body propeller guard 3 may be partially joined to the other propeller guard.

[0054] In this disclosure in English, 'a' and 'an' mean one or more. Therefore, 'a', 'an', 'one or more' and 'at least one' can be used interchangeably.

[0055] It should be noted that the embodiments and modifications may be freely combined, and the embodiments and modifications may be modified or omitted as appropriate.

[0056] Various aspects of the present disclosure are summarized below as appendices.

[0057] (Appendix 1) A propeller guard for a propellant provided to a propellant including a propeller and an object located on the suction side of the propeller and overlapping at least a portion of the propeller when viewed from the suction side of the propeller, the propellant body propeller guard is provided at a distance from the propeller along at least a portion of the rotation direction of the propeller when viewed from the suction side of the propeller, the propellant body propeller guard has a blade shape when viewed in a cross section including a rotation axis passing through the center of the propeller, A position that is separated from the center of the propeller in the radial direction of the propeller by a total length obtained by adding the radius R of the propeller to the chord length l of the blade shape is defined as the starting position, A propeller guard for a propellant, wherein the deflection angle φ from the radial direction of the propeller to the chord of the blade shape satisfies the following formula (4), using the length L of a line segment extending from the starting position as a point to the bottom surface of the object along the rotation axis direction, which is the direction of the rotation axis of the propeller.

[0058]

number

[0059] (Appendix 2) 2. A propeller guard for a propellant body according to claim 1, The deflection angle φ satisfies the following formula (5) using the length L.

[0060]

number

[0061] (Appendix 3) A propeller guard for a propellant body according to claim 1 or 2, A propeller guard for a propulsion body, wherein a leading edge of the wing shape is located on the opposite side of the propeller from the trailing edge of the wing shape.

[0062] (Appendix 4) A propeller guard for a propellant body according to any one of Supplementary Note 1 and Supplementary Note 3, a position of the trailing edge of the blade shape in the direction of the rotation axis of the propellant body within a range of a thickness of the propeller in the direction of the rotation axis of the propeller;

[0063] (Appendix 5) A propeller guard for a propellant body according to any one of Supplementary Note 1 and Supplementary Note 4, A propeller guard for a propellant body, wherein a position of the trailing edge of the blade shape in the rotation axis direction coincides with a center of thickness of the propeller in the rotation axis direction.

[0064] (Appendix 6) A propeller guard for a propellant body according to any one of Supplementary Note 1 and Supplementary Note 5, A propeller guard for a propellant body, wherein the object has a shape that is rotationally symmetrical with respect to the rotation axis of the propeller.

[0065] (Appendix 7) A propeller guard for a propellant body according to any one of Supplementary Note 1 and Supplementary Note 6, A propeller guard for a propellant body, wherein at least one of the position of the trailing edge of the blade shape relative to the propeller and the deflection angle φ is changeable over time.

[0066] (Appendix 8) A propeller guard for a propellant body according to any one of Supplementary Note 1 and Supplementary Note 7, A propeller guard for a propellant body, wherein the length L is 0.5 times or more the total length.

[0067] (Appendix 9) A propeller guard for a propellant body according to any one of Supplementary Note 1 and Supplementary Note 8, A propeller guard for a propellant body, wherein the entire propellant guard for a propellant body overlaps the object when viewed from the suction side of the propeller.

[0068] (Appendix 10) A propeller guard for a propellant body according to any one of Supplementary Note 1 and Supplementary Note 9, The propeller guard for a propellant body has an annular shape when viewed from the suction side of the propeller, and is provided at a distance from the propeller along the entire rotation direction of the propeller. [Explanation of symbols]

[0069] 1 propeller, 2 object, 3 propeller guard for propulsion body, 31 trailing edge, 32 leading edge, 41 starting position.

Claims

1. A propeller guard for a propellant provided to a propellant including a propeller and an object located on the suction side of the propeller and overlapping at least a portion of the propeller when viewed from the suction side of the propeller, the propellant body propeller guard is provided at a distance from the propeller along at least a portion of the rotation direction of the propeller when viewed from the suction side of the propeller, the propellant body propeller guard has a blade shape when viewed in a cross section including a rotation axis passing through the center of the propeller, A position that is spaced apart from the center of the propeller in the radial direction of the propeller by a total length obtained by adding the radius R of the propeller to the chord length l of the blade shape is defined as a starting position, a deflection angle φ from the radial direction of the propeller to the chord of the blade shape satisfies the following formula (1), where L is the length of a line segment extending from the starting position as a point to a bottom surface of the object along a rotational axis direction that is the direction of the rotational axis of the propeller: [Equation 1]

2. 2. A propeller guard for a propellant body according to claim 1, The deflection angle φ satisfies the following formula (2) using the length L. [Equation 2]

3. The propeller guard for a propellant body according to claim 1 or 2, A propeller guard for a propulsion body, wherein a leading edge of the wing shape is located on the opposite side of the propeller from the trailing edge of the wing shape.

4. The propeller guard for a propellant body according to claim 1 or 2, a position of the trailing edge of the blade shape in the direction of the rotation axis of the propellant body within a range of a thickness of the propeller in the direction of the rotation axis of the propeller;

5. The propeller guard for a propellant body according to claim 1 or 2, A propeller guard for a propellant body, wherein a position of the trailing edge of the blade shape in the rotation axis direction coincides with a center of thickness of the propeller in the rotation axis direction.

6. The propeller guard for a propellant body according to claim 1 or 2, A propeller guard for a propellant body, wherein the object has a shape that is rotationally symmetrical with respect to the rotation axis of the propeller.

7. The propeller guard for a propellant body according to claim 1 or 2, A propeller guard for a propellant body, wherein at least one of the position of the trailing edge of the airfoil shape relative to the propeller and the deflection angle φ is changeable over time.

8. The propeller guard for a propellant body according to claim 1 or 2, A propeller guard for a propellant body, wherein the length L is 0.5 times or more the total length.

9. The propeller guard for a propellant body according to claim 1 or 2, A propeller guard for a propellant body, wherein the entire propellant guard for a propellant body overlaps the object when viewed from the suction side of the propeller.

10. The propeller guard for a propellant body according to claim 1 or 2, The propeller guard for a propellant body has an annular shape when viewed from the suction side of the propeller, and is provided at a distance from the propeller along the entire rotation direction of the propeller.

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