A two-stroke aero-piston engine exhaust resonance structure and method for a drone

Abstract

The application discloses a two-stroke aviation piston engine exhaust resonance structure and method for a UAV, and belongs to the field of UAV power. The structure is suitable for matching a UAV with a pull-type propeller. The propeller is connected with the power output end of the two-stroke aviation piston engine through a speed reducer. Two equal-diameter exhaust pipes are symmetrically arranged on the exhaust port of the engine, and the exhaust outlets of the exhaust pipes are located behind the propeller. The pressure wave behind the propeller blade is matched with the engine sweep exhaust phase, so that the pressure wave generated by the rotation of the propeller produces a resonance effect in the exhaust pipe. The equal-diameter exhaust pipe is used to replace the traditional variable-diameter exhaust resonance pipe, the exhaust resonance effect is realized, the weight and volume of the exhaust resonance system are effectively reduced, and the power-to-weight ratio of the engine is improved.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicle (UAV) power, specifically to an exhaust resonance structure and method for a two-stroke aero-piston engine used in UAVs. Background Technology

[0002] Two-stroke piston engines, with their high power-to-weight ratio, have become the most commonly used power source for small and medium-sized unmanned aerial vehicles (UAVs). Exhaust resonance technology, by installing an exhaust resonance pipe at the engine's exhaust port and adjusting the exhaust back pressure through the pipe, can effectively improve the engine's ventilation quality, thereby increasing engine power and reducing fuel consumption.

[0003] Existing engines use traditional exhaust resonator pipes, such as Figure 4 As shown, exhaust resonator pipes are typically divided into inlet, expansion, constant-diameter, contraction, and outlet sections. By designing the exhaust resonator structure, the pressure at the cylinder block exhaust port and the scavenging phase can be rationally matched without changing the engine's mechanical structure, thus optimizing the engine's scavenging action. The expansion section is designed so that the reflected expansion wave generated by the engine's scavenging reaches its peak near the bottom dead center, resulting in a smaller exhaust back pressure throughout the scavenging process, accelerating the discharge of residual exhaust gas and the intake of fresh air-fuel mixture. The contraction section is designed so that the reflected compression wave reaches its peak during the engine's post-exhaust phase, reducing scavenging short-circuit losses in this stage. However, traditional exhaust resonator pipes are long and bulky, significantly increasing the engine's size and weight, and reducing its power-to-weight ratio. For the two-stroke aero-piston engines commonly used in small and medium-sized UAVs, this type of exhaust resonator pipe is not suitable, as it reduces the engine's power-to-weight ratio and makes engine installation inconvenient due to the large size of the exhaust resonator pipe.

[0004] Therefore, there is a need to provide an exhaust resonance structure and method for a two-stroke aero-piston engine for unmanned aerial vehicles to solve the above problems. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides an exhaust resonance structure and method for a two-stroke aero-piston engine for unmanned aerial vehicles (UAVs). By replacing the traditional exhaust resonance pipe with an equal-diameter exhaust pipe, and in conjunction with the pressure wave generated by the rotation of the pull propeller, a resonance effect is produced in the exhaust pipe, thereby solving the problem that existing exhaust resonance pipes are too bulky to be suitable for two-stroke aero-piston engines for UAVs.

[0006] The technical solution of this invention is: an exhaust resonance structure for a two-stroke aero-piston engine used in unmanned aerial vehicles, comprising:

[0007] The propeller is a pull propeller, which is connected to the power output end of the two-stroke aircraft piston engine through a reduction gear.

[0008] Two exhaust pipes are symmetrically installed on the exhaust ports on both sides of the two-stroke aircraft piston engine; the intake section of the exhaust pipe is connected to the two exhaust ports on the same side of the engine, and its exhaust section is parallel to the plane of rotation of the propeller blades, and the exhaust port of the exhaust pipe is located behind the propeller.

[0009] When the propeller rotates, a pressure wave is generated behind its blades and enters the exhaust pipe from the outlet, generating an exhaust resonance effect in the exhaust pipe.

[0010] A further technical solution of the present invention is: the propeller is installed on the nose or leading edge of the side wing of the UAV, and the two-stroke aviation piston engine is fixedly installed inside the nose or on the side wing of the UAV corresponding to the propeller, with the two-stroke aviation piston engine located behind the propeller.

[0011] A further technical solution of the present invention is: the exhaust pipe is a through pipe structure with equal diameter, the intake section is perpendicular to the exhaust section, and the intake section is provided with two intake ports that are respectively connected to two exhaust ports on the same side of the engine.

[0012] A further technical solution of the present invention is that the exhaust pipe is an integral pipe structure with an arc transition between the intake section and the exhaust section.

[0013] A further technical solution of the present invention is: the air inlet end of the exhaust pipe is provided with a mounting flange, and the mounting flange is fixedly connected to the exhaust port of the two-stroke aviation piston engine by fasteners.

[0014] A further technical solution of the present invention is: a sealing gasket is installed between the mounting flange of the exhaust pipe and the exhaust port of the two-stroke aviation piston engine, and the sealing gasket is used for gas sealing at the connection between the two.

[0015] A further technical solution of the present invention is that the number of blades of the propeller is the same as the reduction ratio of the reducer.

[0016] An exhaust resonance method for a two-stroke aircraft piston engine used in unmanned aerial vehicles (UAVs), the method utilizing the exhaust resonance structure of the two-stroke aircraft piston engine, the method comprising:

[0017] The pressure fluctuations behind the propeller blades are matched with the engine's scavenging phase, so that the pressure wave behind the propeller reaches its trough when the engine exhaust port is open and its peak during the exhaust phase when the exhaust port is about to close. The pressure wave enters the exhaust outlet of the exhaust pipe and generates an exhaust resonance effect in the exhaust pipe.

[0018] A further technical solution of the present invention is: the method for matching the pressure fluctuation behind the propeller blades with the engine scavenging exhaust phase is as follows:

[0019] The crankshaft rotation frequency is determined based on the engine crankshaft speed.

[0020] The propeller's pass frequency is determined based on the number of propeller blades and the propeller's rotational speed.

[0021] The reduction ratio of the reducer is determined based on the crankshaft speed and the propeller speed.

[0022] By making the propeller's pass frequency equal to the engine's crankshaft rotation frequency and the number of propeller blades equal to the reduction ratio of the reducer, the pressure fluctuation behind the propeller blades can be matched with the engine's scavenging and exhaust phase.

[0023] A further technical solution of the present invention is: the propeller's passing frequency is the number of blades passing through a fixed point in space per second, and the crankshaft's rotation frequency is the number of crankshaft rotations per second.

[0024] The beneficial effects of this invention are as follows: This invention provides an exhaust resonance structure and method for a two-stroke aero-piston engine used in unmanned aerial vehicles (UAVs). By employing a conventional exhaust pipe of equal diameter in conjunction with a pull-type propeller, the exhaust outlet of the pipe is located in the pressure wave generation zone behind the propeller. When the propeller rotates, the pressure wave generated by its blades enters the exhaust outlet of the pipe, generating exhaust resonance within the pipe. This invention, by combining the propeller and exhaust pipe, achieves the effect of generating resonance in the exhaust pipe using the pressure wave generated by the engine driving the propeller's rotation, thereby improving engine power. Simultaneously, by avoiding the use of traditional bulky variable-diameter resonant tubes, the weight and volume of the resonant system are effectively reduced, thus improving the engine's power-to-weight ratio. Compared to traditional exhaust resonant tube structures, the conventional equal-diameter exhaust pipe of this invention is smaller, lighter, and simpler in structure, occupying less external engine space and facilitating engine installation on UAVs.

[0025] This invention's exhaust resonance method matches the pressure fluctuations behind the propeller blades with the engine's scavenging exhaust phase. The pressure wave behind the propeller reaches its trough when the engine exhaust port opens, promoting the scavenging process; and reaches its peak in the post-exhaust phase when the exhaust port is about to close, increasing the energy of the exhaust reflection wave and hindering short-circuit losses of fresh charge, thus achieving the exhaust resonance effect. Matching the pressure fluctuations behind the propeller blades with the engine's scavenging exhaust phase is achieved by making the engine crankshaft rotation frequency the same as the propeller's passing frequency, and by ensuring the reduction ratio of the reducer connecting the crankshaft and propeller is the same as the number of propeller blades. This method provides a novel exhaust resonance technology for two-stroke aero-piston engines. Experimental tests comparing a two-stroke aero-piston engine using the original exhaust pipe and one using the exhaust pipe of this invention combined with the exhaust resonance method described herein demonstrate that this invention increases the engine speed by 200 r / min, improving engine power. Furthermore, at the same engine speed, this invention significantly reduces fuel consumption, proving the effectiveness of the exhaust resonance structure and method of this invention. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the exhaust resonance structure of a two-stroke aviation piston engine for unmanned aerial vehicles according to the present invention;

[0028] Figure 2 This is a schematic diagram of the exhaust pipe structure in this invention;

[0029] Figure 3 The structure is based on the existing traditional exhaust resonator.

[0030] Figure 4 This is a structural diagram of the original exhaust pipe of a two-stroke aviation piston engine used in unmanned aerial vehicles.

[0031] In the diagram: 1. Propeller; 2. Two-stroke aircraft piston engine; 3. Exhaust pipe; 31. Inlet section; 32. Outlet section; 33. Inlet port; 34. Outlet port; 35. Mounting flange; 4. Traditional exhaust resonant pipe; 41. Inlet section; 42. Expansion section; 43. Constant diameter section; 44. Contraction section; 45. Outlet section. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] An embodiment of the exhaust resonance structure of a two-stroke aero-piston engine for unmanned aerial vehicles (UAVs) according to the present invention is as follows: Figure 1 As shown, it includes: a propeller 1, a two-stroke aircraft piston engine 2, and two exhaust pipes 3 mounted on the two-stroke aircraft piston engine 2. This structure is suitable for unmanned aerial vehicles (UAVs) that are matched with pull propellers, which are generally mounted on the nose or leading edge of the side wing of an aircraft. When the propeller rotates, it accelerates the airflow backward, generating a forward thrust on the UAV through the reaction force.

[0034] Specifically, in this embodiment, the propeller 1 is a pull propeller. The rotating shaft of the propeller 1 and the power output end (crankshaft) of the two-stroke aviation piston engine 2 are connected via a reducer. The input end of the reducer is connected to the crankshaft of the engine 2, and the output end of the reducer is connected to the rotating shaft of the propeller 1. The reducer has a certain reduction ratio, which serves to reduce speed. The two-stroke aviation piston engine 2 drives the propeller 1 to rotate, providing the driving force for the UAV's movement.

[0035] The propeller 1 and the two-stroke aviation piston engine 2 are installed correspondingly. When the propeller 1 is installed in the nose of the UAV, the two-stroke aviation piston engine 2 is installed inside the nose. When the propeller 1 is installed on the leading edge of the UAV's side wing, the two-stroke aviation piston engine 2 is installed on the side wing. When the UAV is mounted on the side wing, the propeller 1 is symmetrically installed on both side wings.

[0036] Two exhaust pipes 3 are symmetrically installed on the exhaust ports on both sides of the two-stroke aircraft piston engine 2. For example... Figure 2 As shown, the exhaust pipe 3 is a through-pipe structure with equal diameter, comprising an intake section 31 and an exhaust section 32. The intake section 31 is perpendicular to the exhaust section 32. The intake section 31 has two branching air inlets 33, which are located on the same straight line and connected to the two exhaust ports on the same side of the engine. The axis of the exhaust section 32 is parallel to the plane of rotation of the propeller 1 blades. The end of the exhaust section 32 away from the intake section 31 is the exhaust outlet 34 of the exhaust pipe. The exhaust outlet 34 is located behind the propeller 1 (the front of the propeller 1 is the direction of the UAV's movement), that is, within the area covered by the pressure wave generated by the rotation of the propeller 1 blades. This allows the pressure wave generated behind the blades of the propeller 1 to enter the exhaust outlet 34 of the exhaust pipe 3 when the propeller 1 rotates, generating an exhaust resonance effect within the exhaust pipe 3.

[0037] In this embodiment, the exhaust pipe 3 is an integral pipe structure with an arc transition between the intake section 31 and the exhaust section 32. Each end of the two intake ports 33 is equipped with a mounting flange 35, which is fixedly connected to the exhaust port of the two-stroke aero-piston engine 2 using fasteners. To ensure a tight seal between the exhaust pipe 3 and the engine exhaust port, a sealing gasket is installed between the mounting flange 35 and the exhaust port of the two-stroke aero-piston engine 2.

[0038] This invention achieves exhaust resonance by installing an exhaust pipe 3 of equal diameter on a two-stroke aero piston engine 2 and cooperating with a pull propeller 1. This is done without using a traditional exhaust resonance pipe, by matching the pressure fluctuation behind the propeller blades with the engine's scavenging exhaust phase.

[0039] Specifically, the method for achieving exhaust resonance using the exhaust resonance structure of the aforementioned two-stroke aero-piston engine is as follows:

[0040] The pressure fluctuation behind the propeller blade 1 is matched with the scavenging phase of the two-stroke aero-piston engine 2. This ensures that the pressure wave behind the propeller 1 reaches its trough when the engine exhaust port opens, thus promoting the scavenging process; and reaches its peak during the exhaust phase when the exhaust port is about to close, increasing the energy of the exhaust reflection wave and hindering short-circuit losses of fresh charge. The pressure wave enters the exhaust outlet 34 of the exhaust pipe 3, generating exhaust resonance within the exhaust pipe 3.

[0041] When the two-stroke aero piston engine 2 is running, the engine's crankshaft drives the propeller 1 to rotate. Each blade of the propeller 1 periodically cuts through the air, and the area behind the blade exhibits regular pressure fluctuations due to the periodic passage of the blade. The frequency of these pressure fluctuations is related to the rotational speed of the propeller 1 and the number of blades. After each blade passes through, it leaves alternating low-pressure (vortex core) and high-pressure (accelerated airflow) regions in the wake, forming a periodic pressure gradient, that is, forming crests and troughs.

[0042] The frequency of the pressure fluctuation behind the propeller blades 1 is the propeller's pass-through frequency. During design, by matching the propeller's pass-through frequency to the crankshaft rotation frequency of the two-stroke aero-piston engine 2, and by ensuring the number of propeller blades equals the reduction ratio of the reducer connecting the engine and propeller, the pressure fluctuation behind the propeller blades can be matched to the engine's exhaust phase. This ensures the pressure wave behind propeller 1 reaches its trough when the engine exhaust port opens and its peak during the exhaust phase as the port closes. Specifically, the propeller's pass-through frequency is determined by the number of propeller blades and the propeller's rotational speed; the engine crankshaft rotation frequency is determined by the crankshaft rotational speed; and the reducer's reduction ratio is determined by the crankshaft rotational speed and the propeller rotational speed.

[0043] The specific calculation method is as follows:

[0044] The propeller pass frequency is defined as the number of propeller blades passing a fixed point in space per second, and it is calculated by the following formula:

[0045]

[0046] In the formula, The propeller's passing frequency, measured in Hz; This refers to the number of propeller blades, expressed in units. This refers to the rotational speed of the propeller, measured in r / min. The rotational speed of the propeller is set within a range based on the performance requirements of the UAV and the structural characteristics of the propeller.

[0047] The rotational frequency of the engine crankshaft, which is the number of revolutions the crankshaft makes per second, is calculated using the following formula:

[0048]

[0049] In the formula, The crankshaft's rotational frequency, measured in Hz; The crankshaft speed is given in r / min. The engine crankshaft speed is known.

[0050] The reduction ratio of the reducer is the ratio of the engine crankshaft speed to the propeller speed, i.e. .

[0051] To match the pressure fluctuations behind the propeller blades with the scavenging phase of a two-stroke aero-piston engine, the crankshaft rotation frequency needs to be... Equal to the propeller's passing frequency ,Right now The crankshaft of the engine and the rotating shaft of the propeller are connected by a reducer. The reduction ratio of the reducer is equal to the number of propeller blades, which can achieve a reasonable match between the pressure fluctuation behind the propeller blades and the scavenging and exhaust phase of the engine.

[0052] During operation, the crankshaft of the two-stroke aviation piston engine 2 drives the propeller 1 to rotate. As the propeller 1 rotates, it accelerates the airflow backward, generating a forward thrust on the UAV through a reaction force. The rotation of propeller 1 causes each blade to periodically cut the air, creating periodic pressure fluctuations. When the two-stroke aviation piston engine 2 is at the end of its expansion stroke, the exhaust port of engine 2 opens, and combustion exhaust gas rushes into the exhaust pipe 3, forming an exhaust pulse. The piston of engine 2 reaches near bottom dead center, at which point the pressure wave behind propeller 1 reaches its trough, reducing the exhaust back pressure in exhaust pipe 3. This accelerates the discharge of residual exhaust gas from the engine cylinder and the intake of fresh air-fuel mixture, promoting the engine's scavenging process. When the two-stroke aviation piston engine 2 is in the after-exhaust phase, the scavenging process has ended, and the exhaust port of engine 2 is about to close. At this point, the pressure wave behind propeller 1 reaches its peak, increasing the energy of the exhaust reflection wave in exhaust pipe 3, hindering the outflow of fresh charge, reducing short-circuit losses, and thus ensuring the charge coefficient within the engine cylinder.

[0053] To test the impact of the exhaust resonance structure and method for a two-stroke aero-piston engine of the present invention on engine performance, the original exhaust pipes (such as those for unmanned aerial vehicles) were installed on two-stroke piston engines of the same model. Figure 4 (as shown) and the exhaust pipe of the present invention (as shown) Figure 2 As shown), the engine's power and fuel consumption were tested. The original exhaust pipes of the two-stroke aviation piston engine consisted of four straight, slightly expanded exhaust pipes. Each exhaust pipe was independent of the others and was installed vertically at each exhaust port of the engine, without any exhaust resonance effect.

[0054] Test data shows that using the exhaust pipe and exhaust resonance method of this invention increases the engine's maximum speed by 200 r / min compared to when the original exhaust pipe is installed. At the same engine speed, installing the exhaust pipe and combining it with the exhaust resonance technology results in lower fuel consumption compared to an engine with the original exhaust pipe. Test results demonstrate that, compared to an engine with the original exhaust pipe, this invention increases engine power and reduces fuel consumption.

[0055] Meanwhile, compared with the traditional variable-diameter exhaust resonant pipe, the exhaust resonant pipe of this invention, using the exhaust resonance technology of this invention, is smaller in size, lighter in weight, and simpler in structure, does not occupy too much external space of the engine, and is more convenient for the engine to be installed on the UAV.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An exhaust resonance structure for a two-stroke aero-piston engine used in unmanned aerial vehicles, characterized in that, include: The propeller is a pull propeller, which is connected to the power output end of the two-stroke aircraft piston engine through a reduction gear. Two exhaust pipes are symmetrically installed on the exhaust ports on both sides of the two-stroke aircraft piston engine; the intake section of the exhaust pipe is connected to the two exhaust ports on the same side of the engine, and its exhaust section is parallel to the plane of rotation of the propeller blades, and the exhaust port of the exhaust pipe is located behind the propeller. When the propeller rotates, a pressure wave is generated behind its blades and enters the exhaust pipe from the outlet, generating an exhaust resonance effect in the exhaust pipe. The pressure wave behind the propeller reaches its trough when the engine exhaust port is open and its peak in the exhaust phase when the exhaust port is about to close. The number of propeller blades is the same as the reduction ratio of the reducer.

2. The exhaust resonance structure for a two-stroke aero-piston engine for unmanned aerial vehicles according to claim 1, characterized in that, The propeller is mounted on the nose or leading edge of the side wing of the UAV, and the two-stroke aviation piston engine is fixedly mounted inside the nose or on the side wing of the UAV, with the two-stroke aviation piston engine located behind the propeller.

3. The exhaust resonance structure for a two-stroke aero-piston engine for unmanned aerial vehicles according to claim 1, characterized in that, The exhaust pipe is a through pipe structure with equal diameter. Its intake section is perpendicular to the exhaust section. The intake section has two intake ports that are respectively connected to two exhaust ports on the same side of the engine.

4. The exhaust resonance structure for a two-stroke aero-piston engine for unmanned aerial vehicles according to claim 3, characterized in that, The exhaust pipe is an integral pipe structure with an arc transition between the intake and exhaust sections.

5. The exhaust resonance structure for a two-stroke aero-piston engine for unmanned aerial vehicles according to claim 3, characterized in that, The exhaust pipe is equipped with a mounting flange at the air inlet end, and the mounting flange is fixedly connected to the exhaust port of the two-stroke aviation piston engine by fasteners.

6. The exhaust resonance structure for a two-stroke aero-piston engine for unmanned aerial vehicles according to claim 5, characterized in that, A sealing gasket is installed between the mounting flange of the exhaust pipe and the exhaust port of the two-stroke aircraft piston engine. The sealing gasket is used for gas sealing at the connection between the two.

7. An exhaust resonance method for a two-stroke aero-piston engine for unmanned aerial vehicles (UAVs), the method employing the exhaust resonance structure of the two-stroke aero-piston engine for UAVs as described in any one of claims 1-6, characterized in that, The methods include: The pressure fluctuations behind the propeller blades are matched with the engine's scavenging phase, so that the pressure wave behind the propeller reaches its trough when the engine exhaust port is open and its peak during the exhaust phase when the exhaust port is about to close. The pressure wave enters the exhaust outlet of the exhaust pipe and generates an exhaust resonance effect in the exhaust pipe.

8. The exhaust resonance method for a two-stroke aero-piston engine for unmanned aerial vehicles according to claim 7, characterized in that, The method for matching the pressure fluctuation behind the propeller blades with the engine's scavenging exhaust phase is as follows: The crankshaft rotation frequency is determined based on the engine crankshaft speed. The propeller's pass frequency is determined based on the number of propeller blades and the propeller's rotational speed. The reduction ratio of the reducer is determined based on the crankshaft speed and the propeller speed. By making the propeller's pass frequency equal to the engine's crankshaft rotation frequency and the number of propeller blades equal to the reduction ratio of the reducer, the pressure fluctuation behind the propeller blades can be matched with the engine's scavenging and exhaust phase.

9. The exhaust resonance method for a two-stroke aero-piston engine for unmanned aerial vehicles according to claim 8, characterized in that, The propeller's passing frequency is the number of blades passing a fixed point in space per second, and the crankshaft's rotation frequency is the number of revolutions the crankshaft makes per second.

Images