Air injection two-stroke heavy fuel aircraft engine cylinder and exhaust pipe layout structure

Abstract

The present application belongs to the technical field of aviation piston engine. Disclosed is a kind of air injection two-stroke heavy oil aviation engine cylinder and exhaust pipe layout structure, including cylinder and exhaust system. To solve the problem of high pressure aviation kerosene in lubricating oil solubility, difficult to separate, resulting in ignition difficult, serious carbon deposition and high content of exhaust pollution, the present application sets weak rigid structure in the top area of cylinder near the combustion chamber, through the stepped hole of connecting screw hole, non-full thread structure weakens the rigidity of this area, so that the top of cylinder expands elastically along the radial direction under the pressure of gas to increase the lubricating oil storage space of piston ring groove; The exhaust pipe is bent around the outer wall of the cylinder, and the exhaust gas is heated to 110-120 DEG C by using the exhaust heat to reduce the solubility of aviation kerosene in lubricating oil. The two measures work together to achieve deep separation of fuel and lubricating oil in the physical space in the cylinder, taking into account the safe operation of friction pair and high efficient and stable combustion, and at the same time improving the thermal efficiency of the whole machine.

Description

Technical Field

[0001] This invention belongs to the field of aviation piston engine technology, specifically relating to a cylinder block and exhaust pipe layout structure of a two-stroke heavy oil aviation engine with air-jet injection. Background Technology

[0002] With the booming development of the low-altitude unmanned industry and the rapid evolution of diversified market demands, the aviation piston engine technology, which supports the development of this industry, has undergone rapid iteration in recent years, driven by the needs of industrial development. The resulting two-stroke heavy oil engines have been widely used in various fields due to their advantages such as higher safety, higher power density, and easier management. Among them, the aviation kerosene piston engine, as a typical representative of heavy oil engines, has broad application prospects in low-altitude flight, general aviation, disaster relief, and emergency rescue compared to traditional gasoline piston engines.

[0003] The core of the power conversion device in a two-stroke kerosene piston engine consists of components such as the piston, piston rings, and cylinder. In the combustion chamber, fuel converts chemical energy into thermodynamic energy through combustion, and further converts this into mechanical energy through expansion and work. However, the lubricating oil, which ensures the safe movement of the cylinder, piston, and piston ring friction pairs, also participates in combustion during this process. Due to the significant differences in properties between kerosene and gasoline, the premixing characteristics with the lubricating oil change, leading to a sharp decline in lubrication performance at high temperatures. Under the same conditions, piston surface wear is severe, cylinder scoring occurs more frequently, and engine reliability decreases. Simultaneously, the cylinder pressure increases as the ignition phase approaches, and the increased solubility of fuel in the lubricating oil reduces the proportion of kerosene in the air, further increasing the difficulty of ignition, especially noticeable during high-altitude flight. Furthermore, the premixing between aviation kerosene and lubricating oil results in poor fuel combustion in the combustion chamber, exacerbating carbon buildup on the piston surface and combustion chamber walls, leading to severely excessive pollutant emissions. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to solve the above problems and provide a cylinder block and exhaust pipe layout structure for a two-stroke heavy oil aero engine with air-jet injection.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A cylinder block and exhaust pipe layout structure for a two-stroke heavy oil aero engine with air-jet injection includes a cylinder block and an exhaust system. The top region of the cylinder block near the combustion chamber is configured with a weakly rigid structure. The weakly rigid structure allows the top of the cylinder block to elastically expand radially under the gas pressure in the combustion chamber, thereby increasing the lubricating oil storage space between the piston rings and the cylinder block. This allows the lubricating oil scraped off the cylinder wall by the piston rings to be stored in the piston ring grooves instead of overflowing to the piston top surface, reducing the amount of lubricating oil exposed in the combustion chamber. The exhaust system includes an exhaust pipe that is wound around the outer wall of the cylinder body. The exhaust pipe uses the waste heat of the exhaust to heat the cylinder body, thereby controlling the cylinder body wall temperature at 110°C to 120°C, reducing the solubility of heavy oil in the lubricating oil, and maintaining the lubricating performance of the lubricating oil.

[0006] Furthermore, the cylinder block and cylinder head are connected by connecting screws. The weakened rigidity structure is a connecting screw hole set in the top area of ​​the cylinder block. The connecting screw hole adopts a stepped hole and a non-fully threaded structure. The depth of the stepped hole is not less than 3mm. The stepped transition part adopts a chamfered connection. The diameter of the stepped hole is larger than the specification size of the connecting screw to form a radial expansion clearance space and weaken the rigidity of the top area of ​​the cylinder block.

[0007] Furthermore, the exhaust pipe is designed to be bent and fits around the outer wall of the cylinder block; for multi-cylinder engines, the exhaust pipes corresponding to each cylinder are arranged crosswise.

[0008] Furthermore, the exhaust pipe is arranged around the windward area of ​​the cylinder block to ensure that heat is evenly transferred to the outer perimeter of the cylinder block.

[0009] Furthermore, the outer wall surface of the cylinder is subjected to black anodizing or sandblasting treatment to improve the thermal radiation absorption rate and heat transfer uniformity of the cylinder surface.

[0010] Furthermore, a scavenging zone and an ignition zone are sequentially formed along the piston stroke direction within the cylinder body. In the scavenging zone, the exhaust heat maintains the cylinder wall temperature at 110°C to 120°C, and the piston rings scrape off the lubricating oil that maintains lubrication performance from the cylinder wall and store it in the piston ring grooves. In the ignition zone, the top of the cylinder body undergoes radial elastic expansion under gas pressure, and the piston rings expand along with the cylinder body under elastic action. The space within the piston ring grooves increases, reducing the amount of lubricating oil overflowing from the piston top surface, thus achieving separation of fuel and lubricating oil in the physical space within the cylinder.

[0011] Furthermore, the heavy oil is aviation kerosene.

[0012] Furthermore, the lubricating oil is MOTUL 700 engine oil.

[0013] The beneficial effects of this invention are as follows: The cylinder block and exhaust pipe layout structure of the two-stroke heavy oil aero engine with air-jet injection provided by this invention achieves the following beneficial effects through the organic combination of the weak rigidity structure in the top region of the cylinder block and the coordinated layout of the exhaust system: First, it effectively reduces the solubility of aviation kerosene in lubricating oil. By wrapping the exhaust pipe around the outer wall of the cylinder block, the waste heat from the engine exhaust is fully utilized to heat the cylinder block wall, keeping the cylinder block wall temperature within the range of 110℃ to 120℃. This significantly reduces the solubility of aviation kerosene in lubricating oil, ensuring the viscosity and lubrication performance of the lubricating oil, and fundamentally alleviating the lubrication failure problem caused by kerosene dissolution.

[0014] Secondly, it achieves deep separation of fuel and lubricating oil in the physical space within the cylinder. Through the weakly rigid structural design of the cylinder top region, the cylinder top can elastically expand radially under the action of high-pressure gas in the combustion chamber. The piston rings expand accordingly under elastic action, increasing the space within the piston ring grooves. This allows the lubricating oil scraped from the cylinder wall by the piston rings to be more fully stored in the ring grooves, reducing the amount of lubricating oil that overflows onto the piston top surface and is exposed to the combustion chamber, thus achieving deep spatial separation of fuel and lubricating oil.

[0015] Third, it significantly improves the operational safety and reliability of engine friction pairs. The increased cylinder wall temperature allows the lubricating oil to maintain good fluidity and oil film strength at operating temperatures. The friction pairs between the piston and cylinder, and piston rings, can obtain sufficient and effective lubrication protection, greatly reducing the probability of piston surface wear and cylinder scoring failure, and improving the engine's operational reliability and service life.

[0016] Fourth, it improves in-cylinder combustion conditions, enhancing ignition reliability and combustion efficiency. Effective separation of fuel and lubricating oil ensures sufficient fuel concentration in the in-cylinder gas phase space, avoiding insufficient fuel concentration caused by a large amount of kerosene dissolved in the lubricating oil. This effectively improves ignition reliability and success rate, especially showing significant improvement under high-altitude flight conditions.

[0017] Fifth, it reduces carbon buildup and exhaust emissions. Effective separation of fuel and lubricating oil in the cylinder makes the combustion process more complete and stable, reduces incomplete combustion products caused by lubricating oil participation in combustion, effectively reduces carbon buildup on the piston surface and combustion chamber walls, and significantly reduces the pollutant content in the exhaust, helping to meet aviation emission standards.

[0018] Sixth, fully utilize exhaust waste heat to improve overall engine thermal efficiency. Through the coordinated layout design of the exhaust system and cylinder block, the exhaust waste heat that would otherwise be lost to the environment is used to heat the cylinder block walls, realizing the recovery and utilization of waste heat. This not only solves the problem of fuel and lubricating oil separation but also improves the overall thermal efficiency of the engine, resulting in excellent energy-saving effects.

[0019] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the layout of the engine block lubrication and heat recovery system in this invention.

[0021] Figure 2 This is a schematic diagram of the engine block structure.

[0022] Figure 3 This is a schematic diagram of the threaded hole structure connecting the cylinder block and cylinder head. Detailed Implementation

[0023] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0024] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures, and should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0025] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0026] Example 1 Please see Figures 1-3 This invention relates to a cylinder block and exhaust pipe layout structure for a two-stroke heavy fuel oil aero engine with air-jet injection, including a cylinder block and an exhaust system, and is applied to an air-cooled two-stroke aero piston engine. In this type of engine, heavy fuel oil is injected into the cylinder in a gas-liquid coexistence state under the action of high-pressure gas, forming a premixed mixture with air.

[0027] To ensure safety, aviation kerosene is used as fuel and MOTUL 700 engine oil as lubricant in this embodiment, so as to ensure the safe operation of the engine friction pairs.

[0028] like Figure 1 As shown, this invention integrates the exhaust system with the cylinder block in a coordinated layout design, forming an engine cylinder block lubrication and reheat system. The exhaust pipe employs a bent design, wrapping around the outer wall of the cylinder block to fully utilize the waste heat from engine exhaust to heat the cylinder block, thereby controlling the cylinder block wall temperature between 110°C and 120°C. For multi-cylinder engines (such as twin-cylinder engines), the exhaust pipes corresponding to each cylinder are arranged in a cross pattern, allowing the exhaust pipes to cover as much of the cylinder block outer wall area as possible, thus improving the heating effect.

[0029] Furthermore, the exhaust pipe is positioned around the windward area of ​​the cylinder block. Since the windward area is directly exposed to cooling airflow during engine operation, its temperature is lower than that of the leeward area. Positioning the exhaust pipe around the windward area allows the exhaust waste heat to complement the cooling airflow, ensuring uniform temperature distribution across the cylinder block's outer wall and preventing localized overheating or undercooling.

[0030] To further improve the heat absorption and heat transfer uniformity of the cylinder block surface, the outer wall of the cylinder block undergoes black anodizing or sandblasting treatment. After surface treatment, the heat radiation absorption rate and heat conduction uniformity of the outer wall of the cylinder block are improved, allowing the heat transferred by the exhaust pipe to be more evenly distributed across the entire surface of the cylinder block.

[0031] Through the coordinated layout of the exhaust system, the cylinder wall temperature is controlled within the range of 110℃ to 120℃. Within this temperature range, the solubility of aviation kerosene in the lubricating oil is effectively controlled, and the content of aviation kerosene in the lubricating oil film inside the cylinder is significantly reduced, thereby ensuring the viscosity and lubrication performance of the lubricating oil. The cylinder wall area swept by the piston during rapid upward movement can maintain a good lubricating oil film, and the friction pairs are effectively lubricated and protected.

[0032] like Figure 2As shown, the present invention provides a weakly rigid structure in the top region of the cylinder block near the combustion chamber, so that the top of the cylinder block can elastically expand radially under the action of gas pressure in the combustion chamber, thereby increasing the lubricating oil storage space between the piston ring and the cylinder block, so that the lubricating oil scraped off the cylinder wall by the piston ring is stored in the piston ring groove and does not overflow to the piston top surface, thereby reducing the amount of lubricating oil exposed in the combustion chamber.

[0033] like Figure 3 As shown, the cylinder block and cylinder head are connected by connecting screws. A weakened rigidity structure is employed, with the connecting screw holes located in the top region of the cylinder block. These holes are stepped, not fully threaded. The depth of the stepped hole is no less than 3mm, and the transition area is chamfered to ensure a smooth transition and avoid stress concentration. The diameter of the stepped hole is larger than the specification size of the connecting screw to create a radial adjustment clearance, providing space for expansion. By controlling the position of the thread in the threaded hole and the clearance between the stepped hole and the screw, the rigidity of this connection area is weakened, allowing the top region of the cylinder block to expand freely radially under gas pressure.

[0034] When the piston reaches near top dead center, the gas pressure enclosed in the combustion chamber increases, exerting radial pressure on the cylinder wall and causing the cylinder top to expand radially. The piston rings expand along with the cylinder due to elasticity, correspondingly increasing the available space in the piston ring grooves. During the piston's upward movement, the piston rings continuously scrape lubricating oil off the cylinder wall and store it in the ring grooves. When the piston reaches the area near top dead center, the additional space in the ring grooves due to the cylinder expansion significantly reduces the amount of lubricating oil overflowing from the piston-cylinder contact edge, thus reducing the amount of lubricating oil exposed in the combustion chamber and achieving effective spatial separation of fuel and lubricating oil.

[0035] The two technical measures of this invention work synergistically during engine operation. A scavenging zone and an ignition zone are sequentially formed within the cylinder along the piston stroke direction.

[0036] During the scavenging phase: Exhaust heat is channeled through the exhaust pipe surrounding the cylinder wall to maintain the cylinder wall temperature at 110℃~120℃. This appropriate cylinder wall temperature reduces the solubility of aviation kerosene in the lubricating oil, ensuring effective lubrication of the cylinder wall by the piston rings during the scavenging phase. The piston rings scrape off the lubricating oil from the cylinder wall and store it in the ring grooves.

[0037] During the ignition phase: When the piston moves to near top dead center, the top of the cylinder expands radially under the action of high-pressure gas in the combustion chamber. The piston rings expand along with the cylinder under elastic action, and the space in the piston ring grooves increases, which reduces the amount of lubricating oil overflowing from the piston top surface and the amount of lubricating oil exposed in the combustion chamber, thus achieving the separation of fuel and lubricating oil in the physical space inside the cylinder.

[0038] The two measures work together: the first line of defense reduces the solubility of kerosene in lubricating oil through exhaust waste heat, ensuring lubricating oil performance; the second line of defense increases the storage space in the annular grooves through elastic expansion at the top of the cylinder, storing lubricating oil in the annular grooves. These two lines of defense work together to achieve deep separation of fuel and lubricating oil in the physical space within the cylinder.

[0039] Meanwhile, the coordinated layout of the exhaust system and cylinder block enables the recovery and utilization of exhaust waste heat, using the originally dissipated waste heat to maintain the cylinder block wall temperature, thus solving the problem of fuel and lubricating oil separation while improving the overall thermal efficiency of the engine.

[0040] During the piston's upward movement, the exhaust radiation heat raises the temperature of the cylinder wall, ensuring that the kerosene injected into the cylinder can be fully separated from the lubricating oil. At the same time, through the weak rigidity structure design of the connecting screw hole at the top of the cylinder, the gas pressure in the combustion chamber causes the top of the cylinder to expand elastically, increasing the piston ring groove space. This ensures that the lubricating oil can be fully stored in the piston ring groove without overflowing into the combustion chamber, which is beneficial for the recycling of lubricating oil and reduces pollutant emissions.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A cylinder block and exhaust pipe layout structure for a two-stroke heavy oil aero engine with air-jet injection, comprising a cylinder block and an exhaust system, characterized in that: The top area of ​​the cylinder block near the combustion chamber is set as a weak rigid structure. The weak rigid structure allows the top of the cylinder block to elastically expand radially under the action of gas pressure in the combustion chamber, thereby increasing the lubricating oil storage space between the piston ring and the cylinder block. This allows the lubricating oil scraped off the cylinder wall by the piston ring to be stored in the piston ring groove and not overflow to the piston top surface, thus reducing the amount of lubricating oil exposed in the combustion chamber. The exhaust system includes an exhaust pipe that is wound around the outer wall of the cylinder body. The exhaust pipe uses the waste heat of the exhaust to heat the cylinder body, thereby controlling the cylinder body wall temperature at 110°C to 120°C, reducing the solubility of heavy oil in the lubricating oil, and maintaining the lubricating performance of the lubricating oil.

2. The cylinder block and exhaust pipe layout structure of the two-stroke heavy oil aero engine with air injection as described in claim 1, characterized in that, The cylinder block and cylinder head are connected by connecting screws. The weakened rigidity structure is a connecting screw hole set in the top area of ​​the cylinder block. The connecting screw hole adopts a stepped hole and non-fully threaded structure. The depth of the stepped hole is not less than 3mm. The stepped transition part adopts a chamfered connection. The diameter of the stepped hole is larger than the specification size of the connecting screw to form a radial expansion clearance space and weaken the rigidity of the top area of ​​the cylinder block.

3. The cylinder block and exhaust pipe layout structure of the air-jet two-stroke heavy oil aero engine according to claim 1, characterized in that, The exhaust pipe is designed to be bent and fits around the outer wall of the cylinder; for multi-cylinder engines, the exhaust pipes corresponding to each cylinder are arranged crosswise.

4. The cylinder block and exhaust pipe layout structure of the two-stroke heavy oil aero engine with air-jet injection as described in claim 3, characterized in that, The exhaust pipe is arranged around the windward area of ​​the cylinder block to ensure that heat is evenly transferred to the outer side of the cylinder block.

5. The cylinder block and exhaust pipe layout structure of the two-stroke heavy oil aero engine with air-jet injection as described in claim 1, characterized in that, The outer wall of the cylinder is treated with black anodizing or sandblasting to improve the thermal radiation absorption rate and heat transfer uniformity of the cylinder surface.

6. The cylinder block and exhaust pipe layout structure of the two-stroke heavy oil aero engine with air-jet injection as described in claim 1, characterized in that, The cylinder body is formed sequentially with a scavenging zone and an ignition zone along the piston stroke direction. In the scavenging zone, the exhaust heat maintains the cylinder wall temperature at 110℃~120℃, and the piston rings scrape off the lubricating oil on the cylinder wall to maintain its lubricating properties and store it in the piston ring grooves. In the ignition zone, the top of the cylinder body undergoes radial elastic expansion under the action of gas pressure, and the piston rings expand with the cylinder body under elastic action. The space inside the piston ring grooves increases, reducing the amount of lubricating oil overflowing from the piston top surface, thus achieving the separation of fuel and lubricating oil in the physical space inside the cylinder.

7. The cylinder block and exhaust pipe layout structure of the two-stroke heavy oil aero engine with air-jet injection as described in claim 1, characterized in that, The heavy oil is aviation kerosene.

8. The cylinder block and exhaust pipe layout structure of the two-stroke heavy oil aero engine with air-jet injection as described in claim 1, characterized in that, The lubricating oil is MOTUL 700 engine oil.

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