Abstract. The piston is a "heart" of the engine and its working condition is the worst one of the key parts of the engine in the working environment. So it is very important for structural analysis of thepiston. This paper analies and calculates the piston by ProENGEER software to gain a result, which improves and optimizes the structure of the piston.
Introduction
In recent years, digital simulation technology has been developing rapidly. Virtual piston is
established by ProENGEER easily. As is well-known that virtual piston can simulate the product all kinds of chatacter in the real environment. The results of simulation will be used to optimize piston design, in order to shorten the cycle, reduce the cost and improve the quality of products. Piston is one of the key components in a motor and it closely relates to the machine performance, carbon emissions and the economy. With the engine higher speed and strengthen developing, its higher pressure ratio and higher power improve constantly. Pistons work condition is more and more bad, so its reliability has becomed the key factors to improve engine reliability. Structure and working environment of pistons are very complex. In the working environment, the pistons will produce stress and deformation because of the periodic load effect, which are from high gas pressure, high speed reciprocating motion from the inertia force, lateral pressure, friction and so on. Burning of the high pressure gas products high temperature, which makes piston expands in order that its interior produces thermal stress and thermal deformation. The thermal deformation and mechanical deformation will cause piston cracks, tortuosity, etc. Therefore, it is essential to analy the stress field, temperature field, heat transfer, thermal load and mechanical load coupling of piston in order to lower the heat load and improve the thermal stress distribution and improve its working reliability during the piston designed. Analysis method of the finite element provides a powerful calculation tool, which is better than test method and theory analysis method and has become an important means for internal combustion engine performance study.
Piston Structure Design
Design Engine Piston
According to the design parameters, we use Pro/E software to establish the piston model. In this paper, we consider the symmetry of the piston geometry structure and adopt 1 /4 model to analy the piston, which can simplify the calculation process of finite element, shorten the time of analysis and also can get a good analysis result. We establish piston model by Pro/E as shown in figure 1.
Model Parameter Settings
Select the "Mechanica" in the "application" of menu and set the parameters. First, set model
material for aluminum alloy AL6061. Then, set the tensile strength definition for 240 Mpa, tensile
stress limit definition for 290 Mpa, surface finish for already glazing.
Defining Constraints and Createing Load
Piston pin hole is constrainted by displacemen and symmetry in order to make the pin hole
produce the correct constraint condition.
By analysis of the piston working process, we find that stress and deformation of the piston is themost serious under the steady speed conditions when thegas-fired pressure is the maximum. At the same time, the strength of piston is especially outstanding. Therefore, it is essensial to choose the piston under the rated power and we only analy distribution force in the axis of the force, including the maximum explosion pressure and reciprocating inertia force. Pressure load of piston is that gas pressure effects piston top surface by high pressure in the cylinder. For simplified analysis, we can use the steady state process, but cannot ignore the effect that combustion power stroke products
impact load for piston. Using cylinder fluid dynamics simulation results, we can calculate that average pressure of piston top is 9Mpa in a working cycle, which will be surface pressure load. Such as shown in figure 2.
Computation and Mechanical Analysis
Mechanical Analysis of The Piston
After the simulation model established, it can get strain distribution and fatigue analysis under the effect of mechanical load by operating the mechanical program. The simulation results of piston are shown as in figure 3.
Piston is affected by gas explosion pressure and the reciprocating inertia force and their common feature is that they effect along the axis direction of the piston, so the axis direction of piston bears the bigger load. From the Fig4, we can see that the maximum stress appears the centre of piston pintop, which is accordance to engine design manual. Piston pin top is the easiest fracture parts. When piston operating, the maximum equivalent stress value of piston pin is about 8 M Pa and equivalent stress value of the other parts is under6 M Pa. From the analysis of strain, the maximum strain appears in the piston top, the maximum strain is about 0. 06%. The results of these simulations analysis provides a strong theory basis for failure problems of the piston.
The piston Thermal Analysis
Create a Thermal Load. When Pistons are operating, they directly touch the high temperature gas and their transient temperature can reach more than 2500K and generates the 18KW power. Piston is heated seriously and its heat transfer coefficient is 167 w/m ° C and its heat dissipation condition is poor, so the piston temperature can reach 600 ~ 700 K approximately and the temperature distributes unevenly. On the basis of these conditions, we will make thermal analysised for the piston.
Results and Analysis. Through the analysis of the operation, we can get the pistons temperature field distribution, as shown in figure4. The piston temperature distibutes unevenly. The maximum steady state temperature of the piston is 2500K under the temperature effect of the repeated changes in the high temperature gas. The highest temperature appears the top surface of the piston. The temperature of piston pin changs between 700K and 800K. The temperature of the first ring groove is the important evaluation index of thermal load of piston and its temperature is between 1300 K and 1500K. The highest temperature differs by 1800 K from the minimum temperature, which will
make piston cause larger thermal stress and thermal damage. From the diagram, we can find the piston temperature is gradient descent along the piston axis direction from up to down, but the temperature change of piston skirt is lesser. The diagram indicates that thermal deformation of the piston is bigger from bottom to top and heat distortion of the bottom is minimum. These findings are consistent with domestic researchers results.
Summary
Optimal design is the essence of structure analysis and it is also the final stage of the analysis.
Through the given parameter scope and general optimization goal, we Comprehensively use the front analysis result to gain the most optimized results. As shown in figure5, the result meets the design requirements.
บทคัดย่อ ลูกสูบเป็น "หัวใจ" ของเครื่องยนต์ และสภาพการทำงานคือเลวส่วนสำคัญของเครื่องยนต์ทำงาน ดังนั้น จึงเป็นสิ่งสำคัญมากสำหรับการวิเคราะห์โครงสร้างของ thepiston Analies กระดาษนี้คำนวณนอก โดยซอฟต์แวร์ ProENGEER เพื่อให้ได้ผล การปรับปรุง และเพิ่มประสิทธิภาพโครงสร้างของลูกสูบแนะนำในปีที่ผ่านมา ดิจิตอลเทคโนโลยีได้พัฒนาอย่างรวดเร็ว ลูกสูบเสมือนเป็นสร้าง โดย ProENGEER ได้อย่างง่ายดาย เป็นรู้จัก ลูกสูบเสมือนที่สามารถจำลองผลิตภัณฑ์ทุกชนิดของ chatacter ในสภาพแวดล้อมจริง ผลการจำลองจะถูกใช้เพื่อเพิ่มประสิทธิภาพการออกแบบลูกสูบ ย่นวงจรการ ลดต้นทุน และปรับปรุงคุณภาพของผลิตภัณฑ์ ลูกสูบเป็นหนึ่งในองค์ประกอบที่สำคัญในมอเตอร์ และมันเกี่ยวข้องกับประสิทธิภาพการทำงานของเครื่อง การปล่อยก๊าซคาร์บอน และเศรษฐกิจอย่างใกล้ชิด ด้วยเครื่องยนต์ความเร็วสูงเสริมพัฒนา ความดันสูงและพลังงานสูงปรับปรุงตลอดเวลา สภาพลูกสูบทำงานได้ดีขึ้น เพื่อความน่าเชื่อถือเป็นปัจจัยสำคัญในการปรับปรุงความน่าเชื่อถือของเครื่องยนต์ becomed มี โครงสร้างและสภาพแวดล้อมในการทำงานของลูกสูบจะซับซ้อนมาก ในสภาพแวดล้อมการทำงาน ลูกสูบจะผลิตความเครียดและแมพเนื่องจากผลผลิตเป็นครั้งคราว ซึ่งมาจากแรงดันก๊าซสูง ความเร็วสูงแอร์ลูกสูบเคลื่อนไหวจากแรงเฉื่อยแรง แรงดันด้านข้าง แรงเสียดทานและ การ เผาอุณหภูมิสูงผลิตภัณฑ์ก๊าซแรงดันสูง ซึ่งทำให้ลูกสูบขยายเพื่อให้การตกแต่งภายในทำให้เกิดความเครียดความร้อนและความร้อนแมพ แมพร้อนและแมพกลจะทำให้เกิดรอยแตกนอก tortuosity ฯลฯ ดังนั้น มันเป็นสิ่งสำคัญการ analy ฟิลด์ฟิลด์ความเครียด อุณหภูมิ ถ่ายเทความร้อน โหลดความร้อน และคลัปโหลดทางกลของลูกสูบเพื่อลดปริมาณความร้อน และปรับปรุงการกระจายความร้อนความเครียด และปรับปรุงเสถียรภาพการทำงานในระหว่างลูกสูบมีการออกแบบ วิธีการวิเคราะห์องค์ประกอบจำกัดมีเครื่องมือคำนวณที่มีประสิทธิภาพ ซึ่งดีกว่าวิธีการวิเคราะห์ทฤษฎีและวิธีทดสอบ และได้กลายเป็นวิธีการสำคัญสำหรับการศึกษาประสิทธิภาพของเครื่องยนต์สันดาปภายในPiston Structure DesignDesign Engine PistonAccording to the design parameters, we use Pro/E software to establish the piston model. In this paper, we consider the symmetry of the piston geometry structure and adopt 1 /4 model to analy the piston, which can simplify the calculation process of finite element, shorten the time of analysis and also can get a good analysis result. We establish piston model by Pro/E as shown in figure 1.Model Parameter SettingsSelect the "Mechanica" in the "application" of menu and set the parameters. First, set modelmaterial for aluminum alloy AL6061. Then, set the tensile strength definition for 240 Mpa, tensilestress limit definition for 290 Mpa, surface finish for already glazing.Defining Constraints and Createing LoadPiston pin hole is constrainted by displacemen and symmetry in order to make the pin holeproduce the correct constraint condition.By analysis of the piston working process, we find that stress and deformation of the piston is themost serious under the steady speed conditions when thegas-fired pressure is the maximum. At the same time, the strength of piston is especially outstanding. Therefore, it is essensial to choose the piston under the rated power and we only analy distribution force in the axis of the force, including the maximum explosion pressure and reciprocating inertia force. Pressure load of piston is that gas pressure effects piston top surface by high pressure in the cylinder. For simplified analysis, we can use the steady state process, but cannot ignore the effect that combustion power stroke productsimpact load for piston. Using cylinder fluid dynamics simulation results, we can calculate that average pressure of piston top is 9Mpa in a working cycle, which will be surface pressure load. Such as shown in figure 2.
Computation and Mechanical Analysis
Mechanical Analysis of The Piston
After the simulation model established, it can get strain distribution and fatigue analysis under the effect of mechanical load by operating the mechanical program. The simulation results of piston are shown as in figure 3.
Piston is affected by gas explosion pressure and the reciprocating inertia force and their common feature is that they effect along the axis direction of the piston, so the axis direction of piston bears the bigger load. From the Fig4, we can see that the maximum stress appears the centre of piston pintop, which is accordance to engine design manual. Piston pin top is the easiest fracture parts. When piston operating, the maximum equivalent stress value of piston pin is about 8 M Pa and equivalent stress value of the other parts is under6 M Pa. From the analysis of strain, the maximum strain appears in the piston top, the maximum strain is about 0. 06%. The results of these simulations analysis provides a strong theory basis for failure problems of the piston.
The piston Thermal Analysis
Create a Thermal Load. When Pistons are operating, they directly touch the high temperature gas and their transient temperature can reach more than 2500K and generates the 18KW power. Piston is heated seriously and its heat transfer coefficient is 167 w/m ° C and its heat dissipation condition is poor, so the piston temperature can reach 600 ~ 700 K approximately and the temperature distributes unevenly. On the basis of these conditions, we will make thermal analysised for the piston.
Results and Analysis. Through the analysis of the operation, we can get the pistons temperature field distribution, as shown in figure4. The piston temperature distibutes unevenly. The maximum steady state temperature of the piston is 2500K under the temperature effect of the repeated changes in the high temperature gas. The highest temperature appears the top surface of the piston. The temperature of piston pin changs between 700K and 800K. The temperature of the first ring groove is the important evaluation index of thermal load of piston and its temperature is between 1300 K and 1500K. The highest temperature differs by 1800 K from the minimum temperature, which will
make piston cause larger thermal stress and thermal damage. From the diagram, we can find the piston temperature is gradient descent along the piston axis direction from up to down, but the temperature change of piston skirt is lesser. The diagram indicates that thermal deformation of the piston is bigger from bottom to top and heat distortion of the bottom is minimum. These findings are consistent with domestic researchers results.
Summary
Optimal design is the essence of structure analysis and it is also the final stage of the analysis.
Through the given parameter scope and general optimization goal, we Comprehensively use the front analysis result to gain the most optimized results. As shown in figure5, the result meets the design requirements.
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