Foreword:
The aero engine, known as the "flower of industry", is one of the core technologies that constitute the foundation of the country's strength and military strategy. Developed countries have priority in strategic development and are tightly sealed externally. China's aviation engine development has a long way to go, breaking through key technologies and taking the road of independently developing aero-engines is an inevitable choice for China. This paper mainly introduces the status quo of China's aviation engine industry and the application of digital manufacturing technology, PDM, PLM and CIMS systems in the industry, and introduces the development of the core technologies that restrict the development of China's aviation industry.
First, the main characteristics of the aero engine industry and bottleneck technology
From the development history of aviation engine industry in developed countries, the aviation engine industry mainly has the following characteristics:
1. The aero engine industry is the core of maintaining the status of a big country and a symbol of an industrial power.
The US government has been strictly controlling aero-engine technology, not only maintaining a blockade to our country, but even imposing an embargo on its European allies on certain core technologies. In the next 10 to 20 years, the aero engine industry still occupies the core position of the US defense technology strategy. At the same time, developed countries have implemented an invisible blockade on human resources, which not only restricts the entry of personnel from other countries into the core research and development of aviation engines, but also restricts the transfer of relevant talents from abroad to maintain their industrial strength.
2. The aero-engine industry needs long-term and stable support and input from the state.
The aviation industry is a typical high-tech, high-investment, high-risk, high-value-added and internationalized industry, and the aero-engine is even more so, with a long development cycle and huge cost. According to foreign experience, the typical engine development cycle is about 8 to 14 years, and the life of the entire engine is about 30 years. The development funds have increased over the years. According to the engine model size and development conditions, an advanced large and medium-sized aviation turbine engine will be developed, which will cost approximately 1.5 billion to 3 billion US dollars. The United States has long been through the country's long-term, stable and strong support and investment, and implemented a number of medium- and long-term research plans and short-term special research projects that are purely comprehensive technology research models that are ahead of specific models, providing sufficient technical reserves for engine development. Reduce the technical risks of engineering development and shorten the development cycle. It is because of this long-term huge investment that the United States has maintained its leading position in the aero engine industry.
3. The technical threshold of aero engines is very high.
3.1 The difficulty of aero engine design
In an aero-engine, the most critical compressor, combustion chamber, and turbine form the core of the engine. The turbo-driven compressor rotates at a high speed of thousands of revolutions per second, and the air entering the engine is stepped up in the compressor, and the multi-stage compressor has a boost ratio of more than 25. The pressurized air enters the engine combustion chamber and mixes with the fuel and burns. It is necessary to keep the fuel flame stable in high-pressure airflow flowing at a high speed of 100m/s or more. At the same time, it is necessary to protect the combustion chamber flame wall from ablation by high-temperature gas. It is not enough to select high-temperature resistant materials and heat-resistant coatings. Through the structural design of the combustion chamber, cooling means are adopted to reduce the temperature of the wall of the combustion chamber to ensure the normal operation of the combustion chamber. The high temperature, high pressure gas stream exiting the combustion chamber drives the turbine blades to operate at thousands of revolutions per minute or even tens of thousands of revolutions, typically before the turbine exceeds the melting point of the turbine blade material. In addition, the external operating environment of the aero-engine is extremely demanding, adapting to the anoxic environment from the ground level to the height of 10,000 meters, from the ground still state to the supersonic state of several kilometers per hour and from the desert dry environment to the tropical humid surroundings. In short, aero-engines need to reach thousands of hours of normal working life in extreme environments such as high temperature, high cold, high speed, high pressure, high speed, high load, lack of oxygen, vibration, etc., which makes the development of aeroengines structural mechanics, Materials science, gas dynamics, engineering thermodynamics, rotor dynamics, fluid mechanics, electronics, control theory and other disciplines have extremely high requirements. The picture below shows the complex internal structure of an aero engine:
Figure 1 Schematic diagram of the internal structure of a foreign model
3.2 Difficulties in aero engine materials
The most critical engines are compressors, combustion chambers and turbines. Especially in the turbine, during the working process, the turbine blades of modern jet engines usually have to withstand the high temperature of 1600~1800 °C, and also withstand the wind speed of about 300m / s, and the resulting huge air pressure. Thousands of hours of reliable work in extremely harsh work environments. Such a harsh working environment far exceeds the capabilities of general metal materials, and other special materials are required for this purpose. These are directional solidification superalloys, single crystals, intermetallic compounds, metal matrix composites and ceramic matrix composites, such as SiC fiber reinforced ceramic matrix composites, which can be used up to 1500 ° C, far exceeding the superalloy turbine blades. Use temperature (1100 ° C).
At present, the gap between China and the foreign countries in the application of aero-engine materials is so great that Chinese engines are all dependent on imports. The application of military engine materials is also not ideal. The average time-to-failure time of the engine, the average overhaul time, and the average life expectancy are still far from the foreign countries.
The main bearing of the aero engine is one of the key components of the aeroengine. It operates under high speed, high temperature and complicated conditions. Its quality and performance directly affect the engine performance, life and reliability. At present, the life span of aero-engine main bearings in developed countries can reach more than 10,000 hours, which can fully meet the life expectancy of the main bearings of large aircraft engines. At present, the main bearing life of aviation engines in China is basically less than 900h, and the life of main bearings is not as good as 1/10 in the West. However, in recent years, China has made gratifying progress in aviation engines. The following picture shows the 30 cm long turbo single crystal blade independently approved by Shanghai University in September 2012. It is the last breakthrough in crystal growth process and the longest single crystal blade independently cultivated in China, but it is the most advanced technology abroad. In comparison, there is a gap of 5-10 cm.
Figure 2 Single crystal blade independently developed in China
3.3 Difficulties in aero engine manufacturing
In order for the aero-engine to maintain sufficient strength and normal operation under extremely harsh working conditions, in addition to the need for new high-temperature materials, the engine manufacturing requires a number of sophisticated and advanced manufacturing processes.
The manufacture of aero engines involves many difficult industrial technologies such as materials, structures, and welding. For example, high-strength materials and high-temperature resistant alloys are used on jet engines. The precision of parts is required to reach μm level, the blade profile is complex, and the combustion system and afterburning system have many thin-wall welded parts. A large number of directional solidification, powder metallurgy and complex hollow are used. Advanced manufacturing techniques such as blade casting, complex ceramic core manufacturing, titanium alloy forging, micro-hole processing, coating and special welding. For example, the overall blade of an aeroengine has a cost of about 200,000 and 300,000 yuan. The finished product has to go through dozens of processes, hundreds of times of tool change, and thousands of advances and retreats. The A4 paper-sized whole leaf blade has a thickness of 2 mm and the thinnest part is only 0.2 to 0.3 mm. No flaws are allowed. Another example is that the turbine blades need to be carefully designed to produce multi-channel hollow turbine blades, and the film cooling is used to reduce the surface temperature of the blades so that the blades on the engine can meet the needs of the engine in an extremely harsh working environment.
Second, the status quo and development of China's aviation engine manufacturing industry
The manufacturing process of aero-engine parts has always been a key area for the application of new technologies and new processes, as well as an industry that has urgent requirements for technology updates. The digital manufacturing technology of aero-engine parts involves many technical contents such as CAD/CAM technology, numerical control equipment, product data management, information integration, etc. The core of which is the digital expression, storage and exchange of product data. The basic platform is computer network and digital equipment. The way is synergy, parallelism and integration. Digital process design, CNC machining technology, virtual manufacturing technology, intelligent control technology and enterprise resource data management technology constitute the basic supporting technology in product development collaborative design and manufacturing process. In recent years, the continuous deepening of CAD/CAM/CAE technology, high-performance CNC machine tools and control system applications has promoted the development of digital manufacturing technology for aero-engine products, fundamentally changing the traditional process design and manufacturing mode, and digital manufacturing has become One of the important means to improve the manufacturing capabilities and research capabilities of aero-engine manufacturers.
1. The status and development of lean engine production in China
1.1 Status of lean production in China's aviation engine enterprises
In recent years, the number of domestic aviation products has increased significantly, which has brought benefits to enterprises. At the same time, it has exposed the problems of lean production in related engine manufacturers. Now it is manufactured by China’s aero engine manufacturer Dawn Company and foreign famous military engines. For example, we will compare the gap between the two lean production companies:
(1) The gap in organizational model
Pratt & Whitney is a specialized engine company, and the engine factory established by Dawn Company in accordance with the original Soviet model of the year is a "big and complete" model.
(2) Differences in the number of self-made parts
After a second lean in 1995, Pratt & Whitney had 30,000 employees and only 2,000 homemade parts. Dawn Company has only 5,000 employees, but there are more than 10,000 kinds of homemade parts.
(3) Differences in resource allocation methods
Most of China's aero-engine enterprises are cluster-based organization models. The production lines are under construction. Most of them are not capable of forming, and the established production lines are only partial pipelines. Although the local efficiency has improved, it has little contribution to the overall lean. .
(4) Differences in production efficiency
After the completion of the second lean production reform, Pratt & Whitney's supply cycle was reduced to less than 4 months, inventory was reduced by 70%, quality problems were reduced by 50%, and parts costs were reduced by 20%. Dawn Company's delivery cycle is 6~8 months. The inventory is huge, inventory costs are high, quality problems are frequent, and manufacturing costs are very high.
1.2 Lean Production Path of China's Aero Engine Manufacturing Enterprises
Based on the current situation of aero-engine enterprises, compared with the target company Pratt & Whitney, the methods and ways for China's aero-engine enterprises to promote lean production:
(1) Adhering to product specialization is the premise of promoting lean production
Aeroengine companies must take the road of specialization, which is the premise to promote lean production. The simplest reason is that the lean manufacturing of each part requires a large number of fixtures. The gap between 2000 parts and 10,000 parts is not as simple as 8000, but more than ten times that of 8000. There is no specialization to promote lean. It is impossible.
(II) Implementing the layout of production layout is the basis for promoting lean production
Guided by product value stream, optimize product production process, change the cluster organization mode of production units in the past, and establish several pipelines set up in the direction of value stream, logistics and information flow, so that products are closed in the shortest possible assembly line. Responsible for the delivery of the finished product, realize the flow of parts production, and maximize the "single piece flow". The relevant personnel responsible for technology and preparation are allocated to the production line to support the operation of the production line, which can ensure the smooth flow of value flow and logistics, reduce the blockage of information flow and reduce the management difficulty.
“Production Pipeline†and “Team Unitization†are practices initiated by Pratt & Whitney in 1985. Dawn Company started its implementation in 2010, and combined with the company’s characteristics of scientific research and low production, it proposed “independent researchâ€. Under the conditions of improving the efficiency of existing equipment and supplementing some resources, the scientific research and batch production lines will be partially realized. The implementation of the two years has achieved remarkable results, and the production capacity has more than doubled.
(3) Grasping the fineness of production preparation is the key to promoting lean production
The core of lean production is in philosophy, but the most critical is production preparation. Establish a lean concept and optimize the process. Process optimization is to establish a lean concept, in order to improve the overall efficiency, to be too short to be combined in a single process, a single process to take too long to increase efficiency, processing difficult to rely on tooling or equipment to ensure quality Reduce the "short board" and "bottleneck" to ensure the equalization of each process.
(4) Accelerating the informationization of production management is the means to promote lean production
The biggest problem in China's aero-engine production system is that the information flow is not smooth, because the means are backward, the information is inaccurate, the information is delayed, and the information cannot be shared. It is necessary to accelerate the application of information systems such as ERP, MES, PDM, and barcode. The application of these information systems should be worked on integration and enterprise, and secondary development is of great significance for promoting lean production.
2. Digital technology based on MBD technology and its application
MBD (ModelBased Definition), a model-based engineering definition, is a method body that fully integrates product definition information with an integrated 3D solid model. It specifies the product size, tolerance labeling rules and process information in the 3D solid model. Expression method. MBD changes the digital definition of step-by-step products that use three-dimensional solid models to describe geometric shape information and two-dimensional engineering drawings to define dimensions, tolerances, and process information.
The MBD design data mainly includes geometric models, annotations, and attributes. Decomposed into the geometric model of the part, the dimension and tolerance of the part, the geometric definition part of the part structure tree, the definition part of the part structure tree, the annotation of the key features, the annotation description of the part, and the product descriptive that must be provided in the part processing process Define information and assembly connection definitions.
MBD design data is based on the ability to accurately express the design concept. On the one hand, the data information that can be directly obtained includes model, annotation and attribute information. The data information must be established on the premise that the relevant standard system is perfect. Directly referenced by process design; on the other hand, process design requires complete data information. Since MBD data has a large amount of uninjected geometric information, it needs to be defined or formulated with corresponding rules to ensure the uniqueness of MBD data. It can only be obtained indirectly through technical means such as extraction, analysis, and query. Therefore, we must find a solution to convert MBD design data into process data based on accurate design ideas. The main technologies involved are as follows:
· 3D model size and tolerance marking technology;
Multi-view generation technology;
· Processing requirements marking technology;
Feature view capture creation and management techniques;
· Additional standards are based on information technology;
· The part model is used to mark the 3D assembly model.
At present, domestic aviation companies still have a big gap with foreign developed aviation companies in the application of MBD technology, mainly in:
(1) Product definition work based on MBD technology is still in the exploration stage;
(2) The digital process design and product manufacturing model with MBD as the core is still not mature;
(3) The three-dimensional digital model does not run through the digital manufacturing process of the entire product;
(4) The design, manufacturing and management specifications of MBD have yet to be improved;
(5) The integrated application system of three-dimensional digital design and manufacturing has not been completed.
The following picture shows the application of MBD technology in the full three-dimensional design and spatial layout of aero-engine piping:
Figure 3 Full three-dimensional design and spatial layout of the aeroengine piping system
3. The road of CIMS of China's aviation engine enterprises
3.1 In China's aviation engine manufacturing industry, FMS should be slowed down
The difficulty in manufacturing aero engines is well known. No supplier in the world is in a position to provide users with FMS for aero engine manufacturing alone. At present, foreign aero-engine enterprises still use the operating mechanism of “CNC machining adjustment workersâ€. For each batch of parts, the first CNC machining is carried out by the adjustment workers, and can be transferred to the normal production before being transferred to the operator for processing. Under such circumstances, don't say that "unmanned" is absolutely unworkable, that is, there are people, but the quality of people is not enough.
In the technological transformation of the famous foreign aero engine manufacturer France Turbomeca and Canada Pratt & Whitney, although the two companies have considerable strength, they are not involved in the wave of FMS. Therefore, domestic aero-engine manufacturers have no plans to do FMS in the last 10 years.
3.2 CIMS structure should be different due to the process characteristics of components
The components of aero-engines can be mainly divided into casings, discs, shafts, integral impellers and blades. The demand for CNC equipment varies greatly from the manufacture of various components. If we regard the CIMS of the whole enterprise as a large framework, then the actual structure of CIMS must be refined in order to implement the production of various parts and components.
1) CIMS structure of the machine parts
For parts of aero engine casings, CIMS=CAD/CAM+FMC should be used. The FMC is a flexible manufacturing unit that is the primary stage of FMS. Although it is primary, it is much more mature. The recent development of FMC also
It is very rapid and exceeds the development speed of FMS.
On the one hand, FMC is more mature than FMS, and its reliability is relatively high.
Second, because FMC management, operation and programming are much easier than FMS, users who have experience with CNC machining centers will not have any difficulty switching to FMC. This facilitates the outsourcing of machine parts.
In recent years, vertical and horizontal machining centers and five-face machining centers have developed greatly, which is beneficial for aircraft engine machining. Therefore, when planning the FMC on the machine production line, priority should be given to the integration of these CNC machines with more complete functions and wider processing range.
2) CIMS structure of the disk shaft parts
The main machine tool for the processing of disc shaft parts is CNC lathe, which is mainly horizontal and supplemented by vertical. The processing and installation of the shaft parts are widely used, and the soft claws are widely used. The online correction of the soft jaws and the clamping of the workpiece on the soft jaws depend on the correct operation. It is very difficult and not necessary to fully automate such operations. The aero-engine shaft parts are mostly titanium alloy, stainless steel and high-temperature alloy. It should not be bumped. A large number of thin-walled parts require the operator to install and remove carefully. However, if the CNC machining is stopped at the stand-alone level of the CNC lathe for this reason, the management of the program and the transmission of information will not be smooth. Therefore, it is necessary to raise the numerical control machining to the DNC level, that is, CIMS=CAD/CAM+DNC should be used for the disc shaft parts.
In terms of equipment type, attention should be paid to the choice of turning machining centers. At present, the domestic aero engine manufacturing has not used a turning machining center.
3) CIMS structure of integral impeller parts
The integral impeller includes a compressor axial impeller and a centrifugal impeller, and may be developed to the impeller of the hot end component in the future. Various types of impellers can also be referred to as blade discs.
The processing characteristics of such parts are poor material machinability, long cutting time, large tool consumption, high value of workpieces, multi-axis linkage of equipment, and expensive equipment. The basic equipment for machining is a CNC milling machine or machining center with 4 to 5 axes. When the production lot is large, a multi-spindle machine should be considered. For the characteristics of long cutting time and short loading and unloading time, the choice of the changeable table (tray) should be abandoned. The capacity of the tool magazine does not have to be too large, and there is no need to have much correlation between the machine tools. Therefore, the processing of the whole impeller parts should adopt CIMS=CAD/CAM+CNC.
When France Turbomeca and Canada Pratt & Whitney set up their impeller production lines, they included the CMM in the production site. Pratt & Whitney even arranged the tool grinding equipment on the impeller production line. The purpose of these practices is to minimize the on-site processing downtime. Impellers are expensive parts, and JIT (Just-in-time) can achieve good economic benefits.
In summary, with the professional development of aero-engine manufacturing, due to the different components and the like, aero-engine production should adopt adaptive CIMS mode, so as to improve the level of specialization and enhance competitiveness.
The inner surface of the Zirconia Ceramic Plunger adopts a fluid structure with no dead angle and groove; and the inner cavity surface is matched with the surface of the plunger, and is also processed to the mirror surface by an advanced high-precision inner and outer cylindrical grinding machine, and the outer surface is vibrated and polished for convenient cleaning. ,disinfection.
Since Zirconia Ceramic plungers have so many advantages, they certainly attract more users. Compared with metal plungers, zirconia ceramic plungers are not only more durable, but also have better effects and can meet some special requirements. Application requirements under working conditions.
Zirconia Ceramic Plunger
Zirconia Ceramic Plunger,Heating Ceramic Zirconia Rod,Hydraulic Cylinder Piston Rod,Ceramic Zirconia Jet Plunger
SHENZHEN HARD PRECISION CERAMIC CO.,LTD , https://www.hardcm.com