The application of virtual reality technology in valve design

Virtual reality technology has been widely used in engineering structure design and manu2facture due to its high efficiency and obvious characteristics which are different from traditional way.The paper gave a detailed introduction of its application in valve design. A virtual experiment was con2ducted to calculate the extreme stress in order to optimize the valve structure. Stress concentration ofopenings on valve is discussed and the relationship between sealing face and seal pressure is establishedby employing effective seal pressure. The simulation results show that the virtual reality technologycan provide a quantitative evaluation for valve strength and seal properties , which is necessary forvalve design both theoretically and practically.


Simulation test steps The valve product has a high degree of structural similarity and is suitable for using modules Normalization and parameterization design have the same or similar design calculation modes Like. In addition, there are many standard and universal parts for valves, which facilitates the application of group technology and feature modeling technology in CAD systems. In valve installation During the development process, virtual design and simulation experiments are used to conduct valve testing Door optimization can not only obtain high-quality products, but also reduce costs. For valve testing, the strength of the valve body and the sealing of the sealing surface Performance is within the main scope of testing. Stress and sealing on the valve body The distribution of pressure on the sealing surface is used in practical design Testing or correcting formulas, although this method has a high safety factor, is difficult To meet the requirements of valve design development. Using practical means, these two The parameters are difficult to accurately measure. By conducting simulation experiments, designers can To obtain precise separation of stress and sealing ratio pressure on the valve body and sealing surface The distribution of results makes the design and improvement of valves more targeted and accurate Accuracy. Valve simulation belongs to static structural analysis, and its testing steps are as follows As shown in Figure 1. During the valve simulation test, it is necessary to establish a valve Door solid model, finite element model mesh division, defining boundary conditions The work of analyzing and calculating results 

(1) establishes a solid model of the valve from the purpose of analysis Establish a model and make necessary changes to the model structure, such as analyzing The target is the flow characteristics when the valve is fully open and the fluid inside the flow channel The velocity distribution is irrelevant to the characteristics of the valve outer wall and the analysis target It can be completely omitted or simplified. 


(2) The quality of mesh division in finite element models affects the calculation time The spacing and accuracy are greatly affected. Generally, before ensuring the quality of grid generation The finer the grid, the higher the computational accuracy, but the required calculations The longer the time. The analysis of the contact relationship between valve components requires multiple iterations Proxy solving consumes a lot of computation time and resources. For large Calculate the sealing pressure ratio of the sealing surface of the caliber butterfly valve, and compare it with the diameter size, The width of the sealing surface is relatively small, as it is the focus of analysis, Therefore, the grid at this location should be appropriately refined for other positions of the valve Placing a grid can reduce distribution density and save computation time. 


(3) The definition of boundary conditions and virtual operating conditions is mainly based on the actual operating conditions of the valve, which constrains and loads its model. For valves with simple structures, the plane formed by the operating axis and the centerline of the flow channel can serve as the symmetry plane of the valve structure. Applying constraints on the valve body section at this position can make the results more accurate. When considering the stress caused by temperature difference on the valve body, the displacement constraint applied on the symmetrical section can completely eliminate the stress concentration caused by the constraint. Without affecting the analysis results, some components unrelated to the analysis target can be omitted to reduce calculation time, which is particularly effective in situations with large computational loads. For example, when calculating the specific pressure of the sealing surface, equivalent constraints can be applied to the sealing components (valve seat, sealing ring, etc.), and fastening components can be omitted according to the situation.


 (4) For the final analysis and calculation results, targeted data extraction and analysis should be carried out. If a hydraulic strength test is conducted on a hard sealed butterfly valve to obtain the stress distribution of the entire valve, the main focus is usually on the stress distribution on the valve body, and only the stress results of the valve body need to be extracted. To observe the sealing effect of the valve, it is necessary to extract the pressure distribution data on the sealing surface.


Valve and pump several important differences, together to talk about the valve and pump which industry is good?

Valve as an important part of general machinery products, its market capacity is no less than pump products, according to the National Association of General Machinery Valve Branch statistics, the domestic market capacity of the valve in more than 60 billion yuan (excluding exports to foreign valve dosage); This fully demonstrates the great potential of the valve market. It is often said that "pump valve is one, there must be a pump valve," as two highly relevant products, its products, Prices, channels, etc., have a lot of similarities, but it can not be understood as a pump only related products or ancillary products, and in fact in addition to the pump valve, such as steel, petroleum, chemical, electricity, Food, aviation and other fields require a large number of valves in the pipeway, so rather than saying "there must be valves in a pump," it is more accurate to say "there must have valves in an pipeline." It is also very different from pumps in the marketing process in terms of product, channel and price, which can be summarized as follows:

At present, the number of valve enterprises in China ranks first in the world, and has been able to produce more than a dozen major categories of products. Such as gate valves, globe valves, ball valves, butterfly valves, safety valves, boiler check valves, throttle valves, plug valves, pressure reducing valves, diaphragm valves, steam traps, emergency shut-off valves, etc. However, there are still external leakage, internal leakage, poor appearance quality, short life, inflexible operation and unreliable valve electric devices and pneumatic devices, some products are only equivalent to the foreign level of the 1990s. This main reason may be with our country so far almost no colleges and universities have opened a valve professional, there is no basic systematic education has a lot to do; Usually in mechanical design or fluid machinery and other professional with a little knowledge of the valve. There is no professional product design learning, so it caused a relative shortage of designers in the valve industry, and procurement personnel in engineering projects also know little about the valve; Therefore, the design, manufacturing, procurement and other personnel in the valve industry are relying on self-learning to improve, so individuals have a certain deviation in their understanding of valve products. This has created a strange phenomenon that often produces inexplicable problems in the process of valve design, manufacturing and sales, which should be a process of slow progress from disorder to maturity in the entire valve industry, and the difference between valves and pumps in products is mainly reflected in the following aspects. (1) The product structure and working principle are simpler than the pump and do not involve the power system; General valves generally do not perform professional calculations and tests on flow, vapor corrosion and other data, and there is a large gap compared with foreign valve companies, and domestic valve product samples do not reflect the corresponding data, only staying on installation dimensions and materials, and there are still a lot of room for learning and improving. 2, the degree of product standardization is higher than the pump, China's valve standards are mainly national standards (GB), the Ministry of Machinery standard (JB), the Ministry of Chemical Industry standard (HG), etc., these standards mainly refer to the former Soviet Union and Germany's valve standards. The structure, size, material, testing and other aspects of the general-purpose valve have been standardized, so the interchangeability of the domestic valve is higher than that of the pump, and there are generally no major technical obstacles (except for a small number of patented technology products). 3, the product type is more than the pump and miscellaneous, China's existing about more than 2300 valve types, about 30000 kinds of specifications, in such a wide variety of valve types, Cut off the type of valve connected to the use of the entire 80%, such as gate valves, globe valves, ball valves, butterfly valves are connected to cut off the type of valve, other non-return, regulation, steam water separation, reversing and other uses of the type of valve accounted for only 20% of the total amount; Among them, many types of valves connected to the cut-off class can be replaced by each other, mainly depending on the selection in engineering design; Such as in the municipal water supply pipeline on the original extensive use of long structure, bulky valve, to the present majority of the use of light weight, soft sealing butterfly valve transition. 4, before the valve factory must go through the relevant testing and debugging, product quality than pump products better grasp, so on-site guidance installation, debugging and other after-sales service is relatively small; Such as safety valve, mud relief valve, etc., involving take-off pressure, pressure reducing valve, such as the need for commissioning, generally in the factory before the manufacturers have been in accordance with the technical requirements of the contract to do a good job of commissioning, on-site installation only in accordance with the instructions connected to the pipeline can be used normally. 5, the manufacturers of external procurement more frequent; Due to the variety and variety of the valve itself, the valve company cannot produce all of its own, so when the manufacturer performs the contract, it is necessary to integrate the advantages of other suppliers to organize the supply. Then rely on the enterprise's own management process to good quality, which is also the inevitable industry segmentation and market competition; Such as my company's electric valve, pneumatically operated valve, hydraulic valve, such as automatic valve electric, pneumatic, hydraulic actuators are also supporting the outside, but because over the years I control system manufacturing experience, the assembly of the automatic valve and control system debugging more obvious advantages. 6, key industries, key enterprises, key parts of the valve are required once a year maintenance period, such as power, petroleum, chemical and other industries in the application of most of the valves, Every year, valves that have reached the service life are serviced and replaced, and the inspection of valves is generally directly replaced in a set of new valves, completely different from the service and replacement of spare parts for pump products, which is an important reason for the huge market capacity of valves and its growth year by year.

Second, the sales channels of China's existing valve of various sizes about more than 5000 enterprises, of which the annual output value of more than 10 million yuan has more than 500, the output value of more than 100 million yuan just a few dozen, in addition to the valve product variety, demand and scattered positioning of the various industries other than the different reasons,A very important reason is that the valve company's own sales channels, and imports or joint venture valve enterprises in their own channel construction, maintenance and control there is a large gap, the domestic valve enterprises sales channels and the following forms. 1, almost no own sales channels, this kind of main low-level, small-scale, family-type enterprises, long-term survival by OEM processing; The starting point of the enterprise is low, the management level and technical force are very weak, the equipment is simple, and most of the products are imitation production, mainly producing low-pressure valves for water supply and drainage. 2, the vast majority of domestic valve companies imitate the sales model of fast-moving consumer goods, using a relatively extensive agency system, relying on intermediate agents to achieve enterprise sales activities to end users; This model makes the risk of valve enterprises smaller, because the general valve company's settlement method for agent intermediaries is payment to delivery. Valve companies sacrifice their own sales gross profit and brand added value to achieve rapid return of funds, to avoid the risk of return, while most of the pre-sale, sale, after-sales costs transferred to the head of the middleman; However, the disadvantage of this model is that the valve enterprise itself is difficult to manage and control the agent. In order to maximize profits, middlemen usually find cheaper small factories to brand. Shoddy, serious damage to the brand of the valve company itself, while the agent middleman loyalty to the valve company is very low, and even the agent at the same time 35 valve brand, in the project bidding Wai standard illegal phenomenon occurs. 3, a small number of domestic valves have set up their own sales branches, directly facing end users; This part of the valve enterprises mainly in a specific industry or a specific region of the private valve enterprises, but also only belongs to the initial stage, its management of direct selling companies is more extensive; Unlike most of the pump manufacturers, which have their own controllable direct sales network, there is still a big gap in project information collection, large project tracking, bid negotiation, business personnel training, after-sales tracking and return visit, and communication with design institutes. Three product price valve target customers and pumps are consistent, are used in all kinds of civil construction, municipal, industrial and mining projects, but in the market price is still relatively chaotic. (1) In particular, the market price of civil construction and municipal project valves is because such project valves generally use low-pressure cast iron valves with low value and technical content, and the manufacturers producing such valves mostly use agents and middlemen to sell them, resulting in low-quality and low-price competition among each other in the bids. It is easy to mislead purchasers to win tenders at low prices, even sales below the cost price of the product, and valve manufacturers or middlemen must cut corners in the process and materials in order not to lose money, and the valves produced are subject to quality hazards, and it is the users themselves who will eventually suffer. Such as the so-called "hometown of Chinese valves" in Wenzhou Oubei town part of the valve prices to attract intermediaries OEM processing orders, the valve products based on its weight, material, wall thickness is divided into standard, heavy, light and many other levels to meet the demands of intermediaries to maximize profits. 2, industrial and mining project valve its product itself in the material, weight, control system and other aspects have certain technical requirements, Therefore, the market price of valves for such projects is relatively reasonable, and many professional valve manufacturers for industrial and mining industries use the principle of value engineering, strengthen the main functions of products, remove redundant functions, optimize system configuration, and develop a number of patented products; At the same time, strengthen the internal management of enterprises, work hard on cost accounting, and have a better price positioning in the market of their own superior products and industries. 3, environmental protection, nuclear power and other emerging industries with the valve is a breakthrough, increase technical research and development input to design new industry with the valve can be in the price chaos in the general valve market another way; Such as China's next five years will invest about 900 billion to the nuclear power industry, and in accordance with the relevant national provisions of which 70% of the equipment must be localized, in which the amount of valve equipment is bound to be huge, is another new domestic valve profit growth point. To sum up, although the market potential of the valve industry is huge, but the valve industry is still clearly in an industry reshuffle stage, at the same time, such as environmental protection, nuclear power valves and other new industries to the domestic valve enterprises put forward more opportunities and challenges. I believe that there will be a long-term vision of the domestic valve enterprises, in this reshuffle process rely on technological innovation, product quality management process reengineering, integration of social advantages of resources, building their own strong sales network to achieve brand status in the industry.