Research Of Computer-aided Conceptual Design Technology For Process-form Mechanical Systems

Mechanical system conceptual design determined many key factors of target products including function, quality, and costs, which was the key node in the products design process. Currently, CAD technology was becoming mature for regular mechanical system in the design information expression, structure performance analysis and data management, et cetera. But it was still weak in the node of supporting conceptual design. Considering mechanical system conceptual CAD technology usually relied on professional knowledge for special field, specialized design model and intelligent design methodology might needed according to the characteristic of the target design, which resulted in research of specific design systems for mechical system of particular range and special classification.This paper focused on specialized mechical systems which with process system characteristic, e.g. Boiler, steam turbine, compressor etc. Process-form Mechanical System (PMS for short) was proposed to classify these mechanical systems whose function principle was similar to process systems. The function principle of PMS could be described as converting material and energy that flowed in and out of PMS by interworking of several parts. Further, combining the design theory and methods of mechanical system and process system, we could develop the generally applicable CAD technology for PMS including function principle analysis, design model, and design process and methods, in order to improve design efficiency and quality by developing CAD technology for PMS.The main content of the paper were listed as follows:(?) The paper proposed the classified concept of PMS, and defined key concepts such as""and "general layout". Process part refered to mechanical parts which made specialized deal with material and energy that flowed in and out. Several process parts consisted of general layout for PMS according to special logic. The main characteristic of PMS was analyzed, and it was proposed to acknowledge the function principle of PMS with material conversion of unit and system level. The former was performanced as converting the brance number, type and properties of material that flowed in and out. The later mainly described the performance of all the process parts working together under specialized logic of general layout, to convert material that flowed in and out of PMS step by step.(?) Based on the acknowledgement of concet and characteristic of PMS, the conceptual design of PMS was devided into two levels, general layout design and process part design, by drawing on relevant theories of mechanics engineering and process systems engineering. By the general layout design process, the interworking problem of system level was solved, and the process part design helped to get the detailed part structure that satisfied specific material conversion target. Combining the Function-Behavior-Structure (FBS) model, the general layout design model and the process part design model of PMS were expressed by four components (function, behavior, structure and knowledge) which were constructed by system level and unit level. The structure refered to both of any process part in PMS and the general layout consisted of several parts.The function expressed the material conversion requirement, while behavior was described by details of material conversion that was achieved by specific structure. Knowledge involved the rules, experience and methods used in the process of PMS design.(?) The desription and expression for material conversion was most important for the conceptual design model of PMS. Abstracting any process part and material of PMS respectively as "General Process Part"(GPP) and "General Material"(GM), the material conversion logic of unit level could be described by one GPP and GM with in-out GPP. Further more, the material conversion logic of system level was composed by many GM and GPP with some logical relations. An ID linked description method was proposed for the expression of the conversion logic mentioned above, which used ID to mark the corresponding object uniquely, and built up the relationships between each other by record the ID of object relatively.(?) The PMS scheme design activities was decomposed into four sub activities including scheme creation, scheme analysis, scheme evaluation and scheme adjustment. PMS design process was realized by the four sub activities in the two design levels containing general layout design and process part design. The main intelligent CAD methods which supported the PMS design process were generalized and the application of these methods in the PMS design process was expounded.(?) Based on the PMS conceptual CAD theoretical frame stated previously, the software model for boiler conceptual CAD was proposed with object-oriented technology. The system prototype was developed, and the application details were given.This paper developed the generally applicable CAD technology for PMS, which established the basis for further research and application of this fied. It filled up the research gap of interdisciplinary areas with process systems and mechanical systems, and was of reference value for the computer-aided conceptual design technology development of the other systems.