Feature Solution in the Process of Parameterizing Port Model

Transactions of Tianjin UniversityVol. 10 No. 2Jun.2004Feature Soluton in the Process of Parameterizing Port Model*PENG Yu(彭禹)' , HAO Zhl-yong(郝志勇), SUN Xlu-yong(孙秀永)',LU Dong-hang (刘东航)' , FU Lu-hua (付鲁华)'(1. Schol of Mechanical Engineering, Tianjin University , Tianjin 300072, China;2. School of Mechanical Engineering, Zhejiang University, Hangzhou 310027, China;3. Changchun Automobile Research Institute, Changchun 130011, China)Abstract:Aimed at ataining to an integrated and efective pattem to guide the port design process, this paperputs forward a new conception of feature solution, which is based on the parameterized feature modeling. Withthis solution, the overall port pre-design process can be conducted in a vitual pattem. Moreover, to evaluatethe advantages of the new design pattem, an aplcation of port system has been involved in this paper; and inthe process of application a computational fluid dynamic analysis is concerned. An ideal effect of cleannes,high eficiency and high precision has been achieved.Keywords :feature solution; port modeling; parameterization; port computational fluid dynamics; internal-com-bustion engine; intake-exhaust systemArticle ID:1006- 4982(2004)02-0118-08Since the appearance of the internal combustion en-gine, its combustion system research has been always the 1 Definition of feature solutionkey to improving the engine performance, and the designof the ports of intake- exhaust system is the most sensitiveThe above-mentioned parameterized modeling is a newfactor in the whole process of the design of combustion sys- efctive modeling technology in CAD process, which de-tem. Therefore, ports design, including all kinds of intake nives from a design ennolation in r field named objet-and exhaust ports, plays a predominant role not only in orientation[2]. Based on this conception, designers canshortening the development eyele, but also in improving construet their model without specifying all the geometythe engine performance. Objectively speaking, the techni information like point cordinates, curve or surface fune-cians have made some proges in the design method of in tions. The object model is simplied into several rltivelytake-exhaust ports, but it is. far from being cllel “a simple fetures by which the desiger acomplishes thebreakthrough". The most troublesome obstacle in this as-modeling tasks with some sort of parameterized modelingpect, as widely known, is the exeeding complexity of the software. And in this way, the designer could conceive thesufaces of these ports, due to which they cannot be pa- design object ll-roundy.rameterized in a similar way as other parts of interal-com-Therefore , considering all these facts, we regard thebustion engine, which, generlly,y cen be analyed into feature solution as an efecivee measure. As for the tangen-eletively simple feture stucue. With the advance of tial ports and helical ports, athough they are located in allCAD tenol , by suface rcsnetine, a 3D dgitized types of ilmeal-combuston engine, gell，they sharemodel can be costnucted, and the sufce smoohnes can some unifrm ( or sinilar ) geometrical stucture. Thatbe impoved to some extendt!. But all these dferent即- mens ,in the poes of reated moden,his uifom(orproaches of port design never ceast of the taditional pat- similar) geometrical structure cean be descibed with a uni-temn, which is symbolied by an oil sludge model. This form( or smilar) suit of feture combinaion. Therelore,patterm still operates in nowadays port design. To enhancethe eficiency' and qualty， a new general conception ofAcceped date :2003.10- 30.“feature solution" is introduced as the“template" in theprocess of port 3D parameterized modeling in this paper.中国煤化工- udent.:ndaion of China:fYHCNMHGPENG Yu et al :Feature Solution in the Process of Parameterizing Port Model“feature solution" can be defined as a combination of fea- ted merely by computer;ture with which the uniform( or similar ) geometrical struc-7) Poisonous reagents and exhausting manual workture can be descrbed in the parameterized modeling can be avoided;process. In case that one feature solution is designed for the8) Sharply shorten development cycle.whole process of parameterizing port model, then this kindThe comparison between the traditional and intro-of solution is defined as the“template" of the port 3D pa-duced methods is shown in Fig. 1. The two flow charts Arameterized modeling process in this paper.and B shown in Fig. 1 , are traditional ways which both be-This method shows its overwhelming advantages whengin with the same phase -“making oil sludge port". Al-compared with the traditional ways. Some advantages are though the pattem in flow chart B , developed from the for-shown as follows:mer , conducts a reverse engineering process to improve the1) Better smoothness and higher precision of the port' smoothness and precision of the ports surface, practically,s extermal surface can be achieved;to generate point nebular and reconstruct port surface2) Sections of flows in ports are much easier to modi- means more exhausting and time-consuming work. Compar-fy and control;atively ,flow chart C ilustrates a whole new patterm to con-3) Precise geometry for further analysis can be direct- duct the port design proces. This pattern begins first withly provided to computational fluid dynamics ( CFD) soft-the parameterized model and then the process of CFD. Nec-ware;essarily , after several times of refinement , a port test should4) Directly project into engineering drawing to guide be carried out to verify our virtual design in the last step.shaping water jacket dies;All the phases based on parameterized digital data in the5) Easy NC code for machine tool in CAM process is computer and the development working operate in a cleanavailable ;and eficient way.6) Interference check related to ports can be conduc-Making oil sludge port+-Making oil sludge port +Parameterizing model+↓Making core boxGenerating point nebularCFDI Reconstructing port surfacePort test__NAchieve object?↓YYY工[ Reconstructing port surfaceTN.Confirming model(旧) Flow chart A(b) Flow chartB(C) Flow chartCFig.1 Comparison between traditional and introduced methodsvided into intake ports (including tangential port and heli-2 Object analysiscal port) and exhaust ports, whereas, in regard to thedifference existing in the solutions of parameterization, thiUsually, according to the function, ports can be di- paper中国煤化工- helical, straightfYHCNMHG一119一Transactions of Tianjin UniversityVol. 10 No.2 2004and comering. The difference in these solutions depends As for the straight port, it is defined as having two topolog-on what style of the joint line each kind of port has, rather ically parallel and non-intersecting joint lines. Exactly ，than the difference in their geometry. Typical styles of the the inlet and the outlet are both located at one end of thejoint line are shown in Fig.2. In this figure, the joint line joint lines. Whereas, the joint line of the cormering port,of the helical port consists of two segments:port head seg- presents a semi-closed spatial curve, something like thement and guiding segment which are connected with one letter “U" , and the inlet of this port is located beneath thepiece of high order B-spline curve-marked with a circle. topological plane where the joint line lies.Joint linesInlet-(@) Helical port(b) Straight port(C) Comnering portFg.2 Port styles and their joint lines3 Parameterization processAs for this process , this paper has to mention a designconception named as“TOP-DOWN" , which is defined to一analyze the object 8ystem of complexity into several or moresimple enough subeystems , and then determine the solutionto the original task(2).Based on this conception of “TOP-DOWN", theprocess of parameterization should be detailed into severalphases. In the terminology of the author, these phases arerespectively called layout, constructing basic surfaces ,Flg.3 Layout of portadding rounds and accomplishment.curves, making surfaces and merging them. As the straight3.1 Layoutport and cormering port share similar sub-phases in thisThe pase“layout" is aranged 8s the first step, con- phase, their modeling will be introduced in advance, andsidering the cylinder head layout secheme and the previous as the helical port has a diferent method to conduct theexperience of port design, a broad outline of port must be phase of constructing basic surfaces, its introduction willdetermined in this phase.be presented in the later part of this paper.Fig.3 shows this phase “layout" with a sketch map.3.2. 1 Straight and comering portFig.3 represents one possible spatial layout in the eylinderBased on the scheme obtained in the above-mentionedheed of some Chinese engine products. The double line layout phase, the control curves are generated to ensurecirles in this figure indicate the positions of oil circuit and that all the surfaces constucted with these curves shouldbolt which have potential risk of inference with our port. be within the llowable space. Moreover, the section areaAnd then, the next phase is constructing basic surfaces.property of ports, which directly affects the performance of3.2 From constructing basic surfaces to accomplish. the port, must be considered in this sub-phase. In Fig. 4,mentthe control curves of straight and cormering ports areTo provide closed-surfaces for the next features,shown.“basic surfaces" must be constructed according to the de-These curves , including joint lines, side centerlines,sign requirements before the“round" phase.and so on, are helpful when a specific surface shape is re-Entering this phase , constructing basic surfaces, itquire中国煤化itions ( BC) and oherconsits of three sub-phases in order: generating control desround feasibility in theYHCNMHG一.120一PENG Yu et al; Feature Solution in the Process of Parameterizing Port ModelUp-down-sideInletcenterlinesJoint linesJoint lines Upside centerlineOutletValve centerlineFlow pathDownside centerline(a) Straight port(b)Comering portFig.4 Control curvesnext phase，the direction of airflow, must be paid enough similar method to generate, this means, they have similarattention to.BC and employ the same feature-- “ sweep".Therefore,Fig. 5 ilustrates the process of generating basic sur- this paper only clarifies the specifc method aimed at thefaces of the straight port and comering port. The wall sur- straight port, whereas the similar part of the comering portfaces and upside surfaces of these two types, which are should follow the example of the former and doesn't appearswept out with their joint lines and centerlines, share a in Fig. 5.Vaive centerincDcstelire(a) Wall surfiaces(b) Uip-down-side surfaces(C) Revolved surfaceFig.5 Generating basic surfacesReferring to the feature,“ sweep" is a common com-1) Each sweep section plane must have linear projec-mand of all CAD graphics software.Although the feature tion on the cylinder head baseplane , that is, they must besolution, introduced in this paper, is developed with PTC/ kept in a normal state;Pro/ENGINEER, when we choose other features employed2) The projectins of the joint lines or centerlines onin the further process of modeling, we also consider this the eylinder head baseplane must be normnal to the projec-versatility as a very important factor, and have alreadytions of sweep section planes about the intersection point ofconducted a solution test in several mainstream CAD them. The results of this operation have been shown ingraphics softwares, including IBM/CATIA, Unigraphics;Fig.5(a) and (b).and the same modeling effects have been achieved.In regard to the case of a comering port, the downsideTo obtain fine smoohness of the ports model, the BC surface and the inlet should be smoohly connected, theare very important factors in the course of using the feature downside surface of the cormering port cannot be generatedof“sweep". A loose surface without any BC generally with the same feature of“sweep" , which is still applicableleads to an unpredictable shape , which cannot match our for generating that piece of the straight port. Here, an al-design requirements. In this case, this paper puts forward termative feature is to“revolve" with the downside center-a simple but efective method to cope with this problem. line about the valve centerline as its axis. The result of thisSpeifially, when sweeping out the wall surfaces and up- feature is shown in Fig. 5(c).side surfaces, this feature must meet the fllowing two BCf the straight port andat the same time:comer中国煤化工They ate shown inYHCNMHG-121-Transactions of Tianjin University Vol. 10 No.2 2004Fig. 6.the values on these points both are very sensitive factors.To make closed surfaces prepared for the next phases,An unsuitable scheme means not only the risk of rounda“merge”sub-phase is necessary. Fig. 7 presents the ap- failure but also unideal performance. Therefore, the con-pearance of this sub-phase's results. All the edges, which trol points should be located at the positions , which can a-are defined as common boundary of two trimmed surfaces void the potential dificulty of round, meanwhile, are lia-in merging operation, should be added rounds in the next ble to affect the performance of the port.phase.The following work is to add valve guides, and roundthe edges related to the guides, then the parameterizationprocess of the straight port and cormnering port has been ac-complished. The final appearances are shown in Fig. 9.(0: strigl port(o) Smaigh por(b) Comaring potNig. Round edgs(B) Coring portPig.6 AI basic surfaces(a) Stuighipart(4: Stright port《b) Corneing portFig.9 Final models3.2.2 Helical port0b; Conering panAs mentioned before, the helical port has a diferentmethod to conduct the phase of constructing basic sur-Fig.7 Merged surfacesfaces, its feature solution is relatively more complex thanFig.8 presents the appearance of ports after the the two formers. Generally, on the constructing basic sur-“round” phase. What deserve enough atention is the faces, this phase of helical port begins with a wedge-re-round values of those edges. To be precise , there is a rela- volved section of its valve chamber where no variance oftively smal posibility of using constant-valued round in a section area occus. Even though, in some pracical cass,practical cease. Whereas, when making variable -valued this中国煤化工S paper umosly ree-round, the positions of the round value control points and ommefor the reason that it一122-TYHCNMHGPENG Yu et al: Feature Solution in the Process of Parameterizing Port Modelil provide BC for the next feture. The feature“revolve” clude A,B ,D and R which are shown in Fig. 10'2).A is the .deseribing this wedge section is shown in the middle of slope of top profile , contoling the direction of the swir;BFig. 10. In sketching section of this feature, some factors is the maximal helix radius, controling the intensity heli-must be paid enough attention:cal swirl;D is offset- a larger offset increases the helicalflows extend;R is the bending radius, a sensitive dimen-sion affects the airflow.As for the next sub-phase, the first feature fllwingthe port head is another “blend-revolve" feature ，whichcomposes the downside of the guide segment. This featureof the surface is shown in the basic surfaces of Fig. 11.However, in some practical cases , this feature is chosen asa simple feature of revolve. Choosing which feature de-pends on what transferring state from the guide segment tohe helical head our designer expects. No matter whichfeature would be chosen, it must ensure a smooth connec-BC ourfaccstion to the previous feature. Other basic surfaces, exceptEnd soationfor the connecting surface marked with a white line in Fig.Palth scctions11(a), are constructed by“sweep" feature with the sameBC as those of the ports introduced before. Generally, thisconnecting surface has two altemative feature choices. Oneis“blend sweep" , which is defined as a sweeping featurewith variable sections along its trajectory, as a rule, theSart scainjoint line. This is similar to the discrepancy between theFlg.10 Hllcal port headfeatures“revolve”and“blend revolve". The other alter-1) The sketch segments must compose a closed line; native feature is“boundary surface"，which is constructed2) The vertex number of this sketch must match that with no less than four closed boundary curves. Althoughof the helical section constructed next;the frame curves located in the closed area ( marked by3) The start vertex of this sketch must be located ina white color) are optional, this paper utmostly recommendsgiven position which matches the counterparts of the next employing them, because a surface only constrained withhelical sections.four boundaries and the BC on them can lead to difficultiesIn constructing the helical section of the port head，in further adjusting the spatial shape of the closed area.which connects the above-eferred wedge section to the port After merging all these basic surfaces, a closed surface hasguide segment, a feature called“blend-revolve" is used as been prepared as shown in Fig. 11(b) for the next rounda recommendable choice. Compared with the“revolve”features. Analogous to the“round" phase of the two for-feature used before, in which only an unchangeable sketch mers, the postions of the round value control points andsection drives this operation,“blend-revolve" is named af- the values on these points both are very sensitive factors.ter the different sections which can be introduced in the In addition, designers should avoid the“overlap”amongcourse of revolving. Similarly ，there are also some factors the round features in the whole way, which is defined asthat must be paid enough attention :the matter that a round feature is constructed upon at least1) All the sketch sections must be closed lines;one surface created by previous round features. This is be-2) These sketch sections must have the same vertex cause the overlap not only could cause more risk of roundnumber as the previous feature constructed by“revolve"; failure but also, even though one round feature created3) The start vertex of these sketches must be located successfully, could cause unpredictable variance on thein the same position as the previous feature.volume of the overlap area. A completed helical port isBefore this feature is completed, we must prepare a shown in Fig. 11(c).series of curves and surfaces as controlling BC in advance.So far, the parameterization process of all the threeSpecifically , during this term , some important engineering types of norts has heen finished, A. for the process of thefactors must be attached enough consideration. These in- comple中国煤化工onceming the mergeTYHCNMHG-123-Transactions of Tianjin UniversityVol.10 No.2 2004Fjlcand-rovulved sur[accCrmnsansftrfaco4 Basic sufaces() Magot sriacas(6) F'bal mndelFig. 11 Modeling processor trim operation upon high-order surface. In this case, the CFD. This course of post-processing includes smoothnessfine surface quality can be expected in mathematical con- analysis and detailed adjustment( if the analysis results in-notation, however, some unexpectable problems, such as dicate an unideal smoohness). Fig. 12 ilustrates the re-unideal surface quality, interface model distortion or fail- sults of smoothness analysis of these three ports; the colorsure, could occur because of the high tension modulus or in it present the slope to a given direction. If no cliff hap-other factors. To ensure a better smoohness, a post-pro- pens to the color gradient in the results, this means thecessing must be conducted before transferring the data to modeling tasks have been accomplished.0599-1000间Hdliea pert(b) Srighi port(0) Comoring prtFig 12 Smoothness analysishas relatively reasonable layout, however, a series of de-4 Applicationtailed adjustments must be conducted aimed at its localstructure. By modifying, comparing and searching, severalTo evaluate the advantages of the new design pattern sensitive areas, marked with circles in Fig. 13, have beenbased on the feature solution , we conducted an application located; they are, respectively, the areas near the cylin-upon the intake system of one 6110 turbo-diesel engine in der-head bolts ( eircle A)，the shape of valve-seat ( circleChinese market. As shown in Fig. 13, a tangent port and a B), the connecting area of the inlet and valve- seat ( circlehelical port compose this system, which is expected to gen-erate a high intensity of swirl. The initial scheme had beenparameterized by the above-introduced feature solution inthree working days. Then a CFD process was conducted.Referring to the output of the calculation, we realized that,for some inherent flaws, this original scheme didn't attachthe expected inlet swirl ratio. Therefore, a further analysismust be carried out. Considering that the contours of thestatic pressure and the path lines of particles ( shown inFig. 14) indicate a low swirl intensity and unreasonablepressure field, it can be concluded that the original scheme中国煤化Inodel一124-MHCNMHGPENG Yu et al:Feature Solution in the Process of Parameterizing Port ModelB), the blast groove of the tangent port (dot in circle B). process based on CFD results is shown in Fig. 15. It isAccording to this idea, after several times of refine- worthy of mentioning that all the work costs only sevenment, the final scheme is obtained. By comparison to the working days.original scheme, the refined scheme generates a more rea-In traditional consideration, the port test, which en-sonable pressure distribution and airflow field, and the in- sures a kind of security of the process of virtual design, islet swirl ratio is increasedy 26. 4%( from 2.01 to2.54) regarded as an indispensable part of the whole task. lroniand meets the design expectation. Part of refinement cally, when the test data were obtained after one month ,-2.60X 10*1 2.40X101.20x 10z-xL-3.70X 10Lh.8X10.2552三-3.50X 10Fig. 14 CFD results of original scheme( only for reference)1.20x 10P1.20X10|1.58X10-1.58X 10-1I 1.58X10()Original schame(b)Midway scheme(<) Final schemeFIg.15 Refinement proces (partial)there exists an alowable tolerance of 5. 6% between the 5 Conclusionssimulation calculation and the test. That is to say，wespent nearly 80% working time on the test to confrm the s0-The feature solution introduced in this paper actuallycalled security merely because of a small tolerance of is an efective and practical method in the proces of pa-5. 6%. Therefore, this paper brings fonward an audacious raneterization. Its value embodies not only in a narrow con-assumpion:; after apling this new method to a large e cepion of modeling, but also in the whole proces of portnough number of new products and comparing the calcula- design. The resuts from aplicaion indicate that the newtion with the tet output, if there exits a stable and small pttem cean sharply shorten the development eirele, mean-tolerance between them, then we should believe thaet it is while, meet the requiremets of beter smohness,s preinot indispensable to spend 80 much time merely to confrm sion and perfomance.the so-called security. After al, there are 80 many unpre-Referencesdictable factors to afet the reliability of tests. However, toprove this assumption certainly should depend on further[1] Jin Tao,Chen Janling,Tog Shigung Research derelopment in地research and the accumulation of a large quantity of testverse engineering technology [J] China MecharicalEngineering,data. Once this assumption had been proved to be true, it2] Wang Tongheng,Zhang Lianfang Apicaions Itroducion of Compua.2002,13(16) :1430-1436( in Chinee).would provide a very important foundation of methodologyer Technology and Enginering[ M]. Tianjin:Tianjin University Press,for the intermal-combustion engine port“fast design" in the199(in Chinese).case of the man-made or natural calamity. Naturally, the [3] Zhou Baolong. Inemal-Combustion EnginTechnology[ M. Bejing:analogical pattern can be spread into other domains.中国煤化工):YHCNMHG-125-