, pp.59-63 http://dx.doi.org/10.14257/astl.2015.118.12 Flow Analysis of Exhaust Manifolds for Engine Jae Ung Cho 1 1 Division of Mechanical & Automotive Engineering, Kongju National University, 1223-24, Cheonan Daero, Seobuk-gu, Cheonan-si, Chungnam of Korea 31080, jucho@kongju.ac.kr Abstract. In the exhaustion manifold, which emits exhaust gas, thermal deformation by flow occurs due to periodically recurring thermic conditions of overheat and overcooling time. Therefore, we need to properly understand the thermal deformation by the flow of high temperature exhaust gas occurring in the manifold. In this study, two forms of exhaust manifolds used in turbo diesel engines are analyzed to find out which form shows more efficiency. This research used ANSYS program for analysis. Keywords: Exhaust manifold, Flow analysis, High temperature, Thermal deformation 1 Introduction Exhaust manifold, which is connected to the cylinder head, emits exhaust gas in the cylinder. Model 1 in this research is the manifold used in the engine of D2848T, and model 2 is modeled as the manifold which is often found in heavy equipment vehicles such as an excavator by using CATIA program. We conducted the ANSYS program and compared the thermal effects by the flow analyses of the two models and tried to find out which one is more efficient. If this analysis result is applied in later designs of manifolds for turbo diesel engines, we expect to develop an exhaust manifold with the improved the thermal characteristics by flow, durability, and engine performance[1-5]. 2 Model and Analysis 2.1 Model To investigate about thermal stress by flow and the characteristics of turbo diesel engine exhaust manifolds, a restriction effect occurring from thermal expansion of the cylinder head must be considered. The analysis model of exhaust manifold is made by simplifying the actual model. Exhaust manifold models were made by using CATIA ISSN: 2287-1233 ASTL Copyright 2015 SERSC
program. The configuration and mesh of model 1 and model 2 are shown as Fig. 1(a ) and (b). Table 1 shows the numbers of finite elements necessary for analysis. Material property of the models are AISI 5000 series steel among gray cast iron, and the property is presented in Table 2. Fig. 1 Mesh configuration. Table 1. Numbers of nodes and elements at models. Nodes Elements Model 1 38397 19239 Model 2 43300 21571 Table 2. Material property. Young's Modulus 2 10 5 MPa Poisson's Ratio 0.3 Density 7850kg/m³ Thermal Expension 1.2 10 5 Tensile Yield Strength 1070MPa Compressive Yield Strength 1070MPa Tensile Ultimate Strength 1170 MPa 2.2 Analysis of Thermal Stress by Flow When the vehicle runs at the speed of 60km/h, the entrance temperature of the manifold by flow is 300 and its pressure is 5MPa. The exit pressure is 0.65MPa and pressure ratio is 10. In this experiment, the convection coefficient of heat transfer is set at and the manifold is exposed to 22 of air. We conducted the analysis by assuming that the average inner temperature of manifold by flow is 139.5. For the boundary condition of the model's thermal conduction, 139.5 is given as the average temperature inside the manifold, as can be seen in Fig. 2 60 Copyright 2015 SERSC
Fig. 2. Thermal constraint condition by flow. Fig. 3. Contour of thermal temperature at steady state by flow. In Fig.3, the temperature contour of the manifold due to thermal conduction by flow is provided when the vehicle runs at the speed of 60km/h at the normal state. The boundary condition of the model's thermal stress analysis by flow is as follows; the surfaces of the manifold's entrance and exit are fixed, bolt condition is applied where there is a bolt, the entrance pressure is 5MPa, and the exit pressure is 0.65MPa as shown by Fig. 4. Fig. 5 shows each model's amount of the stress equivalent stress caused by heat. Fig. 4. Constraint conditions of fixed support, pressure and frictionless support by flow. Copyright 2015 SERSC 61
Fig. 5. Contour of equivalent stress by thermal load. In this research, thermal stress of engine joint parts by flow were analyzed, which were found to affect the durability of these manifolds. In Fig.5, at the inner entrance of flange, jointed with the manifold and the entrance through which the exhaust gas of each engine's cylinder enters, the highest stress level of 1369.1MPa in model 1 and 2520.7MPa in model 2 at the same part was shown. 3 Conclusion In this research, we obtained the following results through the analysis of thermal stress by flow of two forms of turbo diesel engine exhaust manifolds. At the equivalent thermal stress levels of model 1and mode 2, at the inner entrance of flange, jointed with the manifold and the entrance through which the exhaust gas of each engine's cylinder enters, the highest stress levels of 1369.1MPa in model 1 and 2520.7MPa in model 2 at the same part was shown. By flow analysis on thermal stress, model 1 showed thermal stress less than model 2, so we expect that manifold of model 1 will show superior performance than model 2. If we apply these analysis results to turbo diesel engine manifolds to be designed later, we expect to develop products with improved the thermal characteristics by flow, durability, structure, and engine performance. References 1. Rahim, R., Mamat, R., Taib, M. Y. and Abdullah, A.: A Influence of Fuel Temperature on a Diesel Engine Performance Operating with Biodiesel Blended. International Journal of Advanced Science and Technology, vol. 43, pp. 115--126 (2012) 2. Adepoju, G. A. and Komolafe, O.A.: Analysis and Modelling of Static Synchronous Compensator (STATCOM): A comparison of Power Injection and Current Injection Models in Power Flow Study. International Journal of Advanced Science and Technology, vol. 36, pp. 357--384(2011) 62 Copyright 2015 SERSC
3. Palhade, R. D., Tungikar, V. B., Dhole, G. M., Kherde, S. M.: Transient Thermal Conduction Analysis of High Voltage Cap and Pin Type Ceramic Disc Insulator Assembly. International Journal of Advanced Science and Technology, vol. 56, pp.73-- 86 (2013) 4. Huang, D. S., Huang, F. C.: Coupled thermo-fluid stress analysis of Kambara Reactor with various anchors in the stirring of molten iron at extremely high temperatures. Applied Thermal Engineering, vol. 73, no. 1, pp. 220--226 (2014) 5. Tomas U. G. Jr.: Investigation on the use of Coco Coir Polypropylene as Thermal Insulator. International Journal of Advanced Science and Technology, vol. 59, pp.13-- 26 (2013) Copyright 2015 SERSC 63