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Flow Analysis of Exhaust Manifolds for Engine

Jae Ung Cho1

1Division of Mechanical & Automotive Engineering, Kongju National University, 1223-24,

Cheonan Daero, Seobuk-gu, Cheonan-si, Chungnam of Korea 31080, [email protected]

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

Advanced Science and Technology Letters Vol.118 (Mechanical Engineering 2015), pp.59-63

http://dx.doi.org/10.14257/astl.2015.118.12

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.

(a) Model 1 (b) Model 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× 105MPa

Poisson's Ratio 0.3

Density 7850kg/m³

Thermal Expension 1.2× 105

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

Advanced Science and Technology Letters Vol.118 (Mechanical Engineering 2015)

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

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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

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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)


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