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Author(s): Anand Pathak1, Saurabh Deshmukh2

Email(s): 1anandpathak519@gmail.com

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    1Department of Mechanical Engineering, R. V. College of Engineering, Bangalore, 560059, Karnataka, India
    College of Engineering & Technology, Bhilai, Chhattisgarh, 490024, CG, India.

Published In:   Volume - 1,      Issue - 1,     Year - 2021


Cite this article:
Anand Pathak, Saurabh Deshmukh (2021).Thermal analysis of Exhaust manifold system using computational fluid dynamics. Spectrum of Emerging Sciences, 1(1), pp. 50-55.

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Spectrum of Emerging Sciences, 1 (1) 2021, 50-55

 

Spectrum of Emerging Sciences

          

 

Journal homepage: https://esciencesspectrum.com

 

Thermal analysis of Exhaust manifold system using computational fluid dynamics

Anand Pathak 1*, Saurabh Deshmukh2  

1* Department of Mechanical Engineering, R. V. College of Engineering, Bangalore, 560059, Karnataka, India.

2 College of Engineering & Technology, Bhilai,  Chhattisgarh,  490024, CG, India.                       

                                                                                                                

*Corresponding Author:

E-mail Address: anandpathak519@gmail.com

Article available online at: https://esciencesspectrum.com/AbstractView.aspx?PID=2021-1-1-11

 

ARTICLE INFO

 

ABSTRACT

Original Research Article

Received: 18 November 2021

Accepted:  7 December 2021

 

 

KEYWORDS

Exhaust system,

CFD,

Thermal

 

 

Exhaust system has vital role in performance of IC engine which can significantly affect the fuel consumption, exhaust smoke emission and temperature. The objective of current research is to investigate the heat transfer characteristics of exhaust manifold incorporated with fins. The CAD design of exhaust manifold is developed using Creo design software and its thermal analysis was conducted using ANSYS v21 simulation package. The CFD analysis is also conducted to determine the effect of fins on heat transfer characteristics of exhaust manifold. Thermal characteristics of exhaust manifold system using CFD have shown an enhancement of heat dissipation capability by 3.01%. The incorporation of fins augmented turbulent flow which enhanced heat dissipation capability of exhaust manifold with 2.42% reduction in maximum temperature.

 

 

 


Introduction

Exhaust system has vital role in performance of IC engine which can significantly affect the fuel consumption, exhaust smoke emission and temperature. The back pressure in exhaust system should be limited to specific value in order to contain emissions.  The allowable back pressure should be less than half of permissible value. The design consideration for exhaust system designs is pipe size, silencer type and configuration of system.

 

Figure 1: Four-cylinder engine exhaust manifold [15]

The exhaust gases from engine cylinder head are carried away to exhaust system using exhaust manifold. The emission efficiency and fuel consumption are also dependent upon design and type of exhaust manifold.

The exhaust gases from engine cylinder head are carried away to exhaust system using exhaust manifold. The emission efficiency and fuel consumption are also dependent upon design and type of exhaust manifold. The exhaust gases from engine cylinder head are carried away to exhaust system using exhaust manifold. The emission efficiency and fuel consumption are also dependent upon design and type of exhaust manifold. Exhaust Manifolds are affected by “thermal stresses and deformations due the temperature distribution, heat accumulation or dissipation and other related thermal characteristics” [14]. The exhaust stroke piston work, gas exchange process is also influenced by exhaust manifold. The backpressure is one of the important parameter which requires consideration in the design of exhaust system. The backpressure has undesirable effect on engine performance due to increase in residuals in the engine head. The temperature increases at the beginning of the compression due to increased residuals and deteriorate the thermal efficiency of engine.  

II. Literature review

Jafar M Hassan et.al. [1] have conducted thermal analysis on exhaust manifold design using FEA. The effect of longitudinal tapered design on performance of exhaust manifold are also evaluated and the results have shown enhanced performance of exhaust manifold with tapered design. M. Usan et.al. [2] have conducted design optimization of catalytic converter and exhaust manifold using integrated software. The optimized design with varying shapes and dimensions of exhaust manifold is presented.  Hessamed in Naemi et.al. [3] have conducted CFD analysis on exhaust manifold to determine thermal and fluid flow characteristics. The flow loss coefficient of manifold is evaluated and the variables affecting the flow are presented. Masahiro Kanazaki et. al. [4] have used multi objective genetic algorithm in optimization of exhaust manifold.  Hong Han-Chi et.al. [5] In their research paper they used GT-Power, 1-dimensional software, for estimating the engine performance of a single cylinder IC engine. Taner Gocmez et.al. [6] have conducted experimental investigation on exhaust manifold to improve its strength using design optimization technique. The stresses and deformation are evaluated from the analysis and critical failure regions are identified. Martinez-Martinez et.al. [7] have evaluated performance of exhaust manifold using techniques of Computational Fluid Dynamics. In the analysis, the exhaust manifold is placed nearer to catalytic converter. Benny Paul et.al. [8] have conducted CFD simulation on exhaust system of FI engine using RANS solver. The turbulence model used in the analysis was RNG k-ε turbulence mode and pressure, temperature is evaluated. MohdSajid Ahmed et.al. [9] have worked on optimization of exhaust manifold of 4-cylinder IC engine. The result shave shown exhaust tube bending radius and thickness has significant effect on temperature and pressure. Kandylas et.al. [10] have conducted steady state thermal analysis on exhaust manifold. The temperature and radiation boundary conditions are applied on the exhaust system. The heat dissipation plot (heat flux) and temperature plots are evaluated. Bin Zou et al. [11] have conducted CFD investigation on exhaust manifold to determine the effect of temperature on engine performance. The free vibration analysis of exhaust manifold is also conducted to determine natural frequency and mode shapes. P.L.S. Muthaiah et.al. [12] have worked on improving performance of exhaust manifold using techniques of Computational Fluid Dynamics. The back pressure is evaluated and essential design changes to reduce backpressure are presented.

 

III. Objective

The objective of current research is to investigate the heat transfer characteristics of exhaust manifold incorporated with fins. The CAD design of exhaust manifold is developed using Creo design software and its thermal analysis was conducted using ANSYS v21 simulation package. The CFD analysis is also conducted to determine the effect of fins on heat transfer characteristics of exhaust manifold.

 

IV. Methodology

The FEA simulation of exhaust manifold involves 3 stages i.e. preprocessing, solution and post processing. The CAD model of exhaust system is developed by using the dimensions from literature [13].

Figure 2: Dimensions of exhaust manifold [13]

Figure 3: Exhaust manifold design

The CAD design of exhaust manifold is developed using sketch, extrude and fillet tool. The sketch profile is generated and sweep tool is used to generate tube profile. The shell tool is used create hollow structure inside. The developed CAD model is shown in figure 3 above. 

Figure 4: Imported exhaust design

The exhaust design is imported in ANSYS 21 design modeler. The inner cavity of exhaust system is filled using tools. The other geometric errors like edge defects, curvature defects are rectified. The exhaust manifold is discretized using tetrahedral elements. The transition ratio is set to 0.77 and growth rate is set to 1.2. The number of elements generated is 372548 and number of nodes generated is 85527. The discretized model of exhaust design is shown in figure 5 below.

 

Figure 5: Discretized model

Figure 6: Copper domain definition (without fins)

The domains are defined for the simulation, i.e., solid domain and fluid domain. The solid domain is defined using copper material as shown in figure 6 above. The energy model is defined as thermal energy. The fluid domain is also defined in the analysis with reference pressure set to 1atm and turbulence model is set to k-omega. The material defined in fluid domain is exhaust gas. The domain definition of fluid is shown in figure 7 below.

Figure 7: Fluid domain definition (without fins)

The similar boundary conditions are also applied on exhaust manifold with fins as shown in figure 8 below. The fins are placed at small distance from the inlet of exhaust gas tubes. In single tube, 3 fins are placed and multiple copies are presented using pattern tool.

Figure 8: Fluid domain definition (with fins)

The simulation is run by defining RMS residual target values of .0001 and number of iterations are set to 200. The convergence plot of mass, momentum and energy are generated at the solution stage. .

V. Results and discussion

The simulation results are obtained for exhaust manifold with and without fins. The results obtained from the analysis include total pressure, temperature, eddy dissipation and turbulence kinetic energy.

Figure 9: Wall heat flux (without fins design)

The wall heat flux plot is obtained from the analysis which represented heat dissipation. The heat flux is observed to be maximum at the intersection region of longitudinal member and 4 inlet tubes. The zones of maximum heat flux are shown in blue color and magnitude of heat flux at this region is 9283W/m2.

Figure 10: Temperature plot (without fins design)

The temperature plot is obtained from the analysis of exhaust manifold without fin design as shown in figure 10 above. The temperature is maximum at the exhaust gas inlet region. As the gas move towards the exit, the temperature increases at the bottom region of exit tube which is shown in blue color with magnitude of 530.7K. The pressure plot is obtained from the CFD analysis and is shown in figure 11 below. The plot shows higher magnitude at the inlet section of tube with magnitude of 3105Pa which is shown in red color. The exhaust gas pressure reduces as it moves towards the exit tube where the pressure is nearly 86.96Pa.

Figure 11: Pressure plot (without fins design)

The turbulence kinetic energy and eddy dissipation plot is generated which is shown in figure 11 and figure 12 below. The turbulence kinetic energy is maximum at the intersection of exit tube and longitudinal member with magnitude of 51.85m2/s2. The change of fluid flow behavior at the corner region causes an increase in turbulence which is represented by high magnitude of turbulence kinetic energy at this zone.

Figure 12 (a): Turbulence kinetic energy (without fins design)

Figure 12 (b): Turbulence eddy dissipation (without fins design)

Similar analysis is also conducted on exhaust system with fins. The heat flux plot obtained from the analysis of finned exhaust manifold is shown in figure 13 below.

Figure 13: Wall heat flux (with fins design)

The heat flux is observed to be maximum at the intersection region of longitudinal member and 4 inlet tubes. The zones of maximum heat flux are shown in blue color and magnitude of heat flux at this region is 9572W/m2.

Figure 14: Temperature plot (with fins design)

The temperature is maximum at the exhaust gas inlet region and then reduces suddenly due to enhanced heat dissipation by incorporated fins. The temperature at the regions near the fins is low. As the gas move towards the exit, the temperature increases at the bottom region of exit tube which is shown in blue color with magnitude of 522.3K.

Figure 15: Turbulence kinetic energy (with fins design)

The turbulence kinetic energy is maximum at the intersection of exit tube and longitudinal member with magnitude of 53.78m2/s2. The change of fluid flow behavior at the corner region causes an increase in turbulence which is represented by high magnitude of turbulence kinetic energy at this zone.

Table 1: Comparison of output

Design Type

Without Fins

With Fins

Turbulence Kinetic Energy  (m2/s2)

51.85

53.78

Max. Temperature (K)

535

522

Heat Flux (W/m2)

9283

9572

 

Figure 16: Turbulence kinetic energy comparison

The turbulence kinetic energy comparison shows higher magnitude for exhaust manifold design with fins as compared to exhaust system design without fins. Similarly, heat flux plot comparison shows higher magnitude for exhaust system with fins which represents higher heat dissipation rate. The exhaust manifold with fins has 289 W/m2 higher heat flux as compared to exhaust system without fins. 

Figure 17: Heat flux comparison

 

Figure 18: Maximum temperature comparison

The temperature comparison plot is obtained for both designs as shown in figure 18 above. The plot shows higher maximum temperature for exhaust system design without fins with magnitude of 535K and maximum temperature for design with fins has 522K. 

 

 

VI. Conclusion

The heat dissipation from exhaust system design can be significantly improved by incorporating fins attached to tubes of exhaust manifold. The thermal characteristics of exhaust manifold system using CFD has shown an enhancement of heat dissipation capability by 3.01%. The incorporation of fins augmented turbulent flow which enhanced heat dissipation capability of exhaust manifold with 2.42% reduction in maximum temperature. Further research can be done in changing material of exhaust system and also by changing turbulence models.  




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