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@IJRTER-2016, All Rights Reserved 105 Analysis of Charge Motion on Inlet Port of Internal Combustion Engines Using CFD Ajoko, Tolumoye John 1 , Tuaweri, Tolumoye Johnnie 2 1 Department of Mechanical/Marine Engineering, Faculty of Engineering. Niger Delta University, Wilberforce Island, Bayelsa State, Nigeria. 2 Department of Mechanical/Marine Engineering, Faculty of Engineering. Niger Delta University, Wilberforce Island, Bayelsa State, Nigeria. AbstractThe task to improve the design and manufacture of Internal Combustion Engines (ICEs) is of significant importance to researchers due to its environmental challenges. Therefore, the presentation of Computational Fluid Dynamics (CFD) code to analyze the charge motion on inlet port of ICEs is focused to meet this target. Hence, this study was carried out by modeling the inlet port of ICE with given engine design specification using Solidworks tool. This computer based tool is user friendly, cost effective and can perform modeling/simulation at a shorter duration with analysis of results. Simulated results attest that irregularities and randomness of the flow motion are caused by turbulence. Results also confirm that the intensity of Turbulent Kinetic Energy (TKE) is maximum at the axial position x = 27 mm which represents the highest strength of the turbulence in the flow. Nevertheless, turbulence is recognised as an important factor that affects charge motion of ICEs. Thus, a critical study on how to control turbulence in the design process of ICE equally controls the combustion process hence limiting exhaust gas emission from the engine system. Therefore, the conducted simulation analysis for charge motion in the inlet port of ICEs is considered feasible and reliable. KeywordsCFD, Charge Motion, ICE, In-Cylinder, Inlet Port, TKE I. INTRODUCTION Environmental degradation such as photochemical smog, acidic rain, dearth of forests and reduction of atmospheric visibility are negative factors emanated from exhaust pollutants of ICEs. Also, incomplete combustion of fossil fuel in ICEs is capable of emitting greenhouse gases which has the tendency of causing global warming of the earth’s climates. These challenges of the ICEs can easily be optimized by controlling the in-cylinder gas motion before ignition process because the charge motion is an important and influential factor responsible for combustion and emission of exhaust gases [1]. Several researchers in their different contributions have demonstrated the substantial role of charge motion on the inlet port of ICEs. In accordance to a reviewed literature; charge motion has a significant impact on heat transfer, also both the gas motion and the turbulence characteristics of the flow are important features in consideration of inlet port analysis [2]. Thus, the in-cylinder flow pattern which is set up by the intake flow process through the intake port is a major element to be considered in the design optimization process of ICEs, since intake flow generates charge motion responsible for quality mixture and combustion [3]. However, an accurate estimation of ICEs volumetric efficiency depends on the charge motion generated at the intake stroke [4]. Comprehensive study reveals charge motion at the in-cylinder as swirl and tumble motion producing rotational flow about the cylinder axis and rotation of the in-cylinder charge about the axis perpendicular to the cylinder bore respectively inside the combustion chamber to increase turbulence intensity (u') and mean gas flow velocity before spark timing [5]. Also swirl is an important factor in both Spark Ignition (SI) and ICEs because it speeds up the combustion process in SI engines as well as controls the air-fuel mixture to give homogeneous mixture in a very short period of time in diesel
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Page 1: Analysis Of Charge Motion On Inlet Port Of Internal ... · PDF fileAnalysis of Charge Motion on Inlet Port of Internal Combustion Engines Using CFD Ajoko, Tolumoye John 1, Tuaweri,

@IJRTER-2016, All Rights Reserved 105

Analysis of Charge Motion on Inlet Port of Internal Combustion

Engines Using CFD

Ajoko, Tolumoye John1, Tuaweri, Tolumoye Johnnie

2

1Department of Mechanical/Marine Engineering, Faculty of Engineering. Niger Delta University, Wilberforce Island, Bayelsa State, Nigeria.

2Department of Mechanical/Marine Engineering, Faculty of Engineering. Niger Delta University, Wilberforce Island, Bayelsa State, Nigeria.

Abstract— The task to improve the design and manufacture of Internal Combustion Engines (ICEs) is of significant importance to researchers due to its environmental challenges. Therefore, the presentation of Computational Fluid Dynamics (CFD) code to analyze the charge motion on inlet port of ICEs is focused to meet this target. Hence, this study was carried out by modeling the inlet port of ICE with given engine design specification using Solidworks tool. This computer based tool is user friendly, cost effective and can perform modeling/simulation at a shorter duration with analysis of results. Simulated results attest that irregularities and randomness of the flow motion are caused by turbulence. Results also confirm that the intensity of Turbulent Kinetic Energy (TKE) is maximum at the axial position x = 27 mm which represents the highest strength of the turbulence in the flow. Nevertheless, turbulence is recognised as an important factor that affects charge motion of ICEs. Thus, a critical study on how to control turbulence in the design process of ICE equally controls the combustion process hence limiting exhaust gas emission from the engine system. Therefore, the conducted simulation analysis for charge motion in the inlet port of ICEs is considered feasible and reliable. Keywords— CFD, Charge Motion, ICE, In-Cylinder, Inlet Port, TKE

I. INTRODUCTION Environmental degradation such as photochemical smog, acidic rain, dearth of forests and

reduction of atmospheric visibility are negative factors emanated from exhaust pollutants of ICEs. Also, incomplete combustion of fossil fuel in ICEs is capable of emitting greenhouse gases which has the tendency of causing global warming of the earth’s climates. These challenges of the ICEs can easily be optimized by controlling the in-cylinder gas motion before ignition process because the charge motion is an important and influential factor responsible for combustion and emission of exhaust gases [1].

Several researchers in their different contributions have demonstrated the substantial role of charge motion on the inlet port of ICEs. In accordance to a reviewed literature; charge motion has a significant impact on heat transfer, also both the gas motion and the turbulence characteristics of the flow are important features in consideration of inlet port analysis [2]. Thus, the in-cylinder flow pattern which is set up by the intake flow process through the intake port is a major element to be considered in the design optimization process of ICEs, since intake flow generates charge motion responsible for quality mixture and combustion [3]. However, an accurate estimation of ICEs volumetric efficiency depends on the charge motion generated at the intake stroke [4]. Comprehensive study reveals charge motion at the in-cylinder as swirl and tumble motion producing rotational flow about the cylinder axis and rotation of the in-cylinder charge about the axis perpendicular to the cylinder bore respectively inside the combustion chamber to increase turbulence intensity (u') and mean gas flow velocity before spark timing [5]. Also swirl is an important factor in both Spark Ignition (SI) and ICEs because it speeds up the combustion process in SI engines as well as controls the air-fuel mixture to give homogeneous mixture in a very short period of time in diesel

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International Journal of Recent Trends in Engineering & Research (IJRTER)

Volume 02, Issue 10; October - 2016 [ISSN: 2455-1457]

@IJRTER-2016, All Rights Reserved 106

engines as the rotation of charges is about the cylinder axis [6]. Therefore, this is a baseline support that the charge motion of the in-cylinder fluid of ICEs is a controlling tool of combustion process in these engines. Meanwhile, the swirl and tumble are created in the intake and compression strokes of the engine as a result of the inlet port shape and orientations because they are known approaches to enhance in-cylinder turbulence accelerating combustion process by promoting higher levels of combustion efficiency [7].

This performance analysis in the ICEs can be proficiently handled by the use of a computer based tool popularly known as Computational Fluid Dynamics (CFD). Meanwhile, a research paper identifies the capability of CFD simulation of tumble and swirl flow motions at the intake of an inlet port; analyzing the mixture of a single phase flow with air inside the swept volume for a steady state condition [8]. CFD is an effective and efficient tool designers used to evaluate and modify boundary conditions on ICE ports which reduces the amount of experimentation necessary to develop a new product in reducing design time and cost. However, with the difficulties to model the combustion process in ICEs; CFD has been proven capable to characterize engine performance, gas flow, and heat transfer within and outside the engine system, etc. [9,10].

Hence, the CFD code is capable of generating accurate results in few hours by exploring Ansys Fluent package of the tool to provide complete information of charge motion on the inlet port of the model. Thus, this investigation is carried out to aid the design of effective inlet port of ICEs in order to reduce the numerical errors with fewer numbers of iterations with proper analysis of charge motion. Therefore, the significance of the study is toward the development of ICEs as the optimization of the inflow through intake ports since the charge movement generated by the intake flow considerably influences the quality of mixture and combustion especially in diesel engines. Also, the task for the engine to meet the demands for increased performance, decreased emissions and increased efficiency is a focal point of the study. Layout of the intake ports is one major concern because an increase in specific power; for instance needs a subsequent increase in mass flow rate through the intake and exhaust ports. However, this study highlights and analyses a new concept for intake port design aimed at meeting existing and future challenges of ICEs.

II. SIMULATION FLOW CHART Figure 1 is a simulation flow chart describing the summary of ICE inlet port modeling process in solidworks and CFD simulation calculation.

III. ICE INLET PORT MODELING The modeling of the inlet port of the ICE is carried out in Solidworks interface. This design tool

has the capacity and clear understanding of the fluid dynamics of turbulent reacting flows with moving parts through the intake/exhaust manifolds, valves, cylinder, and piston of ICEs. In order to capture the actual design configuration of the inlet port; engine specifications and calculation

Figure 1. Flow Chart for Summary of the Simulation Process

Hybrid Mesh Generation Hexcore Mesh Generation

Running Simulation Calculation

Post-processing of results

CFD Solver

Modeling of Inlet Port

Meshing Generation of Model

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International Journal of Recent Trends in Engineering & Research (IJRTER)

Volume 02, Issue 10; October - 2016 [ISSN: 2455-1457]

@IJRTER-2016, All Rights Reserved 107

parameters on table 1 was used. Thus, for accurate analysis of charge motion in ICEs inlet port, certain performance parameters are considered. For instance, the air charge in the cylinder is compressed to high temperature to ensure that fuel ignites spontaneously when it is injected into the cylinder. Meanwhile, this compression ratio is chosen to achieve the desired air temperature in the cylinder at the end of compression [11]. Hence, equations 1 and 2 are governing equations to determine the temperature and pressure of charge motion of air while the final temperature, T2 in equation 3 depends upon the initial temperature of the air in the cylinder as well as the compression ratio, V1/V2. It is observed that reduction in initial temperature or leakage of air from the cylinder will reduce the final air temperature which could influence fuel ignition process. Therefore, this is considered with top priority in the design/modeling process.

Table 1. Engine Specifications and Calculation parameters

Parameter Specification Bore by Stroke 95mm × 99mm Compression ratio 09:01 Max power at WOT 12.2BHP at 4950RPM Intake Valve diameter 42mm Maximum Intake valve lift 12mm Piston Cavity Flat Exhaust Valve Opening 64o BBDC Exhaust Valve closure 5o ATDC Intake Valve Opening 5o BTDC Intake Valve Closure 60o ABDC Fuel C8H18

= (1)

= (2)

T2 = T1[ (3)

IV. MODEL DISCRETIZATION

The model is discretized using a finite volume method, the advanced meshing tools in Ansys Fluent is use for the meshing. Boundary meshes created in Solidworks package are imported using the appropriate menu item in the file/import of CFD Ansys fluent tool. A hybrid volume mesh is generated based on meshing objects from a faceted geometry. In this case, conformal connected surface mesh is created using the object wrapping and sewing operations before generating the volume mesh. Alternatively, the Cut Cell mesher is used to directly create a hex-dominant volume mesh for the geometry imported from based on meshing objects. Elements generated are tetrahedron while others are hexahedron and triangular in shape. Ansys Fluent functions as a robust, unstructured grid generation program that can handle grids of virtually unlimited size and complexity. The unstructured grid generation techniques couple basic geometric building blocks with extensive geometric data to automate the grid generation process. Figure 2 shows the mesh of the model using Ansys meshing tool. The mesh patching approach is used in a way that allow for mesh control in regions of interest. The meshing allows the fluid equations to be solved for each volume and each node.

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International Journal of Recent Trends in Engineering & Research (IJRTER)

Volume 02, Issue 10; October - 2016 [ISSN: 2455-1457]

@IJRTER-2016, All Rights Reserved 108

Figure 2. Mesh of the Computational Domain

V. STEADY STATE CFD CALCULATION

At the completion of the mesh generation process, the meshed model is transferred to solution mode using the mode toolbar or the command switch-to-solution-mode. Thus, at this interface; operations like the boundary conditions setting, definition of the fluid properties; solution execution, run simulation calculation, viewing and post-processing of the results are performed. The solution is set as multiphase flow since it includes fuel and air at the inlet port of the ICE with definition of fuel mass flow rate as 0.0325kg/s. Other fluid properties of the solution defined are the temperature, density, pressure, velocity, etc. Boundary zone type is set to ‘pressure-far-field’ with walls assumed as adiabatic and no-slip condition.

This multidimensional CFD simulation tool allows designers to simulate and visualize the complex fluid dynamics by solving the governing physical laws for mass, momentum, and energy transport on the 3D geometry. In this study were charge motion on inlet port of ICE is analyses, it is imperative to evaluate the Turbulence Kinetic Energy (TKE) equation to measure the intensity of turbulence. Therefore, to measure the intensity of turbulence; the separation of turbulent scale motions from non-turbulent scale motions and TKE equation in equations 4 & 5 respectively are obtained from a review literature for the corresponding CFD calculation [12].

Ã(S) = (4)

TKE/m = ē = (uˊ2 + vˊ2 + wˊ2) = ( ) (5)

Also in order to perform perfect simulation analysis, the compressible Navier-Strokes equation for

mass, momentum and energy calculations are performed. Thus pressure based segregated solver is used to solve the transport equation with respect to the above measurement parameters. In this case, Realizable κ − ε is used to capture the rotational charge motion and other features of the flow. Meanwhile, the accurate presentation of flow in the wall region request the non-equilibrium wall function used to predict wall restricted turbulent flows because the flow walls are characterized as the source of vorticity and turbulence. Hence, the steady air flow calculations for circumferential air speed, axial speed of the air flow and theoretical volumetric flow rate across the system are performed for different lift conditions to investigate the fluid charge motion in respect to equations 6 – 8.

Cu = πDMFLN (6)

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International Journal of Recent Trends in Engineering & Research (IJRTER)

Volume 02, Issue 10; October - 2016 [ISSN: 2455-1457]

@IJRTER-2016, All Rights Reserved 109

(7)

(8)

VI. ANALYSIS OF RESULTS

Graphical illustration presented in figure 3 shows a plot of circumferential air speed against theoretical volumetric flow rate of the system. Also a similar relationship between circumferential air speed and axial velocity is demonstrated in figure 4. These plots are made possible with the help of simulated results presented in table 2. However, other procedures in the set – up – physics carried out in the modelling/simulation process of the charge motion in the inlet port of ICE are shown in appendix – 1.

4.5

4.6

4.7

4.8

4.9

5

0.00768 0.00772 0.00776 0.0078 0.00784 0.00788 0.00792

Theoretical Volumetric Flow Rate

Circum

fere

ncia

l Air S

peed

Figure 3. Circumferential Air Speed against Theoretical Volumetric Flow Rate

4.5

4.6

4.7

4.8

4.9

5

5.66 5.68 5.7 5.72 5.74 5.76 5.78 5.8 5.82

Axial Velocity

Circum

fere

ncia

l Air S

peed

Figure 4. Circumferential Air Speed against Axial Velocity

Table 2. CFD Simulation Results

Lift Circumferential Velocity (Cu) Vreal Axial Velocity, CA Low 4.925085 0.00787 5.681522046

Medium 4.62725482 0.00779 5.738911158 High 4.56268672 0.00771 5.797471476

The distribution of turbulent kinetic energy in the whole space of the combustion chamber was

studied; hence figure 5 shows graphical plot of TKE against the increasing radial coordinate which gives distance from the cylinder axis to the lateral wall. All plots are taken for crank angle ϴ equal to 90°.

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International Journal of Recent Trends in Engineering & Research (IJRTER)

Volume 02, Issue 10; October - 2016 [ISSN: 2455-1457]

@IJRTER-2016, All Rights Reserved 110

Figure 5. TKE for ϴ=90

o

VII. DISCUSSIONS

From the CFD prediction of the plot of circumferential velocity against theoretical volumetric flow rate in figure 3 and axial velocity in figure 4; it is obvious that the graphs are identical though reversely plotted. The symmetric line of plot for the two graphs demonstrates linearity at the low and medium lifts but suddenly it tends to the high lift as curve. This deviation is due to non-uniform mass flow rate across the engine system under study. This also verifies that the charge motion around the inlet port of ICEs is not the same, mostly in the combustion chamber of the engine.

Again, results from the plots confirm TKE analysis in figure 5. It shows TKE simulation of axial position, x of 77mm (green plot), 52mm (blue plot) and 27mm (red plot) obtaining TKE values as 27m2s-2, 26.5m2s-2 and 37m2s-2 respectively from the CFD graphical result. This difference in values gives the different curves presented. Thus, figure 5 confirms that for the same time setup, the intensity of the TKE is maximum for the axial position x = 27 mm which represents the highest strength of the turbulence in the flow. This explains that the region is near the air admission zone where flow motion is disorganized. Hence; in the three curves, the peak of turbulence is obtainable for radial coordinate r = 2.9m, whereas the smaller peak of turbulence appears near the cylinder axis and simulation flow of axial position 52mm lying on the cylinder wall as indicated in the illustration.

VIII. CONCLUSION

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International Journal of Recent Trends in Engineering & Research (IJRTER)

Volume 02, Issue 10; October - 2016 [ISSN: 2455-1457]

@IJRTER-2016, All Rights Reserved 111

The aim and objective of the present are justifiable due to the following reasons as also confirmed from open literature. Thus established results reveal that:-

� The CFD simulation tool was capable to recognise turbulence as a prime cause of irregularities and randomness of the flow motion close to the air admission zone.

� The flow motion otherwise known as charge motion is disorganised due to the intensity of turbulence.

� Turbulence is identified as an important factor that affects charge motion of ÏCEs. Thus the control turbulence in the design process of ICE equally controls the combustion process hence limiting exhaust gas emission from the system.

� CFD simulation tool identified TKE as a unique measure of turbulence in engine systems. Consequently, the relevance of this study leads to an improved design of ICEs free of

environmental risk and challenges which can stand the test of time. Also this application can be extended to other models of diesel engines. However for future research, simulation of multiphase fuel/air mixing process in the clearance and swept volumes of ICEs will further enhance the design process. NOMENCLATURE

P1 Initial Air Pressure in Cylinder P2 Final Air Pressure in Cylinder T1 Initial Air Temperature in Cylinder T2 Final Air Temperature in Cylinder V1 Initial Cylinder Volume V2 Final Cylinder Volume � Index of Air Compression à Mean of non-turbulent flow T Time interval of spectral gap S Spatial variable A Variables (e.g temperature or velocity field) DMFL Mean paddle wheel diameter N Paddlewheel speed Cu Circumferential air speed CA Axial speed of the air flow

Theoretical volume flow rate Dcyl Cylinder bore diameter

Density under test ambient conditions Density under standard ambient conditions

Test ambient pressure Test ambient temperature

Standard ambient pressure Standard ambient temperature

REFERENCES 1. D. Nureddin and Y. Nuri, “Numerical Simulation of Flow and Combustion in an Axisymmetric Internal Combustion

Engine,” International Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing Engineering, Vol.1, No.12, pp.692 – 697. 2007.

2. J. B.L. Heywood, Internal Combustion Engine Fundamentals, New York: McGraw-Hill, Inc., 1988. 3. P. Laxmikant and A. P. Narkhede, “Optimization for Intake Port,” International Journal of Mechanical and

Production Engineering Research and Development (IJMPERD), Vol.4, No.2, pp.35-42, 2014. 4. H. Mohamed Niyaz and A. S. Dhekane, “Twin Helical Intake Port Design Optimization and Validation By Using

CFD Analysis,” International Journal of Emerging Technology and Advanced Engineering, Vol.4, No.4, 2014. 5. M. S. Yuesheng He, Effect of Intake Primary Runner Blockages on Combustion Characteristics and Emissions in

Spark Ignition Engines, ( Unpublished doctoral dissertation). Ohio State University, Columbus, United States. 2007.

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International Journal of Recent Trends in Engineering & Research (IJRTER)

Volume 02, Issue 10; October - 2016 [ISSN: 2455-1457]

@IJRTER-2016, All Rights Reserved 112

6. K. M. Pandey and R. Bidesh, “CFD Analysis of Intake Valve for Port Petrol Injection SI Engine,” Global Journal of Researches in Engineering, Vol.12, No.5, pp.13 – 19, 2012.

7. F. Stefania, B. Federico and P. Piero, “3D CFD analysis of the influence of some geometrical engine parameters on small PFI engine performances – the effects on the tumble motion and the mean turbulent intensity distribution,” 68th Conference of the Italian Thermal Machines Engineering Association, ATI2013, Vol. 45, pp.701-710, 2014.

8. A. M. Mohd Shafie1, M. T. Musthafah, M. S. Ali, A. B. Rosli, and A. Y. Mohamed, “Intake Analysis on Four-Stroke Engine using CFD,” ARPN Journal of Engineering and Applied Sciences, Vol.10, No.17, 2015.

9. T. George, “CFD modelling and analysis of an opposed piston internal combustion engine,” (Unpublished MSc Thesis). University of Wollongong, Australia, 2009.

10. K. B. Vinodh, N. Sivagaminathan, N. Gopalakrishnan, M. Scott, and R. Paul, “Air Flow and Charge Motion Study of Engine Intake Port.,” Proc. 37th National and 4th International Conference on Fluid Mechanics and Fluid Power, Vol.10, pp.26-30, 2009.

11. G. Denis, Steam Plant and Diesel Engines. (Unpublished MSc Lecture Note). Cranfield University, Cranfield – UK, 2008.

12. Š. Matic, and Ž. Nedjeljka,, Turbulence kinetic energy – TKE (Unpublished Seminar). University of Ljubljana, Slovenia, 2012.

APPENDIX

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International Journal of Recent Trends in Engineering & Research (IJRTER)

Volume 02, Issue 10; October - 2016 [ISSN: 2455-1457]

@IJRTER-2016, All Rights Reserved 113


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