Effect of Spark Plug Position on Performance of Engine Using Openfoam

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International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 11, November 2018, pp. 114–120, Article ID: IJMET_09_11_014 Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=9&IType=11 ISSN Print: 0976-6340 and ISSN Online: 0976-6359

EFFECT OF SPARK PLUG POSITION ON PERFORMANCE OF ENGINE USING OPENFOAM

Akhil Joshi Department of Mechanical Engineering, JSPM’s Rajarshi Shahu College of Engineering, Pune, India

Sachin L. Borse Dawdimi College of Engineering, Shaqra University, Kingdom of Saudi Arabia

Adel Alblawi Dawdimi College of Engineering, Shaqra University, Kingdom of Saudi Arabia

Abed Alrzaq Alshqirate Dawdimi College of Engineering, Shaqra University, Kingdom of Saudi Arabia Alshoubak University College, Al-Balqa' Applied University, Alsalt, Jordan

ABSTRACT The present work is the numerical investigation of Spark Ignition (SI) engines to assess the effect of spark plug positions using open source Computational Fluid Dynamics (CFD) tool, OpenFoam is used. The standard k—ε turbulence model is used along with the Reynolds Averaged Navier Stokes equations for simulating the flow field. Average piston pressure is tracked for different Crank Angles (CA) from −180 o to 180 o for two different sized engines (560cc and 70cc). Results clearly show that spark plug position affects power output of engine. Spark plug position affect p-θ graph, hence performance of engine, this effect is dominant in bigger engine than smaller one. Spark plug position is expressed in dimensionless form in fraction away from centre. Key words: OpenFOAM, Spark Ignition Engine (SI), kivaTest, engineFoam, CFD Cite this Article Akhil Joshi, Sachin L. Borse, Adel Alblawi and Abed Alrzaq Alshqirate, Effect of Spark Plug Position on Performance of Engine Using Openfoam, International Journal of Mechanical Engineering and Technology, 9(11), 2018, pp. 114–120. http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=9&IType=11 1. INTRODUCTION The Spark Ignition (SI) engines are mostly used in bikes, cars and also in small generator. Engine needs to follow certain regulations norms for pollution and at the same time give desired performance. Nowadays Computational Fluid Dynamics (CFD) is used to conduct analysis and optimization of Spark Ignition engine. OpenFOAM, an open source CFD tool has gained

http://www.iaeme.com/IJMET/index.asp 114 [email protected] Akhil Joshi, Sachin L. Borse, Adel Alblawi and Abed Alrzaq Alshqirate researchers attention for CFD analysis in various fields. Module used for spark ignition engine called engineFoam is used has very few papers. The above said CFD tool has not been used like other commercial tools that are available in the market. For SI engine premixed combustion model are used. SI engines are easy to simulate than CI engines as spay physics is not involved [1]. Joshi and Borse [2] used OpenFoam to simulate SI engine with different situations. The effect of spark advance, engine speed variation and number of spark plugs on engine per-formance was studied. Kannan and Srivathsan [3] compared for Cold flow compression and combustion simulations in terms of temperature and pressure for various crank angles. The temperature contours were plotted on a vertical plane inside the cylinder indicates the rise in temperature due to combustion. A new intake port configuration was designed, analyzed by means of 3D CFD simulation and experimentally tested on a turbocharged Spark Ignition (SI) engine, with the aim of addressing the issue of the poor in-cylinder turbulence levels which are typical of the Early-Intake-Valve- Closing (EIVC) adopted at part load to reduce pumping losses. The proposed intake port layout promoted turbulence by increasing the tumble motion at low valve lifts in order to achieve a proper flame propagation speed at part load. A block-structured grid of the above described engine, from the intake to the exhaust duct, was created using the commercial software Star-CD. A standard k–ε turbulence model was used. The calculated in cylinder flow characteristics were related to the experimental combustion [4]. AVL FIRE code was used to simulating spark ignition engine and results were compared with experiments. Computational Fluid Dynamics reduces number of experiments and thus reduces development time and costs. CFD simulated result showed good agreement with experimental results [6]. Full open cycle simulations was performed using the commercial code CONVERGE. The combustion process was simulated using detailed chemistry and adaptive mesh refinement (AMR) to resolve in detail and track the reaction zone. Incylinder pressure, heat release, and flame morphology were compared with experimental indicating and imaging data. Simulations were able to predict experimental data with high accuracy. Variations due to changing fuel type and air-fuel ratio were well captured[5]. A computer simulation was performed by Hepkaya et al.[7] to visualize fluid flow and combustion characteristics of a single cylinder spark ignition engine. The complete engine cycle process (inlet, compression, expansion and exhaust strokes) in gasoline engine model was investigated using RANS (Reynolds Averaged Navier-Stokes) and CFM (Coherent Flame Model) approaches offered by Star-CD/es-ice. Present interesting but difficult to conduct experimentally study was done using free source CFD software OpenFoam. 2. NOMENCLATURE CA Crank Angle L Stroke, m N Speed in rpm P Indicated power between -180 o crank angle to 180 o SI Spark Ignition W work done during -180 o to 180 o Φ Relative Air Fuel Ratio Γ Compression Ratio b Reaction Regress Variable

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d Bore, m l connecting rod length p pressure, Pa r Radial distance of spark from centerline v volume, m3 w work done during 5 degree crank angle 3. COMPUTATIONAL METHODOLOGY Two SI engines are selected for the present work to assess to effect of scale. The engine –A selected for the present work is a pent-roof type with four valves. Engine geometry selected is from openFoam tutorial called KIVA test. This case engine- A with stroke volume 560cc, having dimensions as shown in table 1. Engine-B with stroke volume 70 cc is scaled down geometry of same engine. Dimensions of engine-B are shown in table 1. Computational domain is shown in Figure 1 at crank angle -180 degree. Here one mesh covers the whole simulation. Mesh motion is combined with topological changes. Care is required during generation of mesh so that in top dead centre position aspect ratio of cells is acceptable. Here mesh contains 27544 cells.

Figure 1 Mesh at -180 degree crank angle To access effect of spark plug positions, spark is given at different radial location as shown in table 2 and figure 2. Same dimensionless spark plug location is considered for engine-A and engine-B. Location of spark is considered radial r from cylinder center line as given in table 2 and figure 2. Position are only consider maximum till r/d = 0.7 as it becomes difficult to locate spark plug at near to circumference.

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Table 1 Engine details for the simulation

Items Engine-A Engine-B Engine Pent-roof, 4-valve Pent-roof, 4-valve Connecting rod length 0.147 0.0735 Bore, d, m 0.092 0.046 Stroke, L, m 0.08423 0.042 Clearance, C, m 0.00115 0.000575 RPM, N 1500 1500 spark advance, degree 15 15 fuel iso-octane iso-octane Relative Air Fuel Ratio, Φ 1 1 Compression Ratio, Γ 7.85 7.85

Table 2 Engine details for the simulation Location of spark Location of spark Position r/d ratio Engine-A, r, m Engine-B, r, m 1 0.7 0.0322 0.0161 2 0.6 0.0276 0.0138 3 0.5 0.023 0.0115 4 0.4 0.0184 0.0092 5 0.3 0.0138 0.0069 6 0.2 0.0092 0.0046 7 0.1 0.0046 0.0023 8 0 0 0

Figure 2 Different spark positions in engine (Inside Top view)

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4. RESULTS Engine-A simulation was done from -180 degree crank angle to +180 degree crank angle using engineFoam. As spark advance considered here was 15 degree. Calculations were performed in two steps from -180 degree to -15 degree and -15 degree to 180 degree. To capture combustion, time step is reduced by 10 times from time of spark. Average pressure on piston is calculated after each 5 degree crank angle. Also volume is calculated at each 5 degree crank angle. Figure 3 shows pressure- crank angle diagram. This graph shows that different spark positions give different power curves. But quantitatively not clear about amount of power. Hence to find work done, area under p-v diagram was calculated using numerical technique for integration- trapezoidal rule between each 5 degree crank angle. Indicated power was calculated from work done and RPM of engine. Indicated power for different spark plug positions of engine-A is tabulated in table 3. It is observed that maximum power is obtained if spark plug is at centre of engine. Maximum power reduction found was by 31.5% for spark plug position is 70% offset from center.

Figure 3 Piston averaged pressure vs crank angle for engine-A Engine-B simulation was done from -180 degree crank angle to +180 degree crank angle using engineFoam. Calculations were performed in two steps from -180 degree to -15 degree and -15 degree to 180 degree. To capture combustion, computational time step is reduced by 10 times from time of spark i.e. -15 degree crank angle. Aver-age pressure on piston is calculated after each 5 degree crank angle. Engine volume is calculated at each 5 degree crank angle. Figure 4 shows pressure- crank angle diagram. This graph shows that different spark positions give different power curves. But quantitatively not clear about amount of power. Hence to find work done W, area under p-v diagram was calculated using trapezoidal rule as shown in equation 1-2. As integration is done from -180 crank angle to 180 crank angle, in step of 5 degree crank angle, there will to total 72 terms of trapezoidal to be added. Indicated power was calculated from work done and RPM of engine as shown in equation 3. It is divided by 2 as in two RPM there is one power stroke. Indicated power for different spark plug positions of engine-B is tabulated in table 4. It is observed that maximum power is obtained if spark plug is at center of engine. Maximum power reduction found was by 8.6 % if spark plug position is 70% offset from center. Here spark plug position affects power but not high as big engine-A.

(1) = = ∑

∑ (2) = −

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(3) = ∗ Table 3 Indicated power generated with different spark plug position for engine-A

Spark plug Indicated power, P, Percentage change in power as spark position is shifted position Watt away from center 70% offset 3989 -31.57 60% offset 4908 -15.80 50% offset 5103 -12.45 40% offset 5531 -5.11 30% offset 5326 -8.63 20% offset 5480 -5.99 10% offset 5790 -0.67 No offset 5829 0

Figure 4 Piston averaged pressure vs crank angle for engine-B

Table 4 Indicated power generated with different spark plug position for engine-B Indicated power, P, Percentage change in power as spark Spark plug position Watt position is shifted away from center 70% offset 993.5 -8.60 60% offset 1067 -1.84 50% offset 1051 -3.31 40% offset 1041 -4.23 30% offset 1051 -3.31 20% offset 1064 -2.12 10% offset 1087 0.00 No offset 1087 0.00

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5. CONCLUSION Following conclusions can be drawn from current study, 1. Spark plug positions affect combustion and power output of engine 2. In small engine, spark plug position has little influence on power. But large size SI engine has large effect of spark plug position on power. It was observed that if spark plug is 70% offset from the center then there is reduction of 31.5% power in large engine and 8.6% reduction in small SI engine power as compared to power with spark plug at center. 3. It necessitates that to have more than one spark plug in big engine to complete combustion. REFERENCES

[1] Ganesan, V. Computer Simulation of Spark-Ignition Processes, First Ed. Universities Press, Hyderabad. 1996. [2] Joshi, A. and Borse, S. Study of The Effect of Spark Advance Engine Speed Variation and Number of Spark Plugs on Engine Performance Using CFD Software. Journal of Ocean Mechanical and Aerospace . 48 ,2017 pp. 1-9. [3] Kannan, B.T. and Srivathsan, P. S. Numerical Simulation of Spark Ignition Engine using OpenFOAM. Perspectives in Science . 8, 2016, pp. 13-15. [4] Millo, F., Luisi, S., Borean, F. and Stroppiana, A. Numerical and experimental investigation on combustion characteristics of a spark ignition engine with an early intake valve closing load control. Fuel . 121 , 2014, pp. 298–310. [5] Battistoni, M., Mariani, F., Risi, F., Poggiani, C. Combustion CFD modeling of a spark ignited optical access engine fueled with gasoline and ethanol. Energy Procedia . 82 , 2015, pp. 424 – 431. [6] Mobasheri, R., Fotrosy, Y., Jalalifar and S. Modelling of a spark ignition engine combustion a computational and experimental study of combustion process effects on NOx emission. Asian Journal of Applied Sciences . 2 (4) , 2009, pp. 318-330. [7] Hepkaya E., Karaaslan, S., Uslu, S., Dinler, N. and Yucel, N. A case study of combustion modeling in a spark ignition engine using coherent flame model. Journal of Thermal Science and Technology , 34( 2) , 2010, pp. 111-121.

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