Simulation of Suction Process of Gasohol Fuelled S. I. Engine Using Computer Program

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1 Simulation of Suction Process of Gasohol Fuelled S. I. Engine Using Computer Program MAHENDRAKUMAR MAISURIA, DIPAKKUMAR GOHIL & Dr. SALIM CHANNIWALA Department of Mechanical Engineering S. V. National Institute of Technology Surat , Gujarat State INDIA Abstract: - This paper pertains to the modeling of the suction stroke in the engine of the Fiat car. The modeling of the suction stroke is done and its simulation is carried out using computer program. Subsequently the values of pressure, volume, temperature and mass fraction are found out for each increment in crank angle (θ) using the same model by simulation. Key words: - Simulation, Modeling, Realistic, Analytical, Algorithm, Gasohol, Stoichiometry, Suction, S. I. Engine. 1 Introduction Computers are used to imitate or simulate the operations of various kinds of real world facility processes. The facility or process of interest is usually called a system, and in order to study it scientifically, we often have to make a set of assumptions and how it works. These assumptions, which usually take a form of mathematical or logical relationship, constitute a model that is used to try to gain some understanding, how the corresponding system behaves. If the relationships that compose the model are simple enough, it may be possible to use mathematical models (such as algebra, calculus or probability theory) to obtain exact information on questions of interest; this is called an analytical solution. However most world systems are too complex to allow realistic models to be evaluated analytically and these models must be studied by means of simulation. In a simulation, we use a computer to evaluate a model numerically, and data is gathered in order to estimate true characteristics of the model. Application areas are for simulation and numerous and diverse. Below is a list of some particular kinds of problems for which simulation has been found to be useful and powerful tool: Designing and analyzing manufacturing systems. Evaluating hardware and software requirements for a computer system. Evaluating a military weapons systems or tactic. Determining ordering policies for inventory system. Designing communications system and message protocols for them. Designing and operating transportation facilities such as hospitals, post offices or fast food restaurants. Analyzing financial or economic systems. 2 Simulation of the gasohol fuelled 4- stroke S. I. engine 2.1 Stoichiometry Equations of combustion Gasoline C 8.26 H (O N 2 ) 8.26 CO H 2 O N 2 Ethanol C 2 H 5 OH + 3 (O N 2 ) 2 CO 2 + 3H 2 O N 2 Suppose we take combustion of 90% Gasoline and 10% of Ethanol separately, Gasoline 0.9[(C 8.26 H (O N 2 )] [8.26CO H 2 O N 2 ] x 0.9 Ethanol 0.1[C 2 H 5 OH +3(O N 2 )] [2 CO 2 +3 H 2 O N 2 ] x 0.1 Hence, the total combustion equation becomes 0.9 C 8.26 H C 2 H 5 OH (O N 2 ) CO H 2 O N Calculation of fuel air ratio Mass of one mole of gasohol 0.9 C 8.26 H C 2 H 5 OH ISSN: ISBN:

2 (0.9 x (12 x x 15.5)) + (0.1 x (12 x x x 1)) gm wt Mass of air (O N 2 ) ( x (16 x x 28)) gm wt Air/Fuel Ratio (Mass of air)/ (Mass of one mole of gasohol) / Calculation of mass fraction, R, C p, C v, γ of various species for charge on reactant side Mass of one mole of Gasoline (0.9 x (12 x )) gm wt Mass on one mole of Ethanol (0.1 x (12 x )) 4.6 gm wt Mass of one mole of Oxygen x (16 x 2) gm wt Mass of one mole of Nitrogen (28 x 3.761) gm wt Total mass of mole of charge gm wt 1. Mass fraction of Gasoline / Mass Fraction of Ethanol 4.6 / Mass Fraction of Oxygen / Mass Fraction of Nitrogen / R gasoline R / (molecular mass) 8314 / J/kg K R ethanol R / (molecular mass) 8314 / J/kg K RO 2 R / (molecular mass) 8314 / J/kg K RN 2 R / (molecular mass) 8314 / J/kg K R charge m gasoline R gasoline + m ethanol R ethanol + mo 2 RO 2 + mn 2 RN x x x x J/kg K Cp gasoline [ T 8.44 x 10-4 x T x 10-7 x T 3 + (2.431 X 10 6 / T 2 )] / J/kg K Cp ethanol [ T x 10-5 x T 2 ] / kj/kg K CpO 2 [ x 10-2 T x 10-5 x T x 10-9 T3] / kj/kg K CpN 2 [ x 10-2 T T 2 ] / kj/kg K Where T is in Kelvin for charge 300 K Cp charge Σ (m i Cp i ) m gasoline Cp gasoline + m ethanol Cp ethanol + mo 2 CpO 2 + mn 2 CpN x x x x kj/kg K Cp Cv R Cv J/kg K γ Cp / Cv / Calculation of mass fraction, R, Cp, Cv, γ of various species for charge on product side ISSN: ISBN:

3 Mass of one mole of CO ( x 2) gm wt Mass of one mole of H 2 O (1 x ) gm wt Mass of one mole of N (14 x 2) gm wt Total Mass of one mole of exhaust gm wt 1. Mass Fraction of CO 2 (Mass of one mole of CO 2 / Total mass of one mole of exhaust products) / Mass Fraction of H 2 O (Mass of one mole of H 2 O / Total mass of one mole of exhaust products / Mass Fraction of N 2 (Mass of one mole of N 2 / Total mass of one mole of exhaust products) / R CO2 R H2O R N2 R / (molecular mass) 8314 / J/kg K R / (molecular mass) 8314 / J/kg K R / (molecular mass) 8314 / J/kg K R exhaust Σ (m i R i ) m H2O R H2O + m CO2 R CO2 + m N2 R N x x x J/kg K Cp CO2 [ x 10-2 T x 10-5 x T x 10-9 T 3 ] / kj/kg K Cp H2O [ x 10-2 T x 10-5 x T x 10-9 T 3 ] / kj/kg K Cp N2 [ x 10-2 T x 10-5 x T 2 ]/ kj/kg K Where T is in Kelvin for charge 553 K Cp exhaust Σ (m i Cp i ) m H2O Cp H2O + m CO2 Cp CO2 + m N2 Cp N x x x kj/kg K Cp exhaust Cv exhaust R exhaust Cv exhaust J/kg K γ exhaust Cp exhaust / Cv exhaust γ exhaust Modeling of suction process During this stroke, the charge (Gasohol + Air) enters into the cylinder. It mixes the exhaust gases that are left out in the exhaust stroke. Entry of the charge takes place only when pressure inside the cylinder falls below the atmospheric pressure even when the inlet valve is opened. In the modeling of this process, we assumed that the initial pressure of the exhaust gases inside the cylinder to be bar and the temperature to be 553 K. Later the final values of pressure and temperature obtained at the end of exhaust stroke are re-iterated back to get correct pressure and temperature for this stroke. This process gives the in formation about when the valve should open and when it should close. Hence, the final properties of the charge inside the cylinder depend only on the ambient temperature and pressure for a given engine. 3.1 Assumptions The assumptions made for the analysis of the suction process are as follows: The suction process starts at TDC i.e. θ 12º and ends at BDC i.e. θ 236º. Charge is taken as to behave as an ideal gas. Heat transfer area comprises of piston head, cylinder head and cylinder wall surface only. Leakage of gases is neglected. ISSN: ISBN:

4 4 Suction process algorithms The algorithm of the suction process includes the formulae of change in volume, mass, specific heat of charge, temperature, piston velocity, fluid velocity, heat transfer coefficient of the assembly, surface area of heat transfer, wall temperature, convective heat transfer, specific heat of charge and exhaust gases, gas constants of charge and exhaust gases and change in pressure. The algorithm calculates the values of pressure, volume, temperature, and mass of charge for each increment of crank angle (Theta) and these values are represented graphically. The values of crank angle are iterated at regular intervals of 2 starting from 12 to 236. Step 1: START Step 2: Assume values of P old, T old, γ. Here γ is of exhaust gases. Step 3: Find volume inside the cylinder π V V 0+ 4 B l + r - l - r sin θ - rcosθ Step 4: Find the mass of charge enter in to cylinder 1/γ γ - 1/γ C*A d planner*patm P old 2γ P old dm 1 - dt R P charge*tatm atm γ-1 P atm Step 5: Now total mass in to the cylinder, M M old + dm. Here M old initially will be M exh. Step 6: Now Cp of mixture inside cylinder will be, M old*cp old +dm*cpcharge Cp M Step 7: Now temperature of mixture will be, dm*cp *T +M *Cp *T T M *Cp charge atm old old old Step 8: Find the velocity of piston, sin2θ Vωr p sinθ n - sin θ Step 9: Fluid Velocity will be, W mv C 1 V p. Step 10: Heat Transfer coefficient, Woschni s equation h 0.82 * B * P * W * T 1/ old mv Step 11: Surface area of heat transfer will be π 2 πbl 2 2 A surface B + n cosθ - n - sin θ 2 2 Step 12: Wall temperature, T wall ( θ) Step 13: Q conv h x A surface (T wall T mean ) dt Step 14: Find Cp N2, Cp H2O, Cp CO2, Cp gasoline, Cp ethanol & Cp O2. Step 15: Find value of Cp for whole mixture, Cp [m exh / m total] mn Cp 2 N + m 2 H2OCp H2O+ mco Cp 2 CO2 + (m charge /m total) [mgasolinecp gasoline + methanolcp ethanol + mo Cp 2 O + 2 m Cp ] N2 N2 Step 16: Corresponding value of gas constant ( dm*r charge +M old*r old ) R Mtotal Step 17: Corresponding value of Cv and γ will be Cv Cp R γ Cp / Cv Step 18: Now, correct temperature with heat transfer consideration will be, Q T + T ( M *Cv ) Step 19: Find corrected pressure using, T *R *M P corr V Step 20: Now if (γ γ) and (P corr P old ) out of certain limit, then assign γ γ and P old P corr and put it in step 4 and repeat procedure. Step 21: When (γ γ) and (P corr P old ) fall within certain limit, print P corr, V, T, γ, dm. Step 22: Replace old values of P, V, γ, T & Cp by values and repeat whole procedure for whole suction process. Step 23: STOP 5 Results & discussion From the results of simulation (refer Fig. 1, 2, 3, 4) it is concluded that the trend of pressure & temperature with increase in crank angle is quite logical to the actual ISSN: ISBN:

S.I. engine. The Experimental results are shown alongwith and found in good agreements. During suction process, pressure falls to 0.789 bar at 54 degree crank angle (Fig. 4) after TDC.

According to Winterborne & Pierson, if the wave action theory is included in the intake system, it utilizes the ramming effect of the traveling compression wave in the inlet system, which will

The valve flow area calculated by Heywood & Gordon s approach shows that due to stamp area correction employed by Heywood, during dwell period, more flow area is obtained by the Gordon s approach.

This may be explained on the basis of the fact that the increase in initial valve lift is very slow and hence the flow area is not sufficient; as a result the rate of charge intake is less than the

5 S.I. engine. The Experimental results are shown alongwith and found in good agreements. During suction process, pressure falls to bar at 54 degree crank angle (Fig. 4) after TDC. Initial fall of pressure in the suction stroke was also observed by Blair & Lumley. According to Winterborne & Pierson, if the wave action theory is included in the intake system, it utilizes the ramming effect of the traveling compression wave in the inlet system, which will improve the trend of pressure curve. The valve flow area calculated by Heywood & Gordon s approach shows that due to stamp area correction employed by Heywood, during dwell period, more flow area is obtained by the Gordon s approach. To indirectly take care of ramming effect in the present analysis, Gordon s approach is adopted. This may be explained on the basis of the fact that the increase in initial valve lift is very slow and hence the flow area is not sufficient; as a result the rate of charge intake is less than the rate at which volume expansion occurs in cylinder due to piston movement. It is obvious by initial period of suction process, one is the flow area increased the rate of charge intake increase and hence the pressure continues to increase. However during the latter stage of the suction once again due to charge availability of flow rate area, the rate of pressure rise gradually decreases. Due to this, temperature also decreases rapidly and than slowly approaches to a value of atmosphere. 6 Conclusions In nut-shell it is stated that the present simulation program, which takes care of Cp, Cv and heat transfer variation at every 2 o of crank rotation and thus offer quite realistic results. Hence, it may be considered as a versatile program to stimulate gasohol fueled S. I. Engine. References: [1] Blair G.P., Design and Simulation of Four Stroke Engines, SAE Publication, [2] Low S.C. and Baruah P.C., A Computerized Aided Design package for IC Engine Manifold System SAE Paper No , [3] Blair G.P., Empiricism and simulation in the design of the high performance four strokes engine, SAE , [4] Heywood J.B., Internal combustion engine fundamentals, Tata Mcgraw Hill Book Company, [5] Woschni G. A universally applicable equation for the instantaneous heat transfer coefficient in the internal combustion engine, SAE , [6] Nusselt W., VDI-Forsch, [7] Ogury T. Determination of rate of heat transfer between the gases and the cylinder walls of spark ignited ISSN: ISBN:

6 engines, Bulletin of the faculty of engineering, Yokohama National University, Vol. IX, [8] Wimmer A., Pivec R. and Sams T., Heat transfer to the combustion chamber and port walls of IC engines measurement and prediction, SAE , [9] Ganesan V., Computer Simulation SI engine process, Universities Press (India) limited, [10] Benson R.S., Anand W.J.D. & Baruah P.C., A simulation model including intake and exhaust systems for a single cylinder four stroke engine, Int. J. Mech. Sci. Pergamon Press, Vol. 17, [11] Benson R.S., Internal Combustion Engines, Vol. II, Claredon Press, Oxford, [12] Borman G.L., Mathematical simulation of internal combustion engine processes and performance including comparison with experiment, Ph-D. Thesis, Submitted at University of Wiscosin, [13] Fan L. & Reitz R.D., Development of an ignition and combustion model of spark ignition engines, SAE , [14] Shen H., Hinze P.C., and Heywood, J. B., A Study of Cycle to cycle variations in SI engine using a modified Quasi-Dimensional Model, SAE , [15] Tinaut F.V. Gimenez B., Horrilo A.J. & Cabaco G. Use of multi-zone combustion models and predicts the effects of cyclic variations on SI engine, SAE , [16] Rattan S.S., Theory of Machines, Tata Mc Graw Hill, Publishing Co., Ltd., New Delhi, [17] Nedunchezhian, N & Dhandapani, S., Experimental investigations of cyclic variation of combustion chamber, Indian journal of Engineering Today, Vol-2 (2000). [18] Jehlik, Forrest, Jones, Mark, Shephard, Paul, Development of a Low-emission, Dedicated Ethanol- Fuel Vehicle with cold start Distillation system, [19] M.V.S. Murlikrishna, &C.M. Vara Prasad Investigations on reduction of CO from copper coated spark ignition engine with catalytic converter, FNCTS ISSN: ISBN:

Temperature distribution and heat flow across the combustion chamber wall.

ΜΕΤΑΔΟΣΗ ΘΕΡΜΟΤΗΤΑΣ ΣΤΟΝ ΚΥΛΙΝΔΡΟ (J.B. Heywood: Internal Combustion Engine Fundamentals McGraw Hill 1988) Temperature distribution and heat flow across the combustion chamber wall. Throughout each engine