6340(Print), ISSN (Online) TECHNOLOGY Volume 3, Issue (IJMET) 2, May-August (2012), IAEME

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1 INTERNATIONAL International Journal of JOURNAL Mechanical Engineering OF MECHANICAL and Technology ENGINEERING (IJMET), ISSN 0976 AND 6340(Print), ISSN (Online) TECHNOLOGY Volume 3, Issue (IJMET) 2, May-August (2012), IAEME ISSN (Print) ISSN (Online) Volume 3, Issue 2, May-August (2012), pp IAEME: Journal Impact Factor (2012): (Calculated by GISI) IJMET I A E M E ANALYSIS OF INTERNAL COMBUSTION ENGINE HEAT TRANSFER RATE TO IMPROVE ENGINE EFFICIENCY, SPECIFIC POWER & COMBUSTION PERFORMANCE PREDICTION ABSTRACT Pratima S. Patil 1, S.N.Belsare 2, Dr.S.L.Borse 3 1 Mechanical Department, JSPM s RSCOE, Pune University, Pune, India 2 Mechanical Department JSPM s RSCOE, Pune University, Pune, India 3 Mechanical Department JSPM s RSCOE, Pune University, Pune, India (pratima.image@gmail.com,shrikantbelsare@gmail.com, sachinlb@yahoo.co.uk) This paper addresses the analysis of Internal Combustion Engine heat transfer rate at various locations, which is very important for thermal load analysis, combustion performance prediction & efficiency of an internal combustion engine. Specific power and efficiency are affected by the magnitude of engine heat transfer. This paper focuses on a substantial difference of heat flux exists for various places in the cylinder of an engine. Numerical computation is an appropriate tool to study heat transfer in comparison with available experimental correlations. Keywords Spark ignition engine, Heat flux, Thermocouples, Heat transfer, Energy distribution 1. INTRODUCTION The peak burned gas temperature in the cylinder of an internal combustion engine is of order 2500 C. Maximum metal temperatures for the inside of the combustion chamber space are limited to much lower values by a number of considerations. These conditions lead to heat fluxes to the chamber walls that can reach as high as 10 MW/m 2 during the combustion period. However, during other parts of the operating cycle, the heat flux is essentially zero. The flux varies substantially with location; moving high-temperature burned gases generally experience the highest fluxes. In regions of high heat flux, thermal stresses must be kept below levels that would cause fatigue cracking. The gas-side surface of the cylinder wall must be kept below about 180 C to prevent deterioration of the lubricating oil film. Spark plug and valves must be 447

2 kept cool to avoid knock and preignition problems, which result from overheated spark plug electrodes or exhaust valves. Solving these engine heat-transfer problems is obviously a major design task. Heat transfer affects engine performance, efficiency and emissions. For a given mass of fuel within the cylinder, higher heat transfer to the combustion chamber walls will lower the average combustion gas temperature and pressure. 2. DESIGN OF THE PROJECT 2.1Experimental setup One 100 c.c. four-stroke air-cooled spark-ignition engines with single cylinder were employed for developing the heat transfer coefficient. with specifications as shown in Table 1. Table 1 Sr. No. Part list Specifications 1 Engine model BAJAJ/Kinetic/Hero- Honda 2 Engine type Four-stroke, air cooled, 3 Bore X stroke 52.0 X 58.6 mm 4 Fuel system Carburetor 5 Number of valves 2 6 Displacement 100 c.c. volume 7 Compression ratio Idle speed 1800 rpm 9 Ignition type CDI 10 Spark advance 5 /1500 rpm, 26 / 4500 rpm 11 Cylinder head Aluminum alloy material 12 Combustion Hemisphere shaped chamber The combustion chambers of engine is hemisphere- shaped. Five thermocouples were used to measure the temperatures of the cylinder head at specific positions, as shown in Fig. 2. Figure 1: Proposed inside view of the locations of thermocouples. 448

3 Figure 2: Instrumented Cylinder Head Schematic Showing FRT Placement Two E-type coaxial thermocouples were used to measure the instantaneous temperatures of the inside surface of the cylinder wall near the exhaust and intake valves, respectively. The E-type thermocouples offer measurement ranges from - 70 to C and temperature tolerance of ±1.7 C or 0.75%. Two K-type thermocouples with temperature indicator, th3 and th4, were used to measure the steady- state temperatures of the outside surface of the cylinder wall near the exhaust and intake valves, respectively. Another K-type thermocouple, th sp, was used to measure the temperature of the spark plug T sp. The K-type thermocouples offer measurement ranges from 270 C to C and temperature tolerance of ± 2.2 C or 0.75%. Moreover, since the measuring probe of E - type and K-type thermocouples are very small, the sizes are 1/32 and 1/16 inch, respectively, which can minimize the error of measured temperature. In most heat flux calculation, the heat flux through the cylinder head wall is assumed to be one-dimensional unsteady heat conduction. Since the unsteady heat conduction of the in wall temperature field exists only within a very small distance from the wall surface, the unsteady component of the temperature gradient perpendicular to the surface is usually much larger than that parallel to the surface. Therefore, one-dimensionality is safely assumed for the unsteady component of the surface heat flux calculation. The heat flux at the combustion chamber can be obtained by solving the following partial differential equation with two boundary conditions: where, T is the temperature of the cylinder wall, which is a function of t and x; t is the time; x is the distance from the wall surface; α = k/ qc is the thermal diffusivity; k is the thermal conductivity; and c is the specific heat. 3. CALCULATION OF ENERGY DISTRIBUTION 3.1 Energy available from the fuel The amount of energy available for use in an engine is W = m f Q HV 449

4 where, mf = fuel flow rate into the engine Q HV = heating value of the fuel The mass flow of fuel is limited by the mass of air that is needed to react with the fuel. Brake thermal efficiency gives the percentage of this total energy, which is converted to useful output at the crankshaft (µ t)brake = W/ m f Q HV µ c where, µ t = thermal efficiency, µ c = combustion efficiency, W b = brake power. The rest of the energy can be divided into heat losses, parasitic loads, and what is lost in the exhaust flow. Power generated = W shaft + Q exhaust + Q loss + W acc W shaft = brake output power off of the crankshaft Q exhaust = energy lost in the exhaust flow Q loss = all other energy lost to the surroundings by heat transfer. W acc = power to run engine accessories. W shaft % Q exhaust % Q loss % W acc 5-10 % Heat loss can be subdivided Q loss = Q coolant + Q oil + Q ambient Q coolant = % Q oil = 5-15 % Q ambient = 2-10 % 4. HEAT TRANSFER IN INTAKE SYSTEM 4.1 Heat transfer in intake system The walls of the intake manifold are hotter than the flowing gases, heating them by convection Q = h. A. (T wall T gas ) Where, T = temperature h = convection heat transfer coefficient A = inside surface area of the manifold 5. HEAT TRANSFER IN COMBUSTION CHAMBERS 5.1 Heat transfer in combustion chamber In the combustion chamber of an engine, one can discern three very different surfaces: the cylinder liner, the fire deck and the piston. It is assumed that the piston and the liner have a uniform temperature. The fire deck surface however consists for one half of valves and for the other half of the cylinder head. So heat is transferred from the gas to the cylinder head by two different paths: (1) directly from the gas to the cylinder head (2) first from the gas to the valve plates and then through the valve seats to the cylinder head. Heat transfer per unit surface area will be: 450

5 q = Q/A = (T g - T c )/[(1/h g ) + ( x/k) (1 + h c )] where, T g = gas temperature in the combustion chamber T c= coolant temperature h g = convective heat transfer coefficient on the gas side h c = convective heat transfer coefficient on the coolant side. x = thickness of the combustion chamber wall k = thermal conductivity of the cylinder wall. 5.2 Heat flux at cylinder head. Normally, the heat flux is highest in the center of the cylinder head, in the exhaust valve seat region, and to the center of the piston. It is lowest to the cylinder walls. Cast-iron pistons run about 40 C to 80 C hotter than aluminium pistons. With flat-topped pistons (typical of spark ignition engines) the center of the crown is hottest and the outer edge cooler by 20 C to 50 C. Graph I: Heat outflow from various zones of piston as percentage of heat flow in, from combustion chamber. 6. HEAT TRANSFER IN EXHAUST SYSTEM 6.1 Heat transfer in exhaust system To calculate heat losses in an exhaust pipe, normal internal convection flow models can be used with one major modification: Due to the pulsing cyclic flow, the Nusselt number is about 50% higher than would be predicted for the same mass flow in the same pipe at steady flow conditions. Heat losses from the exhaust system affect emissions and turbo charging. 7. CONCLUSION Under normal operating conditions, the cylinder walls of an internal combustion engine are subjected to extremely large heat fluxes resulting from the flame propagation processes within the chamber. 451

6 For normal operating conditions, significant material wear and degradation does not occur, however, in unusual circumstances, cylinder wear from thermal stresses can take place. A substantial difference of heat flux exists for various places in the cylinder of an engine. Maximum heat flux in each part occurs when pressure in the cylinder is maximum. Heat flux on the intake valves is higher than other place of the cylinder. Heat flux on the cylinder head is more than piston and it has the lowest value on the cylinder liner. Numerical computation is an appropriate tool to study heat transfer in comparison with available experimental correlations. ACKNOWLEDGEMENT P.S.Patil, S.N.Belsare & Dr S.L.Borse would like to express our gratitude to all those who gave me the possibility to complete this paper. We want to thank the Department of Mechanical Engineering of RSCOE. We are deeply indebted to our Dr. S.L.Borse, Prof. Sable, Prof. Suhas Deshpande, Dr.Utgikar Dr.Pawar from RSCOE whose help, stimulating suggestions and encouragement helped us in all the time of work. We would like to give our special thanks to all who enabled us to complete this work. REFERENCES 1. Yuh-Yih Wu, Bo-Chiuan Chen, Cheng-Ting Ke, Feng-Chi Hsieh,from Hua-Chuang, Heat transfer model for small-scale spark-ignitionengines. /International Journal of Heat and Mass Transfer, 52 (2009) A. Mohammadi, M. Yaghoubi, M. Rashidi, Analysis of local convective heat transfer in a spark ignition engine. / International Communications in Heat and Mass Transfer, 35 (2008) Paulius V. Puzinauskas, Gary Hutcherson, Bryan D. Willson, Ignition and boost effects on large-bore engine in-cylinder heat transfer / Applied Thermal Engineering 23 (2003) Michael A. Marr, James S. Wallace1, LarryPershin, Sanjeev Chandra and Javad Mostaghimi, Preliminary Testing of Metal-Based Thermal Barrier Coating in a Spark-Ignition Engine. / Journal of Engineering for Gas Turbines and Power JULY 2010, Vol. 132 / O.A.EZEKOYE Heat Transfer Modeling During Knock and Flame Quenching In An Engine Chamber Twenty Sixth Symposium International Combustion/The Combustion Institute, 1996/pp Kukwon Cho, Ronald O. Grover, Jr., Dennis Assanis, Zoran Filipi, Gerald Szekely, Paul Najt and Rod Rask, Combining Instantaneous Temperature Measurements and CFD for Analysis of Fuel Impingement on the DISI Engine Piston Top. / Journal of Engineering for Gas Turbines and Power JULY 2010, Vol. 132 / Books 1. Internal Combustion Engine, John B.L Heywood. 2. Engineering Fundamentals of the Internal Combustion Engine, Willard W. Pulkrabek 3. Internal Combustion Engines, Mathur Sharma. 4. Internal Combustion Engines, V. Ganeshan. 452