Exhaust Gas Heat Recovery Using Airpreheater for Ci Engine
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International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 5, May 2017, pp. 135–145, Article ID: IJMET_08_05_015 Available online at http://iaeme.com/Home/issue/IJMET?Volume=8&Issue=5 ISSN Print: 0976-6340 and ISSN Online: 0976-6359 © IAEME Publication Scopus Indexed EXHAUST GAS HEAT RECOVERY USING AIRPREHEATER FOR CI ENGINE N Santhisree, P Sudheer Kumar, S Ashok, B Srikanth Mechanical Engineering, IARE - Institute of Aeronautical Engineering, Hyderabad, India ABSTRACT In an IC Engine the complete combustion of fuel generates energy as heat in which is some energy is converted in the form of mechanical work. And the remaining is wasted to atmosphere through exhaust. That is only 30 to 40% of heat energy is in the form of work remaining 60-70%as waste heat ,this causes the engine efficiency only 20 to 30%.This heat is treated as waste heat .The recovery of this heat depends on the exhaust gas temperature and its economics involved. If some amount of this heat is recovered considerable amount of fuel will be saved, some of the examples would be preheating of combustion air, or pre-heating boiler feed water or process water and space heating. The present study describes the experimental analysis of a CI engine by incorporating an air to air heat exchanger that is air preheater for preheating of air from exhaust gas from the engine and before supplying it to the inlet of the cylinder of CI engine. The preheated air at the engine intake manifold results in performance of engine and on emission control. The exhaust gas passed through the preheater increases the temperature at inlet. Higher the inlet air temperature increases brake thermal efficiency, decreases the specific fuel consumption, reduces emissions and also reduces the lower ignition delay. Due to preheating of inlet air uniform combustion takes place causes to reduce engine noise. This paper describes the performance of CI engine with and without preheater. Key words: Air preheater, CI engine, Efficiency, Exhaust gases, heat losses, heat exchanger, Waste Heat recovery Cite this Article: N Santhisree, P Sudheer Kumar, S Ashok and B Srikanth, Exhaust Gas Heat Recovery Using Airpreheater for CI Engine. International Journal of Mechanical Engineering and Technology, 8(5), 2017, pp. 135–145. http://iaeme.com/Home/issue/IJMET?Volume=8&Issue=5 1. INTRODUCTION CI engines takes diesel as fossil fuel .The combustion of the mixture releases chemical energy is converted into heat energy .The heat energy is partly converted into useful mechanical work to drive any load and the rest is exposed to the ambient in the form of exhaust gases and coolant, resulting rise in the entropy and severe environmental pollution. The conservation of http://iaeme.com/Home/journal/IJMET 135 [email protected] Exhaust Gas Heat Recovery Using Airpreheater for CI Engine fuel and efficiency of an engine can be improved by optimizing combustion phenomena or by recover waste heat of engine. The engine efficiency depends upon some of the major parameters like heat losses during cooling of engine, friction losses, losses due to exhaust gases and transmissive efficiency. One of the best methods for conservation of fuel and improving efficiency of the engine is Waste heat Recovery. This conserves not only fuel but also reduces the emissions of the engine. To characterize diesel fuel the important properties to be considered are fuel volatility, density, viscosity, cetane number and sulphur content. To improve these properties Air preheating plays a vital role. An air preheater is positioned in communication with the inlet of the engine. With the help of waste heat recovered from the exhaust of the engine the inlet air has been preheated. Preheating ensures proper combustion of the fuel mixture and rise in inlet temperature .this higher inlet temperature leads to increase in efficiency, torque, horse power and evaporation of fuel[3]. Air preheating decreases ignition delay and improves the combustion rate [2]. Diesel exhaust include emissions like NO, HC and CO. Preheating intake air up to elevated temperature subsequently reduces CO and HC emissions[1]. Approximately 60 to 70 %energy losses as waste heat through exhaust (30 to 40%as environment and 30% as engine cooling system)[5].In general the temperatures of the exhaust gases are as high as 450-6000C. In the present study this waste heat is recovered by using an air preheater (a shell and tube heat exchanger.). It comprise of a shell with matrix material and copper tubes. When the exhaust gas passes through the pre heater it slows down the velocity of exhaust gas which allows extracting more heat from exhaust gas. Then the heat of exhaust gas is transferred to counter flowing fresh air in copper tubes which increases the temperature of air. The heated air is then transferred to engine intake manifold. 2. MODELLING OF AIRPREHEATER The air preheater has been designed by using a design modular SOLIDWORKS and it is fabricated and has been equipped with Single cylinder Diesel Engine test rig.3D solid modelling design by using SOLIDWORKS speeds the creation of complex parts and large assemblies. Figure 1 Air preheater http://iaeme.com/Home/journal/IJMET 136 [email protected] N Santhisree, P Sudheer Kumar, S Ashok and B Srikanth 3. FABRICATION OF AIRPREHEATER Air preheater is basically a shell and tube heat exchanger. The air preheater consists of the preheater box, heating coil, thermocouples, filter box, inlet pipe, and outlet pipe. The below figure shows the complete overview of air preheater. Figure 2 Copper tubes with baffles Figure 3 Outer shell 3.1. Components of Air Preheater 3.1.1. Copper Tubes The tubes are made with copper because of its high thermal conductivity (k=401 w/mk) and easy availability. Dimensions: Diameter: 28mm Length: 430mm x3 Thickness: 1mm 3.1.2. Shell Shell is made up of mild steel which covers the copper tube inside the shell. Outer Diameter: 150mm Length: 450mm Thickness: 4mm Material: mild steel 3.1.3. Baffle Plates Thickness: 2 mm No: 4 Material: Aluminium 3.1.4. Inlet and Out Let Piping Diameter: 30mm Material: GI 3.1.5. Procedure for Manufacturing • The required copper tubes with u-bands were selected (say 28mm) and brazed together for leak proof joint. http://iaeme.com/Home/journal/IJMET 137 [email protected] Exhaust Gas Heat Recovery Using Airpreheater for CI Engine • The shell of outer diameter 155mm has been taken and turned on lathe machine to a final diameter of 150mm OD. • Two holes each of diameter 30mm has been drilled over the shell with equal spacing which fumes inlet and outlet exhaust air passage. • While the baffle plates were connected/brazed with copper tubes with equal spacing. • The MS Plates of dimension 200x200mm with thickness 3mm has been taken and made 4holes of each 6mm diameter to each of the corner. • These plates were carefully welded to the shell on both sides. Chipping must be done after regular interval of welding. • The copper tubes with baffles were carefully inserted into the shell and closed with ms plates which has a 29mm hole before. • Meanwhile gaskets cuts has been shaped and applied over the side walls of shell which have already been filed smoothly. • Nuts and bolts (6mm) were taken and fastened around all corners of MS plates both the sides. Tightening of nut were done by using required spanner. • Now the whole product is connected to engine and construct the exhaust air passage unit with required piping. • Anabond solution is applied on gaps and leak prone areas which seals the gases leaving or entering in to the shell. • Connect the inlet air unit with preheater and attach the thermocouples in required places to note down the readings. • Now give the necessary connections and test start the engine and make sure that everything is working fine. • If everything works as per planed manually start the engine and take down the readings in different loads. 4. EXPERIMENTAL METHODOLOGY 4.1. Experimental Setup The engine used in this experimental work is a four stroke, Single Cylinder, water cooled Diesel Engine. Air preheater is connected to the engine exhaust piping as shown in Fig. and various piping connections are made. The experiment was conducted on a four-stroke DI diesel engine of cubic capacity 550 cc. The engine has a piston that moves up and down in the cylinder. A cylinder has a piston which is slightly smaller in size than the cylinder the piston is a metal plug that slides up and down in the cylinder bore diameter and stroke length of the engine are 80mm and 110mm respectively. http://iaeme.com/Home/journal/IJMET 138 [email protected] N Santhisree, P Sudheer Kumar, S Ashok and B Srikanth Figure 4 Schematic Diagram of Experimental Setup with Airpreheater 4.2. Components Used • Single cylinder diesel engine • Air-Preheater • Piping arrangement • Electrical dynamometer 4.3. Instrumentation Used for Performance Analysis • Thermocouples • Temperature controller • Tachometer • Stopwatch 4.4. Diesel Engine Specification • Engine Type : Compression Ignition Type • Engine Make : Kirlosker • Engine Speed : 1500 RPM • BHP : 10 • Bore Diameter : 80 mm • Stroke : 110 mm • Orifice Diameter : 25 mm • Method of Loading : Electrical Dynamometer • Method of Starting : Manually Started • Method of Cooling : Water Cooled 4.5. Experimental Procedure Connect the air preheater with the engine setup. Then run the engine first without switching on the air preheater by fixing some parameters of the engines. Collect the data to calculate performance characteristics. Repeat the same with Preheater and recorded the data. In each load, the brake power, specific fuel consumption, brake thermal efficiency, mechanical efficiency etc. Like performance characteristics have been calculated. http://iaeme.com/Home/journal/IJMET 139 [email protected] Exhaust Gas Heat Recovery Using Airpreheater for CI Engine The step by step procedure is given below: • Fill up sufficient diesel in diesel tank.