Experimental Investigation and Analysis of Single Cylinder Four Stroke C.I. Engine Exhaust System

Transcription

1 International Journal of Energy and Power (IJEP) Volume 3 Issue 1, February Experimental Investigation and Analysis of Single Cylinder Four Stroke C.I. Engine Exhaust System Atul A. Patil 1, L.G. Navale 2, V.S. Patil 3 1 Research student, North Maharashtra University, Umavi Nagar, Jalgaon, (M. S.) India 2 Research guide, North Maharashtra University, Umavi Nagar, Jalgaon, (M. S.) India 3 Research guide, North Maharashtra University, Umavi Nagar, Jalgaon, (M. S.) India 1 patilatul20@rediffmail.com; 2 lgnavale2006@yahoo.com; 3 vilaspatil24@yahoo.com Abstract Energy efficient exhaust system development requires minimum fuel consumption and maximum utilization of exhaust energy for reduction of the exhaust emissions and also for effective waste energy recovery system such as in turbocharger, heat pipe etc. from C.I. engine. To analyse the exhaust energies available at different engine operating conditions an exhaust system developed for maximum utilization of available energy at the exhaust of engine cylinder is studied. Design of each device should offer minimum pressure drop across the device, so that it should not adversely affect the engine performance. Back pressure acting on engine is the most important controllable factor which basically deteriorates the engine and emission control performance. So numbers of methods to increase the performance of the CI engine have been established. A better method of utilising the exhaust is achieved in this paper which uses the exhaust gases from an optimal sized engine currently used, to convert available Kinetic energy and enthalpy of exhaust gases into the pressure after treatment of exhaust gases. This pressure is used and sent through diffuser which reduces the back pressure. Keywords Compression Ignition Engine; Pressure Drop; Diffuser; Back Pressure; Performance Introduction Automobile, one of the most valuable searches of mankind, is a boon as well as a bane. It is boon because of automobiles is ease in transport, serving people at remote places. Considerable time saving is possible as against ancient transport means such as bullock carts etc. Automobiles provide not only a fast and easy means of transport but also economical. It serves mankind from last century and continues in future. Although automobiles importance is really undoubted, its drawbacks matter due to haphazard growth of vehicles. With the growing population, increasing toll of accidents, noise, traffic congestion and public medical problems, offsets the benefit of automobiles. ( ) Diesel engine is the most efficient power plant among all known types of internal combustion engines. The increased use of diesel driven vehicles for all categories of commercial automobiles and even for private cars is the major trend observed worldwide over the last two decades in transportation field. While the energy advantages of the diesel engines are unquestioned, lower cost of diesel fuel is also responsible for its increasing popularity, particularly in less developed countries. Although, inherently cleaner than gasoline engines from the standpoint of view of carbon monoxide (CO) and hydrocarbons (HCs), diesels produce more aldehydes, sulphur oxides (because of the higher sulphur content in diesel fuel) and nitrogen oxides. Offensive smoke and odor emissions are also a problem of great concern, most importantly; however, uncontrolled diesel engines emit significant amounts of particulate being a direct health concern as well as a serious source of overall environmental degradation. In this way, despite the technical and commercial advantages of diesel engines over the conventional gasoline fuelled Otto cycle power plants, concerns have been aggravated as early as in 1980ʹs over the environmental consequences of increased dieselization. Increasingly tighter environmental regulations worldwide, call for advanced emission controls and near zero diesel emission levels in the years to come. Pollutants are produced due to incomplete combustion of the fuel in the engine cylinder. To obtain the lowest vehicle tailpipe emission whole system approach is required, where the design of the engine, the control system and exhaust gas after treatment should be balanced. 1

2 International Journal of Energy and Power (IJEP) Volume 3 Issue 1, February 2014 The exhaust system of an IC engine has significant influence on the global engine operation. Among the different component of the system the exhaust manifold is having paramount relevance on the gas exchange process. Though the intake system is dominant on the cylinder filling process, the exhaust manifold is capable to influence the gas exchange process in several aspects, like the piston work during the exhaust stroke, the short circuit of fresh charge from the intake into the exhaust and even the filling of the cylinder. In this sense, the most influential boundary condition imposed by the manifold is the pressure at the valve and especially the instantaneous pressure evolution. The mean backpressure is determined mainly by the singular elements, such as the turbine, the catalytic converter and the silencer. The instantaneous pressure evolution imposed by the manifold at the exhaust valve depends essentially on the layout and dimensions of the pipes, therefore an adequate design of the manifold geometry can improve the engine power and efficiency, and reduce the emissions of pollutants. To reduce the exhaust emissions from C.I. engines, it is very important to understand the overall effects of devices installed in the exhaust system. Effective utilization of exhaust energy is economically possible to reduce exhaust emissions from old engines instead of engine and fuel modifications. More efforts are required on the development of the after treatment devices, by further study of the theory of operation for diesel engines. At last, providing favourable operating parameters in the after treatment devices during the whole operating range of the engine requires proper design of after treatment devices by considering overall effects of its installation, in the exhaust system. Obtaining economically, maximum conversion efficiency of the pollutants without adversely affecting the engine performance with durability is the ideal requirement from the after treatment devices. (Barry 2001) Diesel Exhaust Systems Backpressure on engine cylinder is completely dependent on exhaust system design, its operating condition and atmospheric pressure (i.e. almost constant). The exhaust system routes exhaust gas from the engine and then exhaust it into the environment, while providing noise attenuation, after treatment of the exhaust gas to reduce emissions and energy recovery. One of the most important sources of vehicle noise, the noise associated with exhausting combustion gases from the engine, is controlled using mufflers. A number of sound reduction techniques are employed in mufflers, including reactive silencing, resistive silencing, absorptive silencing, and shell damping. Exhaust gas properties which are important for the exhaust system design include its physical properties; exhaust gas temperature, which depends on the vehicle duty and/or test cycle and the exhaust gas flow rate. Exhaust system materials are exposed to a variety of harsh conditions, and must be resistant to such degradation mechanisms as high temperature oxidation, condensate and salt corrosion, elevated temperature mechanical failure, stress corrosion cracking, and inter granular corrosion. (H. M. Gousha USA, ) Experimental setup of the diffuser with different angles i.e.v1=22.5, v2=25, v3=30, v4=45, v5=60, v6=75, v7=90 degree is designed and fabricated. With the help of C.I. engine test rig and suitable instrumentation different parameters pressure, temperature, mass of exhaust gases is determined. Effective Utilization of Exhaust Energy To develop application specific view, it is very important to consider overall effects of each component added to the system, so as to improve the overall system performance. In the case of aftertreatment devices used in exhaust system of engine, automobile power plant considered as a complete system is a complex system made up of several other equally complex sub systems, each of which is distinct from the others but they all share some common features and goals that allow them to work together. Even though an after treatment device operates at high temperature excessive temperatures can damage it. The most common cause of catalyst overheating is too much unburned fuel reaching the after treatment device, which happens when a cylinder misfires as well as if the air fuel mixture is continually too rich, long periods of idling with rich mixture, thus raising temperature. Heat carried by exhaust gases is around 35% of the total supply. Energy available at different operating conditions of each specific engine must be optimally utilized for performance improvement, for example a turbocharger installed in exhaust system could be used without any increase in backpressure by suitable design of exhaust system for conversion of enthalpy available at exhaust in to useful pressure rise only. Otherwise, heat carried by exhaust gases is going to be wasted. After treatment devices installation should be in such position that the operating parameters of the devices must be favourable considering following points: 1) To 2

3 International Journal of Energy and Power (IJEP) Volume 3 Issue 1, February obtain the different oxidation and reduction reaction, the light off temperature required and ability to sustain the maximum temperature by the catalysts. 2) To reduce the backpressure and keep it within limit. 3) To provide ease for accommodation and modification in the exhaust system such as EGR system requires backpressure for optimum performance. 4) To obtain maximum conversion efficiencies without affecting the overall engine performance throughout the operating range. 5) To obtain maximum space utilization without interfering the other system operations. (C. Lahousse, 2006) Temperature management of exhaust gas is to increasing interest because of the need to maintain efficiency in after treatment devices. More effective temperature management places requirements on heat exchange systems, and offers the potential for bottoming and heat recovery cycles that use energy transferred from the exhaust stream. Turbo compounding has already been established in heavy duty engines, where a reduction in exhaust gas temperature is the consequence of an additional stage of expansion through an exhaust turbine. A new concept in electric turbo compounding offers flexibility in the control of energy extracted from the exhaust stream. For lightduty applications, the fluid cycle can utilize stored thermal energy after prolonged high load conditions at a time when the traction battery may be depleted. In heavy duty engines, the cycle will simply provide a means of recovering exhaust energy and thereby boosting the vehicleʹs fuel economy. The particular relevance to hybrid vehicles comes through the architectural advantages of generating electricity using the recovered heat energy. Thermo electric devices represent one, but by no means the only way to build heat recovery from an engine system. In summary, the economically feasible after treatment methods for medium and high speed diesel engines are different. The particulate filters developed for passenger cars can also be rather easily adapted for heavy duty road vehicles and thus for off road applications using high speed diesel engines. NOx emissions are primarily reduced by engine design measures such as EGR. In medium and low speed engines, the strategy could be the opposite to that in high speed engines. Until larger particulate filters possibly come on to the market, PM emissions must be reduced by internal engine measures, which also helps maintain good fuel economy, because it is rather easy to achieve low fuel consumption and low PM emissions simultaneously. For further PM reductions, a water scrubber system or an electrostatic precipitator can be an alternative. NOx emissions are removed by SCR catalysts. Governing Equations in Fluid Dynamics All of Computational Fluid Dynamics, in one form or other is based on fundamental governing equations of fluid dynamics, Continuity Equation, Momentum Equation, Energy Equation. These equations associated with physics of fluid flow are the mathematical statements of three fundamental physical principles upon which all fluid dynamics is based (1) and (2). Continuity Equation It is based on the principle of conservation of mass. Net mass flow out of control volume = Time rate of decrease of mass inside control volume Mass Conservation Equation u Sm (1) t Momentum Equation It is based on the law of conservation of momentum, which states that the net force acting in a fluid mass is equal to change in momentum of flow per unit time in that direction. The force acting on a fluid element mass m given by Newton s second law of motion is F = m.a (2) Where a is the acceleration acting in the same direction as force F Momentum Equation u t Energy Equation uu P g S mom It is based on the principle that total energy is conserved. Total energy entering control volume = Total Energy leaving Control volume Energy Equation e uepu kt Se (4) t Where, Partial derivative; Mass density; u Velocity; S Source; t Time; mom = Momentum; g Gravitational acceleration; (3) Viscosity; e Specific internal energy; k Thermal conductivity; T Temperature; Viscous dissipation (J. B. 3

4 International Journal of Energy and Power (IJEP) Volume 3 Issue 1, February 2014 Heywood, 1988) Experimentation Experimental setup of the new design diffuser with different angles i.e. 22.5, 25, 30,45, 60, 75, 90 degree is use. With the help of C.I. engine test rig and suitable instrumentation different parameters pressure, temperature, mass of exhaust gases are determined. In the present work, throughout the complete trials conducted engine jacket cooling water is kept constant at litters /sec, so as to provide easiness in comparison with different parameters. Diffuser with different angles is used as a test piece for back pressure variations. Load and speed of the engine are kept constant at 5 kg and 1500 rpm respectively. The different parameters are compared with the values of same parameters without using new design of exhaust system, for the same engine output conditions. During the trials, 20 test runs are conducted and distinct observations are obtained. Each observation is taken when the engine setup reaches at steady state condition to minimize error. diffuser inlet and outlet are m 0.15 m respectively. In this test, the outlet pressure was recorded as gauge pressure. (D.S. Deshmukh 2010) DinD= Inlet Diameter Diffuser, DexD = Exit Diameter Diffuser, FIGURE 1DIFFUSER NOMENCLATURE Performance Characteristics Engine Specifications 1. Make: COMET Type VRC1, single cylinder, four stroke Compression Ignition engine 2. Rated power output: 5 H.P 3. Stroke length: 110 mm 4. Bore diameter: 80mm 5. Loading type: Rope brake dynamometer 6. Moment arm: 0.2 m 7. Orifice diameter (for air box): 25mm 8. Co efficient of discharge of orifice: 0.64 (V. Ganeshan, 2006) Modelling the Exhaust System The coordinates are provided for the development of the 2D model of the exhaust system. The model is then rotated about 360 degrees to get the 3D profile. For design purposes, the diffuser can be seen as an assembly of three separate sections operating in series a short parallel section and the diverging section. The short parallel section of the system acts as a case of the engine. The straight portion of the diffuser helps in reducing the non uniformity of flow, and in the diverging section, the pressure recovery takes place. (R.G. Silver, 1991) The geometrical specifications of the diffuser have been chosen somewhat arbitrarily. Diameter of GRAPH 1: VARIATIONS IN FUEL CONSUMPTION VS VOLUME OF DIFFUSER (AT CONSTANT SPEED 1500 RPM AND LOAD 5 KG). GRAPH 2: VARIATIONS IN BRAKE THERMAL EFFICIENCY VS VOLUME OF DIFFUSER (AT CONSTANT SPEED 1500 RPM AND LOAD 5 KG). GRAPH 3: VARIATIONS IN OUTLET PRESSURE OF DIFFUSER VS VOLUME OF DIFFUSER (AT CONSTANT SPEED 1500 RPM AND LOAD 5 KG). 4

5 International Journal of Energy and Power (IJEP) Volume 3 Issue 1, February Results and Discussions Exhaust system outlet pressure of engine cylinder is completely dependent on exhaust system design, engine as well as exhaust system operating condition and atmospheric pressure. From the graph 1, it is clear that brake thermal efficiency is directly proportional to the pressure at outlet for different volume of diffuser exhaust system. At the same engine output condition, that is at 5 kg load and 1500 rpm. There is confirmation from the graph 2 that fuel consumption rate is inversely proportional to the diffuser volume of exhaust system. At the same engine output condition that is at 5 kg load and 1500 rpm. There is confirmation from the graph 3 that pressure at outlet of diffuser is directly proportional to the diffuser volume of exhaust system. At the same engine output condition, that is at 5 kg load and 1500 rpm. Diffuser design is done in such a way considering the complete system objectives. Constructional features of device should offer minimum pressure drop across the device, so that it should not adversely affect the engine performance as well the installation of the device in the exhaust system should be such to obtain the desired feed conditions during the entire useful operating range of the specific engine. The operating parameters existing in device should be within the required range so as to obtain the maximum conservation with the durability requirements. Backpressure on engine is found as an important parameter having a strong influence on engine efficiency and need to be minimised for maximum fuel efficiency. Backpressure problem is subject to specific interest of design and development of exhaust system to minimize the problem of back pressure rise because of after treatment techniques applications. Effective after treatment techniques utilization specifically for C.I. engines, requires critical analysis of the complete exhaust system employed. The different volume is obtained by change in diffuser angle by 22.5,25,30,35,45,60,75,90 degrees for pressure change. The exhaust gases from an optimal sized engine are currently used, to convert available Kinetic energy and enthalpy of exhaust gases into the pressure energy for useful after treatment of exhaust gases. This pressure is used and sent through diffuser which reduces the back pressure. Conclusion Energy efficient exhaust system development requires minimum fuel consumption and maximum utilization of exhaust energy for reduction of the exhaust emissions as well for effective waste energy recovery system such as in turbocharger, heat pipe etc. from C.I. engine. Back pressure on engine is found as an important parameter having a strong influence on engine efficiency and need to be minimised for maximum fuel efficiency. Design of each device should offer minimum pressure drop across the device, so that it should not adversely affect the engine performance. Diffuser design is done in such a way considering the complete system objectives. The operating parameters existing in device should be within the required range so as to obtain the maximum conservation with the durability requirements. Experimental setup of the diffuser with different angles i.e.22.5, 25, 30, 45, 60, 75, 90 degree is designed and fabricated. With the help of C.I. engine test rig and suitable instrumentation different parameters pressure, temperature, mass of exhaust gases are determined. The exhaust gases from an optimal sized engine currently used, to convert available Kinetic energy and enthalpy of exhaust gases into the pressure energy for useful after treatment of exhaust gases. This pressure is used and sent through diffuser which reduces the back pressure. ACKNOWLEDGMENTS Authors are thankful to the Godavari College of engineering, Jalgaon for providing financial assistance and laboratory facility. The authors gratefully acknowledge the support of the Ph.D. research centre SSBTE S College of engineering Jalgaon, without which experimentation could not have been done. REFERENCES Barry A.A.L. vansetten, MichealMakkee, Jacob. A. Moulin, Science and Technology of Diesel Particulate Filter, Faculty of Applied Sciences, Delft University of technology, Julianalaan 136, 2626, Delft, the Netherlands, Catalysis review, Publisher Reviews, Publisher: Taylor 5

6 International Journal of Energy and Power (IJEP) Volume 3 Issue 1, February 2014 and Francis, Issue: Volume 43, number 4/ 2001, pages C. Lahousse, B. Kern, H. Hadrane and L. Faillon, Backpressure Characteristics of Modern Three way Catalysts, Benefit on Engine Performance, SAE Paper No ,2006 SAE World Congress, Detroit, Michigan, April 3 6, D.S. Deshmukh, J.P. Modak and K.M. Nayak, ʺExperimental Analysis of Backpressure Phenomenon Consideration for C.I. Engine Performance Improvementʺ SAE Paper No , International Powertrains, Fuels & Lubricants Meeting, Rio De Janeiro, Brazil, on dated 5 May D.S. Deshmukh, M.S. Deshmukh and J.P. Modak, Design Considerations for Diesel Particulate Filter for Enhancement of Engine Performance and Emission Controlʺ International Journal ofengineering Research and Technology. ISSN Volume 3, Number 3 (2010), pp H. M. Gousha, Fuel system & Emission Controlsʺ Second Edition Harper Collins Publisher Heinz J. Robota, Karl C. C. Kharas, Owen Bailey Controlling Particulate Emission from Diesel Engines with Catalytic Aftertreatment, ASEC Manufacturing, Tulsa, USA, J. B. Heywood; Internal Combustion Engine Fundamentals ; McGraw Hill, ISBN , R.G. Silver, J. C. Summers and W. B. Williamson Design and Performance Evaluation of Automotive Emission Control 1991 Elsevier Science Publishers B. V. Amsterdam. V. Ganeshan, Internal Combustion Enginesʺ, Tata McGraw Hill Technology guide, paper abstracts. 6