IORD Journal of Science & Technology E-ISSN: 2348-0831 Volume 3, Issue 1 (Mar–April 2016) PP 163-168 IMPACT FACTOR 1.719 www.iord.in

A review on effect of backpressure on exhaust system Niraj B. Dole #1, Jayant H. Bhangale *2 Mech Department, MCOERC Nasik ,University Of Pune Pune India 1

[email protected] [email protected]

2

Abstract— In internal combustion engines, exhaust system plays a vital role in the improvement of the combustion efficiency. A good conditioned exhaust system increase the performance of the engine. 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 analyses the exhaust energies available at different engine operating conditions and to develop an exhaust system 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. During the exhaust stroke when the piston moves from BDC to TDC, pressure rises and gases are pushed into exhaust pipe. Thus the power required to drive exhaust gases is called exhaust stroke loss and increase in speed increases the exhaust stroke loss. The network output per cycle from the engine is dependent on the pumping work consumed, which is directly proportional to the backpressure. To minimize the pumping work, backpressure must be low as possible. The backpressure is directly proportional to the exhaust diffuser system design. The shape of the inlet cone of exhaust diffuser system contributes the backpressure. This increase in backpressure causes increase in fuel consumption. Indeed, an increased pressure drop is a very important challenge to overcome. [1], [2] Keywords—EDS(Exhaust diffuser system)

I. Introduction The exhaust system of an internal combustion engine has a significant influence on the global engine operation. Among the different component of the system the exhaust manifold has a paramount relevance on the gas exchange process. The exhaust system routes exhaust gas from the engine and exhaust it into the environment, while providing noise attenuation, waste energy recovery and after treatment of the exhaust gas to reduce emissions. Though the intake system is dominant on the cylinder filling process, the exhaust manifold is able 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

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is the pressure at the valve and especially the instantaneous pressure evolution. 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, efficiency, and reduce the emissions of pollutants [1]. The exhaust system of an IC engine has a significant influence on the global engine operation. Among the different component of the system the exhaust System has a paramount relevance on the gas exchange process. Though the intake system is dominant on the cylinder filling process, the exhaust system is able 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 system 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 system at the exhaust valve depends essentially on the layout and dimensions of the pipes, therefore an adequate design of the system geometry can improve the engine power and efficiency, and reduce the emissions of pollutants. Exhaust system design parameters are 1) Minimum possible resistance in runners. 2) Properly design of System geometry to reduce the pressure drop. 3) Eliminate the unnecessary turbulence & eddies in the system. 1.1 Important Operating Parameters of C.I. Engine Based upon the review of literatures [3, 4, and 5] the following main engine operating variables are selected for discussion in brief the impacts of these variables on engine performance:1.1.1 Fuel consumption rate

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IORD Journal of Science & Technology E-ISSN: 2348-0831 Volume 3, Issue 1 (Mar–April 2016) PP 163-168 IMPACT FACTOR 1.719 www.iord.in Engine performance is dependent on fuel consumption, which bears direct influence on efficiency and engine out emissions. So, fuel consumption rate is a basic dependent variable, It is an important parameter of an engine, varies because of any possible variations such as type of engine, type of fuel used, After treatment system employed (flow resistance offered by exhaust system) and engine operating conditions. 1.1.2 Load on engine Load factor on engine is an independent variable, as per the total load requirements such as vehicle weight, weight of passengers, road resistance or slope condition, drag force variations, electrical load etc. which is based upon the traffic environment in which the engine operates, state of maintenance and repair which is not easily measured in terms of energy consumption also driver’s skill is very important parameter since use of gear, clutch and brake is very crucial aspects of engine operating performance [6]. 1.1.3 Speed Engine speed is also an independent variable, as per the availability of time or time requirements; speed can be kept constant as in case of diesel generator applications with the help of a governor. Speed can be increased or decreased using accelerator or gear box mechanisms. At constant brake power these values of speed and load are varied using gear box arrangement as per engines operating needs, for example during starting a vehicle speed is kept low but high torque is supplied to the wheels. Frictional power loss variations are also depends on load and speed variations [3]. 1.1.4 Backpressure on engine Suction pressure remains constant in naturally aspirated engine so it is not considered as a variable in this investigation. Pressure at exhaust end, which opposes the exhaust gases flowing outside the engine cylinder, is also called as backpressure on engine. Ideally it should be atmospheric pressure. It is also an independent variable. As per the complete exhaust system component design and their operating conditions the value of backpressure varies [6]. Since effects of load and speed variations on fuel consumption are very well known. Load and speed variations are operating conditional parameters, related to break power or output power only. Speed and load can be easily controlled also at drivers or operators will. Future modifications must be done in such a way that each alternation should not cause backpressure rise. Backpressure on engine is a variable that can be controlled with proper system design and maintenance practices. So, more stress is given on the variable backpressure on engine in this work [3].

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1.2 Causes, Effects and Possible Remedies for Backpressure Rise Problem To minimize the pumping work the backpressure must be as low as possible for obtaining the optimal output from the engine. The backpressure is directly proportional to the pressure drop across the design of complete exhaust system components. Each alternation in exhaust system causes variations in backpressure on C.I. engine. There are various factors because of which backpressure rise problem exists in old as well as new properly designed C.I. engine applications during complete operating life. Few of them are discussed here - An increased C.I. engine population has created pressures on controlling engine out emissions. In most of the C.I. engine applications lack of space availability needs compactness of after treatment devices, it creates restriction in exhaust flow hence causes backpressure rise. Diesel after treatment strategies may include muffler, particulate filter or catalytic converter, thermal reactor, turbocharger, EGR system etc. in the exhaust system for heat recovery and emission control activities. Particulate filters are designed to trap particulate matter (PM) to achieve a net decrease in PM emissions. The device captures ash, but the accumulation of ash in the device is sufficient to cause a rise in backpressure. In practice, these devices need to be regenerate quickly and relatively cheaply when they become blocked. The failure of catalyst may be due to system component meltdown, carbon deposit, catalyst fracture, deactivation of diesel catalyst etc. After treatment device component failure may cause backpressure rise, mostly it happens because particulate matter consists of non-combustible compounds. Poor engine performance may happen as a result of a clogged or choked after treatment device. The broken pieces can move around and get in position to plug up the flow of exhaust through the device. They are just melted enough and reduce surface area. Either way, it doesn’t work much anymore, even though it may look good on the outside. Engine emissions increase as the engine deteriorates. Normal engine wear typically causes an increase of particulate matter (PM) emissions and a decrease of NOx emissions. The major categories of fuel additives include engine performance, fuel handling, fuel stability, and contaminant control additives. Engine lubricants are composed of base oil, viscosity modifier and an additive package. One of the main drivers in the development of oil formulations for engines with exhaust after treatment is the reduction of sulphated ash, phosphorous and sulphur. Sulphur increases PM in all classes of engines. Sulphur is also known to interfere with several engine emission control strategies. Development of alternative fuels once promoted by the desire to reduce exhaust emissions is now increasingly driven by

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IORD Journal of Science & Technology E-ISSN: 2348-0831 Volume 3, Issue 1 (Mar–April 2016) PP 163-168 IMPACT FACTOR 1.719 www.iord.in climate change issues and energy security. There is a clear correlation between some fuel properties and regulated emissions. Drawing general conclusions is, however, difficult due to such factors as Inter corelation of different fuel properties, different engine technologies, or engine test cycles. Hence a comprehensive and practically feasible approach is a must to improve the complex system of after treatment. Thus, any modification in engine system causes rise in backpressure on engine in internal combustion engines. As a remedial action for modern internal combustion engine performance enhancement through controlling the rise in backpressure following points must be considered. II. Literature review Study of advanced internal combustion engine research the abstract is given here. In this manuscript, research on hydrogen internal combustion engines is discussed. The objective of this project is to provide a means of renewable hydrogen based fuel utilization. The development of a high efficiency, low emissions electrical generator will lead to establishing a path for renewable hydrogen based fuel utilization. A full-scale prototype will be produced in collaboration with commercial manufacturers. The electrical generator is based on developed internal combustion engine technology. It is able to operate on many hydrogen-containing fuels. The efficiency and emissions are comparable to fuel cells (50% fuel to electricity, NOx). This electrical generator is applicable to both stationary power and hybrid vehicles. It also allows specific markets to utilize hydrogen economically and painlessly [3]. During investigation on effect of EGR on the exhaust gas temperature and exhaust opacity in compression ignition engines, the abstract is given here. In diesel engines, NOx formation is a highly temperature-dependent phenomenon and takes place when the temperature in the combustion chamber exceeds 2000K. Therefore, in order to reduce NOx emissions in the exhaust, it is necessary to keep peak combustion temperatures under control.One simple way of reducing the NOx emission of a diesel engine is by late injection of fuel into the combustion chamber. This technique is effective but increases fuel consumption by 10–15%, which necessitates the use of more effective NOx reduction techniques like exhaust gas recirculation (EGR). Re-circulating part of the exhaust gas helps in reducing NOx, but appreciable particulate emissions are observed at high loads, hence there is a trade-off between NOx and smoke emission. To get maximum benefit from this trade-off, a particulate trap may be used to reduce the amount of unburnt particulates in EGR, which in turn reduce the particulate emission also. An experimental investigation was conducted to observe the effect of exhaust gas recirculation on

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the exhaust gas temperatures and exhaust opacity. The experimental setup for the proposed experiments was developed on a two-cylinder, direct injection, air-cooled, compression ignition engine. A matrix of experiments was conducted for observing the effect of different quantities of EGR on exhaust gas temperatures and opacity [6]. The study targets at finding the effects of engine design parameter (compression ratio) on the performance with regard to brake specific fuel consumption and brake thermal efficiency, Combustion parameter viz. Cylinder pressure, Hear Release rate (HRR), Rate of Pressure Rise (RPR) and emission of CO, CO2, HC, NOx with diesel as a fuel. The study was carried out at different compression ratios (14-17) to find the optimum value at which lesser emissions and better performance and combustion characteristics are obtained. It was found that as the compression ratio is increased the Brake thermal efficiency and brake power increases and brake specific fuel consumption is slightly reduced. The combustion parameters CP, HRR, RPR all increase with increase with increase in compression ratio. The emission of CO2 and NOx increases steeply at high compression ratio. A combustion model of the engine is created in Star CD software and the experimental and the theoretical cylinder pressure values are validated [7]. The work is aimed at experimental investigation of the effect of exhaust gas recirculation on performance and emissions characteristics of a diesel engine, fuelled with biodiesel. An effort has been taken to study performance and emission characteristics of a diesel engine fueled with biodiesel and diesel fuel using EGR. All the experiments were conducted on a single-cylinder, four-stroke, water cooled, indirect injection (Lister 8-1) diesel engine at the engine full load operation and constant engine speed of 730 rpm. The results obtained with biodiesel (canola oil ethyl ester) were compared with the diesel fuel as reference fuel. The engine performance and efficiency obtained in biodiesel case were less, which could be attributed to lower calorific value of biodiesel. CO and UHC emissions for biodiesel were lower than that of diesel fuel. However, it was observed that NOx emissions for biodiesel were higher than that of diesel fuel. Exhaust gas recirculation (EGR) is a very effective technique to reduce NOx emissions from a diesel engine. In this study the venturi type EGR system was used. When similar percentages (%by volume) of exhaust gas recirculation (EGR) were used in the cases of diesel and canola oil ethyl ester, NOx emissions were considerably reduced to lower values [9]. The review of effect of exhaust gas recirculation (EGR) on NOx Emission from C.I. engine, Internal

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IORD Journal of Science & Technology E-ISSN: 2348-0831 Volume 3, Issue 1 (Mar–April 2016) PP 163-168 IMPACT FACTOR 1.719 www.iord.in combustion engines are established as the main power source for the automobile vehicles. At present emission norms becomes strict for any I.C. engine. The main pollutant are CO, HC, NOx, PM, soot, etc. from which NOx are one of the most harmful component. It is possible to limit the negative effect of NOx on the environment by various methods like exhaust gas recirculation (EGR), catalyst and water injection. The aim of this work is to review the effect of exhaust gas recirculation (EGR) to reduce the NOx emission from tailpipe of homogeneous charged C.I.engines. Cooled exhaust gas recirculation (EGR) is a common way to control the NOx generation in engine cylinder. It was found that adding EGR to the fresh air charge to homogeneous charged engines will beneficial to reduce theNOx emission substantially. Substantial reductions in NOx emission are achieved by previous investigators with 10% to 30% EGR. However, EGR has other effects on combustion and emission production that are increase of intake charge temperature, delay in heat release, decrease of peak cylinder temperature and decrease in O2 concentration in cylinder charge and decrease the air-fuel ratio [11]. Since last 3 to 4 decades after treatment techniques are being increasingly utilized and research work is well under progress. Effective after treatment system, specifically for I.C. engines, requires critical analysis of the overall effect of backpressure on each particular I.C. engine performance. More efforts are required for the analysis of the after treatment System, by further study of the theory of operation of each device related to I.C. engines. Search on diesel particulate filters as a modern technology is very active because particulate matter is designated as a major cancer material. Regeneration phenomenon in after treatment devices is a subject of special interest for design and development of particulate matter emission control activities. The Backpressure acting on engine is most important factor which basically deteriorates the engine and emission control performance. In the present work, dimensional analysis technique is used for determining the relationship between operating variables of internal combustion engines, then validation of the effect of back pressure generated on a C.I. engine, with and without the use of a specially designed diesel particulate filter is done[12]. The objective of this work is to provide an estimate of the potential effect of substrate and exhaust system backpressure on engine performance. Parameters include fuel consumption, CO2 emissions, and horsepower. Results were obtained on an engine test stand, and statistical analysis was used to understand the relationships between variables. Tradeoffs between catalyst substrate selection and engine performance for the particular engine used in this study are

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described. Finally, the potential impact of exhaust system backpressure on real world driving conditions is discussed [13]. Work done on CFD analysis of exhaust manifold of multi-cylinder S.I. engine to determine optimal geometry for reducing emissions, the abstract is given here. Exhaust manifold is one of the most critical components of an I.C. engine. The designing of exhaust manifold is a complex procedure and is dependent on many parameters viz. back pressure, exhaust velocity, mechanical efficiency etc. Preference for any of this parameter varies as per designer’s needs. Usually fuel economy, emissions and power requirement are three different streams or thought regarding exhaust manifold design. This work comprehensively analyses eight different models of exhaust manifold and concludes the best possible design for least emissions and complete combustion of fuel to ensure least pollution [14]. It is quite well known that a properly designed intake manifold is vital for the optimal performance of an I.C. engine. This work will present 3-D simulation of a 1.6L MPFI engine intake manifold by using the FLUENT code and the results will be discussed. Both steady and unsteady state simulations have been accomplished for this case. Steady state simulation results are compared with flow bench rig data for validation. Boundary condition for unsteady state simulation was obtained from 1-D WAVE code. Finally according to the results of steady and unsteady simulations, some suggestions are recommended to improve the performance of this intake manifold [15]. During the investigation on optimization of exhaust systems, the abstract is given here. Some design optimization studies of automotive exhaust systems are carried out using numerical simulation. The numerical simulation involves computational fluid dynamics for fluid flow and temperature distribution and finite element analysis (FEA) for subsequent structural analysis. The emphasis is given to optimization related to exhaust system design parameters such as shape and profile of manifold, catalyst inlet tube, inlet cone, exit cone, and exit tube under a given exhaust gas conditions. Several examples of optimization involving study of design parameters on the index of flow uniformity and backpressure are illustrated. Some studies in the past have shown that angular inflow in to catalyst substrate would give high flow uniformity index and flow out let profiles may not significantly affect the uniformity flow index near the inlet of catalyst. The present study shows that this is not always the case and some examples are illustrated to highlight these aspects.

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IORD Journal of Science & Technology E-ISSN: 2348-0831 Volume 3, Issue 1 (Mar–April 2016) PP 163-168 IMPACT FACTOR 1.719 www.iord.in The second part of this study involves finite element calculation of stresses and strains. Due to high temperatures involved in the exhaust system both material and geometric non-linearity are considered in structural analysis. Specifically, the study involves the calculation of material response behaviour under several thermal cycles, each cycle involving a heating and a cooling stages, and finally comparative study of suitability of cast steel and fabricated steel for exhaust manifolds are discussed [16]. During the investigation on the effect of intake manifold runners length on the volumetric efficiency by 3D CFD Model, the abstract is given here. It is quite well known that a properly designed intake manifold is vital for the optimal performance of an I.C. engine. This work will present 3-D Simulation of a XU7 engine intake manifold and the results will be discussed. Both steady and unsteady state simulations have been accomplished for this case. Steady state simulation results are compared with flow bench rig data for validation. Boundary condition for unsteady state simulation was obtained from 1-D WAVE code. In the present research the effect of length of runners on the volumetric efficiency has been analyzed by 3-D CFD model at different speeds. Three hypothetical models have been made that all of their runner’s length is increased to 110,120 and 130% of initial value. In the model with 20% extended runners, the volumetric efficiency increases at 3500 and 4500 rpm. Finally according to the results of steady and unsteady simulations, some suggestions are recommended to improve the performance of this intake manifold [17]. During the investigation on pre-design criteria for exhaust manifolds in I.C. automotive engines, the abstract is given here. A modelling study is presented in this work, whose objective is to obtain design criteria for optimum layouts and dimensions of exhaust manifolds in automotive engines. The first step has been the characterisation of the pulsating flow phenomena in the exhaust manifold, focusing on the pressure wave propagation process and on the interaction between cylinders across the manifold. Two relevant phenomena have been studied: the reflection of under-pressure pulses at pipe junctions and open ends, and the interference between exhaust processes of different cylinders. These phenomena have been characterised respectively by non-dimensional parameters, related to the layout and dimensions of the manifold. A parametric modelling study has been performed in order to evaluate the effects of the manifold dimensions on the engine performance. The work has been focused on a four-cylinder engine with a four-branch manifold. Significant results have been obtained from the research and some are clear design criteria, for the manifold dimensions, in terms of key values of the described non-dimensional parameters [18].

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III. Conclusions This work has presented a powerful method to evaluate exhaust system performance. Traditional method of analysis by experiments is time consuming and expensive. Also it does not give the flow structure. CFD simulation is a powerful method to give flow structure, pressure variation in the flow domain. CFD results are experimentally validated for analysis. From the results of it we are getting the flow structure. According to these results geometry is modified. Analysis is carried out on each modified geometry. The geometry, which gives minimum pressure drop and hence minimum backpressure and increased velocity, is the necessary geometry.

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IORD Journal of Science & Technology E-ISSN: 2348-0831 Volume 3, Issue 1 (Mar–April 2016) PP 163-168 IMPACT FACTOR 1.719 www.iord.in Hydrogen-Ethanol Dual Fuel, IJE Transactions B: Applications Vol. 21, No. 2, August 2008, pp 203 – 210. [9] Paykani, A. Akbarzadeh and M. T. Shervani Tabar, Experimental Investigation of the Effect of Exhaust Gas Recirculation on Performance and Emissions Characteristics of a Diesel Engine Fueled with Biodiesel, IACSIT International Journal of Engineering and Technology, Vol. 3, No. 3, June 2011, pp 239 – 243. [10] Ranbir Singh, Sagar Maji, Performance and Exhaust Gas Emissions Analysis of Direct Injection CNG-Diesel Dual Fuel Engine, International Journal of Engineering Science & Technology Vol. 4 NO.3, March 2012, pp 833 – 847. [11] Harilal S. Sorathia, Pravin P. Rahhod and Arvind S. Sorathiya, Effect of Exhaust Gas Recirculation (EGR) on Nox Emission from C.I. Engine - A Review Study, International Journal of Advanced Engineering Research and Studies, E-ISSN2249–8974, pp 223-227. [12] D.S. Deshmukh, M.S. Deshmukh and J.P. Modak ,Experimental Investigation of the Effect of Backpressure on an I.C. Engine Operating Performance, International Journal of Emerging Technologies and Applications in Engineering, Technology and Sciences, ISSN: 09743588, 1 April 2010, pp 23-28. [13] Jonathan D. Pesansky, Nathan A. Majiros , The effect of three-way catalyst section on component pressure drop and system performance, SAE Paper NO.2009-01-1072. [14] K. S. Umesh, V. K. Pravin & K. Rajagopal ,CFD Analysis of Exhaust Manifold of Multi-Cylinder SI Engine to Determine Optimal Geometry for Reducing Emissions, International Journal of Automobile Engineering Research and Development, ISSN 22774785 Vol. 3, Issue 4, Oct 2013, 45-56 pp 45-56. [15] M. Safari & M. Ghamari, A. Nasirtosi ,Intake Manifold Optimization by using 3-D CFD Analysis, SAE Paper No. 2003-32-0073. [16] Meda Lakshmikantha & Mathias Keck, Optimization of Exhaust Systems, SAE Paper No. 2002-01-0059. [17] Negin Moffouni & Reza Ebrahimi, SiamacHossein Pour ,The effect of Intake Manifold Runners Length on the volumetric Efficiency by 3D CFD Model, SAE Paper No. 2006-32-0118. [18] J. Benojes, E. Royes, V. Bermuder & J. R. Serrano , PreDesign Criteria for Exhaust Manifolds in I.C. Automotive Engines, SAE Paper No. 980783.

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