Efficient Working of CI Engine with Utilization of Exhaust Gas

Advance Research and Innovations in Mechanical, Material Science, Industrial Engineering and Management - ICARMMIEM-2014 224 Efficient Working of CI Engine with Utilization of Exhaust Gas Hirday Ram and J.M.L. Gupta Abstract--- Fuel in any engine is burnt with air. Air is a mixture of gases and it contains approximately 78% nitrogen and 21% oxygen. Some of the oxygen is used to burn the fuel during the combustion process and the rest is supposed to just pass through unreacted. But when the peak temperatures are high enough for long periods of time, the nitrogen and oxygen combine to form a class of compounds called nitrogen oxides, collectively referred to as NOx. These compounds are one of the chief constituents of smog, which have an adverse effect on ecological systems. They also contribute to the formation of acid rain. NOx emissions can be reduced by lowering the cylinder temperatures. This can be done by two ways - 1) Enriching the air fuel mixture 2) reducing the amount of Oxygen in the cylinder that inhibits the combustion process. The first method reduce the efficiency of combustion and so the best way is to reduce the amount of Oxygen. This is done by re-circulating some exhaust gas and mixing it into the engine inlet air. This process is known as Exhaust Gas Recirculation. The goal of Exhaust Gas Recirculation (EGR) is to reduce the amount of NOx produced. The EGR valve recirculates gases into the intake stream. Exhaust gases have already combusted, so they do not burn again when they are re-circulated. These gases displace some of the normal intake charge. This chemically slows and cools the combustion process by several hundred degrees thus reducing NOx formation. A Keywords--- Diesel Engine, NO x, EGR and Pollution I. INTRODUCTION LL INTERNAL COMBUSTION(IC) engines generate power by creating explosions using air and fuel. These explosions occur inside the engine's cylinders and push the pistons down, which results in turns the crankshaft. Thus power produced is used to prepare the cylinders for the next explosion by forcing the exhaust gases out of the cylinder, drawing air in (or fuel-air mixture in non-diesel engines), and compressing the air or air-fuel mixture before the fuel is ignited. There are several differences between diesel engines and gasoline engines. Gasoline engines combine a fuel mist with air before the mixture is taken into the cylinder, while diesel engines inject fuel into the cylinder after the air is taken Hirday Ram, College of Engineering Roorkee, Mechanical Engineering Department, Uttarakhand, India. E-mail: hridaysirola09@gmail.com Dr.J.M.L. Gupta, Associate Professor of Mechanical Department, College of Engineering Roorkee, Uttarakhand, India. E-mail: nigraj0000@gmail.com in and compressed. Gasoline (Non-diesel) engines use a spark plug to ignite the fuel-air mixture, while diesel engines use the heat created by compressing the air in the cylinder to ignite the fuel, which is injected into the hot air after compression. In order to create the high temperatures needed to ignite diesel fuel, diesel engines have much higher compression ratios than gasoline engines. Because diesel fuel is made of larger molecules than gasoline, burning diesel fuel produces more energy than burning the same volume of gasoline. The higher compression ratio in a diesel engine and the higher energy content of diesel fuel allow diesel engines to be more efficient than gasoline engines. A. Formation of Nitrogen Oxides (NOx) Since the diesel engine is more efficient than the gasoline engine and it also runs at a higher temperature than the gasoline engine. This lead to a pollution problem, the creation of Nitrogen Oxides(NOx) and other harmful gases. As we see that the excess air is introduced for the complete burning of fuel. This air is approximately 21% Oxygen by volume and 79% Nitrogen. When air is compressed inside the cylinder during compression stroke of the diesel engine the temperature of the air increase to a certain level ( i.e. self ignition temperature of the fuel) to ignite diesel fuel. When diesel fuel ignites, the temperature of air increases to more than 1500F and air expands pushing the piston downward direction and rotating the crankshaft. As mentioned earlier that at higher temperature the engine is more efficient because more heat developed more power inside the cylinder. Some of the content of the oxygen is used to burn the fuel and rest is supposed to pass through the engine unreacted. The nitrogen does not participate in combustion process and is also pass though the engine unchanged. When the peak temperature high enough for long duration, the Nitrogen and Oxygen with air combine to form new compounds namely Nitrogen Oxides and Nitrogen dioxides(no2).these are collectively known as NOx. The principle reaction governing the formation of NO form moleculer Nitrogen of NO. N2 + O NO + N; N + O2 NO + O; N + OH NO + H Chemical equilibrium consideration indicates that for burnt gases at typical flame temperatures, NO2/NO ratios should be negligibly small. While experimental data show that this is true for spark ignition engines, in diesels, NO2 can be 10 to

Advance Research and Innovations in Mechanical, Material Science, Industrial Engineering and Management - ICARMMIEM-2014 225 30% of total exhaust emissions of oxides of nitrogen. A plausible mechanism for the persistence of NO2 is as follows. NO formed in the flame zone can be rapidly converted to NO2 via reactions such as NO + HO2 NO2 + OH: Subsequently, conversion of this NO2 to NO occurs via NO2 + O NO + O2; unless the NO2 formed in the flame is quenched by mixing with cooler fluid. B. Problem of NOx Nitrogen oxides(nox) are one of the main pollutants emitted by vehicle engines. Once they enter into the atmosphere, they are spread over a large area by the wind. When it rains, water then combines with the nitrogen oxides to form acid rain. This has been known to damage buildings and have an adverse effect on ecological systems. Too much NOx in the atmosphere also contributes to the production of SMOG. When the sunrays hit these pollutants SMOG is formed. NOx also causes breathing illness in human lungs. C. How can be NOx Reduce Since the higher temperatures(2000k) of cylinder causes NOx formation and the NOx can be reduced by lowering the cylinders temperatures. Air cooler is already commonly used for this purpose. Reduced cylinder temperature can be achieved in two ways: Enriching the Air-Fuel ratio and Lowering the amount of Oxygen. The first technique lowers the efficiency of the engine and affects other parameter too. But second technique lowers the cylinder temperature, reducing NOx, but it also reduces fuel economy and performance, and creates excess soot, which results in more frequent oil changes. So, the best way is to limit the amount of Oxygen in the cylinder. Reduced oxygen results in lower cylinder temperatures. This is done by circulating some exhaust gas and mixing it into the engine inlet air. This process is known as Exhaust Gas Re-circulation(EGR). II. LITERATURE SURVEY NOx formation in diesel engine is a highly temperaturedependent phenomenon and takes place when the temperature in the combustion chamber exceeds 2000 K. So 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 16%, 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, therefore 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 un-burnt particulates in EGR, which in turn reduce the particulate emission also. An experimental investigation was conducted to observe the effect of exhaust gas re-circulation on the exhaust gas temperatures and exhaust opacity. The experimental setup for the proposed experiments was developed on a one-cylinder, direct injection, water-cooled, compression ignition engine. No. of experiments was conducted for observing the effect of different quantities of EGR on exhaust gas temperatures and opacity. Over recent past years, stringent emission legislations have been imposed on NOx, smoke and particulate emissions emitted from automotive diesel engines worldwide. Diesel engines are typically characterized by low fuel consumption and very low CO emissions. However, the NOx emissions from diesel engines still remain high. Hence, in order to meet the environmental Legislations, it is highly desirable to reduce the amount of NOx level in the exhaust gas. Diesel engines are most commonly used to drive tractors, heavy lorries and trucks. Owing to their low fuel consumption, they have become increasingly attractive for smaller lorries and Passenger cars also. But higher NOx emissions from diesel engine remain a major problem in the pollution aspect. In order to reducing vehicular emissions, baseline technologies are being used which include direct injection, turbo-charging, air-to-air inter-cooling, combustion optimization with and without swirl support, multi-valve cylinder head, advanced high pressure injection system i.e. split injection or rate shaping, electronic management system, lube oil consumption control etc. However, technologies like exhaust gas recirculation (EGR), soot traps and exhaust gas after treatment are essential to cater to the challenges posed by increasingly stringent environmental emission legislations. A major obstruction in understanding the mechanism of formation and controlling its emission is that combustion is highly heterogeneous and transient in diesel engines. While NO and NO2 are react together at peak higher temperatures to form NOx, there are some distinctive differences between these two pollutants. NO is a colourless and odourless gas, while NO2 is a reddish brown gas with pungent odour. Both gases are considered toxic, but NO2 having a level of toxicity 5 times greater than that of NO. Although NO2 is largely formed from oxidation of NO, attention had been given on how NO can be controlled before and after combustion process. Nitrogen Oxides are formed during the post flame combustion process in a high temperature region. The most widely accepted technique/mechanism was suggested by Zeldovich (Heywood 1988). The principal source of NO formation is the oxidation of the nitrogen present in atmospheric air. The nitric oxide formation chain

Advance Research and Innovations in Mechanical, Material Science, Industrial Engineering and Management - ICARMMIEM-2014 226 reactions are initiated by atomic oxygen, which forms from the dissociation of oxygen molecules at the high temperatures reached during the combustion process. In diesels, NO2 can be 10 to 30% of total exhaust emissions of oxides of nitrogen. A plausible mechanism for the persistence of NO2 is described in previous section. The local atomic oxygen concentration depends on molecular oxygen concentration as well as local temperatures. Formation of NOx is almost absent at temperatures below 2000 K. Hence EGR technique that can keep the instantaneous local temperature in the combustion chamber below 2000 K, will be able to reduce NOx formation. Recirculation System Part of the exhaust gas is to be recirculated and put back to the combustion chamber along with the intake air. The quantity of this EGR has to be measured and controlled accurately hence a by-pass for the exhaust gas is provided along with the manually controlled EGR valve. The exhaust gas comes out of the engine during the exhaust stroke at high pressure. It is pulsating in nature. It is desirable to remove these pulses in order to make the volumetric flow rate measurements of the re-circulating gas possible. For this purpose, another smaller air box with a diaphragm is installed in the EGR route. An orifice meter is designed and installed to measure the volumetric flow rate of the EGR. A U-tube manometer is mounted across the orifice in order to measure the EGR flow rate. Suitable instrumentation is provided to acquire useful data from various locations. Thermocouples are provided at the intake manifold, exhaust manifold and various points along the EGR route. An AVL smoke-meter is used to measure the smoke opacity of the exhaust gas. The pressure difference across the orifice is used to calculate the EGR rate. A matrix of test conditions is used to investigate the effect of EGR on exhaust gas temperature and exhaust smoke opacity. III. OBJECTIVE Our main objective is to reduce the NOx level by recirculating the exhaust gas inside the engine cylinder with air so that the amount of excess Oxygen can be reduced and hence reduction in cylinder temperature can be achieved. IV. EXPERIMENTAL SETUP A one cylinder constant speed engine is used for the purpose. This is is basically a Direct Injection, water cooled, vertical four stroke engine. The setup mainly consists of air box. pressure gauges, regulating valve, thermocouples. orifice plate U-Tube manomter etc. Air box is designed for measuring the volumetric flow of intake air to the engine. It is mounted on Inlet pipe between the inlet manifold and air filter of the the engine as shown in figure 1. The air box dampens out the fluctuation of intake air. A diaphragm is provided at the side of air box for damping out the undulation effectively. The air box is fitted withan orifice for volumetric flow rate measurement of air. A U-Tube manometer is mounted across the orifice plate to measure the pressure difference in the air box and atmosphere. Pressure gauges are used to measuring the pressure at high pressure side and low pressure side. Orifice plate is also coupled which measures the rate of flow of mixture of air and exhaust gas. Thermocouples are used to measure the temperature at different sites as shown in figure1. Regulating valve is used to control the firinf of exaust gas to the air box so that a constant mass of exhaust gas is introduced to the air box. A valve is provided at inlet pipe to control the air intake. From the experiment we observed that at different EGR rate the NOx level are different that is when increasing the EGR, the NOx level is reduced to a great extent. The objective of developing this experimental setup is to investigate the effect of various EGR rates and other engine parameter on exhaust emission from the engine. A study conducted on two cylinder vertical air cooled four stroke engine shown that at the rated speed 1500 RPM the engine developed approximately 9 to 10 KW power output. The inlet valve opens 4.5 degree BTDC and closes at 45.5 degree ABDC. The exhaust valve opens at 35.5 BBDC and closes at 4.5 degree ATDC. The engine is coupled with 220 volts AC generator (Avinas Kumar Agarwal). We can see in fig.2 that when the % EGR is zero and that time the PPM count of NOx is about 120 at 30 % load condition. Similarly when % EGR is Zero at 60% load condition then the PPm count of NOx is about 140.But when the % EGR is increasing then the ppm count of NOx is appreciably reduced to a great extent at different load condition. So we can conclude from fig.2 that at different EGR rate and different load condition, the NOx level is reduced. From the fig.1, when the fresh air is taken by the engine during suction stroke, then it is compressed during the compression stroke. At the time of compression the temperature of air inside the cylinder increases to a maximum level (self ignition temperature of fuel).after that fuel is injected to the cylinder in the form of fine. Fuel is ignited due to self ignition temperature of the fuel is attained and combustion takes place. After combustion, combustion product (exhaust gas) comes out from exhaust manifold. About 20% of Exhaust gas is delivered to air box where it passes through a regulating valve and rest of exhaust gas will goes to atmosphere as shown in fig.1.

Advance Research and Innovations in Mechanical, Material Science, Industrial Engineering and Management - ICARMMIEM-2014 227 Air is also drawn to air box (Mixing chamber) so that mixing takes place and a temperature difference is observed which result in reduction of temperature of exhaust gas. Now we have a control temperature exhaust gas which is again pass through a orifice plate where a manometer measures its pressure and orifice plate measures the rate of flow of exhaust gas. Here thermocouples measures the temperature at different sites of combustion chamber. Now this air is circulated to the engine by inlet pipe where it reduce the level of excess Oxygen so that temperature inside the engine cylinder can be controlled and cycle is repeated again and again. This process is known as Exhaust gas re-circulation by which the temperature inside the engine cylinder can be control to a great extent and appreciable amount of NOx can be controlled. Fig. 1: Line Diagram of Exhaust Gas Re-circulating System Table 1: The Technical Specifications of the Engine S.No. Engine Description Specification 1. Type of Injection Direct Injection 2. Engine Manufacturer Kirlosker 3. No. of Cylinder One 4. Bore/ Stroke 80mm/110mm 5. Max. Power/Engine Speed 5 BHP/1500RPM 6. Compression Ratio 16.5:1 V. RESULT AND DISCUSSION At fixed power conditions, as the percentage EGR increases (0 21%), the temperature of the exhaust gas continuously decreases. Earlier it had been mentioned that the most important reason for the formation of NOx in the combustion chamber is extremely high temperature. Our experimental results indicate a decrease in the exhaust temperatures with increasing EGR, therefore it can be concluded that the combustion chamber temperatures also decrease and thus the formation of NOx is decreased. Fig.2: Effect of EGR on Knox (Avinas Agarwal) This reduction in exhaust gas temperature does not affect the thermal efficiency. It is clear that thermal efficiency remains unaffected by EGR. However, at high loads and at EGR rates above 15%, thermal efficiency tends to decrease slightly. This may be due to the fact that the amount of fresh oxygen available for combustion gets decreased due to mixing of exhaust gas with air. Opacity of the exhaust gas increases as the rate of EGR is increased. At low loads, the rate of increase in opacity is almost the same with increase in EGR but at higher loads and higher rates of EGR, opacity increases rapidly. Further it was also found that the brake specify fuel consumption (BSFC) is

Advance Research and Innovations in Mechanical, Material Science, Industrial Engineering and Management - ICARMMIEM-2014 228 fairly independent of EGR. As load increases, BSFC decreases rapidly. At 3kW the BSFC gets almost saturated at 0.22 kg/kw. VI. CONCLUSION AND FUTURE ENHANCEMENT An experimental set-up to measure the effects of exhaust gas recirculation on engine characteristics like exhaust gas temperature, thermal efficiency, brake specific fuel consumption and smoke opacity has been developed. Experiments had been carried out using the setup to prove the efficiency of EGR as a technique for NOx reduction. It had seen that the exhaust gas temperatures reduce drastically by employing EGR. This indirectly shows the potential for reduction of NOx emission. Here we can concluded from the fact that the most important reason for the formation of NOx in the combustion chamber is the high temperature of about 2000K at the site of combustion. Thermal efficiency and brake specific fuel consumption are not affected significantly by EGR. However particulate matter emission in the exhaust increases, as evident from smoke opacity observations. Diesel engines score higher than that of other engines in most aspects like fuel consumption and low CO emissions, but loses in NOx emissions. EGR has been proved to be one of the most efficient methods of NOx reduction in diesel engines. The increase in particulate matter emissions due to EGR can be taken care by employing particulate traps and adequate regeneration techniques. CartellieriW1998 Cooled EGR A technology for future efficient HD diesels. SAE 980190, vol.11, pp.25-36, August 1951, 1998. Hirday Ram Pursuing in B. Tech 4 th year, Mechanical Engineering, College of Engineering Roorkee, Uttarakhand, India. DOB: 20/05/1991. My work is under the guidance of Dr.J.M.L. Gupta, Associate Professor of Mechanical Department. ACKNOWLEDGEMENT I express my gratitude and appreciation to my project guide Mr.J.M.L. GUPTA for his constant supervision, inspiration and encouragement right from the beginning of this paper entitled. EFFICIENT WORKING OF CI ENGINES WITH UTILISATION OF EXHAUST GAS I am also grateful and indebted to Mr. Thiru Ph.d Student at IIT Roorkee, Physics Department and Mr. Uday for both of them help and advice in the completion of this paper. I further take this opportunity to thanks all my classmates for taking active participation during the preparation of my work so as to make it lively and a great success. REFERENCES [1] Avinas Kumar Agarwal and Shrawan Kumar Singh Effect of EGR on the Exhaust gas Temperature and Exhaust Opacity in Compression Ignition Engines Bonafiring Sadhana publication Indian journal of Mechanical Engineering Department, Vol. 29, Part 3, pp. 275 284,June 2014. [2] Sher E Handbook of Air Pollution from IC Engine Pollolutant Formation and Control Bonafiring San Diego, CA: Academic Press, vol.02, pp.9-10, 1998. [3] Mehta S, Oey F, Sumburg C L, Levendis Y A An aerodynamically regenerated diesel particulate trap with a flow-through soot incinerator section. Bonafiring published by SAE under section 940461, vol.09, pp19-25, May 1998. [4] Stearns R F, Johnson R R, Jackson R M, Larson C A Derivation of flow equations, Flow measurements with orifice meters. Bonafiring (Princeton, N J: D V N Com.) p-4, zelenka P, Aufinger H, ReczekW,