1. Ph.D Theses
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Item Thermal Depolymerization of Scrap Tires Into Liquid Fuels: Upgradation and Utilization In Diesel Engine(National Institute of Technology Karnataka, Surathkal, 2022) Mohan, Akhil; Madav, Vasudeva; Dutta, SaikatConversion of scrap tire into fuel oils has attracted commercial attention since revenue can be generated from inexpensive and abundant feedstock while easing waste management issues. Globally, 1.5 billion scrap tires are generated every year. Environmental accumulation of tire waste is a global problem, and one way to control the problem is to convert them into fuels and specialty chemicals. There are various approaches for recycling scrap tires, such as re-treading, reclaiming useful products for playgrounds, open incineration, pyrolysis, gasification, and illegal dumping. Illegal dumping often provides a site for breeding mosquitoes, rodents, and larvae formation. Open burning releases a thick black plume of smoke with 1,3-butadiene, nitrogen, carbon, and sulfur oxides with the release of hazardous polyaromatic hydrocarbons. Out of the approaches mentioned above to recycle tires, pyrolysis is an interesting energy recovery process due to the formation of solid (carbon black) and steel wires (in the case of the tire), pyro-gas, along oil products. Production of crude tire pyrolysis oil from scrap tires is a promising approach by thermal depolymerization at an oxygen starved atmosphere and a temperature of 400-600 oC. The primary objective of present study is to refine CTPO by the principle of selective adsorption and preferential solubility using cost-effective adsorbent and solvent and utilization as a fuel in a single-cylinder diesel engine. A field study was conducted in a 10-ton rotating autoclave reactor to optimize scrap tire pyrolysis parameters (400 oC, 10 oC/min, 0.2 bar, 4 rpm), and investigate the existing problems in the industry with a special focus on applying CTPO in diesel engines. Crude tire pyrolysis oil (CTPO) is a dark brown to black colored syrupy liquid with C6-C24 organic compounds with various classes such as paraffin, olefins, terpenes, aromatics, nitrogen, and sulfur-containing compounds, oxygen-containing compounds. The major challenge for utilizing CTPO in engine or furnace is the inferior fuel properties such as low heat content, low flash point, high acidity, low cetane index, creaming or phase separation in storage tanks, pungent smell due to the presence of dibenzothiophenes and mercaptans. However, thermal distillation is widely used as an upgradation technology implemented in most of the small scale tire pyrolysis units. Distillation needs huge capital investment and energy, making the process less attractive and unsuitable for the long-term run. In the present study, a straightforward, robust, inexpensive, and scalable up-gradation strategy for refining CTPO by preferential solubility and selective adsorption to utilize single-cylinder direct-injected stationary engines is formulated. A limited study has been attempted for the up- gradation of CTPO using adsorbents and solvents. The present study also envisages extensive characterization of CTPO, StTPO and diesel to comprehend the fuel chemistry in terms of physical, thermal, and chemical analysis through various analytical techniques. GC×GC TOF- MS analysis showed that sulfur, benzene derivatives, naphthalene’s and polyaromatic hydrocarbons were lowered by 48.86%, 25.68%, 43.69%, and 27.79%, respectively. The batch scale process's oil yield is improved by 95% compared to the laboratory scale upgradation strategy. Experimental results found that StTPO40 is a binary optimal blend in terms of performance, combustion, and emissions. The emissions from StTPOxx were significantly improved after upgradation by silica gel as adsorbent and petroleum ether as a diluent. Furthermore, ethyl levulinate, a potential bio-diluent with high oxygenate, was also utilized as an additive to StTPOxx blends to scrutinize performance, combustion, and emissions of single- cylinder, direct-injected stationary diesel engine, which is another novelty of the present study. The emission components are significantly dropped down after the upgradation of CTPO, but the performance was slightly lowered after the refining process. The nitrous oxide emission from StTPO40 and StTPO40EL10 was significantly reduced by 43.09% and 44.54%, respectively. Heat release from StTPOxx and StTPOxxEL10 were higher than diesel due to the high amount of polyaromatics hydrocarbons, naphthalenes, and benzene derivatives. StTPO40EL10 is a ternary optimal blend in terms of performance, combustion, and emission, with EL as a potential diesel additive. It can be concluded that the StTPOxx and StTPOxxEL10 can be fully utilized in a diesel engine without any modifications and operational failures. In short, the lower blend percentage of StTPO40EL10 and StTPO40 can be used as an alternative fuel for a single-cylinder direct- injected diesel engine. In contrast, the higher blend percentage (StTPO60EL10, StTPO80EL10, StTPO90EL10, StTPO60, StTPO80, and StTPO100) can be utilized in boilers, furnaces, burners and marine engines.Item Studies on The Performance, Combustion & Emission Characteristics of A Multicylinder Si Engine Fueled with lpg Along with Varying Steam Induction Rates(National Institute of Technology Karnataka, Surathkal, 2013) K. S, Shankar; Mohanan, PVehicle and fuel technologies have undergone important developments in the last 30 years. The volatility of oil prices and increasing concerns about the environment has influenced researchers to look in to possible alternatives to petroleum based fuels. Efforts are on to improve the combustion efficiency of the engines operating with conventional fuels. The various alternative fuels for spark ignition (SI) engines on which research is going on at present includes alcohols, liquefied petroleum gas (LPG), natural gas etc. Ethanol enriched gasoline blends are increasingly being used in SI engines due to the renewable nature of ethanol as well as increased governmental regulatory mandates. Ethanol can be produced from natural products or waste materials, compared with gasoline which is produced from non-renewable natural sources. In addition, ethanol shows good antiknock characteristics. Gaseous fuels are promising alternative fuels due to their economical costs, high octane numbers, higher heating values and lower polluting exhaust emissions. From the point of view of reduction of exhaust emissions such as unburnt hydrocarbon (HC) and carbon monoxide (CO), liquefied petroleum gas (LPG) is a useful alternative fuel for SI engines. Due to its higher octane value, LPG fuel can be used under the higher compression ratios. Combustion of LPG results in greater emissions of the oxides of nitrogen (NOX) than that for gasoline, the values reaching more than double at some operating conditions. Injection of water into the intake manifold has been found to be an effective way to reduce NOX emission in SI, CI and LPG engines. The present study deals with experimental investigations on the effect of steam induction with the intake air while using LPG as fuel on engine performance, combustion and emissions in a modified multi-cylinder SI engine. The engine operating parameters of speed, throttle opening positions and static ignition timings are varied. To compare the results of the above experiments, an ethanol enriched gasoline blend is optimized as a baseline fuel based on engine performance, combustion and emissions. The experimental setup consists of a stationary, fourstroke, four cylinder, multipoint port fuel injection (MPFI) engine of 44 kW capacity at 6000 rpm, which is connected to an eddy current dynamometer for loading. A piezo-electric pressure transducer is used for recording the cylinder pressure. The setup has a stand-alone panel box consisting of air box, fuel tank, manometer, fuel measuring unit, differential pressure transmitters for air and fuel flow measurements, process indicator and engine indicator. An AVL Digas 444 five gas Exhaust gas analyzer is used to measure the NOX (ppm), CO (%vol.), CO2 (%vol.) and HC (ppm) emissions in the exhaust. Initially experiments are conducted to study the performance, combustion and emission characteristics of the test engine fueled with ethanol enriched gasoline blends viz: E5, E10, E15 and E20 (on volume basis, and E5 means 5% ethanol and 95% gasoline) to optimize a baseline fuel. In the next part tests are conducted on the engine modified to run with injection of LPG as fuel and the combustion, performance and emission characteristics are evaluated. Separate four gas injectors are installed in the inlet manifold near the inlet port of each cylinder for injecting LPG. The gas injectors are operated by solenoid valves driven by 12V DC power supply. A separate gas ECU has been used for driving the solenoid valves. Experiments are conducted at wide open throttle (WOT) and part throttle conditions with varying loads in the engine speed range of 2000 rpm to 4500 rpm. Tests with ethanol enriched gasoline are conducted at the pre-set static ignition timing of 5 degree before top dead center (bTDC). The LPG performance and emissions are evaluated at various static ignition timings of 3, 4, 5 and 6 deg. bDTC. In the last part of the investigations, the engine tests are conducted with LPG along with steam induction. The waste heat from the exhaust gas has been used to generate steam from deionized water. Steam to LPG flow rates of 10, 15, 20 and 25% (on mass basis) are used. The steam is mixed with the intake air in the intake manifold of the engine. Results of the experiments have shown that among the various ethanol enriched blends, the blend of 20% ethanol was the most suitable one from the engine performance and CO & HC emissions points of view. At WOT operations the effect of ethanol blending on coefficient of variation of IMEP is to reduce it by an average of 2% with E15 fuel blend when compared to gasoline fuel operation over the entire speed range. All the ethanol-gasoline blends exhibit better cyclic variation pattern compared to gasoline at WOT operation. The engine performance has improved with the addition of ethanol, increasing the thermal efficiency and reducing the brakespecific energy consumption. A significant reduction in the HC emission was observed as a result of leaning effect and additional fuel oxygen caused by the ethanol addition. CO emission is reduced by addition of ethanol to gasoline. All engine exhaust emissions were lower at 3500-4000 rpm at various throttle valve opening condition except NOX which has shown an increasing trend with ethanol blended fuel. Hence it can be concluded that blending ethanol up to 20% to gasoline will reduce the cycle-by-cycle combustion variations and emissions though a marginal increase in NOX emissions results. The findings of the experiments with LPG suggest that higher thermal efficiency and therefore improved fuel economy can be obtained from SI engines running on LPG as against gasoline at the pre-set static ignition timing of 5 deg. bTDC. Also the exhaust emissions of CO, HC have reduced considerably. But the emissions of NOX have increased significantly at higher engine speeds. The CO emission has reduced from an average value of 5 % to about 1.3 % and corresponding change in HC noticed was from 350 ppm to 22 ppm when LPG was used instead of gasoline at pre-set static ignition timing. The NOX emission with LPG was almost double when compared to that with gasoline at higher engine speeds. When engine runs with LPG, better performance has been observed when static ignition timing is advanced to 6 deg. bTDC. Advancing the static ignition timing has also resulted in reduced CO and HC emissions. But the advanced ignition timing shows a further increase in NOX emissions. Retarding the ignition timing achieves lesser NOX emissions at higher engine speeds. Steam induction is one of the methods to reduce NOX emissions. Steam induction will reduce the peak temperature of the engine cylinder so that NOX formation will be reduced. The experimental results showed that steam induction worked as a cooling means for the fuel-air charge and slowing the burning rates, resulting in reduction of the peak combustion temperature. It is found that NOX emissions have reduced significantly by 20 - 45% over the entire operating range when compared to LPG operation. No considerable changes in CO and HC emissions are observed. Hence use of LPG with advanced ignition timing of 6deg. bTDC with steam induction up to 25% steam to fuel mass ratio at higher engine speeds and up to 10% steam to fuel massratio at lower engine speeds can be used from the point of view of improved engine performance and reduced exhaust emissions. When comparing the performance and emissions of ethanol enriched gasoline and LPG with steam induction, it is noted that, comparatively E20 blends performs better that LPG alone. With steam induction the performance with LPG deteriorates. The brake thermal efficiency of 15% steam with LPG at wide open throttle condition and 3500 rpm is lower by 3.5% when compared to E20. CO reduces with LPG when compared to E20. But a slight increment is noted when steam is inducted. NOX emissions are higher for both E20 and LPG when compared to gasoline. However, with the induction of steam along with LPG, the NOX can be substantially brought down. At 3500 rpm and wide open throttle condition, the NOX emissions of E20 and 15% steam with LPG are similar. But at 4500 rpm, NOX emission is higher by 580 ppm. From the experimental investigations it can be concluded that use of ethanol enriched blends in unmodified engine is an alternative for the use of gasoline as a sole fuel. However with the current option of LPG as alternative fuel to SI engines, it can be used along with steam induction as a means to considerably reduce NOX emissions, with marginal reduction in engine performanceItem Experimental Investigation on Performance and Emission Characteristics of Non Road CI Engines Operated With Cardanol Biodiesel Blends(National Institute of Technology Karnataka, Surathkal, 2014) Mallikappa; Murthy, Ch. S. N.; Reddy, N. Rana PratapDiesel engines dominate the field of commercial transportation and agricultural machinery because of their superior fuel efficiency. There is a limited reserve of the fossil fuels and the world has already faced the energy crisis of the seventies concerning uncertainties in their supply. Import of petroleum products is a major drain on our foreign exchange sources and with growing demand. Research has shown that, these vehicular emissions are the source of air pollution and have adverse implications on health and air quality. Lead, carbon monoxide, nitrogen oxides, particulate matter and hydrocarbons together with the unavoidable production of carbon dioxide are the harmful components of exhaust gases from internal combustion engines [4]. Energy is considered as a critical factor for economic growth, social development and human welfare. More than 6.5 million diesel engines are being used in the Indian Agricultural sectors for various activities. With increasing trend of modernization and industrialization, the world energy demand is also growing at a faster rate. India, facing the challenge of meeting a rapidly increasing demand for energy, and ranks sixth in the world in terms of energy demand. Its economy is projected to grow 7%- 8% over the next two decades and there will be a substantial increase in demand for oil to manage transportation and also to meet various other energy needs. The primary problem associated with straight vegetable oils as a fuel in diesel engines is caused by high viscosity and low volatility, which, in turn cause improper atomization of fuel during injection and lead to incomplete combustion and result in formation of deposits on the injectors and cylinder heads, leading to poor performance, higher emissions and reduced engine life. The high viscosity of vegetable oils can be reduced by using transesterification process. The concept of transesterification process of non-edible oil with an alcohol provides a clean burning fuel (commonly known as biodiesel) having less viscosity. Its main advantage is that many of its properties are quite close to those of diesel and it can be grown and processed in rural areas. Keeping in view the plight of the energy crisis, in this work cardanol biodiesel has been used for investigation in various single and multi-cylinder diesel engines.ii A single cylinder diesel engine was used to evaluate the performance and emission characteristics of cardanol biodiesel. A single cylinder VCR (variable compression ratio) engine was fuelled with volumetric blends of cardanol biofuel and the performance and emission characteristics were compared with petro diesel and PE characteristics were evaluated for 18:1 and 17:1compression ratios. An extended experimental study was conducted on a Kirloskar double cylinder CI engine to evaluate the performance and emission characteristics. The cardanol biodiesel volumetric blends like 0 %, 5% ,10% ,15% ,20% , 25% and base fuel (Petro diesel) were tested at various loads like 0 %, 25 %, 50%,75% and full load, and at a constant speed of 1500 rpm. From the results, it is found that the brake specific energy consumption decreased by 30 to 40% approximately with increase in load conditions. Brake thermal efficiency increased with increase in load. The brake specific energy consumption decreased by 30 to 40% approximately at higher CR and 25 to 30% at lower CR with increase in brake power. The HC emissions are nominal up to B20, and more at B25, the reason for this being the incomplete combustion. The Nox emissions (ppm) increased with increased proportion of blends and with higher EGT. The Carbon monoxide emissions increased with higher blends, and increased slightly more after 20% blends. From this investigation it is observed that up to 20% blends of cardanol biodiesel may be used in CI engines without any hardware modifications.Item Combustion Control and Performance Analysis of CI Modified HCCI Engine Using Lean Combustion Technology(National Institute of Technology Karnataka, Surathkal, 2018) M. R, Sumanlal; Mohanan, P.Amongst the numerous research papers published over the last decade, the homogenous charge compression ignition (HCCI) has often been considered as a new combustion process in reciprocating internal combustion engines. With increasingly stringent emission legislation and demand for significant reduction in CO2 emission, research and development of cleaner and more efficient combustion engines has been intensified. HCCI combustion has emerged as an effective and viable technology that has the potential of simultaneously reducing pollutant emissions and fuel consumption from internal combustion engines. The investigation focuses on the effect of diesel vapour induction on the engine performance and to try and achieve Homogeneous Charge Compression Ignition (HCCI) mode of combustion in the engine. An existing direct injection CI engine is modified to work as an HCCI engine by using a shell and tube heat exchanger which aids in the production of diesel vapour by utilising heat content of exhaust gases . The external mixture formation is adopted for the preparation of homogenous charge. The diesel vapour coming out of the heat exchanger is mixed with air near the intake manifold. The experimental set up is modified so that the flow of exhaust gas to the heat exchanger and the flow of diesel vapour to the engine can be controlled. A separate fuel tank is provided to measure the amount of diesel vapour utilized. Vapour utilization studies were carried out. It is found that a maximum utilization was limited to 60 percentage at different load conditions. After that knocking occurs and engine stops working. The loading of HCCI mode was limited from 50 to 100 % due to poor vapour quality at lower loads. The performance and emission characteristics of HCCI engine is studied at different injection pressures and injection timings and is compared with conventional engine. It is found that a higher injection pressure of 200 bar and advancing the injection timing to 31.50 bTDC improved the brake thermal efficiency of the engine and reduced NOx emissions with increase in Hydrocarbon and Carbon Monoxide emissions. A maximum of 20.54 % increase in brake thermal efficiency is obtained at 75 % load condition. NOx emissionsare reduced upto a maximum of around 50% at 31.5 deg. bTDC, 200 bar injection pressure and in vapour induction by 37% whereas CO emissions are increased around 31% and HC emissions are increased by 47%. Normally Research engines are fitted with piezoelectric pressure transducer for the measurement of in cylinder pressure. But strong ion concentration is formed in the cylinder by the combustion process. If the ion concentration is detected, it can be used as a combustion diagnosis tool. Here a standard spark plug is converted to work as the ion sensor. It is carefully mounted over the cylinder head without affecting the passage of cooling water. An electrical circuit is designed to measure the ion voltage produced during the combustion process. Then a correlation between ion voltage and cylinder pressure is developed from the measured data so that ion voltage is calibrated in to in cylinder pressure. The results show that there is only 10% difference between the pressure given by the pressure sensor and ion sensor. Therefore the expensive pressure transducer is replaced by cheap and reliable ion sensor for combustion monitoring. Extending the operation range in HCCI mode is a very important factor. For every load condition the amount vapour inducted to the engine is limited. Preheating of intake charge reduces the possibility of condensation of diesel vapour near intake manifold. Therefore the effect of preheating was also studied by heating the inlet air by using a heating coil. Preheating always improved the percentage vapour utilization. A percentage increase of 5.91 %, 7.93 % and 7.3 % in percentage vapour utilization is found for 50 %, 75 % and 100 % load conditions respectively. Preheating improved the brake thermal efficiency and brought down CO and HC emissions however it slightly increased NOx emissions. The maximum efficiency is 33. 5% seen at 75% load condition for preheating temperature of 65 °C and at percentage vapour utilization of 37.95 %. A maximum percentage reduction of 78.33 %, 45.15 % and 57.14 % in CO emissions was attained by preheating of air at 50, 75 and 100 % load conditions respectively. A maximum percentage decrease of 48.3 %, 50 % and 44.82 % in Unburned Hydrocarbon emissions was attained by preheating for 50, 75 and 100 % load conditions respectively. NOx emissions are increased by almost 5% for different load conditions by preheating of theintake air. Preheating of vapour was limited to 65 °C due to continuous increase in NOx emissions. Thus the most suitable operating condition for HCCI mode can be identified as 75 % load coupled with 65 °C preheating. The increase in vapor mass fraction increased the performance of the engine. This was mainly because the HCCI mode of combustion was approached. At the same time the start of combustion was still governed by the injection of vapor fuel. This gave a method of control of combustion which is normally difficult in HCCI engines