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International Journal of Applied Environmental Sciences ISSN 0973-6077 Volume 11, Number 1 (2016), pp. 155-163 © Research India Publications http://www.ripublication.com

Investigating the as Secondary Fuel for Ci

K. Senthilkumar1, * and S. Vivekanandan2

1 Assistant Professor, Department of Mechanical Engineering, Annamalai University, Annamalai Nagar, Chidambaram, Tamil Nadu, India. 2 Associate Professor, Department of Mechanical Engineering, Annamalai University, Annamalai Nagar, Chidambaram, Tamil Nadu, India. 1, 2E-mail:[email protected], [email protected]

Abstract

The aim of this study is to determine the performance characteristics of CI engine using biogas and diesel as dual fuel mode. Biogas a clean and renewable form of energy derived from organic wastes. To determine the engine performance characteristics using biogas and diesel for practical use, the of the engine is modified to operate with dual fuel mode. This study reveals the effect on engine performance such as brake , specific fuel consumption and temperature fueled with biogas-diesel by varying engine load and maintained at rated speed. The experimental test results shows that when the engine operated with 60%biogas+40% diesel perform better brake thermal efficiency with minimum fuel consumption when compare to diesel. The results also suggest when the engine operating with biogas-air rich mixture performed better thermal efficiency compares the engine operated with diesel-air mixture under the same operating condition. In addition to this the exhaust gas temperature was lower than that in diesel fuelling at all test conditions.

Keywords: anaerobic digestion, biogas, brake thermal efficiency, dual fuel, performance test, renewable energy, SFC

Introduction Due to changing global scenario and population explosion, the need to provide more energy and also proper energy conservation is required. In India, energy demand from is as high resulting large proportion of the country’s energy imports nearly 70% of required fuel which affects the total foreign exchange and problem of 156 K. Senthilkumar and S. Vivekanandan increasing the prices of the fossil fuels [1]. The transport sector plays a major role for consuming products, more over 60% of total caused by the automobile exhausts from the vehicles run on petroleum products. In order to avoid this, there is an urgent need to introduce alternate fuels as substitutes for diesel and petrol in the transport sector [2]. Hence there is a need to exploit the renewable energy resources for the energy demand. Biogas is one of the best available energy sources to meet this demand both in rural and urban areas. Our country ranks second in the world of utilizing biogas. It is clearly known that the renewable energy sources already contribute about 5% of the total power generation in our country [3]. Among all types of renewable energy, biogas production from anaerobic digestion seems to be one of the most promising options[4]. Biogas is produced by anaerobic digestion of various organic substances like industrial waste, kitchen waste, sewage waste, cattle dung etc. which offers low cost than any other secondary fuels. Biogas can be used in CI engine as a dual fuel and improves engine performance. The biogas can be introduced in the engine with air during induction and diesel is injected towards the end of compression to initiate the of gas air mixture [5]. So, it can be used as substitute to petroleum products. Biogas consists of mainly methane (CH4) and dioxide (CO2). It also contains traces of other gases; its composition slightly varies depending on the type of biomass used. Biogas calorific value is proportional to the CH4 concentration. It can be used as partial substitution fuel for internal combustion engine. As reported in previous publication, biogas composed of various composition such as methane (60-70%), (30-40%), (‹1%) and sulphide(10-2000ppm). This composition make difficult to run the [6]. Among all the impurities in the biogas, CO2 and moisture content should be eliminated to be used as fuel for the engine. Most studies indicate that all combustion devices are easily adaptable to be used as gaseous fuels. Biogas being a clean fuel causes clean combustion and reduces the contamination of engine oil, because biogas cannot be directly used in automobiles as it contains some other gases like CO2, H2S and vapor. For use of biogas as a vehicle fuel, it is upgraded first by removing the impurities such as CO2, H2S and water vapor [7]. Biogas can be used in both light and heavy duty vehicles. Light duty vehicles can normally run on biogas without any modifications, where diesel require combination of biogas and diesel for combustion [8]. CI engines are widely used as power source for automobile due to their high thermal efficiency, excellent fuel economy and low regulated emissions of unburnt , and carbon dioxide [9]. Methane is the main component of biogas and exhibits greater resistance to the knock phenomenon due to its higher and auto ignition temperature, making it appropriate for engines with high compression ratios. In addition to the carbon content of methane is also relatively low compared to that of conventional , resulting in a significant decrease of pollutant exhaust emission [10]. This paper aims at developing a CI engine that can run using biogas as secondary fuel. The engine performance with the diesel and biogas was to evaluate in terms of brake specific fuel consumption, brake thermal efficiency and exhaust gas temperature at different load conditions of the engine. Investigating the biogas as secondary fuel for CI engine 157

Experimental Programme The main objectives of this study to generate biogas from a 1m3 capacity floating drum type biogas plant with 700 litres gas holder capacity and by operating the digester in a continuous process with mesophilic temperature range between 27ºc-37ºc by charging the digester with cow manure mixed with water as 50:50 ratio. The digester was operated for 60 days hydro retention time. The digester slurry was charged with inoculums and maintained the slurry by volume as 50:50 ratios. The initial digester slurry pH was adjusted to optimum value between7 to 7. 5. Other important parameters like carbon nitrogen ratio, and loading rate are maintained for a continuous biogas production. In this study the biogas produced from the plant is fed to the engine in the inlet manifold mixed with air. Before supplied to the engine the biogas was upgraded by purification process [11]. The effect on performance of engine using biogas-diesel dual fuelled and to evaluate the performance characteristics of CI engine.

Experimental setup: The experimental investigation was conducted in the Department of Mechanical Engineering, Annamalai university. Biogas generates from anaerobic digestion of 1m3 capacity plant was supplied gas to the engine continuously after removing carbon dioxide and moisture. The experiment was carried out with the conventional diesel fuel engine of single 5kW with the rated speed of 1500 rpm water cooled engine as illustrated in Fig. 1 and specification noted in Table 1[12]. The engine manifold is provided with gas kit to mix biogas and air in one chamber and supplied to the engine inlet manifold with the help of T-joint. During suction stroke the engine will take air from the along with biogas. Mass of diesel supplied to the engine measured with the help of manometer [13]. The quantity of gas flow from the digester is measured with the help of gas flow meter before it is supplied to the engine. The quantity of air and biogas flow can be increased with respect to engine load condition with the help of different sets of [14]. The schematic view of experimental set up and photographic view are shown in Fig. 1 and Fig 2.

Table 1: Engine specifications

Engine Kirloskar Type Water cooled BHP 5kW No. of cylinders 1 87. 5 Stroke 110mm Rated speed 1500 rpm Combustion Compression ignition

158 K. Senthilkumar and S. Vivekanandan

Figure 1: Schematic view of experimental set up

Figure 2: Photographic view of experimental set up

Table 2: Properties of biogas and diesel

Property Biogas Diesel - 50 Heating value(MJ/Kg) 24. 50 45. 92 @40°c - 3. 32 Specific gravity@15ºc 0. 001 0. 830 Sulphur content(%wt. ) 0. 12 0. 037

Experiment methods and materials: The experiment was carried out in CI engine at constant speed. The engine was run at the idling condition for a certain period of time. The test was conducted by varying the load with properly fitted mechanical loading arrangement. The speed was kept Investigating the biogas as secondary fuel for CI engine 159 constant for various load conditions from no load to the full load condition of the engine as equation 1

Brake power = X angular velocity = (1) N = 1500 rpm Re = Torque arm length= 0. 305m

To evaluate comparatively of performance characteristics of CI engine using diesel and biogas for various load conditions as 20%, 40%, 60% and 80% respectively. Moreover, time for fuel consumption by the engine was also noted to calculate specific fuel consumption under various load conditions[15]. Volume of biogas also varied over wide range with respect to different load conditions. The brake thermal efficiency, brake specific fuel consumption and exhaust gas temperatures were calculated from equation 2.

Fuel consumption [FC] =

Specific fuel consumption [SFC]

Fuel power

Brake thermal efficiency

Result and Discussion Brake Power: Brake power of the engine is measured by mechanical dynamometer. The experiment was conducted by varying the load and kept engine speed at 1500 rpm. The engine was operated at the same conditions with diesel and different ratios of biogas-diesel. In general brake power of same engine running with diesel is higher than that of using biogas as a fuel due to the reason that diesel fuel having higher calorific value [16]. The variations of brake power at different load conditions as shown in Fig. 3. The brake power of the engine increases with the increase of load at the rated speed. The brake power decreases when more biogas mixture supplied to the engine. It tends to shows the lower energy contents in the fuel mixture. The experiment result reveals diesel always has higher brake power as compared to mixture of diesel and biogas. 160 K. Senthilkumar and S. Vivekanandan

Figure 3: Variation of Brake power Vs Applied load

Specific fuel consumption: The variation in brake specific fuel consumption at different load conditions for diesel and biogas-diesel as shown in the Fig. 4. Specific fuel consumption depends on mass of fuel consumed and engine brake power. Specific fuel consumption of the engine is lower when operated with diesel alone compared to biogas-diesel mixture. Due to the low energy content in biogas-diesel mixture the SFC increases as the percentage of biogas increases with diesel fuel at various load conditions [17]. When the engine load increases from no load to 80% load conditions the differences of specific fuel consumption is about 20%. Shows increasing of fuel consumption by the engine operated with biogas- diesel mixture for the same brake power. At no load condition, SFC is almost similar with diesel and diesel-biogas.

Figure 4: Variation of SFC Vs Brake Power

Investigating the biogas as secondary fuel for CI engine 161

Brake thermal efficiency: BTE is found to be higher in case of diesel fuel compare with diesel-biogas mixture. This is due to the low specific fuel consumption for conventional diesel fuel alone. The variation in brake thermal efficiency at different load conditions is shown in the Fig. 5. It is evident from the figure the brake thermal efficiency decreases as the percentage of biogas increased with biogas-diesel mixture. This is due to the lower calorific value of the biogas results the thermal efficiency of the engine is inversely proportional to SFC. For all the engine load conditions thermal efficiency of biogas- diesel mixture is lower compare to thermal efficiency of diesel alone. This is due to the limitations of biogas like impurities and other combustion mechanical durability of the engine. Decreasing brake power of the engine leads to reduction in brake thermal efficiency.

Figure 5: Variation of BTE Vs Brake Power.

Exhaust gas temperature: When the load increases exhaust gas temperatures also increases in both diesel and biogas-diesel used as a fuel as shown in Fig. 6. Due to the combustion temperature is higher in diesel fuel the exhaust gas temperature slightly more compares to the temperature of biogas-diesel fuelled engine. This is also due to the lower heating value of biogas there is a reduction of EGT in biogas-diesel operating engine.

162 K. Senthilkumar and S. Vivekanandan

Figure 6: Variation of EGT Vs Brake Power

Conclusion In this investigation the engine operated with biogas-diesel as a dual fuel at different load conditions with constant rated speed compare with engine operated with diesel at same conditions. The performance and EGT has been experimentally studied and the following conclusions may be drawn. (i) Biogas from organic wastes can be used as an alternative partial substitution of diesel fuel which may save 40-50% diesel at different engine load conditions. (ii) Brake thermal efficiency decreases in all the biogas-diesel mixtures compare to diesel fuel due to the low energy content of biogas mixture. (iii) Brake thermal efficiency is high in diesel alone when compare to other ratios of biogas-diesel mixture due to the low heating value of biogas. (iv) EGT decreases in case of biogas-diesel fuelled engine compare to diesel engine. (v) Engine brake power also reported lower in case of biogas-diesel mixture compare to diesel fuelled engine. (vi) It is also found that conventional diesel engine perform better compare to biogas-diesel followed by 20%biogas+80%diesel performed better than other ratios. So partial substitution of biogas may be suggested for alternative use of diesel in case of CI engine.

References

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