An experimental study on Performance of CI engine fuelled with waste cooking oil

Day by day depletion of fossil fuel and their growing pollution has become a real concern for the researchers worldwide. Growing concern regarding energy resources and the environment has increased interest in the study of alternative sources of energy like wind energy, solar energy, biomass, bio-diesel etc. Now-a-days people are getting interest in biodiesel to provide a suitable diesel oil substitute for internal combustion engines. It is found to be a promising field to reduce the dependence of India’s foreign imports of oils. Biodiesel is an alternative fuel for conventional diesel engines and can be used without major modification of the engines. This study represents the effects of biodiesel obtained from waste frying oil (mustard oil) which is obtained from local restaurant and hotels, on 4-stroke direct injection engine performance and exhaust emissions. A comparative study of performance of normal diesel and various proportion blend of bio-diesels with normal diesel is done. Performance of diesel engine using varying blends of biodiesel like B5, B10 and B 15 is tested for this case.


Introduction
Energy is the most important aspect to economic and social development to improve quality of life. Majority of the current energy sources in the world are based on fossil fuels, which will someday deplete if we do not develop technologies that could utilize alternative fuels for energy supply. The consumption of energy demand around the world is growing faster than population growth [1]. In this century it is believed that crude oil and petroleum products will come very scare and costly [2]. Day to day fuel economy of engines is getting improved and that will be continued for years. But because of the substantial increase of the number of vehicle the demand of fuel increases rapidly [3]. This increment projection is estimated to increase up to 1.5% in 2030, due to great energy consumption in developing countries, especially in the Asian region [4].
The increasing demand for energy forces the major exporters of fuel energy around the world to find the alternative fuels to replace products based on fossil fuel, and not to be dependent on it. Sustainability is the main issue that causes the energy sector not being fully developed, thus various agencies are required to utilize new and renewable energy sources [5][6]. Biodiesel is one of the most promising alternative fuels to solve this problem. Biodiesel is renewable, biodegradable, and non-toxic and has almost very close property to that of diesel fuel [7]. It can be produced from vegetable oils, as well as animal fats. These oils, however, have high viscosity and is therefore cannot be directly used as fuel. In order to reduce viscosity, the raw oils must undergo trans-esterification process to remove glycerin as by product and esters, thus creating biodiesel. Biodiesel can operate in compressionignition engines with little or no modification, similar to petroleum diesel. Moreover, biodiesel has more advantages regarding the engine wear, cost, and availability. When burned, biodiesel produces pollutants that are less detrimental to human health. In addition, it provides better lubricity as
The broad vision behind India's integrated energy policy is to reliably meet the demand for energy services of all sectors including the transport sector in all parts of the country with safe, clean and convenient energy at the least-cost [10]. This must be done in a technically efficient, economically viable and environmentally sustainable manner using different fuels and forms of energy, conventional and non-conventional. In other words, the goal of the energy policy is to provide energy security to all. India's energy demand is expected to grow at an annual rate at 4.8 % over the next couple of decades [11]. Most of the energy requirements are currently satisfied by fossils fuel -coal, petroleum based product and natural gas [12]. Domestic production of crude oil can only fulfil 25-30 percent of national consumption, rest we are importing from other countries [13]. In these circumstances bio fuels are going to play an important role in meeting India's growing energy needs. At the same time the world reserves of primary energy and raw materials are obviously limited. According to an estimate, the reserves will last only another 218 years for coal, 41 years for oil and 63 years for natural gas, under a business-as usual scenario [14].
Biodiesel is a renewable fuel that can be produced from vegetable oils, animal fats, used cooking oil, and waste from the paper industry. It can be used in its neat form, or as a blend with conventional diesel fuel, in diesel engines without any modifications. Since biodiesel is produced from renewable, domestically grown feedstock, it can reduce the use of petroleum based fuels and possibly lower the overall greenhouse gas (carbon dioxide, methane, nitrous oxide & ozone) emissions from the use of internal combustion engines.

Transesterification reaction
The specific features of organic compound (such as the hydroxyl groups in alcohols) are responsible for the fact that many compounds can react with other compounds to form new compounds. The new may then belong to a different class of compounds. These structural features are also responsible for the differences in physical properties (melting point, boiling point, etc.) of the organic compounds.
In a variation of the formation of esters from acids and alcohols, an ester can react with other alcohol. In that case, the new alcohol is derived from the original ester and the new ester is derived from the original alcohol. Thus, an ethyl ester can react with methanol to from a methyl ester and ethanol. This process is called transesterification [15][16][17]. Transesterification of natural glycerides with methanol to methyl esters is a technically important reaction that has been used extensively in the soap and detergent manufacturing industry worldwide for many years. Almost all biodiesel is produced in a similar chemical process using base catalyzed transesterification as it is the most economical process, requiring only low temperatures and pressures while producing a 98% conversion yield. A successful transesterification reaction is signified by the separation of the methyl ester (biodiesel) and glycerol layers after the reaction time. The heavier co-product, glycerol, settles out and may be sold as is or purified for use in other industries, e.g. pharmaceutical, cosmetics, and detergents. After the transesterification reaction and the separation of the crude heavy glycerine phase, the producer is left with a crude light biodiesel phase. This crude biodiesel requires some purification prior to use. Transesterification is extremely important for biodiesel. Biodiesel as it is defined today is obtained by transesterifying the triglycerides with methanol. Methanol is the preferred alcohol for obtaining biodiesel because it is the cheapest (and most available) alcohol [18]. However, for the reaction to occur in a reasonable time, a substance called catalyst must be added to the mixture of the vegetable oil and methanol. Enzymes, alkalis (e.g. NaOH, KOH) or acids can catalyze the reaction [19][20]. Among these alkalis transesterification is faster and hence it is used commercially.

Methodology
Waste frying oil (mustard oil) which is obtained from local restaurant and hotels contains many impurities in the form of sediments. This sediment present in the oil was removed using filter paper. Then the waste frying oil is taken in a round bottom flask and mixed with methanol in the ratio 1:6.A solution containing 0.1N HCL was poured into round bottom flask containing the oil alcohol mixture while stirring the mixture continuously. The mixture was then heated in a heating mantle at 80 deg. Celsius for 4h and then allowed to settle under gravity in a separating funnel. Out of two layers formed, upper layer is the Biodiesel and lower layer was of glycerol. The lower was separated out and ester was mixed with hexane in the same amount and shaken properly and again allowed to settle down for 24h. The remaining mixture from the purified ester was removed. Then the hexane was allowed to vaporize in the atmosphere by keeping the mixture open for 48 hours. The ester was then blended with diesel oil in various concentrations for preparing biodiesel blends, which were subsequently used in the engine performance tests. The level of blending for convenience is referred as BXX. The XX indicates the amounts of biodiesel in percentage in the blend (like a B05 blend is 05% biodiesel and 95% diesel oil). Fig. 1 shows the test rig set up for the experimental study. It consists of a test-bed, a four stroke diesel engine, a dynamometer, a fuel tank, a data acquisition system, a computer, an operating panel, four exhaust emission analyzers, and various sensors to measure the oil pressure, the exhaust temperature at the manifold, etc.

Experimental set-up
Engine

Properties of Fuel
Before testing engine performance the main properties of the fuel tested are shown in Table 1. The density of fuel is measured by density meter at 40ºC. The density meter has been calibrated with dry air and pure water. After some time the bio diesel has been sampled by sampling pump and reading were taken down. Calorific value of pure diesel and its blend with biodiesel has been successfully found out by using an apparatus called Bomb calorimeter. Kinematic viscosity of the fuel is measured by kinematic viscometer bath (220/440V, single/Three phase) using ASTM D-445 and D-2171 method. The other properties like cloud point, pour point, flash point, fire point, cetane index etc. are collected from literatures [21][22][23][24]. As shown in the table, pure diesel has the highest gross calorific value and the lowest viscosity. When diesel mixed with vegetable oil to make blends, it is found that the more percentage of vegetable oil in the blends, the higher of the viscosity and the lower the gross calorific value. Pure vegetable oil has the lowest gross calorific value and the highest viscosity. --------9 [21] 0.0133 35.081 0.769 0.997 58 [21] 162 [22] 172 [23] -5 [21] ----

Engine Performance
The diesel engine ran well on all the fuels mentioned above. There were no faults happening during the whole experiment process. The test results are plotted and explained in the figures 2, 3 And 4 for different blends of biodiesel.

Comparison of Performance
The followings are the graphical representations of the test results of engine brake specific fuel consumptions (BSFCs) for different blends of bio-fuels with the variation of load. The engine BSFC decreased with the increase of engine loads, as showed in the figure. The differences of BSFC are very small at different engine load, when using different fuels. The graphical representations also show the test results of the engine specific fuel consumption for different blends of fuels.  Figure 2 represents the specific fuel consumption of normal diesel and various blends of bio-diesel (here B05, B10 and B15) with variation of load. The various blends of bio-diesel with normal diesel show very little variation compared to normal diesel. At low and medium load consumption of B05, B10 and B15 increases than normal diesel but not significantly. At higher load complete combustion of mustard oil decreases for higher blends such as B15 & B10. It is seen that BSFC is highest for pure biodiesel and lowest for diesel because of high viscosity, density, low volatility and low heat content of pure biodiesel when compared with that of diesel. However with increase of percentage of biodiesel, BSFC decreases with respect to load and shows close results to that of diesel. This may be due to improved combustion, low viscosity, high volatility of the test fuels.  Figure 3 represents Brake Thermal Efficiency of normal diesel and various blends of bio-diesel (here B05, B10 and B15) with break power. It is found that brake thermal efficiency of all blends of bio-diesel is higher than that of normal diesel. Though at lower load B10 is more efficient than other two blends but at higher loads B15 becomes more efficient than that of diesel while other blends become less efficient.  with the increase of load. B15 also gives nearly same value of heat input as B05. But at higher loads B15 sample emits less heat than all other samples.

Conclusion
The experimental results show that the engine performance run by waste cooking oil and its blends are comparable with the performance run by pure diesel fuel. The engine power output and the fuel consumption of the engine are almost the same when the engine is fueled with waste cooking oil and its blends compared with that of pure diesel. The results from the experiments prove that waste cooking oil and its blends are potentially good substitute fuels for diesel engine in the near future when petroleum deposits become scarcer. The use of 100% biodiesel, in diesel engine, is still theoretical and requires engine modification for a long run. But, the motto is to gradually shift these vegetable oil based fuels from petroleum based fuels or otherwise about 50 years from now the term 'Diesel or Petrol' will be aliens to the coming generation. Though a practical and theoretical study is necessary to find the emission characteristic of diesel engine fuelled by waste cooking oil and its blends.