18 CHAPTER 2 LITERATURE REVIEW This chapter presents the literature review on biodiesel production from animal fats, analysis of using different kinds of animal fat biodiesel in a direct injection diesel engine, optimization of engine performance parameters using Taguchi method, the limitations of the existing research and the research gap. The main objective is to provide an overview of the past and ongoing scientific investigations related to the usage of animal fat biodiesel in compression ignition engines. 2.1 REVIEWS ON ANIMAL FAT BIODIESEL Biodiesel production from animal fats has been broadly studied in current literature reviews. Researchers have proved that oils and fats can be converted into biodiesel by variety of methods. Wyatt et al (2005) described biodiesel production from lard, beef tallow and chicken fat by base-catalyzed transesterification. The obtained biodiesel and its properties like kinematic viscosity, cloud point, pour point closely follow ASTM specifications. Nelson & Schrock (2006) reviewed biodiesel production, biodiesel standard, resource availability, energetic efficiency, environmental considerations, economic feasibility, and benefits of converting inedible beef tallow as a substitute to diesel fuel.
19 Bhatti et al (2008) reviewed biodiesel production from chicken fat and mutton fat using acid catalyst and base catalyst methods. Acid catalysis resulted in higher yield in comparison to base catalysis. The use of chicken and mutton fats was very suitable as low cost feed stocks for biodiesel production. Berrios et al (2009) described biodiesel production from lard through transesterification process and analysed through regression model to predict methyl ester concentration. Standard biodiesel was obtained with operational conditions like an agitation speed of 600rpm and 0.9wt.% catalyst concentrations. Oner & Altun (2009) explained conversion of animal tallow into useful biodiesel by transesterification process and investigated performance and emission characteristics of a direct injection diesel engine. From their study it was concluded that animal tallow methyl esters and its blends with diesel fuel can be used as a substitute for diesel in direct injection diesel engines without any engine modification. Guru et al (2010) described biodiesel production from chicken fat with synthetic Mg additive by a two-step catalytic process. Methanol, sulphuric acid and sodium hydroxide catalyst were used in the reaction. Encinar et al (2011) discussed biodiesel production from animal fats, an inedible feed stock. Three different types of fats were used to produce biodiesel with high free fatty acid content. Around 97.3 wt.% biodiesel was obtained using acid-catalyzed transesterification process. Most of the biodiesel properties were well within EN14214. Liu et al (2011) achieved efficient biodiesel production from beef tallow with radio frequency (RF) heating. A conversion rate of 96.3+ 0.5% was obtained with a NaOH concentration of 0.6% (based on tallow), RF
20 heating for 5 minutes and a methanol/tallow molar ratio of 9:1. Response surface methodology was employed to evaluate the optimum values for the influence of NaOH dose, RF heating time, and methanol/tallow ratio. Mutreja et al (2011) discussed biodiesel production from mutton fat using KOH impregnated MgO as heterogeneous catalyst. In their study, 98% of fat was converted into biodiesel in just 20 minutes. Shin et al (2012) performed transesterification of refined lard and waste lard in supercritical methanol without pretreatment in a temperature range of 320-350 C, molar ratios of methanol to oil from 30 to 60 and agitation speeds of 0-1000 rpm. From their study, it was concluded that waste lard can be utilized as an alternative feedstock for biodiesel production using a supercritical process, thus replacing the high-cost refined vegetable oil feed stock. Varuvel et al (2012) performed biodiesel production from waste fish fat by catalytic cracking method. In their research work, they have prepared biodiesel in a laboratory scale reactor with temperatures ranging from 350 C to 480 C with a heating rate of 2-3 C per minute. John Abraham (2013) has developed processes that can extract biodiesel from poultry carcasses in a cost effective manner. He conducted biodiesel production from bird s fat by using solvent extraction method and centrifugal method. He concluded that solvent extraction method requires 6 bird s fat to produce one litre of biodiesel (extraction of fat is 97%) by comparing it with centrifugal method which requires 16 bird s fat (extraction of fat is 63%) for producing the same quantity of biodiesel. He also concluded that the cost of producing a litre of biodiesel using centrifugal method is Rs.35.68 against the solvent extraction method where it is only Rs.22 per litre. Hence, in this research work biodiesel from waste pork lard is used as a fuel for diesel engine.
21 2.2 REVIEWS ON ENGINE ANALYSIS USING BIODIESEL AND DIESEL BLENDS More number of experimental investigations has been reported in the literatures related to performance, emission and combustion characteristics of a diesel engine using biodiesel and diesel blends. Senthil Kumar et al (2005) investigated preheating of animal fat at five different temperatures and tested it as a fuel in CI engine. In their investigation, animal fat is preheated to 30 C, 40 C, 50 C, 60 C and 70 C before it is injected into combustion chamber of an engine. The results showed that preheated animal fat reduces ignition delay and combustion duration whereas maximum combustion pressure and rate of pressure rise are high with animal fat at high fuel inlet temperatures. Wyatt et al (2005) analyzed biodiesel production and properties of lard, beef tallow and chicken fat by base-catalyzed transesterification. Nitrogen oxide (NO x ) emission tests were conducted in a Yanmar L100 single cylinder direct injection diesel engine using animal fat-derived esters and soybean oil biodiesel as 20% by volume (B20 blend) with diesel. The results indicated that the three animal fat-based B20 fuels had lower NO x emission levels (3.2 6.2%) than did the soy oil-based B20 fuel. Guru et al (2009) tested waste animal fat methyl ester and diesel blends in a direct injection diesel engine. They reported an increase in specific fuel consumption of 3.12% obtained with neat biodiesel (methyl ester of animal fat) at 2200 rpm and the maximum increase in SFC of 4.79% was obtained at 3000 rpm. This may be due to the relatively higher density and lower calorific value of animal fat biodiesel compared with pure diesel.
22 Oner & Altun (2009) investigated performance and emission analysis of diesel engine with methyl esters of animal tallow and diesel blends. From their experimental investigations, it is found that emissions of carbon monoxide, oxides of nitrogen, sulphur dioxide and smoke opacity reduced to 15%, 38.5%, 72.7% and 56.8% respectively in the case of tallow methyl esters (B100) compared to diesel fuel. Puhan et al (2009) investigated performance, emission and combustion characteristics of a DI diesel engine using linseed oil methyl ester at different injection pressures of 200 bar, 220 bar and 240 bar. The test results showed that optimum fuel injection pressure was obtained at 240 bar with linseed methyl ester. At this optimized injection pressure, a reduction in CO, HC and smoke emission was observed with an increase in NO x while compared to diesel. The combustion analysis showed that the ignition delay was lower and peak pressure was higher at higher injection pressures and full load. Purushothaman & Nagarajan (2009) conducted experimental work in a CI engine using orange skin powder diesel solution (OSPDS) by varying injection pressures. They varied injection pressures as 215 bar, 235 bar and 255 bar respectively. The results showed that brake thermal efficiency was better than diesel fuel at 235 bar pressure with 30% OSPDS. CO, HC and smoke emission were marginally lower with 30% OSPDS at 235 bar. Roy (2009) investigated the effect of fuel injection timing and injection pressure on combustion and odorous emissions in a direct injection diesel engine. From the experimental results, he concluded that when injection pressure is increased from 20 MPa to 60 MPa, there is a 2-2.25 CA shortening of ignition delay. The peak cylinder pressure and temperature are increased with higher injection pressures. The shortest ignition delay and minimum emissions is found at around 60 MPa of injection pressure.
23 Moderate injection pressures (60-80MPa) showed lower emissions including total hydrocarbon, aldehydes, odor and irritation due to proper mixture formation. Prem Anand et al (2010) evaluated combustion, performance and exhaust emission characteristics of turpentine oil fuel blended with conventional diesel fuel in a diesel engine. The results showed that the addition of 30% turpentine oil with diesel produced higher brake power and heat release rate with a net reduction in exhaust emissions such as CO, HC, NO x, smoke and particulate matter. Mani et al (2011) studied the effect of using waste plastic oil and diesel blends in compression ignition engine. It has been reported that carbon monoxide, hydrocarbon, oxides of nitrogen and smoke emission were increased by 5%, 15%, 25% and 40% respectively for waste plastic oil when compared to diesel fuel. Waste plastic oil can be used as fuel in diesel engines without any modifications. Waste plastic oil fueled diesel engine exhibits higher thermal efficiency up to 80% at full load and the exhaust gas temperature was higher at all loads compared to diesel fuel operation. Gumus et al (2012) studied the effects of fuel injection pressure on the exhaust emissions of a DI diesel engine. The engine was fueled with biodiesel-diesel blends at four different fuel injection pressures (18, 20, 22 and 24 MPa). The results confirmed that the increased injection pressure caused decrease in BSFC, CO, HC, smoke opacity and increased emissions of CO 2, O 2 and NO x. Varuvel et al (2012) analyzed performance, emission and combustion characteristics of 4.5 kw diesel engine using waste fish fat oil (bio-oil) blended with diesel. The results indicated that addition of bio-oil
24 with diesel improves the brake thermal efficiency and reduces PM, and CO emissions due to improvement in the rate of combustion. Sayin et al (2012) performed experimental analysis of a DI diesel engine using canola oil methyl ester (COME) and diesel blends for four different injection pressures (18, 20, 22 and 24 MPa) at constant engine speed and different loads. Investigation on the injection characteristics showed that maximum cylinder pressure, maximum rate of pressure rise and maximum heat release rate were slightly lower for COME and its blends. The increased injection pressure gave better results for BSFC and BTE compared to the original and decreased injection pressures. Agarwal et al (2013) discussed combustion and performance analysis of a diesel engine for different fuel injection timings and injection pressures. The results showed that CO 2 and HC emissions decreased however nitrogen oxide emissions (NO x ) increased with increasing fuel injection pressure and fuel injection timing. Brake thermal efficiency (BTE) increased with increased injection pressures. Taymaz & Coban (2013) compared performance and emission characteristics of a diesel engine with methyl esters of beef tallow and diesel. From their investigations, increase in brake thermal efficiency and decrease in carbon monoxide and hydrocarbon emissions were obtained with neat animal fat biodiesel. Hence, in this research work biodiesel from waste pork lard is used as an alternative fuel for diesel engine and performance, emission and combustion characteristics are determined with neat biodiesel and biodieseldiesel blends.
25 2.3 REVIEWS ON ENGINE ANALYSIS USING BIODIESEL AND ETHANOL BLENDS The use of ethanol in diesel engines has received a considerable attention in the recent literature. Ethanol is a low cost oxygenated compound with high oxygen content (34.8%). It is a biomass based renewable fuel that can be produced from vegetable materials such as corn and sugarcane and it is expected to improve low temperature flow properties. Kumar et al (2006) discussed the ethanol-animal fat emulsions in a diesel engine and compared the performance and emission analysis with neat fat. The results showed that there was a drastic reduction in CO, HC, NO x and smoke emissions, when compared to neat fat and neat diesel at higher loading conditions. Animal fats offer the advantage of freely mixing with alcohols (both methanol and ethanol) and the obtained blends can be used in the existing diesel engines without any engine modifications (Kerihuel et al 2006). Arul Mozhi Selvan et al (2009) tested a single cylinder, four stroke, direct injection variable compression ratio (VCR) diesel engine under different compression ratios of 15:1, 17:1, and 19:1 using diesel and biodiesel-ethanol blends. From their investigation, it was concluded that the combustion characteristics like cylinder pressure, maximum rate of pressure rise and heat release rate increase with higher ethanol concentration due to longer ignition delay. The study also examined the fuel burning characteristics of diesel-biodiesel-ethanol blends under various compression ratios and loading conditions. Aydin & Ilkilic (2010) investigated the effect of ethanol blending with biodiesel on engine performance and exhaust emissions in a CI engine. In their study, they tested the engine with diesel fuel, B20 biodiesel blend and
26 BE20 biodiesel-ethanol blend. The experimental results showed that the performance of a CI engine improved with the use of BE20 when compared to B20. The exhaust emissions for BE20 were fairly reduced. Venkata Subbaiah & Raja Gopal (2011) reported in their study about the performance and emission characteristics of a diesel engine fueled with rice bran biodiesel and ethanol blends. The brake thermal efficiency of 2.5% ethanol blended rice bran biodiesel increases by 6.98% and 3.93% respectively when compared to diesel fuel and biodiesel. Carbon monoxide, hydrocarbon, unused oxygen and smoke emission decreased by 17.39%, 62.2%, 14.4% and 27.4% respectively for 2.5% ethanol blended biodiesel when compared to standard diesel. Zhu et al (2011) investigated combustion, performance and emission characteristics of a DI diesel engine fueled with ethanol-biodiesel blends. In their research work, biodiesel was produced from waste cooking oil. The results indicated that when compared to neat biodiesel, the combustion characteristics of ethanol-biodiesel blends were slightly improved. For biodiesel-ethanol blends, the maximum cylinder pressure and heat release rate increased with increase of ethanol fraction in the blended fuel. Brake thermal efficiency of BE5 biodiesel-ethanol blend was slightly higher than that of neat biodiesel. Compared to neat biodiesel, BE5 gave slightly lower BSCO and BSHC emissions in all test modes. Sivalakshmi & Balusamy (2012) investigated ethanol addition on a diesel engine fueled with neem oil methyl ester. They concluded that peak cylinder pressure and peak heat release rate were higher for ethanol blended biodiesel. There was an improvement in brake thermal efficiency for all loads with the addition of ethanol to biodiesel. Smoke intensity and CO emissions were found to be lower at higher loads with the addition of ethanol to neem oil methyl ester.
27 Hence, in this research work biodiesel from waste pork lard is used as an alternative fuel for diesel engine and performance, emission and combustion characteristics are determined with neat biodiesel and biodieselethanol blends. 2.4 REVIEWS ON ENGINE ANALYSIS USING TAGUCHI METHOD Taguchi method provides simple and effective solutions for investigating the effect of parameters on the performance as well as experimental planning. The most common optimization techniques used for engine analysis are response surface methodology, grey relational analysis, non linear regression, genetic algorithm and Taguchi method. Taguchi technique has been most popular for parameter optimization in design of experiments. Nataraj et al (2005) carried out optimization of diesel engine parameters for low emissions using Taguchi method. The experimental results revealed that CO, HC and smoke emission obtained from the confirmation experiments using the optimum parameter combination showed excellent agreement with the predicted results. Win et al (2005) investigated diesel engine operating parameters and injection parameters for low noise, emissions and fuel consumption using Taguchi method. They conducted an experimental work in a single cylinder 3.5 kw diesel engine for different engine speeds, loads and injection pressures. They analyzed engine noise, combustion noise, smoke, brake specific fuel consumption (BSFC) and emissions of unburned hydrocarbons (HC), oxides of nitrogen (NO x ), and carbon monoxide (CO). The optimum values of engine noise, combustion noise, smoke, brake specific fuel consumption and emissions were predicted using signal-to-noise (S/N) ratios.
28 Results of confirmation runs of the engine showed good agreement with the predicted quantities of interest based on Taguchi analysis. Finally they concluded that Taguchi method of experimental design was found to be robust and cost effective for understanding the relationship between diesel engine operating parameters, noise, emissions, and brake specific fuel consumption than full factorial design. Ganapathy et al (2009) performed thermodynamic model analysis of jatropha biodiesel engine in combination with Taguchi optimization approach to determine the optimum engine design and operating parameters. Using linear graph theory and Taguchi method an L 16 orthogonal array was utilized to determine engine test trials. From Taguchi approach, the critical parameters that affect the performance of the engine were correctly predicted. Parlak et al (2012) investigated various factors affecting emissions of a diesel engine running with tobacco oil seed methyl ester using Taguchi method. With the application of Taguchi method, they investigated different parameters that affect the yield of biodiesel and its interactions on emissions of a diesel engine. Two different catalysts (KOH and NaOH), four different blends (B10, B20, B50 and B100) and four engine speeds were used during full load tests. Optimal catalyst type, engine speed and TSOME (Tobacco Seed Oil Methyl Ester) blends on exhaust emissions were determined using Taguchi technique. From Taguchi design method they revealed that minimization of engine exhaust emissions depends on two important factors ie. choosing the right catalyst and the blend rate. Sivaramakrishnan & Ravikumar (2012) conducted performance optimization of karanja biodiesel operated diesel engine using Taguchi approach. They varied five different parameters of an engine like compression ratio, injection pressure, injection timing, fuel fraction and brake power at four levels. The results indicated that brake specific fuel consumption and
29 brake thermal efficiency were higher at increased compression ratio, injection pressure and injection timing. The optimum engine performance and emission parameters were obtained for the combinations of B30 biodiesel blend, compression ratio of 17.9, nozzle opening pressure of 230 bar, injection timing of 27 btdc and at 70% load. Wu & Wu (2013) determined the optimal combinations of concentrations for a diesel engine with diesel/biodiesel blend using H 2 and cooled exhaust gas recirculation (EGR) at the inlet port by Taguchi method. Experimental results showed that predictions by Taguchi parameter design technique were in satisfactory agreement with the confirmation results, with a confidence interval of 95%, and saved 67% of the time taken to perform the experiment. The best brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC), NO x and smoke at each load were achieved for a combination of B20 biodiesel blend, 30% hydrogen and 40% EGR ratio. This combination was suitable for obtaining various parameters that affect the combustion performance such as cylinder pressure and heat release rate, than that of baseline fuel for various loads. At 60% load, the reduction rate was 25.4% for BSFC, 74.1% for NO x and 29.6% for smoke. Wu et al (2014) determined optimal operating factors which affect the combustion characteristics of a diesel engine using diesel/biodiesel mixture with liquefied petroleum gas and cooled exhaust gas recirculation (EGR) inducted in the intake port by Taguchi method. They conducted the experiment for acquiring the largest fuel consumption time, the lowest smoke and NO x emission at constant engine speed of 1500 rpm and at different loads. They also compared the combustion characteristics (heat release rate and ignition delay) and emissions (NO x and smoke) between the optimum combination of factors and baseline diesel engine. The results indicated that predictions by Taguchi method are in fair consistence with the confirmation
30 results and decreased the number of experimental runs. The combination of B10 biodiesel blend, 40% LPG and 20% EGR gives lower specific fuel consumption and exhaust emissions. The decrease rate in engine exhaust emission is 52% for smoke and 31% for NO x at 60% engine load. In the existing literatures, it is shown that numerous studies have been conducted in all types of engines with biodiesel obtained from different kinds of animal fats and vegetable oils. However, it is evident that the application of Taguchi method with animal fat biodiesel in the direct injection diesel engine is very limited. So the main objective of this research work is to produce biodiesel from waste pork lard and develop a Taguchi parameter design technique for predicting the performance, emission and combustion characteristics of a direct injection diesel engine. 2.5 LIMITATIONS OF THE PREVIOUS RESEARCH In the existing literatures, it is described that numerous studies have been conducted in different types of engines with a variety of animal fat biodiesel. A few literatures are available on the production of biodiesel from pork lard. The performance and emission characteristics of different animal fat biodiesel are discussed in most of the studies and discussion on combustion characteristics is inadequate. The study on direct injection diesel engine using waste pork lard biodiesel is very much limited. In the literature, most of the researchers only concentrated on biodiesel production and its properties from different kinds of animal fats. Very few experimental works have been carried out using animal fat biodiesel and analyzed performance and emission characteristics of a diesel engine.
31 The combustion parameters such as heat release rate, combustion pressure, ignition delay, and combustion duration are not discussed completely. The effects of ethanol addition with animal fat biodiesel on performance, emission and combustion parameters are not discussed completely. The application of Taguchi method for biodiesel operated diesel engine is a topic of interest in the recent research. The effects of varying engine operating parameters on the performance, emission and combustion characteristics of vegetable oil biodiesel has been mostly studied and analyzed with the aid of Taguchi approach. However, it is evident that the application of Taguchi method with animal fat biodiesel in the direct injection diesel engine is very limited. The application of Taguchi method for the prediction of engine operating parameters is also limited. Many of the researchers have used Taguchi method for prediction of engine operating parameters for vegetable oil biodiesel. For animal fat biodiesel, Taguchi method is not used effectively in prediction of engine operating parameters. Prediction of performance, emission and combustion characteristics of animal fat biodiesel operated diesel engine using Taguchi method is not studied completely. 2.6 CONTRIBUTION OF THE PRESENT THESIS More than two decades most of the research work is carried out in internal combustion engine using variety of biodiesel mostly obtained from different vegetable oil (seeds). However, animal fat feedstock is sidelined due
32 to less availability. The innovation in the present research work is to investigate the possibility of producing less expensive animal fat biodiesel from waste pork lard and its use in compression ignition engine. In some rural parts of Tamilnadu, the availability of pork lard is high with low or zero cost. In the present research work, experimental investigation on the performance, emission and combustion characteristics of a direct injection diesel engine has been conducted for different proportions of blends of waste pork lard methyl esters with diesel at different injection pressures and at varying load conditions. Similarly, different proportions of ethanol blends with waste pork lard methyl ester on diesel engine performance, emission and combustion characteristics are also analyzed for different loading conditions. The application of Taguchi method for the prediction of engine operating parameters has been investigated. Separate regression models are developed for performance, emission and combustion characteristics of a diesel engine. These models are of great significance due to their capability to predict the engine operating parameters under varying conditions. 2.7 CONCLUSION The review on earlier and current research about the study of animal fat biodiesel production, engine analysis using biodiesel-diesel blends and biodiesel-ethanol blends and engine operating parameters optimization using Taguchi method have been discussed in detail in this chapter. From the literature review, it is understood that study on direct injection diesel engine using waste pork lard biodiesel is inadequate. A detailed analysis of combustion characteristics and emissions of waste pork lard biodiesel and its blend with diesel fuel in compression ignition engines appears to be scarce, especially on a scientific level. The optimization of engine operating and performance parameters using Taguchi method in direct injection diesel engine is also limited. Hence, in the present research work, an attempt has
33 been made to analyze the suitability of using waste pork lard biodiesel in direct injection diesel engine for the evaluation of performance, emission and combustion characteristics. In the next chapter, procedure for biodiesel production from waste pork lard, biodiesel properties and transesterification method are discussed in detail.