Experimental investigation on diesel engine using fish oil biodiesel and its diesel blends.

Karthikeyan, A. ; Prasad, B. Durga

Introduction

The world is on the brink of energy crisis. The limited fossil fuel sources are unable to provide for the continuously increasing demand of energy. This associated with increasing price of fossil fuels and the awareness of the impacts of environmental pollution and global warming, has forced a search for an alternative source of energy, which is renewable, safe and non-polluting. (1, 2) Since compression ignition (CI) engines are more widely used compared to spark ignition (SI) engines, greater attention is being devoted to develop an alternative source of fuel for the same. Since vegetable oils and animal fats satisfy the major requirements, necessary for a diesel engine fuel, their suitability as alternative to diesel fuel have been a topic of research. However, their higher viscosity and storage ability issues restrict their direct use as alternate fuels (1, 2)

The use of vegetable oils in I.C engines dates back to 1900 when Rudolph diesel, the inventor of compression ignition engines, used peanut oil as an engine fuel. The energy crises of 1974 brought pressure on various nations to search for non petroleum based alternate fuels. Since then many vegetable oils of commercial and non commercial have been tried and possible difficulties identified. The observed major differences between diesel fuel and vegetable oil, included, for the latter, the significantly higher viscosities and moderately higher densities, lower heating values, rise in the stoichiometric fuel/air ratio due the presence of molecular oxygen and the possibility of thermal cracking at the temperatures encountered by the fuel spray in naturally aspirated diesel engines (2). These differences contribute to the poor atomization, choking tendencies, carbon deposits, heavy smoke emissions and wear that were generally experienced and which adversely affect the durability of the engine (3, 4 and 5).

Most research on biodiesel has focused on using plant based oils as feed stocks. There has been much less research on converting animal-based oils into biodiesel (6). One potential source of oil is fish oil. It has been estimated that over a million tons of fish by-products are generated from the fishing industry. Some of these products are converted into fish meal and oil, but approximately 60% are not utilized. The major fish by-products include fish heads, viscera and some frames, with much of oil stored in the head (5). Fish by-products can also be converted into hydrolysate through hydrolysis. Hydrolysis involves multiple enzyme and heat treatments to break down proteins into smaller peptides. The final hydrolysate product is usually stabilized by acidification and can be used as fertilizer or as feed ingredients. Hydrolysates of fish by-products contain a significant amount of oil, which can be extracted and converted into biodiesel. (7)

The objective of this work was to study the performance, emission and combustion characteristics of a single cylinder, direct injection diesel engine using fish oil biodiesel and their blends with diesel in varying proportions. The results were compared with the results obtained for diesel.

Materials and Methods

Production of the biodiesel from the refined fish oil

Several technologies are available to manufacture biodiesel, such as transesterification, amidation with diethylamine, catalyzing pyrolysis, and transesterification in supercritical methanol. Of these techniques, transesterification is the most widely applied in industrial biodiesel production. Three types of catalysts can be used in the transesterification process: a strong alkali, strong acid or enzyme. A strong alkali catalyst is frequently used in the transesterification reaction due to its dominant advantages of a shorter reaction time and smaller amount of catalyst required (8).

The refined fish oil was transesterified with methyl alcohol to produce biodiesel. Sodium methoxide was prepared by mixing 25% (by volume of oil) of pure methanol and 6.25g (Per liter of oil) of sodium hydroxide (NaOH). The sodium methoxide, which played a role of enhancing the transesterification process was poured in to a reaction vessel and mixed with the refined fish oil. To prevent the methanol from being vaporized by the reactant mixture, the reacting temperature was fixed at 60[degrees]C, which is just below the boiling point of methanol at 63[degrees]C. The mixing was done for 50 to 60 minutes. Then the mixture was poured in to a separating funnel and it was allowed to rest for 12 hours. The glycerin was formed at the bottom and the bio-diesel at the top. Bio-diesel was separated from the glycerin. Finally, it was washed and dried to remove the excess alcohol.

Experimental setup

A vertical water cooled single cylinder four stroke, direct injection diesel engine was used for this study. The engine was coupled with eddy current dynamometer for load measurement. The smoke density was measured using AVL smoke meter. N[O.sub.x] emissions were measured using exhaust gas analyzer. Particulate matter was measured using high volume sampler. Experiments were conducted with pure diesel, pure biodiesel and the blends of biodiesel with diesel.

Results and discussions

Experiments were conducted when the engine was fuelled with fish oil biodiesel and their blends with diesel in proportions of 20:80, 40:60, 60:40 and 100% (by volume), which are generally called as B-20, B-40, B-60 and B-100 respectively. The experiment covered a range of loads.

The performance of the engine was evaluated in terms of brake specific fuel consumption, brake thermal efficiency, volumetric efficiency and air fuel ratio. The combustion characteristics of the engine were studied in terms of cylinder pressure and rate of pressure rise with respect to crank angle. The emission characteristics of the engine were studied in terms exhaust gas temperature, concentration of NOx, CO, particulate matter and smoke density. The results obtained for Fish oil biodiesel and their blends with diesel were compared with the results of diesel.

Brake specific fuel consumption

The result for the variations in the brake specific fuel consumption (BSFC) is presented in the fig.1. For all the fuels the BSFC falls with increasing load. The differences of BSFC are very small when using different fuels. The minimum BSFC values are 0.34 kg/kW hr for diesel, 0.37 kg/kW hr for B-20, 0.38 kg/kW hr for B-60 and 0.4 kg/kW hr for B-100. The higher BSFC values in the case of pure Fish oil biodiesel are due to their low energy content.

[FIGURE 1 OMITTED]

Brake thermal efficiency

The variation of brake thermal efficiency with load is shown in fig. 2. Brake thermal efficiency gives an idea of the output generated by the engine with respect to heat supplied in the form of fuel. For all the fuels the brake thermal efficiency increases with load. The brake thermal efficiency values at full load are 25.52% for diesel, 23.37% for B-20, 22.64% for B-40, 25.57 For B-60 and 23.82% for B-100. The brake thermal efficiencies of B-60 and B-100 are very close to the brake thermal efficiencies of diesel at all loads. This may be due to their low heat input requirement for higher power output at a given load.

[FIGURE 2 OMITTED]

Volumetric efficiency

The fig.3 shows the variation of volumetric efficiency with load for various blends. Volumetric efficiency is a measure of success with which the air supply, and thus the charge, is inducted in to the engine. It indicates the breathing capacity of the engine. From the figure it is evident that the volumetric efficiency values of B-40, B-60 and B-100 are exceeding the volumetric efficiency values of diesel at all loads.

[FIGURE 3 OMITTED]

Air fuel ratio

Fig.4 shows the variation of air-fuel ratio with load. In C.I engines at a given speed the air flow do not vary with load, it is the fuel flow that varies directly with load. From the figure it can be seen that, air fuel ratio values of fish oil biodiesel and its diesel blends are slightly less than diesel.

[FIGURE 4 OMITTED]

Exhaust gas Temperature

Fig.5 shows the variation of exhaust gas temperature with load for various test fuels. It is observed that the exhaust gas temperature increases with load because more fuel is burnt at higher loads to meet the power requirement. It is also observed that the exhaust temperature increases for B-20 and B-40 blends at all loads. This may be due to the oxygen content of the biodiesel, which improves combustion and thus may increase the exhaust gas temperature. But the exhaust gas temperatures of B-60 blend and B-100 are very close to the exhaust temperature of diesel and even less than diesel at higher loads. This reduction in exhaust gas temperature for B-60 and B-100 at higher loads may be due to their high latent heat of vaporization than the diesel fuel.

[FIGURE 5 OMITTED]

N[O.sub.x] emission

Fig.6 shows gradual increase in emission of nitrogen oxides (N[O.sub.x]) with increase in percentage of fish oil biodiesel in the fuel. The N[O.sub.x] emission increase for biodiesel may be associated with the oxygen content of the biodiesel, since the oxygen present in the fuel may provide additional oxygen for N[O.sub.x] formation. Another factor causing the increase of N[O.sub.x] could be the possibility of higher combustion temperature arising from improved combustion. The N[O.sub.x] emission is found to be lower for diesel.

[FIGURE 6 OMITTED]

Smoke density

Fig.7 shows the variation of smoke density with brake power for various test fuels. A reduction is observed with increase in percentage of fish oil biodiesel in the fuel. This may be due to improved combustion characteristics of biodiesel. It is observed that smoke density is lower for pure fish oil biodiesel.

[FIGURE 7 OMITTED]

CO Emission

Fig.8 shows the reduction of CO emission with the addition of fish oil biodiesel to diesel. CO is predominantly formed due to the lack of oxygen. Since biodiesel is an oxygenated fuel, it leads to better combustion of fuel resulting in decrease in CO emission. The CO emission is found to be lower for pure fish oil biodiesel.

[FIGURE 8 OMITTED]

Particulate matter

Particulate emissions are as a result of incomplete combustion. Fig.9 shows the particulate matter emission decreases with increase in percentage of biodiesel in the fuel. Since biodiesel is an oxygenated fuel, it promotes better combustion and results in reduction of particulate matter emissions. The particulate emission is lower for pure fish oil biodiesel.

[FIGURE 9 OMITTED]

Pressure variation with Crank angle

The pressure variation in the cycle is important in the analysis of the performance characteristics of any fuel. Fig.10 and 11 shows the variation of cylinder pressure with crank angle for various fuels at rated load. Similar trends are observed for other loads also. Fish oil biodiesel and its diesel blends exhibit slightly lower pressure at all crank angles compared to diesel. The peak pressure values are 69.5 bar for diesel, 67.31 for B20, 68.16 bar for B40, 67.48 bar for B60 and 67.99 bar for B100. The peak pressures for diesel, B60 and B100 occur at 13[degrees] after TDC. The peak pressures for B20 and B40 occur at 11[degrees] after TDC.

[FIGURE 10 OMITTED]

[FIGURE 11 OMITTED]

Rate of Pressure Rise

Fig.12 shows rate of pressure rise with crank angle at rated load for test fuels. All the tests are performed at an injection timing 23[degrees] before top dead centre (bTDC). It can be observed that the rate of pressure rise for Fish oil biodiesel and its diesel blends are higher compared to diesel. The maximum rate of pressure rise is for B60 and B100. This may be due to improved combustion characteristics of biodiesel and its Diesel blends.

[FIGURE 12 OMITTED]

Conclusions

Following are the conclusions based on the experimental results obtained while operating single cylinder diesel engine fuelled with biodiesel from fish oil and its diesel blends.

* Fish oil biodiesel and its diesel blends can be directly used in diesel engines without any modifications.

* Brake specific fuel consumption values of fish oil biodiesel and its diesel blends are slightly higher than diesel.

* Brake thermal efficiency of B60 blend and B-100 are very close to the brake thermal efficiency of diesel at all loads.

* Volumetric efficiency values of fish oil biodiesel and its diesel blends are exceeding the volumetric efficiency values of diesel at all loads.

* Smoke, CO and particulate matter emissions decrease with increase in percentage of fish oil biodiesel in the fuel.

* N[O.sub.x] emissions of fish oil biodiesel and its diesel blends are slightly higher than that of diesel.

* Fish oil biodiesel and its diesel blends exhibit slightly lower pressure at all crank angles compared to diesel. The peak pressure value of B40 blend is very close to diesel.

* Rate of pressure rise for fish oil biodiesel and its diesel blends are higher compared to diesel. The maximum rate of pressure rise is for B60 and B100.

* From the above analysis the main conclusion is fish oil biodiesel and its diesel blends are suitable substitute for diesel as they produce lesser emissions than diesel and have satisfactory combustion and performance characteristics.

Engine details:

Kirloskar TV1 Engine

Engine specification:

Type of engine             : Vertical, 4stroke

Water cooled

Rated power                : 5.2 @1500rpm

Cylinder diameter          : 0.0875 m

Stroke length              : 0.11 m

Compression ratio          : 17.5: 1

Injection timing           : 23[degrees] bTDC

Air measurement

Orifice diameter           : 0.02 m

Eddy current dynamometer

Dynamometer arm length     : 0.195 m

Nomenclature

N[O.sub.x] = Oxides of Nitrogen HSU = Hatridge Smoke Unit BSFC = Brake Specific Fuel Consumption TDC = Top Dead Centre B20 = 20% Biodiesel+80% Diesel B40 = 40% Biodiesel+60% Diesel B60 = 60% Biodiesel+40% Diesel B100 = 100% Diesel.

References

[1] A.K. Agarwal, L.M. Das, "Biodiesel development and characterization for use as a fuel in C.I Engine", Journal of Engineering, Gas turbine and power (ASME), Vol.123, 2000, 440-447.

[2] A.S.Ramadhas, S.Jayaraj, C.Muraleedharan, "Use of vegetable oils as I.C engine fuels: A Review", Renewable Energy, Vol.29, 2004, 727- 742.

[3] A.Srivastava, R.Prasad, "Triglycerides- based diesel fuels" Renewable Energy Reviews, Vol.24, 2004, 111-133.

[4] B.K.Barnwal, M.P. Sharma, "Prospects of bio-diesel production from vegetable oils in India" Renewable and sustainable energy reviews, Vol. 9, 2005, 363-378.

[5] F. Karaoamanoplu, "Vegetable oil fuels: A review", Energy sources, Vol.70, 1999, 221-231.

[6] M.A. Fangrui, M.A.Hanna, "Biodiesel production: A review", Bio source Technology, Vol.70, 1999, 1-15.

[7] B.S. Chiou, H.M. El-mashad, R.J. Avena-Bustillos, R.O. Dunn, P.J. Bechtel, " Biodiesel from waste salmon oil" American society of Agricultural and Biological Engineers, Vol. 51(3), 2008, 797-802

[8] Cherng Yuan Lin, Rong Ji Li, "Fuel properties of biodiesel produced from the crude fish oil from the soap stock of marine fish", Science direct, Fuel processing technology 90 (2009) 130-136.

[9] El-mashad, H.M., R. Zhang, and R.J.Avena-Bustillos, "A two-step process for biodiesel production from salmon oil" Biosystems Eng. Vol.99 (2), 2008 220-227.

A. Karthikeyan (a), * and B. Durga Prasad (b)

(a) Sathyabama University, Chennai, Tamil Nadu, India

(b) J.N.T.U College of Engineering, Anatapur, A.P, India

* E-mail address: karthikeyan_sist@yahoo.co.in

Table 1: Fuel properties.

Properties                                 Diesel   Fish oil biodiesel

Kinematic viscosity at 40[degrees]C (Cst)   3.52          4.96
Density at 15[degrees]C (kg/[m.sup.3])      830            850
Flash point ([degrees]C)                     49            162
Cetane number                                50            51
Calorific value (kJ/kg)                    43000          37800
Total sulphur (% by mass)                   0.01          0.05
Distillation (% by volume)                          90 at 333[degrees]C
Ash (% by mass)                             0.01           Nil
Oil ester (biodiesel) %                                   89.96