Investigation of Best Performing Biofuel Among Various Bio Oils Diesel Engine

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Investigation of Best Performing Biofuel Among Various Bio Oils Diesel Engine

Harishchandra V Astagi Department of Mechanical Engineering, PDA College of Engineering, Gulbarga,

Karnataka, India

Dr. Prashant Kamble

Professor, Department of Ind. & Production Engineering, PDA College of Engineering, Gulbarga,

Karnataka, India

Abstract The various available non-edible vegetable oils have been investigated experimentally for engine characteristics on a diesel engine. The non-edible straight vegetable oils used are Mahua, Neem, Castor and Linseed oil. These oils posed operational and durability problems with the long term usage. Poly-unsaturated character of straight vegetable oils, low volatility and, high viscosity are the main cause for poor performance. Hence, fuel pre-heating is done to reduce the viscosity of neat oils and experiment is carried out on single cylinder diesel engine. The various performance and emission parameters are investigated and compared with the baseline data of diesel. The experimental results showed the significant improvements found with use of neem oil and castor oil for performance and exhaust emissions characteristics of the engine.

Keywords Engine, Non-edible vegitable oils, Performance characteristics, Exhaust Emission Characteristics


    The limited resources of petroleum fuels and its products need for increasing concerns for environment, and steep rise in crude oil prices there has been renewed focus on vegetable oils as an alternative to petroleum fuels. Vegetable oil is environment friendly, renewable fuel and is easily available worldwide. These are the triggering factors to consider vegetable oils and their derivatives as substitute fuel to petroleum diesel. However, high viscosity and low volatility which are major disadvantages of vegetable oil cause poor fuel atomization, poor combustion, ring sticking, injector cocking, injector deposits, and lubricating oil dilution. The modern fuel injection system of engines is more sensitive to fuel viscosity. Viscosity of the vegetable oils needs to be reduced in order to improve fuel flow, combustion and engine performance. Heating is one of the methods adopted to reduce viscosity of vegetable oils. However transesterification and Blending with diesel are common methods used.

    Though many researchers worked on the various bio oils and investigated that vegetable oils are feasible substitutes for diesel fuel, but still a lot of work that needs to be carried to use vegetable oil in diesel engine.

    The literature review shows that many researchers have investigated non-edible vegetable oils such as Jatropha, kusum (Schlerlchera trijuga), Karanja (Pongamia glabra), Rice bran, linseed etc. and also some of the edible vegetable oils for the performance, combustion and emission characteristics of diesel engine. The present energy crisis inspired the authors to compare the engine characteristics of diesel engine using

    some of the non-edible oils such as Neem, Linseed, Mahua and Castor oil and select the best performing oil to be used as alternate fuel for diesel engine.


    Compared to conventional diesel, Vegetable oils have very low heat content, comparable cetane number, low volatality, and stoichiometric air/fuel ratio. Calorific value decreases with increasing un-saturation as a result of fewer hydrogen atoms in their molecular structure. The typical vegetable oil has following molecule structure:

    The molecule of vegetable oil contains R1, R2 and R3 straight chain alkyl groups and free fatty acids. The vegetable oil poses high viscosity and low volatility compared to mineral diesel. Two types of problems are associated with the use of vegetable oils in the engines – operational and durability problems. Operational problems are related to starting ability, ignition, combustion and performance. Durability problems are related to deposit formation, carbonization of injector tip, ring sticking and lubricating oil dilution. The extremely low volatility, high viscosity, polyunsaturated character of vegetable oils is the cause for the operational and durability problems. High viscosity of oils results in poor fuel atomization, large droplet size and thus high spray jet penetration. The jet tends to emerge in the form of solid stream instead of small droplets. This results in poor premixing and distribution with air in combustion chamber which lead to poor combustion, loss of power and economy.

    Blending with diesel, cracking / pyrolysis of oil, emulsification or transesterification of vegetable oils may overcome these problems.


    The Mahua, Neem, Castor and Linseed oil used for this work were collected, crushed in mechanical expeller from the seeds collected from Biofuel centre, Gulbarga University, Kalaburagi (Karnataka).

  4. EXPERIMENTAL SET UP AND PROCEDURES The experimental setup consists of a diesel engine fitted

    with an eddy current dynamometer. Fuel tank is fitted with

    thermostat-controlled heater with built in control panel. The setup has complete PC based data acquisition system. The fuel filters are fitted at the inlet and outlet of the fuel pump. Fuel flows to the injector pump under gravity. Thermocouple are used for measuring Lubricating oil temperature and water temperature. The constant flow rate of cooling water is maintained at temperature 65 to 700C throughout the experiment. The emission characteristics are analyzed by using 5- gas analyzer and smoke meter.

    Fig. 1. Experimental test rig


    Diesel engine


    Exhaust gas calorimeter


    Eddy current dynamometer


    Exhaust temperature indicator


    Dynamometer control


    Air inlet temperature


    Anti pulsating drum


    Two way valve


    Fuel tank


    Fuel injection pump


    Computer with DAQ


    Crank angle encoder


    Smoke meter




    The physical and chemical properties of various oils under test are measured in fuel testing laboratory as per Indian standards (IS) methods and are shown Table 1. Calorific value are measured found by using Bomb calorimeter and viscosity by Redwood viscometer. The flash point and fire point are evaluated by Pensky-Martens apparatus.

    Table 1: Properties of vegetable oils and diesel.







    Viscosity, cSt (at 40°C)






    Calorific Value, kJ/kg






    Sp. Gr. At 25°C






    Density, kg/m3






    Flash point, °C






    Fire point, °C





    The performance test on the engine are conducted at constant speed of 1500 rpm and varying load from 0 to full load. The performance parameters, such as brake thermal efficiency, fuel consumption, sp. Fuel consumption and exhaust gas temperature are evaluated. The exhaust gas emissions were measured by 5 gas analyser. All the

    observations and results are analyzed on data acquisition system.


    Manufacturer Kirloskar Oil Engines Ltd., India

    Model TV-SR II, naturally aspirated

    Engine Single cylinder, DI

    Bore / stroke 87.5mm/110mm

    Compression ratio 16.5:1

    Speed 1500 r/min, constant

    Rated power 5.2kW

    Working cycle four stroke

    Injection pressure 200bar/23° deg BTDC IVO/ IVC 4.5° BTDC/35.5° ABDC

    EVO/ EVC 4.5° BTDC/35.5° ABDC

    Type of sensor Piezo electric

    Response time 4 micro seconds Crank angle sensor 1-degree crank angle

    Resolution of 1 degree 360 encoder with a resolution of 10


      1. Kinematic viscosity

        Fig 2 Effect of temperature on kinematic viscosity

        Figure-2 shows the effect of temperature on kinematic viscosity of different neat vegetable oils under test. Result shows that the viscosity of oils is approximately close to that of diesel at the temperature of 80°C. This shows that preheating is required all the oils for easy flow through pump and nozzle.

      2. Brake thermal efficiency

        Figure-3 shows variation of brake thermal efficiency with brake power for diesel and different vegetable oils. Brake thermal efficiency of Linseed, mahua, and castor are very less and neem has higher efficiency and very close to diesel for entire range of operation. Maximum brake thermal efficiency of Neem, Castor and Mahua,are 27% , 25.12% and 23.03% respectively against 30.95% of diesel oil, which are well comparable with diesel

        Fig 3: Brake thermal efficiency with brake power.

        . The drop in brake thermal efficiency is attributed due to high viscosity and poor volatility of the vegetable oils, which leads to poor combustion. It seen that the thermal efficiency of neem oil is better in comparison to all oils, due to its higher calorific Value.

      3. Brake Specific Fuel Consumption:

    Fig 4. Brake specific fuel consumption vs brake power

    Figure-4 shows variation of Brake specific fuel consumption of different vegetable oils with brake power. BSFC of Neem oil is found close to diesel. Neem, Castor oil have minimum BSFC of 0.349 and 0.399 kg/kW-hr respectively against 0.275 kg/kW-hr diesel. It was observed that sfc of the preheated oil was higher than diesel. Due to lower calorific values, higher density, higher viscosity and oxygen content of the vegetable oils, more quantity is required to be injected to produce same amount of power. Poor volatility leads to the poor combustion characteristic of vegetable oils and hence drop in thermal efficiency and increase in BSFC.

    5.4. Exhaust gas temperature

    Fig. 5. Exhaust temperature vs brake power.

    Figure-5 shows variation of exhaust temperature with brake power for vegetable oils under test. Exhaust temperature of Neem is almost same as that of diesel through out the operating range. This is an indication of lower exhaust loss and could be possible reason for higher performance. Linseed and mahua shows higher exhaust temperature compared to diesel.

      1. Smoke density

        Fig 6. Smoke emission vs brake power

        Figure 6 indicate smoke emission with brake power for Diesel and vegetable oils under test. Smoke emission of neem is close to the diesel for entire range of operation. Linseed oil has more smoke emission among all the test oils. The higher viscosity and higher composition of CO in preheated oils lead to incomplete combustion. Hence, smoke composition was found much higher in vegetable oil.


Experimental investigations on Neem, Mahua, Linseed and Castor are carried out on a single cylinder DI diesel engine to find their suitability to use as alternate fuels. Further the performance and emission characteristics are evaluated and compared with diesel and best performing fuel is determined.

From the investigations, it is concluded that:

  • The physical and chemical properties like viscosity, density, flash point and fire point of vegetable oils under test are higher. Calorific values are lower than that of diesel.

  • Neem, Mahua and linseed oil attain viscosity very close to the diesel when heated at at 80oC. Hence preheating of oils is required for smooth flow and injection.

  • Neem, Castor and Mahua are found to be better in performance and emission characteristics compared to other fuels.

  • Smoke emission of Castor and Neem are well comparable compared with other oils. The smoke emission of Linseed oil is on higher side for entire range of operation.

From the above discussion, it may be concluded that that Neem with preheating has acceptable performance with lower emissions. Hence it can be substituted as fuel for diesel engine without any modification.


Authors are very thankful to the Mechanical Engineering Department, Poojya Doddappa Appa College of Engineering, Kalaburagi, Karnataka for financial help and necessary steps for setting up experiments.


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