1.INTRODUCTION:

Due to change in global scenario there is a huge demand to provide more and more energy for day to day life. As we know that 70% of required fuel is imported from other countries affecting total foreign exchange and problem of increasing the fossil fuels prices. Due to increasing cost of the fuels it is also required to use that kind of fuel is cheaper and also available easily. India’s transport sector plays an important role in the consumption of petrol and diesel. Due to these, more than 60% of total air pollution is caused by automobile exhausts. So there is an immense need for the use of alternate eco-friendly engines in urban as well as rural areas. The use of gas kit engines which are designed especially for the engines which totally run on gas i.e. methane. There are also engines which could run on dual fuel mode i.e. both on diesel and biogas being diesel as the pilot fuel. In the following experiment we have seen that when we used 98% pure methane biogas, the performance of the engine improved as compared to the biogas containing 60-70% methane. Also between particular range of biogas flow rate, it was found that the brake thermal efficiency increased up to certain flow rates of biogas and after a certain limit it started to decrease on different load conditions. numbers of research papers has reported on application of biogas for running C.I. and S.I. engines. [1] Saawomir Wierzbicki investigated the main constituents, physical and chemical characteristics of biogas which also highlights the problems associated with engines performance . They have suggested about the improving of fuel ignitability, burning velocity, back burning effects, high temperature exhausts and heat transfer mechanism, during the diesel injection in the IC engines. Baraik and Murugan [2], have firstly reported to use of biogas for I.C. engines. They realized that the enormous growth of industries could be achieved by exploitation of biogas instead of conventional fossil fuels. Sorathia et al. have performed some experiments and demonstrated constant speed, single cylinder, vertical air cooled, biogas premixed diesel dual fuelled C.I. engine which are largely used in agricultural and water pumping application in rural areas [3]. Stefan Mihic has worked for problems and their solution during use of biogas for powering internal combustion engines. Modification of internal combustion engines for stationary electrical generators and for tractors and light duty trucks has also been demonstrated [4]. The main objective of the current work is cost analysis of the fuels being used in a single cylinder, 4-stroke compression ignition (C.I.) engine containing dual fuel mode.

2.EXPERIMENTAL METHODOLOGY:

2.1EXPERIMENTAL SET UP

A single cylinder, 3.7 kW diesel engine has been used in the experiment. Set up of the engine has been shown in the Figure.1. The technical specifications of engine system are presented in the Table 1. The engine having a water cooling provision is in-built in the system. The modification has also been made in the existing system to connect intake manifold with compressed biogas pipe line like a Y-junction to operate it on a dual fuel mode. For a certain period of time, the engine operation was idle i.e. on no load condition. The engine was loaded with a mechanical loading arrangement for obtaining results on different loading conditions. The readings were noted down, after running the engine at idling condition for certain period of time and thereafter readings were taken for different loading conditions.

Figure 1. Experimental setup of engine system

The performance test was carried out with same test set up and then the engine was run on a dual fuel mode (i.e. diesel and biogas both) and again readings were taken for different loading conditions in dual fuel mode with different flow rates of biogas.

Table 1. Engine specification

B.P.	3.7 kW
Number of Cylinder	1
Bore	85
Stroke	110
Rated Speed	1500 rpm
Type of cooling	water
Combustion	Compressed Ignition

Biogas used in the experiment was bought from biogas plant in a compressed and purified form (98% methane content) in high pressurized cylinders having a pressure of more than 50 kg/cm². The gas was purified in the biogas plant before filling into the cylinder which is moisture free in nature.

2.2 EXPERIMENTAL PROCEDURE

The experiment has been preformed with the conventional diesel fuel and kept in running condition till the temperature reached the operating temperature. The r.p.m. of the engine has been kept constant for the various loads throughout the experiment. For diesel and biogas consumption of the engine, all the parameters were observed at different loads of the engine. The loading was done till the limit 4kg (i.e. 2.034 kW). Moreover, amount of diesel consumption was also noted for different loads at different flow rates of biogas to calculate the brake specific fuel consumption. To reduce error in the data each reading was repeated twice. The brake power (B.P.), diesel consumption, cost of fuel consumption of different loads at varying biogas flow rates were noted and calculated.

Figure 2. Schematic diagram of experimental setup

3. RESULTS AND DISCUSSION:

3.1 MASS FLOW RATE OF DIESEL (M_D) ON DIFFERENT FLOW RATES OF BIOGAS AT DIFFERENT

BRAKE POWER

From Figure 3, it is very clear that when the flow rate of biogas increases the flow rate of diesel found to decrease. Since the purified biogas (98% Methane) has been used in the experiment whose calorific value is 39,820 kJ/kg which was supplied to the combustion chamber having high purity as compared to non-purified biogas. The calorific value of biogas adds to the calorific value of diesel (44,800 kJ/kg), and makes total 84,620 kJ/kg energy value as estimated and supplied to the combustion chamber.

Figure 3. Variation of M_Dwith B.P. for varying flow rates of biogas

From Figure 3, when engine operates on diesel alone, the consumption of diesel is high as compared to in dual fuel mode till the flow rate range of 0 – 0.350 kg/hr. When we increase the flow rate of biogas, the consumption rate of diesel starts to increase beyond the flow rate of 0.350 kg/hr. This is because of flow rate of biogas increases above 0.350 kg/hr where it stops the air intake i.e. oxygen needed for combustion and slows down the engine performance by deficient diesel supply. In this condition, some biogas remains un-burnt as a residual mass in the expansion stroke and there combustion starts after expansion which leads to extra blasting called ignition delay and results in abnormal sound of engine.

3.2 COST OF DIESEL (M_D) ON DIFFERENT FLOW RATES OF BIOGAS AT DIFFERENT

BRAKE POWER

Cost of diesel and cost of biogas per hour is calculated. Price of diesel is considered to be Rs 80.950/kg and biogas is Rs.50/kg. A comparison is done between cost of flow rate of diesel alone and cost of flow rate of diesel on different flow rates of biogas at different loading conditions of engine. It can be seen from figure 4, the variation of cost of flow rate of diesel on different flow rates of biogas at different brake power. Though the variation of cost of fuel at different loading conditions are quite less but if we analyze the cost on large scale i.e. increased no. of hours of operation of engine & high power generation required we can observe a good amount of savings on dual fuel mode as compared to single fuel mode operation. According to the figure 4, engine when operated on diesel alone, cost price ranges from Rs 58.50/kg-Rs70.59/kg but when the supply of biogas is turned on this cost price starts decreasing until the flow rate of 0.150 kg/hr of biogas. When we increase the flow rate of biogas, the gas gets wasted i.e. it is not needed by the engine in operation thereby increasing the cost price of the fuel. So, the most optimal flow rate of biogas for an internal combustion engine of the above mentioned specifications in Table no.1 is of 150 kg/hr.

Figure 4. Variation of Cost of Fuelwith B.P. for varying flow rates of biogas

Equations and Formulas

The experiment involves certain formulas and values used for the calculation:

· B.P.= 2*Pi*N*T/60

·B.P. = W*N/C

·Density of diesel = 737.8 kg/cubic meter = 0.7378 g/ml

·Cost of diesel =Rs 59.40 /liter

·Cost of diesel =Rs 80.590/kg

·Cost of biogas = Rs 50/kg

·Cost of fuel = Cost of diesel + Cost of biogas

Abbreviations

B.P. - Brake Power

B.S.F.C. - Brake Specific Fuel Consumption

B.T.E. - Brake Thermal Efficiency

M_D- Mass flow rate of Diesel

M_B- Mass flow rate of Biogas

W - Load

N – Revolutions per minute

CV_B- Calorific Value of Biogas

CV_D- Calorific Value of Diesel

C - Dynamometer Constant 2950

T - Torque

4. CONCLUSION:

One of the most interesting utilization of biogas is as vehicle fuel. The substitution of conventional fossil fuels with biogas can provide up to 80% less of green-house gases emissions. The success of biogas as a diesel engine fuel requires a readily build infrastructure therefore biogas now a days could mostly be used in public transportation and generators. The performance of the engine could be concluded as follows:

· From the above result we can conclude that a diesel engine when operated on a dual fuel mode gives better performance than single fuel mode.

· As diesel is a conventional fuel, the demand is increasing day by day thereby increasing its cost.

Therefore use of biogas along with diesel is smarter way to make the use of I.C. engine economical.

· 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.

· The combustion velocity of biogas is little slow as compared to diesel because of which combustion period is long thereby decreasing efficiency and reliability. Therefore it is required to purify the biogas properly before using it for combustion in diesel engine.

· A problem of high exhaust temperature due to excessive burning of biogas persists.

· Due to micro blasting, the sound of the engine becomes abnormal.

· By designing suitable combustion chamber and high compression ratio, performance of the engine could be improved.

· The exhaust emissions from biogas fuelled vehicles are relatively low in particulates and Nitrogen Dioxide hence contribute to improve local air and climate quality.

· As a renewable fuel, biogas helps to reduce dependence on conventional fossil fuels.

5. REFERENCES:

[1] Saawomir Wierzbicki, “Biogas as a fuel for diesel engines” Journal of KONES Power train and Transport, Vol. 19, No. 3 2012, University of Warmia and Mazury.

[2] Debabrata Baraik and S. Murugan, “Production and application of biogas as a gaseous fuel for international combustion engines” , IJERT ISSN 2278-0181 Vol.1 issue7, September2012.

[3] Harilal S. Sorathia, Bhagirathsinh H. Zala, Dinesh L.Suthar Vasant K. Pipaliya, “Performance of biogas premixed charge constant speed diesel engines used in an agricultural field.” International journal of advanced engineering technology E-ISSN 0976-3945.

[4] Stefan MIHIC, “biogas fuel for internal combustion engine”, Annals of the faculty of engineering Hunedoara, Faculty of engineering, University of NOVI SAD, Serbia and Montenegro, Tome 2, Fascicole 3,20014

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Received on 03.10.2016 Accepted on 14.10.2016

Research J. Engineering and Tech. 2016; 7(4): 151-155.

DOI: 10.5958/2321-581X.2016.00027.1