Biogas as a Vehicle FuelSuryavanshi N. D, Shaha S. S, Varpe D.G

Department of Mechanical Engg., S.V.P.M.’s College of Engineering

Abstract— This work concerns a systematic study of IC engine operation with 100% biogas as fuel (as opposed to the dual-fuel mode) with particular emphasis on operational issues and the quest for high efficiency strategies.

As a first step, In Biogas CO2 does not help in combustion process but reduce the calorific value of biogas. H2S is in minor quantity but it has corrosive action on combustion chamber and also reduces calorific value of biogas. Also traces of moisture are to be removing for better thermal efficiency. So harmful gradients are removed and use only methane as a fuel.

Subsequently, the model of KINETIC GF is used to predict effect of different parameters such as compression ratio, spark timing and combustion durations on engine performance and efficiency.

The results show very high overall efficiencies with the manifold injection strategy. The main reasons are the higher volumetric efficiency and overall lean operation of the engine across the entire load range. Predictions show excellent agreement with measurements, enabling the model to be used as a tool for further study. Simulations suggest that a higher compression ratio (up to 13) and appropriate spark advance can lead to higher engine power output and efficiency.

Keywords—Anaerobic Digestion, Gasoline, Scrubber.

1. Introduction

For developing countries such as India, energy is at a premium due to the large dependence on crude oil imports. At the same time substantial part of the rural population still does not have access to electricity. While fossil fuel usage increases it is only a matter of time before reserves

run out. The use of renewable energies would provide the benefit of alternative possibilities to future energy needs. One of the sources of renewable energy is biomass.There are different ways of utilizing biomass. Firstly, it can be burnt directly; this method is most common. The heat generated can be used to power boilers and the steam produced is used in various industrial processes or can be used for running steam turbines. It can be subjected to gasification where part of the biomass is converted to producer gas consisting of CO, H2, CH4, CO2, N2, which can be used for cooking, heating or for running internal combustion engines. The different methods to use biogas in IC engines are1. Dual-Fuel Operation (C.I. Engines)2. C.I. Engine conversion3. S.I. Engine conversion 2. Background

Operation of SI engines on biogas requires changes in the intake system to supply gas. Keeping in mind the requirement of a simple system, an earlier investigation looked into the possibility of modifying a commercially available Shriram Honda EBK 1200 genset on biogas. The genset was successfully run on 100% biogas. An initial modification to the engine so as to supply gas at the intake manifold was done. The gas was introduced directly into the intake manifold. The system utilized a pump to supply gas with manual control for gas flow rate. A maximum of 400 W of electrical energy was obtained in comparison to 1000 W for kerosene operation. An overall efficiency of 8% was obtained on gas operation with 5%

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improvement in efficiency as compared to kerosene operation. This is attributed to the simpler combustion process of gases when compared to liquid fuels. The overall efficiency of the system is very low as a result of the low compression ratio of the engine (4.5). This is due to the low octane number corresponding to kerosene.

3. Theory3.1 Preparation of Bio-gas

Micro Organisms and Mechanism of Bio-Gas Production areA. Micro Organisms-

An organic waste consist of many organisms but the organisms useful for

Biogas productions are i. Aerobic ii. Anaerobic

B. Constituents of Organic Waste – The organic waste contains many

constituents such as cellulose, Hemicelluloses, lignin, proteins, and starch, water-soluble, fats Soluble etc. C. Mechanism of biogas production: - Stage 1 -

It involves the decomposition of cellulose, hemi cellulose, Lignin, starch, protein, fats etc. Into simpler organic compounds like acids, alcohols and gases like CO2, H2, and NH3, H2S etc. by aerobic and anaerobic Micro-organisms. Stage 2 -

The anaerobic organism or methane bacteria utilize Simple carbon compounds available from first stage and produce methane. There are two types of plants-

i. Daily fed or continuous type. ii. Batch fed or periodic type.

Biogas coming from tank contains

Components Composition

Methane(CH4) 50-68%

Carbon monoxide (CO2) 25-35%

Hydrogen(H2) 1-5%

Nitrogen (N2) 2-7%

Hydrogen Sulphide (H2S) 1-5%

3.2 Purification of Biogas

1) Removal of CO2 -

CO2 is highly corrosive when wet

and it has no combustion value so its

removal is must to improve the biogas

quality. To remove CO2 we use Caustic

solution of NaOH 25%

NaOH + CO2 = NaHCO3

2) Removal of H2S -

The ferrous materials are placed in a

closed gas tight container the gas to be

purified flows through the ferrous absorbing

agent from the bottom & leave the container

at top.

CuSO4+H2S= CuS+H2SO4

By using following setup Biogas can

be pure.

Fig. Setup for Purification of Biogas

3.3 Properties of bio-gas

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In its pure state, it is color less, odorless, tasteless. For safety reason, an odorant is added so that any leak can be easily detected because of typical smell

The composition of bio gas is never constant. Methane is by far the largest component, its presence accounting for about 95% of the total volume. Methane is a simple hydrocarbon, a substance consisting of carbon & hydrogen. There are many of these compounds each has its own carbon & hydrogen atoms joined together to for a particular hydrocarbon gas as fuel gas. Methane is very light fuel gas. If we increase the number of hydrogen & carbon atoms, we have got progressively heavier gases, releasing more heat, therefore more energy, when ignited. Specific gravity of methane is .55 which is less than petrol & LPG. This means that biogas will rise if escaping, thus dissipating from the site of a leak. This important characteristic makes biogas safer than other fuels. It does not contain any toxic component; therefore there is no health hazard in handling of fuel. The air to biogas (stoichiometric) ratio by volume for complete combustion is 9.5:1 to 10:1.

Biogas has a very slow flame velocity, only .290 m/s. at its highest. The range of flammability is 4 to 14% which can give good combustion efficiency

Biogas has very high octane number approximately 130. By comparison, gasoline is 90 to 94 & alcohol 105 at best. This means that a higher compression ratio engine can be used with biogas than petrol. Hence, cylinder head of the engine is faced so that clearance volume will be reduced & compression ratio can sufficiently increase. Thus volumetric efficiency & power output are increased. Because of its high octane value the detonation occur however high the compression may be. The Boiling point of

biogas is above 300 degree Celsius while the calorific value is 35.390 MJ/m3.

3.4 Advantages of Biogas : - 1) It is light fuel gas.2) It mixes easily with the air.3) It is highly knocked resistant.4) Due to uniform distribution

thermal efficiency is higher.5) Biogas has a high octane number.6) It reduces pollution.7) Higher compression ratio can be

used with biogas.8) Plants capital cost is low.9) Domestic fuels for burners used in kitchen10) No toxic to skin

3.5 Methane combustion duration

The flame propagation speed of methane is known to be lesser than that of gasoline the ignition delay for methane is also greater using natural gas in spark ignition engine therefore requires the spark timing to be advanced spark timing is not sufficient with conventional conversion .the long duration combustion implies that merely advancing spark plug timing is not sufficient with conventional conversion this is because the temperature in cylinder at an timing would be lesser. These lower temperature would further hinder early flame development. The longer the time taken for combustion implies lower heat release rate and therefore lower indicated power. The long ignition delay for these engines is result of strong initial endothermic phase in case of natural gas combustion.

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The presence of CO2 in biogas further extends the combustion period experiment were preformed on a single cylinder engine CFR engine. He reports a significant increase in the average length of combustion period, ignition lag and lower associated burning rates for with increasing proportions of carbon dioxide.

3.6 Efficiency

Natural gas and biogas have been found to posses good resistance to knocking their octane numbers are higher than that of petrol with natural gas at 120 relative to natural gas and gasoline were studied using experiment simulated biogases with three compositions 15% CO2, 25% CO2 and 38% CO2 by volumes were tested the compression ratios were varies from 8.5 to 13. The gaseous fuels were found to have leaner operation limits in comparison to gasoline. The maximum compression ratios recommended for gas operation is 1.3 the use of higher compression ratios increases the indicated power but the mechanical losses also increases thereby reducing the net brake power available. Compression ratios beyond 15 led to knocking. The long combustion duration of biogas requires the spark timing to be advanced. The choice of compression ratio for biogas thus based on to some extent.

3.7 Modification in IC Engine

Dual-fuel operation refers to utilizing biogas in diesel engines with diesel as pilot fuel for the purpose of ignition of fuel. In this method, in place of pure air that fills the combustion chamber of the engine prior to diesel injection, a suitable mixture of air and biogas is introduced. A small amount of diesel usually 10 – 20% is sprayed so as to initiate combustion. Thus, a mixing device for air and biogas is required. For stationary applications speed control is obtained using

a regular governor. This method requires a constant supply of diesel.

A conventional C.I. engines can be converted for biogas operation. However, as diesel engines usually have compression ratios higher than 14, this can cause problems of knocking with biogas. Hence a reduction in compression ratio below 13 is required for biogas operation. Also, the injector present needs to be replaced with a spark plug to provide for the ignition of the air-biogas mixture. Thus, significant changes to the engine are required.

Gasoline spark ignition engine conversion is relatively straightforward requiring a mixing device for the purpose of air-fuel ratio control and spark timing modification to account for the slow combustion of biogas. Thus, either one could adapt a diesel engine by reducing its compression ratio for safe biogas operation or convert a spark ignition engine to higher compression ratio for more efficiency.

4. Experimental procedure

Following description gives detailed procedure of performance test on 4 stroke petrol engine. The experimental setup is done as stated above. First of all make all colorimeter and Alternator connection to engine. Calorimeter and Alternator is on the desired flow rate and pressure, make sure fuel supply on. After conditioning the equipment, the engine is started and warm up for 10 min without applying any load. Observe the fuel flow timer when started the engine. Two tests are taken viz. varying speed and load & second are by keeping speed constant & varying the load. Respective readings are noted and calculations are done to find performance parameters. Repeat same procedure for biogas and LPG.

A) On CI engine (Diesel):-

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Fig.5.2.1 Setup for CI engine testing

B) On SI engine (Petrol):-

Fig.5.2.2 Setup for SI engine testing

5. Conclusion Biogas appears to be a feasible fuel

for internal combustion engines because it can be derived from agricultural surpluses and residues, which provide the raw material for biogas production. By feeding the byproduct of the biogas production process, a farmer may even incorporate the production of his own fuel as an integral part of the food production system. Biogas for power generation has been recognized as an important component of the renewable energy program in India. Biogas collection and storage of biogas are the most serious constraints in the widespread utilization of this resource for I.C. engine. From the performance test it can be seen that mass flow rate is varies for the various load condition. Also the percentage of CO conditions when both fuels are used.

From the performance test can be concluded that the mass flow rate of Bio-Gas is more as compare to the L.P.G. for same operating conditions .at the maximum load conditions the mass flow rate greater for Bio-Gas as compared to the L.P.G. The motivation is that for present work is systematic study of engine performance with 100% biogas operation. The use of biogas injection close to the intake manifold for biogas involved higher volumetric efficiency than the conventional method of premising air and biogas commonly used for biogas operation. The higher volumetric efficiency of engine however did not result in any gain in performance. The reason for this was a low compression ratio of engine.

5.1 Future scopePower generation in India was only

4.1 billion kWh in the year 1947-48 and in the year 2002-03 it was more than 600 billion kWh. Now it is up to 900 billion. considering the past record, the future economy growth scenario and likely boost to captive. This animal wealth produces about 37 million kg animal dung, which has potential of producing about 1.2 million cubic meter bio-gas. This huge amount can suffice the cooking fuel requirement of about 50 lacks families. Power plant sector as a result of changes arising due to Electricity Act 2003, the target of generating about 8000 billion kWh per year by 2042 is achievable. In only Maharashtra State enriched livestock population of about 18.3 million.

6. References

1. Singh. A., “Conversion of a 1.2 kW Genset for 100% biogas operation”.

2. Jawuerk, H. H., Lane, N. W., Rallis, “Biogas/petrol dual fuelling of SI engine for rural third use”,

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3. Karim, G.A., “Combustion in gas fueled compression ignition engines of the dual-fuel type”, Journal of Engineering Gas Turbines and Power, July 2003,

4. Badr, O, Karim, G.A., Liu, B., “An examination of flame spread limits in a dual fuel engine”,

5. Mitzlaff, Klaus von, “Engines for Biogas”, A publication of Deutsches Zentrum fűr Entwicklungstechnologie

6. V. Ganeshan, Internal Combustion Engines, second edition.

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