EMULSIFIED ETHANOL USAGE AS A
ALTERNATE FUEL
ABSTRACT
At the end of this century it’s believed that there must be scarcity for petroleum products. More over that, we are seeking to control the emission by finding alternative source of fuels. Another reason in the fact that a large percentage of crude oil must be imported from other countries. By considering the cost point of view it is a significant factor. So we must go for an various options of using fuel.
Among the various options, Ethanol, an alcohol seems to be a most promising option for countries like India because of its availability from agriculture products. Alcohol can be used in diesel engines in following ways.
One method is injection of ethanol with inlet air using carburetion or electronic injection system and other is emulsion of diesel and ethanol. And also enable a reduction in exhaust NOX, smoke and particulate matter.
This paper critically reviews different aspects of ethanol as an alternative fuel for diesel engine. They are_
Ethanol properties & comparison with diesel. Use of ethanol in I.C engines Experimental set up for single cylinder air-cooled direct injection diesel engine.
Emulsion preparation Engine test procedure for emulsion. Modifications requirements. Performance characteristics curves & Experimental setup photos.INTRODUCTION
Diesel engines are now preferred due to its high fuel economy in various applications. However they have unsatisfactory emission characteristics. Hence there is a constant search for alternate fuels, which will meet the present emission norms [1, 2, 3 and 4].
Researches are more concentrating on the efficient combustion by employing,
Ø Highly pressurized fuel injection like CRDI
Ø Advanced engine and exhaust gas management systems
Ø Enriched fuel with additives like ignition accelerators, antiknock agents
Ø Alternate fuels to have more colorific value
The reasons for opting alternate fuels are_
v High cost of petroleum products and surge the cost of hydrocarbon fuels
v Increased demand for petroleum products.
v Strict emissions norms like EURO NORMS, BHARAT NORMS,
KYOTO PROTOCOL, etc.
v Global warming and adverse environment effect due to pollution from the automobiles.
q Many alternate fuels are being considered for automotive vehicles and ETHANOL of the best alternate fuels. Ethanol is produced from molasses, which is a by-product of sugarcane.
q Ethanol can be produced in large quantities at low cost from these molasses. It is a renewable fuel and its high oxygen content improves the combustion characteristics.
q Ethanol reduces harmful emissions from I.C engines of
Sulphur-di-oxide, oxides of nitrogen and particulate emissions.
PROPERTIES OF ETHANOL
Ø . viscosity of ethanol is less.
Ø Specific gravity of ethanol is 0.794.
Ø Boiling temperature of ethanol is 78C.
Ø Ethanol has a low cetane rating.
Ø It is inflammable and its vapour form explosive mixtures with air.
Ø It is an excellent solvent for fuels, oils, fats etc.,
Ø It is miscible with water in all proportionate mixing being attended
by a concentration of volume.
ETHANOL PROPERTIES COMPARED TO DIESEL:
S.NO | PROPERTY | ETHANOL | DIESEL |
01. | Density kg/m3 | 785 | 840 |
02. | Volume lower heating value kg/litre | 21000 | 36500 |
03. | Latent heat of vaporization kj/kg | 840 | 251 |
04. | Cetane number | 8 | 50 |
05 | Enthalpy of vaporization kj/kg | 837 | 225-600 |
06 | Auto ignition temperature | 365- 425 | 204-260 |
07 | Stoichiometric Air fuel ratio | 9 | 14.5 |
USE OF ETHANOL IN I.C ENGINES
The various techniques by which the ethanol can be used as a fuel for compression ignition engines are_
Ø Blend formation
Ø Fumigation
Ø Dual injection
Ø Spark ignition
Ø Ignition improvers
Ø Surface ignition
BLEND FORMATION:
The easiest method by which ethanol could be used is in the form of diesel ethanol blend. But ethanol has limited solubility in diesel; hence ethanol/diesel solutions are restricted to small percentages (typically 20%). This problem of limited solubility has been overcome by emulsions, which have the capability of accommodation larger displacement of diesel up to 40% by volume. But the major drawbacks of emulsions are the cost of emulsifiers and poor low temperatures physical properties.
DUAL INJECTION:
Dual injection is a method by which nearly 90%
Displacement of diesel by ethanol is possible. The drawback of this method includes the complexity and expense of a second injection system and a second fuel tank and system.
SPARK IGNITION:
Spark ignition of neat ethanol in diesel engines provides a way of displacing 100% of diesel. A spark plug and the associated ignition system components must be added to the engine. Space must be available for spark plugs in the cylinder head and its also important for sparkplugs in the cylinder head and it’s also important for proper plug cooling.
IGNITION IMPROVERS:
Another method of using neat ethanol is to increase their cetane numbers sufficiently with ignition improving additives to ensure that compression ignition will occur. This method saves the expense and complexity of engine components changes, but adds fuel costs.
SURFACE IGNITION:
This is another method of using ethanol 100% ethanol in diesel engines. Surface ignition occurs when the temperature of the air-fuel mixture adjacent to a hot surface exceeds its self-ignition limit.
FUMIGATION:
Fumigation is a method by which ethanol is introduced in to engine by carbureting or vaporizing the ethanol into the intake stream. This method requires addition of a carburetor or vaporizer along with a separate fuel tank, lines and controls. But with the emergence of electronic injection techniques the fumigation technique has been made possible by using an injector in the intake manifold.
EXPERIMENTAL SETUP
The experimental setup was carried in a single cylinder air cooled direct injection diesel engine. Table 1 shows the specification of the engine.
v Engine type : single cylinder 4 stroke DI engine.
v Displacement volume : 779.70CC
v Bore : 95mm
v Compression ratio : 18:1
v Rated speed/power :1500 rpm/5.5kw
EXPERIMENTAL SETUP
The engine is coupled with a BENZ make eddy current dynamometer.
An electronically operated control panel was used to vary the load and the fuel flow rate was measured by an electronically operated solenoid switch control fuel flow meter.
An AVL smoke meter and 5-gas analyzer were connected to the exhaust manifold to measure the smoke and the exhaust pollutants respectively. The smoke meter works on the light abstraction principle and the level of smoke was given in Hatridge equivalent percentage. The exhaust pollutants carbon monoxide (CO) and unburned hydrocarbon (UBHC) where measured using non-depressive infra-red (NDIR) principle and for the oxides on nitrogen electric chemical absorbent principle were used. A thermocouple was fixed at the exhaust manifold to measure the exhaust gas temperature. A separate fuel tank was fabricated to prepare the emulsion.
PREPARATION OF EMULSION:
Emulsion is prepared by shaking or stirring by the dispersed phase on dispersed medium or subjecting them to vibration when the emulsifiers are present. Emulsors, stirrers and collide mills and alter sound are used for emulsification. Emulsification consists of dispersion property, the formation of droplets of the dispersed phase face in dispersion medium and their stabilization by absorption in the emulsifier surface. Emulsion stabilized by non-ionogenic emulsifiers is more difficult to destroy.
ENGINE TEST PROCEDURE FOR EMULSIFIER:
The engine was run with a constant injection timing of 27.BTDC with diesel as fuel as under various loads.
For each load condition time taken for 100cc fuel consumption, the dynamometer and the smoke emission was measured. After this the engine is run with diesel +10% of ethanol. Various readings were tabulated and graphs were plotted.
MODIFICATION REQUIRED FOR USING ETHANOL
Though alcohols have been identified as successful contenders for replacing diesel fuel, a large number of innovative concepts need to be used to overcome the problems associated with ethanol in a diesel engine, either neat or its blends with diesel. Modification like hot surface ignition, continuously operated glow plugs, spark plugs, fuel additives, exhaust gas re-circulation, diesel injection, special piston design like sonex combustion system (SCS) [8], intake air heating either by controls on flow from turbocharger or by electric heater are some of the successful methods by which the best performance and also higher percentage of energy replacement are achieved.
RESULTS AND DISCUSSIONS
GRAPH: 1
GRAPH: 2
The variation of TFC with power of the engine operated with diesel and substitution of diesel with ethanol by fumigation and emulsification is shown in the Graph-2
GRAPH: 3
It can be seen from the Graph-3 that the smoke emitted by the engine with ethanol is always much lower than the engine running with diesel. This may be due to the fact that the addition on ethanol reduces the peak temperature their thermal cracking is reduced. Smoke is nothing but the carbon present in the exhaust, which is mainly caused by thermal cracking fuels.
GRAPH: 4
It can be seen from Graph-4 that the CO formed is equal to diesel at low loads, but there is a great change at high loads. This may be attributed to the fact that availability of enough oxygen at higher loads. Also emission is low for injection when compared to emulsion.
GRAPH: 5
It is observed from the Graph-5 in the case of emulsification NOx emission is reduced than the base diesel. This may be attributed to the fact that at part loads the ethanol absorbs much heat in the combustion chamber and also during combustion process due its high latent heat evaporation reduces the peak temperature during the combustion. The amount of NOx formation is low for injection when compared with emulsion due to better vaporization of fuel.
GRAPH: 6
It can be observed from the Graph-6 shows that HC emission of the engine running with ethanol as partial substitute is much higher than the engine running with diesel at all loads. This may be attributed to the following reasons.
High latent heat of vaporization which increases the amount of heat absorbed by the ethanol and as a consequence of slow rate of burn. But time available of combustion is very low. All these factors lead to increase HC emission.
CONCLUSIONS
v Brake thermal efficiency increases with ethanol substitution at all loads.
v The emissions like CO, CO2, SMOKE and NOX from the engine running with ethanol are reduced when compared to diesel.
v From the results, it is observed that the amount of ethanol substituted can be increased up to 40% in diesel.
v The gas temperature is reduced for the ethanol emulsion engine at all loads.
v The main drawback of ethanol substitution is the increase of Hydro Carbon emission.
As of now the quest for the alternate fuels is never ending one,
The following are some of future developments in this paper
Ø Using CFD location of ethanol injector in the inlet manifold can be optimized for better engine performance and vapourization phenomenon.
Ø Engine performance can be improved by making the engine into adiabatic one.
Ø The stability of emulsion can be increased by identifying the most effective bifurcants.
PRESSURE PICKUP IN ENGINE
MODIFIED INLET MANIFOLD
