EXPERIMENTAL STUDIES ON BIODIESEL OPERATED CI ENGINE

EXPERIMENTAL STUDIES ON BIODIESEL OPERATED CI ENGINE

EXPERIMENTAL STUDIES ON BIODIESEL OPERATED CI ENGINE

ABSTRACT

The world is confronted with two abysses of petroleum oil depletion and environmental pollution. The indiscriminate extraction and consumption of petroleum oils have led to a reduction in petroleum reserves. In recent years, much research has been carried out to find suitable alternative fuel to petroleum products.

The use of renewable fuels like biodiesel, biogas and ethanol in diesel engines is cardinal in this context. Biodiesel obtained from vegetable oils has been considered a promising option for diesel engine.

In the present work, biodiesel is produced using unrefined jatropha oil. A transesterification process is developed for the production of methyl-esters of jatropha oil. The properties of this biodiesel are closely matched with those of diesel fuel.

The performance tests are carried out on a CI engine using biodiesel and its blends with diesel (B20, B40, B60 and B100) as fuel. The effects of relative air-fuel ratio and compression ration on the engine performance for different fuels are also analyzed using this model.

INTRODUCTION

NON-EDIBLE VEGETABLE OILS – AS SUBSTITUTE FUELS FOR DIESEL ENGINES:

Interest in vegetable oils as alternative diesel engine fuels dates back several decades. Dr. Rudolf diesel was first to use vegetable oil in CI engine. During Second World War, attempts were made to use vegetable oil as diesel engine fuel. However, due to their viscosity, poor volatility and high cost, the vegetable oils were not accepted as diesel engine fuels for a long time. The vegetable oils including soyabean oil, cottonseed oil, sunflower oil, rapeseed oil, palm oil, coconut oil, linseed oil, Karanji oil, Jatropha oil, their Cetane numbers and calorific values are comparable with those of diesel oil and they are also compatible with the materials used in distribution and vehicle fuel system.

The main disadvantages are of high viscosity gives difficulties with fuel injection and with cold flow pumping. The unsaturated oils are less chemically stable, which affect storage and promotes deposits on injector components and piston. There are also problems of incompatibility with engine lubricants. Difficulties with physical properties may well be overcome by fairly simple chemical processing like esterification. Irrespective of all the difficulties mentioned above, vegetable oils may prove an alternative option as diesel fuel in some countries in future.

India being an agricultural based country, it will not be a big problem of cultivating crops for vegetable oils. Vegetable oils can be classified as edible and non-edible oils. Only non-edible vegetable oils can be considered as diesel engine fuel as edible oils are in great demand and are too expensive to be used as fuel. Different oil crops can be cultivated in different areas depending on the climatic conditions and can be met with rural demands for diesel during crisis.

Jatropha curcas oil known as moglaerand, beghierand, chandsaiyoti or nepalam in India can be as a substitute for diesel. India imports jatropha oil worth about Rs. 400 crore annually, which is used for making soap. It can be cultivated in arid and semi-arid area conditions.About 1500 liters of oils can be extracted from the yield per acre of 5000 kg of jatropha curcas in irrigated area and 400 litres of oil from 2000 kg yield per acre in arid area. The Nasik Zilla Nilgiri Sangh in Maharashtra has planted jatropha on 12000 acres this year and plans to cultivate this crop of 1,00,000 acres next year. At present, different oil crops are cultivated at different areas. One can choose the utilization of locally available oil for the experiments.

PRODUCTION OF BIODIESEL BY TRANSESTERIFICATION PROCESS

Vegetable oils and animal fats are triglycerides containing glycerin. The biodiesel process turns the oils into esters, separating out the glycerin. The glycerin sinks to the bottom and the biodiesel floats on top and can be siphoned off. We use methanol to make methyl esters.Using ethanol is better, because most methanols comes from fossil fuels. Ethanol is plant based and we can distill it our self, but the biodiesel process is more complicated. The catalyst can be either sodium hydroxide or potassium hydroxide, which is easier to use and it can provide a potash fertilizer as a by-product. Sodium hydroxide is often easier to get and it is cheaper to use. If you use potassium hydroxide the process is same, but we need to use 1.4 times as much. KOH can be easily obtained from chemicals suppliers. Other chemical such as isopropyl alcohol for titration are available from chemicals suppliers.

Ingredients:

· Vegetable oil

· Methanol (CH₃OH) 99% Pure

· Sodium hydroxide (NaOH)

Procedure:

Ø Measure the vegetable oil and pour in to the reaction vessel

Ø Prepare methoxide:- mixture 25% by volume of vegetable oil (it is about 200 ml per one litre of vegetable oil) and 3.25 g/litre of vegetable oil of sodium hydroxide and Heat the vegetable oil to 40-52°C

Ø Pour the sodium hydroxide into the vegetable oil while stirring

Ø Stir the mixture for 50 minute to an hour; keep the initial temperature through out the process. 55 °C is an ideal temperature.

Ø Allow the solution to settle down at least for eight hours

Ø Separate the glycerin from the biodiesel

This procedure is called transesterification. In transesterification, sodium hydroxide and methanol are mixed to create sodium methoxide (Na + CH₃OH) mixed in with the vegetable oil this strong polar bonded chemical breaks the transfatty acid into glycerin and also ester chains (biodiesel) along with some soap. The ester becomes ethyl esters if reacted with ethanol instead of methanol.

TESTING PROCEDURE:

The engine was started and warmed-up, at low idle, long enough to establish the recommend oil pressure, and was checked for any fuel, oil and water leaks. After completion of the warm-up procedure, the engine was run on no-load condition and the speed was adjusted to 1500 ±10 rpm by adjusting the fuel injection pump.

The engine was run to gain uniform speed after which it was gradually loaded. The experiments were conducted at seven engine torque levels viz, 0, 4, 8, 12, 16, 20 and 24 Nm.

For each load condition the engine was run at a minimum of 5 minute and data were collected during the last 2-minute of operation. Simultaneously, engine exhaust emission (Nox, CO, HC and SMOKE) was determined. The experiment was replicated three times and the average value was taken. For each test, the easy of starting the engine with all fuels was also observed. Tables represent the experimental results.

Fig. Shows the variation of BSFC with brake power. As the brake power increases combustion efficiency increases. The delay period decrease with increasing load because the operating temperature of the engine increases, leading to better combustion. Therefore the BSFC decrease with an increase in brake power.

This character is same for all blends of fuel. Compared to diesel, BSFC is 9%, 5% and 3% higher for JME-100, JME-60, and JME-40 respectively. This higher is due to the lower calorific value of the JME fuel. But JME-20 test fuel BSFC of only 3% higher than that of diesel fuel. The reduction in BSFC of JME-20 may be due to the better combustion of JME-20 test fuel than that of the other blends. If the blend is further increased, the effectiveness of combustion does not increase much. But calorific value decreases more rapidly and that is the reason for increasing BSFC beyond 20% JME addition.

BRAKE THERMAL EFFICIENCY:

The variation of brake thermal efficiency of the engine with various blends of JME is shown in fig. And compared with the brake thermal efficiency obtained with diesel fuel. JME-100, JEM-60 and JME-40 has a slightly lower thermal efficiency than diesel fuel. The difference was more noticeable at high engine torque. This is may be due to mass based fuel heating value differences, i.e. the calorific heating value of JME is some how less than diesel.

In addition to this the drop in brake thermal efficiency of JME and its blends may be attributed to the poor combustion characteristics of JME fuel due to its high viscosity and poor volatility.But JME-20 fuel shows only 3.13% lower brake thermal efficiency than that of diesel fuel; this is may be due to the combined effect of having better combustion quality and good lubricious property of JME-20 than that of the other blends.

EXHAUST EMISSION RESULT

UNBURNT HYDROCARBON (UBHC):

Fig. Represents hydrocarbon emission of various test fuels as a function of brake power. The increase in hydrocarbon emission for JME-100, JME-60 and JME-40 is primarily due to operation at high equivalence ratios, as reported in brake specific fuel consumption discussion. Barisca (1986) reported that fuel physical properties such as density, and viscosity could have a great influence on hydrocarbon emission that that of fuel chemical properties.

Since fuel viscosity differed more than other physical properties, the consequences of the fuel viscosity were nozzle exit Reynolds numbers and higher fuel spray droplet sizes for the JME fuel and thereby, hydrocarbon emission were higher for JME fuel, because diesel engine fuel systems were designed for maximum operational efficiency with diesel fuel.

CARBOM MONOXIDE:

The carbon monoxide emission rate for JME-100 fuel is much higher than that of diesel fuel at high engine-load. Fig shows the increased CO emission as the percentage of JME blends increase. The reason for this is may be fuel physical properties as was discussed for hydrocarbon emission increase and brake thermal efficiency decrease discussion.

NITROGEN OXIDES:

The nitrogen oxides resulting from the oxidation of atmospheric nitrogen at high temperature inside the combustion chamber of the engine, slightly higher for JME-20 and diesel fuel than that of JME-100 fuel as shown in the fig. JME-20 fuel have higher emission of Nox may be due to the more oxygen content of the fuel chemistry and better combustion quality of this fuel, as we have seen in the discussion of BSFC.

SMOKE:

The Bosch smokes data as a function of brake power for various test is reported in fig. It was found that the smoke level of the engine significantly increases with JME-100 fuel. This is mainly attributed to the poor combustion characteristics of JME-100 fuel due to its high viscosity and poor volatility. Almost all blends of JME have lower smoke level; this is may be due to the reduction of its viscosity and the combustion of additional diesel will improve the combustion quality of JME blends.

P-q DIAGRAM:

Fig. Shows the variations of cylinder pressure with respect to crank angle. The measurement of cylinder pressure has been made with the help of pressure transducer. The cylinder pressure with JME-20 test fuel depicted almost the same as that of diesel. While the percentage of JME oil increases the cylinder pressure reduce noticeably, this is may be due to the combined effect of lower combustion efficiency and heating value of JME test fuels.

CONCLUSION:

Among the various blends the blend containing up to 20% JME oil have closest brake thermal efficiency and brake specific fuel consumption to diesel fuel. Blends with higher percentage of JME oil showed low Nox emission than that of diesel.

Therefore from the engine test results, it has been concluded that JME0-20 can be substituted diesel for a CI engine with out any major operational difficulties. However, the long-term durability of the engine using biodiesel as fuel requires further study.