Performance Characteristics of Diesel Engine Using Biodiesel Blends

Abstract

Diesel vehicles are similar to gasoline vehicles because they both use internal combustion engines. One difference is that diesel engines have a compression-ignited injection system rather than the spark-ignited system used by most gasoline vehicles. In recent years, the acceptance of fatty acid methyl esters (biodiesel) as a substitute to petroleum diesel has rapidly grown in India. The raw materials for biodiesel production in this country mainly include traditional seed oils and used frying oils. In the search for new low-cost alternative feed stocks for biodiesel production, this study emphasizes the evaluation of lemon grassoil. The experimental results showed that the oil content of Lemon grass were remarkably high (45%). The main emphasis has been laid on optimum production of biodiesel from Lemongrass Oil then using the biodiesel blends with diesel studying the comparative characteristics and engine performance and the blends made from the biodiesel with diesel. The oil was chemically converted via an alkaline transesterification reaction with methanol to methyl esters, with a yield nearly 97.5 wt.%. All of the measured properties of the produced biodiesel met the current quality requirements. Oils were esterifying (butyl esters) before blending with pure diesel in the ratio of 4:96, 8:92, 12:80 by volume. Pure diesel was used as control. Initially the properties of the lemongrass Oil blends were determined density, viscosity, dynamic viscosity, flashes point, fire point and calorific value. An assessment of engine performance brake power (BP), brake specific fuel consumption (BSFC), brake thermal efficiency (BTE) etc., was carried out for pure diesel and the oil blends. However, lemongrass oil at 12% blend with diesel gave best performance as compared to other blends

Introduction

I. INTRODUCTION

Diesel engines work by compressing only air, or air plus residual combustion gases from the exhaust (known as exhaust gas recirculation, ?EGR?). Air is inducted into the chamber during the intake stroke, and compressed during the compression stroke. This increases the air temperature inside the cylinder so that atomised diesel fuel injected into the combustion chamber ignites. With the fuel being injected into the air just before combustion, the dispersion of the fuel is uneven; this is called a heterogeneous air-fuel mixture. The torque a diesel engine produces is controlled by manipulating the air-fuel ratio (λ); instead of throttling the intake air, the diesel engine relies on altering the amount of fuel that is injected, and the air-fuel ratio is usually high. The diesel engine has the highest thermal efficiency (engine efficiency) of any practical internal or external combustion engine due to its very high expansion ratio and inherent lean burn which enables heat dissipation by the excess air. A small efficiency loss is also avoided compared with non-direct-injection gasoline engines since unburned fuel is not present during valve overlap and therefore no fuel goes directly from the intake/injection to the exhaust. Low-speed diesel engines (as used in ships and other applications where overall engine weight is relatively unimportant) can reach effective efficiencies of up to 55%.The combined cycle gas turbine (Brayton and Rankin cycle) is a combustion engine that is more efficient than a diesel engine, but it is, due to its mass and dimensions, unsuited for vehicles, watercraft, or aircraft. The world‘s largest diesel engines put in service are 14-cylinder, two-stroke marine diesel engines; they produce a peak power of almost 100 MW each.

Diesel engines may be designed with either two-stroke or four-stroke combustion cycles. They were originally used as a more efficient replacement for stationary steam engines. Since the 1910s, they have been used in submarines and ships. Use in locomotives, buses, trucks, heavy equipment, agricultural equipment and electricity generation plants followed later. In the 1930s, they slowly began to be used in a few automobiles. Since the 1970s energy crisis, demand for higher fuel efficiency has resulted in most major automakers, at some point, offering diesel-powered models, even in very small cars.

According to Konrad Reif (2012), the EU average for diesel cars at the time accounted for half of newly registered cars.However, air pollution emissions are harder to control in diesel engines than in gasoline engines, so the use of diesel auto engines in the U.S. is now largely relegated to larger on-road and off-road vehicles.

Though aviation has traditionally avoided diesel engines, aircraft diesel engines have become increasingly available in the 21st century. Since the late 1990s, for various reasons – including the diesel‘s normal advantages over gasoline engines, but also for recent issues peculiar to aviation – development and production of diesel engines for aircraft has surged, with over 5,000 such engines delivered worldwide between 2002 and 2018, particularly for light airplanes and unmanned aerial vehicles.

A. Operating Principle

The characteristics of a diesel engine are

1. Use of compression ignition, instead of an ignition apparatus such as a spark plug.
2. Internal mixture formation. In diesel engines, the mixture of air and fuel is only formed inside the combustion chamber.
3. Quality torque control. The amount of torque a diesel engine produces is not controlled by throttling the intake air (unlike a traditional spark-ignition petrol engine, where the airflow is reduced in order to regulate the torque output), instead, the volume of air entering the engine is maximised at all times, and the torque output is regulated solely by controlling the amount of injected fuel.
4. High air-fuel ratio. Diesel engines run at global air-fuel ratios significantly leaner than the stoichiometric ratio.
5. Diffusion flame: At combustion, oxygen first has to diffuse into the flame, rather than having oxygen and fuel already mixed before combustion, which would result in a premixed flame.
6. Heterogeneous air-fuel mixture: In diesel engines, there is no even dispersion of fuel and air inside the cylinder. That is because the combustion process begins at the end of the injection phase, before a homogeneous mixture of air and fuel can be formed.
7. Preference for the fuel to have a high ignition performance (Cetane number), rather than a high knocking resistance (octane rating) that is preferred for petrol engines.

II. MATERIALS AND METHODS

A. Cymbopogon Citratus Extraction

Cymbopogon citratus, commonly known as West Indian lemon grass or simply lemon grass, is a tropical plant native to Maritime Southeast Asia and introduced to many tropical regions.

Cymbopogon citratus is often sold in stem form. While it can be grown in warmer tempera regions, such as the UK, it is not hardy to frost.

Lemongrass is native aromatic tall sedge which grows in many parts of tropical and sub-tropical South East Asia and Africa. In India, it is cultivated along Maharashtra,  Kerala, Karnataka and Tamil Nadu states besides foothills of Arunachal Pradesh and Sikkim. It was introduced in India about a century back and   is   now   commercially   cultivated   in   these   mentioned   States.   What   is lemongrass oil good for? Lemongrass has been used to treat digestive problems and high blood pressure, the essential oil has many other  potential  health benefits   and,  it‘s  becoming  popular  oil  in  aromatherapy  to  help  relieve  stress, anxiety, and depression.

Lemongrass  is  a  tropical  and  sub-tropical,  grassy  plant  used  in cooking and herbal medicine. Extracted  oil from  the  lemon  leaves and  stalks of the lemongrass plant, lemongrass essential oil has a powerful, citrus scent. It does often establish in soaps and other personal care products.

B. Cultivating and Harvesting Lemongrass Oil

Lemongrass is native to the tropical countries of India, Cambodia, Indonesia,   Guatemala,   Sri  Lanka,   and   Malaysia.   It   grows   upright  in   dense bunches and thrives in moist, warm climates with well-drained, loose, dry, loam soils that have a pH level between 4.3 and 8.4. Lemongrass leaves are a green color with sharp edges much like grass that grows onlawns but much larger. It requires full sun and a soil temperature that is between 21°C and 24°C (70°F to 75°F).

Lemongrass requires adequate water drainage requirement, as disproportionate watering will lead to lower oil content. Lemongrass flowers grow in the winter season.  The first harvest is normally obtained after 4 to 6 months of transplanting seedlings. Subsequent harvests are done at intervals of 60 to 70 days depending upon the fertility of the soil and other seasonal factors. Under normal conditions, three harvests are possible through the first year, and 3 to 4 in subsequent years, depending on the management practices followed. Lemongrass can be harvested 6-9 months after the slips are planted and can be harvested as frequently as once every month through the growing season. Cutting stimulates growth and allowing the plant to develop too large will lead to a reduced oil yield. The lemongrass is harvested in the morning on a dry day to allow the evaporation of dew and to avoid loss of the plant‘s color due to heat. When harvested mechanically, sharp tools and machinery are used in order to make sure a clean cut and to avoid splitting the edges of the leaves. If the plant is cut too low, the lemongrass leaves will retain less oil, thus the optimal oil quality is in the higher parts of the leaves. Allowing the plants to mature until before the winter months will make sure that the root reserves are fortified and that the foliage will protect the  plant   against   winter   frost.   After   winter, Lemongrass can be used for compost or mulch or it may be harvested and distilled.  Ideally,  Lemongrass  leaves  will  keep  their  green  color  and  be  free  of fungi.  In  organize  to  ensure  this,  Lemongrass  leaves  must  be  dried  as  soon  as possible  within  24  hours  and  a  conventional dryer may be used for this. An extended drying period, such as in the case of it being left out in the sun to dry, will cause the leaves to lose color and the aroma value to diminish. Once harvested, leaves can be stored in shade for up to 3 days without  the oil yield or quality being compromised. Harvesting is completed with the help of sickles; the lemongrass plants are cut 10 cm above ground-level and allowed to wilt in the field, before transporting  to  the  distillation  site.  The  Lemongrass  is  then  steam  or  hydro distilled.

1. Post-harvest Management Drying

The lemongrass has been allowed to wilt for 24 hours before the distillation as it reduces the moisture content by 30% and improves oil yield. The lemon  crop  is  chopped  into  small  pieces  before  filling  in  the  stills.  It  can  be distilled in similar distilleries as used for Japanese mint in India.

a. Plant Samples

Lemongrass (Cymbopogon Citratus) leaves were collected from plants. The lemongrass plant sample was freshly cut, 10cm from the root, in the morning of the day they were collected. Lemongrass, the percentage essential oil yield for the partially dried leaves was established to be higher than that of the fresh   leaves.   Thus,   once   collected,   the   plant   material   was   dried   at   room temperature for a maximum four days, then kept in a sealed plastic bag  at ambient temperature and protected from the light. Extraction yield increase by decreasing the particle size due to the higher amount of lemongrass oil released as the leave cells are destroyed by milling. In order to develop the collection efficiency, the plant material was soaked in its distilled water for 30min before the extraction performed. N-hexane was used as analytical grade reagent in this process.

2. Lemongrass oil Extraction Techniques How is Lemongrass oil Extracted?

Lemongrass Essential Oil is derived from the steam distillation  of the fresh or partly dried leaves. After distillation, the oil ranges in color from a yellow color to amber color and exudes a fresh, sweet, grassy and citrus-like aroma.

Lemongrass oil is collected by distillation unit of the herbage for 1.5 to 2 hrs. The distillate on cooling separates out into a layer of oil, floating over the bulk of  water  which  is  composed  by  decantation.  The  lemongrass  is  distilled  either fresh or after wilting.

a. Distillation

Lemongrass oil is obtained through steam distillation. Lemongrass oil has a strong lemon-like odor. The oil is yellowish in color having 75 to 85% citral and a small amount of other minor aroma compounds. The recovery of oil from the grass ranges from 0.5 to 0.8  percent.  It takes about four hours for the complete recovery of the oil.

b. Solvent Extraction Method

150g of the dry sample of lemongrass were weighed from the sliced lemongrass sample and placed in a one-liter clean at bottom ask. After that, 500ml of N-hexane solvent was poured into the ask.

The bottom asks and content were allowed to stand for 36 hrs; this was made to extract all the oil content in the lemongrass and  for complete  extraction. After which the extract was decanted into another one-liter beaker. 200ml of Ethanol was added to extract the essential oil since lemongrass essential oil is soluble in Ethanol. The mixture was then transferred to a 500ml separating funnel and separated by a procedure called liquid separation process. The content of the separating funnel was and allowed to approach to equilibrium, which separated into 2 layers (depending on their different density).

The lower Ethanol extract and the upper Hexane layer were collected into 2 separate 250ml beakers and were placed in a water bath at 78oC. This was done to remove the Ethanol leaving the natural essential oil. The yield of lemongrass oil was determined by weighing the extract on an electronic weighing balance. The variation between the nal weight of the beaker with extract and the initial weight of the empty beaker gave the weight of essential oil.

3. Raw Materials Required

The main raw material is lemongrass. And the grass plants grow well in soils  not  proper  for  richer  production  plants. From  sandy  and  rather  dry  soils yield moderately more oil and oil of higher citral content than plants from very fertile soils. A lemongrass plantation has a life cycle of 6 – 8 years.  The oil yield reaches its maximum around the third year or fourth year and  its annual average value range between 15 and 20 kg/ha with three crops per year. The ratio of lemongrass oil to leaves is equal to 0.348%. 

Therefore,  you will need  to obtain about 288 kg of lemongrass to produce 1 kg of essential lemongrass oil. Depending upon soil and climatic conditions, plantation lasts on  an average, for three to four years only. The yield of lemongrass oil is less during the rst year, but it increases in the second year and reaches a maximum in the third year; after  this,  the  yield  declines.  On  average,  25  tonnes  to  30  tonnes  of  fresh herbage  harvest per hectare  per  annum  from four to six cuttings,  which  yields about  80  kg  of  oil.  Under  irrigated  conditions  from  newly  bred  varieties,  a lemongrass  oil  yield  of  100  to  150  kg/ha  is  obtained.  The  clean  and  fresh  herb contains on average 0.3% oil and thick stems are removed before distillation as these are devoid of oil.

4. Formulation of oil

Lemongrass  essential  oil  10ml  extract  was  measured  and  placed  in  a 120ml beaker containing 5ml of Methanol. Fixatives of 5ml quantity were added to the mixture to improve  the  longevity  of the  perfume.  The  resulting  solution was shaken and poured into a 50ml bottle.

The yield of essential oil formula that obtained was calculated by:

The yield of the essential oil = amount of essential oil (in grams) obtained / amount of raw materials (in grams) used

5. Cost of Lemongrass oil distillation unit

• Steam distillation unit cost approximately– Rs 8 Lakh/ Piece
• Lemongrass oil price approximately Rs.600/ pper kg.

6. Purification of oil

The insoluble particles present in the lemongrass oil are removed by a simple filtration process after mixing it with anhydrous sodium sulfate and keeping it overnight or for 4 to 5 hours. In case the color of the lemongrass oil changes due to rusting then it should be cleaned by steam rectification process.

7. Storage and Packing of Oil

The lemongrass oil can be stored in containers made up of stainless steel or aluminum or galvanized iron, depending upon the quantity of oil to be stored. The oil must be Pulled up to the brim and the containers should be kept away from direct heat and sunlight in cool or shaded places.

C. Transesterification

Transesterification is the process of conversion of triglyceride to glycerol and ester in the presence of alcohol and catalyst. This reaction, also known as alcoholics in whom the displacement of alcohol from an ester by another alcohol in a process similar to hydrolysis except that an alcohol is used instead of water. This reaction has been widely used to reduce the viscosity of the triglycerides.

Experimental study shows that the major variables affecting the transesterification reaction are: The free fatty acid (FFA) and the moisture content. The rate of reaction is strongly influenced by the reaction temperature i.e. (50±2) º C approximate. Then with the help of washing remove the catalyst, soap and excess methanol from bio diese

In our work we have been use the Dr.Peepersstyle, for the transesterification of Celosia oil. According to Dr.Peepersstyle, first of all, take a 250 ml methanol CH3OH (90% pure) in the glass container then mixed 150 ml NaOH of 1 Normality and swirl the container until methanol is completely dissolved in NaOH.

When NaOH reacts with methanol CH3OH an exothermic reaction is take place due to which the glass containers get warm so it is very carefully done to swirl the mixture, safety precautions.

The biodiesel was produced in the School of Energy and Environment labs at Thapar University Patiala, Punjab (India) and the engine experiments and testing was done in internal Combustion Engine Laboratory, Department of Mechanical Engineering, Thapar University, Patiala, Punjab (India). Further the methodology is divided in to two parts:First part shows the optimum production of biodiesel from non-edible oil i.e. lemon grass oil.Second part shows the emission and performance of the biodiesel blends tested on an engine.

1. Methodology For The Production Of Biodiesel From Lemon Grass Oil

Here in this from starting the raw materials used for biodiesel production is discussed and after it with each step with which the whole production process was undergone.   The   biodiesel    properties    are    also    discussed    in    this    section.

Raw materials

a. Lemon grass oil

b. Methanol (methyl alcohol)

c. Potassium hydroxide (KOH) as base catalyst

d. Sulphuric acid (H2SO4) as acid catalyst

Dewaxed and degummed crude lemon grass oil was bought from the local general store. The Methanol (methyl alcohol), Potassium hydroxide (KOH), Sulphur acid (H2SO4) were available in the chemistry laboratories, kings college of engineering punalkulam .The transesterification was then carried out in the labs on a hot plate magnetic stirrer.

D. Biodiesel Preparation

As the crude lemon grass oil was used for the preparation of biodiesel therefore due to high Free Fatty Acid FFA content of lemon grass oil i.e. approx. 7% the transesterification process was carried out in two stages. The first stage included an acid catalyzed transesterification reaction and in second the base catalyzed transesterification reaction was carried out.

Lemon grass Oil was procured from an oil mill. The oil was filtered to remove the impurities. Diesel fuel was used as baseline fuel. The viscosity was determined at different temperatures using redwood viscometer to find the effect of temperature on the viscosity of lemon grass oil . The viscosity of lemongrass oil was found to be 9 times higher than that of diesel fuel. The flash point of lemon grass Oil was higher than diesel and hence it is safer to store. It is seen that the boiling range of lemon grass oil was different from that of diesel. This lemon grass oil trasnsesterified before blend with diesel because of the oils have glycerol. It must extract from the bio fuel because it will affect the engine performance.

Among these, the transesterification is the most commonly used commercial process to produce clean and environmental friendly fuel. Methyl/ethyl/butyl esters of, lemon grass oil have been successfully tested on C.I. engines and their performance has been studied.\

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Conclusion

1) Lemongrass oil prepared by stem distillation method and convert to the biodiesel by trasesterification process. 2) Lemongrass oil blended with diesel in the ratio of L4,L8,L12. 3) Performance test was conducted in the 5hp diesel engine 4) Methyl ester of lemon grass oil at 12% blend with diesel at gave best performance in terms of Total fuel consumption, brake power; specific fuel consumption and brake thermal efficiency were almost equal when engine was run on pure diesel. 5) The transesterification process, used for making biodiesel, is simple and cost effective to solve viscosity problems encountered with vegetable oils. 6) Brake Thermal Efficiency of lemon grass oil 12% at load 3.17 is more compared to diesel. 7) Brake specific fuel consumption of lemon gras oil (4%&12%) at load 3.17 is less than diesel. 8) Mechanical efficiency of lemon grass oil 12% higher than diesel. 9) High calorific value of lemon grass oil was the main reason of this reduction in the specific fuel consumption. 10) The difference in density also was one of the reason for this reduction.comparison of oil blends with diesel. 11) However, lemon grass oil blends gave the best results.

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Copyright

Copyright © 2023 P. P. Santharaman, E. Priya, R. Rajadurai, M. Vivekananthan, S. Balaganesh. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.