327 sanjay bajpeyi

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Experimental investigations of an IC Engine operating with alkyl esters of Jatropha, Karanja and Castor seed oil

Sanjay Bajpai, Lalit Mohan Das

Centre for Energy Studies, Indian Institute of Technology Delhi

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Background

Need for Alternate fuels - depletion of limited fossil fuel reserves

- greater concern for Climate Change Importance in Indian context - energy security - environment protection - employment generation

Vegetable oils sources as Alternate Fuel - edible oils such as sunflower, rapeseed, soybean etc - non-edible oils such as Jatropha, Karanja, Castor etc

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Vegetable Oils as Alternate to Diesel Fuels

Straight Vegetable Oils (SVOs) derived from oilseeds are promising alternatives to diesel fuel and have proven to be advantageous for certain application in specific engines. However, High viscosity and low volatility are major hindrances for utilising Straight Vegetable Oil as fuel for wider applications.

Lower blends of SVOs could compensate for reduced lubricity due to desulphurisation of diesel as an additive.

For higher blends, options are available to improve fuel properties of SVOs for utilisation in CI engines.

Transesterification converts glycerides into an alkyl ester where alcohol replaces the glycerine reducing molecular weight and viscosity while increasing cetane number.

Properties of alkyl esters (Bio-diesel) produced by transesterification close to diesel.

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Biodiesel as diesel substitute

Advantages Renewable Local feedstock Low toxicity Superior flash point Biodegradable Negligible sulfur content Lower exhaust emissions

Limitations Higher feedstock cost Inferior storage &

oxidation stability Lower volumetric energy

content Inferior cold temperature

operability Higher NOx emissions

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Objectives

Application of environmentally benign renewable higher alcohols for alcoholysis of oils derived from non edible feedstocks to produce higher alkyl esters

Characterisation of fuel relevant properties of higher alkyl esters

Assessment of suitability of higher alkyl esters as fuels through

measurement of performance and emission characteristics

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Selection of Test Fuel Components

Feedstocks Karanja - High yield, high oil content, grows in all soils except

dry, wide range of rainfall Jatropha - High yield, grows in wasteland, high oil content,

withstands high temperature and low rainfall Castor - higher lubricity due to unique type of hydroxylated

fatty acid, so high density and viscosity, amenable to chemical processes, large domestic produce

Alcohols (Carbon Chain length, Degree of unsaturation and Branching of Chain affect structure of fatty esters)Methyl Alcohol - low cost, widely used , high yieldEthyl Alcohol - standardised process for deriving biogenically

Propyl Alcohol - superior cold flow properties Butyl Alcohol - can be totally bio-based

Fuels selected Blends of alkyl esters in various proportions with diesel

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Test Fuels

Karanja Oil Methyl Ester (KOME), Karanja Oil Ethyl Ester (KOEE), Karanja Oil Propyl Ester (KOPE), Karanja Oil Butyl Ester (KOBE)

Jatropha Oil Methyl Ester (JOME), Jatropha Oil Ethyl Ester (JOEE), Jatropha Oil Propyl Ester (JOPE), Jatropha Oil Butyl Ester (JOBE)

Castor Oil Methyl Ester (COME), Castor Oil Ethyl Ester (COEE), Castor Oil Propyl Ester (COPE), Castor Oil Butyl Ester (COBE)

Blends of Alkyl Esters with Diesel (20%, 40%, 60% & 80% )

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Methodology

1. Preparation and characterisation of Straight Vegetable Oils

2. Optimize various parameters for the production of alkyl esters from non-edible Jatropha, Karanja and Castor oil in two stage process: Acid Treatment followed by Base Catalysed Transesterification

3. Formulation of alkyl ester-diesel blends for use as test fuels4. Determine fuel properties like calorific value, relative density,

kinematic viscosity, flash point, fire point, cloud point , pour point etc of various alkyl esters and their blends with diesel

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Methodology

6. Set up an experimental test rig with necessary instrumentation for carrying out the performance and emission tests with alkyl esters- diesel blends.

7. Experiments at constant speed with different brake load conditions on experimental test rig with alkyl esters- diesel blends.

8. Collect, collate, analyse and compare the performance and exhaust emission data obtained from the above experimentation for various test fuels

9. Infer the results to determine technical feasibilty of selected test fuels for utilisation in CI engines

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Fuel Characterisation

Properties of Straight Vegetable Oils

Oil Properties Jatropha (Jatropha curcas)

Karanja (Pongamia pinnata)

Castor (Ricinus communis)

Fatty acid composition (%)I)Palmitic acid C16:0

II)Stearic acid C18:0

III)Oleic acid C18:1

IV)Linoleic acid C18:2

V)Linolenic acid C18:3

VI)Ricinoleic acid C18:3

17.11 7.1746.3531.72 0.78-

12.36 8.2150.9215.45 2.86-

0.9 0.8 3.6 3.82 0.889.13

Specific gravity 0.922 0.938 0.955

K. Viscosity (cSt) at 40oC 35.60 28.31 98.16

Flash point (oC) 172 208 237

Calorific value (MJ/kg) 39.211 35.674 36.116

Acid value (mg KOH/gm) 13.44 16.34 21.37

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Inferences from fuel properties of SVOs

High percentage of oleic and linoleic acids is likely to impart better low temperature properties and stability to Jatropha oil compared to Karanja and Castor

Higher viscosity and polyunsaturated character of all three vegetable oils may affect injection process. Lower specific gravity and kinematic viscosity of jatropha oil closer to diesel imparts it better fuel properties.

Higher FFA content in castor oil may lead to higher carbon residues and deposits

Presence of oxygen reduces calorific value with Jatopha oil being closest to diesel

All three oils safe to use as flash and fire points are higher

Cloud and pour point of all test fuels less, so less suitable in cold conditions ( e.g. Cloud point of diesel 6.5ºC, Karanja 13.2ºC Pour point 3.1ºC Karanja 6.4ºC).

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Production of Alkyl Esters

Heating mantle Reaction flask (2 Ltr) Mechanical Stirrer

Process Parameters Reaction Temperature Reaction Duration Catalyst Concentration Oil Alcohol Molar Ratio Stirring Speed

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Optimisation of yield of Alkyl esters

Higher Esters required- more amount of alcohol

- higher catalyst quantity- longer reaction duration

- higher reaction temperature For same feedstock, yield of lower esters was higher than

corresponding higher esters Yield of Jatropha esters was highest followed by Karanja

and then Castor

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Effect of blending on Density of Jatropha derived Alkyl Ester- Diesel blends

760

780

800

820

840

860

880

900

Den

sity

(K

g/ m

3)

Effect of blending on Density of Jatropha derived Alkyl -Esters- Diesel blends Effect of blending on Density of Jatropha derived Alkyl -Esters- Diesel blends

Characteristics of Test Fuels -Density

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Characteristics of Test Fuels - ViscosityComparison of Viscosity of Diesel and 100% Alkyl Esters derived from Jatropha, Karanja and Castor

0

1

2

3

4

5

6

Diesel JOME JOEE JOPE JOBE KOME KOEE KOPE KOBE COME COEE COPE COBE

Visc

osity

(cSt

)

Comparison of Viscosity of Diesel and 100% Alkyl Esters derived from Jatropha, Karanja and Castor Comparison of Viscosity of Diesel and 100% Alkyl Esters derived from Jatropha, Karanja and Castor

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Characteristics of Test Fuels - Carbon Residue

Carbon Residue of various Alkyl Esters Carbon Residue of various Alkyl Esters

Carbon Residue of various Alkyl Esters

0

0.01

0.02

0.03

0.04

0.05

0.06

Methyl Ester Ethyl Ester Propyl Ester Butyl EsterAlkyl Esters

Car

bo

n R

esid

ue

(% m

ass)

Jatropha Karanja Castor

BIS Limit

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Characteristics of Test Fuels- Oxidation Stability

Oxidation Stability of Alkyl Esters derived from Jatropha, Karanja and Castor Oxidation Stability of Alkyl Esters derived from Jatropha, Karanja and Castor

Oxidation Stability of Alkyl Esters derived from Jatropha, Karanja and Castor

5

5.5

6

6.5

7

7.5

8

8.5

9

9.5

JOME JOEE JOPE JOBE KOME KOEE KOPE KOBE COME COEE COPE COBE

Indu

ctio

n Pe

riod

(hrs

)

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Fuel CharacterisationInferences from Fuel Properties of Alkyl Esters

Density, viscosity, flash point, sulphur content, carbon residue, sulphated ash, water content , cetane number, acid value, alcohol content, ester content, total glycerol, free glycerol and phosphorous content of all blends of all feedstocks conform to IS:15607 .

Oxidation stability is relatively low for higher alkyl esters. The choice of feedstock does not made much difference.

Density of all alkyl esters blends higher than diesel. Density of higher alkyl esters higher for the same blend percentage. Jatropha blends have lowest density followed by corresponding blends of Karanja and then Castor.

Calorific value of all alkyl esters and their blends lower than neat diesel. The gap widened for higher blends. Jatropha derived alkyl esters blends possess higher calorific value compared to corresponding Karanja and Castor derived alkyl esters blends. Higher alkyl esters had relatively lesser calorific values.

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Inferences from Fuel Properties of Alkyl Esters

Transesterification process improves the fuel properties of the oil with respect to density, calorific value, viscosity, flash point, cloud point and pour point.

Lower alkyl esters of Jatropha in lower blends has closest distillation temperature, oxidation stability, calorific value and density characteristics to diesel compared to any other blend of Jatropha or any feedstock followed by lower blends of Karanja.

Jatropha oil derived esters have lowest cloud point followed by Karanja and then Castor. Higher alkyl esters of Jatropha and Karanja have similar low temperature operability as lower alkyl esters. Castor derived alkyl esters may not give similar cold operability.

Higher alkyl esters of Jatropha up to relatively higher blends and karanja at relatively lesser blends with diesel are likely to give comparable performance to methyl esters.

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Engine Selection

Direct Injection - Stationary Application- Mixture Formation

Widely used for - Agriculture application - Decentralised Energy generation

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No. of cylinders One

Bore x Stroke 80 x 110 mm

Cubic Capacity 0.553 lit

Compression Ratio 16.5 : 1

Rated Output as per BS5514/ISO 3046/IS 10001 3.7 kW(5.0 hp) at 1500 rpm.

SFC at rated hp/1500 rpm 245 g/kWh(180 g/bhp-hr)

Lub Oil Consumption 1.0 % of SFC max.

Lub Oil Sump Capacity 3.3 lit.

Fuel Tank Capacity 6.5 lit

Fuel Tank re-filling time period Every 6 hours engine running at rated output

Engine Weight(dry) w/o flywheel 114 kg

Weight of flywheel 33kg – Standard

Rotation while looking at the flywheel Clockwise. Optional – Anticlockwise

Power Take-off Flywheel end. Optional-Gear end half or full speed

Starting Hand start with cranking handle.

Engine Specifications Model: AV1 (Kirloskar Make)

Engine Specifications Model: AV1 (Kirloskar Make)

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AMPLIFIER

JUNCTION

BOX

AIR SURGE TANK

PRESSURE TRANSDUCER

GAS ANALYSER & SMOKE METER

SILENCER

EGT AMPLIFIER

WATER OUT

MAGNETIC PICK UP

WATER OUTLET TEMPERATURE

ENGINE EDDY CURRENT DYNAMOMETER

WATER FLOW TANK

WATER INLET TEMPRATURE

FUEL TANK

PHOTOCELL FUEL METER

COMPUTER

LOAD CONTROLLER

CHARGE AMPLIFIER

Schematic diagram of test set up for DI diesel engine Schematic diagram of test set up for DI diesel engine

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Engine

Eddy Current Dynamometer

Load controller

Parameters measured by Experimental Setup

Coolant water inlet temperature

Coolant water engine outlet temperature

Exhaust Gas Temperature

Engine Speed

Engine Load

Crank Movement

Fuel consumption

Air Mass Flow

D A T

A

A C Q U I S I T I O N

SYSTEM

COMPUTER

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Test Matrix for Short Term Engine Performance and Emissions

Sl.No. Variables Types of variables studied Details of variables studied

1 Independent 1. Fuels used Jatropha, Karanja, Castor methyl, ethyl, propyl, butyl esters and their blends with Diesel

Diesel 100% neat

Alkyl Ester– Diesel blends (v/v), % 20%,40%,60%,80% and 100% blends of methyl, ethyl, propyl and butyl esters of Jatropha, Karanja and Castor

2. Load 0% , 20%, 40%, 60%, 80%, 100%

2 Dependent 1. Brake Specific Fuel Consumption (BSFC) At 0% , 20%, 40%, 60%, 80%, 100% load

2. Brake Thermal Efficiency (BTE) At 0% , 20%, 40%, 60%, 80%, 100% load

3. Exhaust Gas Temperature At 0% , 20%, 40%, 60%, 80%, 100% load

4. Engine Exhaust Emissions Carbon monoxide (CO), Hydrocarbon (HC), Nitrogen oxides (NOx), Smoke ( Opacity %)

At 0% , 20%, 40%, 60%, 80%, 100% load

25BSFC comparisons of 20% and 100% Alkyl Esters at full load BSFC comparisons of 20% and 100% Alkyl Esters at full load

BSFC comparison of 20% and 100% Alkyl Esters at full load

0

0.05

0.1

0.15

0.2

0.25

0.3

Blends

BS

FC

(kg

/ kW

h)

Results of Engine Performance

Brake Specific Fuel Consumption (BSFC)

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Brake Specific Fuel Consumption (BSFC)

All alkyl esters derived from all the three feedstocks and their blends demonstrated higher BSFC than diesel. This is due to lower calorific value of alkyl ester blends

Karanja derived alkyl esters showed lower BSFC compared to Jatropha and Castor. However difference was marginal which shows limited effect of feedstock.

BSFC difference between diesel and blends was larger for part loads and the gap narrowed with increasing loads.

For all three feedstocks, methyl esters demonstrated lowest BSFC followed by ethyl esters, propyl esters and butyl esters. The deviation from diesel BSFC was least for 20% blends and increased with blend percentage. This implies that structural features of the alcohol moiety that comprise fatty esters affect BSFC.

27BTE of Diesel and Jatropha Alkyl Ester blends at full load BTE of Diesel and Jatropha Alkyl Ester blends at full load

BTE of Diesel and Jatropha Alkyl Ester blends at full load

36.5

36.7

36.9

37.1

37.3

37.5

37.7

37.9

38.1

38.3

Jatropha 20 Jatropha 40 Jatropha 60 Jatropha 80 Jatropha 100

BTE

(%

)

Methyl Ester Ethyl Ester Propyl Ester Butyl Ester

Diesel


Brake Thermal Efficiency (BTE)

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BTE of Diesel and Karanja Alkyl Ester blends at full load BTE of Diesel and Karanja Alkyl Ester blends at full load

BTE of Diesel and Karanja Alkyl Ester blends at full load

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36.5

37

37.5

38

38.5

Blends

BTE

(%)

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BTE of Diesel and Castor Alkyl Ester blends at full load BTE of Diesel and Castor Alkyl Ester blends at full load

BTE of Diesel and Castor Alkyl Ester blends at full load

35

35.5

36

36.5

37

37.5

38

38.5

Blends

BTE

(%)

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Jatropha derived ethyl and methyl esters showed higher BTE than corresponding blends of Karanja and Castor, which could be attributed to better fatty acid characteristics of Jatropha.

BTE is generally higher for higher blends, higher loads and higher alkyl esters.

Engine operating on Castor oil based propyl and butyl esters demonstrated marginally higher BTE than Karanja and Jatropha. This could be due to prominent effect of enhanced lubricity of higher alkyl esters.

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Inferences from Performance Studies The brake thermal efficiency (BTE) improves when diesel engine is fueled with

diesel-biodiesel blends of Jatropha and Karanja. Higher alkyl esters blends demonstrate higher thermal efficiency.

Brake specific fuel consumption (BSFC) of all selected diesel-biodiesel fuel blends is more than diesel. BSFC amongst corresponding blends is least for Karanja followed by Jatropha alkyl esters. BSFC increases with the increase of alkyl ester percentage in blends for all blends .

Lower blends of Jatropha derived methyl and ethyl esters or Karanja derived propyl and butyl esters offer a trade-off between BSFC and BTE.

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Results of Engine Emissions

Carbon monoxide (CO)

The CO emissions for all alkyl ester blends are higher than diesel due to unfavourable properties offsetting above advantages.

CO emissions decrease for diesel and all test fuels with increase in load up to 80%. At full load CO emissions are higher than 80% load but lower than all other loads.

CO emissions for Jatropha, Karanja and Castor derived alkyl esters and blends fall within a narrow range showing very limited effect of source of alkyl esters. However, the emissions are much higher for higher alkyl esters showing effect of alcohol used.

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Oxides of Nitrogen (NOx)

NOx emissions decrease with increase in load and are least at 100% due to supply of more fuel at larger load and relatively less time for preparation of mixture leading to less temperature rise.

The NOx emissions are higher for higher alkyl esters and higher than diesel for all alkyl ester blends. This implies that NOx emissions are affected by alcohol used.

Jatropha derived alkyl esters emit lesser NOx compared to Karanja and Castor. This implies that NOx emissions are affected by feedstock.

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Hydrocarbons

Methyl esters of Jatropha up to 80% blend and Karanja up to 40% give lesser HC emissions than diesel at all loads. Emissions for all castor esters are higher than diesel.

20% blends of ethyl, propyl and butyl esters give lesser emissions than diesel for 60% and above loads, HC emissions relative to diesel increase at lower loads. This is due to fuller combustion at higher loads and dominant role of higher oxygen content.

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Smoke

Methyl esters of Jatropha up to 60%, ethyl esters up to 40% and butyl and propyl esters up to 20% blends give emissions comparable to diesel at all loads, though difference in emissions relative to diesel increase at higher loads.

The smoke emission increased with biodiesel addition to diesel fuel.

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Inferences from Emission Results

Smoke, HC, CO and NOx emissions were least for 20% blend of lower alkyl esters derived from Jatropha followed by Karanja.

While smoke and HC emissions were lesser, CO was marginally and NOx was significantly higher than diesel for 20% blends of alkyl esters. NOx and CO emissions of 20% Jatropha oil methyl esters were closest to diesel.

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Conclusions Ethyl, propyl and butyl esters of Jatropha and Karanja feedstock have

physicochemical properties similar to methyl esters and engine performance, emission and combustion characteristics were inferior to methyl esters while operating on these blends.

To get engine performance in close range of diesel, the blending ratio of higher alkyl esters need to be further reduced below 20%. Lower blends of higher alkyl esters are expected to give better engine characteristics in close proximity to diesel overcoming the limitations of bio-diesel, while retaining the advantages.

20% Jatropha oil methyl esters is optimum blends as per this study. It is also extrapolated that 5% to 20 % blends of Jatropha or Karanja alkyl esters have the potential for consideration as viable alternate fuels to existing options.

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Conclusions Methyl alcohol proved to be a preferred alcohol for conventional

transesterification ; ethyl, propyl and butyl alcohol can also be used for producing alkyl esters following conventional process and may have certain advantages while using newer process such as enzymatic and ultrasonic transesterification.

Jatropha emerged as preferred feedstock closely followed by Karanja for producing alkyl esters. The advantages of using Castor feedstock could not be established.

A trade off between blending proportion and engine performance, emission and combustion is required to be arrived for utilisation of higher alkyl esters in CI engines. The blending proportion of higher alkyl esters should be much less than methyl esters to obtain comparable performance and emission characteristics.

327 sanjay bajpeyi

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