Experimental Investigations on Combustion and Vibration Analysis of an Indirect Injection Diesel...

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Original Paper

International Journal of Informative & Futuristic Research ISSN (Online): 2347-1697

Volume 2 Issue 8 April 2015

Abstract Research on various bio-fuels has been carried out as an alternate to the fossil fuels as the

geological survey has indicated depletion of fossil fuel reserves in the near future. In the

present work, investigations were made to analyse the combustion and vibration

characteristics of an indirect injection (IDI) diesel engine fuelled with conventional diesel

fuel, Palm Methyl Ester (PME) and 1, 4-Dioxane as an additive in biodiesel at different

percentages viz. 1%, 2%, 3% and 4% on volume fraction basis. The net and cumulative

heat release rates were calculated on the basis of first law of thermodynamics using

pressure-crank angle data, cylinder volume model and process coefficient which varies

with the temperature in the combustion chamber. Three strategic points are considered to

measure the engine vibration and analysed to obtain information about the nature of

combustion since the combustion itself is basic exciter. The vibration studies reveal the

combustion propensity with different fuel samples. Time signal plots are recorded on the

engine cylinder head in vertical direction of the piston movement to analyse knocking

aspect with the fuels tested. Quantum burning is observed in the case of 3 percent additive

in biodiesel with more harmonics in the main chamber as per the time waves.

Experimental Investigations on Combustion

and Vibration Analysis of an Indirect Injection

Diesel Engine Fuelled With Palm Methyl Ester

(PME) and 1, 4-Dioxane as an Additive Paper ID IJIFR/ V2/ E8/ 083 Page No. 2770-2780 Research Area

Mechanical

Engineering

Key Words Bio Diesel, Combustion, First Law Of Thermodynamics, IDI Engine, Palm

Methyl Ester (PME), Vibration, 1,4-Dioxane Additive

S C V Ramana Murty Naidu 1 Professor, Department Of Mechanical Engineering Kallam Haranadhareddy Institute of Technology Guntur- Andhra Pradesh, India

B V Appa Rao 2 Professor, Department of Marine Engineering Andhra University College of Engineering (A) Visakhapatnam- Andhra Pradesh ,India

Aditya Kolakoti 3 Research Scholar, Department of Marine Engineering Andhra University College of Engineering(A) Visakhapatnam- Andhra Pradesh ,India

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ISSN (Online): 2347-1697 International Journal of Informative & Futuristic Research (IJIFR)

Volume - 2, Issue - 8, April 2015 20th Edition, Page No: 2770- 2779

S C V Ramana Murty Naidu, B V Appa Rao, Aditya Kolakoti:: Experimental Investigations on Combustion and Vibration Analysis of an Indirect

Injection Diesel Engine Fuelled With Palm Methyl Ester (PME) and 1, 4-Dioxane as an Additive

1. Introduction Fast depletion of fossil fuel, increasing of pollution to peak levels and to follow stringent rules in

controlling emissions made to shift over to alternate, renewable, pollution free fuels. Oxides of

Nitrogen and CO are the two important harmful emissions in C.I. engines. Fuel companies and

researchers are devoted to reduce such emissions. In this context, engine researchers are striving for

suitable renewable alternate fuels for diesel engine. Biodiesel is an oxygenated fuel derived from

vegetable oil. an increase in maximum cylinder pressure and premixed combustion rate with

advanced fuel injection timings for all fuel samples. From the combustion characteristics of the

test fuels, it was clear that ignition delay, total combustion duration and maximum pressure rise

rate increased with advanced fuel delivery timing. Increasing the amount of methanol or ethanol

in the fuel blends caused to increase in ignition delay and to decrease in total combustion duration at

all injection timings[1]. The effects of antioxidants on the oxidation stability of biodiesel are

investigated on an indirect-injection (IDI) diesel engine and examined the combustion

characteristics, performance and exhaust gas emissions using soybean oil biodiesel[2]. Effects of

engine speed, engine output, injection timing ,engine compression ratio on the engine output torque,

combustion noise, maximum pressure and maximum heat release rate have been studied in an

indirect injection diesel engine fuelled with the algae biodiesel. The inferences are the physical and

chemical properties of the micro algae oil methyl ester are similar to both the biodiesel and diesel

fuel. The algae oil biodiesel exhibited more combustion noise compared to the diesel fuel or raw

algae oil. The biodiesel produced less engine torque output than the diesel fuel and raw algae oil.

The biodiesel produced slightly higher heat release rate compared to diesel fuel[3]. The effect of

diesel/methanol blend on combustion characteristics and heat release rate analysis were studied on

a diesel engine and concluded that increase in methanol quantity in the diesel/methanol blends

caused to increase in the heat release rate at the premixed burning phase and limits the combustion

duration of the diffusive burning phase[4,5]. The high pressure amplitude may indicate early

ignition or presence of a more amount of fuel in the cylinder prior to ignition. The lower amplitude

may show delay in ignition, injection malfunction or engine compression malfunction[6,7]. In the

field of DI diesel engine, trails were conducted to analyze engine vibration with the introduction

of neat biodiesel and biodiesel with additives[8].Vibration diagnostics of an engine based on the

analysis of accelerometer data have earned a greater success[9]. The Injection pressure and

injected quantities over an energy release threshold really affect the vibration signals in a

typical way; injection timing effects the engine block vibrations in any way less evident

[10].10%Triacetin in coconut oil biodiesel produced lowest amplitude at knocking frequency of

6500Hz taking overall combustion temperature as20000F. Narrow changes in combustion

temperatures may vary the knocking frequencies by smallest margin around 6500Hz (which is

resonant frequency for the cylinder dimensions)[11].Investigations were done on an IDI diesel

engine operated with preheated Jatropha Methyl Ester and inferred that considerable reduction of

the vibration in the high frequency regions with the JME preheated to 600C. Biodiesel heated to

600C predict better combustion since at higher frequencies more than 10000 Hz, the amplitudes

are lower comparatively <50dB(V). There is more high frequency vibration for diesel fuel

compared with biodiesel and heated oils [12].Experimental work on IDI diesel engine fuelled with

Pongamia Methyl Ester and Isobutanol as an additive infer better combustion phenomena for 6% of

additive in biodiesel. The amount of heat release is more in the diffused combustion stage

indicating better torque conversion and load lifting capacity of the engine with the tested fuels.

Uniform amplitude modulation putting forth the information that prevalence of smoother

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combustion for the 6% of additive in biodiesel[13].Experimental studies on an IDI-Diesel Engine

with Rice Bran Methyl Ester and Isopropanol Injection concluded that, the combustion in both the

chambers are distributed uniformly in the case of 2% additive mixing because of smoother start of

combustion. Rapid combustion in the pre combustion chamber is slowed down to marginal extent

leading to less friction losses in the transit from one chamber to another and this aspect saves the

combustion energy to greater extent, thereby increasing the thermal efficiency of the engine. Higher

pressure generation in the pre combustion also increases the heat transfer from pre-chamber surface

area[14].Investigations were made on single cylinder Indirect injection (IDI) diesel engine

operated with Mahua Methyl Ester (MME) and Methanol as an additive at normal room

temperatures and concluded that 3% additive in bio-diesel led to smoother performance in

combustion pressure development. The net heat release rate and cumulative heat release rates are

better. The maximum relief of exhaust gas temperature for 3% additive indicates the ensued

combustion is low temperature combustion in which methanol has burned at later stages

because of lower cetane number[15].Experimental results shown that flame additives are used to

improve combustion efficiency, to increase cetane number, to reduce formation of carbon deposits,

to avoid oxidation reactions[16].

2. Experimental Set up

The experimental test rig as shown in figure.1 consists of the following equipments:

I. Single cylinder IDI diesel engine loaded with eddy current dynamometer

II. Engine Data Logger(M/S. APEX Innovations Ltd, India)

III. Exhaust Gas Analyzer (AVL DI TEST)

IV. Smoke Analyzer (Diesel Tune 114) and

V. Vibration Analyser

Figure1: Experimental test rig set up

Table 1: Specifications of the engine test rig

Engine manufacturer Bajaj RE Diesel Engine

Engine type Four Stroke, Forced air and Oil Cooled

No. Cylinders One

Bore 86.00mm

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The line diagram of experimental setup is shown in Figure.2

Figure 2: Schematic arrangements of engine test bed, instrumentation and data logging system.

3. Experimental Procedure

The present work deals with the study of engine combustion and vibration characteristics of variable

speed IDI engine with the new fuel replacement. The experimentation is conducted on the single

cylinder indirect injection (IDI) diesel engine which is operated at normal room temperatures of

280C to 330C.The fuels used are Diesel fuel in neat condition and as well as Palm Methyl Ester

(PME) with 1%,2%,3%, and 4% additive 1,4-Dioxane in biodiesel and at five discrete part load

Stroke 77.00mm

Engine displacement 447.3cm3

Compression ratio 24±1:1

Maximum net power 5.04 kW at 3000 rpm

Maximum net torque 18.7 Nm at 2200 rpm

Idling rpm 1250±150 rpm

Injection Timings 8.50 to 9.5

0 BTDC

Injector Pintle

Injector Pressure 142 to 148 kg/cm2

Fuel High Speed Diesel

Starting Electric Start

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conditions viz. No Load, 0.77 kW, 1.54 kW, 2.31 kW and 2.70 kW loads without gear box and

clutch assembly measuring stable engine operation. The data collection is done independently for the

above said fuels. Properties of the fuels used in the experimentation are shown in the table 2.The net

heat release rates and the cumulative heat release rates are derived from the recorded Pressure-Crank

angle data, cylinder volume model and implementing process coefficient at every degree of crank

revolution. Cylinder vibration is recorded using vibration analyzer (Fig.3) with accelerometer

mounted on the cylinder head in the two desired directions (one is in the piston slap direction and the

other being vertical). DC-11 data logger is used to ascertain the spectral data in the form of FFT and

overall vibration levels. This FFT data recorded is collected by the data logger is analyzed by Vast-

an software designed by VAST INC Russia. The time waveforms are obtained on the cylinder head

by DC-11 in OFF-ROUT mode and are presented in graphic form by Vast-an DOS based software.

Table 2: Properties of the Fuels Used

S. No

Name of the fuel Diesel PME 1,4-Dioxane

Properties

1 Density at 330C, (kg/m

3 ) 830 860.6 1033

2 Gross Calorific

value,(kJ/kg) 43000 38050 26960

3 Viscosity at 330C, (cSt.) 2.75 4.545 1.16

4 Cetane Number 45-55 65 50

6 Flash Point (oC) 50 164 12

7 Latent Heat of

Vaporization (KJ/Kg) 280 300 413

8 Auto ignition temperature

(oC)

316 363 180

Figure 3: DC-11 Vibration Analyser with acceleration pickup

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30

35

40

45

50

55

60

340 350 360 370 380 390 400

Co

mb

ust

ion

Pre

ssu

re(b

ar)

Crank Angle(Degree)

Combustion Pressure Vs Crank Angle at 2.7kW Engine Load

DIESEL

PME

PME+1% 1,4-

DIOXANE

PME+2% 1,4-

DIOXANE

PME+3% 1,4-

DIOXANE

PME+4% 1,4-

DIOXANE

4. Results and Discussion

4.1. Combustion Pressure variation with different fuels

Combustion pressures in the combustion chamber were recorded with respect to the TDC

position .For specific study, the crank angle duration from 3500 to 400

0 which encompasses TDC

position at 3600 has been selected. Figure.4 indicate the combustion pressure variation with respect

to crank angle. Each plot is an average of six samples taken at each load. From the graph it is clear

that an improvement in the combustion pressure generation starting from the beginning of the

combustion at maximum load. This additive in biodiesel has proved its consistent performance in the

exhaust gas emissions and engine cylinder vibrations. Generally diesel engines are advised to run at

maximum load and at other part loads in the proximity of the maximum load. 3percent 1,4-Dioxane

additive in the PME exhibited smooth variation of pressure in both the combustion chambers out of

all the fuels tested( pressure sensor mounted in the main chamber).It can be observed from the plot

4, there is visible fluctuation in the combustion pressure generation with other samples indicating

more heterogeneity when compared to the sample with 3percent additive in the biodiesel.

Figure 4: Combustion Pressure verses Crank Angle for all fuel samples at maximum engine load.

4.2. Cumulative and Net heat release rate comparison

Cumulative heat release for maximum load operation as shown in fig.5 envisages that the peak

pressure is occurring earlier by 50 of crank approximately. Economical cumulative heat release has

been observed with 3 percent 1,4-Dioxane in PME and at other percentages except at 4% additive

,the heat release is superseding the other percentages of additive in biodiesel. Sharp initial rise in

cumulative heat is observed with 3 percent additive in biodiesel. The net heat release with 3 percent

additive in biodiesel is observed in systematic quantum burning as shown in fig.6.Erratic

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combustion has been taken place in the case of 4 percent additive in biodiesel with irreversible in the

combustion within the cycle.

Figure 5: Cumulative heat release rate Verses Crank angle at 2.31 kW engine load

Figure 6: Net heat release rate Verses Crank angle

0

100

200

300

400

500

600

700

300 350 400 450 500

Cu

mu

lati

ve

Hea

t R

elea

se R

ate

(J/D

egre

e)

Crank Angle(Degree)

DIESEL

PME

PME+1% 1,4-

DIOXANE

PME+2% 1,4-

DIOXANE

PME+3% 1,4-

DIOXANE

PME+4% 1,4-

DIOXANE

-6

-1

4

9

14

19

24

29

340 350 360 370 380 390 400 410 420

Net

Hea

t R

elea

se R

ate

(J/D

egre

e)

Crank Angle(Degree)

DIESEL

PME

PME+1% 1,4-

DIOXANE

PME+2% 1,4-

DIOXANE

PME+3% 1,4-

DIOXANE

PME+4% 1,4-

DIOXANE

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4.3. Engine Vibration Analysis

Figure7 depict the vibration acceleration on the cylinder head in vertical direction at two different

loads. Since engine is vertical cylinder engine, the vibration recording on the cylinder head in

vertical direction truly reflect the engine combustion propensity. Combustion propensity can be

predicted from the deliverance of frequencies within time period taken for one degree of crank.

Hence, vibration analysis in FFT form both in the form of narrow band and log-log form have been

analyzed to assess the merit of the bio fuel in comparison to the neat diesel fuel. Frequency zone of

12800 Hz is considered for the measurement of vibration acceleration amplitude and velocity

amplitude to assess the knocking and detonation in the highest order of vibration. Log-Log FFT

graph (figure 8) give ample information about the combustion trend with the new fuel.

Figure 7: FFT plot of vibration acceleration on the Figure 8: Log-Log plot of vibration Acceleration on

Cylinder Head in vertical direction with the Cylinder Head in vertical direction

different fuel combinations at 2.7kW load with different fuel combinations at 2.7kW

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Time wave amplitude modulation is comparatively smoother replete with harmonies for 3% 1,4-

Dioxane in biodiesel as shown in figure.9. The longer time band widths of combustion in the main

chamber may indicate better torque conversion. The vibration excitation is on par with diesel fuel

which is near to 10g in the pre combustion chamber. In the case of bio diesel the excitation levels in

the time wave are less than 10g indicating lower power generation. Considering 3% 1,4-Dioxane in

biodiesel, the heat generation in pre chamber and main chamber has been economically adjusted

with the introduction of additive leading to load tackling on par with diesel fuel. This has taken place

vis-a-vis lower heat value of the biodiesel and the additive. Hence, it can be acclaimed better

combustion propensity in the case of the defined additive in the biodiesel. This assessment is also

agreeing with the cumulative heat release curves already explained.

Fig.9. Time wave recorded vertical on the Cylinder Head with different fuel combinations at 2.7kW load

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5. Conclusion

i. It can be realized that the 3 percent 1, 4-Dioxanea additive in PME is the right choice for the

replacement of conventional diesel fuel in IDI Engine chosen and tested in the laboratory.

This conclusion is based on the real pressure plots obtained, the cumulative and net heat

release rate plots derived and vibration plots compared.

ii. Three percent 1, 4-Dioxane additive in the PME exhibited smooth variation of pressure in

both the combustion chambers out of all the fuels tested.

iii. Quantum burning is observed in the case of 3 percent additive in biodiesel with more

harmonics in the main chamber as per the time waves.

iv. Since it is accepted that the vibration plots give grater insight in to the one degree of crank

revolution in time domain, assessment has been made with narrow brand, log-log FFT plots

with higher range of frequency and time wave forms.

v. Knocking or any abnormality in combustion which obviously give set back to the power

generation can be easily investigated by the micro level study of cylinder excitation with

vibration.

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[13] N. Prasada Raju, B. V. Appa Rao, “Experimental study on Combustion and Emission Characteristics of

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Biographies

1st S C V Ramana Murty Naidu has 16 years of teaching experience and area of interest is Alternate

fuels and its Applications in C.I. Engines.

2nd Prof. B V Appa Rao has been working in the Department of Marine Engineering, Andhra

University from the past 30 years. His expertise is in the area of Biodiesel applications in the Diesel

engines without changing the basic design of the engine. He is also adept in Condition monitoring of

Machinery and engines, He has produced 20 doctorates, 8 are in progress and published about 87

papers.

3rd Aditya Kolakoti is a full time research scholar in the Dept.of Marine Engineering,AUCE(A).

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