PERFORMANCE EVALUATION OF A CONVENTIONAL DIESEL ENGINE RUNNING IN DUAL FUEL MODE WITH DIESEL & LPG

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International Journal of Mechanical Engineering and Technology (IJMET)
Volume 6, Issue 11, Nov 2015, pp. 64-76, Article ID: IJMET_06_11_008
Available online at
http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=6&IType=11
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication
PERFORMANCE EVALUATION OF A
CONVENTIONAL DIESEL ENGINE
RUNNING IN DUAL FUEL MODE WITH
DIESEL & LPG
Suraj Dev Singh, Chandrabhan Singh Tomar and Ravindra Randa
Department of Mechanical Engineering, University Institute of Technology,
Rajiv Gandhi Technical University, Bhopal,
Madhya-Pradesh, India
ABSTRACT
Present study evaluates the performance of a compression ignition engine
running in dual fuel mode with Liquefied Petroleum Gas and Petroleum
Diesel. The LPG was inducted in the engine by Fumigation method at the rate
of 0.094, 0.189 & 0.283 Kg/hr. Major performance parameters such as Brake
power, Brake thermal efficiency, Brake specific fuel consumption etc. were
evaluated at different load & different fuel combinations. A reduction of up to
11% in diesel consumption and up to 32% improvement in Brake specific fuel
consumption was observed in dual fuel mode. Whereas, brake thermal
efficiency didn’t improved due to poor utilization of high energy content of
LPG. Although the diesel fuel was saved but that came on sacrificing LPG
which cost more than saved diesel. It’s a loss in terms of cost and performance
to use LPG in conventional Diesel engine by fumigation method used in this
experiment but the concept of experiment can be advanced to make more
subtle dual fuel diesel engine with advance techniques and improved cylinder
designs.
Cite this Article: Suraj Dev Singh, Chandrabhan Singh Tomar and Ravindra
Randa. Performance Evaluation of A Conventional Diesel Engine Running In
Dual Fuel Mode with Diesel & LPG, International Journal of Mechanical
Engineering and Technology, 6(11), 2015, pp. 64-76
http://www.iaeme.com/currentissue.asp?JType=IJMET&VType=6&IType=11
1. INTRODUCTION
For more than a century, internal combustion engines have been relied upon as a
principal source of power in a variety of applications. Of those engines, the most
widely used are the reciprocating piston engines which are found in automobiles or
other forms of transportation, as well as a variety of industrial and consumer
applications. Of those variations, Diesel engines have a number of important
advantages over gasoline engines. They provide reliability, long life, and good fuel

Performance Evaluation of A Conventional Diesel Engine Running In Dual Fuel Mode with
Diesel & LPG
economy, and are expected to remain the dominant heavy-duty transport power plants
for many years. The rapidly depleting petroleum reserves and stringent emission
norms have made it mandatory to look for alternate and cleaner sources. Bio-fuels
pose a good role as alternate resources but neutral government policies and matters
like food security have dominated the yielding of bio-crops and made them much
expensive than conventional petro-diesel. So, in the present scenario, we are focusing
on methods to improve the performance of CI engine and are trying to minimize the
harmful emissions coming out of exhaust which have poisoning effect over the
respiratory system along with climate change and global warming effects. A lots of
researches are going on in this field to improve performance and reduce emissions by
completely burning the diesel inside the combustion chamber, by adding additives to
fuel or by modifying the engine to run in the Dual-fuel mode.
One of the major problem attached with combustion in conventional diesel
engines is that fuel and air doesn’t mix homogeneously, a large fraction of fuel exists
at very rich fuel-air equivalence ratio due to which incomplete combustion of diesel
fuel occurs which results in high Particulate matter (PM) and Furthermore, the fuel-
rich equivalence ratio can also lead to high flame temperatures residing in a small area
in the combustion process, which results in increased NOx emissions. As tougher
environmental standards are being enacted for diesel sources, users of diesel engines
are looking for ways to lower emissions. One solution is to reduce the amount of
diesel injected into the combustion chamber, which reduces the equivalence ratio and
works to reduce particulate and NOx emissions. However, it also reduces engine
power.
Another solution is to partially or completely convert the engine for use with
alternative fuels such as, compressed natural gas (CNG), liquid natural fuels (LNF)
such as ethanol, and liquid or liquefied petroleum gas (LPG) such as propane.
Utilization of such alternative fuels with diesel engines not only provides for more
stable and complete combustion and thereby enhanced fuel economy, but also
typically results in lower engine emissions. However, alternative fuels, and more
particularly gaseous fuels, typically do not have the cetane value required to allow for
their ignition through compression. Accordingly, diesel engines must be modified to
use such fuels. Methods for converting a diesel engine to consume alternative fuels
typically fall into three categories. The first is to convert the engine to a spark-ignited
engine; a second is to convert the engine to allow for the direct injection of gaseous-
fuels into the combustion chamber; and a third is "fogging" or "fumigation" of the
gaseous-fuel with all or a portion of the intake air charge entering the engine. As will
be appreciated, the second and third methods utilize injected diesel (i.e., pilot diesel)
to ignite the gaseous-fuel. In this regard, the combustion of the gaseous-fuel results in
more complete combustion of the diesel. Furthermore, the combination of gaseous-
fuel and diesel allows the engine to produce additional power while less diesel fuel is
injected into the cylinders.
However, conversion to a spark-ignition system and/or a direct gaseous-fuel
injection system for utilizing gaseous-fuels with a diesel engine each typically require
substantial modification to the diesel engine. Such modifications may include
replacement of cylinder heads, pistons, fuel injection system and/or duplication of
many engine components (e.g., injection systems). Accordingly, these systems are
typically expensive and often times unreliable.
On the other hand, fogging or fumigation type dual-fuel systems require little
modification to existing engines. The mixture of gaseous-fuel with the intake air

charge is introduced into each cylinder of the engine during the intake stroke. During
the compression stroke of the piston, the pressure and temperature of the mixture are
increased in the conventional manner. Near the end of the compression stroke, a
smaller than normal quantity of diesel fuel from the engine's existing diesel fuel
injection system is injected into the cylinder. The diesel ignites due to compression
and in turn ignites the mixture of gaseous-fuel and intake air, which in turn,
accelerates the flame front of the Diesel Fuel, enhancing the combustion process. As
will be appreciated, such fumigation systems may be retrofit onto existing diesel
engines with little or no modification of the existing engine. Furthermore, engines
using such fumigation systems may typically be operated in a dual-fuel mode or in a
strictly diesel mode (e.g., when gaseous-fuel is not available).
(1)
In our experiment,
we will be using this method of fumigation to run the governor controlled constant
speed diesel engine in dual fuel mode using Diesel and LPG. For the purpose, we
have attached a convergent divergent steel nozzle in the path of air supply to
combustion chamber and made a very small hole at the throat of nozzle to
accommodate the gas welding torch tip for supplying LPG during operating the
engine. The supply of LPG has been varied at 0.094, 0.189 & 0.283 Kg/hr, as the
engine is governor controlled; the supply of diesel got regulated by engine itself, at
every LPG concentration; the Load on the engine was changed and performances
were observed.
2. COMPARISON BETWEEN PROPERTIES OF DIESEL AND
LPG
In the table below, the physiochemical properties of Diesel and LPG are listed.
PROPERTIES DIESEL(2)
LPG(3,4)
NORMAL STATE LIQUID GASEOUS
FORMULAE C12H23 C3H8
CALORIFIC VALUE(KJ/KG) LHV: 44000
HHV: 44800
LHV: 46350
HHV: 50350
SPECIFIC GRAVITY(RELATIVE TO WATER) 0.82-0.95 0.525-O.580(liquid)
AUTO IGNITION TEMPERATURE(0
C) 176.4 TO 329.44 410-580
FLASH POINT(0
C) 62 -104
CETANE NUMBER 40-60 05-10
STICHIOMETRIC A/F RATIO (MASS) 14.5 15.7
PEAK FLAME TEMPERATURE(0
C) 2054 1990
BOILING POINT(0
C) 149-371 -42
DENSITY(KG/M3
) 820-950 525-580(liquid)
1.888-2.45(gaseous)
It is clear from the table that LPG has a quite low Cetane number which makes it
inefficient for self ignition, that’s why engine needs some of the Diesel known as pilot
fuel to provoke ignition in the combustion chamber. The power is supplied jointly by
the combustion of Diesel & LPG. And since LPG has a grater Calorific value, its
combustion facilitates in providing required or greater power consuming a lesser
quantity of diesel fuel thus improving the fuel economy.
With Dual Fuel operation, there is no change to the basic architecture of the diesel
engine – or to the principle of diesel combustion. The engine itself is virtually
unaltered, but for the addition of a gas injection system. The Dual-Fuel in-cylinder

Diesel & LPG
temperatures and pressures remain within the limits of pure diesel operation, so the
converted engine operates within the parameters of the original engine.
In a Dual-Fuel engine, however, the diesel fuel injector works like a liquid spark
plug. Highly pressurized, it ignites a mixture of compressed gas and air in the
cylinder.
3. SPECIFICATIONS OF THE TEST ENGINE
The engine used in this experiment is installed at University Institute of Technology,
Rajiv Gandhi Technical University, Bhopal. The RGPV engine test contains a
complete system for measuring all the parameters relating to the diesel engine
performance analysis. The experimental set-up contains mainly a dynamometer to
load the engine. Figure below gives a diagram of the experimental system used.
Figure 1 Diesel Engine Test Rig Showing Dynamometer
Figure 2 Diesel Engine Test Rig Showing Fuel Consumption Meter, Temp. Indicator
Etc

Parameter Details
Engine Company and Model
Type
Cooling System
Cylinder Number
Bore
Stroke
Swept volume
Compression Ratio (R)
Rated Power (P) (kW)
Nominal Revolution
Kirloskar Oil Engine, SV1
Vertical, Totally Enclosed, Compression
Ignition, Four Stroke Engine,
Water Cooled
Single cylinder
87.5 mm
110 mm
662 CC
16.5:1
8 HP
1500 RPM
In order to convert the conventional diesel engine into a Dual-Fuel engine, we
attached an Inspirator, an LPG fuel injector along with a flow controller to send LPG
in a controlled way. For measuring the LPG flow we attached a Hot Wire
Anemometer which measures the velocity of LPG in the delivery pipe and when this
velocity is multiplied with area of cross section of Pipe, we get the volume flow rate
of LPG which can be further converted into mass flow rate by multiplying it to the
Density of LPG.
For measuring the performance parameters, other devices such as Fuel
consumption meter, belt dynamometer, thermocouples, rota meters etc are already
attached with the engine test rig. In addition to this, we have supported the engine
base with hard rubber dampers to reduce the vibrations. A water tank is used as a
reservoir for the cooling of engine and exhaust calorimeter.
Figure 3 Inspirator Setup for LPG Introduction

Diesel & LPG
Figure 4 Hot Wire Anemometer for Measuring
4. VELOCITY OF LPG SUPPLY
4.1. LPG Kit
We have used a 3 kg gas capacity LPG gas cylinder for the experiment. The gas is
supplied through a PVC hose pipe, which hosts a Gas welding torch nozzle at the
other end for producing a jet of LPG gas.
4.2. Hot Wire Anemometer
A Hot Wire Anemometer is inserted in the PVC pipe between the cylinder and engine
to measure the velocity of the gas in the pipe. The velocity obtained is later used for
measuring the volume flow rate or mass flow rate for measuring the performance
parameters.
The volume flow rate is given by
s
where:
= Flow Velocity
= Cross-Sectional vector Area/surface
When the mass flow rate is known, and the density can be assumed constant, this
is an easy way to get .
Where:
= mass flow rate(kg/s).
= density(kg/m3).

The above formulae can also be used to calculate the mass flow rate if the Volume
flow rate and density are known.
4.3. Inspirator
An Inspirator is a device, similar to Venturi tube and an Orifice plate, which mixes a
fuel gas with atmospheric air in a precise ratio to regulate burn characteristics. Only
the pressure of the fuel gas is used to draw in and mix the air. They are the most
simple and common type of mixing device commonly used in gas stoves and
furnaces. Burners using an inspirator are considered to be naturally aspirated.
In an inspirator there are 2 tubes. The first is a fuel gas pipe with an Orifice at the
end where the gas comes out. Then in front of this there is another section of tubing
with a larger diameter that the gas blows into. Usually (but not always) this second
piece of tubing is tapered so that it starts getting narrower downstream from the
orifice. Then, at a certain point, it stops getting narrower and either straightens out or
starts getting larger again. This gives the fuel and air time to mix. The fuel/air ratio is
determined by the ratio of the diameter of the orifice to the diameter of the mixing
tube. In our experiment, we have used a gas welding torch nozzle of hole diameter of
0.1 mm as an orifice to supply fuel gas to engine. It supplies gaseous fuel at the throat
of Venturi or Inspirator after which the diameter of Venturi starts increasing and
gaseous fuel and air mix homogeneously and burn completely and give their full
power to engine for running minimizing the quantity of liquid fuel to be used by the
engine for producing the required power at that speed and load.
5. RESEARCH METHODOLOGY
As discussed earlier, we are using Diesel, & the Diesel-LPG fuel mix to run our
engine and LPG is been mixed by Fumigation technique. As our engine is governor
controlled, it takes the Diesel fuel in accordance with its need. We provide LPG in a
controlled way in different concentrations with help of a control valve and hot wire
anemometer and observe the diesel fuel consumption in every step. We observe
performance parameters in every case & try to determine the suitability of Diesel-
LPG mix for improved performance in dual fuel mode.
At first we start the engine and switch on every accessory such as water supply,
temperature indicators and let the engine run for 20 minutes so that it can achieve its
steady state. In the first set we run the engine on pure diesel fuel purchased from a
Petrol Pump. We, initially run the engine at Zero load at take readings of all the
parameters required for our performance and emission results. Following parameters
are to be noted:-
1. Air Velocity in the air passage(m/s)
2. Fuel consumption(ml/minute)
3. Temperatures
T1 = Temperature of the water entering into the engine jacket.
T2 = Temperature of the water coming out from the engine jacket.
T3 = Temperature of the Exhaust gases entering into the exhaust calorimeter.
T4 = Temperature of the Exhaust gases coming out from the exhaust calorimeter.
T5 = Temperature of the water entering into the Exhaust Calorimeter.
T6 = Temperature of water coming out from the Exhaust calorimeter.
4. Load on the engine applied by the Belt Dynamometer.(Kg.)

Diesel & LPG
5. Water flow to the engine Jacket and To the Exhaust Calorimeter.(Liter per Minute)
6. After noting down all the parameters, we apply a load of 1 Kg on the engine and let it
run for 15 minutes to achieve the steady state and then point down all the parameters
again.
7. In the same manner, we increase the load to 2 kg than 4 kg and than 8 Kg and note
down all the parameters like before.
8. The results of the experiment are tabulated. These are our reference values.
9. In the next phase, we introduce LPG with the Diesel and note down the readings. In
this stage, we have to take reading of one additional parameter i.e. LPG fuel
consumption. We measure the LPG gas velocity with the help of a Hot Wire
Anemometer and then covert it into volume flow rate as discussed in earlier sections
to measure its quantity in m3
/s or mass flow rate in Kg/s or Kg/hr. The results are
noted down in the same fashion as Pure Diesel.
10. We repeat this process with different LPG concentration of 0.094, 0.189 & 0.283
Kg/hr.
11. After all the values are obtained, these values are scrutinized for the preparation of
final results and for comparing the performance parameters.
6. RESULTS AND DISCUSSION
The results are then tabulated and calculated thus for the results and then plotted in
the terms of line graphs. 5 different graphs have been plotted and discussed.
1. Fuel consumption v/s Load
Graph 1 Fuel consumption vs Load
Fuel consumption increases with increase in load as for maintaining the RPM of
engine more brake power is required which is harnessed by burning more fuel at
higher load. The graph shows the consumption of liquid diesel fuel only in case of
dual fuel operation. Now looking at the plot of neat diesel fuel, it rises a little during
initial increase in loading from 0 to 2 kg but falls a little on subsequent loadings to 4
0.2
0.3
0.3
0.4
0.4
0.5
0.5
0.6
0.6
0.7
0 2 4 6 8 10
F.C.(Kg/hr.)
LOAD (Kgs)
Fuel Consumption Vs Load
Diesel
Diesel + LPG at 0.1 m/sec

and 8 kg and stabilizes and shows a linear gradual increment from 0.3366 kg/hr. at no
load to 0.6120 kg/hr. at full load. The other three plots of varying LPG flow rates of
0.094, 0.189 & 0.283 Kg/hr indicate the decrease in diesel consumption with increase
in LPG flow rate; although LPG flow rates of 0.189 & 0.283 Kg/hr show very little
difference at all loads and 0.094 kg/hr. shows highest diesel consumption in dual fuel
league.
2. Brake specific fuel consumption vs Load
Graph 2 Brake specific fuel consumption vs Load
BSFC states that how much amount of fuel is consumed for generation of per unit
brake power. It is governed by the quality of the combustion of fuel. As brake power
varies with load thus BSFC also changes with load. The graph shows the
consumption of diesel, and only diesel in dual fuel mode for generating per unit brake
power. It is apparent that BSFC for neat diesel is worst at all loads. In dual fuel mode,
diesel with 0.1 m/s LPG flow rate shows poor BSFC than other two dual fuel
operational modes but better BSFC than neat diesel. BSFC for 0.189 & 0.283 Kg/hr
LPG flow rates operation are nearly similar and overlap each other. BSFC at 1 kg load
for diesel was 1.53 kg/kwhr which reduced to a mere 1.03 kg/kwhr. in dual fuel mode
with LPG flow rate of 0.189 Kg/hr. The LPG being the gas facilitates in smoother and
complete burning of diesel fuel and thus reduces the BSFC. In all cases BSFC reduces
with increase in load and thus increased break power. It is because of higher HC
emission and incomplete burning of fuel at low loads. LPG induction helps in
reducing the ignition delay and reduces the BSFC thus improving the performance.
e.g. at top load of 8 kg, the BSFC of diesel is at 0.31 kg/kwhr while diesel with 0.189
Kg/hr LPG flow rate show improved BSFC of 0.21 m/s i.e.32.25% reduction is
observed.
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
0 2 4 6 8 10
BSFC(Kg/KW.hr.)
LOAD (Kgs)
BSFC Vs Load
Diesel
Diesel + LPG at
0.1 m/sec
Diesel + LPG at
0.2 m/sec
Diesel + LPG at
0.3 m/sec

Diesel & LPG
3. Brake specific energy consumption vs Load
Graph 3 Brake specific energy consumption vs load
Brake specific energy consumption shows the required energy of the fuel for
generating per unit of brake power. In this graph total energy content of the fuels in
dual fuel mode has been taken in account. Neat Diesel shows lowest BSEC at all
loads. The highest BSEC was observed in Dual fuel mode with LPG flow rate of 0.3
m/s. Other two flow rates of 0.1 and 0.2 m/s of LPG flow show very similar
characteristics. The high energy content of LPG is not completely utilized thus
resulting in higher BSEC. At lower loads this difference is apparent while at higher
loads this difference is very minor and can be ignored.
4. Brake thermal efficiency vs Load
Graph 4 Brake thermal efficiency vs load
Brake thermal efficiency is a dimensionless number which indicates the extent to
which energy given by the fuel is converted to brake power i.e. net work output. Here
in this graph it is represented in percentage. The poorest BTE is observed in dual fuel
mode at LPG flow rate of 0.283 kg/hr followed by O.189 kg/hr and then 0.094 kg/hr.
0
5
10
15
20
25
30
0 2 4 6 8 10
BSEC
LOAD (Kgs)
BSEC Vs Load
Diesel
0.00
5.00
10.00
15.00
20.00
25.00
30.00
0 2 4 6 8 10
Diesel

BTE is less at low loads and improves at higher loads. Neat Diesel shows best BTE at
all loads. The cause of poor BTE in case of dual fuel operation is high calorific value
of LPG, which increases overall energy input to the engine thus reducing BTE at all
loads. With increasing concentration of LPG gas, diesel fuel is substituted by a little
amount but the energy provided by LPG increases greatly thus reducing BTE.
5. Exhaust gas temperature vs load.
Graph 5 Exhaust gas temperature vs Load
EGT is an important parameter in engine performance check, it is an indication of
how hot the combustion process is in the cylinders, and the amount of "afterburning"
that is occurring in the exhaust manifold. EGT is also directly related to the air/fuel
ratio. The richer the air/fuel ratio in a diesel, the higher the EGT will be. Two things
can create a rich mixture under heavy loads or at full throttle: the first is too much
fuel, and the second is not enough air. That seems simple enough, but it's the second
part, not enough air, could get an engine in trouble. Anything that restricts intake
airflow, or intake air density, limits the air mass or amount of oxygen that gets to the
cylinders for supporting the combustion of fuel. This could include: a dirty or
restrictive air cleaner, a partially blocked air intake, high outside air temperature, high
altitude, restricted airflow to or through the radiator or intercooler, and high water
temperature.
Looking at the graph, it is obvious that with increase in load the EGT increases,
but the increment is not linear. Higher EGT’s were observed in dual fuel modes, the
causes of it may be less air for combustion in the combustion chamber and high
heating value of LPG gas. In a surprising way, in dual fuel mode, LPG flowing at 0.3
m/s shows lesser temperature than other two dual fuel modes only at highest load of 8
kg. It may be due to excess LPG unburned which cooled the EG.
Neat diesel shows better and lower EGT’s than all other fuels except at low loads
it is little more than the diesel+LPG 0.1m/s, but otherwise it is lower at all other loads.
The highest temperature reached in neat diesel case was 2070
C while the overall
highest EGT observed was 2380
C in case of diesel+LPG 0.2 m/s.
125
145
165
185
205
225
245
0 2 4 6 8 10
ExhaustGasTemp.(0C)
LOAD (Kgs)
EGT Vs Load
Diesel

Diesel & LPG
7. CONCLUSION
A comprehensive experimental work on the performance measurement of diesel
engine and to convert it into dual fuel engine with the help of LPG kit has been
carried out successfully. Following important outcomes derived from the experiment.
1. Fuel consumption was reduced in dual fuel mode. At no load, neat diesel
consumption was reduced by 9.09%, 24.24% & 25.49% in dual fuel mode at LPG
induction rates of 0.094, 0.189 & 0.283 Kg/hr respectively. While At top load of 8
kg’s this reduction falls to 5%, 6.67% & 10.72% respectively. To support the load
while maintaining the speed requires more fuel thus fuel consumption increases.
2. Brake specific fuel consumption also reduced in dual fuel mode, BSFC in dual fuel
mode of 0.189 & 0.283 Kg/hr LPG flow rate are quite similar. BSFC in case of neat
diesel at top load was 0.31 kg/kwhr while in case of dual fuel (LPG flow of 0.2 m/s)
it was 0.21 kg/kwhr. Thus, we are able to save 0.1 kg/kwhr of diesel.
3. BSEC and BTE didn’t got improved in dual fuel modes, although low LPG flow rates
give comparable results but increased concentration of LPG in successive stages
worsen the BTE. The higher calorific value of LPG and lower utilization of it causes
to reduce BTE by increasing the overall non utilized energy input to the engine. This
can be overcame by using advance techniques such as electronically timed and
controlled injection of fuel to determine the needed quantity of fuel in engine, exhaust
gas recirculation to utilize unburned HC, glow plugs for reducing the ignition delay at
higher speeds and loads etc. but it is still unsure that they will improve BTE to great
extent.
4. Exhaust gas temperature increased in dual fuel modes. The high heating value of LPG
is the main cause behind it. Better cooling systems in which the cooling fluid
quantities are also changeable are needed to employ dual fuel systems in diesel
engines to keep the EGT in limit at higher loads. High temperature inside the
combustion chamber may also harm the engine parts and reduce the mechanical
strength it is very essential to take care of cooling inside the combustion chamber.
5. The cost of cooking LPG used in experiment is 455 INR per 14.2 kg i.e. 32.04 INR
per kg maximum while the Diesel cost is 52.08 INR per litre which when converted
to kg comes to 61.27 INR per kg (taking diesel density as 850 kg/m3
). The price of
diesel is just double the LPG and it seems that there may be a saving in cost in using
LPG in diesel engine. Taking the case of no load in which nearly 26% diesel fuel was
saved while using diesel+ LPG at flow rate 0.283 Kg/hr, in neat diesel operation,
0.3366 kg/hr fuel was used which costs 20.62 INR/hr., when LPG at 0.283 Kg/hr was
inducted, only 0.2508 kg/hr fuel was used which costs 15.367 INR/hr that means 5.25
INR were saved but for this sake 0.283 kg/hr of LPG was used which costs 9.06
INR/hr, it is apparent that saving done in diesel was overcame in expense done on
LPG and we incur a loss off 3.81 INR/hr. If we take the case of full load of 8 kg’s
then this loss is increased to around 5 INR/hr. Taking the case of LPG flow rate of
0.094 Kg/hr, at no load, this loss is 1.13 INR/hr. which remains same at full load also.
At LPG flow rate of 0.189 Kg/hr, at no load, the loss is 1.06556 INR/hr and at full
load it is increased to 3.555 INR/hr. that means in every case , mixing LPG with
Diesel doesn’t show any profit cost wise or performance wise if seen the thermal
efficiency.
6. There are other problems to consider as well - The unmodified Diesel engine was
relatively slow-revving, producing its maximum torque at lower RPM than a similar
Petrol version. This is not the case when it is converted to run on Diesel and LPG
mix. The revised engine has to'rev' more when running on Diesel / LPG mix because
its maximum torque will have been moved higher up the rev. band. This can bring
new problems of reliability and longevity. The crankshaft, bearings and connecting
rods (to mention but a few components) were all designed to rev. at a lower rate.

These components will suffer much higher stresses (stress increases at the square of
RPM) at the increased RPM necessary to get sufficient torque when running on LPG.
Mechanical breakdown may result in far less time, whilst increased wear and reduced
component life are certain. Given the low overall savings achieved (to date) and the
cost of the adaption (often equal to that of an injected Petrol engine conversion)
many miles would have to be covered before any real savings are realised whilst
reliability has been reduced. This does not seem to be an economically viable
alternative.
7. One more benefit of using LPG is that Diesel engine becomes quieter and more
responsive when using the LPG / Diesel mix. The classic Diesel 'Knock' can be
greatly reduced. The main reason for increased smoothness and reduced noise
(vibration) is that the LPG element begins its combustion before the Diesel fuel does,
a result of 'detonation' due to the compression ratio being so high. The engine may
also get up to its optimum temperature more quickly, whilst harmful emissions like
Particulates and Carbon Monoxide can be reduced. These all appear to be benefits but
a new set of problems arises when LPG is used to increase performance of an engine
that wasn't designed to rev to the new, higher levels. As a result of this apparent
improvement in performance, one of the best attributes of the Diesel engine (relative
longevity and reliability) is dramatically reduced by the Diesel / LPG adaption.
8. Thus as a conclusion, the fumigation method used in this experiment does not appear
to be an attractive or useful alternative for the average diesel engine. The economic
benefits are not supportive in favor of the mixing of LPG with diesel. On a purely
running cost reduction basis adapting the conversion technology for average diesel
engine does not appear to be a viable option.
8. SCOPE OF FUTURE WORK
Although there are many problems encountered in running a diesel engine in dual fuel
mode with LPG, several researches are going on all over the world to eliminate these
problems. LPG is quite cheaper than Diesel and if total energy of its can be utilized to
run the diesel engine without harming its reliability and longevity, it would be a great
boon. To improve the performance of a dual fuel engine, a turbocharger to provide
more air (or oxygen) for the combustion, must be installed. It will help in complete
combustion of fuel and will reduce exhaust gas temperature thus improving the engine
life. Apart from that, precise electronic control system must be installed to watch the
combustion patterns and needs in combustion chambers and for providing best ratio of
diesel and LPG. A good exhaust gas recirculation system monitored electronically
must be employed to engine to utilize any unburned HC. Some advance additives and
catalyst might be added to fuel for smoother and efficient combustion. The concept of
present work might be employed with some modifications and with other fuels such
as CNG and Natural gas.
ACKNOWLEDGMENT
The authors wish to acknowledge the support rendered by University Institute of
Technology, Bhopal in preparation of this Manuscript.
REFERENCES
[1] http://americandieselsystems.com/diesel-reduction-technology.php
[2] http://depts.washington.edu/vehfire/fuels/detailedresults.html
[3] http://www.elgas.com.au/blog/453-the-science-a-properties-of-lpg
[4] https://iocl.com/Products/LPGSpecifications.pdf

PERFORMANCE EVALUATION OF A CONVENTIONAL DIESEL ENGINE RUNNING IN DUAL FUEL MODE WITH DIESEL & LPG

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PERFORMANCE EVALUATION OF A CONVENTIONAL DIESEL ENGINE RUNNING IN DUAL FUEL MODE WITH DIESEL & LPG