Article

AL-QADISIYAH JOURNAL FOR ENGINEERING SCIENCES 14 (2021) 054–0 16

Contents lists available at http://qu.edu.iq

Al-Qadisiyah Journal for Engineering Sciences

Journal homepage: http://qu.edu.iq/journaleng/index.php/JQES

* Corresponding author.

E-mail address: mohamed.aldawody@qu.edu.iq (Mohamed Al-Dawody)

https://doi.org/10.30772/qjes.v14i1.751

Use Of LPG In SI Engine- A Review Study

Ghufran Talib Hashem a, Mohamed Al-Dawody a*

a Department of mechanical engineering, University of Al-Qadisiyah, Al-Qadisiyah, Iraq.

A R T I C L E I N F O

Article history:

Received 22 March 2021

Received in revised form 18 May 2021

Accepted 23 May 2021

Keywords:

LPG

SI Engine

Dual Fuel

Performance

Exhaust Emission.

A B S T R A C T

The depletion rate of conventional petroleum fuels is very fast. Gasoline is used as conventional fuel in

the SI engine. Emissions from this fuel cause environmental pollution because it produces harmful

emissions for the environment such as CO2, CO, HC, and NOx. Liquefied petroleum gas (LPG) has

physical and chemical properties that make it a favorable fuel for IC engines. It can be used as a fuel alone

or combined with gasoline with some minor engine modifications. The engine running on LPG showed

improved performance - in terms of fuel economy, overall efficiency compared to petrol. In addition, it is

noted that LPG emissions are greatly lower than petrol. This work reviews the research conducted by

previous researchers on LPG-powered SI engines under several working conditions.

1. Introduction

Consumption of petroleum products has risen dramatically in the last

decade due to the rise in car use and the rapid pace of technological and

industrial growth worldwide. Gasoline is traditional fuel used in spark

ignition engines Chung et al. [1]. Petrol is derived from crude oil, and its

cost is increasing due to limited crude oil reserves. Furthermore, the

limited reserves of fossil fuels would not be adequate to satisfy energy

requirements in the close future, and the difficult of fuel paucity will

become very serious [2-3]. In addition, One of the most important interest

around the world is the ecological issue due to vehicle emissions. Eco-

friendly pollution and modification of energy sources arise from the

necessity for substitute fuels for automobile uses Mistry et al. [4].

Alternative fuels are classified into industrial gasoline, alcohols,

gaseous fuels and others[5-6]. Alternative fuels are promising in the future

in the transportation sector, as shown in Fig. 1. It is expected that the use

of conventional fuels in transportation will decrease by about 24% by

2050 compared to 2005, and the trend towards the use of alternative fuels,

mainly due to reducing emissions, and also to improve the efficiency of

the transportation system Fuels and Reports [9]. Gaseous fuels such as

LPG have been used extensively around the world in SIE because it has

less impact on global warming emissions than any other fossil fuel in

addition to its distinct properties such as higher octane number, lesser

polluting exhaust emission, greater calorific value and economic

expenses. Several researchers have conducted a large number of

educations on LPG as a fuel in the SIE and it has been described that the

use of LPG has a important impact on emissions regulator and

performance [7-8].

http://qu.edu.iq/
mailto:mohamed.aldawody@qu.edu.iq
https://doi.org/10.30772/qjes.v13i
http://creativecommons.org/licenses/by/4.0/

55 GHUFRAN TALIB HASHEM AND MOHAMED F. AL-DAWODY /AL-QADISIYAH JOURNAL FOR ENGINEERING SCIENCES 14 (2021) 054–0 16

Figure 1. Total energy consumption in the transport sector [45]

2. Introduction to LPG

liquefied petroleum gas (LPG), 55% of LPG is obtained from

Natural gas refining and the remaining 45% extraction from refining crude

oil Taha et al. [10]. LPG is a gas consisting mainly of propane and butane,

except that it could likewise contain various hydrocarbons such as

propane, and n-butane in different amounts as presented in Table 1. It is

only compressed 5 -20 bar and it works perfectly as an alternative fuel in

SI engines Zhang [11] .It is odorless and for safety reasons, odorless has

been added to detect undetected leaks that could lead to hazardous

situations, because LPG is heavier than Air. One of the most important

alternative fuels in SI engine is LPG because of several reasons, including

the high octane number (110+) which enables the compression ratio (CR)

to be as great as 15: 1, which is in the variety of 8: 1 to 9.5: 1 for petrol

engines[10], the large global reserve of these gases, high heating value,

and low emissions from burning in engines, in addition to their lower

prices compared to gasoline Chaichan et al.[12]. LPG has a greater

ignition temp. than petrol, which delays self-ignition of fuel and thus

avoids knocking Bisen et al. [13].

Table 1: Composition of Iraqi LPG

No. Components % vol.

1 methane -

2 Ethane 0.03

3 Propane 20.13
4 Iso-Butane 19.35

5 n-butane 59.97

6 Total C4 79.32

7 Iso-pentane 0.50
8 n-pentene 0.02

9 Pentane and heavier 0.52

3. LPG In Internal Combustion Engine

Vehicles running on liquefied petroleum gas (LPG) have been

rapidly developed, as they are more economical and less polluting [14,

15]. Expected benefits of using LPG in SI are inexpensive and

environmentally friendly. The SIE can be easily reformed to work on LPG

[9]. Note in double fuel gas engines, gaseous fuel is introduced with air,

and this mix of air and gas is compacted as is the state in conventional

engines Saraf et al. [16]. The LPG device runs under high pressure ratio.

Thus, it has better thermal efficiency than a petrol engine due to its high

octane rating Elnajjar et al. [17]. This means that it is possible to increase

engine power output and fuel efficiency to what is possible with a petrol

engine without producing a damaging phenomenon knocking . Also,

given that LPG arrives the engine's combustion chambers as vapour, it

does not remove the oil from cylinder sides or weak oil while the engine

is cold. This helps to get a longer lifetime as well as reduce Engine

maintenance costs. LPG is less hazardous than any other petroleum-based

fuel and is expected to produce fewer emissions of carbon dioxide,

nitrogen oxides, and May cause less ozone formation than gasoline

engines Pundkar et al. [18] . Several scientists have studied with LPG as

an substitute fuel for SI engines. A amount of proposals have been put

forward by them to improves performance with this new fuel. A

comparison of the physical properties and combustion characteristics of

Iraqi LPG and traditional fuels(Iraqi gasoline) is shown in Table 2.

Table 2: Fuel properties at 25°C and 1 atm [19-20]

Property Gasoline LPG

Density, kg/m3 730 1.85/505

Flammability limits (Ø) 0.7-4 0.7-1.7

Auto Ignition Temperature in air, (K) 550 588

Lower heating value (MJ/kg) 44.79 46.22

Stoichiometric fuel/air mass ratio 0.068 0.064

Flame velocity (m/s) 0.37-0.43 0.48

Adiabatic flame temperature (K) 2580 2263

4. Literature Review

In the recent period, the price of liquid fuel extracted from crude oil

as well as the increasing concerns about environmental pollution emitted

by cars have led to an increase in interest in alternative engine fuels [16].

Several researchers have studied the usage of LPG as an alternative fuel in

the SIE. Experts and researchers conducted many experimental and

theoretical investigations on the SIE supplied with LPG under dissimilar

working conditions and standards and favourable results were obtained in

terms of thermal efficiency, fuel cheap, as well as exhaust emissions. LPG

combustion properties are higher to petrol in lean engines Jothi et al. [21].

Because of its effective combustion properties, LPG is commonly used in

SIE but vehicles running on LPG fuels, in which fuel systems have been

overridden from those of petrol engines, cannot realize a higher

compression ratio and thus greater thermal efficiency where no Converted

engines can take advantage of the high octane number of LPG [16]. LPG

gas as a low carbon and high octane number fuel produces lower carbon

dioxide (CO2) emission as compared to gasoline[22-23].

Ehsan M.d. et al. [24] Described working on 200 CC 1- cylinder, 4

stroke, SI coupled to generator with output power of 1.5 kW, 220V, 50Hz

of electricity. The engine set's air inlet has been changed to use LPG. The

load was applied to the motor as an electrical load. The test exhibited

under the similar loading conditions, the fuel consumption of petrol was

higher than that of LPG. In the absence of a load the flow of gasoline was

0.52 kg / hr and at a full load around 1kg / hr. Whereas in the situation of

LPG from (0 to 400) watts the fuel consumed was 0.55 and 0.62 kg per

hour respectively.The consumption of LPG fuel was 0.78 kg / hour ,at the

maximum load of 1.3 kW.

Choi et al.[25] estimated of combustion and emission characteristics

of the LPG fed by SIE was presented with some simple modifications in

standard SIE on LPG fuel with variable proportions of LPG ( 5%, 10%,

56 GHUFRAN TALIB HASHEM AND MOHAMED F. AL-DAWODY /AL-QADISIYAH JOURNAL FOR ENGINEERING SCIENCES 14 (2021) 054–0 16

20%) with assistance of the PLC control. Engine velocity is fixed at 4000

rpm, and the relative (air-to-fuel) ratio ranges ( 0.8 to 1.3). The five gases

analyzer was used to measure the exhaust gas components (CO2, CO, HC,

and NOx). it was also observed that the maximum CO2 emission at about

λ=1 and displays smaller fractions at rich and lean mixtures. Increase

percentage of LPG in petrol increases the speed of combustion of the

mixture significantly and thus reduces the combustion period and thus

increases the maximum temperature inside the cylinder. At a high fuel-to-

air ratio, The amount of measured nitrogen oxides was much higher, and

UHC showed a noticeable decrease as the relative fuel air ratio exceeded

stoichiometric.

Lee Hyung Ki et al. [26] investigated the combustion properties as

well as the flame spread of LPG and petrol through a laser diffraction

process and high-speed photographic technique in a fixed-size combustion

chamber. The researcher showed that as the initial temperature increased

and the primary pressure decreased, the flame spread velocity increased.

The equivalence ratio was quite specifically influenced by the flame

velocity, combustion pressure and therefore the time of combustion of the

fuel-air mixture. In addition, the comparison of the flame spread between

LPG and petrol showed that for the lean mixture, the flame spread of LPG

was faster than gasoline, whereas for the rich mixture, the flame speed of

petrol was faster than that of LPG.

Mistry C. S. and Gandhi A. H [4] modified the unoriginal multi-

cylinder water-cooled, vertical, SI engine to operate on LPG and gasoline

as dual fuel. Morse test was performed for modified motor under changing

loading conditions with changing speed. From the results of the Morse

test, it was noticed that the frictional force in case of using gasoline was

less compared to LPG. It had been noticed that in the case of gasoline the

thermal efficiency of the brake and the indicated thermal efficiency is

higher than that of LPG. Moreover, and the flame speed of LPG is less

than that of gasoline, thus spark timing should be developed to get the

best results Ignition condition for LPG.

Hakan B. and Orhan D.[7] developed a computer program to make

numerical calculations for the semi_dimensional SIE to guess

performance, cycle and exhaust emission of automobile engines in case of

the use of LPG as a replacement fuel under changed engine speed and

equivalence ratio of fuel and air, and the equations governing the study of

the mathematical model consisted mainly of ordinary differential

equations derived for temperature and cylinder pressure. The results of

simulation comparison showed that SI engines using LPG fuel showed a

significant improvement in the exhaust emission characteristics.

S. Murillo et al. [27] conducted an experimental study to determine

the performance and measurement of the emission index of the Si engine

liquefied petroleum gas. The results showed that with the use of LPG, the

specific fuel consumption decreases CO and CO2 emissions were much

lower. Without noticeable loss of energy but noticeable NOx emissions It

was high.

Radu B. et al.[28] investigative some knockdown characteristics by

focusing on the development of a simple Arrhenius type correlation to the

delay time of the strike was performed on a SIE for heavyweight vehicles

using commercial LPG based on experimental data for the crank angle of

the strike, pressure and simulation temperatures of un-burned gases.

Temperatures were computed in addition to subtracting some of the auto-

ignition characteristics of LPG in the engine, taking into account the heat

release rates due to auto-ignition, and they were compared with former

results of unmixed propane. Results showed a qualitative correlation

between the rate of heat release through the intensity of the blow and the

self-ignition reactions.

Ristovski Z.D. et al.[29] studied carbon dioxide emissions and

particulate matter at changed vehicle velocities (0 (passive), 40, 60, 80

and 100) km / hour . The study was conducted on five Ford Falcon Forte

(ULP) passenger cars and six custom passenger cars running on liquefied

petroleum gas. The results showed that in all operating methods, the

particle number emission factor using LPG was lower compared to ULP.

CMD in LPG condition was greater than unleaded petrol in all types

excepting in no-lood mode, where numerical analysis at 60 and 80 km / hr

showed significant differences. In addition, the CO2 emission factors for

ULP were greater than that of LPG, and at 100 km / h a statistically

significant difference was observed.

Ceviz M.A. and Yuksel F. [30] compared cyclical difference and

emissions of LPG with petrol fuel fired under poor operating conditions.

The testing was carried out on four (air,fuel) gasoline mixes and five

mixtures values for LPG. It was observed that a rise in the relative ratio

between air and fuel leads to an increase in the coefficient of variation in

the composition. However, the higher flame speed of LPG combined with

the good mixing of the gaseous fuel with the air leads to a decrease in the

periodic variations, and the higher H / C ratio of LPG reduces engine

emissions and thus LPG is a more convenience fuel in a light internal

combustion engine comparable with petrol.

Arslan O. et al. [31] attempted an experimental investigation on a SI

four-cylinder engine modified to operate with liquefied petroleum gas

(LPG) to study engine characteristics under cold weather conditions. It is

found that BSFC of LPG is higher than that of gasoline. While the carbon

dioxide concentration was decreasing with increasing engine speed in

both fuels, the decrease was higher for LPG, and the hydrocarbon

emissions were great at 1000 rpm, and with the increase in speed the HC

concentration decreased, In comparison with petrol, HC concentration for

LPG was found to be poor at all speeds. Lower hydrocarbons emission of

LPG is reported for all ranges of engine speed compared to gasoline. It

has been found that CO emissions on unloading and loading are reduced

at different engine speeds.

Gumus M.[32] had been investigatived the effect of difference in

volumetric efficiency on the emission characteristics of the SI engine with

the use of LPG in different proportions (25%, 50%, 75%, 100%),

experiments conducted at constant speed of 3800 rpm and with different

load (5, 30, 60 and 90) percent. Differences in brake thermal efficiency,

air-to-fuel ratio, bsfc, and exhaust gases were examined. Significantly

when using LPG, the volumetric efficiency is decreased. The air to fuel

ratio decreases as the level of LPG usage increases. Bsfc and Bsec are

reduced while preserving thermal efficiency. In terms of exhaust

emissions, positive results were obtained at all levels of LPG

consumption. When using 100 percent LPG for exhaust emissions, the

best results are obtained.

Salhab Z. et. al. [33] studied of 4-stroke SI outboard engine powered

by LPG. It is modified to run on alternative fuel and on gasoline. Two

different operating methods have been developed with LPG; The first is

by using the vacuum produced by the engine, which provides a stable

mixture to the engine's carburetion, while the second method was

implemented using fuel injection (LPG). The results showed that Low

engine brake power, specific brake fuel consumption. The results show

that with the use of injected LPG; The brake power, engine torque and

specific fuel consumption of the brakes were lower compared to gasoline,

while the vacuum system was higher excluding brake force. The

emissions of CO, CO2 and NOx were lowered in the LPG mode

compared to the petrol mode while the HC emissions were High.

Shankar K. S, Mohanan P [34] studied the performance of four-

cylinder petrol engine. The engine was modified to operate with LPG

57 GHUFRAN TALIB HASHEM AND MOHAMED F. AL-DAWODY /AL-QADISIYAH JOURNAL FOR ENGINEERING SCIENCES 14 (2021) 054–0 16

injection. The experimental study is conducted on variable motor speed

adjustment at 5 ° BTDC then advance and delay timing to 6° BTDC, 4°

and 3° BTDC respectively. The results showed lower thermal efficiency

indicated at low engine speed and 5 degrees BTDC for LPG but beyond

3,500 rpm higher efficiency for LPG detected compared to gasoline.

Reduced CO2 and HC emissions with LPG. While there was an increase

in nitrogen oxide emissions of LPG at 4,500 rpm. When the ignition

timing is brought up to 6 ° BTDC, the efficiency is high at low engine

speed and when delayed to 4 ° and 3 ° BTDC results in an increased

specified power consumption. emissions of 6 ° BTDC, HC and CO are

found to be lower for LPG. Delayed time of ignition caused incomplete

combustion and consequently high CO emission at 6 ° BTDC and lower at

3 ° and 4 ° BTDC.

Hwang I G. et al. [35] compared the combustion phenomena as well as

the emission characteristics of nanoparticles from the spark ignition

engine by direct wall-directed injection (DI) of liquefied petroleum gas

(LPG) and benzene. The Gasoline Direct Injection (GDI) fuel supply

system has been modified for the liquid-type LPG injection fuel supply

system. To confirm the clean combustion properties of the LPG DI

engine, emissions and concentrations of nanoparticles for an LPG-

powered engine were compared with those of the petrol engine. The

results showed that the emissions of nanoparticles and exhaust of the LPG

DI engine were significantly lower than those of the GDI engine.

Combustion performance at full LPG loading was similar to that of

gasoline fuel.

Masi Massimo [36] took into their considerations the following

factors: brake performance comparison for a SI 4-stroke , five-cylinder

engine feeding with LPG in addition to petrol. The engine is converted by

the standard third-generation kit to dual fuel operation. The kit is an

injection system. The fuel is electronically multi-port and serial delivers

LPG in the gaseous state to the upstream intake holes of the gasoline

injector. The results showed that the engine brake force was more in the

petrol mode for the same test conditions. In addition, the operating

performance of LPG decreased due to lack of LPG feeding in the

combustor.

Erkus B. et al.[37] reported the impact of multi-phase LPG injection

system on the performance of SI engine was investigated. Experiments

were conducted at engine speeds of 2000-4000 rpm. A stable throttle

position of (25-50) percent of the fully open position were performed

experiments. To compare the performance of mixing systems and

different fuels, LPG with gasoline and carbon LPG. The results showed a

higher brake force achieved for LPG injection system compared to

gasoline and LPG carbonate. The volumetric efficiency also presented an

perfection in the LPG injection system compared to the carbonization

systems at each throttle position. Both modes of throttle have lower BSFC

with the LPG injection system except 2500 rpm it raised by 25percent.

Sulaiman M.Y. et al. [38] analyzed engine speed and torque under

WOT (wide open throttle) of an SI LPG powered SI engine with a global

dynamometer. Tests were conducted with an air-cooled four-stroke spark-

ignition engine. The test was conducted in three modes. The first mode is

ULP fuel system, the second is LPG evaporator (LPG V) and the third is

the LPG capsule valve (LPG B). The results showed that the SFC and the

energy produced from Mode II LPG V and Mode III LPG B are lower

than that of ULP.

Çinar C. et al. [39] performed a comparative study of the performance

and emissions of the SI engine powered by LPG and unleaded gasoline.

The engine was modified to run on LPG. The results showed a decrease in

engine torque and power and an increase in BSFC when the engine was

running Converted to LPG fuel and a 7mm valve lift. Additionally,

improvements to CO and HC emissions were observed with LPG fuels

while emissions of nitrogen oxides rise. Also, improvements are on

engine performance results depending on the increased quantity of

mixture taken in A cylinder with LPG .

Chaichan M. T. et al.[12] conducted a practical study using 2-types of

gaseous fuel (NG, LPG) with single cylinder SI-engine with compression

ratio variable, velocity and spark timing. Ricardo E6 / USA then

comparing its performance with gasoline engine. Results It appears that a

greater useful compression ratio for gasoline, LPG and natural gas are

(8/1), (10.5/1) and (13/1) respectively. The findings showed that when

using NG, spark timing was more advanced than other fuels, due to

decreased flame spread in the combustion chamber. The findings showed

that the consumption of fuel was determined on a mass basis for LPG,

which was lower than gasoline and higher than natural gas. It was also

found that the temperature of the exhaust gas of LPG is lower than

gasoline and more expensive than natural gas.

Bielaczyc Piotr et al. [40] tested two SI vehicles. The vehicles were

adapted by the manufacturers of binary fuels Gasoline and gaseous fuels.

The first vehicle works with (liquefied petroleum gas and gasoline) and

the other works with (compressed natural gas and benzene). The

emissions of THC, NOx , CO and CO2 were analyzed. using special

additional equipment installed on the existing gasoline refueling system.

Cars in this test feature multi-point gas injection systems. The objective of

the work is an analysis of the effect of gaseous fuels on exhaust emissions

on the emissions comparison of gasoline-powered vehicles. The

researcher noticed that emissions of carbon dioxide and THC increased in

CNG fuel vehicles while emissions of nitrogen oxides were lower

compared to gasoline. In vehicles running on LPG fuel, CO emissions

were much lower than gasoline and THC emissions were similar to

gasoline but nitrogen oxides emissions were higher compared to gasoline,

however, CO2 emissions were reduced for both LPG and compressed

natural gas vehicles.

Suyabodha A.[41] considered the use of LPG and Gasoline 95 as

substitute fuel in petrol engines in continuous and fast driving conditions.

The results of the study showed that the best fuel consumption at an

average speed of 100 km / h. The difference in energy consumption is due

to LPG properties which is compared to gasoline 95 has a higher flame

intensity. The injection of LPG resulted in a successful preparation of the

mixture. Hence, the pressure in the combustion chamber increased,

resulting in greater output power than the 95th gasoline under partial load

conditions.

Tukiman M. M. et al.[42] studied and investigated of the performance

and emissions of the petrol engine when LPG substitutes gasoline in

addition to determining the effect of the LPG system in the liquid state.

The engine was modified by adding a multi-port injection system (MPI) to

deliver fuel to the engine in addition to installing a near-intake valve with

a sequential injection system Liquid LPG (LSI) without affecting the

gasoline injector. The performance result showed with LPG increased

efficiency, power and decreased BSFC. The exhaust emission of CO, HC

and NOX increased compared to gasoline.

Mustaffa N. et al.[43] studied the combustion, performance and

emissions characteristics of a four-stroke spark ignition engine using LPG

as an alternative fuel and compare the results with unleaded gasoline

(ULP). The experiments were conducted at a constant speed of 3000 r.p.m

at various load conditions. The results of the combustion analysis showed

that LPG had a higher pressure inside the cylinder and a higher pressure

rate compared to ULP. The heat release rate (ROHR) of LPG had

increased before ULP. The results showed that brake effective pressure

(BMEP) and torque were higher for LPG compared to ULP. And that

58 GHUFRAN TALIB HASHEM AND MOHAMED F. AL-DAWODY /AL-QADISIYAH JOURNAL FOR ENGINEERING SCIENCES 14 (2021) 054–0 16

Brake Specific Fuel Consumption (BSFC) for LPG injection is lower as

compared to ULP. Meanwhile, emissions of carbon monoxide (CO),

nitrogen oxides (NOx) and hydrocarbon (HC) for LPG recorded higher.

Usman Muhammad and Hayat Nasir [44] studied the performance and

emissions in addition to the deterioration of lubricant oil for 125 cc

motorcycle engines running on liquefied petroleum gas and gasoline. The

result showed a deterioration of the lubricant oil when operating the

motorcycle for both types of fuels. Also, the brake force, torque and

maximum speed of the LPG-powered motorcycle were lower compared

With gasoline and lower emissions from LPG compared to gasoline.

Mohammed H.A. and Abdulhaleem S.M.[46] studied the effect of

adding LPG fuel in different proportions with naphtha or gasoline on

engine performance and pollutant emissions. Experiments were conducted

on the spark ignition engine under different load conditions, constant CR

(6: 1) and different mixing ratios (10-25)%. The results showed that

mixing LPG improves the thermal efficiency of the brakes and the

specific fuel consumption of the brakes and reduces carbon monoxide,

carbon dioxide and nitrogen oxides, but it increases the concentration of

hydrocarbons.

Table 3: Summary of researchers contributions of LPG

Mustafa K. F. and Gitano-Briggs H.W.[47] performed an experimental

study to measure exhaust emissions from a four-stroke spark ignition

engine modified to run with both LPG and gasoline. Experiments were

done at different mixing ratios (5%, 10% and 20%) at a constant speed of

4000 rpm. It has been found that by increasing the proportion of LPG in

gasoline, the level of carbon dioxide (CO2) reaches a peak at a relative air

fuel ratio of 1.0, and that carbon monoxide (CO) shows a sharp decrease

with the increase in the relative proportion of air fuel. The unburned

hydrocarbons (UHC) also show a marked decrease as the relative air-fuel

ratio exceeds the stoichiometric measures and nitrogen oxides (NOx)

show an increasing trend as the air-to-fuel relative ratio increases.

Researcher name Experimental Fuels Results Summary

[23] Dr. Md.

Ehsan2001

Gasoline and LPG which

consists of Propane 85%

min. Propylene 5% max.

Butane and heavier HC

2.5% max Sulphur 120

ppm max

Better mixing and combustion, lower fuel consumption and improved emission

characteristics. The power output decreased. More economical than gasoline

[24] G. Choi

2002

LPG was approximately

mixture of 95% butane and

5% propane

using fuel LPG 100%

propane

The power output of LPG system with liquid-phase is approximately 17% higher

than that of vapor -phase Mixer. CR is increased, power output is decreased &

maximum cylinder pressure decreased

[25] K.H. Lee

2002
LPG and gasoline

The maximum flame propagation speed appeared at the stoichiometric equivalence

ratio condition (Ø=1.0) for LPG, but at equivalence ratio of 1.1 for gasoline, the

flame speed of LPG is faster than that of gasoline at the range of lean or

stoichiometric equivalence ratios. However at the range of rich equivalence ratio

conditions, the speed of flame propagation for the gasoline was superior to that of

LPG.

[4] C.S. Mistry

2004

Dual fuel mode LPG and

petrol

Brake thermal and indicated thermal efficiencies were higher for petrol .Fuel

consumption was higher in the case of LPG. Friction power was higher in the case of

LPG.

[7] Hakan B.

2005

1- LPG is considered to

consist of only propane.

Decrements of about 3–4% in engine power output

and volumetric efficiency computed for the LPG fueled engine are lower than those

for gasoline. LPG increases the specific fuel consumption of the engine.

[26] S. Murillo

2005 Gasoline and LPG Reduction in power outboard engine, fuel consumption and pollutant emission

[27] Radu B 2005

Commercial LPG, (83-

87 ) % propane, (9-15) %

alkenes,

It was proved that reactions leading to auto ignition in the case of LPG proceed via

chemical kinetics with cool flames. A qualitative correlation between the rate of heat

release by auto ignition reactions and knock intensity is apparent.

[28] Z. Ristovski

2005
2- ULP and LPG

LPG was found to be the cleaner fuel with respect to both particle and carbon dioxide

emissions

59 GHUFRAN TALIB HASHEM AND MOHAMED F. AL-DAWODY /AL-QADISIYAH JOURNAL FOR ENGINEERING SCIENCES 14 (2021) 054–0 16

[29] M. Ceviz 2006 Gasoline and LPG

3- Relative air–fuel ratio increases. CO emissions decreases, and there is no

serious change over the lean burn operating condition. CO2 emission

decreased with lower C number of fuel (LPG) and leaner mixture

[30] O. Arslan 2010

Leaded gasoline C8H18

LPG (30% C3H8 +,70%

C4H10)

Without mixer CO &CO2 emission has been reduced with mixer the specific

fuel consumption increases. As a result of this increasing, the emissions t are

relatively higher in comparison of the gasoline usage

[31] M. Gumus 2011

gasoline and LPG fuel is

composed of (50% C3H8

and 50% C4H10)

The volumetric effi. was shown a decrease depending on the LPG usage. A/F

decreases with the increase in LPG usage level and the minimum A/F value

was obtained at 100% LPG usage. With the use of mixture containing 25%

LPG, BSFC and BSEC decreased while the BTE was maintained. Best results

in terms of exhaust emissions were achieved at using 100% LPG.

[32] Z. Salhab 2011 Gasoline and LPG It was concluded that using LPG instead of conventional gasoline results in

reduced engine brake power, pollutant emissions and specific brake fuel

consumption, with energy loss (7%).

[33] K. Shankar 2011 4- Gasoline and LPG

The advanced ignition timing when using LPG has resulted in reduced

emissions of CO and HC. But it shows an increase in NOx emissions. and gives

better thermal efficiency

[34] I. Hwang 2012

Gasoline and LPG of ( n-

butane 46.4 % i-butane

29.9 % and propane 23% )

The particle emission levels of the LPG DI engine were lower than those of

the GDI engine by one order of magnitude. The engine-out HC emission levels

decreased, but the NOx concentration increased

[35] M. Masi 2012
gasoline and dual-fuel

operation petrol and LPG

Performance deterioration in LPG operation due to deterioration in Volumetric

efficiency and insufficient fuel delivery.

[36] B. Erkuş 2013

Gasoline and LPG

Engine has higher power outputs. Less fuel consumption. Lower exhaust

emissions.

[37] M. Sulaiman

2013

Unleaded petrol and LPG

( 40 % propane and 60 %

butane)

Slight power output reduction, due to the lower volumetric efficiencies and

unaltered ignition timing of the engine. LPG consume less fuel. LPG has

better energy price as compared to the conventional fuel, which is ULP

[38] C.Çinar 2016
Dual fuel (Gasoline and

LPG)

Torque and power decreased and BSFC increased when the engine was

converted to LPG. HC and CO emissions decrease were observed with LPG

fuel while NOx emissions increased. Improvements on the engine

performance results

[40] P. Bielaczyc

2016
Gasoline , LPG and CNG

In CNG fuelled vehicle CO and HC emissions were increased in while NOx

emissions lower in comparison to petrol. In case of LPG fuelled vehicles HC

emissions were similar to petrol and CO lower but NOx higher, However, the

CO2 emissions were decreased for both LPG and CNG operated vehicle

[41] A. Suyabodha

2017

Gasoline 95 Stoichiometric

ratio 14.7 :1, Phase of

injection liquid O.N 80-95

LPG Stoichiometric ratio

15.6:1, Phase of injection

vapour, O.N 106-111

The energy consumption rate of LPG was less than using Gasoline95 under

constant speed test although the vehicle consumed LPG slightly higher than

Gasoline95. The engine power was generated more than LPG under full throttle

position.

[42] M.M. Tukiman

2018

LPG (60% C4H10 +

40%C3H8)

The LPG liquid phase was improved BT and BP compared with gasoline

fuel. Variation of exhaust emission from CO has significantly reduced &

Emission exhaust HC emitted from LPG is higher than gasoline as the

engine speed increased. The concentrations of NOx emission for LPG are

higher compared to gasoline. BSFC improvement when using LPG at low

speed engine

[43] N. Mustaffa 2019 Petrol and LPG

Engine torque and BMEP as compared with ULP and BSFC significantly

improved. average NOx, HC and CO emissions were higher for liquid LPG as

compared with the ULP.

[44] M. Usman 2020
Petrol and LPG (Propane

95 , % Butane 5%)

Reduced maximum speed, torque and power. LPG produced lower HC ,CO

,CO2 and NOx emissions comparison to petrol, lower. Flash point and ash

contents decreased for petrol whereas the same for LPG.

60 GHUFRAN TALIB HASHEM AND MOHAMED F. AL-DAWODY /AL-QADISIYAH JOURNAL FOR ENGINEERING SCIENCES 14 (2021) 054–0 16

5. Summary/ Conclusions

This paper offers a review of the researchers’ works conducted on the

use of petrol engines powered by LPG. It has been found that the most

effective way to eliminate the problem of fossil fuel scarcity and exhaust

emissions is the dual fuel process. The performance, combustion and

emission characteristics of engines running on LPG fuel as an alternative

fuel to gasoline reviewed extensively. Studies have indicated that

performance, combustion and emission properties can be improved by

improving compression ratio, ignition timing, engine speed, loading

status, test fuel supply, injection timing, and inlet manifold condition.

Based on current study the next conclusions are summarized below:

1. The use of LPG in the SI system can be exchanged instantly from

LPG to petrol fuel and no much cost is required.

2. Feeding SI engine with LPG improved combustion characteristics,

reduced emissions and fuel consumption.

3. Since the entry of LPG into the combustion chamber in the gaseous

state, this causes air and LPG to form a homogeneous mixture of

fats. It significantly reduces NOx emissions.

4. Fuel consumption for braking is lower for LPG-using engine

compared to conventional fuel under same loading conditions.

5. LPG has a high calorific value, which leads to the increase of the

fuel burning rate and the shortening of the combustion time, thus

the fuel consumption specified for the brakes is reduced.

6. LPG can be used with higher compression ratios and lower

thumping level, thus enhancing engine efficiency.

7. LPG engines have higher cylinder temperature and pressure

compared to conventional fuels.

REFERENCES

[1] S. Chung, J. Yeom, J. Yoon, S.J.J.o.M.S. Hwang, Technology, An

experimental study on spray and combustion characteristics of LPG for

application in direct-injection, 30(5) (2016) 2343-2351.

[2] S. Lee, S. Oh, Y.J.F. Choi, Performance and emission characteristics of an

SI engine operated with DME blended LPG fuel, 88(6) (2009) 1009-1015.

[3] M.J.T.I.J.f.M. Chaichan, M. Engineering, Study of NOx and CO emissions

for SIE fueled with Supplementary methane to LPG, 6(2) (2006) 85-97.

[4] C.S. Mistry, A.H. Gandhi, Experimental Investigation on Multi-cylinder

Engine Using Petrol and LPG as A Fuel, SAE Technical Paper, 2004.

[5] H. Bayraktar, O. Durgun, Theoretical investigation of using ethanol–

gasoline blends on SI engine combustion and performance, 10th

International Conference on Thermal Engineering and Thermogrammetry,

1997, pp. 240-249.

[6] R.J.S.t. Thring, Alternative fuels for spark-ignition engines, (1983) 715-

725.

[7] H. Bayraktar, O.J.E.c. Durgun, management, Investigating the effects of

LPG on spark ignition engine combustion and performance, 46(13-14)

(2005) 2317-2333.

[8] H.S. Kim, V.K. Arghode, A.K.J.I.j.o.h.e. Gupta, Combustion characteristics

of a lean premixed LPG–air combustor, 34(2) (2009) 1045-1053.

[9] A. J. S. Fuels and Reports, "Expert Group Report."

[10] A.A. Taha, T. Abdel-Salam, M. Vellakal, ALTERNATIVE FUELS FOR

INTERNAL COMBUSTION ENGINES: AN OVERVIEW OF THE

CURRENT RESEARCH (2013).

[11] T. Zhang, Possibilities of Alternative Vehicle Fuels: a literature review,

2015.

[12] M.T. Chaichan, J.A. Kadhum, K.S.J.e. Riza, Spark Ignition Engine

Performance When Fueled with NG, LPG and Gasolin, 12 (2016) 59.

[13] M.H.B. Bisen, M.Y.J.I.J.O.M.E.R. Suple, Experimental Investigations of

Exhaust Emissions of four Stroke SI Engine by using direct injection of

LPG and its analysis, 3 (2013).

[14] K. Lee, J.J.F. Ryu, An experimental study of the flame propagation and

combustion characteristics of LPG fuel, 84(9) (2005) 1116-1127.

[15] M.T.J.I.J.o.E.R. Chaichan, Development, Measurements of laminar

burning velocities and Markstein length for LPG–hydrogen–air mixtures,

9(3) (2013) 1-9.

[16] R. Saraf, S. Thipse, P.J.I.J.o.C. Saxena, E. Engineering, Comparative

emission analysis of gasoline/LPG automotive bifuel engine, 1(4) (2009)

199-202.

[17] E. Elnajjar, M.Y. Selim, M.O.J.E.c. Hamdan, Management, Experimental

study of dual fuel engine performance using variable LPG composition

and engine parameters, 76 (2013) 32-42.

[18] A.H. Pundkar, S. Lawankar, S.J.r. Deshmukh, Performance and emissions

of LPG fueled internal combustion engine: a review, 14(14.7) (2012) 15.5.

[19] M.T.J.S.J.f.E.S. Chaichan, Evaluation of the effect of cooled EGR on

knock of SI engine fueled with alternative gaseous fuels, 1(1) (2014) 7-17.

[20]H.A. Mohammed, S.M.J.B.o.t.F.o.E.M.U.Abdulhaleem, Experimental

Study of Spark Ignition Engine Operated with Naphtha or Gasoline

Blended LPG Fuel, 41(2) (2020) 9-17.

[21] N.M. Jothi, G. Nagarajan, S.J.I.J.o.T.S. Renganarayanan, LPG fueled

diesel engine using diethyl ether with exhaust gas recirculation, 47(4)

(2008) 450-457.

[22] T. Mamidi, J.J.I.J.o.E.R. Suryawnshi, Applications, Investigations on SI

engine using liquefied petroleum gas (LPG) as an alternative fuel, (2012)

362-367.

[23] A. Huzayyin, H. Moneib, M. Shehatta, A.J.F. Attia, Laminar burning

velocity and explosion index of LPG–air and propane–air mixtures, 87(1)

(2008) 39-57.

[24] M. Ehsan, S.Z. Rahman, K.M. Javed, M.M. Mahboob, Performance of a

LPG run SI engine for small scale power generation, Proc., 4th

International Conference on Mechanical Engineering, pp. 97-102.

[25] G. Choi, J. Kim, C. Homeyer, Effects of different LPG fuel systems on

performances of variable compression ratio single cylinder engine,

Internal Combustion Engine Division Fall Technical Conference, 2002,

pp. 369-375.

[26] K.H. Lee, C.S. Lee, J.D. Ryu, G.-M.J.K.I.J. Choi, Analysis of combustion

and flame propagation characteristics of LPG and gasoline fuels by Laser

Deflection Method, 16(7) (2002) 935-941.

[27] S. Murillo, J. Míguez, J. Porteiro, L.L. González, E. Granada, J.J.A.t.e.

Morán, LPG: Pollutant emission and performance enhancement for spark-

ignition four strokes outboard engines, 25(13) (2005) 1882-1893.

[28] B. Radu, G. Martin, R. Chiriac, N. Apostolescu, On the Knock

Characteristics of LPG in a Spark Ignition Engine, SAE Technical Paper,

2005.

[29] Z. Ristovski, E. Jayaratne, L. Morawska, G.A. Ayoko, M.J.S.o.t.T.E. Lim,

Particle and carbon dioxide emissions from passenger vehicles operating

on unleaded petrol and LPG fuel, 345(1-3) (2005) 93-98.

[30] M. Ceviz, F.J.R.E. Yüksel, Cyclic variations on LPG and gasoline-fuelled

lean burn SI engine, 31(12) (2006) 1950-1960.

[31] O. Arslan, R. Kose, N.J.E.S. Ceylan, Part A: Recovery, Utilization,, E.

Effects, Experimental analysis of consumption and exhaust emissions of

gasoline and LPG in car engines under cold climatic conditions, 33(3)

(2010) 244-253.

61 GHUFRAN TALIB HASHEM AND MOHAMED F. AL-DAWODY /AL-QADISIYAH JOURNAL FOR ENGINEERING SCIENCES 14 (2021) 054–0 16

[32] M.J.F.P.T. Gumus, Effects of volumetric efficiency on the performance

and emissions characteristics of a dual fueled (gasoline and LPG) spark

ignition engine, 92(10) (2011) 1862-1867.

[33] Z. Salhab, M.G. Qawasmi, H. Amro, M. Zalloum, M.S. Qawasmi,

N.J.J.J.o.M. Sharawi, I. Engineering, Comparative performance and

emission properties of spark-ignition outboard engine powered by

gasoline and LPG, 5(1) (2011) 47-52.

[34] K. Shankar, P.J.I.j.o.E. Mohanan, Environment, MPFI gasoline engine

combustion, performance and emission characteristics with LPG injection,

2(4) (2011) 761-770.

[35] I. Hwang, K. Choi, J. Kim, C. Myung, S.J.P.o.t.I.o.M.E. Park, Part D:

Journal of Automobile Engineering, Experimental evaluation of

combustion phenomena in and nanoparticle emissions from a side-

mounted direct-injection engine with gasoline and liquid-phase liquefied

petroleum gas fuel, 226(1) (2012) 112-122.

[36] M.J.E. Masi, Experimental analysis on a spark ignition petrol engine

fuelled with LPG (liquefied petroleum gas), 41(1) (2012) 252-260.

[37] B. Erkuş, A. Sürmen, M.I.J.F. Karamangil, A comparative study of

carburation and injection fuel supply methods in an LPG-fuelled SI

engine, 107 (2013) 511-517.

[38] M. Sulaiman, M.R. Ayob, I.J.P.E. Meran, Performance of single cylinder

spark ignition engine fueled by LPG, 53 (2013) 579-585.

[39] C. Çinar, F. Şahin, Ö. Can, A.J.A.T.E. Uyumaz, A comparison of

performance and exhaust emissions with different valve lift profiles

between gasoline and LPG fuels in a SI engine, 107 (2016) 1261-1268.

[40] P. Bielaczyc, A. Szczotka, J. Woodburn, A comparison of exhaust

emissions from vehicles fuelled with petrol, LPG and CNG, IOP

Conference Series: Materials Science and Engineering, IOP Publishing,

2016, p. 012060.

[41] A.J.E.P. Suyabodha, Comparison the rate of energy consumption between

gasoline95 and LPG in spark ignition engine under real driving conditions,

118 (2017) 164-171.

[42] M.M. Tukiman, S.A. Osman, M. Fawzi, N. Mustaffa, R.H.J.I.J.o.I.E.

Madon, Effect of Performance and Exhaust Emission using Liquid Phase

LPG Sequential Injection as an Alternative Fuel in Spark Ignition Engine,

10(8) (2018).

[43] N. Mustaffa, M. Fawzi, S.A. Osman, M.M. Tukiman, Experimental

analysis of liquid LPG injection on the combustion, performance and

emissions in a spark ignition engine, IOP Conference Series: Materials

Science and Engineering, IOP Publishing, 2019, p. 012033.

[44] M. Usman, N.J.J.o.t.C.I.o.E. Hayat, Lubrication, emissions, and

performance analyses of LPG and petrol in a motorbike engine: a

comparative study, 43(1) (2020) 47-57.

[45] T.J.R.C.a.D.M.a.T.F. 2020, State of the Art on Alternative Fuels

Transport Systems in the European Union (2020).

[46] S.M. Abdulhaleem, H.A. Mohammed, Experimental Investigation of a

Four Stroke Spark Ignition Engine Operated with Naphtha or Gasoline

Blended LPG, Applied Mechanics and Materials, Trans Tech Publ, 2016,

pp. 272-277.

[47]K. Mustafa, H. Gitano-Briggs, Effect of variation in liquefied petroleum

gas (LPG) proportions in spark ignition engine emissions, International

conference on environment, 2008.