Experimental Combustion Emission Characteristics of ... · Duel fuel engine, HCCI, PCCI, RCCI engines are some best of the modified engines using alternate fuel with the conventional

Experimental Combustion Emission

Characteristics of Premixed Charged

Compression Ignition Engine 1V. Pugalendhi,

2K. Annamalai,

3S. Lingesan and

4Krishnan

1Department of Mechanical Engineering,

Tagore Engineering College,

Chennai.

[email protected] 2Department of Automobile Engineering,

MIT Campus,

Chennai.


MIT Campus, Chennai.


MIT Campus, Chennai.

Abstract Premixed Charge Compression Ignition (PCCI) is the solution for

efficient diesel combustion. Ethanol blended fuel is premixed with the air,

vaporized using the exhaust gas to increase its temperature before entry

into the combustion chamber . Therefore the reduction of temperature

sensitive oxide emission, increased mechanical energy conversion, reduced

specific energy consumption resulted from preheated ethanol. Also there

will be reduction in exhaust temperature because of preheating using

exhaust gas.Thus the performance and emission characteristics of the

preheated ethanol blend fuel PCCI direct injection diesel engine has been

compared with the conventional diesel engine and found that this as

perfect alternative.

International Journal of Pure and Applied MathematicsVolume 119 No. 12 2018, 2961-2973ISSN: 1314-3395 (on-line version)url: http://www.ijpam.euSpecial Issue ijpam.eu

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Key Words: PCCI Engine; Ethanol fuel; Preheat; Vapourizing.

International Journal of Pure and Applied Mathematics Special Issue

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1. Introduction

In this century, it is believed that crude oil and petroleum will become very

scarce and costly in the near future. Day to day, fuel economy of engines is

getting improved and will continue to improve. However, enormous increase in

number of vehicles has dictating the demand for fuel. With increased use and

the depletion of fossil fuel, alternative fuel technology will become very

common is the coming decades.

All these years there have always been some IC engines filled with non-gasoline

or diesel oil fuels. Because of the high cost of petroleum products, some

developing countries are trying to use alternate fuels for their vehicles.

However, their numbers have been relatively very small.

Another reason motivating the development of alternate fuels for the IC engine

is the concern over the emission problems of gasoline and diesel engines

combined with other air polluting systems, the large number of automobiles is a

major contributor to the air quality problem of the world. Quite a lot of

improvements have been made in reducing emissions from automobile engines.

Government bodies aremaking stringent mandates to reducing the polluting

emissions and they are constantly constricting the polluting emission level.

Further, it also closely scrutinizes the engine makers to follow up the emission

standards. But, if a 35% improvement made over period of years, it is to be

noted that during the same time the number of automobiles in the world

increases by 40% thereby nullifying the improvement. Lot of efforts has gone

into for achieving the net improvement in cleaning up automobile exhaust.

However, more improvements are needed to bring down the ever increasing air

pollution due to automobile population.

A Third reason for alternate fuel development is the fact that a large percentage

crude oil must be imported from other countries which control the larger oil

fields. Notably, India ranks top in the highest crude oil importing nations. As of

now many alternate fuels have been used in limited quantities in automobiles.

The above reasons paves way for the compulsion in development of in alternate

for the gasoline and diesel fuels.

The engines used for alternate fuels are modified engines which were originally

designed for gasoline or diesel fuelling. They are, therefore, not the optimum

design for the other fuels. Only when extensive research and development is

done over a period of years, maximum performance and efficiency can be

realized from those engines. However, the research and development is difficult

to justify until the fuels are accepted as variable for large number of engines.

On the other hand, the gasoline and diesel fuelled engines in use have crossed

huge numbers where if an perfect alternate fuel has been placed, a large amount

of money has to be spent to fine tune the exiting diesel engine tom work with

new alternative.Else, the old engine has to be replaced with a new one.Both the


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options will cost much where this too makes an obstacle for taking an alternate

fuel. So a perfect solution for the above problem is reduce the diesel fuel

consumption without making any modifications in the engine.

Duel fuel engine, HCCI, PCCI, RCCI engines are some best of the modified

engines using alternate fuel with the conventional fuel. On the abovementioned

engines PCCI engine serves good with less modifications it has its own

disadvantages.

Similarly in the alternate fuels ethanol, methanol, CNG, LPG, Bio-diesel and

vegetable oils are some good and extensively using alternate fuels. Out of them

ethanol, methanol and CNG has the highest availability and can be made as on

alternative for the conventional fuels.

Our objective is to reduce the diesel fuel consumption without compromising its

performance characteristics and reduced and polluting emissions by adding an

alternate fuel with the conventional fuel without any engine modification we

studied many textbooks and done through a large number of literature studies on

alternate fuels and engine modifications at lastwe found ethanol to be best

alternative and in PCCI engine.

But the problem of using ethanol in diesel engine is the auto ignition

temperature which is higher for ethanol then diesel so, ethanol is heated to

vapour state before mixing it with air by using the exhaust gas. Since the heat in

the exhaust gas is usually wasted, we use the waste heat in exhaust gas to

vaporise ethanol. Various ratios of ethanol and diesel is used in the PCCI DI

diesel engine and its performance and emission characteristics are compared

with the conventional diesel engine.

2. Literature Survey

1. Valentina Fraioli et al

IstitutoMotori – CNR, Napoli, Italy

ETHANOL EFFECT AS PREMIXED FUEL IN DUAL-FUEL CI

ENGINES: EXPERIMENTAL AND NUMERICAL INVESTIGATIONS

The results of two research activities are reported and compared: tests on an

optical single cylinder research engine and numerical simulations, so achieving

a combined approach to the study of dual-fuel configuration. Optical

diagnostics has been applied in a transparent direct injection diesel engine

equipped with the head of a Euro5 commercial engine and the latest generation

common rail injection system. Pure ethanol is injected in the intake manifold,

while n-heptane is directly injected in the cylinder. UV digital imaging is

applied to the optical engine allowing to detect crucial chemical intermediates,

like OH, HCO, and CO, in terms of their spatial distribution and temporal


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evolution. This analysis allows to identify in-cylinder zones with high reactivity

of mixed fuels and to investigate the effect of the presence of ethanol on the

burning dynamics of the directly injected fuel.

2. Abhishek Paul et al

Department of Mechanical Engineering, National Institute of Technology,

Agartala 799055, India

AN EXPERIMENTAL INVESTIGATION OF PERFORMANCE-

EMISSION TRADE OFF OF A CI ENGINE FUELED BY DIESEL-

COMPRESSED NATURAL GAS (CNG) COMBINATION AND DIESEL

ETHANOL BLENDS WITH CNG ENRICHMENT

The potential of diesel ethanol blending and subsequent CNG (compressed

natural gas) enrichment have been investigated. The study starts with a

miscibility test of ethanol in diesel, which paves the way for an experimental

comparison between performance and emission characteristics of Diesel-

Ethanol blends, Diesel-CNG combinations and Diesel-Ethanol blends with

CNG enrichment. The results indicates that diesel ethanol blend D95E5 (95%

diesel 5% ethanol) with low CNG enrichment produces a better performance-

emission characteristics as compared to base diesel operation as well as diesel-

ethanol blend operation. Results also portrayed ethanol’s potential in reducing

NOx emission, BSEC and smoke opacity.

3. Methodology

The research was based on a single cylinder, fourstroke, air cooled, constant

speed direct injection diesel engine developing 4.4 Kw t aconstant speed of

1500 rpm. This experiment consists of two fuel tanks. One contains diesel fuel

and the another one is for secondary fuel.Before mixing the ethanol with air it is

preheated to vapor state using the exhaust gas. Then the vaporized ethanol flows

through a flow controller which regulates the amount of ethanol into the engine.

The vaporized ethanol is mixed with the use of carburetor. It reduces the

consumption of diesel fuel and makes complete combustion. An AVL 365c

angle decoder test rig is mounted on the cam shaft of the engine for obtaining

various results during engine operation. AVL 415 smoke meter is used to

measure the smoke opacity. A gas analyzer is used to determine the gas

composition. A counter flow heat exchanger is used to exchange heat from

exhaust gas to ethanol fuel. Fig 1 shows the construction of the experimental

setup. Table 1 contains the specifications of the test engine and table 2 shows

the properties of diesel and ethanol fuel.


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Figure 1 Block Diagram of experimental setup

Table 1 Technical specifications of the test engine

Engine type Four stroke diesel engine

Fuel used Diesel

Bore 87.5 mm

Stroke 110 mm

Swept volume 661.5 cc

Injection timing 230bTDC

Nozzle opening pressure 220 bar

Rated output 4.4 kW

Rated speed 1500 rpm

Compression ratio 17.5 : 1

Cooling system Air

Table 2 Properties of Diesel and Ethanol fuel

Fuel properties Diesel Ethanol

Density (g/cm3) 0.82 0.7863

Boiling point( oc) 240-360 79

L.H. of vaporization (MJ/kg) 0.256 0.839

Auto ignition temperature ( oc) 260 423

Calorific value (MJ/kg) 44.9 29.8

Cetane number 40-60 8

Stoichiometric air fuel ratio 14.5 8.97

4. Result

In this work, the combustion characteristic such as Pressure with respect to

crank angle of preheatedethanol fuel is compared with the baseline

directinjection diesel combustion. Similarly the performance characteristicssuch

as brake thermal efficiency and brake specificenergy consumption and emission


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characteristics such as oxides of nitrogen and smoke emissions were

comparedwith baseline diesel fuel. The result of this exhaustive researchhas

brought out the significance of dual fuel to the emergingneeds of complete

combustion.

COMBUSTION CHARACTERISTICS Pressure vs. crank angle

The variation of cylinder pressure with the crank angle diagramis shown in Fig.

2. It is observed that the preheatedethanol fuel exhibits a higher cylinder

pressure compared to that of baseline diesel fuel. The maximum peak pressure

of 68.85bar and68.2 bar occurs at 70and 8

0aTDC for preheated ethanol and neat

diesel fuel. The cylinder peak pressure andmaximum rate of pressure rise for

preheated ethanol werefound as higher due to improvement in premixed

combustiondue to increased flame rapidity that leads to a complete combustion.

Another reason might be higher energy releaserate, so the peak cylinder

pressure shifted 20CAbTDC and it is slightly away from the diesel peak

pressureregime for preheated ethanol fuel. The increasedignition delay would

increase the amount of fuel burnt duringthe premixed combustion phase. Hence

there is an increase inpeak pressure that would have only been to shift in the

heatrelease pattern on premixed combustion region.

Figure 2Variation of pressure with crank angle.

PERFORMANCE CHARACTERISTICS Brake thermal efficiency

The variation of brake thermal efficiency with brake meaneffective pressure is

shown in Fig. 3. It is evident from thegraph that brake thermal efficiency

increases in dual fuelmode. The increase in brake thermal efficiency from no

loadto full load condition indicates the capability of the combustionsystem to

convert the fuel energy into mechanical work.Generally, the highest thermal

efficiency occurs at the full load,where only the combustion efficiency is

maximized. The brakethermal efficiency at full load is 31.86% preheated

ethanol fueled diesel, which is 3.69% higher as compared to diesel. The BTE

increases dueto an enhanced combustion rate of premixed fuel. The


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combinedeffect of lower density and lower fire point of the preheatedethanol

increases the combustion rate.

Figure 3Variation of brake thermal efficiency with respect tobrake mean

effective pressure.

Brake specific energy consumption

The mass of fuel consumption is shown in Fig. 4. If two differentfuels of

varying density are blended, then the brake specificenergy consumption is

measured as a replacement for BrakeSpecific Fuel Consumption (BSFC).

BSEC =BSFC * CV

where CV is the calorific value of the fuel, the brake specificenergy

consumption is represented in terms of MJ/kW h. Itis clear that BSEC is lower

for ethanolfuel compared to the normal diesel mode. Generally BSECdecreases

with an increase in the brake power. This may be due to the decrease of the

calorific value by adding the premixedethanol fuel. The brake specific energy

consumptionfor preheated ethanol fuel at 20% load is21.69 MJ/kW h, and at

fullload is 11.29 MJ/kW h. Fordiesel it is 27.19 MJ/kW h at 20% load and 13.59

MJ/kWhat full load. The above trend agrees with the result ofHansah et al. [6].

Figure 4Variation of brake specific energy consumption with respect to

brake mean effective pressure.


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EMISSION CHARACTERISTICS Brake specific nitrogen oxides

The variation of brake specific nitrogen oxide given in terms ofg/kW h with

respect to diesel is shown in Fig. 5. It is observedfrom the graph that oxides of

nitrogen emissions are reduced to 24% on average for preheated ethanolfuel

than the neat diesel fuel operation. The reason might bethe formation of

partially lean air fuel mixture inside the combustion chamber compared to

diesel combustion due tolower combustion temperatures, since oxides of

nitrogen formationare very sensitive to the temperature of the cycle. Inparticular

premixed ethanol shows 9.5% lesser NOx emissionat the full load than the

diesel due to lower combustion temperaturecaused by the lower heating value of

the ethanol.Another reason may be due to high latent heat of vaporizationwhich

increases the specific heat of the premixed fuel mixture.The increase in specific

heat reduced the peak combustion temperature.But at the fully loaded condition

oxides of nitrogenemission increases slightly for the preheated ethanol fuel. The

cause may be due to the increased fuel octanenumber of the premixed fuel,

since a higher temperature isrequired to get auto ignition. Another reason might

be due to the strength of air fuel mixture which is rich that increasesthe

combustion rate and higher rates of pressure rise. It isdue to the reason that at

the richest zones, sudden auto ignitionof the mixture takes place and

combustion temperaturewill also locally be higher. At the instance of higher

combustiontemperature few diatomic nitrogen breakdown of

monatomicnitrogen forms more oxides of nitrogen.

Figure 5Variation of oxides of nitrogen with brake mean effective pressure.

Smoke Opacity

The variation of smoke emission with respect to brake meaneffective pressure is

shown in Fig. 6. The smoke emissiondecreased significantly for preheated

ethanol fuelthan with conventional mode of diesel operation owing tomore

oxygen and less carbon in the premixed fuel. The reasonmight be that premixed

combustion will be more as comparedto conventional engines, during which the

fixed oxygen atomin the premixed ethanol can improve combustionin fuel rich

regions, which reduces the smoke formation. Thesmoke emissions are

significantly reduced to 67%for preheated ethanol fuel as compared to

normalmode of operation. The other reason for the reduction insmoke emission


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at the part loads is due to the disappearanceof rich regions of mixture around the

fuel spray in diesel combustionand air fuel mixture becomes partially

homogeneous.This may also due to the high latent heat of premixed fuelwhich

increases ignition delay period. Smoke emission isdecreased due to reduced

quantity of diesel that was injectedfor premixed combustion and the absence of

localized fuel–air mixture is also the one of the reasons for the reduction

insmoke emission.

5. Conclusion

`This research work has been done with concerning about the current and future

needs of PCCI engine. Various parameters such as brake thermal efficiency,

brake specific energy consumption, Oxides of nitrogen ,smoke are measured

and analyzed. It is observed that

1. There is an increase in the brake thermal efficiency by 3.69% higher as

compared to conventional diesel engine.

2. There is reduction in the emission of oxides of nitrogen and smoke by

9.5% and 67% respectively as compared to conventional diesel engine.

3. Since preheating is done using exhaust gas, exhaust temperature gets

reduced.

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Experimental Combustion Emission Characteristics of ... · Duel fuel engine, HCCI, PCCI, RCCI engines are some best of the modified engines using alternate fuel with the conventional