Effect Of Compression Ratio And Injection Pressure On The Performance And Emission Of C.I. Engine With Multiple Injection Techniques -A Review Study

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459,ISO 9001:2008 Certified Journal, Volume 3, Issue 3, March 2013)

405

Effect Of Compression Ratio And Injection Pressure On The

Performance And Emission Of C.I. Engine With Multiple

Injection Techniques -A Review Study

Jay K. Pandya

1

, Dr. Pravin P. Rathod

2

, Arvind S. Sorathiya

3

, Ramesh Patel

4

1_PG-Student, 2,3_{Associate professor, Mechanical Engineering Department, Government Engineering College-Bhuj}

4_{Senior Manager-R&D Department,}_{P.M. DIESELS PVT. LTD-Rajkot}

Government Engineering College Bhuj-370001 (India)

Abstract—The most dominant source of transportation in modern world is Diesel Engines. But the biggest problem associated with the diesel engines is the harmful exhaust

emission. Each emission (NOx, soot, CO, HC) is the outcome

of chemical reactions and hence depends upon temperature and reactant concentration.

The study shows the effect of compression ratio and in-jection pressure on the performance and emission charac-teristics of C.I. engine. The study shows that the reduction in compression ratio will reduce the combustion peak

tem-perature and that will reduce NOx but there will slight

in-crease in CO and HC. By increasing compression ratio, it is possible to extract maximum possible mechanical efficiency from the engine. The temperature of the combustion cham-ber will also increase and that is beneficial for complete combustion which will reduce CO and HC but there will be

slight penalty in NOx.

Increasing injection pressure is beneficial for achieving better atomization which will directly increase the surface area of injected fuel. By braking droplet of 3mm into 30µm will increase the surface area about 30,000 times. Better atomization will lead to complete combustion and by that there will be reduction in CO and HC but this will also in-crease the temperature of combustion chamber which leads

to slight increase in NOx.

The effect of multiple injections on the performance in a diesel engine research results shows that, it is possible to increase the combustion efficiency, fuel economy under limiting value of exhaust emission and decreasing the com-bustion noise by multiple injection.

Keywords— Compression ratio, injection pressure, ex-haust emissions, fuel injection system, heat release rate, multiple injection, atomization.

I. INTRODUCTION

A major concern with the increasing attention of diesel-powered vehicles is the resultant increased level of pollution. Diesel engines are a source of two ma-jor pollutants; nitrogen oxides (NOX) and particulate

matter, which both have an adverse effect on public health and the environment.

They are also a source of carbon dioxide, one of the most important green house gases. The pollution level of the diesel engine can be controlled and the performance of the engine can be enhanced by following methods:-

A.Multiple injections

Multiple injections are nothing but one kind of inter-vention in combustion process, which may decrease the exhaust emissions. The double injection strategy with proper dwell time may decrease emissions considerably with a minor decrease in engine efficiency.

B.Varying Compression ratio

Studies will be carried out regarding the effect of compression ratio on the performance and emissions of diesel engines. It is assumed that by increasing the com-pression ratio, Brake Specific fuel consumption will de-crease, whereas Thermal Efficiency and exhaust gas temperature increases. By reducing the compression ra-tio, it is assumed that there will be reduction in NOx and PM but there will be small penalty in CO and HC.

C.Increasing Injection Opening Pressure

Generally, increasing injection pressure involves two methods:

i) Increasing Injection Opening Pressure ii) Increasing System Pressure

The Injection Opening Pressure can be increased fur-ther by two methods:-

 By placing seams of certain thickness in nozzle head,

 By tightening the nozzle spring

II. LITERATURE REVIEW

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Author Year Technique Engine type and

oper-ating point

Fuel Injec-tion system

Results

M.K. Du-raisamy et al.

2012 In this paper, an attempt has been made to investigate the effect of compression ratio on performance and emission characteristics of 20% methyl ester Thevetia Peruviana Seed Oil (TPSO) blended with 80% diesel (B20) when used as fuel in a diesel engine.

A Kirloskar make vari-able compression, single cylinder, four strokes, water cooled engine (2.27 KW)

1) Experiments were conducted in a Variable Compression Ratio (VCR) diesel engine with different compres-sion ratios and base line experiment was also conducted with neat diesel operation at high-er compression ratio for comparison.

Fuel pump is used for fuel injection.

1) For the biofuel blend, brake thermal efficiency, volumetric efficiency, CO, HC, NOx and smoke were 2.5%, 1.1%, 33.3%, 27.2%, 10.3% and 9.72% less compared to that of diesel, respectively at the higher CR (20.6:1). On the other hand, bsfc and CO2were 2.6% and 3.4% higher.

2)While increasing CR from 14.5:1 to 20.6:2, brake thermal efficiency, A/F, CO2 and NOx were increased to 4%, 43.66%, 30.4% and 68.7% at the maximum load operation. At the same time, bsfc, volumet-ric efficiency, CO, HC and smoke were decreased to 18.75%, 3.4%, 66.6%, 55.5% and 20.7%, respectively.

H Raheman et al.

2011 1) An attempt is made to assess the suitability of vegetable oil for diesel engine operation, without any modifications in its existing construction.

2)In the present investigation a vegetable oil, Sea lemon oil has been investigated in a constant speed, DI diesel engine with varied fuel injection pressures

(170, 190,210 and 230 bar).

Single cylinder DI Die-sel Engine

1) The injection pres-sure was changed by adjusting the fuel injec-tor spring tension.

The changes noted at maximum engine output were:

1. Brake thermal efficiency increases from 27.3% to 29.1%,

2. HC reduced from 166 to 130ppm, 3. NOx level increases with increasing IOP due to faster combustion and higher tem-peratures reached in the cycle and 4. Smoke level reduced from 4.6BSU to 3.2 BSU.

Y.C. Bhatt et al.

2011 Short-term engine performance tests were conducted using four different blends of karanja methyl ester (Biodiesel) oil in diesel having a concentration of 20,40,60 and 100 percent by volume at three fuel tempera-ture (30,50 and 70oC) and two injection pressure (180 and

245 kg/cm2).

Single cylinder DI Die-sel Engine.

1) Pure diesel at 30oC and 180 kg/cm2 was used as control experi-ment.

2) It was found that KME at fuel tempera-ture of 70oC and injec-tion pressure of 245 kg/cm2 gave significant-ly higher power output to that of diesel with increased BSFC.

1) Power output and brake thermal effi-ciency decreased with the increase in con-centration of KME in diesel and increased with the increase in injection pressure and fuel temperature.

2) The brake specific fuel consumption and BSEC increased with the increase in the concentration of KME in diesel and de-creased with the increase in injection pres-sure and fuel temperature.

3) Exhaust gas temperature increase with the increase in concentration of KME in diesel, the increase in exhaust gas tempera-ture was no significant with increase in fuel temperature and injection pressure.

Nagarhalli et al.

2011 Experimental work has been carried out to analyze the emis-sion and performance charac-teristics of a compression igni-tion engine fuelled with miner-al diesel and diesel Karanja biodiesel blends at fuel injec-tion pressures of 190 bar, 200

bar and 210 bar.

Single cylinder 3.67 kW, compression igni-tion engine.

1) The results of exper-imental investigation with biodiesel blends are compared with that of baseline diesel.

1) Hydrocarbon emissions decreased for B20 and B40 blends by 15-25% at an in-jection pressure of 190 bar.

2) NOx emissions showed a drop of 24% for B20 blend and 16% for B40 blend. 3) HC emissions at 200 bar injection pres-sure decreased by upto 3% for B20 and B40 whereas NOx decreased by 30-39% in comparison with diesel.

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emissions were unchanged for B20 blend and decreased by 18% for B40 blend whereas NOx showed an increasing trend (8-18%).

Cenk Sayin et al.

2011 This work investigates the influence of compression ratio (CR) and injection parameters such injection timing (IT) and injection pressure (IP) on the performance and emissions of a DI diesel engine using bio-diesel (%5, 20%, 50%, and 10 0%) blended-dies el fuel. 1)Tests were carried out using three different CRs(17, 18, and 19/1),

2) ITs (150,200, and 250CA BTD C and

3) IPs (18, 20 and 22 MPa) at 20 Nm engine load and 2200 rpm.

Direct Injection natural-ly aspirated four stroke diesel engine.

1) All the tests were carried out at 20 Nm engine load and 2200 rpm.

1) BSFC, BTE and BSEC are considerably improved with the increase in CR com-pared to the ORG and decreased CRs. 2) For all CRs, the emissions of HC, OP and CO with biodiesel blends are lower than that of diesel fuel.

3) With the increase in CR, the tempera-ture reached is also high and so less OP, CO and HC emissions but, this effect in-creased NOx emissions.

4) The ORG IT gave the best results of BSFC, BSEC and BTE compared to the other ITs. The increased IT causes more time for carbon oxidation and leads to higher temperatures during the expansion stroke and so OP, HC, and CO reduce. 5)Finer breakup fuel droplets obtained with increased IP provide more surface area and better mixing with air and this effect improve combustion. OP, HC, and CO emissions decreased and NOx emis-sions increased with the increase in IP for the all fuel blends.

Hyun et al.

2011 The experimental analysis was conducted for the better under-standing of combustion stabil-ity and reduction of exhaust emission in low compression ratio (CR) engine. The com-bustion stability was analyzed in terms of combustion pres-sure, rate of heat release, indi-cated mean effective pressure and coefficient of variation of indicated mean effective pres-sure, and formation of exhaust emissions such as CO, HC, NOX, and soot particles was

measured and compared in low compression ratio single cylin-der CI engine.

Single cylinder HSDI Diesel engine.

1) Maximum value of combustion pressure in two pilot injections was increased to almost same level of single injection combustion.

Electron-ically con-trolled fuel injection system

1) In one pilot injection combustion, the maximum heat release rate decreases to 27.8% because of low charge gas tempera-ture, and maximum combustion pressure is also reduced to 3.2% compared to single injection.

2) Pressure rise rate of two pilot injection is fastest because 1/3 mass of fuel is inject-ed before main injection.

3) The IMEP of two pilot injection in-creased about 2.1% compared to single injection.

4) More CO formation in multiple injec-tion because the low combusinjec-tion tempera-ture reduces the rate of CO oxidation.

David James MacMil-lan

2009 The utility of different injection strategies, timings and quanti-ties is investigated when vary-ing test temperature and engine speed through a range of values encountered during the cold start phase of engine operation.

Puma direct injection single cylinder four stroke diesel engine. 1) Initial studies were carried out at 300 rpm, a speed representative of post-first-fire condi-tions.

2) Studies were then conducted at higher engine speeds repre-sentative of cold idle.

1350 bar Bosch HP Pump, Common Rail system with solenoid injector

1) A small pilot injection reduces ignition delay.

2) The increased IP gave the better results for BSFC, BSEC and BTE compared to the ORG and decreased IP.

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et al.

2009 This study targets at finding the effects of the engine design parameters viz. compression ratio (CR) and fuel injection pressure (IP) jointly on the performance with regard to fuel consumption (BSFC), brake thermal efficiency (BTHE) and emissions of CO, CO2 , HC,

NOx and Smoke opacity with Jathropha Methyl ester as fuel. Trials with three values of IP (150, 200 and 250) and three values of CR (16, 17 and 18) as against the standard values set by manufacturer for diesel as fuel (210 IP and 17.5 CR) has demonstrated that increase in CR associated with increase in IP improves the performance of the engine used in study with regard to the engine perfor-mance measured in terms of BSFC and BTHE.

Kirloskar model, single cylinder four stroke DI Engine of 3.5 kw. 1) Initially the engine was run on no load con-dition and its speed was adjusted to 1600 ± 10 rpm.

2) The engine was then tested at no load and at 25%, 50%, 75%, 100% and 125% loads. 3) As per the test rig specifications, at rated power, i.e. at full load (100%), the eddy cur-rent dynamometer is to be loaded with 12 kg load for given arm length.

1) The highest performance is delivered by the engine at 250 bar injection pressure and compression ratio of 18 at which BSFC improves by 10% and BTHE im-proves by 8.9%. With regard to emission aspects, increase in compression ratio leads to increase in emission of HC and exhaust temperature whereas Smoke and CO emis-sion reduces.

3) NOx emissions are found to remain unaffected at higher injection pressure. The higher injection pressure helps in keeping the emissions of HC, NOx and Smoke at a lower level while increasing the CO and temperature of exhaust. For all combina-tions of compression ratio and injection pressure, the emissions of HC, NOx, smoke opacity and exhaust temperature are lower with pure biodiesel against that of diesel fuel.

Zhiyu Han et al.

2009 In order to understand the mechanism of emissions reduc-tion, multidimensional compu-tations were carried out for a heavy-duty diesel engine with multiple injections. Different injection schemes were consid-ered, and the predicted cylinder pressure, heat release rate and soot and NOx emissions were compared with measured data. The improvements include using a RNG k-ε turbulence model, adopting a new wall heat transfer model and intro-ducing the nozzle discharge coefficient to account for the contraction of fuel jet at the nozzle exit.

Caterpillar model of single cylinder four stroke engine.

1) Different injection schemes were consid-ered, and the predicted cylinder pressure, heat release rate and soot and NOx emissions were compared with meas-ured data.

2) Excellent agreements between predictions and measurements were achieved after im-provements in the mod-els were made.

Common rail di-rect in-jection system.

1) The present model was validated by comparisons with different measured mul-tiple injection schemes.

2) The computed cylinder pressure, heat release rate and soot and NOx emissions were compared with measured data. How-ever, some disagreement was found in the premixed-burn phase for the cases with 10% fuel injected in the first injection pulse.

3) This indicates more model improvement may be necessary. The computations show that a split injection with a small percent-age (e.g., 25%) of fuel in the second injec-tion pulse can significantly reduce soot production while not increasing NO for-mation levels appreciably. By using a split injection scheme with retarded injection timings, both soot and NOx can be reduced simultaneously.

B.k. Ven-kanna et al.

2009 Few literatures are available on the use of neat methyl esters of honge oil and blend with diesel fuel in diesel engines. This research work presents some findings of the use of honge oil and diesel fuel blend in direct injection diesel engine with increased injection opening pressure (IOP).

1) The performance, emissions and combus-tion parameters of 20% honge oil and 80% die-sel fuel (volume basis) were found very close to neat diesel fuel where as higher blend ratios were found inferior compared to neat diesel fuel.

2) Improved premixed heat release rate were

1. BSFC of H20 is close to that of diesel fuel, thereafter increased compared to die-sel fuel.

2. BSEC of H20 is close to that of diesel fuel, thereafter increased compared to die-sel fuel.

3. Emission parameters such as smoke opacity, CO, HC and NOx up to H20 were

found to be close to that of diesel fuel, thereafter increased compared to diesel fuel.

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noticed with H30 when the IOP is enhanced.

higher CD compared to neat diesel fuel. 5. Performance, emission and combustion parameters of H20 are almost similar to that of neat diesel fuel.

6. Performance and emissions of H30 were improved at IOP 225 bars.

O. Laguitton et al.

2009 The objective was to establish how engine out NOx emissions can be reduced to the estimat-ed levels requirestimat-ed by the next emissions target ‗Euro 6‘ and thus be able to apply the findings to the original 4-cylinder engine and minimize the requirement for currently immature

NOx after treatment.

To meet these needs, both the intake and exhaust sys-tems were developed so that inlet air conditions and ex-haust back-pressure could be individually varied over wide ranges independently of the other engine operating condi-tions.

Single cylinder four stroke diesel engine.

High pressure Delphi pump.

1) The impact of reducing compression ratio has been assessed across three part load conditions. In each case, as injection timing was varied, fuelling was adjusted to maintain constant GIMEP. With the low compression build at part load, soot and NOx emissions were reduced with the latter effect diminishing as injection timing was retarded.

2) It was concluded that lower pressure and temperature during the injection and combustion promoted fuel-air mixing, which reduced both the rate of tion and proportion of diffusion combus-tion. When diffusion combustion was suppressed, the results showed NOx emissions to be less sensitive to in-cylinder pressure and temperature. 3) It was found that when the starting point was a fully-premixed-charge combustion, reducing the compression ratio decreased the maximum rate of pressure change, whereas when diffusion combustion was present, its reduction fuelled the premixed combustion thereby increasing the maxi-mum rate of pressure change.

Rosli Abu bakar et al.

2008 The experiment investigated effects of fuel injection pres-sure on engine performance.

Four-cylinder, two-stroke, direct injection. The fuel consumptions experiment result for 1)Fixed load-variation speeds and 2)Fixed speed-variation loads

Electron-ically con-trolled Common rail fuel injection system used for experi-ment.

1)The experiment results shows that, the fixed load variation speeds and fixed speed-variation loads have been given that the higher engine speed given higher en-gine power. The increasing injection pres-sure is inline with increasing power. 2) The best engine performance for indi-cated pressure, indiindi-cated horse power, shaft horse power, break horse power and BMEP obtained at 220 bar and the best engine SFC obtained at 200 bar or in cur-rent fuel IP.

S.S. Karhale et al.

2006 This paper presents the results of investigations carried out on performance of Karanja methyl ester and its blends with diesel from 20%, 40% and 60% by volume for running a diesel engine.

Performance tests were carried out to evaluate and compute power output.

1) The engine was test-ed with the above test fuels and at two injec-tion pressures i.e. 180 kg/cm2 and 245 kg/cm2 and temperatures of 30, 50 and 70° C.

Based on the results of the study conclu-sions drawn were methyl ester of karanja oil was prepared and at a recovery of 81.20 percent liter from raw karanja oil. 1) Engine starting was normal with karanja methyl ester and its blend with diesel. 2) Injection pressure and fuel temperature were found to be significant effects on engine performance parameters.

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et al.

2006 The main objective of this study is to investigate the effect of injection pressures on per-formance, emissions and com-bustion characteristics of the engine. In the present investi-gation a high linolenic linseed oil methyl ester has been inves-tigated.

1) Constant speed, DI diesel engine with var-ied fuel injection pres-sures (200, 220 and 240 bar).

1. Linseed oil having high viscosity and low volatility makes the oil unsuitable for a diesel engine.

2. By transesterification process the fuel properties are closer to diesel fuel. 3. LOME, derived from non-edible oil, which is an oxygenated fuel, used in a diesel engine reduces HC, CO and CO2 emissions except NOx at 200 bar injection pressure.

4. At 240 bar injection pressure, the ther-mal efficiency improved with increased emissions. This may probably be due to the changes in the fuel spray structure which affects combustion. Thermal efficiency at 200 bar injection pressure was compara-tively lower than that of diesel.

III. CONCLUSION

A Diesel combustion engine has been the centre of at-traction for many past decades. Diesel powered automo-biles has been in use as a main transportation system. But one drawback of diesel powered engines is the alarming rate of exhaust emissions.

 It is possible to increase the maximum torque, which is limited by the exhaust smoke number, while reducing the combustion noise under low speed, full load condi-tions by advancing the timing of the pilot injection.

 When biodiesel is used as a fuel, NOx emission in-creased by 3.23%, 14.41%, 30.04% and 38.46% for B5, B20, B50 and B10, respectively at reduced CR.

 Increasing Compression ratio enhances density of air charge in cylinder. The more density is the higher an-gles of spray cone results in increase of amount of air entrainment in the spray. Enough air in the fuel spray contributes to the completion of combustion.

 Brake thermal efficiency increases from 27.3% to 29.1%, HC reduced from 166 to 130ppm, NOx level increases with increasing IOP (Injection Opening Pres-sure) due to faster combustion and higher temperatures reached in the cycle and Smoke level reduced from 4.6BSU to 3.2 BSU.

 By Combination of variation in compression ratio and injection pressure shows that, the best effect is seen with the combination of injecting fuel at 250 bar while maintaining the compression ratio as 18:1, where the BSFC is minimum for whole of the load range with an improvement of about 10% over standard setting (17.5 CR/210 IP) of the engine (reduction from 0.39 to 0.36 kg/kW-h) at full load.

ABBREVIATION

BMEP Brake mean effective pressure BSEC Brake Specific Energy Consumption BSFC Brake Specific Fuel Consumption BTHE Brake Thermal Efficiency CA Crank Angle

CI ENGINE Compression Ignition Engine CO Carbon Monoxide

CO2 Carbon Dioxide

HC Hydrocarbons NOX Oxides of Nitrogen

NO2 Nitrogen Dioxide

DI ENGINE Direct Injection Engine HC Hydrocarbon

HSDI High speed direct injection ECM Electronic Control Module CC Cubic Centimeter PPM Particles Per Million RPM Revolutions per Minute TDC Top Dead Center BDC Bottom Dead Center ATDC After Top Dead Center BTDC Before Top Dead Center CR Compression Ratio EGR Exhaust Gas Recirculation

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