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Indian Journal of Engineering & Materials SciencesVol. 12, December 2005, pp. 505-514

Optimizing diesel engine parameters for emission reduction using Taguchimethod: Variation risk analysis approach – Part II

M Nataraj*, V P Arunachalam & N Dhandapani

Mechanical Engineering, Government College of Technology, Coimbatore 641 013, India

Received 29 July 2004; accepted 1 August 2005

Taguchi parameter design research methodology allows one to make products or processes robust to uncontrollablenoise factors and will also reduce the number of experiments to be carried out to arrive an optimized system. The mainobjective of this work is to study the various operating parameters of diesel engine to propose modified engine parameter(optimum) settings for reduction in NOX, HC, CO and smoke concentrations simultaneously in diesel emission by applying

Taguchi parameter design concept. Taguchi L18 (21

×37

) quality design concept mixed orthogonal array has been used todetermine the S/N ratio (dB), analysis of variance (ANOVA) and F 0 test values for recognizing most significant engineoperating parameters that influence exhaust emission. The experimental results give an idea about how the variations inengine settings like nozzle spray holes, piston-to-head clearance, nozzle protrusion, injection control pressure, start ofinjection timing and swirl level alter the pollutant (NOX, HC, CO and smoke) intensity in emission. Considering thesesignificant engine-operating parameters, verification of the improvement in the quality characteristics for emission reductionhas been done through confirmation test with reference to the chosen initial or reference parameter settings. Theseconfirmation test results prove that the optimal combination of diesel engine parameters obtained from the investigationreducing the pollutant levels in exhaust emission in reality.

IPC Code: F02B

The feasibility of using the Taguchi method tooptimize selected engine design/operating parameters

for low emission was investigated using a DhandapaniFoundary (DPF) diesel engine in Part-I1. In order toexamine whether the variation in key combustion parameters have the same effect and influence onevery diesel engine of any make, the same researchmethodology was adopted on TEXVEL diesel enginewith the same hardware configurations. Extensiveresearch into the mechanisms governing dieselcombustion and emissions has already beenreported 2,3. The vast amount of investigation done inthe diesel combustion and emissions still not wellunderstood due to the complex interrelationships thatexist between combustion system parameters and fuelinjection system parameters. Taguchi developedmultivariate experimental techniques4,5 usingorthogonal design arrays that allow one to isolate theeffect of a single parameter on a particular responsecharacteristic. Taguchi methods have been mostextensively used in industrial and manufacturingsectors; their application to investigate dieselcombustion and emissions has been very limited 6. The

objective of this research study was to examine theeffects of changes in several key combustion and fuel

injection system parameters on engine exhaust usingTaguchi methods to have a better understanding ofhow these changes affect the diesel combustion andemission formation processes.

Experimental ProcedureTest set-up and experimentation

A test rig has been installed for experimentation tomeasure the NOX, CO, HC and smoke levels ofengine emissions. The rig comprises of fuel tank,manometer, air tank, electronic temperaturemeasuring unit, fuel injection system, and exhaust gasanalyzer. A single cylinder, direct injection TEXVEL

engine having bore (114 mm) and stroke (140 mm)was taken for investigation. Fig. 1 shows theexperimental test set-up put in the research laboratoryat Government College of Technology, Coimbatore.

Steady state tests were conducted on diesel enginewith 18 different hardware configurations at 40% and60% of maximum load during the experiment. Theinjector unit was removed often to change thenozzle/nozzle protrusion. The trials associated withthe change of piston-to-head clearance (gasketchange) were tested in random order to save testing

___________*For correspondence (E-mail: [email protected])

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INDIAN J. ENG. MATER. SCI., DECEMBER 2005506

time as well as avoid introducing any noise otherwisewould be caused by hardware change. Extra precautions were taken to ensure that each part was

re-installed according to specifications. A total of 288data points were recorded in this experiment with thehelp of exhaust gas analyzers (Kane-May 900combustion analyzer for measuring NOX level, NPM-SM11B meter for measuring smoke level and NPM-CH1 exhaust gas analyzer for measuring CO and HClevels). NOX, CO, HC and smoke emission responseswere obtained for the 18 engine configurations. Theresponse of the system is measured using Eq. (1)

S/N ratio (dB)STB = -10 log [1/n 1

i n

i

i

Y =

=∑ 2] ... (1)

where, n is number of trials and Y i are the emissiondata for each trial.

Parameter selection

The engine parameters that are most likely toinfluence diesel exhaust emissions are nozzle sprayholes, piston-to-head clearance, nozzle protrusion,injection control pressure, start of injection timing andswirl level7.

Selection of factor levels and orthogonal array

Due to the non-linearly of the diesel exhaustemissions over the normal speed and load operating

Fig. 1—Diesel engine test rig.

Table 1 ⎯ Parameter with Levels

LevelsParameters

1 2 3Unit

A. Number of holes 3 holes 4 holes - -B. Piston-to-head

clearance1.2 1.4 1.8 mm

C. Nozzle Potrusion 2.5 3.4 4.35 mmD. Start of Injection

Timing25.3

bTDC28.3

bTDC31.3

bTDCdeg.

F. Injection ControlPressure

160 170 180 atm

G. Swirl Level

(Throttle Position) ¼ open ½ open Full open

Table 2 ⎯ Mixed orthogonal arrays [L18 (21×37)]

1 2 3 4 5 6

Column No. No. ofholes

Piston-to-head clearance(mm2)

Nozzle protrusion(mm)

Injection control pr.(atm)

Start of inj. timing(degree)

Swirl level

1 Three 1.2 2.9 160 25.3bTDC Low2 Three 1.2 3.95 170 28.3bTDC Medium3 Three 1.2 4.0 180 31.3bTDC High4 Three 1.4 2.9 160 28.3bTDC Medium5 Three 1.4 4.0 170 31.3bTDC High

6 Three 1.4 4.0 180 25.3bTDC Low7 Three 1.6 2.9 170 25.3bTDC High8 Three 1.6 3.95 180 28.3bTDC Low9 Three 1.6 4.0 160 31.3bTDC Medium10 Four 1.2 2.9 180 31.3bTDC Medium11 Four 1.2 3.95 160 25.3bTDC High12 Four 1.2 4.0 170 28.3bTDC Low13 Four 1.4 2.9 170 31.3bTDC Low14 Four 1.4 3.95 180 25.3bTDC Medium15 Four 1.4 4.0 160 28.3bTDC High16 Four 1.6 2.9 180 28.3bTDC High17 Four 1.6 3.95 160 31.3bTDC Low18 Four 1.6 4.0 170 25.3bTDC Medium

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NATARAJ et al.: DIESEL ENGINE PARAMETERS FOR EMISSION REDUCTION USING TAGUCHI METHOD 507

range of the engine, two levels for nozzle spray holes(A) and three levels for the remaining parameters wasconsidered. Control parameters and their levels are

given in Table 1. L18 [2

1

× 37

] mixed orthogonal arrayshown in Table 2 was selected for the experimentalinvestigation. “smaller-the-better” is being taken as aquality characteristic, since the objective function isto minimize NOx, CO, HC and smoke emission.

Statistical analysis

A statistical analysis was done for the experimentaldata obtained which are shown in Table A2 from theL18 experiment. The average emission responses andS/N ratios were calculated for each control factor.Analysis of variance (ANOVA) was performed to

identify the most significant control parameters and toquantify their effects on NOX, CO, HC and smoke.Table 3 shows variance (F o) and percentage of

contribution ratio (ρ).

Response curve analysis

Response curve analysis is aimed at determininginfluential parameters and their optimum levels. Figs2 and 3 show significant effects for each emissionresponse at each factor level for 40% W max and 60%W max respectively. The S/N ratios for the differentemission responses were calculated at each factorlevel and the average effects were determined bytaking the total of each factor level and dividing bythe number of data points in that total. The greaterdifference between the levels, the parametricinfluence will be much. The parameter level havingthe highest S/N ratio corresponds to the parameterssetting indicates lowest emission.

Referring (Fig. 2) the response curve at 40% W max

for the CO emissions, the highest S/N ratio wasobserved at nozzle spray holes (4 holes), piston-to-head clearance (1.8 mm), nozzle protrusion (4.35mm), start of injection timing (25.3 bTDC), injection

Table 3—ANOVA results for 40% and 60% of W max

40% of W max 60% of W max

CO (%) HC (ppm) Smoke (HSU) NOX (ppm) CO (%) HC (ppm) Smoke (HSU) NOx (ppm)C F

F0 ρ % F0 ρ % F0 ρ % F0 ρ % F0 ρ % F0 ρ % F0 ρ % F0 ρ %

A 102.5* 35.2 5.1* 14.6 25.3* 42.8 12.1‡ 19.2 20.8‡ 16.3 12‡ 16.9 29.0* 26.5 11.3‡ 18.5B 0.7 0.5 3.5 ! 19.9 1.7 5.8 1.0 3.1 1.5 2.4 1.9 5.4 4.1• 7.4 0.3 1.0C 4.2† 2.9 1.9 11.1 0.2 0.5 0.2 0.5 1.3 2.0 1.4 4.0 0.1 0.1 0.4 1.3D 16.0 ! 11.0 1.6 9.1 0.8 2.8 17.8* 56.5 1.0 1.6 1.2 3.4 0.4 0.7 20.0* 65.6

F 6.0• 4.1 4.5‡ 25.5 1.4 4.6 0.04 0.1 5.9 ! 9.3 4.8 ! 13.6 4.2 ! 7.7 0.2 0.6G 64.4‡ 44.2 0.5 2.7 9.9‡ 33.4 3.5 ! 11.1 40.6* 63.7 17 * 48.2 28.6‡ 52.2 1.0 3.2(e) - 2.1 - 17.1 - 10.2 - 9.5 - 4.7 - 8.5 - 5.5 - 9.8

(e)-pooled error [e1+e2] * Most significant ‡ More significant ! Significant • Less significant† Very less significant

Fig. 2—Response curves for 40% W max.

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control pressure (170 mm) and swirl level (fullthrottle open). Similarly the optimum parametersetting for lowest HC emissions were found to be anozzle spray holes (4 holes), piston-to-head clearance(1.8 mm), nozzle protrusion (4.35 mm), start ofinjection timing (25.3 before TDC), injection control pressure (170 atm) and swirl level (full throttle open).Smoke emissions were lowest at nozzle spray holes (4

holes), piston-to-head clearance (1.4 mm), nozzle protrusion (4.35 mm), start of injection timing (25.3 before TDC), injection control pressure (160 atm) andswirl level (full throttle open). NOX emissions werelower at nozzle spray holes (3 holes), piston-to-headclearance (1.2 mm), nozzle protrusion (3.4 mm), startof injection timing (25.3 before TDC), injectioncontrol pressure (180 atm) and swirl level (fullthrottle).

Referring (Fig. 3) the response curve, looking 60%W max for the CO emissions, the highest S/N ratio wasobserved at nozzle spray holes (4 holes), piston-to-

head clearance (1.8 mm), nozzle protrusion (4.35mm), start of injection timing (25.3 before TDC),injection control pressure (170 atm) and swirl level(full throttle open). Average HC emission was lowestfor nozzle spray holes (4 holes), piston-to-headclearance (1.8 mm), nozzle protrusion (4.35 mm),start of injection timing (25.3 bTDC), injectioncontrol pressure (170 mm) and swirl level (fullthrottle open). Smoke emission were lowest at nozzlespray holes (4 holes), piston-to-head clearance (1.8mm), nozzle protrusion (2.5 mm), start of injection

timing (25.3 before TDC), injection control pressure(160 atm) and swirl level (full throttle open). NOXemissions were lowest at nozzle spray holes (3 holes), piston-to-head clearance (1.2 mm), nozzle protrusion(3.4 mm), start of injection timing (25.3 before TDC),injection control pressure (170 atm) and swirl level(full throttle open).

Finding optimum parameter settings

Table 4 summarize the optimum parameter settingdetermined for each response at 40% W max and 60%W max. Note that the term optimum reflects only theoptimal combination of the parameters defined by thisexperiment. Summary table needs to be constructed,in which only the level sums of SN ratio of significantfactors appear. The optimum setting is determined bychoosing the level with the highest SN ratio. Controlfactor A is most significant in CO, HC, and smokethan NOX. However, since factor A is less meaningfulin HC, smoke emission than CO emission. So the

optimum condition is A2. In respect of control factorB and C; factors B and C are significant only in HCemission and CO emission respectively. Hence B3and C3 are predicted as the optimal levels for the parameters B and C. For factors D, F and G, morethan one response is significant. So it is confirmedthat D1, F2 and G3 are the optimal conditions for parameter D, F and G respectively at 40% maximumload. Same combination of parameters was obtainedin a similar way for the 60% maximum load.Therefore, the optimal combinations of control factors

Fig. 3—Response curves for 60% W max.

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are A2 B3 C3 D1 F2 G3 for minimized concentrationof NOX, CO, HC, and smoke in the diesel engineemission both at 40% and 60% of W max.

Results and Discussion

The optimum parameter combinations are differingfrom base line engine parameter settings. The baseline

and optimum parameter combinations are shown withlevels in Table 5. The results point out that the parametercombinations are not changed with load variation. Table6 shows that the emission data for baseline engine and

optimized engine.

Fig. 4 shows visually the composition of CO, HC, NOX and smoke in emissions for the baseline andoptimized engine at 40% W max and 60% W max. CO,HC and smoke level in emission varies proportionallywith the load for both baseline and optimized engine. NOX emission was not reduced that much whatever bethe load variation. Noticed that there was remarkablereduction in emission with load variation for theoptimized engine when compared to baseline enginefor the CO, HC and smoke.

Performance analysis

Fig. 5 demonstrates the comparative study on performance evaluation of base line engine versusoptimized engine. It was made clear that the performance of the optimized engine is better than the base line engine for the entire load range from minimumto maximum. Also proves that Taguchi parameter designconcept is more powerful and efficient tool for reducingthe concentration of pollutants in the exhaust emissionof diesel engine.

Table 4—Overall summary table for optimal conditions

Sum of signal-to-noise ratio for 40% W max Sum of signal-to-noise ratio for 60% W max

CO HC Smoke NOX CO HC Smoke NOX Control FactorLevel A*G‡D!

F•C† A*F‡B ! A* G‡ D*A‡

G !

Parameterlevel foroptimalemission G*A‡F !

G*A‡

F ! C• A*G‡

F ! B• D*A‡

Parameterlevel foroptimalemission

1 115.52 55.53 19.01 61.54 54.3 86.17 20.88 59.84

2 167.06 93.62 50.54 38.86 113.17 137.66 41.1 40.58 A

-

A2 A2

1 31.05 17.98

2 50.78 18.31 B

3 67.32

B3

25.69

B3

1 87.73 65.51

2 95.41 72.65 C

3 99.71

C3

85.67

C3

1 104.1 45.85 45.53

2 97.27 38.99 37.96 D

3 81.21 15.57

D1

16.93

D1

1 98.01 32.48 54.06 63.41 24.21

2 98.68 72.48 74.79 96.42 22.1 F

3 85.89 44.19

F2

38.61 64.00 15.67

F2

1 67.89 10.45 25.78 1.01 34.07 7.29

2 101.26 26.81 35.07 82.51 89.36 26.9 G

3 113.46 32.3 39.56

G3

83.95 100.4 27.8

G3

(e)-pooled error [e1+e2] * Most significant ‡ More significant ! Significant • Less significant† Very less significant

Table 5— Baseline and optimum engine parameter combinations

Parameter settingsParameters

Baseline Optimized

Nozzle spray hole 3 holes 4 holes

Piston-to-head clearance 1.4 mm 1.8 mm Nozzle protrusion 3.4 mm 4.35 mmStart of inj. timing 28.3 before TDC 25.3 before TDCInj. control pr. 170 atm 170 atm

Swirl level Full throttle open Full throttle open

Table 6—Baseline versus optimized engine emission

Emission data for 40%W max

Emission data for 60%W max Emissions

Baseline Optimized Baseline Optimized

CO (%) 0.280.06, 0.06,0.06

0.520.09, 0.08,0.08

HC (ppm) 70 20,10, 10 110 20, 20, 10

Smoke (HSU) 71 32, 33, 32 86 51, 52, 51

(No)x (ppm) 570510, 512,510

690 633, 633, 635

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Fig. 4a—CO Emission versus load conditions.

Fig. 4b—HC Emission versus load conditions.

Fig. 4c—Smoke emission versus load conditions.

Fig. 4d—Nox emission versus load conditions.

Fig. 5a—Brake power versus brake thermal efficiency.

Fig. 5b—Brake power versus indicated thermal efficiency.

Fig. 5c—Brake power versus specific fuel consumption.

Fig. 5d—Brake power versus CO emission.

Fig. 5e—Brake power versus HC emission.

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Conclusions

The feasibility of using the Taguchi method tooptimize selected diesel engine design parameters forlow emissions was investigated using a single

cylinder, research diesel engine. The conclusionsfrom this work are summarizes as follows: TheTaguchi method was found to be an efficienttechnique for quantifying the effects of engine designand operating parameters on exhaust emissions. COemission level was influenced by nozzle spray holes,swirl level, start of injection timing, injection control pressure and nozzle protrusion. HC emission levelwas influenced by nozzle spray holes, injectioncontrol pressure, piston-to-head clearance, nozzle protrusion and swirl level. Smoke emission level wasinfluenced by nozzle spray holes, swirl level, injection

control pressure and piston-to-head clearance. NOX emission level was influenced by start of injectiontiming, nozzle spray holes and swirl level. NOX, CO,HC and smoke emission results obtained from theconfirmation experiments fell in good agreement withthe predicted results. The parameter settings ofoptimized engine were not found in any of 18 trialruns of the L18 orthogonal array. 18 trials wereconducted to find the optimized parameter settings.The performance of the optimized engine is betterthan the base line engine and also proves that Taguchi

parameter design concept is more powerful andefficient tool for reducing the concentration of pollutants in the exhaust emission of diesel engine.

Acknowledgements

The authors would like to thank Thiru M.Rajasakar, Faculty of Thermal EngineeringDepartment, Government College of Technology,Coimbatore, for the professional and technical supportrendered during this study.

References1 Nataraj M, Arunachalam V P & Dhandapani N, Indian J Eng

Mater Sci., 12 (2005) 169-181.2 Gill A P, SAE Paper No. 880350, (1988) 461-473.3 Hunter C E, Cikanek H A & Gardner T P, J Eng Gas

Turbines Power, 111 (1989) 916-929.4

Antony J, Int J Adv Manufact Technol, 17 (2001) 134-138.5 Sung H Park, Robust design and analysis for quality

engineering (Chapman & Hall India, London), 1996.6 Hames R J, Merrion D F & Borman G L, SAE Paper No.

710671, (1971) 738-751.7 Ganesan V, Internal combustion engines (Tata McGraw-Hill

Publising Company, New Delhi), 2002.8 Ross P J, Taguchi technique for quality engineering

(McGraw-Hill, New York), 1988.9 Logothetis N, Total quality management-from Deming to

Taguchi and SPC (Printice-Hall International, UK), 1992.

Appendix

Predicting emissions at optimum conditions for 40% W max

The parameter setting for the optimum conditions are shown infollowing table:

ControlFactor

Parameters Levels

A No. of holes (Four holes) A2

B Piston-to-head clearance (1.8 mm) B3

C Nozzle Protrusion (4.35 mm) C3

D Start of Injection Timing (25.3° bTDC) D1F Injection Control Pressure (170 atm) F2

G Swirl Level (Full throttle open) G3

To estimate the emission responses at the optimum conditions,Eqs (A1) and (A2) is used;

Effective number of replications (neff )neff = N / [1+(Total D.O.F associated with items used in μ̂

estimate)] … (A1)

where N is number of trial runs; and μ̂ is Mean

Estimate of error variance (V e)

-

-e

Pooled Variation of non significant sourcesV

Pooled degrees of non significant sources= … (A2)

Estimation of predicted confidence interval (CI)

The confidence interval8,9 of the above-predicted estimation iscalculated using the following equation.

Fig. 5f— Brake power versus smoke emission

Fig. 5g—Brake power versus NOX emission.

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( , ) e

eff

V CI t

n= Φ α … (A3)

In calculating the estimates, only the parameters with a strongeffect on the emission response are used to allow for experimentalerror (variance).

For CO emission at 40% W max

The S/N ratios for each emission response level are listed in TableA4. For carbon monoxide (CO) emission, the parameters with thestrongest effects were;

Strong effects: A2 D1 G3The average S/N ratio for CO, i.e., T was determined using the

values shown in Table A3 for nozzle spray holes as;

T =115.52 167.06

18

+=

( )282.58

18

= 31.40

μ̂ = ˆ (A2D1G3) = A2+D1+G3 – 2T

= 167.06

9+

104.1

6+

113.46

6−2(31.40)= 23.42

neff =( )

18

1 1 2 2+ + + = 3

V e =1 2 12

18 18 18 18 18 B C F e eS S S S S ⎡ ⎤+ + + +⎢ ⎥⎣ ⎦

=37.28 219.31 310.93 108.12 47.34

12

18 18 18 18 18

⎡ ⎤+ + + +⎢ ⎥

⎣ ⎦

= 3.347

A 99.995% confidence interval for CO was determined by;

t (Φ,α) = t (12, 0.005) = 3.055 (from t-Distribution Table)

ˆ ±t (Φ,α) = 23.42±t (12,0.005)

= 23.42 ± 3.055eff

eV

n

⎡ ⎤⎢ ⎥⎢ ⎥⎣ ⎦

= 23.42 ± 3.0553.347

3

⎡ ⎤⎢ ⎥⎢ ⎥⎣ ⎦

= 20.19 to 26.65

The confirmation test is conducted to check whether theobtained optimal condition (A2 B3 C3 D1 F2 G3) falls within theConfidence Interval. The CO emission data’s are 0.06, 0.06, 0.06

SN ratio for these observations (CO emission) is

SN ratio(dB) = -10 log [1/n ∑=

=

ni

i

Yi1

2].

= -10 log { }2 2 21

0.06 0.06 0.063

⎡ ⎤+ +⎢ ⎥⎣ ⎦

= 24.44 dB

The SN ratio value is contained within the 99.995% confidence

interval obtained. So the optimum condition is confirmed by aconfirmation test.

Similar calculations were made for other emissions in 40% and60% of maximum load using the following strong effects;

40% Maximum load

Strong effects for hydrocarbon (HC) : A2 B3 C3 D1 F2

Strong effects for smoke : A2 B2 G3

Strong effects for Oxides of Nitrogen(NOX) : A1 D1 G3

60% Maximum load

Strong effects for carbon monoxide (CO) : A2 F2 G3

Strong effects for hydrocarbon (HC) : A2 B3 F2G3

Strong effects for smoke : A2 B3 F1 G3

Strong effects for oxides of nitrogen(NOX) : A1 D1

Table A1 illustrate a comparison of the actual S/N ratioscomputed from the measured emission responses and the

predicted S/N ratios computed using Eqs (A1)-(A3). The rangesof the predicted S/N values were computed for 99.995%confidence interval about the mean. In the usual course of events,all three-emission responses fell within their predicted ranges,which indicated good reproducibility and confirmed that theexperiment results were valid.

Table A1—Comparison of predicted and actual S/N ratios using optimum setting for 40% W max

For 40 % W max For 60 % W max

Emissions Predicted range of S/N ratio( 99.995% confidence )

Actual S/N RatioPredicted range of S/N ratio

( 99.995 % confidence )Actual S/N ratio

CO (%) 20.19 to 26.65 24.44 16.37 to 24.49 21.57

HC (ppm) -21.12 to -7.04 -23.01 -25.5 to -9.78 -24.77

Smoke (HSU) -32.69 to -27.77 -30.19 -34.36 to -31.25 -34.21

NOX(ppm) -54.35 to -49.83 -54.16 -56.18 to -54.5 -56.03

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Table A2—Experimental data

AT 40% W max AT 60% W max

CO data(%)

HC data(ppm)

Smoke data(HSU)

NOX data(ppm)

CO data(%)

HC data(ppm)

Smoke data(HSU)

NOX data(ppm)Run

No. Trial1(X1)

Trial2(X2)

Trial1(X1)

Trial2(X2)

Trial1(X1)

Trial2(X2)

Trial1(X1)

Trial2(X2)

Trial1(X1)

Trial2(X2)

Trial1(X1)

Trial2(X2)

Trial1(X1)

Trial2(X2)

Trial1(X1)

Trial2(X2)

1 0.41 0.41 50 60 63 72 480 478 2.71 2.7 130 150 95 95 571 580

2 0.26 0.26 50 50 78 78 411 388 0.52 0.53 50 50 79 81 620 625

3 0.25 0.26 40 30 71 72 757 750 0.53 0.52 60 60 85 88 976 973

4 0.11 0.12 10 10 42 45 531 540 0.12 0.14 20 20 62 63 676 672

5 0.12 0.12 20 20 41 42 467 466 0.35 0.36 20 10 67 70 658 660

6 0.34 0.36 50 50 67 71 968 960 1.38 1.36 130 140 91 93 1161 1155

7 0.17 0.17 40 50 61 58 534 536 0.31 0.3 40 40 64 65 717 715

8 0.4 0.41 30 30 78 77 961 960 0.5 0.49 60 60 82 83 922 920

9 0.19 0.18 20 20 64 66 372 373 0.27 0.27 20 30 63 68 543 542

10 0.15 0.16 40 50 41 43 1059 1056 0.19 0.18 30 30 54 57 1458 145211 0.06 0.04 40 40 37 36 455 452 0.08 0.08 20 20 43 45 603 590

12 0.12 0.12 10 10 53 58 809 800 0.38 0.39 20 20 81 76 930 935

13 0.34 0.32 50 70 66 74 760 764 1.46 1.42 120 130 94 91 739 744

14 0.15 0.16 30 30 39 46 1137 1141 0.22 0.24 30 40 58 63 1433 1428

15 0.08 0.08 10 10 29 31 625 620 0.09 0.09 10 10 57 53 782 780

16 0.1 0.1 10 10 31 32 785 793 0.15 0.16 10 10 45 43 1040 1046

17 0.17 0.18 10 10 54 53 753 752 0.87 0.88 60 50 83 82 856 854

18 0.06 0.07 10 10 28 30 732 731 0.09 0.1 10 10 40 42 984 989

Table A3— Average emission responses from L18 experiment

For 40% W max For 60% W max

ParametersCO (%) HC (ppm)

Smoke

(HSU)

NOX

(ppm)

CO (%) HC (ppm)Smoke

(HSU)

NOX

(ppm)A. No. of holes

1. Three 12.84 6.17 2.11 6.84 6.03 9.57 2.32 6.65

2. Four 18.56 10.40 5.62 4.32 12.57 15.30 4.57 4.51

B. Piston-to-head clearance (mm)

1. 1.2 15.29 5.17 2.98 6.18 7.91 10.65 3.00 5.83

2. 1.4 15.68 8.46 4.50 4.95 9.08 12.08 3.05 5.23

3. 1.8 16.12 11.22 4.11 5.60 10.93 14.57 4.28 5.67

C. Nozzle protrusion (mm)

1. 2.5 14.62 6.54 3.96 5.53 7.84 10.92 3.54 5.68

2. 3.4 15.86 7.48 3.60 5.86 9.43 12.11 3.34 5.87

3. 4.35 16.62 10.84 4.03 5.35 10.65 14.28 3.45 5.19

D. Start of injection timing (Deg)

1. 25.3 before TDC 17.35 10.52 4.50 7.64 10.74 13.34 3.70 7.592. 28.3 before TDC 16.21 7.87 3.54 6.50 8.41 13.34 3.26 6.33

3. 31.3 before TDC 13.54 6.47 3.55 2.59 8.76 10.62 3.38 2.82

F. Injection Control Pressure (atm)

1. 160 16.33 5.41 4.34 5.43 9.01 10.57 4.03 5.32

2. 170 16.45 12.08 4.20 5.63 12.47 16.07 3.68 5.77

3. 180 14.31 7.37 3.06 5.67 6.43 10.67 2.61 5.64

G. Swirl Level

1. ¼ throttle open 11.31 6.99 1.74 4.30 0.17 5.68 1.21 5.47

2. ½ throttle open 16.87 8.89 4.47 5.84 13.75 14.89 4.48 5.10

3. Full throttle open 18.91 8.98 5.38 6.59 13.99 16.73 4.63 6.17

8/19/2019 IJEMS 12(6) 505-514

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Table A4—SN ratios for NOX, CO, HC and Smoke data at 40% W max

AT 40% W max AT 60% W max

CO

(%)

HC

(ppm)

SMOKE

(HSU)

NOX

(ppm)

CO

(%)

HC

(ppm)

SMOKE

(HSU)

NOX

(ppm)Run

No.SN ratio(dB)

SN ratio+36(dB)

SN ratio+38(dB)

SN ratio+62(dB)

SN ratio(dB)

SN ratio+43(dB)

SN ratio+40(dB)

SN ratio+64(dB)

1 7.74 1.16 1.39 8.39 -8.643 0.06 0.45 8.80

2 11.70 2.02 0.16 9.97 5.596 9.02 1.94 8.12

3 11.87 5.03 0.91 4.46 5.596 7.44 1.26 4.22

4 18.78 16.00 5.23 7.42 17.696 16.98 4.08 7.43

5 18.42 9.98 5.64 8.62 8.995 19.02 3.28 7.62

6 9.12 2.02 1.22 2.32 -2.735 0.39 0.72 2.73

7 15.39 2.88 2.51 7.43 10.313 10.96 3.81 6.90

8 7.85 6.46 0.21 2.35 6.107 7.44 1.67 4.71

9 14.65 9.98 1.74 10.58 11.373 14.87 3.67 9.31

10 16.19 2.88 5.53 1.51 14.653 13.46 5.11 0.74

11 25.85 3.96 6.75 8.87 21.938 16.98 7.13 8.49

12 18.42 16.00 3.11 3.89 8.290 16.98 2.10 4.61

13 9.63 0.32 1.08 4.36 -3.168 1.05 0.68 6.60

14 16.19 6.46 5.40 0.87 12.757 12.03 4.36 0.89

15 21.94 16.00 8.45 6.12 20.915 23.00 5.19 6.15

16 20.00 16.00 8.03 4.06 16.189 23.00 7.13 3.63

17 15.14 16.00 3.43 4.47 1.160 8.16 1.67 5.36

18 23.72 16.00 8.75 4.72 20.434 23.00 7.74 4.12

IJEMS 12(6) 505-514

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