482317

Hindawi Publishing CorporationAdvances in Mechanical EngineeringVolume 2013, Article ID 482317, 11 pageshttp://dx.doi.org/10.1155/2013/482317

Research ArticleThe Effect of Various Test Parameters on the Steady Flow TestResults of a Four-Valve Spark Ignition Engine:A Tentative Approach toward Standardization

A. Mohammadebrahim,1,2 M. B. Shafii,1 and S. K. Hannani1

1 Sharif University of Technology, Azadi Avenue, P.O. Box 11365-8639, Tehran, Iran2 Engine Research Center, Makhsous Road, P.O. Box 13445-1497, Tehran, Iran

Correspondence should be addressed to M. B. Shafii; [email protected]

Received 15 May 2013; Revised 31 August 2013; Accepted 19 September 2013

Academic Editor: Marco Ceccarelli

Copyright 2013 A. Mohammadebrahim et al.This is an open access article distributed under the Creative Commons AttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properlycited.

The present paper is an account of an experimental analysis carried out to investigate to what extent the flow characteristics in theintake system of a 4-valve, spark ignition internal combustion engine depend on the experimental conditions at the steady flowtest bench. In this respect, the study is aimed at determining the influences of the intake adaptor, test pressure, adaptor length anddiameter, adaptor roughness, paddle wheel diameter, and asymmetric valves lifting on the flow coefficient and the swirl intensitymeasurements. In studies of this kind, researchers generally tend to adopt different test parameters to arrive at a nonuniform baseto compare results from several investigations. This work is aimed at verifying the quantitative differences detected using thesetest parameters. The findings revealed that the swirl intensity depends on the pressure test, adaptor length, and the entry type toa significant degree. Moreover, it was observed that the intake adaptor is the most effective test parameter on the flow coefficient.Finally, the sensitivity analysis has been performed in order to investigate the experimental results and to correlate them with thetest parameters.

1. Introduction

A deep knowledge of the intake and exhaust processesis fundamental to design and optimize modern internalcombustion engines. The development of efficient intake andexhaust systems, in fact, plays a key role both in reducingexhaust emissions and fuel consumptions and in improvingthe performances of actual engines [1, 2].

In-cylinder charge motion has been receiving increasingattention since the introduction of new technologies such asgasoline direct injection or homogeneous charge compres-sion ignition. Therefore, understanding the dynamics of thein-cylinder flow structures is the first step to control fuelstratification, turbulence, and heat transfer efficiently.

An air flowbench (steady flow test) is essentially a deviceused to measure the resistance of a test piece (such as thecylinder head, manifold, carburetor, throttle body, exhaustsystems, etc.) against air flow [3, 4]. In addition, it is easy toimplement and is considered as a low-cost option to estimate

the ability of the cylinder head to convert the linearmotion ofthe inlet flow to rotationalmotion including swirl and tumbleflow (Figure 1). It is due to these features that currently suchtests are being widely used to estimate the effects of geometricchanges on the cylinder head and the inlet port with the aimof comparing and thus improving engine performance.

Although considerable efforts have been made byresearchers to explore the most effective methodology forsteady flow tests, there are substantial diversities in thedefinitions of the technical terms and the techniques used inthe existing experiments [4, 5] and thus the configurations ofthe flow bench vary considerably from user to user.

The absence of a standard methodology has obviouslyraised difficulties in the interpretation of the available dataand has posed an obstacle in drawing comparisons betweenthe intake flows characterized by different engine groups [6].Therefore, it is important to report not only the test resultsbut also the test conditions [79].

2 Advances in Mechanical Engineering

Swirl Tumble

Figure 1: Swirl and tumble in the engine cylinder.

The experimental techniques, their implications, and theimportant technical issues involved in the steady flow benchtest have been discussed in the early works [1012]; however,the literature appears to lack a comprehensive study of theeffect of the test parameters on the steady flow test results.In this regard, the current paper presents and discusses thesensitivity of various test parameters to the flow coefficientand the swirl intensity measurements. This study is expectedto be of much application to engineers working on thedevelopment of engine cylinder heads, particularly thoseinvolved in the steady flow tests.

In this study, basic test parameters are first considered andthen are modified so that the effect of each parameter on theflow coefficient and the swirl intensity can be studied.

2. Experimental Test

The experimental setup is schematically presented inFigure 2. Special mechanisms and fixtures are used to setvalves lift by clock (1) (Figure 3). In standard tests on engineswith four valves per cylinder, inlet or outlet valves are opensimultaneously. The test is performed on a cylinder head(2) and a dummy cylinder (3) is used with a diameterequal to the engine bore. Pressure drop is measured witha stagnation pressure gauge (4) relative to atmosphericpressure. A manometer (7) is also utilized to determine thepressure drop in orifice (8) and consequently to measure thevolume flow rate. Desired differential pressures are suppliedwith a bypass valve (10) and the air flow temperature isrecorded using a temperature gauge (11) for air mass flowrate correction. In the orientation shown in Figure 2, theswirl meter (12) generally measures the tumble intensity.In this paper, however, the swirl meter is placed under thedummy cylinder (Figure 4) to measure the swirl intensity.

Besides, a fan (13) is employed to suck the air from theambient to simulate actual state in the engine.

The nature of the swirling flow in an actual operatingengine is extremely difficult to determine.Accordingly, steadyflow tests are often used to characterize the swirl. To this end,the air is blown steadily through the inlet port and the valveassembly in the cylinder head of an appropriately locatedequivalent cylinder.

The swirling flow is usually characterized by the lightpaddle wheel, pivoted on the cylinder centerline (with lowfriction bearings) (Figure 4(a)) or by the moment of angular

momentum about a chosen axis (Figure 4(b)). In this paper,the rotation rate of the paddle wheel is used as a measure ofthe air swirl and is reported as the swirl intensity ().

Given the present study, at the time of measurement,the valve is first adjusted to the desired lift (from 1mm to9mmwith 1mm increment).Then at each valve lift, the massflow and the swirl intensity are recorded for 5 times andtheir average value is reported. Finally, the test procedureis repeated 10 times. Based on the described repetitioninstruction, the uncertainties of the flow coefficient and theswirl intensitymeasurement are calculated to be about 1% and3%, respectively (Figures 5 and 6).

3. Governing Equations

The flow and discharge coefficient are defined as the ratioof the experimentally obtained mass flow rate meas to thetheoretical mass flow rate

:

=meas

. (1)

If the flow is subsonic, the reference mass flow rate can bearrived at by the following formula:

= ref

0

0

(

0

)

1/

{[2

1] [1 (

0

)

(1)/

]}

1/2

.

(2)

At the same time, if the flow is choked, the mass flow iscalculated as follows:

= ref

0

0

1/2

(2

+ 1)

(+1)/[2(1)]

, (3)

where 0is the intake system pressure,

is the cylinder

pressure, 0is the intake system temperature, and ref is the

reference area.It is noteworthy here that the difference between the

discharge and flow coefficient lies in the definition of thereference area ref [10].

Regarding the discharge coefficient, the reference area isthe valve curtain area and, therefore, it is a linear function ofvalve lift V, expressed as

ref = V V. (4)

Given the flow coefficient, however, the reference area isdefined as the valve inner seat area:

ref = 2V

4. (5)

Furthermore, the mean flow coefficient is computed

by integration over the crank angle between TDC (top deadcenter) and BDC (bottom dead center), considering the valve

Advances in Mechanical Engineering 3

(1) Setting lift by clock

(2) Cylinder head

(3) Dummy cylinder(4) Stagnation pressure gauge

(5) Air box

(6) Rigid pipe

(7) Manometer

(8) Orifice

(9) Manometer(12) Swirl meter(11) Temperature gauge

(10) Bypass valve

(13) fan

Figure 2: Schematic diagram of the flow bench.

Figure 3: Valve lift adjustment with fixtures and dial indicator.

lift, the actual piston speed (), and the mean piston speedas

=

1

(1/)

0

( () /)3

(1/()2

)

.(6)

Considering the above formula, it can be viewed that thevalue of

is a weighted flow efficiency parameter dependent

upon the cam profile and on the inner seat diameter definingthe reference cross section. The value of

is therefore a

measure of the overall flow efficiency of the port, weightedby the valve lift curve.

The rotation of the cylinder charge is measured by apaddle wheel anemometer as the swirl intensity () at eachvalve lift.The mean swirl intensity is obtained in a similarway to themean flow coefficient by integration over the crankangle, having the valve lift and the piston speed:

=1

0

( ()

)

2

. (7)

Table 1: Engine specification.

Bore (mm) 78.6Stroke (mm) 85Displacement (cc) 1650Inlet port diameter (mm) 26Inlet valve

Diameter (mm) 30.6Stem diameter (mm) 6Maximum lift (mm) 10Seat angle (deg.) 44.5Inclination (deg.) 26

4. Reference Test

In this section, the results of the reference test for the baseconfiguration and test parameters are investigated so thatcomparisons can be drawn against the results obtained fromother tests. The test is performed on the cylinder head of a4-valve spark ignition engine. The engine specifications aregiven in Table 1.

The reference test used for the purpose of this study is ofthe following features:

(1) 50 cm-H2O differential pressure;

(2) inlet flow temperature = 30C;(3) volume flow rate measured by the orifice, in the range

of 2071 liters per second;(4) symmetric intake valve lifting from 1mm to 9mm.

Figures 5 and 6 illustrate the flow coefficient and the swirlintensity versus the valve lift, respectively. As it is viewed inFigure 5, in the case of the low valve lift region, the value ofthe flow coefficient linearly increases with the valve lift. Onthe other hand, in the case of a high valve lift region, theflow coefficient converges to the specific value based on portdesign and is independent of valve lift. The flow coefficient


Intake port

H

D

B

Hp

Dp

Paddle wheel

L

Swirl adapterfixture

w

(a)

Intake port

H

D

B

T

Hi

Di

Impulse

meter

L

Swirl adapterfixture

torque

(b)

Figure 4: Swirl meter types: (a) rotational speed measurement and (b) torque measurement [13].

is calculated according to the equations described in theprevious section.

Figure 6 represents the reference test for swirl measure-ment.Theoretically, because of the symmetry in the ports, theswirl intensity in 4-valve SI engines is nearly equal to zero, yetsome factors such as nonuniformity in the ports productionand asymmetric valve lifting can create swirl in the cylinder.

According to Figure 6, at the lift of 1mm, the swirlintensity is zero, while the maximum swirl intensity is at thelift of 2mm. Following this lift, the swirl intensity graduallydecreases toward zero.

5. Results and Discussion

In this section, the effects of some parameters on the flowcoefficient and the swirl intensity is studied and comparisonsare made with the reference test.

5.1. Entry Types. In the steady flow test, in order to allow theair to evenly enter into the intake duct, generally one of thefollowing parts are added to the air entry location:

(a) the intake manifold (Figure 7);(b) the flexible materials such as pulp (Figure 8);(c) the radius inlet guide (Figure 9) provides a smooth

approach to the port being tested and decreases theedge effect at the port flange.The radius used shouldbe as large as possible and be at least 1/2. Thethickness of the inlet guide and the size outside theport cross section should be at least 1/2 of the height ofthe port so that all directions have a smooth approach.

Figure 10 illustrates the variations of the flow coefficientas a function of the valve lift for various types of entry. Thepulp has a significant influence on the flow coefficient; that is,the value of

increases as the pulp is added.The results also

reveal that the rate of the increase in the case of high valve liftis more remarkable. There is a difference of about 1.5 percentin the lift of 3mmandmore than 14 percent in the lift of 8mm.It is with the help of the pulp that the sharpness of entrancedecreases which in turn reduces the pressure drop.

In the case of connection intake manifold to the airentrance location, as it is shown in Figure 10, because of


0.000

0.026

0.055

0.085

0.111

0.1300.142

0.149 0.1560.162

0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

0.160

0.180

0 2 4 6 8 10Lift (mm)

Cf

Figure 5:The effect of the valve lift on the flow coefficient (base test)including error bar.

0

200

400

600

800

1000

0 2 4 6 8 10Lift (mm)200

(r

pm)

Figure 6:The effect of the valve lift on the swirl intensity (base test)including error bar.

the longer flow path, the pressure drop increases and conse-quently, the flow coefficient decreases slightly. The decreaseof in the case of high valve lift is more significant between

3 and 4.5 percent.The effect of mounting the intake manifold and the pulp

on the swirl intensity is represented in Figure 11. As it canbe observed, in both cases, the swirl intensity increases dueto the even entry of the air into the intake duct. It is visiblethat the swirl intensity at the lifts of 1 and 9mm is close tozero while at the lift of 2mm, the swirl intensity of all entrytypes is near. The graph also indicates that the swirl is moresignificantly affected at the middle valve lifts.

5.2. Test Pressure. As it was discussed in the previous section,in this study, a pressure drop of 50 cm-H

2O is considered

as a reference. The effects of air pressure drop (betweenthe ambient pressure and the cylinder pressure) on the flowcoefficient and the swirl intensity are illustrated in Figures 12and 13, respectively.

As it can be seen in Figure 12, the effect of pressure dropon the results is in the same order as that of the measurement

Figure 7: The intake manifold on the air entry location.

Figure 8: The flexible materials such as pulp on the air entry loca-tion.

Figure 9: Cylinder head with radius inlet guide in place.

0.0000.0200.0400.0600.0800.1000.1200.1400.1600.1800.200

0 1 2 3 4 5 6 7 8 9 10Lift (mm)

BaseWith pulpWith manifold

Cf

Figure 10: The effect of the entrance on the flow coefficient.


BaseWith pulpWith manifold

0

200

400

600

800

1000

1200

0 1 2 3 4 5 6 7 8 9 10Lift (mm)

(r

pm)

200

Figure 11: The effect of the entrance on the swirl intensity.

0.0000.0200.0400.0600.0800.1000.1200.1400.1600.180

0 1 2 3 4 5 6 7 8 9 10Lift (mm)

Cf

50 cm-H2O25 cm-H2O

75 cm-H2O100 cm-H2O

Figure 12: The effect of the flow test pressure drop on the flowcoefficient.

errors.That is, a 25 cm-H2O increase in the test pressure drop

increases the flow coefficient by about 1% at the middle liftsand by about 1.5% in the case of the high lifts.

In a similar vein, according to Figure 13, increasing theinlet mass flow rate escalates the paddle wheel rotationalspeed and the swirl intensity at the lifts of 1, 8, and 9mmremains near zero. Interestingly, at the lift of 6mm, the swirlintensity appears to be independent of the test pressure. Witha 25 cm-H

2O increase in the pressure drop, the maximum

difference is about 50% at the lift of 2mm.The adaptor length (distance H), which is depicted in

Figure 4, is generally considered as a function of the cylinderbore (e.g., 1.75 times of the cylinder bore) or a fixed length(e.g., 100mm).

5.3. Adaptor Length. As another part of the study, analyseswere carried out to investigate the effects of different lengthson the flow coefficient as well as the swirl intensity. Asdisplayed in Figure 14, in the case of themiddle andhigh valvelift region, the value of the flow coefficient decreases as theadaptor length increases. Similarly, when the adaptor length

0

200

400

600

800

1000

1200

1400

1600

0 1 2 3 4 5 6 7 8 9 10Lift (mm)

(r

pm)

200

50 cm-H2O25 cm-H2O

75 cm-H2O100 cm-H2O

Figure 13: The effect of the flow test pressure drop on the swirlintensity.

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0 2 4 6 8 10Lift (mm)

Base

Cf

2base3base4base

Figure 14: The effect of the adaptor length on the flow coefficient.

increases to 4 times as long as the original length, the flowcoefficient is reduced by 5%.

As indicated in Figure 15, the adaptor length has aninfluence on the swirl intensity and the rotation rate ofthe paddle wheel decreases as the adaptor length increases.The results also imply that the rate of the increase is moreremarkable at the medium valve lift region. This is due to thefact that the radial flow weakens through the longer adaptor.

5.4. Diameter and Roughness of the Adaptor. The adaptordiameter is typically equal to the cylinder bore. In this section,the effect of the adaptor diameter on the flow coefficientand the swirl intensity is being studied. Figure 16 illustratesthe variations of the flow coefficient as a function of thevalve lifts for three various adaptor diameters. As one canclearly view, this parameter is of no influence on the flowcoefficient. It can also be understood from the figure that


0100200300400500600700800900

1000

0 1 2 3 4 5 6 7 8 9 10Lift (mm)

Base2base

3base4base

(r

pm)

100

Figure 15: The effect of the adaptor length on the swirl intensity.

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0 2 4 6 8 10Lift (mm)

Base83 mm

Cf

89 mm good roughness89 mm normal roughness

Figure 16: The effect of the adaptor diameter and roughness on theflow coefficient.

the effect of the surface roughness is not considerable. Inthe case of the polished adaptor surface though, the flowcoefficient increases by about 3%.

Since with the increase of the adaptor diameter thepaddle wheel diameter remains fixed, it is predictable that theangular momentum at the adaptor edges is not detectable bythe paddle wheel. This fact is depicted in Figure 17. It is alsorevealed that this parameter is not significantly influenced bythe surface roughness.

5.5. Paddle Wheel Diameter. At this stage, a larger diameter(83mm instead 79mm) is considered for the adaptor in orderto study the larger paddle wheel diameters.

Figure 18 illustrates the variations of the flow coefficientas a function of the valve lift for various paddle wheelmean diameters. As the figure implies, this parameter has noinfluence on the flow coefficient.

Figure 19 also indicates that at the lifts of 2 and 3mm,the smaller diameters lead to a larger swirl intensity, while

Base83 mm

0100200300400500600700800900

1000

0 2 4 6 8 10Lift (mm)

(r

pm)

100

89 mm good roughness89 mm normal roughness

Figure 17: The effect of the adaptor diameter and roughness on theswirl intensity.

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0 2 4 6 8 10Lift (mm)

Cf

= 79mm = 83mm = 87mm

Figure 18: The effect of the paddle wheel diameter on the flowcoefficient.

0100200300400500600700800900

1000

0 2 4 6 8 10Lift (mm)

= 79mm = 83mm = 87mm

(r

pm)

100

Figure 19: The effect of paddle wheel diameter on swirl intensity.


0.03750

0.061250.08500

0.1087

0.1325

0.1562

0 2 4 6 8 100

2

4

6

8

10

Lift (mm)

Lift

(mm

)

0.01375

0.03750

0.06125

0.08500

0.1087

0.1325

0.1562

0.1800

Figure 20: The flow coefficient at the different valves lifts.

0

1000

20003000

0 2 4 6 8 100

2

4

6

8

10

Lift (mm)

Lift

(mm

)

0

1000

2000

3000

4000

3000

3000

4000

2000 2000

10001000

Figure 21: The swirl intensity at the different valves lifts.

at the lifts of 5mm until 9mm, a larger swirl intensity isobtained for larger diameters. Therefore, the findings signifythat the effect of paddle wheel diameters on the swirl intensityis not substantial.

5.6. Asymmetric Valve Lifting. In the standard test of afour-valve engine (two intake and two exhaust valves), theintake valves should be open uniformly, and the previousdiagrams are obtained based on this condition. Sometimes,the asymmetric valve lifts occur due to following reasons: (1)creation of a vortex flow, (2) inaccurate production processes,and (3) nonprecise valve lift fixtures.

The interactions of valve lifts signify the ability to varythe cylinder swirl by having asymmetric lifts or completevalve deactivation. Tests were carried out with the lifts ofleft and right intake valves varying separately. Figures 20 and21 represent the results obtained for the flow coefficient andthe swirl intensity, respectively. As it is observable in thesefigures, when the lifts of left and right valves are changedsimultaneously, the intensity of the swirl remains about zero,whereas the flow coefficient increases with the increase of thevalve lift. Furthermore, a significant increase in the swirl isobserved when a valve is completely deactivated.

0.095

0.1

0.105

0.11

0.115

0.12

0.125

0.13

Base

Pulp

Man

ifold

25 cm

-H2O

75 cm

-H2O

100 c

m-H

2O

2ba

se3

base

4ba

se83

mm

89 m

m n

orm

al R

89 m

m g

ood

R

whe

el 7

9 mm

w

heel

83 m

m

whe

el 8

7 mm

Cf

Figure 22: The mean flow coefficient at the different tests.

0

100

200

300

400

500

600

700

(r

pm)

Base

Pulp

Man

ifold

25 cm

-H2O

75 cm

-H2O

100 c

m-H

2O

2ba

se

3ba

se

4ba

se

83 m

m

89 m

m n

orm

al R

89 m

m g

ood

R

w

heel

79 m

m

w

heel

83 m

m

w

heel

87 m

m

Figure 23: The mean swirl intensity at the different tests.

At each position of the engine performance map, one ofthese conditions might be met to cause a better compromisebetween the combustion efficiency and volumetric efficiency.

6. Data Correlation

In order to conduct the analyses, first the mean flow coeffi-cient and the mean swirl intensity of each test are calculatedbased on the above results (6), (7).The values obtained for

and are reported in Figures 22 and 23, respectively.According to Figure 22, the entry type and the adaptor

length have significant influences on the mean flow coeffi-cient

. Moreover, Figure 23 indicates that the pressure test,

the entry type, and the adaptor length are the most effectiveparameters on the . In summary, the variation trend ofthe mean values (

, ) is similar to that of the base values

discussed earlier in detail.In order to find out the relationship between the effective

and quantitative test parameters, including the test pressure,the adaptor length and the adaptor diameter, and the


0.111

0.1115

0.112

0.1125

0.113

0.1135

0.114

0.1145

0.115

0.1155

0 20 40 60 80 100 120

y = 5E 05x + 0.11

R2 = 0.9963

P (cm-H2O)

Cf

(a) Pressure test () versus

0.106

0.107

0.108

0.109

0.11

0.111

0.112

0.113

0.114

0 50 100 150 200 250 300 350 400 450LA (mm)

y = 2E 05x + 0.1147

R2 = 0.9971

Cf

(b) Adaptor length (LA) versus

0.11275

0.1128

0.11285

0.1129

0.11295

0.113

78 80 82 84 86 88 90DA (mm)

y = 2E 05x + 0.1114

R2 = 0.9786

Cf

(c) Adaptor diameter (DA) versus

Figure 24: regression analysis results.

and , regression analysis was performed. Graphs (a) to(c) of Figures 24 and 25 represent the results. The slopeof each diagram determines the sensitivity of the effect ofeach parameter to the flow parameters. The 2 (coefficientof determination) value of the regression curve for eachparameter was also found to be high. Therefore, it can beconcluded that it is possible to obtain useful correlationsthrough the regression analysis.

Finally, the correlation equations from the analysis couldbe obtained as shown in (8) and (9) below:

Cest = (5 5) (2 5) LA + (2 5)DA + 0.1107,

(8)

est = (3.2206) (0.4027) LA (10.205)DA + 942.024.(9)

The errors between and were also measured and

estimated by the equation to be less than 5% and 11%,respectively (Figures 26 and 27).

Through this analysis, it was found that the most effectiveparameter on is the adaptor diameter since it is respon-sible of the largest variations in . Yet another importantobservation was related to the dependency of on the testpressure. However, the

dependency on the test parameter

is relatively less effective. As was expected, the results suggestthat

is proportional to adaptor diameter since a larger

bore has relatively less surface friction as well as a lower flowresistance.

The correlation equations achieved can be used forfurther investigation of the test parameters effects to preventunnecessary additional works. In some aspects, it will be alsouseful to compare different results obtained with regard todifferent test conditions.

7. Conclusion

The experimental work presented in this paper was aimed atanalyzing the influence of different steady flow test bench testparameters on the flow coefficient and the swirl intensity.The


050

100150200250300350400450500

0 20 40 60 80 100 120

(r

pm)

y = 3.2206x + 107.44

R2 = 0.9973

P (cm-H2O)

(a) Pressure test () versus

0

50

100

150

200

250

300

0 50 100 150 200 250 300 350 400 450LA (mm)

y = 0.4027x + 313.89

R2 = 0.8325

(r

pm)

(b) Adaptor length (LA) versus

0

50

100

150

200

250

300

78 80 82 84 86 88 90DA (mm)

(r

pm)

y = 10.205x + 1045.7

R2 = 0.8117

(c) Adaptor diameter (DA) versus

Figure 25: regression analysis results.

0.104

0.106

0.108

0.11

0.112

0.114

0.116

0.118

0.104 0.106 0.108 0.11 0.112 0.114 0.116 0.118

Estimation error < 2%

(esti

mat

ed v

alue

by

(8))

Cf

(tested value)Cf

Figure 26: The comparison of measured and estimated .

analyses results indicated thatmounting the pulp at the intakeport increases the flow coefficient in the case of the highvalve lift region, while when the intake manifold is mounted,because of a longer flow path, the flow coefficient decreases.In addition, it was observed that the rotational speed ofthe swirl meter (swirl intensity) increases when the pulp or

0

100

200

300

400

500

600

0 100 200 300 400 500 600 (rpm) (tested value)

Estimation error < 11%

(r

pm) (

estim

ated

val

ue b

y (9

))

Figure 27: The comparison of measured and estimated .

the manifold is connected to the cylinder head. The testsalso revealed that the mass flow rate increases slightly asthe drop pressure grows, while the swirl intensity increasesconsiderably. Furthermore, the flow coefficient and the swirlintensity decline as the length of the adaptor increases.


In the limited range of paddle wheel diameter variation,no change in the flow coefficient was observed and the effectof this diameter on the swirl intensity turned out to benegligible.

Therefore, based on the observations made, it can beconcluded that, except for the type of the intake adaptorand asymmetric valve lifting, the other parameters have noclear effect on the flow coefficient. In fact, with mounting thestandard intake adaptor and precise symmetric valve lifters,the result of various test centers can be used by others. Yet ithas to be noted that the swirl intensity is sensitive and varieswith different test parameters.

Moreover, asymmetric valve lifting can be used for loadcontrol of a spark ignition engine. In the idle mode or lowload of an engine, because of the low turbulence in cylinder,it is possible to use this concept to increase the turbulencewith swirl intensity.

Finally, the analyses were performed to correlate sometest parameters with the mean flow coefficient and the meanswirl intensity.

Nomenclature

V: Inlet valve inner seat area: Cylinder bore, swirl adapter fixture bore: Discharge coefficient: Flow coefficient: Mean flow coefficient(): Actual piston speed: Mean piston speedV: Inlet valve inner seat diameterV: Valve liftLA: Adaptor lengthDA: Adaptor diameter: Air mass flow rate: Pressure: Temperature: Crank angle: Pressure testV: Volumetric efficiency: Density of air: Paddle wheel angular velocity (swirl intensity): Mean swirl intensity.

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