EVALUATION OF THE TECHNICAL STATE OF AN

Transkrypt

TEKA Kom. Mot. Energ. Roln., 2005, 5, 177-191
EVALUATION OF THE TECHNICAL STATE
OF AN ENGINE PRC SYSTEM BY MEANS OF FUMES CONTENTS
Wiesław Piekarski∗, Grzegorz Dzieniszewski∗∗
∗Department of Power Industry and Vehicles, Agricultural University of Lublin
∗∗Institute of Technology, Rzeszów University
Summary. The paper presents an evaluation of validity of engine fumes contents for a diagnosis
of the technical state of the piston – rings – cylinder system (PRC). The most valid for the description of the state of PRC system toxic contents of fumes were selected by statistical methods.
Mathematical formulas were worked out to describe changes of the technical state. It was verified
experimentally whether the values found out by the formulas agreed with the real ones. The areas
were pointed out for the use of the tested method in non-invasive diagnostics and in motor diagnostics.
Key words: diagnostics, PRC system, fumes analysis, working parameters
INTRODUCTION
The processes of wear and regulation parameters change during a vehicle’s exploitation, whose total values describe its technical state, are directly reflected in the intensity and character of the accompanying processes. The dominant part among them is
played by the output processes, characterized by diagnostic signals parameters and by an
engine’s work effectiveness indicators. The basis for a vehicle’s technical diagnosis is an
assumption of a close relationship between physical values of diagnostic signals during
an object’s work and its inner structure determining a particular technical state [Hebda et
al. 1984, Merkisz and Mazurek 2002].
Hence there is a need for finding such diagnostic methods which would use the signals of easily accessible output processes. Engine fumes contents are a carrier of diagnostic information available for use mainly for an evaluation of the combustion process,
which is significantly affected by its wear. It should be assumed that there is a correlation between PRC system’s state, amount of oil used by an engine and fume contents.
178
Wiesław Piekarski, Grzegorz Dzieniszewski
THE CONCEPT OF THE DIAGNOSTIC METHOD
Transmission radiate [%]
The aim of the presented research problem is to describe the correlation between the
wear of the piston – rings – cylinder system (PRC) and the changeability in the emission
levels of basic fumes contents, assessment of the usefulness of the tested method in the
broadly understood diagnostics and verification of the universality and repeatability of
the method.
The changeability of hydrocarbons – HC, carbon monoxides – CO and carbon dioxides CO2 were precisely analysed in fumes at different states of an engine’s work. An
important aspect of the presented research was to select the fume content of the highest
reliability as to an evaluation of the PRC system’s wear.
In view of the character of oil consumption in a spark-ignition engine (PRC system
and timing gear) additional analyses of fumes contents were carried out to exclude interference due to oil consumption in timing the gear.
Lenght wave [µm]
Fig.1. Transmission spectrum of infrared radiation in the analyzer’s system
The research involved engines of different, randomly selected working period, of
the following types: SKODA781.135, FSO 115C.086, FIAT 170A1.000 and 126A0,
testing 30 items of each type.
During research serving to determine parameters of diagnostic signals, assumptions
were accepted which maximally reduced interference with PRC system during the fumes
contents dependence analysis.
Research on engines involved measurements of parameters of the emitted fumes
contents diagnostic signals, compression pressure, relative drop of compressed air pressure in cylinders and compression pressure. Tests on the relative drop of the compressed
air pressure in cylinders and compression pressure were carried out in two trials: without
oil and with oil injected to the cylinder. Fumes analyses were carried out for three states
of an engine’s work:
EVALUATION OF THE TECHNICAL STATE OF AN ENGINE PRC...
179
–
–
–
rotational speed at idle running;
mean rotational speed – 2000…3000 rpm;
unstable state, i.e. rotational speed’s acceleration to a maximum speed for a particular engine and at sudden throttle close.
During the fumes analyses the following measurements were taken: HC [ppm],
CO[%], CO2 [%], O2 [%], γ .
During the fumes analyses were carried out by means of analyzer MULTIGAS
PLUS 488.
Fumes analyzer of the type Multigas Plus mod. 488 uses the method based on infrared radiation absorption (NDIR) to measure the concentration of carbon monoxide, carbon dioxide and hydrocarbons. Transmission spectrum of this analyzer’s radiation is
presented in Figure 1. Oxygen and nitrate oxides contents are measured by the electrochemical method, and the presented analyzer is included in the class I according to
OIML (Organization Internationale Metrology Legal).
AN ANALYSIS OF RESULTS
Although the research was carried out on four engine types, due to their analogy, this
paper presents the full analysis cycle only for the engine FSO 115C.076 of the Polonez car.
Fig. 2 presents the results of tests on the dependence of compression pressure
changeability on hydrocarbons contents in fumes for the rotational speed at idle running;
Fig. 3 – the dependence of cylinder tightness on hydrocarbons contents in fumes; Fig. 4
– the relation of compression pressure changeability to carbon monoxide content in
fumes; Fig. 5 – the dependence of cylinder tightness on carbon monoxide content in
fumes.
Fig. 6 presents the dependence of compression pressure changeability on hydrocarbons contents in fumes tested at the rotational speed 3000 rpm; Fig. 7 – the dependence
of cylinder tightness on hydrocarbons contents in fumes; Fig. 8 – the relation of compression pressure changeability to carbon monoxide content in fumes; Fig. 9 – the dependence of cylinder tightness on carbon monoxide content in fumes.
Compression pressure [x 0.1 MPa]
Rotational speed of idle running
15
Pressure
14
Oil trial
Linear (Pressure)
13
Linear (Oil trial)
12
y = -0,0033x + 12,575
2
R = 0,1838
11
10
9
8
7
y = -0,0048x + 11,645
2
R = 0,2325
6
5
0
100
200
300
400
500
600
700
800
900
1000
HC [ppm]
Fig. 2. Dependence of changeability of compression pressure on hydrocarbons contents in fumes
180
Tightness [%]
Tightness
100
Linear (Tightness )
95
90
85
80
75
70
y = -0,0189x + 89,155
R2 = 0,17
65
60
55
50
0
100
200
300
400
500
600
700
800
900
1000
HC [ppm]
Fig. 3. Relation of changeability of cylinders tightness to hydrocarbons contents in fumes
Pressure
Oil trial
Linear (Pressure )
Linear (Oil trial)
15
14
13
y = -0,2294x + 12,203
2
R = 0,191
12
11
10
9
y = -0,2403x + 10,872
2
R = 0,1251
8
7
6
5
0
2
4
6
8
10
CO [%]
Fig. 4. Dependence of changeability of compression pressure on carbon monoxide content
in fumes
Tightness
100
Linear (Tightness)
Tightness [%]
95
90
85
80
75
70
y = -1,3654x + 87,122
R2 = 0,1885
65
60
55
50
0
1
2
3
4
5
6
7
8
9
10
CO [%]
Fig. 5. Relation of changeability of cylinders tightness to carbon monoxide content in fumes
181
Rotational speed 3000 rpm
Pressure
15
Oil trial
14
Linear (Pressure )
13
Linear (Oil trial)
12
11
y = -0,0003x + 11,74
10
R 2 = 0,0131
9
8
y = -0,0008x + 10,557
7
R 2 = 0,0557
6
5
0
300
600
900
1200
1500
1800
2100
2400
2700
3000
HC [ppm]
Tightness
Tightness [%]
100
Linear (Tightness )
95
90
85
80
75
70
65
y = -0,0057x + 85,753
R2 = 0,1343
60
55
50
0
300
600
900
1200
1500
1800
2100
2400
2700
3000
HC [ppm]
Pressure
15
14
Oil trial
Linear (Pressure)
13
Linear (Oil trial)
12
11
10
9
y = -0,0874x + 11,839
R 2 = 0,0216
8
7
y = -0,0707x + 10,442
R 2 = 0,0084
6
5
0
2
4
6
8
10
12
CO [%]
Fig. 8. Dependence of changeability of compression pressure on carbon monoxide content
in fumes
182
Tightness
Linear (Tightness)
100
95
Tightness [%]
90
85
80
75
70
y = -0,6017x + 85,149
R2 = 0,0286
65
60
55
50
0
2
4
6
8
10
12
CO [%]
Fig. 9. Relation of changeability of cylinders tightness to carbon monoxide content in fumes
Unstable states
Pressure
Oil trial
Linear (Pressure )
Linear (Oil trial)
15
14
13
12
11
y = -0,001x + 12,128
R2 = 0,3778
10
9
8
7
y = -0,0012x + 10,861
R2 = 0,3177
6
5
0
500
1000
1500
2000
2500
3000
3500
4000
4500
HC [ppm]
Tightness [%]
Unstable states
Tightness
Linear (Teghtness )
100
95
90
85
80
75
70
65
y = -0,0034x + 85,391
R2 = 0,1181
60
55
50
0
500
1000
1500
2000
2500
3000
3500
4000
4500
HC [ppm]
Fig. 10 presents the dependence of compression pressure changeability on hydrocarbons contents in fumes for unstable engine’s states; Fig. 11 – the dependence of cylinder tightness on hydrocarbons contents in fumes.
183
Aiming at the determination of diagnostic signals for border states, an additional
analysis of the obtained measurements results was carried out accepting the maximum
value and then the minimum one as the significant parameters of cylinder tightness [Hebda et al. 1984].
The minimum parameters
Coefficient R2 got improved for the dependence of minimum compression pressure
changeability on HC contents in fumes for the rotational speed at idle running (Fig. 12).
The improvement also concerns the compression pressure in oil trial.
A much better compatibility was also obtained for the parameter of cylinder tightness (Fig. 13).
Minimum parameters
Pressure
Oil trial
15
Linear (Pressure)
14
Linear (Oil trial)
13
12
y = -0,004x + 12,301
R2 = 0,2282
11
10
9
8
7
y = -0,0052x + 11,214
R2 = 0,2563
6
5
0
100
200
300
400
500
600
700
800
900
1000
HC [ppm]
Fig. 12. Dependence of changeability of minimum compression pressure on hydrocarbons contents
in fumes
Minimum parameters
Tightness [%]
100
95
90
Tightness
85
Linear (Tightness )
80
75
70
65
60
y = -0,0238x + 86,696
R2 = 0,1997
55
50
0
100
200
300
400
500
600
700
800
900
1000
HC [ppm]
Fig. 13. Dependence of changeability of minimum cylinder tightness on hydrocarbons contents
in fumes
184
Unstable states
Minimum parameters
Pressure
15
Oil trial
Linear (Pressure)
14
Linear (Oil trial)
13
12
11
10
y = -0,0011x + 11,707
R2 = 0,3998
9
8
7
y = -0,0012x + 10,339
R2 = 0,3202
6
5
0
500
1000
1500
2000
2500
3000
3500
4000
4500
HC [ppm]
Fig. 14. Dependence of changeability of minimum compression pressure on hydrocarbons contents
in fumes
Moreover an improvement of R2 was obtained for the dependence of minimum
compression pressure and tightness on hydrocarbons contents in fumes for the measurements results obtained in the unstable states (Fig. 14); for the oil trial the abovementioned improvement of coefficient R2 was slightly more significant
The maximum parameters
There was no improvement of coefficient R2 for any of the considered dependencies
accepting values equal to or much worse than those for mean parameters. This supports
the fact of a very significant influence of the technical state of a single cylinder in the
condition of border wear on mean toxicity of an engine’s fumes.
An analysis of the tests results shows that there exist dual mechanisms of the drop
in the above-piston space tightness [Korematsu 1990]:
–
PRC system’s wear,
–
wear of timing gear (sockets and valves connections).
Thus, it is inspiring to consider a quantitative evaluation of an influence of particular factors on the drop in the above-piston space tightness and to correlate the obtained
dependencies with fumes contents.
In connection to this aspect of the problem, for each engine type, compression pressure difference was calculated for all the tested items in oil trial and during the measurement of compression pressure without oil trial. The obtained differences from the
measurements of compression pressure were presented in the function of toxic elements
content in fumes from engines working in particular states.
The dependence of compression pressures difference in oil trial and without oil for
an engine of the Polonez car in the function of hydrocarbons contents in fumes for the
rotational speed at idle running is presented in Fig. 15, whereas the dependency of the
above-mentioned parameters on carbon monoxide content in fumes in fig. 16.
A statistical analysis was carried out to determine the dependencies: mean compression pressure (without oil), mean compression pressure (oil trial), mean tightness (group
185
I, explained variables) on: HC, CO, CO2, O2 contents in fumes and on the coefficient γ at
the rotational speed at idle running, at mean rotational speed and in unstable states
(group II, explaining variables).
Pressures difference [x 0.1 Mpa]
4
3,5
3
2,5
2
1,5
y = 0,0015x + 0,9301
1
0,5
0
0
100
200
300
400
500
600
700
800
900
1000
HC [ppm]
Fig. 15. Dependence of changeability of compression pressures difference in oil trial
and without oil on hydrocarbons contents in fumes
4
Pressure difference [x 0.1 Mpa]
3,5
3
2,5
2
y = 0,0109x + 1,3313
1,5
1
0,5
0
0
1
2
3
4
5
6
7
8
9
10
CO [%]
Fig. 16. Dependence of changeability of compression pressures difference in oil trial
and without oil on CO content in fumes
The statistical method of the analysis of multiple regression was used. For every
variable from group I progressive stepwise regression was carried out, appointing all the
variables from group II as the set of independent variables. Then, standard regression
was carried out for the statistically significant group II variables.
Tables were given with regression results (coefficients and their significance levels)
tab.1, 3, 5, 7 as well as tables of the variance analysis for regression and values pointing
at the assessment ‘goodness’ tab. 2, 4, 6, 8. Also, graphs of the scattering of the explained
variable in relation to each of the explaining variables were given.
186
The explained variable: mean compression pressure
Table 1. Regression results for mean compression pressure
Coefficients
Standard coefficient
error
Test function
value t(28)
Level p
10.86122
-0.0012
0.313531
-0.0012
34.64165
0.000334
1.55E-24
0.001181
W. free
HCM/M
Table 2. Variance analysis for mean compression pressure
Total root
square
Independence
levels
Mean root
square
F
Level p
28.19173
60.55443
88.74617
1
28
28.19173
2.162658
13.46324
0.001181
Regression
Error
Total
Regression equation
mean compression pressure = 10.861 – 0.001 . HCM/M
Where:
HC M/M – hydrocarbons contents in fumes in unstable states
Figures 17, 18, 19, 20 present a graphic interpretation of statistical analysis for the
explained variable of mean compression pressure
ŚREDNIE CIŚNIENIE SPRĘśANIA [x 0,1 MPa]
15
13
11
9
7
5
-500
500
1500
2500
3500
4500
HC [ppm]
Fig. 17. Chart of the scattering of dependence changeability of mean compression pressure
on hydrocarbons contents in fumes for unstable states
187
10
9
8
7
Liczba obs.
6
5
4
3
2
1
0
-2,5
-2,0
-1,5
-1,0
-0,5
0,0
0,5
1,0
1,5
2,0
Oczekiwane
Normalne
2,5
Fig. 18. Distribution of the standardized remainder for the analysis of mean compression pressure
2,5
Oczekiwana wartość
1,5
0,5
-0,5
-1,5
-2,5
-3,5
-2,5
-1,5
-0,5
0,5
1,5
2,5
3,5
Reszty
Fig. 19. The standard chart of remainders probability for the analysis of mean compression pressure
3,5
2,5
1,5
Reszty
0,5
-0,5
-1,5
-2,5
-3,5
5
6
7
8
9
10
11
12
Regresja
95% p.ufności
Wartość przewidywana
Fig. 20. Predictability in relation to the remainder values for an analysis of mean compression
pressure
188
The explained variable: mean compression pressure (oil trial)
Table 3. Regression results for mean compression pressure (oil trial)
Coefficients
W. free
HCW
Standard coefficient Test function value
error
t(28)
12.57466
-0.00329
0.437663
0.001309
Level p
28.73136
-2.51077
2.54E-22
0.018097
Table 4. Variance analysis for mean compression pressure (oil trial)
Regression
Error
Total
Total root
square
Independence
levels
Mean root
square
F
Level p
9.736858
43.24764
52.9845
1
28
9.736858
1.544559
6.303975
0.018097
Regression equation:
mean compression pressure oil trial = 12.575 – 0.003 . HCw
Where:
HCw – hydrocarbons contents in fumes for the rotational speed at idle running
Figures 21, 22, 23, 24 present a graphic interpretation of the statistical analysis for
the explained variable of mean compression pressure in the oil trial
ŚREDNIE CIŚNIENIE SPRĘśANIA (Próba olejowa) [x 0,1 MPa]
14
13
12
11
10
9
8
7
6
-100
100
300
500
700
900
1100
HC[ppm]
Fig. 21. Chart of the scattering of dependence changeability of mean compression pressure
in the oil trial on hydrocarbons contents in fumes for the rotational speed at idle running
189
11
10
9
8
Liczba obs
7
6
5
4
3
2
1
0
-3,5
-3,0
-2,5
-2,0
-1,5
-1,0
-0,5
0,0
0,5
1,0
1,5
Oczekiwane
Normalne
2,0
Fig. 22. Distribution of the standardized remainder for the analysis of mean compression pressure
in oil trial
2,5
Oczekiwana wartość
1,5
0,5
-0,5
-1,5
-2,5
-4
-3
-2
-1
0
1
2
Reszty
Fig. 23. The standard chart of remainders probability for the analysis
of mean compression pressure
2
1
Reszty
0
-1
-2
-3
-4
9,0
9,5
10,0
10,5
11,0
11,5
12,0
12,5
13,0
Regresja
95% p.ufności
Wart. przewidywana
Fig. 24. Predictability in relation to the remainder values for an analysis
of mean compression pressure in oil trial
190
The explained variable: mean tightness
Table 5. Regression results for mean tightness
W. free
HCW
Coefficients
error
Test function
value t(28)
Level p
89.155
-0.01894
2.643518
0.007908
33.72589
-2.39475
3.23E-24
0.023566
Table 6. Variance analysis for mean tightness
Regression
Error
Total
Total root
square
Independence levels
Mean root
square
F
Level p
323.1534
1577.782
1900.935
1
28
323.1534
56.34936
5.73482
0.023566
Regression equation:
mean tightness = 89.155 – 0.019 . HCw
where:
Table 7. Regression results for mean tightness
W. free
O2W
HC W
Coefficients
error
Test function
value t(27)
Level p
83.88395
1.13713
-0.01757
2.941943
0.384695
0.007015
28.51311
2.95593
-2.50447
0.000000
0.006399
0.018604
Table 8. Variance analysis for mean tightness
Regression
Error
Total
Total root
square
Independence
levels
Mean root
square
F
Level p
708.908
1192.028
1900.935
2
27
354.4538
44.1492
8.028548
0.001836
Regression equation
mean tightness = 83.884 + 1.137 . O2w – 0.018 . HCw
where:
O2w - oxygen content in fumes for the rotational speed at idle running
191
CONCLUSION
On the basis of the carried out research and analyses supported by theoretical science the following general conclusions can be formulated:
1. PRC system’s wear is connected with an increased oil consumption in an engine
and change of cylinder space tightness. Due to oil combustion, toxic contents level rises
in fumes. During tests on a 115C.076 engine of the Polonez car in unstable states it was
found out that the compression pressure drop by 42% (from 1.35 to 0.78) is accompanied
by the 38 times increase of hydrocarbons HC contents in fumes (from 60 to 2380 ppm).
However, a further drop of compression pressure from 0.78 to 0.59 MPa i.e. by 24% is
accompanied by an increase of hydrocarbons HC contents in fumes by 76% (from 2380
to 4190 ppm). This confirms the correlation of PRC system’s wear, described by the
drop of compression pressure, with oil consumption and the emitted fumes contents.
2. There exists a strict correlation between the level of toxic contents in fumes and
PRC system’s wear. In the case of a 115C.076 engine the following exemplary dependencies take place – compression pressure drop from 1.35 to 0.78 MPa causes a 340 times
increase of CO contents in fumes in the conditions of an engine running with the rotational speed 3000 rpm (from 0.02 to 1.14% CO).
3. Fume contents fulfill all the requirements for diagnostic signals and may be exploited for a diagnosis of PRC system’s technical state, being an exceptionally easily
accessible diagnostic parameter. What is more, the dependencies pattern for the parameters of PRC system’s parameters on toxic contents in fumes is described by linear regression, consequently, the pattern is clear and linear, which fulfills the requirements for
diagnostic signals.
4. An evaluation of an engine’s technical state by fumes’ analysis can be used
within the broadly understood motor diagnostics. There are premises for the use of the
presented method in a continuous self-evaluation of the PRC system’s state, realized by
the systems of deck diagnostics in vehicles, due to easy accessibility of fumes contents
diagnostic signal.
5. The most valid fume content for the description of the PRC system’s wear are
hydrocarbons HC, which is a natural consequence of the thermal process of oil consumption in the combustion chamber.
REFERENCES
Hebda M., Niziński S., Pelc H. 1984: Podstawy diagnostyki pojazdów mechanicznych. WKiŁ
Warszawa.
Korematsu K. 1990: Effects of Fuel Absorbed in Oil Film on Unburt Hydrocarbon Emissions from
Spark Ignition Engines. JSME International Journal. Series II. Vol. 33, No 3.
Merkisz J., Mazurek S.: Pokładowe systemy diagnostyczne pojazdów samochodowych, WKiŁ,
Warszawa 2002.
Merkisz J. 1989: Analiza wpływu wybranych czynników na zuŜycie oleju w czterosuwowych
silnikach spalinowych. Silniki Spalinowe 4.
Oktaba W. 1976: Elementy statystyki matematycznej i metodyka doświadczalnictwa. PWN, Warszawa.
Wajand J. A. 1969: Uszkodzenia trakcyjnych silników spalinowych. WNT, Warszawa.

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