Article citation information:
Marzec, P. An examination of vehicles at the
brake-chassis test bed in the range of the partial engine load. Scientific Journal of Silesian University of
Technology. Series Transport. 2017,
95, 121-131. ISSN: 0209-3324. DOI: https://doi.org/10.20858/sjsutst.2017.95.12.
Paweł MARZEC[1]
AN EXAMINATION OF VEHICLES AT
THE BRAKE-CHASSIS TEST BED IN THE RANGE OF THE PARTIAL ENGINE LOAD
Summary. The performance of a ZI engine is presented in
the paper, as well as a project involving a device for applying a partial load
in the performed examinations of a brake-chassis test bed. The device was
prepared for an Opel Astra and enabled the determination of exterior
characteristics of the engine for different values of the engine load. The
indicating pressure sensor and the angle marker on the crankshaft allowed for
the recording of the indicating pressure obtained at different values of the
load. The analysis of heat evolution in the process of burning, based on the
registered results of the measurements at the brake-chassis test bed, has also
been included in the presentation.
Keywords: Partial load of the engine; external
characteristics of the engine; indicated pressure.
1. INTRODUCTION
The advancement of technologies, as
applied in vehicles, forces the development of the automotive market as well as
the testing and diagnosing of vehicles. Therefore, servicing and diagnosing
service workshops are a vital issue. The used measuring equipment should be
universal, precise, reliable and easy to use for different types of vehicles.
The brake-chassis test bed has become commonly used in car servicing. This
equipment enables the testing of a vehicle’s parameters in a non-invasive way
and shows the actual conditions of the engine. The brake-chassis test bed is
not only used for testing vehicles in use, but also for testing vehicles
straight after they have been produced in the form of quality tests.
The
performed examinations are of the same type for all kinds of engines and cars.
Measuring wheels’ torque at the total engine load and at the full range of
rotational speed is the basic test procedure and shows the engine’s
characteristics, which, in turn, can be compared with the technical documentation
of the vehicle. It must be noted here, however, that the engine’s full load is
not a typical state of a car’s exploitation. In practice, only a certain part
of an engine’s power is used. It is problematic to carry out tests with a
partial load of the engine because the used standards are not repeatable in
terms of obtaining the applied loads. The brake-chassis test bed regarding
R&D and vehicle diagnoses calls for further solutions of this problem. The
method presented in this paper allows for the use of partial loads, which
correspond to the mode of street traffic.
2. THE IDEA AND THE CONSTRUCTION OF THE DEVICE
The
measuring method requires a device to be constructed, which can be placed under
the accelerator pedal and comprise pads limiting the pedal travel (Fig. 1).
Fig. 1. The work of an accelerator
pedal with an applied device mounted on the original flat bar of the cabin
floor
The device has been made for a car,
but it can also be used in other types of vehicles because of its simple
construction. The possibility of fixing the device on the cabin floor, instead
of the original limiter under the accelerator pedal, has to be checked first.
Such a solution ensures a stable and repeatable fixing of the device during the
performed measuring tests.
A set
of pads limiting the pedal travel concerning different heights has to be
constructed so that the pads can be easily changed. The length of pads is
adjusted by the depth of pressing the accelerator pedal, which, in turn,
correlates with the degree of the throttling valve’s opening.
Dimensioning of the space under the accelerator pedal makes it possible
to determine the maximal dimensions of the device, as well as the angle between
the floor and the flat bar, which stands out. This is essential for the proper
position of a device (against the flat bar), which must convey the load force
applied by the operator from the accelerator pedal through the base of the
device on the cabin floor.
Fig. 2. Drawing of the device
The drawing of the device was
created using the SolidWorks 2013 program. The following elements have been
taken into consideration at the stage of graphic designing: the base of the
device, the assembly jig and the seat where the pads of different length can be
placed. The dimensions are presented in Fig. 4.
Fig. 3. Mounted device in a car Fig. 4. The device’s changeable pads
for adjusting
the depth when pressing the accelerator pad
3. CALIBRATION OF THE DEVICE
The next step is to define the
dependence between the height of the limiting pads and the degree of the
opening of throttling valve. The linear dependence of the degree of the opening
of the throttling valve regarding the function of TPS signal has been
elaborated first. Meanwhile, the diagnostic tester, which can measure a signal
from the TPS sensor, has been used. The dependence of the tension values of the
TPS sensor from the position of the pedal has been established, taking into
account the boundary values of the tension in terms of the minimal and maximal
pressing of the accelerator pedal. In turn, the degree of opening of the
throttling valve for every pad in a given set has been determined. The results
are presented in Table 1.
Fig. 5. Linear dependence of the
throttling valve opening in the function of the TPS signal
Table 1. Defining the degree of the
throttling valve opening for the produced pads
|
No. |
Tension values of TPS [V] |
Height pads limiting the pedal [mm] |
The degree of throttling valve opening [%] |
|
1 |
4.32 |
26 |
98 |
|
2 |
3.95 |
33 |
90 |
|
3 |
3.30 |
42 |
75 |
|
4 |
3.03 |
46 |
69 |
|
5 |
2.85 |
49 |
65 |
|
6 |
2.66 |
52 |
60 |
|
7 |
2.36 |
56 |
54 |
|
8 |
2.09 |
61 |
48 |
|
9 |
1.93 |
63 |
44 |
|
10 |
1.66 |
67 |
38 |
|
11 |
1.44 |
71 |
33 |
|
12 |
0.94 |
73 |
21 |
4. THE SUBJECT AND THE RANGE OF PERFORMED EXAMINATIONS
The Opel Astra F with a 1.6 dm3
engine for unleaded fuel has been examined (Fig. 6).
Fig. 6. Car at a test stand
Table 2. Technical data of the tested engine
|
Engine
designation |
X16SZR |
|
Number/cylinder layout |
4 R |
|
Engine capacity |
1,596 cm3 |
|
Degree of
compression |
9.6 |
|
Cylinder
diameter |
79.0 mm |
|
Stroke of
the piston |
81.5 mm |
|
Max. power |
55 kW |
|
Power
rotation max. |
5,200 obr/min |
|
Torque max. |
128 N۰m |
|
Torque
rotation max. |
2,800 obr/min |
The range of performed examinations
comprise the external characteristics of the engine, its maximal power, and the
torque depending on the level of load. The performed examinations are in
accordance with procedures of the BOSCH FLA203 brake test bed producer, whereby
the direct gear speeds up to the maximal engine rotation and then freely slows
down when idle running. Unleaded fuel 95 was used in the tests. The following
engine loads have been used in the tests: 21, 33, 48, 60, 75, 90 and 100%. The
car engine was also equipped with an indicating pressure sensor placed in the
sparking plug and a KISTLER angle marker mounted on a pulley of a crankshaft.
The measurement and acquisition of indicating pressure values were therefore
possible. On the basis of the obtained data, further simulation calculations of
the burning process were carried out.
5. ELABORATION OF MEASUREMENT RESULTS
5.1. Exterior characteristics of the engine
Maximal values of power and moment,
as well as respective rotational speed, are presented in Table 3.
It can
be easily noticed that the increase of power and torque depend directly on the
rotational speed of the engine and load. The bigger the load, the higher the
torque and engine power.
Fig. 7. Course of power depending on
the engine rotation at different engine loads
The course of engine power at 100
and 90% is almost identical, whereas the lower the load, the bigger the
diversity of the obtained power for the examined loads. It is particularly so
at high rotational speed. The smallest differences can be observed at low
rotational speed: at 2,000 rotations/min, the obtained power is almost the same
for loads of 100, 90, 75, 60 and 48%. Loads of 33 and 21% feature low power and
a characteristic course within the whole range of rotational speed. The
obtained curves are almost flat, while power is at a constant level (Fig. 7).
Comparing all measured curves of
torque, it can be noticed that clear anomalies occur at the lowest loads (33
and 21%), as well as the power curves. The diagrams feature a linear course,
while they intensively drop down with an increase in rotational speed. They
feature big differences in the value of torque between the initial and final
parts of curves up to more than half of their value. The other curves have
natural curve-like shapes. The smallest differences of rotational moment values
are at the highest loads (75, 90 and 100%). A diagram of obtained maximal
values is made based on the values in the table below (also see Fig. 9).
Fig. 8. Course of the vehicle’s
torque depending on engine rotations at different engine loads
Table 3. Maximal values of power and
torque of the engine at different loads
|
Engine load |
Engine speed [rev/min] |
Maximum
power [kW] |
Engine speed [rev/min] |
Maximum
torque [Nm] |
|
100% |
5,469 |
59.87 |
2,630 |
139.41 |
|
90% |
5,618 |
60.56 |
2,760 |
139.08 |
|
75% |
5,260 |
57.24 |
2,770 |
132.56 |
|
60% |
4,981 |
50.76 |
2,640 |
127.81 |
|
48% |
4,025 |
40.95 |
1,784 |
122.56 |
|
33% |
3,317 |
23.56 |
1,455 |
100.83 |
|
21% |
2,760 |
18.32 |
1,375 |
94.42 |
5.2.
Changes of indicating pressure and heat evolution in the process of burning
A representative sample of the
examined states of engine load has been elaborated on the basis of 200
registered consecutive cycles of indicated pressure changes. The pressure
changes have been presented in the form of a closed indicating diagram. The
analysis of this diagram reveals the fact that, at loads above 50%, there are
slight differences, whereas the value of the pressure drops dramatically,
together with a decrease in the load below 50%, while the area of loop gets
smaller (Fig. 10).
Fig. 9. Cumulative diagram, with
maximal values (power and torque) in the total range of the examined loads
Fig. 10. Cumulative diagram of
pressure change depending on the volume of combustion chamber; n=2,500
rotations/min
Fig. 11. Obtained energy in the
process of burning
Experimental results were the basis
for calculating the changes in functions of heat evolution in the process of
burning. These changes are presented in diagram form (Fig. 12 and Fig. 13).
Fig. 12. Percentage degree of load
burning
Fig. 13. Speed of heat emission
The speed of heat evolution is comparable to
the highest engine loads (69 and 90%). The smaller the load, the lower the
speed of heat emission and the longer the process of burning.
6.
FINAL CONCLUSIONS
-
Vehicles in city
traffic and road traffic use maximal rotational speeds of the engine. Most
frequently, they work within the range of low and medium rotational speeds due
to the requirements of torque. Such engine conditions work with partial engine
loads.
-
The designed
device presented in this paper allows for repetitive conditions of the engine
to be obtained for the load in the course of examinations involving the
brake-chassis test bed.
-
The presented
design is suitable for the Opel Astra in terms of dimensions, while the idea
seems to be fairly universal.
-
Above 60% of
engine load, there is a slight change in the torque value and power. Below 50%,
the values drop dramatically.
-
The amount of
produced energy (Fig. 11), which changes in the engine’s work at different
loads, is due to a new load that is closely connected with the efficiency of
engine feeding.
References
1.
Tadeusz Rychter,
Andrzej Teodorczyk. 2006. The Theory of Piston Engines. Warsaw: Publishing
House of Communications and Connections.
2.
Sławomir Luft.
2006. Basics of
Engine Construction. Warsaw: Publishing House
of Communications and Connections.
3.
Kubica G. 2013. Efficient Energy Conversion in a Spark Ignition Engine Fueled
with Low-carbon Gaseous Fuels. Radom: Publishing House of the
Institute for Sustainable Technologies. ISBN 978-83-7789-218-3.
4.
Maciej Bernhardt,
Stanisław Dobrzyński, Edward Loth. 1988. Car Engines. Warsaw: Publishing House of Communications and Connections.
5.
Janusz Mysłowski,
Józef Kołtun. 2000. Flexibility Piston Internal Combustion Engines. Warsaw: Scientific and Technical Publishing House.
Received 14.02.2017; accepted in revised form 24.04.2017
Scientific Journal of Silesian
University of Technology. Series Transport is licensed under a Creative
Commons Attribution 4.0 International License
[1] Faculty of Transport, The Silesian
University of Technology, Krasińskiego 8 Street, 40-019 Katowice, Poland.
E-mail: pawel.marzec@polsl.pl.