The measurement accuracy of vehicle pollutant gases

Interdisplinary Journal of Research and Development
“Alexander Moisiu“ University, Durrës, Albania
Vol (I), No.1, 2014
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RESEARCH ARTICLE
The measurement accuracy of vehicle pollutant gases
ASLLAN HAJDERI*, ELI VYSHKA
Department of Mechanics and Transport,”Aleksander Moisiu” University Durres, ALBANIA.
*Author of correspondence: Email: [email protected]
Abstract:
In this study analyzed the current methods used to measure pollutant gases, that vehicles issue into
the atmosphere. The goal is to apply methods that provide precise values of pollution during technical
inspection of vehicles in Albania. In beginning theoretical study of pollutant gases arising from
exhaust system is performed, where it results that the pollution amount depends on the regimes of
speed and engine load. From the analysis of methods it results that the pollution values measured
with loaded test mode are two times more accurate than the no loaded test mode. In conclusion, it is
proposed that during technical control of vehicles in Albania, it should use the loaded test mode and
remote testing mode and become the control of nitrogen oxides, which have important impact for
environmental pollution and global warming.
Keywords: pollutant gases, pollution measurement, loaded test.
Introduction
Number of vehicles with internal combustion engine,
which use thermal energy released from burning fuel is
currently increased greatly. Fuels used today are
massively fossil hydrocarbons. By burning them into the
atmosphere it is issued some harmful gases as
hydrocarbons (HC), carbon monoxide (CO), carbon
dioxide (CO2), oxides of nitrogen (NOx) and particles
matter (PM)[7].
Also these emissions contribute to global warming, the
creation of smog and toxic odors, exacerbating human
health [4]. Recognizing the impact that they have on the
environment it should be taken measures to reduce them
and to increase the air quality.
The study relies on the theoretical study of the emissions
creation in the combustion chamber in order to see from
depend them and to determine that which regimes are to
be measured to find more accurate values of vehicle
pollution level. For this it is explored in the used methods
in the world for vehicle pollution inspection in order to
they be applied in our country.
Theoretical analysis of pollution gases creation from
vehicles
Development of burned emissions in a engine with
gasoline is given in figure 1. It shows that most of them
produced when the amount of air entering into the engine
is lower, than the proper rate for burning of fuel and the
amount of oxygen is deficiency [8]. The level of HC and
CO emissions is a function of the mixing ratio air/fuel and
depends on the ingredients of fuel, the combustion
process, combustion chamber geometry and operating
parameters of the engine.[3],[8]. This occurs because in a
rich mixture, where is not enough oxygen to oxidize all
carbon and hydrogen and it will result high levels of HC
and CO in the burned gases. So in no-load regime and
maximal regime the amount of HC and CO emissions is
greater
81
Diesel engines use poor mixture, therefore the creating of
HC and CO emissions is smaller than in petrol engines.
Here is inhomogeneous mixture and the fuel is added
during combustion. In the process of burning have many
flames fronts at the same time. In each regime there is
very rich area and many poor areas too [5].
So in loaded regime it will created more HC, CO than at
no loaded regime.
Carbon dioxide (CO2) is the result of complete
combustion of carbon of gasoline. If the level of CO2 is
low, the mixture can be very rich or very poor. A higher
reading, it indicates an efficient work of engine.
Oxygen (O2 ) is in the air, that introduced into the engine
and it is used to burn the carbon and hydrogen of fuel
(hydrocarbons). For an efficient work of engine, the
reading of O2 in the burned gases it should be very low
(about 0.5 %). Nitrogen oxides (NOx) are generated in
very high
Figure 1. Development of combustion emissions in a
spark ignition engine
The measurement accuracy….
A. Hajderi, E. Vyshka
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temperatures (over 13700 C), that occur in the combustion
For diesel engines it measured the opacity coefficient,
chamber. Chemical nitrogen balance is dependent on the
which indicates the degree of gases blur caused by HC,
temperature. So, in creating of NOx it affects high
NOx and particulate matter PM.
temperature, excess amounts of oxygen and hinders the
According to existing methodology of no-load test, in
combustion process speed. (This show at modern engines
measurements values affect some factors that reduce the
with high revolution ) [3], [5].
degree of confidence in the safety of pollution levels.
Peak of NOx formed for mixture less poor (k = 0.95) and
Test types for inspection of vehicle pollution level
most of it is created around spark plug, where
To measure the level of vehicle pollutant gases, several
temperatures are higher.
types of tests are used:
So in the average load regime and small revolution, NOx
Idle test mode (no-loaded test)
formation is greater, than the no-loaded regime.
For vehicles with spark ignition, the measurement of
-The diesel engines produce more NOx, because poorer
exhaust emissions become from vehicle exhaust pipe in
mixture is used. While in diesel engines the temperature
idling speed and /or 2500 rpm. Advantage of this testing
of burning contributes to a increasing of rigid soot
is that the device is relatively cheap, but has the
(particulate matter PM). The maximum amount of
disadvantage that performs measurements only for 2
particles occurs when the engine is under load in terms of
gases ( HC and CO) and does not measure NOx.
fuel injection with maximum power (rich mixture)
From the analysis made it seems that in no loaded mode
So in the regime with small revolution the creation of
in high revolution to have poor little mixture (α = 1,05),
NOx and PM is many times greater than in the no-loaded
while in the loaded regime the mixture becomes richer (α
regime and in high revolutions.
= 0.95) and HC, CO increase over 2 time and in noHigh pressure injection provides a finely spraying of
loaded mode NOx can not be measured.
diesel, which reduces HC and PM emissions, but
For vehicles with diesel engine the measurement of
increases the temperature and NOx emissions.
emissions is made by determining the degree of turbidity
of the exhaust gases during the acceleration of engine
The control of vehicles pollution level
To limit the vehicles pollution level, CE has issued
without load up to higher speeds. For this it made 3
directive 2009/40/CE of May 5, 2009 which in technical
measurements consecutive of opacity coefficient and it
control of vehicles sets conditions for pollution tests,
taked their average value (test is successful if values of
which are [1]:
measurements differ less than 60%, otherwise the
operations should be repeated).
In this case the
For engines with spark ignition
a) When there is no emission control system
measurements of opacity coefficient depends from the
-After a period of engine work (at normal temperature) it
degree of acceleration performed by the inspector
measure the content of carbon monoxide (CO) of exhaust
(method accepts that error goes above 60%)
gases, when the engine is idling speed.
Loaded test mode
b) With the advanced control system (with catalytic
This test uses a test table, that simulates placing a load on
converter):
the vehicle. Applied load responds road resistances
-After a period of engine work (at normal temperature) it
coefficient at a given vehicle speed and it depends from
is measured lambda value (O) and CO content in the nothe engine cylinders. Equipment measure equally HC and
loaded regime, with minimum speed and high speed (at
CO emissions from the samples taken from the exhaust
least 2,000 rpm )
gas for two speed [3] (Fig. 2).
While for diesel engine the opacity coefficient is
For diesel engines
After a period of engine work (at normal temperature), it
measured
during engine acceleration with a load of
is measured opacity coefficient of exhaust gases, which
vehicle.
is considered an adequate indicator of vehicle
maintenance conditions, to respect emissions.
Opacity of the gas is
measured during engine
accelerationon no-load regime from the minimum speed
to a high speed (or ½Vmax ) with the gear lever in neutral
and the open clutch.
This directive defines and conditions prior to vehicle
inspection, according to which in Albania applies
guidance of MPPT [6], where given the maximum
allowable values of emissions.
For measuring the emission of gases it is used gas
analyzer, which is used to detect the amount of harmful
Figure 2. Measurement of vehicle emissions during
gases in the exhaust emissions of the vehicle. This
loaded test
information can be used to control the work of the fuel
Acceleration simulation test mode of vehicle
and ignition system, which are associated with the
This test uses a simulated load, and measurements are
performance of the engine. For engines with spark
performed in acceleration regime with given acceleration
ignition analyzers measure the gas content of CO, HC,
(3.3 mph / sec) to get a fixed speed. So during loaded test
CO2, O2 and NOx, which measure only with
with 50% of power and speed 15 mph (ASM 50/15) it
5 gases analyzers [2].
produced high level of NOx, while at loaded test with
82
Interdisplinary Journal of Research and Development
“Alexander Moisiu“ University, Durrës,
Albania
Vol (I), No.1, 2014
________________________________________________________________________________________________
25% of power and speed 25 mph (ASM 25/25) it
test mode and remote testing mode. Also measurements
produced higher level of HC and CO[3].
made in technical inspection center in Durres with no
Remote testing mode
loaded test mode for 3 vehicles, which did not receive the
This test is carried out in real conditions of speed and load
maximum revolutions, shows that the increase of fuel
(in sloping road) [3].
quantity leads to an extreme increase of the opacity
The device for measuring of the pollution level is remote
coefficient (Fig. 3)
and through a infrared light, that passes in the gas flow of
The analysis of used tests for vehicle gases and
a vehicle that is running. The device is portable analyzer.
experience show that, also in Albania it should applied
This test is used during random roadside testing,
the loaded test mode notwithstanding that tecnic
including visual inspection to detect the intervention in
inspection have higher cost.
emission control equipment (Many users after pass
Remote testing mode is accurate and free. This can be
annual technical inspection,
intervene in control
used by the public sector on the road, giving a
equipment). This can be used in large areas, where
contribution to improving air quality, by making stopping
environmental pollution is problem and when the owners
of vehicles with high pollution over allowed limits, but
come to be equipped with plates, or to make changes to
also it servis to detect interventions in the emissions
the property
systems of the vehicle. (This is a requirement of the
EPA)[3]. Using of the more accurate modes of measuring
Test mode from board (OBD-II testing)
This test makes precise control of exhaust gas emissions,
of the vehicle pollution level, affects in the reduction of
using OBD-II systems, that are located in the vehicle,
smog in urban areas and global warming in general and
which monitor the efficiency of catalytic converters,
increase of human life.
engine ignition system, the lambda sensor, EGR valve
In terms of the large increase of vehicles in our country it
action, performance of injection system, etc..
should be strengthened technical inspection for pollution
level, because it leads to the improvement of technical
Discussions
From the analysis of the combustion process is clear that
maintenance of vehicles and reduction of air pollution.
in the loaded mode test, the emission level of HC, CO is
For this it should that criterion of pollution level during
about 2 times higher than in no-loaded mode. Also in the
technical inspection become stopper criteria for vehicle
loaded test the pollution level of NOx and PM is higher,
circulation and it should used loaded test mode and
due to the high temperatures generated. Using of catalytic
remote testing mode. The owner should maintain vehicle
converters make the reduction of emissions, but does not
or he removes it from circulation.
change the report and for loaded mode test.
Therefore to contribute in improving of the air quality it
Using of EGR valve, especially in diesel engines, not
should be used stimulus to reduce the tax of circulation
only reduces NOx, but it affects in avoiding of the
for existing vehicles, that provide low pollution level [9].
detonation phenomenon, in power reduction and in the
While for imported vehicles should be lowered customs
damage that causes in engine tools.
duties for less polluting vehicles and for vehicles
In order to reduce environmental pollution and global
manufactured after 2001
warming, Directives of CE advise a more rigorous control
regarding vehicle emissions, looking introducing of
Conclusions
OBD- II system for new vehicles
-Pollution values issued with no load test mode have an
inaccuracy up 2 times and not measure NOx, which is a
gas too dangerous for the world. Current methodologies
for vehicle tecnic inspection must change.
-Loaded test mode and remote testing mode give the
pollution values closer to reality. They can be applied
easily by technical inspection center. Remote testing
mode is accurate and cheaper. This should be applied in
our country from the public sector, after technical
inspection for detect interventions in exhaust system.
-Using of the more accurate methods for assessing of the
vehicle pollution level directly affects in improving of air
quality, in global warming and the human life.
-Environment pollution reduction from vehicles in our
Figure 3. Dependence of the opacity coefficient from the
country can be arrived by improving the technical
engine revolutions
maintenance of the vehicle from user. For this it should
that criterion of pollution during technical inspection of
From analysis of vehicle gases testing modes it seems
vehicles become the stopper criteria for vehicle
that no-loaded test mode (for 1 and 2 speed) does not
circulation.
show the actual level of vehicle pollution. Method of
measurement itself admits inaccuracy to 60% for diesel
Leterature
engines. Therefore to get more exact pollution level, it
should used loaded test mode , acceleration simulation
83
The measurement accuracy….
A. Hajderi, E. Vyshka
________________________________________________________________________________________________
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%2FEC%20&nfpr=1&ei=hvtMTsOhKc_oOcunvPgG&sq
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