**1. Introduction**

Exhaust emissions have long been the leading factor determining the improvement of powertrains and combustion engines. The technological advancement causes an increased emission of the greenhouse gases, CO2 in particular, while one of the most important sources of its emission is the combustion of fuel in engines. Another aspect tightly related to the operation of combustion engines is engine exhaust emissions. Today, we know that the exhaust components generated by engines such as CO, HC, NOx , and PM are hazardous to humans. The report published in 2012, International Agency for Research of Cancer (IARC), one of the branches of World Health Organization (WHO), informed that diesel exhaust gas causes cancer (IARC) [1]. Earlier, this exhaust gas was classified in a group containing factors referred to as probably carcinogenic. Upon analysis of the results of the most recent environmental research, the WHO scientists unanimously concluded that diesel exhaust gas causes cancer [2–4]. In the report of the US Environmental Protection Agency (EPA), following decades of research and laboratory tests on animals, it was confirmed that the particles are carcinogenic, and significantly contribute to the development of cancer, lung cancer in particular [5]. Therefore, carmakers treat the problem of exhaust emissions with priority.

included the application of tests performed under actual driving conditions. This type of research, however, requires technologically advanced equipment (PEMS) that is increasingly often proposed by automotive measurement equipment manufacturers in their portfolio (AVL List GmbH, Horiba Ltd. and Sensors Inc.). This type of equipment can be used for testing machines and vehicles fueled with different fuels such as gasoline, diesel fuel, CNG, LPG, or oxygenated fuels. This also requires the application of special filters or exhaust gas diluters. Besides, the discussed equipment is characterized by high sampling frequency—a minimum of 1 Hz and reaching 500 Hz [e.g., high speed exhaust flow meter

Measurement of Exhaust Emissions under Actual Operating Conditions with the Use of PEMS...

http://dx.doi.org/10.5772/intechopen.70442

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Due to the fast varying parameters of engines under actual conditions of operation and the advancement of aftertreatment systems, the equipment must be characterized by high measurement accuracy. The recording of ambient conditions is also necessary (pressure, temperature, humidity) as they have great impact on the measured values, hence additional corrective calculations are necessary. Therefore, the said measurement equipment often includes solutions (sensors, algorithms) that perform such procedures. What is more, the equipment must be characterized by low energy consumption, low weight and size, let alone high reliability. In order to perform a full analysis of the impact of a given type of powertrains and motion parameters of city buses on the environmental indexes, the following were utilized: SEMTECH DS (exhaust component concentration, oxygen content exhaust gas mass flow) as

The presented measurement equipment is a unique set of analyzers allowing the determination of energy consumption and environmental performance of vehicles under actual conditions of

• SEMTECH DS (**Figure 1**)—designed for the testing of gaseous exhaust components: NDIR:

• AVL MSS (Micro Soot Sensor—**Figure 2a**)—used to calculate the concentration of PM [mg/m3

• TSI 3090 EEPS™ (Engine Exhaust Particle Sizer™ Spectrometer—**Figure 2b**)—allows

• SEMTECH ECOSTAR (**Figure 3**)—allows measurement of both gaseous components and

• AVL OTR (On The Road) OPACIMETER—used to test the exhaust gas opacity [%]; and

• SEMTECH LASAR—allows determination of the content of the exhaust gas including NH3

The complementary analyzers are as follows: SEMTECH PPMD, SEMTECH LAM, AVL M.O.V.E., SEMTECH NMHC, AVL PARTICULATE COUNTER, TEXA NAVIGATOR TXT,

[ppm], and electrochemical O2

]

,

[%]; FID: THC [ppm]; NDUV: NO [ppm], NO2

well as AVL MSS (used to determine the concentration of PM).

determination of the size distribution of PM [nm];

(EFM-HS)].

operation:

[%];

N2

O, CH4

and AVL INDIMICRO.

CO [%], CO2

with the photo-acoustic method;

particulates (mass and number);

[ppm].

Toxic exhaust emissions studies conducted in real operating conditions clearly show that the level of actual emissions from vehicles is greater than the test limit values [6]. Real driving emission (RDE) tests are very often used to optimize engine performance in terms of emissions and fuel economy. May et al. [7] point out that the emission of nitrogen oxides is greater in the RDE studies than that obtained in laboratory tests. Consequently, they recommend using the RDE test results for the optimization of engine control systems. Similar conclusions were reached in [8]. In this paper, the authors compared RDE emissions to simulation results using the COPERT simulating tool. Nitrogen oxides emissions in simulation tests were about 30% of the values obtained in the RDE tests. The authors of papers [9–11] point out that the important factors influencing the results of RDE tests are the conditions in which the research is conducted: traffic intensity, driver predisposition, or weather. Hence, the need to regulate the RDE testing procedures. It can therefore be concluded that due to the serious risk posed to human health and the need to develop techniques and methods for measuring toxic emissions, the RDE emissions tests are highly desirable.

The issue tightly related to the problem of exhaust emissions is the legislation controlling the exhaust emissions from engines and vehicles. Throughout the years, this legislation has evolved mainly toward reduction of the admissible levels of individual exhaust components and advancement of research methodology. Today, the procedures of exhaust emissions measurement include driving under actual operating conditions (RDE) using portable emission measurement system (PEMS). This type of research is becoming commonplace for all vehicle categories.
