**5. Exhaust emissions legislation for engines of HDV vehicles**

For the HDV group of vehicles, due to their specific design characterized by significant size and power outputs, homologation in terms of unit emissions is performed for the engine alone on engine test beds. For all Euro standards, performing tests at preset points of work in stationary tests is necessary. Since 2000, the Euro III standard is applicable for the homologated vehicles. It is based on: European transient cycle (ETC), European stationary cycle (ESC), and European load response (ELR). The same procedures are applicable for the Euro IV, V, and EEV standards, but the exhaust opacity test for heavy-duty vehicles is performed in the ELR test. The boundary values of the exhaust emissions for diesel engines have been reduced with the introduction of further directives and regulations (**Figure 12**). A relative reduction of the unit emissions of individual exhaust components was: CO—67%, HC—88%, NOx —95%, and particulate mass—98%, respectively. For exhaust opacity, limits were applicable throughout the Euro III–V standards. Following the technological advancement of combustion engines and aftertreatment systems, an introduction of boundary values [particle number (PN)] in the Euro VI became necessary. Along with the introduction of the Euro III standard, an European transient cycle (ETC) became applicable in which the combustion engine was tested for dynamic operating parameters (**Figure 13**).

In the Euro VI standard, in relation to the previous regulations, requirements related to the diesel engine have been more extensively defined. The latest regulations do not allow for the additional division into regular standards and EEV.

During the development of the transient *World harmonized transient cycle* (WHTC) and stationary *World harmonized stationary cycle* (WHSC), road test results performed in selected EU member states, Japan and USA were taken into account. This aimed at approximating the test bed measurement cycles to the actual conditions of operation worldwide. The

previously applied tests were developed based on the European conditions exclusively. Detailed data on the realization of the tests are included in the *Global technical regulations* (GTR) no. 4 developed by UNECE [27]. Similarly to the transient cycle applicable for the Euro V standard, the WHTC trials can be realized on both chassis dynamometers and engine dynamometers, yet for the homologation, the latter option applies (**Figure 14**). There are three parts to the tests—urban driving, extra-urban driving, and expressway driving. The length of the trial is 1800 s. The length of the subsequent phases of the tests is

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The WHSC test was designed to measure the exhaust emissions under steady state conditions and is composed of 13 phases, similarly to the ESC test (**Figure 15**). The main difference between the said cycles is different engine speeds (the latter standard provides for six main engine speeds) and the application of different weight coefficients, resulting from the durations for each point of work. Besides, the measurement at idle occurs twice. It is noteworthy that the average values of n and T are lower than in the ESC test, which indicates that the

In the Euro V and Euro VI standards, mileages and periods of operation are given corresponding to a regular life cycle of a heavy-duty vehicle. Minimum mileages are also provided for the durability trials depending on the category and gross vehicle weight of the tested object. The legislation is supplemented with data related to the determination of coefficients of deterioration (more precise and unambiguous definitions have been included in the Euro VI standard) [18]. Important changes in the regulations were introduced in terms of the scope of supervision of the conformity in operation—it is now necessary to perform exhaust emission measurements under actual traffic conditions using PEMS. Earlier, only engines

900 s, 481 s, and 419 s, respectively.

engine is under smaller load.

(removed from the vehicle) were tested.

**Figure 14.** The engine torque and speed curves during the WHTC test [27].

**Figure 12.** Relative reduction of the admissible unit emission values related to the subsequent Euro standards for stationary tests [24, 25].

**Figure 13.** The engine torque and speed curves during the ETC test [26].

previously applied tests were developed based on the European conditions exclusively. Detailed data on the realization of the tests are included in the *Global technical regulations* (GTR) no. 4 developed by UNECE [27]. Similarly to the transient cycle applicable for the Euro V standard, the WHTC trials can be realized on both chassis dynamometers and engine dynamometers, yet for the homologation, the latter option applies (**Figure 14**). There are three parts to the tests—urban driving, extra-urban driving, and expressway driving. The length of the trial is 1800 s. The length of the subsequent phases of the tests is 900 s, 481 s, and 419 s, respectively.

The WHSC test was designed to measure the exhaust emissions under steady state conditions and is composed of 13 phases, similarly to the ESC test (**Figure 15**). The main difference between the said cycles is different engine speeds (the latter standard provides for six main engine speeds) and the application of different weight coefficients, resulting from the durations for each point of work. Besides, the measurement at idle occurs twice. It is noteworthy that the average values of n and T are lower than in the ESC test, which indicates that the engine is under smaller load.

In the Euro V and Euro VI standards, mileages and periods of operation are given corresponding to a regular life cycle of a heavy-duty vehicle. Minimum mileages are also provided for the durability trials depending on the category and gross vehicle weight of the tested object. The legislation is supplemented with data related to the determination of coefficients of deterioration (more precise and unambiguous definitions have been included in the Euro VI standard) [18]. Important changes in the regulations were introduced in terms of the scope of supervision of the conformity in operation—it is now necessary to perform exhaust emission measurements under actual traffic conditions using PEMS. Earlier, only engines (removed from the vehicle) were tested.

**Figure 14.** The engine torque and speed curves during the WHTC test [27].

**Figure 13.** The engine torque and speed curves during the ETC test [26].

stationary tests [24, 25].

112 Improvement Trends for Internal Combustion Engines

**Figure 12.** Relative reduction of the admissible unit emission values related to the subsequent Euro standards for

process, in order to issue a decision, only the second variant should be performed. The tests include the unit emission of gaseous exhaust components: CO and THC (for diesel engines),

**Urban Rural Motorway**

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

engines). Currently, the mass and number of particulates is not taken into account. Besides, it is necessary to measure the exhaust gas mass flow, engine parameters, vehicle speed, ambient

The assessment of the unit exhaust emissions is made using variable averaging windows (**Figure 16**). Their determination consists in obtaining the mass rate of the exhaust emissions for subsets of a complete data set, whose length is determined so that they correspond to the mass of

generated by the engine or work measured under transient conditions on a test bed (WHTC).

The condition for accepting the measurement window as valid is fulfilling the requirement of reaching an average power output exceeding 20% Ne max in that window. In the entire test, the percentage of measurement windows must be 50% or more. If this is not obtained, the data

(for diesel and spark ignition

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(for spark ignition engines) as well as NOx

**Figure 16.** Determination of the measurement windows in the method based on reference work [28].

, N1 45 25 30

N2 45 25 30 N3 20 25 55

**Table 3.** Share of the operating conditions during the conformity in operation tests (HDV) [28].

Class I, II & A 70 30 0

other 45 25 30

**Category Share of operating conditions [%]**

NMHC and CH4

conditions, etc.

CO2

M1

M2 , M3

M2 , M3

**Figure 15.** The course of the harmonized WHSC test (numbers 1 through 13 represent the order of phase completion; percentage values at subsequent phases indicate their weights) [27].

Regulation UE 582/2011 (schedule II) includes detailed requirements related to the determination of conformity in operation of the engines or vehicles. Out of the most vital information, it should be mentioned that the measurements must be performed on public roads of the UE member states, using typical driving styles and loads. This means that the tests are performed for standard (most frequently occurring) conditions of operation. During the test procedure, it is also important that the driver has sufficient skills and is properly trained to use the vehicle, preferably a person who uses this particular vehicle on a daily basis. If the tests cannot be performed under standard operating conditions, it is possible to use alternative routes. In light of the shortage of information on representative vehicle load, a replacement load is applied ensuring 50–60% of the maximum load.

Upon first registration of a complete vehicle fitted with a combustion engine from the homologated group of engines, the manufacturer must perform tests in operation within 18 months reaching a mileage of at least 25,000 km [28]. According to [29], the measurements must be repeated periodically, at least every 24 months throughout typical vehicle life cycle. The test route must include urban roads (speed range: 0–13.89 m/s), extra-urban roads (13.89–20.83 m/s), and expressways (in excess of 20.83 m/s). In justified cases, the order of the test routes may be changed. The shares of the drives under individual conditions depend on the category of the tested vehicle (**Table 3**). They are determined with the accuracy of ±5%, due to the actual traffic conditions that are hard to predict. It is very important that in the realized test route, five times the work performed during the WHTC test is obtained or five times the reference mass of CO<sup>2</sup> from the same test is reached.

The coefficients of conformity are determined for measurement windows identified with two methods: based on the mass of CO2 or total work performed by the engine. In the legislation


**Table 3.** Share of the operating conditions during the conformity in operation tests (HDV) [28].

Regulation UE 582/2011 (schedule II) includes detailed requirements related to the determination of conformity in operation of the engines or vehicles. Out of the most vital information, it should be mentioned that the measurements must be performed on public roads of the UE member states, using typical driving styles and loads. This means that the tests are performed for standard (most frequently occurring) conditions of operation. During the test procedure, it is also important that the driver has sufficient skills and is properly trained to use the vehicle, preferably a person who uses this particular vehicle on a daily basis. If the tests cannot be performed under standard operating conditions, it is possible to use alternative routes. In light of the shortage of information on representative vehicle load, a replacement load is applied

**Figure 15.** The course of the harmonized WHSC test (numbers 1 through 13 represent the order of phase completion;

Upon first registration of a complete vehicle fitted with a combustion engine from the homologated group of engines, the manufacturer must perform tests in operation within 18 months reaching a mileage of at least 25,000 km [28]. According to [29], the measurements must be repeated periodically, at least every 24 months throughout typical vehicle life cycle. The test route must include urban roads (speed range: 0–13.89 m/s), extra-urban roads (13.89–20.83 m/s), and expressways (in excess of 20.83 m/s). In justified cases, the order of the test routes may be changed. The shares of the drives under individual conditions depend on the category of the tested vehicle (**Table 3**). They are determined with the accuracy of ±5%, due to the actual traffic conditions that are hard to predict. It is very important that in the realized test route, five times the work performed during the WHTC test is obtained or five times the reference mass of CO<sup>2</sup>

The coefficients of conformity are determined for measurement windows identified with two

or total work performed by the engine. In the legislation

ensuring 50–60% of the maximum load.

percentage values at subsequent phases indicate their weights) [27].

114 Improvement Trends for Internal Combustion Engines

from the same test is reached.

methods: based on the mass of CO2

process, in order to issue a decision, only the second variant should be performed. The tests include the unit emission of gaseous exhaust components: CO and THC (for diesel engines), NMHC and CH4 (for spark ignition engines) as well as NOx (for diesel and spark ignition engines). Currently, the mass and number of particulates is not taken into account. Besides, it is necessary to measure the exhaust gas mass flow, engine parameters, vehicle speed, ambient conditions, etc.

The assessment of the unit exhaust emissions is made using variable averaging windows (**Figure 16**). Their determination consists in obtaining the mass rate of the exhaust emissions for subsets of a complete data set, whose length is determined so that they correspond to the mass of CO2 generated by the engine or work measured under transient conditions on a test bed (WHTC).

The condition for accepting the measurement window as valid is fulfilling the requirement of reaching an average power output exceeding 20% Ne max in that window. In the entire test, the percentage of measurement windows must be 50% or more. If this is not obtained, the data

**Figure 16.** Determination of the measurement windows in the method based on reference work [28].

evaluation is repeated applying lower power output thresholds. The reduction is made with 1% resolution, maximum 15% Ne max. Lower value renders the results invalid.

The coefficient of conformity in operation in terms of exhaust emissions *conformity factor* (CF) is determined in all windows for each analyzed exhaust component as per Eq. (1). In order to render the evaluation in a given averaging interval positive, the determined coefficients cannot be greater than 1.5. The vehicle is considered compliant if 90% of the calculated CF values meet this criterion.

$$\mathbf{CF} = \frac{e\_j}{L\_j} \tag{1}$$

The test procedure does not determine any specific driving cycle, but it contains guidelines related to the determination of the area for which the emission is measured. The tests can be performed under any operating conditions. It is vital that in a certain range, the engine operates for at least 30 s in the control area. In this period, the values of engine speed and load may not exceed a predetermined area. The obtained values of exhaust emissions are averaged and in the final stage compared to the applicable NTE emission limits. In order to determine the control area, it is necessary to determine the basic engine characteristics and

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• the minimum engine speed (engine A) is analogical to the engine speeds of the European

• all points of work in which the engine develops power lower than 30% of the maximum

• the engine manufacturer may apply for an exclusion from the NTE area of engine speeds and loads for which the unit fuel consumption is greater than 5% of the minimum fuel consumption, if he expects that the engine will not work in these areas during regular operation. This does not apply to engines coupled with automatic transmissions of a specified

Due to the obtained maximum engine speeds (2400 rpm), there are small differences in defin-

For the tests, the authors selected a road portion of the length of 27 km (**Figure 18**). The road portion well characterizes the operation of vehicles of the GVW exceeding 16,000 kg (long haulage) in the area where the measurements were carried out. The test route started and ended in the industrial zone (point A) where a production facility is located at which approximately 50 heavy-duty vehicles are handled daily. The test road portion can be divided into two parts: a drive on urban roads (portion A–B) and national and regional roads. The drive on national or regional roads depends on the driving direction from/to the entrance to the A2 expressway (Koło) (point D). In the case of driving to the "Koło" expressway entrance, the route went through points B–C and C–D. In the reverse situation, i.e., exiting the expressway and driving to the production facility via bypasses: points D–C and C–B (on the D–C road portion heavy-duty trucks of the GVW in excess of 7000 kg are not permitted.) The above route can be deemed representative of the national transport and logistic infrastructure representing the road infrastructure and the distribution of production facilities in small and

stationary cycle (ESC) test, just as is in the case of engine B;

number of speeds and vehicles with manual transmissions.

ing the area excluded from the measurement of particulate matter.

power are excluded from the NTE area; and

• engine load is equal or greater than 30% of the maximum engine torque;

meet the following conditions [25]:

**6. Testing heavy-duty vehicles**

**6.1. The route**

medium-sized towns.

where CF—coefficient of conformity in a given averaging window; *Lj* —admissible emission of a *j*th component in the WHTC test [mg/(kW h)].

The American *United States Environmental Protection Agency* (US EPA) has proposed a test serving the purpose of controlling the exhaust emissions from heavy-duty vehicles under non-test conditions *not-to-exceed* (NTE) that could be applied during the assessment of the actual environmental indexes. The NTE requirements were introduced in 1998 as an ordinance with the consent of the HDV engine manufacturers [25]. The test stringent requirements were gradually extended to other engine categories. As an assumption, the limits and procedures of the test performance were developed as an additional confirmation that exhaust emissions are in conformity with the legislation in the entire range of engine speeds and loads. The NTE test area of an example engine has been shown in **Figure 17**.

**Figure 17.** The NTE test area for the engine of a heavy-duty vehicle.

The test procedure does not determine any specific driving cycle, but it contains guidelines related to the determination of the area for which the emission is measured. The tests can be performed under any operating conditions. It is vital that in a certain range, the engine operates for at least 30 s in the control area. In this period, the values of engine speed and load may not exceed a predetermined area. The obtained values of exhaust emissions are averaged and in the final stage compared to the applicable NTE emission limits. In order to determine the control area, it is necessary to determine the basic engine characteristics and meet the following conditions [25]:


Due to the obtained maximum engine speeds (2400 rpm), there are small differences in defining the area excluded from the measurement of particulate matter.
