Test cycles, exhaust emissions

Fig. 1. CO and hydrocarbon tailpipe emissions. Data from a test vehicle during a test cycle where the catalyst was mounted - 1.2 m from the exhaust part...

Figure 1.1. General trend of the NOx and particulate emissions in Europe, Japan and the U.S. for light- and medium-duty engines (ESC test cycle) and effect of engine tuning on NOx/particulate emissions and fuel consumption. EGR exhaust gas recirculation. ESC test cycle European stationary cycle (http //www.dieselnet.com/standards/cycles/esc.html).

Typical emission factors for metals cannot be derived from baseline characterization of auto exhaust by dynamometer tests, as performed by EPA, since attempts are made to keep variability of additives, oils, and lubricants to a minimum. Emphasis is placed rather on the eflFect of emissions as a function of variations in operating conditions. The data cited in Table X reflect this because test cycles identified as FTP, HWFET, and CFS differ significantly in the average speed (19.9, 49.9, and 35.0 mph, respectively) and in the extent of variability in operating mode (acceleration, deceleration, and cruise). 

Figure 8. Vehicle test cycles in use in 1995 to measure the exhaust gas emissions from passenger cars (a) USA (b) the European Union (c) Japan.

Table 6. Key features of the test cycles used in 1995 to measure exhaust emissions from passenger cars and light duty vehicles in the USA, the European Union and Japan. ...

Figure 9. Correlation between the exhaust emission values obtained in the US FTP 75 and the European vehicle test cycle (MVEG-A), with gasoline-powered passenger cars. Adapted from [4].

Table 7. Exhaust emission results obtained with gasoline powered passenger cars in sions of the European test cycle. Adapted from [5] different ver-...

Figure 11. Effect of the preconditioning and the test temperature on the exhaust emission of gasoline fueled passenger cars in the European test cycle. Adapted from [6].

Figure 13. Engine load and revolution set points in the European 13-mode test cycle, to measure the exhaust emissions from heavy duty engines. Reprinted from ref. [13] with kind permission of Elsevier Science.

Three-way catalyses (TWC) require a minimum temperature of approx. 3500C for proper catalytic combustion. Due to the heat capacity of the exhaust system it takes about 1 min after engine start until this temperature level is reached if the catalyst is only heated by the exhaust gas. The amount of toxics produced during this cold-start period presents a considerable fraction of the total amount during one test cycle [1]. Due to more stringent legal purification requirements several concepts were developed to reduce the catalyst heat up time. Presently the main approaches to lower the cold-start emissions are the use of an electrically heated catalyst (EHC) [2], a burner heated catalyst (BHC) [3, 4] and hydrocarbon adsorber systems [5, 61. 

Country Exhaust Emissions Driving Cycle Sampling Methods Evap. Emissions Methods Test Fuels... 

The formulation of emission factors for mobile sources, the major sources of VOCs and NO, is based on rather complex emission estimation models used in conjunction with data from laboratory testing of representative groups of motor vehicles. Vehicle testing is performed with a chassis dynamometer, which determines the exhaust emission of a vehicle as a function of a specified ambient temperature and humidity, speed, and load cycle. The current specified testing cycle is called the Federal Test Procedure (FTP). On the basis of results from this set of vehicle emissions data, a... 

Another advantage of wire-screen units for treating auto exhaust is the low mass, which leads to more rapid warm-up. With typical catalytic converters, 60-80% of the total emissions in the test cycle occur during the 2- to 3-minute warm-up period following a cold start [25]. The emissions can be greatly decreased by reducing the warm-up period to 1/2 to 1 minute. 

Back where it all began, the increasing vehicle population and the increasing frequency of red-eye days led the California Legislature in 1959 to require the State Department of Public Health to develop and publish standards for the quality of air and for vehicle exhaust emissions before February 1, 1960 (14). These standards, which were adopted on December 4, 1959, were based on the judgement that in order to achieve desirable air quality standards, 80% reduction of hydrocarbon (HC) and 60% reduction of carbon monoxide (CO) emissions were needed. In terms of the test cycle which was also established, the standards were 275 ppm (volume) of hydrocarbons as hexane (or 0.165% as C] ) and 1.5% (volume) of CO. 

Gasoline emission tests were conducted on a 1.6 1 Ford Escort car on a rolling road dynamometer. The vehicle was modified to incorporate secondary air Injection into the exhaust to ensure an exhaust composition which was consistently oxygen rich. The car was driven over the European ECE-15 test cycle, and throughout the cycle exhaust gas was sampled at a... 

Other tests have shown higher lead emissions from cars with standard exhaust systems than the 33% shown in Figure 7. This low value is probably due to varying lead salt purging levels of standard vehicles due to different test cycles. 

All exhaust emission tests were carried out on a chassis dynamometer using different driving cycles. 

To assess exhaust emissions, R49 driving cycles (equivalent to Euro 2 emission standard—the one currently applied for heavy duty vehicle engines in Vietnam) were used for the testing engines. 

Exhaust emissions were measured before, after 150 h, and after 300 h durability test following R49 driving cycle. The results are given in Fig. 23.23. 

The first step in analyzing the performance of a catalyst in an emission control system is to determine "what the catalyst sees" in terms of temperature, exhaust composition, and exhaust flow rate variations during the driving cycle. The nature of the conditions that a catalyst is exposed to is not only a function of the driving cycle and the vehicle type, but also is dependent upon the air-fuel control system. Tests which record the dynamic conditions have to be repeated and evaluated statistically since the detailed results of each test will vary as a result of random test-to-test variations. 

The results presented in this section were obtained with a carbureted vehicle that was mounted on a chassis dynamometer and that was driven through the U.S. FTP. All of the data presented are for operation following warm-up of the catalyst (i.e., accel-decel cycles number four and greater). Two complete sets of emission analyzers allowed simultaneous measurement of exhaust composition at the inlet and outlet of the pellet-type catalytic converter. Here we present a brief review of the results of these tests. A more detailed description is given in (ref.4). 

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