Characterisation of Exhaust Particulate Emissions from Road Vehicles

Transcription

1 PARTICULATES Characterisation of Exhaust Particulate Emissions from Road Vehicles Deliverable 11: Comparison of PM Exhaust Emissions Measured at a Chassis Dynamometer and On-Road Chasing on a Test Track Final Version September 2003 A project sponsored by: In the framework of: EUROPEAN COMMISSION Directorate General Transport and Environment Fifth Framework Programme Competitive and Sustainable Growth Sustainable Mobility and Intermodality

2 Contractors LAT/AUTh: Aristotle University of Thessaloniki, Laboratory of Applied Thermodynamics - EL CONCAWE: CONCAWE, the oil companies' European organisation for environment, health and safety - B VOLVO: AB Volvo - S AVL: AVL List GmbH - A EMPA: Swiss Federal Laboratories for Material Testing and Research - CH MTC: MTC AB - S TUT: Tampere University of Technology - FIN TUG: Institute for Internal Combustion Engines and Thermodynamics, Tech. University Graz - A IFP: Institut Français du Pétrole - F AEA: AEA Technology plc - UK JRC: European Commission Joint Research Centre - NL REGIENOV: REGIENOV - RENAULT Recherche Innovation - F INRETS: Institut National de Recherche sur les Transports et leur Securité - F DEKATI: DEKATI Oy - FIN SU: Department of Analytical Chemistry, Stockholm University - S DHEUAMS: Department of Hygiene and Epidemiology, University of Athens Medical School - EL INERIS: Institut National de l Environment Industriel et des Risques - F LWA: Les White Associates - UK TRL: Transport Research Laboratory - UK VKA: Institute for Internal Combustion Engines, Aachen University of Technology D FFA: Ford Forschungszentrum Aachen GmbH D 2

3 Publication data form 1. Framework Programme European Commission DG TrEn, 5 th Framework Programme Competitive and Sustainable Growth Sustainable Mobility and Intermodality 3. Project Title Characterisation of Exhaust Particulate Emissions from Road Vehicles (PARTICULATES) 5. Deliverable Title Comparison of PM exhaust emissions measured at a chassis dynamometer and on-road chasing on a test track 7. Deliverable Responsible 8. Language FFA, LAT English 10. Author(s) Barouch Giechaskiel a, Leonidas Ntziachristos a, Zissis Samaras a Roberto Casati b, Volker Scheer b, Rainer Vogt b Erkki Lamminen c, Pirita Mikkanen c 12. Summary See Abstract on p Notes Final Version September Internet reference Key Words chasing experiment, real-world emissions, particle sampling systems 17. No of Pages 18. Price 40 FREE 16. Distribution statement FREE 19. Declassification date April Contract No 2000-RD Coordinator LAT/AUTh 6. Deliverable No Publication Date August Affiliation a LAT/AUTh b FFA c DEKATI 20. Bibliography NO 3

4 Table of Contents Publication data form... 3 Table of Contents Abstract Introduction Chasing Experiments Experimental method Results Laboratory measurements Experimental set up Results Discussion Instruments comparison Dilution system (Lab Chasing Matter) comparison Car comparison Conclusions Summary

5 1 Abstract In the frame of the PARTICULATES project some measurements were conducted at FFA in cooperation with LAT to compare the operation of the PARTICULATES dilution system to the results of real world vehicle emissions. Specifically, the PM and number emissions of a VW Golf TDI Euro III (D2 fuel, 280 ppm S) were measured by chasing the exhaust plume with the Ford Mobile Laboratory at three constant speeds and fixed distance on a test track. Moreover the legislated emissions (PM, CO, NOx, CO2 with the reference method) and the non legislated emissions (active surface, solids, number concentration with the PARTICULATES system) were measured on the FFA chassis dynamometer at the same constant speeds and during cold and hot NEDCs. Moreover, a second car was also measured (Ford Focus Euro III) and a FPS and a Matter dilution system are also compared with the PARTICULATES system. The results showed that: The PARTICULATES primary dilutor is capable of producing a distinct nucleation mode, depending on the sampling conditions selected. Dilution ratio of the primary dilution and dilution air temperature are 12,5 and 32 C correspondingly. Longer residence time favours the growth of the nucleation particles and shifts the nucleation mode to larger diameters. Lower dilution air temperature enhances the formation of nucleation particles, so that their number increases and a distinct mode is formed at lower speed. Mass collected in the gravimetric impactor agrees with the CVS PM over steady state tests. This is a good indication of the overall system performance and aspiration efficiency. Over transients tests, there is underestimation of the mass collected, as expected for a constant sample flowrate sampling system. Combination of information provided by different instruments can provide powerful tools to deduce particle properties in real-time. Additionally, cross-checking of different properties can provide an overall quality framework for the measurement. Chasing and lab experiments show that nucleation is not stable in a time scale of several minutes; it might also depend on previous events, because the nucleation mode is not identical in the two phases at the same speed during speed ramp tests. The particle size distributions measured during chasing at 50 km/h is in very good agreement with dynamometer measurements with PARTICULATES and Matter dilution systems. Under these conditions only the soot mode and no nucleation mode was observed. At about 100 km/h nucleation particles occur during the chasing experiment. The occurrence and, to a certain extent, the emission rate of these particles can be reproduced with the PARTICULATES system, if the dilution parameters are chosen in order to match the ambient conditions. The Matter diluter does not show nucleation particles at this speed. At 120 km/h a strong nucleation mode is observed in the exhaust plume. While the PARTICULATES system is capable to reproduce the soot mode also under these conditions, it shows a nucleation mode, which is somewhat lower in particle number, but larger in diameter. This effect is enhanced with long residence time. 5

6 2 Introduction In the frame of the PARTICULATES project some measurements were conducted at FFA in cooperation with LAT to compare the operation of the PARTICULATES dilution system to the results of real world vehicle emissions. Specifically, the objectives of this report are: To measure the PM emissions of the VW TDI by chasing the exhaust plume with the Ford Mobile Laboratory (FML) at three constant speeds and fixed distance on a test track. To measure the PM emissions of the VW TDI with the PARTICULATES dilution system on the FFA chassis dynamometer at the same constant speeds and during the NEDC. To compare the results obtained with the PARTICULATES dilution system with real-world dilution measured during chasing the exhaust plume with special focus on nucleation particles. Based on these objectives the structure of this report is: Chasing Experiments Laboratory measurements Comparison Discussion of the results Summary & Conclusions Moreover, a second car was also measured and a FPS and a Matter dilution system are also compared with the particulates system. 6

7 3 Chasing Experiments 3.1 Experimental method On-road measurements of the exhaust emissions of a VW Golf TDI were performed on a highspeed oval track of 4 km length. The exhaust plume was sampled and analysed by the Ford Mobile Laboratory (FML), which is a Ford Transit van equipped with instrumentation for the measurement of gaseous and particle emissions. In these experiments the FML followed the test car at a distance of approximately 14 m, that corresponds to a residence time in the atmosphere of 0.4 s at 120 km/h, 0.5 s at 100 km/h and 1 s at 50 km/h. The air was sampled through a 4 mm i.d. stainless steel inlet located in front of the radiator grill and then transported to the instruments through a 10.3 mm i.d. stainless steel line of 420 cm length. The instruments sampled at their specified flow rates and the resulting volume flow through the sampling line was 15.5 l min -1. The residence time inside the stainless steel line was 1.35 s. For these experiments the following instruments were used: a scanning mobility particle sizer (SMPS Mod. 3934L, TSI Inc.), a condensation nucleus counter (CPC Model 3022a, TSI Inc.), CO 2 and NO X analyzers (NGA 2000, Rosemount, and 200A, API, respectively) and data acquisition instruments. Moreover, the FML is equipped with meteorological sensors for temperature and relative humidity Test vehicle The test vehicle is a VW Golf TDI 1.9 l, equipped with oxidation catalyst and Euro III certified Fuel EN590 diesel fuel with a sulfur content of 280 ppm was used (D2) Lube oil The lube oil is BP Vanellus C4 multi SAE 20W Results The particle size distribution was measured in two different test-sets. The temperature during the measurements was 3-6 C and the relative humidity between 50 and 55%. The first test consisted of three phases of 8 minutes each at 120, 100 and 50 km/h; at each speed 4 SMPS scans were taken (the upscan time was 60 s). Before the test the car was warmed up for about 10 minutes at 120 km/h, while the FML drove in front of it in order to determine the background; a background measurement was also performed immediately after the end of the test. The SMPS data were corrected for the background and the size-dependent efficiency of the counter and multiplied by the dilution factor, which was calculated by comparing the CO 2 emission rate measured during chasing with the emission rate in the undiluted exhaust obtained at the same speed in the emission lab. The typical value of the dilution factor in the chasing experiments was about During the run shown in Figure 1 at 120 km/h the dilution ratio was higher (about 8400). The dilution factor was derived from the fuel consumption measured during chasing and the CO2 measured in the diluted exhaust plume. 7

8 Figure 1 shows the size distribution obtained in the first test at 120, 100 and 50 km/h. At 50 km/h the distribution is unimodal, while at 100 km/h a small nucleation mode appears and at 120 km/h a large number of nucleation particles is present. Figure 2 shows the geometric mean diameter of the accumulation mode, obtained from a lognormal fit of the experimental data. The diameters at the three speeds are very similar, in the range of 55 to 58 nm. The second test was a speed ramp. The speed was increased stepwise by 10 km/h from 70 km/h to 120 km/h; the steps were then repeated backwards. Each step lasted 4 minutes, except the phase at 120 km/h that lasted 8 minutes. The SMPS scans were taken in the 2 nd and 4 th minute of each step (at 120 km/h also in the 6 th and 8 th minute). The test was preceded and followed by background measurements. Figure 3 shows the results of the speed ramp test. In order to make the graph better readable, the size distributions obtained at 70 and 80 km/h have been omitted. It can be seen that 100 km/h is the lowest speed at which the distribution is bimodal, under the given conditions. The accumulation mode is identical in the two repetitions at each speed, while the emission rate of nucleation particles changes. Number emission rate dn/dlog(dp) [km -1 ] 1.0E E E E km/h 100 km/h 50 km/h 1.0E Mobility Diameter [nm] Figure 1: Particle size distribution from on-road measurements of the VW Golf TDI at different speeds (14 m distance). 8

9 Geometric mean diameter [nm] km/h 100 km/h 120 km/h Figure 2: Geometric mean diameter of the accumulation mode at different speeds. Number emission rate dn/dlog(dp) [km -1 ] 1.0E E E E E km/h (1) 100 km/h (1) 110 km/h (1) 120 km/h 110 km/h (2) 100 km/h (2) 90 km/h (2) Mobility Diameter [nm] Figure 3: Particle size distributions measured during the speed ramp chasing test with the VW Golf TDI. 9

10 4 Laboratory measurements 4.1 Experimental set up Tests with a Golf TDI and a Ford Focus were carried out on a single roll chassis dynamometer equipped with full flow dilution tunnel and analysis instruments for the regulated pollutants. NEDC and constant speeds were carried out. Particle emissions were measured with three partial dilution systems: FPS, MATTER and PARTICULATES dilution system. In the following paragraphs only the results from the PARTICULATES dilution system will be given. The results from the FPS and MATTER dilution systems will be given at the end of the chapter (paragraphs and 4.2.5). The results from the Ford Focus will be given at the next chapter (paragraph 5.3). At the PARTICULATES system particle mass was measured with a cascade impactor (DGI). Particle number concentration was measured using a Condensation Particle Counter (CPC) and active surface area with a Diffusion Charger (DDC). Number concentration and size distribution of particles was measured with a Scanning Mobility Particle Sizer (SMPS) at steady state tests. Number concentration and size distribution of solid particles only were measured with an Electrical Low Pressure Impactor (ELPI) downstream of a thermodenuder Test vehicle The vehicle used in the test procedure was a Euro III car with oxidation catalyst (VW Golf TDI). This car was used for the chasing experiments. Information about the vehicle is given in chapter 3. Information and results about Ford Focus will be given in chapter Fuel EN590 diesel fuel was used (the same was used for the chasing experiments) Lube oil Information about the oil can be found in chapter Instruments The description of the instruments that were used can be found in Deliverable 2. Specific information about each instrument are given below: DGI: The gravimetric impactor was used with all stages. For the stages 47 mm T60A20 filters were used. For the back up filters 70 mm TX40H120-WW filters were used. The flow through DGI was 68 lpm. SMPS: The SMPS models used were 3934L (PARTICULATES) and 3934U, TSI Inc (Matter). For the measurements in this report an upscan time of 300 s was used for steady state tests and 60 s for speed ramp tests. At cycles SMPS was used at a constant diameter (20 or 70 nm, corresponding to the peaks of nucleation and accumulation mode). CPC: The CPC model used was 3022A, TSI Inc. DDC: A prototype diffusion charger model from Dekati (calibrated at LAT) was used. 10

11 ELPI: ELPI was used with sintered plates (without oil) and a new Dekati final filter stage. The range that was used was fa with averaging of 5 s. In FFA s experiments the currents from the four upper stages (> 1 µm) were so low that they were not considered for the data evaluation. As ELPI is placed downstream of a thermodenuder, only solids particles are being measured. So the current from the filter stage is also low and was not taken into account for the calculations, so the results in this report are from stages 1 7. As particle density affects the aerodynamic equivalent diameter in contrast to the electrical mobility equivalent diameter, size distributions determined by ELPI are not directly comparable to the SMPS data. Thermodenuder - TD: In this study the TD was set on a fixed temperature of 250 C which has been shown to adequately remove most of the volatile material. Losses through the TD were not corrected in the measurements with TD shown in this report, unless differently specified Dilution systems The dilution systems that were used are: CVS dilution system: The tunnel operates in the turbulent flow regime, at a constant total flow set between 10 and 30 m 3 /min. The flow rate of dilution air and the total flow are measured with subsonic venturis. Dilution air is heated to 38 C, filtered and conditioned to low humidity (-9 C dew point). Since the total flow of diluted exhaust is maintained constant, the dilution ratio varies during drive cycles. PARTICULATES dilution system: Primary dilution directly from the exhaust of the vehicle was achieved with a Dekati porous dilutor. The primary dilution ratio was measured with CO 2 analysers. Secondary dilution at the PARTICULATES system was done with ejector dilutors. As the dilution ratio of ejector type dilution unit depends on the pressure drop across the nozzle and the temperature of the gases, all dilution units were calibrated by CO 2 concentration measurements. The ejector based dilution unit used provides a constant dilution factor of about During the tests, the actual dilution ratio can be determined by differential pressure measurement based on the calibration, but as it was nearly constant the dilution ratio of the ejector dilutor was also considered constant at all measurements. For some measurements two ejector dilutors were used with a nozzle type dilution stage in between with a total dilution ratio of Rotating Disk: The rotating disk diluter (type MD19-2E, Matter Engineering AG, Wohlen, CH) was used to perform a single stage dilution. This system has two separate channels: the raw gas channel and the diluted measurement channel. The cavities in the rotating disk transport small volumes of raw gas to the measurement channel, where they are mixed with the dilution air. The dilution ratio depends on the number and volume of the cavities, the rotation speed and the flow in the diluted gas channel. With the settings used for these experiments a dilution ratio of 100 was established. Fine Particle Sampler (FPS): In Dekati FPS the primary dilution is carried out with a porous tube, where distinct modes for nucleation and soot particles can be created. An ejector pump acts as a secondary diluter. Since the dilution ratio is a function of sample pressure and temperature, these values are constantly monitored and the dilution ratio is determined on-line Experimental configurations In the following paragraphs only CVS and PARTICULATES dilution systems will be described. The FPS and the MATTER dilution system will be described at the end of the chapter. The set up of the three dilution systems can be seen in Figure 4. 11

12 MATTER PARTICULATES FPS Figure 4: Position of the three dilution systems CVS The exhaust is transported to the tunnel through a heated and insulated corrugated stainless steel tube with a length of 6 m. It is introduced along the tunnel axis, near an orifice plate that ensures rapid mixing with the dilution air. Particles are sampled isokinetically at a rate of 0.66 l/s and collected on 47 mm Teflon filters. During steady state tests particles are collected separately on three filters (one for each 7 min phase); in the NEDC two filters are used for the two phases of the cycle and the third one collects particles over the entire test. Measurements of total hydrocarbons, CO, NO x and CO 2 are also routinely performed PARTICULATES dilution system The typical experimental setup used in these measurements is shown in Figure 5. A small portion of the exhaust gas enters the primary diluter (porous diluter) and is diluted with dehumidified (dew point = -10 C as measured in FFA) and filtered air at quasi-constant temperature. Conditions reached with this process are a nominal dilution ratio of 12,5: 1 and a dilution temperature of 32 C. However, at some experiments the temperature or the dilution ratio was varied to check its effect on the particulate measurements. The diluted exhaust gas stream is further divided into 2 branches, called wet and dry branch by convention. In the heater of the dry branch the diluted sample is heated up to 250 C to evaporate all volatile material, which is subsequently adsorbed in the denuder. The volatile-free sample is then fed to the ELPI. The particles measured at this branch by ELPI are called by convention solids. In the wet branch the sample passes through a long tube in order to grow in the counting range of the instruments and the main quantity enters DGI (long residence time, about 3 s). For some measurements the tube was removed (short residence time, about 0,5 s). A small quantity is further diluted (secondary dilution with ejector dilutors) and fed to DDC (Total DR = 180 for cycles and steady state tests or for speed ramp tests) and SMPS for steady state tests (or CPC for transient tests) (Total DR = 180 or 16000). 12

13 DGI CPC SMPS or DMA/CPC Water Flow on/off Valve Cooling Water Inlet Aging Chamber Flowmeter Ejector Dilutor mixing throttle Ejector dilutor Exhaust Denuder filter Mass Flow Controller Heater ELPI Diffusion Charger 3 bar 3 bar Dilution Air Line Sample Line HEPA Filter Charcoal Silica Gel 3 bar Figure 5: PARTICULATES dilution system Procedure / Test protocol Steady state, cycle and speed ramp tests were conducted with the two vehicles. The procedure that was followed for each test is given below: Steady state: 31 minutes of continuous measurements as follows: 3 min accelerations, 7 min warm up of the car at the defined speed, 7 min measurements (phase a), 7 min measurements (phase b), 7 min measurements (phase c). Cycles: Only cold and hot NEDC (UDC + EUDC) cycles were conducted. The cycles were conducted according to the legislated procedure. Hot NEDC cycles followed a 10 min warm up of the car at 50 km/h. 13

14 Speed ramp: 5 min warm up of the car and stabilization of the car at 80 km/h. 4 min at 80 km/h, 4 min at 90 km/h, 4 min at 100 km/h, 4 min at 110 km/h, 8 min at 120 km/h, 4 min at 110 km/h, 4 min at 100 km/h, 4 min at 90 km/h, 4 min at 80 km/h. Most steady state test (except 120 and 110 km/h) and cycles with the Golf were conducted with the particulates window (LR). All tests with the Focus were conducted with the particulates window, but with short residence time (SR). For some steady state test (120 km/h and 110 km/h), two hot NEDC cycles and the speed ramp tests with the Golf car some parameters were changed. In the figures the following symbols are being used: LR: PDR = 12,5 DT = 32 C RT = long (Particulates window) LR-D: PDR = 55,0 DT = 32 C RT = long (For 120 and 110 km/h only) LR-H: PDR = 12,5 DT = 50 C RT = long (For some hot NEDCs only) SR: PDR = 12,5 DT = 32 C RT = short (For speed ramp and all Focus tests) HD: PDR = 12,5 DT = 50 C RT = short (For one speed ramp test) CD: PDR = 12,5 DT = 10 C RT = short (For one speed ramp test) L: PDR = 12,5 DT = 32 C RT = short (100 & 120 km/h at different loads) PDR = Primary Dilution Ratio, DT = Dilution Air Temperature, RT = Residence Time, long = 3 s, short = 0,5 s Table 1 shows the chronological order of the measurements and Table 2 shows the test matrix of the measurements. More details of the measurements can be found in Table 3. Table 1: Chronological test order GOLF FOCUS Day 1 (11/3) Day 2 (12/3) Day 3 (13/3) Day 4 (14/3) Day 5 (18/3) Day 6 (19/3) Day 7 (20/3) 120 km/h LR-D cold NEDC LR cold NEDC LR cold NEDC LR 50 km/h LR Speed ramp L 120 km/h SR 100 km/h LR hot NEDC LR hot NEDC LR-H 110 km/h LR-D Speed ramp LR Speed ramp HD 100 km/h SR NEDC hot LR hot NEDC LR hot NEDC LR-H 90 km/h LR Speed ramp SR Speed ramp CD Speed ramp SR 14

15 Table 2: Test matrix. Numbers indicate repetitions of tests. Steady State Cycles Speed Ramp 50 LR 90 LR 100 LR 110 LR 120 LR cold NEDC LR hot NEDC LR hot NEDC LR-H LR SR L HD CD Golf Focus 1 (SR) 1 (SR) 1 Table 3: Details for the measurements. PDR = Primary Dilution Ratio, SDR = Secondary Dilution Ratio, DT = Dilution air Temperature, DA = Dilution Air flowrate, RT = Residence Time, LR = Long Residence Time, SR = Short Residence Time, w = wet branch, d = dry branch. Date Code Speed PDR SDR DT DA RT SMPS CPC DDC DGI ELPI 11/3/2003 FOGO LR w - w w d 11/3/2003 FOGO LR w - w w d 11/3/2003 FOGO05 NEDC LR w - w /3/2003 FOGO06 NEDC cold LR w w w w d 12/3/2003 FOGO08 NEDC LR w w w w d 12/3/2003 FOGO10 NEDC LR w w w /3/2003 FOGO11 NEDC cold LR w w w w d 13/3/2003 FOGO13 NEDC LR w w w w d 13/3/2003 FOGO15 NEDC LR w w w /3/2003 FOGO16 NEDC cold LR w w w w d 14/3/2003 FOGO LR w w w w d 14/3/2003 FOGO LR w w w w d 18/3/2003 FOGO LR w w w w d 18/3/2003 FOGO20 Speed ramp LR w w w - d 18/3/2003 FOGO21 Speed ramp SR w w w - d 19/3/2003 FOGO22 Load ramp SR w w w - d 19/3/2003 FOGO23 Speed ramp SR w w w - d 19/3/2003 FOGO24 Speed ramp SR w w w - d 20/3/2003 FOFO SR w - w w d 20/3/2003 FOFO SR w - w w d 20/3/2003 FOFO27 Speed ramp SR w - w w d 4.2 Results In the following paragraphs the results from the CVS and the PARTICULATES dilution system for the Golf car will be given. Results from the FPS and the Matter diluter will be given at the end of the chapter (paragraph 4.2.4). The Focus vehicle will be examined at the next chapter (paragraph 5.3). 15

16 4.2.1 Measured parameters and calculations The raw data processing of the measured particle characteristics includes the following steps: Software corrections of recorded data: Raw data of the SMPS measurements are corrected by the commercial TSI SMPS software (v. 4.3) for charging efficiency and counting efficiency of the CPC. The commercial DEKATI ELPI software (v. 3.1 rev. 454) corrects the raw data for losses in the charging unit. The current that the diffusion charger measures, was converted to particle surface area according to an instrument's preliminary calibration according to the equation: S [µm 2 /cm 3 ] = 11,46 x I [fa] / Q [lpm] Where I is DDC s current indication and Q is the flow through DDC. Adjustment of losses: The measurement data are NOT corrected by the size dependent diffusion losses in the sampling lines (which should be calculated for each instrument separately). Diffusion and thermophoretic losses inside the thermodenuder are NOT corrected by means of the experimentally determined losses, unless otherwise specified. However, they are assumed to be equal in all tests and for both vehicles. Offset correction: The number emission data are corrected for offset levels, which were measured prior to each test. Offset levels were measured using the dilution air at the beginning and at the end of the measurements every day. Background correction: No background correction was necessary as purified air was used for the dilution. The particle concentration of the dilution air was measured before the measurements with CPC and showed particle concentration less than 0,1 cm -3. Range bars: The range bars shown in the following diagrams represent the minimum and maximum values of the three repetitions (when data exist). This definition is widely used and representative for measurements with only a few numbers of repetitions. Conversion to raw exhaust concentration: The recorded concentrations are multiplied by the total dilution ratio for each instrument, which was determined for each individual test. Following the above calculations the results are presented in the following way: DGI (mass): g/km. DDC (active surface): cm 2 /km. CPC (number emission rate): km -1 SMPS (size distribution): km -1 (total number emission rate) or dn/dlogdp km -1 (size distributions). ELPI (solid number emission rate): km -1 (total number emission rate) or dn/dlogdp km -1 (size distributions) Legislated Emissions (CVS) In all the drive cycles and steady state tests bag analysis for total hydrocarbons (THC), CO, NO x and CO 2 were performed and PM filters were collected. The filters were also analyzed for SO 4 2- and volatile organic fraction (VOF). The data were corrected for the tunnel background (with exception of PM, SO 4 2- and VOF) and converted in emission rates (g km -1 ). The results are presented in Figures

17 Figure 6 shows the emissions during NEDCs. The data from three cold and five hot cycles were separately averaged. One of the cold cycles gave much lower THC and CO emissions than the other two (CO was close to zero), as can be noticed from the wide range bars. CO during hot cycles was at background levels. Figure 7 presents the average PM mass emission rates during cold and hot cycles together with the results of the chemical analysis. Sulfate and VOF account for less than 10% of the total PM emissions. Figure 8 shows the emissions in the steady state tests. Total hydrocarbons have not been included because they were always at background level except at 50 km/h, when the emission rate was 0,004 g/km. Also CO at 90 km/h was at background level. Figure 9 shows the results of the chemical analysis of PM for steady state tests, which yielded significant sulfate levels at 120 km/h and 110 km/h. Obviously, the oxidation catalyst is fully active at 120 and 110 km/h, converting the fuel sulfur to sulfate and oxidizing efficiently the VOF. This is in agreement with the occurrence of nucleation mode particles (see Chapter , Figure 15). At 50 and 90 km/h a small amount of VOF was detected, indicating a less efficient oxidation catalyst at this load Mass emission rate [g km -1 ] cold NEDC hot NEDC THC*10 CO NOx CO2/1000 PM Figure 6: Regulated emissions during drive cycles. 17

18 Mass emission rate [g km -1 ] sulfate VOF non-volatile PM cold NEDC hot NEDC Figure 7: Average PM emissions (total height of the bars) during cold and hot NEDC and chemical speciation for sulfate and volatile organic fraction. Mass emission rate [g km -1 ] km/h 110 km/h 100 km/h 90 km/h 50 km/h CO*100 NOx CO2/1000 PM Figure 8: Regulated emissions during steady state tests. 18

19 Mass emission rate [g km -1 ] sulfate VOF non-volatile PM 120 km/h 110 km/h 100 km/h 90 km/h 50 km/h Figure 9: Average PM emissions (total height of the bars) during steady state tests and chemical speciation for sulfate and volatile organic fraction PARTICULATES dilution system Total Mass Total mass and mass size distribution is recorded with the DGI, a cascade mass impactor. The equation that was used for the DGI calculations is the following: DGI PM m DRVexh = V Distance DGI where m is the net weight on the filter, DR the primary dilution ratio, V exh the exhaust gas volume of the car, V DGI the volume through DGI and Distance the total distance of the car. Figure 10 compares the total mass measured from DGI at the particulates system following the CVS procedure at steady state tests. The percentage difference between the two methods is less than +/-15%. Figure 11 compares the mass measured following the CVS procedure and the DGI at the PARTICULATES system for UDC cycles. Due to the different sampling conditions (variable dilution ratio at the tunnel, constant dilution ratio at the PARTICULATES system) the mass as given from DGI is about 10 25% lower. This should be expected for transient tests. Figure 12 shows the mass size distribution over UDCs and steady state tests. The peak is at 316 nm (the geometric mean diameter of stages 2 and 3 of DGI) which collects 45 50% of the total mass collected on DGI, irrespective of test. It is also evident that about 90% of the mass is less than 1 µm. 19

20 Mass emission rate [mg/km] DGI CVS % diff 50 km/h 90 km/h 100 km/h 110 km/h 120 km/h 20% 15% 10% 5% 0% -5% -10% -15% -20% -25% -30% % difference DGI-CVS Figure 10: Total mass emission rate from dilution tunnel CVS and cascade impactor at the particulates system (DGI). Only one repetition for each speed (Golf, LR). Mass emission rate [mg/km] DGI CVS % diff cold UDC LR hot UDC CD hot UDC HD 10% 5% 0% -5% -10% -15% -20% -25% -30% % difference DGI-CVS Figure 11: Total mass emission rates from dilution tunnel CVS and cascade impactor at the particulates system (DGI). (Golf, LR) 20

21 dn/dlogdp % concentration km/h 90 km/h 100 km/h 110 km/h 120 km/h UDC cold UDC hot CD UDC hot HD Aerodynamic Diameter [nm] Figure 12: Mass Size Distribution at the wet branch as given by the DGI for different steady state tests. CD = Cold Dilution, HD = Hot Dilution. Measurements with long residence time. (Golf, LR) Number emission rate The number concentration is measured with an SMPS 3934L and a CPC 3022A. For the steady state tests the total number concentration is obtained integrating the size distribution and the median diameter was calculated from a lognormal fit of the experimental data. For NEDCs the total concentration is given by the CPC and the concentration at a specific diameter is measured by the SMPS with the DMA set at a fixed voltage. Figure 13 shows the total number emission rate of particles below and above 50 nm. The increase of particle emissions below 50 nm at high speeds is an indication of nucleation mode. Figure 14 presents the geometric mean diameter of the particles during the steady state tests. The diameter of the accumulation mode at different speeds is about 60 nm, except at 90 km/h where it is higher. The nucleation mode, when present, has a median diameter between 15 and 20 nm. Figure 15 shows the size distributions measured by the SMPS during steady state and speed ramp tests. In the steady state tests nucleation mode particles start to appear at 100 km/h (Figure 15b). In the speed ramp with DT=32 C this happens at 110 km/h, but when cold dilution air is used a relatively well defined nucleation mode is observed at 100 km/h (Figure 15a). Figure 16 compares the number emission rates with different dilution conditions at 80 km/h, where no nucleation mode exists. There is a small effect of the long residence time (the peak increases slightly). However, this variation can be considered an effect of the variability of different days measurement. Figure 17 shows the decrease of the nucleation mode over time at 120 km/h (PDR = 50, DT = 32 C, long residence time). The 3 scans were taken with 7 min difference. Figure 18 shows the effect of the dilution ratio on nucleation mode (PDR = 50 was a steady state test at 120 km/h, PDR = 12,5 was 120 km/h from speed ramp test). Long residence time, DT = 32 C. Figure 19 shows the effect of the residence time on the nucleation mode. The scans are taken at 120 km/h during speed ramp tests. 21

22 Figure 20 shows the effect of the dilution air temperature on the nucleation mode. The scans are taken at 120 km/h during speed ramp tests on different days. In Figures 21 and 22 the effect of load on particle emissions at 100 and 120 km/h is presented. The reason for this experiment was to reproduce the fuel consumption measured during chasing, which was not the same as with the standard dynamometer settings. The slope that was simulated at the dynamometer and the corresponding values of load and fuel consumption are presented in Table 4. Table4: Details of the load ramp test. Speed (km/h) Slope (%) Load (kw) Fuel consumption (mg/stroke) At 100 km/h (Figure 21) the nucleation mode particles are much more affected from load variation than the accumulation mode For example lowered load (-0.33% grade) no nucleation mode is present. The fuel consumption with a slope of 0.67% was approximately the same as during chasing. It should be noted that the magnitude of the nucleation mode could be influenced due to temperature changes in the exhaust pipe and a release effect when the load was increased. Figure 22 shows the effect of load on particle emissions at 120 km/h. The accumulation mode is not affected; the difference in nucleation particles emission is less evident than at 100 km/h and the distribution is bimodal also with lowered load. The fuel consumption with a slope of 1% was approximately the same as during chasing. Figure 23 shows the particle flux (total particles and 70 nm) during a cold NEDC with PDR = 12.5, DT = 32 C and long RT. Nucleation is likely to occur in the last seconds of the test, when the highest speed is reached (the total particle emission rate increases more than the soot particles of 70 nm). Figure 24 shows the effect of the dilution air temperature on particle emission rate in a drive cycle. The data come from four hot NEDCs. The emission rate of 20 nm particles is unaffected during the UDC and decreases in the EUDC with hot dilution; this can be due to the enhancement of nucleation at the end of the test when colder dilution air is used, while in the UDC nucleation never 22

23 occurred. The 70 nm particles show lower emission rate with hot dilution in both phases; this is more likely to be an effect of variability in the emissions from test to test. Figure 25 shows the average number emissions for the cycles. There is no effect of the sampling conditions (32 C or 50 C) for long residence time set up. The cold UDC has higher emissions than the hot. Total number emission rate [km -1 ] 1.0E E E+13 below 50 nm above 50 nm 50 km/h 90 km/h 100 km/h 110 km/h 120 km/h Figure 13: Number emission rate measured at constant speed at the wet branch with the SMPS (Golf, LR) Geometric mean diameter [nm] nucl. mode acc. mode 50 km/h 90 km/h 100 km/h 110 km/h 120 km/h Figure 14: Geometric mean diameter of particles calculated from lognormal fit at constant speed at the wet branch (Golf, LR). 23

24 Number emission rate dn/dlog(dp) [km -1 ] 1.0E E E km/h (1) 110 km/h (1) 120 km/h 110 km/h (2) 100 km/h (2) 90 km/h (2) 1.0E Mobility diameter [nm] Number emission rate dn/dlog(dp) [km -1 ] 1.E+16 1.E+15 1.E+14 1.E km/h (1) 100 km/h (1) 110 km/h (1) 120 km/h 110 km/h (2) 100 km/h (2) 90 km/h (2) 1.E Mobility diameter [nm] Figure 15a: Particle size distribution measured: i) and ii) in two speed ramp tests, with SR and SR-CD respectively. 24

25 Number emission rate dn/dlog(dp) [km -1 ] 1.0E E E E km/h 110 km/h 100 km/h 90 km/h 50 km/h 1.0E Mobility diameter [nm] Figure 15b: Particle size distribution measured at different steady state tests (Golf, LR) Number emission rate dn/dlog(dp) [km -1 ] 1.0E E E+12 DT=32 C LR DT=32 C SR DT=50 C HD DT=10 C CD 1.0E Mobility diameter [nm] Figure 16: Dilution conditions effect on the accumulation mode measured at 80 km/h in different speed ramp tests (Golf, all short residence time, except LR). 25

26 Number emission rate dn/dlog(dp) [km -1 ] 1.0E E E E+13 scan 1 scan 2 scan 3 1.0E Mobility diameter [nm] Figure 17: Nucleation mode decrease over time at 120 km/h (scans have 7 min difference) (Golf, LR). 1.0E+16 Number emission rate dn/dlog(dp) [km -1 ] 1.0E E+13 PDR=50 SDR=14 PDR=13 SDR= E Mobility diameter [nm] Figure 18: Effect of dilution ratio on nucleation mode at 120 km/h (Golf, LR). 26

27 Number emission rate dn/dlog(dp) [km -1 ] 1.0E E E+13 LR first scan LR last scan SR first scan SR last scan 1.0E Mobility diameter [nm] Figure 19: Effect of residence time on nucleation mode at 120 km/h during speed ramp tests (scans with the same residence time have 5 min difference; arrows indicate time sequence). Number emission rate dn/dlog(dp) [km -1 ] 1.0E E E+13 DT=10 C first scan DT=10 C last scan DT=32 C first scan DT=32 C last scan DT=50 C 1.0E Mobility diameter [nm] Figure 20: Effect of dilution air temperature on nucleation mode; 120 km/h, speed ramp tests with SR. 27

28 Number emission rate dn/dlog(dp) [km -1 ] 1.0E E E+13-0,33 % 0 % 0,33 % 0,67 % 1 % 1.0E Mobility diameter [nm] Figure 21: Effect of load on particle emissions at 100 km/h (SR). Positive numbers indicate additional dynamometer load, negative numbers lowered dynamometer load. Number emission rate dn/dlog(dp) [km -1 ] 1.0E E E+13-0,5 % 0 % 0,5 % 1 % 1,5 % 1.0E Mobility diameter [nm] Figure 22: Effect of load on particle emissions at 120 km/h (SR). Positive numbers indicate additional dynamometer load, negative numbers lowered dynamometer load. 28

29 Speed [km h -1 ] speed tot. part. 70 nm 1.25E E E E E+12 Number flux dn/dlog(dp) [s -1 ] E Time [s] Figure 23: Particle emissions in a cold NEDC. PDR = 12.5, DT = 32 C, LR. Number emission rate dn/dlog(dp) [km -1 ] 1.2E E E E E+13 UDC, DT = 32 C UDC, DT = 50 C EUDC, DT = 32 C EUDC, DT = 50 C 0.0E nm 70 nm Figure 24: Effect of dilution air temperature on particle emissions during NEDC. 29

30 Number emission rate (CPC) [km -1 ] 4.0E E E E E E E E+00 cold LR hot LR hot LR-H UDC EUDC NEDC Figure 25: Total number emission rate of particles at the wet branch as given from CPC at cycles. PARTICULATES window was used, except HD (Dilution air temperature 50 C) Active Surface The active surface of the particles is measured with DDC. Figure 26 shows the active surface at different steady state tests. The increase of the active surface at 110 and 120 km/h is an indication of nucleation mode. Figure 27 compares the active surface at different cycles and sampling conditions. There is no effect of the sampling conditions (32 C or 50 C) for long residence time set up. The cold UDC has higher emissions than the hot. Figure 28 shows the active surface for the speed ramp tests. Different sampling conditions are examined for the Golf vehicle. Cold dilution increases nucleation mode and hot dilution suppresses it for short residence time. 30

31 Active Surface from DDC [cm 2 /km] 1.4E E E E E E E E Speed [km/h] Figure 26: Active Surface of particles at the wet branch as given from DDC at steady state tests (Golf, LR) Active Surface from DDC [cm 2 /km] 1.8E E E E E E E E E E+00 cold LR hot LR hot LR-H UDC EUDC NEDC Figure 27: Active Surface of particles at the wet branch as given from DDC at cycles. PARTICULATES window was used, except HD (Dilution air temperature 50 C). 31

32 Active Surface from DDC [cm 2 /km] 1.E+06 1.E+06 1.E+06 8.E+05 6.E+05 4.E+05 2.E+05 0.E+00 LR SR HD CD Speed [km/h] Figure 28: Active Surface of particles at the wet branch as given from DDC at speed ramp tests Solid particles Solid particles are measured with ELPI at the dry branch. Figure 29 shows the total number emission rate at different steady state tests. Figure 30 shows the size distribution as given from ELPI and Figure 31 shows the mean aerodynamic diameter for the same tests. The peak is at 78 nm (the geometric mean diameter of stage 3 of ELPI) and the mean diameter is 50 to 52 nm. Figure 32 shows the total number emission rate at different cycles and sampling conditions. There is no significant difference between the different sampling conditions for the solid particles. Figure 33 shows the total number emission rate at different speed ramp tests. Dilution temperature does not affect solid emissions, as hot dilution and cold dilution emissions are nearly the same. Moreover, emissions with different residence time (short and long) are also nearly the same. Solid Number emission rate [km -1 ] 1.80E E E E E E E E E E km/h 90 km/h 100 km/h 110 km/h 120 km/h Figure 29: Solid number emission rate at the dry branch as given by ELPI (Golf, LR) 32

33 Solid Number emission rate (ELPI) dn/dlogdp [km -1 ] 3.5E E km/h 2.5E km/h 2.0E km/h 1.5E km/h 120 km/h 5.0E E Aerodynamic Diameter [nm] Figure 30: Solid Number Size Distribution at the dry branch as given from ELPI Mean Aerodynamic Dp [nm] km/h 90 km/h 100 km/h 110 km/h 120 km/h Figure 31: Mean Aerodynamic particle diameter Dp as given from ELPI 33

34 Solid Number emission rate [km -1 ] 1.6E E E E E E E E+00 cold LR hot LR hot LR-H UDC EUDC NEDC Figure 32: Solid number emission rate at the dry branch as given by ELPI. Solid Number emission rate [km -1 ] 1.60E E E E E E E E E+00 LR SR HD CD FOCUS (SR) Speed [km/h] Figure 33: Solid number emission rate at the dry branch as given by ELPI measured during speed ramp tests. 34

35 4.2.4 Matter Eng. dilution system Number emission rate The number concentration is measured with an SMPS 3934U. All the tests have been carried out with a dilution ratio of 100 and dry dilution air at ambient temperature (20 C), except a NEDC for which hot dilution was performed (dilution air T = 80 C). Figure 34 shows the total number emission rate of particles below and above 50 nm. The increase of particle emissions below 50 nm at high speeds is an indication of the appearance of a nucleation mode. Figure 35 presents the geometric mean diameter of particles in steady state tests. Nucleation occurs at 110 and 120 km/h; at these speeds the accumulation mode is shifted towards larger diameters, likely due to the condensation and growth if more condensable material is available. Figure 36 shows the particle size distributions measured at different steady states. When present, the nucleation particles have a maximum emission rate comparable to the peak of the soot mode. Note that with the PARTICULATES system the difference was more than an order of magnitude larger. Figure 37 shows the size distributions measured in a speed ramp test. A nucleation mode appears at 100 km/h, but only in the second phase, after having driven at higher speed (in the first phase at 100 km/h there is just a small trace of nucleation). The emission rate of nucleation particles changes in the two repetitions at each speed, while the accumulation mode is nearly the same (with the exception of 110 km/h). Figure 38 compares particle emissions during two hot NEDCs with different dilution air temperature. The emission rate of 20 nm particles is essentially identical for almost all the test, but with hot dilution the peak that corresponds to the deceleration from 120 km/h disappears, indicating that nucleation occurs at this point when colder dilution air is used. Number emission rate [km -1 ] 1.8E E E E E E E+00 below 50 nm above 50 nm 50 km/h 90 km/h 100 km/h 110 km/h 120 km/h Figure 34: Particle number emission rate during steady state tests. 35

36 Geometric mean diameter [nm] nucl. mode acc. mode 50 km/h 90 km/h 100 km/h 110 km/h 120 km/h Figure 35: Geometric mean diameter of particles during steady state tests. Number emission rate dn/dlog(dp) [km -1 ] 1.0E E E km/h 110 km/h 100 km/h 90 km/h 50 km/h 1.0E Mobility diameter [nm] Figure 36: Particle size distribution measured with the Matter diluter during different steady state tests. 36

37 Number emission rate dn/dlog(dp) [km -1 ] 1.0E E km/h (1) 100 km/h (1) 110 km/h (1) 120 km/h 110 km/h (2) 100 km/h (2) 90 km/h (2) 1.0E Mobility diameter [nm] Figure 37: Particle size distributions in a speed ramp test measured with the Matter diluter. 150 speed 1.0E+13 Speed [km h -1 ] C 80 C 1.0E E+11 Number flux dn/dlog(dp) [s -1 ] E Time [s] Figure 38: Emission rates of 20 nm particles sampled with the Matter diluter during two hot NEDCs with different dilution air T. 37

38 4.2.5 FPS dilution system In Dekati FPS the primary dilution is carried out with a porous tube, where distinct modes for nucleation and soot particles can be created. An ejector pump acts as a secondary diluter. Since the dilution ratio is a function of sample pressure and temperature, these values are constantly monitored and the dilution ratio is determined on-line. Table 5 gives the measurements with this dilution system. The only instruments that were used were ELPI (with a final filter) and DMM. DMM (Dekati s Mass Monitor) is a real time instrument for particle mass emission measurements. Table 5: Measurements carried out with FPS, (only DMM and ELPI were used). Date Cycle DR ELPI DMM Notes 11/3/2003 hot NEDC 107 Yes FPS Yes TD FPS cooled (DT=25-30 C) 12/3/2003 cold NEDC 174 No Yes TD FPS cooled (DT=25-30 C) 12/3/2003 hot NEDC 171 No Yes TD FPS cooled (DT=25-30 C) 12/3/2003 hot NEDC 28 Yes FPS Yes TD FPS cooled (DT=25-30 C) 13/3/2003 cold NEDC 64 No Yes FPS FPS heated (DT=150 C) 13/3/2003 hot NEDC 62 No Yes FPS FPS heated (DT=150 C) 13/3/2003 hot NEDC 60 No Yes FPS FPS heated (DT=150 C) Figure 39 compares the particle number flux for hot NEDC cycles as measured from ELPI with different dilution ratios (60 and 28) and residence times. Figure 40 compares the mass emission rate as given from DMM using hot dilution or a TD at 250 C. The use of a TD gave higher mass emissions. Figure 41 compares the mass flux as given from DMM as used at FPS with hot dilution or downstream of a TD. Number Flux [s -1 ] 6.E+12 5.E+12 4.E+12 3.E+12 2.E+12 1.E+12 0.E+00 hot NEDC1 [#/s] hot NEDC2 [#/s] Time [s] Figure 39: Particle number concentration as measured with ELPI (stages 1-7) for hot NEDC cycles in separate days, FPS diluter with dilution ratios of 107 (black) and 28 (gray). ELPI measured from FPS with cold dilution (wet particles). 38