TECHNICAL REPORT

Demonstration of multi gasexhaust measurements during

cold start conditions

Bror Tingvall, Esbjörn Pettersson

ISSN: 1402-1536 ISBN 978-91-86233-84-6

Luleå University of Technology 2009

Department of Human Work SciencesDivision of Sound and Vibration

Department of Applied Physics and Mechanical EngineeringDivision of Energy Engineering

2009-12-11

CASTT - Center for Automotive Systems Technologies and Testing

Demonstration of multi gas exhaust measurements during cold start conditions

The project is focused on testing and demonstration of exhaust gas measurements in cold climate using FTIR multigas exhaust analyser.

Bror Tingvall/Research engineer

Department of Human Work Sciences Division of Sound & vibration

Esbjörn Pettersson/ Tekn. Lic.

Analytical Chemist Department of Applied Physics and Mechanical Engineering

Division of Energy Engineering

Printed by Universitetstryckeriet, Luleå

ISSN: 1402-1536ISBN 978-91-86233-84-6

Luleå 2009

www.ltu.se

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CONTENTS 1 Background ...................................................................................................................................................4 2 Multi gas exhausts measurement....................................................................................................................5

2.1 Introduction .........................................................................................................................................5 2.2 Project focus.........................................................................................................................................5 2.3 Expected results from the project.........................................................................................................6

3 Measurements................................................................................................................................................6 3.1 FTIR advantages ..................................................................................................................................6 3.2 Performed measurements .....................................................................................................................7 3.3 Conclusions of performed measurements.............................................................................................7

4 Multi gas exhausts measurement systems – solutions .....................................................................................8 4.1 Mobile measurement system with the FTIR .......................................................................................8

4.1.1 Hardware – a mobile FTIR system .................................................................................................8 4.1.2 Cost estimates for a mobile FTIR ...................................................................................................8 4.1.3 Power requirement ..........................................................................................................................8

4.2 Mobile measurement system with the FTIR on-board. ......................................................................9 4.2.1 Hardware – onboard FTIR system................................................................................................10 4.2.2 Cost estimate – an on board FTIR system ....................................................................................10 4.2.3 Power requirement ........................................................................................................................11

4.3 Vehicle test system using a dynamometer system...............................................................................11 4.3.1 Vehicle test system including chassis dynamometer.......................................................................12 4.3.2 Example of chassis dynamometer...................................................................................................12

5 Conclusions .................................................................................................................................................13 6 Recommendations ......................................................................................................................................14

6.1 Proposal - Step 1 - Cold start measurement system ...........................................................................14 6.2 Proposal - Step 2 – Onboard measurement system ............................................................................15 6.3 Proposal - Step 3 – Complete vehicle test stand ................................................................................15

7 Project organisation .....................................................................................................................................16 Table 1. Industrial network .........................................................................................................................16 Table 2. Scientific partners...........................................................................................................................16

8 References ...................................................................................................................................................17 Appendix .............................................................................................................................................................18 Demonstration of cold start measurements..........................................................................................................18

1.1 Performed measurements ...................................................................................................................18 1.2 Used measurement procedure............................................................................................................18 1.3 Test-vehicles ......................................................................................................................................19 1.4 General results ....................................................................................................................................19 1.5 Ford Focus .........................................................................................................................................20 1.6 Nissan Micra ......................................................................................................................................21 1.7 Toyota Camry....................................................................................................................................22 1.8 Observations about the FTIR measurements.....................................................................................22 1.9 Pictures on the sampling system and on the FTIR ............................................................................23 1.10 Notes on different instruments...........................................................................................................28 1.11 References .........................................................................................................................................32

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1 Background Car producers have expressed a wish to test the cars for e. g. exhaust emissions in cold climate in cooperation with the vehicle testing companies. The car producers and component producers anticipate that the testing times could be shortened and thereby the testing efficiency can be increased. The companies perform many measurements today at the testing sites with their own equipment often brought from abroad. A growth potential for the vehicle testing companies is therefore to offer different kind of measurements, e. g. exhaust emission measurements, requiring measurement systems and equipment as well as competence to perform and evaluate the measurements. The measurements should be able to be performed during applied testing procedures such as cold start testing. Acceleration and deceleration tests with loading according to applied test cycles require a mobile system 4.2 or a full test stand 4.3. The measurements also have to be performed in cold climate. The test systems have to handle all kind of vehicles, primarily though passenger cars of different models and brands. The measurement equipment has to be easy to use with short notice and with available trained personnel. One of the most important factors is that the test data has to be managed in a safe way, from the car producer’s point of view. The data should also be available to the car producer shortly after the performed measurements. LTU (Luleå University of Technology) has initiated a number of research projects within CASTT (Center for Automotive Systems Technologies and Testing) where the aim has been to increase the long-term knowledge in areas potentially important to the vehicle testing companies. At the same time the vehicle testing companies activities are mostly focused on daily or seasonally practical problems. Therefore there is a gap between the long-term research projects at LTU and the vehicle testing companies, which both sides are interested in over-bridging. The objective is to give vehicle testing companies a broader variety of services which they can provide giving more revenues to the vehicle testing companies and an extension of the test season. This project is a continuation of the first project “Vehicle test system – A pilot study” (Tingvall 2007) aimed at demonstrating how cold start measurements could be performed using FTIR technology. Therefore this project is directly focused on applied development work with the goal to build knowledge, measurement facilities, reputation and trust regarding measurement activities in the Arjeplog/Arvidsjaur area. This project will give both commercial possibilities for the vehicle testing companies and possibility to find relevant research questions giving possibilities for research projects for academia.

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2 Multi gas exhausts measurement

2.1 Introduction The ever increasing demands on the car manufactures to produce vehicles with lower emission and lower fuel consumption requires tools to accurate measure the performance of the engine in combination with the control and cleaning devices/systems. One of those tools is to measure speciated emissions and also measure at sufficient speed to be able to understand and evaluate the complete system. Some 30 years ago this would have required several instruments not possible to apply in routine resting. One of the instruments identified for advanced power trains are mass spectrometers (e.g. Airsense) (Adachi 2000), which can perform speciated measurements faster than 1 Hz with an accuracy identical as off-line GC for e.g. hydrocarbons (Dearth 1999) for up to 50 components. The instrument requires fairly frequent calibration. The instrument may therefore not be suitable for field work on a routine basis. The other instrument identified was FTIR (Fourier Transform Infra Red spectroscopy), which since the 80´s has been applied to automotive emissions. There was an extensive development in the beginning of the 90´s to replace the standard instruments because FTIR does not require frequent calibration with skilled personnel. FTIR did not replace many set-ups because of the inherent difficulty in finding usable conversion factors between the regulated THC (total hydro carbon) emission measurements and the components measured with FTIR. There were also problems related to that FTIR requires extensive calculations and that the FTIR, at the time, gave too low time resolution of the measurements. The method has therefore not spread extensively until fairly recently when instruments has been further developed and can now acquire data at a rate faster than 1 Hz. The testing companies would like to offer more services to the car companies. Emission measurements are possible services which can be applied directly. The aim of the current project is to demonstrate emission measurements in cold climate.

2.2 Project focus The project work is focused on testing instrumentation and demonstration of multi gas exhaust measurements in cold climate. The multi gas measurements are possible to use in mobile field condition as well as in stationary condition on a routine basis. The objective is to demonstrate how cold start measurements (without exhaust gas flow measurement) can be performed with FTIR. The main questions are how to assemble and maintain system/systems for routine measurements by the testing companies which fulfils the requirement of the car manufactures. Cold start testing is in certification performed with a sophisticated dynamometers system to obtain the standard heating rates for the system (including the catalyst). The catalyst starts to work at a certain temperature. Emissions emitted before this temperature gives the cold start emissions. The easiest way to measure cold start emissions would be to measure the emissions at idling. If this is not sufficient to give usable data for the car manufactures a brake system would be required, which is very costly. A cheaper system would be to use an onboard measurement system. Therefore is the major question; is it required to have a brake system to be able to obtain usable emission data for the car manufactures and if yes, what is the requirement on the dynamometer system. Or could a mobile system fulfil the requirements and obtain acceptance for real driving tests.

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This report discusses three different options of which option 1 and 2 is movable and option 3 is stationary;

1. Mobile measurement system - cold start emission testing at idling 2. Mobile measurement system with the FTIR on-board. 3. Vehicle test system using a dynamometer system

It demonstrates also a cold start emission test. A suggested step is planning of a new complete vehicle test plant for multi gas measurements in cold climate.

2.3 Expected results from the project Many parameters have effects on vehicles in cold climate. Lower temperature and higher friction have effects on fuel consumption and exhaust emission. Exhaust measurements in cold climate gives an increased value of the tests and could in combination with driving tests give useful data for vehicle adjustments and optimizations. The purpose of the project is not primarily for research, but with equipment and competence in place it opens up research possibilities in the future. The vehicle testing companies will have a broader variety of services which they can provide giving more revenues to the vehicle testing companies and an extension of the test season. The mining industry has expressed a need to evaluate emissions from large underground machinery related to work environment problems, costs of ventilation and questions about emissions of green house gases requiring both new fuels and new after-treat technology. Experience obtained in the project can probably be applied in the mining industry and will give a base for cooperation between Luleå University of Technology and the mining industry.

3 Measurements

3.1 FTIR advantages The advantage of FTIR is that it does not need calibration at all, or at least as frequent calibration as the standard systems. The current set-up for certification measurements involves direct showing instruments for at least CO, CO2, NOx and THC. The instruments require frequent calibration and also THC with FID (flame ionisation detection) requires a continuous supply of hydrogen and air. The recent FTIR systems do have a shorter response time than the older ones. With a proper design the instrument can be used in mobile applications and cold climate. The focus of the project is to measure emissions from a cold start because the major part of the real world emissions of CO and hydrocarbons do stem from the cold start emissions before the catalyst start

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to operate (Weilenmann 2009). In EU does all gasoline cars from 2002 have to pass a cold start test at -7 °C, but the requirement is so generous that if the car passes testing at 23 °C it normally also pass this cold start test at -7 °C.

3.2 Performed measurements Cold start tests were performed with three different cars with a MKS FTIR instrument (2030 HS) running the instrument at 1 Hz with sampling flow rate of 3 l/min. Further information is given in Appendix. In the figure below is some components shown during a cold start at idling.

Cold start at idling

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Figure 1. Five emission components measured during a cold start at idling.

3.3 Conclusions of performed measurements The measurements were performed without any problems and to obtain faster response the only thing which has to be modified is to increase the sampling flow by increasing size of tubing, pump and filter, compared with what was used in the performed measurements.

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4 Multi gas exhausts measurement systems – solutions

4.1 Mobile measurement system with the FTIR A simple but appropriate experimental set-up for car exhaust measurement under cold start and idling applications is shown in figure 2. Cold start emission testing at idling requires only a few pieces of equipment, which are the measurement instrument, the heated tubing from exhaust pipe to the measure instrument and a heated pump and filter. To be able to measure the emissions the exhaust flow must be measured or estimated in one or another way. Inclusion of an annubar (pitot tube) measurement device has been reported. 4.1.1 Hardware – a mobile FTIR system The measurement system can be built in a mobile compact design including all optional equipments. The FTIR-system can easily be moved and can be operated in different measurement places.

- FTIR (MKS 2030HS) including data interfaces, data logging system and software - Heated pump and filter system - Exhaust flow meter system (option) - Heated sampling tubes

4.1.2 Cost estimates for a mobile FTIR The investment cost of a FTIR (MKS 2030HS), heated tubing from exhaust pipe to instrument and heated pump and filtering system is approximately 1.000.000 SEK. Exhaust gas flow measurement system is an option by an annubar (pitot tube) or a single-point insertion thermal mass flow transmitter (Kurz 454FTB). A cost estimate of an exhaust flow measurement system is about 30.000 SEK. The cost of additional equipments such as mechanical systems, mountings and supply system of liquid nitrogen is about 50.000 SEK. 4.1.3 Power requirement FTIR itself 350 W Laptop 20 W Unheated pump 400 W (Heated pump 900 W) Heated tubing and filter 2000 W 2770 W (3270 W with heated pump)

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Figure 2. Mobile measurement system – cold start measurement system

4.2 Mobile measurement system with the FTIR on-board. A field test solution using the measurement instrument for on-board measurements are using the same hardware set-up as the system for cold start emission testing at idling, 4.1. A simple but appropriate experimental set-up for onboard car exhaust measurement applications is shown in figure 3. The components are the same as in 4.1.1, except that provision has to be for external electric supply through e.g. a battery. The electric system of a car can not supply the required electric power supply. In Li (2007) batteries were used to supply a heated FTIR (Gasmet CR2000) on-board system requiring 1200 W. Batteries weighing 70 kg gave 2-3 hours running time. The system is very similar to the proposed, except that the flow-rate was 2-3 l/min instead of over 50 l/min, which can be obtained with the pump which gives 100 l/min free-blowing. The CR 2000 requires only 300 W showing that the major power is used to heat the pumping and cleaning system. The power requirement seems to be the problem with a FTIR on-board using fast measurement. One idea is to use a trailer equipped with the measurement system and a power unit. An electric generator using a liquid or gaseous fueled engine could easily supply the power.

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Figure 3. Mobile measurement system – on-board measurements 4.2.1 Hardware – onboard FTIR system

- FTIR (MKS 2030HS) including data interfaces, data logging system and software - Heated pump and filter system - Exhaust flow meter system (option) - Heated sampling tubes - Power supply unit alt. battery system - Installation options, external trailer etc

4.2.2 Cost estimate – an on board FTIR system The investment cost of a FTIR (MKS 2030HS), Heated tubing from exhaust pipe to instrument and heated pump and filtering system is approximately 1.000.000 SEK. Exhaust gas flow measurement system by an annubar (pitot tube) measurement system is an option. A cost estimate of an exhaust flow system is about 30.000 SEK. The cost of a power supply unit is approximately 25.000 SEK. The cost of additional equipments such as mechanical systems, mountings and supply system of liquid nitrogen is about 50.000 SEK. The cost of a covered trailer for all equipment is about 40.000 SEK. Power supply from a battery system is also an extra option, if the carried weight is acceptable, with a cost about 10.000 SEK.

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4.2.3 Power requirement FTIR itself 350 W Laptop 20 W Unheated pump 400 W (Heated pump 900 W) Heated tubing and filter 2000 W 2770 W (3270 W with heated pump)

4.3 Vehicle test system using a dynamometer system A third step is to plan a new complete vehicle test stand including control of all vehicle parameters utilizing existing temperature controlled rooms or special designed cold climate chambers as shown in figure 4.

Figure 4. Stationary vehicle test stand

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4.3.1 Vehicle test system including chassis dynamometer A complete vehicle test stand is an advanced car test system. The total investment costs have to be calculated according to specified requirements and standards. Such project has to be planned by professional people who have experience of such complex technical solutions. In the pilot study “Tingvall 2007” it can be found short information of different car test systems. A total system includes following parts;

- Chassis dynamometer system, two wheel or four wheel drive system - Control system - Cooling system - Electrical power system and converter - Inlet air system - Exhaust gas outlet fan - Measurement system, exhaust gas, physical parameters - Signal communication - Special building, cold chamber - Training of technical personnel

4.3.2 Example of chassis dynamometer AVL 48" Compact 2WD climatic chassis dyno single roller with moveable axle The 48“- Compact 2WD vehicle test bench is designed to test front wheel drive and rear wheel drive vehicles. It is possible to simulate vehicle weights from light cars up to light commercial vehicles. The vehicle test bench can be operated in the control modes road load simulation, speed control, tractive force control and acceleration control.

Figure 5. 48” Chassis dynamometer system

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Technical facts of the chassis dynamometer

- AC technology with IGBT converter - Road load simulation - Fulfils US EPA specification of accuracy and dynamics - No warm-up required - Front/rear wheel drive with constant 150 kW (max. 258 kW) - Speed up to 250 km/h - Vehicle mass up to 5.400 kg - Axle load of 4500 kg - Roller track of ca. 2800 mm - Ca. 6000 N permanent tractive force - Ca. 10000 N peak tractive force - Electric inertia simulation between 1000 lbs and 12000 lbs - Operation temperature of 0 ... 40 °C or –30 °C ... +60 °C - Relative humidity 35% - 55%

Air stream blower;

- Max. Volume flow rate 60.000 m³/h - Vmax 120 km/h - Manual or automated control of wind speed - Controlled by chassis dyno speed or - Controlled engine oil/coolant temperature

5 Conclusions Cold start multi gas exhaust measurements have been done at idle conditions on cars in cold climate, showing that this can be performed easily without any development work at the testing companies. Measurements of exhaust gas flow have been done formerly and, if required, can easily be added. The investment costs are in the order of 1 million SEK (Equipment). The main question is: does measurement at idling produce usable results for the car manufacturer, and if not, what kind of dynamometer system is required. The investment costs of a dynamometer system are well above 10 million SEK mostly depending of the costs for dynamometer system, the building and the instrumentation. Mobile measurements have been shown to work formerly in research projects. All components can mechanically withstand mobile measurements. The weight of the equipment is substantial but the major problem is the power supply in onboard use. The experience from other research projects show that batteries can supply the power, but it requires that the equipment is well designed to have low power consumption. The published research project was using instruments with power consumption about 1200 W. One idea is to use a trailer equipped with the measurement systems and the power unit. An electric generator using a liquid or gaseous fueled engine could easily supply the power.

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6 Recommendations The major obstacles with the idea to expand the services provided by the testing companies with emission measurements are that it seems difficult to get valid answers from the car producers about their commitment to buy this kind of services. Therefore the service has to be offered to the cars producers to evaluate the idea. Division of Sound and Vibration at Luleå University of Technology will support in writing an application with a testing company to obtain and contribute to the economic recourses to invest in system for cold start measurements at idling as the proposal at step 1 described in section 6.1.

6.1 Proposal - Step 1 - Cold start measurement system Figure 6 shows a simple but appropriate experimental set-up for car exhaust measurements under cold start and idling conditions, which could serve as the first step to introduce exhaust measurement as a service to car manufacturers. Cold start emission testing at idling require only the measurement instrument itself, heated tubing from the exhaust pipe to the measurement instrument and a heated pump and filter. To be able to measure the emissions the exhaust flow must be measured or estimated in one or another way. Inclusion of a measurement device is quite simple and do not require any development work provided the measurement device can handle the exhaust conditions. Some sort of Pitot tubes has been applied formerly. A suitable system could include the following;

- A FTIR exhaust measurement analyzer, (e.g. MKS 2030 HS) - Heated measurement tubes - A exhaust gas pump and filter - A mass gas flow measurement system, e.g. Kurz 454 - Mechanical system construction, building and testing - Field testing at cold starts - Training of personnel

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Figure 6. Cold start measurement system

6.2 Proposal - Step 2 – Onboard measurement system Going from step 1 to step 2 only a few items need to be added. The same instrument setup as in 6.1 can be used. The main addition is to supply a way to provide the required power supply, which could include options such as extended battery system or a power supply unit possibly on an external trailer. A suitable work programme could include;

- Investigate the requirements of onboard measurements - Develop options for onboard measurements - Mechanical system construction, building and testing - Field application testing onboard vehicles - Training of personnel

6.3 Proposal - Step 3 – Complete vehicle test stand Projecting of a complete vehicle test stand is an advanced engineering work. If that’s an alternative and there are such requests from the customers we suggest that a project group with the right competence handle the project. There also requires large investments in such system. Only the equipment costs are larger than 10 million SEK.

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7 Project organisation Cooperation has been established between Division of Sound & Vibration and some vehicle testing companies in the region.

Table 1. Industrial network Name Affiliation Role

Ove Berggren Arctic Falls Industrial advisor

Lars Holmgren Harald Fjällström Michael Lindeman

ATM Arjeplog Test Management AB Colmis AB Ice makers

Industrial advisor Industrial advisor Industrial advisor

Karl-Erik Söderberg Karsten Boettcher

Tjitjokk Mercedes AMG

Industrial advisor Industrial advisor

Table 2. Scientific partners Name Affiliation Role E-mail Telephone

Anders Ågren Professor LTU Academic Advisor anders.agren@ltu.se +46 920 – 491683

Bror Tingvall Research engineer

LTU Project leader, Academic Co-Advisor

bror.tingvall@ltu.se +46 920 – 491471

Esbjörn Pettersson Licentiate

ETC/LTU

Academic advisor and measurement expert

esbjorn.pettersson@ltu.se

+46 70 – 380 78 14

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8 References Adachi 2000 Emission measurement techniques for advanced powertrains / Adachi,

Masayuki. Meas. Sci. Technol. 11 (2000) R113–R129.

Dearth 1999 Evaluation of a Commercial Mass Spectrometer for Its Potential To Measure Auto Exhaust Constituents in Real Time. / Dearth, Mark.

Ind. Eng. Chem. Res. 1999, 38, 2203-2209 Li 2007 Study of thermal characteristics, fuel consumption and emissions

during cold start using an on-board measuring method for SI car real world urban driving / Li, Hu; Andrews, Gordon E; Savvidis, Dimitrios; Daham, Basil; Ropkins, Karl; Bell, Margret; Tate, James. Energy and Resources Research Institute, UK, JSAE 20077355; SAE 2007-01-2065

Tingvall 2007 Vehicle test system: a pilot study. / Tingvall, Bror; Pettersson, Esbjörn;

Ågren, Anders. Luleå: Luleå tekniska universitet, 2007. 49 s. (Technical report / Luleå University of Technology; 2007:11).

Weilenmann 2000 Cold-start emissions of modern passenger cars at different low

ambient temperatures and their evolution over vehicle legislation categories / Weilenmann, Martin; Favez, Jean-Yves; Alvarez, Robert. Atmospheric Environment 43 (2009) 2419–2429

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Appendix

Demonstration of cold start measurements

1.1 Performed measurements The FTIR from MKS (2030HS) has the ability to measure at true 5 Hz, provided that the sample flow is high enough. The measurement cell is designed to have fairly small volume (0.2 litres) despite an optic path length of over 5 metres. The measurement cell is also designed to allow high gas velocities to be able to perform true 5 Hz measurement. Connections to the measurement cell are ½”. The used system is not aimed for 5 Hz, but consists of an external heated probe filter, a heated exhaust tubing 6 mm Teflon tubing and a heated pump and a metal filter in a heated oven and the FTIR itself. During the measurement was a 10 mm Teflon tubing put into the exhaust pipe. No extra heating was used because the 10 mm Teflon tubing could be inserted directly into the exhaust pipe. If the probe filter could not be placed in the vicinity of the exhaust pipe heated Teflon tubing should have used to transfer the exhaust into the probe filter, which was heated to 145 oC. The heated Teflon tubing was heated to 147 oC as well as the heated oven and the transfer tubing from the heated oven to the FTIR, which was run at 150 oC. The calibration spectra for the applied method, Gasoline, had been acquired at 150 oC. In the heated oven there is a rotameter, which showed that the flow was about 3 litres/min. Before start of the measurement the detector was cooled with liquid nitrogen and a zero spectrum was acquired while nitrogen of instrument quality was flowing through the instrument. Before starting the actual measurement the instrument was set to use the method Gasoline. After the run a result file has been created which contains calculated concentrations according to the method which has used. The method comes with the instrument. During the run spectra was saved which is useful if one wants to re-evaluate the run with a modified method, in case that the used method does not work satisfactorily during phase of a run. This is found by looking at the residuals. In the used method Gasoline the concentrations of CO2, H2O, CO, NO, NO2, acetaldehyde, acetylene, ammonia, methane, dodecane, ethylene, formaldehyde, formic acid, hydrogen sulphide, sulphuric acid, laughing gas, propane, sulphur dioxide, sulphur trioxide and toluene were determined. After preparation the Teflon tubing was put into the exhaust pipe, the car was started and was allowed to run at idling until both CO and NOx obtained low values. Ambient temperature was -15o C at time of measurement (29th of November 2008). The cars had been standing out doors over night until five in the after noon when the measurement was performed.

1.2 Used measurement procedure The following procedure to use the measurement system is applied;

- Start heating of the FTIR, heated lines and filter/sampling probes - Purge N2 through the measurement cell and purge the interferometer and the detector

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- Fill liquid nitrogen (There is a container which can be mounted on FTIR which gives several days between fillings with liquid nitrogen).

- Set required method and name and where the result file should be saved and (if required) base name of spectra and where to save the spectra.

- Set FTIR in Run position. - Start the pump and the FTIR is measuring a cold start when the car starts. - Stop the pump. - Take the FTIR out of Run position and the measurement is stopped. - The result file consists of time stamp (5 Hz) and calculated concentrations (Gasoline gives 19

components). The concentrations are calculated with the used method based on calibrations for each component. Are all concentrations within the range of used calibration gases the residuals are fairly small, which can be seen on the screen. When the residuals are large it indicates that the concentration of one or more components is outside of the calibrated range or an important component is missing. Sometimes does the software handle largely different concentrations for one substance as two or more separate components, e. g. CO low, CO middle and CO high. During the start CO low showed large residuals while CO high showed small residuals. This means that CO low showed wrong value while CO high showed correct values. This type of checking may be needed to obtain accurate values. When the methods have been checked and possible been developed for the real working conditions no further controls need to be done except that the FTIR itself works properly.

1.3 Test-vehicles Following cars have been used for the cold start tests; Ford Focus, model year 2001 Normal condition Nissan Micra, model year 1994 The Nissan Micra was in very bad shape with leaking

exhaust pipe and badly adjusted ignition. The car would fail at the yearly vehicle inspection and was aimed being trashed.

Toyota Camry, model year 1995 The car was started at a later occasion when ambient

temperature was -10 o Celsius.

1.4 General results The instrument worked perfectly and the system is easy to use for multi gas measurement. In the following paragraphs are measurements shown for the cars above with comments. The measurements were performed on old cars which gave large emissions. Newer cars complying with Euro 4 regulation gives lower emissions both regarding cold start up and legislative emissions, and the cold start emissions are comparatively larger with newer cars than older ones ((Weilenmann 2009).

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1.5 Ford Focus In Figure 1 and 2 the results from cold start with the Ford Focus are shown.

Ford Focus cold start CO2, CO and NO

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Figure 1.The Figure shows that both CO and NOx have come down to low values after approximately 5 minutes, i.e. the catalyst has ignited.

Ford Focus coldstart CO2, CO and NO

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Figure 2. The figure shows that the control system of the car lowers the exhaust temperature after long time idling that the conversion in the catalyst lowers somewhat which shows up in that the CO concentration increases somewhat. After 18:04 the FTIR started sucking ambient air.

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In Figure 3 measured concentration of some hydrocarbons during cold start of the Ford Focus is shown.

Ford Focus CO, acetylene, ethylene, acetaldehyde and methane

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Figure 3. Some hydrocarbons measured during the cold start of the Ford Focus along with CO. The figure shows that the catalyst has different conversion rates for different hydrocarbons, i.e. the different hydrocarbons burn differently in the catalyst.

1.6 Nissan Micra In Figure 4 is the measurement on an old Nissan Micra during a cold start shown.

Nissan Nicra CO2, CO and NO

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Figure 4. For an old Nissan Micra the values of CO and NO does not come down to really low values during idling.

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1.7 Toyota Camry In Figure 5 are the measurements during a cold start for an old Toyota Camry shown.

Toyota Camry with throttling at 12:11 and 12:14

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CO2*100NO CO

Figure 5. Toyota Camry with throttling at 12:11 and 12:14. The figure shows that the values do not go down during idling at all. The throttling at 12:11 gave increased CO and NO emissions while the throttling at 12:14 (3000-4000 rpm) only gave heavily increased NO emission.

1.8 Observations about the FTIR measurements FTIR is based on that each component absorbs differently in different wavelengths. The concentration is proportional to the absorbance for each component. The problem being that some light has to come to the detector to be able to determine the concentration while on the other hand if too small amount of light does come to the detector the noise becomes too large. That means the absorbance must be within a certain range to be useful. To determine the concentration for a single substance at low and high concentrations different wavelengths should therefore be used to get the highest accuracy. This is seen Figure 6 where COlow and COmid are compare for Ford Focus. Firstly is COlow always below COmid, which is reasonable considering a single component. Later is COlow higher than COmid and the reason for this is probably that some nitrogen compound starts forming in the catalyst which is not fully accounted for by the method, which “disturbs” the calculation of COlow. These things can be seen in the residual plot which is shown at the same time as the calculated concentrations. In the residual plot it can be seen which wavelengths are used for each component and if the calculated concentrations of the determined gases extracts all information which is in the “x” or if there is other components or higher concentrations of measured components than accounted for.

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CO low and CO mid

0

10000

20000

30000

40000

50000

60000

70000

17:54:30 17:55:30 17:56:31 17:57:32 17:58:33

CO

ppm

CO LOWCO MID

Figure 6. COlow and COmid versus time for the Ford Focus measurement. In the development of the methods, observations similar to this one, has to be accounted for at an extent which is accepted by the car manufacturers.

1.9 Pictures on the sampling system and on the FTIR Figure 7 shows the heated probe filter with the ceramic filter and the Teflon tubing, which was put into the exhaust pipe.

Figure 7. The heated filter with the Teflon tubing was put into the exhaust pipe.

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Figure 8. The Teflon tubing put into the exhaust pipe.

The Teflon tubing, shown in figure 8, was a little bit short which may have caused air to get sucked by the pump. The pump is a single headed diaphragm gas pump, which increases the risk of sucking air due to pulsations in the flow. One solution is to use longer Teflon tubing. Figure 9 shows the heated oven with the heated pump, filter and a rotameter to get an idea about the sampling flow.

Figure 9. Oven with pump, filter and rotameter.

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The detector is cooled by liquid nitrogen which is dispatched in the funnel before each run. A filling lasts for about 12 hours. There exists additional equipment which supplies liquid nitrogen for several days, if required. Figure 10 shows that when the reservoir is completely filled with liquid nitrogen by the upcoming liquid from the container.

Figure 10. The container is completely filled with liquid nitrogen which is shown by the fact that liquid nitrogen comes out of the container.

Figure 11 shows the computer screen during settings before a run. One needs to give a file name and a method which shall be used to calculate the concentrations.

Figure 11. Computer screen showing the settings before a run.

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Figure 12 shows spectra during a run and Figure 13 shows calculated values during a run.

Figure 12. Computer screen showing spectra during a run.

Figure 13. Computer screen which shows calculated composition in real time during a run.

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Figure 14 shows the front of the FTIR itself with the protective cover on and Figure 15 shows it without the cover.

Figure 14. The front side of the FTIR with the cover.

Figure 15. The front side of the FTIR with the cover removed. The two regulators are temperature controls of the measuring cell and the transfer line inside the FTIR. The two flow indicators (rotameters) are used for purging of detector optics and the interferometer volume. The detector is situated behind the quadratic cover.

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Figure 16. The picture shows the backside where the sample lines goes in and out of the FTIR with the electrical connections and the analogy input card for 4-20 mA signals (connected directly to the computer). The red tubing’s are the heated lines from the heated oven (in) and the heated lines to the lambda sensor (out). Earlier experiences showed that the lines to the lambda sensor had to be heated.

1.10 Notes on different instruments Adachi (2000) identified FTIR and Mass spectrometers with soft ionisation for analysis of gaseous compounds and Fast Flame Ionisation for real-time measurements of particulate matter as tools in the development of advanced power-trains. In the 21st century has FTIR mostly, in the research literature, been used to measure ammonia (NH3) and laughing gas (N2O). Most measurement has been performed in raw exhaust without dilution. Available instruments on the Swedish market suitable for automotive measurements include Nicolet, Gasmet and MKS. AVL does sell there own developed system based on a MKS FTIR. Horiba has also there own developed system. The instruments use liquid nitrogen to cool the detector to obtain fast response and obtain low detection limit. They can all measure at 1 Hz or faster. Sensitivity depends on the compound. In the same instrument H2S can have a high detection limit of approximately 50 ppm, which means that FTIR is not the choice for H2S in automotive exhaust, while on the other hand the detection limit for SF6 can be as low as 0.01 ppm, which shows that there is an influence from the chemical structure on the detection limit. For most compounds it is in the order of 1 ppm for instruments useful for automotive measurements. The difference between the instruments can be described with the highest possible flow-rate through the measurement cell versus volume giving the exchange rate of the exhaust gases combined with the highest rate of measurement and calculation, versus detection limit. The detection limit has to be

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compared at the same data rate because the signal to noise ratio can be improved by addition of several spectra. For some instruments all calculated concentrations are based on several spectra while others can calculate concentrations from only one spectrum. Above averaging 10 to 20 spectra the improvement in signal to noise ratio is limited. Table 1 shows the lowest obtainable detection limit for one of the suppliers while Table 2 shows that the limit of detection becomes higher in combination with water which is major constituent in all exhaust gases. The same effects on the limit of detection are found for some components with carbon dioxide but water is the worst disturbing component in normal exhaust gases. Table 1. Low level detection limit in the absence of interfering compounds for different measurement times (MKS1, MKS2) Name Formula 5 min 1sec 0.2 sec (5 Hz) Ammonia NH3 30 ppb 0.5 ppm 0.5 ppm Carbon Dioxide CO2 12 ppb 0.2 ppm 0.2 ppm Carbon Monoxide CO 72 ppb 1.0 ppm Formaldehyde HCOH 36 ppb 0.5 ppm 0.6 ppm Hydrogen Chloride HCl 87 ppb 1.5 ppm Hydrofluoric Acid HF 12 ppb 0.2 ppm Methane CH4 36 ppb 0.6 ppm 1.0 ppm Nitrogen Dioxide NO2 24 ppb 0.4 ppm 0.5 ppm Nitric Oxide NO 210 ppb 1.0 ppm Nitrogen Trifluoride

NF3 30 ppb 0.5 ppm

Silicon Tetrafluoride

SiF4 10 ppb 0.15 ppm

Sulfur Dioxide SO2 36 ppb 0.8 ppm 1.0 ppm Tetrafluoromethane CF4 2.5 ppb 40 ppb Xylenes C8H10 60 ppb 1.0 ppm Table 2. “Real” detection limit. Typical detection limits in 10 % H2O, 5 min measurement time (MKS3) Contaminant Typical detection limits CO 0.1 ppm CO2 0.1 ppm CH4 0.5 ppm NO2 0.2 ppm NO 0.5 ppm N2O 0.5 ppm NH3 0.2 ppm SO2 0.5 ppm SO3 0.5 ppm As shown in Table 3 the detection limit is depending on the concentration of water vapour, the optic path length in the measurement cell, measurement frequency (often related to number of spectra added) and spectral resolution. A long optical path length gives lower detection limit but limits also the highest possible water and carbon dioxide concentrations which the instrument can handle. Too much material in the optical path cause complete absorption of the light meaning that those wave-lengths can not be used in evaluations to obtain the concentrations. The noise level also increases with increasing absorption. The absorption is proportional to the amount of material in the optic path. Nicolet and Gasmet recommend an optical path length of 2 meters for automotive measurements,

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while MKS has only one length which is 5.11 meters. Another difference between the instruments is that Nicolet and MKS can use a spectral resolution down to 0.5 cm-1, while Gasmet uses 8 cm-1. The noise level is considerably higher with a high spectral resolution, but does on the hand resolve the different components better making the identification of the compounds easier and less prone for false results. With a lower resolution one normally can perform measurement at faster rate. To obtain correct results the calibration has to be performed at the identical conditions as the measurement are performed. In reality the user has no choice but to use the conditions for which the calibrations were done. Table 3. Detection limits depending on water vapour, optic path length, measurement frequency and spectral resolution (Nicolet1) DL 1 cm-1 /

4 Hz / 2 m with less than 8%

water vapor

DL 1 cm-1 / 4 Hz / 2 m with less than 35% water vapor

DL 0.5 cm-1 / 2 Hz / 2 m , up to 35 % water

vapor

DL 1 cm-1 / 4 Hz / 10 m with

less than 3% water vapor

DL 0.5 cm-1 / 2 Hz / 10 m with less than

5% water vapor

NO (ppm) 5 15 7 3 2 NO2 (ppm) 3 10 5 1.5 2 N2O (ppm) 3 5 4 1 1 NH3 (ppm) 0.5 2 1 0.1 0.1 SO2 (ppm) 3 10 8 2 4 SO3 (ppm) 3 11 8 2 4 H2O (ppm) purge dependant

6 NA 6 3 3

CO (ppm) 3 4 4 1 1 CO2 (ppm) purge dependant

1 1 1 1 1

CH4 (ppm) 2 3 3 1 1.5 C2H4 (ppm) 2 3 3 1 1.5 C3H6 (ppm) 2 3 3 1 1.5 C3H8 (ppm) 1 2 1,5 1 1.5 The optic path length of 2 metres is recommended for applications having higher CO2 and H2O concentrations than 3 volume %. For automotive applications a measurement cell with 2 meters optical path and a spectral resolution of 0.5 cm-1 is recommended even if instruments with 10 meters cell have been sold for automotive applications. In Table 4 is detection limit for a CR2000 from Gasmet presented. The information is taken from Murtonen (2009) which states that the detection limit is according to the instrument manufacturer. Table 4. Detection limit for CR2000 from Gasmet. Information taken from Murtonen (2009) Measurement time 1 sec Measurement time 5 sec CO 7 ppm 3 ppm NO 19 ppm 4 ppm NO2 10 ppm 6 ppm N2O 4 ppm 1 ppm NH3 2 ppm 1 ppm CH4 2 ppm 1 ppm Formaldehyde 20 ppm 9 ppm

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The only instrument manufacturer who sells complete systems including the FTIR and sampling and cleaning system is Gasmet, while MKS relies on other companies supplying the sampling and cleaning system. In Sweden does Rowaco sell the MKS FTIR and provides sampling and cleaning systems. Rowaco and Gasmet use the same pump from KNF Neuberger giving similar gas-exchange rates for the cell. Nicolet does not sell complete systems, while AVL and Horiba do sell complete systems with FTIR and sampling and cleaning system. The Tables above has concentrated on the detection limit which is in practical application not that important, because FTIR is normally applied in raw exhaust with fairly high concentrations. The most important parameters is that the system really does work continuously and are practical to use, which is more depending on the cleaning system and how data can be handled in a system and combined with other measurement devices. The authors experience is that despite the data handling system was seemingly working perfectly annoying behaviour was found when using the system. The actual performance of a complete system has to be evaluated carefully concentrating mostly on data handling. MS (mass spectrometer) with soft ionisation can measure a value each 10 msec. giving very fast measurements for a single component. For, say 25 compounds, the cycle time will be 0.25 sec which anyway is fast. The benefit of MS is low detection limit which is in the ppb-range for most compounds. This means that this instrument will be the choice in the normally used dilution tunnels. For H2S gives MS a low detection limit meaning that MS is the choice for H2S. Though, it requires calibration on a monthly basis for at least one component (e.g. CO2) and less frequent for all measured components. The required sample volume is only a few ml per minute requiring small sample flows to measure at several Hz. The price of an instrument exceeds 200 000 euro. It has not yet been applied for on-board measurements. The power requirement of the instrument is the order 800 W (PMSAB). AVL does also sell a MS, which most probably is based on the same instrument as sold by PMSAB. On-board measurement with FTIR has been applied for a long time. The major problems with on-board measurements are the requirement for electric power, especially when fast measurements are required. The MKS system require about 2,8 kW while a Gasmet system (Gasmet) system require about 2,3 kW, both system do require too much power for the electric system on a passenger vehicle or for extra batteries. A commercial on-board system is OBS-2000 sold by Horiba, which is based on ordinary instruments requiring daily calibrations. CO and CO2 are measured with NDIR, NOx is measured with a CLD and THC is measured with a FID requiring fuel gas (hydrogen). The system includes measurement of exhaust gas flow with a Pitot-tube and requires only 200-500 W, which can be supplied with an extra battery. The lower power requirement is for a cold system with no heated lines, while the higher number is for a system with heated lines. T90 is in the order of 1 second. OBS-2000 has been used in some research reports on passenger cars and is applied on a routine basis for heavy-duty vehicles, but has not yet been applied on routine basis for passenger cars to a large extent. The instrument price is about 100 000 euro (Horiba). There are additional investment costs for calibration gases. The benefit of the system is that it is commercial, has been proven for along time and has limited power requirements. The drawback is that it does not give any speciation of the exhaust gases and requires daily calibration. On-board system does also have a problem with safety in case of accidents. OBS-2000 requires a cylinder with fuel gas on-board, while the FTIR uses liquid nitrogen. In an accident in which the car is turned upside down the liquid nitrogen can flow out of the instrument and evaporate replacing oxygen and suffocate people trapped in the car. This can solved if provision is made that the evaporated liquid nitrogen leaves the compartment. In case of fire can a gas cylinder burst. This shows that on-board measurements need safety considerations.

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1.11 References Gasmet Personal communication Lennart Messerer, Alnab

Horiba Personal communication Ulf Fransson, Horiba and http://www.testing-

expo.com/europe/05txeu_conf/pres/nakamura.pdf Retrieved 20091130 MKS1 http://www.mksinst.com/docs/UR/2030hsds.pdf Retrieved 20091130 MKS2 http://www.mksinst.com/docs/UR/onlinemultigas2030ds.pdf Retrieved 20091130 MKS3 Personal communication Peter Schef, Rowaco Murtonen 2009 Alternative fuels with heavy-duty engines and vehicles. VTT´s contribution. /

Murtonen, Timo; Aakko-Saksa, Päivi: VTT Working Papers 128,VTT-WORK-128,http://www.vtt.fi/inf/pdf/workingpapers/2009/W128.pdf

Nicolet1 Personal communication Tommy Larsson, Thermofisher PMSAB Personal communication Göran Sandström, PMSAB