OBS-TRPM On Board System Transient PM Mass Measurement

Transcription

1 OBS-TRPM On Board System Transient PM Mass Measurement PEMS-PM Evaluation Program Meeting

2 PM is a complex, variable mixture of several components Tail Pipe Formation continues in ambient upon dilution with air SO 4 Ash Carbon Nitrate SO 4 Soot SOF HC H 2 O Soot: Carbonaceous Solid (Combustion Generated) SOF: Heavy HC condensed/absorbed on soot (Unburned fuel, Oil, Compounds formed during combustion) SO 4 : (Sulfur from the Fuel and Oil) combined with H2O Nitrate : Formed as by-product from some exhaust aftertreatments Ash : solid particles formed from combustion of oil or additives in fuel

3 OB Real Time Mass Measurement Technical Difficulties Accuracy Specifically, correlation to the filter based gravimetric measurement principle that is used currently for all engine / vehicle certification Sensitivity Requires higher sensitivity than filter gravimetric principle Laboratory has whole test cycle for PM loading, real time can have as little as 30 seconds of PM mass loading Traceability Calibration method Traceability to a mass standard Repeatability / Reproducibility Short term and long term drift PM Sensitivity to Fuel Composition, After-Treatment, Test Cycle, Ambient Conditions etc PM composition can change with the above, not consistent Rugged and Practical for On Board Use Insensitive to vibration, ambient temperature change, altitude, ambient humidity Size, power consumption, control signals etc

4 Combination of PFDS and Real Time Detector Filter Gravimetric Method Real time instruments Advantage Conventional Method Gravimetric result Disadvantage Low Sensitivity Batch result Disadvantage Correlation? Traceability? Advantage High sensitivity Real time result

5 Basic Components for the Combined System A filter based partial flow diluter (proportional control) A cyclone has the cut point at 6.0 µm Dilution and PM sampling at 47 deg C, same as 1065 An diffusion charge sensor (DCS) used as a real-time PM detector TSI OEM of their EAD (Electrical Aerosol Detector) Measure particle length in real-time Integrated cyclone has the cut point at 1.0 µm Pitot tube flow meter and OBS-2200 providing exhaust flow signal for proportional control Assumption that the PM mass being collected on the filter is proportional to the PM length parameter

6 Schematic For OB-PFDS Module Short transfer tube Mixer 47degC Cyclone Makeup Air MFC Venturi Filter holder Venturi P FO Dilution Air Piezo Valve Potential for multiple filters Accurate Flow Measurement Venturi flow meter has low effect of exhaust composition Fast Flow Control Piezo Valve & FO is applied for dilution air flow control

7 Layout for the prototype PFDS 47mm Filter holder (47±5 degree C) Heated Enclosure Control Unit Open Exhaust Flow Signal (for proportional dilution control)

8 Dilution Ratio Verification 0 Difference to reference [%] Dilution ratio Dilution factor verified using high accuracy flow measurement of net sample flow rate under steady state conditions

9 Proportional control for FTP cycle Using air flow + fuel flow data 8 7 Sample ratio: 4000:1 Sample Ideal sample y = x R 2 = Sample flow [slpm] Sample flow [slpm] Standard error: 0.948% Time [s] Exhaust flow [slpm] Standard Error = (>0.95 ; ISO-16183) Correlation Coefficient(R 2 ) = 2.93% (<5.0% ; ISO-16183)

10 Proportional control for FTP cycle Using exhaust flow meter Flow [slpm] Sample flow [slpm] y = x R 2 = Standard error: 5.499% Max. delay time: 0.1 s Time [s] Sample Ideal sample Negative exhaust flow obtained from exhaust flow meter Exhaust flow [slpm] Sample flow Linear (Sample flow) Exhaust flow metering system accuracy / characteristics are important factor in the performance of PM Mass measurement

11 Test Engine SWRI Test Engine Specification Description Specification Model Year Designation Engine Family Power Rating Torque Rating 1998 DDC Series 60 with CRT-DPF 400hp at 1810rpm 1550 lb-ft at 1200rpm CRT-DPF Bypass

12 Test Sample Probe Test Engine On Board PM Pitot tube & Sample Probe OBS (Gaseous) Primary Dilution Tunnel Analyzers Dilute Exhaust Measurement Secondary Dilution Tunnel CVS F P B EPA 2007 sampling protocol Partial Flow Sampling for PM Measurement Raw Exhaust Gas & Flow Measurement

13 PM Emission Results

14 Combination of PFSS and EAD Exhaust Pipe Note : Second stage diluter has proved not to be necessary due to the wide dynamic range of the EAD module Mixer Dilution Air Dilution Air Cyclone FO Mixer EAD Filter P 47degC P 2 nd Stage Diluter Partial Flow Sampling System

15 Concept for NTE or real time PM mass measurement procedures EAD signal (mm/m3) NTE-1 NTE-2 NTE-3 NTE-4 NTE-5 Invalid event Bypass Bypass Bypass Bypass Bypass Filter Filter Filter Filter Filter PM mass in VALID NTE events = Total PM X Ratio EAD Ratio of PM ( EAD t ) i ( t) n EAD i i = 1 PFDS Total PM

16 Advantage of the combination method Advantage Total PM measurement over NTE events same as conventional method. Filtering PM in NTE region (with 0 secs averaging) for more than 2 hours should typically load sufficient PM on the filter (depending on the road cycle) EAD has sensitivity for real time measurement of post 2007 PM standard. EAD measures all particles soot, sulfate, volatile particle, etc.

17 Minimizing the Assumptions Assumptions; Same size distribution, Same density Minimizing factors By using filter gravimetric mass result as reference on each specific engine, this will eliminate assumption errors for engine family, after treatment strategy, etc. By using EAD to gravimetric mass ratio, we will reduce the impact of different PM species on measurement. Method can be adapted for a variety of measurement models (NTE, Moving Work Window etc) Assumed Composition, Density or Size Distribution parameters are not used to calculate mass

18 Real Time Data : EU Stage 3 vehicle on chassis dynamometer Length [mm/cm3] Speed [km/h] Time [s] Hot 1, L Hot 2, L Hot 3, L Hot 1, S Hot 2, S Hot 3, S

19 Accumulative particle diameter length v time Particle length [mm/cm3], Exhaust flow [slpm] NEDC, Hot Speed [km/h], Fraction of the length [%] Time [s] Length Speed Fraction of Length

20 Accumulative particle diameter length v Gravimetric PM Mass Total Length [mm] PM mass [mg/km] Hot 1 Hot 2 Hot 3 Test 10 Length Mass

21 CE-CERT Trial Installation

22 Current Status : EPA PM Mass Measurement Allowance Program Three systems supplied to SWRI Systems are undergoing preliminary evaluation Auditing, calibration, simulation Additional systems Under quotation to interested regulatory and technical authorities Participation in the EU PEMS-PM program