Title / Discussion Document on Experimental Protocol for PM/PN emissions of Periodically Regenerating Exhaust After-treatment Devices
Working Paper Number / WLTP-DTP-PM/PN-10-02
Authors / Christos Dardiotis, Massimo Carriero
Contents
1INTRODUCTION
2TEST SPECIFICATIONS
2.1Testing Environment
2.2Vehicle Specifications
2.3Lubricating Oil
2.4Lubricant Flush and Fill
2.5Test Fuel
2.6Test Cycles-repetitions
2.7Test Order and System Preconditioning
3MEASUREMENT AND SAMPLING SYSTEM FOR GASEOUS EMISSIONS
4MEASUREMENT AND SAMPLING SYSTEM FOR PARTICULATES
5PARTICLE NUMBER MEASUREMENT SYSTEM
6TEST PROCEDURES
6.1Dynamometer Preparation
6.2Preparation of the Vehicle
6.3Test Protocols
6.3.1Emission test just after regeneration
6.3.2Loading of the after-treatment device
6.3.3Emission test just before regeneration
6.3.4Regeneration emission test and subsequent hot start cycle(s)
7LIST OF SPECIAL TERMS AND ABBREVIATIONS
APPENDIX 1: FILL AND FLUSH PROCEDURE
References
1INTRODUCTION
This document has been prepared in response to a request from Worldwide Harmonized Light-duty Test Procedures (WLTP) PM/PN subgroup. The document’s purpose is to specify the testing guidelines and protocol for an experimental investigation of Particulate Matter (PM) and Particle Number (PN) emissions during exhaust after-treatment device regeneration.
2TEST SPECIFICATIONS
2.1Testing Environment
The participating laboratories shall provide facilities and resources required to perform light duty vehicle emissions tests according to the Regulation 83, plus additional capability as required for particle measurements as defined in this document.
2.2Vehicle Specifications
Diesel-fuelled vehicles should be tested, at least one Euro5 and preferable one Euro6 emission standards compliant.
2.3Lubricating Oil
The lubrication oil shall meet the standard specified by the engine manufacturer. Each vehicle should be tested running on two oils: One with the minimum and one the maximum allowed sulphur content according to the manufacturers’ specifications.
2.4Lubricant Flush and Fill
A defined flush and fill procedure will be employed upon arrival of each vehicle at each test laboratory. The flush and fill procedure is presented in Appendix 1.
2.5Test Fuel
For each vehicle two diesel fuels with different sulphur content will be employed during this programme. The first one should have below 10ppm of sulphur content, complying with Annex 2 of Directive 2009/30/EC of European Parliament and of the Council [[1]], describing fuel specifications to be employed after 1 January 2011.The second fuel should have sulphur content of 80ppm, which is currently the maximum allowed in the United States.
2.6Test Cycles-repetitions
All vehicles shall be tested according to the WLTP procedures, defined by the relevant WLTP subgroup. Two series of complete test protocol shall be performed for each vehicle/oil/fuel combination. The test protocol sequence is described below in section 6 of this document.
2.7Test Order and System Preconditioning
In the case where more than one vehicles are tested the same day in a laboratory, the test order shall consider the possibility of contamination of test results by a previously tested vehicle. The test order and the entire transfer and dilution system should be preconditioned according to the specifications of the WLTP procedures.
3MEASUREMENT AND SAMPLING SYSTEM FOR GASEOUS EMISSIONS
The mass of gaseous emissions shall be measured during all emission tests in accordance with the WLTP procedures, defined by the relevant WLTP subgroup. If possible, raw tailpipe and engine out emissions shall also be measured on a continuous basis throughout the test sequence.
4MEASUREMENT AND SAMPLING SYSTEM FOR PARTICULATES
The mass of particulate emissions shall be measured during all emission tests in accordance with the WLTP procedures, defined by the relevant WLTP subgroup.
5PARTICLE NUMBER MEASUREMENT SYSTEM
The number of particlesemitted shall be measured during the test sequence in accordance with the WLTP procedures, defined by the relevant WLTP subgroup.In order to investigate a potential cross interference of volatile particles emitted during regeneration in the Particle Measurement Programme (PMP) PN results, two PMP compliant systems shall be employed in parallel operating at Particle Concentration Reduction Factor (PCRF) values differing by at least one order of magnitude (i.e. 100 and 1000).
6TEST PROCEDURES
6.1Dynamometer Preparation
The chassis dynamometer controller shall be adjusted to simulate the inertia of the test vehicle. The inertia shall be set according to the generic inertia classes given in the WLTP procedures, with corresponding coefficients for the road load curve.
6.2Preparation of the Vehicle
The vehicle shall be conditioned prior to each test in accordance with the WLTP procedures.The fuel and lube oil used shall be as specified in section 2 of this document.
Before testing the vehicle the manufacturer is crucial to provide data concerning:
- A switch/procedure to prevent active regeneration (to deactivate post injection)
- Data concerning the interval of the active regeneration in terms of kilometres of driving in loading mode.
- A switch to trigger the active regeneration (post injection)
- An indicator (e.g. a signal from Engine Control Unit – ECU) that the post injection is activated (i.e. regeneration takes place)
- An indicator (e.g. a signal from ECU) that the regeneration should initiate
In order to measure the emissions during regeneration a sequence of protocols should be followed. Figure 1 presents a flow chart of the experimental protocols should be followed for the scope of these measurements.
Figure 1 – Flow chart of the proposed experimental protocol for measuring PM/PN emissions during periodic regeneration.
In order to start the test sequence ensuring the same initial clean state of the after-treatment device the regeneration has to take place. The regeneration can be triggered using the respective switch. During the regeneration protocol the vehicle should be driven on the chassis dynamometer over a high load engine mode in accordance to the recommendations of the manufacturer. The ECU indicator of the state of the post injection (on or off) could be used to stop the driving protocol on time. It is not necessary to measure the emissions during this phase.
If technically feasible, thermocouples should be used to measure the exhaust gas temperature upstream and downstream of the after-treatment device. The temperatures should be monitored during each test (i.e. loading, regeneration).
6.3Test Protocols
6.3.1Emissiontestjust after regeneration
Each emission test is described by a preconditioning [cd1]procedure, a soak time and acold start WLTP cycle, all defined by the WLTP procedure. After the preparation of the vehicle anemission test should follow. The switch to prevent regeneration should be activated and measurements of the emissions of the vehicle should take place.
6.3.2Loading of the after-treatment device
The loading of the after-treatment deviceshould be conducted by driving the vehicle on the chassisdynamometer overconsecutive WLTP cycles[cd2], not necessary cold start. The vehicle should be driven for so many cycles required to load the after-treatment device effectively, in order to ensure the initiation of the regeneration and in accordance with the recommendations of the vehicle’s manufacturer. The switch to prevent regeneration should be enabled during the loading protocol. PM and PN emissions should be measured for each WLTP cycle during loading. All the other setting of the vehicle (e.g. Exhaust Gas Recirculation (EGR), should be according to the ones prescribed by the vehicle’s manufacturer.
6.3.3Emission test just before regeneration
After the loading of the after-treatment device an emission test should be carried out (preconditioning, soak time and cold start WLTP cycle). The device to prevent regeneration should be activated and measurement of the emissions of the vehicle should be conducted. During the test the ECU shall yield a signal that the after-treatment device is about to regenerate, either during the WLTP or the preconditioning. If not, the same procedure (preconditioning & cold start WLTP) shall be performed until this happens.
6.3.4Regeneration emissiontest and subsequent hot start cycle(s)
The regeneration emission test consists of a preconditioning, a soak period and a cold start WLTP cycle, in accordance with the WLTP procedures.The switch to prevent regeneration should be enabled during the preconditioning, but after the completion of the preconditioning should be disabled and remain disabled during the cold start WLPT cycle. An ECU indicator should have been activated over the previous conducted emission test, as described in section 6.3.3.If the regeneration will not be completed during the cycle,subsequent WLTP cycle(s) shall be driver immediately until complete regeneration has been achieved (each cycle shall be completed). The time necessary to set up a new test should be as short as possible (e.g. particular matter filter change, analysis of bag gaseous emissions). The engine shall run on idle mode during this period withoutswitched off. Emission measurements should be conducted during all the regeneration cycles.
7LIST OF SPECIAL TERMS AND ABBREVIATIONS
ECU / Engine Control UnitEGR / Exhaust Gas Recirculation
PCRF / Particle Concentration Reduction Factor
PM / Particulate Matter
PMP / Particle Measurement Programme
PN / Particle Number
WLTP / Worldwide Harmonized Light-duty Test Procedures
APPENDIX 1: FILL AND FLUSH PROCEDURE
- Warm the oil by 10 minutes low load driving.
- Install vehicle on elevated rump.
- Release sump plug and drain oil.
- Drain oil filter and refit.
- Lower ramp, add the specified by the manufacturer quantity of fresh test oil to the engine.
- Start engine and idle for a fixed period (40min), sufficient to reach operating temperature.
- Install vehicle on elevated rump. Drain oil again.
- Remove oil filter and discard.
- Fill engine with the specified by the manufacturer quantity of test oil.
- Switch ignition off and allow to settle for 5min. Check dipstick to ensure correct level.
References
1
[1]Directive 2009/30/EC of the European Parliament and of the Council of 23 April 2009, “Amending Directive 98/70/EC as regards the specification of petrol, diesel and gas-oil and introducing a mechanism to monitor and reduce greenhouse gas emissions and amending Council Directive 1999/32/EC as regards the specification of the fuel used by inland waterway vessels and repealing Directive 93/12/EEC”.
[cd1]To avoid/minimize passive regeneration, it is recommended that the vehicle will be preconditioned using a low load/speed driving pattern (e.g. the urban and/or rural part of the WLTP cycle)
[cd2]Sulphates originating from oil and/or fuel were identified as having a key role in both PM and PN emissions. It seems therefore necessary to load the DPF using test cycles representative of real world operation (e.g. to avoid the use of a constant engine speed mode where lube consumption is minimal).