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WO2003038393A1 - Obtention de donnees d'emissions de gaz d'echappement - Google Patents

Obtention de donnees d'emissions de gaz d'echappement Download PDF

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Publication number
WO2003038393A1
WO2003038393A1 PCT/GB2002/004826 GB0204826W WO03038393A1 WO 2003038393 A1 WO2003038393 A1 WO 2003038393A1 GB 0204826 W GB0204826 W GB 0204826W WO 03038393 A1 WO03038393 A1 WO 03038393A1
Authority
WO
WIPO (PCT)
Prior art keywords
fuel
air
flow rate
exhaust
engine
Prior art date
Application number
PCT/GB2002/004826
Other languages
English (en)
Inventor
David Paul Clarke
Original Assignee
Ricardo Consulting Engineer Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ricardo Consulting Engineer Limited filed Critical Ricardo Consulting Engineer Limited
Publication of WO2003038393A1 publication Critical patent/WO2003038393A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M15/00—Testing of engines
    • G01M15/04—Testing internal-combustion engines
    • G01M15/10—Testing internal-combustion engines by monitoring exhaust gases or combustion flame
    • G01M15/102—Testing internal-combustion engines by monitoring exhaust gases or combustion flame by monitoring exhaust gases

Definitions

  • the invention relates to a method and system for obtaining exhaust emissions data.
  • Engine exhaust emissions are normally measured using gas analysis equipment which determines component gas concentrations on a volumetric basis (% or ppm). Emissions legislation is generally written in terms of the mass of emissions produced for a given amount of work done by the engine (kWh or distance driven over a defined drivecycle). The calculation of mass emissions from volumetric data requires a measure of exhaust flow rate on a molar
  • the dilute approach is required for most legislative testing because it is non- intrusive and requires no instrumentation on the engine - the exhaust gas simply flows into a sensing space allowing the exhaust flow rate to be derived from the volume collected in a given time, and the emissions to be measured.
  • the total dilute exhaust flow is measured directly, often relying on the fair assumption that the properties of diluted exhaust are similar to those of air.
  • Dilution systems of this type are normally controlled so that the total flow of dilute exhaust remains constant throughout the test, hence the term Constant Volume Sampling, or CVS.
  • Dilute sampling is well suited for measurement of the total (integrated) emissions over a transient drive cycle. However, there are serious problems with the technique.
  • the second approach, raw emissions sampling, is used for most development testing, particularly on the engine testbed.
  • This approach requires additional instrumentation on the engine, for example fuel/air mass flow meters.
  • the exhaust molar flow rate is then inferred from measured flows and exhaust gas composition data as described below.
  • Standard testbed flow measurement systems have very limited dynamic capability, so these methods for raw sampling are generally unsuitable for transient testing.
  • the conventional approach is to assume that density of exhaust is the same as that of air (as the proportion of fuel is comparatively low), so the molar exhaust flow rate - the base value measured in emissions testing - can be derived from the sum of air and fuel mass flow rates and the molar mass of air according to equation (1):
  • a further problem with raw emissions sampling is that it is carried out in a sequence of steady state condition of engine speed and load in order that a 3- dimensional mapping can be constructed. As a result, this approach is overly rigid and time consuming and deals poorly with transients.
  • a method of obtaining a measure of exhaust flow rate in an engine comprising the steps of obtaining air flow, fuel H:C ratio, C0 2 , CO and HC data and deriving the exhaust flow rate measure therefrom and an exhaust flow rate monitoring system comprising air flow, fuel H:C ratio, C0 , CO and HC measurements extractors and a processor arranged to process said measures to obtain the exhaust flow rate.
  • the invention further extends to a vehicle control system comprising a monitoring system as described above and a controller arranged to control a vehicle engine based on monitored values and a method of evaluating a fuel or engine comprising the steps of driving an engine with a fuel and obtaining a measure of exhaust flow value according to a method as described above.
  • T e invention provides a range of advantages. It allows emissions evaluation without the extensive facilities or poor reproducibility of the CVS system making it more cost and time effective for emissions development as a result of the improved mathematical modelling used.
  • Fig. 1 which is a simplified diagram of an engine and monitoring system
  • Fig. 2 is a diagram of an on- vehicle monitoring system.
  • An engine emissions monitoring system is shown generally in Fig. 1.
  • An engine 10 is controlled by an engine control unit (ECU) 12 controlling, inter alia, air flow, fuel flow and air to fuel ratio (AFR or ) into the engine.
  • the engine exhaust gases are exhausted through an exhaust outlet 14 to a monitoring space 15 having CO, HC and C0 2 , sensors mounted thereon.
  • a processor 20 is provided for processing the various data required to monitor exhaust emissions.
  • the processor 20 is shown as a separate component but can be part of the ECU, separately mounted in a vehicle or a stand-alone system in a test-bed environment.
  • the system allows the determination of transient mass emissions from raw sampled emissions data.
  • the transient mass emissions can then be integrated over a drive cycle to give a result comparable to that from a CVS test.
  • the system shown in Fig. 1 provides dynamic instrumentation for flows and emissions and minimises the effects of errors in the dynamic "time-alignment" of measured signals.
  • Dynamic measurements of air flow, fuel flow and AFR are generally available from the ECU 12 interface, based on the control sensor information available to the ECU. These signals can be calibrated against testbed instrumentation under steady-state conditions.
  • This ECU data is, by definition, synchronised with engine combustion events, which means that the time alignment problem is only concerned with the variable transport times between the engine and emissions analyser.
  • the system assumes constant transport delay between engine and emissions sampling points or that the transport delay is known.
  • the system further makes use of more sophisticated processing of the data to provide more accurate representations of mass emissions.
  • Equation (2) can be rewritten dependent on airflow rather than fuel flow data where the fuel flow is derived from air flow and AFR as equation (3):
  • a problem with this approach is that it relates to obtaining a value for 0 2 which requests an additional sensor and one that is known to be affected by measurement error. Although 0 2 tends toward 0.21 as C0 2 goes to zero, any time errors will lead to large erroneous features in exhaust flow.
  • the invention addresses this by expressing AFR in terms of C0 2 , CO and HC only, and discussed in more detail below.
  • AFR molar flow rate dry exhaust
  • the inputs to the system are:
  • the fuel H:C ratio - the average number of hydrogen atoms per carbon atoms in the fuel molecules is of importance because it determines the ratio of carbon dioxide to water resulting from complete combustion of the fuel.
  • hydrocarbon fuel can be characterised by CH n and that the combustion process of fuel in dry air does not produce any Nox.
  • A AFR 2—— S - (4)
  • N d can be written in terms of a, b and f :
  • N d a + b + f + + ⁇ -(l + f)- - dry b
  • N d is the number of mols of dry exhaust that are produced per mol of CH n fuel, so the molar flow rate of dry exhaust is given by:
  • Equations 20 to 22 provide a measure of dry exhaust flow rate which is independent of the value of oxygen measurement.
  • a "1/(1+X)" form of equation is obtained which is representative of the physical situation, namely that dry exhaust is expected to be similar to, but less than, the volume of air.
  • X is typically less than approximately 0.07, the result is insensitive to errors in X and hence to fluctuations in transport time and emissions.
  • the possibility of formulating the exhaust flow equation in this form arises because it expresses a relationship between the volume of the dry products of combustion (QMExha- y ) and air consumed in the reaction G a i M a i,.. This relationship depends on fuel properties, air/fuel ratio and the completeness of combustion. These same factors uniquely determine the composition of the exhaust. It is therefore possible to express the relationship between dry exhaust volume and air flow in terms of fuel properties and exhaust composition alone without explicit determination of the air fuel ratio or completeness of combustion.
  • the equations in the form independent of the 0 2 value the equation further represents intuitively the physical situation in which the 0 2 has effectively disappeared from the air leaving the major component of nitrogen in both air and exhaust which has minimal involvement in combustion reactions.
  • equation (3a) is of the form 1/(X+Y) where X and Y are of similar magnitude and measurement error, giving rise to a similar uncertainty in the derived result.
  • Use of the new formula reduces the effect on exhaust flow of errors in time alignment between emissions and airflow traces. It is also important to minimise the magnitude of these errors. The problem is that during transient operation the time taken for exhaust to travel from the engine to the emissions sample point is variable and may be unknown.
  • the transport time is always small, and the absolute magnitude of the variation is small compared with the response time of the emissions analysers, and this is implemented in the preferred embodiment. This means that a simple fixed time shift is acceptable for alignment of traces.
  • FIG. 2 A further implementation of the invention is shown in Fig. 2 where like reference numerals relates to like elements.
  • the system forms part of an in-car unit for real-time monitoring.
  • CO, HC and C0 2 sensors 16, 17, 18 respectively are mounted on the exhaust gas outlet (exhaust pipe) 14 and provide monitoring signals to the ECU 12.
  • the emission data can be used for a range of purposes including on-board diagnostics for emissions, engine management, catalyst failure and so forth.
  • Mass air flow can be measured using testbed instrumentation or engine management system sensors, or determined from fuel flow and air fuel ratio (universal exhaust gas oxygen sensor or UEGO) data.
  • the method can be applied to both engine-out and post-catalysts/tailpipe emissions data and can be used in any appropriate type of combustion engine including gasoline and diesel engines.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Testing Of Engines (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)

Abstract

Une approche de déduction d'un débit de gaz d'échappement comprend la mesure de variables telles que le débit d'air, le rapport hydrogène/carbone dans le carburant, les données de CO2, CO et HC et la déduction d'une mesure d'un nouveau débit de gaz d'échappement sur la base d'une nouvelle formule. Par rapport aux procédures connues le débit ainsi déduit est moins sensible aux fluctuations de valeurs d'émission et/ou de temps de transport entre le moteur et l'échappement.
PCT/GB2002/004826 2001-10-31 2002-10-25 Obtention de donnees d'emissions de gaz d'echappement WO2003038393A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0126112A GB0126112D0 (en) 2001-10-31 2001-10-31 Obtaining exhaust emissions data
GB0126112.2 2001-10-31

Publications (1)

Publication Number Publication Date
WO2003038393A1 true WO2003038393A1 (fr) 2003-05-08

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PCT/GB2002/004826 WO2003038393A1 (fr) 2001-10-31 2002-10-25 Obtention de donnees d'emissions de gaz d'echappement

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GB (1) GB0126112D0 (fr)
WO (1) WO2003038393A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2434270A1 (fr) * 2010-09-27 2012-03-28 MAHA Maschinenbau Haldenwang GmbH & Co. KG Procédé et systeme pour la détermination du taux d'émission massique d'un polluant dans le gaz d'échappement d'un équipment mobile

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4727746A (en) * 1985-12-31 1988-03-01 Horiba, Ltd. Method of modal mass analysis of exhaust gas from a motor vehicle
US5621166A (en) * 1995-04-06 1997-04-15 Ford Motor Company Exhaust emissions analysis apparatus and method
US6230103B1 (en) * 1998-11-18 2001-05-08 Power Tech Associates, Inc. Method of determining concentration of exhaust components in a gas turbine engine

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4727746A (en) * 1985-12-31 1988-03-01 Horiba, Ltd. Method of modal mass analysis of exhaust gas from a motor vehicle
US5621166A (en) * 1995-04-06 1997-04-15 Ford Motor Company Exhaust emissions analysis apparatus and method
US6230103B1 (en) * 1998-11-18 2001-05-08 Power Tech Associates, Inc. Method of determining concentration of exhaust components in a gas turbine engine

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2434270A1 (fr) * 2010-09-27 2012-03-28 MAHA Maschinenbau Haldenwang GmbH & Co. KG Procédé et systeme pour la détermination du taux d'émission massique d'un polluant dans le gaz d'échappement d'un équipment mobile

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GB0126112D0 (en) 2002-01-02

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