Exhaust Emission Measurement System and Method

Abstract

An exhaust emission measurement method comprises the steps: testing a Plug-In Hybrid Vehicle having a combustion engine and an electric motor during a test phase of a predetermined time length; sampling of exhaust into dilution air; collecting the diluted exhaust in a diluted exhaust bag, when the combustion engine is operating; intermittently filling of the bag when a combustion engine of the Plug-In Hybrid Vehicle is operating; at a certain time before the end of the test phase, changing sampling from intermittent filling to continuous filling of the bag in order to get enough bag volume for an accurate analyzer reading.

Claims

1-6. (canceled)

7. An exhaust emission measurement method, comprising: starting a test phase having a predetermined test phase time length; testing a Plug-In Hybrid Vehicle having a combustion engine and an electric motor during the test phase; sampling exhaust from the combustion engine into dilution air; intermittently filling a diluted exhaust bag with diluted exhaust, when the combustion engine is operating; at a certain time before the end of the test phase, changing sampling from intermittent filling to continuous filling of the diluted exhaust bag to provide enough bag volume for an accurate analyzer reading; counting an accumulated filling time as a parameter for the time during which the diluted exhaust bag is filled; calculating a remaining filling time as a difference between a minimum filling time and the accumulated filling time; if the combustion engine is not operating and if the remaining phase time until the end of the test phase is lower than or equal to the remaining filling time, filling the diluted exhaust bag; and continuing filling of the diluted exhaust bag for a predetermined post filling time after the combustion engine has stopped.

8. The method of claim 7, further comprising: if the combustion engine is not operating and if the remaining phase time until the end of the test phase is greater than the remaining filling time, stop filling the diluted exhaust bag.

9. The method of claim 7, wherein filling the diluted exhaust bag comprises: providing a valve between sampling means and the diluted exhaust bag; and switching the valve in accordance with the operation of the combustion engine such that, when the combustion engine is operated, the valve opens to the diluted exhaust bag so that the diluted exhaust bag is filled, and when the combustion engine is stopped, the valve switches to a bypass where the sample is dismissed so that the diluted exhaust bag is not filled.

10. The method of claim 7, further comprising: predefining the minimum filling time as a time needed for filling sufficient diluted exhaust in the diluted exhaust bag to measure concentrations of gaseous components in the diluted.

11. The method of claim 7, wherein at least two bags are provided, wherein one of the at least two bags is the diluted exhaust bag, and wherein the other of the at least two bags is a bag for dilution air.

12. An exhaust emission measurement system, comprising: an exhaust gas analyzer system configured to start a test phase having a predetermined test phase time length during which a Plug-In Hybrid Vehicle having a combustion engine and an electric motor is tested, count an accumulated filling time as a parameter for a time during which the diluted exhaust bag is filled, and calculate a remaining filling time as a difference between a minimum filling time and the accumulated filling time; a diluted exhaust bag configured to draw in diluted exhaust from the combustion engine; a sampling venturis configured to sample exhaust from the combustion engine into dilution air; and one or more valves configured to open to the diluted exhaust bag for intermittently filling the diluted exhaust bag with diluted exhaust when the combustion engine is operating, and at a certain time before the end of the test phase to change sampling from intermittent filling to continuous filling of the diluted exhaust bag to provide enough bag volume for an accurate analyzer reading, wherein if the combustion engine is not operating and if the remaining phase time until the end of the test phase is lower than or equal to the remaining filling time, the diluted exhaust bag is filled, wherein the one or more valves are configured to open to the diluted exhaust bag for continuing filling of the diluted exhaust bag for a predetermined post filling time after the combustion engine has stopped.

13. The exhaust emission measurement system of claim 12, wherein if the combustion engine is not operating and if the remaining phase time until the end of the test phase is greater than the remaining filling time, the one or more valves are configured to stop filling the diluted exhaust bag.

14. The exhaust emission measurement system of claim 12, wherein the one or more valves are configured to switch in accordance with the operation of the combustion engine such that, when the combustion engine is operated, the one or more valves open to the diluted exhaust bag so that the diluted exhaust bag is filled, and when the combustion engine is stopped, the one or more valves switch to a bypass where the sample is dismissed so that the diluted exhaust bag is not filled.

15. The exhaust emission measurement system of claim 12, wherein the exhaust gas analyzer system configured to predefine the minimum filling time as a time needed for filling sufficient diluted exhaust in the diluted exhaust bag to measure concentrations of gaseous components in the diluted.

16. The exhaust gas analyzer system of claim 12, wherein at least two bags are provided, wherein one of the at least two bags is the diluted exhaust bag, and wherein the other of the at least two bags is a bag for dilution air.

Description

[0035] Hereinafter, the invention is described in more detail by means of the following Figures, wherein

[0036] FIG. 1 shows an emission measurement system according to the present invention;

[0037] FIG. 2 shows a flow chart with an exhaust emission measurement method according to the present invention;

[0038] FIG. 3 is a time scheme showing a partial bag-fill without adjusted bag-fill time;

[0039] FIG. 4 shows a partial bag-fill with adjusted bag-fill time according to the present invention;

[0040] FIG. 5 shows a partial bag-fill with multiple engine on/off phases; and

[0041] FIG. 6 shows a partial bag-fill considering a post-fill time.

[0042] The test cell and emission sampling system configuration according to the invention is schematically illustrated in FIG. 1.

[0043] A Plug-In Hybrid Electric Vehicle 1 (PHEV) is driven on a 4WD chassis dynamometer 2. The vehicle's tailpipe 3 is connected to a heated transfer tube (3.5 m flexible and 2.5 m steel tube) and the entire exhaust flow is diluted by a CVS system 4 (dilution tunnel 5 positioned in 2.5 m height), with critical flow venturis 6 (CFV) assuring a constant diluted exhaust flow.

[0044] A sample 7 of diluted exhaust is drawn into bags 8 (here: bag 8a) for post-test analysis. Modal sampling lines 9, connected directly to an exhaust gas analyzer system 10, allow modal diluted exhaust measurement during driving cycles.

[0045] 3-2 way valves 11 are arranged between sampling venturis 12 and the batches (bags 8). The valves 11 are used to switch according to the operation of the combustion engine in the PHEV 1: When the combustion engine is operated the valves 11 open to the bags 8 (diluted exhaust 8a and dilution air 8b). When the combustion engine is stopped the valves 11 switch to a bypass 13 where the sample is dismissed. Yet this entire system configuration is the same as a conventional CVS system.

[0046] FIG. 2 shows a flow chart according to the measurement system.

[0047] At the beginning at the test phase start in step S10, a value of the minimum filling time (MinFillTime) is determined depending on the expected exhaust volume per time unit, the testing conditions, technical regulations etc. The minimum filling time is the time which is necessary for filling sufficient volume into the respective bag so that after the test end, sufficient material (diluted exhaust or dilution air) can be used for the following analysis procedures.

[0048] In step S11 it is decided whether the test phase can already end, if the total test time has been reached. If the end of the test phase has been reached, filling of the bag is stopped.

[0049] If the test phase has not been ended, in step S12, the remaining filling time is calculated as the difference between the minimum filling time and an accumulated filling time. The accumulated filling time is the time during which the bag is filled. If the bag is not filled, the accumulated filling time is not increased (not counted upwards).

[0050] Thus, the remaining filling time is the value which shows how long the bag still must be filled until the minimum filling time has been reached.

[0051] In step S13, it is determined whether the engine is running or not.

[0052] If the engine is running, the method continues with filling the bag in step S15. During this phase, exhaust from the combustion engine enters the dilution tunnel and can thus be filled as diluted exhaust into the bag.

[0053] Filling the bag in step S15 is possible by switching the corresponding valve 11 accordingly. The valve 11 can be switched such that air from the dilution tunnel 5 can be guided to the bag. This air can be just dilution air (without any exhaust, if the engine is not running) or diluted exhaust from the engine.

[0054] In step S16, the accumulated filling time is thus counted upwards, since the filling of the bag is continued.

[0055] If, however, it is determined in step S13 that the engine is not running, it is decided in the following step S14 whether the remaining phase time is equal to or less than the remaining filling time. If the remaining phase time has reached (is greater than) the remaining filling time, there is no filling of the bag (step S17) and the method continues to step S11.

[0056] In step S17, the valve 11 is switched such that no further from the dilution tunnel 5 can flow into the bag.

[0057] If, however, the remaining phase time is less than the remaining filling time, the filling of the bag is continued by switching the valves accordingly (step S15).

[0058] By this procedure, the filling of the bag at the end of the test phase is independent of whether the engine is running or not. Rather, if it can be calculated that the filling of the bag has not reached the required minimum, the bag is filled by the dilution air in the CVS tunnel (dilution tunnel 5) even if the engine is not running.

[0059] Examples for different method principles and time schemes are given below.

[0060] FIG. 3 shows a conventional method, where the combustion engine only kicks in at the end of the emission-phase.

[0061] In particular, FIG. 3 shows the time of a complete test phase (Emission-Phase) during which a PHEV is tested, wherein the combustion engine is only running at the very end of the total test phase. As the diluted exhaust bag is only filled during the run-time of the engine, the filling of the bag also only takes place at the end of the phase.

[0062] As the exhaust in the sample bag shall not be over-diluted with ambient air, the bag-pair is only filled while the combustion-engine is running. If the bag-pair is only filled for a certain time during the emission-phase, this will be called a partial bag-fill.

[0063] Partial bag-fill, however, leads to the problem that it is difficult to determine the length of the total bag-fill time within one emission-phase (the engine might kick-in not only one time). The system will require a minimum bag-fill time to get enough gas into the bags for a complete bag-read of those bags.

[0064] FIG. 4 shows the effect of the method according to the present invention.

[0065] Depending on the selected bag-fill venturi (e.g. venturi 12 in FIG. 1) and the used bag-bench a minimum bag-fill time can be defined in advance of a test phase (MinFillTime in FIG. 2).

[0066] If the time (where the combustion engine is not running) is shorter than the required bag-fill time, the bag-fill starts even without the combustion engine running and thus earlier than the engine.

[0067] Assuming a required bag-fill time of 180 seconds, the bag-fill needs to be started latest 180 seconds before the end of the emission-phase. This is shown in the FIG. 4 scenario where the bag-fill starts even when the combustion engine has not started yet.

[0068] FIG. 5 shows a scenario where the combustion engine will kick-in twice.

[0069] With the first start of the combustion engine bag-fill will start and stop when the engine is going off, as the remaining time is still long enough. As there is now already a certain amount of sample-gas in the bags, the second bag-fill will start later, still to achieve a total fill time of 180 seconds.

[0070] FIG. 6 shows a situation where the bag-fill is continued (see the circle) although the engine has already stopped. The filling of the bag thus can be continued for a certain time (e.g. 5 s) after the engine stopped in order to sample the diluted exhaust gas delayed by the volume of the system piping.

[0071] Thus, on partial bag-fill the post filling time can be applied to the bag-fill to catch the remaining gas in the tubing.