Particulate sampling system and method of reducing oversampling during transients
First Claim
1. A method of operating an exhaust sampling system, comprising the steps of:
- determining an expected pressure rise at a test probe location to occur during a specific transient to be tested;
selecting a flow opening with an L/D ratio responsive to the expected pressure rise;
flowing exhaust through the flow opening into a test probe positioned in an exhaust stack at the test probe location during an actual testing procedure for the specific transient;
unrestricting the flow into the test probe responsive to the L/D ratio when a pressure differential between the exhaust stack at a probe location and atmospheric pressure is small at a beginning of the specific transient during the actual testing procedure, but restricting the flow into the test probe responsive to the L/D ratio when the pressure differential is large due to the expected pressure rise during the specific transient of the actual testing procedure.
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Accused Products
Abstract
Testing of engine particulate matter production during a transient is made more accurate by selecting an appropriate sized opening for a test probe of the sampling system located in the exhaust line upstream from a particulate trap. By examining the pressure signature at the test probe location and utilizing that information in conjunction with a desired volumetric flow rate into the sampling system, a flow opening size for the test probe can be selected that reduces potential oversampling which may be otherwise induced due to the back pressure increases in the exhaust line caused by the presence of the particulate trap. The flow opening into the test probe of the sampling system behaves relative unrestricted when pressure differentials at the test probe location are relatively low, such as during steady state operating conditions, but restricts flow into the sampling system when pressure differentials are relatively high, such as at a pressure during a transient event.
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Citations
19 Claims
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1. A method of operating an exhaust sampling system, comprising the steps of:
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determining an expected pressure rise at a test probe location to occur during a specific transient to be tested; selecting a flow opening with an L/D ratio responsive to the expected pressure rise; flowing exhaust through the flow opening into a test probe positioned in an exhaust stack at the test probe location during an actual testing procedure for the specific transient; unrestricting the flow into the test probe responsive to the L/D ratio when a pressure differential between the exhaust stack at a probe location and atmospheric pressure is small at a beginning of the specific transient during the actual testing procedure, but restricting the flow into the test probe responsive to the L/D ratio when the pressure differential is large due to the expected pressure rise during the specific transient of the actual testing procedure. - View Dependent Claims (2, 3, 4, 5, 6, 7, 14)
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8. A method of reducing over sampling of exhaust with an exhaust sampling system during a transient, comprising the steps of:
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determining an expected pressure rise at a test probe location to occur during a specific transient to be tested; selecting a flow opening with an L/D ratio responsive to the expected pressure rise; unrestricting flow into the sampling system responsive to the L/D ratio at a beginning of the transient; restricting flow into the sampling system responsive to the L/D ratio when pressure at a test probe location increases after a beginning of the transient; and the restricting step includes sizing the L/D ratio to be an orifice in a flow path into the test probe when pressure at the test probe location is increasing during the transient. - View Dependent Claims (9, 10, 11, 12, 13, 15)
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16. A test cell comprising;
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a power source fluidly connected to an exhaust line; an exhaust sampling system with a test probe with a flow opening positioned in the exhaust line for receiving exhaust flow originating from the power source; the flow opening having an L/D ratio that is selected based upon an expected pressure rise to occur at the test probe during a specific transient to be tested; and wherein the L/D ratio results in a desired unrestricted flow rate into the exhaust sampling system at a beginning of the specific transient to be tested and the L/D ratio resulting in a restricted flow rate into the test probe during the specific transient to be tested responsive to the expected pressure rise. - View Dependent Claims (17, 18, 19)
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Specification