Sampler for engine exhaust dilution
View Patent ↗A partial flow sampling system includes a system inlet for receiving an exhaust sample flow from a sample inlet probe and transfer line. The system further includes a dilution air control system for controlling a dilution air flow rate, and a mixer. The mixer receives and mixes the exhaust sample flow and the dilution air flow to produce a mixture flow. A total flow control system controls the mixture flow rate. An orifice flow meter installed at the system inlet measures the exhaust sample flow rate in. real-time. This provides accurate sample flow measurements over a wide range of dilution ratios and sample ratios.
1. A partial flow sampling system wherein a sample inlet probe and transfer line receive an exhaust sample flow, the system comprising:
a system inlet for receiving the exhaust sample flow;
a dilution air control system for selectively controlling a dilution air flow rate;
a mixer receiving and mixing the exhaust sample flow and the dilution air flow to produce a mixture flow;
a total flow control system for controlling the mixture flow rate; and
an orifice flow meter installed at the system inlet for measuring the exhaust sample flow rate in real-time, thereby providing accurate sample flow measurements over a wide range of dilution ratios and sample ratios, wherein the dilution air control system selectively controls the dilution air flow rate based on either one or the other of
(i) a desired dilution ratio and the measured exhaust sample flow rate to cause a system dilution ratio to track the desired dilution ratio, and
(ii) a desired sample ratio and the measured exhaust sample flow rate to cause a system sample ratio to track the desired sample ratio.
2. The system of claim 1 further comprising:
a control loop receiving a signal indicative of the measured exhaust sample flow rate and receiving a reference signal, the control loop producing a signal to drive the dilution air control system.
3. The system of claim 2 wherein the control loop includes a proportional, integral, derivative controller.
4. The system of claim 1 further comprising:
an outlet port after the mixer to provide a sample to a particle instrument.
5. The system of claim 1 wherein the orifice flow meter includes a first orifice, a first differential pressure transducer, an absolute pressure transducer, and a first thermocouple.
6. The system of claim 5 wherein the orifice flow meter further includes a second differential pressure transducer.
7. A partial flow sampling system wherein a sample inlet probe and transfer line receive an exhaust sample flow, the system comprising:
a system inlet for receiving the exhaust sample flow;
a dilution air control system for controlling a dilution air flow rate;
a mixer receiving and mixing the exhaust sample flow and the dilution air flow to produce a mixture flow;
a total flow control system for controlling the mixture flow rate;
a sample filter between the mixer and the total flow control system;
a bypass filter between the mixer and the total flow control system, wherein flow through the bypass filter bypasses the sample filter; and
an orifice flow meter installed at the system inlet for measuring the exhaust sample flow rate in real-time, thereby providing accurate sample flow measurements over a wide range of dilution ratios and sample ratios.
8. The system of claim 7 further comprising:
a first valve associated with and downstream of the sample filter; and
a second valve associated with and downstream of the bypass filter.
9. A partial flow sampling system wherein a sample inlet probe and transfer line receive an exhaust sample flow, the system comprising:
a system inlet for receiving the exhaust sample flow;
a dilution air control system for controlling a dilution air flow rate;
a mixer receiving and mixing the exhaust sample flow and the dilution air flow to produce a mixture flow;
a total flow control system for controlling the mixture flow rate; and
an orifice flow meter installed at the system inlet for measuring the exhaust sample flow rate in real-time wherein the orifice flow meter includes a first orifice, a first differential pressure transducer, an absolute pressure transducer, and a first thermocouple and wherein the orifice flow meter further includes a second orifice, a second thermocouple, a first valve associated with the first orifice, and a second valve associated with the second orifice, thereby providing accurate sample flow measurements over a wide range of dilution ratios and sample ratios.
10. A method of operating a partial flow sampling system wherein a sample inlet probe and transfer line receive an exhaust sample flow, the system including a system inlet for receiving the exhaust sample flow, a dilution air control system for controlling a dilution air flow rate, a mixer receiving and mixing the exhaust sample flow and the dilution air flow to produce a mixture flow, a total flow control system for controlling the mixture flow rate and an orifice flow meter installed at the system inlet for measuring the exhaust sample flow rate in real-time, thereby providing accurate sample flow measurements over a wide range of dilution ratios and sample ratios, the method comprising:
determining a desired dilution ratio;
driving the dilution air control system based on the desired dilution ratio and the measured exhaust sample flow rate to cause a system dilution ratio to track the desired dilution ratio.