Secondary air introduction system and method for system operation
A vehicle system operation method is provided. The method comprises, during a first operating condition, increasing back pressure in a first exhaust conduit positioned upstream of a turbine and downstream of a first emission control device and during a second operating condition, reducing back pressure in the first exhaust conduit and flowing boosted air from downstream of a compressor into a second exhaust conduit positioned upstream of a second emission control device and downstream of the turbine.
1. A vehicle system operation method comprising:
determining engine operating conditions;
during a first operating condition, increasing exhaust gas back pressure in a first exhaust conduit positioned upstream of a turbine and downstream of a first emission control device; and
during a second operating condition, reducing exhaust gas back pressure in the first exhaust conduit and flowing boosted air from downstream of a compressor into a second exhaust conduit positioned upstream of a second emission control device and downstream of the turbine.
2. The method of claim 1 , further comprising during a third operating condition, reducing boosted air flow from downstream of the compressor into the second exhaust conduit and further reducing the exhaust gas back pressure in the first exhaust conduit.
3. The method of claim 2 , where reducing boosted air flow from downstream of the compressor to the second exhaust conduit includes inhibiting exhaust gas flow.
4. The method of claim 1 , further comprising during the second operating condition exothermically reacting a reductant with the boosted air upstream of the second emission control device.
5. The method of claim 1 , where the first and second emission control devices are catalysts.
6. The method of claim 1 , where the first operating condition is when an engine is below a threshold temperature and the second operating condition is when the engine is above the threshold temperature.
7. The method of claim 1 , where the first operating condition is when engine braking is requested in a vehicle.
8. The method of claim 1 , where the exhaust gas back pressure is increased and reduced via operation of a turbine inlet valve and a turbine bypass valve.
9. The method of claim 1 , where the boosted air is flowed from downstream of the compressor into the second exhaust conduit via operation of a flow valve positioned in a secondary air conduit coupled to an intake conduit and the second exhaust conduit.
10. A vehicle system comprising:
an engine in fluidic communication with a turbocharger;
the turbocharger including a compressor disposed in an intake conduit upstream of the engine and a turbine disposed in a first exhaust conduit downstream of the engine;
a secondary air conduit having a flow valve coupled thereto and in fluidic communication with an intake passage downstream of the compressor and a first exhaust passage upstream of the turbine and downstream of a first emission control device;
a turbine inlet valve positioned at a turbine inlet upstream of a second emission control device; and
a control sub-system determining engine conditions, increasing exhaust gas back pressure in a second exhaust conduit upstream of the turbine and downstream of the second emission control device via operation of the turbine inlet valve during a first operating condition and flowing boosted air from the intake passage to the first exhaust passage via operation of the flow valve.
11. The vehicle system of claim 10 , where the control sub-system increases and reduces exhaust gas back pressure in the first exhaust conduit through operation of the turbine inlet valve during a second operating condition.
12. The vehicle system of claim 10 , where the control sub-system increases and reduces the exhaust gas back pressure in the first exhaust conduit via operation of a turbine bypass valve positioned in a turbine bypass conduit.
13. The vehicle system of claim 10 , where the control sub-system reduces boosted air flow from downstream of the compressor into the second exhaust conduit and further reduces the exhaust gas back pressure in the first exhaust conduit during a third operating condition.
14. The vehicle system of claim 10 , further comprising a turbine bypass conduit having a turbine bypass valve positioned therein.
15. The vehicle system of claim 10 , where the flow valve is a 3-way valve and includes an outlet in fluidic communication with a second intake conduit upstream of the compressor.
16. A method for operation of a vehicle system comprising:
determining engine operating conditions;
during a first operating condition, increasing exhaust gas back pressure in a first exhaust conduit positioned upstream of a turbine and downstream of a first catalyst through operation of at least one of a turbine inlet valve and a turbine bypass valve, the turbine inlet valve positioned in an inlet of the turbine and the turbine bypass valve positioned in a turbine bypass conduit coupled upstream and downstream of the turbine; and
during a second operating condition, decreasing exhaust gas back pressure in the first exhaust conduit and flowing boosted air from an intake conduit downstream of a compressor to a second exhaust conduit positioned downstream of the turbine and upstream of a second catalyst.
17. The method of claim 16 , comprising during a third operating condition, inhibiting boosted air flow from downstream of the compressor into the second exhaust conduit and further reducing the exhaust gas back pressure in the first exhaust conduit.
18. The method of claim 16 , where the first operating condition is when the first catalyst is below a threshold temperature and the second operating condition is when the first catalyst is above a threshold temperature.
19. The method of claim 16 , where the first operating condition includes when engine braking is requested.