Techniques for determining condensation accumulation and depletion at a charge air cooler of a turbocharged engine having a low pressure cooled EGR system

Patent metadata

Field	Value
Publication number	US-11041418-B2
Application number	US-201916664057-A
Country	US
Kind code	B2
Filing date	Oct 25, 2019
Priority date	Nov 16, 2018
Publication date	Jun 22, 2021
Grant date	Jun 22, 2021

Abstract

Turbocharged engine water vapor ingestion control techniques determine a dew point of a charge air cooler (CAC) in an induction system of the engine based on measured humidity and temperature of a mixture of (i) air drawn into the induction system and (ii) exhaust gas produced by the engine that is cooled and recirculated by a low pressure cooled exhaust gas recirculation (LPCEGR) system of the engine back into the induction system. When the mixture temperature is less than the CAC dew point, a condensate accumulation in the CAC is determined. When the CAC condensate accumulation does not satisfy a set of one or more thresholds, the mixture temperature is increased. When the CAC condensate accumulation satisfies the set of one or more thresholds, an amount of the exhaust gas that is cooled and recirculated by the LPCEGR system is decreased until the mixture temperature meets the CAC dew point.

First claim

What is claimed is:

1. A control system for a turbocharged engine having a low pressure cooled exhaust gas recirculation (LPCEGR) system and an induction system with a charge air cooler (CAC), the control system comprising:
a set of one or more sensors configured to measure humidity and temperature of a mixture of (i) air drawn into the induction system and (ii) exhaust gas produced by the engine that is cooled and recirculated by the LPCEGR system back into the induction system; and
a controller configured to:
determine a dew point of the CAC based on the air/exhaust gas mixture humidity and temperature; and
when the air/exhaust gas mixture temperature is less than the CAC dew point:
determine a condensate accumulation in the CAC,
when the CAC condensate accumulation does not satisfy a set of one or more thresholds, increase the air/exhaust gas mixture temperature, and
when the CAC condensate accumulation satisfies the set of one or more thresholds, decrease an amount of the exhaust gas that is cooled and recirculated by the LPCEGR system until the air/exhaust gas mixture temperature meets the CAC dew point.

2. The control system of claim 1 , wherein the controller is configured to determine the CAC dew point by:
determining a partial pressure of water vapor at a turbocharger compressor inlet;
determining a mass fraction of water vapor at the turbocharger compressor inlet based on the water vapor partial pressure;
determining a total intake water vapor fraction at a current EGR fraction based on the water vapor mass fraction at the turbocharger compressor inlet;
determining a water vapor fraction resulting from combustion based on the total intake water vapor fraction at the current EGR fraction; and
determining the CAC dew point based on the water vapor fraction resulting from combustion.

3. The control system of claim 2 , wherein the controller is further configured to determine a condensate production in the CAC and a CAC condensate depletion from the CAC based on (i) a velocity of the air/exhaust gas mixture, (ii) a blow off fraction indicative of a portion of the CAC condensate production that is depleted at a given air/exhaust gas mixture velocity, and (iii) capacity for condensate accumulation in the CAC.

4. The control system of claim 3 , wherein the controller is configured to determine the CAC condensate production by subtracting a saturated mass fraction of water vapor at the CAC the total intake water vapor fraction at the current EGR fraction.

5. The control system of claim 3 , wherein the controller is configured to determine the CAC condensate accumulation by subtracting the CAC condensate depletion from the CAC condensate production.

6. The control system of claim 5 , wherein the controller is further configured to:
set the blow off fraction equal to one when the CAC condensate accumulation exceeds the CAC condensate accumulation capacity;
determine the CAC condensate depletion to be zero when the CAC condensate accumulation remains in excess of the CAC condensate accumulation capacity; and
adjust the CAC condensate accumulation by subtracting the CAC condensate depletion from the CAC condensate accumulation when the CAC condensate accumulation falls below the CAC condensate accumulation capacity.

7. The control system of claim 1 , wherein the CAC does not have a deflector shield or a drain plug for preventing or discarding at least some of the CAC condensate accumulation.

8. The control system of claim 1 , wherein the engine is a twin-turbocharged six cylinder engine.

9. A method of controlling ingestion of water vapor into a turbocharged engine having a low pressure cooled exhaust gas recirculation (LPCEGR) system and an induction system with a charge air cooler (CAC), the method comprising:
receiving, by a controller and from a set of one or more sensors, measured humidity and temperature of a mixture of (i) air drawn into the induction system and (ii) exhaust gas produced by the engine that is cooled and recirculated by the LPCEGR system back into the induction system;
determining, by the controller, a dew point of the CAC based on the air/exhaust gas mixture humidity and temperature; and
when the air/exhaust gas mixture temperature is less than the CAC dew point:
determining, by the controller, a condensate accumulation in the CAC,
when the CAC condensate accumulation does not satisfy a set of one or more thresholds, increasing, by the controller, the air/exhaust gas mixture temperature, and
when the CAC condensate accumulation satisfies the set of one or more thresholds, decreasing, by the controller, an amount of the exhaust gas that is cooled and recirculated by the LPCEGR system until the air/exhaust gas mixture temperature meets the CAC dew point.

10. The method of claim 9 , wherein determining the CAC dew point comprises:
determining a partial pressure of water vapor at a turbocharger compressor inlet;
determining a mass fraction of water vapor at the turbocharger compressor inlet based on the water vapor partial pressure;
determining a total intake water vapor fraction at a current EGR fraction based on the water vapor mass fraction at the turbocharger compressor inlet;
determining a water vapor fraction resulting from combustion based on the total intake water vapor fraction at the current EGR fraction; and
determining the CAC dew point based on the water vapor fraction resulting from combustion.

11. The method of claim 10 , further comprising determining, by the controller, a condensate production in the CAC and a CAC condensate depletion from the CAC based on (i) a velocity of the air/exhaust gas mixture, (ii) a blow off fraction indicative of a portion of the CAC condensate production that is depleted at a given air/exhaust gas mixture velocity, and (iii) capacity for condensate accumulation in the CAC.

12. The method of claim 11 , wherein determining the CAC condensate production comprises subtracting a saturated mass fraction of water vapor at the CAC the total intake water vapor fraction at the current EGR fraction.

13. The method of claim 11 , wherein determining the CAC condensate accumulation comprises subtracting the CAC condensate depletion from the CAC condensate production.

14. The method of claim 13 , further comprising:
set the blow off fraction equal to one when the CAC condensate accumulation exceeds the CAC condensate accumulation capacity;
determine the CAC condensate depletion to be zero when the CAC condensate accumulation remains in excess of the CAC condensate accumulation capacity; and
adjust the CAC condensate accumulation by subtracting the CAC condensate depletion from the CAC condensate accumulation when the CAC condensate accumulation falls below the CAC condensate accumulation capacity.

15. The method of claim 9 , wherein the CAC does not have a deflector shield or a drain plug for preventing or discarding at least some of the CAC condensate accumulation.

16. The method of claim 9 , wherein the engine is a twin-turbocharged six cylinder engine.

Assignees

• Patil Nikhil
• Theru Sangeeta
• Bayer Ethan E
• Fca Us Llc

Inventors

• Patil Nikhil
• Theru Sangeeta
• Bayer Ethan E

Classifications

• F02B29/0468 Primary

  Water separation or drainage means · CPC title

• F02M26/06

  Low pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust downstream of the turbocharger turbine and reintroduced into the intake system upstream of the compressor · CPC title

• F02B27/0205

  characterised by the charging effect · CPC title

• F02B29/04

  Cooling of air intake supply · CPC title

• F01N3/0205

  using heat exchangers · CPC title