Waste Heat Recovery System for Controlling EGR Outlet Temperature

摘要

An engine system and various methods for controlling the outlet temperature of an EGR stream before entering an engine intake system are disclosed. In a system and the various methods, an exhaust gas recirculation (EGR) valve is positioned within an EGR passage fluidly connecting an engine exhaust stream and an engine intake stream, while a waste heat recovery (WHR) system is used to recover heat from the EGR stream. An engine control unit (ECU) is coupled to various sensors and valves to divert working fluid in the WHR system from cooling the EGR exhaust flow below a level which favors production of condensation in the engine intake system. The ECU operates to divert working fluid flow away from the EGR boiler when sensors indicate characteristics of either the exhaust flow or the intake stream which might lead to heavy condensation. A three-way valve is also used to divert the working fluid to a variable expansion valve fluidly coupled to the three-way valve in response to a signal from one of the sensors to prevent damage to the system turbine.

主权项

1. A system for controlling EGR stream outlet temperature before entering an engine intake system, the control system comprising:
an exhaust gas recirculation (EGR) valve positioned within an EGR passage fluidly connecting an engine exhaust stream and an engine intake stream; a super heater fluidly coupled by an inlet and an outlet to the EGR passage after the EGR valve; a boiler fluidly coupled by an inlet to the super heater and by an outlet to the EGR passage; a first sensor for determining a characteristic of an EGR stream exiting the boiler; a waste heat recovery (WHR) system for recovering heat from an EGR stream passing through the EGR passage, the WHR system comprising:
a fluid loop including a fluid pump continuously circulating a working fluid from an outlet end of the pump to an inlet end of the pump, wherein the loop passes into and out of the boiler and then into and out of the super heater;a condenser coupled to the fluid loop;a turbine coupled to the fluid loop;a recuperator coupled to the fluid loop; anda bypass valve coupled to the fluid loop for diverting the working fluid away from the boiler; and a controller electronically coupled to the first sensor and the bypass valve, wherein the controller opens the bypass valve in response to a signal from the first sensor.