Patent ID: 8596252
Filing Date: 2013-12-03
Classification: F02B,F02D,F02M,Y02T

Abstract:
1. A compression ignition engine comprising: engine cylinders within which combustion occurs to operate the engine; an intake system for introducing charge air into the engine cylinders; a fueling system for introducing fuel into the engine cylinders to combust with the charge air; an exhaust system through which exhaust gas resulting from combustion of fuel in the engine cylinders exits; a turbocharger comprising a high-pressure turbine and a low-pressure turbine downstream of the high-pressure turbine through which exhaust gas exiting through the exhaust system successively passes and a low-pressure compressor operated by the low-pressure turbine and a high-pressure compressor downstream of the low-pressure compressor and operated by the high-pressure turbine through which air that has entered the intake system successively passes to create the charge air; a primary EGR control loop having a pierce point to the exhaust system upstream of the high-pressure turbine and a pierce point to the intake system downstream of the high-pressure compressor for conveying some of the exhaust gas to the intake system; a secondary EGR control loop having a pierce point to the exhaust system downstream of the high-pressure turbine and a pierce point to the intake system upstream of the high-pressure compressor for conveying some of the exhaust gas to the intake system; a control system for processing data for certain engine operating parameters while the engine is operating to calculate a quantity of exhaust gas needed to satisfy an exhaust gas recirculation requirement for the engine based on those engine operating parameters to determine if the primary EGR control loop alone can satisfy the calculated quantity of exhaust gas, for causing the secondary EGR control loop to be closed while the primary EGR loop is controlled to satisfy the calculated quantity of exhaust gas when the processing determines that the primary EGR control loop alone can satisfy the calculated quantity of exhaust gas, and for causing the secondary EGR control loop to be open concurrently with the primary EGR control loop and both the primary EGR loop and the secondary EGR loop controlled to cause the combined flow of exhaust gas through the primary EGR control loop and flow of exhaust gas through the secondary EGR control loop to satisfy the calculated quantity of exhaust gas when the processing determines that the primary EGR control loop alone cannot satisfy the calculated quantity of exhaust gas, wherein the pierce point of the secondary EGR control loop to the exhaust system is upstream of the low-pressure turbine and the pierce point of the secondary EGR control loop to the intake system is downstream of the low-pressure compressor, the intake system comprises a cooler having an inlet downstream of the pierce point of the secondary EGR control loop to the intake system and an outlet to the high-pressure compressor and the intake system comprises a throttle valve under control of the control system for selectively throttling air flow from the low-pressure compressor to the high-pressure compressor, and the pierce point of the secondary EGR control loop to the intake system is downstream of the throttle valve and upstream of the cooler.