SYSTEM AND METHOD FOR COOLING AND PRESSURIZING EXHAUST GAS FOR EXHAUST GAS RECIRCULATION (18-Jan-2010)

RP13279

SYSTEM AND METHOD FOR COOLING AND PRESSURIZING EXHAUST GAS FOR EXHAUST GAS RECIRCULATION

BRIEF ABSTRACT

    A system and method for cooling and pressurizing exhaust gas for exhaust gas re-circulation (EGR) is disclosed. This method utilizes a water injection for exhaust gas cooling and use of exhaust gas heat for a pressure rise of the exhaust gas. Further the system provides means for recovering part of injected water stream to minimize water consumption.

KEYWORDS

    NOx, Oxides of nitrogen, exhaust gas, EGR, Exhaust Gas Recirculation, water cooler, steam, pressure, combustion temperature, specific fuel consumption (SFC).

DETAILED DESCRIPTION

    Exhaust gas recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction technique used in most internal combustion engines, such as petrol / gasoline and diesel engines. Oxides of nitrogen (NOx) are formed when temperatures in the combustion chamber reach to about 2500 degrees Fahrenheit or above. The EGR works by increasing the amount of inert components in the cylinder which in turn brings down the combustion temperature, and hence NOx emission. The EGR involves cooling and pumping

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RP13279

a fraction of exhaust gas into the intake stream. Exhaust gases have already combusted, so they do not burn again and behave as inert components. Cooled EGR further reduces the in-cylinder temperature, and hence NOx levels in the exhaust emission.

    The air intake manifold is at a higher pressure than the exhaust manifold pressure. Thus the EGR system requires means of cooling a fraction of high temperature exhaust gas to bring it close to manifold air temperature (MAT). Additionally, the EGR system requires increasing the pressure of exhaust gas above the pressure of the air in intake manifold. Therefore an efficient method of cooling and pumping the exhaust gas into intake manifold while minimizing hit on specific fuel consumption and cooling system load is required for efficient functioning of the EGR system.

    The amount of EGR and EGR cooling temperature depends on the desired NOx reduction. Generally, for exhaust gas cooling, water and air based coolers are used. For pressurizing exhaust gas, convergent nozzles (venturies) and externally driven pumps/blowers are frequently used. However, the conventional cooling and pressurizing techniques have cumbersome sizes, limited efficiency and poor control over the amount of EGR and EGR cooling. Therefore there is a need for an efficient EGR system that has a reduced size and provides high control over the amount of EGR and EGR cooling to enable optimal operation.

    Figure 1 is a block diagram illustrating a system and method of Exhaust Gas Recirculation (EGR). The proposed EGR system pumps and cools exhaust gas from a multi-cylinder diesel engine into an intake manifold for minimizing nitrous oxides (NOx) emissions and specific fuel consumption (SFC) from the multi-cylinder diesel engine. Water is inj...