Air driven reductant dosing system

Abstract

A dosing system for delivering reductant into an exhaust gas treatment system of an internal combustion engine using an air driven hydraulic pump, which includes a pressure pump tank and a liquid supply tank, for closed-loop controlling reductant pressure, and a three-stage PWM control method for dosing rate control. Reductant residue in the dosing system is purged by using compressed air, and when the air driven hydraulic pumps is positioned inside a reductant tank, heating means in the reductant tank can also be used for heating the air driven hydraulic pump. The closed-loop pressure control together with the three-stage PWM control allow dosing accuracy insensitive to pressure variations in compressed air, thereby a variety of compressed air sources can be used.

Description

[0001]This present application claims priority from U.S. provisional application No. 61 / 689,517 having the same title as the present invention and filed on Jun. 7, 2012.TECHNICAL FIELD OF THE INVENTION[0002]The present invention relates to an apparatus and method for delivering reductant into an exhaust gas treatment system of an internal combustion engine for removing regulated species in exhaust gas, and more specifically, to an apparatus and method using an air driven hydraulic pump to deliver liquid reducing agents into an exhaust gas treatment system of an internal combustion engine.BACKGROUND OF THE INVENTION[0003]Environmentally harmful species in the exhaust gas emitted from an internal combustion engine, such as hydrocarbons (HC), carbon monoxide (CO), particulate matters (PM), and nitric oxides (NOx) are regulated species that need to be removed from the exhaust gas. In lean combustion engines, due to the existence of large amount oxygen excess, passive means without extra...

AI Technical Summary

Benefits of technology

The patent describes a method for controlling the dosage of a reductant used in a vehicle exhaust system. The system uses a pressure sensor and a three-stage PWM controller to compensate for any changes in pressure in the exhaust gas. This allows for more accurate dosage control regardless of pressure variations in the exhaust system. The technical effect of this method is improved accuracy in the dosage control of the reductant, which can help to improve the performance and efficiency of the vehicle exhaust system.

Problems solved by technology

In lean combustion engines, due to the existence of large amount oxygen excess, passive means without extra dosing agents, such as that using a three-way catalyst, normally are not able to effectively remove the oxidative specie NOx, as that in most of spark-ignition engines.

However, due to safety concerns and difficulties in handling pure ammonia, normally urea solution is used in ammonia SCR systems.

The requirements of a continuous air flow and a precisely controlled metering pump limit the application of this method.

However, in this method, due to the requirement of pressure control, typically a liquid pump, such as a membrane pump driven by a motor, is needed in establishing and maintaining the rail pressure, and a motor control system is required.

Different from reductant tank heating control, line heating is a distributed heating and it is difficult to use closed-loop controls.

Except using costly PTC (Positive Temperature Coefficient) materials, heating efficiency or heating power and line durability need to be carefully balanced, since locally high temperature could damage the heating line.

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