1. Field of the Invention
This invention relates to delivering fluid and more particularly relates to intermittently delivering fluid with minimal disruption to a primary fluid supply system.
2. Description of the Related Art
A mechanical device such as an internal combustion engine often includes a primary fluid supply system. For example, a diesel engine may include a fuel supply system to deliver fuel from a storage tank to a fuel injection system. The mechanical device typically requires the primary fluid supply system to deliver the fluid within specified flow rate and pressure ranges. Devices receiving the fluid often only function properly if the fluid is within the specified flow rate and pressure ranges. The primary fluid supply system may require one or more pumps, filters, regulators, controllers, and the like to supply the fluid within the specified flow rate and pressure ranges.
The mechanical device may also have a secondary use for the fluid. For example, a catalytic converter of an internal combustion engine is often regenerated by intermittently injecting fuel into the exhaust gas upstream of the converter. Unfortunately, the intermittent diversion of fuel from a primary fluid supply system demand such as a fuel supply system may reduce the flow rate and fluid pressure below the specified flow rate and pressure ranges. As a result, the mechanical device may require a separate auxiliary fluid supply system including additional pumps, filters, regulators, and controllers to supply the secondary fluid use without disrupting the primary fluid supply system demand.
Unfortunately, adding an auxiliary fluid delivery system increases the component, reliability, and packaging costs associated with satisfying the secondary fluid use. For example, in a diesel engine, providing a separate auxiliary fluid supply system to deliver fuel to a catalytic converter increases the cost of exhaust emission control.
A fluid delivery system such as the auxiliary fluid delivery system may need to intermittently deliver precise quantities of fluid. For example, the reducant fluid delivery system of a catalytic converter may only deliver reducant for a second every minute. Yet the quantity of reducant may need to be precisely controlled. Excess reducant may result in excess unburned hydrocarbon emission in the exhaust while insufficient reducant may not adequately regenerate the catalytic converter resulting in increased emission of nitrogen oxides (“NOX”).
The fluid delivery system may employ a closed loop control system to increase the precision of the fluid delivery. The closed loop control system may include a flow sensor and a control module. The flow sensor measures the fluid flow rate and the control module adjusts the delivery of fluid so as to deliver the precise, required amount of fluid.
Unfortunately, current flow sensors typically only precisely measure the fluid flow rate when averaged over a lengthy time interval. Measurements of intermittent fluid flows are often less precise, decreasing the effectiveness of closed loop control. In addition, current flow sensors may be unable to supply diagnostic information in addition to the fluid flow rate, such as a flow failure. Finally, current flow sensors are typically not easily packaged within fluid lines and injectors.
In addition, cooling the injector may further add to the costs of delivering fluid diverted from the primary fluid supply system. For example, the injector may require additional cooling components such as coolant lines and the like.
From the foregoing discussion, it should be apparent that a need exists for an apparatus, system, and method for intermittently delivering fluid that employ a primary fluid supply system without disrupting the primary fluid supply system's capabilities to service the primary fluid supply system demand. In addition, such an apparatus, system, and method would preferably precisely measure the delivered fluid flow and efficiently cool the injector. Beneficially, such an apparatus, system, and method would reduce the costs associated with secondary uses of a fluid.