FLEXIBLE INJECTOR FOR DUAL FUEL ENGINES
Publication Date: 2015-May-20
The IP.com Prior Art Database
A technique to control high turn-down diesel flow rate for dual fuel engines is disclosed. . The technique employs a standard needle that operates over same length and duration for entire range of full diesel flow rate to very low diesel flows. The technique controls fuel flow rate by changing free flowing section of nozzles. The technique uses a rotating cylinder to change free flow-line areas of the nozzles. Further, a rotating nozzle cache is used to open more or less nozzles, or change free areas in the nozzles. The nozzle cache is perforated such that the perforations are aligned to various degrees depending on angular position of the nozzle cache. The technique is implemented by rotating a part of the flexible injector around a needle axis without a vertical movement of the needle. The cylinder may be rotated using an electric, hydraulic or magnetic actuation mechanism.
The present disclosure relates generally to dual fuel engines and more particularly to a concept and method for operating a high-turndown injector.
Relationship between maximum and minimum quantities of fuel within a range of a fuel system is known as turn-down ratio. An effective fuel injector that delivers precisely controlled quantities of fuel, varying between a minimum and a maximum is a challenge.
In a dual fuel engine, usually, the amount of diesel injected in a cylinder varies from 100% to 1% or less. Therefore, range of flow rates of diesel fuel that is required to be accommodated by the injector is very large. Such accommodation is achieved by complex movements of an injector needle. The injector needle operates in a ballistic chamber for a very low quantity of the diesel injected into the chamber. In order to achieve effective needle operation for controlled fuel flow, it is required to have an optimal control of a depressurization mechanism that lifts the needle.
Conventional techniques rely on complex needle valve operation. For example, in a conventional technique, a conical nozzle valve seat of a diesel injection nozzle is shaped to form a notch. The technique relies on different height for the injector needle to let the fuel flow through such various numbers of notches. However, such a complex needle valve operation causes inaccuracies when a very low amount of diesel is injected.
In another conventional technique, a programmable diesel fuel injector is used. Such programmable injector uses an alloy in a magnetic field to change length of a rod that controls the injection rate. However, the assembly of components used in the technique is cumbersome. One other conventional technique employs a rotating element to spray diesel at various angles in a cylinder. However, the technique does not control fuel flow rate in the cylinder. Yet another conventional technique employs a bore element that is placed close to nozzles and improves strength of an injector device. However, there is no movement of such bore element to control the amount of fuel delivered for combustion.
It would be desirable to have a technique that improves control of dual fuel engines and enables easy operation of high turndown injectors.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 depicts rotation of a cylinder that changes free flow areas of nozzles.
Figure 2 depicts a nozzle blocking mechanism in which number of nozzles on a nozzle plate is changed.
Figure 3 depicts the nozzle blocking mechanism in which geometry of the nozzles is changed.
Figure 4 depicts a cross-sectional view of a rotating nozzle cache of the injector for typical heavy duty injectors.
Figure 5 depicts placement of a step motor and a seal in the injector of the engine for integration of nozzle movement.
Figure 6 depicts placement of an electric motor in the injector.
Figure 7 depicts the power circuit shared with hydraulic valve for needle movemen...