Liquid Fuel Injector Segmentation for Low Airflow Ignitability
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Solution Overview
Problem
The existing liquid fuel injectors with a multiple-injector structure experience deteriorated atomization performance at low air flow velocities, leading to ignitability issues during engine start-up and combustion stability problems under varying load conditions, particularly during lean burning and rapid load changes in gas turbine engines.
Innovation Solution
A liquid fuel injector design featuring a cylindrical primary fuel injecting body with an annular shroud and secondary fuel injecting body, equipped with inner and outer swirlers, where the primary injector operates as a pressure spray-type and the secondary injector as an airblast-type, ensuring improved atomization performance across a wide range of air flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If an airblast-type injector is used with a small flow rate of air, then the structure is compact and suitable for pilot injection, but atomization performance deteriorates and ignitability is poor
Solution Approach 1:
The injector is divided into multiple independent airblast-type injectors with different air flow rates, each responsible for specific operating ranges. The pilot injector handles low flow rates while main injectors handle high flow rates, ensuring optimal atomization and ignitability across the entire operating range.
Solution Approach 2:
The invention changes the air flow rate parameter by providing multiple injectors with different air flow characteristics. The pilot injector is designed with specific air passage dimensions and swirler configurations to generate sufficient swirling flow and atomization performance even at low air flow rates, thereby improving ignitability during engine start-up.
2Productivity
If an airblast-type injector is used with a large flow rate of air, then atomization performance is good for high-load operation, but combustion stability degrades under low-load conditions
Solution Approach 1:
The fuel injection system is segmented into pilot injector and main injector. The main injector with large air flow rate is activated only during high-load operations when high productivity is required, while the pilot injector maintains combustion stability during low-load operations. This segmentation allows each injector to operate in its optimal range.
Solution Approach 2:
The system dynamically switches between pilot injector and main injector based on operating conditions. During rapid acceleration or deceleration, the control system adjusts which injector is active, ensuring combustion stability is maintained while meeting the required fuel injection flow rate for the current load condition.
3Shape
If throttle portions are added to air passages to generate strong swirling air flow, then spray expansion is improved, but device complexity increases
Solution Approach 1:
The swirler and air passage are merged into an integrated structure. The swirler is positioned at the outlet of the air passage, and the swirling flow generated by the swirler naturally expands the spray in a conical shape without requiring additional throttle portions or complex air passage modifications. This merging reduces device complexity while achieving the desired spray expansion.
Solution Approach 2:
The swirler generates strong swirling air flow that automatically causes the spray to expand in a conical shape through the effect of centrifugal force. The system uses the kinetic energy of the swirling air flow itself to achieve spray expansion, eliminating the need for additional throttle portions or complex control mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design enhances ignitability at low air flow rates and combustion stability across various operating conditions, preventing blowing-off during rapid load changes and maintaining efficient fuel atomization.
Implementation Method 1
a strong swirling air flow spreads to the outside in the radial direction by an effect of a centrifugal force and thus has an effect of causing spray of the liquid fuel to expand in a conical shape
Implementation Method 2
a liquid fuel injected as an annular liquid film is atomized using a shear force (caused by a velocity difference) acting between the annular liquid film and swirling air flows adjacently flowing on a radially inner and outer side of the annular liquid film
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
Provided is a liquid fuel injector capable of improving ignitability under an operating condition of a small flow rate of air and combustion stability under a wide range of operating conditions. A liquid fuel injector includes a cylindrical primary fuel injecting body having a central axis; an annular shroud concentrically placed radially outside; and an annular secondary fuel injecting body placed concentrically with the primary fuel injecting body and the shroud between the primary fuel injecting body and the shroud, in which a plurality of inner swirlers placed at equal intervals in a circumferential direction are provided in an annular inner air passage formed between the primary fuel injecting body and the secondary fuel injecting body, a plurality of outer swirlers placed at equal intervals in the circumferential direction are provided in an annular outer air passage formed between the secondary fuel injecting body and the shroud, the primary fuel injecting body is formed as a pressure spray-type injector, and the secondary fuel injecting body and the inner and outer air passages cooperatively constitute an airblast-type injector.