Annular Splitter Pilot Nozzle for Gas Turbine Flow Capacity
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Solution Overview
Problem
Twin Annular Premixing Swirler (TAPS) fuel nozzles in gas turbine engines face limitations in pilot stage tip flow number and flow capacity, particularly at low flow conditions such as starting and idling, due to atomization performance constraints.
Innovation Solution
The fuel nozzle design includes an axially-elongated inner pilot centerbody wall, an outer pilot centerbody wall, an annular splitter with a cylindrical upstream section, a splitter throat, and a downstream diverging surface with a specific angle, along with a pilot fuel film surface and a main injection ring, to enhance fuel flow and atomization efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the pilot stage tip flow number is increased to improve flow capacity, then high flow capacity is achieved, but atomization performance deteriorates at low flow conditions
Solution Approach 1:
The fuel nozzle is divided into multiple discrete stages (pilot stage and main stage) with separate fuel flowpaths. The pilot stage uses a centerbody injector for high flow capacity at low engine power, while the main stage uses annular injectors for high emissions performance at higher power levels. This segmentation allows each stage to be optimized for its specific operating conditions without compromising the other.
Solution Approach 2:
The fuel flowrate is made variable within each stage through controlled valve mechanisms. The pilot stage can dynamically adjust fuel flow from low (for atomization) to high (for flow capacity) conditions, and the main stage similarly varies its flow. This dynamic control allows the system to adapt atomization performance to match the required flow capacity at different operating points.
2Power
If the pilot stage operates at high flow capacity, then engine output is improved, but emissions increase
Solution Approach 1:
The combustor is divided into a pilot zone and a main combustion zone with separate fuel injection systems. The pilot stage provides high flow capacity at low power settings with acceptable emissions, while the main stage engages at higher power levels to provide clean, efficient combustion. This spatial and functional segmentation allows the system to achieve high engine output when needed without continuously operating in high-emission mode.
Solution Approach 2:
The system changes operational parameters by transitioning between pilot-only mode (low power, higher emissions acceptable), main stage mode (high power, low emissions required), and combined modes. The fuel flowrate, air-to-fuel ratio, and combustion air distribution are dynamically adjusted based on engine power requirements, allowing optimal emissions performance across the entire operating range.
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 increases the flow capacity of the pilot stage, improving atomization performance and operational efficiency, especially at low engine power conditions, thereby addressing the limitations of TAPS-style fuel nozzles.
Implementation Method 1
a downstream diverging surface having an average diverging angle of about 24° to about 40° in relation to a centerline axis
Implementation Method 2
a pilot fuel film surface downstream from the annular fuel passage
Implementation Method 3
The fuel passage intersects with the inner pilot centerbody wall at a pilot fuel metering orifice
Data Source
AI summary
A fuel nozzle is provided for a gas turbine engine, and can include a pilot fuel injector having an axially-elongated, inner pilot centerbody wall and an outer pilot centerbody wall, with the axially-elongated, inner pilot centerbody wall extending from an upstream end to an annular fuel passage defining the downstream end of the pilot fuel injector. The fuel passage intersects with the inner pilot centerbody wall at a pilot fuel metering orifice. The fuel nozzle also includes a pilot fuel film surface downstream from the annular fuel passage and an annular splitter surrounding the pilot fuel injector. The annular splitter comprises, in axial sequence: an upstream section, a splitter throat having a diameter that is larger than a downstream diameter defined by the pilot fuel film surface, and a downstream diverging surface having an average diverging angle of about 24° to about 40° in relation to a centerline axis.