Session: 04-53 High Hydrogen IV

Paper Number: 123935

123935 - Investigation of Pressure Effects on Combustion Characteristics of Hydrogen Annular Micro-Mixing Nozzles 

Abstract:In pursuit of achieving near-zero emissions and preventing flashback, Micro-mixing Combustion technology has been developed and implemented in hydrogen gas turbines. It represents an innovative approach to combustion, wherein traditional large-diameter nozzles are replaced by numerous structurally simple micro nozzles. The Micro-mixing Combustion technology achieves a reduction in flow mixing scales which enhances the uniformity of mixing and equivalence ratio, reduces flame length and achieves near-zero emissions combustion. Additionally, Micro-mixing Combustion technology reduces the volume of the premixed combustion zone and increases the relative heat dissipation area of the nozzles, which improves the ability to resist flashback and self-ignition.

According to the nozzle outlet form, micro-mixing nozzles have two types: circular nozzles and annular nozzles. Compared to circular nozzles, annular nozzles exhibit recirculation zones at downstream of the bluff bodies and the areas between nozzles. When facing variations in inlet conditions, it has higher working condition adaptability and flame stability. Therefore, for hydrogen fuels with high flame speeds, annular micro-mixing nozzles emerge as a viable option. However, the annular nozzles comprise inner and outer shear layers, resulting in a more intricate generation, evolution, and dissipation of vortex structures at different scales. Concurrently, the research on the influence of flames interactions on the combustion characteristics of micro-mixing nozzles diverse boundary and inlet conditions remains insufficiently profound.

This investigation proposed an annular micro-mixing nozzles comprising seven annular nozzles arranged in a regular hexagonal pattern. Air and fuel were mixed in vertical cross-flow jet method in the premixing section. Experimental investigations based on OH* spontaneous emission with OH-PLIF synchronous measurement technique and numerical simulations based on the Flamelet Generated Manifolds (FGM) model were conducted on this annular micro-mixing nozzles, This investigation explored the impact of equivalence ratio, flow velocity, combustion pressure, nozzle diameter, and distance between nozzles on the interactions of annular micro-mixing flames from the perspectives of mass, momentum, and energy exchange. This investigation aimed to reveal the flames interactions rules of annular micro-mixing nozzles.

In the experimental investigations, the air inlet temperature 418°C aligned with the requirements of F-class gas turbines, the equivalence ratio ranged from 0.39 to 0.42, the flow velocity ranged from 33.7 m/s and 101.6 m/s, and the air pressure ranged from 0.1 MPa to 0.6 MPa. The numerical simulations expanded the range of pressure, equivalence ratio, and flow velocity, supplied the effects of changes in nozzle diameter, and distance between nozzles. It was observed that the numerical simulation results exhibited a significant concordance with the experimental data, thereby validating the accuracy of numerical predictions for hydrogen annular micro-mixing flames based on the FGM model; neighboring flows interacted with each other, generating a highly turbulent interacting zone, significantly enhancing combustion reactions; the equivalence ratio and distance between nozzles emerged as the most sensitive parameters governing flames interactions; as equivalence ratio was decreased, flame liftoff height increased gradually and the flames interactions became weaken; the interactions disappeared when equivalence ratio was less than 0.3; as the distance between nozzles was increased ,flames interactions became weaken and there was an optimal configuration that ensures both flame stability and the lowest emissions.

In conclusion, this investigation delves deeply into the flames interactions rules of hydrogen annular micro-mixing nozzles under comprehensive boundary and inlet conditions. The findings contribute significantly to provide theoretical foundations and support for the design and development of nozzles in hydrogen gas turbines aiming for high pressure ratios, high temperature rises, and near-zero emissions.

Keywords: Micro-mixing nozzles; Hydrogen flames; Flames interactions; Pressurized air; Annular nozzles

Presenting Author: Jian Liu Harbin Institute of Technology

Presenting Author Biography: JianLiu, male, born in 1997. PhD, School of Energy Science and Engineering, Harbin Institute of Technology
The main research areas are gas turbine combustion, zero-carbon energy systems, advanced combustion theory and experiments, combustion optical diagnosis and turbulent combustion numerical simulation, etc.

Authors:

Jian Liu Harbin Institute of Technology
Penghua Qiu Harbin Institute of Technology
Xiyu Wang Harbin Institute of Technology
Qiming Hu Harbin Institute of Technology
Li Liu Harbin Institute of Technology
Linyao Zhang Harbin Institute of Technology
Chang Xing Harbin Institute of Technology