CITC2024 New Session：Combustion


Title：Decarbonized Combustion: Research Needs for Zero Pollution
Speaker: Yannis Hardalupas,Imperial College London
Abstract:Climate change is the biggest challenge that our society faces. To deliver the required reduction of carbon emissions, a smooth transition is needed from the existing infrastructure to a new approach that is yet to be agreed at an international level. Consequently, combustion technologies are expected to remain important during the development of new infrastructure over the next 30 years. However, combustion technologies must be able to deliver zero pollution, which include carbon dioxide, Unburned Hydrocarbons, NOx and particulates and other substances, specific to different industrial processes. The talk will identify and review different combustion technologies that can deliver net zero carbon emissions and overall zero pollution within short and medium timescales, which include: 1.Hydrogen and its vectors (e.g. Ammonia) 2.Supercritical CO2 3.Solar or e-fuels 4.Metal nanoparticle fuel The relevance of these approaches to aviation, land and marine transport and power generation will be considered. The scientific challenges that future research must address to deliver these combustion technologies will be presented.


Title: Gas turbine combustion instability generation mechanisms and practical control approaches
Speaker: Dan Zhao, Royal Society of New Zealand (Academician)
Abstract:In engine combustion systems such as gas turbines and ramjets, pressure fluctuations are always present, even during normal operation. One of design prerequisites for the engine combustors is stable operation, since large-amplitude self-sustained pressure fluctuations (also known as combustion instability) have the potential to cause serious structural damage and catastrophic engine failure. The typical generation mechanisms of such undesirable combustion instability are discussed and highlighted. To dampen pressure fluctuations and to reduce noise, acoustic dampers are widely applied as a passive control means to stabilize combustion/engine systems. However, they cannot respond to the dynamic changes of operating conditions and tend to be effective over certain narrow range of frequencies. To maintain their optimum damping performance over a broad frequency range, extensive researches have been conducted during the past four decades. The present work is to summarize the status, challenges and progress of implementing such acoustic dampers on engine systems. The damping effect and mechanism of various acoustic dampers, such as Helmholtz resonators, perforated liners, baffles, half- and quarter-wave tube are introduced first. A summary of numerical, experimental and theoretical studies are then presented to review the progress made so far. Finally, as an alternative means,‘tunable acoustic dampers’are discussed. Potential, challenges and issues associated with the dampers practical implementation are highlighted. 


Title:Thermoacoustic instability-taming the 'ghost' of aero-and land- based gas turbine combustors.
Speaker: Prof.Dong Yang,Southern University of Science and Technology
Abstract:Thermoacoustic instabilities (or “combustion instabilities”) come from the positive feedback between acoustics and unsteady combustion; unsteady combustion generates acoustic waves which propagate within the combustor, being reflected by the boundaries, and further disturb the flame to generate more acoustics. Due to the compactness and intensive heat release in gas turbine combustors, this coupling can generate catastrophically large pressure oscillations. Predicting it is very difficult since it requires resolving couplings across very different scales (acoustics, turbulence, and combustion). Full-scale experiments are extremely expensive, but lab-scale rig does not capture all key physics – a process of trial and error involving many very expensive full-scale tests (high pressure and temperature tests covering all operating cases) is usually needed to ensure that this instability is safely avoided. Thermoacoustic instabilities are thus called the “ghost” of engines. This talk presents the state-of-the-art treatments in predicting and damping of this instability. More specifically, the state-of-the-art low-order network modelling methodology, and relevant vortex-sound-entropy coupling theories will be presented.

Title: Physics-based model reduction of multi-species mixing and combustion processes.
Speaker: Prof.Xing-jian Wang,Tsinghua University
Abstract:High-fidelity simulations of mixing and combustion processes are computationally demanding and time-consuming, hindering their wide application in industrial design and optimization. The present study proposes projection-based reduced order models (ROMs) to predict spatial distributions of physical fields for multi-species mixing and combustion problems in a fast and accurate manner. The developed ROMs explore the suitability of various regression methods, including kriging, multivariate polynomial regression (MPR), k-nearest neighbors (KNN), deep neural network (DNN), and support vector regression (SVR), for the functional mapping between input parameters and reduced model coefficients of mixing and combustion problems. The ROMs are systematically examined using two distinct configurations: steam-diluted hydrogen-enriched oxy-combustion and fuel-flexible combustion in a practical gas-turbine combustor. The projected low-dimensional manifolds are capable of capturing most important combustion physics, and the response surfaces of reduced model coefficients present pronounced nonlinear characteristics of the flowfields with varying input parameters. The ROMs with kriging present a superior performance of establishing the input-output mapping to predict almost all physical fields, such as temperature, velocity magnitude, and combustion products for both test problems. The accuracy of DNN is less encouraging owing to the stringent requirement on the size of training database. KNN performs well in the region near the design points but its effectiveness diminishes when the test points are distant from the sampling points, whereas SVR and MPR exhibit large prediction errors. For the spatial prediction at unseen design points, the ROMs achieve a prediction time of up to eight orders of magnitude faster than conventional numerical simulations, rendering an efficient tool for the fast prediction of mixing and combustion fields and potentially an alternative of full-order numerical solver.


Title: The status, challenges and progress of hydrogen turbine engine combustor
Speaker：Chi Zhang，Beihang University
Abstract: As a part of the global energy system in the future, hydrogen is an important carrier to achieve green and low-carbon transformation for energy terminals. Air transport is one of the most difficult industries to decarbonize, and the development and application of hydrogen energy in the aviation field has attracted much attention. In particular, the combination of China's green electricity from wind and solar energy to produce green hydrogen will help to achieve the carbon reduction in China's air transport. Compared with other low-carbon or zero-carbon technologies such as pure electric propulsion, fuel cells, and sustainable aviation fuels (SAF), hydrogen turbine engines have unique advantages and technical difficulties. At present, hydrogen turbine engines are mainly suitable for medium and large aircraft as regional and trunk air transport. This report will introduce the background requirements and current development situation of the hydrogen turbine engine and combustor, and compare the operating and combustion characteristics of hydrogen, ammonia and SAF. Hydrogen combustion faces technical problems such as NOx emission, flashback and combustion oscillation, which brings new challenges to the design and testing of the hot-end components such as combustor in turbine engines. By comparing different hydrogen combustion technology routes, the countermeasures of hydrogen combustor are recommended. Finally, the progress of the basic research will be introduced for hydrogen-blended swirl combustion, hydrogen micro-mixed combustion, and high-efficiency zero-emission hydrogen combustion, which provides support for the research and development of the hydrogen turbine engine combustor.


Title:Experimental investigation on the characteristics of thermoacoustic oscillation in an axial staged burner 
Speaker:Lei Li, Beihang University
Abstract: In this paper, the characteristics of thermoacoustic oscillation under axial staged conditions are studied experimentally. The experimental device is an axial staged burner. A ‘5+1’-swirling-nozzle layout is used in the first stage, and the two nozzles in the second stage are arranged symmetrically. The lean-premixed combustion of natural gas and air was adopted, and dynamic pressure data was collected. Several typical oscillation signals are analyzed, and the dominant frequency is confirmed to correspond to Helmholtz mode in the flame tube. The effects of the second-stage equivalence ratio, air flow rate, second-stage position and inlet temperature on combustion oscillation characteristics are studied, and the influence mechanism of these parameters on two-stage unsteady heat release coupling and its coupling with pressure oscillation is preliminarily revealed.


Title:Research on Mechanisms and Suppression Methods of Combustion Instability
Speaker: Prof.Ying-wen Yan, NUAA(Nanjing University of Aeronautics and Astronautics)
Abstract: This report summarizes the mechanisms of combustion instability and suppression methods in diffusion flames. In the experimental studies, the measurement and correction methods of pulsating pressure were investigated, as well as the boundary and oscillation characteristics of swirl combustion oscillation. In numerical simulations, a numerical simulation method for the pulsation characteristics of the flow field was established. Regarding the thermoacoustic coupling mechanism of combustion instability, a phase-locked loop mechanism was proposed, and based on this mechanism, suppression methods of combustion instability through phase control and sound absorption were developed.


Title:Design Optimization of Outlet Temperature Distribution of Hydrogen Micromixing Diffusion Combustor Based on Micro-turbojet Engine
Speaker: Da Mo, AECC Shenyang Engine Research Institute 
Abstract: This paper focuses on the optimization of the outlet temperature field of a hydrogen micromixing diffusion combustor for a micro-turbojet engine with a thrust of 20kgf. The joint simulation optimization platform combining Workbench and UG was established and the multi-parameter driven optimization design process was developed. The surrogate models and genetic algorithms were employed to investigate the influences of key parameters on the hotspot temperature at the combustor exit. It was found that smaller diameters of the dilution holes and positions further from the exit lead to lower hotspot temperatures. Additionally, an optimal solution for achieving a uniform temperature distribution at the combustor outlet was obtained. This solution involves a single row of dilution holes on both the inner and outer walls of the flame tube, arranged in an alternating axial and angular pattern. Through aerothermal process analysis, it was determined that the outlet temperature distribution coefficient (OTDF) of the combustion chamber is below 0.2. Meanwhile, the axial dimension of the flame is short, approximately one-third of the flame tube length. The conclusions derived from this study provide important guidance for the design of hydrogen micromixing diffusion combustor.


Title:Combustion Technology Research of Gas Turbine Firing Hydrogen Contained Fuels
Speaker: Prof.Peng-hua Qiu, HIT(Harbin Institute of Technology)
Abstract:The use of hydrogen-rich and pure hydrogen fuels are key components of China's future carbon neutrality strategy, as they represent low-carbon and zero-carbon energy sources. The use of hydrogen fuel in gas turbines is a crucial pathway for achieving significant pollution and carbon reduction in the power generation sector. Because of its highly reactive combustion chemistry and superior mass transport properties, hydrogen fuel exhibits characteristics that are significantly distinct from traditional fuels such as natural gas. Balancing low NOx emissions with flame instability in combustion systems is essential for effective hydrogen combustion. This report systematically investigates the combustion characteristics of hydrogen micro-mix nozzles, providing performance evaluations from single nozzles, combined nozzles, to unit nozzle design simulations and pressurized tests. 


Title: 多点直喷直混燃烧技术
Speaker: ：Prof.Jian-qin Suo, NWPU (Northwestern Polytechnical University)