Changshuai Du’s scientific contributions

[Significance] Microgravity combustion research is essential for understanding fundamental combustion phenomena and advancing combustion theory. However, conducting experiments in orbit involves significant technical challenges and resource demands. The Combustion Science Rack (CSR) aboard the Chinese Space Station (CSS) has been operational since October 2022. To further support combustion science research aboard CSS, consolidate critical scientific questions in microgravity combustion, and validate the in-orbit experiment feasibility, a ground-based research platform has been established at the space experiment center in Huairou District, Beijing. This platform replicates the combustion environment and apparatus dimensions of the in-orbit CSR. Equipped with high-precision diagnostic tools and versatile experimental modules, the platform enables researchers to validate in-orbit experiment feasibility, conduct ground-based validation tests, and generate baseline control data for CSS experiments. The paper highlights the platform􀆳s design, operational principles, and preliminary test results. Together, these demonstrate its ability to meet the diverse requirements of current and future microgravity combustion research projects. [Progress] The platform consists of the experimental insert subsystem, the supporting facility subsystem, and the combustion diagnostic subsystem. Designed to match the experimental space and apparatus sizes of the in-orbit CSR, this ground-based platform takes full advantage of laboratory amenities, including gas supply, ventilation, power supply, and thermal control facilities. The platform comprises three subsystems: the experimental insert subsystem, the supporting facility subsystem, and the combustion diagnostic subsystem. The experimental insert subsystem supports a wide range of experiments with its gas, liquid, and solid combustion modules. The combustion diagnostic subsystem is equipped with high-precision measurement devices such as high-speed cameras, particle image velocimetry, and planar laser-induced fluorescence, enabling real-time measurements of flame morphology, flow velocity, and intermediate species distribution. Initial tests demonstrate that the platform can generate various types of gas flames, including premixed, diffusion, and partially premixed flames, by adjusting the fuel-to-oxidizer flow ratio. The liquid combustion module conducted suspension and ignition tests for single and multiple droplets, while the solid combustion module examined how planar, cylindrical, and linear materials combust under microgravity conditions. The system precision and reliability were validated by comparing diagnostic data with established data on flame oscillation. Additionally, the platform􀆳s modular design supports upgrades to both future software and hardware. [Conclusions and Prospects] The ground-based research platform replicating on-orbit combustion environments plays a crucial role in supporting and complementing future combustion studies conducted aboard the space station. With its advanced experimental modules and diagnostic tools, the platform enables systematic and in-depth combustion experiments, advancing fundamental research in space combustion. Notably, the diagnostic system facilitates high-precision measurements across diverse combustion experiments. This ensures accurate analysis of flame structures, flow velocity fields, and chemical component distributions, providing critical ground-based validation and comparative data for addressing key scientific questions faced in space-based research. Overall, the platform is equipped with comprehensive facilities necessary for conducting combustion experiments. By supporting systematic experimentation, it helps optimize the design of space-based experiments, strengthening the cutting-edge and innovative aspects of space combustion studies. Furthermore, the extensive diagnostic resources and results from ground experiment results offer valuable data for in-orbit combustion experiments, driving the advancement of space combustion science theories and applied technologies.

[Significance] Experimental conditions in microgravity differ considerably from those in Earth‘s normal gravity. Combustion experiments conducted in microgravity eliminate the effects of natural convection and simplify the complex factors of combustion processes. Combustion experiments can reveal many physical and chemical phenomena only under normal gravity conditions, providing significant insights for fundamental scientific research. Meanwhile, microgravity combustion experiments allow a deeper investigation into the fundamental physical phenomena of advanced combustion issues, serving as a crucial means for basic research. This research supports China􀆳s energy and power industries in addressing the needs related to energy conservation, emission reduction, and green energy transition, as well as those related to fire prevention on the ground and in space. [Progress] The Chinese Space Station (CSS) is planned to support combustion science experiments using multiple fuel types, including gaseous, liquid, and solid fuels, in orbit. The first series of CSS combustion experiments consisted of gaseous combustion experiments, a few of which were conducted in the combustion science rack (CSR). This article reviews the progress of microgravity jet flame research and introduces types of scientific research that can potentially be supported by the combustion science application system and gaseous combustion experiment insert (GCEI) in the CSR. The combustion science experiment system provides the GCEI with the necessary resources, such as water cooling, electricity, and gas emissions. The GCEI supports gas-flow regulation functions, allowing the adjustment of the gas type, flow rate, and ignition power based on the project􀆳s scientific objectives. The GCEI features a universal burner platform and can adjust the gas composition, flow rate, and ignition energy. Various types of flames can be generated by replacing the project burners. Optical diagnostics conducted outside the optical windows of the combustion chamber provide data on the flame dynamics, flow fields, and spatial distributions of OH and CH. Currently, astronauts aboard the CSS have installed an igniter in the gas experiment module and mounted the GCEI in the CSR combustion chamber. The GCEI automatically completes a series of actions, including configuring the combustion environment gas, ejecting the fuel gas, heating the igniter, determining parameters, performing optical diagnostics, filtering and circulating, and exhausting waste gases. Because of the lack of buoyancy effects, microgravity flames exhibit considerable differences compared to normal gravity flames. After transmitting the experimental data to the ground operation control center, the control and monitoring of the experimental conditions are performed to confirm the normal operation of each subsystem. The fuel, oxidizer, and inert-gas flow rates are set according to predetermined delays and settings, demonstrating the normal operation of key modules, such as the GCEI􀆳s fuel gas cylinder module, gas-distribution solenoid valve, igniter, and oxidizer and diluent subsystems of the CSR. The image intensifier camera of the combustion diagnostic subsystem captures corresponding OH and CH emission images, demonstrating an increase in the flame width and a rapid decrease in the flame height until localized extinction occurs at the end of the non-premixed flame. [Conclusions and Prospects] The present study verifies that the GCEI can effectively realize microgravity flames for gaseous experiments in orbit and provide a support and design basis for subsequent diversified combustion science experiments. The GCEI is expected to provide valuable data and platform support for subsequent microgravity experiments aboard the CSS.

The radiation and strain effect can be comparably influential in a partially premixed flame (PPF), especially in microgravity environments. The present study reports the first batch of combustion experiments aboard the Chinese Space Station. The experiments were conducted using a co-flow burner installed on the Gas Combustion Experiment Insert inside the Combustion Science Rack. With both in-orbit experiments and numerical simulations, transient dynamics of extinction in the non-premixed flames (NPFs) and PPFs are analyzed. Results suggested that the NPF branch in a PPF exhibits a “ring-like” structure with partially premixed hooks at its edges prior to global extinction. The extinction is associated with strain rate and radiation effect as analyzed by numerical simulation and comparison with the experimental results. The overall NPF branch exhibits a reduced range of equivalence ratios with two edges retracting in a premixed manner under the considerable influence of radiative heat loss. The contribution of strain and radiation effect for the local extinction is demonstrated through normalized flame stretch rate, radiative heat loss, and local Damköhler number. Results suggested that radiative heat loss for the edges of NPF region can occupy 40 % of the local heat release. A diminishing influence of the strain rate effect on flame propagation leads to a shift towards radiation-controlled extinction. The local radiative extinction at the end of the NPF region ultimately triggering the extinction of the entire NPF region.

With the development of space science in China, the scale of space application payloads continues to increase, and the demand for heat dissipation is also gradually increasing. The fluid loop thermal control is a more efficient way of heat dissipation. In order to optimize the heat dissipation effect of the fluid loop system, this paper establishes a thermal model of the fluid loop system and converts it into a constrained optimization problem. The generalized Lagrange multiplier method is used to calculate the optimal flow distribution strategy, and the influence of the weight is analyzed, which provides a reference for the setting of the weight in practical applications.