基于机械形变的碳同位素稳定性提升研究

The concentration and carbon isotopes analysis of CH4 and CO2 play a key role in identifying the target area and predicting the reserves of the gas hydrate. However, the spectrum absorption of carbon isotopes is very sensitive to temperature change, it is urgent to solve the problem of how to reduce the influence of gas absorption cell temperature changing which effect on carbon isotopes absorption. The research intends to study the stability of carbon isotopes based on the mechanical deformation analysis by combining the system and synthesis, the theory and the experiment, which includes the key points: 1) Gas cell analysis of thermal deformation and optimization of structural design; 2) Performance optimization of overlap-free optical design with long optical path. 3) The efficient coupling of the coordination configuration between the structure and the optical design. The major contributions of this proposal lie in: clarifying the optimized mechanism of boundary parameters of gas cell and the beam propagation in interference-free mode with multiple control parameters, which will provides a theoretical basis of the synchronous coupling of the optical and mechanical, and then finish the optimization design of a new type of gas cell. In addition, a control method with systematic coordination which takes into account the accuracy and economy of the system will be proposed for providing effective ways and technical support to improve the stability of carbon isotope analysis.

甲烷和二氧化碳气体浓度及其碳同位素比值分析对识别水合物靶区并预测其储量起到关键作用。但碳同位素光谱吸收对温度变化响应十分敏感，如何降低气体吸收气室温度变化对碳同位素光谱吸收影响的问题亟须解决。本项目拟采用系统与综合、理论与试验相结合的方法研究基于机械形变分析的碳同位素稳定性提升问题。主要包括：1)气室热变形分析及结构设计寻优；2) 长光程、无重叠光路设计性能指标优化；3)结构与光路设计协调配置的高效耦合。预期贡献为：明确气室形体边界参数优化机理、明确多控制参数的抑制干涉光束传播机理，为光机高效耦合并完成新型气室优化设计提供理论依据；建立综合考虑精确性和经济性的系统协调控制方法，为提升碳同位素分析的稳定性提供有效途径和技术支撑。

本项目突破国际上采用的基于近轴近似理论的气体吸收气室（气室）传统光路设计思想，创新性地引入了一种基于矢量反射理论的空间三维坐标矩阵方法，通过建立精确的数学模型并实现相对应的光学仿真，不仅可以精确地追踪光束传播轨迹，还能准确地计算每条射线的长度和角度，有效避免“近轴近似”所产生的累计误差，减小因光束传播精确度的可控度不足而产生的结构设计优化效率低、光机耦合协同性不足等问题，提升气体探测的稳定性。首先,仿真分析了气室形变状态与其温度变化的关系，研究了结构优化方案，初步确立了符合需求的气室参数信息。然后，进行了多参量、无重叠光路设计及光束传播控制策略寻优，提出了三维坐标矩阵方法，并确定了气室机械结构与光路配置的耦合方案，模拟实现了多参量、多光斑形态的气室。最后，研制了有效光程为4.52米、11.45 米和36.48米等多个气室样机并优化了设计参数。气室的利用率指标L/V达到1.18，实现气室利用率现有最优。七圆环光斑图案气室的光程最长，利用率L/V也最大。调整3D打印版光程为11.45米样机参数后研制了基于此气室的气体传感系统并进行了甲烷浓度、精确度和线性度等相关测试验证。积分时间为1s时可实现8.86 ppmv的探测极限，积分时间为78s时可实现0.91 ppmv的探测极限。项目执行期间发表SCI论文3篇，EI论文1篇，已接收待发表SCI论文1篇。