# A Temperature Measurement and System Identification Method for Confined Cavity Explosions Based on an Improved Type C Thermocouple Sensor

## TL;DR

This paper introduces a new thermocouple sensor and system identification method to measure and analyze temperatures in confined explosions.

## Contribution

The novel design of the thermocouple sensor and the least square-based system identification method for temperature field reconstruction in explosions.

## Key findings

- The improved thermocouple sensor shows good survivability and measurement reliability in extreme explosive conditions.
- The proposed system identification method accurately reconstructs the temperature field with high fitting accuracy.
- The sensor design suppresses contact issues and improves structural stability under impact.

## Abstract

This paper proposes a temperature measurement and system identification method for confined cavity explosions based on an improved type C thermocouple sensor. On the one hand, to address the extreme conditions caused by high-speed fragments and intense shock waves in an enclosed explosive environment, a thermocouple probe structure employing alloy strips of different widths with an alumina insulating layer in between is designed. By optimizing the strip width, the contact issues arising from edge-cutting burrs are effectively suppressed, thereby significantly enhancing the electrical insulation performance and overall reliability of the sensor. Additionally, a wedge-shaped alumina ceramic piece is designed to secure the thermocouple probe, further improving its structural stability under impact conditions. On the other hand, to tackle the highly nonlinear and multi-field coupled characteristics of the post-explosion temperature field, a system identification method based on the least square method is proposed. This method constructs a polynomial function in terms of radial distance and time variables, enabling effective reconstruction of the temperature field from limited measurement points. It provides a useful reference for understanding of the temperature distribution in confined cavity explosions and supports improved estimation of the temperature field. Finally, experimental results demonstrate that the improved sensor exhibits good survivability and measurement reliability under extreme explosive conditions. Meanwhile, the reconstructed temperature field model shows high fitting accuracy and good capability for describing the temperature distribution, confirming the effectiveness of the proposed identification method.