This article presents a novel high temperature heat flux (HTHF) sensor based on micromachined thermocouple (MTC) to meet the needs of transient high heat flux detection in ultrahigh temperature environments, such as fire research, high-power pulsed lasers testing, and aerospace engineering. The targeted design, fabrication, and package of an MTC-based HTHF sensor with excellent heat dissipation capacity are proposed, and relevant experiments were conducted in two aspects. First, powerful laser tube-based tests at ambient temperature show that such a sensor can detect a heat flux high to 10.8 MW/m ² with an extremely fast response; its response time, in this case, is 1.9 ms. And then, turbine engine test pipe based tests at high temperature reveal that the sensor with water cooling could survive at 1200 °C for at least 100 s. Compared to conventional heat flux sensors, it is more sensitive to transient heat flux changes and has a faster response speed. Such satisfactory performance makes the sensor extremely competitive in ultrahigh heat flux detection in extremely harsh environments.

In this article, novel thermal gas sensors with newly designed diffusion gas channels are proposed to reduce the flow-rate disturbance. Simulation studies suggest that by lowering the gas flow velocity near the hot film, the maximum normalized temperature changes caused by flow-rate variations in the two new designs (Type-H and Type-U) are decreased to only 1.22% and 0.02%, which is much smaller than in the traditional straight design (Type-I) of 20.16%. Experiment results are in agreement with the simulations that the maximum normalized flow-rate interferences in Type-H and Type-U are only 1.51% and 1.65%, compared to 24.91% in Type-I. As the introduced CO₂ flow varied from 1 to 20 sccm, the normalized output deviations in Type-H and Type-U are 0.38% and 0.02%, respectively, which are 2 and 3 orders of magnitude lower than in Type-I of 10.20%. In addition, the recovery time is almost the same in all these sensors. These results indicate that the principle of decreasing the flow velocity near the hot film caused by the two novel diffusion designs can enhance the flow-rate independence and improve the accuracy of the thermal conductivity as well as the gas detection.