Ramp Heating in High-Speed Transient Thermal Measurement With Reduced Uncertainty

The uncertainty associated with the convective heat transfer coefficient (HTC) obtained in transient thermal measurement is often high, especially in high speed flow. The present study demonstrates that the experimental accuracy could be much improved by an actively controlled ramp heating instead of the conventional step heating approach. A general design guideline for the proposed ramp heating method is derived theoretically and further demonstrated by simulation cases. This paper also presents a detailed experimental study for transonic turbine blade tip heat transfer. Repeatable, high-resolution tip HTC contour was obtained through transient IR measurement with the proposed ramp heating method. Detailed uncertainty analysis shows that the resulting HTC uncertainty level is much lower than the experimental data currently available in the open literature. The ramp heating approach is specially recommended to the high-speed heat transfer experimental research community to improve the accuracy of the transient thermal measurement technique.