Development of Novel Thermal Diffusivity Analysis by Spot Periodic Heating and Infrared Radiation Thermometer Method

A spot periodic heating method is a highly accurate, non-contact method for the evaluation of anisotropy and relative thermophysical property distribution. However, accurately evaluating thermal diffusivity is difficult due to the influence of temperature wave reflection from the whole surface of the sample. This study proposes a method to derive thermal diffusivity using a parameter table based on heat transfer equations using the concept of optimum distance between heating-point and measurement point. This method considers finite sample size, sensitivity distribution of infrared ray detector, intensity distribution of heating laser and sample thickness. In these results, the obtained thermal diffusivity of pure copper corresponded well with previous literature values. In conclusion, this method is considered highly effective in evaluating the thermal diffusivity in the horizontal direction.

Solid Fraction Examination at Flow Cessation and Flow Cessation Mechanism of Al-Si-Mg Alloy

The aim of this study is to experimentally determine the solid fraction at the cessation of the flow of a molten Al-Si-Mg alloy (JIS-AC4CH) ceases. In this study, an experimental apparatus to measure the melt temperature during flow was developed and was used to perform highly accurate temperature measurements. An immersion-type optical-fiber radiation thermometer without emissivity correction was used for the temperature measurement device in this apparatus. The solid fraction was calculated from the area of primary crystals when the molten metal at any temperature was quenched. The melt temperature at flow cessation was higher than the eutectic reaction temperature, and the solid fraction in the melt front was approximately 0.2. However, the maximum solid fraction was found at a position slightly away from the melt front toward the pouring gate, and was approximately 0.3. It was inferred for this Al-Si-Mg alloy, that the flow cessation mechanism was a mixture of skin formation and mushy formation types.

Zero Drift Infrared Radiation Thermometer Using Chopper Stabilised Pre-Amplifier

A zero-drift, mid–wave infrared (MWIR) thermometer constructed using a chopper stabilised operational amplifier (op-amp) was compared against an identical thermometer that utilised a precision op-amp. The chopper stabilised op-amp resulted in a zero-drift infrared radiation thermometer (IRT) with approximately 75% lower offset voltage, 50% lower voltage noise and less susceptibility to perturbation by external sources. This was in comparison to the precision op-amp IRT when blanked by a cover at ambient temperature. Significantly, the zero-drift IRT demonstrated improved linearity for the measurement of target temperatures between 20 °C and 70 °C compared to the precision IRT. This eases the IRT calibration procedure, leading to improvement in the tolerance of the temperature measurement of such low target temperatures. The zero-drift IRT was demonstrated to measure a target temperature of 40 °C with a reduction in the root mean square (RMS) noise from 5 K to 1 K compared to the precision IRT.

Identification of wavelength regions for non-contact temperature measurement of combustion gases at high temperatures and high pressures

Stationary gas turbines are still an important part of today’s power supply. With increasing temperature of the hot combustion gas inside a gas turbine, the efficiency factor of the turbine increases. For this reason, it is intended to operate turbines at the highest possible gas temperature. Therefore, in the combustion chamber and especially at the position of the first stage guide vanes the gas temperature needs to be measured reliably. To determine the gas temperature, one promising approach is the application of a non-contact measurement method using a radiation thermometer. A radiation thermometer can measure the gas temperature remotely from outside of the harsh environment. At ZAE Bayern, a high temperature and high-pressure gas cell has been developed for this purpose in order to investigate gases and gas mixtures under defined conditions at high pressures and high temperatures. This gas cell can be placed in a FTIR-spectrometer in order to characterize the infrared-optical properties of the gases. In this work the measurement setup is introduced and gas mixtures, which are relevant for gas turbine applications are analyzed thoroughly. The derived results are presented and discussed in detail. To identify suitable wavelength regions for non-contact gas temperature measurements, first tests have been performed. Based on these tests, an appropriate wavelength region could be chosen, where future gas temperature measurements can be carried out.