Effects of Thermal Shock Protection Methods on Pressure Measurements in a Rapid Compression Machine

The study investigates the impact of thermal shock protection methods on pressure measurements in Rapid Compression Machines (RCMs). It focuses on the performance of various pressure transducers, specifically 601A, 701A, 6061B, and 7005, under atmospheric initial conditions. The research emphasizes the importance of mounting techniques and coatings, revealing their significant effects on pressure trace accuracy. Special mounting adaptors for the pressure transducers were designed and manufactured, this enabled simultaneous measurements for all transducers to be made in a single compression stroke. Instantaneous pressure within combustion chamber was measured when air was compressed in RCM from initial pressure and temperatures of 0.1 MPa and 293K respectively, compression ratio was fixed at 13.58. Pressure traces revealed that all pressure values measured using the selected transducers were affected by thermal shock effect, this led into significant deduced end of compression temperature error of up to 8.7 K. Different temperature protection measures were tested and their effectiveness in reducing thermal shock effect was studied. A combination of recessed mounting and silicon coating provided the best thermal shock protection for the pressure transducers tested in this work. The insights gained from this study are crucial for optimizing accuracy of pressure measurements and interpretation in combustion testing rigs.