A New High-Performance Engine Indicator of the Strain-Gage Type

Pressure changes in the working fluid largely determine the performance of heat engines. For this reason, accurate pressure indications are of primary importance for studies of engine operation. Pressure indicators have been in use for many years, but performance defects have restricted their value even for laboratory and test-stand work. The operating limitations have been due to the fact that available pressure receivers have been sensitive not only to pressure but also to temperature, to mechanical strains due to mounting effects, and to mechanical vibrations in the walls of the pressure chamber. I t is the purpose of this paper to describe the features of a new pressure receiver using a high-flexibility catenary-type diaphragm and a temperature-compensating wirewound strain gage to give satisfactory pressure-measuring characteristics with greatly reduced response to temperature and extraneous mechanical effects. (I) PERFORMANCE REQUIREMENTS FOR ENGINE