Abstract: In a schlieren optical system, a laser beam is passed through the jet flow and the ambient around the jet flow, and a high speed sampling is performed using a high speed photo sensor while displacing measurement points. The value obtained by sampling represents a result of the optical path caused curved by a density gradient generated in an arc-shape from the center of the jet flow. The value is subjected to a high speed discrete Fourier transform and decomposed into frequency components which constitute the noise. Thereafter, Abel inversion is performed on data belonging to a particular frequency to obtain a density gradient in the radial direction from the center of the jet flow. The obtained density gradient is visualized in a graph display, so that the position of the sound source and the state of the jet flow can be accurately grasped.

Abstract: A gaseous fuel injector 3 supplies gaseous fuel from a compressed gas cylinder 1 into a measuring portion thin tube 5 and pressure change in the tube is measured by a pressure measuring device 4 through a small hole provided in the thin tube 5. An extension thin tube 6 for removing the influence of reflected waves is provided on the downstream side of the measuring portion thin tube 5. There is provided at the downstream side end of the extension thin tube a back pressure valve 13 for uniformly increasing the pressure in the tube and for bringing the pressure close to the actual environment in the engine cylinder. Also, a tapered-shape nozzle is arranged in the measuring portion thin tube 5. Pressure measured by the pressure measuring device 4 is transduced into mass flow rate in the thin tube according to a predetermined calculation formula. Accordingly, it is possible to measure instantaneous mass flow rate of gaseous fuel injected from the gaseous fuel injector.

Abstract: In a schlieren optical system, a laser beam is passed through the jet flow and the ambient around the jet flow, and a high speed sampling is performed using a high speed photo sensor while displacing measurement points. The value obtained by sampling represents a result of the optical path caused curved by a density gradient generated in an arc-shape from the center of the jet flow. The value is subjected to a high speed discrete Fourier transform and decomposed into frequency components which constitute the noise. Thereafter, Abel inversion is performed on data belonging to a particular frequency to obtain a density gradient in the radial direction from the center of the jet flow. The obtained density gradient is visualized in a graph display, so that the position of the sound source and the state of the jet flow can be accurately grasped.

Abstract: A gaseous fuel injector 3 supplies gaseous fuel from a compressed gas cylinder 1 into a measuring portion thin tube 5 and pressure change in the tube is measured by a pressure measuring device 4 through a small hole provided in the thin tube 5. An extension thin tube 6 for removing the influence of reflected waves is provided on the downstream side of the measuring portion thin tube 5. There is provided at the downstream side end of the extension thin tube a back pressure valve 13 for uniformly increasing the pressure in the tube and for bringing the pressure close to the actual environment in the engine cylinder. Also, a tapered-shape nozzle is arranged in the measuring portion thin tube 5. Pressure measured by the pressure measuring device 4 is transduced into mass flow rate in the thin tube according to a predetermined calculation formula. Accordingly, it is possible to measure instantaneous mass flow rate of gaseous fuel injected from the gaseous fuel injector.