Katsuyoshi Tanimizu

Thrust Nozzle Design Study for a Quasi-Axisymmetric Scramjet-Powered Vehicle

The design of a nozzle of an unfueled quasi-axisymmetric scramjet model is optimized for minimum drag for a Mach 8 flight condition. The approach to the nozzle design is to develop a simple force-prediction methodology in an optimization study. The study is completed for an unfueled configuration, but the approach could be used for fueled configuration by including appropriate combustion modeling. The effects of the nozzle design on the overall vehicle performance are included. The overall drag of the baseline model for the optimization study was measured in the T4 shock tunnel for Mach numbers ranging from 5.7 to 10.3, confirming the suitability of the force-prediction methodology. The results of the nozzle-optimization study show that performance is limited by the nozzle area ratio that can be incorporated into the vehicle without leading to too large of a base diameter of the vehicle and increasing the external drag of the vehicle. The drag of vehicle designs at different flight Mach numbers is investigated in a parametric study for Mach numbers from 6 to 10. The results confirm that longer nozzles are better at higher Mach numbers. Copyright

Experimental Investigation of Heat Transfer Characteristics of Pseudocritical Carbon Dioxide in a Circular Horizontal Tube

Forced convection heat transfer of supercritical carbon dioxide in circular horizontal tube, d = 8.7 mm, at relatively high Reynolds number (2×104 < Re < 105) is investigated. Experiments are carried out at two mass flow rates of 0.011 and 0.014 kg/s, for fluid inlet temperatures from 20 to 70°C, system pressures from 75 to 90 bar and constant heat flux of 20 kW/m2. Averaged heat transfer coefficients at several locations are obtained to investigate the influence of the fluid bulk temperature and pressure, respectively, on the forced convection heat transfer in the tube. The, the experimental results are then compared with a widely used empirical correlation. The results indicate that the effect of buoyancy on the heat transfer coefficient cannot be ignored in the near-critical and pseudocritical regions of fluid in this flow geometry. This dependency is believed to be due to the extreme dependence of fluid properties to temperature and pressure in this region.© 2012 ASME

Measurement and prediction of the force of an unfuelled axisymmetric scramjet model

A stress wave force balance has been used to measure the net drag force of a non-fueled axisymmetric scramjet model in the T4 free piston shock tunnel at The University of Queensland. The nozzle-supply enthalpy was varied from 2.5 to 8.0 MJ/kg. The measured results compare well with predictions based on combining a simple hypersonic theoretical model and CFD results. A reduction in drag coefficient with increasing Reynolds number was observed. Numerical simulations are being used to redesign the thrust nozzle of the scramjet to improve the thrust performance of the nozzle. An initial optimization study was conducted in order to minimize the net drag of the scramjet model. The results indicate that a 5% reduction in drag coefficient of the scramjet is possible by nozzle redesign.

Parallel self-mixing flow sensor using monolithic VCSEL array

This paper describes the first multi-channel velocity sensor based on a self mixing effect in a monolithic VCSEL array. The self-mixing signals are obtained directly via the feedback caused variation in laser junction voltage, omitting the need for a photodetector. This solution, enabling concurrent acquisition of a plurality of signals, offers significant technological advantage over single channel implementation as it removes the need to scan the target in a raster fashion. In comparison with the spot-raster imaging sensors, the acquisition time is significantly shortened - the mechanical scanning process in is replaced by concurrent acquisition of several channels enabling flow velocity to be sensed on a 2D grid by performing a single sweep of the area. The system was used to measure the velocity profile of fluid flow resembling that of blood circulation in peripheral blood vessels.