Jet Mass Flow Rate Research Articles

区画火災における開口噴流の流量測定

Reduced scale experiments were conducted to measure the mass flow rate of door jet from a model fire compartment as the first step of the study on door jet plume and convective heat transfer in compartment fires. As a results, the following findings have been obtained. (1) The mass flow rates of door jet can be obtained based on measurements of O_2 concentration and CO_2 concentration. (2) The mass flow rates of door jet calculated based on the gas analysis and the temperature measurement agreed well when 0.52 is used as the flow coefficient in the latter. (3) Heat release rates of fire source calculated based on gas concentration agreed in average with the heat release rate obtained from mass burning rate of fuel in the free space, but some of them differed significantly from the latter. The difference is thought to be caused by the change of fuel vaporization rate depending on ventilation factor of the compartment.

回転液中紡糸法におけるSn-37 mass%Pb合金細線の断面形状変化

It is difficult to produce the continuous fiber of a low surface tension alloy with a round cross-section by using the In-Rotating-Liquid-Spinning process. The relation between the cross-sectional shape of the fiber and the spinning conditions has been examined by using a Sn-37 mass%Pb alloy. The mean mass flow rate of molten metal jet was almost independent of the superheat of the melt. However, the direction of the jet stream became unstable with increasing superheat of the melt and the fluctuation of the jet diameter at the outlet of the nozzle also increased. The roundness of the cross-section of the obtained fiber increased with decreasing ejection pressure, circumferencial velocity of rotating liquid layer, nozzle diameter, jet incidence angle and density of coolant and with increasing superheat of the melt. The fiber with high roundness could be produced, when the inner pressure of jet was higher than the dynamic pressure of coolant acting on the jet at the incidence point of jet into the liquid layer. The computer simulation of the cooling process of jet has been performed in the temperature range from the ejection to the liquidus temperature of the alloy. The average cooling rates were evaluated to be 0.5∼2.4×105 Ks−1, in the water layer, 1.4∼3.0×104 Ks−1 in the methanol layer and 4.7∼6.5×103 Ks−1 in the salad oil layer, respectively. By using methanol and salad oil as a coolant, a more round fiber could be produced, even if the superheat of the melt was low. The double layers, such as the methanol-water layer and the salad oil-water layer, and the triple layer such as salad oil-methanol-water layers were also effective in producing the fiber with round cross-section.

Influence of inlet conditions on the flowfield in a model gas turbine combustor

The flowfields in gas turbine combustors have not been well understood in either experiments or numerical simulations. To increase the accuracy of flow prediction, numerical errors, which come from turbulence model, mesh size, iteration number, and inlet conditions, should be reduced with the assistance of measurements. However, so far very few experimental data have been obtained to evaluate the numerical models and the predicted results. The purpose of the present study is to obtain the inlet conditions for a combustor in an isothermal model of the gas turbine combustor that was made to demonstrate the fundamental flow structure of swirling flow and jet flow interactions, in order to compare predicted results with measured results and demonstrate the influence of inlet conditions on the flowfield. A very small fiber laser-Doppler velocimeter was used to measure radial velocity in order to understand the recirculating flow and flow interactions. The momentum ratio of the swirl mass flow rate to the jet mass flow rate was taken to be 1.78–7.01, which would cover all loading conditions. The results indicated that the radial velocity at the swirler exit should be given; otherwise the radial velocity should be half the axial velocity, and the swirl velocity at the jet exit also should be considered, so we propose a way to determine swirl velocity at the jet exits. The predicted flow patterns and turbulent kinetic energy profiles show the major flow structure that can be seen in the experiments. The errors due to the influence of inlet conditions on the flowfield could be reduced and the accuracy of prediction increased if the proposed modification is used.

Local Heat Transfer in Turbine Disk Cavities: Part II—Rotor Cooling With Radial Location Injection of Coolant

Detailed radial distributions of rotor heat transfer coefficients are presented for three basic disk-cavity geometries applicable to gas turbines. The experimental apparatus has been designed to obtain local heat transfer data on a number of easily interchangeable rotor surfaces. The method employs thin thermochromic liquid crystal coatings upon the rotor surfaces together with video system data acquisition and computer-assisted image analysis to detect surface color display and to extract heat transfer information. A thermally transient, aerodynamically steady technique is used, which attains consistent thermal boundary conditions over the entire disk cavity. Cooling air is introduced into the disk cavity via a single circular jet mounted perpendicularly into the stator at one of the three radial locations: 0.4, 0.6, or 0.8 times the rotor radius. Rotor heat transfer coefficients have been obtained over a range of parameters including disk rotational Reynolds numbers of 2 to 5 × 105, rotor/stator hub spacing-to-disk radius ratios of 0.025 to 0.15, and jet mass flow rates between 0.10 and 0.40 times the turbulent pumped flow rate of a free disk. The rotor surfaces include a parallel rotor-stator system, a rotor with 5 percent diverging taper, and a similarly tapered rotor with a rim sealing lip at its extreme radius. Results are presented showing the effects of the parallel rotor, which indicate strong variations in local Nusselt numbers for all but rotational speed. These results are compared to associated hub injection data of Part I of this study, demonstrating that overall rotor heat transfer is optimized by either hub injection or radial location injection of coolant dependent upon the configuration. Results with the use of the tapered rotor show significant variations in local Nusselt number compared with those of the parallel rotor, while the addition of a rim sealing lip appears to increase the Nusselt number level.

Local Heat Transfer in Turbine Disk Cavities: Part I—Rotor and Stator Cooling With Hub Injection of Coolant

Results are presented from an experimental study designed to obtain detailed radial heat transfer coefficient distributions applicable to the cooling of disk-cavity regions of gas turbines. An experimental apparatus has been designed to obtain local heat transfer data on both the rotating and stationary surfaces of a parallel geometry disk-cavity system. The method employed utilizes thin thermochromic liquid crystal coatings together with video system data acquisition and computer-assisted image analysis to extract heat transfer information. The color display of the liquid crystal coatings is detected through the analysis of standard video chromanance signals. The experimental technique used is an aerodynamically steady but thermally transient one, which provides consistent disk-cavity thermal boundary conditions yet is inexpensive and highly versatile. A single circular jet is used to introduce fluid from the stator into the disk cavity by impingement normal to the rotor surface. The present study investigates hub injection of coolant over a wide range of parameters including disk rotational Reynolds numbers of 2 to 5 × 105, rotor/stator spacing-to-disk radius ratios of 0.025 to 0.15, and jet mass flow rates between 0.10 and 0.40 times the turbulent pumped flow rate of a free disk. The results are presented as radial distributions of local Nusselt numbers. Rotor heat transfer exhibits regions of impingement and rotational domination with a transition region between, while stator heat transfer shows flow reattachment and convection regions with evidence of an inner recirculation zone. The local effects of rotation, spacing, and mass flow rate are all displayed. The significant magnitude of stator heat transfer in many cases indicates the importance of proper stator modeling to rotor and disk-cavity heat transfer results.

Combustion and flow in a two dimensional spouted bed

A planar, two-dimensional spouted bed laboratory combustor has been studied to determine the interaction among the gas flow, particle flow, and combustion. The facility designed for a maximum thermal power of 5 kW, has a quartz front wall providing full optical access to particle flows and combustion processes. The combustor was characterized in terms of pressure, temperature, gas velocity, and particle velocity profiles and operating limits. Premixed propane and air and a fixed bed height, bed material, injector slot width, and combustor geometry were employed. As in previous investigations of axisymmetric spouted beds, the ratio of particle mass circulation rate to jet mass flow rate was observed to be about ten. Combustion increased this ratio by about ten percent. A pulsating mode of operation was noted with a characteristic frequency of about ten Hz, controlled by the interaction of the particle and gas flows. A simple model for the prediction of particle velocities in the spout agrees with experimental observation.

Two-dimensional jet interaction studies at large values of Reynolds and Mach numbers

The situation chosen for study is a gaseous jet that is injected through a transverse slot nozzle in a wall and into a supersonic external flow which is uniform outside of a turbulent boundary layer. Experiments were conducted with normal, sonic jets and forward-facing steps at external flow Mach numbers of 2.5 to 13, and Reynolds numbers based on running length of 7.5 X 10 to 5.5 x 10. The amplification factor (the upstream interaction force plus the jet thrust normalized by the vacuum thrust of a sonic jet) is relatively insensitive to variations in external flow Mach number and Reynolds number. The effect of pressure ratio on amplification factor is very small when the external flow properties and jet mass flow rate are held constant. Plateau pressures associated with separation upstream of the jet or step, and wall static pressure distributions near the separation line are in good agreement with existing correlations.

Experimental Investigation of Swirling Vortex Motion in Jets

Experiments have been carried out in a series of axisymmetric free turbulent jets with degrees of swirl covering the weak, moderate, and strong ranges, including the case of the onset of reversed flow in the central region of the jet. Measurements are reported of mean axial and swirl velocities, static pressure, and jet width at axial stations up to 15 orifice diameters. Mean velocity and pressure profiles are shown to be effectively similar from an axial distance of four diameters for weak and moderate swirl. For the case of strong swirl, a vortex is generated in the region close to the orifice resulting in a displacement of the axial velocity maximum from the jet axis. After a distance of 10 diameters, the influence of the vortex motion becomes small, and similarity of the profiles is obtained farther downstream. Experimentally determined profiles are described in terms of Gaussian error curves and third-order polynomials. Jet width and mass flow rates of entrained fluid are shown to increase according to the degree of swirl so that, for strong swirl, jet width and rate of entrainment are almost twice those for the nonswirling jet. Results of the decay of velocity and pressure along the axis are compared with values predicted by an approximate theory based on the integration of the Reynolds’ equations of motion. Good agreement is found between results and predictions, and a set of semi-empirical equations is provided from which a complete description of the mean velocity and pressure fields can be obtained for swirling jets.