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The present study systematically investigates through experiments the influence of Reynolds number on a plane jet issuing from a radially contoured, rectangular slot nozzle of large aspect ratio. Detailed velocity measurements were performed for a jet exit Reynolds number spanning the range 1500≤Reh≤16 500, where Reh≡Ubh/υ with Ub as the momentum-averaged exit mean velocity, h as the slot height, and υ as the kinematic viscosity. Additional centerline measurements were also performed for jets from two different nozzles in the same facility to achieve Reh=57 500. All measurements were conducted using single hot-wire anemometry to an axial distance (x) of x≤160h. These measurements revealed a significant dependence of the exit and the downstream flows on Reh despite all exit velocity profiles closely approximating a “top-hat” shape. The effect of Reh on both the mean and turbulent fields is substantial for Reh<10 000 but becomes weaker with increasing Reh. The length of the jet’s potential core, initial primary-vortex shedding frequency, and far-field rates of decay and spread all depend on Reh. The local Reynolds number, Rey0.5≡2Ucy0.5/υ, where Uc and y0.5 are the local centerline velocity and half-width, respectively, are found to scale as Rey0.5∼x1/2. It is also shown that, for Reh≥1500, self-preserving relations of both the turbulence dissipation rate (ε) and smallest scale (η), i.e., ε∼Reh3(x/h)−5/2 and η∼Reh−3/4(x/h)5/8, become valid for x/h≥20.

The influence of initial flow conditions on the passive scalar field of a turbulent free jet issuing from the round nozzle is investigated in this paper by a review of the literature and a detailed experimental study. Two sets of distinctly different initial conditions are generated using two nozzle types: a smooth contraction and a long straight pipe. The present measurements of the passive scalar (temperature) field were conducted in a slightly heated air jet from each nozzle at a Reynolds number of 16 000 using identical experimental facilities and a single measurement technique. Significant differences between the flows from the two nozzles are revealed throughout the measured flow region which covers the axial range from 0 to 70 jet exit diameters. The study suggests that the differences observed in the statistics of the scalar field may be related to differences in the underlying turbulence structure of the jet in the near field. The present findings support the analytical result of George (1989) that the entire flow is influenced by the initial conditions, resulting in a variety of self-similar states in the far field.

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The first measurement of the influence of Stokes number on the distributions of particle concentration and velocity at the exit of a long pipe are reported, together with the subsequent influence on the downstream evolution of these distributions through a particle-laden jet in co-flow. The data were obtained by simultaneous particle image velocimetry and planar nephelometry using four cameras to provide high resolution through the first 30 jet diameters and also correction for optical attenuation. These data provide much more detailed information than is available from previous measurements. From them, new understanding is obtained of how the Stokes number influences the flow at the jet exit plane and how this influence propagates throughout the jet.

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An analysis of system operation and performance has been undertaken, for the first time, of a solar-hybrid coal-toliquids polygeneration facility incorporating solar resource variability. The energetic and environmental performance of a coal-toliquids process that is integrated with a solar hybridized, oxygen blown, atmospheric pressure gasifier (CTL sol ) is compared with that of a reference, nonsolar, autothermal, pressurized gasification integrated, CTL ref configuration. To allow the plant to respond to solar resource transience, pressurized storage of upgraded syngas and oxygen is incorporated into the proposed CTL sol system. The CTL sol process is simulated using a dynamic model that assumes pseudosteady state operation at each time-step, for a 12month, hourly averaged solar insolation time-series. Both the CTL sol and CTL ref systems were modeled using AspenPlus and Aspen HYSYS (v 7.1) software. The analysis of the CTL sol system's performance showed an annually averaged improvement of 21% to the total energetic output and a reduction of 30% in the mine-to-tank greenhouse gas emissions relative to the CTL ref system assuming equilibrium gasification conditions of 1400 °C and 1 bar-a. The integration of a pressurized syngas storage facility was shown to enable the CTL sol system to allow the variation in throughput of each unit of process equipment to be maintained within normal operational ranges despite the fluctuations in the transient solar input to the solar-hybrid coal gasification process.