Inlet Area Ratio Research Articles

Ventilation of Poultry Buildings with Exhaust Fans at One End and Continuous Slot Inlets Along the Sidewalls

Ventilation of buildings for housing floor-raised poultry, with exhaust fans clustered at one end and continuous slot inlets along the sidewalls, was analyzed using relationships for airflow in manifolds. Air velocities measured along the inlets in two poultry buildings were compared to velocities computed using theoretical relationships. The parameter with the greatest effect on uniformity of airflow along the inlets was the inlet discharge coefficient multiplied by the ratio of total slot inlet area to the flow area in the building cross-section, defined as a. For typical poultry buildings without substantial internal obstructions to airflow, variation in air velocity at the slot inlets along the building length was less than 10% when a was less than 0.4. Reductions in air velocity along the inlets are developed from manifold relationships for a range of values of a and F, a dimensionless friction parameter. An example demonstrates application of results to sizing sidewall inlet openings in buildings designed for tunnel ventilation.

Non-uniform velocity effect in a constant-area ejector without a diffuser

A determinate mathematical compressible-flow model, with different velocity profiles applicable in the relevant governing equations for a constant-area ejector without diffuser, was formulated. The twelve governing equations were reduced to a single implicit equation for the primary variable P 0. The flow parameters of the primary, secondary and mixed flow can be calculated directly using the solved value of P 0. Some empirical data for an existing system with a duct area ratio of 0·9643 of the secondary flow to the mixed flow were compared with predicted values. The comparisons show that the one-dimensional compressible-flow analysis gives a fairly good agreement. A shock-like jump phenomenon of the ejector flow was observed experimentally in a previous paper and was also found theoretically in the present study. The performances of a stationary ejector, with different inlet area ratios, and secondary-to-primary stagnation pressure ratios are discussed.

Reply by Authors to G. Y. Anderson

A comments and conclusions about the contents of Ref. 1 appear to be based on a misinterpretation or misunderstanding of its content and intent and a displeasure with the integral analysis used as the standard. The intent of Ref. 1 was and is to show the limitations of assuming a constant-area/constant Mach combustion process for closure of the integral equations of motion in predicting scramjet engine performance compared to the widely accepted one...developed by Billig. The content of the Note does just that, using a representative case. Anderson's attempt to discredit the results presented (using Table 1 in his comment from Fig. 55 of Ref. 8) is a misrepresentation of the facts. First, there are no scramjet performance data given in Ref. 8 for a freestream Mach number of 3.5 at any altitude. Second, the performance numbers at Mach 6 are for a different engine configuration with different values assumed for a number of component efficiencies. Specifically, the performance given in Ref. 8 at Mach 6 is for an aft-mounted engine rather than a nose-mounted configuration with a combustor area ratio of 2.5 rather than 3 and a nozzle exit-to-diffuser inlet area ratio of 2 rather than 1.7. Furthermore, at Mach 6, Ref. 8 assumes an inlet air capture of 0.97 rather than 1.0, an inlet kinetic energy efficiency of 0.975 without including forebody bow shock losses, combustion skin-friction losses that are a factor of 2 to 3 lower than those measured, an exit nozzle efficiency of 0.985 rather than 0.975, and equilibrium thermo-chemistry is the exit nozzle rather than two-thirds frozen. In addition, the integral analysis used in Ref. 8 does not incorporate an oblique precombustion shock model; it permits only no shock or a normal shock. Table 1 of the comment is, therefore, a comparison of apples-to-oranges, and is, at best, misleading in the context presented. Finally, if the same assumptions, geometries, and efficiencies used in Ref. 8 are used in our integral technique, one obtains identical performance predictions. These issues aside, the intent of any integral analysis technique is to provide an accurate engineering tool for predicting overall engine performance and parametric or sensitivity studies at minimum cost. No claim is made that it can predict the details of the flow between the initial and final stations assumed. Multidimensional models (see, e.g., Refs. 9 and 10) are required for that. However, even though a number of increasing complex multidimensional models have been developed and solutions obtained using advanced computational fluid dynamic (CFD) techniques, none have been validated, even for inlet diffusors, because of a lack of experimental data. More importantly, no current CFD technique using the full Navier-Stokes equations can solve for the flow in the region of the precombustion shock because it requires an estimated 10-10 grid points for resolution and 10 time steps for convergence, the combination of which is well beyond the capabilities of the most advanced class VI computer. Alternative methods, such as using an integral solution for the initial and boundary conditions downstream of the precombustion shock and then using CFD codes to iteratively solve for

Combustion Behavior of Solid-Fuel Ramjets

AN experimental investigation was conducted of the combustion behavior in solid fuel ramjets in order to determine the effects of configuration variables and operating conditions on combustion performance. Variables considered were fuel port flow rates, bypass dump momentum and geometry, and bypass ratio. Contents To be used in a tactical situation, the solid-fuel ramjet has to demonstrate combustion stability and high efficiency over the expected operating envelope of altitudes and Mach numbers. It must also show performance comparable to that of liquid-fuel ramjets and ducted rockets. Combustion studies on the solid-fuel ramjet have been underway at United Technologies—Chemical Systems Division since 1971.l The solid-fuel ramjet has two distinct combustion zones within the fuel grain: the recirculation zone behind the sudden expansion inlet, which provides flame stabiliation; and a diffusion flame in the developing boundary layer region after flow reattachment. Unburned gaseous fuel escapes from under the flame at the aft end of the fuel grain and results in decreased combustion efficiency. Aft mixing chambers and bypass air designs are being used to increase the efficiency. A schematic of the solid-fuel ramjet is shown in Fig. 1. The apparatus employed a polymethylmeth acrylate (PMM) fuel with a fuel port to dump inlet area ratio of 9.0 and a fuel port to nozzle throat area ratio of 4.0. The exit area of the grain was held fixed at the initial port area by using a thin orifice plate. The aft mixing chamber had a length to diameter ratio of 2.93. The aft mixing chamber consisted of three interchangeable sections such that the axial location and angular orientation of the bypass dumps could be varied. A summary of the test conditions is presented in Table 1. Figure 2 presents data obtained without bypass air. The regression rate expression indicates a weaker dependence on pressure than the earlier data of Boaz and Netzer.2 Figure 3 presents data obtained with bypass air. A slightly stronger dependence on pressure was shown while regression rate indicated very little or no dependence on air flux for the values tested. In the bypass situation, the mass flux through the grain is low but the pressure is maintained high, due to the total mass flux through the nozzle throat. These conditions minimize the convective heat flux to the fuel surface. For lower mass flux through the grain, the regression rate increases relative to the air flux; thus, more gas with radiative properties (fuel rich) is present. These results indicate that using bypass with PMM fuel changes the principal wall heat flux mechanism from convection to radiation.

Interactions between Screech Tones and Ejector Performance

The thrust augmentation and the dominant acoustic frequency of a family of simple ejectors have been measured at primary stagnation pressures up to 6 atm. The convergent primary nozzle induced atmospheric air into a selection of constant diameter ducts that provided length-diameter ratios between 1 and 11 and an inlet area ratio around 25. The thrust-augmentation data tended to follow the monotonic reduction in performance that theory predicts with increasing pressures, except at certain pressures where the trend reversed. At these pressures, the acoustic frequency tuned to a transverse resonant mode of the mixing duct. It is speculated that resonance intensifies the large-scale vortices that mix the two streams and, at the same time, give rise to screech tones by interacting with the shock structure in the underexpanded jet.

Typical Performance Characteristics of Gas Turbine Radial Compressors

If the peak impeller and diffuser efficiencies are prescribed, it is found that the characteristics of high-speed radial compressors with straight radial blades are basically functions of the inducer and diffuser throat areas. Estimated characteristics for twenty-seven compressor geometries are presented to indicate the effects of inducer blade angle, diffuser throat to impeller inlet area ratio, and impeller tip to inducer RMS diameter ratio. The probable location of compressor surge as influenced by inducer and diffuser blade stalling is discussed, and comparisons of estimated and test compressor characteristics are given.