Search results

IT is usual in theory to treat questions on gas‐flow, as if the flow takes place isentropically, i.e. is subject to the law. This is equivalent to assuming the gas is frictionless or non‐viscous: it also implies that the gas is non‐conducting, for in writing down the equations of motion of a particle we must assume there is no transfer of heat to a neighbouring particle if the changes involved are to be even adiabatic. By ‘adiabatic’ we mean there is no heat transfer between the particle considered and neighbouring particles: by ‘isentropic’ we mean there is no change of entropy, so that an isentropic change implies while an adiabatic change does not.

When the flow in long pipes is considered, the frictional losses occurring before the pipe entry can usually be neglected. If thus an isentropic flow up to the pipe entry were assumed, the Grashof and Zeuner equation (A. 12) could be represented in the ψ—p plane of the dimensionless de Saint Venant and Wantzel equation (A.23). Using the dimensionless equations of Appendix II, the above plane is developed to cover adiabatic flows in general.

In this paper the isothermal flow of perfect gases is discussed following the gas dynamic approach of applying the continuity, momentum and energy equations. Flow functions for isothermal, reversible, one‐dimen‐sional flow are derived and these are represented graphically. Isothermal flow in convergent‐divergent nozzles is analysed and the variation of the derived flow functions is depicted.

THE flow of gases in nozzles has been considered by many authors. The results are usually shown in the form of curves or tables of figures. Practical use of these diagrams or tables is, however, made difficult by the large number of variables concerned and the difficulty of finding convenient scales.

The purpose of the study is to measure the mass flow in the flow through the labyrinth seal of the gas turbine and compare it to the results of numerical simulation. Moreover the capability of two turbulence models to reflect the phenomenon will be assessed. The studied case will later be used as a reference case for the new, original design of flow control method to limit the leakage flow through the labyrinth seal.

Experimental measurements were conducted, measuring the mass flow and the pressure in the model of the labyrinth seal. It was compared to the results of numerical simulation performed in ANSYS/Fluent commercial code for the same geometry.

The precise machining of parts was identified as crucial for obtaining correct results in the experiment. The model characteristics were documented, allowing for its future use as the reference case for testing the new labyrinth seal geometry. Experimentally validated numerical model of the flow in the labyrinth seal was developed.

The research studies the basic case, future research on the case with a new labyrinth seal geometry is planned. Research is conducted on simplified case without rotation and the impact of the turbine main channel.

Importance of machining accuracy up to 0.01 mm was found to be important for measuring leakage in small gaps and decision making on the optimal configuration selection.

The research is an important step in the development of original modification of the labyrinth seal, resulting in leakage reduction, by serving as a reference case.

The first compressible flow solution based solely on the locally analytical method is developed. This is accomplished by developing the flow model and locally analytical solution for inviscid subsonic compressible flow. The stream function for irrotational, compressible flow without body forces was chosen as the governing differential equation. To demonstrate the modelling and locally analytical solution, this analysis is then applied to predict the flow in convergent nozzles, both planar and axially symmetric, for different back pressures. Results are presented which demonstrate the effectiveness of this technique.

A GENERAL outline of the processes occurring in the working fluid of a rocket engine has been summarized previously, but the total picture is still far from complete, a number of important phenomena not having been taken into account. Their full analysis would be, however, beyond the scope of this paper, and may be left to specialists more qualified than the author to give an account of combustion processes.

DEAR SIR, It is doubtful whether great practical importance can be attached to the precise location of the sonic section in a de Laval nozzle with friction present, under the assumptions of the one‐dimensional theory of flow. The truth of the matter, however, is that the equations of this approximation do lead to the conclusion that the condition of M 1, where M is the Mach number, prevails in the throat of a convergent‐divergent nozzle only in the limiting case of no friction, contrary to Mr Spalding's assertion in the August issue of AIRCRAFT ENGINEERING. It can occur in a section for which dA/dx 0 only if that section is at the exit of a convergent nozzle.

Describes the propagation of pressure waves when a train passes through a plain tunnel or tunnel equipped with side branches. A non‐homentropic one‐dimensional model is used to predict the flow generated. This model takes into consideration the train and tunnel geometry, the wall friction and heat transfer. The numerical calculation is performed using the classical method of characteristics. Near the train and tunnel ends, or at the junctions with the side branches, the flow is three dimensional. In the one‐dimensional theory, boundary conditions are applied to model the flows across these regions. The model used is validated by comparisons with experimental results. The use of airshafts to attenuate pressure waves is discussed.

This is a reprint of a book that was first published in 1932. As there has been no revision of the contents since the original publication, no work done in the last twenty‐five years is included. Nevertheless, the book includes a con‐siderable amount of material that is still of interest.