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The paper is mainly concerned with how the gas‐turbine designer can choose the best design of liquid or gaseous fuel combustion chamber for his purpose. In the method proposed, combustion chamber test data are expressed in a way which gives the most general information about the design, by introducing dimensionless performance criteria. These criteria are then plotted in ways which enable the various chamber designs to be compared. The treatment deals implicitly with the conditions which satisfactory model tests must fulfil. An idealized model of a gas‐turbine combustion chamber is introduced in the light of which the effects of changes in overall fuel/air ratio can be explained more satisfactorily than when conditions in the flame‐tube are supposed homogeneous.

The purpose is to develop and apply a systematic simulation approach for dynamic analysis in order to study a two combustion chambers liquid propellant engine.

The logic of the simulation method and the software is based on following the liquids. The implicit nonlinear algebraic equations are solved using a number of nested Newton‐Raphson loops, and the nonlinear and time varying differential equations are solved using a first‐order Euler technique.

It is found that the developed simulation code predicts the steady‐state values with errors under 5 percent, and this code has the capability to be used in studying the effect of various elements and subsystems parameters on the forecasting the performance and operation of the engine system.

At present, the research is limited to a specific liquid propellant engine. Development of a general purpose software package for simulation of liquid propellant engines, based on the developed simulation algorithm, is subject of future research.

The major outcome of this research is that verifies liquid engine simulation code may be used as a suitable tool to optimize the engine.

This is the first paper in the area of a two combustion chambers engine simulation and dynamic analysis that is based on the application of an existing simulation algorithm.

Typical performance data for combustion chambers with separate introduction of fuel and air have already been presented in FIG. 1. Comparison with FIG. 7, typical of one‐stream chambers, reveals some important differences. Firstly, the data are neither confined within the inflammability limits nor have their peak at the stoichiometric O.F.A.R.; the shift is usually towards the weak side. Secondly, the ratio of the maximum O.F.A.R. to minimum O.F.A.R. of a given curve may be many times the corresponding range of a one‐stream chamber. Thirdly, the curves do not all terminate at substantially the same value of combustion efficiency. Particularly the second of these features is of great practical importance, for, in gas turbines, combustion chambers are required to cope with a very wide range of O.F.A.R. and must maintain a high efficiency throughout this range. The possibility of designing for a wide O.F.A.R. range is one of the reasons for using a two‐stream in preference to a one‐stream chamber. Some of the design features influencing O.F.A.R. range will be discussed below.

The purpose of this computational fluid dynamics (CFD) study is to give insight about the influence of the piston bowl geometry and the fuel ignition features on the resonance of direct injection diesel engines combustion chambers in order to provide support to the experimental findings on combustion noise.

The resonance due to the burned gases oscillations in a diesel combustion chamber is caused by the sudden rise in pressure due to the initial ignition of the air‐fuel mixture, and leads to the resonance noise. In the CFD study presented here the excitation source is represented by imposing locally in a small area (excitation zone) the pressure and temperature gradients of the start of combustion. The CFD approach is first validated against the acoustic modal theory. A parametric study representing different ignition conditions is then performed with a real bowl geometry.

The solutions obtained are analysed in terms of the energy of resonance (ER) and the response in the frequency domain. It was found that the response in frequency only varies with the diameter of the bowl, while the ER varies significantly in function of the injection conditions.

These first conclusions need to be verified on the one hand by taking into account the piston motion, and, on the other hand, by modelling in a more realistic way the combustion excitation.

This CFD study has brought some insight into the flow phenomena that affect the resonance modes of a combustion chamber.

This CFD study uses a novel methodology to model the effect of the combustion excitation on the resonance modes of a combustion chamber.

THE advent of gas‐turbines as power plants for military and civil aircraft has demonstrated certain actual and potential advantages over the use of conventional piston engines which ensure the increased adoption and importance of this type of prime mover. This increased use of gas‐turbines in the aircraft field has necessitated careful reconsideration of the fuel supply position in the light of the new engine requirements. It is clear therefore that a detailed knowledge of all aspects of fuel performance in gas‐turbine‐powered aircraft is needed in order to enable the necessary usable fuel supply position to be assessed, and any resulting problems to be surmounted.

An engine of the character described comprising a centrifugal compressor having intake eyes symmetrically disposed on opposite sides of its plane of rotation and a plurality of outlets symmetrically disposed in circular disposition about its axis of rotation, a corresponding and similarly disposed plurality of air ducts leading from said outlets towards one side of said plane, an axial flow turbine arranged coaxial with said compressor on the same side thereof as that of said ducts and adapted to directly mechanically drive the compressor, a plurality of combustion chambers arranged in circular disposition around said axis, an air duct connecting each of said outlets to one of said chambers, means for introducing fuel into each of said chambers for continuous combustion therein, a combustion product duct leading from each of said chambers to said turbine on the side thereof to which said compressor is located, the construction formed by said air ducts, combustion chambers and combustion product ducts constituting a skeleton structure leaving open access through which air is permitted to enter the compressor intake eye situated nearer the turbine, and an exhaust conduit leading axially away from the side of the turbine opposite to the side to which said combustion products are admitted.

THE performance of a gas turbine fuel can be estimated most conveniently by using a single combustion chamber test unit. Such fuel testing has often shown a lack of repeatability that is difficult to ascribe to normal experimental errors only. In reviewing possible sources of error, the uncontrolled variable of atmospheric humidity has been considered. From past records the average specific humidity in the British Isles is 0·006 lb. water per lb. of dry air while the maximum on any day is unlikely to exceed 0·020 lb. water per lb. of dry air.

The lack of integrity of the piston machine combustion chamber manifests itself in leakages of the working fluid between the piston and the cylinder liner, at valves mounted in the cylinder head and between the head and the liner. An untight combustion chamber leads to decreased power output or efficiency of the engine, while leaks of a fluid may cause damage to many components of the chamber. The actual value of working chamber leak is a desired and essential piece of information for planning operations of a given machine.

This research paper describes causes and mechanisms of leakage from the working chamber of internal combustion engines. Besides, the paper outlines presently used methods and means of leak identification and states that their further development and improvements are needed. New methods and their applicability are presented.

The methods of leak identification have been divided into diagnostic and non-working machine leak identification methods. The need has been justified for the identification of leakage from the combustion chamber of a non-working machine and for using the leakage measure as the value of the cross-sectional area of the equivalent leak, defined as the sum of cross-section areas of all leaking paths. The analysis of possible developments of tightness assessment methods referring to the combustion chamber of a non-working machine consisted in modelling subsequent combustion chamber leaks as gas-filled tank leak, leak from another element of gas-filled tank and as a regulator of gas flow through a nozzle.

A measurement system was built allowing the measurement of pressure drop in a tank with the connected engine combustion chamber, which indicated the usefulness of the system for leakage measurement in units as defined in applicable standards. A pneumatic sensor was built for measuring the cross-sectional area of the equivalent leak of the combustion chamber connected to the sensor where the chamber functioned as a regulator of gas flow through the sensor nozzle. It has been shown that the sensor can be calibrated by means of reference leaks implemented as nozzles of specific diameters and lengths. The schematic diagram of a system for measuring the combustion chamber leakage and a diagram of a sensor for measuring the cross-sectional area of the equivalent leak of the combustion chamber leakage are presented. The results are given of tightness tests of a small one-cylinder combustion engine conducted by means of the set up measurement system and a pre-prototype pneumatic sensor. The two solutions proved to be practically useful.

THE use of metals at temperatures in excess of 1,200 deg. F. and up to temperatures in the vicinity of their melting points is a challenging and fascinating portion of the fight to pass the heat barrier in the design and performance of aircraft and their power plants. The materials available for service in this temperature range are restricted. The considerations of designing structural components involve many more problems than the old criteria of strength to weight ratio and fabrication costs. Such properties as thermal expansion, heat conductivity, surface emissivity and scaling resistance are as important in determining which metal should be used for a given application as are the various measurements of strength heretofore the primary considerations in material selection.

EVERYBODY travelling in air or water by its own power applies the reaction or “repulse” principle, that is to say, it either takes up parts of masses contained within itself or, by means of suitable organs, gathers up parts of the surrounding fluid medium and accelerates these masses at a speed greater than its own travelling speed, and this generally in the direction opposite to that in which it desires to travel; whilst in certain cases, in addition to the force produced by the repulse, a further force is obtained through the forward suction of the fluid medium. Devices intended to utilize only the negative pressure produced by suction, e.g. through lateral ejection by means of radial surfaces running at very high (five‐figure) r.p.m. have not, in spite of repeated endeavours, proved successful.