This thesis outlines past work on solid-handling jet pumps and reviews both practical and theoretical approaches made by workers investigating jet pumps. It was found that there were no theoretical studies of solids-handling jet pumps although these devices have been, and are increasingly being, used for solids-handling applications. Theoretical studies of jet-pumps, without entrained solids, suggest that the integral moment equations can be used to predict events in the mixing tube. It was considered reasonable to adopt this approach when trying to predict mixing tube events when solids were entrained in the jet pump secondary flow, and equations are developed to include solid material. The solids are assumed to be completely separate from the fluid with no interaction between them. An experimental rig was built with provision to eject air into a pipe, which represented a jet pump mixing tube. The ejected air entrained secondary air which contained polystyrene beads of mean diameter 700 microns. Measurements made included the wall static pressure, air velocity, obtained from measurements taken with a Pitot-static tube, and solids mass flow, obtained from measurements taken with an isokinetic sampling device. Using the information gained from the experimental work, profiles of velocity and mass flow were obtained for up to twelve axial locations. These data were used as input for a computer program written especially to solve the integral momentum equations previously set up. The computer used was an ICL 1906A. The object was to compare the experimental and theoretical axial pressure, velocity and solid concentration changes. It was found that good agreement was obtained between experimental and computed values when no solids were present, but only limited agreement when solids were present. The lack of good agreement is this latter case was attributed to the fact that it had been assumed that the solid particles would, at all time, be at the same velocity as the air, whereas this was not found to be so. It is concluded that this work provides a basis from which others can proceed to provide design data for solids-handling jet pumps; devices which will find increasing use in the future.

A digital computer model to simulate the starting and low speed running characteristics of an Hydrostatic Transmissions Ltd hydraulic motor has been developed. The inelasticity of the oil columns connected to, and within, the motor cause extremely high instantaneous rates of change of pressure. This produces numerical stability problems if normal integration methods are employed and a 'pseudo-analytical' method has been developed to overcome this. A rigorous evaluation of the technique shows that it can be applied to a wide range of hydraulic simulations. The hydraulic motor is of the radial piston-eccentric type with the piston forces transmitted to the eccentric by a fully floating pentagon. A detailed analysis of the torque developed by the motor is derived with the motor internal friction described by the three coefficients of friction between piston-cylinder wall, piston-pentagon and pentagon-eccentric. The evaluation of these coefficients is from empirically derived MON torque efficiencies measured at different motor speeds and pressures. It has been shown conclusively by experimental means that the tor developed when the motor shaft is held stationary is dependent not only on the motor pressure level and angle of rotation, but c significantly, on the rate at which the pressure is raised to the measuring level. A simple theoretical model is used to explain the reasons for this effect and it is deduced that in general motor with significant internal friction will exhibit this effect. The overall model of the motor and system is compared to experience results and is shown to exhibit the sort of characteristics exp. The levels of motor pressure, torque and speed predicted by the are, in the first instance, less than those measured and this is shown to be due to the oversimplification of certain parts of the model.

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Intermittent gas flow through the suction and discharge ports of a screw compressor generates pressure oscillations in the suction and discharge systems. These have been recognised as the main source of structural vibration and noise within the compressor system. Parameters proposed in earlier studies did not help in finding a means to reduce these gas pulsations. This thesis describes a detailed analytical and experimental study of the screw compressor process, which was therefore carried out to predict the level of gas pulsations thus generated and how they could be reduced. Three different simulation models were used to determine the pressure variations within the discharge chamber. These comprised a thermodynamic model of the screw compressor discharge process, a 3-D CFD model of flow through the compressor, originally used to predict pressure variations, and a coupled model which joins the 3-D model of flow in the discharge chamber with a thermodynamic model of the working chamber and the discharge system. The last model accounts for the complex geometry of the discharge chamber and reduces computational time. It was shown in the simulation results that the shape of the discharge port is an important parameter which influences the level of gas pulsations in the discharge chamber. If selected carefully it can reduce gas pulsations without a substantially adverse effect on the compressor performance. The analytical procedure used was then validated in a test programme, carried out on a standard oil injected air compressor to compare predicted and measured pulsations within it. Test results confirmed the trends shown by the predictions.

The conventional quasi-steady theory for the behaviour of meters in pulsating flow is that at any instant the differential pressure is only dependent on the acceleration of the flow due to the contraction and is given by the steady flow relationship. The analysis presented in this thesis is based on a quasi-steady theory modified to take into account the additional instantaneous differential pressure due to the temporal acceleration of the flow. Relationships are derived for metering errors in terms of the r. m. s. amplitude of the differential pressure pulsation and a Strouhal Number dependent on the waveform of the velocity pulsation. To test the validity of the derived theoretical relationships the behaviour of square edge orifice plates with corner tappings and of venturi nozzles were investigated in pulsating air flows. A piston pulsator was built on which the stroke can be varied to obtain a required pulsation amplitude while the machine is running at frequencies up to 50 Hz. The results of the tests showed that, although there were some discrepancies, the theoretical relationships were basically sound. It was found that it was possible to define when pulsations were significant in terms of the r. m. s. amplitude of the differential pressure fluctuation. It was also possible to determine an effective Strouhal Number when temporal inertia effects became significant. No basic differences in the behaviour of the two types of meter were detected but certain predictable effects due to compressibility were observed in tests on the venturi nozzles. The techniques for reducing metering errors due to pulsations are reviewed In the light of the analysis and experimental results. Criteria by which the pulsation conditions can be properly assessed and appropriate courses of action for reducing metering error are suggested.

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