Use Of New Generation Instruments In Measurement Of New Steam Expander
For the past twenty years the Centre for Positive Displacement Compressor Technology, at City University, has employed experimental techniques for the measurement of screw compressors’ performance where both experimental data and predicted mathematical models are found to be in agreement with each other. Some of the experimental measuring techniques involve the use of pressure and temperature transducers installed in the housing to determine the vital thermodynamic process characteristics and functioning performance of compressors. Moreover, as advanced technologies were available, measurements were performed in an optical compressor with a transparent window near the discharge port to allow the application of a laser technique, Laser Doppler Velocimetry (LDV), to investigate the axial mean flow and turbulence characteristics inside the working chamber of the male rotor. Recently a prototype two-phase screw steam expander has been designed and developed as a means of power recovery from liquid geothermal brine. An experimental setup has been designed by using a set of new generation instruments to complement the unit’s numerical modeling, from which predictions of an adiabatic efficiency in the order of 70%, were obtained. The testing includes measurements of instantaneous pressure and temperature in the suction and discharge port, instantaneous torque, speed and flow rate as well as monitoring the temperature and pressure of its lubrication system. Furthermore, four miniature high resolution pressure transducers were installed in the expander unit to measure the main rotor inter lobe temporal pressures with respect to crank angle of the main rotor. The high dynamic characteristics and response of the instrument are captured by a real time processor, National Instrument Compact-RIO, data logger and the programming is done using LabVIEW. The paper presents the measuring method, preparation of the instruments, acquisition and processing of the results obtained during experimental investigation of the two-phase screw expander.
Screw Expanders Increase Output and Decrease the Cost of Geothermal Binary Power Plant Systems
A study has been carried out on the feasibility of using screw expanders, as an alternative to turbines, in three types of binary systems, suitable for recovering power from liquid dominated brines. The maximum power that one machine can generate is of the order of 1-3 MW per unit, depending on the type of system, and the brine and cooling conditions. They are shown to be roughly as efficient as turbines, when expanding dry vapour, and they can be coupled directly to a generator, without an intermediate gearbox. They have similar characteristics as two-phase expanders, when their efficiencies are not much reduced. This latter feature enables improvements to be made in the conversion of heat to power, of the order of 30% over conventional ORC systems, from brines in the 100 – 140C temperature range. The costs of these machines are very competitive and it is shown that in a cycle designed for power recovery from brines in the 170210C range, the cost per unit output of the first expander stage may be less than 50% of that of a radial inflow turbine-generator set.
Mathematical Simulation of Combustion of Boron Powder Gas Suspension
Based on a two-phase two-velocity model of a reacting gas-dispersed medium, a mathematical model of combustion of a boron powder gas suspension has been formulated. The results of numerical solution of the problem are presented. The influence of the composition of the gas suspension, its size, size distribution of particles, mass concentration of particles, as well as of the presence of aluminum powder in the suspension on the visible and normal velocities of flame propagation in the gas suspension, is shown. A comparison of the results of calculation with the well-known experimental and theoretical data is carried out. Satisfactory agreement of the predicted results with experimental data is shown.