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R J Miller - One of the best experts on this subject based on the ideXlab platform.
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The Development of Turbine Exit Flow in a Swan-Necked Inter-Stage Diffuser
2020Co-Authors: R J MillerAbstract:ABSTRACT This paper describes both the migration and dissipation of Flow phenomena downstream of a transonic high-pressure turbine stage. The geometry of the HP stage Exit duct considered is a swan-necked diffuser similar to those likely to be used in future engine designs. The paper contains results both from an experimental programme in a turbine test facility and from numerical predictions. Experimental data was acquired using three fast-response aerodynamic probes capable of measuring Mach number, whirl angle, pitch angle, total pressure and static pressure. The probes were used to make time-resolved area traverses at two axial locations downstream of the rotor trailing edge. A 3D time-unsteady viscous NavierStokes solver was used for the numerical predictions. The unsteady Exit Flow from a turbine stage is formed from rotordependent phenomena (such as the rotor wake, the rotor trailing edge recompression shock, the tip-leakage Flow and the hub secondary Flow) and vane-rotor interaction dependant phenomena. This paper describes the time-resolved behaviour and three-dimensional migration paths of both of these phenomena as they convect downstream. It is shown that the inlet Flow to a downstream vane is dominated by two corotating vortices, the first caused by the rotor tip-leakage Flow and the second by the rotor hub secondary Flow. At the inlet plane of the downstream vane the wake is extremely weak and the radial pressure gradient is shown to have caused the majority of the high loss wake fluid to be located between the mid-height of the passage and the casing wall. The structure of the Flow indicates that between a high pressure stage and a downstream vane simple two-dimensional blade row interaction does not occur. The results presented in this paper indicate that the presence of an upstream stage is likely to significantly alter the structure of the secondary Flow within a downstream vane. The paper also shows that vane-rotor interaction within the upstream stage causes a 10° circumferential variation in the inlet Flow angle of the 2 nd stage vane
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Performance of Choked Unsteady Ejector-Nozzles for use in
2016Co-Authors: Pressure-gain Combustors, Jonathan Jh Heffer, R J MillerAbstract:If the conventional steady Flow combustor of a gas turbine is replaced with a device which achieves a pressure gain during the combustion process then the thermal efficiency of the cycle is raised. All such ‘Pressure Gain Combustors ’ (e.g. PDEs, pulse combustors or wave rotors) are inherently unsteady Flow devices. For such a device to be practically installed in a gas turbine it is necessary to design a downstream row of turbine vanes which will both accept the combustors unsteady Exit Flow and deliver a Flow which the turbine rotor can accept. The design requirements of such a vane are that its Exit Flow both retains the maximum time-mean stagnation pressure gain (the pressure gain produced by the combustor is not lost) and minimises the amplitude of unsteadiness (reduces unsteadiness entering the downstream rotor). In this paper the Exit of the pressure gain combustor is simulated with a cold unsteady jet. The first stage vane is simulated by a one-dimensional choked ejector nozzle with no turning. The time-mean and rms stagnation pressure at nozzle Exit is measured. A number of geometric configurations are investigated and it is shown that the optimal geometry both maximizes time mean stagnation pressure gain (75% of that in the Exit of the unsteady jet) and minimizes the amplitude of unsteadiness (1/3 of that in the primary jet). The structure of the unsteady Flow within the ejector nozzle is determined computationally
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the development of turbine Exit Flow in a swan necked inter stage diffuser
American Society of Mechanical Engineers International Gas Turbine Institute Turbo Expo (Publication) IGTI, 2003Co-Authors: R J Miller, Roger Moss, R W Ainsworth, Neil William HarveyAbstract:This paper describes both the migration and dissipation of Flow phenomena downstream of a transonic high-pressure turbine stage. The geometry of the HP stage Exit duct considered is a swan-necked diffuser similar to those likely to be used in future engine designs. The paper contains results both from an experimental programme in a turbine test facility and from numerical predictions. Experimental data was acquired using three fast-response aerodynamic probes capable of measuring Mach number, whirl angle, pitch angle, total pressure and static pressure. The probes were used to make time-resolved area traverses at two axial locations downstream of the rotor trailing edge. A 3D time-unsteady viscous Navier-Stokes solver was used for the numerical predictions. The unsteady Exit Flow from a turbine stage is formed from rotor-dependent phenomena (such as the rotor wake, the rotor trailing edge recompression shock, the tip-leakage Flow and the hub secondary Flow) and vane-rotor interaction dependant phenomena. This paper describes the time-resolved behaviour and three-dimensional migration paths of both of these phenomena as they convect downstream. It is shown that the inlet Flow to a downstream vane is dominated by two corotating vortices, the first caused by the rotor tip-leakage Flow and the second by the rotor hub secondary Flow. At the inlet plane of the downstream vane the wake is extremely weak and the radial pressure gradient is shown to have caused the majority of the high loss wake fluid to be located between the mid-height of the passage and the casing wall. The structure of the Flow indicates that between a high pressure stage and a downstream vane simple two-dimensional blade row interaction does not occur. The results presented in this paper indicate that the presence of an upstream stage is likely to significantly alter the structure of the secondary Flow within a downstream vane. The paper also shows that vane-rotor interaction within the upstream stage causes a 10° circumferential variation in the inlet Flow angle of the 2nd stage vane.© 2003 ASME
Geoffrey M Dailey - One of the best experts on this subject based on the ideXlab platform.
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the effect of blade tip geometry on the tip leakage Flow in axial turbine cascades
Journal of Turbomachinery-transactions of The Asme, 1992Co-Authors: F J G Heyes, H P Hodson, Geoffrey M DaileyAbstract:The phenomenon of tip leakage has been studied in two linear cascades of turbine blades. The investigation includes an examination of the performance of the cascades with a variety of tip geometries. The effects of using plain tips, suction side squealers, and pressure side squealers are reported. Traverses of the Exit Flow field were made in order to determine the overall performance. A method of calculating the tip discharge coefficients for squealer geometries is put forward. In linking the tip discharge coefficient and cascade losses, a procedure for predicting the relative performance of tip geometries is developed
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the effect of blade tip geometry on the tip leakage Flow in axial turbine cascades
ASME 1991 International Gas Turbine and Aeroengine Congress and Exposition, 1991Co-Authors: F J G Heyes, H P Hodson, Geoffrey M DaileyAbstract:The phenomenon of tip leakage has been studied in two linear cascades of turbine blades.The investigation includes an examination of the performance of the cascades with a variety of tip geometries. The effects of using plain tips, suction side squealers and pressure side squealers are reported. Traverses of the Exit Flow field were made in order to determine the overall performance.A method of calculating the tip discharge coefficients for squealer geometries is put forward. In linking the tip discharge coefficient and cascade losses a procedure for predicting the relative performance of tip geometries is developed. The model is used to examine the results obtained using the different tip treatments and to highlight the important aspects of the loss generation process.Copyright © 1991 by ASME
Zhiqiang Han - One of the best experts on this subject based on the ideXlab platform.
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numerical study of the impact on high pressure and evaporating spray behavior of nozzle cavitation at typical diesel engine conditions
International Communications in Heat and Mass Transfer, 2017Co-Authors: Xiang Wang, Zhiqiang HanAbstract:Abstract In order to more accurately reproduce diesel sprays a strategy including measurement of nozzle inlet pressure at the realistic diesel injection condition, modeling of nozzle cavitating Flow and detailed coupling of nozzle Exit Flow and spray was presented, moreover, the validity of this strategy was firstly verified against the quantitative spray data obtained by planar laser induced exciplex fluorescence (PLIEF) technique. Based on the above strategy, the effect of cavitation phenomenon on spray formation at the typical diesel engine condition was further evaluated. The final numerical results mainly clarified that the contribution of cavitation phenomena to primary breakup is quite appreciable, and subsequently the evolution of the high-pressure and evaporating diesel spray structure greatly changes as cavitation occurs inside fuel injection nozzles. Moreover, evaluating the effects of cavitation phenomena on realistic diesel spray cannot be only confined to primary breakup or near-nozzle field.
Ricardo Martinezbotas - One of the best experts on this subject based on the ideXlab platform.
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mixed Flow turbines inlet and Exit Flow under steady and pulsating conditions
Journal of Turbomachinery-transactions of The Asme, 2001Co-Authors: N Karamanis, Ricardo MartinezbotasAbstract:The performance and detailed Flow characteristics of a high pressure ratio mixed Flow turbine has been investigated under steady and pulsating Flow conditions. The rotor has been designed to have a nominal constant incidence (based on free vortex Flow in the volute) and it is for use in an automotive high speed diesel turbocharger. The results indicated a departure from the quasi-steady analysis commonly used in turbocharger turbine design. The pulsations from the engine have been followed through the inlet pipe and around the volute; the pulse has been shown to propagate close to the speed of sound and not according to the bulk Flow velocity as stated by some researchers. The Flow entering and Exiting the blades has been quantified by a laser Doppler velocimetry system. The measurements were performed at a plane 3.0 mm ahead of the rotor leading edge and 9.5 mm behind the rotor trailing edge. The turbine test conditions corresponded to the peak efficiency point at 29,400 and 41,300 rpm. The results were resolved in a blade-to-blade sense to examine in greater detail the nature of the Flow at turbocharger representative conditions. A correlation between the combined effects of incidence and Exit Flow angle with the isentropic efficiency has been shown. The unsteady Flow characteristics have been investigated at two Flow pulse frequencies, corresponding to internal combustion engine speeds of 1600 and 2400 rpm. Four measurement planes have been investigated: one in the pipe feeding the volute, two in the volute (40 deg and 130 deg downstream of the tongue) and one at the Exit of the turbine. The pulse propagation at these planes has been investigated; the effect of the different planes on the evaluation of the unsteady isentropic efficiency is shown to be significant. Overall, the unsteady performance efficiency results indicated a significant departure from the corresponding steady performance, in accordance with the inlet and Exit Flow measurements.
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mixed Flow turbines inlet and Exit Flow under steady and pulsating conditions
Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery, 2000Co-Authors: N Karamanis, Ricardo MartinezbotasAbstract:The performance and detailed Flow characteristics of a high pressure ratio mixed Flow turbine has been investigated under steady and pulsating Flow conditions. The rotor has been designed to have a nominal constant incidence (based on free vortex Flow in the volute) and it is for use in an automotive high speed diesel turbocharger. The results indicated a departure from the quasi-steady analysis commonly used in turbocharger turbine design. The pulsations from the engine have been followed through the inlet pipe and around the volute; the pulse has been shown to propagate close to the speed of sound and not according to the bulk Flow velocity as stated by some researchers.The Flow entering and Exiting the blades has been quantified by a laser Doppler velocimetry system. The measurements were performed at a plane 3.0 mm ahead of the rotor leading edge and 9.5 mm behind the rotor trailing edge. The turbine test conditions corresponded to the peak efficiency point at 29,400 and 41,300 rpm. The results were resolved in a blade-to-blade sense to examine in greater detail the nature of the Flow at turbocharger representative conditions. A correlation between the combined effects of incidence and Exit Flow angle with the isentropic efficiency has been shown.The unsteady Flow characteristics have been investigated at two Flow pulse frequencies, corresponding to internal combustion engine speeds of 1600 and 2400 rpm. Four measurement planes have been investigated: one in the pipe feeding the volute, two in the volute (40° and 130° downstream of the tongue) and one at the Exit of the turbine. The pulse propagation at these planes has been investigated; the effect of the different planes on the evaluation of the unsteady isentropic efficiency is shown to be significant. Overall, the unsteady performance efficiency results indicated a significant departure from the corresponding steady performance, in accordance with the inlet and Exit Flow measurements.© 2000 ASME
Shinhyoung Kang - One of the best experts on this subject based on the ideXlab platform.
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Flow at the centrifugal pump impeller Exit with circumferential distortion of the outlet static pressure
Journal of Fluids Engineering-transactions of The Asme, 2004Co-Authors: Soonsam Hong, Shinhyoung KangAbstract:The effects of circumferential outlet distortion of a centrifugal pump diffuser on the impeller Exit Flow were investigated. A fence with sinusoidal width variation was installed at the vaneless diffuser Exit. The Flow field was measured at the impeller Exit with and without the fence, using a hot film probe and an unsteady pressure sensor. Flow parameters varied with the circumferential position and the mean Flow parameters plotted against the local Flow rate at each circumferential position showed loops along the quasi-steady curves, which were obtained from the result without the fence. Simple theoretical calculations were used to predict the velocity components at the impeller Exit with the relative Flow angle or total pressure assumed. Good result was obtained when the relative Flow angle was assumed to vary quasi-steadily, not constant with the local Flow rate. The radial velocity was also reasonably predicted when the total pressure was assumed to vary quasi-steadily. A simple method is proposed to predict the impeller Exit Flow with downstream blockage in two-step sequence
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Exit Flow measurements of a centrifugal pump impeller
KSME International Journal, 2002Co-Authors: Soonsam Hong, Shinhyoung KangAbstract:Discharge Flows from a centrifugal pump impeller with a specific speed of 150 [rpm, m^3/min, m] were experimentally investigated. A large axisymmetric collector instead of a volute casing was installed to obtain circumferentially uniform Flow, i.e. without interaction of the impeller and the volute. The unsteady Flow was measured at the impeller Exit and vaneless diffuser using a hot film probe and a pressure transducer. The Flow at impeller Exit showed pronounced jet-wake Flow patterns. The wake, which was on the suction/hub side at high Flow rate, became enlarged pitchwisely on both the hub and the shroud side as the Flow rate decreases. The pitchwise non-uniformity of the Flow rapidly decreased along the downstream and the nonuniformity almost disappeared at radius ratio of 1.18 for medium Flow rate. The mean vaneless diffuser Flow was reasonably predicted using a one dimensional analysis when an empirical constant was used to specify the skin friction coefficient. The data can be used for a centrifugal pump impeller design and validation of CFD codes and Flow modeling.