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Showing papers on "Axial compressor published in 1994"


Journal ArticleDOI
TL;DR: Steady flow results that model the inspiratory phase at Reynolds numbers of 518, 1036 and 2089, corresponding to Dean numbers of 98, 196 and 395, show that in the bifurcation plane velocity profiles in the daughter branches are skewed toward the inner wall.
Abstract: Flow in a bifurcating tube system typifying a major bronchial bifurcation is studied experimentally with a two color, two velocity component laser Doppler anemometer. The flow loop is composed of a pumping station, flow stratifiers and a constant head pressure tank; it can accommodate steady, pulsatile or oscillatory flow. The test section is a symmetric bifurcation of constant cross sectional area and has a branching angle of 70 deg. The test section is a cast of clear silicon rubber in a plexiglass mold that was milled on a numerically controlled milling machine. The flow division ratio from the parent to daughter branches is about unity. Steady flow results that model the inspiratory phase at Reynolds numbers of 518, 1036 and 2089, corresponding to Dean numbers of 98, 196 and 395, show that in the bifurcation plane velocity profiles in the daughter branches are skewed toward the inner wall. In the transverse plane, "m" shaped velocity profiles are found with low velocity at the center. Secondary flow patterns, which are responsible for such phenomena, are first observed at the axial position where the flow begins to turn. Flow separation was not observed at any point in the bifurcation.

142 citations


Proceedings ArticleDOI
29 Jun 1994
TL;DR: In this paper, a nonlinear formulation of the Moore-Greitzer rotating stall model is presented for control analysis and design, and the model is validated by comparing stall inception experiments to simulated stall inception transients.
Abstract: This paper presents a nonlinear formulation of the Moore-Greitzer rotating stall model that is suitable for control analysis and design. The model is validated by comparing stall inception experiments to simulated stall inception transients. The shape of the nonlinear compressor characteristic is shown to be a primary determinant of stall inception transient behavior. A Lyapunov stability analysis procedure is then presented. This procedure allows basins of attraction to be determined for various system operating points. Examples are given, and implications for design of rotating stall/surge control systems are discussed.

111 citations


Journal ArticleDOI
TL;DR: In this paper, a three-stage axial research compressor has been actively stabilized by damping low-amplitude circumferentially traveling waves, which can grow into rotating stall.
Abstract: A three-stage, low-speed axial research compressor has been actively stabilized by damping low-amplitude circumferentially traveling waves, which can grow into rotating stall. Using a circumferential array of hot-wire sensors, and an array of high-speed individually positioned control vanes as the actuator, the first and second spatial harmonics of the compressor were stabilized down to a characteristic slope of 0.9, yielding an 8 percent increase in operating flow range. Stabilization of the third spatial harmonic did not alter the stalling flow coefficient. The actuators were also used open loop to determine the forced response behavior of the compressor

107 citations


Patent
28 Jun 1994
TL;DR: In this paper, an inner and/or outer cylindrical wall limiting the working fluid flow path of an axial compressor radially has an ondulating contour, where at the intersection with the leading edge of an airfoil the wall shows a convex contour followed by a concave contour in the region of the airfoils maximum thickness.
Abstract: An inner and/or outer cylindrical wall limiting the working fluid flow path of an axial compressor radially has an ondulating contour. At the intersection with the leading edge of an airfoil the wall shows a convex contour (54) followed by a concave contour (58) in the region of the airfoils maximum thickness while at the intersection with the trailing edge of the airfoil the contour (56) is convex again. The airfoil can either be a rotor blade or a stator vane.

98 citations


Proceedings ArticleDOI
Martin Rose1
13 Jun 1994
TL;DR: In this paper, a non-axisymmetric hub endwall shape for axial gas turbine NGVs is proposed to improve engine performance by cutting the leakage of coolant from the disc rim seal.
Abstract: The Nozzle Guide Vanes (NGV's) of an axial gas turbine generate circumferential non-uniformities in static pressure after their trailing edges. This paper aims to show that these non- uniformities can be removed locally by re-shaping the hub endwall. The ultimate objective is to improve engine performance by cutting the leakage of coolant from the disc rim seal. The technique is demonstrated theoretically using 3D viscous CFD. The required endwall shape is non-axisymmetric and is generated parametrically by altering a calculation grid for an existing NGV. The results show a reduction of the static pressure non- uniformities by 70%. Other favourable effects are also predicted and are commented upon. NOMENCLATURE

97 citations


Patent
08 Jul 1994
TL;DR: In this article, a method of controlling the operation of a centrifugal compressor in a water chiller system is presented, where the compressor's capacity is variable by modulating its speed of rotation or by modifying its inlet guide vane's position.
Abstract: A method of controlling the operation of a centrifugal compressor in a water chiller system. The compressor's capacity is variable by modulating its speed of rotation or by modulating its inlet guide vane's position. The water chiller includes an evaporator having a leaving water temperature. The method comprises the steps of: monitoring the leaving water temperature; determining if the leaving water temperature is in a steady state; modulating the compressor capacity by modulating speed of rotation if the leaving water temperature is in a steady state; and modulating the compressor capacity by modulating inlet guide vane position if the leaving water temperature is not in a steady state.

97 citations


Proceedings ArticleDOI
13 Jun 1994
TL;DR: Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1993 as discussed by the authors, Boston, Massachusetts, USA.
Abstract: Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1993.

87 citations


Journal ArticleDOI
TL;DR: Detailed measurements from a low-speed test rig instrumented to pick up details of axial and circumferential flow disturbances show that surge is initiated by rotating stall, and that the ensuing surge cycle is a sequence of well ordered cause-and-effect events.
Abstract: There is limited information available in the literature about flow conditions in axial compressors during surge. This article presents detailed measurements from a low-speed test rig instrumented to pick up details of axial and circumferential flow disturbances. The results show that surge is initiated by rotating stall, and that the ensuing surge cycle is a sequence of well ordered cause-and-effect events. The differences in cycle behavior between "classic surge" and "deep surge" are investigated, and it is shown that the shape of the compressor characteristic determines which of these will occur. From the results it is also concluded that some important factors, such as overall pressure rise and size of hysteresis loop, have not received sufficient attention in existing techniques for predicting the rotating stall/surge boundary. In line with these findings an Appendix by E. M. Greitzer presents a more general version of the "B Parameter," which takes into account the influence of compressor design variables on the stalling behavior of the compressor.

82 citations


Journal ArticleDOI
TL;DR: In this article, a correlation of variables which predict the vortex minimum pressure has been formulated, and measurements of the important variables for this correlation have been made on a high Reynolds number (3×10 6 ) axial-flow test rig.
Abstract: Tip clearance flow in turbomachinery can lead to losses in efficiency and stall margin. In liquid handling turbomachinery, the vortical flow field, formed from the interaction of the leakage flow with the through-flow, is subject to cavitation. Furthermore, this flow field is complex and not well understood. A correlation of variables which predict the vortex minimum pressure has been formulated. Measurements of the important variables for this correlation have been made on a high Reynolds number (3×10 6 ) axial-flow test rig. The correlation has been applied to the measured data and other data sets from the literature with good agreement. An optimum tip clearance has been theoretically identified as experiments have shown

77 citations


Proceedings ArticleDOI
13 Jun 1994
TL;DR: In this article, the role of the passage shock/vortex interaction in generating endwall blockage is discussed, and the radial influence of the tip clearance flow extends to 20 times the physical tip clearance height.
Abstract: Experimental and computational techniques are used to investigate tip clearance flows in a transonic axial compressor rotor at design and part speed conditions. Laser anemometer data acquired in the endwall region are presented for operating conditions near peak efficiency and near stall at 100% design speed and at near peak efficiency at 60% design speed. The role of the passage shock / leakage vortex interaction in generating endwall blockage is discussed. As a result of the shock / vortex interaction at design speed, the radial influence of the tip clearance flow extends to 20 times the physical tip clearance height. At part speed, in the absence of the shock, the radial extent is only 5 times the tip clearance height. Both measurements and analysis indicate that under part-speed operating conditions a second vortex, which does not originate from the tip leakage flow, forms in the endwall region within the blade passage and exits the passage near midpitch. Mixing of the leakage vortex with the primary flow downstream of the rotor at both design and part speed conditions is also discussed.Copyright © 1994 by ASME

60 citations


Proceedings ArticleDOI
13 Jun 1994
TL;DR: In this paper, a 2D, compressible hydrodynamic stability analysis is applied to the geometry of two of the compressors and gives results in agreement with data, showing that, at low corrected speeds, these compressors behave predominantly as incompressible machines.
Abstract: High speed compressor data immediately prior to rotating stall inception are analyzed and compared to stability theory. New techniques for the detection of small amplitude rotating waves in the presence of noise are detailed and experimental and signal processing pitfalls discussed. In all nine compressors examined, rotating stall precedes surge. Prior to rotating stall inception, all the machines support small-amplitude (<1% of fully developed stall) waves travelling about the circumference. Travelling wave strength and structure are shown to be a strong function of corrected speed. At low speeds, a −0.5 times shaft speed wave is present for hundreds of rotor revolutions prior to stall initiation. At 100% speed, a shaft speed rotating wave dominates, growing as stall initiation is approached (fully developed rotating stall occurs at about 1/2 of shaft speed). A new, 2-D, compressible hydrodynamic stability analysis is applied to the geometry of two of the compressors and gives results in agreement with data. The calculations show that, at low corrected speeds, these compressors behave predominantly as incompressible machines. The wave which first goes unstable is the 1/2 shaft frequency mode predicted by the incompressible Moore-Greitzer analysis and previously observed in low speed compressors. Compressibility becomes important at high corrected speeds and adds axial structure to the rotating waves. At 100% corrected speed, it is one of these hitherto unrecognized compressible modes which goes unstable first. The rotating frequency of this mode is constant and predicted to be approximately coincident with shaft speed at design. Thus, it is susceptible to excitation by geometric nonuniformities in the compressor. This new understanding of compressor dynamics is used to introduce the concept of travelling wave energy as a measure of compressor stability. Such a wave energy-based scheme is shown to consistently give an indication of low stability for significant periods (100–200 rotor revolutions) before stall initiation, even at 100% corrected speed.Copyright © 1994 by ASME

Journal ArticleDOI
TL;DR: In this article, a theoretical study has been conducted to determine the influence of actuator and sensor choice on active control of rotating stall in axial-flow compressors, which is achieved by feeding the sensed quantity back to the actuator with a suitable gain and spatial phase shift relative to the measured wave.
Abstract: A theoretical study has been conducted to determine the influence of actuator and sensor choice on active control of rotating stall in axial-flow compressors. The sensors are used to detect small amplitude traveling waves that have been observed at the inception of rotating stall in several different compressors. Control is achieved by feeding the sensed quantity back to the actuator with a suitable gain and spatial phase shift relative to the measured wave. Actuators using circumferential arrays of jets, intake ports, and movable inlet guide vanes upstream of the compressor, and valves downstream of the compressor were considered. The effect of axial velocity, static pressure, or total pressure measurement on control effectiveness was investigated. In addition, the influence of the actuator bandwidth on the performance of the controlled system was determined. The results of the study indicate that the potential for active control of rotating stall is greater than that achieved thus far with movable inlet guide vanes. Furthermore, axial velocity sensing was most effective. Actuator bandwidth affected the performance of the controlled compressors significantly, but certain actuators were affected less severely than others.

Proceedings ArticleDOI
13 Jun 1994
TL;DR: In this paper, a control-theoretic input-output model is derived for rotating stall/surge active control of axial compressors, based on a 2D stage stacking technique.
Abstract: Using a two dimensional compressible flow representation of axial compressor dynamics, a control-theoretic input-output model is derived which is of general utility in rotating stall/surge active control studies. The derivation presented here begins with a review of the fluid dynamic model, which is a 2D stage stacking technique that accounts for blade row pressure rise, loss and deviation as well as blade row and inter-blade row compressible flow. This model is extended to include the effects of the upstream and downstream geometry and boundary conditions, and then manipulated into a transfer function form that dynamically relates actuator motion to sensor measurements. Key relationships in this input-output form are then approximated using rational polynomials. Further manipulation yields an approximate model which is in standard form for studying active control of rotating stall and surge. As an example of high current relevance, the transfer function from an array of jet actuators to an array of static pressure sensors is derived. Numerical examples are also presented, including a demonstration of the importance of proper choice of sensor and actuator locations, as well as a comparison between sensor types. Under a variety of conditions, it was found that sensor locations near the front of the compressor or in the downstream gap are consistently the best choices, based on a quadratic optimization criterion and a specific 3-stage compressor model. The modeling and evaluation procedures presented here are a first step toward a rigorous approach to the design of active control systems for high speed axial compressors.Copyright © 1994 by ASME

Journal Article
TL;DR: In this article, the effects of axial flow impeller position and sparger geometry on flow pattern, power consumption and mass transfer are studied in a vessel 0.444 m in diameter, using liquids of different viscosity.
Abstract: We focuse on the gas-dispersion characteristics of axial flow impellers. Various impellers are compared: an inclined blade impeller with flat blades, an A315 impeller and a Leeuwrik impeller. The goal is to gain insight in the gas-dispersion properties of such axial flow impellers. Therefore, the effects of impeller position and sparger geometry on flow pattern, power consumption and mass transfer are studied in a vessel 0.444 m in diameter, using liquids of different viscosity. The power consumption is strongly related to the different flow patterns and different types of cavities. Under certain conditions time-dependent, asymmetrical flow patterns can occur. The sparger type influences both the power needed to prevent flooding and the overall mass transfer coefficient k l a. The liquid viscosity does not affect the basic hydrodynamic phenomena in the vessel for viscosities not exceeding 80 m Pa s

Journal ArticleDOI
TL;DR: In this article, the effects of tip clearance, secondary flow, skew, and corner stall on the performance of a multistage compressor with controlled diffusion blading have been studied experimentally Measurements between 1 and 99 percent annulus height were carried out in both the first and the third stages of a four-stage low speed compressor with repeating-stage blading.
Abstract: Effects of tip clearance, secondary flow, skew, and corner stall on the performance of a multistage compressor with controlled diffusion blading have been studied experimentally Measurements between 1 and 99 percent annulus height were carried out in both the first and the third stages of a four-stage low-speed compressor with repeating-stage blading Measurements were obtained at a datum rotor tip clearance and at a more aerodynamically desirable lower clearance The consequences of the modified rotor tip clearance on both rotor and stator performance are examined in terms of loss coefficient and gas exit angle Stator losses close to the casing are found to increase significantly when the clearance of an upstream rotor is increased These increased stator losses cause 30 percent of the stage efficiency reduction that arises with increased rotor tip clearance

Patent
11 Oct 1994
TL;DR: In this article, an apparatus for modulating a flow of cooling air from a compressor to a turbine in a gas turbine engine is described, which includes a support member which forms a channel for receiving the cooling flow and has a throat at a downstream end with a radial orientation.
Abstract: An apparatus for modulating a flow of cooling air from a compressor to a turbine in a gas turbine engine is disclosed. The apparatus includes a support member which forms a channel for receiving the cooling flow and has a throat at a downstream end with a radial orientation. A radial flow inducer is connected to the support member adjacent to the channel downstream end for accelerating the cooling flow through the throat of the support member. Apparatus for modulating the quantity of the cooling air flowing through the throat and into the turbine is provided in the form of an axially translating endwall, wherein variation of the throat area is accomplished through modulation of the endwall with respect to the support member. The support member may also house either a stationary, unmodulated axial flow inducer or a second modulated radial flow inducer in addition to the modulated radial flow inducer.

Journal ArticleDOI
TL;DR: In this paper, a linear compressor cascade of NACA 65-1810 profiles is inuestigated, for tip clearance levels of 7.0, 2.0 and 3.25 percent of chord at design and off-design flow conditions.
Abstract: Tip leakage flow in a linear compressor cascade of NACA 65-1810 profiles is inuestigated, for tip clearance levels of 7.0, 2.0, and 3.25 percent of chord at design and off-design flow conditions. Velocity and pressure data are collected from three transverse sections inside tip clearance and sixteen sections within flow passage. Tip separation vortex influence is identified from the data. Leakage flow mixing is clearly present inside the clearance and has a significant influence on the internal loss

Patent
Kim Tae-Duk1
27 Sep 1994
TL;DR: In this paper, a compressor of a refrigeration cycle is normally driven by a commercial power source and during a power failure, the compressor is driven by an auxiliary solar power source.
Abstract: A compressor of a refrigeration cycle is normally driven by a commercial power source. During a power failure, the compressor is driven by an auxiliary solar power source, wherein the compressor is initially driven at a minimum frequency for a delay period and is thereafter driven at a higher frequency.

Journal ArticleDOI
TL;DR: In this article, a random vibration theory for the prediction of motion of clustered cylinders subjected to axial flow is presented, where the response is assumed to stem from both mean flow effects and random pressure fluctuations in the turbulent boundary layer, the latter being required as an input to the analytical model.

Patent
Walter Whipple1
07 Sep 1994
TL;DR: In this article, a dual-cylinder compressor is coupled with a controller coupled to the compressor to control compressor capacity by selection of a predetermined refrigerant flow path through the compressor.
Abstract: An energy-efficient refrigeration system includes a dual cylinder compressor and a compressor controller coupled to the compressor to control compressor capacity by selection of a predetermined refrigerant flow path through the compressor. The dual cylinder compressor includes first and second cylinders with respective first and second pistons that are horizontally opposed and coupled together by a fixed and non-pivoting connecting rod. The void volume of one cylinder is typically greater than the void volume of the other cylinder, and the compressor typically is a scotch-yoke drive apparatus or, alternatively, a linear voice coil drive apparatus. Respective refrigerant flow paths are established by means of a plurality of control valves disposed in a compressor plumbing manifold, to provide a first-cylinder only flow path, a second-cylinder only flow path, a combined first and second cylinder series flow path and a combined first and second cylinder parallel flow path, thereby providing different compressor capacities for meeting different cooling demands in the refrigerator.

Proceedings ArticleDOI
29 Jun 1994
TL;DR: In this article, a low-order discretisation model of a PDE compressor model is found to exhibit a stationary (pitchfork) bifurcation at the onset of stall using 1D throttle opening (eg bleed valve) as a control, analysis of the linearized system at stall shows that the critical mode (zero eigenvalue) is unaffected by linear feedback.
Abstract: Analysis and active control of stall instabilities in axial flow compressors are pursued using a combination of bifurcation analysis and nonlinear control A low-order discretisation model of a PDE compressor model is found to exhibit a stationary (pitchfork) bifurcation at the onset of stall Using 1D throttle opening (eg bleed valve) as a control, analysis of the linearized system at stall shows that the critical mode (zero eigenvalue) is unaffected by linear feedback Hence, nonlinear stabilization techniques are necessary A quadratic feedback control law is proposed based on the lower-order model and is found to adequately serve the control purposes for both the lower order and higher order discretizations

DissertationDOI
01 Jan 1994
TL;DR: In this paper, the rotordynamic and lateral forces of axial flow pump runners were investigated under varying conditions of flow and whirl. But, the authors did not consider the effect of inlet distortion on rotordynamics.
Abstract: Axial flow pump runners known as inducers are subject to complex internal flows and fluid-induced lateral and rotordynamic forces. The internal flows in inducers are three dimensional and are characterized by complicated secondary flows. The current research investigates the boundary layer flows on the blades, hub and housing of unshrouded and shrouded axial flow inducers using flow visualization techniques. Rotordynamic and lateral force data on unshrouded inducers were also obtained under varying conditions of flow and whirl. Studies on the internal flows showed that the blade boundary layer flow had strong radial components at off-design conditions. The flow remains attached to the blade surface of unshrouded inducers at all flow coefficients tested. The origin of the upstream swirling backflow was found to be at the discharge plane of the inducer. In addition, flow reversal was observed at the suction side blade tip near the leading edge in a shrouded inducer. Re-entry of the hub boundary layer flow (a downstream backflow) into the blade passage area was observed at flow coefficients below design. For unshrouded inducers the radially outward flow near the blade tip mixed with the tip clearance leakage flow to form the upstream backflow. These observations provide a better understanding of the internal flows and the occurrence of upstream backflows in inducers. The rotordynamic forces acting on an inducer due to an imposed whirl motion was also investigated. It was found that the rotordynamic force data at various whirl frequency ratios does not allow a normal quadratic fit; consequently the conventional inertial, stiffness and damping coefficients cannot be obtained and a definite whirl ratio describing the instability region does not result. Rotordynamic forces were found to be significantly dependent on the flow coefficient. At flow coefficients below design, these forces are characterized by multiple zero crossings at various whirl frequencies and large destabilizing peeks. Theoretical estimates of the tangential rotordynamic force on a non-whirling inducer using actuator disk theory were significantly different, both in magnitude and direction, from the experimentally measured forces. The effect of upstream and downstream flow distortions on the rotordynamic and lateral forces on an inducer were studied. It was found that at flow coefficients below design, large lateral forces occurred in the presence of a downstream asymmetry. The reverse flows occurring downstream which consist of high energy fluid are the possible cause of these large forces. The imposition of a uniform downstream condition reduced these forces to near zero values. Results of inlet distortion experiments show that a strong inlet shear causes a significant increase in the lateral force. However, weak inlet shear flows and the flow asymmetry due to a 180° upstream bend did not cause a significant lateral force. It was found that flow distortions upstream or downstream did not cause any significant effect on the rotordynamic forces. Cavitation was found to have important consequences for fluid-induced rotordynamic forces. These forces become destabilizing for both forward and reverse whirl. The magnitudes of the destabilizing forces were found to increase with decreasing cavitation numbers.

Patent
11 Oct 1994
TL;DR: In an axial-flow turbine, at least one of the front and rear side contact surfaces of the axial flow turbine is formed at a certain angle with respect to a radial line connecting the rotor center and the contact surface as discussed by the authors.
Abstract: In an axial-flow turbine, at least one of front and rear side contact surfaces of shrouds (3a or 3b) of blades (1a or 1b) with respect to the turbine rotational direction is formed at certain angle with respect to a radial line connecting the rotor center and the contact surface. The shroud (3a) of the blade (1a) of a first kind is formed in a trapezoidal shape converging radially outward in cross section taken in a plane perpendicular to the turbine axial direction, and the shroud (3b) of the blade (1b) of a second kind is formed in an inverted trapezoidal shape converging radially inward in the cross section. Further, half of an angle (2α) between the front and rear side contact surfaces of the shrouds (3a or 3b) is made smaller than a static frictional angle of the contact surface. Since the shroud contact surfaces of two adjacent blades can be kept in pressure contact with each other under all operating conditions, a large dynamic stress reduction and superior damping properties can be obtained without producing excessive initial stresses at the blade airfoil and blade dovetail attachment portion.

Journal ArticleDOI
TL;DR: In this article, the authors used a hot-wire probe with x-wires and a temperature wire to measure the turbulent quantities such as the turbulent kinetic energy, the Reynolds-stresses and the turbulent heat fluxes.

Patent
28 Oct 1994
TL;DR: In this article, a rotary compressor system consisting of a compressor unit, a drive motor and a single pressure vessel is described. And a control system and a method to control the oil flowing into the compressor unit at start-up and prior to cessation of rotation of the unit is presented.
Abstract: A rotary compressor system (10) comprising a compressor unit (11), a drive motor (12) and a single pressure vessel (14), wherein the pressure vessel (14) acts both as a separator vessel and as a compressed gas storage tank. Additionally, a control system and a method to control the oil flowing into the compressor unit (11) at start-up and prior to cessation of rotation of the compressor unit (11) is also disclosed.

Patent
Yasuhiro Katoh1, Yoshihiro Tsuda1, Mitsuaki Yanagida1, Hajime Toriya1, Tetsuo Sasada1 
08 Sep 1994
TL;DR: In this paper, the curvature distribution on the suction surface of the stator blade rows or rotor blade rows of the axial flow compressor is adapted to have a local minimum in a region toward the leading edge of the blade, and then a local maximum.
Abstract: An axial flow compressor for use in a gas turbine or other industrial application having an improved efficiency is provided through modification of the blade shape and profile of the blades subject to a subsonic high velocity inlet flow so as to avoid shock losses in the blade rows, and improve the total efficiency. The curvature distribution on the suction surface of the stator blade rows or rotor blade rows of the axial flow compressor is adapted to have a local minimum in a region toward the leading edge of the blade, and then a local maximum. Thereby, an excessive increment in velocity on the suction surface from the leading edge to the position of the maximum velocity can be suppressed, and the occurrence of a shock wave can be avoided so as to minimize pressure loss in the blade rows, thus increasing the total efficiency of the axial compressor.


Patent
17 Oct 1994
TL;DR: In this paper, the working liquid oil is atomized through nozzles suspended in, and parallel to, the suction gas flow, or alternatively mounted on suction piping.
Abstract: In a compression system which incorporates a rotary helical screw compressor, and for any type of gas or refrigerant, the working liquid oil is atomized through nozzles suspended in, and parallel to, the suction gas flow, or alternatively the nozzles are mounted on the suction piping In either case, the aim is to create positively a homogeneous mixture of oil droplets to maximize the effectiveness of the working liquid oil in improving the isothermal and volumetric efficiencies The oil stream to be atomized may first be degassed at compressor discharge pressure by heating within a pressure vessel and recovering the energy added by using the outgoing oil stream to heat the incoming oil stream The stripped gas is typically returned to the compressor discharge flow In the preferred case, the compressor rotors both contain a hollow cavity through which working liquid oil is injected into channels along the edges of the rotors, thereby forming a continuous and positive seal between the rotor edges and the compressor casing In the alternative method, working liquid oil is injected either in the same direction as the rotor rotation or counter to rotor rotation through channels in the compressor casing which are tangential to the rotor edges and parallel to the rotor centerlines or alternatively the channel paths coincide with the helical path of the rotor edges

Patent
22 Dec 1994
TL;DR: In this paper, when an abrupt load variation occurs in a centrifugal compressor which increases pressures of a fuel such as city gas or liquefied natural gas to feed the fuel, a gas turbine control device effects a control so that a discharge pressure can be kept to within a predetermined pressure range.
Abstract: In a gas turbine apparatus including a turbine stage and a compressor stage, when an abrupt load variation occurs in a centrifugal compressor which increases pressures of a fuel such as city gas or liquefied natural gas to feed the fuel, a gas turbine control device effects a control so that a discharge pressure of the centrifugal compressor can be kept to within a predetermined pressure range. When a fuel flow demand for the centrifugal compressor is inputted to the gas turbine control device, a signal corresponding to this fuel control signal is inputted to a bypass valve of the centrifugal compressor simultaneously when it is inputted to gas turbine fuel control valves provided in the gas turbine apparatus. When the load is abruptly varied, the degree of opening of the bypass valve of the centrifugal compressor is changed to a value determined by a prestored relation between the fuel control signal and the degree of opening of the bypass valve.

Proceedings ArticleDOI
C. Y. Wu1
13 Jun 1994
TL;DR: In this article, it was shown that many complex arbitrary surfaces typical of our blades in fans, axial compressors, and centrifugal impellers in aviation gas turbines can be rendered exactly flank millable with one or more passes per surface often without sacrificing, indeed with gain, in performance.
Abstract: It is generally conceived that a blade surface is flank millable if it can be closely approximated by a ruled surface; otherwise the slow machining process of point milling has to be employed. However, we have now demonstrated that the ruled surface criterion for flank milling is neither necessary nor sufficient Furthermore, many complex arbitrary surfaces typical of our blades in fans, axial compressors, and centrifugal impellers in aviation gas turbines are actually closely flank millable and can be rendered exactly flank millable with one or more passes per surface often without sacrificing, indeed sometimes with gain, in performance.Copyright © 1994 by ASME