A Model for System Instability Analysis in a Multi-Stage Intercooled Industrial Compressor

2019 ◽  
Author(s):  
Jiaye Gan ◽  
Ahmed Abdelwahab ◽  
Viktor Kilchyk
Keyword(s):  
Guide Vane ◽  
Transient Behavior ◽  
Industrial Applications ◽  
Operating Conditions ◽  
System Response ◽  
Stable Operation ◽  
System Behavior ◽  
Multi Stage ◽  
Performance Reduction ◽  
Inlet Conditions

Abstract Compression equipment used for industrial applications are typically comprised of multi-stage intercooled compressor stages. The presence of large volume intercoolers between individual stages adds a layer of complexity currently not present in publicly available surge models both in terms of system behavior and recovery analysis. In this work a compressible, temporal, and spatial model is developed in which the conservation equations are solved numerically for each of the system components, i.e. pipes, plenums and heat exchangers, valves, and individual compressor stages. The model can identify the onset of instability on an individual stage basis as well as the switching that can occur between the controlling stages of the instability onset when the operating conditions change, e.g. changes in inlet conditions, intercooler fouling or cooling tower performance reduction, and speed or guide vane changes. The model is therefore used both as a stage stacking model during the compressor stable operation as well as a model of the transient behavior of the system past the stable operation. An inertial model of the compressor drive train is also incorporated to analyze the effects of power transients, e.g. emergency shut down (ESD), on the system behavior. In this article details of the developed model are provided. Several test cases are presented. The model is then used to demonstrate the proper sizing of a vent valve of a base load compressor to meet the required system response specification in a surge event. The developed model represents an improvement over available transient system models in terms of predicting the post stable behavior of multi-stage intercooled compressors.

Mechanical Design and Testing of a 2.5 MW sCO2 Compressor Loop

2021 ◽  
Author(s):  
Stefan D. Cich ◽  
J. Jeffrey Moore ◽  
Chris Kulhanek ◽  
Meera Day Towler ◽  
Jason Mortzheim
Keyword(s):  
High Efficiency ◽  
Mechanical Design ◽  
Guide Vane ◽  
Operating Conditions ◽  
Inlet Guide Vane ◽  
Inlet Temperature ◽  
Design Changes ◽  
Wide Range ◽  
Inlet Conditions ◽  
Design And Testing

Abstract An enabling technology for a successful deployment of the sCO2 close-loop recompression Brayton cycle is the development of a compressor that can maintain high efficiency for a wide range of inlet conditions due to large variation in properties of CO2 operating near its dome. One solution is to develop an internal actuated variable Inlet Guide Vane (IGV) system that can maintain high efficiency in the main and re-compressor with varying inlet temperature. A compressor for this system has recently been manufactured and tested at various operating conditions to determine its compression efficiency. This compressor was developed with funding from the US DOE Apollo program and industry partners. This paper will focus on the design and testing of the main compressor operating near the CO2 dome. It will look at design challenges that went into some of the decisions for rotor and case construction and how that can affect the mechanical and aerodynamic performance of the compressor. This paper will also go into results from testing at the various operating conditions and how the change in density of CO2 affected rotordynamics and overall performance of the machine. Results will be compared to expected performance and how design changes were implanted to properly counter challenges during testing.

scholarly journals A Wide-Range Axial-Flow Compressor Stage Performance Model

1992 ◽  
Author(s):  
Gregory S. Bloch ◽  
Walter F. O’Brien
Keyword(s):  
Axial Flow ◽  
Operating Conditions ◽  
System Response ◽  
Compressor Stage ◽  
Operating Characteristics ◽  
Compression System ◽  
Axial Flow Compressor ◽  
Multi Stage ◽  
Wide Range ◽  
Flow Compressor

Dynamic compression system response is a major concern in the operability of aircraft gas turbine engines. Multi-stage compression system computer models have been developed to predict compressor response to changing operating conditions. These models require a knowledge of the wide-range, steady-state operating characteristics as inputs, which has limited their use as predicting tools. The full range of dynamic axial-flow compressor operation spans forward and reversed flow conditions. A model for predicting the wide flow range characteristics of axial-flow compressor stages was developed and applied to a 3-stage, low-speed compressor with very favorable results and to a 10-stage, high-speed compressor with mixed results. Conclusions were made regarding the inception of stall and the effects associated with operating a stage in a multistage environment. It was also concluded that there are operating points of an isolated compressor stage that are not attainable when that stage is operated in a multi-stage environment.

Multiphase Modelling of the Steel Grade Transition in a Continuous Casting Tundish

2009 ◽  
Author(s):  
Jesu´s Manuel Ferna´ndez Oro ◽  
Carlos Santolaria Morros ◽  
Javier Rodri´guez Somoano ◽  
Mo´nica Alvarez Ordieres
Keyword(s):  
Continuous Casting ◽  
Transient Behavior ◽  
Steel Grade ◽  
Operating Conditions ◽  
Stable Operation ◽  
Experimental Calibration ◽  
Grade Transition ◽  
Steel Grades ◽  
On Line ◽  
Unsteady Numerical Simulation

Nowadays, continuous casting is extremely conditioned by sequences of different steel grades that produce a large amount of intermixed steel. Due to customer requirements, steel producers are forced to deliver a few slabs of high-specialized steels, so the number of castings handling steels of dissimilar grades has been significantly increased in recent years. As a consequence, manufacturers are particularly concerned with the development of practical methods to know exactly where the mixed regions begin and end, in order to make a precise classification of the steel grade that has been produced and avoid further downgrading. Pioneering works by Huang and Thomas introduced a 1-D model to estimate the intermixed region during a grade transition. This model reached a notable popularity because of its ability to provide on-line predictions, though it is assumed that mixing inside the tundish is globally determined with a number of fixed parameters. Recently, Cho and Kim have introduced a modification reducing the number of parameters required, but with the full unsteady description of the tundish flow still unresolved. Moreover, all these models require experimental calibration, using the results from full-scale water models. Additionally, other researchers have been focused on the development of numerical simulations to analyze the flow structures and mixing features of the tundish, mainly during stable operation, but using limiting simplifications and/or steady schemes. In the present investigation, to the author’s knowledge, a 3D, unsteady numerical simulation using a volume-of-fluid formulation is carried out for the first time. With this technique, the transient behavior of the tundish during the ladle change can be fully modelled, tracking the free surface and extending the computations towards the steady state. A transport equation is resolved for a non-reactive scalar, representing a dimensionless concentration, so it is possible to predict the mixing degree of the steel at the tundish exit for different operating conditions. The final objective is the development of an off-line methodology to estimate precise intermixing periods during grade transition in continuous casting.

Experimental and Numerical Investigation of the Performance Impact of a Heavily Off-Design Inlet Swirl Angle in a Steam Turbine Stage

2017 ◽  
Author(s):  
Berardo Paradiso ◽  
Giacomo Gatti ◽  
Alessandro Mora ◽  
Vincenzo Dossena ◽  
Lorenzo Arcangeli ◽  
...  
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Steam Turbine ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Turbine Stage ◽  
Test Rig ◽  
Speed Test ◽  
Performance Reduction ◽  
Inlet Conditions

The aim of this work is to provide an insight into the performance reduction of a 1.5 axial steam turbine stage working under extreme incidence conditions at the inlet. In particular, the main object of the study is the propagation of the loss cores across the blade rows, so as to assess how such operating conditions affect the full machine. Experimental data have been used to validate an unsteady three-dimensional numerical simulation, which provided the tools to investigate the flowfield in detail. To do so, the 1.5 turbine stage installed in the Low Speed Test Rig at Politecnico di Milano has been tested with design and off-design inlet conditions by modifying the IGV orientation. The inter-stage flowfield was investigated by traversing pressure probes in three different axial planes, downstream of each blade row. The numerical simulation has been carried out at University of Florence. The experimental data from probes traversing was used as boundary conditions so as to match as closely as possible the actual operative parameters of the stage. Data from flange-to-flange measurements on the test rig were also used to compare the stage efficiency. After the successful validation of the numerical results, the loss cores propagation study itself was carried out. Using CFD results, the unsteady nature of the separation occurring on the first stator in off-design condition is investigated. Subsequently, a detailed analysis of the propagation of the loss cores is presented, including loss coefficients calculation and entropy trends along the machines axial coordinate. The main outcome is that at the machine exit the loss structures appear to be mainly mixed out and, therefore, subsequent stages would operate under conditions not far from the nominal ones.

scholarly journals Problems of aviation leaded gasoline application on aircraft

2020 ◽  
Vol 23 (3) ◽  
pp. 8-16
Author(s):  
K. I. Gryadunov ◽  
A. N. Timoshenko ◽  
E. U. Starkov
Keyword(s):  
Aircraft Engine ◽  
Combustion Products ◽  
Point Of View ◽  
Operating Conditions ◽  
Stable Operation ◽  
Negative Consequences ◽  
Aviation Gasoline ◽  
Liquid Form ◽  
Engine Operation ◽  
Multi Stage

A steady trend of expanding the small aircraft fleet equipped with piston engines is observed today. Special fuel (aviation gasoline with specified operational properties) for aircraft piston engines (PE) ensuring their stable operation in all modes and under all operating conditions is used. The indicators of aviation fuels operational properties including gasoline are achieved by means of adding special additives. One of these additives is an anti-knock additive – tetraethyl lead (TEL) that is added into the fuel in a certain amount in an ethyl liquid form. Despite the excellent TEL properties as an anti-knock additive, it also has a number of significant disadvantages. From the point of view of aircraft engine operation, it is noted that the TEL combustion products (decomposition) that are not effectively removed from the combustion chamber, enter the oil system in a significant amount, causing fine oil filters clogging. The article notes that even a small content of TEL decomposition products in aviation oils deteriorates dramatically their pumping capacity and leads to complete fine oil filters clogging for few minutes of engine operation, even on fresh oil. Moreover, the multi-stage oil cleaning stipulated by the design of some PE does not have a significant impact on this negative factor posing a threat to flight safety. These days the lead-containing gasoline use for aviation PE has no alternative, so solutions to reduce the negative consequences while applying are required.

A Theory of Post-Stall Transients in Axial Compression Systems: Part II—Application

1986 ◽  
Vol 108 (2) ◽  
pp. 231-239 ◽  
Author(s):  
E. M. Greitzer ◽  
F. K. Moore
Keyword(s):  
Axial Compression ◽  
Parametric Study ◽  
Pressure Rise ◽  
Transient Behavior ◽  
Rotating Stall ◽  
Future Research ◽  
System Response ◽  
System Behavior ◽  
Flow Pressure ◽  
The Impact

Using the theory developed in Part I, calculations have been carried out to show the evolution of the mass flow, pressure rise, and rotating-stall cell amplitude during compression system post-stall transients. In particular, it is shown that the unsteady growth or decay of the stall cell can have a significant effect on the instantaneous compressor pumping characteristic and hence on the overall system behavior. A limited parametric study is carried out to illustrate the impact of different system features on transient behavior. It is shown, for example, that the ultimate mode of system response, surge or stable rotating stall, depends not only on the B parameter, but also on the compressor length-to-radius ratio. Small values of the latter quantity tend to favor the occurrence of surge, as do large values of B. Based on the analytical and numerical results, some specific topics are suggested for future research on post-stall transients.

Using CFD to Improve Stall Margin

1999 ◽  
Author(s):  
James R. Hardin ◽  
Charles F. Boal
Keyword(s):  
High Efficiency ◽  
Industrial Applications ◽  
Stable Operation ◽  
Test Results ◽  
Peak Efficiency ◽  
Centrifugal Compressors ◽  
Stall Margin ◽  
Operating Range ◽  
Multi Stage ◽  
Cfd Analyses

Abstract Centrifugal compressors for multi-stage industrial applications must have both high efficiency and stable operation over a wide flow range. CFD analyses were used to evaluate the stall margins of candidate impeller designs compared to a baseline semi-inducer design. With this guidance, a new full-inducer impeller was designed with predicted wider operating range and slightly higher peak efficiency. Prototype tests confirmed these predictions. This paper presents predictions from two CFD codes and test results, for both the original and the redesigned impeller, and discusses the application of CFD for predicting impeller stall.

Treatment system response to transient AOX (adsorbable organic halogen) loadings

1997 ◽  
Vol 35 (2-3) ◽  
pp. 85-91
Author(s):  
D. A. Barton ◽  
J. D. Woodruff ◽  
T. M. Bousquet ◽  
A. M. Parrish
Keyword(s):  
Paper Industry ◽  
Model Development ◽  
Operating Conditions ◽  
System Response ◽  
Additional Information ◽  
Organic Halogen ◽  
Aox Removal ◽  
Variable Operating Conditions ◽  
Plant Shutdown

If promulgated as proposed, effluent guidelines for the U.S. pulp and paper industry will impose average monthly and maximum daily numerical limits of discharged AOX (adsorbable organic halogen). At this time, it is unclear whether the maximum-day variability factor used to establish the proposed effluent guidelines will provide sufficient margin for mills to achieve compliance during periods of normal but variable operating conditions within the pulping and bleaching processes. Consequently, additional information is needed to relate transient AOX loadings with final AOX discharges. This paper presents a simplistic dynamic model of AOX decay during treatment. The model consists of hydraulic characterization of an activated sludge process and a first-order decay coefficient for AOX removal. Data for model development were acquired by frequent collection of influent and effluent samples at a bleach kraft mill during a bleach plant shutdown and startup sequence.

Stability of Ring-Type MEMS Gyroscopes Subjected to Stochastic Angular Speed Fluctuation

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Samuel F. Asokanthan ◽  
Soroush Arghavan ◽  
Mohamed Bognash
Keyword(s):  
Angular Velocity ◽  
Degrees Of Freedom ◽  
Microelectromechanical Systems ◽  
Damping Ratio ◽  
Operating Conditions ◽  
System Stability ◽  
System Response ◽  
Ring Type ◽  
Mems Gyroscopes ◽  
The Stability

Effect of stochastic fluctuations in angular velocity on the stability of two degrees-of-freedom ring-type microelectromechanical systems (MEMS) gyroscopes is investigated. The governing stochastic differential equations (SDEs) are discretized using the higher-order Milstein scheme in order to numerically predict the system response assuming the fluctuations to be white noise. Simulations via Euler scheme as well as a measure of largest Lyapunov exponents (LLEs) are employed for validation purposes due to lack of similar analytical or experimental data. The response of the gyroscope under different noise fluctuation magnitudes has been computed to ascertain the stability behavior of the system. External noise that affect the gyroscope dynamic behavior typically results from environment factors and the nature of the system operation can be exerted on the system at any frequency range depending on the source. Hence, a parametric study is performed to assess the noise intensity stability threshold for a number of damping ratio values. The stability investigation predicts the form of threshold fluctuation intensity dependence on damping ratio. Under typical gyroscope operating conditions, nominal input angular velocity magnitude and mass mismatch appear to have minimal influence on system stability.

Identification of Bearing Coefficients of Flexible Rotor-Bearing Systems

2000 ◽  
Author(s):  
Tachung Yang ◽  
Wei-Ching Chaung
Keyword(s):  
Industrial Applications ◽  
Operating Conditions ◽  
Least Square ◽  
Flexible Rotor ◽  
Fem Modeling ◽  
Identification Method ◽  
Reaction Forces ◽  
Manufacturing Assembly ◽  
Stiffness And Damping

The accuracy of stiffness and damping coefficients of bearings is critical for the rotordynamic analysis of rotating machinery. However, the influence of bearings depends on the design, manufacturing, assembly, and operating conditions of the bearings. Uncertainties occur quite often in manufacturing and assembly, which causes the inaccuracy of bearing predictions. An accurate and reliable in-situ identification method for the bearing coefficients is valuable to both analyses and industrial applications. The identification method developed in this research used the receptance matrices of flexible shafts from FEM modeling and the unbalance forces of trial masses to derive the displacements and reaction forces at bearing locations. Eight bearing coefficients are identified through a Total Least Square (TLS) procedure, which can handle noise effectively. A special feature of this method is that it can identify bearing coefficients at a specific operating speed, which make it suitable for the measurement of speed-dependent bearings, like hydrodynamic bearings. Numerical validation of this method is presented. The configurations of unbalance mass arrangements are discussed.

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