scholarly journals Aerodynamic Optimization Design of a Multistage Centrifugal Steam Turbine and Its Off-Design Performance Analysis

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Hui Li ◽  
Dian-Gui Huang
Keyword(s):  
Steam Turbine ◽  
Mass Flow ◽  
Pressure Ratio ◽  
Aerodynamic Performance ◽  
Constant Speed ◽  
Medium Size ◽  
Aerodynamic Design ◽  
One Dimensional ◽  
Design Program ◽  
The One

Centrifugal turbine which has less land occupation, simple structure, and high aerodynamic efficiency is suitable to be used as small to medium size steam turbines or waste heat recovery plant. In this paper, one-dimensional design of a multistage centrifugal steam turbine was performed by using in-house one-dimensional aerodynamic design program. In addition, three-dimensional numerical simulation was also performed in order to analyze design and off-design aerodynamic performance of the proposed centrifugal steam turbine. The results exhibit reasonable flow field and smooth streamline; the aerodynamic performance of the designed turbine meets our initial expectations. These results indicate that the one-dimensional aerodynamic design program is reliable and effective. The off-design aerodynamic performance of centrifugal steam turbine was analyzed, and the results show that the mass flow increases with the decrease of the pressure ratio at a constant speed, until the critical mass flow is reached. The efficiency curve with the pressure ratio has an optimum efficiency point. And the pressure ratio of the optimum efficiency agrees well with that of the one-dimensional design. The shaft power decreases as the pressure ratio increases at a constant speed. Overall, the centrifugal turbine has a wide range and good off-design aerodynamic performance.

On the Dynamics of Compressor Surge

1976 ◽  
Vol 18 (5) ◽  
pp. 234-238 ◽  
Author(s):  
D. H. McQueen
Keyword(s):  
Mass Flow Rate ◽  
Limit Cycle ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Head ◽  
Centrifugal Compressors ◽  
One Dimensional ◽  
Acoustical Properties ◽  
Compressor Surge ◽  
The One

The one-dimensional equations of surge in centrifugal compressors are solved graphically for the pressure head and mass flow rate as functions of time for a variety of situations, and the results are discussed in terms of the acoustical properties of the external piping. Two important parameters affecting the nature of the surge limit cycle are found to be simply related to the acoustic capacitance and acoustic inductance of the system.

Mass Flow and Thrust Performance of Nozzles With Mixed and Unmixed Nonuniform Flow

1995 ◽  
Vol 117 (4) ◽  
pp. 617-622 ◽  
Author(s):  
Reiner Decher
Keyword(s):  
Mass Flow ◽  
Total Pressure ◽  
Nonuniform Flow ◽  
Flow Properties ◽  
One Dimensional ◽  
Flow Equations ◽  
Design Variables ◽  
Analytic Expressions ◽  
The One ◽  
Thrust Performance

The calculated thrust and mass flow rate of a nozzle depend on the uniformity of the entering flow. The one-dimensional flow equations are extended to arrive at analytic expressions for the predicted performance of a nozzle processing two streams whose properties are determined ahead of the throat. The analysis approach forms the basis for the understanding of flows which have more complex distributions of total pressure and temperature. The uncertainty associated with mixing is examined by the consideration of the two limiting cases: compound flow with no mixing and completely mixed flow. Nozzle discharge and velocity coefficients accounting for non-uniformity are derived. The methodology can be extended to experimentally measured variations of flow properties so that proper geometric design variables may be obtained.

A Simplified Analytical Approach for Calculating the Start-Up Time of Industrial Steam Turbines for Optimal and Fast Start-Up Procedures

2015 ◽  
Author(s):  
Wolfgang Beer ◽  
Lukas Propp ◽  
Lutz Voelker
Keyword(s):  
Steam Turbine ◽  
Analytical Approach ◽  
Three Dimensional ◽  
Steam Turbines ◽  
Time Step ◽  
One Dimensional ◽  
Start Up ◽  
Time Calculation ◽  
Fast Start ◽  
The One

New flexible operational regimes with fast start-ups and fast-changing load cycles for steam turbines require calculation procedures for determining optimal start-up times in order not to exceed the limits of thermal stress for the steam turbine parts. This work presents a start-up time calculation for various kinds of industrial steam turbines. An analytical approach for estimating the optimal thermal load of a turbine from quasi-steady or steady condition is developed. The geometry of the respective turbine components, the changing of the steam parameters and heat transfer effects during the start-up procedure are taken into account while observing the respective material properties and stress limits. The temperature distributions of the respective turbine parts are calculated with a one-dimensional numerical algorithm of Fourier’s heat conduction equation. Three-dimensional influences of the geometry and of the the heat flux are considered analytically by adjusting the numerical solutions of elementary bodies (e.g. one-dimensional plate). The start-up time calculation is performed in small time steps to guarantee the stability of the numerical solution. The unsteady stress analysis for the start-up procedure does not uniquely identify one critical component. The calculation must be repeated for each time step to identify the component which limits the start-up gradient. Other boundary conditions, such as restricted speed ranges of the rotor with minimum transients and time for synchronization with the electrical grid, are considered by the model too and can further limit the start-up gradient and lead to slower start-up procedures. The one-dimensional calculation models were verified with a three-dimensional FEA of the casing and a two axis symmetrical FEA of the rotor. The results for the temperature distribution are presented and compared to the one-dimensional results. The final result of the analytical approach for an optimized start-up time calculation is verified with two typical start-up calculations, one for a generator drive steam turbine and one for a mechanical-drive steam turbine.

Impact of the wastegate opening on radial turbine performance under steady and pulsating flow conditions

2019 ◽  
Vol 234 (2-3) ◽  
pp. 652-668 ◽  
Author(s):  
Ahmed Ketata ◽  
Zied Driss ◽  
Mohamed Salah Abid
Keyword(s):  
Mass Flow ◽  
Large Deviation ◽  
Pulse Frequency ◽  
Pulsating Flow ◽  
Flow Conditions ◽  
One Dimensional ◽  
Loop Area ◽  
Modeling Methodology ◽  
Turbine Performance ◽  
The One

The present article attempts to describe the behavior of wastegated turbines under various steady and pulsating flow conditions. For this, meanline and one-dimensional numerical codes including appropriate modeling approaches for wastegated turbines have been developed with the FORTRAN language. These codes were validated against experiments with an established test rig at the National School of Engineers of Sfax. The discharge coefficient map of the wastegate was determined with a developed correlation built from experiments, and it was served as an input to the developed codes for interpolations during computation. This correlation is based on a two-dimensional non-linear dose-response fitting relationship instead of classical polynomial function which is one novelty of the article in addition to the one-dimensional modeling methodology. The normalized root mean square error (NRMSE) of both cycle-averaged efficiency and mass flow parameter (MFP) remains below 2% which confirms the validity of the proposed calculation approach. The results indicated a large deviation in the turbine performance under pulsating flow conditions compared to the steady state ones. The shape of the hysteresis loop of the turbine efficiency remains unchanged toward the variation of the wastegate valve angle at the same pulse frequency. The mass flow hystereses loop area is decreased by around 50% as the pulse frequency increases from 33 up to 133.33 Hz. An increase of less than 1% of the cycle-averaged efficiency has been reported when the bypass flow through the wastegate increases. The fluctuation of the efficiency is decreased by 1.5% when the wastegate valve becomes fully opened under the whole range of the pulse frequency.

scholarly journals Performance Investigation of a Turbocharger Compressor

2012 ◽  
Author(s):  
A. L. de Wet ◽  
T. W. von Backström ◽  
S. J. van der Spuy
Keyword(s):  
Pressure Ratio ◽  
Three Dimensional ◽  
Rotating Stall ◽  
Test Case ◽  
Test Cases ◽  
Vaned Diffuser ◽  
One Dimensional ◽  
Verification Process ◽  
The One ◽  
Modelling Methods

The compressor section of a diesel locomotive turbocharger was re-designed to increase its maximum total-to-total pressure ratio and efficiency. Tests conducted on the prototype compressor showed possible rotating stall in the diffuser section before the designed higher pressure ratio could be achieved. It was decided to simulate the prototype compressor’s operation by using one-dimensional theory [1], followed by a three-dimensional CFD analysis of the compressor. This publication focuses on implementation of the impeller, vaneless annular passage and vaned diffuser one-dimensional theories. A verification process was followed to show the accuracy of the one- and three-dimensional modelling methods using two well-known centrifugal compressor test cases found in the literature [2–5]. Comparing the test case modelling results to available experimental results indicated sufficient accuracy to investigate the prototype compressor’s impeller and diffuser. Conclusions drawn on the prototype compressor’s performance using the one- and three-dimensional modelling methods led to a recommendation to redesign the impeller and diffuser of the prototype compressor.

The Dissipation Function-Based Efficiency for Turbomachinery: Part 1 — The Efficiency of a Cooled Turbine Row

2014 ◽  
Author(s):  
Chong M. Cha
Keyword(s):  
Aerodynamic Performance ◽  
Dissipation Function ◽  
Second Law ◽  
Efficiency Measure ◽  
One Dimensional ◽  
Specific Heats ◽  
Gas Streams ◽  
The One ◽  
The Impact ◽  
Mixing Problem

The effect of coolant addition or “mixing loss” on aerodynamic performance is formulated for the turbine, where mixing takes place between gas streams of different compositions as well as static temperatures. To do this, a second law efficiency measure is applied to a generalization of the one-dimensional mixing problem between a main gas stream and a single coolant feed, first introduced and studied by Hartsel [1] for the turbine application. Hartsel’s 1972 model for mass-transfer cooling loss still remains the standard for estimating mixing loss in today’s turbines. The present generalization includes losses due to the additional contributions of “compositional mixing” (mixing between unlike compositions of the main and coolant streams) as well as the effect of chemical reaction between the two streams. Scaling of the present dissipation function-based loss model to the mainstream Mach number and relative cooling massflow and static temperature is given. Limitations of the constant specific heats assumptions and the impact of fuel-to-air ratio are also quantified.

scholarly journals Theoretical and Experimental Investigation of a 34 Watt Radial-Inflow Steam Turbine With Partial-Admission

2020 ◽  
Author(s):  
Patrick H. Wagner ◽  
Jan Van herle ◽  
Jürg Schiffmann
Keyword(s):  
Steam Turbine ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Ratio ◽  
Turbine Blades ◽  
Tip Clearance ◽  
Experimental Results ◽  
Partial Admission ◽  
Blade Tip

Abstract A micro steam turbine with a tip diameter of 15 mm was designed and experimentally characterized. At the nominal mass flow rate and total-to-total pressure ratio of 2.3 kg h−1 and 2, respectively, the turbine yields a power of 34 W and a total-to-static isentropic efficiency of 37%. The steam turbine is conceived as a radial-inflow, low-reaction (15%), and partial admission (21%) machine. Since the steam mass flow rate is limited by the heat provided of the system (solid oxide fuel cell), a low-reaction and high-power-density design is preferred. The partial-admission design allows for reduced losses: The turbine rotor and stator blades are prismatic, have a radial chord length of 1 mm and a height of 0.59 mm. Since the relative rotor blade tip clearance (0.24) is high, the blade tip leakage losses are significant. Considering a fixed steam supply, this design allows to increase the blade height, and thus reducing the losses. The steam turbine drives a fan, which operates at low Mach numbers. The rotor is supported on dynamic steam-lubricated bearings; the nominal rotational speed is 175 krpm. A numerical simulation of the steam turbine is in good agreement with the experimental results. Furthermore, a novel test rig setup, featuring extremely-thin thermocouples (ϕ0.15 mm) is investigated for an operation with ambient and hot air at 220 °C. Conventional zero and one-dimensional pre-design models correlate well to the experimental results, despite the small size of the turbine blades.

Time-marching solution of transonic flows at axial turbomachinery meanline

2020 ◽  
pp. 095441002097735
Author(s):  
Simone Rosa Taddei
Keyword(s):  
Mass Flow ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Force Model ◽  
Trailing Edge ◽  
One Dimensional ◽  
Flow Equations ◽  
Transonic Compressor ◽  
Viscous Losses ◽  
Time Marching

A new blade force model is coupled to quasi-one dimensional Euler equations for a variable geometry flowpath. After analytical inclusion of the blade force, the flow equations take a strictly one-dimensional form with specific expressions of the convective flux and blade load source terms. Regardless of the flow turning, that is simply achieved by the load source term as an explicit function of the blade camber, the new form describes a perfect analogy between the average flow inside a blade passage and strictly one-dimensional flows, especially concerning wave propagation. This property allows capture of passage choking and shocks. Other types of shock more important for turbomachinery analysis, like leading edge strong shocks in compressors and trailing edge weak shocks in choked turbines, are modelled by properly matching the new set of equations inside blade regions with the standard quasi-one dimensional equations outside. Upon specification of viscous losses and subsonic deviations fitted from experimental results, the model predicts the choke mass flow of a transonic compressor stage (NASA stage 37) at a 0.1% to 0.4% accuracy both in the absence and in the presence of the leading edge shock. This result supports the effectiveness of the leading edge shock model. The accuracy on choke mass flow would decrease to around 1% if empirical input was specified from open-literature experimental correlations. The model captures the typical trend of exit angle with total pressure ratio for a choked turbine (NASA Lewis two-stage). This result involves satisfactory prediction of not only choke mass flow, but also trailing edge shock loss and supersonic deviation. The complete turbine operational map in terms of shaft torque and pressure ratio is also re-obtained with noticeable accuracy except in strong off-design conditions, where experimental correlations likely fail.

scholarly journals Horizontal pressures in cylindrical metal silos and comparison with different international standards

2013 ◽  
Vol 33 (4) ◽  
pp. 601-611 ◽  
Author(s):  
José W. B. do Nascimento ◽  
José P. Lopes Neto ◽  
Michael D. Montross
Keyword(s):  
Mass Flow ◽  
International Standards ◽  
Constant Speed ◽  
Flat Bottom ◽  
Cylindrical Metal ◽  
The One ◽  
Funnel Flow ◽  
Type Pressure

The focus of this research was to evaluate the horizontal pressures on a cylindrical metal silo of corrugated walls and flat bottom with 1.82m diameter and 5.4m high, and to compare the values with those obtained theoretically by the ISO 11697, EP 433 and AS 3774 standards. The silo was symmetrically filled and constant speed with wheat cv. soft red for two different height/diameter ratios (H/D) and was unloaded through three orifices with a diameter of 71.6mm, one concentric and two eccentrics. Horizontal pressures were measured on the walls of the silo at three positions using hydraulic type pressure cells. The results showed that shortly after the start of the unloading, there was a mass flow above the quota of H/D = 1.2, whereas below this quota funnel flow occurred. It can be said that the EP 433 standard was more appropriate to predict horizontal pressures in silos in H/D ratio = 1.0, with eccentric unloading. For the H/D ratio = 1.5, AS 3774 standard was the one that produced values closer to the experimental.

A new method for rapid shock loss evaluation and reduction for the optimization design of a supersonic compressor cascade

2017 ◽  
Vol 232 (13) ◽  
pp. 2458-2476 ◽  
Author(s):  
Baojie Liu ◽  
Hengtao Shi ◽  
Xianjun Yu
Keyword(s):  
Optimization Design ◽  
Pressure Ratio ◽  
Prediction Method ◽  
Compressor Cascade ◽  
First Passage ◽  
One Dimensional ◽  
Loss Prediction ◽  
Shock System ◽  
The One ◽  
Shock Loss

A one-dimensional analytical shock loss prediction method was proposed to tailor the shock system, i.e. the strength of the first and second passage shock, and reduce the shock loss in a supersonic cascade. To develop the one-dimensional analytical model, the shock system in a supersonic cascade was divided into four processes which can be seen in most supersonic compressor cascade, i.e. the flow upstream the extending-external shock, the flow between the extending-external shock and the first passage shock, the accelerating flow from the first passage shock to the second passage shock, and the flow downstream of the second passage shock. Based on some flow assumptions and experimental empirical correlations, the complex flows, containing the shock system, in the blade passage of a supersonic compressor cascade could be described with one-dimensional relationships, which can be used to predict shock losses along the flow passage rapidly and determine the shock system improving direction for achieving lower shock loss while keeping the same cascade static pressure ratio. In order to validate the one-dimensional analytical method, the shock system of two supersonic cascades ARL-SL19 and DLR-PAV-1.5 are modified based on the analysis of the model. The modified cascades achieved about 29% and 25% reduction of shock loss at redesign point compared with baseline cascades, respectively.

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