scholarly journals Influence of Different Gases on the Design Point of an Industrial Axial Compressor and Deduced Aerodynamical Rematching Methodology

2020 ◽  
Vol 4 ◽  
pp. 238-252
Author(s):  
Henrik Hoffmann ◽  
Lukas Stuhldreier ◽  
Ruben van Rennings ◽  
Peter Jeschke
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Operating Point ◽  
Air Compressor ◽  
Isentropic Exponent ◽  
Compressor Inlet ◽  
Downstream Flow ◽  
Carbon Dioxide Co2

This paper presents a numerical investigation of the effects of compressing various gases, for example, carbon dioxide (CO2) and methane (CH4), on an eight-stage axial air compressor. Several adaptation methods are applied to achieve a similar operating point as for air. Theoretically, the operating point depends on Mach number, flow angles, Reynolds number and isentropic exponent. Numerical results show mismatch effects which arise in the parameters using a non-adapted geometry. A rematching procedure is described, including deduced speed adjustments, in order to achieve Mach number equality at compressor inlet. Only shroud modifications are performed to rematch the flow angles of the air simulation. Although Reynolds and Mach number are kept constant at compressor inlet, an inevitable deviation in downstream flow causes mismatches in efficiency and pressure ratio. Both analytical and numerical methodologies show that the scale of shroud adjustments, as well as the size of mismatch in Mach and Reynolds number, can be correlated to the isentropic gas exponent. In summary, the main impact on gas behavior in an axial air compressor is attributable to the change in isentropic exponent. Derivations of shroud adaptation and analyses of inevitable aerodynamic mismatch are therefore developed depending on the isentropic exponent.

Investigation of the 3D Unsteady Rotor Pressure Field in a HP Turbine Stage

2002 ◽  
Author(s):  
E. Valenti ◽  
J. Halama ◽  
R. De´nos ◽  
T. Arts
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Pressure Field ◽  
Pressure Ratio ◽  
Turbine Stage ◽  
Time Resolved ◽  
Mach Number Distribution ◽  
Rotor Surface ◽  
Exit Mach Number ◽  
Unsteady Pressure Measurements

This paper presents steady and unsteady pressure measurements at three span locations (15, 50 and 85%) on the rotor surface of a transonic turbine stage. The data are compared with the results of a 3D unsteady Euler stage calculation. The overall agreement between the measurements and the prediction is satisfactory. The effects of pressure ratio and Reynolds number are discussed. The rotor time-averaged Mach number distribution is very sensitive to the pressure ratio of the stage since the incidence of the flow changes as well as the rotor exit Mach number. The time-resolved pressure field is dominated by the vane trailing edge shock waves. The incidence and intensity of the shock strongly varies from hub to tip due to the radial equilibrium of the flow at the vane exit. The decrease of the pressure ratio attenuates significantly the amplitude of the fluctuations. An increase of the pressure ratio has less significant effect since the change in the vane exit Mach number is small. The effect of the Reynolds number is weak for both the time-averaged and the time-resolved rotor static pressure at mid-span, while it causes an increase of the pressure amplitudes at the two other spans.

A Comparison between Measured and Computed Flow Fields in a Transonic Compressor Rotor

1980 ◽  
Vol 102 (4) ◽  
pp. 883-889 ◽  
Author(s):  
P. W. McDonald ◽  
C. R. Bolt ◽  
R. J. Dunker ◽  
H. B. Weyer
Keyword(s):  
Mach Number ◽  
Total Pressure ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Computational Procedure ◽  
Operating Conditions ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Pressure Profiles

The flow field within the rotor of a transonic axial compressor has been computed and compared to measurements obtained with an advanced laser velocimeter. The compressor was designed for a total pressure ratio of 1.51 at a relative tip Mach number of 1.4. The comparisons are made at 100 percent design speed (20,260 RPM) with pressure ratios corresponding to peak efficiency, near surge, and wide open discharge operating conditions. The computational procedure iterates between a blade-to-blade calculation and an intrablade through flow calculation. Calculated Mach number contours, surface pressure distributions, and exit total pressure profiles are in agreement with the experimental data demonstrating the usefulness of quasi three-dimensional calculations in compressor design.

scholarly journals Engine Vane Control

1969 ◽  
Author(s):  
George M. Babic ◽  
Louis A. Urban
Keyword(s):  
Mach Number ◽  
High Performance ◽  
Pressure Ratio ◽  
Performance Variable ◽  
Compressor Inlet ◽  
Variable Stator

This paper presents some of the basic considerations underlying the choice of compressor inlet Mach number as a parameter to control the geometry of high performance variable stator compressors. One particular mechanization of the concept utilizing a pressure ratio sensor is described.

Reconciling Compressor Performance Differences for Varying Ambient Inlet Conditions

2015 ◽  
Vol 137 (12) ◽  
Author(s):  
Natalie R. Smith ◽  
Reid A. Berdanier ◽  
John C. Fabian ◽  
Nicole L. Key
Keyword(s):  
Pressure Ratio ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Ambient Conditions ◽  
Thermal Growth ◽  
Reynolds Number Effects ◽  
Compressor Inlet ◽  
Compressor Performance ◽  
Inlet Conditions ◽  
Research Facilities

Careful experimental measurements can capture small changes in compressor total pressure ratio (TPR), which arise with subtle changes in an experiment's configuration. Research facilities that use unconditioned atmospheric air must account for changes in ambient compressor inlet conditions to establish repeatable performance maps. A unique dataset from a three-stage axial compressor has been acquired over the duration of 12 months in the Midwest U.S., where ambient conditions change significantly. The trends show a difference in compressor TPR measured on a cold day versus a warm day despite correcting inlet conditions to sea level standard day. To reconcile these differences, this paper explores correcting the compressor exit thermodynamic state, Reynolds number effects, and variations in rotor tip clearance (TC) as a result of differences in thermal growth.

Three-Dimensional Aerodynamic Optimization of a Multi-Stage Axial Compressor

2016 ◽  
Author(s):  
Tao Ning ◽  
Chun-wei Gu ◽  
Xiao-tang Li ◽  
Tai-qiu Liu
Keyword(s):  
Genetic Algorithm ◽  
Surrogate Model ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Optimization Method ◽  
Operating Point ◽  
Design Parameters ◽  
Aerodynamic Optimization ◽  
Stall Margin

An optimization method combined of a genetic algorithm, an artificial neural network, a CFD solver and a blade generator, is developed in this research and applied in the three-dimensional blading design of a newly designed highly-loaded 5-stage axial compressor. The adaptive probabilities of crossover and mutation, non-uniform mutation operator and elitism operator are employed to improve the convergence of the genetic algorithm. Considering both the optimization efficiency and effectiveness, a mixture of high-fidelity multistage CFD method and approximate surrogate model of the feed-forward ANN is used to evaluate the fitness. In particular, the database is updated dynamically and used to re-train the surrogate model of ANN for improving the accuracy for predicting. The last stator of the compressor is optimized at the near stall operating point. The tip bow with relative bow height Hb and bow angle αb are treated as design parameters. The adiabatic efficiency as well as the penalty of mass flow and total pressure ratio constitute the objective functions to be maximized. The optimum (Hb = 0.881, αb = 14.7°) obtains 0.4% adiabatic efficiency increase for the whole compressor at the optimized operating point. The detailed aerodynamic is compared between the baseline and optimized stator, and the mechanism is analyzed. The optimized version obtains 5.1% increase in stall margin and maintains the efficiency at the design point.

Preliminary Fan Design for a Silent Aircraft

2006 ◽  
Author(s):  
Daniel Crichton ◽  
Liping Xu ◽  
Cesare A. Hall
Keyword(s):  
Mach Number ◽  
Noise Reduction ◽  
High Efficiency ◽  
Pressure Ratio ◽  
Low Pressure ◽  
Shock Structure ◽  
Operating Point ◽  
Blade Passage ◽  
Fuel Burn ◽  
Primary Shock

Preliminary fan design for a functionally silent aircraft has been performed with noise reduction as the primary goal. For such an aircraft the fan design must, in addition to delivering low cruise fuel burn, enable low jet and fan source noise during take-off. This requires the fan to be operating at low pressure ratio and high efficiency during take-off and, for conditions where the relative tip Mach number onto the fan is supersonic, ensuring the primary shock structure is ingested into the blade passage. To meet these requirements, flyover and cruise flow coefficients are matched using a variable area nozzle at the same time as delivering low take-off FPR. This places the sideline operating point near the shoulder of the characteristic and fixes the top of climb and cruise fan pressure ratios. For a 4-engine, 250pax, 4000nm silent aircraft this approach leads to a top of climb FPR of 1.45 requiring a 39% increase in nozzle area at take-off. A fan rotor has been designed for this cycle with 20 blades, low tip loading and a 350m/s top of climb tip speed.

Preliminary Fan Design for a Silent Aircraft

2006 ◽  
Vol 129 (1) ◽  
pp. 184-191 ◽  
Author(s):  
Daniel Crichton ◽  
Liping Xu ◽  
Cesare A. Hall
Keyword(s):  
Mach Number ◽  
Noise Reduction ◽  
High Efficiency ◽  
Pressure Ratio ◽  
Low Pressure ◽  
Shock Structure ◽  
Operating Point ◽  
Blade Passage ◽  
Fuel Burn ◽  
Primary Shock

Preliminary fan design for a functionally silent aircraft has been performed with noise reduction as the primary goal. For such an aircraft the fan design must, in addition to delivering low cruise fuel burn, enable low jet and fan source noise during takeoff. This requires the fan to be operating at low pressure ratio and high efficiency during takeoff and, for conditions where the relative tip Mach number onto the fan is supersonic, ensuring the primary shock structure is ingested into the blade passage. To meet these requirements, flyover and cruise flow coefficients are matched using a variable area nozzle at the same time as delivering low takeoff FPR. This places the sideline operating point near the shoulder of the characteristic and fixes the top of climb and cruise fan pressure ratios. For a 4-engine, 250pax, 4000nm silent aircraft this approach leads to a top of climb FPR of 1.45, requiring a 39% increase in nozzle area at takeoff. A fan rotor has been designed for this cycle with 20 blades, low tip loading during takeoff, and a 350m∕s top of climb tip speed.

An Analytical Approach for Gas Turbine Parameter Corrections

2008 ◽  
Author(s):  
Vasileios E. Kyritsis ◽  
Pericles Pilidis
Keyword(s):  
Mach Number ◽  
Mass Flow ◽  
Pressure Ratio ◽  
Mathematical Formulation ◽  
Flow Speed ◽  
Correction Factors ◽  
Specific Heats ◽  
Isentropic Exponent ◽  
Scaling Parameters ◽  
Mach Numbers

Turbomachinery component behavior depends on dimensionless parameters, such as inlet and circumferential Mach numbers and the ratio of specific heats. Regarding mass flow and speed, their dimensionless scaling parameters are usually used instead based on Mach number similarity. A given dimensionless aerodynamic operating point is defined by certain values of axial and circumferential Mach numbers. To such a point and for a certain value of isentropic exponent, a given dimensionless enthalpy variation corresponds as the work parameter. When turbo-machinery performance sizes, such as the work parameter and efficiency, are plotted against mass flow and speed to form a characteristic, the absence of the isentropic exponent as an additional dimension causes inaccuracies. The extent of the inaccuracies firstly depends on the scaling groups used for mass low, speed and work, that is whether they include the gas property parameters, such as the isentropic exponent and the gas constant. The aforementioned shows that for rigorous calculations correction factors have to be applied, especially when quasi-dimensionless groups are used and/or pressure ratio is used as the work parameter. Typically, the corrections for mass flow and speed may take the form of multipliers, which consist of ratios of the isentropic exponent and/or the gas constant between the examined condition and the reference one. Alternatively, for the case of mass flow the exponents of temperature and pressure can deviate from their theoretical values of 0.5 and 1.0 respectively. Scope of the current work is the mathematical formulation of such exponents for a variety of scaling groups regarding mass flow, speed and work. The correction factors are a strong function of the operating condition, temperature and gas composition, which fully define gas properties. Among the findings of the current study, evidence is provided that the practically one-to-one relationship considered between dimensionless mass flow and inlet Mach number holds for low Mach number values. This is particularly true, since its sensitivity to variations of the isentropic exponent gets increasingly larger with Mach number. Additionally, for a given dimensionless enthalpy change, the exchange rate of pressure ratio against variations of the isentropic exponent is much more increased for an expansion rather than a compression. The latter justifies the use of dimensionless enthalpy drop in turbine characteristics.

scholarly journals Experimental Investigations on Leakages in Positive Displacement Machines

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Hitesh H. Patel ◽  
Vikas J. Lakhera
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Pressure Ratio ◽  
Flow Coefficient ◽  
Experimental Investigations ◽  
Mean Deviation ◽  
Leakage Flow ◽  
Positive Displacement ◽  
Flow Through ◽  
The Mean

The clearance gaps in positive displacement machines such as compressors, pumps, expanders, and turbines are critical for their performance and reliability. The leakage flow through these clearances influences the volumetric and adiabatic efficiencies of the machines. The extent of the leakage flow depends on the size and shape of clearance paths and pressure differences across these paths. Usually, the mass flow through the gaps is estimated using the isentropic nozzle equation with the flow coefficients applied to correct for the real flow conditions. However, the flow coefficients applied generally do not take into account the shape and size of these leakage paths. For that reason, a proper understanding of the relationship between flow coefficients and shape parameters is crucial for an accurate prediction of leakage flows. The present study investigates the influence of the various dimensionless parameters such as Reynolds number, Mach number, and pressure ratio on the flow coefficients for circular and rectangular clearance shapes. The flow coefficients are determined by comparing the experimental values obtained in an experimental test rig and the flow rates obtained from the isentropic nozzle equation. It is observed that in the case of circular clearances, the mean deviation of the experimental leakage results (in comparison to the analytical results using isotropic nozzle equations) is +9.1%, which is significantly lower than the mean deviation (+20.5%) in the case of rectangular clearance leakages. The study indicates that the isentropic nozzle equation method is more suitable for predicting the leakages through the circular clearances and needs modifications for consideration of the rectangular clearances. Using regression analysis, empirical correlations are developed to predict the flow coefficient in terms of Reynolds number, Mach number, pressure ratio, aspect ratio, and β ratio, which are found to match within ±6.4 percent of the numerical results for the rectangular clearance and within the range of -3.6 percent to +5.1 percent of the numerical result for the circular clearance. The empirical relationships presented in this study can be extended to evaluate the flow coefficients in a positive displacement machine.

Influence of key geometric parameters on the aerodynamic performance of a supersonic compressor cascade

2017 ◽  
Vol 232 (12) ◽  
pp. 2338-2348 ◽  
Author(s):  
Cui Cui ◽  
Zhenggui Zhou ◽  
Jinhuan Zhang ◽  
Sheng Tao
Keyword(s):  
Mach Number ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Leading Edge ◽  
Simulation Method ◽  
Wave Pattern ◽  
Aerodynamic Performance ◽  
Compressor Cascade ◽  
Stall Margin ◽  
Edge Radius

The shocks in a supersonic/transonic axial compressor can increase the pressure ratio and cause flow losses. Therefore, it is essential to organize the shock wave pattern in the flow passage to reduce these losses. This study uses a numerical simulation method to study the influences of the leading-edge radius, cascade solidity, and pre-compression on the aerodynamic performance of a supersonic cascade. The cascade is designed using the pre-compression method to reduce shock losses; the inlet Mach number is 2.0 and the total pressure ratio is approximately 3.4. The results indicate that the cascade efficiency and stall margin decrease with an increase in the leading-edge radius; however, when the leading-edge radius is less than 0.1 mm, the influences of its change decrease. As cascade solidity increases, the stall margin first increases and then decreases. The larger the degree of pre-compression, the smaller the Mach number in front of the first oblique passage shock and the higher the efficiency; however, a large pre-compression effect can cause the ending normal shock to move upstream, decreasing the stall margin.

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