Preliminary Design Tool for Centrifugal Compressors

2021 ◽  
Author(s):  
Lily Baye-Wallace ◽  
Grant O. Musgrove
Keyword(s):  
Pressure Ratio ◽  
Operating Parameter ◽  
Ideal Gas ◽  
Design Tool ◽  
Design Parameters ◽  
Compressor Design ◽  
Previous Design ◽  
Inlet Conditions ◽  
Total Pressure Ratio ◽  
Design Experience

Abstract Commonly, compressor designs rely on previous machines that can be slightly modified to achieve new operating requirements. In some cases, however, a completely new design is needed because no previous designs are available for the specific operating range of interest. Without a previous design, it is difficult to make initial trade studies of an appropriate impeller diameter, speed, and number of compression stages. While new compressor designs are a common occurrence in applied research applications, conceptual design typically require a point-by-point process to balance the requirements with acceptable design parameters. This can be done manually or through automation to optimize for a specific operating parameter, such as efficiency. The authors are unaware of any tool available that bounds the range of design parameters for a centrifugal compressor stage without applying a point-by-point method. In this work, two common references for conceptual compressor design were cross-checked to develop an Excel-based tool to quickly determine the design space for a given set of compressor requirements. The tool relies on design experience presented by Aungier and Baljé as well as other experience drawn from available literature [1],[2]. The sheet functions from a series of assumptions based within the design experience and requires inputs regarding the desired power, fluid flow rate, and total-to-total pressure ratio, as well as inlet conditions. While the tool currently assumes an ideal gas, future revisions can include calls to REFPROP for a real gas.

scholarly journals A Design Tool for Supercritical CO2 Radial Compressors Based on the Two-Zone Model

2020 ◽  
Author(s):  
Ihab Abd El Hussein ◽  
Alexander Johannes Hacks ◽  
Sebastian Schuster ◽  
Dieter Brillert
Keyword(s):  
Pressure Ratio ◽  
Compressibility Factor ◽  
Ideal Gas ◽  
Design Tool ◽  
Design Approach ◽  
Maximum Deviation ◽  
Zone Model ◽  
Plausibility Check ◽  
Compressor Inlet ◽  
Inlet Conditions

Abstract In supercritical Carbon Dioxide (sCO2) cycles, the compressor inlet conditions are selected near the critical point where compressibility factor reaches values as low as 0.2. Consequently, conventional compressor design approaches formulated for fluids obeying the ideal gas law are not verified. Therefore, this paper proposes a design approach for sCO2 radial compressors that consists of a performance prediction model in addition to a set of geometry parameters suitable for radial compressors. The compressor model is based on the two-zone modeling approach, in which the Span and Wagner equation of state for CO2 is integrated. At first, the compressor model is presented in addition to the required correlations. Afterwards, a sensitivity analysis is performed on the model main parameters. Thereafter, a plausibility check is performed against experimentally obtained data. Finally, an overall design approach is proposed and its capability to deliver new geometries is assessed by comparing the tool predictions against the results from a verified CFD code for several test cases. The Comparison shows a maximum deviation of less than 2 percent for the pressure ratio and less than 3.5 percentage points for the efficiency. The results indicate the ability of the proposed approach to predict the performance of sCO2 compressor from correlations that originate from experience with conventional fluids. Additionally, the adopted geometric relations proved its applicability to sCO2 compressors.

Comprehensive Application of a First Principles Based Methodology for Design of Axial Compressor Configurations

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Vishwas Iyengar ◽  
Lakshmi N. Sankar
Keyword(s):  
First Principles ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Design Parameters ◽  
Axial Compressors ◽  
Design Variables ◽  
Improved Accuracy ◽  
Total Pressure Ratio

Axial compressors are widely used in many aerodynamic applications. The design of an axial compressor configuration presents many challenges. It is necessary to retool the design methodologies to take advantage of the improved accuracy and physical fidelity of these advanced methods. Here, a first-principles based multiobjective technique for designing single stage compressors is described. The study accounts for stage aerodynamic characteristics and rotor-stator interactions. The proposed methodology provides a way to systematically screen through the plethora of design variables. This method has been applied to a rotor-stator stage similar to NASA Stage 35. By selecting the most influential design parameters and by optimizing the blade leading edge and trailing edge mean camber line angles, phenomena such as tip blockages, blade-to-blade shock structures and other loss mechanisms can be weakened or alleviated. It is found that these changes to the configuration can have a beneficial effect on total pressure ratio and stage adiabatic efficiency, thereby improving the performance of the axial compression system.

On a Model of a Pneumatically Actuated Mechanical System

1971 ◽  
Vol 93 (1) ◽  
pp. 211-220 ◽  
Author(s):  
M. Skreiner ◽  
P. Barkan
Keyword(s):  
Differential Equations ◽  
Mechanical System ◽  
Transient Flow ◽  
Pressure Ratio ◽  
Design Tool ◽  
Time Dependent ◽  
Pneumatic System ◽  
Design Parameters ◽  
Strong Nonlinearity ◽  
Linkage Mechanism

A model of a general mechanical system, comprising a pneumatic system coupled to a linkage mechanism, is developed. The dynamic system behavior is studied using the digital computer as a design tool to determine the effect on the performance of changing design parameters. Within practical limitations, models of this kind have been used to achieve optimum design. Novel methods are used to treat the two major components of the system. The pneumatic system is modeled using an equivalent flow area which is a function of the time-dependent pressure ratio. Differential equations used to solve for the transient flow in the reservoir/piping/piston system are derived here. The mechanism driven by the pneumatic system consists of multiple series chains of four-bar linkages. The first- and second-order kinematic ratios required in the dynamics are computed from new explicit expressions derived here. Frictional losses, impact, and flexibility of the mechanism are included in the dynamic model. The nonlinearity of the differential equations arises from: (a) the kinematics, (b) drag forces depending on velocity squared, (c) magnetic forces depending on time squared, and (d) the strong nonlinearity of the time-dependent pneumatic system. The system of equations is solved numerically to obtain the record of pressure, temperature, and leakage in the pneumatic system and the travel of the mechanisms versus time. Good agreement is obtained between the theoretical solution and actual tests.

scholarly journals Ultrashort Nacelles for Low Fan Pressure Ratio Propulsors

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Andreas Peters ◽  
Zoltán S. Spakovszky ◽  
Wesley K. Lord ◽  
Becky Rose
Keyword(s):  
Mach Number ◽  
Pressure Ratio ◽  
Design Tool ◽  
Operating Conditions ◽  
Design Parameters ◽  
Flow Distortion ◽  
Flow Area ◽  
Propulsive Efficiency ◽  
Flow Acceleration ◽  
Fuel Burn

As the propulsor fan pressure ratio (FPR) is decreased for improved fuel burn, reduced emissions and noise, the fan diameter grows and innovative nacelle concepts with short inlets are required to reduce their weight and drag. This paper addresses the uncharted inlet and nacelle design space for low-FPR propulsors where fan and nacelle are more closely coupled than in current turbofan engines. The paper presents an integrated fan–nacelle design framework, combining a spline-based inlet design tool with a fast and reliable body-force-based approach for the fan rotor and stator blade rows to capture the inlet–fan and fan–exhaust interactions and flow distortion at the fan face. The new capability enables parametric studies of characteristic inlet and nacelle design parameters with a short turn-around time. The interaction of the rotor with a region of high streamwise Mach number at the fan face is identified as the key mechanism limiting the design of short inlets. The local increase in Mach number is due to flow acceleration along the inlet internal surface coupled with a reduction in effective flow area. For a candidate short-inlet design with length over diameter ratio L/D = 0.19, the streamwise Mach number at the fan face near the shroud increases by up to 0.16 at cruise and by up to 0.36 at off-design conditions relative to a long-inlet propulsor with L/D = 0.5. As a consequence, the rotor locally operates close to choke resulting in fan efficiency penalties of up to 1.6% at cruise and 3.9% at off-design. For inlets with L/D < 0.25, the benefit from reduced nacelle drag is offset by the reduction in fan efficiency, resulting in propulsive efficiency penalties. Based on a parametric inlet study, the recommended inlet L/D is suggested to be between 0.25 and 0.4. The performance of a candidate short inlet with L/D = 0.25 was assessed using full-annulus unsteady Reynolds-averaged Navier–Stokes (RANS) simulations at critical design and off-design operating conditions. The candidate design maintains the propulsive efficiency of the baseline case and fuel burn benefits are conjectured due to reductions in nacelle weight and drag compared to an aircraft powered by the baseline propulsor.

scholarly journals Mean-Line Design of a Supercritical CO2 Micro Axial Turbine

2020 ◽  
Vol 10 (15) ◽  
pp. 5069 ◽  
Author(s):  
Salma I. Salah ◽  
Mahmoud A. Khader ◽  
Martin T. White ◽  
Abdulnaser I. Sayma
Keyword(s):  
Waste Heat ◽  
Expansion Ratio ◽  
Design Tool ◽  
Single Stage ◽  
Flow Coefficient ◽  
Low Flow ◽  
Design Parameters ◽  
Axial Turbine ◽  
Inlet Conditions ◽  
Line Design

Supercritical carbon dioxide (sCO2) power cycles are promising candidates for concentrated-solar power and waste-heat recovery applications, having advantages of compact turbomachinery and high cycle efficiencies at heat-source temperature in the range of 400 to 800 ∘C. However, for distributed-scale systems (0.1–1.0 MW) the choice of turbomachinery type is unclear. Radial turbines are known to be an effective machine for micro-scale applications. Alternatively, feasible single-stage axial turbine designs could be achieved allowing for better heat transfer control and improved bearing life. Thus, the aim of this study is to investigate the design of a single-stage 100 kW sCO2 axial turbine through the identification of optimal turbine design parameters from both mechanical and aerodynamic performance perspectives. For this purpose, a preliminary design tool has been developed and refined by accounting for passage losses using loss models that are widely used for the design of turbomachinery operating with fluids such as air or steam. The designs were assessed for a turbine that runs at inlet conditions of 923 K, 170 bar, expansion ratio of 3 and shaft speeds of 150k, 200k and 250k RPM respectively. It was found that feasible single-stage designs could be achieved if the turbine is designed with a high loading coefficient and low flow coefficient. Moreover, a turbine with the lowest degree of reaction, over a specified range from 0 to 0.5, was found to achieve the highest efficiency and highest inlet rotor angles.

Reconciling Compressor Performance Differences for Varying Ambient Inlet Conditions

2015 ◽  
Author(s):  
Natalie R. Smith ◽  
Reid A. Berdanier ◽  
John C. Fabian ◽  
Nicole L. Key
Keyword(s):  
Total Pressure ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Ambient Conditions ◽  
Midwest United States ◽  
Thermal Growth ◽  
Reynolds Number Effects ◽  
Inlet Conditions ◽  
Total Pressure Ratio

Careful experimental measurements can capture small changes in compressor total pressure ratio that 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 threestage axial compressor has been acquired over the duration of 12 months in the Midwest United States where ambient conditions change significantly. The trends show a difference in compressor total pressure ratio 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 as a result of differences in thermal growth.

Comprehensive Application of a First Principles Based Methodology for Design of Axial Compressor Configurations

2011 ◽  
Author(s):  
Vishwas Iyengar ◽  
Lakshmi N. Sankar
Keyword(s):  
First Principles ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Design Parameters ◽  
Axial Compressors ◽  
Design Variables ◽  
Improved Accuracy ◽  
Total Pressure Ratio

Axial compressors are widely used in many aerodynamic applications. The design of an axial compressor configuration presents many challenges. It is necessary to retool the design methodologies to take advantage of the improved accuracy and physical fidelity of these advanced methods. Here, a first-principles based multi-objective technique for designing single stage compressors is described. The study accounts for stage aerodynamic characteristics and rotor-stator interactions. The proposed methodology provides a way to systematically screen through the plethora of design variables. This method has been applied to a rotor-stator stage similar to NASA Stage 35. By selecting the most influential design parameters and by optimizing the blade leading edge and trailing edge mean camber line angles, phenomena such as tip blockages, blade-to-blade shock structures and other loss mechanisms can be weakened or alleviated. It is found that these changes to the configuration can have a beneficial effect on total pressure ratio and stage adiabatic efficiency, thereby improving the performance of the axial compression system.

scholarly journals Ultra-Short Nacelles for Low Fan Pressure Ratio Propulsors

2014 ◽  
Author(s):  
Andreas Peters ◽  
Zoltán S. Spakovszky ◽  
Wesley K. Lord ◽  
Becky Rose
Keyword(s):  
Mach Number ◽  
Pressure Ratio ◽  
Design Tool ◽  
Operating Conditions ◽  
Design Parameters ◽  
Flow Distortion ◽  
Flow Area ◽  
Propulsive Efficiency ◽  
Flow Acceleration ◽  
Fuel Burn

As the propulsor fan pressure ratio (FPR) is decreased for improved fuel burn, reduced emissions and noise, the fan diameter grows and innovative nacelle concepts with short inlets are required to reduce their weight and drag. This paper addresses the uncharted inlet and nacelle design space for low-FPR propulsors where fan and nacelle are more closely coupled than in current turbofan engines. The paper presents an integrated fan-nacelle design framework, combining a spline-based inlet design tool with a fast and reliable body-force-based approach for the fan rotor and stator blade rows to capture the inlet-fan and fan-exhaust interactions and flow distortion at the fan face. The new capability enables parametric studies of characteristic inlet and nacelle design parameters with a short turn-around time. The interaction of the rotor with a region of high streamwise Mach number at the fan face is identified as the key mechanism limiting the design of short inlets. The local increase in Mach number is due to flow acceleration along the inlet internal surface coupled with a reduction in effective flow area. For a candidate short-inlet design with length over diameter ratio L/D = 0.19, the streamwise Mach number at the fan face near the shroud increases by up to 0.16 at cruise and by up to 0.36 at off-design conditions relative to a long-inlet propulsor with L/D = 0.5. As a consequence, the rotor locally operates close to choke resulting in fan efficiency penalties of up to 1.6 % at cruise and 3.9 % at off-design. For inlets with L/D < 0.25, the benefit from reduced nacelle drag is offset by the reduction in fan efficiency, resulting in propulsive efficiency penalties. Based on a parametric inlet study, the recommended inlet L/D is suggested to be between 0.25 and 0.4. The performance of a candidate short inlet with L/D = 0.25 was assessed using full-annulus unsteady RANS simulations at critical design and off-design operating conditions. The candidate design maintains the propulsive efficiency of the baseline case and fuel burn benefits are conjectured due to reductions in nacelle weight and drag compared to an aircraft powered by the baseline propulsor.

On Calculation of Leakage Flow in Screw Compressor Elements

2020 ◽  
Author(s):  
Nikola Stosic
Keyword(s):  
Pressure Drop ◽  
Kinetic Energy ◽  
Labyrinth Seal ◽  
Ideal Gas ◽  
Wall Friction ◽  
Design Parameters ◽  
Leakage Flow ◽  
Local Loss ◽  
Compressor Design ◽  
Energy And Momentum

Abstract The computation of the gas velocity in leaking paths which may contain labyrinth elements of screw compressors is developed from the continuity, energy and momentum equations. It accounts for the effects of the local loss of flow kinetic energy and line fluid-wall friction by assuming that the fluid is an ideal gas at constant temperature to eliminate gas density. This is straightforward situation if the clearance leakage flow is considered to happen in a single leakage gap element, however, if a series of leakage elements are applied, as for example, it happens in a labyrinth seal components, there will be a pressure drop in each groove which in sum will give the overall pressure drop. A sensitivity analysis of the compressor design parameters that influence such a sequence of the labyrinth seal performance upon that the leakage flow strongly depends upon the gap clearance and only weakly depends on the clearance length and the number of labyrinth grooves. The influence of the number of grooves becomes even weaker if the entire kinetic energy of the leakage flow is not fully dissipated in the labyrinth grooves.

scholarly journals Large Eddy Simulations of Strongly Non-Ideal Compressible Flows through a Transonic Cascade

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 772
Author(s):  
Jean-Christophe Hoarau ◽  
Paola Cinnella ◽  
Xavier Gloerfelt
Keyword(s):  
Compressible Flows ◽  
Flow Behavior ◽  
Pressure Ratio ◽  
Organic Rankine Cycle ◽  
Ideal Gas ◽  
Operating Conditions ◽  
Large Eddy Simulations ◽  
Working Fluid ◽  
Viscous Effects ◽  
Large Eddy

Transonic flows of a molecularly complex organic fluid through a stator cascade were investigated by means of large eddy simulations (LESs). The selected configuration was considered as representative of the high-pressure stages of high-temperature Organic Rankine Cycle (ORC) axial turbines, which may exhibit significant non-ideal gas effects. A heavy fluorocarbon, perhydrophenanthrene (PP11), was selected as the working fluid to exacerbate deviations from the ideal flow behavior. The LESs were carried out at various operating conditions (pressure ratio and total conditions at inlet), and their influence on compressibility and viscous effects is discussed. The complex thermodynamic behavior of the fluid generates highly non-ideal shock systems at the blade trailing edge. These are shown to undergo complex interactions with the transitional viscous boundary layers and wakes, with an impact on the loss mechanisms and predicted loss coefficients compared to lower-fidelity models relying on the Reynolds-averaged Navier–Stokes (RANS) equations.

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