The Role of Turbomachinery in Enabling the Hydrogen Economy

2021 ◽  
Author(s):  
Simone Corbò ◽  
Tommaso Wolfler ◽  
Nicola Banchi ◽  
Ippolito Furgiuele ◽  
Majid Farooq
Keyword(s):  
Centrifugal Compressor ◽  
High Pressures ◽  
Pressure Ratio ◽  
Optimal Solution ◽  
Low Flow ◽  
Process Conditions ◽  
Flow Rates ◽  
Rotating Speed ◽  
High Compression ◽  
Delivery Pressure

Abstract The purpose of this paper is to present the various technological solutions optimized for the use of hydrogen, in transport, distribution, storage and utilization, analyzing their criticalities and advantages. Hydrogen compression is a fundamental step in the transportation and storage segments and continuous improvement are required. The greatest technological challenges are certainly the high pressures required for the various fields of use, the need to maintain a clean gas and to use materials that are not subject to embrittlement. The choice between the different compression technologies is based on the need for pressures and flow rates; in the case of high flow rates and low compression ratios a centrifugal compressor is preferable, while for low flow rates and high compression ratios the choice goes to piston compressors. To prevent gas contamination, dry reciprocating compressor are preferred because they allow to avoid an oil separator filter on the discharge. Current technology of reciprocating compressors allows to compress hydrogen up to 300 bar with lubricated machines, while with dry technology it is possible to reach up to 250 bar. A second criticality on reciprocating compressors is maintenance: the parts subject to wear need to be serviced every 8000 hour of operation. The use of innovative materials will increase the maintenance intervals reaching higher pressures without lubrication. To increase the pressure ratio with centrifugal compressor, it's needed to increase the rotating speed, therefore the peripheral speed, with materials suitable for H2, stages get high compression to reduce the number of compressor bodies. If the process conditions require high delivery pressures combined with large flow rates, a solution of centrifugal compressors alone would be able to manage the flow rate but not the required delivery pressure. On the other hand, the use of reciprocating compressors would require a considerable number of units. In this case, therefore, the optimal solution is to combine the two technologies, centrifugal and pistons, using the best features. A case study in which the superior performances of the hybrid solution in terms of total cost of ownership will be described and compared with traditional single technology compression train

3D CFD Approach to Predict the Performance of a Centrifugal Compressor With Surge and Choke Limits

2021 ◽  
Author(s):  
Abishek Sriram ◽  
Jeff Schlautman ◽  
Mehul Varshney ◽  
Dipak Maiti ◽  
Shyam Sundar Pasunurthi ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Cfd Simulation ◽  
Pressure Ratio ◽  
Low Flow ◽  
Design Stage ◽  
Test Bed ◽  
Process Industries ◽  
Flow Rates ◽  
Compressor Surge ◽  
Wear And Tear

Abstract Centrifugal compressor has widespread applications in areas such as aerospace, automotive, power and process industries and hence the prediction of its performance is crucial at the design stage. Traditional design, build and test are accelerated through numerical simulation as a virtual test bed for compressor development. In this work, a CFD methodology has been developed to predict the performance of a centrifugal compressor with its surge and choke limits. The transient, compressible flow in a moving domain with body-fitted unstructured mesh is solved in Simerics-MP. The distributed parallel solver of Simerics-MP enables to perform the complete performance map of a centrifugal compressor in a day. The phenomena of surge and choke in a centrifugal compressor is of paramount importance as it determines the limiting points of operation for a particular speed of the compressor. Surge occurs at low flow rates, and it is characterized by instabilities causing undesirable noises that lead to drop in the operational efficiency. It can also result in wear and tear of the impeller blades. Whereas choke occurs at high flow rates with no further increase in pressure and it is accompanied by aberrant vibrations. The CFD simulation predicts the instabilities occurring at surge such as pressure oscillations and flow reversal accurately, which is used as a criterion for the prediction of surge point. The choke phenomenon is characterized by fluid attaining sonic velocity in the impeller or diffuser region of the compressor. The CFD predicted results showed a fair comparison with the experimental results of pressure ratio, power, and efficiency at different speeds.

Dynamic Model of Multistage Centrifugal Compressor With a Stage-by-Stage Anti-Surge Recirculating System

2021 ◽  
Author(s):  
Nicola Casari ◽  
Michele Pinelli ◽  
Alessio Suman ◽  
Matteo Manganelli ◽  
Mirko Morini ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Suction Side ◽  
System Level ◽  
Low Flow ◽  
Return Flow ◽  
Control Line ◽  
Compressor Surge ◽  
Surge Control ◽  
Surge Line

Abstract The operability region of a centrifugal compressor is bounded by the low-flow (or high-pressure ratio) limit, commonly referred to as surge. The exact location of the surge line on the map can vary depending on the operating condition and, as a result, a typical Surge Avoidance Line is established at 10% to 15% above the stated flow for the theoretical surge line. The current state of the art of centrifugal compressor surge control is to utilize a global recycle valve to return flow from the discharge side of a centrifugal compressor to the suction side to increase the flow through the compressor and, thus, avoid entering the surge region. This is conventionally handled by defining a compressor surge control line that conservatively assumes that all stages must be kept out of surge at all the time. In compressors with multiple stages, the amount of energy loss is disproportion-ally large since the energy that was added in each stage is lost during system level (or global) recycling. This work proposes an internal stage-wise recycling that provides a much more controlled flow recycling to affect only those stages that may be on the verge of surge. The amount of flow needed for such a scheme will be much smaller than highly conservative global recycling approach. Also, the flow does not leave the compressor casing and therefore does not cross the pressure boundary. Compared to global recycling this inherently has less loss depending upon application and specific of control design.

scholarly journals Experimental Investigation of Diffuser Hub Injection to Improve Centrifugal Compressor Stability

2005 ◽  
Vol 127 (1) ◽  
pp. 107-117 ◽  
Author(s):  
Gary J. Skoch
Keyword(s):  
Centrifugal Compressor ◽  
Surface Resistance ◽  
Flow Resistance ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Injection Rate ◽  
Flow Rates ◽  
Injection Flow ◽  
Air Supply ◽  
Series Of Experiments

Results from a series of experiments to investigate whether centrifugal compressor stability could be improved by injecting air through the diffuser hub surface are reported. The research was conducted in a 4:1 pressure ratio centrifugal compressor configured with a vane-island diffuser. Injector nozzles were located just upstream of the leading edge of the diffuser vanes. Nozzle orientations were set to produce injected streams angled at −8, 0, and +8 degrees relative to the vane mean camber line. Several injection flow rates were tested using both an external air supply and recirculation from the diffuser exit. Compressor flow range did not improve at any injection flow rate that was tested, and generally diminished as injection rate increased. Compressor flow range did improve slightly at zero injection due to the flow resistance created by injector openings on the hub surface. Resistance and flow range both increased as the injector orientation was turned toward radial. Leading edge loading and semivaneless space diffusion showed trends that are similar to those reported earlier from shroud surface experiments that did improve compressor range. Opposite trends are seen for hub injection cases where compressor flow range decreased. The hub injection data further explain the range improvement provided by shroud-side injection and suggest that stability factors cited in the discussion of shroud surface techniques are valid. The results also suggest that a different application of hub-side techniques may produce a range improvement in centrifugal compressors.

scholarly journals The Effect of Variable Geometry on the Operating Range and Surge Margin of a Centrifugal Compressor

1976 ◽  
Author(s):  
A. Whitfield ◽  
F. J. Wallace ◽  
R. C. Atkey
Keyword(s):  
Centrifugal Compressor ◽  
Peak Pressure ◽  
Pressure Ratio ◽  
Variable Geometry ◽  
Vaneless Diffuser ◽  
Flow Rates ◽  
Lower Flow ◽  
Operating Range ◽  
Surge Margin ◽  
Isentropic Efficiency

Two variable geometry techniques have been applied to a small turbocharger compressor, with the objective of trying to move the peak pressure ratio operating point to lower flow rates, thereby yielding a broad flow range map. Variable prewhirl guide vanes and variable vaneless diffuser passage height have been studied separately. The results obtained with both techniques are compared and the relative merits and demerits with respect to improved flow range and isentropic efficiency penalties are considered.

A Fast Method for Determining the Flow Conductance of Gas Microfluidic Devices

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Matteo Martinelli ◽  
Vladimir Viktorov
Keyword(s):  
Pressure Ratio ◽  
Time Derivative ◽  
Microfluidic Devices ◽  
Low Flow ◽  
Thermal Bath ◽  
Fast Method ◽  
Flow Rates ◽  
Pressure Drops ◽  
Upstream Pressure ◽  
Computerized Data Processing

This paper presents a fast method for determining the conductance of gas microfluidic devices with low flow rates and very small pressure drops starting from 30 Pa, corresponding to Re=0.3. This method is based on discharging a gas-pressurized chamber through the microfluidic device under test. The microfluidic device’s conductance can be estimated as a function of inlet pressure and the Reynolds number of the flow by recording the upstream pressure during the discharging process and calculating the time derivative of the gas pressure. The pressurized chamber is considered as an isothermal chamber. Experimental results show that a sufficiently accurate isothermal discharging process up to an upstream-to-downstream pressure ratio of 0.8 can be achieved by immersing the chamber in a thermal bath. The method presented here is very fast, requiring only a few seconds for the acquisition procedure and computerized data processing.

Managing Transient Operating Conditions of Hyper Compressors

2014 ◽  
Author(s):  
Marcello Agostini ◽  
Cosimo Carcasci ◽  
Alessio Cristofani
Keyword(s):  
High Pressures ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Process Conditions ◽  
Operator Experience ◽  
Start Up ◽  
Reactor Operating ◽  
Two Stages ◽  
Gas Expansion ◽  
Plant Automation

Special reciprocating compressors are required to reach the very high pressures necessary to feed the reactors used in LDPE plants. The working conditions of the compressors are determined by the reactor operating pressures and are considered for evaluation of the loads, torsional, pulsation and vibration conditions. Performance and safety are key considerations and operator experience is essential for optimal and safe plant operation. Plant automation contributes to safety and optimizes process conditions. The compressor start-up and shutdown procedures, commonly detailed in maintenance manuals, are analyzed studying the operating parameters to draw up guidelines for avoiding damage to plunger seals and keeping loads within design limits, without compromising the design performance. The multiple gas compositions of co-polymers and the fact that gas expansion can cause a reduction in temperature, need adequate consideration to avoid damage caused by polymer inside the compressor cylinders. The paper will also give recommendations on the necessary procedures to reach the operating pressures with correct distribution of the total pressure ratio between the two stages. These will also include the requirement of minimum pressure on the plunger head to maintain contact with the crosshead and avoid failure of such a brittle component.

scholarly journals The Performance of a Centrifugal Compressor With High Inlet Prewhirl

1997 ◽  
Author(s):  
A. Whitfield ◽  
A. H. Abdullah
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Low Flow ◽  
Variable Geometry ◽  
Pressure Pulsations ◽  
Operating Range ◽  
Swirl Generator ◽  
Geometry Design ◽  
Wide Range ◽  
Inlet Swirl

The performance requirements of centrifugal compressors usually include a broad operating range between surge and choke. This becomes increasingly difficult to achieve as increased pressure ratio is demanded. In order to suppress the tendency to surge and extend the operating range at low flow rates inlet swirl is often considered through the application of inlet guide vanes. To generate high inlet swirl angles efficiently an inlet volute has been applied as the swirl generator, and a variable geometry design developed in order to provide zero swirl. The variable geometry approach can be applied to progressively increase the swirl or to switch rapidly from zero swirl to maximum swirl. The variable geometry volute and the swirl conditions generated are described. The performance of a small centrifugal compressor is presented for a wide range of inlet swirl angles. In addition to the basic performance characteristics of the compressor the onset of flow reversals at impeller inlet are presented, together with the development of pressure pulsations, in the inlet and discharge ducts, through to full surge. The flow rate at which surge occurred was shown, by the shift of the peak pressure condition and by the measurement of the pressure pulsations, to be reduced by over 40%.

Performance Characteristics of a Centrifugal Compressor with Air Injection

1973 ◽  
Vol 187 (1) ◽  
pp. 425-434 ◽  
Author(s):  
J. D. Ledger ◽  
R. S. Benson ◽  
H. Furukawa
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Total Mass ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Performance Characteristics ◽  
Air Injection ◽  
Delivery Pressure ◽  
Mass Flow Rates ◽  
The Right

The parameters which influence the performance characteristics of centrifugal compressors with air injection through nozzles at the rotor tip are developed using both dimensional analysis and a simple model. Experiments on a small centrifugal compressor show that the injection air pressure is the main influence on the overall performance such as excess torque, increased delivery pressure and increased delivery flow. With air injection the pressure-mass flow characteristics are displaced to the right with surge occurring at increased total mass flow rates and the overall pressure ratio across the compressor is increased for the same total mass flow.

scholarly journals Research on the Simplified Design of a Centrifugal Compressor Impeller Based on Meridional Plane Modification

2018 ◽  
Vol 8 (8) ◽  
pp. 1339 ◽  
Author(s):  
Hong Xie ◽  
Moru Song ◽  
XiaoLan Liu ◽  
Bo Yang ◽  
Chuangang Gu
Keyword(s):  
Centrifugal Compressor ◽  
Design Method ◽  
Pressure Ratio ◽  
Aerodynamic Characteristics ◽  
Low Flow ◽  
Measure Data ◽  
Meridional Plane ◽  
Stall Margin ◽  
Numerical Result ◽  
Compressor Impeller

This study mainly focuses on investigating the influence of meridional contour of a steam centrifugal compressor on aerodynamic performance. An optimal design method is put forwards, in which the hub-line on the meridional plane is modified and optimized. Based on the data from numerical simulation, aerodynamic characteristics are compared in detail among a prototype and three modified impellers. It is shown that stall margin of the optimized impeller can be enlarged by approximately 50%, though at design point efficiency and pressure ratio is decreased a little bit. Under the working conditions with low flow rate, the optimized impeller exhibits the best performance compared with the prototype and two other impellers. Furthermore, numerical result is validated by the experiment and is matched the measure data very well.

Numerical Investigation of the Effect of Tip Clearance to the Performance of a Small Centrifugal Compressor

2006 ◽  
Author(s):  
Jin Tang ◽  
Teemu Turunen-Saaresti ◽  
Arttu Reunanen ◽  
Juha Honkatukia ◽  
Jaakko Larjola
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Flow Distribution ◽  
Ideal Gas ◽  
Tip Clearance ◽  
Flow Angle ◽  
Flow Rates ◽  
Real Gas ◽  
Mass Flow Rates

Numerical analysis is conducted for the 3-dimensional impeller and vaneless diffuser of a small centrifugal compressor. The influence of impeller tip clearance is investigated. A Navier-Stokes flow solver Finflo has been applied for the simulation. A practical real gas model has been generated for the calculation. Simulations with different sizes of tip clearance at different mass flow rates have been made. The results are compared to experimental results at a certain tip clearance and one operating point. Reasonable agreement has been obtained. The ideal gas model has also been applied to compare with the real gas model. The numerical results show that tip clearance has a significant effect on the performance of a small centrifugal compressor. As the size of tip clearance increases, both the pressure ratio and the efficiency decrease. The decreasing rate of efficiency is higher at higher mass flow rates and lower at lower mass flow rates. The input power of the compressor hardly changes with different sizes of tip clearance, but increases as the mass flow rate increases. The incidence of impeller and flow angle at the exit of the impeller increase as the size of tip clearance increases. Correlations of the size of tip clearance with the efficiency drop and change of flow angle at the exit of impeller are given. The detailed flow distribution shows that as the size of tip clearance increases, the tangential leaking flow at the tip clearance makes the low velocity flow region grow larger and move from the suction-shroud corner to the center of the flow channel. The main flow at the pressure side is compressed and accelerated. Therefore the uniformity of the flow in the whole channel decreases. The detailed flow distribution also shows that the leaking flow is stronger at higher mass flow rates.

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