Investigation of Slip Models for High-Speed Centrifugal Compressors

2021 ◽  
Vol 37 (1) ◽  
pp. 3-12
Author(s):  
Herbert M. Harrison ◽  
Fangyuan Lou ◽  
Nicole L. Key
Keyword(s):  
High Speed ◽  
Centrifugal Compressors

Criteria for the Stability Limit Prediction of High Speed Centrifugal Compressors With Vaneless Diffuser: Part I — Flow Structure Analysis

2020 ◽  
Author(s):  
Carlo Cravero ◽  
Davide Marsano
Keyword(s):  
Rotational Speed ◽  
High Speed ◽  
Stability Limit ◽  
Vaneless Diffuser ◽  
Centrifugal Compressors ◽  
Vaned Diffuser ◽  
High Rotational Speed ◽  
Lower Accuracy ◽  
The Stability ◽  
Computational Resources

Abstract High-speed centrifugal compressor requirements include a wide operating range between choking and stall especially for turbocharging applications. The prediction of the stability limit at different speeds is still challenging. In literature, several studies have been published on the phenomena that trigger the compressor instability. However, a comprehensive analysis of criteria that can be used in the first steps of centrifugal compressors design to predict the stability limit is still missing. In previous work the authors have already presented a criterion, so called “Stability Parameter”, to predict the surge line of centrifugal compressors based on a simplified CFD approach that does not require excessive computational resources and that can be efficiently used in the preliminary design phases. The above methodology has demonstrated its accuracy for centrifugal compressors with vaned diffuser, but a lower accuracy has been detected for vaneless diffusers. Before proceeding to identify additional criteria focused on compressors with vaneless diffuser, an in-depth fluid dynamics analysis has been necessary. This analysis has been also carried out through fully 3D unsteady simulations to allow identifying the real phenomena linked to the trigger of the instability of centrifugal compressors. It has been found how these phenomena are strongly related to the rotational speed, in particular have been shown the key role of the volute at high rotational speed.

Improvement of Rotordynamic Performance of Integrally Geared Centrifugal Compressors Through a Systematic Design Modification Approach

2019 ◽  
Author(s):  
Zhusan Luo ◽  
Carl Schwarz
Keyword(s):  
High Speed ◽  
High Efficiency ◽  
High Reliability ◽  
Air Separation ◽  
Centrifugal Compressors ◽  
Design Modification ◽  
Design Variables ◽  
Short Period ◽  
Key Indicators ◽  
Bearing System

Abstract Integrally geared centrifugal compressors have found wide applications in air separation plants and the petrochemical industry because they can be readily designed to run at a higher efficiency than in-line compressors. Many of these compressors with multiple stages are designed to meet the demands for high power and high speed applications with high efficiency and high reliability. These requirements are challenges for their rotordynamic designs. Some compressors may experience excessive synchronous or subsynchronous vibrations during commissioning or in a short period of service. This study starts with discussing the vibration characteristics of a compressor pinion-bearing system, including undamped critical speeds, unbalance responses, and rotordynamic stability. To improve the rotordynamic performance, a systematic and feasible approach for modifying a rotordynamic design has been proposed. It has been showed that damped modes at an operating speed are key indicators of the rotordynamic performance. The sensitivities of damped modes to main design variables, i.e. bearing geometry, shaft geometry and impeller mass properties, are thoroughly examined. A procedure for design modification is proposed for general guidance. The feasibility and effectiveness of this method have been demonstrated in the modification of a pinion-bearing system. In addition, this paper also proposes a method to evaluate the torsional natural frequencies of an equivalent pinion model and briefly discusses the application of optimal design methodology to the rotordynamic design modification.

Blade Forcing Function and Aerodynamic Work Measurements in a High Speed Centrifugal Compressor With Inlet Distortion

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
Albert Kammerer ◽  
Reza S. Abhari
Keyword(s):  
High Speed ◽  
Pressure Sensors ◽  
Forced Response ◽  
Blade Surface ◽  
Centrifugal Compressors ◽  
Flow Distortion ◽  
Unsteady Pressure ◽  
Inlet Distortion ◽  
Forcing Function ◽  
Work Distribution

Centrifugal compressors operating at varying rotational speeds, such as in helicopters or turbochargers, can experience forced response failure modes. The response of the compressors can be triggered by aerodynamic flow nonuniformities such as with diffuser-impeller interaction or with inlet distortions. The work presented here addresses experimental investigations of forced response in centrifugal compressors with inlet distortions. This research is part of an ongoing effort to develop related experimental techniques and to provide data for validation of computational tools. In this work, measurements of blade surface pressure and aerodynamic work distribution were addressed. A series of pressure sensors were designed and installed on rotating impeller blades and simultaneous measurements with blade-mounted strain gauges were performed under engine representative conditions. To the best knowledge of the authors, this is the first publication, which presents comprehensive experimental unsteady pressure measurements during forced response, for high-speed radial compressors. The experimental data were obtained for both resonance and off-resonance conditions with uniquely tailored inlet distortion. This paper covers aspects relating to the design of fast response pressure sensors and their installation on thin impeller blades. Additionally, sensor properties are outlined with a focus on calibration and measurement uncertainty estimations. The second part of this paper presents unsteady pressure results taken for a number of inlet distortion cases. It will be shown that the intended excitation order due to inlet flow distortion is of comparable magnitude to the second and third harmonics, which are consistently observed in all measurements. Finally, an experimental method will be outlined that enables the measurement of aerodynamic work on the blade surface during resonant crossing. This approach quantifies the energy exchange between the blade and the flow in terms of cyclic work along the blade surface. The phase angle between the unsteady pressure and the blade movement will be shown to determine the direction of energy transfer.

Criteria for the Stability Limit Prediction of High Speed Centrifugal Compressors With Vaneless Diffuser: Part II — The Development of Prediction Criteria

2020 ◽  
Author(s):  
Carlo Cravero ◽  
Davide Marsano
Keyword(s):  
High Speed ◽  
Numerical Models ◽  
Fluid Dynamic ◽  
Stability Limit ◽  
Design Phase ◽  
Vaneless Diffuser ◽  
Centrifugal Compressors ◽  
Vaned Diffuser ◽  
The Stability ◽  
Computational Resources

Abstract The challenge to be able to predict the stability limit in high speed centrifugal compressor is particularly strategic in an initial design phase. Furthermore, to be able to predict the limit massflow rate through the use of simplified numerical models (which does not require excessive computational resources) is very important. In the literature there are several methods to predict the chocking condition, while there is a lack as regards the surge condition. The authors have already presented a criterion to predict the surge line valid for centrifugal compressors with vaned diffuser. Instead those with vaneless diffuser have a very different behavior. For this reason, in the first paper an in-depth fluid dynamic analysis has been carried out, in order to identify the main phenomena linked to the trigger of instability in this type of compressors. This analysis has allowed understanding that the rotational speed is a discriminating factor in the phenomenology. In this second part, using the previous information, different criteria to predict the limit massflow rate for centrifugal compressors with vaneless diffuser are described. All the criteria are based on different simplified CFD approaches that can be routinely used during the design phase.

Characteristics of potential forcing functions in high speed centrifugal compressors

2001 ◽  
Author(s):  
Albert Sanders ◽  
William Carnell, Jr. ◽  
William Oakes ◽  
Patrick Lawless ◽  
Sanford Fleeter
Keyword(s):  
High Speed ◽  
Centrifugal Compressors ◽  
Forcing Functions

Impact of Heat Transfer on Centrifugal Compressors of Micro Turbines

2012 ◽  
Author(s):  
Dries Verstraete ◽  
Yasitha Hewakuruppu
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
High Speed ◽  
Power Level ◽  
Centrifugal Compressors ◽  
Detail Design ◽  
Heavy Duty Diesel ◽  
And Performance ◽  
Competitive Efficiency ◽  
The Impact

Micro turbines are small, high-speed gas turbine engines. When designed for a power output of 5 to 15 kW, micro turbines could provide the power for a household or a small set of units, serve as a range extender for hybrid electrical vehicles, or an auxiliary power unit to meet anti-idling requirements for heavy-duty diesel truck engines. The smaller the gas turbine, the harder it however is to achieve a competitive efficiency. At the considered power level, manufacturing limitations become significant and heat transfer and fluid leaks start to dominate. Significant development in material science has enabled higher temperatures to be sustained, so that reasonable efficiencies could be obtained. Achieving these efficiencies however depends critically on limiting the effect of inter component heat transfer. In this paper the impact of heat losses on the performance of small centrifugal compressors are investigated. The paper presents the adaptation of a 1D design and performance analysis code to accommodate heat transfer effects. The modifications made to the code to account for heat transfer will be discussed and a validation of the adapted code will be given. After that the performance of several non-adiabatic compressor impellers will be discussed in detail. Design modifications will be presented that reduce the impact of heat transfer for the investigated compressors. The impact on heat transfer on the compressor maps will also be detailed.

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