Design Of Compression System Research Articles

Experimental investigation of the flow instability of a compression system with an upstream plenum

Under the trend of engine downsizing, limited installation space leads to the intake pipe configuration becoming more complex, and the components, such as the air filter and the intercooler in two-stage compression systems, are much closer to the compressor inlet. The intake pipe configuration becomes essential and nonnegligible for the flow stability of the compression system. Experimental investigations on the flow instability evolution of two compression systems with and without an upstream plenum, which represents the volume influence of the air filter or the intercooler, were carried out in this paper. The results show that there exists a two-regime-surge phenomenon in the compression system without the plenum at the medium- and high-speed lines while this phenomenon disappears in the system with the plenum in which the instability evolution is straightforward. Although the deep surge boundary shifts to the right compared to the system without the plenum, the mild surge boundary shifts to the left, which demonstrates that the pipe configuration with the plenum is beneficial for extending the compressor stable work range. From the perspective of energy input and dissipation, the dissipation ability of the system with the plenum is weaker, so once mild surge occurs, the compression system will fall into deep surge very soon. In contrast, the system without the plenum can stand the oscillations from mild surge much longer before falling into deep surge. These findings shed more light on the flow instability mechanism of compression systems and provide some guidance for the installation and integrated design of compression systems.

Criteria for the matching of inlet and outlet distortions in centrifugal compressors

The centrifugal compressor is a very common type of effective energy conversion device, which is used in a range of industrial processing equipment and automotive turbochargers. Due to the requirements and the limited installation space, centrifugal compressors are always connected with complex inlet and outlet pipe systems, including various kinds of bends, struts, and volutes with asymmetric geometries. These asymmetric components induce distortions at the compressor inlet and the outlet, which exert a strong influence on the compressor performance and flow field. This paper employs full-annulus unsteady simulations to study the matching of inlet and outlet distortions by adding a distortion model to compressor inlet and outlet. The results show that the matching does have a large influence on the compressor performance and flow field and there does exists the best matching. The best matching can neutralize the inlet and outlet distortions, keep the uniformity of flow parameters in the impeller and the diffuser, and inhibit the oscillation of mass flow in one blade passage. In addition, the peak efficiency under the best matching can be improved 0.67% and 1.16% at 80% and 100% nominal rotation speed, respectively. Finally, the matching criteria are proposed and validated, and an estimate formula is established to provide some guidance for the installation and integrated design of compression system.

EXPERIMENTAL STUDY AND MINIMIZATION OF (LMTD) OF A REFRIGATOR BY BALANCING COOLING WATER

This work involves an experimental investigation of the refrigerator equipment. To complete of the study model, an inside and outside temperatures of refrigerant (R12) and cooling water through heat exchanger is assumed to be steady state flow. Special tables of refrigerant (R12) and cooling water are used to know properties at specified temperature , by using refrigeration system basically which work between two pressures, and specific enthalpy is one of the most useful properties which it is need in energy equation application to determine condenser and evaporator tube length of system , which takes as carefully to compression system design for giving temperature difference in cooling or heating systems. Also, tube length of condenser and evaporator are calculated (18 , 9) m respectively. A pressure - specific enthalpy or (p-h) chart of refrigerant R12 is depended on to determine specific enthalpy for each run at present pressure. This investigation is to study the influence of the volume flow rate of cooling water as range (2,4,6,and 8) liter /min which it supplies by control valve to the heat exchangers of system on logarithm mean temperature difference (LMTDe) and cooling coefficient of performance. Also, this work investigates the minimization of the (LMTDe) evaporator by using valve controlled of cooling water. The present results show that, the degree (LMTDe) is decrease as the volume flow rate of cooling water increasing then, due to increase of refrigerating effect at same time cooling coefficient of performance (COP)RF is increasing. Also, in the compression cooling system has been get temperature difference about(6)◦C. Comparison between the obtained experimental performance results and the previous theoretical work shows a good agreement with (±3.8) percentage.

An Integrated System for the Aerodynamic Design of Compression Systems—Part II: Application

The complexity of modern gas turbine engines has led to the adoption of a modular design approach, in which a conceptual design phase fixes the values for a number of parameters and dimensions in order to facilitate the subdivision of the overall task into a number of simpler design problems. While making the overall problem more tractable, the introduction of these process-intrinsic constraints (such as flow areas and radii between adjacent stages) at a very early phase of the design process can limit the level of performance achievable, neglecting important regions of the design space and concealing important trade-offs between different modules or disciplines. While this approach has worked satisfactorily in the past, the continuous increase in components’ efficiencies and performance makes further advances more difficult to achieve. Part I of this paper described the development of a system for the integrated design optimization of gas turbine engines: postponing the setting of the interface constraints to a point where more information is available facilitates better exploration of the available design space and better exploitation of the trade-offs between different disciplines and modules. In this second part of the paper, the proposed approach is applied to several test cases from the design of a three-spool gas turbine engine core compression system, demonstrating the risks associated with a modular design approach and the consistent gains achievable through the proposed integrated optimization approach.

An Integrated System for the Aerodynamic Design of Compression Systems—Part I: Development

The design of gas turbine engines is a complex problem. This complexity has led to the adoption of a modular design approach, in which a conceptual design phase fixes the values for some global parameters and dimensions in order to facilitate the subdivision of the overall task into a number of simpler subproblems. This approach, while making a complex problem more tractable, necessarily has to rely on designer experience and simple evaluations to specify these process-intrinsic constraints at a point in the design process where very little knowledge about the final design exists. Later phases of the design process, using higher-fidelity tools but acting on a limited region of the design space, can only refine an already established design. While substantial improvements in performance have been possible with the current approach, further gains are becoming increasingly hard to achieve. A gas turbine is a complex multidisciplinary system: a more integrated design approach can facilitate a better exploitation of the trade-offs between different modules and disciplines, postponing the setting of these critical interface parameters (such as flow areas, radii, etc.) to a point where more information exists, reducing their impact on the final design. In the resulting large, possibly multimodal, highly constrained design space, and with a large number of objectives to be considered simultaneously, finding an optimal solution by simple trial-and-error can prove extremely difficult. A more intelligent search approach, in which a numerical optimizer takes the place of the human designer in seeking optimal designs, can enable the design space to be explored significantly more effectively, while also yielding a substantial reduction in development times thanks to the automation of the design process. This paper describes the development of a system for the integrated design and optimization of gas turbine engines, linking a metaheuristic optimizer to a geometry modeler and to evaluation tools with different levels of fidelity. In recognition of the substantial increase in design space size required by the integrated approach, an improved parameterization based on the concept of principal components’ analysis was implemented, allowing a rotation of the design space along its most significant directions and a reduction in its dimensionality, proving essential for a faster and more effective exploration of the design space.

High-performance Computing to Simulate Large-scale Industrial Flows in Multistage Compressors

The aim of this study is to propose a computing method to obtain a detailed simulation of the unsteady flow that develops in multistage turbomachines. The three-dimensional unsteady Reynolds-averaged Navier—Stokes equations are solved using a structured multiblock decomposition method. Although this kind of flow solver is very popular in the turbomachine community nowadays, the complex block connectivities used in meshes of industrial configurations can be penalizing for parallel computing. The computing strategy implemented in a modern flow solver is investigated in this paper, with a particular interest in mesh partitioning, communications and load balancing. Advantages and drawbacks of different computing platforms are then discussed, ranging from vector supercomputers to massively scalar platforms. Comparisons are performed regarding criteria such as the elapsed time and the electrical power consumption. The results show that the use of a large number of computing cores (>128) is heavily penalized by communications and load balancing errors, whereas computing performance with a moderate number of computing cores (<128) is mainly driven by the peak power of the architecture. To help users estimate a priori the parallel performance of a task, a tool based on an extension of Amdahl’s law is proposed, showing satisfying results when compared with observations. Finally, an unsteady flow simulation is performed in a complete three-stage compressor at the design operating point. While still far beyond industrial resources, this numerical flow simulation shows that potential breakthroughs in the design of compression systems can be expected.

Analysis of the Effects of Pulsations on the Operational Stability of Centrifugal Compressors in Mixed Reciprocating and Centrifugal Compressor Stations

Mixed operation with both centrifugal and reciprocating compressors in a compression plant poses significant operational challenges as pressure pulsations and machine mismatches lead to centrifugal compressors’ instabilities or poor performance. Arrangements with reciprocating compressors placed in series with centrifugal compressors generally lead to higher suction/discharge pulsations on the centrifugal compressor than conventional parallel operation. This paper demonstrates that by properly analyzing and designing the interconnecting piping between the compressors, utilizing pulsation attenuation devices, and matching the compressors’ volumetric-flow rates, a satisfactory functional compression system design can be achieved for even the worst cases of mixed centrifugal and reciprocating compressor operation. However, even small analysis errors, design deviations, or machine mismatches result in a severely limited (or even inoperable) compression system. Also, pulsation attenuation often leads to a significant pressure loss in the interconnect piping system. Utilizing analysis tools in the design process that can accurately model the transient fluid dynamics of the piping system, the pulsation attenuation devices, and the compressor machine behaviors is critical to avoid potentially costly design mistakes and minimize pressured losses. This paper presents the methodology and examples of such an analysis using a 1D transient Navier–Stokes code for complex compression piping networks. The code development, application, and example results for a set of mixed operational cases are discussed. This code serves as a design tool to avoid critical piping layout and compressor matching mistakes early in the compressor station design process.

Delivering Diagnostic Quality Video over Mobile Wireless Networks for Telemedicine

In real-time remote diagnosis of emergency medical events, mobility can be enabled by wireless video communications. However, clinical use of this potential advance will depend on definitive and compelling demonstrations of the reliability of diagnostic quality video. Because the medical domain has its own fidelity criteria, it is important to incorporate diagnostic video quality criteria into any video compression system design. To this end, we used flexible algorithms for region-of-interest (ROI) video compression and obtained feedback from medical experts to develop criteria for diagnostically lossless (DL) quality. The design of the system occurred in three steps-measurement of bit rate at which DL quality is achieved through evaluation of videos by medical experts, incorporation of that information into a flexible video encoder through the notion of encoder states, and an encoder state update option based on a built-in quality criterion. Medical experts then evaluated our system for the diagnostic quality of the video, allowing us to verify that it is possible to realize DL quality in the ROI at practical communication data transfer rates, enabling mobile medical assessment over bit-rate limited wireless channels. This work lays the scientific foundation for additional validation through prototyped technology, field testing, and clinical trials.

Model‐based signal processing for hearing aids

The aim of the work presented in this talk is to investigate potential applications of models of human auditory processing to signal processing in hearing aids. In particular, it is shown that auditory models may be used as objective indicators of the perceptual quality of single‐ and multichannel noise reduction strategies. Furthermore, a general framework for computational auditory scene analysis (CASA) is introduced and applied to the problem of estimating spatial direction and spectral envelope of super‐imposed sound sources from a binaural input signal. Finally, implications of using nonlinear peripheral models for the design of compression systems in hearing aids are discussed. In particular, results from a multiband instantaneous compression scheme are presented, which is based on a novel nonlinear auditory filterbank controlled by the instantaneous frequency calculated in frequency sub‐bands.

Optimal modeling for complex system design [data compression

The article begins with a brief introduction to the theory describing optimal data compression systems and their performance. A brief outline is then given of a representative algorithm that employs these lessons for optimal data compression system design. The implications of rate-distortion theory for practical data compression system design is then described, followed by a description of the tensions between theoretical optimality and system practicality and a discussion of common tools used in current algorithms to resolve these tensions. Next, the generalization of rate-distortion principles to the design of optimal collections of models is presented. The discussion focuses initially on data compression systems, but later widens to describe how rate-distortion theory principles generalize to model design for a wide variety of modeling applications. The article ends with a discussion of the performance benefits to be achieved using the multiple-model design algorithms.