1,357 research outputs found

    Reservoir Computing for Detection of Steady State in Performance Tests of Compressors

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    Fabrication of devices in industrial plants often includes undergoing quality assurance tests or tests that seek to determine some attributes or capacities of the device. For instance, in testing refrigeration compressors, we want to find the true refrigeration capacity of the compressor being tested. Such test (also called an episode) may take up to four hours, being an actual hindrance to applying it to the total number of compressors produced. This work seeks to reduce the time spent on such industrial trials by employing Recurrent Neural Networks (RNNs) as dynamical models for detecting when a test is entering the so-called steady-state region. Specifically, we use Reservoir Computing (RC) networks which simplify the learning of RNNs by speeding up training time and showing convergence to a global optimum. Also, this work proposes a self-organized subspace projection method for RC networks which uses information from the beginning of the episode to define a cluster to which the episode belongs to. This assigned cluster defines a particular binary input that shifts the operating point of the reservoir to a subspace of trajectories for the duration of the episode. This new method is shown to turn the RC model robust in performance with respect to varying combination of reservoir parameters, such as spectral radius and leak rate, when compared to a standard RC network

    Characterizing Steady State Compressor Performance by Using Transient Test Data

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    Compressor testing is an essential task to characterize compressor performance, but often requires significant time to be executed. This study suggests a method that could greatly reduce time needed for compressor testing by inferring steady state performance from transient data rather than waiting for true steady state conditions to be measured. The key finding is that the overall isentropic efficiency in transient operation is almost identical to its true steady state performance value after applying very simple data processing. The paper describes a simple data processing method that extracts steady-state performance from transient data. The proposed processing should not be understood as a general rule to all compressors, but as a positive result for this particular compressor and a first glimpse into the value of transient data for performance estimation

    An inventory of aeronautical ground research facilities. Volume 1: Wind tunnels

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    A survey of wind tunnel research facilities in the United States is presented. The inventory includes all subsonic, transonic, and hypersonic wind tunnels operated by governmental and private organizations. Each wind tunnel is described with respect to size, mechanical operation, construction, testing capabilities, and operating costs. Facility performance data are presented in charts and tables

    Experimental Analysis and 1D Model Simulation of an Advanced Twin Stage Hybrid Boosting System

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    Due to the increasingly restrictive limits of pollutant emissions, electrification of automotive engines is now mandatory. For this reason, adopting hybrid boosting systems to improve brake specific fuel consumption and time-to-boost is becoming common practice. In this thesis an innovative turbocharging system is analysed, consisting in an electrically assisted radial compressor and a traditional turbocharger. As a first step, the steady-state performance of each component was measured at the University of Genoa test rig. Due to problems related to over temperature, the working time of the e-compressor coupled to the electric motor is limited avoiding an accurate evaluation of compressor efficiency. For this reason a driving system (instead of the electric machine) was designed to provide a more accurate evaluation of the compressor map. Subsequently another experimental campaign was carried out to evaluate the transient response of the entire turbocharging system. Two different layouts were compared: upstream and downstream. In the upstream configuration the electrically assisted compressor was placed in front of the traditional turbocharger, in the downstream configuration the e-compressor was positioned after the traditional turbocharger. The two different coupling configurations, upstream and downstream, were then modelled in 1-D simulation software following the dimensions and characteristics of the experimental line from which the exploited data originates. The models were first validated by emulating the steady-state condition and subsequently the transient response was simulated and analysed. Secondly, the transient response of the two layouts was compared, removing the constraints imposed by the experimental activity

    Research and technology

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    The NASA Lewis Research Center's research and technology accomplishments for fiscal year 1987 are summarized. It comprises approximately 100 short articles submitted by staff members of the technical directorates and is organized into four sections: aeronautics, aerospace technology (which includes space communications), space station systems, and computational support. A table of contents by subject was developed to assist the reader in finding articles of special interest

    Aeronautical Engineering: A continuing bibliography, supplement 120

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    This bibliography contains abstracts for 297 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1980
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