On Active Surge Control of Compression Systems Via Characteristic Linearization and Model Nonlinearity Cancellation

A simple approach of active surge control of compression systems is presented. Specifically, nonlinear components of the pressure ratio and rotating speed states of the Moore-Greitzer model are transferred into the input vectors. Subsequently, the compressor characteristic is linearized into two modes, which describe the stable region and the unstable region respectively. As a result, the system\u27s state and input matrices both appear linear, to which linear realization and analysis are applicable. A linear quadratic regulator plus integrator is then chosen as closed-loop controller. By simulation it was shown that the modified model and characteristics can describe surge behavior, while the closed-loop controller can stabilize the system in the unstable operating region. The last-mentioned was achieved when massflow was 5.38 per cent less than the surge point

The influence of mechanical faults on induction machines with electrical faults

The study of the interaction between faults of different natures is a crucial step for the development of effective systems for fault detection. The analysis of the electrical signals using the actual motor current signature analysis (MCSA) techniques may lead to different results and, as a consequence, an incorrect diagnosis of the fault due to the fact that the non-linear interactions between both faults are difficult to predict with high precision. The relationship between the electrical and mechanical components has been extensively studied in the past, but despite the progress made, the introduction of new control systems or the nonlinearities presented in the electrical machine, still makes it hard to diagnose faults. The study below attempts to show the evolution of the induction motor signatures when electrical and mechanical faults occur simultaneously. The Fourier analysis of the signatures presented in this paper indicates that the typical analysis carried out to diagnose the state of the electrical machine may be interpreted as an indicator of a different type of fault

A high-speed valve for surge control in a centrifugal compression system

This paper deals with the critical problem of actuator limitations for the successful implementation of active surge control. We specify the capacity, bandwidth and allowable time delay for a control valve that can be used to actively suppress surge in a specific full-scale centrifugal compression system. The actuator requirements are obtained from closed-loop simulations with a nonlinear simulation model of the compressor test rig. In order to meet the requirements, a new high-speed valve actuator had to be developed. We present the resulting actuator design and provide test results to illustrate that the control valve meets our design specifications

Adaptation of a 1-D tool to study transient thermal in turbocharger bearing housing

[EN] The heat transfer model can be used in a one-dimensional (1-D) engine simulation. When the engine speed is reduced to zero, the codes have been upgraded to calculate transient turbocharger thermal conditions. The turbocharger model has been used as an external plugin. Analysis of the temperature evolution at different parts of the turbocharger is done by using a hot spot engine cycle. A turbocharger bypassing strategy is done by means of a 9 bypass valve system. By using this method, instabilities can be found in the binary on-off state of an engine. During engine hot-stops, the lack of oil flow inside the turbocharger makes the trapped oil in the bearings burnt as the turbine housing exchanges heat with the central housing. Coke formation can appear and produce big reductions in turbocharger endurance, as bearings clogged and damage the shaft. Several strategies can be used in order to minimize possibilities of coke formation, including an increase in the turbocharger cooling during normal operation and the use of electrically-driven pumps acting after the engine is shut down. These strategies can be simulated in acceptable calculation times thanks to modelling strategy proposed in this paper. The presented methodology allows a detailed study of the temperature rise of the central housing of an automotive turbocharger after a hot-stop process, simulating several combinations of cooling strategies in order to find the optimum one in terms of minimising extra energy consumption per K of housing temperature reduction.We thank Przemek Kmiec for his support in the language editing. This work has been partially supported by the Spanish Ministry of Economyand Competitiveness through [grant No. TRA2013-40853-R].Serrano, J.; Tiseira, A.; García-Cuevas González, LM.; Rodriguez-Usaquen, YT. (2018). Adaptation of a 1-D tool to study transient thermal in turbocharger bearing housing. Applied Thermal Engineering. 134:564-575. https://doi.org/10.1016/j.applthermaleng.2018.01.085S56457513

Supercritical fluid recycle for surge control of CO2 centrifugal compressors

AbstractThis paper presents computer-based design and analysis of control systems for centrifugal compressors when the operating fluid is supercritical CO2.It reports a non-linear dynamic model including a main forward compression line and two different configurations for the recycle antisurge line. Disturbance scenarios are proposed for testing the configurations and performance indicators are suggested to evaluate control performance and power consumption of the compression system.The paper demonstrates that compared to the hot recycle, the process configuration including a cold gas recycle has better overall stability, but higher power consumption and lower values for the control performance indicators. Based on the previous considerations, the paper gives suggestions regarding the choice of the recycle configuration. Moreover it compares subcritical and supercritical compression during surge prevention and highlights the importance of the selection of the gas recycle configuration when full recycle is needed

Controlling an electrically assisted turbocharger

Tässä työssä tutkittiin LQR-menetelmän soveltuvuutta dieselmoottorin ahtopaineen säätöön sähköavusteisella turboahtimella. Työn tavoitteena oli tuottaa sähköturbon ohjaus, joka mahdollistaisi sähköturbollisen dieselmoottorin tutkimuskäytön moottoridynamometrissä. Säädön suunnitteluun käytettiin yksinkertaistettua kompressorimallia, jossa ainoana tilana on turboahtimen kulmataajuus. Kompressorin ja dieselmoottorin välisen imukanavan tuottamaa dynamiikkaa tai järjestelmän viiveitä ei säätösuunnittelussa huomioitu, sillä kohdejärjestelmässä ei ollut riittäviä mittauksia niiden tarkkaan estimointiin. Suunnittelumallin epälineaarisuuden takia LQR-menetelmällä laskettiin soveltuvat viritykset useisiin sähköturbon toimintapisteisiin, joita käytettiin turboahtimen kulmataajuuden ja imukanavan massavirran mukaan skeduloidussa tilasäätimessä. Ohjauksessa keskityttiin dieselmoottorin ahtopaineen hallintaan – sähköturbon energiankulutusta tai muita dieselmoottorin ilmajärjestelmän suureita ei otettu säädössä huomioon. Säätimen kehitystyön tueksi työssä kehitettiin myös dieselmoottorin ilmajärjestelmän simulaatiomalli Simulink-ympäristöön. Simulaattorissa käytettiin monimutkaisempaa 3-tilaista kompressorimallia, joka huomioi myös imukanavan pituudesta ja tilavuudesta aiheutuvan dynamiikan. Simulaattorin avulla tutkittiin kehitetyn säädön stabiiliutta ja suoritettiin tarvittava ohjelmistotestaus. Kehitettyä sähköturboa käyttävää ahtopaineen säädintä testattiin simulaattorin lisäksi myös oikealla dieselmoottorilla dynamometrissä. Kehitetyn säätimen todettiin omaavan riittävä suorituskyky sähköturbolla varustetun dieselmoottorin tutkimuskäyttöä varten. Järjestelmän havaittiin kuitenkin sisältävän merkittäviä viiveitä, jotka haittasivat säätimen suorituskykyä. Näistä huolimatta kehitetyllä säätimellä saavutettiin riittävä regulointikyky ja asetusarvon seurantakyky. Sähköturbon havaittiin mahdollistavan perinteiseen turboahtimeen verrattuna huomattavasti nopeammat dieselmoottorin kuormannostot etenkin matalilla kierrosluvuilla. Alhaisella kierrosluvulla suoritetussa kokeessa kuormannostoaika lyheni 8,5 sekunnista 1 sekuntiin käytettäessä sähköavustusta. Sähköturbon havaittiin myös mahdollistavan dieselmoottorin vääntömomentin kasvattamisen alhaisilla kierroksilla verrattuna samaan ahtimeen ilman sähköavustusta