PL
 |
EN
Preferencje help
Polish version English version Język
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 10

Liczba wyników na stronie
first rewind previous Strona / 1 next fast forward last
Wyniki wyszukiwania
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
1
Content available Stable or not stable? Recognizing surge based on the pressure signal
Garcia D., Liśkiewicz G.
Transactions of the Institute of Fluid-Flow Machinery
|
2016
|
nr 133
55--68
EN
The surge protection may be worth millions of dollars. This is typical price of a centrifugal compressor repair combined with additional cost of nonfunctionality of an industry employing it. This threat is normally secured by application of an antisurge systems. Typically they are activated at predefined working conditions when compressor mass flow rate approaches region affected by the surge. As a result those systems are vastly limiting its operational range usually by a desirable region where compressor attains large pressure ratio. Therefore, a modern antisurge systems are aiming at diminishing this tradeoff by reacting to the real pressure signal gathered at high frequency. This paper presents one of those methods employing singular spectrum analysis. This algorithm has not been widely used for this application, while it was shown herein that it may bring clear distinction between stable and nonstable working condition, even at presurge conditions. Hence in further perspective it may bring anti-surge protection quality, that was not met with another methods.
2
Content available Numerical study of surge predecessors in centrifugal blower — inlet recirculation
Chmielecki J., Liśkiewicz G., Kryłłowicz  W.
Transactions of the Institute of Fluid-Flow Machinery
|
2016
|
nr 134
29--44
EN
Paper presents the numerical investigation of inlet recirculation in a centrifugal blower. This phenomenon is known as a local flow instability that is not too harmful in centrifugal compressors compared to centrifugal pumps. However recent findings have shown that it can be regarded as a surge predecessor, and hence very significant for compressors. Therefore there is strong need to understand its physics. One of ways to understand it to apply computational fluid dynamic (CFD) simulations. Therefore in this study the transient numerical simulations were conducted and results were related to the experimental data presented in other papers. Simulation confirmed that the inlet recirculation structure can be resolved by means of CFD and the results are in agreement with some available models. Inlet recirculation structure built up gradually along the circumference increasing the power loss. Obtained structure also explained pressure variations observed in experiments. This has shown that CFD can bring significant improvement in existing antisurge systems and recirculation bleeds that extend the machine operating range.
3
Content available Mathematical surge modeling based on the pressure oscillations in the stable operation range of the compressor
Jaeschke A., Liśkiewicz G.
Transactions of the Institute of Fluid-Flow Machinery
|
2016
|
nr 133
91--108
EN
Prevention of surge phenomenon is a very active field of research in last decades. The Greitzer model is the most widely applied mathematical model describing the surge phenomenon. Two parameters that characterize the given compressing system: the Helmholtz oscillator frequency and the so-called B parameter have to be given as the input to Greitzer model. Although those parameters are easy to determine for simplified compressor models, they are extremely hard to predict in case of real industrial compressors. Moreover, in most cases it is impossible to analyse compressor unstable work, which makes this prediction even more speculative. Therefore the method that determines the parameters basing on the compressor stable operation is indispensable. In paper the regularly perturbed Greitzer model based method of predicting the behaviour of a compressor in the unstable operation basing on signals from its stable operation is proposed and discussed.
4
Content available Compressor modeling using Greitzer model validated by pressure oscillations
Grapow F., Liśkiewicz G.
Transactions of the Institute of Fluid-Flow Machinery
|
2016
|
nr 133
69--89
EN
Nowadays compressors are used in almost every industry. Compressor failure can suspend production of the whole system so the importance of preventing from failures is obvious and essential. One of the most dangerous flow instabilities which is capable of destroying machine in few seconds is surge, which occurs in conditions of low mass flow rate. Greitzer model, apart from its long history, is still most common mathematical model describing surge. It is widely used to predict the surge onset and pressure oscillations during it. However, it is based on parameters that are not directly related to real machine and their choice is not always obvious. Therefore, the calculations may be inaccurate which results in wrong surge prediction. The other approach to Greitzer model is presented in this paper, which in some cases can assure that the process of compressor modeling is more accurate. The applicability of Greitzer surge model for real machines has been analyzed. Method of implementation is based on experimental pressure signal gathered during unstable work of compressor. Presented method is based on experimental compressor characteristic and outlet pressure signal from unstable work of compressor. From that data it is possible to determinate the value of Greitzer model’s parameters for selected operational point. Thanks to this method this model could be applied for reliable antisurge protection.
5
Content available remote Prediction of Centrifugal Blower Performance Curve for Purpose of Surge Simulation
Grapow F., Liśkiewicz G.
Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka
|
2015
|
nr 148
65--76
EN
In this paper the method of prediction of centrifugal compressor performance curve for the purpose of surge simulation is presented. The centrifugal blower has been modeled using Greitzer model and different performance curves have been analyzed. Results show that the most commonly used third order polynomial is not always the best for modeling. Therefore a new polynomial for compressor performance curve has been proposed to enhance mathematical surge modelling with the Greitzer model.
PL
W artykule przedstawiona została metoda przewidywania przebiegu charakterystyki sprężarki na potrzeby symulacji pompowania. Dmuchawa odśrodkowa została zamodelowana za pomoc modelu Greitzer’a i zbadane zostały różne krzywe charakterystyki. Wyniki pokazują, że najczęściej używana metoda wykorzystująca wielomian trzeciego stopnia nie zawsze jest najlepszym wyborem. Zaproponowany został zatem nowy wielomian, który pozwala poprawić dokładność matematycznego modelowania pompowania za pomocą modelu Greitzer’a.
6
Content available remote Badania symulacyjne aktywnego systemu antypompażowego dmuchawy odśrodkowej
Grapow F., Liśkiewicz G.
Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka
|
2015
|
nr 147
1--12
PL
W pracy zaprezentowano projekt systemu antypompażowego kontroli aktywnej oparty na modelu Greitzer’a dla dmuchawy odśrodkowej. Jego istotą jest dodatkowy zawór upustowy sterowany regulatorem proporcjonalnym, a symulacja jego działania przeprowadzona w programie Simulink potwierdziła możliwość zastosowania takiego systemu dla maszyny pracującej w obszarze pompowania. Uzyskane wyniki pokazują, że zaprojektowany system tłumi oscylacje ciśnienia i pozwala na pracę maszyny w obszarze pompowania.
EN
In this paper the active control, anti-surge system for centrifugal blower has been designed and simulated. It has been accomplished by additional blow-off valve controlled by proportional controller. System was simulated in Simulink and it shows possibility to apply this system into machine working in surge region. The results show that designed system has ability to damp pressure oscillations and provide stable working conditions of centrifugal blower.
7
Konstrukcja małej turbiny parowej typu Elektra dla energetyki rozproszonej
Kryłłowicz  W., Liśkiewicz G., Szwaja S.
Energetyka
|
2015
|
nr 11
719--722
PL
Opisano konstrukcję prototypowej małej turbiny parowej przeznaczonej do pracy w instalacji stacjonarnego silnika spalinowego zasilanego biogazem. Omówiono zasady doboru układu przepływowego (dwustopniowy układ Electra) oraz przedstawiono budowę podstawowych podzespołów konstrukcyjnych. Artykuł zawiera wnioski dotyczące doświadczeń osiągniętych w trakcie projektowania i budowy prototypu.
EN
Described is the construction of a prototype small steam turbine dedicated to co-operate with a stationary biogas-fuelled combustion engine. Discussed are main principles that contributed to a selection of the flow system (two-stage Electra turbine) and presented is the construction of basic subassemblies. Contained are conclusions concerning the experience gained during designing and construction of the prototype.
8
Content available remote Time-frequency analysis of the surge onset in the centrifugal blower
Liśkiewicz G., Horodko L.
Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka
|
2014
|
nr 145
81--84
EN
Time frequency analysis of the surge onset was performed in centrifugal blower. Pressure signal was registered at the blower inlet, blower outlet and three locations at the impeller shroud. The time-frequency scalograms were obtained by means of the Continuous Wavelet Transform (CWT). The blower was found to successively operate in four different conditions: stable working conditions, inlet recirculation, transient phase and the deep surge. Scalograms revealed different spectral structure of aforementioned phases and suggest possible ways of detecting the surge predecessors.
9
Content available remote Dynamical system analysis of unstable flow phenomena in centrifugal blower
Garcia D., Stickland M., Liśkiewicz G.
Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka
|
2014
|
nr 145
43--46
EN
Methods of dynamical system analysis were employed to analyze unsteady phenomena in the centrifugal blower. Pressure signals gathered at different control points were decomposed into their Principal Components (PCs) by means of Singular Spectrum Analysis (SSA). Certain number of PCs was considered in the analysis based on their statistical correlation. Projection of the original signal onto its PCs allowed to draw the phase trajectory that clearly separated non-stable blower working conditions from its regular operation.
10
Content available remote Koncepcja numerycznych i eksperymentalnych badań niestatecznej pracy promieniowego stopnia sprężającego
Kryłłowicz  W., Liśkiewicz G.
Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka
|
2010
|
nr 137
33-42
PL
Artykuł zawiera przegląd stanu wiedzy w dziedzinie zjawiska pompowania w sprężarkach promieniowych oraz zarys niestacjonarnych badań numerycznych które pozwoliłyby na jego usystematyzowanie. Symulacje numeryczne poparte będą eksperymentami przeprowadzonymi na stanowisku jednostopniowej dmuchawy promieniowej DP.1.12
EN
The article presents the state-of-the-art in understanding of the surge phenomenon in centrifugal compressors and the concept of a non-stationary numerical simulations that will allow to systematize knowledge in that field. Numerical computations will be supported by the experiments conducted on the single stage centrifugal blower DP.1.12.
first rewind previous Strona / 1 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.