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POWER AUGMENTATION OF PGE GORZOW’S GAS TURBINE BY STEAM INJECTION – THERMODYNAMIC OVERVIEW Paweł Ziółkowski, Marcin Lemański, Janusz Badur, Lucjan Nastałek Key words: Cheng cycle, STIG cycle, combined cycle, steam injection, gas turbine Summary. The impact of steam injection upon a gas turbine and a combined power plant performance has been investigated. This article describes and summarizes possibilities of modification for current gas turbine in PGE Gorzow power plant into the Cheng cycle. Our modification deals with a thermal cycle, in which steam produced in a heat recovery steam generator is injected into the gas turbine’s combustion chamber. It has been proved that an increase of the mass flow rate of the expanded exhaust gases causes an increase in both the power and efficiency of gas turbine. Steam injection also helps to reduce NOx formation and is profitable from a thermodynamic, economic and ecological standpoint. The numerical analysis of thermal cycles, before and after the modification, has been carried out by means of an in-house COM-GAS code and Aspen Plus commercial package.
1. INTRODUCTION Nowadays, energy companies to reach out the environmental requirements of Directive 2010/75/EU of European Parliament and of the Council, have to generate electricity at the highest efficiency and at minimum emission level of both nitrogen and carbon oxides [19]. Hence, to fulfill this, it is necessary to carry out number of modernization of many old existing power stations or construct new highefficient units such as coal and combined power plants. One manner of the modification of the existing gas-steam units is steam or water injection into the gas turbine combustion chamber, usually realized by CHENG or STIG cycle [4,5]. It is well documented that steam injection improves both the efficiency and power of the gas turbine and also reduces harmful emissions of nitrogen and carbon oxides into the atmosphere [4]. At present, the steam injection system for power augmentation and reduction of NOx is offered by dominant gas turbine companies such as General Electric, Rolls-Royce, Kawasaki, etc. [12]. Apart from that, these companies offer other methods for reducing nitrogen oxides to comply with emissions regulations. Among them, one can distinguish the following pre- and post-combustion techniques: dry low NOx burners, water injection, selective catalytic and non-catalytic reduction or SCONOx [9,10].
2. LITERATURE SURVEY Many studies have been carried out on the gas turbine with the steam injection. As of 1978, when Cheng proposed a gas turbine with the steam injection, the retrofitted gas turbines have been widely analyzed and developed [4,5,21]. Cheng suggested that the whole steam produced in heat recovery steam generator HRSG can be used for injection into a gas
turbine combustion chamber which results in both power and efficiency increase and NOx reduction. Saad and Cheng [13], proposed a modification of a gas turbine General Electric LM2500 into the Cheng cycle. After that, a lot of attempts have been made to analyze gas turbine retrofitted to operate on the Cheng or STIG cycle. Poullikkas [12] reported that the positive effect of a steam or water injection can be also applied in more complicated cycle like DRIASI and LOTHECO cycle or turbocharged steam injected gas turbine. Wang and Chiou [16] showed that the STIG modification of a simple cycle gas turbine General Electric Frame 6B can boost its efficiency from about 30 % to 40 % and the power output from 38 to 50 MWe. Carapellucci and Milazzo [3] analyzed the existing gas-steam power plant repowered by an additional gas turbine and heat recovery stem generator. These new equipments are integrated within the original thermal cycle and produce steam for a steam injection into the gas turbine combustion chamber. In this way, the existing gas turbine can be transformed into the steam injected gas turbine (STIG). As a result, the power of such repowered power plant can be increased by 50 %, simultaneously decreasing the overall efficiency by 3-6 %. Srinivas et al. [14] reviewed STIG cycle with dual pressure HRSG. They investigated the effect of steam injection mass ratio (steam to fuel mass ratio) and concluded that for complete combustion in the gas turbine combustion chamber the maximum limit for the steam injection mass ratio is identified as m s / m f 6.0 . However, to get a stable combustion, steam is only injected up to the ratio of 3.0 . Additionally, they noted that with the steam injection increase, the gas and steam cycle’s efficiency changes accordingly [14].
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Some of discussed results are directly related to the present paper. We describe the thermodynamic analysis of modification of PGE Gorzow combined power plant (gas and steam one) into the Cheng idea. The numerical calculations have been carried out in the CFM (Computational Flow Mechanics) code i.e. COM-GAS code [15] and Aspen Plus software. The main aim of this work is to estimate the modified power plant’s parameters i.e. power output, efficiency, emission, etc. and compare it to operational parameters of the same class gas turbine with the steam injection. It should be emphasized that this method of modification has already been successfully implemented in a gas-steam power plant in ECK Generating Kladno, Czech Republic [22]. Both ECK Generating Kladno and PGE Gorzow power plants operate on a 54.5 MWe-class gas turbine (GT8C) manufactured by Alstom Power.
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The gain of gas turbine power is possible, because mass flow rate of the expanded exhaust gases increases due to the steam injection. In addition, the power consumed by the compressor remains practically unchanged. Steam or water injection can take place both at the inlet and outlet of the gas turbine combustion chamber. Greater benefits may be expected when steam is injected at the inlet of the combustion chamber, because it leads to the drop of combustion temperature. As a result, the emission of nitrogen oxides decreases, since the temperature of the combustion process is the main factor influencing on the rate of formation of nitrogen oxides. The water or steam injection at the outlet of the combustion chamber lowers only the temperature of the exhaust gases expanded in the turbine increasing its power. Typically, the injection is used at the inlet and at the outlet of the combustion chamber to obtain optimal benefits [6,8].
3. CHENG CYCLE The numerical analysis of PGE Gorzow combined plant has been carried out for the modernization of a simple gas turbine into the turbine with the steam injection in the so-called CHENG cycle. As presented in Fig.1, this cycle in comparison to typical gas-steam cycle contains only restricted number of components. There is no steam turbine and classical condenser in the modified cycle. Nevertheless, an additional heat exchanger is necessary to recover water from the exhaust gases outgoing from heat recovery steam generator [18]. By introducing the steam injection into the combustion chamber, the efficiency gain and the power increase are expected. On the other hand, steam expansion in the gas turbine proceeds only to the atmosphere pressure, so the efficiency of gas turbine cycle is always lower than the steam turbine one, in which the available drop of pressure is significantly higher [12].
4. GORZOW COMBINED POWER PLANT PGE Gorzow combined power plant is situated in western part of Poland delivering heat and power for Gorzow city using natural gas, with high content of nitrogen, coming from BMB resources near Debno Lubuskie. The detailed composition of the gas is presented in Table 1. Table 1 Natural gas for PGE Gorzow combined power plant [17] Compounds Nitrogen Methane Ethane Propane Iso-butane n-butane Pentane Hexane Total
Mole fraction [%] 52,66 39,79 5,12 1,94 0,20 0,24 0,04 0,01 100
Low Heating Value [MJ/um3] 0,000 35,808 63,740 91,150 118,560 118,560 145,960 173,410 19,870
PGE Gorzow power station was the first in Poland to employ the gas-steam production unit. The scheme of this unit, presented in COM-GAS code, is shown in Fig.2. The power plant consists of the following main elements: gas turbine Alstom GT8C, 54.49 MWe, steam turbine DDM-5, 5MWe,
Fig.1. Scheme of Cheng system (GT – gas turbine, C – compressor, G – generator, HRSG – heat recovery steam generator, CC – combustion chamber) [13].
steam turbine 3P6-6, 6 MWe, heat recovery steam generator, Foster Wheeler,
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The overall power and electrical efficiency of the combined power plant at the ISO conditions are about N el =65.49 MWe and el =41 %, respectively. Other
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technical parameters of power plant are summarized in Table 2 [17].
Fig. 2. Outline of the thermal cycle of PGE Gorzow combined power plant (GT – gas turbine, ST – steam turbine and condenser, C – compressor, HRSG – heat recovery steam generator, CC – combustion chamber) [18]
5. NUMERICAL CALCULATIONS OF COMBINED POWER PLANT The numerical calculations of conventional combined power plant have been carried out using two numerical codes i.e. COM-GAS and Aspen Plus. The detailed information concerning numerical modeling and its assumptions can be found in [18]. Table 2 summarizes the results of thermodynamic calculations in comparison to data included in available literature for the thermal cycle presented in Fig.2 [11,17,20]. As it is shown in Table 2, the electrical efficiency of the only 54.5 MWe - class gas turbine averages between el* =33.64 % and el* =34.29 % depending on the software used during modeling process. Moreover, the electrical efficiency of the combined power plant have been estimated at el =40.43 % by means of COM-GAS code and el =41.21 % with the aid of Aspen Plus package. The carbon dioxide emission CO2 and nitrogen oxides emission NOx, estimated in Aspen Plus code, approaches nearly 493 kg/MWh and 0.324 kg/MWh, respectively. The obtained results should be regarded as satisfactory in spite of existing differences between results from both codes and literature data.
Table 2 The results of calculations of Gorzow combined power plant in Aspen Plus and COM-GAS code [11,17,20], the superscript “*” means the gas turbine. Parameter
Unit o
Data COM- Aspen [11,17,20] GAS Plus
ta pa tf pf
C bar o C bar
15 1.013 15 40.5
15 1.013 15 40.5
15 1.013 15 40.5
m f
kg/s
-
8.51
8.36
m ex
kg/s
182.3
182.3
182.3
tGT tTIT
o
C C
520 1100
520 1100
520 1100
el*
%
34.60
33.64
34.29
N el*
MWe
54.49
54.49
54.49
C
100
100
100
m s
kg/s
23.2
23.2
23.2
ps ts
bar o C
40 450
40 450
40 450
N el
MWe
65,49
65,49
65,49
el
%
-
40.43
41.21
CO2 NOx
kg/MWh kg/MWh
313.01 0.324
tout
o
o
505.48 492.65 0.324
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6. MODIFICATION OF COMBINED POWER PLANT INTO THE CHENG CYCLE Scheme of Cheng cycle applied into the gas turbine is presented in Fig.3. The numerical calculations of the modified cycle have been carried out in Aspen Plus package. It has been assumed that steam produced by HRSG has the following thermodynamic parameters: - steam pressure ps=40 bar, - steam temperature ts=450 oC, s =23.2 kg/s (β=2.77). - steam mass flow rate m The remaining operational parameters of gas turbine have been kept unchanged as it is presented in Table 2.
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Generally, the discussion involving the influence of steam injection mass ratio β on the electrical efficiency and power of gas turbine is conducted f under the assumption that the fuel mass flow rate m remains constant. Thus, the comparison of results for the gas turbine performance with different steam injection mass ratio β is presented in this paragraph. According to the literature [14], the present analysis has been carried out for steam injection mass ratio only in the range of β=0-2.77 due to a fact that the heat recovery steam generator can only produce steam s =23.2 kg/s. at maximum steam mass flow rate of m In the Cheng cycle, steam injection mass ratio β is usually close to the value of 3.0 to prevent unstable combustion conditions in combustion chamber [14].
Fig. 3. Scheme of Cheng system with the GT8C gas turbine in Aspen Plus code [18].
In order to find the optimal β ratio some additional calculations of the combustion chamber by means of CFD software (Computational Fluid Dynamics) are needed. It should be noticed that the mass flow rate of s is the only variable factor that injected steam m influences both the drop of the exhaust gas temperature and an increase of gas turbine power [18]. The results of calculations of the thermal cycle with various β ratios are shown in Fig.4 - Fig.9. The analysis shows that despite of the steam turbine’s power decrease, the overall power of combined power plant increases. Analyzing the results, it can be seen that electrical efficiency of combined power plant averages el =41.21 % (no steam injection, β=0), however the modification of this cycle to Cheng cycle
gives an additional gain in both power and efficiency. The power and electrical efficiency of modified cycle averages el =42.05 % (maximum steam injection, β=2.77) and N el =66.92 MWe, respectively [18]. It should be also emphasized that the power of N el =66.92 MWe has been estimated for β=2.77. It means that the power generated by steam turbines is s is zero, because the entire steam mass flow rate m injected into the gas turbine. Fig.4 shows that the increase of steam injection mass ratio leads to increase the gas turbine power, as well as the power of the combined cycle, although the power output of steam turbines decreases. The gas turbine reaches
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mentioned above value of N el = 66.92 MWe of power output, which is comparable with the performance of similar Cheng cycle in Kladno, in Czech Republic ( N el =66.90 MWe). A significant increase of both power output and electrical efficiency of Cheng cycle is obtained by the gas turbine, whose power output has increased by approximately N el =12.4 MWe. This implies that the power output of gas turbine is approximately of 23% higher than the initial power output of the gas turbine without the steam injection [18]. For the maximum load of the heat recovery steam generator (HRSG), the maximum mass flow rate of s =23.2 kg/s (β=2.77) can be injected into steam of m the combustion chamber. It can be achieved for the minimum temperature difference between produced steam and exhaust gases. According to literature survey, the value of pitch point should be at least ΔTk=8 K [2]. The minimal pitch point in the HRSG has been assumed as ΔTk=8 K [18]. This value is acceptable at this level in case of the heat recovery steam generators used in polish combined power plants. For instance, combined power plant in Zielona Gora works under the similar thermal conditions (ΔTk=8.9 K). Fig.5 shows the temperature diagram versus thermal loading of heat recovery steam generator for the case, when β ratio is kept constant and equal to β=2.77.
450 400 350 300 250 200 150 100 50 0 0
20
40
exhaust gas
43,00
40,00 39,00
60,00
water
steam
0,3240 o
tTIT=1100 C 492,00
38,00
0,3230
o
tTIT=1080 C o tTIT=1061 C
490,00
37,00
58,00
100
494,00
h el [%]
41,00
62,00
80
Fig. 5. The temperature diagram versus thermal loading of heat recovery steam generator (for β=2.77)
42,00 64,00
60
HRSG thermal loa ding [MWt]
44,00
66,00
Nel [MWe]
500
0,3220 o
tTIT=1044 C
0,3210
54,00 0,00
35,00 0,50
1,00
1,50
2,00
2,50
34,00 3,00
steam injection mass ratio b [-]
CO2 [kg/MWh]
36,00 56,00
488,00
o
tTIT=1028 C
0,3200 o
tTIT=1012 C
486,00
0,3190
tTIT=997oC o
tTIT=983 C
484,00
o
power of gas turbine
power of modified cycle
electrical efficiency of gas turbine
electrical efficiency of modified cycle
tTIT=974 C
482,00
el of modified cycle versus β ratio Apart from thermodynamic benefits, the steam injection also leads to decrease nitrogen and carbon oxides of harmful emissions. Fig.6 presents emission level of carbon dioxide CO2 and nitrogen oxides NOx as a function of β ratio. Fig.7 shows the corresponding temperature change of exhaust gas at outlet of combustion chamber and gas turbine. As it is shown in Fig.6 and Fig.7, the increase of injected
0,3170 0,3160
480,00
Fig. 4. The power N el and electrical efficiency
0,3180
NOx [kg/MWh]
68,00
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steam, characterized by β ratio, decreases both the temperature of combustion tTIT and emission of nitrogen oxides NOx. For the analyzed case, the carbon dioxide and nitrogen oxides emission decreased approximately by ΔCO2=10 kg/MWh and ΔNOx=0.008 kg/MWh, respectively. The trend of changes in emission of nitrogen oxides NOx versus the combustion temperature has been kept linear, instead of exponential character reported in literature [7], due to a constant value of the conversion rate of nitrogen assumed in the calculations. This assumption is acceptable because the real emissions should be much lower in a range of analyzed combustion temperatures [18]. To estimate an accurate emission level of nitrogen oxides, it is necessary to use a 3D model of combustion chamber and burners in CFD framework [1].
Tempertaure [ o C]
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478,00 0,00
0,3150
0,50
1,00
1,50
2,00
2,50
0,3140 3,00
steam injection mass ratio b [-] CO2 emission
NOx emission
Fig. 6. Emission of carbon dioxide CO2 and nitrogen oxides NOx versus β ratio
The steam injection is the favorable solution, which would be used during the breakdown of steam turbines or during lower heat demand in the summer period, when the turbine would be oriented either on the electricity generation or heat production [18].
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HRSG is not necessary, since the minimum temperature difference between the exhaust gas and steam is maintained at an acceptable level, i.e. about ΔTk=8 K. As a result, the β ratio increases from β=2.77 (ps=40 bar) to β=2.82 (ps=25 bar). In Cheng cycle, steam temperature is desired to be as high as possible, since the higher thermal energy is then extracted from the exhaust gases. Summarized results of the calculations are presented in Table 3.
1200,00 1100,00 1000,00 Temperature [ o C]
900,00 800,00 700,00 600,00 500,00 400,00 300,00 200,00 100,00 0,00 0,00
0,50
1,00
1,50
2,00
2,50
3,00
8. CONCLUSIONS
steam injection mass ratio b [-] combustion temperature tTIT exhaust gas tempertaure at turbine outlet tGT steam temperature ts
Fig. 7. Temperature change of gas turbine’s exhaust gas versus β ratio.
7. COMPARISON OF PGE EC GORZÓW AND ECK GENERATING KLADNO To compare the performance of PGE Gorzow and ECK Generating Kladno, the numerical calculations of PGE Gorzow in Cheng cycle at identical operating parameters coming from ECK Kladno power plant have been carried out. In ECK Kladno, steam is injected at the following steam parameters: temperature ts=400 oC, pressure ps=25 bar and mass s =23.6 kg/s. As a result, the power output flow rate m of gas turbine due to the steam injection increases to N el =66.90 MWe. For these steam parameters, the calculations of modified cycle of PGE Gorzow power plant have been performed. The estimated power output of gas turbine is about N el =66.15 MWe, what is shown in Table 3 [18]. Table 3 The calculations results of modified cycle of Gorzow power plant for different temperature of steam for β ratio equal to β=2.82 Parameter ts β
Unit o C -
400 2.82
The value of parameter 410 420 430 440 2.82 2.82 2.82 2.82
450 2.82
m f
kg/s
8.36
8.36
8.36
8.36
8.36
8.36
N el
MWe
66.15
66.35
66.54
66.74
66.94
67.14
%
41.63
41.75
41.88
42.00
42.13
42.25
el tGT tTIT CO2 NOx
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o
C 451.53 452.66 453.79 454.93 456.07 457.22 o C 963.03 964.81 966.58 968.37 970.16 971.95 kg/MWh 487.73 486.28 484.84 483.40 481.96 480.53 kg/MWh 0.305 0.304 0.303 0.302 0.301 0.300
The numerical analyses of proposed modernization show that the power augmentation by steam injection into gas turbine’s combustion chamber gives an increase of efficiency and power. The main conclusions concerning the modification of PGE Gorzow power plant into the so - called Cheng cycle are listed below: - Steam for power augmentation can be produced in the current heat recovery steam generator up to steam injection mass ratio β=2.77. - Electrical efficiency of classical combined power plant approximates el =41.21 %. The steam injection (Cheng cycle) increases the electrical efficiency to el =42.05 %, for steam injection mass ratio equal to β=2.77 (power generation by the gas turbine only, excluding steam turbines). - The power of classical combined power plant has been estimated at N el =65.49 MWe. Modification of thermal cycle into the Cheng cycle (β=2.77) increases the power to N el =66.92 MWe. - The gain of power and electrical efficiency by steam injection is about 23 %. - Application of Cheng cycle reduces carbon dioxide emission CO2 and nitrogen oxide emission about 10 kg/MWh and 0.008 kg/MWh, respectively, in comparison to pre- modernization power plant. - Comparison of results of numerical simulation with technical data for ECK Generating Kladno confirms possibilities of modification of PGE Gorzow power plant into the Cheng idea. The estimated operational parameters of PGE Gorzow for the same steam parameters are in a good agreement with real operational parameters of ECK Kladno power plant.
ACKNOWLEDGMENTS It should be noted that lowering of steam pressure from ps=40 bar to ps=25 bar does not require afterburning process. Fuel combustion before the
The authors would like to thank to Dr Michal Karcz from IMP PAN Gdansk for his scientific support and advice during the article’s preparation.
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REFERENCES [1] Badur J.: Rozwój pojęcia energii. IMP PAN Gdansk 2009, (in polish). [2] Boyce M.P.: Gas turbine engineering handbook. Butterworth-Heinemann 2002. [3] Carapellucci R., Milazzo A.: Repowering combined cycle power plants by a modified STIG configuration. Energy Conversion and Management 2007, vol.48. [4] Cheng D.Y.: Regenerative parallel compound dual-fluid heat engine. US Patent 1978, no. 4128994. [5] Cheng D.Y.: The distinction between Cheng and STIG cycle. Proceedings of ASME EXPO 2006, GT-2006-90382. [6] Chrzczonowski A.: Układ Chenga jako proekologiczne źródło energii elektrycznej i cieplnej. Rozprawa doktorska, ITCiMP PW Wrocław 2006. [7] Jarociński J.: Techniki czystego spalania. WNT Warszawa 1996. [8] Jesionek K., Chrzczonowski A., Badur J., Lemański M.: Analiza parametryczna pracy zaawansowanego obiegu Chenga. Zeszyty Naukowe Katedry Mechaniki Stosowanej, Politechnika Śląska 2004, vol.23. [9] Jonson M., Yan J.: Humidified gas turbine - a review of proposed and implemented cycles. Energy 2005, vol. 30. [10] Normann F., Andersson K., Leckner B., Johnson F.: Emission control of nitrogen oxides in the oxy-fuel process. Progress in Energy and Combustion Science 2009, vol.35. [11] Pawlik M., Kotlicki T.: Układy gazowo - parowe w energetyce. Konferencja „Elektrownie cieplne” Słok 2001 (in polish). [12] Poullikkas,A.: An overview of current and future sustainable gas turbine technologies. Renewable and Sustainable Energy Reviews 2005, vol.9. [13] Saad M.A., Cheng D.Y.: The new LM2500 Cheng cycle for power generation and cogeneration. Energy Conversion and Management 1997, vol. 38. [14] Srinivas T., Gupta A.V.S.S.K.S., Reddy B.V.: Sensitivity analysis of STIG based combined cycle with dual pressure HRSG. International Journal of Thermal Sciences 2008, vol.47. [15] Topolski J., Lemański M., Badur J.: Model matematyczny wysokotemperaturowego ogniwa paliwowego SOFC w kodzie COM-GAS. Konferencja „Problemy badawcze Energetyki Cieplnej 2003,Warszawa. [16] Wang F.J., Chiou J.S.: Performance improvement for a simple cycle gas turbine GENSET - a retrofitting example. Applied Thermal Engineering 2002, vol.22. [17] Wołoncewicz Z., Buraczewski J.: Doświadczenia z eksploatacji bloku gazowo - parowego w EC Gorzów S.A. 19992003. Konferencja Elektrownie i elektrociepłownie gazowe i gazowo - parowe 2003. [18] Ziółkowski P.: Analiza numeryczna parametrów eksploatacyjnych obiegu cieplnego elektrociepłowni EC Gorzów przed i po modernizacji. Praca magisterska 2011, Politechnika Gdańska (in polish). [19] Directive 2010/75/eu of the European Parliament and of the Council of 24 November 2010 on industrial emissions (integrated pollution prevention and control). [20] http://www.ecgorzow.pgegiek.pl [21] http://www.chengpower.com [22] http://kladno.alpiq.cz WZROST MOCY TURBINY GAZOWEJ PGE GORZÓW ZA POMOCĄ WTRYSKU PARY – PRZEGLĄD TERMODYNAMICZNY Słowa kluczowe: obieg Chenga, obieg STIG, obiegi kombinowane, wtrysk pary, turbina gazowa Streszczenie. W artykule zbadano wpływ wtrysk pary wodnej na wydajność turbiny gazowej i obiegu gazowo-parowego. Artykuł opisuje i podsumowuje możliwości zmodyfikowania turbiny gazowej elektrociepłowni PGE Gorzów do obiegu Chenga. Modyfikacja związana jest z obiegiem cieplnym, w którym produkowana para w kotle utylizacyjnym wtryskiwana jest do komory spalania turbiny gazowej. Udowodniono, że wzrost strumienia masy ekspandujących spalin powoduje wzrost mocy i sprawności turbiny gazowej. Dodatkowo, wtrysk pary wodnej powoduje obniżenie tlenków azotu NOx i z punktu widzenia termodynamicznego, ekonomicznego i ekologicznego jest zabiegiem korzystnym. Obliczenia numeryczne obiegu cieplnego przed i po modyfikacji wykonano za pomocą własnego kodu COM – GAS oraz komercyjnego programu Aspen Plus. Janusz Badur, Prof., D.Sc., Ph.D., Eng., The Szewalski Institute of Fluid-Flow Machinery Polish Academy of Sciences, Head of Energy Conversion Department. Marcin Lemański, Ph.D., Eng., The Szewalski Institute of Fluid-Flow Machinery Polish Academy of Sciences, Energy Conversion Department,
[email protected] Lucjan Nastałek, M.Sc., Eng., The Szewalski Institute of Fluid-Flow Machinery Polish Academy of Sciences, Energy Conversion Department. Paweł Ziółkowski, M.Sc., Eng., The Szewalski Institute of Fluid-Flow Machinery Polish Academy of Sciences, Energy Conversion Department.
