Acta Polytechnica doi:10.14311/AP.2016.56.0118 Acta Polytechnica 56(2):118–125, 2016 © Czech Technical University in Prague, 2016 available online at http://ojs.cvut.cz/ojs/index.php/ap MEASUREMENTS IN THE VT 400 AIR TURBINE Marek Klimko∗, Daniel Okresa Department of Power System Engineering, Faculty of Mechanical Engineering, University of West Bohemia in Pilsen, Univerzitní 22, 306 14 Pilsen, Czech Republic ∗ corresponding author: klimko@kke.zcu.cz Abstract. This paper presents a basic description of measurements on the experimental air turbine located in the laboratories of the Department of Power System Engineering (KKE). The research on this turbine focuses on the flow in a one-stage air turbine. It monitors the influence of the spatial formation of the blades on the efficiency of the stage. A new geometry with reaction blading is currently being tested. This work has been carried out in cooperation with an industrial partner, Doosan Skoda Power (DSPW). Keywords: air turbine, pressurized blading, pneumatic probe. 1. Introduction Steam turbine constructers consider the methodology and the rules for calculating blading efficiency, when designing turbine stages, to be one of the most valu- able and most confidential parts of their know-how. Guaranteed efficiency values are one of the key factors in the competition to retain and gain customers. Ob- taining new data for specifying the so-called efficiency prediction, and also research focused on optimizing efficiency prediction, are important long-term devel- opment objectives for all steam turbine producers. Generally, blade spatial forming is one of the main in- struments for increasing blading efficiency. It focuses particularly on reducing the influence of so-called sec- ondary flow and related losses, but also deals with targeted redistribution of particular flow parameters, not only along the length of the blades, but also within the stage, or indeed within the whole flow section. 2. Cooperation on the development of blading Doosan Skoda Power (DSPW) has engaged in intense development of new types of blading in recent years, and cooperation with the Department of Power Sys- tem Engineering (KKE) has been an integral aspect of this development work. Between 2000 and 2005, the development work aimed at forming stationary blades. Variants with both lean and compound lean peripheral inclination, and also a controlled flow blade, were investigated (see Figure 1). These types of blading were tested on a SKODA 1MW trial steam turbine, and simultaneous tests were carried out on the KKE air turbine at the University of West Bohemia in Pilsen. The studies concentrated on forming stator blades, while preserving the original prismatic moving blades. One of the outcomes of the research, which was car- ried out within the framework of several grant-funded projects (FD-K/0111, GA101/01/14482), was the de- sign by DSPW of the so-called banana blade. Some results of the cooperation between DSPW and KKE have been presented, e.g. in [1–4]. In the following period, DSPW, a traditional pro- ducer of action conception turbines, began to develop 3D blading with so-called slightly increased hub re- action. This blading included the formation of both stationary blades and moving blades. Compound lean blading, combined with controlled flow access of stationary blades, supplemented by an appropriately formed (twisted) moving blade, was designed and tested within the framework of grant- funded projects (e.g. FT-TA/0853, FT-TA2/0374, FT- TA5/0675) and ongoing cooperation. Experimental testing of these “Full3D” stages was one of the princi- pal topics of the cooperation between KKE, a univer- sity department, and DSPW, an industrial company, between 2008 and 2012. Three variants with differ- ent compactness of the blades were tested stepwise (Figure 2). The results were published for example in [5–9]. This development raised the efficiency by approx. 2% in the HP component and by 1.5% in the MP component, in comparison with classic pris- matic or warped blading. In many cases, improved design principles have been transferred into practical applications. Stages with an increased hub reaction basically rep- resent a developmental transition between action and reaction stage conceptions. Current developments in 3D blading have been leading DSPW logically to- 1Project FD-K/011 — Development of high efficiency steam turbines 150–500 MW. (2001-2003, MPO/FD) 2Project GA101/01/1448 — Development of a new gener- ation of steam turbine high-pressure blades with low losses (2001-2003, GA0/GA) 3Project FT-TA/085 – Steam turbine of high efficiency (2004- 2006, MPO/FT) 4Project FT-TA2/037 – Steam turbine for power units with high steam parameters. (2005-2007, MPO/FT) 5Project FT-TA5/067 – Research of non-stationaryflow in an axial-flow turbine stage(2008-2010, MPO/FT) 118 http://dx.doi.org/10.14311/AP.2016.56.0118 http://ojs.cvut.cz/ojs/index.php/ap vol. 56 no. 2/2016 Measurements in the VT 400 Air Turbine Blading type Prismatic Lean Compound Compound Lean Twist Blade shape Figure 1. Formation of stator blades. Stationary blade Stationary blade Stationary blade Moving bladevariant 1 (2010) variant 2 (2011) variant 3 (2012) Figure 2. Forms of blades tested in the “Full3D” stage. wards reaction blading. A vast internal developmental project has been proceeding since 2011, when the first stage of the development focused on blading for the HP component of turbines with an approximate efficiency of 300 MW. The goal was to increase the efficiency of the HP component of a steam turbine by up to 1.6% in comparison with the efficiency of commonly designed HP components with blading with a slightly increased hub reaction. The development of new profiles and subsequent experimental verification of the new conception formed a part of project FR- TI3/4326, which was solved in cooperation with the Aerospace Research and Test Establishment in Prague. Complex verification on a Skoda 10 MW trial steam turbine forms a significant part of the development of reaction blading. KKE is also involved in follow- up research work, and collaborates in experimental testing of reaction blading on air turbines. However, the development trends and objectives of individual competing companies have not been focused and profiled only on action blading or reaction blading. Much work is also being done on so–called variable reaction stages, i.e. the optimized use of blades with a different reaction, with regard to the design require- ments and attempts to achieve higher efficiency. This is a present-day developmental direction at DSPW, and it foms the topic of a follow-up internal project, where the application of reaction blades to high effi- ciency turbines is also being investigated. 6FR-TI3/432 – Complex development of a turbine reaction stage with high efficiency (2011-2013, MPO/FR) 3. Experimental air turbine at KKE The experimental air turbine at KKE is a single-stage air turbine located in the compressor suction. The turbine is a model of a high-pressure steam turbine component stage on a scale of 1:2. In addition to almost constant air input parameters, this layout also provides easy access to the turbine and to the mea- suring points. Figure 3. View into the laboratory. A part of the machine is the direct dynamometer, which determines the speed and the resulting moment. Air, the volume of which is measured by a nozzle, 119 Marek Klimko, Daniel Okresa Acta Polytechnica Stator var1 Stator var2 Rotor No. of blades N [1] 78 40 56 Blade length L [mm] 45,5 45,5 47 Hub diameter Dp [mm] 400 400 400 Relative length L/Dp [1] 0,114 0,114 0,118 Medium pitch ts [mm] 17,94 34,99 25,08 Profile chord c [mm] 22,51 43,90 32,09 Blade width Bax [mm] 15,85 30,47 21,43 Relative pitch ts/c [1] 0,797 0,797 0,782 Leanness L/c [1] 2,021 1,036 1,465 Figure 4. Basic geometric characteristics. leaves the compressor pressure discharge and goes out of the laboratory. The turbine is equipped with a traverse device. The traverser enables the probe to move radially (under the blade hub section and above the blade tip), and peripherally (across two stationary blade pitches). It also allows the probe to turn auto- matically in the flow direction. This enables thorough measurements of the flow field behind stationary and moving blades. There are several static pressure ex- tractors on the turbine – in front of the stage, inside it, and behind it – always on the hub section and tip di- ameter. There are holes at the input, for inserting e.g. a Prandtl probe, and for measuring the input flow. All pressures are scanned by a fast, 16-channel pressure transducer. Temperatures are scanned by a resistance thermometer in front of and behind the stage. The probe measurement and motion are automatic; the utility program is created in LabView 7. 4. New blading for the experiment In 2013, DSPW proposed two variants of a stage de- signed for testing on the air turbine of the University of West Bohemia, in accordance with newly prepared methodologies, and using new profiles for reaction 7 1 2 38 9 5 4 6 Figure 5. Scheme of the device: 1 – Filter, 2 – Turbine, 3 – Dynamometer, 4 – Traverser, 5 – Nozzle, 6 – Silencer, 7 – Compressor, 8 – Gearbox, 9 – Electric motor. blading. The aim was to verify the design data con- cerning aerodynamics, and to obtain data for the specifications of a loss model of the reaction stages. The variants differ in the leanness of the stationary blade, the main parameter influencing the creation of secondary losses. The basic geometric data are sum- marized in Figure 4. The figure has been produced, and the first tests the first tests were performed early in 2015. All the experiments were completed by the middle of 2015. 120 vol. 56 no. 2/2016 Measurements in the VT 400 Air Turbine 5. Evaluation process Measurements behind the stator and rotor blades were made with the use of a 5-hole pneumatic probe which allows movement around its own axis and also in the radial and circumferential directions. Calculating the air flow rate. The air flow rate is calculated using the ASME standard bases ṁV = f(pc,∆pc, Tout). Calculating the isentropic gradient of the stage. The isentropic gradient of the stage is con- sidered to lie between static pressures T INT 02iz = T INT 0s ( pINT 2s pINT 0s )κ−1 κ , HST iz = cp ( T INT 0s − T INT 02iz ) ⇒ c02iz = √ 2HST iz . Calculating the input and output velocity. The input and output velocities are axial velocities c0a = c0 = ṁV s0ρ0s , ρ0s = pINT 0s RVT INT 0s , c2a ≈ c2 = ṁV S2ρ2s , ρ2s ≈ ρ02iz = pINT 2s RVT INT 02iz . Calculating the total output state. T INT 0c = T INT 0s + c2 0 2cp . Calculating the performance and effective pressure drop. P = Mkω = Mk 2πn 60 = Pobv − Pf , HST = Pobv ṁV = P + Pf ṁV = cp ( T INT 0c − T INT 2c ) . Calculating the efficiency and the moment of torsion. ηST ts = HST HST iz + c2 0 2 = HST cp ( T INT 0s − T INT 02iz ) + c2 0 2 , ηST tt = HST HST iz + c2 0 2 + c2 2 2 . Traversing behind stationary blades. To evalu- ate the traversing data, we need to know the integral values and we need data from the 5-hole pneumatic probe, after re-calculation according to the calibration (p1c, p1s, φ, θ). 5 휌 ≈ 휌 푝 푅 ∙ 푇 5.4. Calculation of the total output state 푻ퟎ푪푰푵푻 = 푻ퟎ푺푰푵푻 + 풄ퟎퟐ ퟐ ∙ 풄풑 5.5. Calculation of the performance and effective pressure drop 푃 = 푀 ∙ 휔 = 푀 ∙ 2 ∙ 휋 ∙ 푛 60 = = 푃 − 푃 퐻 = 푃 푚̇ = 푃 + 푃 푚̇ = = 푐 ∙ (푇 − 푇 ) 5.6. Calculation of efficiency and moment of torsion 휂 = 퐻 퐻 + = = 퐻 푐 ∙ (푇 − 푇 ) + 휂 = 퐻 퐻 + − Fig. 6 T-s diagram of expansion 5.7. Traversing behind stationary blades To evaluate the traversing data, we need to know integral values and data from 5-hole pneumatic probe after re-calculation according to the calibration (p1c, p1s, φ, ϑ). 5.7.1 Calculation of stationary blades gradient and reaction Fig. 7 T-s diagram of expansion Figure 6. T–s expansion diagram. 5 휌 ≈ 휌 푝 푅 ∙ 푇 5.4. Calculation of the total output state 푻ퟎ푪푰푵푻 = 푻ퟎ푺푰푵푻 + 풄ퟎퟐ ퟐ ∙ 풄풑 5.5. Calculation of the performance and effective pressure drop 푃 = 푀 ∙ 휔 = 푀 ∙ 2 ∙ 휋 ∙ 푛 60 = = 푃 − 푃 퐻 = 푃 푚̇ = 푃 + 푃 푚̇ = = 푐 ∙ (푇 − 푇 ) 5.6. Calculation of efficiency and moment of torsion 휂 = 퐻 퐻 + = = 퐻 푐 ∙ (푇 − 푇 ) + 휂 = 퐻 퐻 + − Fig. 6 T-s diagram of expansion 5.7. Traversing behind stationary blades To evaluate the traversing data, we need to know integral values and data from 5-hole pneumatic probe after re-calculation according to the calibration (p1c, p1s, φ, ϑ). 5.7.1 Calculation of stationary blades gradient and reaction Fig. 7 T-s diagram of expansionFigure 7. T–s expansion diagram. Calculating the gradient and the reaction of stationary blades. T1iz = T INT 0s ( p1s pINT 0s )κ−1 κ , HRL iz = cp(T INT 0s − T1iz), HOL iz = cp(T1iz − T INT 02iz ) = HST iz −HRL iz . Velocity triangles. T1s = T INT 0c ( p1s p1c )κ−1 κ , 121 Marek Klimko, Daniel Okresa Acta Polytechnica c1 = √ 2cp(T INT 0c − T1s), c1a = c1 cos θ cos(90− ϕ), c1u = c1 cos θ sin(90− ϕ), c1r = c1 sin θ w1u = c1u − u1, w1 = √ c2 1a + c2 1u, β1t = acosw1u w1 . Calculating the efficiency of stationary blades. ηRL = T INT 0c − T1s T INT 0c − T1iz = c2 1 2 HRL iz + c2 0 2 . Traversing behind moving blades. To evaluate the traversing data, we need to know the integral values, and we need data from the 5-hole pneumatic probe, after re-calculation according to the calibration (p2c, p1s, ϕ, θ). The state in front of moving blades. ρSS, c1 c02iz , w1 c02iz , HRL iz = (1− ρSS)HST iz , p1s = pINT 0s ( T1iz T INT 0s ) κ κ−1 , c1 = ( c1 c02iz ) c02iz, w1 = ( w1 c02iz ) c02iz, T1s = T INT 0c − c2 1 2cp . Calculating the expansion of moving blades. T1w = T1s + w2 1 2cp , T2iz = T1s ( p2s p1s )κ−1 κ . Estimating the velocity c2. T2ciz = T1s ( p2c p1s )κ−1 κ , c̃2 = √ 2cp(T2ciz − T2iz), c̃2a = c̃2 cos θ cos(90− ϕ), c̃2u = c̃2 cos θ sin(90− ϕ), w̃2u = c̃2u − u2, w̃2 = √ c̃2 2a + w̃2 2u. Recalculating the expansion. T2s = T1w − w̃2 2 2cp , T2c = T2s ( p2c p2s )κ−1 κ , c2 = √ 2cp (T2c − T2s), c2a = c2 cos θ cos(90− ϕ), c2u = c2 cos θ sin(90− ϕ), c2r = c2 sin θ, w2u = c2u − u2, w2 = √ c2 2a + w2 2u, β2f = acosw2u w2 . 7 훽 = 푎푐표푠 푤 푤 5.8.5. Moving blades efficiency 휂 = 푇 − 푇 푇 − 푇 Figure 8. T-s diagram of expansion 6. Results of experiments For initial experiments the variant of the stage with a no lean stationary blade was chosen. The second variant test launch is expected at the end of this year. All experiments proceed according to the established methodology. First, integral characteristics depending on the velocity ratio u/c are identified. Individual measurements are executed at constant speed; and changes in values of the velocity ratio u/c occur due to the change of pressure drop in a turbine. Those measurements are realized at several levels of speed (in the extent of approx. 2000 – 3000 revolutions per minute), which leads to changes in the pressure drop, Mach number and partly also Reynolds number. Those measurements result in setting the optimal operating state, during which further experiments can proceed, particularly measurements of flow fields behind stationary and moving blades by a 5-hole pneumatic probe. One of the basic properties of a turbine stage is a dependence of a peripheral efficiency on the velocity ratio u/c. These dependences provide an idea about an optimal operating regime of the stage in order to reach the maximal efficiency. The optimal operating state differs according to the blading type. The results of the initial experiments are presented on the graph (Fig. 9) in comparison with the results of the previous experiments. Figure 8. T–s expansion diagram. Efficiency of moving blades. ηOL = T1w − T2s T1w − T2iz . 6. Results of experiments The variant of the stage with no leanstationary blade was chosen for the initial experiments. All experiments proceeded according to the established methodology. First, integral characteristics depending on the veloc- ity ratio u/c were identified. Individual measurements were executed at a constant speed; and changes in the 122 vol. 56 no. 2/2016 Measurements in the VT 400 Air Turbine 8 Figure 9. Comparison of results of particular variants of blading This comparison shows a sequential contribution to relative peripheral stage efficiencies. Existing test results show a progressive trend in increasing efficiency, and originally confirm that the newly designed reaction blading represents an appropriately chosen development direction. By determining an optimal operating regime, we have moved towards another phase, in which flow fields behind stationary as well as moving blades will be measured. Results of efficiency are presented as relative values. Data from measurements are property of DSPW. It is apparent from the reaction dependence along the length of the blade that we reach thereaction value around 0.5 in the middle of the blade, which corresponds to our expectations. Figure 10. The reaction course along the relative length of the blade Figure 9. A comparison of the results for different blading variants. 8 Figure 9. Comparison of results of particular variants of blading This comparison shows a sequential contribution to relative peripheral stage efficiencies. Existing test results show a progressive trend in increasing efficiency, and originally confirm that the newly designed reaction blading represents an appropriately chosen development direction. By determining an optimal operating regime, we have moved towards another phase, in which flow fields behind stationary as well as moving blades will be measured. Results of efficiency are presented as relative values. Data from measurements are property of DSPW. It is apparent from the reaction dependence along the length of the blade that we reach thereaction value around 0.5 in the middle of the blade, which corresponds to our expectations. Figure 10. The reaction course along the relative length of the blade Figure 10. The course of the reaction along the relative length of the blade. values of the velocity ratio u/c occurred due to the change in the pressure drop in the turbine. The measurements were made at several levels of speed (within the range of approx. 2000–3000 revolu- tions per minute), which led to changes in the pressure drop, the Mach number and partly also the Reynolds number. These measurements were used to set the optimal operating state in which further experiments can proceed, particularly measurements by a 5-hole pneumatic probe of the flow fields behind stationary 9 Fig. 11The Reynolds number course along the blade Fig. 12. The Mach number course along the blade The average value of Mach number in the middle of the blade is 0.15; it means that it is a deeply sub-sonic flowing. Reynolds number oscillates around 160,000. 7. Conclusion Experimental verification of a new reaction blading on the air turbine is still in its initial phase. However, the preliminary results already show further substantial improvement of the stage efficiency (estimated by 0.7% in comparison with the Full3D variant, and in comparison with prismatic blades by up to approximately 2%). Further slight increase in peripheral efficiency is expected for the second tested variant with lean stationary blades. For the future, flow fields behind stationary and, consequently, behind moving blades, using 5-hole pneumatic probe shall be measured. The measurement shall be carried out in the cooperation with DSPW, and its output will be e.g. distribution of losses and angles, or the reaction along the length of the blade. LIST OF SYMBOLS: c Velocity [m.s-1] H Enthalpy [J] M Moment [N.m-1] 푚̇ Mass flow[kg.s-1] n Rotational speed [RPM] P Performance [W] p Pressure [Pa] s Entropy [J.K-1] T Temperature [K] u Circumferential velocity [m.s-1] w Relative velocity [m.s-1] η Efficiency [1] κ Adiabatic exponent [1] ρ Density [kg.m-3] Superscripts: INT Integral characteristics OL Bucket RL Nozzle ST Stage Subscripts: c absolute iz isentropic s static ts total to static tt total to total Figure 11. The course of the Reynolds number along the blade. and moving blades. One of the basic properties of a turbine stage is the dependence of the peripheral efficiency on the velocity ratio u/c. These dependences provide an idea about the optimal operating regime for the stage in order to achieve maximum efficiency. The optimum operating state differs according to the type of blading. The results of the initial experiments are presented in a 123 Marek Klimko, Daniel Okresa Acta Polytechnica 9 Fig. 11The Reynolds number course along the blade Fig. 12. The Mach number course along the blade The average value of Mach number in the middle of the blade is 0.15; it means that it is a deeply sub-sonic flowing. Reynolds number oscillates around 160,000. 7. Conclusion Experimental verification of a new reaction blading on the air turbine is still in its initial phase. However, the preliminary results already show further substantial improvement of the stage efficiency (estimated by 0.7% in comparison with the Full3D variant, and in comparison with prismatic blades by up to approximately 2%). Further slight increase in peripheral efficiency is expected for the second tested variant with lean stationary blades. For the future, flow fields behind stationary and, consequently, behind moving blades, using 5-hole pneumatic probe shall be measured. The measurement shall be carried out in the cooperation with DSPW, and its output will be e.g. distribution of losses and angles, or the reaction along the length of the blade. LIST OF SYMBOLS: c Velocity [m.s-1] H Enthalpy [J] M Moment [N.m-1] 푚̇ Mass flow[kg.s-1] n Rotational speed [RPM] P Performance [W] p Pressure [Pa] s Entropy [J.K-1] T Temperature [K] u Circumferential velocity [m.s-1] w Relative velocity [m.s-1] η Efficiency [1] κ Adiabatic exponent [1] ρ Density [kg.m-3] Superscripts: INT Integral characteristics OL Bucket RL Nozzle ST Stage Subscripts: c absolute iz isentropic s static ts total to static tt total to total Figure 12. The course of the Mach number along the blade. graph (Figure 9), in comparison with the results of previous experiments. This comparison shows a sequential contribution to relative peripheral stage efficiencies. Existing test results show a progressive trend toward increasing effi- ciency, and originally confirm that the newly designed reaction blading is a well-selected development direc- tion. By determining an optimal operating regime, we have moved towards another phase, in which the flow fields behind both stationary blades and moving blades will be measured. The efficiency results are presented as relative values. The data from the measurements are the property of DSPW. It is apparent from the reaction dependence along the length of the blade that a reaction value around 0.5 is reached in the middle of the blade, which corresponds to our expectations. The average Mach number value in the middle of the blade is 0.15, which means that it is a deeply sub- sonic flow. The Reynolds number oscillates around 160 000. 7. Conclusion Experimental verification of new reaction blading on air turbines is still in its initial phase. However, the preliminary results already show further substantial improvement of the stage efficiency (by 0.7% (esti- mated) in comparison with the Full3D variant, and by up to approximately 2% in comparison with pris- matic blades). A further slight increase in peripheral efficiency is expected for the second tested variant with lean stationary blades. For the future, the flow fields behind stationary blades and, subsequently, be- hind moving blades, will be measured using a 5-hole pneumatic probe. The measurements will be carried out in cooperation with DSPW. The output of the measurements will be the distribution of losses and angles, or the reaction along the length of the blade. List of symbols c Velocity [m s−1] H Enthalpy [J] M Moment [N m−1] ṁ Mass flow [kg s−1] n Rotatinal speed [RPM] P Performance [W] p Pressure [Pa] s Entropy [J K−1] T Temperature [K] u Circumferential velocity [m s−1] w Relative velocity [m s−1] η Efficiency [–] κ Adiabatic exponent [–] ρ Density [kg m−3] Superscripts INT Integral characteristics OL Bucket RL Nozzle ST Stage Subscripts c absolute iz isentropic s static ts total to static tt total to total Acknowledgements This study originated within the student project SGS- 2014-070 (Increase of efficiency, reliability and lifespan of power system machines and equipment 3), and the project CZ.1.05/2.1.00/03.0108SUSEN (Sustainable energetics). References [1] J. Vomlela. Experimental and numerical development of turbine blades of high efficiency. In 5th European conference on turbomachinery, pp. 699–708. Praha: A.S.I., 2003. [2] J. Vomlela, P. Milčák. The development of high-efficiency turbine blades. In Cieplne maszyny przeplywowe. Turbomachinery., pp. 557–564. Technical University of Łódź, 2005. [3] B. Haller. Full 3d turbine blade design. In Lecture series “Secondary and Tip Clearance Flows in Axial Turbines”. von Karman Institute for Fluid Dynamics, 1997. [4] C. Sieverding. Recent progress in the understanding of basic aspects of secondary flows in turbine blade passages. Journal of Engineering for Gas Turbines and Power 107:248–257, 1985. 124 vol. 56 no. 2/2016 Measurements in the VT 400 Air Turbine [5] P. Milčák, K. Sobczak. Experimental and numerical investigations of a flow in the stage with compound lean and compound twist stator blades. In Power System Engineering, Thermodynamics & Fluid Flow ES 2007, pp. 153–160. Západočeská univerzita v Plzni, 2007. [6] S. Harrison. The influence of blade lean on turbine losses. J Turbomach 114(1):184–190, 2016. doi:10.1115/1.2927982. [7] P. Milčák, M. Hoznedl. Measurement of flow fields on a turbine stage with 3D blades. In Experimental Fluid Mechanics, pp. 417–422. Technical University of Liberec, 2010. [8] P. Milčák, M. Hoznedl, P. Žitek. Measurement on stages with 3D bladings and different relative width of stator blades. In EFM11 – Experimental Fluid Mechanics 2011, vol. 25 of EPJ Web of Conferences. 2012. doi:10.1051/epjconf/20122501054. [9] P. Milčák, P. Žitek, M. Hoznedl. Comparison of results from experimental testing of three variants of turbine stage with modern 3D blades. In EFM12 – Experimental Fluid Mechanics 2012, vol. 45 of EPJ Web of Conferences. 2013. doi:10.1051/epjconf/20134501063. 125 http://dx.doi.org/10.1115/1.2927982 http://dx.doi.org/10.1051/epjconf/20122501054 http://dx.doi.org/10.1051/epjconf/20134501063 Acta Polytechnica 56(2):118–125, 2016 1 Introduction 2 Cooperation on the development of blading 3 Experimental air turbine at KKE 4 New blading for the experiment 5 Evaluation process 6 Results of experiments 7 Conclusion List of symbols Acknowledgements References