Influence of a rotating nozzle diaphragm on the characteristics of axial low-consumption turbines

Экспериментально исследуются различные компоновки турбинных ступеней с целью обеспечения многорежимности у осевых малорасходных турбин. Определено, что под многорежимностью понимается способность турбины поддерживать величину КПД неизменной, или с небольшими изменениями в достаточно широком диапазоне изменения внешних нагрузок. С новой точки зрения обращено внимание на то, что наиболее выраженными свойствами многорежимности обладают турбины в состав которых входит вращающийся сопловой аппарат. В этой связи рассмотрены авторские результаты экспериментальных исследований биротативных турбин с большим углом поворота потока и двух-ступенчатых осевых турбин с частичным облопачиванием рабочего колеса. Выявлено, у исследованных биротативных турбин свойство многорежимности проявляется при степени парциальности, близкой к единице и регулируется путем изменения соотношения частот вращения соплового аппарата и рабочего колеса. А у одновальных турбин с частичным облопачиванием рабочего колеса свойство многорежимности проявляется в широком диапазоне изменения степени расширения в турбине также при полном подводе рабочего тела. Various arrangements of turbine stages are experimentally investigated in order to ensure multiplicity of operating levels for axial low-consumption turbines. It has been determined that multiplicity is understood as the ability of a turbine to maintain the efficiency value unchanged, or with small changes in a fairly wide range of external loads. From a new point of view, attention is drawn to the fact that the most marked properties of operating levels multiplicity are relevant to the turbines which include a rotating nozzle diaphragm. In this regard, the author's results of experimental studies of birotative turbines with a large flow angle and two-stage axial turbines with partial blading of the running wheel are considered. It was revealed that in the investigated birotative turbines the property of multiplicity is manifested at a degree of partiality close to 1 and is regulated by changing the ratio of the rotation frequencies of the nozzle diaphragm and the running wheel. And in single-shaft turbines with partial blading of the running wheel, the multiplicity property is manifested in a wide range of changes in the degree of expansion in the turbine, also with full supply of the working fluid.

Preliminary Aerodynamic Design of a S-CO2 Axial Turbine

Axial turbines are gaining prominence in supercritical carbon-di-oxide (S-CO2) Brayton cycle power blocks. S-CO2 Brayton cycle power systems designed for 10 MW and upwards will need axial turbines for efficient energy conversion and compact construction. The real gas behavior of S-CO2 and its rapid property variations with temperature presents a strong challenge for turbomachinery design. Applying gas and steam turbine philosophies directly to S-CO2 turbine could lead to erroneous designs. Very little information is available in the open literature on the design of S-CO2 axial turbines. In this paper, design of a 10 MW axial turbine for a simple recuperated Brayton cycle waste heat recovery system is presented. Three repeating stages with nominal stage loading coefficient of 2.3 and flow coefficient of 0.37 were designed. An axial turbine mean-line design method tuned to S-CO2 real gas fluid medium is discussed. 3D blade design was made suing commercial turbomachinery design software AxSTREAM. The turbine was designed for inlet temperature of 818.15 K, pressure ratio of 2.2, rotational speed of 12000 rpm and mass flow rate of 104.5 kg/s. 3D CFD simulations were carried out using the commercial RANS solver ANSYS CFX 2020 R2 with SST turbulence model for closure. S-CO2 was modelled as real gas with Refrigerant Gas Property tables generated over the appropriate pressure and temperature ranges using NIST Refprop database. CFD studies were carried out over a range of mass flow rates and speeds, covering the design and several off-design conditions. The performance maps generated using 3D CFD simulations of the turbine are presented. The geometrical parameters obtained with the mean-line design matched well with that of the 3D turbine design arrived using AxSTREAM. It was observed that the turbine produced 10 MW power at the design condition while passing the required mass flow. CFD studies also showed that the preliminary turbine design achieved a moderate total-to-total efficiency of 80 % at the design condition. The design has potential for further optimization to obtain improved efficiency and for reducing the number of stages from three to two.

The Potential of Hydro Renewable Energy Technology to Electricity Remote Villages in Papua and Maluku Islands, Indonesia

The islands of Papua and Maluku are eastern Indonesia which consists of remote islands and villages. The Papua Islands consist of 3,749 islands divided into two provinces, namely Papua and West Papua, while the Maluku Islands are 1,735 islands into two provinces of Maluku and North Maluku, the number of inhabited islands in Papua and Maluku around 230 islands and around 100 newly electrified islands. The electrification ratio for Papua is 47.69%, West Papua is 89.94%, Maluku is 87.02% and North Maluku is 88.68%. The electrification ratio is still below the national average. Maluku Islands and Papua Indonesia has abundant renewable energy natural resources, namely hydro potential. The total hydro energy potential of Papua and Maluku is 808 MW. To overcome this shortage of electricity, it is necessary to develop a renewable energy generation system according to the potential of the area, namely hydro power. Energy generation technology that is environmentally friendly, efficient, effective, and reliable can be a solution for electrification in Papua and Maluku. Hydro power plants using vortex turbines, picohydro turbines and axial turbines for permanent magnet generators can be a solution to electrify areas or villages remote in Papua and Maluku.

Analysis and Classification of Low Head Hydro Power Based on Advanced Morphological Approach

The paper discusses hydrokinetic systems low head hydro power as an element renewable resource. In the paper a review of the existing and upcoming orthogonal and axial turbines schemes is outlined. Based on a morphological approach comprehensive survey of various schemes and qualitative comparison, is presented. The proposed engineering solutions reduce the structure weight and the processability increases. These factors lead to a decrease in the cost. The engineering solutions under consideration are designed to operate in low-pressure flows, regardless of their direction. Thanks to these features, the scope of their use expands. They can be used both in high tide and in the use of the sea currents kinetic energy.

A Code for the Preliminary Design of Cooled Supercritical CO2 Turbines and Application to the Allam Cycle

This paper documents a thermo-fluid-dynamic mean-line model for the preliminary design of multi-stage axial turbines with blade cooling applicable to supercritical CO2 turbines. Given the working fluid and coolant inlet thermodynamic conditions, blade geometry, number of stages and load criterion, the model computes the stage-by-stage design along with the cooling requirement and ultimately provides an estimate of turbine efficiency via a semi-empirical loss model. Different cooling modes are available and can be selected by the user (stand-alone or combination): convective cooling, film cooling, thermal barrier coating. The model is applied to attain the preliminary aero-thermal design of the 600 MW cooled axial supercritical CO2 turbine of the Allam cycle. Results show that a load coefficient varying from 3 to 1 throughout the machine, and a reaction degree ranging from 0.1 to 0.5 lead to the maximum total-to-static turbine efficiency of about 85 %. Consequently, as opposed to uncooled CO2 turbines, a repeated stage configuration is an unsuited design choice for cooled sCO2 machines. Moreover, the study highlights that film cooling is considerably less effective compared to conventional gas turbines, while increasing the number of stages from 5 to 6 and adopting higher rotational speeds leads to an increased efficiency.

The Effect of Inlet Conditions on Turbine Endwall Loss

There can be significant variation and uncertainty in the flow conditions entering a blade row. This paper explores how this variability can affect endwall loss in axial turbines. A computational study of three cascades with collinear inlet boundary layers is conducted. Endwall loss varies by more than a factor of 3 depending on the inlet conditions. This variation is caused by dissipation of Secondary Kinetic Energy (SKE). The results can be understood by observing that the inlet conditions predominantly control how secondary vorticity is distributed within the blade passage. Modestly-thick inlet boundary layers with high shape factor tend to displace vorticity towards the center of the passage. This displacement reduces vorticity cancellation, increasing secondary velocities and SKE. A general method is formulated to estimate SKE in preliminary design. Optimum aspect ratio is shown to depend on the inlet boundary condition. Strategies to reduce endwall loss and minimize sensitivity to inlet conditions are then highlighted.

Selection of Optimal Gas-Dynamic Parameters of Radial-Axial Turbines in Their Joint Operation with Reciprocating Internal Combustion Engines

The study of radial-axial (centripetal) turbines is important for science and technology. They are widely used in the refrigeration industry, internal combustion engines, and power engineering, both in the form of auxiliary units and in autonomous power units. The article offers a method for selecting the gas-dynamic parameters of the centripetal turbine in order to obtain the highest efficiency and the best size of the turbine. The increased manufacturability of the turbine is provided due to the absence of a straightener at the outlet of the impeller and the use of straight blades in the impeller. The dependence of the efficiency of a centripetal turbine on the profiles of the blades and the radial dimensions of the nozzle apparatus and the impeller, as well as on the length of the impeller blades is investigated. Considering the recommended optimal parameters, the calculation of a pulsed centripetal turbine operating in conjunction with a four-stroke piston internal combustion engine is performed.