scholarly journals ВПЛИВ ЗАЗОРУ МІЖ РЯДАМИ СПІВВІСНОГО ПОВІТРЯНОГО ГВИНТА НА ТЯГУ

2020 ◽  
pp. 19-23
Author(s):  
Вячеслав Юрьевич Усенко ◽  
Екатерина Викторовна Дорошенко ◽  
Михаил Владимирович Хижняк
Keyword(s):  
Guide Vane ◽  
Turbulent Viscosity ◽  
External Environment ◽  
Calculation Model ◽  
Hydraulic Loss ◽  
Flow Modeling ◽  
Turboprop Engine ◽  
Air Intake ◽  
Axial Clearance ◽  
Propeller Blades

The thrust of a turboprop engine depends on many factors, one of which is hydraulic loss when flowing around the propeller blades. When using coaxial propellers, this factor plays an even greater role, since in this case the losses associated with the swirl sheet behind the first propeller were added. The aim of the work is to assess the influence of the axial clearance between the rows of the coaxial propeller on the thrust. The object of the study is a coaxial propeller. The axial clearance between the rows of the propeller ranged from 650 mm to 950 mm. Geometrically, the calculation model was a cylinder with a radius of 75 m and a height of 150 m. A coaxial propeller was located in the center of the cylinder. The investigated computational model is divided into four subregions: the external environment, the input guide vane, the first row of the propeller, the second row of the propeller. Separation of the calculation model into those listed below for the region allows us to evaluate the effect of the engine air intake on the propeller parameters and to ensure the correct modeling of flow around two rows of the propeller. In the first step of the study, a comparison was made of the results of numerical simulation with the results of an approved mathematical model for a version of a propeller with an axial clearance of 650 mm. The calculations were carried out with three models of turbulent viscosity: k-ω, SST, SST Gamma Theta Transitional. Based on the comparison, the SST turbulent viscosity model was selected for further research. The second research step included flow modeling for a modified coaxial propeller with an axial clearance between the propeller rows of 950 mm. According to the results of the study, it was found that the magnitude of the axial clearance between the rows of coaxial propeller affects the thrust. It is shown that when the clearance between the rows of the propeller increases from 650 mm to 950 mm, the thrust of the propeller increases by 17 %. This can be explained by a decrease in the level of unevenness and hydraulic losses behind the second row of the propeller. In the future, the obtained results of a numerical experiment require agreement with a field experiment.

scholarly journals The Influence of Bulb Position on Hydraulic Performance of Submersible Tubular Pump Device

2021 ◽  
Vol 9 (8) ◽  
pp. 831
Author(s):  
Zhuangzhuang Sun ◽  
Jie Yu ◽  
Fangping Tang
Keyword(s):  
Entropy Production ◽  
Large Scale ◽  
Experimental Testing ◽  
Guide Vane ◽  
Outer Wall ◽  
Hydraulic Performance ◽  
Hydraulic Loss ◽  
Optimized Design ◽  
Outlet Channel ◽  
Wall Area

In order to study the influence of the position of the bulb on the hydraulic performance of asubmersible tubular pump device, based on a large-scale pumping station, two schemes—involving a front-mounted bulb and a rear-mounted bulb, respectively—were designed. The front-mounted scheme uses the GL-2008-03 hydraulic model and its conventional guide vane, while the rearmounted scheme uses the optimized design of a diffuser vane. The method of combining numerical simulation and experimental testing was used to analyze the differences between the external and internal characteristics of the two schemes. The results show that, under the condition of reasonable diffusion guide vane design, the efficiency under the rear-mounted scheme is higher than that under the front-mounted scheme, where the highest efficiency difference is about 1%. Although the frontmounted bulb scheme reduces the hydraulic loss of the bulb section, the placement of the bulb on the water inlet side reduces the flow conditions of the impeller. Affected by the circulation of the guide vane outlet, the hydraulic loss of the outlet channel is greater than the rear-mounted scheme. The bulb plays a rectifying function when the bulb is placed behind, which greatly eliminates the annular volume of the guide vane outlet, and the water outlet channel has a smaller hydraulic loss. In the front-mounted scheme, the water flow inside the outlet channel squeezes to the outer wall, causing higher entropy production near the outer wall area. The entropy production of the rear-mounted scheme is mainly in the bulb section and the bulb support. This research can provide reference for the design and form selection of a submersible tubular pump device, which has great engineering significance.

Influence of Guide Ring on Energy Loss in a Multistage Centrifugal Pump

2018 ◽  
Vol 141 (6) ◽  
Author(s):  
Ren Yun ◽  
Zhu Zuchao ◽  
Wu Denghao ◽  
Li Xiaojun
Keyword(s):  
Energy Loss ◽  
Entropy Production ◽  
Evaluation Method ◽  
Guide Vane ◽  
Load Flow ◽  
Hydraulic Loss ◽  
Pump Efficiency ◽  
Centrifugal Pumps ◽  
Multistage Pump ◽  
Guide Ring

Multistage centrifugal pumps are highly efficient and compact in structure. Pump efficiency can be improved by an effective understanding of hydraulic behavior and energy loss, however, the traditional hydraulic loss evaluation method does not readily reveal the specific locations of energy loss in the pump. In this study, a guide ring was imposed in multistage pumps, and an entropy production theory was applied to investigate irreversible energy loss of a multistage pump with and without guide ring. Detailed distributions of energy losses in the pumps were calculated to determine the respective entropy production rates (EPRs). The EPR values as calculated are in close accordance with actual hydraulic loss values in the pumps. EPR values were higher in the multistage pump with the guide ring than the pump without a guide ring under part-load flow conditions (0.2Qd). However, the vortex flow in the pump was weakened (or eliminated) by the guide ring as flow rate increased; this reduced energy loss in the chambers. Flow passing the chamber was stabilized by the guide ring, which decreased shock and vortex loss in the chamber and guide vane. Under both designed flow condition and overload conditions, the EPR values of the guide ring-equipped multistage pump were lower than those without the guide ring. Furthermore, minimum efficiency index (MEI) values were also calculated for the two chamber structures; it was found that overall efficiency of pump with guide ring is better than that without.

Study on effect of air intake method to prevent cavitation in various guide vane opening ratio of cross-flow turbine.

2021 ◽  
Vol 2021.27 (0) ◽  
pp. 11E05
Author(s):  
Kouki OHIRA ◽  
Yuuki NISHIKAWA ◽  
Xiangtong MENG ◽  
Takaya KITAHORA ◽  
Sho KAMODA ◽  
...  
Keyword(s):  
Guide Vane ◽  
Cross Flow ◽  
Air Intake ◽  
Opening Ratio

scholarly journals Calculation of Pressure Pulsations in the Flow Part of the First Stage of an Axial Turbine in the Rotor-Stator Interaction Zone

2021 ◽  
Vol 320 ◽  
pp. 04011
Author(s):  
S. F. Timushev ◽  
A. V. Kondratov
Keyword(s):  
Gas Turbines ◽  
Stokes Equations ◽  
Stationary Regime ◽  
Turbine Rotor ◽  
Calculation Model ◽  
Rocket Engines ◽  
Interaction Zone ◽  
Pressure Pulsations ◽  
High Resource ◽  
Axial Clearance

A serious problem in the development of reusable liquid-propellant rocket engines (LRE) is the provision of a high resource and reliability of gas turbines of turbopump, which supply fuel to the combustion chamber. This problem can be solved by reducing the level of pressure pulsations in the interaction zone of the turbine rotor-stator and dynamic loads acting on the working and stator blades. In this regard, a useful tool is the method of numerical simulation of the unsteady turbulent flow of a compressible gas in the turbine flow path with the determination of the amplitude of pressure pulsations in the axial clearance between the stator and rotor blade cascades. The calculation model includes the Navier-Stokes equations and equation of energy. Density, thermal conductivity and diffusion coefficient are linearly dependent on temperature and concentration. Calculations were performed on different meshes, proving the mesh convergence of the method upon reaching the quasi-stationary regime. The calculation results show that the pressure pulsations vary greatly with the axial clearance, and the main frequency of the pressure pulsations in the spectrum is the blade passing frequency. The frequency of dynamic moment acting on the blade also coincides with the indicated frequency.

scholarly journals Influence of Circumferential Placement Position of Guide Vanes on Performance and Dynamic Characteristics of Nuclear Reactor Coolant Pump

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Xiaorui Cheng ◽  
Boru Lv ◽  
Chenying Ji ◽  
Ningning Jia ◽  
Dorah N
Keyword(s):  
Nuclear Reactor ◽  
Guide Vane ◽  
Equivalent Stress ◽  
Hydraulic Loss ◽  
Stress Strain ◽  
Coolant Pump ◽  
Guide Vanes ◽  
Reactor Coolant ◽  
Maximum Equivalent Stress ◽  
Exit Edge

In order to study the influence of the circumferential placement position of the guide vane on the flow field and stress-strain of a nuclear reactor coolant pump, the CAP1400 nuclear reactor coolant pump is taken as the research object. Based on numerical calculation and test results, the influence of circumferential placement position of the guide vane on the performance of the nuclear reactor coolant pump and stress-strain of guide vanes are analyzed by the unidirectional fluid-solid coupling method. The results show that the physical model and calculation method used in the study can accurately reflect the influence of the circumferential placement position of the guide vane on the nuclear reactor coolant pump. In the design condition, guide vane position has a great influence on the nuclear reactor coolant pump efficiency value, suction surface of the guide vane blade, and the maximum equivalent stress on the hub. However, it has a weak effect on the head value, pressure surface of the guide vane blade, and the maximum equivalent stress on the shroud. When the center line of the outlet diffuser channel of the case is located at the center of the outlet of flow channel of the guide vane, it is an optimal guide vane circumferential placement position, which can reduce the hydraulic loss of half of the case. Finally, it is found that the high stress concentration area is at the intersection of the exit edge of the vane blade and the front and rear cover, and the exit edge of the guide vane blade and its intersection with the front cover are areas where the strength damage is most likely to occur. This study provides a reference for nuclear reactor coolant pump installation, shock absorption design, and structural optimization.

scholarly journals Propeller Efficiency - Simple Methods

2021 ◽  
Author(s):  
Dieter Scholz
Keyword(s):  
Angular Momentum ◽  
Characteristic Parameter ◽  
Flight Speed ◽  
Engine Torque ◽  
Turboprop Engine ◽  
Disc Area ◽  
Blade Tip ◽  
Exit Speed ◽  
Propeller Blades ◽  
Drag Ratio

In order to produce thrust, the air needs to be accelerated by the propulsor (the propeller or the jet engine). The more the air gets accelerated from flight speed v = v_1 to exit speed v_4 (i.e. the higher v_4/v_1), the lower the efficiency. However, without accelerating the air, no power or thrust is produced. The efficiency depends on the non-dimensional thrust, called thrust loading, c_S, which is a function of aircraft speed. Disc loading k_P is calculated from power, P air density, rho and propeller disc area, A_S. k_P is independent of speed and as such a good characteristic parameter of a propeller. Together, this makes the propulsive efficiency a function of disc loading, k_P and flight speed, v. Further losses come from angular momentum. The efficiency calculated considering angular momentum in addition dependents on the ratio of forward speed, v and tip speed u (v/u). A constant speed propeller can run at a favorable speed for the piston or turboprop engine at a limited Mach number of the blade tips. At higher speeds, v and also v/u increases and hence required engine torque. This increases the angular momentum and reduces the efficiency. At low speeds, the ratio v_4/v_1 gets unfavorably high and the efficiency is low. At zero speed v_4/v_1 goes to infinity and the efficiency to zero. For an example calculation, optimum efficiencies were obtained at v/u between 3 and 5 depending on disc loading. Not considered is the limited lift-to-drag ratio (L/D) of the propeller blades and losses at blade tip (which could be accounted for by a performance factor between 0.85 and 0.9).

Inlet Passage’s Development and Optimization of New Tidal Unit-Shaft Tubular Turbine

2014 ◽  
Vol 607 ◽  
pp. 312-316
Author(s):  
Chun Xia Yang ◽  
Meng Tian Lu ◽  
Yuan Zheng ◽  
Xiao Qing Tian ◽  
Yu Quan Zhang
Keyword(s):  
Flow Rate ◽  
High Efficiency ◽  
Guide Vane ◽  
Simulation Software ◽  
Hydraulic Loss ◽  
Vertical Shaft ◽  
Tidal Power ◽  
Large Power ◽  
Flow Passage ◽  
Water Head

A new type of tidal unit-vertical shaft tubular turbine is designed with high efficiency, large flow rate and low water head ,which has large power under the 2~3 meters water head. According to the data of the being installed tidal units and principles of tubular turbine’s design, the high efficiency vertical shaft tubular turbine was designed under large discharge and low head, which was suitable for the tidal power station. The design also considered the requirements of turbine’s size and the details of flow through the whole flow passage were attained. The turbine’s property was predicted by the 3-d numerical simulation software on the whole flow passage. Moreover, the influences of vertical shaft’s sizes were analyzed. And the terminal of vertical shaft with or without transverse brace and longitudinal brace were analyzed to get the influence. Considering the hydraulic performance of various methods, the best guide vane opening was chosen. The results show that, the turbine unit has the best performance on efficiency, hydraulic loss, etc. with the guide vane opening 62°, meeting the power station’s design requirements. The results show that the optimal designed flow passage’s efficiency reaches up to 88.4%, the flow rate becomes much larger and the power reaches 174.63kW. Without partial vortex, the flow pattern is smooth through the whole passage also with lower hydraulic loss.

scholarly journals Effects of an Inlet Vortex on the Performance of an Axial-Flow Pump

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2854
Author(s):  
Wenpeng Zhang ◽  
Fangping Tang ◽  
Lijian Shi ◽  
Qiujin Hu ◽  
Ying Zhou
Keyword(s):  
Pressure Fluctuation ◽  
Axial Velocity ◽  
Guide Vane ◽  
Shape Change ◽  
Axial Flow ◽  
Weighted Average ◽  
Stable Operation ◽  
Hydraulic Loss ◽  
Axial Flow Pump ◽  
Flow Pump

The formation of an inlet vortex seriously restricts axial-flow pump device performance and poses a great threat to the safe and stable operation of the entire system. In this study, the change trends of an inlet vortex and its influence on an axial-flow pump are investigated numerically and experimentally in a vertical axial-flow pump device. Four groups of fixed vortex generators (VGs) are installed in front of the impeller to create stable vortices at the impeller inlet. The vortex influence on the performance of pump device is qualitatively and quantitatively analyzed. The vortex patterns at different positions and moments in the pump device are explored to reveal the vortex shape change trend in the impeller and the pressure fluctuation induced by the vortex. The reliability and accuracy of steady and unsteady numerical results are verified by external characteristics and pressure fluctuation experimental results. Results show that it is feasible to install VGs before the impeller inlet to generate stable vortices. The vortex disturbs the inlet flow fields of the impeller, resulting in significant reductions of the axial velocity weighted average angle and the axial velocity uniformity. The vortex increases the inlet passage hydraulic loss and reduces the impeller efficiency, while it only slightly affects the guide vane and outlet passage performance. The vortex causes a low-frequency pressure pulsation and interacts with the impeller. The closer the vortex is to the impeller inlet, the more significant the impeller influence on the vortex. The blade cuts off the vortex in the impeller; afterwards, the vortex follows the blade rotation, and its strength weakens.

scholarly journals Influence of Inlet Angle of Guide Vane on Hydraulic Performance of an Axial Flow Pump Based on CFD

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Lei Xu ◽  
Dongtao Ji ◽  
Wei Shi ◽  
Bo Xu ◽  
Weigang Lu ◽  
...  
Keyword(s):  
Working Conditions ◽  
Flow Rate ◽  
Guide Vane ◽  
Axial Flow ◽  
Hydraulic Performance ◽  
Hydraulic Loss ◽  
Rate Region ◽  
Axial Flow Pump ◽  
Inlet Angle ◽  
Flow Pump

Axial flow pump has been widely used in hydraulic engineering, agriculture engineering, water supply and sewerage works, and shipbuilding industry. In order to improve the hydraulic performance of pump under off-design working conditions, the influence of the inlet segment axial chord and inlet angle adjustment of the guide vane on the pump segment efficiency and flow filed was simulated by using the renormalization group (RNG) k − ε turbulent model based on the Reynolds-averaged Navier–Stokes equations. The results indicate that the inlet segment axial chord and inlet angle adjustment of guide vane have a strong influence on the pump segment efficiency. Considering the support function and hydraulic loss of the guide vane, the inlet segment axial chord is set to 0.25 times the axial chord of guide vane. On the basis of the inlet angle of the guide vane under design conditions, when the inlet segment angle is turned counterclockwise, the pump segment efficiency is improved in the lower flow rate region; moreover, the pump segment efficiency is improved in the larger flow rate region when the inlet segment angle is turned clockwise. As the conditions deviate from the design working conditions, the influence of the guide vane inlet angle on the pump segment efficiency increases. If the inlet segment angle is properly adjusted under off-design working conditions, the flow pattern in the guide vane is improved and the hydraulic loss is decreased, because the inlet segment angle matches with the flow direction of impeller outlet; consequently, the pump segment efficiency is increased.

Sign in / Sign up

Export Citation Format

Share Document