Numerical Research on the Mixing Mechanism of Lobed Mixer With New De-Swirling Structure

2016 ◽  
Author(s):  
Zhijun Lei ◽  
Jianbo Gong ◽  
Yanfeng Zhang ◽  
Shangmei Su ◽  
Chunyan Hu
Keyword(s):  
Numerical Simulation ◽  
Pressure Loss ◽  
Total Pressure ◽  
Recirculation Zone ◽  
Swirling Flow ◽  
Separation Bubble ◽  
Total Pressure Loss ◽  
Mixing Efficiency ◽  
Flow Mixing ◽  
Inlet Swirl

A detailed numerical simulation is presented to investigate the new de-swirling methods and their effect on the mixing mechanisms of a turbofan mixer with 12 lobes. The numerical simulation employed a commercial solver, ANSYS CFX, using k-ω SST model. The core-to-bypass temperature ratio and pressure ratio were set to 2.59, and 0.97 respectively, giving the Mach number of 0.66 and bypass ratio of 2.65 at mixing nozzle outlet. The inlet swirl typically accelerates the jet-flow mixing by enhancing the vortices intensity and interaction, but leakage swirling flow can cause a three-dimensional separation bubble and the recirculation zone resulting in the dramatic increasing the total pressure loss and thrust loss. Removal of the leakage swirling flow between the lobes’ trough and centre-body was the key to limit the negative influence of inlet swirl. Two IGV design were investigated, DS1 and DS2. DS1 was installed at the upstream of the lobed mixer, could remove the negative effect of inlet swirl properly, but also inhibited the active role of the inlet swirl. The total pressure and thrust loss reduced by 0.31% and 3.8%, respectively, but the mixing efficiency also decreased by 1.72%. DS2, an integrated strut with the lobed mixer design, not only ensured the structure strength of the lobed mixer, but also reduced the length and weight of the exhaust system. This method suppressed the flow separation bubble on centre-body to some extent, and eliminated the recirculation zone downstream of the cenrebody, resulting in the total pressure loss decrease of 0.31% and thrust gain of 3.63%. On the other hand, the method DS2 also made full use of the inlet swirl to enhance the jet-flow mixing, resulting in the mixing efficiency increased 1.54% compared with that of the DS1 case. Under the off-design conditions with the incidence angle of ±10°, the aerodynamic performance of the DS2 cases didn’t changed too much such as the DS1 cases.

Numerical Simulation of Cold Swirl Field for Solid Fuel Ramjet with NACA Airfoil

2014 ◽  
Vol 716-717 ◽  
pp. 711-716
Author(s):  
Jie Yu ◽  
Xiong Chen ◽  
Hong Wen Li
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Radial Velocity ◽  
Solid Fuel ◽  
Velocity Gradient ◽  
Pressure Loss ◽  
Total Pressure ◽  
Swirl Flow ◽  
Total Pressure Loss ◽  
Swirl Number

In order to study the swirl flow characteristics in the solid fuel ramjet chamber, a new type of annular vane swirler with NACA airfoil is designed. The cold swirl flow field in the chamber is numerically simulated with different camber and t attack angle, while the swirl number , swirl flow field structure, total pressure recovery coefficient were studied. According to numerical simulation result, the main factors in swirl number are camber and angle of attack, the greater angle of attack, the greater the camber ,the stronger swirl will be. Results show that the total pressure loss is mainly concentrated in the inlet section, the total pressure loss cause by vane swirler is small. Radial velocity gradient exists in swirling flow, and increases with the swirl number. With the influence of centrifugal force and combustion chamber structure, the radial velocity gradient increases.

Numerical Simulation of Deposition Phenomena on High-Pressure Turbine Vane Using UPACS

2019 ◽  
Author(s):  
Kenta Mizutori ◽  
Koji Fukudome ◽  
Makoto Yamamoto ◽  
Masaya Suzuki
Keyword(s):  
Numerical Simulation ◽  
High Pressure ◽  
Flow Field ◽  
Pressure Loss ◽  
Total Pressure ◽  
Total Pressure Loss ◽  
High Pressure Turbine ◽  
Pressure Loss Coefficient ◽  
Turbine Vane ◽  
Total Pressure Loss Coefficient

Abstract We performed numerical simulation to understand deposition phenomena on high-pressure turbine vane. Several deposition models were compared and the OSU model showed good adaptation to any flow field and material, so it was implemented on UPACS. After the implementation, the simulations of deposition phenomenon in several cases of the flow field were conducted. From the results, particles adhere on the leading edge and the trailing edge side of the pressure surface. Also, the calculation of the total pressure loss coefficient was conducted after computing the flow field after deposition. The total pressure loss coefficient increased after deposition and it was revealed that the deposition deteriorates aerodynamic performance.

scholarly journals A LES Study on Passive Mixing in Supersonic Shear Layer Flows Considering Effects of Baffle Configuration

2014 ◽  
Vol 6 ◽  
pp. 836146 ◽  
Author(s):  
Ren Zhao-Xin ◽  
Wang Bing
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Large Scale ◽  
Mixing Layer ◽  
Total Pressure Loss ◽  
Mixing Efficiency ◽  
Mixing Enhancement ◽  
Supersonic Mixing ◽  
Passive Mixing ◽  
Supersonic Mixing Layer

Under the background of dual combustor ramjet (DCR), a numerical investigation of supersonic mixing layer was launched, focused on the mixing enhancement method of applying baffles with different geometric configurations. Large eddy simulation with high order schemes, containing a fifth-order hybrid WENO compact scheme for the convective flux and sixth-order compact one for the viscous flux, was utilized to numerically study the development of the supersonic mixing layer. The supersonic cavity flow was simulated and the cavity configuration could influence the mixing characteristics, since the impingement process of large scale structures formed inside the cavity could raise the vorticity and promote the mixing. The effect of baffle's configurations on the mixing process was analyzed by comparing the flow properties, mixing efficiency, and total pressure loss. The baffle could induce large scale vortexes, promote the mixing layer to lose its stability easily, and then lead to the mixing efficiency enhancement. However, the baffle could increase the total pressure loss. The present investigation could provide guidance for applying new passive mixing enhancement methods for the supersonic mixing.

Experimental Investigation of the Clocking Effect in a 1.5-Stage Axial Turbine—Part I: Time-Averaged Results

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Sven König ◽  
Bernd Stoffel ◽  
M. Taher Schobeiri
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Separation Bubble ◽  
Measurement Techniques ◽  
Suction Side ◽  
Total Pressure Loss ◽  
Experimental Investigations ◽  
Flow Angle ◽  
Factors Affecting ◽  
Lp Turbine

Comprehensive experimental investigations were conducted to get deeper insight into the physics of stator clocking in turbomachines. Different measurement techniques were used to investigate the influence of varying clocking positions on the highly unsteady flow field in a 1.5-stage axial low-pressure (LP) turbine. A Reynolds number typical for LP turbines as well as a two-dimensional blade design were chosen. Stator 2 was developed as a high-lift profile with a separation bubble on the suction side. This paper presents the results that were obtained by means of static pressure tappings and five-hole probes as well as the time-averaged results of unsteady x-wire measurements. The probes were traversed in different measuring planes for ten clocking positions. Depending on the clocking position, a variation in total pressure loss for Stator 2, a change of the rotor exit flow angle, and a dependency of the Stator 2 exit flow angle were found. The influence of these parameters on turbine efficiency was studied. Three main factors affecting the total pressure loss could be separated: the size of the separation bubble, the production of turbulent kinetic energy, and the strength of the periodic fluctuations downstream of Stator 2.

Aerodynamic Optimization of a Winglet-Shroud Tip Geometry for a Linear Turbine Cascade

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Min Zhang ◽  
Yan Liu ◽  
Tianlong Zhang ◽  
Mengchao Zhang ◽  
Ying He
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Separation Bubble ◽  
Aerodynamic Performance ◽  
Total Pressure Loss ◽  
Turbine Cascade ◽  
Aerodynamic Optimization ◽  
Tip Leakage ◽  
Viscous Loss ◽  
Partial Shroud

This paper presents a continued study on a previously investigated novel winglet-shroud (WS) (or partial shroud) geometry for a linear turbine cascade. Various widths of double-side winglets (DSW) and different locations of a partial shroud are considered. In addition, both a plain tip and a full shroud tip are applied as the datum cases which were examined experimentally and numerically. Total pressure loss and viscous loss coefficients are comparatively employed to execute a quantitative analysis of aerodynamic performance. The effectiveness of various widths (w) of DSW set at 3%, 5%, 7%, and 9% of the blade pitch (p) is numerically investigated. Skin-friction lines on the tip surface indicate that different DSW cases do not alter flow field features including the separation bubble and reattachment flow within the tip gap region, even for the case with the broadest width (w/p = 9%). However, the pressure side extension of the DSW exhibits the formation of separation bubble, while the suction side platform of the DSW turns the tip leakage vortex (TLV) away from the suction surface (SS). Meanwhile, the horse-shoe vortex (HV) near the casing is not generated even for the case with the smallest width (w/p = 3%). As a result, both the tip leakage and the upper passage vortices are weakened and further dissipated with wider w/p in the DSW cases. Larger width of the DSW geometry is indeed able to improve the aerodynamic performance, but only to a slight degree. With the w/p increasing from 3% to 9%, the mass-averaged total pressure loss coefficient over an exit plane is reduced by only 2.61%. Therefore, considering both the enlarged (or reduced) tip area and the enhanced (or deteriorated) performance compared to the datum cases, a favorable width of w/p = 5% is chosen to design the WS structure. Three locations for the partial shroud (linkage segment) are devised, locating them near the leading edge, in the middle and close to the trailing edge, respectively. Results demonstrate that all three cases of the WS design have advantages over the DSW arrangement in lessening the aerodynamic loss, with the middle linkage segment location producing the optimal effect. This conclusion verifies the feasibility of the previously studied WS configuration.

Characteristics of a Turbine Cascade at Low Reynolds Numbers

1997 ◽  
Author(s):  
Koji Murata ◽  
Hiroyuki Abe ◽  
Yasukata Tsutsui
Keyword(s):  
Reynolds Number ◽  
Gas Turbines ◽  
Pressure Loss ◽  
Total Pressure ◽  
Separation Bubble ◽  
Reynolds Numbers ◽  
Boundary Layer Separation ◽  
Total Pressure Loss ◽  
Turbine Cascade ◽  
Low Reynolds

The aerodynamic characteristics of turbine cascades are thought to be relatively satisfactory due to the favorable pressure of the accelerating flow. But within the low Reynolds number region of 50,000 where the 300kW ceramic gas turbines which are being developed under the New-Sunshine Project of Japan operate, the characteristics such as boundary layer separation and reattachment which lead to prominent power losses cannot be easily predicted. In this research, experiments have been conducted to evaluate the performance of a linear two dimensional turbine cascade. Surface pressure distributions of the airfoil were measured for a range of blade chord Reynolds numbers from 40,000 to 160,000 (at inlet), and at 1.3% inlet turbulence intensity. In addition, the wake of the cascade was measured simultaneously using a five hole pilot tube. Traverses of the wake show that there is a drastic increase in the mean total pressure loss at the wake between the Reynolds number of 80,000 to 40,000, and in some conditions, a rise as much as 10% was confirmed. Thus, in accordance with the pressure distribution of the surface of the airfoil, a relation between the total pressure loss and the length of the laminar separation bubble formed on the airfoil could be seen.

Active flow control by means of endwall synthetic jet on a high-speed compressor stator cascade

2017 ◽  
Vol 232 (6) ◽  
pp. 641-659
Author(s):  
Yong Qin ◽  
Yanping Song ◽  
Fu Chen ◽  
Ruoyu Wang ◽  
Huaping Liu
Keyword(s):  
Flow Control ◽  
Pressure Loss ◽  
Total Pressure ◽  
High Speed ◽  
Pressure Rise ◽  
Synthetic Jet ◽  
Total Pressure Loss ◽  
Momentum Exchange ◽  
Actuation Frequency ◽  
Flow Mixing

The underlying physics of the endwall synthetic jet in improving the aerodynamic performance of a high-speed compressor stator cascade is investigated in this paper. The effects of both injected momentum and actuation frequency are discussed in detail. In the investigations, the injected momentum is controlled by either changing the maximum jet velocity or modifying the tube diameter. Numerical results demonstrate that the streamwise momentum addition and flow mixing enhancement are the key factors of the endwall synthetic jet in improving the cascade performance. The high momentum fluid injected into the flow field can reenergize the passage flow, and the generated streamwise jet vortex contributes to the strengthening of flow mixing. Consequently, the momentum exchange between the low momentum fluid region and the main flow is enhanced and boundary layer separation on the blade suction surface is delayed. The loss characteristic in the corner region is improved as well. The intensified flow mixing will also increase the total pressure loss in the near-endwall region, which as a result will worsen the cascade performance, and hence the total effect of the endwall synthetic jet depends on the sum of its impacts. Moreover, the injected momentum and the actuation frequency have strong influences on the flow control effect. With the momentum coefficient and the reduced frequency being Cµ = 0.131% and F+ = 1.0, the reduction in total pressure loss coefficient and the increment in pressure rise coefficient are 7.3% and 3.3%, respectively.

Aerodynamic Optimization of a Winglet-Shroud Tip Geometry for a Linear Turbine Cascade

2016 ◽  
Author(s):  
Min Zhang ◽  
Yan Liu ◽  
Tian-long Zhang ◽  
Meng-chao Zhang ◽  
Hong-kun Li
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Separation Bubble ◽  
Aerodynamic Performance ◽  
Total Pressure Loss ◽  
Turbine Cascade ◽  
Aerodynamic Optimization ◽  
Tip Leakage ◽  
Viscous Loss ◽  
Partial Shroud

This paper presents a continued study on a previously investigated novel winglet-shroud (WS) (or partial shroud) geometry for a linear turbine cascade. Various width of double-side winglets and different locations of a partial shroud are considered. In addition, both a plain tip and a full shroud tip are applied as the datum cases which were examined experimentally and numerically. Total pressure loss and viscous loss coefficients are comparatively employed to execute a quantitative analysis of the aerodynamic performance. The effectiveness of various width (w) of double-side winglets (DSW) involving 3%, 5%, 7% and 9% of the blade pitch (p) is numerically investigated. Skin-friction lines on the tip surface indicate that the different DSW cases do not alter flow field features including the separation bubble and reattachment flow within the tip gap region, even for the case with the broadest width (w/p = 9%). However, the pressure side extension of the DSW exhibits the formation of the separation bubble, while the suction side platform of the DSW turns the tip leakage vortex away from the suction surface. Meanwhile, the horse-shoe vortex near the casing is not generated even for the case with the smallest width (w/p=3%). As a result, both the tip leakage and the upper passage vortices are weakened and further dissipated with wider w/p in the DSW cases. Larger width of the DSW geometry is indeed able to improve the aerodynamic performance, but in a slight degree. With the w/p increasing from 3% to 9%, the mass-averaged total pressure loss coefficient over an exit plane is just reduced by 2.61%. Therefore, considering both the enlarged (or reduced) tip area and the enhanced (or deteriorated) performance compared to the datum cases, a favorable width of w/p=5% is chosen to design the WS structure. Three locations of the partial shroud (linkage segment) are devised, which are located near the leading edge, the middle and close to the trailing edge respectively. Results illustrates that all three cases of the WS have advantages in lessening the aerodynamic loss over the DSW arrangement, but with the linkage segment located in the middle having optimal effect. This conclusion verifies the feasibility of the previously studied WS configuration.

Numerical and Experimental Study of Swirling Flow in a Short Annular to Round Diffuser/Nozzle

2014 ◽  
Author(s):  
A. Namet-Allah ◽  
A. M. Birk
Keyword(s):  
Wind Tunnel ◽  
Pressure Loss ◽  
Total Pressure ◽  
Swirling Flow ◽  
Velocity Profiles ◽  
Back Pressure ◽  
Total Pressure Loss ◽  
Cfd Simulations ◽  
Measured Velocity ◽  
Numerical Predictions

The objective of the current paper is to gain an understanding of the effects of inlet swirling flow on the flow field through short annular transition diffusers and nozzles. These devices are representative of the primary driving nozzles for certain exhaust ejector systems. It is known that strongly swirling flow can degrade ejector performance due to core separation. It is believed that minor changes in driving nozzle shape can improve ejector performance significantly. Two configurations of a diffuser/nozzle were tested experimentally and numerically under different swirl strengths. The two configurations were mounted on an annular flow wind tunnel. Two shapes of the annulus’ centre body end; square and elliptical, were used. Based on the hydraulic inlet diameter, average velocity and temperature in the annulus of the wind tunnel, the measurements were carried out at Mach range of 0.21 to 0.26 with Reynolds number of 2.3 to 2.7×105. Ansys14 was used for the CFD simulations. The measured velocity profiles in the annulus were used as input flow conditions in the CFD investigation. The RNG k-ε turbulence model was used in the CFD simulations. The measured velocity profiles at the device exit, and measured surface pressures on the annulus, duct and nozzle walls were compared with the CFD predictions. The measured back pressure coefficient and total pressure loss through the diffuser systems were compared with the CFD predictions. A reasonable agreement between the experimental data and numerical predictions was observed. It was found computationally that the size of the central recirculation zone behind the annulus centre body has negative effects on the diffuser performance under different swirl numbers. The square shape of the annulus’ centre body end increased the back pressure and total pressure loss coefficients over the elliptical shape. However, the flow uniformity at the duct and nozzle exits improved with the square shape over the elliptical end. These differences may have a significant effect on ejector pumping.

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