A Model for the Estimation of Pressure Ripple in Tandem Gear Pumps

2015 ◽  
Author(s):  
Mattia Battarra ◽  
Emiliano Mucchi ◽  
Giorgio Dalpiaz
Keyword(s):  
High Pressure ◽  
Dynamic Behavior ◽  
Low Pressure ◽  
Variable Pressure ◽  
Geometrical Parameters ◽  
Gear Pump ◽  
Helical Gears ◽  
Pressure Stage ◽  
Outlet Pressure ◽  
Pressure Ripple

The present paper addresses the development of a lumped parameters model used to analyze the dynamic behavior of a so-called tandem gear pump. The pump is composed of two coaxial stages, both with external gears: a high pressure stage with spur gears and a low pressure one with helical gears. In particular, the paper deals with the modelling and the analysis of the phenomena bound to the pressure distribution around the gears, since they have the most important effect in the dynamic behavior of the pump. The pressure variation in the inlet and outlet chambers, the variable pressure in the trapped volume as well as the pressure evolution from the low to the high pressure chamber is estimated based on the Euler’s approach. The model is developed in Matlab environment. Attention is particularly focused on the description of the methodology adopted for modelling the low-pressure stage, constituted by helical gears, and its influence on the calculation of the pump geometrical parameters. The results provided by the numerical model are compared with experimental measurements in terms of outlet pressure ripple and volumetric efficiency under different working conditions. The results of the validation can be considered satisfactory. Predicted pressure ripple is shown and the effects of interconnections between stages are analyzed studying the outlet pressure ripple in the frequency domain as well.

Influence of Hot Streak Temperature Ratio on Low Pressure Stage of a Vaneless Counter-Rotating Turbine

2007 ◽  
Author(s):  
Qingjun Zhao ◽  
Fei Tang ◽  
Huishe Wang ◽  
Jianyi Du ◽  
Xiaolu Zhao ◽  
...  
Keyword(s):  
Shock Wave ◽  
High Pressure ◽  
Secondary Flow ◽  
Low Pressure ◽  
Turbine Rotor ◽  
Temperature Ratio ◽  
High Pressure Turbine ◽  
Pressure Stage ◽  
Low Pressure Turbine ◽  
Hot Streak

In order to explore the influence of hot streak temperature ratio on low pressure stage of a Vaneless Counter-Rotating Turbine, three-dimensional multiblade row unsteady Navier-Stokes simulations have been performed. The predicted results show that hot streaks are not mixed out by the time they reach the exit of the high pressure turbine rotor. The separation of colder and hotter fluids is observed at the inlet of the low pressure turbine rotor. After making interactions with the inner-extending shock wave and outer-extending shock wave in the high pressure turbine rotor, the hotter fluid migrates towards the pressure surface of the low pressure turbine rotor, and the most of colder fluid migrates to the suction surface of the low pressure turbine rotor. The migrating characteristics of the hot streaks are predominated by the secondary flow in the low pressure turbine rotor. The effect of buoyancy on the hotter fluid is very weak in the low pressure turbine rotor. The results also indicate that the secondary flow intensifies in the low pressure turbine rotor when the hot streak temperature ratio is increased. The effects of the hot streak temperature ratio on the relative Mach number and the relative flow angle at the inlet of the low pressure turbine rotor are very remarkable. The isentropic efficiency of the Vaneless Counter-Rotating Turbine decreases as the hot streak temperature ratio is increased.

The Port Width and Position Determination for Pressure-Exchange Ejector

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Wenjing Zhao ◽  
Dapeng Hu ◽  
Peiqi Liu ◽  
Yuqiang Dai ◽  
Jiupeng Zou ◽  
...  
Keyword(s):  
High Pressure ◽  
Performance Optimization ◽  
Pressure Ratio ◽  
Low Pressure ◽  
Operating Conditions ◽  
Maximum Deviation ◽  
Dimensionless Time ◽  
Pressure Flow ◽  
Outlet Pressure ◽  
Pressure Exchange

A pressure-exchange ejector transferring energy by compression and expansion waves has the potential for higher efficiency. The width and position of each port are essential in pressure-exchange ejector design. A dimensionless time τ expressing both port widths and the positions of port ends was introduced. A prototype was designed and the experimental system was set up. Many sets of experiment with different geometrical arrangements were conducted. The results suggest that the efficiency greatly changes with the geometrical arrangements. The efficiency is about 60% at proper port widths and positions, while at improper geometrical arrangements, the efficiency is much lower and the maximum deviation may reach about 20%. The proper dimensionless port widths and positions at different operating conditions are obtained. For a fixed overall pressure ratio, the widths of the high pressure flow inlet and middle pressure flow outlet increase as the outlet pressure increases and the low pressure flow inlet width is reduced with a larger outlet pressure. The middle pressure flow outlet (MO) opening end remains constant at different outlet pressures. The positions of the high pressure flow inlet (HI) closed end and the low pressure flow inlet (LI) open end increase with the elevation of outlet pressure, however, the distance between the HI closing end and the LI opening end is constant. The port widths and positions have a significant influence on the performance of the pressure-exchange ejector. The dimensionless data obtained are very valuable for pressure-exchange ejector design and performance optimization.

Influence of Hot Streak Temperature Ratio on Low Pressure Stage of a Vaneless Counter-Rotating Turbine

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Zhao Qingjun ◽  
Tang Fei ◽  
Wang Huishe ◽  
Du Jianyi ◽  
Zhao Xiaolu ◽  
...  
Keyword(s):  
High Pressure ◽  
Secondary Flow ◽  
Low Pressure ◽  
Turbine Rotor ◽  
Temperature Ratio ◽  
High Pressure Turbine ◽  
Flow Angle ◽  
Pressure Stage ◽  
Low Pressure Turbine ◽  
Hot Streak

In order to explore the influence of hot streak temperature ratio on the low pressure stage of a vaneless counter-rotating turbine, three-dimensional multiblade row unsteady Navier–Stokes simulations have been performed. The predicted results show that hot streaks are not mixed out by the time they reach the exit of the high pressure turbine rotor. The separation of colder and hotter fluids is observed at the inlet of the low pressure turbine rotor. After making interactions with the inner-extending and outer-extending shock waves in the high pressure turbine rotor, the hotter fluid migrates toward the pressure surface of the low pressure turbine rotor, and most of the colder fluid migrates to the suction surface of the low pressure turbine rotor. The migrating characteristics of the hot streaks are dominated by the secondary flow in the low pressure turbine rotor. The results also indicate that the secondary flow intensifies in the low pressure turbine rotor when the hot streak temperature ratio is increased. The effects of the hot streak temperature ratio on the relative flow angle at the inlet of the low pressure turbine rotor are very remarkable. The isentropic efficiency of the vaneless counter-rotating turbine decreases as the hot streak temperature ratio is increased.

scholarly journals Study the Effect of Temperature on Methane Desorption Based on Thermodynamics and Kinetics

2020 ◽  
Author(s):  
Zheng Gao ◽  
Dongmin Ma ◽  
Yue Chen ◽  
Chao Zheng ◽  
Jinxiang Teng
Keyword(s):  
High Pressure ◽  
Adsorption Capacity ◽  
Free Path ◽  
Low Pressure ◽  
Coking Coal ◽  
Desorption Process ◽  
Pressure Stage ◽  
High Pressure Stage ◽  
Desorption Hysteresis ◽  
Methane Desorption

Abstract Desorption hysteresis is important for primary gas production. Temperature may cause serious change in the methane adsorption/desorption behaviors. In order to study the mechanism of methane desorption and desorption hysteresis, three sets of samples of long flame coal, coking coal, and anthracite were collected, and experiments such as microscopic composition determination, liquid nitrogen adsorption, and isothermal adsorption/desorption were performed. From the perspectives of desorption kinetics, desorption thermodynamics and methane occurrence state, the differences in methane and methane desorption characteristics and the desorption hysteresis mechanism are discussed. The results show that at the same temperature, anthracite (SH3#) has the largest saturated adsorption capacity and residual adsorption capacity, followed by coking coal (SGZ11#), and long -flame coal (DFS4#) is the smallest. As the temperature rises, the theoretical desorption rate and residual adsorption capacity of anthracite (SH3#) and coking coal (SGZ11#) will increase first and then decrease. Temperature and methane desorption are not completely positive effects, and temperature may have a threshold for promoting methane desorption. It is necessary to comprehensively consider the influence of temperature on the activation of gas molecules and the pore structure of coal. Under the premise of a certain temperature, as the pressure increases, the desorption hysteresis rate changes in a logarithmic downward trend, and the methane desorption hysteresis rate in the low pressure stage (P 4MPa) is large, and the methane desorption hysteresis rate in the high-pressure stage (P>4MPa) is lower; During the isobaric adsorption process, the adsorption capacity of anthracite (SH3#) increases the fastest, followed by SGZ11#, and DFS4# is the smallest. In the low-pressure stage (P 4MPa), the adsorption capacity increases significantly with the increase of pressure, but in the high pressure stage (P 4MPa), the adsorption capacity does not change significantly with pressure, but gradually stabilizes. Under the same pressure, the molecular free path of methane increases with temperature. Under the premise of constant temperature, in the low-pressure stage (0<P<4MPa), when the pressure continues to decrease, the free path of methane molecules increases significantly, resulting in a decrease in the diffusion capacity. In the high-pressure stage (4<P<8MPa), when the pressure continues to decrease, the free path of methane molecules does not change significantly; DFS4#, SGZ11#, SH3# sample desorption process of three sets of samples, the intermediate adsorption heat is greater than the isometric adsorption heat during the adsorption process, indicating that the desorption process needs to continuously absorb heat from outside the system. The energy difference produced in the process of adsorption and desorption causes the desorption hysteresis effect. The greater the difference in the isometric heat value of adsorption, the more significant the hysteresis.

scholarly journals Analysis and Improvement of a Two-Stage Centrifugal Compressor Used in an MW-Level Gas Turbine

2018 ◽  
Vol 8 (8) ◽  
pp. 1347 ◽  
Author(s):  
Wei Zhu ◽  
Xiao-Dong Ren ◽  
Xue-Song Li ◽  
Chun-Wei Gu
Keyword(s):  
High Pressure ◽  
Gas Turbine ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Low Pressure ◽  
Two Stage ◽  
Vaned Diffuser ◽  
Pressure Stage ◽  
Optimization System ◽  
High Pressure Stage

The performance of a low/high-pressure-stage centrifugal compressor in a land-use MW-level gas turbine with a pressure ratio of approximately 11 is analyzed and optimized with a 1D aerodynamic design and modeling optimization system. 1D optimization results indicate that the diameter ratio of the low-pressure-stage centrifugal compressor with a vane-less diffuser, and the divergent angle of the high-pressure-stage centrifugal compressor with a vaned diffuser, are extremely large and result in low efficiency. Through modeling design and optimization system analysis, a tandem vaned diffuser is used in the low-pressure stage, and a tandem vaned diffuser with splitter vanes is adopted in the high-pressure stage. Computational fluid dynamics (CFD) results show that the pressure ratio and efficiency of the optimized low/high-pressure-stage centrifugal compressor are significantly improved. Coupling calculations of the low/high-pressure stage of the original and optimized designs are conducted based on the results of MW-level gas turbine cycles. CFD results show that the pressure ratio and efficiency of the optimized two-stage centrifugal compressor increase by approximately 8% and 4%, respectively, under three typical load conditions of 100%, 90%, and 60%.

scholarly journals Conformal and Smooth TiN Film Growth by using Variable-Pressure Thermal ALD Method

2020 ◽  
Author(s):  
Hyunchol Cho ◽  
Sung-Hoon Jung
Keyword(s):  
High Pressure ◽  
Growth Condition ◽  
Film Growth ◽  
Semiconductor Device ◽  
Low Pressure ◽  
Variable Pressure ◽  
Deposition Method ◽  
Pressure Condition ◽  
Tin Film ◽  
Step Coverage

Better TiN film quality such as lower roughness and higher step coverage is required in recent semiconductor devices as the semiconductor device is scaled down. In this study, highly conformal ALD TiN film with excellent step coverage was achieved by using variable-pressure deposition method. TiN film grown at low-pressure condition was more conformal and smoother than that grown at high-pressure condition, although step coverage value grown at low-pressure condition was worse than that grown at high-pressure condition. By optimizing low/high pressure two-step TiN growth condition, it was achieved that not only better roughness than that of pure high-pressure TiN, but also, better step coverage value than that of pure low-pressure TiN as well as than that of pure high-pressure TiN.

Optimization of Fuel Two-Stage Screw Centrifugal Pump of Rocket Powerful Turbopump Unit

2018 ◽  
Author(s):  
Vasilii Zubanov ◽  
Andrei Volkov ◽  
Valeriy Matveev ◽  
Grigorii Popov ◽  
Oleg Baturin
Keyword(s):  
High Pressure ◽  
Rocket Engine ◽  
Mathematical Optimization ◽  
Low Pressure ◽  
Working Fluid ◽  
Geometrical Parameters ◽  
Rotor Speed ◽  
Optimization Software ◽  
Centrifugal Stage ◽  
Ansys Cfx

The article describes a refining method for a fuel pump of rocket powerful turbo-pump unit by the joint usage of mathematical optimization software IOSO, meshing complex NUMECA and CFD complex ANSYS CFX. The optimization software was used for automatic change of the geometry of low-pressure impeller, transition duct and high-pressure impeller to find the optimal design. It was mandatory to keep the original variant of the remaining parts of the pump. For this reason, only geometrical parameters of the blades were varied without changing the contours of the pump meridional flow part. The investigated pump consists of five parts: inlet duct, low-pressure screw centrifugal stage, transition duct, high-pressure screw centrifugal stage and volute outlet duct. The pump main parameters with water as the working fluid (based on experiment data) were the following: high-pressure stage rotor speed was 13300 rpm; low-pressure rotor speed was 3617 rpm by gearbox; inlet total pressure was 0.4 MPa; outlet mass flow was 132.6 kg/s at the nominal mode. Creation of vane unit mesh (rotors and stator transition duct) was performed using NUMECA AutoGrid5. Sector models were used for the calculation simplification. The flow around only one blade or screw was considered. Setting up and solution of the task were carried out in the ANSYS CFX solver. Comparison of calculated characteristics of the basic pump with the experimental data was performed before the optimization. The analysis of characteristics for the obtained optimized pump geometry was carried out. It was found that pump with optimized geometry has greater efficiency in comparison with the original pump variant. The obtained reserve can be used to boost the rocket engine, and/or to reduce the loading of the main turbine, which operates in aggressive oxidizing environment.

scholarly journals Dynamic Behavior Analysis of Non-Contacting Hydrodynamic Finger Seal Based on Fluid-Solid-Interaction Method

2018 ◽  
Vol 153 ◽  
pp. 07005
Author(s):  
Hua Su ◽  
Jiru Wang
Keyword(s):  
High Pressure ◽  
Dynamic Behavior ◽  
High Speed ◽  
Gas Flow ◽  
Dynamic Performance ◽  
Low Pressure ◽  
Structure Design ◽  
Structural Deformation ◽  
Dynamic Performance Analysis ◽  
Fluid Solid Interaction

Finger seal is an advanced compliant seal and can be utilized to separate high (HP) and low pressure (LP) zones in high speed rotating shaft environment. The work to be presented concerns the dynamic behavior of a repetitive section of a two-layer finger seal with high-and padded low-pressure laminates. The dynamic performance of the finger seal are analyzed by the coupled fluid-solid-interaction (FSI) simulations. By using the commercial software ANSYS-CFX, the numerical simulation results of interactions between the gas flow and fingers structural deformation are described when the radial periodic excitation from the shaft applies to the finger seal. And the gas film loading capacity, gas film stiffness and leakage varied with time are put forward in different working conditions. Compared with the dynamic performance analysis results based on equivalent dynamic method, the FSI dynamic analysis shows some different characteristics which are more accordance with actual circumstance. Moreover, it is shown that under low pressure differential and high rotation speed the non-contacting finger seal with advance features both in sealing effectiveness and potential unlimited life span can be obtained by rational structure design. But for the non-contacting finger seal with circumferential convergent pad working in high pressure and low rotating speed conditions, it is difficult to improve the sealing performance by the way of changing the structure parameters of finger seal. It is because the high pressure plays a major role on this sealing situation.

Design and performance analysis of a circular-arc gear pump operating at high pressure and high speed

2015 ◽  
Vol 230 (2) ◽  
pp. 189-205 ◽  
Author(s):  
Yang Zhou ◽  
Shuanghui Hao ◽  
Minghui Hao
Keyword(s):  
High Pressure ◽  
High Speed ◽  
Tooth Profile ◽  
Numerical Control ◽  
Gear Pump ◽  
Performance Parameters ◽  
Circular Arc ◽  
Cad System ◽  
Outlet Pressure ◽  
And Performance

This paper presents a high-pressure and high-speed gear pump for aerospace application and introduces a circular-arc tooth profile that has no trapping feature and whose gears are in continuous one-point contact in the plane of rotation. Basic dimensions are determined and performance parameters of the gear pump are obtained by structural design of the gear pump. The performance parameters are discussed for different tooth profiles. A disc tool and hob are designed to generate the circular-arc tooth profile. A computer-aided design (CAD) system for the design of the circular-arc gear pump is developed with features of tooth profile design, tool design, and numerical control. The test gears were processed to verify the correctness of CAD system. A study of the outlet pressure of the circular-arc gear pump reveals that the developed high-pressure and high-speed gear pump has low outlet pressure fluctuations.

On the Flow Evolution Through a LP Turbine With Wide-Chord Vanes in an S-Shaped Channel

2012 ◽  
Author(s):  
Rosario Spataro ◽  
Cornelia Santner ◽  
Davide Lengani ◽  
Emil Göttlich
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Low Pressure ◽  
Meridional Flow ◽  
Secondary Flows ◽  
Test Facility ◽  
Special Focus ◽  
Pressure Stage ◽  
Oil Flow ◽  
Inlet Conditions

The paper discusses the time averaged flow field in a test facility located at the Institute for Thermal Turbomachinery and Machine Dynamics (ITTM) of Graz University of Technology. The rig was designed in order to reproduce the flow leaving a transonic turbine through a following counter rotating low pressure stage. This configuration is common in modern multi-shaft jet engines and will become a standard in the future. The discussion on the flow field is based on numerical results obtained by a commercial CFD code and validated by aerodynamic measurements and oil flow visualization performed on the facility itself. The meridional flow path of the machine is characterized by a diffusing S-shaped duct between the two rotors. Within the duct turning struts lead the flow to the following rotor. The LP stage inlet condition is given by the outlet flow of the high pressure turbine whose spanwise distribution is strongly affected by the shape of the downstream S-channel. A special focus is concentrated on the generation and propagation of secondary flows in such a turning mid turbine frame (TMTF). The aim of the present work is to isolate the flow structures moving from the outlet of the transonic stage through the low pressure stage and identify their effect on the time-averaged flow. The main outcome of this paper is that, whenever a TMTF is placed between counter-rotating high pressure and low pressure turbines, the structures coming from the upstream rotor will not decay (like in a co-rotating setup), but they will be convected and transported towards the downstream rotor. Moreover, the turning of the struts will enhance the vorticities generated by the upstream turbine. The application of technical solutions such as embedded TMTF designs or endwall contouring should be aimed to reach LP rotor uniform inlet conditions, minimize the TMTF secondary flows and thus to damp the rotor-rotor interaction.

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