bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Investigation of Effect of Recess Vane Casing Treatments on an Axial Lift Fan Performance
Authors: Chen Xiangyi , Chu Wuli , Zhang Haoguang , Li Jinge , Lang Jinhua 
Published: August 2017

Lift fans fitted on hovercraft are often subjected to pressure pulse generated by the sea waves. With a high pressure from the pressure pulse, the fan is driven transiently to a low mass flow rate operating point. The probability that a stall can happen is relatively high. The recess vane casing treatment (RVCT) is used to improve the axial lift fan’s stall margin in this paper.
Using the NUMECA software, the fan with solid casing and different RVTC geometry and its flow field are analyzed. The geometry modifications include blade chord exposure variation and cavity outlet axial span. Compared with the solid case, all casing treatments result in a reduction in efficiency. The blade chord exposure is a key factor that affects the efficiency. The RVCT with minimum blade chord exposure provides an inferior stall margin of −0.293% while the others provide 6% to 15% stall margin improvement, respectively.
In the study of the physical flow mechanisms, visualization can provide an insight into the flow field. This reveals that characteristics of the mainstream flow are different between near stall point and design point for the solid casing fan. The three-dimensional (3D) flow field suggests that the flow capacity near the blade tip is damaged by the blockage. The rotor blade is considered as a critical tip based on its stalling behavior. By applying RVCT, the flow field near blade tip is modified, and local mass flow ahead of blade leading edge increases while flow distribution of blade downstream along spanwise is almost the same with the solid casing fan. Also, the flow exchange between RVCT and mainstream is established through the introduction of RVCT. In quantitative analysis, the flow exchange is quantified based on the mass flow passing through the cavity. The ability of RVCT to stabilize the fan is based on the size of cavity, the more mass flow passes through cavity, the more stall margin enhancement can be obtained by the fan. However, the flow exchange between RVCT and mainstream can cause intense mixing, which can lead to efficiency loss.
Investigation of 3D Blade Design on Flow Field and Performance of a Low Pressure Turbine Stage
Authors: Zhao Zhiyuan , Du Xin , Wen Fengbo , Wang Zhongqi 
Published: August 2017

To investigate the effect of blade geometry profiling by 3D bowing and twisting independently and jointly on entropy, efficiency and performance for the turbine cascades, the paper describes the mechanism of how bowed and twisted blades affect the secondary flow. The efficiency of the turbine stage improves considerably and flow structure has been optimized by applying the bowed and twisted blade.
An optimization of low pressure turbine with bowed stator has been performed using steady and transient RANS simulations. Cases with varying bow angles including both positive bow angle and negative bow angle have been discussed to show how bow angle influence the performance of rotor and stator. An optimal case with positive 18-degree bow angle was obtained. It indicates that the entropy increase rises slightly in the region near mid-span, while it reduces distinctly near the hub and shroud in the stator.
In addition to the varying bow angles, further deliberate modification has been made to present a detailed study on the effect of twisted and bowed blade with different stator exit angles. Due to the varying exit flow angles of stator, the mass flow in the spanwise direction has been changed. Meanwhile, the circumferential mass-averaged efficiency in spanwise direction is different. Therefore, the mass flow changing in the spanwise direction leads to redistribution of low energy fluid in the flow passage. The variation of exit flow angles also affects secondary flow and it can be controlled actively by changing the angles. A considerable increase of efficiency has been achieved in this part of investigation.
Considering the unsteady interaction of rotor and stator influenced by applying bowed and twisted stator, the flow through the LPT with relatively low aspect ratio was numerically simulated. It shows clearly how the secondary flow develops in the passage of the stage with bowed and twisted stator and proves several results achieved previously. At the same time, it shows how wakes of the stator and passage vortex develop in the rotor passage.
Numerical Investigation on Mist/Air Cooling in Rectangular Ribbed Channels With Various Aspect Ratios
Authors: Zeng Junxiong , Gao Tieyu , Li Jun , Gong Jianying 
Published: August 2017

Continuously increasing gas turbine inlet temperature to further improve thermal efficiency and power output of gas turbines leads to acquiring a higher cooling effectiveness of gas turbine blades and vanes to protect them from high temperature corrosion and creeping damage. One of the new and promising technologies to greatly increase heat transfer is mist cooling by injecting a small amount of tiny droplets into coolant flow. This paper aims to numerically study the flow and heat transfer behaviors of mist/air coolant in rectangular ribbed channels with various aspect ratios of 1/4, 1/2, 1/1, 2/1 and rib angle of 60°. In addition, the distribution of secondary flows in the four ribbed channels and its effect on heat transfer are analyzed in detail. The effects of Reynolds number ranging from 10,000 to 60,000, mist mass ratios ranging from 1% to 4%, and droplet sizes ranging from 5 μm to 20 μm on heat transfer characteristics of mist/air cooling are investigated. As a comparison, the air-only coolant is also considered in the present study.
The Eulerian-Lagrangian particle tracking method is adopted in this study to simulate the two-phase flow mist/air cooling. Turbulence model validation has been conducted for air-only, indicating that the numerical results with SST k-ω model are fairly consistent with experimental data. The results show that the aspect ratio has insignificant influence on longitudinal secondary flow distribution in the four ribbed channels, but greatly affects the size of main secondary flows. The channel with a smaller aspect ratio obtains a larger size of main secondary flow, which may result in decreasing the heat transfer coefficient. The average Nu on ribbed surfaces presents an increasing trend with Reynolds number and mist mass ratio for mist/air cooling. The heat transfer enhancement of mist/air as compared to air-only increases from 12.3% to 91.86% when Reynolds number ranges from 10,000 to 60,000 with injecting 2% mist into air coolant, while that increases from 7.96% to 113.15% when mist mass ratio increases from 1% to 4%. The average Nu initially increases with droplet size and then decreases. A peak value of average Nu is obtained in the case of 15μm mist among all the sizes of droplets. The case of AR = 2/1 obtains the highest average Nu, followed by the cases of AR = 1/2, 1/1 and 1/4 for both air-only and mist/air. The channel with aspect ratio of 1/2 obtains the best thermal performance in mist/air cooling channel.
Fan Similarity Model for the Fan-Intake Interaction Problem
Authors: Carnevale Mauro , Wang Feng , Parry Anthony B. , Green Jeffrey S. , di Mare Luca 
Published: August 2017

Very high-bypass ratio turbofans with large fan tip diameter are an effective way of improving the propulsive efficiency of civil aero-engines. Such engines, however, require larger and heavier nacelles, which partially offset any gains in specific fuel consumptions. This drawback can be mitigated by adopting thinner walls for the nacelle and by shortening the intake section. This binds the success of very high-bypass ratio technologies to the problem of designing an intake with thin lips and short diffuser section which is well matched to a low speed fan. Consequently the prediction of the mutual influence between the fan and the intake flow represents a crucial step in the design process.
Considerable effort has been devoted in recent years to the study of models for the effects of the fan on the lip stall characteristics and the operability of the whole installation. The study of such models is motivated by the wish to avoid the costs incurred by full, three-dimensional CFD computations. The present contribution documents a fan model for fan-intake computations based on the solution of the double linearization problem for unsteady, transonic flow past a cascade of aerofoils with finite mean load. The computation of the flow in the intake is reduced to a steady problem, whereas the computation of the flow in the fan is reduced to one steady problem and a set of solutions of the linearised model in the frequency domain. The nature of the approximations introduced in the fan representation is such that numerical solutions can be computed inexpensively, whilst the main feature of the flow in the fan passage, namely the shock system and an approximation of the unsteady flow encountered by the fan are retained. The model is applied to a well-documented test case and compares favourably with much more expensive three-dimensional, time domain computations.
Experimental and Numerical Investigation on the Aerodynamic Performance of a Compressor Cascade Using Blended Blade and End Wall
Authors: Li Jiabin , Ji Lucheng , Yi Weilin 
Published: August 2017

Nowadays, the corner separation, occurring near the corner region formed by the suction surface of blade and end wall, has been an important limitation for the increasing of the aerodynamic loading in the compressor. The previous numerical studies indicate that the Blended Blade and End Wall (BBEW) technology is useful in delaying, or reducing, or even eliminating the corner separation. To further validate the concept, this paper presents combined experimental and numerical investigations on a BBEW cascade and its prototype.
Firstly, the NACA65 linear compressor cascade with the turning angle 42 degrees was designed and tested in a low-speed wind tunnel. Then, the cascade with blended blade and end wall design was made and tested in the same wind tunnel. The experimental results show that the design of blended blade and end wall can improve the performance of the cascade when the incidence angle was positive or at the design point, and the total pressure loss coefficient was reduced by 7%–8%. The performance improvement mainly located from 10%–25% span heights.
Secondly, based on the experimental data, the numerical study made by our internal code Turbo-CFD shows the difference of the simulation precision of the results, obtained from four different turbulence model after the mesh independence test. The four turbulence model is Spalart-Allmaras model, standard k-ε model, standard k-ω model, and shear stress transport k-ω model. For this case, the SST turbulence model has better performance compared with others.
Thirdly, based on the results which were calculated with the turbulence model SST, the effect of the blended blade and end wall design was discussed. The numerical study shows that the design with the blended blade and end wall can have a good effect on the corner flow of the cascade. The strong three-dimensional corner separation, caused by the accumulation of the flow happening at the trail of the suction side was avoided, and the flow losses of the prototype cascade were reduced.
Above all, the experiment shows that the design with blended blade and end wall can improve the performance of the cascade. Compared with the experiment data, the SST turbulence model shows the best results of the flow field. Based on the numerical results, the details of the flow field and the effect of the blended blade and end wall design on the corner separation are discussed and analyzed.
Hydraulic Fuel System Simulation Using Newton-Raphson Method and its Integration With a Gas Turbine Performance Model
Authors: Wang C. , Li Y. G. 
Published: August 2017

A fuel system in a gas turbine engine is to meter and deliver required fuel flow to the engine in order to power its operation. A hydraulic fuel system may consist of pumps, valves and metering unit. The fuel has to be sucked from a reservoir, pressurized by the pumps, and regulated by the valves before being injected into an engine combustion chamber. A slight delay of fuel system component response may result in noticeable impact on the engine transient performance response.
In this paper, a novel method for engine hydraulic fuel system performance prediction based on Newton-Raphson approach has been introduced. A gas turbine transient performance simulation system has been set up, where gas turbines are simulated with an inter-component volume method, control systems are simulated with a proportional-integral (PI) controller and hydraulic fuel systems are simulated with a new fuel system model based on Newton-Raphson method introduced in this paper.
The developed performance simulation system has been applied to a model one-spool aero gas turbine engine similar to Rolls-Royce AVON. A typical transient process of the model engine has been simulated to investigate the effectiveness of the introduced fuel system simulation method and the coupling effect between the gas turbine and the fuel system. Results show that the inclusion of a fuel system model will result in a noticeable delay in engine transient behaviour compared with that without the inclusion of the fuel system model although such delay is relatively small. Such modelling method can help set up physics-based fuel system models and analyse the detailed behaviour and mechanism of the fuel systems during engine transient processes. This may provide very useful information to assist the understanding of engine performance behaviour and support the designs of engines, control systems or fuel systems. Such method is generic and can be applied to different hydraulic fuel systems.
Numerical Investigation of Unsteady Shock Wave Motion in a Transonic Centrifugal Compressor
Authors: Adjei Richard Amankwa , Wang Weizhe , Jiang Jishen , Liu Yingzheng , Kawakubo Tomoki 
Published: August 2017

In order to meet the requirements of automobile engines and marine-use diesel engines, turbochargers must be developed with high boost pressure and appreciably high levels of efficiency. The high pressure rise typically achieved in transonic compressors lead to a stage characterized by high inlet relative Mach numbers. Losses generated in transonic compressors are to a large extent due to the formation of shockwaves at the inducer with interactions between the shock, tip leakage vortex and boundary layer. Significant efficiency reduction occurs at the tip region of the impeller due to the complex interaction of the tip clearance flow and shocks, resulting in significant overall performance degradation.
A study has been conducted on the unsteady motion of shockwaves in a transonic centrifugal compressor with vaned diffuser using time-resolved three-dimensional Reynolds average Navier-Stokes simulation. Focus is placed on the impact of the shock motion and post shock unsteadiness on stage performance and impeller-diffuser interaction. The key findings were that the interaction of the shockwave with the tip leakage flow and the boundary layer were the most influential in loss generation with a consequence of increased aerodynamic loss. For the unsteady blade row interaction, the influence of upstream flow unsteadiness on diffuser vanes had significant effect on the flow incidence angle. Periodic jet and wake structure from the impeller and the progressive pressure waves which interacts with the vanes at the interface strongly determines the intensity and position of the vane shock. This has implications on performance in terms of stall inception and static pressure rise across the diffuser.
Thermal Stress and Deformation Analysis of HP Casing During Shutdown of CPR1000 Nuclear Steam Turbine
Authors: Guo Yanan , Xie Danmei 
Published: August 2017

Taking a CPR 1000 nuclear steam turbine HP casing as an example, this paper carried out the numerical study to investigate on the deformation of the casing during shutdown.
Based on ProE software, a 3D model for the HP casing was established at first. Secondly, the heat transfer coefficient of every surface of HP casing of the shutdown was calculated by using convection heat transfer coefficient formula in detail, ignoring radiative heat transfer inside the casing. Then, the finite element method was used to calculate and analyze the shutdown of HP casing’s temperature field. In the calculation process, the third boundary condition was used to apply steam temperature and heat transfer coefficient to each area of the HP casing. Finally, the calculation results of the temperature field were used as the input conditions to calculate the stress and strain of the casing, and the possible reasons for the HP casing’s deformation were obtained.
Numerical Investigation of Diffuser Flow Field and Rotating Stall in a Centrifugal Compressor With Vaned Diffuser
Authors: Zhao Yang , Zhao Jiayi , Wang Zhiheng , Xi Guang 
Published: August 2017

The diffuser rotating stall in a centrifugal compressor with vaned diffuser is one of important unsteady flow phenomena, which limits the operating range of the compressor. In this paper, the unsteady CFD analysis on a low-speed centrifugal compressor has been performed to investigate the flow characteristic in the diffuser and the propagation of the diffuser rotating stall.
The flow behaviors at the outlet of the impeller at design and off-design conditions are firstly investigated. It is found that a reversal flow, induced by the tip leakage flow, exists near the shroud at the impeller outlet and becomes serious with the mass flow rate reduced. Due to the span-wise variation of the flow angle at the diffuser inlet and the inversed pressure gradient in the passage, the leading-edge vortex (LEV) generates on the diffuser leading edge. The LEV then induces the secondary flow in the diffuser passage and then causes the hub-corner separation. Furthermore, the propagation of the diffuser rotating stall is presented in details.
The suction-side separation near the hub induces the blockage in the passage. And the shedding vortex from the suction side moves toward the leading edge of the adjacent blade. When the vortex reaches to the leading edge of the adjacent blade, the incidence increase and a new separation occurs on the suction side. With the development of the new separation, the passage becomes blocked gradually and the upstream stalled passage recovers to a normal condition. The rotating stall propagates along the direction of the impeller rotation at about 4.5% of the impeller rotational speed.
Numerical Investigation on Effect of Compressor Performance in Single Rotor With Micro-Vortex Generator
Authors: Ma Shan , Chu Wuli , Zhang Haoguang , Lang Jinhua , Kuang Haiyang 
Published: August 2017

The performance of axial compressor is considerably influenced by secondary flow, like corner separation between wall and blade in a compressor stage. An extensive experimental study of vortex generator (VG) applied on axial compressor was conducted by many scholars, in order to control these effects and improve the aerodynamic performance. According to their size, they are classified as traditional VGs (h/δ>0.5) and Micro-vortex generators (MVGs, h/δ = 0.1∼0.5).MVGs is one of the hot spots of present research to restrain the secondary flow.
In order to investigate the effect of MVGs used in rotor, this study was carried out on Northwestern Polytecnical University rotor (NPU rotor), which is a subsonic axial flow compressor rotor. The Vane-MVGs were placed at a distance of 11% chord length ahead of the leading edge on the end-wall. The characteristic line of 54% (8130RPM), 71% (10792RPM) and 84% (12768RPM) design speed were calculated by steady 3D RANS simulations with Spalart-Allmar turbulence model and compared with the corresponding MVGs cases, respectively. Results show that the stall margins of the 3 speeds with MVGs were larger than baseline, but the efficiency and pressure ratio were reduced in different degrees. In this paper, the flow characteristics at 54% (8130RPM) design speed and the development process of vortex generated by MVGs are analyzed in detail. The influence of MVGs height and stagger angle on rotor performance is also discussed. Moreover, flow simulation of MVGs used on axial compressor single rotor’s hub offered a guideline to future research.
Characterization of a Novel Porous Injector for Multi-Lean Direct Injection (M-LDI) Combustor
Authors: Li Jianing , Bhayaraju Umesh , Jeng San-Mou 
Published: August 2017

A generic novel injector was designed for multi-Lean Direct Injection (M-LDI) combustors. One of the drawbacks of the conventional pressure swirl and prefilming type airblast atomizers is the difficulty of obtaining a uniform symmetric spray under all operating conditions. Micro-channels are needed inside the injector for uniformly distributing the fuel. The problem of non-uniformity is magnified in smaller sized injectors. The non-uniform liquid sheet causes local fuel rich/lean zones leading to higher NOx emissions. To overcome these problems, a novel fuel injector was designed to improve the fuel delivery to the injector by using a porous stainless steel material with 30 μm porosity. The porous tube also acts as a prefilming surface. Liquid and gaseous fuels can be injected through the injector. In the present study, gaseous fuel was injected to investigate injector fuel-air mixing performance. The gaseous fuel was injected through a porous tube between two radial-radial swirling air streams to facilitate fuel-air mixing. The advantage of this injector is that it increases the contact surface area between the fuel-air at the fuel injection point. The increased contact area enhances fuel-air mixing. Fuel-air mixing and combustion studies were carried out for both gaseous and liquid fuel. Flame visualization, and emissions measurements were carried out inside the exit of the combustor.
The measurements were carried out at atmospheric conditions under fuel lean conditions. Natural gas was used as a fuel in these experiments. Fuel-air mixing studies were carried out at different equivalence ratios with and without confinement. The mass fraction distributions were measured at different downstream locations from the injector exit. Flame characterization was carried out by chemiluminescence at different equivalence ratios and inlet air temperatures. Symmetry of the flame, flame length and heat release distribution were analyzed from the flame images. The effects of inlet air temperature and combustion flame temperature on emissions was studied. Emissions were corrected to 15% O2 concentration. NOx emissions increase with inlet air temperature and flame temperature. Effect of flame temperature on NOx concentration is more significant than effect of inlet air temperature. Fuel-air mixing profile was used to obtain mass fraction Probability Density Function (pdf). The pdfs were used for simulations in Chemkin Pro. The measured emissions concentrations at the exit of the injector was compared with simulations. In Chemkin model, a network model with several PSRs (perfectly stirred reactor) were utilized, followed by a mixer and a PFR (plug flow reactor). The comparison between the simulations and the experimental results was investigated.