Dakun Sun

• Beihang University

The dynamic characteristics of mode behavior in a low-speed, single-stage axial compressor are crucial for studying linear stall inception. An input–output analysis framework has been established, enabling the introduction of forcing into the compressor system and identifying the most energetic mode. Both standard and compressed input–output analys...

A sensitivity analysis method for flow stability of axial compressors based on meridional flow is proposed and employed to reveal the sensitive region of stability in the present paper. The meridional stability model which transforms the stability problem into an eigenvalue problem enables flow stability to be quantitatively expressed by system eig...

Ammonia holds promise as an alternative renewable fuel with significant potential for addressing climate change concerns. Blending ammonia with methane has emerged as a viable strategy to improve the laminar burning velocity of ammonia. In this study, we propose a mechanism for methane/ammonia combustion, comprising 31 species and 131 chemical reac...

Stability studies were conducted on a single-stage, low-speed compressor with different rotor loading-distribution designs under a uniform inlet, 10% intensity, and 20% intensity total tip pressure distortion inlet conditions via numerical calculations, theoretical model predictions, and experimental methods. The steady numerical performance was in...

A sensitivity analysis method for flow stability of axial compressors based on meridional flow is proposed and employed to reveal the sensitive region of stability in the present paper. The meridional stability model which transforms the stability problem into an eigenvalue problem enables flow stability to be quantitatively expressed by system eig...

A resolvent analysis framework for the axial compressor was established, and the impedance optimization was achieved based on the resolvent analysis framework for the impedance boundary condition casing treatment. This framework was derived by treating the nonlinearity in the perturbation equations as an unknown forcing, the linear relationship bet...

Based on a small perturbation stability model for periodic flow, the effects of inlet total temperature ramp distortion on the axial compressor are investigated and the compressor stability is quantitatively evaluated. In the beginning, a small perturbation stability model for the periodic flow in compressors is proposed, referring to the governing...

In this work, we propose a rapid optimization approach to examine its application potential for the design and performance prediction and optimization of a solid fuel ramjet (SFRJ) with a bluff body. For this, the shape of the bluff body is parameterized first using the non-uniform rational B-spline method. We then develop a model for predicting SF...

A wire mesh casing treatment is proposed and numerically tested on the transonic axial compressor (Rotor 37). A theoretical stall inception prediction model was developed to account for the wire mesh casing treatment, which was modeled as an impedance boundary condition. This model was validated on a low-speed compressor, replicating the experiment...

The present work aims to develop a stall warning method that is reliable even when the compressor encounters inlet distortion. For this purpose, multicorrelation analysis (MCA) is proposed to provide an effective indicator for the stall warning method. The relationship between MCA and correlation measures was discussed. It was demonstrated that MCA...

A clear understanding of the turbomachinery wake flow field is one of the key problems in developing turbomachinery aerodynamics. The theoretical model of helical vortices is established in cylindrical coordinates (r,θ,z), and the model corresponds to the experimental scheme, which verifies the feasibility of reconstructing flow field by interpolat...

Experimental results indicate that wire mesh casing treatment (WMCT) enhances the stability of low-speed compressors with little reduction in efficiency. The flow resistance on the surface of the grooves, which are formed by the wire mesh, provides a new variable for the design of WMCT. This paper investigates the stability improvement induced by t...

This paper presents a stability model that can make a rapid prediction of the rotating stall inception in turbomachinery and provide the spatial distribution of the corresponding instability mode. In addition, this model can take the three-dimensional geometry of blades and complex flow details in the compressor into consideration, and the solution...

There has been little research on the system stability of the flow past a blade when the domain is finite in the transverse direction. In this study, we first explore the influence of the domain size and periodic boundary conditions in the transverse direction on the stability of the flow past a single blade in a finite domain. As the transverse wi...

Foam-metal casing treatment (FMCT) installed over the rotor tip has been proved to affect the performance of compressors. To develop a design strategy for FMCTs, different parameters of surface geometries (SGs), including the shape, staggering, and denseness, based on a 2mm-depth groove were designed to model the FM surface morphology, which domina...

Recently, a kind of foam metal casing treatment (FMCT) was proposed and tested in a low-speed axial compressor. It was found that the FMCT performed well in both stall margin improvement and noise emission reduction of the compressor. The result is beneficial to the future advanced turbofan design. As a companion research, the goal of this paper is...

The stall inception prediction method based on eigenvalue theory is established to analyze the effect of rotor blade loading distribution on the flow stability of transonic compressors. The parameterization is implemented to describe the blade geometry with a number of control parameters. Four designs with different blade loading distributions are...

An efficient and reliable stall inception prediction model is established and integrated into the compressor design. And the effect of blade loading distribution on flow stability of axial compressor is studied via the proposed method. Foreloaded, aft-loaded and uniformly loaded rotor blades of a subsonic axial compressor are designed by modifying...

The S-shape inlet is generally the main reason for the occurrence of swirl inlet distortion that is seriously concerned by the manufactures of fighters. The non-uniform inlet combined with large-scale bulk swirl, small-scale tight-wound swirl, or both of them may greatly impact the performance of aero-engines. Focusing on the swirl patterns and the...

Experiments were conducted on a low-speed compressor, and a set of high response transducers were mounted in the casing to collect the over-tip signal. The auto-correlation measure results show that Rc at the first half of the blade will degrade before stall. According to the phase-locked pressure contour and RMS contour at design point and near st...

Turbofan engines are one of the most popular propulsion systems used in commercial aircraft due to their high thrust and good fuel efficiency. To reduce noise generated from turbofan engines-powered aircraft, a number of control approaches have been developed. The dominant noise sources include the fan and the high-speed ‘hot’ and ‘cold’ jet. In en...

The S-shape inlet has been widely used in advanced military aircraft due to their advantage of reducing radar signature. However, the curvature of the inlet usually causes different kinds of intake distortion at the aerodynamic interface plane (AIP). Among them, the swirl distortion has been seriously concerned because of its great impact on the pe...

A set of foam metal casing treatment (FMCT) has been investigated to assess the stability improvement and noise reduction on an axial compressor. Three FMCTs with different PPI (Pores Per Inch), 20, 35, and 50, are tested experimentally. Two installation locations of foam metal in the casing are also considered and investigated. At location 1, it i...

Three compressors with fore-loaded, uniformly loaded and aft-loaded rotor blades are designed via streamline curvature method coupled with blade generation that uses arbitrary camber lines so as to study the effect mechanism of rotor axial blade loading distributions on compressor performance. The rotor blade loading design is achieved by modifying...

Tip clearance flow is not only the source of undesirable noise but also a potential indicator for critical operating conditions with rotating stall or surge. It can induce blade vibration, which would cause premature blade failure when the vibration is strong enough. The paper presents experimental studies on the effects of tip clearance on the sta...

A kind of foam metal casing treatment (FMCT) is proposed and experimentally tested on a low-speed axial flow compressor in this work. Foam metal is a foam-like substance with a lightweight structure but a certain strength. Both time-mean and high-response instrumentation are applied to capture the steady and unsteady performances of the compressor....

Computations of unsteady turbulent flows in turbomachine are still challenging due to the complexity of geometry and relative motion between rotor and stator. A potential solution is using the immersed boundary method (IBM) for its advantages in simulating moving boundary problems, but it loses efficiency with increasing Reynolds number. In the pre...

This paper considers effects of Rotating Inlet Distortion (RID) on a two-stage axial compressor and the stabilization effects of a casing treatment subjected to the considered RID. In multi-spool engines, the downstream compressor suffers a RID when the upstream fan/compressor is in rotating stall. A controlled rotating sectional screen upstream of...

In this work, we conduct experimental investigations on a single-stage axial compressor to shed lights on the dynamic stall phenomena via acoustic measurements. For this, 8 acoustic pressure sensors are installed equally around the circumference of the compressor intake. The acoustic pressure data is simultaneously logged in real-time. Classical an...

This paper will first carry out experimental investigations on a test compressor which is a large-scale, two-stage and low-speed axial one to evaluate the participation of a novel casing treatment (stall precursor-suppressed casing treatment, SPS CT). The compressor performance for its pressure rise characteristics and efficiency are tested and ill...

A stall inception prediction model considering radial inlet distortions is established in this paper in order to quickly and accurately predict the stall limit of a compressor at radially distorted inlet flow conditions. Furthermore, the quantitative effect of the radial inlet distortion on compressor stability is investigated on a low-speed single...

Foam metal is a foam-like substance made out of metal and can be used in flow control, vibration damping and acoustic absorption mainly based on their special physical properties. A kind of foam metal casing treatment is proposed and tested in this study. The impact of the foam metal casing treatment on compressor stability and noise reduction are...

In order to analyze the flow stability of compressors rapidly in the design stage, a fast analysis method is developed in this paper. This method takes the baseflow on each streamline at different spanwise locations as the research object, and characterizes the effect of blade rows on the internal flow by establishing a body force model. Therefore,...

A stall warning approach based on aero-acoustic theory is studied in this paper. For this stall warning approach, a parameter Rc is defined to measure the periodicity of the blade-passing signal. Signal simulation is used to investigate the mechanism of the stall warning approach. The results suggest that the value of Rc is influenced by the power...

Although steady micro-injection is experimentally validated as an attractive method in improving the stall margin of axial compressors, up to now a fast prediction of stall boundary remains some way off. This investigation is to propose such a prediction model. A flow stability model is developed to further consider the effect of high-speed micro-i...

In this paper, the effect of the rotor–stator axial spacing is investigated in an axial pump with the working fluid of water. The pressure-rise performance was tested at a range of flow rates. Results indicate that decreased axial spacing generates improved hydraulic head, especially when the flow rate is low. Particle image velocimetry measurement...

A further investigation of an acoustic theory-based stall-warning approach is presented in this paper, which contains the basis of this approach and an application on a low-speed compressor (LSC) with a stabilization system. In the present work, this stallwarning approach is first explained through a numerical simulation in which the periodicity of...

Casing treatment is a mature stabilization technique which has been widely applied on aero-engines for modern aircrafts and turbo-chargers for automobiles. After the investigations of half century since the 1960s, this technique has been well developed for various configurations with different effectiveness. From the perspective of stabilization me...

In present paper, theoretical investigation on the effect of combined liners of a drum-like liner and a perforated liner with bias flow on controlling thermoacoustic instability in a Rijke tube is carried out by transfer element method (TEM). TEM is used to consider the interactions between the acoustic waves and the soft boundary of the drum-like...

Experimental research about rotating inlet distortion is carried out on a two-stage compressor with emphasis on the compressor stability as well as the stall margin improvement with a kind of stall precursor-suppressed (SPS) casing treatment in this paper. The wire mesh screen is placed at the upstream of the IGV and can rotate at various speeds in...

Short rotor–stator axial spacing has been demonstrated to be beneficial to the aerodynamic performance of subsonic compressors. In this paper, it is further verified that this benefit partly originates from the improvement of the rotor blade lift. A tiny axial pump is investigated both numerically and experimentally with three different rotor–stato...

Swirl inlet distortion is usually encountered in modern flight vehicles since their inlet ducts usually consist of one or two bends, such as S-inlet duct. An experimental device is first designed to simulate the swirl inlet distortion and then used to test the effectiveness of a novel casing treatment (CT) on a low-speed compressor under the swirl...

This paper investigates the effect of a swept airfoil design on the aerodynamic instabilities of transonic axial-flow compressors based on global stability analysis. An approach aimed at predicting the stall inception point is developed by integrating an improved blade force model and a new mathematical treatment method for steady flow. This approa...

This paper presents the stall margin enhancement of a novel casing treatment subjected to circumferential pressure inlet distortion. Experimental results are carried out on a low-speed compressor. Experimental results show that the stall margin of the test compressor is gravely narrowed by circumferential pressure inlet distortion. The stabilizatio...

For a compressor stage, the mechanism of wake recovery leads the rotor wakes to decay in a reversible process through the stator passage. Based on this theory, the rotor-stator axial spacing is believed to be a significant factor bound up with the wake mixing loss. In this paper, the wake decay processes in a tiny axial pump with varied rotor-stato...

A stability model for multi-stage compressor is developed on the basis of the eigenvalue approach. This model assumes that the unsteady flow field can be decomposed into pressure, vortex and entropy waves. Besides, a linear cascade of blades is modeled by three-dimensional semi-actuator disk theory and the characteristics of steady flow field are a...

Unsteady flows caused by rotor-stator interactions are investigated using particle image velocimetry (PIV) method in an axial pump. The pump is designed with rotor with splitters and tandem vanes and the rotor-stator gap is able to be varied. Unsteady flows with three cases of the axial gaps (far, mid and close) between rotor and stator are recorde...

A stall inception model of centrifugal compressors is developed on the basis of the global stability analysis in the present paper. This model takes specific flow patterns and impeller geometry into account, which can be used to analyze the effect of blade design parameters on the stall limit of centrifugal compressors. In particular, the body forc...

Lined ducts are extensively applied to suppress noise emission from aero-engines and other turbomachines. The complex noise/flow interaction in a lined duct possibly leads to acoustic instability in certain conditions. To investigate the instability, the full linearized Navier–Stokes equations with eddy viscosity considered are solved in frequency...

This paper conducts an experimental research of rotating inlet distortion on a low-speed large size test compressor with emphasis on the stability problem of axial fan/compressors, and the stall margin enhancement with a kind of stall precursor-suppressed (SPS) casing treatment. Some results on compressor stall margin and prestall behavior under th...

A kind of casing treatment, named as stall precursor-suppressed (SPS), has been developedrecently, which was proved to be able to effectively improve stall margin (SM) withoutsignificant efficiency loss in low-speed axial flow compressors and a transoniccompressor rotor. In this paper, the effectiveness of the SPS casing treatment is investigatedin...

It is known that a kind of stall precursor-suppressed (SPS) casing treatment can be used to enhance compressor stall margin (SM) without recognizable efficiency loss. The further requirement in this regard is to develop an effective way to determine the variation range of the SM improvement during the design of such SPS casing treatment. In this in...

This paper applies a theoretical model developed recently to calculate the flow instability inception point in axial high speed compressors system with tip clearance. After the mean flow field is computed by 3D steady computational fluid dynamics (CFD) simulation, a body force approach, which is a function of flow field data and comprises of one in...

Generally, casing treatment (CT) is a passivity method to enhance the stall margin of fan/compressor. A novel casing treatment based on the small disturbance theory and vortex and wave interaction suggestion is a method combining passive control and active control, which has been proved effective at enhancing the stall margin of fan/compressor in e...

This paper proposes a novel casing treatment, designated a stall precursor-suppressed casing treatment. It is designed to suppress stall precursors to realize stall margin enhancement in turbomachinery. This paper first presents a physical and mathematical model to describe the casing treatment configuration as a wall boundary condition and then es...

This paper applies a theoretical model developed recently to calculate the flow-instability inception of an axial transonic single stage compressor. After several calculation methods are compared, the singular value decomposition method is adopted to solve the resultant eigenvalue problem in which the involved matrix is rather large due to multista...

A general eigenvalue theory on flow stability in turbomachinery is proposed with the emphasis on flow-instability onset. Based on this theory, a stall-inception model including the effects of complex solid geometry is developed for a multistage fan/compressors system. The capacity of the present model to predict the stall-inception point is assesse...

This paper applies a theoretical model, which has been developed recently, to calculate the flow instability inception of axial transonic fan/compressors system. After the mean flow field is computed by steady CFD simulation, a body force approach, which is a function of flow field data, is taken to represent the effects of discrete blades on the f...

An eigenvalue theory on flow stability in turbomachinery is proposed with the emphasis on flow instability onset. Based on this theory, a stall inception model including the effects of complex solid geometry is developed for multi-stage fan/compressors system. The capacity of the present model to predict the stall inception point is assessed agains...

A three-dimensional compressible flow stability model is presented in this paper, which focuses on stall inception of multi-stage axial flow compressors with a finite large radius annular duct configuration for the first time. It is shown that under some assumptions, the stability equation can be obtained yielding from a group of homogeneous equati...

A stall inception model for transonic fan/compressors is presented in this paper. It can be shown that under some assumptions the solution of unsteady flow field consists of pressure wave which propagates upstream or downstream, vortex wave and entropy wave convected with the mean flow speed. By further using the mode-matching technique and applyin...