Laves phase hydrogen storage alloys for super-high-pressure metal hydride hydrogen compressors

Ti-Cr- and Ti-Mn-based alloys were prepared to be low- and high-pressure stage metals for a double-stage super-high-pressure metal hydride hydrogen compressor. Their crystallographic characteristics and hydrogen storage properties were investigated. The alloy pair Ti0.9Zr0.1Mn1.4- Cr0.35V0.2Fe0.05/TiCr1.55Mn0.2Fe0.2 was optimized based on the comprehensive performance of the studied alloys. The product hydrogen with a pressure of 100 MPa could be produced from 4 MPa feed gas when hot oil was used as a heat reservoir.

Computer-Aided Solution to the Vibrational Effect of Instabilities in Gas Turbine Compressors

Surge and stall are the two main types of instabilities that often occur on the compressor system of gas turbines. The effect of this instability often leads to excessive vibration due to the back pressure imposed to the system by this phenomenon. In this work, fouling was observed as the major cause of the compressor instability. A step to analyze how this phenomenon can be controlled with the continuous examination of the vibration amplitude using a computer approach led to the execution of this work. The forces resulting to vibration in the system is usually external to it. This external force is aerodynamic and the effect was modeled using force damped vibration analysis. A gas turbine plant on industrial duty for electricity generation was used to actualize this research. The data for amplitude of vibration varied between -15 and 15 mm/s while the given mass flow rate and pressure ratio were determined as falling between 6.1 to 6.8 kg/s and 9.3 to 9.6 respectively. A computer program named VICOMS written in C++ programming language was developed. The results show that the machine should not be run beyond 14.0 mm vibration amplitude in order to avoid surge, stall and other flow-induced catastrophic breakdown.

Avelair Compressors采用新型驱动器降低压缩空气成本

近期，Avelair Compressors采用了最新型的Unidrive SP驱动器，对其原有产品进行了可调速改造，改造后的方案与以往的定速方案相比，大约可节省30％以上的能源。常务董事Brian Wood表示：“选用Unidrive SP及板载的PLC，使我们的产品结构更紧凑、效率更高、价格更具竞争力。由于压缩机可随时根据要求调节输出，用户在任何时候都能获得最高效率。”

Experimental Analysis of the Performances of Unit Refrigeration Systems Based on Parallel Compressors with Consideration of the Volumetric and Isentropic Efficiency

The performances of a refrigeration unit relying on compressors working in parallel have been investigated considering the influence of the compressor volumetric efficiency and isentropic efficiency on the compression ratio.Moreover,the following influential factors have been taken into account:evaporation temperature,condensation temperature and compressor suction-exhaust pressure ratio for different opening conditions of the compressor.The following quantities have been selected as the unit performance measurement indicators:refrigeration capacity,energy efficiency ratio(COP),compressor power consumption,and refrigerant flow rate.The experimental results indicate that the system refrigeration capacity and COP decrease with a decrease in evaporation temperature,increase of condensation temperature,and increase in pressure ratio.The refrigerant flow rate increases with the increase in evaporation temperature,decrease in condensing temperature and increase in pressure ratio.The compressor power consumption increases with the increase in condensing temperature and increase in pressure ratio,but is not significantly affected by the evaporation temperature.

Effects of process parameters on semi-solid squeeze casting performance of aluminum alloy scrolls for scroll compressors

The aluminum alloy scroll is one of the key parts of the scroll compressors widely used in the air-conditioning,refrigeration,and heat pump systems.In this work,the semi-solid squeeze casting(SSSC)process was used to fabricate the aluminum alloy scroll.The effects of process parameters including the pouring temperature,mold temperature,and squeezing velocity on the filling and solidification behaviors of the alloys were investigated through simulations based on the power law cut-off(PLCO)material model.Results show that there is a significant increase in the flow velocity of the slurry,and the area of the high-speed region enlarges with the increase of the pouring temperature.The homogeneity of the temperature and velocity fields in the slurry is improved with an increase in mold temperature.Both the filling time and its variation rate decrease with an increase in squeezing velocity.The maximum solidification time exhibits a linear variation with the increase in pouring temperature.The shrinkage area is decreased by increasing the mold temperature.The optimal process parameters of the SSSC process were obtained from simulation analysis,which are the pouring temperature of 595°C,mold temperature of 350°C,and squeezing velocity of 0.3 m·s-1.Moreover,the qualified scroll casting was fabricated using the SSSC process under the optimal process parameters.

Study on effect analysis and parameter optimizing of stepless capacity control system on reciprocating compressors

An improved model of reciprocating compressor operation cycle with a stepless capacity control system is presented and influence of the key parameters of the system is evaluated. In the stepless capacity control system of a reciprocating compressor,mechanical unloaders are used to partially hold suction valves open for a certain time during the compression stroke. The typical working process of the reciprocating compressor is changed by capacity regulation apparatus. However,some critical parameters like the hydraulic force acting at the unloader have not been rigorously studied in previous researches. Here an improved numerical model of a double acting reciprocating compressor under the control stepless capacity is proposed and verified by experimental trials. Numerical simulations are carried out to select and evaluate the acting force which definitely has an influence on indicator diagrams of compressors. It is observed that the optimized range of 350 N to 380 N is preferable for the unloader force such that the intensity of opening and closing impacts are minimized.

Fault Diagnosis of Reciprocating Compressors Valve Based on Cyclostationary Method

The relationship between second-order cyclostationary method and time-frequency distribution is studied, and cyclic autocorrelation（CA） function is indicated to be one sort of special time-frequency distribution method. Furthermore, a fault diagnosis method for reciprocating compressors based on empirical mode decomposition （EMD） and CA function is proposed, and then it is applied to the fault diagnosis of reciprocating compressor valve. Firstly, the vibration signal of reciprocating compressor valve is decomposed by using ENID method, and several intrinsic mode functions （IMFs） are obtained. Secondly, the IMFs are evaluated by some denoising criterions to remove the noise and interfering ones. Finally, the CA functions of the remained IMFs are calculated, which will be used to reconstruct the CA function of the original vibration signal. Engineering application indicates that this method can sufficiently inhibit the cross-interference items of CA function. Therefore, more explicit working conditions of reciprocating compressor components can be achieved.

Study of Failure Diagnostic Methods and Intelligent Diagnostic System for Reciprocating Compressors

Three categories of failure diagnostic methods for reciprocating compressors are classified according to the signals adopted by the diagnosis. They are parameter method, vibration method, and oil analysis method. In this paper, the applicable range and operational difficulties of these methods are discussed on the basis of analysis and induction upon normal failure. It is proposed that a compressor's normal failure can be divided into thermodynamical property failure and mechanical function failure. As to the former, the parameter method that takes a cylinder pressure signal as the main diagnostic signal may be applied; and as to the latter, the vibration signal frequency spectrum can be used to diagnose. At the same time, the structure of an intelligent diagnostic system based on neural networks is introduced, and its schematic is given.

Investigation on Surge in Centrifugal Compressors

A test bench for conducting compressor surge experiments is set up, and different system configurations formed by changing the length of compressor outlet pipeline are tested for surge. Dynamic pressure signals relating to surges are acquired at different locations of the configurations using unsteady measurement ＆ data acquisition system. The sliding window method is adopted to set up quantitative criterion on the surge. Parameters included in the criterion, such as location of data collection, size and step of sliding window, a mathematical quantity surge-judging and its threshold, etc., are given. Flow chart of surge evaluation is shown, and surge frequency was evaluated based on system configurations. With all these, the problem of judging the existence of surge by human experiences in compressor performance experiments can be solved. Hence this new approach may help to achieve intelligent operations on automatic compressor performance testrig.

Compressors for Hyper-Sonic Engines —A Theoretical Study of Future Compressors for Hyper Sonic Engines

This paper is an eye opening to the new horizon of the design of operational Compressors in our jet engines. That are compressors usually perform an operation called isentropic process and which levitate the pressure and temperature to the optimum level which require for effective ignition. Basically, our compressors have several sets of blades to perform this function, more precisely saying Rotor and stator blades. Where rotor blade provides air molecule to push at very high velocity to the Stationary blade and when the air Enders to the Stator, the stator races its pressure to move on to the next stage. And we call this set of Stator and rotor as a stage ref [1]. However, in this work, I consider the geometry of the incoming air molecule and how it transforms its physical quantities such as Pressure and temperature ref [2]. For that I tie the concept of Thermodynamic and mechanics on the platform of Tensor analysis ref [3]. That is, I consider the quantities like Pressure, Temperature and rate of flow are their corresponding vector spaces and energy related quintets like heat, work as the scaling elements on the above vector space. And quantities such as entropy enthalpy and specific heat capacity are corresponding physics of it. Considering the advantages, one of the important advantages of this approach is the applicability of results of this work to the formulation of blade less compression Example: Ram and Scram jet engine. Again, the relevant upgrading which is essential for future hypersonic air crafts can achieve from this study and this will be a mile stone for bright air and space travel. To conclude, this approach will be a great transformation on the conventional idea for realization of compression for operational Scram and Ram jet engines ref [4] [5].

Reducing the Gas Pressure Drop in Suction Mufflers of Hermetic Reciprocating Compressors

The suction muffler of hermetic reciprocating compressors is installed in order to attenuate the noise generated by the gas pulsation of the flow through the suction valve. However, the installation of the suction muffler affects the operation of the compressor owing to gas pressure drop, which causes volumetric and energetic efficiency loss due to the gas specific volume augmentation. Therefore, there is a compromise between sound attenuation and pressure drop increase, which has to be taken into account by compressor designers. In this work, it presents a numerical solution to the flow through a suction muffler in order to analyze the pressure field and point out the main contributions to the overall pressure drop of the flow. A commercial CFD （computational fluid dynamics） code was used to perform the numerical simulations and the results were validated by using experimental data. After analyzing the pressure field, the geometry of the muffler was modified intending to decrease the flow pressure drop. The geometric modification produced a 28% reduction on the overall pressure drop, without influencing the sound attenuation.

Comparative Analysis of Diagonal and Centrifugal Compressors with Synergy Theory in Compressed Air Energy Storage System

Energy storage technology is an essential part of the efficient energy system.Compressed air energy storage(CAES)is considered to be one of the most promising large-scale physical energy storage technologies.It is favored because of its low-cost,long-life,environmentally friendly and low-carbon characteristics.The compressor is the core component of CAES,and the performance is critical to the overall system efficiency.That importance is not only reflected in the design point,but also in the continuous efficient operation under variable working conditions.The diagonal compressor is currently the focus of the developing large-scale CAES because of its stronger flow capacity compared with traditional centrifugal compressors.And the diagonal compressor has the higher single stage pressure ratio compared with axial compressors.In this paper,the full three dimensional numerical simulation technologies with synergy theory are used to compare and analyze the internal flow characteristics.The performance of the centrifugal and diagonal impellers that are optimized under the same requirements for large-scale CAES has been analyzed.The relationship between the internal flow characteristics and performance of the centrifugal and diagonal impellers with the change of mass flow rates and total inlet temperature is given qualitatively and quantitatively.Where the cosine value of the synergy angle is high,the local flow loss is large.The smaller proportion of the positive area is the pursuit of design.Through comparative analysis,it is concluded that the internal flow and performance changes of centrifugal and diagonal impellers are different.The results confirm the superiority and feasibility of the off-design performance of the diagonal compressor applied to the developing large-scale CAES.

An improved deviation model for transonic stages in axial compressors

Deviation model is an important model for through-flow analysis in axial compressors.Theoretical analysis in classical deviation models is developed under the assumption of onedimensional flow,which is controlled by the continuity equation.To consider three-dimensional characteristics in transonic flow,this study proposes an improved theoretical analysis method combining force analysis of the blade-to-blade flow with conventional analysis of the continuity equation.Influences of shock structures on transverse force,streamwise velocity and streamline curvature in the blade-to-blade flow are analyzed,and support the analytical modelling of density flow ratio between inlet and outlet conditions.Thus,a novel deviation model for transonic stages in axial compressors is proposed in this paper.The empirical coefficients are corrected based on the experimental data of a linear cascade,and the prediction accuracy is validated with the experimental data of a three-stage transonic compressor.The novel model provides accurate predictions for meridional flow fields at the design point and performance curves at design speed,and shows obvious improvements on classical models by Carter and C¸etin.

Design Strategy of Diagonal Compressors in Compressed Air Energy Storage System

As a kind of large-scale physical energy storage,compressed air energy storage(CAES)plays an important role in the construction of more efficient energy system based on renewable energy in the future.Compared with traditional industrial compressors,the compressor of CAES has higher off-design performance requirements.From the perspective of design,it needs to pay attention not only to the performance of the design point,but also to the performance of all the stable working range.However,from the previous literature,no diagonal compressor was used in CAES which can meet the requirements,which also reflects the design program can be further improved.Therefore,this paper studies the design strategy of high efficient diagonal compressor for large-scale CAES,and gives the complete strategy algorithms used for different program modules.The pressure ratio,isentropic efficiency and stable working range are comprehensively considered.In the design process,the criteria for the key parameters of the diagonal flow angle of the diagonal compressor are given for the first time.The results show that the isentropic efficiency at the design point is 92.7%,the total pressure ratio is1.97,and the stable working range exceeds 20%,which meets the design requirements of the compressor for CAES and exceeds the overall performance of the previous compressors in the entire working range.

Reducing laser beam fluence and intensity fluctuations in symmetric and asymmetric compressors

All space-time coupling effects arising in an asymmetric optical compressor consisting of two non-identical pairs of diffraction gratings are described analytically.In each pair,the gratings are identical and parallel to each other,whereas the distance between the gratings,the groove density and the angle of incidence are different in different pairs.It is shown that the compressor asymmetry does not affect the far-field fluence and on-axis focal intensity.The main distinctive feature of the asymmetric compressor is spatial noise lagging behind or overtaking the main pulse in proportion to the transverse wave vector.This results in a degraded contrast but reduces beam fluence fluctuations at the compressor output.Exact expressions are obtained for the spectrum of fluence fluctuations and fluence root mean square that depends only on one parameter characterizing compressor asymmetry.The efficiency of small-scale self-focusing suppression at subsequent pulse post-compression is estimated.

Numerical and experimental study of bleed impact in multistage axial compressors

In this study,the influence of inter-stage bleeding on the compressor performance and inter-stage flow field of a multistage axial compressor is investigated by both experimental and numerical methods.The experiment is conducted on a four-stage low-speed axial compressor,and a specific computational model is built to simulate the experiment environment accurately.To illuminate the fluid mechanisms of bleeding effect in detail,both the experiment and the simulation are carried out twice,i.e.,in the first time,the mass flow rate upstream the bleed location is constant under different bleed rate conditions;while in the second time,the mass flow rate downstream the bleed location is constant under different bleed rate conditions.The results demonstrate that inter-stage bleeding has little influence on upstream compressor characteristics,and affects the upstream flow field only in the rear half of the stator.The bleed effect on the downstream flow field is embodied in the variation of an incoming flow profile,an increase as the compressor inlet flow coefficient decreases.Therefore,such an effect is only significant on compressor characteristics at small flow coefficient conditions.In multistage compressors,the variation of compressor characteristics and flow field caused by inter-stage bleeding is the comprehensive result of the bleeding and the variation of the upstream working condition.In addition,the comparison between numerical and experimental results shows that the flow moves towards top half of span through the downstream rotor passage in the numerical simulation,whereas the trend of flow field variation with different bleed rates at the outlet of the downstream rotor and stator is the same with that at the inlet of the downstream rotor in the experiment,which means that the numerical method has overestimated the radial mixing intensity of the flow.

Assessment of advanced RANS turbulence models for prediction of complex flows in compressors

Reynolds-Averaged Navier-Stokes(RANS) Computational Fluid Dynamics(CFD) has been widely used in compressor design and analysis. However, reasonable prediction of compressor flow and its impact on compressor performance remains challenging. In this study, Menter’s Shear Stress Transport(SST) model and its variants, as well as the ω-based Reynolds stress model(Stress-BSL) are assessed. For a single rotor(Rotor 67), under the peak efficiency operating condition, all studied turbulence models predict its performance with reasonable accuracy;under the off-design conditions, SST with Helicity correction(SST-Helicity) shows superiority in predicting the effect of flow on the spanwise distribution of aerodynamic parameters. For Darmstadt’s 1.5-stage transonic axial compressor, SST-Helicity outperforms SST, SST with the Quadratic Constitutive Relation(SST-QCR) and Stress-BSL in predicting the performance as well as the spanwise distribution of aerodynamic parameters. At the design rotating speed, the stall margin given by SST-Helicity(20.90%) is the closest to the experimental measurement(24.81%), which is more than twice that by SST(8.71%) and 1.5 times that by SST-QCR(14.14%). This paper demonstrates that SSTHelicity model, together with a good quality and sufficiently refined grid, can capture the compressor flow features with reasonable accuracy, which results in a credible prediction of compressor performance and stage matching.

Early detection of rotating stallin axial flow compressors via deterministic learning:detectability analysis

Rotating stall and surge are two violent unstable phenomena of an aero-engine compressor.The early detection of rotating stall is a critical and difficult issue in the operation of a compressor.Recently,a deterministic learning based stall inception detection approach(SIDA)has been developed for modeling and detecting stall inception in aero-engine compressors.This paper considers the derivation of analytical results on the detection capabilities for the SIDA based on deterministic learning.First,by utilizing the input/output stability of the residual system,a detectability condition of the SIDA is presented,and how to choose the parameters of the diagnostic system is also analyzed.Second,based on the relationship between NN approximation capabilities and radial basis function(RBF)network structures,the influence of RBF network structures on the performance properties of the SIDA is analyzed.Finally,a simulation study is presented,in which the Mansoux-C2 compressor model is utilized to verify the effectiveness of the proposed SIDA.

Real-Time Instability Detection of Centrifugal Compressors Based on Motor Speed Measurements

Flow instability in the centrifugal compressor should be detected and avoided for stable and safe operation.Due to the popularity of electric centrifugal compressors,instability detection could be achieved by measuring motor signals instead of traditional aerodynamic signals.In this paper,the feasibility of instability detection by motor signals(i.e.rotating speed and phase current)was studied experimentally.The physical structure and control method of the electric centrifugal compressor were discussed to reveal the potential of instability detection by motor signals.Dynamic pressure signals and motor signals measured during unsteady experiments were analyzed in the time domain and frequency domain.Characteristics of these signals were then compared under different operating conditions to indicate the feasibility of instability detection by motor signals.Finally,the ability of Short-Time Fourier Transform(STFT)of rotating speed signals in real-time instability detection was discussed.Results showed that the rotating speed signal is a good alternate for instability detection in spite of signal distortion,while the phase current signal can only detect surge due to the low resolution of the controller.Based on the variations of the amplitude and frequency of rotating speed signals,the real-time instability can be captured accurately by STFT with a window size of 0.5 s.Besides,the interference caused by the controller can be removed by STFT.

Numerical and experimental investigation of quantitative relationship between secondary flow intensity and inviscid blade force in axial compressors

The secondary flow attracts wide concerns in the aeroengine compressors since it has become one of the major loss sources in modern high-performance compressors.But the research about the quantitative relationship between secondary flow and inviscid blade force needs to be more detailed.In this paper,a database of 889 three-dimensional linear cascades was built.An indicator,called Secondary Flow Intensity(SFI),was used to express the loss caused by secondary flow.The quantitative relationship between the SFI and inviscid blade force deterioration was researched.Blade oil flow and Computation Fluid Dynamics(CFD)results of some cascades were also used to cross-validate.Results suggested that all numerical cascade cases can be divided into 3 clusters by the SFI,which are called Clusters A,B and C in the order of the increasing SFI indicator.The corner stall,known as the strong corner separation,only happens when the SFI is high.Both calculations and oil flow experiments show that the SFI would stay at a low level if the vortex core at the endwall surface does not appear.The strong interaction of Kutta condition and endwall cross-flow is considered the dominant mechanism of higher secondary flow losses,rather than the secondary flow penetration depth on the suction surface.In conclusion,the inviscid blade force spanwise deterioration is strongly related to the SFI.The correlation of the SFI and spanwise inviscid blade force deterioration is given in this paper.The correlation could provide a quantitative reference for estimating secondary flow losses in the design.