1991 Vol. 6, No. 1

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2-E FORCING FUNCTION EFFECTS ON TURBOMACHINE GUST UNSTEADY AERODYNAMICS
Steven R.Manwaring, Sanford Fleeter
1991, 6(1): 2-8.
Abstract PDF(460KB) icon1622 icon484
Abstract:
To investigate the forcing function effects on the fundamental 2 E gust unsteady aerodynamic response of a multistage turbomachine blade row,a series of fundamental experiments are performed in an axial flow research compressor.The 2 E unsteady aerodynamic forcing function excitations are generated by both a circumferential inlet flow distortion and the wakes from airfoil type obstructions which are representative of an airfoil,strut,or probe excitation.
NUMERICAL OPTIMIZATION PROGRAM FOR DESIGNING CONTROLLED DIFFUSION COMPRESSOR BLADING
Liu Bo, Zhou Xinhai, Yan Ruqun
1991, 6(1): 9-12,89.
Abstract PDF(297KB) icon1900 icon488
Abstract:
A numerical optimitization design procedure has been worked out for generation of the Controlled Diffusion Airfoil(CDA)of axial-flow compressors.The cascade total pressure loss coefficient is chosen as an objective function.The numerical optimization design procedure is composed of four programs,i.e.,the program for optimization of the prescribed velocity distribution,the initial blade profile generation program,the program for compressible,inviscid flow computation and the program for inverse boundary layer computation.At first the initial blade shape is generated,then the design procedure can be used to optimize the initial blade profile at design and off-design conditions until the final shape of the blade is satisfactory.In order to demonstrate the feasibility of the procedure,the numerical optimization design program was carried out for a compressor stator blade at hub section with high loading and large flow turning angle.The designed cascade has been tested.The test data show that the flow at design conditions is shock-free.Compared with the conventional cascade,the Controlled Diffusion Airfoil(CDA)cascade designed can enlarge the incidence angle range,increase critical Mach number and strengthen the tail edge of the blade.Besides,the CDA cascade has much smaller losses and deviation angle than the conventional cascade.It is verified that the design procedure is feasible for the generation of the Controlled Diffusion Airfoils.
EXPERIMENTAL INVESTIGATION OF TURBULENT DRAG REDUCTION IN COMPRESS CASCADE
Miao Runtian, Wang Liangui, Gao Ge, Tang Zhiming
1991, 6(1): 13-16,89-90.
Abstract PDF(342KB) icon1867 icon369
Abstract:
Recent researches of theory and experiments indicate that turbulent drag is directly related to tiny coherent(organized)structure inside the turbulent boundary,and in turbulent flow field the flow drag of the specially designed non-smooth surface can be less than that of smooth surface.Based upon the above mentioned theory,six compressor cascades with different patterned surfaces have been experimented.The profile of the cascades was chosen from a stator vane of a reference compressor.The experiments have been performed in a near-sonic wind tunnel.The results obtained at the same Mach number as the reference compressor works indicate that the appropriate patterns on the surface improve the performances of cascades.Compared with the reference smooth cascade,the best one of six tested cascades raised the critical Mach number by 7 3 percent.The air flow deflection angle at the design conditions increased by 0 9°.Correspondingly,the deviation angle decreased by 0 9°.And maximum static compression ratio rised by 0 0177.The another one of the tested cascades obtained similar results.A brief analysis of the experimental results is also presented.
PREDICTION OF STALL MARGIN FOR MULTISTAGE AXIAL FLOW COMPRESSORS
Zhu Jiunqiang, Liu Zhiwei
1991, 6(1): 17-20,90.
Abstract PDF(311KB) icon1800 icon440
Abstract:
Two methods for predicting the onset of rotating stall in multistage axial flow compressors are provided in this paper.First,the semi-empirical criterion about the isolated blade row is extended to the analysis of the multistage axial flow compressors.The downstream condition of preceding stage is considered as the upstream one of next stage and similar calculation is made for every stage.By comparison of the flows for each unit at the onset of rotating stall,the stall margin of the multistage compressor can be determined.The results of prediction agree with the experimental data fairly well.Secondly,with the help of the unsteady two-dimensional incompressible flow model,the inception criterion of rotating stall for a double stages axial flow compressor is derived in detail according to a small disturbance stability theory.Characteristic equation is solved iteratively using a Newton-Raphson scheme.Some numerical examples have been predicted with the aid of the written computer codes.Good agreement between the analytical and experimental results indicates that the analysis is believable.The variations of damping factor under the different conditions are compared and the rate of loss variation is analysed as inlet relative airflow angle increases for each blade row.The above-mentioned two approaches both can be used to predict the stall margin for subsonic and transonic multistage axial flow compressors.
EFFECT OF HUB TREATMENT ON PERFORMANCE OF AN AXIAL FLOW COMPRESSOR
Du Zhaohui, Liu Zhiwei
1991, 6(1): 21-24,90-91.
Abstract PDF(338KB) icon1717 icon505
Abstract:
The hub treatment with a circumferential groove was tested on the stator hub and compared with the casing treatment over the rotor tip for a single stage axial flow compressor.The 3D flowfield at the downflow of stator and rotor blade rows,in particular its endwall flowfield,in optimum operating and near stall states were measured by a micro-five-hole probe.It was shown that stall margin can be improved not only for the single-stage(=2 96%),but also for the rotor(=2 79%),even if the onset of stall is at the rotor tip first.The reason is that the stall affected by treatment groove to retard the appearance of stall.Some initial researches have been made for improvement of performance of the single stage and rotor,as well as the relation between the rotor and stator.It is found that the trend in variation of the most performance parameters of the rotor with hub treatment is similar to that of isolated rotor with casing treatment.According to the analysis of downflow,a new flow phenomanon is clarified:the dangenous stall locates at the blade hub and near the pressure surface.The mechanism to extend stability for a hub treatment with circumferential groove is also considered.
CALCULATION OF THREE-DIMENSIONAL LAMINAR BOUNDARY LAYERS ON ROTATING BODIES
Zu Guojun, Chen Maozhang
1991, 6(1): 25-28,91.
Abstract PDF(313KB) icon1707 icon457
Abstract:
The three-dimensional boundary layer equations with rotation terms are formulated in general tensor form.The effects of rotation including p/y≠0 and its consequence have been investigated.The results show that in some cases it is essential to take p/y≠0 into account to obtain accurate boundary layer parameters.A new method to solve this equation system is proposed.The method has been verified through several examples,showing its effectiveness and applicability.
AERODYNAMICAL DESIGN FOR SMALL GASTURBINES
Shi Jing, Han Jianyuan
1991, 6(1): 29-32,91.
Abstract PDF(304KB) icon1640 icon369
Abstract:
The advanced small gasturbines feature small mass flow ratio,short vanes and blades with low aspect, high second flow and blade tip leakage losses,and low efficiency.According to the detail investigation on the advanced small gas turbines,some technical design approaches for improving the efficiency of a small gasturbine,such as vanes with meridional-plane contraction contour,compounded leaned vanes and blades,small blade shroud and soon.
INFLUENCE OF DOWNSTREAM DISTORTION ON PERFORMANCE OF AXIAL COMPRESSOR
Hu Jun, Tang Guocai, Zhang Huimin
1991, 6(1): 33-37,91.
Abstract PDF(345KB) icon1666 icon376
Abstract:
The development of a new method to predict the unstalled characteristics and the onset of flow instability is described for an axial compressor operating in a circumferentially distorted downflow.This method adopts the“semi-actuator disk”to replace the blade rows of the compressor and the downstream distorting component,and assumes the flow fields outside the disks to be two-dimensional,ideal,compressible and unsteady.The effects of total pressure distortion coefficient and spacing between the compressor and the distorting component on the performance of a compressor have been investigated in detail by means of this method.It is found that the losses of both pressure rise and axial flow coefficient at instability increase linearly with the distortion coefficient,this conclusion is similar to that for the inlet flow distortion.And the spacing has crucial effect on the losses of both pressure rise and axial flow coefficient too.
THROUGHFLOW CALCULATION IN AN AXIAL-FLOW COMPRESSOR STAGE USING AVERAGED NAVIER-STOKES EQUATIONS
Zhu Fangyuan
1991, 6(1): 38-40,94.
Abstract PDF(257KB) icon1595 icon394
Abstract:
In order to provide a calculation computing means of the throughflow considering viscous influence for the qausi-three-dimensional design method of the turbomachinery,we put forward the averaged N-S and the zero equations or two-equation models of the turbulent flow to model the viscous flow of the throughflow in the stage and multistage of the turbomachinery.The application of the zero-equation model of the turbulent flow is described.An effective method to handle the end wall conditions is presented;and then the results of the throughflow calculation in the stages of a tranaonic or subsonic axial compressor are given.The comparison of the computing results with the experimental data shows that the model and method provided are feasible and effective.
CYLINDRICAL CASE FATIGUE LIFE PREDICTION BY LOCAL STRAIN APPROACH
Shang Weijun, Liao Xuejun, Xu Tang
1991, 6(1): 41-45,92.
Abstract PDF(333KB) icon1863 icon396
Abstract:
A finite element elastic-plastic stress-strain analysis is completed for the cylindrical case with a hole.According to the stress-strain analysis the equivalent simulation members of thin plate with holes are designed to replace the cylindrical case in the fatigue life predictions and tests.The low cycle fatigue life predictions and tests have been accomplished with the local strain approach for the cylindrical cases and the equivalent simulation members.The results prove that the equivalent simulation is feasible.Finally the design criterion of the equivalent simulation members is found out.Therefore this work provides a basis for designing equivalent simulation members to replace the complex members in the low cycle fatigue life predictions and tests.
CSDT-RICCATI TRANSFER MATRIX INTEGRATION METHOD FOR TRANSIENT ANALYSIS OF NONLINEAR ROTOR-BEARING SYSTEMS
Gu Zhiping, Chen Songqi
1991, 6(1): 46-50,92.
Abstract PDF(349KB) icon1669 icon481
Abstract:
Based on the work of Chu and Pilkey,a new direct integration method for the transient analysis of nonlinear rotor-bearing systems is proposed,called Continuous-Space Discrete-Time(CSDT)-Riccati transfer matrix integration method. In this method,the transfer vector ｛f…｝ Trather than the previous ｛f…e｝ T is used with the aid of the Newmark generalized acceleration formulation;the accelerations of all stations,not the deflections,are computed by the Riccati transfer matrix method,in result the method's numerical instabilities are improved.The method sustains the advantages of the Riccati transfer matrix method,i.e.,it is staightforward,easy to be understood,very convenient to use,quite stable,and capable to reduce the computation time and memory space significantly.So,it is especially fit to calculate the transient response of large complex rotor-bearing systems containing nonlinear elements.The method is illustrated and tested for the transient response of an unbalanced flexible rotor incorporating squeeze-film damper without centralizing spring.The obtained results agree well with those of the lumped mass method.For comparison an numerical example of the transient response of the above system has been also computed,using the transfer vector｛f…e｝ T.The obtained results show that such an integration is unstable.The reason of the unstability is also analyzed in this paper.
A RESEARCH ON CRACKED FAILURES OF FIR-TREE SERRATION IN AEROENGINE TURBINE DISC
Yao Huaxing, Yan Shalin
1991, 6(1): 51-53,95.
Abstract PDF(244KB) icon1804 icon397
Abstract:
A lot of cracked failures of fir-tree serration accurred in the second stage turbine disc of a large numbers of certain types aeroengines in service.The characte of these cracks belongs to mechanical fatigue.In order to find out the cause for the cracked failure,the vibrating stresses of the second stage turbine blades on test bench and their vibrating strains in flight tests have been measured in the conditions of high temperature and high rotational speed.The measured data indicate that several resonance zones really exist in the second stage turbine blades of type A and B engines.Some methods for elimination of the cracked failures of fir-tree serration in the turbine disc are provided.According to the experiece in service,a modification of type B engine hase eliminated the cracked failures of fir-tree serration of turbine disc in its service life.
RELIABILITY ANALYSIS OF DIRECTIONAL SOLIDIFICATION BLADE
Lü Wenlin, Duan Zhenlong
1991, 6(1): 54-56,95.
Abstract PDF(269KB) icon1563 icon459
Abstract:
The stochastic Finite Element Method and Hasofer-Lind Method are adopted to analyse the reliablity influence of stochastic pressure field on the directional solidification blade.This method and program are verified by calculation of the Monte-Carlo Method.
A FLUX VECTOR SPLITTING EXPLICIT SCHEME AND SIMULATION OF 2-D NOZZLE'S PROPULSIVE JET
Shan Peng
1991, 6(1): 57-62,93.
Abstract PDF(435KB) icon1578 icon360
Abstract:
On the basis of two steps explicit methods,author investigates the application of the theory of Flux Vector Splitting(FVS)of J.L.Steger and R.F.Warming.Besides the simplified split flux vector formula,a new explicit scheme is proposed for solving hyperbolic differential equatione.It is a explicit two steps FVS scheme of second order accuracy.At first it was compared with MacCormack's scheme issued in 1972(MC72)in numerical computation.And finally a 2-D flow of a rectangular nozzle with its jet plume was analysed numerically by the present scheme.The results indicate some high performances of the present scheme:1.Numerical vibrations near the front surface of shock waves vanish.2.The scheme runs without artificial viscosity.3.It takes just as much time as MC72 takes to solve a flow field.The scheme features the higher inherent viscosity of the scheme compared with that of MC72.
AN ANALYTICAL STUDY OF COMPONENT MATCHING REGULARITY OF TURBOJET ENGINE
Liu Daozhi
1991, 6(1): 63-66,93.
Abstract PDF(1201KB) icon1493 icon401
Abstract:
Many off-design condition phenomena of a turbojet engine are related with the variation of incidence angles at front and rear compressor stages.Based on the component matching regularity,the simple and clear analytical equations of the variation of incidence angles at front and rear compressor stages under engine operating conditions have been derived.With these analytical equations,a series of the off-design condition phenomena in a low or high design pressure ratio engines or in an,axial,centrifugal or combined axial-centrifugal engines,all well as in a two-spool engines are analyzed systematically,their physical natures are clarified,and various off-design condition problems which may occur can be predicted in advance.
AN EFFICIENT 2D-GRID GENERATION APPROACH USING ARC-LENGTH AS A PARAMETER
Shi Zhouhe, Zhang Huimin, Wang Licheng
1991, 6(1): 67-69,95.
Abstract PDF(714KB) icon1532 icon463
Abstract:
A fast and efficient grid generation program has been developed for any two-dimensional configurations.In this scheme,the separate grids are generated in each zone with a high speed algorithm which makes the ratio of the coordinate increments satisfy a linear distribution along arc-length of a grid curve,and then they smoothly joined along the common boundaries to establish the grid for the complex configuration.The advantages of the scheme are as follows:First,the mesh lines have continuous slopes from one zone to another;Second,the degree of the mesh lines clustering can be well controlled by the distribution of the boundary points;And the third,the computational speed is ten and even several hundred times faster than the elliptic grid generation scheme which has been widely used nowadays.
A SIMILARITY AND INTEGRATION METHOD OF A RECTANGULAR JET
Zhang Zhengke, Jiang Zhengxing
1991, 6(1): 70-72,96.
Abstract PDF(246KB) icon1599 icon406
Abstract:
The similarity laws of a rectangular jet are summarized on the basis of the experimental data in literature.An integration method is also presented for calculating a constant-pressure,compressible rectangular jet to examine the stealth performance of the rectangular jet.The integration method gives a good prediction of the constant-pressure rectangular jet,and the calculated results agree well with the experimental data.A brief analysis of the stealth performance of the rectangular jet is described in the paper as well.
A REVIEW AND PROSPECT OF PULSATING COMBUSTION
Cao Chuanjun, Xu Dengfeng, Zhu Changhain, Ren Yue
1991, 6(1): 73-78,93.
Abstract PDF(399KB) icon1651 icon378
Abstract:
It's well known that pulsating combustion has the advantages in fuel saving,pollutant suppression,enhancement of combustion intensity and efficiency and increase of convective heat and mass transfer rates.The capital investment and operational costs of many systems and processes can be reduced if the pulsating combustion be applied.In this paper,the characteristics of the pulsating combustion are treated and a review with instructive comments on its application is given.The application of the fulsating combustion particularly in the areas of jet propulsion,gas turbine,boiler and heater,drying and ash cleaning is discussed.In the end,its prospects are also remarked.
EMBEDDED STRUCTURE OF RECIRCULATION ZONES IN COAXIAL DUMP COMBUSTOR WITH INNER SWIRL INLET
Yu Qiang, Liu Xingzhou, Situ Min, Hu Mengjue
1991, 6(1): 79-82,94.
Abstract PDF(289KB) icon1734 icon368
Abstract:
The new swirling chamber designed by combining swirlers with bluff bodies is considered in this paper.The cold flowfields in the coaxial dump combustor with inner swirl inlet were measured and investigated by using five-hole probes.It is found that when the flow ratio of the swirling chamber to the outer annular channel decreases and the expansion ability of outer annular flows toward the combustor wall is enhanced,a two-dimensional axisymmetrical central recirculation zone without tangential velocities occurs behind it in the dump combustor in addition to the swirling chamber recirculation zone.Both recirculation zones are embedded in each other.The swirling chamber recirculation zone not only tends to create the central recirculation zone,but also generates the suction which makes the latter bigger and stronger.Experimental results of combustion show that the high combustion efficiency is obtained as the embedded structure exists.
COMBUSTION CHARACTERISTICS OF A DOUBLE SWIRLER COMBUSTOR
Zhang Qingfan, Zhou Biao
1991, 6(1): 83-85,96.
Abstract PDF(235KB) icon1870 icon379
Abstract:
The combustion characteristics at atmospheric pressure for a co-axial double swirler combustor have been investigated.The results show that its combustion performances can be significantly improved by increasing properly swirl number for inner swirler,as outer and inner flows are counter-rotating;the annular recirculation zone is a good source for flame stabilization,which is a important factor for extenting the weak extinction limit;The temperature distribution at the exit section of the combustor can be controlled by varying fuel-air ratio of outer and inner swirling flows.
DEVELOPMENT OF A INTELLIGENT FORCE METER BY AUTOMATIC ELECTRO-MAGNETIC BALANCING
Jiang Zhi, Gao Ge, Ning Huang
1991, 6(1): 86-88,96.
Abstract PDF(244KB) icon1368 icon383
Abstract:
In wind tunnel measurement of surface drag a force meter with high sensitivity and accuracy is urgently needed.This paper reports the development of the automatically balancing force meter which is a new device not yet seen before.The design principle,software and hardware,and the application of this meter are presented in this paper.Its accuracy is 0 5%,repetition 0.1%,responce time 5ms,sampling period 100μs.

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