1987 Vol. 2, No. 4

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AEROACOUSTIC SIMILARITY PRINCIPLES AND THEIR EXPERIMENTAL INVESTIGATON
Gu Dawei, Zhong Fangyuan
1987, 2(4): 289-294,367.
Abstract PDF(606KB) icon1683 icon517
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The general similarity principles in aeroacoustics are studied so as to provide the theoretical basis for aeroacoustic model experimental investigation of jet engine, fan, compressor, propeller etc. The analysis of the characteristics of fundamental aerodynamic noise sources shows that any aeroacoustic phenomenon is a similitude structure phenomenon. The most important result of the study is the establishment of four similarity criteria of aeroacoustic field which are expressed in a suitable form for flow analysis. For the fundamental aerodynamic noise sources,the similarity criteria are the Mach number of the flow,the Strou-hal number of the fluctuating frequency of the aerodynamic noise sources, and the nondi-mensional source strength (q or F or 6)relating to the type of the source, respectively.The main aerodynamic noise sources in turbomachinery are the fluctuating forces of fluid flow acting on the solid surfaces. The analysis of fluctuating force spectra in the un steady flows both of the model and the prototype indicates that the fluctuating force spectra both of them expressed in Strouhal number are also similar provided their flows are entirely similar. In this case, the overall sound pressure levels and the noise spectra measured at geometrically similar points are completely identical when the noise spetra are represented in Strouhal number. The results of the further research on the effect of Reynolds number show that it is unnecessary to maintain the Reynolds number similarity rule if the Reynolds numbers in full-scale fan and model-scale fan are both greater than 4xl05, But in the model test for the purpose of aerodynamic noise research,the strict identity of the blade tip Mach numbers between the model fan and the prototype fan should be ensured even if the flow Mach numbers are very small.The aeroacoustic similarity principles are demonstrated by the experiments for similarity of noise characteristics between the full-scale and model-scale fans.
AERODYNAMIC DESIGN PROBLEMS OF PROPFAN
Liu Daozhi
1987, 2(4): 295-298,367.
Abstract PDF(491KB) icon1515 icon433
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The development of aerodynamic analytical methods of propfan is reviewed. The aerodynamicdesign procedures of propfan and the design philosophy of its supercritical airfoil sections are discussed. Some key points for propfan development are indicated.
ON AEROELASTICITY AND AEROACOUSTICS OF PROPFAN
Sun Xiaofeng, Hu Zongan
1987, 2(4): 299-302,368.
Abstract PDF(493KB) icon1554 icon512
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Aeroelasticity and aeroacoustics of propfan are two keys to development of propfan.The achievements in researches on these subjects are reviewed with the emphasis on the theoretical models and the related numerical techniques. Some comments and proposals for further researches on them are presented.
PERFORMANCE PREDICTION OF A PROPFAN
Tang Diyi, Liu Yumin
1987, 2(4): 303-306,368.
Abstract PDF(401KB) icon1777 icon418
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The airplane/engine performance matching of a propfan requires that the engine performancesare evaluated over the entire range of Mach numbers and altitudes. The problem of the critical engine sizing requirements is considered firstly, an aerodynamic model is then provided to estimate the propfan efficiency trend and to determine the pressure drop in each expansion unit under the off-design conditions. Based on this model, two curves,ηB = f(SHP/D2)and -ηBR = f(J), are recommended to reduce the propfan efficiency map, and a redistributioncurve of the generalized pressure ratio over each expansion unit is obtained. According to these curves the off-design performances of a propfan,inclusive of the flight, take-off, and throttle characteristics, are predicted.
AERODNYAMIC AND ACOUSTIC OPTIMIZATION IN PROPFAN DESIGN
Zhu Nianguo, Chen Maozhang
1987, 2(4): 307-311,368-369.
Abstract PDF(670KB) icon1541 icon407
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Integrated design is the main feature of advanced propfan design. From this point of view, methods adopted for aerodynamic and acoustic design of propfan are reviewed, commentson their application in propfan optimization are made, principles of selecting design parameters, such as power loading, number of blades, blade tip speed, airfoil section and shape of nacelle, are considered. The main objects of aerodynamic and acoustic optimization and the possible performance improvements obtained from the optimization are pointed out. The optimization of the blade tip sweep should be determined from both aerodynamic and acousticconsiderations, and the factors which should be taken into account in integrated or single optimization are indicated accordingly.
ELASTICITY MODEL FOR SCALING GAS TURBINE PERFORMANCE PREDICTION
Zhu Xingjian, W. F. O'Brien
1987, 2(4): 312-316,369.
Abstract PDF(511KB) icon1586 icon427
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Before a gas turbine is designed, many candidate designs with different values of designparameters must be studied. Calculation of design and off-design performances of proposedengines is needed, but actual component maps do not exist. In this paper, new scaling laws are developed and shown to produce component maps and estimates of new engine performanceswhich are predicted to be close to the actual values. This "elasticity"model is based on the fundamental operating principles of the components.
EFFECTS OF ALTERNATIVE FUEL COMPONENTS ON PERFORMANCES OF A GAS TURBINE COMBUSTOR
Wu Wendong, Sha Yingpu, Sun Xiuchan, Yang Jingshang, Zhang Yanan
1987, 2(4): 317-322,369.
Abstract PDF(539KB) icon1515 icon420
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The exchangeability of gaseous fuel for a gas turbine combustor was investigated experimentallyand analysed in terms of indices JH and Jj given in ref. (3).Experimental results show that the effects of the alternative fuel componenets on the combustorexit temperature profile and distribution factor are not significant. It is also found that the ratio of H/C affects the combustion efficiency quite notably provided the inlet air-flowis at nomal pressure and temperature, but this effect weakens when the pressure and temperature of the inlet airflow rise.A conclusion is made that the index Jj can be adopted to predict gaseous fuel combustionefficiency and thereby the exchangeability can be evaluated.
NONSYNCHRONOUS ORBITS IN A FLEXIBLE ROTOR-SQUEEZE FILM DAMPER SYSTEM
Zhu Changsheng, Feng Xinhai
1987, 2(4): 323-327,369-370.
Abstract PDF(624KB) icon1650 icon496
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The possibility and the regularity of occurrence of nonsynchronous orbits ard investigatedbased on experiments of a Jeffcott rotor-squeeze film damper(SFD) with/without a centralizingspring system. The influences of system parameters,such as radial clearance ratio, load length,unbalance and centralizing spring stiffness,on nonsynchronous orbits and the relationbetween nonsynchronous orbits and rotor vibration are studied. It is found that the centralizing spring is a very effective means to suppress the nonsynchronous ordit.The unbalanceof the rotor is a main cause for occurrence of the nonsynchronous orbits. 1/2 subsyn-chronous orbit can be observed no matter whether the bearing parameter is quite small or very large provided the unbalance of the rotor is large enough. In some cases,the subsynchronous orbits with many inter loops can be obtained. Analytical and experimental results are found in good agreement.
EXPERIMENTAL ANALYSIS AND MODIFICATION OF A WINDMILL FAN FOR PREVENTING FLUTTER
Song Zhaohong, Kong Ruilian, Wei Xinglu, Wang Yuwei
1987, 2(4): 328-331,370.
Abstract PDF(458KB) icon1757 icon409
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A Violent vibration emerged in the fan of a 50W wind-driven generator and caused manycracks at its surface as the velocity of wind reached about 8-10m/s. Some of the fans even broke down near the root(about J/3 length to root). Theoretical and experimental analysesof the faults show that the violent vibration is caused essentially by flutter due to flow -induced vibration. Therefore, the fan was modified into two new types (FD-1 and FD-2) to prevent the forced vibration and flutter. According to the flutter theory,the attack angle of the original fan was changed and its weight center was moved ahead so that the modified fans possessed enhanced natural frequence and decreased reduced velocity.The modified fan FD-1 was investigated by testing on the running car. The windmill generator with this fan started smoothly and ran very well. When the velocity of wind was about gm/3, its maximum power was about 74W,nearly 1.5 time of the original. No flutter phenomenon occured.
MODEL SIMPLIFICATION FOR A MARINE GAS TURBINE PROPULSION SYSTEM
Ni Weidou, Lu Siqing
1987, 2(4): 332-335,370.
Abstract PDF(421KB) icon1415 icon477
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Simplification of the mathematical model for a marine gas turbine propulsion system is studied by modal analysis,and selection of remained state variables in the order-reduced modelis considered. The dynamical characteristics of the system are evaluated according to the relationship between the state and the modal variables. The ratio of the output variation to input variation is obtained from the sensitivity snalysis, and then the state vaviables to be remained are determined. The modal variables are adopted to simplify the model,finally they are reduced to remained state variables. Numerical evulation show that this order-reduced model is much better than the simplified model obtained directly from the state equations.
A UNITED OPTIMUM METHOD FOR AN AXIAL TURBINE STAGE
Zou Zixiang, Yuan Ding, Li Xaoling
1987, 2(4): 336-341,371.
Abstract PDF(604KB) icon1751 icon405
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A united optimum method for designing an axial turbine stage is provided which combinesthe blade geometry optimization with the optimization of meridian passage according to the blade twist. The physical models,mathematical expressions and procedures for optimum selection of the blade geometry, meridian passage and its twist are described respectively, and then a united procedure is proposed. A numerical example has been calculated with this procedure.In the result,this method is proven of both theoretical and practical values and may furnish the basis for CAD of a turbine stage.
EFFECT OF BIMODAL AP PARTICLE SIZE DISTRIBUTION ON ALUMINUM COMBUSTION IN PROPELLANTS
Li Shufen, Jin Leji
1987, 2(4): 342-347,371.
Abstract PDF(619KB) icon1550 icon381
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A Series of researches on degree of aluminum agglomeration and combustion in propel-lants have been completed experimentally. The results show that AP particle size distribution is an important factor effective on aluminum combustion in propellants. It is found that the smaller AP particles are, the less the possibility of aluminum agglomeration is. This conclusionsupports the "Pocket Model", submitted by N. S. Cohen and is consistent with the results calculated with empirical formulas. The effect of bimodal AP particle size distributionis elaborated in this paper. It is suggested that the most suitable content of fine AP particle in the composition of propellants be about 40%. The result is helpful to the compositiondesign of new propellants.
PREDICTION OF THE FLAME FRONT IN AN AUGMENTOR WITH SWIRLING FLOW
Tan Haoyuan, Guo Ningqun
1987, 2(4): 348-349,371-372.
Abstract PDF(340KB) icon1731 icon523
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A computing program has been worked out for prediction of the flame front in a swirl augmentor. The positions of flame front and the coefficients of pressure loss have been calculatedfor a variety of swirl angles. The results of the analysis indicate that the ratio of the length of flame front to the diameter of augmentor equals 1.2 (L/D=1.2) when the swirl angle of 45° is selected. The coefficient of pressure loss in the swirl augmentor is not larger than that of a conventional afterburner. There is no obvious effect of pressure on the position of flame front.
MEASUREMENT OF RESIDUAL TIME OF GAS IN RECIRCULATION ZONE BEHIND FLAMEHOLDERS
Jiang Leiyong, Zhang Xunan
1987, 2(4): 350-351,372.
Abstract PDF(300KB) icon1548 icon407
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An instrument has been developed which provides sensitive and reliable measurement of the residual time of gas in the recirculation zone behind flameholders with flame. The experiments with this instrument show that the mean residual time is inversely proportional to the upstream velocity.
FUEL CAPTURE ON THE SURFACE OF V-SHAPED FLAMEHOLDER
Liu Zhigang, Wang Jiahua, Li Gaiqi
1987, 2(4): 352-354,372.
Abstract PDF(348KB) icon1528 icon409
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A new method for measuring the fuel capture on the surface of flameholder by means of V-shaped capture gutters is proposed. The relationship between fuel capture rate and individual parameters has been analysed. An empirical formula has been established. In the calculation, the concept of considering the edge of fuel droplet groups as reference trajectoryhas been set up. The fuel capture rate on the surface of V-gutter flameholder has been calculated and the results are in good agreement with the experimental data.
ENHANCEMENT OF HEAT TRANSFER IN TURBINE BLADE COOLING
Zhang Yuming, Gu Weizao, Liu Changchun
1987, 2(4): 355-357,372.
Abstract PDF(356KB) icon1476 icon519
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An experimental study on fully-developed turbulent air flow in rectangular passages with two opposite rib-grooved roughened walls has been performed to determine the effects of the rib-grooved pitch-to-height ratios on friction factor and heat transfer coefficients. A general method for predicting average friction factor and average Stanton number in rectangular ducts with two smooth and two opposite rib-grooved walls is developed. Experimentalresults show that the performance of the heat transfer in the passages with rib-groovedroughened walls is better than that in the passages with rib roughened walls at the same s/h. This work may be useful to internal cooling design of the gas turbine blade.
EXPERIMENTAL INVESTIGATION ON FLOW IN INTERNAL COOLING STRUCTURE OF TURBINE BLADE LEADING EDGE
Kang Ying, Qiu Xuguang, Guan Leiyang
1987, 2(4): 358-360,373.
Abstract PDF(370KB) icon1569 icon407
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The flow in the internal cooling structure of the leading edge of certain real turbine blade was simulated experimentally. It is found that about more than one third of the area of each impingement hole is actually useless, and the flow distribution of the film-cooling holes is remarkably affected by the relative location between the film-cooling holes and the impingement holes.
APPLICATION OF FFT TEST TECHNIQUE TO DYNAMIC CHARACTERISIIC ANALYSIS OF STRUCTURE FATIGUE TESTING MACHINE
Gao Jinghai, Li Hongren, Fu Peichen
1987, 2(4): 361-363,373.
Abstract PDF(327KB) icon1519 icon419
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In application of the FFT test technique, the wide band and sine exciting methods are used for dynamic characteristic analysis and modelling of electro-hydraulic Servo-System in the structure fatigue testing machine. As a result, it is very useful for optimum design, combined regulation and adjustment of the entire system.
EFFECT OF TRANSDUCER MASS ON DYNAMIC CHARACTERISTICS OF A REAR BEARING-CASE SYSTEM
Wen Weidong, Chen Wujie, Tian Shufang
1987, 2(4): 364-366,373.
Abstract PDF(338KB) icon1331 icon411
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An equivalent method of resonant frequence is provided to determine the magnitude of the required extra mass when an acceleration transducer is applied to measuring the vibrationsof an engine instead of velocity transducer without changing the original technical specifications.The effect of the transducer mass on the dynamic characteristics of the rear bearing-case system is investigated.The experiments show that the first several orders of the resonant frequences and displacement mobility peak values vary to a great extent because of great difference between two transducer masses when the velocity transducer is replaced by the acceleration transducer in measuring the vibrations of the system.
JOURNAL OF AEROSPACE POWER Published quarterly by The Chinese Society of Aeronautics and Astronautics
Mr.WANG ZHENHUA
1987, 2(4): 384-384.
Abstract PDF(128KB) icon1559 icon392
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The Journal of Aerospace Power is a leading publication of its kind in China devoted to the advancement of the science and technology of aerospace power.It provides a common medium through which academic and industrial researchers and designers can communicate results, review progress and identify requirements for further work in this increasingly significant field.

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