Surface Recrystallization in Nickel Base Single Crystal Superalloy DD6

The samples of single crystal superalloy DD6 are grit blasted and then heat treated either with the standard heat treatment procedure or in the temperature range of 1 000-1 250 °C for 4-16 h at vacuum atmosphere, then the recrystallization behavior of DD6 alloy is investigated. The results show that the equiaxed recrystallization grains form in the γ phase region where the as-cast γ′ phases have been dissolved completely, and cellular recrystallization forms in the region where the as-cast γ′ phases have been dissolved partially. The cellular recrystallization area consists of cellular grains, and the cellular grain consists of cubic γ′ phase, lamellar γ′ phase and γ+γ′ The coexistence of the equiaxed recrystallization zones and cellular recrystallization zones is a recrystallized characteristic of the cold worked single crystal samples which are heat treated at a temperature lower than the solution temperature. When the heating temperature is higher than 1 150 °C, with the increase of heat treating temperature, the equiaxed recrystallization zone expands, whereas the cellular recrystallization zone shrinks. All the deformed regions are consumed by equiaxed recrystallization after annealing at solution temperature.     

Experimental investigation on static/dynamic characteristics of a fast-response pressure sensitive paint

An optical-based technique using Pressure-Sensitive Paint(PSP) is a promising method to measure the distribution of surface pressure on an aerodynamic model. The static and dynamic characteristics of a fast-response PSP that is developed in the Chinese Academy of Sciences(CAS)are analyzed and tested to serve as the basis for experiments on unsteady surface measurement using a fast-response PSP. Two calibration systems used for this study are set up to investigate the temperature dependency, response time, and resolution. A data processing method, used for dynamic data, is analyzed and selected carefully to determine the optimum signal. Results show that the fastresponse PSP can be used normally at temperatures from 25 ℃ to 80 ℃. The effect of temperature on the accuracy of the measurement must be considered when temperatures are beyond the temperature range of 30–40 ℃. The dynamic calibration device with a solenoid valve can achieve a pressure jump within a millisecond order. The resolution is determined by the signal-to-noise ratio of the photo-multiplier tube. Results of the measurement show that the response time of the PSP decreases with a large pressure variation, and the response time is below 0.016 s when the pressure variation is under 40 kPa.     

直射式气动雾化喷嘴对燃烧室性能的影响

为了深入分析燃油喷嘴对燃气轮机燃烧室性能的影响，针对燃气轮机燃烧室中的直射式气动雾化喷嘴开展了数值模 拟，获得了气流流量、燃油流量和气液比对雾化性能的影响规律，喷嘴的雾化性能参数包括雾化粒径和雾化锥角。结果表明：气液 比和气流流量对该型喷嘴的雾化性能有显著影响，燃油流量对雾化性能的影响较小；气液两相间相对速度是影响该型喷嘴雾化性 能的决定因素，相对速度增大有利于减小雾化粒径，并增大雾化锥角；气流流量和气液比的增大均有利于雾化粒径的减小，燃油流 量的增加将使雾化粒径增大；增大气流流量、气液比和减小燃油流量均可使雾化锥角增大；该型喷嘴的雾化锥角变化范围为 30.12°～41.24°，雾化粒径变化范围为131.46～ 186.52 μm。喷嘴可实现在较小的雾化锥角变化范围内获得较宽的雾化粒径变化， 以此匹配燃气轮机燃烧室不同工作状态，具有较高的实用价值。     

Numerical investigation on flow and heat transfer characteristics of supercritical RP-3 in inclined pipe

Numerical simulations of flow and heat transfer to supercritical RP-3 through the inclined tubes have been performed using LS k–e model embedded in Fluent. The physical properties of RP-3 were obtained using the generalized corresponding state laws based on the fourcomponent surrogate model. Mass flow rate is 0.3 g/s, system pressure is 3 MPa, inlet temperature is 373 K. Inclination of the inclined pipe varied from -90° to 90°, with heat flux varied from 300 k W/m~2 to 400 kW/m~2. Comparison between the calculated result and the experimental data indicates the range of error reasonable. The results of ±45° show that temperature inhomogeneity in inclined pipe produce the secondary flow in its cross section due to the buoyancy force. Depending on the strength of the temperature inhomogeneity, there will be two different forms of secondary flow and both contribute to the convective heat transfer in the pipe. The secondary flow intensity decreases when the inhomogeneity alleviates and thermal acceleration will play a leading role. It will have a greater impact on the turbulent flow to affect the convective heat transfer in the pipe. When changing the inclination, it affects the magnitude of the buoyant component in flow direction. The angle increases, the buoyancy component decreases. And the peak temperature of wall dominated by the secondary flow will move forward and increase in height.     

A multi-parameter model of heat treatment process for soft magnetic materials on performance of HSERs

Material properties play an important role in the performance of electromagnetic mechanism. For an aeronautic Hermetically-Sealed Electromagnetic Relay (HSER), more than 50% parts are made of soft magnetic materials. Therefore, the performance of soft magnetic materials directly determines the static and dynamic characteristics of the HSER. Based on the theory of crystal recrystallization, this paper analyzes cold extrusion and heat treatment in the processing of soft magnetic materials, simulates the grain change process of an armature at different heat treatment temperatures, establishes a correlation model of temperature, grain size, and magnetic energy, and verifies results by scanning electron microscopy. Results of heat treatment temperatures from 800 °C to 920 °C are obtained and compared. A sample soft magnetic material after heat treatment at different temperatures has the largest difference in the initial magnetization range, up to 22%. In order to verify the fluctuation of the overall output characteristics of an HSER caused by the difference between soft magnetic materials, a static and dynamic analysis model of a typical HSER is established, and the accuracy of the model is verified by a set of actual test system. The difference of dynamic characteristics under different heat treatment temperatures is nearly 3%.     

涡产生器倾角对换热器内流动与换热特性的影响

为优化涡产生器强化传热的性能,通过改变三角翼式涡产生器的倾角,数值分析了倾角变化对板式换热器通道内流动与换热特性的影响,倾角变化范围为-30°～30°。获得了不同倾角下通道内的纵向涡、涡量分布,换热及阻力特性。结果表明涡产生器倾斜方向对流动与换热的影响不同,存在最佳的涡产生器倾角-10°,使得换热通道内涡产生器强化换热的性能最优;改变倾角可进一步提高涡产生器的强化传热性能,不同倾角对应努塞尔数和热性能评价因子间的最大差值分别达到8.9%和5.7%。     

Letter to Editor-electrolysis heat

The letter refers to the Toby Grotz's paper “Novel Means of Hydrogen Production Using Dual Polarity Control” and Waiter Russell's “Experiments with Zero Point Energy” presented at the 27th IECEC in San Diego in 1992. Commercial air to air heat pumps typically exhibit a COP, coefficient of performance, of 1.5, which means they deliver 1.5 units of thermal energy for each 1.0 units of electrical energy input. It is more likely that these 'Zero Point' effects are the electrical analogue of a mechanically powered vapor compression refrigeration cycle. The electrolyzer phenomenon reported by Grotz and others, if true, is a heat pump. Another commercial example of an all electrical, non-mechanical, refrigeration cycle heat pump are the in-room refrigerators in Japanese hotels, which utilize the reverse thermoelectric effect. Readers are reminded that the so-called “Zero Point Effect” is not producing more energy than is supplied to the systems, just that the COP mechanism is not yet understood in this case. The editor's response to the unexplained heat release during electrolysis is presented. He describes the experiment which was carried out with electrolysis currents ranging up to 75 amperes. For each temperature rise the resistance heating required more power than did the electrolysis process. The electrolysis had even delivered additional power in the fuel value of the released hydrogen, which was dissipated into the air. The authors calculated that making a gallon of such water would release the energy equivalent of 30 gallons of gasoline     

Hot deformation behavior and microstructure evolution of the laser solid formed TC4 titanium alloy

Hot compressive experiments of the laser solid formed (LSFed) TC4 titanium alloy were conducted at a wide temperature range of 650–950 °C and strain rate of 0.01–10 s⁻¹. The Arrhenius-type constitutive models of the LSFed TC4 alloy were established at the temperature range of 800–950 °C and of 650–800 °C, respectively. The average relative error between the predicted stresses and experimental values in those two temperature ranges are 10.4% and 8.3%, respectively, indicating that the prediction models constructed in this paper are in a good agreement with experimental data. Processing maps were established by the principle of dynamic materials modeling on the basis of the data achieved from the hot compression experiments. The processing parameters corresponding to the stable and unstable regions of material deformation can be determined from the processing maps. The microstructure evolution of the stable and unstable regions of the samples after tests were observed. Finally, the effect of hot compressive parameters on the microstructure were investigated to research the dynamic recrystallization and the texture of the deformed LSFed TC4 alloy.     

点火参数对煤油活塞发动机燃烧影响的数值模拟

为了了解点火参数对某2冲程航空活塞煤油发动机燃烧及温度场的影响,利用GT-Power和Fire软件对该发动机整机及燃烧室分别建立了仿真模型,选取扭矩、功率以及缸压数据验证了该模型的正确性,并对发动机在6000 r/min、全负荷工况下的燃烧和温度场分布等特性进行分析.结果表明:当点火时刻由335°CA变化至331°CA时,缸内混合气燃烧放热量增多,放热率峰值增大,放热率峰值对应曲轴转角的提前量变大,燃烧放热速率加快,混合气温度和压力上升变快,高温区范围增大;当点火能量由28.02 mJ增加至46.73 mJ时,双火花塞附近的温度升高,火花塞点火产生的火核尺寸增大,缸内燃烧温度与压力升高,燃烧放热速率加快,缸内高温区分布范围增大.     

吸热型碳氢燃料热沉的测定

介绍了一套自制的热导式高温量热系统,热量常数可用电标定法测定。用此仪器可测定各种吸热型碳氢燃料在各种条件下的热沉,用于吸热型碳氢燃料的筛选,为吸热型碳氢燃料的研究提供可靠的热化学数据。用这套装置测定了两种吸热型碳氢燃料在７００°Ｃ的热沉,与文献值接近。     

TC11钛合金的组织及塑性与其断裂韧性及裂纹扩展速率的关系

研究了TCll合金的组织及拉伸塑性(ψ)与断裂韧性(K_(IC)及裂纹扩展(da/dN)的关系。指明:K_(IC)及da/dN与ψ的关系取决于合金的组织类型。对片状组织及等轴组织进行了具体分析。     

Huygens Probe Aerosol Collector Pyrolyser Experiment

ACP's main objective is the chemical analysis of the aerosols in Titan's atmosphere. For this purpose, it will sample the aerosols during descent and prepare the collected matter (by evaporation, pyrolysis and gas products transfer) for analysis by the Huygens Gas Chromatograph Mass Spectrometer (GCMS). A sampling system is required for sampling the aerosols in the 135'32 km and 22'17 km altitude regions of Titan's atmosphere. A pump unit is used to force the gas flow through a filter. In its sampling position, the filter front face extends a few mm beyond the inlet tube. The oven is a pyrolysis furnace where a heating element can heat the filter and hence the sampled aerosols to 250 °C or 600 °C. The oven contains the filter, which has a thimble-like shape (height 28 mm). For transferring effluent gas and pyrolysis products to GCMS, the carrier gas is a labeled nitrogen ¹⁵N₂, to avoid unwanted secondary reactions with Titan's atmospheric nitrogen. Aeraulic tests under cold temperature conditions were conducted by using a cold gas test system developed by ONERA. The objective of the test was to demonstrate the functional ability of the instrument during the descent of the probe and to understand its thermal behavior, that is to test the performance of all its components, pump unit and mechanisms. In order to validate ACP's scientific performance, pyrolysis tests were conducted at LISA on solid phase material synthesized from experimental simulation. The chromatogram obtained by GCMS analysis shows many organic compounds. Some GC peaks appear clearly from the total mass spectra, with specific ions well identified thanks to the very high sensitivity of the mass spectrometer. The program selected for calibrating the flight model is directly linked to the GCMS calibration plan. In order not to pollute the two flight models with products of solid samples such as tholins, we excluded any direct pyrolysis tests through the ACP oven during the first phase of the calibration. Post probe descent simulation of flight results are planned, using the much representative GCMS and ACP spare models. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal stability improvement of sprayable fast-responding pressure-sensitive paint for measurement above 100 °C

The thermal stability of sprayable fast-responding Pressure-Sensitive Paint (fast PSP) was investigated to explore the possibility for application in turbomachinery and hypersonic research with temperature above 100 °C. The first part of the study focused on a widely-used Polymer Ceramic PSP (PC-PSP). The effects of thermal degradation on its key sensing properties, including luminescent intensity, pressure sensitivity and response time, were examined for a temperature range from 60 to 100 °C. Severe degradation in intensity and pressure sensitivity was found as temperature reached 70 °C or higher, which would cause failure of PSP application in these conditions. Subsequently, a fast-responding Mesoporous-Particle PSP (MP-PSP) was developed which did not show degradation effects until 140 °C. The greatly improved thermal stability of MP-PSP was attributed to: selection of polymer with higher glass transition temperature (polystyrene) to delay the saturation effect of oxygen quenching as temperature increased; porous and hollow structure of particles for luminophore deposition that minimizes polymer–luminophore interaction. This new paint formulation has significantly raised the upper temperature limit of fast PSP and offers more opportunities for applications in harsh environment.     

进气角度对旋转盘冷却效果的影响

为了研究不同的预旋角度对高位进气转静系旋转盘冷却与换热特性的影响,分别在三种预旋进气角度(0°,15°,30°)下对转盘的冷却效果进行了试验。通过试验,得到了每种预旋角度下的温度分布、盘面局部努赛尔特数分布、盘面平均努赛尔特数、转盘无量纲总体平均温度和转盘无量纲径向平均温差等参数。试验结果显示:高位垂直进气的冷却效果最好,预旋15°次之,预旋30°最低。并且流量变化对转盘的冷却效果影响较大,而转盘旋转影响较小。     

真空环境中多层隔热材料的隔热性能

通过对一典型多层隔热材料在真空环境下的系列隔热性能实验和分析,分析了多层隔热材料层间温度差(Δt)的分布趋势,揭示了多层隔热材料在不同层间隔热性能的优劣特性及其变化规律。实验结果证明:多层隔热材料的层间温度差(Δt)变化呈U型分布趋势;外层隔热性能优于中间层的隔热性能,4层以内18层以外层间气流状态接近分子流,隔热性能较好,温度差(Δt)大;中间各层气流处于非稳态,隔热性能稍差,温度差(Δt)小;靠近加热板一侧层间温度差小于低温一侧。     

涡轮与冲压组合动力高温进气预冷特性

针对涡轮基冲压组合循环发动机中高温进气影响涡轮发动机性能的问题,开展实际某高空模拟试验进气预冷段的数值分析.基于欧拉-拉格朗日多相流方法解析气液两相热质传输过程,探索射流冷却对不同高空高马赫数进气条件时预冷段内温度和压力的沿程变化规律.结果表明,射流冷却对流场具有明显地温降效果.带有射流装置的预冷段内流动损失是以由黏性...     

Effect of Rhenium Addition on Isothermal Oxidation Behavior of Tribaloy T-800 Alloy

The effects of 4 wt% rhenium (Re) addition on isothermal oxidation behavior of Tribaloy T-800 alloy have been studied at 800 °C and 1 000 °C in air. At 800 °C, T-800 shows nonuniform oxidation between dendritic and eutectic areas. Re addition clearly promotes the nonuniform oxidation, leading to considerably higher mass gains than that of T-800 at this temperature. At 1 000 °C exposure, the thickness of scale on T-800 increases significantly, accompanied by severe scale spallation during cooling to room temperature. On the contrary, T-800Re shows a marked decrease of oxide growth rate compared to the linear one of T-800 at 1 000 °C. The scale adhesion is also improved with Re addition at this higher temperature. Therefore, the role of Re depends on the exposure temperature. Re addition gives high oxidation rate at 800 °C, however, the excellent oxidation resistance is obtained by the addition of Re at a higher temperature of 1 000 °C.     

周期性变截面微通道热沉内流体流动与传热特性

以去离子水为冷却工质,对周期性变截面微通道热沉内流体流动与传热特性进行了实验研究.获得了流体流过周期性变截面微通道热沉内的摩擦阻力系数、Nu数、不同热流密度下的加热膜温度、热阻和泵功的关系,并与传统直通道进行比较分析,结果显示周期性变截面微通道热沉由于流体冲击肋侧壁,增加了局部阻力,导致消耗的泵功增加,但换热能力却有了显著的提高,壁面温差减小,具有非常优越的换热性能,能够满足高热流密度微电子器件冷却的需要.      

Effects of flow parameters on thermal performance of an inner-liner anti-icing system with jets impingement heat transfer

The multiple jets impingement heat transfer is widely applied in the wing anti-icing system. It is challenging to apply the similarity criterion to carry out the anti-icing experiments due to the complex flow and heat transfer behavior. In the present study, the full-scale slat model is used to carry out anti-icing experimental researches in a 2 m × 3 m icing wind tunnel of China Aerodynamics Research and Development Center. The effects of icing parameters Liquid Water Content (LWC) and Median Volume Diameter (MVD) and hot air parameters (mass flow rate and temperature) on the thermal performance of an inner-liner anti-icing system with jets impingement heat transfer are studied. The effects of the experimental parameters are analyzed in detail by combining impingement and evaporation heat transfer mechanisms. The impingement hot air mass flow rate dramatically affects the heat transfer performance of the impingement stagnation region within the range of the experimental parameters. The temperature of impingement hot air and that of wing skin are approximately linear correlated. The experimental results show the effects of LWC and MVD on water film formation and runback ice accretion. The formation of water film is analyzed by an analytical method based on the wing skin temperature difference of dry and wet air conditions.     

电动燃油泵驱动电机浸油冷却性能数值模拟

为了研究电动燃油泵驱动电机浸油冷却性能,基于冷却流体及电机各部件3维模型,充分考虑各部件发热功率以及材 料属性等物理量的影响,采用有限体积法对电机流-热耦合场进行模拟仿真,分析不同边界条件对电机流场和温度场的影响。结 果表明：在最大冷却燃油流量以及电机最高功率下,流道的压力损失和电机的最高温度均能满足电动燃油泵的运行要求;随着冷 却流量增加或燃油粘度的增大,流道的压力损失增大,且在最大冷却流量下,燃油粘度每增大1 mm 2 /s,压力损失增大约2 kPa;电 机功率和入口温度对电机各部件温度的影响较大,各部件温升与燃油进口温度近似呈线性关系,而环境温度对电机温度场影响较 小。研究结果为电动燃油泵电机浸油冷却流道的设计与优化提供了理论依据。