Energy recovery by means of a radial piston expander in a CO2 refrigeration system

Natural refrigeration fluids as CO₂ represent a very promising alternative to hydrofluorocarbons (HFCs) but they generally entail lower COP values. The possibility of recovering the large throttling losses by using an expander could give a substantial contribution to the performance improvement. In this work, a reciprocating expander developed from a hydraulic motor was experimentally analyzed. Despite of the mechanical losses due to the different original application of the machine, the thermodynamic cycles showed very promising results with the adoption of this solution. The machine isentropic efficiency was 19%, while the indicated efficiency was 66%, showing a very interesting potential of the expander. Thus, by considering a reasonable value of mechanical efficiency about 65%, the isentropic efficiency would be around 40%. Consequently, the entailed COP potential improvement, compared to a refrigeration system with simple throttling valve is currently at 7.4%, while it might overcome 20%.     

A preliminary evaluation of the Groll rotary vane compressor

The principles of operation and design of the prototype of a novel design of vane compressor with significant advantages over the conventional sliding vane type are described. Its performance is given and compared to that of equivalent commercially available sliding vane and reciprocating compressors used in refrigeration systems. Its volumetric efficiency on average was 3% greater than that of the sliding vane compressor and 23% more than that of the reciprocating machine. The adiabatic efficiency was on average 15% greater than that of the sliding vane and about equal to that of the reciprocating compressor. Owing to its high rotational speed it is more compact than the reciprocating compressor. Since the vanes are rigidly retained about their axis of rotation they cannot chatter as in a sliding vane compressor. It is therefore smooth and quiet in operation and no mechanical faults were encountered in 432 h of operation.     

CO2跨临界膨胀机的开发与实验研究

作为自然工质,CO2制冷系统越来越受到关注,然而目前CO2跨临界循环研究面临的最大问题是如何提高系统效率,使之能与普通工质循环竞争。为降低CO2跨临界循环的节流损失,开发膨胀机代替节流阀是研究的重要方向。文中给出开发CO2滚动活塞膨胀机的依据,以及在设计过程中需解决的吸气控制系统、泄漏和摩擦等问题采取的措施,同时建立CO2跨临界循环系统带膨胀机系统的实验装置,并对CO2滚动活塞膨胀机进行实验研究,发现膨胀机的输出功与负载有关,同时得出膨胀机的最高效率可达到32％以上,进一步的改进工作仍在进行。     

A novel revolving vane compressor with a fixed-vane

This paper presents design improvements of a Revolving Vane (RV) compressor which significantly reduce the frictional losses. The original RV compressor has a vane that swivels during the operation. Though in general, the frictional losses of the RV compressor are significantly lower than most currently available rotary compressors, this swivel vane design has a disadvantage of relatively high vane side friction loss. The latter is caused by a high vane-side and slot contact force due to a high gas pressure differential force across the vane. In this paper, a new design concept has been introduced to totally eliminate the vane side friction loss caused by the gas pressure differential force across the vane. This is achieved by rigidly fixes the vane onto the rotor or the cylinder. This new design yielded two possible variants, each reduces the frictional losses by 18% and 41% and improves the mechanical efficiency from 93% to 94% and 96% respectively. In this paper, details analysis on the new design that leads to the improvement in performance are presented and shown. The analysis also reveals that the design with the highest mechanical efficiency comes with a small price of a higher instantaneous peak torque requirement.     

新型CO2超音速两相膨胀制冷循环的理论研究

本文提出了以Laval喷管为核心部件的超音速两相膨胀机的概念,构建了以天然制冷剂CO2为工质的超音速两相膨胀制冷循环模型并对其进行理想循环热力学分析和模拟计算研究。结果表明：超音速两相膨胀机入口压力、入口温度和旋流分离段出口压力均对系统制冷性能有影响;在空调温区工况,CO2超音速两相膨胀制冷循环COP为6.69,是现有制冷性能相对最优的CO2跨临界制冷循环COP的1.63倍,且大幅降低系统压力;气液分离时液相速度损失对系统制冷性能有影响,系统COP由9.56减至6.01,相对卡诺效率由0.95减至0.60,但仍然保持在较高水平。通过初步的热力学分析和模拟计算研究表明,新型CO2超音速两相膨胀制冷循环具有较好的原理可行性和发展前景。     

跨临界CO2滑片膨胀机的研究与开发

从结构设计到样机加工阐述一种滑片膨胀机的设计开发过程，并对开发的滑片膨胀机中摩擦、泄漏、膨胀功回收及轴封设计等几个重要的问题进行讨论。     

Study of the separation efficiency of a demister vane with response surface methodology

Numerical simulations of a demister vane with various geometries and operating conditions were performed to study the separation efficiency. The numerical solutions were carried out using commercial CFD code Fluent 6.1. A prediction model of the separation efficiency was obtained based on response surface methodology by means of the statistical software program Minitab V14. The results show that not only the vane spacing and flue gas velocity, but also vane height (including height of curve and upright region) and vane turning angles, play an important role in influencing the separation efficiency. Compared with some experimental and simulative conclusions, the results indicate that present prediction model can estimate the effects of different geometries and operation conditions on the separation efficiency, and can direct the optimum design of demisters.     

Improved component performance of vane pumps by ion-plated TiN coatings

Ion-plated hard and wear-resistant TiN coatings were applied in vane pumps and tested according to standardized tests (DIN 51389 and IP 281/77). A wear reduction by up to a factor of 400 for the coated parts was observed and the uncoated counterparts also showed a decrease in wear by up to a factor of 60. These significant results demonstrate that the application of hard and wear-resistant coatings by ion plating is not limited to tools; there exists a wide range of applications in the field of engineering parts and systems.     

Simultaneous absorption of NOx and SO2 from flue gas with pyrolusite slurry combined with gas-phase oxidation of NO using ozone

NO was oxidized into NO₂ first by injecting ozone into flue gas stream, and then NO₂ was absorbed from flue gas simultaneously with SO₂ by pyrolusite slurry. Reaction mechanism and products during the absorption process were discussed in the followings. Effects of concentrations of injected ozone, inlet NO, pyrolusite and reaction temperature on NO_x/SO₂ removal efficiency and Mn extraction rate were also investigated. The results showed that ozone could oxidize NO to NO₂ with selectivity and high efficiency, furthermore, MnO₂ in pyrolusite slurry could oxidize SO₂ and NO₂ into MnSO₄ and Mn(NO₃)₂ in liquid phase, respectively. Temperature and concentrations of injected ozone and inlet NO had little impact on both SO₂ removal efficiency and Mn extraction rate. Specifically, Mn extraction rate remained steady at around 85% when SO₂ removal efficiency dropped to 90%. NO_x removal efficiency increased with the increasing of ozone concentration, inlet NO concentration and pyrolusite concentration, however, it remained stable when reaction temperature increased from 20 °C to 40 °C and decreased when the flue gas temperature exceeded 40 °C. NO_x removal efficiency reached 82% when inlet NO at 750 ppm, injected ozone at 900 ppm, concentration of pyrolusite at 500 g/L and temperature at 25 °C.     

关于内压缩流程空分设备主换热器热端温差的讨论

分析了内压缩流程空分设备主换热器热端温差对膨胀空气量和高压空气流量及压力的影响,提出选取合适的主换热器热端温差,可以使得空分设备的总功耗达到最小;提出随着内压缩流程空分设备液体比例的增加,适当选取较小一些的主换热器热端温差是有利的;分析了气体膨胀机效率和使用全液体膨胀机对热端温差选取和高压空气压力的影响。     

二氧化碳转子式膨胀机的试验研究

为了对所研制的CO2膨胀机的运行特性和运行效果进行探索和研究，建立用于测试膨胀机性能的CO2跨临界循环水一水热泵试验台，在组态王环境下开发系统运行监控软件，实现试验数据的计算机采集与系统的运行监控。试验结果表明：所研制的CO2膨胀机的效率一般在30％～50％。膨胀机对CO2跨临界循环系统COP具有明显的提高作用，在一般工况下大约可以提高20％～40％，所以膨胀机技术是提高CO2系统性能的有效技术措施。     

Study of high-pressure air curtain and combined dedusting of gas water spray in multilevel ore pass based on CFD-DEM

In order to solve the problem of dust pollution caused by ore unloading in ore pass, this paper, taking Li Lou Mining as a case study, conducted the wind speed variation law in the fluid domain and the impact of the collision between the ore in the unloading process on the fluid to determine the key dust control point based on the CFD-DEM coupling software. By Fluent software, the air curtain dust-proof efficiency under the action of unloading airflow is analyzed, and the relationship between the dust-control wind speed and the impinging airflow is known. And an experimental model of gas water spray is established to analyze the effect of spray dust removal. By analyzing the impact airflow and dust migration caused by ore unloading and the effect of air curtain dust control through numerical simulation, it can be seen that when the ore discharging quantity M_o = 4000 kg, the dust production is mainly concentrated in the fourth middle section. By high-pressure air shield assisting dust removal, dust diffusion can be better controlled when the ratio of impact wind speed of ore pass wellhead (denoted as λ) to high-pressure air curtain wind speed (denoted as ζ) is at least 1:8. When the dust removal effect is optimal, the ratio δ of the water supply amount q_l and the gas supply amount Q_g is determined by the gas water spray dust control experimental platform.     

Sonochemical synthesis of PANI-BiVO4-GO semiconductor nanocomposite highly efficient visible-light photocatalytic performance

Abstract

Polyaniline/Bismuth Vanadate/Graphene Oxide (PANI-BiVO₄-GO) or BGPA composite was prepared by sonochemical deposition of bismuth vanadate-graphene oxide (BiVO₄) nanoparticles on the surface of polyaniline (PANI). The best photocatalytic degradation performance was obtained by 5wt% BGPA composites for MB, RhB, and SO dyes, which is approximately 4 times higher than that of 1% BGPA. Meanwhile, the photocatalytic stability of BiVO₄ was significantly improved by introducing PANI into the PANI-BiVO₄-GO composite. The dramatic promotion of the photocatalytic degradation performance and the photocatalytic stability can be attributed to the formation of a heterojunction free electron between PANI and BiVO₄-GO. The existence of those extra free electrons can dramatically enhance the efficiency of the photogenerated electrons, which accelerate the transfer of photogenerated holes from BiVO₄-GO to PANI, and therefore inhibit the self-oxidation of BiVO₄.     

Wrap of cylinder and its effect on main features of rotary vane compressor for automobile air conditioning system

The rotary vane compressor has been used in the automobile air conditioning system. One of the key factors of its design is the wrap of its cylinder. From the working principle of this type of compressor, it is explained in mathematics why the wrap is composed of four parts: arc of circle, main curve, and two segments of transit curves, and the conditions that the wrap needs to satisfy are derived simultaneously. At the same conditions, we compared to the gas force F_p, contact force F_nc of the blade head, the force acting on rotor by blades, and the suction volume V_s for three kinds of main curves. The wrap composed of trigonometric function can form the biggest value of V_s, while the least suction volume V_s will be reached as the cubic polynomial is taken. The wrap composed of trigonometric function forms the biggest absolute value of the gas force F_p and the middle peak value of the force acting on rotor by blades, while the least absolute value of the gas force F_p and the biggest contact force F_nc of blade head will be reached as the cubic polynomial is taken. The force acting on the rotor by blades takes the biggest peak value if the main curve is the ellipse curve. The frequency of the force acting on the rotor by blades is the same as the number of blades at the range of the crank angle from 0 to 180°.     

CO2跨临界制冷循环膨胀机的开发

开发CO2膨胀机代替节流阀是提高CO2跨临界循环系统性能系数的一个有效途径.根据目前空调制冷CO2膨胀机的研制状况,描述了CO2膨胀机研制过程中的难点,指出研究CO2膨胀机的关键在于解决摩擦和泄漏问题.对自行设计开发的两代膨胀机样机进行了实验研究,发现第二代膨胀机的运行效果明显好于第一代膨胀机.     

以毛细管为节流装置的CO_2小型热泵热水器实验研究

介绍以毛细管为节流装置跨临界CO2热泵热水试验系统。实验研究了不同气冷器进水温度下系统的COP及其变化、气冷器沿管长水温温升梯度变化。分析了不同环境温度下制冷剂充注量对系统高压侧压力的影响。可以得出:以毛细管做节流装置也可以得到较高的COP;气冷器水温在高温CO2进口段温升幅度最大;系统对环境温度的变化很敏感,环境温度较低时要想得到合适的高压侧压力,制冷剂的充注量要比环境温度高时多。     

天然气调压装置不可逆损失的比较与分析

高压长输天然气在进入城市燃气管网前需降压,透平膨胀机、涡流管、节流阀是典型的燃气调压装置。以[火用]概念为基础,以[火用]平衡为工具,对涡流管、节流阀、透平膨胀机三种燃气调压装置进行了全面的热力学分析。结果表明：透平膨胀机的过程[火用]损失最小,效率最高,显示出其在调压过程中的热力学完善性。     

Effect of O2 on NO removal by ammonia radical injection using one-cycle sinusoidal power source

NO reduction experiment was performed by injecting ammonia radicals, which were externally generated by flowing the NH₃ gas diluted with Ar gas through a dielectric barrier discharge with a one-cycle sinusoidal-wave power source. The discharge was intermittently formed between coaxial cylindrical electrodes with a space of 1.5 mm at an applied peak-to-peak voltage of 3-25 kV. The generated radicals were injected into simulation gas (NO/O₂/N₂). The simulation gas contained 0-5.6% O₂, and the effect of O₂ on NO_x removal was discussed. The minimum reaction temperature for NO reduction was low when simulation gas contained O₂. High O₂ concentration (O₂=5.6%) in simulation gas, high repetition rate to NH₃, and high applied power to NH₃ decreased NO removal efficiency.     

八次方定子曲线对叶片泵动态性能的影响

为了降低叶片泵在原油开采过程中的振动,应尽量消除其由于加速度突变而造成的运行冲击。通过推导八次方曲线方程,得到定子内腔过渡曲线的数学模型。采用MATLAB软件对过渡曲线进行拟合。为了验证该叶片泵的动态性能,设计了实验方案,进行叶片泵变速和变压实验。实验结果表明：在500 r/min转速下,扬程达到23.14 m,流量达到2.44 m3/h,满足了低速设计要求;叶片泵对外部压力负载有一定的要求,其最大值不能超过0.5 MPa,若超过此值,叶片泵将失去自吸能力;随着转速的提高,其流量和噪声增大;随着压力负载增大,流量呈先上升后下降的趋势,噪声总体呈上升趋势,但在压力负载大于0.25 MPa后上升有所缓慢,泵内流量逐渐趋近于0,此时泵的噪声主要来源于叶片与定子的摩擦。研究结果为减小叶片泵的振动和噪声以及叶片泵结构的进一步优化提供了参考。     

Development of TiSiN CVD process using TiCl4/SiH4/NH3 chemistry for ULSI anti-oxidation barrier applications

CVD-TiSiN may be promising material for O₂ diffusion-barrier films in ultra-large scale integrated (ULSI) circuit applications, especially for dynamic random-access memory (DRAM) capacitors. We developed a method for introducing Si into TiN, which is a common material used for diffusion-barrier films. TiSiN films were deposited by reacting TiCl₄, SiH₄, and NH₃ in a hot-wall CVD reactor. We measured TiSiN film deposition rates, composition, crystal structure, and resistivity as a function of SiH₄ partial pressure. Adding Si to TiN converts the TiN film structure from columnar grains to columnar-free structure films, thereby effectively removing the diffusion paths for O₂. The resistivity of TiSiN films was increased by adding SiH₄ to the reactant gas. With an increase in SiH₄ partial pressure up to P_siH4 = 0.8 Torr, the resistivity gradually increased, but for P_siH4 = 1.2 Torr, the phase present in the film was almost SiN and its resistivity jumped up. TiSiN film rapid thermal annealing was performed to evaluate the anti-oxidation performance at the temperature range from 400 to 600 °C in 100 Torr of O₂. For an increase the Si concentration up to 4.4 at.% improved anti-oxidation performance of TiSiN films. Flow modulation chemical vapor deposition (FMCVD) was used to create TiSiN films with low Cl concentration and improved anti-oxidation performance.