Methodology for spectral emissivity measurement by means of single color pyrometer

The application of non-intrusive optical devices, such as infrared pyrometers able to measure the temperature of surfaces, makes possible the evaluation of emissivity curve of the tested materials at different temperature values. In this paper the authors propose a methodology for the spectral emissivity measurement by means of a single color pyrometer providing a semi-empirical formula, obtained experimentally at CIRA’s laboratory. The semi-empirical formula allows to know the actual emissivity value of the sample’s surface for whatever emissivity value set up on the pyrometer. The agreement between the experimental emissivity and the emissivity predicted by semi-empirical formula was verified.     

Degradation and chemical change of longlife oils following intensive use in automobile engines

The paper researches the features and quality of longlife oils after the point of being recommended for replacement by the onboard computer. The longlife oils have their service life prolonged to 30 up to 50 thousand kilometres which is being monitored and evaluated by the onboard computer. The onboard computer then, on the basis of several parameters, modifies the interval to optimum value. Kinematic viscosity, TBN, the amount of soot, oxidizing and sulphating products, water, fuel, glycol and high antioxidant presence were measured. The results we obtained from the measurements do not correspond with the conclusions of onboard computers.     

Measuring the thermal conductivity of residue-free suspended graphene bridge using null point scanning thermal microscopy

Despite the importance of the accurate measurement of the thermal conductivity of graphene, deviations in previous data are still quite large due to the low signal-to-noise ratio in the measurement of graphene temperature, the uncertainties in the measurement of the heat dissipation, and the influence of the polymeric residues. Herein, we improve signal-to-noise ratio by using null point scanning thermal microscopy, which profiles temperature quantitatively with nanoscale spatial resolution (∼50 nm), independently of both the heat flux through the air and the variation of the sample surface properties. Also, we control and monitor the heat generation rate accurately by heating the suspended graphene bridge electrically. Furthermore, we prevent the disturbance of the thermal conductivity caused by the polymeric residues by using polydimethylsiloxane stamping method, which leaves much less residue than using polymethylmethacrylate. The thermal conductivity values of graphene, whose length and width are 3.6 and 5.52 μm, respectively, were measured as 2430 ± 190, 2150 ± 170, and 2100 ± 160 W/mK at the peak temperatures of 335, 361, and 366 K, respectively, with much smaller error range compared to the previously reported values. The measured values exceed the highest value (∼2000 W/mK at room temperature) obtained for graphite.     

Time–frequency interpretation of multi-frequency signal from rotating machinery using an improved Hilbert–Huang transform

The Hilbert–Huang transform (HHT) has proven to be a promising tool for the analysis of non-stationary signals commonly occurred in industrial machines. However, in practice, multi-frequency intrinsic mode functions (IMFs) and pseudo IMFs are likely generated and lead to grossly erroneous or even completely meaningless instantaneous frequencies, which raise difficulties in interpreting signal features by the HHT spectrum. To enhance the time–frequency resolution of the traditional HHT, an improved HHT is proposed in this study. By constructing a bank of partially overlapping bandpass filters, a series of filtered signals are obtained at first. Then a subset of filtered signals, each associated with certain energy-dominated components, are selected based on the maximal-spectral kurtosis–minimal-redundancy criterion and the information-related coefficient, and further decomposed by empirical mode decomposition to extract sets of IMFs. Furthermore, IMF selection scheme is applied to select the relevant IMFs on which the HHT spectrum is constructed. The novelty of this method is that the HHT spectrum is just constructed with the relevant, almost monochromatic IMFs rather than with the IMFs possibly with multiple frequency components or with pseudo components. The results on the simulated data, test rig data, and industrial gearbox data show that the proposed method is superior to the traditional HHT in feature extraction and can produce a more accurate time–frequency distribution for the inspected signal.     

Stability of combustion waves in the Zeldovich–Liñán model

In this paper we investigate the stability of the premixed combustion waves in the Zeldovich–Liñán model in the adiabatic limit in two spatial dimensions. It is shown that either wave or cellular instabilities emerge for the Lewis number for fuel greater or smaller than one respectively. On the Lewis number for fuel vs activation energy parameter plane, the critical parameter curve for wave (cellular) instability is a monotonically decaying (increasing) function, which tends to one for large values of activation energies and grows infinitely (vanishes) as the activation energy is decreased to some critical value (zero). Decreasing the recombination parameter, which corresponds to the relation between the characteristic times of the branching and recombination reactions, makes the combustion waves more stable by increasing the region of parameter values for stable traveling wave solutions. Increasing the ambient temperature is demonstrated to have similar stabilizing effect on combustion waves. The effect of the varying the Lewis number for radicals is shown to be more complex and depends on the regime of recombination. It is demonstrated that as the critical parameter values for the onset of instability are crossed, either pulsating or cellular two-dimensional solutions emerge. The properties of these solutions are studied. A comparison of the results of this paper with known data from the literature for deflagration of hydrogen–oxygen mixtures is made.     

Ammonia-water mixture property code (AWProC) development,verification and Kalina cycle design for nuclear power plant

The improvement of thermodynamic efficiency of power plants is of great interest for the whole energy industry. The use of Kalina cycle has a great potential to improve the thermal efficiency of a nuclear power plant. This cycle uses a mixture of ammonia and water as working fluid. In this paper, we discuss the development of an Ammonia-Water mixture Property Code (AWProC). The estimation of the mixture properties are based on the Gibbs free energy functions. The code is verified and validated against experimental data available in the literature and REFPROP code. It is shown that AWProC can accurately estimate the thermodynamic properties of ammonia-water mixtures over a wide range of conditions, including high temperature and pressure regions. The code is then used to investigate the feasibility of applying the Kalina cycle to a typical Pressurizer Water Reactor (PWR) plant as an effective way to improve the plant efficiency. The fundamental of Basic-Kalina (B-K) cycle is described in detail firstly. Then, two modified configurations, Recuperation-Kalina (R-K) and Flash-Kalina (F-K) cycles respectively, are proposed for a typical 1000 MWe PWR. The simulation results indicate that the R-K type cycle can reach about 31.2% efficiency with simple equipment requirements, while the F-K type cycle can reach efficiencies up to about 34.8%, but at the expenses of a slightly more complex design. The present work demonstrates the applicability of the Kalina cycle as a way to improve the thermal efficiency of a nuclear power plant. This concept is meaningful for improving nuclear power plants economic and competitiveness.     

Robust dynamic inversion algorithm for the visualization in electrical capacitance tomography

Electrical capacitance tomography (ECT) is considered as a promising visualization measurement technique, in which reconstructing high-quality images is crucial for real applications. In this paper, a robust dynamic reconstruction model, which incorporates the ECT measurement information and the dynamic evolution information of a dynamic object, is presented. Under the considerations of the low rank property of an ECT image and the inaccuracies on the sensitivity matrix, the reconstruction model and the measurement data, an objective functional that fuses the ECT measurement information, the dynamic evolution information of a dynamic object, the spatial constraint, the temporal constraint and the low rank constraint is proposed. An iteration scheme that integrates the advantages of the fast composite splitting (FCS) algorithm is developed for solving the proposed objective functional. Numerical simulations are implemented to validate the feasibility of the proposed algorithm.     

Analysis of flux-base fins for estimation of heat transfer coefficient

Exact solutions are given for the transient temperature in flux-base fins with the method of Green’s functions (GF) in the form of infinite series for three different tip conditions. The speed of convergence is improved by replacing the steady part by a closed-form steady solution. For the insulated-tip case, a quasi-steady solution is presented. Numerical values are presented and the conditions under which the quasi-steady solution is accurate are determined. An experimental example is given for estimation of the heat transfer coefficient (HTC) on a non-rotating roller bearing, in which the outer bearing race is treated as a transient fin.     

Single phase transformerless wide range ac boost voltage regulator based on z-source network

This paper proposes a new type of voltage regulator based on single-phase z-source converter that compensates wide range voltage variations. This is not only capable of compensating variations at a much higher bandwidth but also boost the voltage level even twice that of input supply. The proposed system employs a pulse width modulation (PWM) z-source ac–ac converter along with a simple closed loop control. The input rms voltage can be sensed and divided by the desired value to find the instantaneous value of gain, which mathematically calculates the possible duty ratio of PWM switching signal based on the open loop characteristics of the converter. High speed IGBTs are used as bi-directional switch of the ac–ac converter and the circuit ultimately can easily and steadily maintain regulated voltage supply to the end user. The whole system operating principle and analysis are provided. Simulation results show the improvement of voltage disturbances both in voltage rise and fall conditions.     

基于生物质–太阳能气化的多联产系统模拟及分析

提出一种基于太阳能–生物质气化技术并用于生产甲醇和发电的多联产系统。利用塔式集热镜场聚焦产生的800~1 200℃高温热源来驱动塔式太阳能气化反应器中的生物质气化反应,产生的合成气经压缩后送至甲醇合成塔,而未反应的合成气送至燃气–蒸汽联合循环系统中用于发电。对该系统进行了热力学分析,同时研究各参数包括水蒸气流量和气化温度对系统性能产生的影响。结果表明,调整水蒸气流量和气化温度将改变合成气的组分,影响到系统的甲醇产量和发电功率,当水蒸气流量为50 kg/s时系统效率达到最高值49.48%。随着水蒸气流量和气化温度增加,太阳能热份额逐步提高,系统相对节省率同步下降,同时系统的生物质节省率维持在50%左右。研究成果为高效利用新疆等西部地区丰富的太阳能和生物质资源提供了新途径。