RV减速器摆线针轮齿廓修形回差影响分析

针对RV减速器回差精度问题,建立了摆线针轮齿廓修形的回差精度数值分析模型,采用几何法求解各种常见修形方式产生的几何回差,同时考虑摆线针轮传动中的弹性回差,推导出摆线轮齿廓修形的回差影响公式,并讨论了同一摆线轮齿廓修形方式下不同的修形参数与同一修形参数下不同的修形方式对回差的影响,得出在同一修形量的条件下,等距加移距的组合修形方式的回差影响最小,移距修形的回差影响最大。对RV-40E型减速器样机进行试验验证,与传统回差公式相比较,文章推导的回差公式精度提高6%左右。     

基于变步长差分迭代方法的河道水面线计算

在计算天然河道水面线时，由于河道的不规则性，导致计算断面间距往往是不相等的。为此，依据水力学能量方程，建立了变步长差分迭代的水面曲线模型。该数学模型简单易行，适应性强，便于程序化实现。通过对河南省南部某河道治理工程水面线的推求验证，证明该方法可有效解决非等间距断面的水面线推求问题，且计算效率和精度较高，可为计算类似工程问题提供参考。     

Numerical Simulation of Dopant Diffusion for Laser-Doped Crystalline Silicon

In this paper, the nonlinear numerical simulation of pulsed laser melting of crystalline silicon and phosphorus dopant liquid-phase diffusion has been established by the finite element method implemented in ANSYS. The melt front behavior as a function of time is described. The experimental SIMS work is intended to be used to validate the numerical model. The numerical simulation result is in good agreement with the corresponding experimental data.     

Effect of nutmeg (Myristica fragrans) essential oil on the oxidative and microbial stability of cooked sausage during refrigerated storage

This paper examines the oxidative and microbial stability of cooked sausages, produced with the addition of 10 ppm (NO1) and 20 ppm (NO2) nutmeg (Myristica fragrans) essential oil. Instrumental parameters of color (CIE L*, CIE a* and CIE b*), Thiobarbituric acid-reactive substance (TBARS) values, microbial profile and sensory properties of aroma have been determined on the 1st, 30th, 45th, and 60th day of storage. Addition of the nutmeg essential oil had no effect on the color of cooked sausages. At the end of the storage, NO2 sausages had the best oxidative and microbial stability. TBARS values of NO1 and NO2 sausages were 1.21 mg MDA/kg and 0.95 mg MDA/kg, respectively, and were significantly lower (P < 0.05) compared to control (1.53 mg MDA/kg). Total number of aerobic mesophilic bacteria was lowest in NO2 sausages (78.3 cfu/g) and highest in control (185 cfu/g). After 45 and 60 days of storage, sensory properties of aroma of NO1 (4.21; 3.92) and NO2 sausages (4.39, 4.28) were better compared to those in control (4.07, 3.25). Hence, the addition of nutmeg essential oil in amount of 20 ppm can be successfully applied in order to extend the shelf life of cooked sausages.     

WSGG models for radiative heat transfer calculations in hydrogen and hydrogen-mixture flames at various pressures

Radiative heat transfer strongly influences pollutant emission prediction in combustion systems. In this work, the weighted sum of gray gas (WSGG) models have been developed for calculating radiative heat transfer in hydrogen and hydrogen-mixture flames. The total pressure effect on cut-off width of the Lorentz line profile is analyzed and properly considered in the line by line (LBL) calculations. Based on the LBL benchmark results, two sets of WSGG model correlations have been proposed for H₂O and its mixture with CO₂ at a molar ratio (Mr) of 3, representing the typical combustion products of the hydrogen and a hydrogen-rich mixture (e.g., 50% hydrogen and 50% methane). The WSGG models are applicable and accurate with a total pressure ranging from 1 to 60 atm. Partial pressure is explicitly applied as an independent variable in the model coefficients to account for its nonlinear effect on gas emissivity, which is particularly important for a participating gas medium with a large amount of H₂O at a total pressure below 5 atm. Detailed studies are carried out to solve radiative heat transfer in non-isothermal and non-homogeneous gas media at different conditions. Results show improvement over the existing WSGG models at the atmospheric pressure and have good agreement with LBL solutions under various conditions.     

Development and analysis of novel six-lobe helical rotors for hydrogen fuel cell vehicle roots blowers

This paper suggests a novel six-lobe Roots profile to improve the performance of Roots blowers in hydrogen fuel cell vehicles. Mathematical models for rotor profile generation and geometric characteristics are established. A working process simulation model for Roots blowers is developed based on the lumped parameter method and is verified by experimental results. The key profile parameters are discussed and optimized in views of geometric and thermodynamic performance. Case studies are conducted to reveal the detailed performance map difference between several design cases. Results show that a trade-off exists between the rotor cavity volume and adiabatic indicated efficiency for Roots blowers. The proposed profile broadens the design space of rotors in tooth height and achieves a flexible adjustment for the leakage through the blow-hole and contact line. As a consequence, compared to conventional Roots profiles, the proposed rotor profile achieves higher adiabatic indicated efficiency under the same rotor cavity volume.