Conjugate heat transfer (CHT) analysis of electric motor cooling was performed, simulating both the standard and paperless stator designs, using the CFD software Simerics-MP+ to assess the predictive accuracy of the numerical simulations. The condition investigated involved the motor operating at 14,000 RPM. This high rotor speed was modeled using a novel hybrid approach for mesh rotation to make the problem more tractable. Oil and air, the two immiscible fluids, were modeled using the explicit interface-capturing Volume of Fluid (VOF) method. The traditional CHT approach is computationally expensive for electric motor cooling applications due to the heat transfer time scale differences between the fluid and the solid. Temperature changes in solids occur over a much slower time scale owning to their higher thermal inertia compared to fluids. Therefore, we model the fluid and solid domains separately and use a mixed-time scale approach to exchange the heat transfer data between them. The heat transfer analysis conducted here is a quasi-steady state simulation. Numerical results for both the standard and paperless stator design were compared against the thermocouple measurements from test and showed very good agreement.

Modern gearboxes are meticulously engineered with three primary objectives: enhancing load-carrying capacity, minimizing noise, vibration, and harshness (NVH), and optimizing efficiency. Efficiency, in particular, holds paramount significance due to gearboxes’ substantial influence on energy consumption. One effective strategy for boosting efficiency involves curbing churning losses, stemming from the movement of oil within the gearbox housing. Computational fluid dynamics (CFD) techniques have emerged as invaluable tools for visualizing oil flow dynamics within gearboxes and pinpointing avenues for mitigating churning losses. In the context of electric vehicles (EVs), specifically battery electric vehicles (BEVs), extending their driving range is a top priority. Achieving this hinges on the design of an efficient gearbox. This study employs an oil/air multi-phase volume of fluid (VOF) method in a commercial CFD solver known as Simerics-MP+ to model the oil flow and churning losses within a single-stage gearbox. The model’s predictions are validated against previously published highspeed camera footage and measurements derived from the FZG noload power loss test rig’s single-stage gearbox. The simulation results underscore the potential of CFD simulations in providing an exceptionally detailed portrayal of oil flow behavior, while also aligning closely with experimental measurements concerning churning losses. Additionally, two different modeling approaches for gearbox simulations are compared and the advantages are discussed. This study provides engineers with a new tool that can be used to improve the efficiency and reliability of gearboxes in BEVs.

The Electric Drive Unit (EDU) for electric vehicles has high power density and unavoidably generates considerable waste heat during its operation. Thermal management of the Electric Drive Unit is crucial for its reliable, optimum operation. This demands efficient cooling technology. Computation Fluid Dynamics (CFD) simulation as a virtual test bed, provides detailed insights into the flow, and temperature fields which help in making the necessary design changes for better thermal performance of Electric Drive Unit at the product development phase. The present work deals with the prediction of temperature of the windings during the warming up cycle using a fast and novel coupled heat transfer approach. A 3-D, quasi-steady state, and transient, multiphase flow with conjugate heat transfer model of Electric Drive Unit is simulated in Simerics-MP+, a CFD software. The 3-D model of the drive unit consists of an e-motor with all the primary parts such as windings, end rings, stator, rotor laminate, shaft, and transmission gears. The oil distribution inside the motor is predicted using an explicit Volume of Fluid (VOF) formulation for multiphase flow with high resolution interface capturing between oil and air phases for proper oil distribution. The oil splashing due to gear rotation is also captured in the simulation. The quasi-steady state and transient evolution temperature field of the motor is predicted with the conditions as considered in the experimental setup. The predicted temperature of the windings is compared with experiment measurements at 29 different locations and the comparison is good.

Conceptually similar to MILD, FLOX, CDC, HiTAC, etc., Homogeneous Combustion (HC) continues to be pursued as an appealing technique towards minimizing NOx emissions. HC combustors are generally driven by high-momentum inlet jets which enable intense dilution of the reactants. This work numerically studies the effectiveness of localized swirling injection in enhancing reactant dilution for an HC combustor running with enriched oxidizers (XO2>21%). Even though localized and low intensity, swirling injection is found to have far-field effects (over ~75 diameters). Effects of swirling injection on the flow field (near and far field) and on NOx emissions are explained. While swirl does help in reducing NOx, there exists an optimal swirl intensity beyond which NOx emissions increase. A mutual competition is seen between swirl assisted and entrainment driven dilution; and at higher swirl intensities, the reduction in the latter overwhelms the gains accrued by the former (in terms of NOx emissions). Along expected trends, thermal NOx is deduced to be the dominant pathway of NOx formation for oxy-enriched cases. Damköhler numbers in the reaction zone are low even for the highest oxygen content tested here (XO2=40%). Volumetric standard deviation of Heat Release Rate (HRR) is seen to perform well as a measure of the tendency of transition to the conventional mode of combustion.

Pinewood particles were pyrolyzed in a vertical tube furnace at 500 degrees C followed by the upgradation of pyrolysis vapors using zeolite ZSM-5 at catalyst temperature from 400 to 600 degrees C. The catalyst was later regenerated to recover its acidity and activity. The bio-oil before catalysis was homogeneous and highly oxygenated, and neither aromatic nor polycyclic aromatic hydrocarbons (PAHs) were detected. The difference in water yield was very small for different catalytic pyrolysis cases, and experimental results indicated that the conversion of oxygen was mainly to CO and CO2 as the catalyst temperature increased. Chemical analysis of the bio-oil showed that aromatic hydrocarbons and PAH were formed in significant amounts upon catalytic treatment. Finally, the content of acids and ketones was reduced after catalysis, showing an improvement in the quality of bio-oil. The overall effect of the usage of regenerated catalyst on the pyrolysis products was not significant in the current study.

Homogeneous Combustion (HC) and its variants (MILD, FLOX, CDC etc.) have emerged as attractive techniques to abate NOx emissions. The underlying theory is the arrest of Damköhler number (Da) to values close to unity by intense dilution (internal or external) of the reactant streams. The main research problem addressed in this work is the attainment of HC with enriched oxidizers (XO2>21%). The complex and three-dimensional in-furnace flow is described by breaking it down into a set of canonical flows and using parameters related to the latter. Further, jet-momentum ratio and stagnation length are used to characterize the flow-field and their effect on NOx emissions is explained. Unlike oxidizer-jet momentum, fuel-jet (<5% inert content) momentum is seen to have a nuanced effect on reaction zone homogeneity and NOx emissions; while reactant inlet temperature is seen to have little effect. Stagnation distance is also suggested as a length scaling parameter to describe arrangements with multiple confined turbulent jets. It is shown to perform well for flows under the jets by yielding velocity curves which are independent of chemistry. CO and hydrocarbon emissions are found to be dependent only on equivalence ratio. Volumetric standard deviation of Heat Release Rate is used to quantify the tendency of transition to the conventional mode of combustion due to oxidizer enrichment.

Pyrolysis of centimeter-scale wood particles of various sizes and shapes needs to be understood to determine their burning rate and life. Such particles may be thought of as firebrands, which are a major reason for spotting ignition in wildland and wildland-urban interface fires. The burning lifetime of firebrands controls the maximum distance they can travel to cause spotting. To understand and model this, experiments are done in a vertical tube furnace with wood particles of different sizes and shapes. For computations, two classes of shapes, prolate and oblate ellipsoids, were chosen to represent the arbitrary geometry of such particles. Prolate ellipsoids include shapes ranging from thin needles to spheres, whereas, oblate ellipsoids include shapes ranging from thin disks to spheres. The choice of these smooth shapes, while facilitating expedient computations also enables the coverage of wide ranges of particle shapes and surface area to volume ratios (SVR). Model simulations show satisfactory agreement with relevant literature and experimental data. Particle aspect ratio (ϵ, the ratio of minor and major axes), SVR, and equivalent radius (Re) are used to define the particle geometry. Mass loss and center temperature profiles are presented and discussed. It is shown that with the decreasing of aspect ratio, wood particle decomposes faster and the final char fraction becomes smaller. A power-law based correlation between conversion time (tcon) and SVR is derived and verified against experiments. Further, it is shown that an increase in the SVR enhances the production of tar and decreases the yield of char while leaving the yield of gas mostly unaffected.

•Pyrolysis of various size and shape wood chips under different conditions is studied.•Effect of shape, size and pyrolysis conditions on heat and mass transfer is quantified.•Extent of pyrolysis is quantified by the pyrolysis duration and the residual char mass.•Data is correlated by parameters based on particle Size, Shape, and Temperature exposure.•Correlations developed are useful to estimate the extent of pyrolysis for an arbitrary particle.

采用HCl、H2SO4和HNO3对废轮胎裂解炭黑(CBp)进行酸洗处理,研究了酸洗改性CBp(WCBp)的基本性质、微观形态和粒度分布,考察了3种WCBp对丁苯橡胶混炼胶的门尼黏度、硫化特性及硫化胶性能的影响.结果表明,酸洗后CBp的灰分明显减少,比表面积明显增大;采用HNO3处理的CBp粒径更小,粒子排列更加紧密,粒径分布变窄;酸洗后CBp表面暴露出了部分极性官能团.填充WCBp的SBR混炼胶的门尼黏度均明显下降.填充WCBp的SBR硫化胶,其拉伸强度、300％定伸应力和撕裂强度均显著提高,耐磨性也有一定的改善.填充采用HNO3处理的WCBp的SBR混炼胶,焦烧时间和正硫化时间明显延长,储能模量趋于稳定时的测量值与初始测量值之差最小,拉伸强度为11.16 MPa,300％定伸应力为4.04 MPa,撕裂强度可达35.93 kN/m,磨耗体积为131.27 mm3.

The aim of this study is to investigate the effect of torrefaction on pyrolysis of centimeter-scale pine wood particles at 520°C. The experiments were conducted in a vertical tube furnace and the yields and compositions of bio-oil were measured. We found that torrefaction at 225°C and 250°C for 15, 25 and 35min had little effect on the pyrolysis products. However, when wood was torrefied at 275°C and 300°C, significant char formation and transformation occurred. During the pyrolysis processes, lower weight loss rate and higher char fraction were observed for wood torrefied at 275°C and 300°C, but the center temperature profiles were not affected. Conversion time for pyrolysis was also not affected by the torrefaction conditions. Pyrolysis yields of liquid, gas and char were calculated and found to be affected by the torrefaction conditions. GC/MS analysis of bio-oil obtained from torrefied wood shows that the acid content decreases with increasing torrefaction intensity, implying improvement of bio-oil quality. Further, phenol content increases and guaiacols content decreases with the increase of torrefaction intensity. On the other hand, no novel species were detected and the overall effect of torrefaction was less remarkable than anticipated for the temperatures tested.