液罐车液体侧向晃动多质量椭圆规摆模型

为深入研究液罐车整车侧向动力学行为, 探讨了椭圆形(圆形) 截面罐体等效机械液体侧向晃动模型; 基于计算流体动力学(CFD) 软件FLUENT, 评价了椭圆规摆(TP) 模型的预测精度, 分析了充液比、罐体截面椭圆率和激励频率对模型预测精度的影响; 提出了广义多质量TP模型, 通过合理分配液摆各部分质量及其间距来适应罐体截面椭圆率和充液比的变化; 基于Lagrange方法推导了广义多质量TP模型动力学方程, 给出了双质量TP (DMTP) 模型的质量比和质量间距参数的获取方法和拟合表达式, 并采用CFD方法评价了DMTP模型的预测精度。分析结果表明: 由TP模型得到的晃动力矩总体较CFD方法的小, 随着充液比和激励频率的增加, 预测误差变大, 充液比由30%增加到80%时, 峰值晃动力矩预测误差由15%增加到65%左右, 这主要是由于TP模型是在液体小初始倾斜角自由晃动条件下拟合所得, 当充液比和晃动频率较高时, 液摆的摆臂长度和参与晃动的液体质量都小于实际情况; DMTP模型在大部分充液比、罐体截面椭圆率和激励频率条件下都有相对稳定且较高的预测精度, 激励频率分别为0.2、0.3Hz时, DMTP模型的最大晃动力矩预测均方根误差均值和标准差分别比TP模型小54.2%、43.9%和45.1%、31.2%, 预测精度较TP模型有明显提高, 特别是能够较好地弥补TP模型在高充液比时预测误差较大的不足。

Multi-mass trammel pendulum model of fluid lateral sloshing for tank vehicle

To deeply investigate the lateral dynamics of tank vehicle, the equivalent mechanical model of fluid lateral sloshing for a tank with elliptical (circular) sectional shape was studied.The predicting precision of the trammel pendulum (TP) model was evaluated by the computational fluid dynamics (CFD) software FLUENT, and the effects of fill level, tank sectional ellipticity, and excitation frequency on the model's predicting precision were analyzed.A generalized multi-mass TP model was proposed, the mass and distance between each part of fluid pendulum were reasonably distributed to adapt to the variations in tank sectional ellipticity and fill level.The dynamics equation for the generalized multi-mass TP model was derived based on the Lagrange approach.The method to determine the parameters of mass ratio and distance between the two masses, and the fitting formulas of double mass TP (DMTP) model were presented.The predicting precision of theproposed DMTP model was evaluated by the CFD method.Analysis result shows that the sloshing moment gained from the TP model is generally less than that computed by the CFD method, and the predicting error generally increases as the fill level increases.The predicting error of the peak sloshing moment increases from 15%to 65% when the fill level increases from 30%to 80%.This is mainly because the TP model is fitted under the conditions of small initial fluid incline angle and free sloshing.When the fill level and sloshing frequency are relatively high, both the length of pendulum arm and the sloshing fluid mass are less than the actual cases.The proposed DMTP model presents a relatively stable and high predicting precision in most conditions of fill levels, tank sectional ellipticities and excitation frequencies.Comparing with the TP model, when excitation frequency is 0.2 and 0.3 Hz, respectively, the mean value of the root mean square error (RMSE) of the predicted maximum sloshing moment in the DMTP model decreases by 54.2% and 43.9%, respectively, and the standard deviation decreases by 45.1% and 31.2%, respectively.The predicting precision of the proposed DMTP model is obviously higher than that of the TP model, and the DMTP model can especially well make up for the deficiency of low predicting precision of the TP model in the case of high fill level.