Supercapacitors are characterized by a long service lifetime and high power density, which can meet the instantaneous high-power demand during the acceleration of electric vehicles. In this study, a fractional-order model is developed to simulate the polarization effect and charging/discharging characteristics of supercapacitors, considering the precision of the electrochemical model and the amount of calculation of the equivalent circuit model and using the adaptive genetic algorithm to identify the parameters. The accurate prediction of the state of charge (SOC) can improve efficiency, prolong the service lifetime, and ensure the safety of supercapacitors. This study proposes a multiinnovation unscented Kalman filter algorithm based on the fractional-order model to improve the SOC estimation accuracy. The proposed algorithm is compared with other algorithms and analyzed under different temperatures and operating conditions to verify the accuracy and effectiveness of the proposed algorithm in estimating the SOC and tracking the terminal voltage.Experimental results show that the root mean squared error and mean absolute error of the proposed algorithm are less than those of the other algorithms. The proposed algorithm accurately estimates the SOC and tracks the terminal voltage. The maximum root mean squared error and mean absolute error of SOC estimation error are 1.8% and 1.78%, respectively.
Compressed-air vehicles have the advantages of zero pollution and low cost. A compressed-air engine test bench is established in this study. The effects of rotational speed, torque, and regulated pressure on the power performance, economy, and energy conversion efficiency of the pneumatic motor are investigated. The differences in power output, compressed-air consumption rate, and energy conversion efficiency between forward and reverse rotation of the pneumatic motor are compared and analyzed. To effectively investigate the performance of a compressed-air vehicle under various road conditions, this study compares and analyzes the power performance, economy, and energy conversion efficiency of pneumatic motors under different road conditions. Experimental results show that the power output and energy conversion efficiency of the pneumatic motor in reverse rotation are less than those in forward rotation, indicating that the pneumatic motor has better power performance and higher efficiency with forward rotation than reverse rotation. The compressed-air consumption rate of the pneumatic motor with reverse rotation is higher than that with forward rotation, indicating that the pneumatic motor with forward rotation has better economic performance than with reverse rotation. The maximum power output and energy conversion efficiency of the pneumatic motor are about 1220 W and 13.23%, respectively.
Summary Power performance of pneumatic motor (PM) limits its application in compressed air vehicle (CAV) as an auxiliary power. This study presents an investigation of the power system with parallel operation mode based on experiments to improve the power performance of PM. First, the test bench of PM in parallel operation mode is built. Then, a series of experiments are conducted to investigate the effect of key parameters on the power performance, economy and energy conversion efficiency of CAV. The interaction among the key parameters of the PM and the influence of them on the power performance are discussed. Subsequently, the power performance, economy and energy conversion efficiency of the PM working in single and parallel operation modes are compared. Experimental results show that the maximum power output of the PM is 979 W, and the energy conversion efficiency of PMs 1 and 2 are 6.54% and 6.80% when the PM works in parallel operation mode. The parallel operation mode of PM can improve the power performance, economy and energy conversion efficiency of CAV.
The structural design and operating strategy of a free piston expander–linear generator (FPE–LG) has a major impact on performance. In this paper, the simulation model of single–piston FPE–LG was built and verified by combining the structural parameters of the existing test rig with a set of kinetic and thermodynamic equations. On this basis, the influence of the design and operating parameters of the device on the performance was studied, while keeping other parameters fixed. Then, a sensitivity analysis of power output and operating frequency was carried out. The results show that within a certain range of external load and intake beginning position, increasing the diameter of the intake and exhaust pipes, or reducing the piston rod diameter can improve the power output. Within a certain range of frictional coefficient and intake time, increasing the cylinder diameter and intake pressure, or reducing the piston assembly mass and back electromotive force (EMF) constant can increase the operating frequency. Both the power output and the operating frequency are most sensitive to the cylinder diameter among the design parameters. Among the operating parameters, power output is the most sensitive to intake pressure, and operating frequency is the most sensitive to intake beginning position. The optimization of structural design and operation strategy in expander provides important guiding significance for ORC waste heat recovery system.
An air-powered vehicle is a low-cost method to achieve low-pollution transportation, and compressed air engines (CAE) have become a research hotspot for their compact structure, low consumption, and wide working conditions. In this study, a pneumatic motor (PM) test bench is built and tested under different inlet pressures, operation modes, and three driving cycles. On the basis of the data obtained by sensors, power output, compressed air consumption rate, and efficiency are calculated to evaluate the pneumatic motor performances. The results show that with an increase in rotation speed, the output power and efficiency first increase and then decrease, and the compression air consumption rate decreases. With an increase in torque, the rotation speed decreases, and the power output and efficiency first increase and then decrease. With an increase in mass flow rate, the torque increases, the power output and efficiency first increase and then decrease. The pneumatic motor achieves the best performance under a rotation speed of 800–1200 rpm, where power output, efficiency, and compressed air consumption rates are 1498 W, 13.6%, and 10 J/g, respectively. The pneumatic motor achieves the best power output and efficiency under the UDDS driving cycle.
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