dynamic simulation

In the presented work, a new rotor circuit is proposed for a brushless doubly-fed induction machine (BDFIM) with 8-/4-pole power/control winding. Using the proposed rotor circuit, the mutual-coupling of the power winding and the rotor circuit, and consequently the cross-coupling between the power and control windings is increased. Therefore, a BDFIM with a higher torque capacity is obtained. A dynamic model is established for BDFIMs and used as a fast tool to investigate and compare the characteristics of the proposed machine with the extant BDFIMs with parallel and series loops. The dynamic model is funded based on the concept of multiple coupled circuits. The machine magnetizing inductances are the parameters of this model and obtained by using the winding function method. The provided dynamic model is validated by means of time-stepping finite element analysis. Finally, it is shown that using the proposed rotor circuit, the cross-coupling of the stator windings is increased. Consequently, the magnetizing current and the Joule losses are decreased in the proposed BDFIM machine.

In this paper, a dynamic model is provided to obtain the waveform of the unbalanced magnetic force in the wound rotor induction machines with static eccentricity. The provided dynamic model is based on the voltage state-space equations of the coupled circuits in the eccentric induction machine. In the model the slotting effect and saturation is neglected and the slot ampere turn is distributed on the slot opening. To avoid computation of the air gap flux density and evade of magnetic pressure integration in each time-step of Runge-Kutta computations and consequently reducing the computation time of dynamic simulations, a static function of the stator and rotor windings’ currents are proposed for computation of the unbalanced magnetic force. The parameter of the proposed function is obtained by analyzing the air gap field density by using winding function theory. Finally, the waveform of the unbalanced magnetic force of the eccentric induction machine is obtained and verified by time-stepping finite elemnt analysis.

The NGL refinery of the Sirri Island has a major role in the production of high-value products. One of the most important refinery units is the demethanizer unit, comprising of a complex network of distillation towers and heat exchangers. In the first step, using the Aspen Hysys software, a proper steady state model was developed for this unit in which the simulation of the main equipment that is, distillation towers and heat exchangers were carried out. The steady state simulation results are in good agreement with the data gathered from the real plant. Then, the simulation was transferred from steady state to dynamic mode in which the main equipment such as distillation towers and control valves were sized. Here, the available controllers which are currently present in the real plant, were added to the simulation. Using the auto tuning variation (ATV) method and by considering the desired behavior namely, stability, fast response, and absence of oscillation, the overall performance of the controllers were examined under different scenarios. Based on the results, it was identified that with carefully tuning the controllers parameters, much better performance can be achieved.

Direct catalytic oxidation of methane to methanol is a novel technique which has eliminated the intermediate and expensive process of synthesis gas production. This technology can be used for low deposit, remote, low-pressure fields, and abundant resources of unconventional gas, without need to manufacture of expensive units of gas-to-liquid (GTL) process. In present study, modeling and simulation of the single step (direct) conversion of methane to methanol has been investigated in a fluidized-bed reactor packed with V2O5/SiO2 particles as the reaction catalyst. Firstly, the reactor was simulated at steady-state conditions and the effect of important parameters such as feed temperature and residence time of reactants within the reactor on methane conversion and product's selectivity was studied. In the next step, dynamic simulation of the process was performed and the effect of disturbances of effective parameters on reactor performance was investigated. In steady state conditions, for the residence time of 9 seconds maximum yield of methanol production was obtained at 50 bar and 773 K and methane conversion was 32.2 and methanol selectivity was 42.1. Results showed that by increasing reactor temperature and residence time, methane conversion increases but methanol selectivity decreases. Cooling fluid temperature and residence time were found to have the greatest effect on reaction rate and rector performance. Also results showed reasonable agreement with the experimental data reported in the literature for fixed-bed reactor.