A Model for Pulse Jet Fabric Filters

<div class="section abstract"><div class="htmlview paragraph">Fundamental engine research is primarily conducted under steady-state conditions, in order to better describe boundary conditions which influence the studied phenomena. However, light-duty automobiles are operated, and tested, under heavily transient conditions. This mismatch between studied conditions and in-use conditions is deemed acceptable due to the fundamental knowledge gained from steady-state experiments. Nonetheless, it is useful to characterize the conditions encountered during transient operation and determine if the governing phenomena are unduly influenced by the differences between steady-state and transient operation, and further, whether transient behavior can be reasonably extrapolated from steady-state behavior.</div><div class="htmlview paragraph">The transient operation mode used in this study consists of 20 fired cycles followed by 80 motored cycles, operating on a continuous basis. The intention of the cycle is to provide a significant transient condition, namely the change from motored to knock-limited fired operation, while also maintaining a repeatable cycle that allows for the collection of statistics during quasi- steady-state operation.</div><div class="htmlview paragraph">This study investigates the effect of transient operation on Knock-Limited Combustion Phasing (KL-CA50) compared to steady-state operation. Three compositionally dissimilar matched Research Octane Number (RON) = 98 fuels are used in this study, allowing for the assessment of fuel-specific effects on differences between steady-state and transient operation.</div><div class="htmlview paragraph">This study first characterizes the 20/80 firing cycle described above, before comparing the transient KL-CA50 measurements to the steady-state KL-CA50 measurements. Analysis of both the steady-state and transient results are used to gain insights into the effects of transient operation on end-gas autoignition, relative to steady-state operation and as a function of fuel composition.</div><div class="htmlview paragraph">The results of this study indicate the significant effect that transient operation has on KL-CA50 behavior of a fuel. This is both universal, in that all fuels show responses to the differences in compression temperatures of the charge, as well as fuel specific, in that the fuel response varies based on the fuel’s sensitivity to temperature, [O2], and trace species. All fuels showed a significant load extension under transient operation, based on tolerance of higher intake pressures. However, transient operation moved operating conditions to “beyond RON” (Octane Index K < 0) conditions, which favored higher-sensitivity fuels. Based on the analysis of system time constants (e.g. cylinder head temperature dynamic response, exhaust gas temperature dynamic response), it is expected that transient operation, and the benefits for knock-limited operation, are highly influential on drive-cycle performance.</div></div>

Optimization of fixed-bed methanation reactors: Safe and efficient operation under transient and steady-state conditions

Manipulation of the catalyst surface coverage for improved conversion and selectivity substantially requires more frequent flow reversals than the classical reverse flow operation for energy saving does (Chapter 1). 2.A reverse flow reactor should be operated at comparable switching time and residence time in order to manipulate the reactor's selectivity (Chapter 3).3. The concept of reverse flow operation with concentration programming provides an engineering tool to control conversion and selectivity, with three benefits: ammonia feedstock savings, increased ammonia conversion, and increased selectivity to NO; a drawback is the decrease of production rate (Chapter 4).4. The concept of reverse flow operation with reactor side feeding shows a fourfold superior performance: higher conversion of ammonia, higher selectivity to NO, no dead gas volume, and high production rate (Chapter 5).5. Intensification of a university study program must assure that the students' residence time distribution for completing their study follows a plug flow model.6.The concept of periodic reactor operation is natural.7. So called relaxation oscillation occurs when the cycling time period is much less than the system's time constant.However, this is not the case during reverse flow operation when operating the reactor at extremely short cycling time.8. The porosity of a fixed bed can be determined elegantly by a combination of reverse flow operation and cycling of the feed concentration.9. Joint bachelor-master-doctor programs improve the selectivity to master and doctor degrees as well as the productivity of a university.10. Assalamu'alaikum is a time-independent greeting.

Grid-forming inverters are the essential components in the effort to integrate renewable energy resources into stand-alone power systems and microgrids. Performance of these inverters directly depends on their control parameters embodied in the controller. Even the most conscientiously designed controller will exhibit suboptimal performance upon implementation due to the presence of parasitic elements in the existing hardware. Hence, the controller has to be tuned and optimized. In the present article, the process of implementation, laboratory verification, and tuning of a matching-controlled grid-forming inverter is presented. In order to assess the efficiency of the grid-forming controller, its operation has been tested and analyzed in blackstart, steady state, and transient operation. For this purpose, a systematic sensitivity analysis has been conducted and the control parameters have been tuned in laboratory tests. The laboratory results verify proper operation of a 7 kW grid-forming inverter in all three test scenarios. After applying the proposed method on the tested grid-forming inverter in steady state operation, total harmonic distortion (THD) of the output voltage is less than 0.5% for its practical loading range (maximum THD is less than 1% in no-load condition). The system is able to blackstart and supply the loads. Finally, the studied grid-forming inverter is stable in the presence of severe step load changes and disturbances, i.e., voltage overshoot is managed well and compensated for with a low settling time using this approach.

A phenomenological multizone combustion model is developed for use in the transient condition analysis of a turbocharged direct injection (DI) diesel engine. The main processes in the cylinder, such as spray penetration, droplet evaporation, air-fuel mixing, spray wall interaction, ignition and fuel combustion, are taken into consideration. In order to predict cylinder pressure and NOx emissions in a wide range of engine speeds, loads and air-fuel ratios under transient conditions, the model has been improved in many respects, especially in the velocity distribution of fuel spray, zonal entrainment and the calculation of gas properties and chemical equilibrium compositions of combustion products including solid carbon. With respect to the turbocharged engine with a high pressure in the cylinder, the compression factor is added to the ideal gas equation of state in order to simulate cylinder pressure accurately. Cylinder pressure, heat release and NOx emission histories for different operating conditions are calculated for two types of engines. The agreement between calculated and measured results is good for a wide range of operating conditions. This indicates that the model has the ability to predict cylinder pressures and NOx emissions in both steady state and transient operating conditions.

Steady state and transient thermal stress analysis in planar solid oxide fuel cells

Microgrids are subjected to limits on system voltage and frequency deviations, for transient and steady state operation. Similar to a conventional power system with rotating generators, inertia and damping of frequency are necessary for frequency profile and stability of an isolated microgrids. This work proposes an approach to analyze inertia and frequency damping coefficient for a system based on the fact that sources relatively close to each other observe similar transients in frequency within an isolated microgrid. This is validated through bode plots and simulation. The approach allows defining the system response to transients in frequency in terms of individual source response using standard frequency mode parameters such as damping and inertia. Further, to optimize the overall system response so that sources share the frequency regulation requirement, an novel strategy is proposed to design individual source inertia and damping coefficient based on the source capacity. An experimental setup consisting of a microgrid system having three inverter based sources working as virtual synchronous generators operating in parallel has been set up to verify the analysis.

This paper presents an averaged model and a small-signal model of a bidirectional dual active bridge (DAB) DC-DC converter. Based on the proposed model, the stability and transient power flow in the system can be analyzed. A novel hybrid controller is proposed for the phase-shift based feed-back and feed-forward control of a 600V/10kW prototype. The hybrid controller can ease the difficulties of the parameter selection of a traditional PI. The effectiveness of the models and proposed hybrid controller are validated by simulations and experiments in both transient and steady state operations.

A digital speed and high resolution position identification algorithm, suitable for brushless DC (BLDC) drives, is presented in the paper. The proposed digital algorithm is synthesized by using the Popov Hyperstability Theory, by means of the current signal samples. The ¿a priori¿ and ¿a posteriori¿ current errors are introduced in the adaptation mechanism to force the estimated samples of speed and position to converge to their respective actual values, as fast as possible. A Matlab-Simulink simulation study, referred to transient and steady state operation, is conducted on a BLDC drive controlled by a predictive algorithm. The results highlight the drive performance in transient and both at low and high speed operation.

In recent years, the amount of non-linear loads has been increasing considerably since there are improvements in power electronic equipment (such as adjustable speed drives or converter ac-dc, ac-ac, dc-ac and dc-dc) in industrial sectors which cause deterioration of the quality of the electric power supply through distortion of supply voltage and supply current. This has led to improvement of many stringent needs regarding generation of harmonic current, which are found in IEEE519 and IEC61000 standards. This paper proposes a non-linear function based closed loop control strategy (without load current extraction) for three-phase Shunt Active Power Line Conditioner and LC passive filter to compensate harmonics, power factor improvement and enhance the dynamic performance of Shunt Hybrid Power Filter (SHPF). By using a PI controller the DC bus voltage of the Shunt Active Power Filter is maintained constant. Results obtained from simulation shows the performance of expected hybrid filter in transient and steady state operation .This indicates that the controller is able to compensate even under severe load current imbalances. DOI: http://dx.doi.org/10.11591/ijpeds.v5i2.6181

The Z-source inverter (ZSI) is a recently proposed single stage converter topology with buck-boost capabilities. The quasi-Z-source inverter (qZSI) has been developed which features several improvements when compared to the traditional ZSI. Control strategies of the ZSI and qZSI are important issue and several feedback control strategies have been investigated so far. This paper presents a model predictive control (MPC) of a grid connected qZSI, where the grid current is properly controlled during transient and steady state operation by including inductor current, capacitor voltage as well as switching frequency as additional control constrains. Both steady-state and transient results show high performance response of the proposed control technique.

This paper presents a novel Stator Current based Model Reference Adaptive System (SC_MRAS) speed observer for high-performance Six Phases Induction Motor (SPIM) drives using linear neural network. The article aim is intended to improve performance of an SC_MRAS observer, which were presented in the literature. In this proposed scheme, the measured stator current components are used as the reference model of the MRAS observer to avoid the use of a pure integrator and reduce the influence of motor parameter variation. The adaptive model uses a two-layer Neural Network (NN) to estimate the stator current, which has been trained online by means of a Least Squares (LS) algorithm instead of uses a nonlinear Back Propagation Network (BPN) algorithm to reduce the complexity and computational burden, it also help to improve some disadvantages cause by the inherent nonlinearity of the BPN algorithm as local minima, two heuristically chosen parameters, initialization, and convergence problems, paralysis of the neural network. The adaptive model of the proposed scheme is employed in prediction mode, not in simulation mode as is usually the case in the literature, this made the proposed observer operate better accuracy and stability. In the proposed observer, stator and rotor resistance values are estimated online, these values thereafter were updated for the current observer and rotor flux identifier to enhance the accuracy, robustness and insensitivity to parameters variation for the proposed observer. The proposed LS SC_MRAS observer has been verified thought the simulation and compared with the BPN MRAS observer. The simulation results have proven that the speed is estimated a consequent quicker convergence, do not need the estimated speed filter, lower estimation errors both in transient and steady state operation, better behavior in low and zero speed operation.

<div class="htmlview paragraph">A flow network method was developed to predict the underhood temperature distribution of an automobile. The method involves the solution of simplified energy and momentum equations of the air flow in control volumes defined by subdividing the air space between the surfaces of the underhood components and the front-end geometry. The control volumes are interconnected by ducts with branches and bends to form a flow network. Conservation of mass and momentum with appropriate pressure-loss coefficients leads to a system of algebraic equations to be solved for the flow rates through each volume. The computed flow rates are transferred to a thermal model to calculate the temperatures of the air and the major vehicle components that affect the underhood environment.</div> <div class="htmlview paragraph">The method was applied to a 1986 3.0L Taurus and compared with vehicle experiments conducted in a windtunnel. Computed results agree with vehicle data to within experimental uncertainty for both transient and steady state operations. Applications illustrated in the paper include the selection of radiator and its effects on air-conditioning, the tradeoff of body styling on underhood temperature and the requirement of high fan speed to compensate for air blockage.</div>

Diesel engines under transient operating conditions are much different from those under steady operating conditions. The paper based on the diesel CA6DL2-35E3 of FAW R&DC with turbocharger, intercooler, four-valve, six-cylinder and high pressure common rail, the diesel displacement is 8.6L. We had established model of the diesel with GT-power and simulated diesel engine working process under transient operating conditions which in constant speed while torque increased, and also analyzed the results. And we had analyzed transient response of burning boundary conditions and max burning pressure.

<div class="section abstract"><div class="htmlview paragraph">Feed-forward low-throughput models have been developed to predict MFB50 and to control SOI in order to achieve a specific MFB50 target for diesel engines. The models have been assessed on a GMPT-E Euro 5 diesel engine, installed at the dynamic test bench at ICEAL-PT (Internal Combustion Engine Advanced Laboratory at the Politecnico di Torino) and applied to both steady state and transient engine operating conditions.</div><div class="htmlview paragraph">MFB50 indicates the crank angle at which 50% of the fuel mass fraction has burned, and is currently used extensively in control algorithms to optimize combustion phasing in diesel engines in real-time. MFB50 is generally used in closed-loop combustion control applications, where it is calculated by the engine control unit, cycle-by-cycle and cylinder by-cylinder, on the basis of the measured in-cylinder pressure trace, and is adjusted in order to reduce the fuel consumption, combustion noise and engine-out emissions.</div><div class="htmlview paragraph">A feed-forward approach has been developed in this paper. This approach is capable of predicting MFB50 on the basis of several parameters, such as, the in-chamber thermodynamic conditions, the injected fuel quantities and timings, the injection pressure, the oxygen concentration and the engine speed and load. The approach has also been inverted in order to predict the start of injection required to achieve a specific MFB50 target in real time. This method can be used in model-based real-time control algorithms to adjust the engine parameters in order to prevent the occurrence of non-optimal combustion cycles.</div></div>