OpenFlow Channel Research Articles

Supervised Gain-Scheduling Multimodel versus Linear Parameter Varying Internal Model Control of Open-Channel Systems for Large Operating Conditions

In this paper, two internal model control (IMC) controllers using gain-scheduling techniques are proposed and compared for open-channel systems that allow to deal with large operating conditions. In particular, in one side, a linear parameter varying (LPV) model for an open-flow channel system based on a second-order delay Hayami model is proposed. This model will allow one to design a classic gain-scheduling strategy for the IMC controller. On the other side, the LPV model is discretized in a set of linear time invariant (LTI) models corresponding to different operating points. For each LTI model a LTI IMC controller is designed off-line. Then, a supervised gain-scheduler detects on-line which is the LTI model that represents better the open-flow channel system at the current operating point and decides which is the LTI controller that should be used. Finally, both approaches will be applied to a simulated open canal: the Lunax gallery located at Gascogne, France.

Effect of anode flow field design on the performance of liquid feed direct methanol fuel cells

In this work, we investigated experimentally the effect of the anode flow field design on the performance of a DMFC. Single serpentine (SSFF) and parallel flow fields (PFF) with different sizes were designed, fabricated and tested. The experimental results showed that the DMFCs equipped with the SSFFs yielded better performance than those with the PFFs. It was also found that gas bubbles blocked the flow channels in the PFF at low methanol solution flow rates and high current densities, but this channel-blocking phenomenon was never found in the SSFF under all the test conditions in the present work. Studies on the effects of SSFF design parameters revealed that both open ratio and flow channel length had significant influences on the cell performance and pressure drop. An open ratio of around 50% led to the best cell performance at moderate and high methanol solution flow rates. However, at low methanol solution flow rates, a larger open ratio yielded a higher power density at higher current densities, corresponding to the mass transfer limitation region. In addition, it was found that a longer flow channel usually gave better cell performance, but caused a larger pressure drop.

Experimental techniques for the development of the turbulent precipitator as a diesel particulate filter

A novel type of diesel particulate filter is introduced: the turbulent precipitator. The aim is to develop a catalytically active filter, based on Cs2SO4⋅V2O5 molten salt catalyst or cerium fuel-borne catalyst. The novel filter type is developed to circumvent obvious problems like plugging and high pressure drop. In addition to that, it should be flexible, robust and possible to tune for different diesel engines. Its main features are an open flow channel (to prevent plugging and high pressure drops) and soot collection plates (to trap diesel soot). Two filter geometries are described, one with metal collector plates and one with ceramic foam collector plates. Results show that different geometries have different capabilities, making tuning for different diesel engines possible. An engine test bench was designed to measure filter efficiencies, both by particle numbers and particle mass. The diesel soot aerosol is measured with an electrical low-pressure impactor (ELPI). These measurements are not straightforward. For evaluation purposes, the engine test bench was divided into three major components to test it for aerosol measurements: diesel setup, aerosol sampling setup, and ELPI. Each part is restricted by a maximum time on stream.

An LDA system yielding long-term averages and velocity distribution (channel flow and erosion experiments)

Describes a frequency tracker for laser Doppler anemometry (LDA). The circuit makes use of the phase-locked loop principle. Special features include a data validation circuit and a twin counter for forming long-term averages of velocity data. A measured profile of average velocity in a turbulent open-flow channel is presented. By suitable programming, a commercial microprocessor is made to function as multichannel analyser for LDA velocity data. Accumulated data are processed for moments of the velocity distribution such as the mean, the mean square deviation and, using LDA optics at +or-45 degrees to the mean flow direction, the Reynolds shear stress. In a differencing mode the analyser gives the distribution function of acceleration which indicates the time scale of velocity fluctuations.

Direct measurement of velocity correlation functions using the Erdmann-Gellert rate correlation technique

By use of a modified laser Doppler anemometer set-up and a commercial digital correlator, velocity auto- and cross-correlation functions are measured directly. These functions determine time scales of velocity fluctuations as well as their first- and second-order statistics. The technique is demonstrated with flows of perfect time periodicity, i.e. Taylor vortices between rotating cylinders, and of a highly random nature, i.e. turbulence in an open flow channel.