Anode Mass Flow Rates Research Articles

Improving dynamic performance of proton-exchange membrane fuel cell system using time delay control

Transient behaviour is a key parameter for the vehicular application of proton-exchange membrane (PEM) fuel cell. The goal of this presentation is to construct better control technology to increase the dynamic performance of a PEM fuel cell. The PEM fuel cell model comprises a compressor, an injection pump, a humidifier, a cooler, inlet and outlet manifolds, and a membrane–electrode assembly. The model includes the dynamic states of current, voltage, relative humidity, stoichiometry of air and hydrogen, cathode and anode pressures, cathode and anode mass flow rates, and power. Anode recirculation is also included with the injection pump, as well as anode purging, for preventing anode flooding. A steady-state, isothermal analytical fuel cell model is constructed to analyze the mass transfer and water transportation in the membrane. In order to prevent the starvation of air and flooding in a PEM fuel cell, time delay control is suggested to regulate the optimum stoichiometry of oxygen and hydrogen, even when there are dynamical fluctuations of the required PEM fuel cell power. To prove the dynamical performance improvement of the present method, feed-forward control and Linear Quadratic Gaussian (LQG) control with a state estimator are compared. Matlab/Simulink simulation is performed to validate the proposed methodology to increase the dynamic performance of a PEM fuel cell system.

Sputter Erosion Sensor for Anode Layer-Type Hall Thrusters Using Cavity Ring-Down Spectroscopy

We report the development of a sputter erosion monitoring system to study Hall thruster lifetime and contamination. The laser-based sensor uses the continuous-wave cavity ring-down spectroscopy technique and allows for in situ measurements in near-real time. The continuous-wave cavity ring-down spectroscopy technique diagnostic allows direct probing of sputter products in their ground state, thereby providing a reliable quantitative measure of their overall number density. Combining the number density of sputtered particles with their velocity allows determination of the flux of sputtered particles and erosion rate. We perform proof of principle experiments, in which sputtered manganese atoms from the acceleration channel of an anode layer-type Hall thruster are measured. The measurement strategy is to detect the manganese atoms via an absorption line from the ground state at a wavelength of 403.076 nm (air). The measured path-integrated number density of sputtered manganese atoms is 1.7 ± 0.3 × 10 13 m -2 for an argon anode mass flow rate of 2.08 mg/s and a discharge voltage of 250 V. A finite element sputter model is used to compare the cavity ring-down spectroscopy results against validating mass loss measurements and shows good agreement.

Numerical Analysis of Hall Thruster Firing Tests

Numerical analysis of the firing tests of several xenon Hall thrusters over the ranges 200-800 V and 0.5-92.7 mg/s anode mass flow rate is presented. The full form of the specific impulse equation is presented. New approximated equations are presented for anode specific impulse and anode efficiency in which a hyperbolic tangent is used as the basic approximating function. Discharge voltage and normalized mass flow are proposed as input performances. The resultant equations characterize small, medium, and large Hall thrusters with the same accuracy. Flow density and normalized mass flow are proposed as scaling factors for correlating anode mass flow rate and thruster geometrical dimensions. Intrathruster parameter values are estimated based on accepted input performances. The ionization degree is shown to be an increasing function of voltage and normalized mass flow. The average voltage ratio is shown to be a decreasing function of voltage. The electron loss parameter is shown to be a decreasing function of voltage and a peculiar V-shaped function of normalized mass flow, with minimums near 50 (mg/s)/m. The average ion charge is shown to be an increasing function of voltage and a parabola-shaped function of normalized mass flow, with maximums near 100 (mg/s)/m. These results will be useful for future analytical investigations.

Spectral investigations of SPT ATON in wide range of discharge voltages

The spectral investigations of plasma of the stationary plasma thruster of ATON type have been carried out under three values of the anode mass flow rates of xenon \(\dot m_a \) = 1.3 mg/s, 2.0 mg/s, 3.8 mg/s and under discharge voltages U d = 300 V, 600 V, 900 V at the same input power of W ≈ 1 200 W. As a result of these experiments the radiation of neutral atoms of XeI, single XeII and double ions XeIII of xenon was fixed in the band (300 ÷ 950) nm along the channel of source. The radiation powers of the powerful lines of single Xe+ and double ions Xe++ of xenon are compared in the pointed out modes. Under the conditions of the suitability of the coronal model, the distribution of ions birth density (mean in section) along the accelerating channel has been calculated for the listed modes. Estimations show, that with the growth of the discharge voltage the redistribution of the ions birth density takes place in the channel.