Supersonic Magnetohydrodynamic (MHD) Power Generation System and Its Preliminary Experiment
Magneto hydrodynamic (MHD) power generation system has an important potential application in high-speed aero craft. According to the principles of MHD power generation, shock tunnel and ionization, a supersonic MHD power generation system is developed and introduced in this paper. Helium is used for driver gas and argon for driven gas. Equilibrium contact surface operating mode is selected to obtain high temperature, and the K2CO3 powder seed is added into the driven section so that the supersonic flow is electric. When M=2.0 and B=0.5 T, the power generation system is set up to know the experimental conditions. The nozzle entry total pressure is about 0.35 MPa while total temperature about 3965.1 K, and the nozzle exit velocity is calculated 1530.8 m/s. A preliminary experimental investigation is at length carried out by measuring the voltage and current of the segmented MHD power generation channel. Average electrical conductivity is estimated to be 15 S/m approximately. When load factor is 0.5, the maximum power density of this MHD power generation channel is about 2.195 MW/m3, while the maximum value of enthalpy extraction rate tends to be about 0.255%.
Magnetohydrodynamic Power Generation Using Externally Ionized, Cold, Supersonic Air as Working Fluid
Magnetohydrodynamic (MHD) power extraction from cold air has been demonstrated using short-duration, high-repetition rate, high-voltage pulses (2 ns, 100 kHz, 5 kV/cm) to ionize a Mach 3 (600 m/s), 0.04 kg/m 3 flow. Because the power used to ionize the flow using such a method was less than 1% of the total flow enthalpy, the flow was not heated significantly. A few tens of milliwatts were extracted from the 3-cm cube region of ionization, which scales to hundreds of kilowatts of power in higher velocity, larger-scale devices that would be appropriate for flight applications. Peak electron number densities between 5 × 10 11 and 10 12 cm -3 are reported from complementary measurements using microwave absorption in a variable magnetic field. The Hall parameter was estimated from the electrical properties of the MHD channel. Modeling predictions were found to be in agreement with experimentally extracted Faraday current measured between the high-voltage pulses. Modeling also confirmed that the electrons have low energy between the pulses and that the resultant cathode and anode voltage falls are quite low, on the order of 1 V.
Impacts of climate and land use changes on flood risk management for the Schijn River, Belgium
Abstract Flooding is the most common natural disaster in Europe. Modern flood risk management relies not only infrastructure development but also on governmental and non-governmental actors applying legal, economic and communicative water management instruments. Within the European Union (EU), flood management closely relies on policy set at the EU and national levels. It is now recognized that a sound understanding of climate change is required in addition to current management by taking into account land use change and socio-political context, as climate and land use changes have major impacts on hydrological responses. This paper investigates the hydrological behavior due to urbanization under current and future climate scenarios of high summer and high winter rainfall for 20 sub-catchments of the Schijn River, located in the Flanders region near Antwerp, Belgium. As urbanization increases and existing rainfall-runoff models neglecting the specific behavior of urban runoff, a hydrological model was developed based on a basic reservoir concept and applied to the existing rainfall-runoff model (PDM) flow to examine the specific urban contribution. Results revealed that peak flow for urban runoff and the total peak flow (i.e. rural and urban runoff) were significantly higher (i.e. ranges from 200% to 500%) than the existing rainfall-runoff model (PDM) flows, because of faster and more peaked urban runoff response. The impact of climate change on current and future conditions was also assessed by estimating peak flows with respect to return periods from the flood frequency curve. The predicted peak flow of high summer future climate scenario was significantly higher (i.e. ranges from 200% to 250%) than that of the current climatic condition for this region. Furthermore, hourly peak flow and daily volume ratios of 100-year return period for the highest, lowest and average impervious area were projected for the time horizon of the year 2100. It is concluded that climate change impacts contribute the most in producing peak flow in coming years, while increased urbanization takes the second place for both hourly and daily values. Results on urbanization effect and climate change impact assessment are useful to the water managers for spatial planning, emergency planning and insurance industry.