Honors Projects for Mechanical Engineering
Permanent URI for this collection
1 - 5 of 5
ItemDESIGNING OF LANDING TRAJECTORIES USING FORWARD AND BACKWARD PROPAGATIONS(University of Hawaii at Manoa, 2018)By 2020, NASA is planning to conduct rover missions to collect samples and data in search of possible signs of life on Mars. To obtain quality results, scientists believe that exploration into hazardous, uneven terrain is essential. To successfully land o
ItemMulti-Walled Carbon Nanotube Nanoforests as Gas Diffusion Layers for Proton Exchange Membrane Fuel Cells(University of Hawaii at Manoa, 2015-05)Proton exchange membrane fuel cells (PEMFCs) are emerging as power conversion devices for stationary, automotive, and portable devices compared to other types of fuel cells. The PEMFCs operate at elevated temperatures to improve the conductivity of the electrolyte and enhance the kinetics of electrode reactions resulting in higher operating efficiencies. However, operation at elevated temperatures requires external humidification to fully humidify the reactant gases to avoid low proton conductivity which results from membrane dehydration. Gas diffusion layers (GDLs) have been developed to manage water as well as to promote gas distribution to the active catalyst regions in an attempt to obtain higher power density at all current density regions. For several years, carbon papers or carbon cloth substrates (macroporous layer) with polytetrafluoroethylene (PTFE) based microporous layer coatings have been the major choice for GDLs. This research focuses on implementing carbon nanotube nanoforests (CNNs) as GDLs in order to increase fuel cell performance in terms of stability, humidity, power density, and operation efficiency, while lowering the weight, size, and costs. Multi-walled carbon nanotubes (MWCNTs), used in this research, have been proven to transport large currents with low resistance, have extremely high hydrophobic properties and inherent oxidation resistance, all of which make the potential application of MWCNTs as GDLs very promising.
ItemManaging Renewable Generation Fluctuations(University of Hawaii at Manoa, 2016-12)Energy and power production are essential to daily life. By the year 2030, HECO desires to increase renewable energy production up to 65%. Increasing renewable energy production will help reduce fuel burning to hopefully minimum. However, power produced from solar panels and wind turbines may be insufficient to meet the load conditions. Therefore, spinning reserves, which are back-up power fuel-burning devices, or energy storage systems such as batteries are used to make up for that power deficiency. These main two back-up plans must be very efficient and cost effective to quickly make up for power deficiency when renewable energy production decreases. The first step is to obtain aggregate power data from household appliances. Then, average power and probability curves of these household appliances will help determine the best-fit daily model of power demand and production in areas in Hawaii. The next step inputs this data and daily solar panel power into a complex valued neural network that considers several variables such as solar irradiation, relative humidity, daily air temperature, and sunshine duration. This neural network will learn patterns from this data to make predictions for short-term load forecasting. The aim of this study is to create a short-term load forecasting model with neural networks to demonstrate how much renewable energy is needed daily to power a home. Excess power can be stored in batteries and used when there is insufficient power from renewable energy sources. If there is sufficient power, then the user can live independently off the power grid.
ItemPower Generation From Geothermal Energy(University of Hawaii at Manoa, 2014-01-15)Geothermal reservoirs may be liquid- or vapor- dominated. Two types of power cycle will be considered in this paper for liquid-dominated reservoirs, the vapor flashing cycle and the binary cycle using isobutane as the working fluid. In vapor flashing cycle, flashing tanks are used to separate steam from brine, and the steam expands in turbine to generate power. In binary cycle, the working fluid is superheated by geothermal fluid and then expands in turbine for power generation. Addition of a regenerator to binary cycle improves the thermal efficiency. For identical conditions of geothermal fluid, the power generated by a regenerative binary cycle is slightly higher than that of basic binary cycle. Another advantage of the regenerative binary cycle is that the heat rejection rate of the system is lowered by using the regenerator. Geothermal fluid from well may exist in two phases, vapor and liquid, if the fluid in well is self-flowing. To avoid scaling, submersible pump may be used to force the fluid out of a well. When pump is used, there will be no vapor at the wellhead. Effects of pumping on power output and heat rejection of binary cycle have been evaluated in Section III. For geothermal fluids with high content of non-condensable gases, a non-condensing plant may be used. Condensing plants have much higher thermal efficiencies than non-condensing plants. If cooling water to condenser is not accessible, a cooling tower can be used to recycle the cooling water. At the end of this paper is an evaluation of multi-effect evaporator used to produce fresh water from the waste brine of regenerative binary plant.
ItemNumerical Solutions of Isothermal Pumping and Re-Injection in a Confined Aquifer(University of Hawaii at Manoa, 2014-01-15)Two numerical schemes are used for the computation of steady and transient pressure distribution in a porous medium. These two schemes are applied to two different types of boundary conditions. Numerical results for pressure distribution in a rectangular reservoir are compared with analytical solutions. It is found that the numerical results based on two different numerical methods are in close agreement with the analytical solutions for the region away from the sites of pumping and re-injection. Both the analytical solutions and the singular finite difference solutions are singular at the points of pumping and re-injection. The regular finite difference method, however, gives finite values of pressure at these points.