Design and Operational Modifications to Model IV FCCUs to Improve Dynamic Performance

Model IV Fluid Catalytic Cracking Units (FCCUs) differ from other cracking units in that model IV FCCUs do not have slide valves in the catalyst circulation lines to enable direct control of catalyst circulation rate through the unit. Reducing fluctuations in catalyst circulation rate is found to significantly improve closed loop performance of the FCCU. Some design and operational modifications that can be made to model IV FCCUs to improve closed loop performance at the regulatory level based on this insight are modeled and compared. Closed loop performance of a model IV FCCU operated with the weir and standpipe always flooded is examined. The achievable performance is significantly better than that of the standard model IV FCCU. The closed loop performance of the model IV FCCU modified to incorporate slide valves in the catalyst circulation lines is also examined. The performance of the FCCU with slide valves is better than the performance achievable by the FCCU with the weir flooded. It is found that model IV FCCUs are ill-conditioned owing to the use of the weir and standpipe arrangement in the regenerator section. Both the operational and design modifications studied reduce plant ill-conditioning appreciably

Electricity powering combustion: hydrogen engines

Hydrogen is ameans to chemically store energy. It can be used to buffer energy in a society increasingly relying on renewable but intermittent energy or as an energy vector for sustainable transportation. It is also attractive for its potential to power vehicles with (near-) zero tailpipe emissions. The use of hydrogen as an energy carrier for transport applications is mostly associated with fuel cells. However, hydrogen can also be used in an internal combustion engine (ICE). When converted to or designed for hydrogen operation, an ICE can attain high power output, high efficiency and ultra low emissions. Also, because of the possibility of bi-fuel operation, the hydrogen engine can act as an accelerator for building up a hydrogen infrastructure. The properties of hydrogen are quite different from the presently used hydrocarbon fuels, which is reflected in the design and operation of a hydrogen fueled ICE (H2ICE). These characteristics also result in more flexibility in engine control strategies and thus more routes for engine optimization. This article describes the most characteristic features of H2ICEs, the current state of H2ICE research and demonstration, and the future prospects

Jet aircraft emissions during cruise: Present and future

Forecasts of engine exhaust emissions that may be practicably achievable for future commercial aircraft operating at high altitude cruise conditions are compared to cruise emission for present day aircraft. The forecasts are based on: (1) knowledge of emission characteristics of combustors and augmentors; (2) combustion research in emission reduction technology, and (3) trends in projected engine designs for advanced subsonic or supersonic commercial aircraft. Recent progress that was made in the evolution of emissions reduction technology is discussed

The experimental clean combustor program: Description and status

The objectives, program plan, schedule, pollution and performance goals, program approaches to pollution reduction, and status of the project are presented. Advanced supersonic transport and combustion noise programs are also discussed. The phases of the program consist of the following: (1) screening of low pollutant combustors, (2) refinement of the best combustors, and (3) engine demonstration of the best combustors. It is stated that all combustor designs investigated appear capable of achieving the idle pollutant goals with additional development effort

Droplet combustion at reduced gravity

The current work involves theoretical analyses of the effects identified, experiments in the NASA Lewis drop towers performed in the middeck areas of the Space Shuttle. In addition, there is laboratory work associated with the design of the flight apparatus. Calculations have shown that some of the test-matrix data can be obtained in drop towers, and some are achievable only in the space experiments. The apparatus consists of a droplet dispensing device (syringes), a droplet positioning device (opposing, retractable, hollow needles), a droplet ignition device (two matched pairs of retractable spark electrodes), gas and liquid handling systems, a data acquisition system (mainly giving motion-picture records of the combustion in two orthogonal views, one with backlighting for droplet resolution), and associated electronics

Ceramic automotive Stirling engine study

A conceptual design study for a Ceramic Automotive Stirling Engine (CASE) is performed. Year 1990 structural ceramic technology is assumed. Structural and performance analyses of the conceptual design are performed as well as a manufacturing and cost analysis. The general conclusions from this study are that such an engine would be 10-26% more efficient over its performance map than the current metal Automotive Stirling Reference Engine (ASRE). Cost of such a ceramic engine is likely to be somewhat higher than that of the ASRE but engine cost is very sensitive to the ultimate cost of the high purity, ceramic powder raw materials required to fabricate high performance parts. When the design study is projected to the year 2000 technology, substantinal net efficiency improvements, on the order of 25 to 46% over the ASRE, are computed

Accommodation requirements for microgravity science and applications research on space station

Scientific research conducted in the microgravity environment of space represents a unique opportunity to explore and exploit the benefits of materials processing in the virtual abscence of gravity induced forces. NASA has initiated the preliminary design of a permanently manned space station that will support technological advances in process science and stimulate the development of new and improved materials having applications across the commercial spectrum. A study is performed to define from the researchers' perspective, the requirements for laboratory equipment to accommodate microgravity experiments on the space station. The accommodation requirements focus on the microgravity science disciplines including combustion science, electronic materials, metals and alloys, fluids and transport phenomena, glasses and ceramics, and polymer science. User requirements have been identified in eleven research classes, each of which contain an envelope of functional requirements for related experiments having similar characteristics, objectives, and equipment needs. Based on these functional requirements seventeen items of experiment apparatus and twenty items of core supporting equipment have been defined which represent currently identified equipment requirements for a pressurized laboratory module at the initial operating capability of the NASA space station

Quantitative measurement of combustion gases in harsh environments using NDIR spectroscopy

The global climate change calls for a more environmental friendly use of energy and has led to stricter limits and regulations for the emissions of various greenhouse gases. Consequently, there is nowadays an increasing need for the detection of exhaust and natural gases. This need leads to an ever-growing market for gas sensors, which, at the moment, is dominated by chemical sensors. Yet, the increasing demands to also measure under harsh environmental conditions pave the way for non-invasive measurements and thus to optical detection techniques. Here, we present the development of a non-dispersive infrared absorption spectroscopy (NDIR) method for application to optical detection systems operating under harsh environments.Comment: 10 pages, 8 figure

An Evaluation of Non-Stochastic Lattice Structures Fabricated Via Electron Beam Melting

Metal foam structures have many applications and can be used as structural supports, heat exchangers, shock absorbers, and implant materials. Stochastic metal foams having different cell sizes and densities have been commercially available for a number of years. This paper addresses a different type of foams which are known as non-stochastic foams, or lattice structures. These foams have a well defined repeating unit cell structure rather than the random cell structure in commercially available stochastic foams. The paper reports on preliminary research on the fabrication of non-stochastic Ti-6Al-4V alloy foams using the Electron Beam Melting process. Behavior of the structures in compression, bending, and low cycle repeating load tests are discussed, and recommendations about cell geometry and processing conditions are made.Mechanical Engineerin

Research on The Ultra-Low Emission Technology in Internal Combustion Engine

Increasing the efficiency of internal combustion engines is a technologically proven and cost effective approach to dramatically improving the fuel economy of the nation’s fleet of vehicles in the near- to midterm, with the corresponding benefits of reducing our dependence on foreign oil and reducing carbon emissions. This review paper discusses on the research of ultra-low emission technology in internal combustion engine. Efficiency can be increased by improving combustion processes, minimizing engine losses such as friction, reducing the energy penalty of the emission control system and using recovered waste energy in propulsion. Compliance with exhaust emission regulations will be mandated and requires after-treatment technologies integrated with the engine combustion approaches. Fuels under consideration include hydrocarbon-based. Because of their relatively low cost, high performance, and ability to utilize renewable fuels, internal combustion engines, including those in hybrid vehicles, will continue to be critical to our transportation infrastructure for decades