Browsing by Subject "combustion"

Now showing 1 - 7 of 7
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    A Characterization of Different Spark Regimes for Ignition Delay Comparison with Conventional Spark Plugs
    (Office of the Vice Chancellor for Research, 2016-04-08) Wozniak, Zachary M.; Burton, Jesse C.; Hedrick, Cameron J.; Deng, Qiuyu; Robinson, Daniel W.
    The introduction of plasma into combustion and ignition processes has continuously proved to be advantageous when compared to the conventional spark ignition in a wide range of categories. From the capability to ignite leaner mixtures and improve fuel economy to an effective reduction of hazardous emissions and ignition delay, the benefits of integrating non-equilibrium plasma can be utilized for numerous applications including hot jet ignition. Detailed design specifications for the electrode configuration, circuit schematic, and combustion rig are developed and presented. Using a CCD camera and high performance oscilloscope, this paper aims to identify, characterize, and compare the different effects of frequency and pulse width of a driver circuit on the plasma sparks quantitatively in terms of the current, voltage, and energy attributes. Four different plasma regimes are investigated with frequencies ranging from 5.44 Hz to 95.46 kHz and pulse energies ranging from 168 μJ to 14.42 J. The maximum voltage and current characteristics of the plasmas indicate a glow discharge referencing previous experiments. Future work is laid out for a comparison of the ignition progression between a non-thermal plasma system and a traditional spark with using Schlieren imaging.
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    Experimental Investigation on the Wave Rotor Constant Volume Combustor
    (AIAA, 2010-07-25) Matsutomi, Yu; Meyer, Scott; Wijeyakulasuriya, Sameera; Izzy, Zuhair; Nalim, M. Razi; Shimo, Masayoshi; Kowalkowski, Mike; Snyder, Philip; Mechanical Engineering, School of Engineering and Technology
    A wave rotor constant volume combustor was designed and built as a collaborative work of Rolls-Royce, Indiana University-Purdue University Indianapolis (IUPUI), and Purdue University. The experiment was designed to operate at rotational speeds of up to 4,200 rpm with air mass flow rates of approximately 18 lbm per second. Initial tests were conducted at 2,100 rpm with ethylene as fuel. The rig was operated with different fuel injection schemes to investigate operational characteristics of the combustor. Successful combustion and pressure gain were achieved over a range of operating conditions.
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    Fire, vegetation, and Holocene climate in a southeastern Tibetan lake: a multi-biomarker reconstruction from Paru Co
    (EGU, 2018-10) Callegaro, Alice; Battistel, Dario; Kehrwald, Natalie M.; Matsubara Pereira, Felipe; Kirchgeorg, Torben; del Carmen Villoslada Hidalgo, Maria; Bird, Broxton W.; Barbante, Carlo; Earth Sciences, School of Science
    The fire history of the Tibetan Plateau over centennial to millennial timescales is not well known. Recent ice core studies reconstruct fire history over the past few decades but do not extend through the Holocene. Lacustrine sedimentary cores, however, can provide continuous records of local environmental change on millennial scales during the Holocene through the accumulation and preservation of specific organic molecular biomarkers. To reconstruct Holocene fire events and vegetation changes occurring on the southeastern Tibetan Plateau and the surrounding areas, we used a multi-proxy approach, investigating multiple biomarkers preserved in core sediment samples retrieved from Paru Co, a small lake located in the Nyainqentanglha Mountains (29∘47′45.6'' N, 92∘21′07.2'' E; 4845 m a.s.l.). Biomarkers include n-alkanes as indicators of vegetation, polycyclic aromatic hydrocarbons (PAHs) as combustion proxies, fecal sterols and stanols (FeSts) as indicators of the presence of humans or grazing animals, and finally monosaccharide anhydrides (MAs) as specific markers of vegetation burning processes. Insolation changes and the associated influence on the Indian summer monsoon (ISM) affect the vegetation distribution and fire types recorded in Paru Co throughout the Holocene. The early Holocene (10.7–7.5 cal kyr BP) n-alkane ratios demonstrate oscillations between grass and conifer communities, resulting in respective smouldering fires represented by levoglucosan peaks, and high-temperature fires represented by high-molecular-weight PAHs. Forest cover increases with a strengthened ISM, where coincident high levoglucosan to mannosan (L ∕ M) ratios are consistent with conifer burning. The decrease in the ISM at 4.2 cal kyr BP corresponds with the expansion of regional civilizations, although the lack of human FeSts above the method detection limits excludes local anthropogenic influence on fire and vegetation changes. The late Holocene is characterized by a relatively shallow lake surrounded by grassland, where all biomarkers other than PAHs display only minor variations. The sum of PAHs steadily increases throughout the late Holocene, suggesting a net increase in local to regional combustion that is separate from vegetation and climate change.
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    Longitudinally Stratified Combustion in Wave Rotors
    (2000-11) Nalim, M. Razi
    A wave rotor may be used as a pressure-gain combustor, effecting wave compression and expansion, and intermittent confined combustion, to enhance gas-turbine engine performance. It will be more compact than an equivalent pressure-exchange wave-rotor system, but will have similar thermodynamic and mechanical characteristics. Because the allowable turbine blade temperature limits overall fuel-air ratio to subftammable values, premixed stratification techniques are necessary to burn hydrocarbon fuels in small engines with compressor discharge temperatures well below autoignition conditions. One-dimensional, nonsteady numerical simulations of stratified-charge combustion are performed using an eddy-diffusivity turbulence model and a simple reaction model incorporating a flammability limit temperature. For good combustion efficiency, a stratification strategy is developed that concentrates fuel at the leading and trailing edges of the inlet port. Rotor and exhaust temperature profiles and performance predictions are presented at three representative operating conditions of the engine: full design load, 40% load, and idle. The results indicate that peak local gas temperatures will cause excessive temperatures in the rotor housing unless additional cooling methods are used. The rotor temperature will be acceptable, but the pattern factor presented to the turbine may be of concern, depending on exhaust duct design and duct-rotor interaction.
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    A Numerical Investigation of Premixed Combustion in Wave Rotors
    (1997-07) Nalim, M. Razi; Paxson, Daniel E.
    Wave rotor cycles that utilize premixed combustion processes within the passages are examined numerically using a one-dimensional CFD-based simulation. Internal-combustion wave rotors are envisioned for use as pressure-gain combustors in gas turbine engines. The simulation methodology is described, including a presentation of the assumed governing equations for the flow and reaction in the channels, the numerical integration method used, and the modeling of external components such as recirculation ducts. A number of cycle simulations are then presented that illustrate both turbulent-deflagration and detonation modes of combustion. Estimates of performance and rotor wall temperatures for the various cycles are made, and the advantages and disadvantages of each are discussed.
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    Thermodynamic Limits of Work and Pressure Gain in Combustion and Evaporation Processes
    (2002-11) Nalim, M. Razi
    Combustion and evaporation processes occurring in a closed chamber can result in significant pressure rise and direct work transfer. The pressure and volumetric changes that accompany such processes allow substantial work potential to be achieved in cyclic nonsteady devices, such as internal combustion engines and pulsed combustion or detonation engines. The ideal pressure gain or work production is a function of the prescribed inflow and outflow conditions, volumetric confinement, fluid properties, and other parameters. The generalized thermodynamic limits of pressure gain and work production in such devices are investigated. Analytic and iterative methods are provided to evaluate cyclic combustion and evaporation processes for enhancing airbreathing combustion engine performance.
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    Trash to Electricity
    (Office of the Vice Chancellor for Research, 2013-04-05) Witte, Drew; Schubert, Peter J.
    In 2009, America generated more than 243 million tons of trash, also known as Municipal Solid Waste (MSW). That generation rate was 275% greater than in 1960 when Americans generated 88.1 million tons of MSW. Today, landfills near urban areas are reaching their capacity and energy prices are soaring. Even after separating out recyclables from MSW, Americans’ trash still contains 11 MJ per kg. This energy value is stored as chemical energy in carbon based biomass and un-recyclable plastics. Many types of technologies exist that transform this trash energy into usable electrical energy. The status-quo for turning waste-to-energy is by combustion. There are 76 waste-to-energy combustion plants in the U.S. Another common way to transform waste to energy is by burning methane produced by landfills. Pyrolysis and gasification are two emerging technologies in the waste-to-energy field. These technologies are attractive because they are more controlled processes; therefore, pyrolysis and gasification is better for the environment and allows for greater rate of metal recycling after the process. Additionally, these emerging technologies show the potential to convert MSW into liquid fuels for transportation.