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diff --git a/background.tex b/background.tex index 8eb4cbf..8c26e4d 100644 --- a/background.tex +++ b/background.tex @@ -25,15 +25,15 @@ The turbine section of the engine, denoted by station numbers 4 through 5, is re \par The final stage of the turbine engine, the exhaust nozzle, denoted by station numbers 5 through 9, is responsible for increasing the velocity of the exhaust gas before discharge such that ample thrust can be generated by the engine. Ideally, the exit pressure of the flow leaving the nozzle should equal ambient pressure, otherwise the engine will operate less efficiently than it is capable. Nozzles are typically either convergent, or convergent-divergent, meaning a convergent duct followed by a divergent duct. Simple convergent ducts are used in the case where the ratio of turbine exit pressure to nozzle exit pressure is less than 2. The convergent-divergent duct is employed in instances where this nozzle pressure ratio is in excess of 2. Such ducts incorporate more sophisticated aerodynamic features and variable geometry in certain applications.\cite{EoPGTR2} \par -Gas turbine engines fall into four categories: turbofan, turboprop, and turboshaft, and turbojet. Turbojets make use of a propelling nozzle to create thrust by allowing the heated exhaust created by a gas turbine to expand, without extracting rotational power from the engine. \cite{nasa_turbojet} -Turbofans make use of a front mounted fan to extract as much as 80 percent of thrust from the engine, significantly more than their turbojet counterparts. The inlets of turbofans differ from other topologies by virtue of their inlet design, as can be visualized in figure \ref{faaturbofan}. -The air driven by the fan will generally bypass the core, the amount of which contributes to the engine's bypass ratio. This ratio is simply the amount of flow through the engine bypass ducts over the flow through its core. The turboprop engine, that which is employed in this paper, drives a propeller through a reduction gearbox. - \begin{figure}[h] \centering \includegraphics[width=\textwidth]{img/faaturbofan.png} \caption{\label{faaturbofan}Turbofan Engine Cross Section} \end{figure} +Gas turbine engines fall into four categories: turbofan, turboprop, and turboshaft, and turbojet. Turbojets make use of a propelling nozzle to create thrust by allowing the heated exhaust created by a gas turbine to expand, without extracting rotational power from the engine. \cite{nasa_turbojet} +Turbofans make use of a front mounted fan to extract as much as 80 percent of thrust from the engine, significantly more than their turbojet counterparts. The inlets of turbofans differ from other topologies by virtue of their inlet design, as can be visualized in figure \ref{faaturbofan}. +The air driven by the fan will generally bypass the core, the amount of which contributes to the engine's bypass ratio. This ratio is simply the amount of flow through the engine bypass ducts over the flow through its core. The turboprop engine, that which is employed in this paper, drives a propeller through a reduction gearbox. +Turboshaft style engines are most often used in helicopters, and are characterized by their transfer of power to a shaft which later connects to another implement such as a propeller transmission or auxilary power unit. \cite{faa_engines} \begin{figure}[h] \centering \includegraphics[width=\textwidth]{img/tp100cutaway.png} @@ -42,11 +42,15 @@ The air driven by the fan will generally bypass the core, the amount of which co \section{Generator Theory} \section{Battery Theory} \section{Turboelectric Theory} +NASA defines turboelectric systems as being at the least a turboshaft coupled to an electric generator, which power electric motors which then drive propellers. This configuration can be further categorized in accordance with whether the turbine engine drives a load directly. +These systems, refered to as "Partial Turbo Electric" \cite{nasa_prop_overview}, employ the use of either turbofans or turboprops in addition to being coupled to electric generators. \begin{figure}[h] \centering \includegraphics[width=\textwidth]{img/turbosystems.png} \caption{\label{turboarch}Turboelectric Architectures} \end{figure} +The last manner in which turboelectric systems can be categorized is with respect to their inclusion of additional power sources. For example, just as is illustrated in figure \ref{turboseriesparallel}, systems with battery supplementation are called "parallel," whereas those which source power exclusively from their turbine engine are "seires." \cite{nasa_prop_overview} +Both systems constructed for this research are partial by virtue of their turboprop engines. However, configuration 1 is parallel due to its inclusion of a battery, whereas configuration 2 is devoid of additional power sources and is thus series. \begin{figure}[h] \centering \includegraphics[width=.6\textwidth]{img/turboseriesparallel.png} |