Progress on Turbine engine section.

1 files changed, 9 insertions, 2 deletions

diff --git a/background.tex b/background.tex
index dbba796..8eb4cbf 100644
--- a/background.tex
+++ b/background.tex
@@ -24,9 +24,16 @@ The combustor, as illustrated in figure \ref{EoPturbojet} between station number
 The turbine section of the engine, denoted by station numbers 4 through 5, is responsible for taking the energy generated in the combustion chamber and turning it into shaft horsepower to drive the compressor stages and external loads. Almost 75 percent of the energy generated from the combustion process is required to drive the compressor alone.\cite{EoPGTR2}The axial-flow turbine is similar to the axial compressor, and is likewise comprised of a series of stages of rotors and stators. However, the turbine has the opposite effect of the compressor: it turns the energy contained within flow into shaft rotation. The stage quantity of the turbine section of a given turbine engine is typically lower than that of its compressor, as the flow is expanding rather than compressing. Axial turbines are either impulse design, which maintain flow velocity across their rotor and decrease pressure across their stator, whereas reaction stages increase pressure across their rotor blades and direct flow within their stator. Most turbines use a combination of these two stage designs, and must be dual or split commensurately with the design of the compressor.
 \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.
 
-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. \cite{nasa_turbojet}
-
+\begin{figure}[h]
+	\centering
+	\includegraphics[width=\textwidth]{img/faaturbofan.png}
+	\caption{\label{faaturbofan}Turbofan Engine Cross Section}
+\end{figure}
 \begin{figure}[h]
 	\centering
 	\includegraphics[width=\textwidth]{img/tp100cutaway.png}