Jet Propulsion Essay, Research Paper

JET PROPULSION

Thermodynamicss ME-304

M, T, W, F =* 2:00 & # 8211 ; 3:00

June 5, 2000

Introduction:

The undermentioned study, submitted to Roy Aircraft Engines Incorporated for an efficiency survey, is an analysis of a fanjet engine completed by thermodynamically analyzing each chief constituent that constitutes a fanjet engine. RAE Incorporated requested package that would cipher the theoretical upper limit end product speed, utilizing input informations imputed by the user of the plan. The computations are made presuming idealised conditions. In the analysis, the fanjet was broken down into its cardinal parts, which consist of an recess, compressor, burner, turbine, and nozzle.

Description of Turbojet Components

First, the recess / diffusor, of a fanjet brings free watercourse air to the engine and does no thermodynamic work on the flow. It is assumed that the flow through the diffusor is isentropic.

Second, the compressor does work onto the gas passing through to raise the force per unit area. Again, this procedure is assumed to be isentropic.

Third, the tight air is combined with fuel and is ignited within the combustor. The procedure within the combustor is assumed to be isentropic. The ensuing high temperature fluid is used to turn the 4th constituent of the fanjet, the turbine.

Next, the turbine is used to pull out energy from the heated flow coming from the burner. This is done by this flow of gas passing through blades on a free spinning shaft. The turbine generates merely plenty energy to drive the compressor. When the flow passes through the turbine, the force per unit area and temperature are decreased.

The following measure is optional within the plan. Here an afterburner is used to reheat the go outing gas from the turbine. This is done by shooting extra fuel into the gas go outing from the turbine. Igniting this mixture produces a higher temperature at the nose, as a consequence the concluding speed of the jet engine is increased.

Finally, the flow comes through the nose where no thermodynamic work is performed on the flow by the nose. The temperature remains changeless through the nose while the force per unit area and speed of the flow will alter as dictated by the design of the nose. The nose is used to bring forth push and used to carry on the fumes gases back to the free air.

For the analysis of the fanjet, several premises were made and are as follows:

1. Air behaves as a compressible, ideal gas.

2. Flow through the diffusor, nozzle, compressor and combustor is

isentropic.

3. The engine is insulated, there is no loss of heat to the environing air.

4. The engine is runing at steady province.

5. Work by

the turbine is equal to the work required by the compressor.

6. Pressure through the compressor / burner is changeless.

7. Kinetic and possible energy are zero except at the consumption of the recess and the issue of the nose.

Using the Plan

The plan is a MATLAB book so the first thing that must be done to run it is to get down MATLAB. On a *nix system, the best manner to run the plan is to get down MATLAB in the directory with the thermo.m and the findvf.m files. After MATLB starts type thermo ( or thermot3 to happen Vf utilizing T3 alternatively of Qin ) , at the MATLAB prompt. On Microsoft Windows systems, make certain the way incorporating the thermo.m, thermot3.m, findvf.m and findvft3.m files is in the MATLAB way and so type thermo at the MATLAB prompt.

Once the plan is running, the user will hold the option to happen Vf for a system without an afterburner, a system with an afterburner or to discontinue. Once the user has made their choice they will be prompted for the indispensable values needed to cipher Vf. When this is done the value for Vf will be displayed and if the system with the afterburner is selected, so the value for Vf with and without the afterburner will be displayed. Entering the compaction ratio is optional and if it is non entered, the plan will happen the maximal value for Vf and the compaction ratio that will give the maximal value.

Final Velocity V. Compression Ratio Graphs

Figure 1 & # 8211 ; Without Afterburner

Figure 2 & # 8211 ; With Afterburner

Conclusion / Discussion

During the development of the package, we were able to see general relationships between the different variables the user imputes and the end product speed of the jet engine. We were able to see that the compaction ratio has a big affect on the concluding speed. As seen from Figure 1 & A ; 2, the relation between the concluding speed and compaction ratio is non additive. Our plan determined the most efficient compaction ratio, while non utilizing an afterburner, was 11.8 while the other variable informations remained changeless.

We were besides able to see a additive relationship between the diffuser/nozzle ratio and the concluding speed. However, we did non happen a ratio that would maximise the end product speed of the jet engine.

We were able to see a non-linear relation between the heat input from the combustor and the concluding speed. Due to a little sample size, we were unable to see the add-on of more heat input cut downing the concluding speed. However, we know there must be a maximal value for heat input to maximise the speed, or one would be able to go on adding any heat input one would desire to hold improbably high end product speeds. Finally, we were able to see a great addition to the concluding speed due to the usage of an afterburner. This can be seen from figure 1 & A ; 2.