This research was funded by the Fundamental Research Funds for the Central Universities, grant number [No. NS2018017].

1. Preparation before modeling
<ol>
	<li>Obtain design point performance.
	<ol>
		<li>Open Gasturb 13. Select Variable Cycle Engine.</li>
		<li>Click on Basic Thermodynamics. Select Cycle Design. Open DemoVarCyc.CVC.</li>
		<li>Obtain the engine design point performance. These are shown on the right side of the window.</li>
	</ol>
	</li>
	<li>Obtain component maps.
	<ol>
		<li>Open Gasturb 13. Select Variable C...

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We have nothing to disclose.

Based on a graphical simulation environment, a VCE component-level model can be built rapidly through modular hierarchical architecture and object-oriented modeling technology. It offers a friendly interface to users and it is convenient to analyze and design the model19.
The main limitation of this method is the execution efficiency of the model. Because the model is written in scripting language, the model needs to be recompiled every time it runs. Thus, the execution...

Modern aircraft demands bring great challenges to the propulsion system, which need more intelligent, more efficient or even more versatile aircraft engines1. Future military propulsion systems also require both higher thrust at high speed and lower specific fuel consumption at low speed1,2,3,4. In order to meet the technical requirements of future flight missions, General Electric (GE) put forward the variable cycle engine (VCE) concept in 19555. A VCE is an aircraft engine that can perform different thermodynamic cycles by changing the geometry size or position of some components6. The Lockheed SR-71 "Blackbird" powered by a J58 turboramjet VCE has held the world record for the fastest air-breathing manned aircraft since 19767. It also proved many potential advantages of supersonic flight. In the past 50 years, GE has improved and invented several other VCEs, including a double bypass VCE8, a controlled pressure ratio engine9 and an adaptive cycle engine10. These studies involved not only the general structure and performance verification, but also the control system of the engine11. These studies have proven that the VCE can work like a high bypass ratio turbofan at subsonic flight and like a low bypass ratio turbofan, even like a turbojet at supersonic flight. Thus, the VCE can realize performance matching under different flight conditions.
When developing a VCE, a large amount of necessary verification works will be carried out. It may cost a large amount of time and outlay if all these works are performed in a physical way12. Computer simulation technology, which has already been adopted in developing a new engine, can not only reduce the cost greatly, but also avoid the potential risks13,14. Based on computer simulation technology, the development cycle of an engine will be reduced to nearly half, and the number of equipment required will be reduced dramatically15. On the other hand, simulation also plays an important role in the analysis of the engine behavior and control law development. For simulating the static design and off-design performance of engines, a program called GENENG16 was developed by the NASA Lewis Research Center in 1972. Then the research center developed DYNGEN17 derived from GENENG, and DYNGEN could simulate the transient performance of a turbojet and the turbofan engines. In 1989, NASA put forward a project, called Numerical Propulsion System Simulation (NPSS), and it encouraged researchers to construct a modular and flexible engine simulation program through the use of object-oriented programming. In 1993, John A. Reed developed the Turbofan Engine Simulation System (TESS) based on the Application Visualization System (AVS) platform through object-oriented programing18.
Meanwhile, rapid modeling based on graphical programming environment is being used gradually in simulation. The Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS) package developed by NASA is based on Matlab/Simulink platform. It is open source and allows users to customize built-in component libraries. T-MATS offers a friendly interface to users and it is convenient to analyze and design the built-in JT9D model19.
In this article, the dynamic model of a type of VCE has been developed here using Simulink software. The modeling object of this protocol is a double bypass VCE. Its schematic layout is shown in Figure 1. The engine can work in both single and double bypass modes. When the Mode Select Valve (MSV) is open, the engine performs better at subsonic conditions with a relatively large bypass ratio. When the Mode Select Valve is closed, the VCE has a small bypass ratio and a better supersonic mission adaptability. To further quantize performance of the engine, a double bypass VCE model is built based on component-level modeling method.

<table>
	<tbody>
		<tr>
			<td>Gasturb</td>
			<td>GasTurb GmbH</td>
			<td>Gasturb 13</td>
			<td></td>
		</tr>
		<tr>
			<td>MATLAB</td>
			<td>MathWorks</td>
			<td>R2017b</td>
			<td></td>
		</tr>
		<tr>
			<td>TMATS</td>
			<td>NASA</td>
			<td>1.2.0</td>
			<td></td>
		</tr>
	</tbody>
</table>

a rapid method for modeling a variable cycle engine

The variable cycle engines (VCE) that combine the advantages of turbofan and turbojet engines, are widely considered to be the next generation aircraft engines. However, developing VCE requires high costs. Thus, it is essential to build a mathematical model when developing an aircraft engine, which may avoid a large number of real tests and reduce the cost dramatically. Modeling is also crucial in control law development. In this article, based on a graphical simulation environment, a rapid method for modeling a double bypass variable cycle engine using object-oriented modeling technology and modular hierarchical architecture is described. Firstly, the mathematical model of each component is built based on the thermodynamic calculation. Then, a hierarchical engine model is built via the combination of each component mathematical model and the N-R solver module. Finally, the static and dynamic simulations are carried out in the model and the simulation results prove the effectiveness of the modeling method. The VCE model built through this method has the advantages of clear structure and real-time observation.

In order to prove the validity of the simulation model, several typical performance parameters selected in static and dynamic simulations are compared with the data in Gasturb.
In a static simulation, we compare several key performance parameters of the model with these parameters in Gasturb to verify the accuracy of the static model. Table 2 shows the result of the comparison at the design point with H=0 m, Ma=0, Wf=0.79334 kg/s under a double bypass ope...

Watch this Scientific Journal Video about A Rapid Method for Modeling a Variable Cycle Engine at JoVE.com

A Rapid Method for Modeling a Variable Cycle Engine

Here, we present a protocol to build a component-level mathematical model for a variable cycle engine.

The variable cycle engines (VCE) that combine the advantages of turbofan and turbojet engines, are widely considered to be the next generation aircraft ...

This method help researchers to quickly build a model of an aircraft engine with existing engine data. This main advantage of this method is that has no high requirements for the programming technology that have happened for traditional modeling. Before beginning the modeling, open GasTurb13 and click Basic Thermodynamics.Select Cycle Design and open demo variable cycle. The engine design point performance parameters will be shown. To obtain the component maps, in the main window click Off Design, More, and standard maps.Open demo variable cycle and select LPC, IPC, HPC, HPT and LPT. To model a single component of a variable cycle engine, open a data analysis program and click Simulink. Double click on blank model and click library to place a function to model.Double click function. The thermodynamic equation of the compressor will be described according to the working principle of the compressor. Click the equation and paste to obtain the input and output of the compressor.Rename the function compressor. In the compressor function window, right click on the function name and select subsystem and model reference and create subsystem from selection to mask the module. When all of the components have been modeled, combine the output of each component with the input of the next component.Here the results of the comparison at the design point under a double bypass operating mode are shown indicating that the maximum error of the performance parameters between the model and the GasTurb is an engine pressure ratio below 2%Here, a result of the comparison at the off design point, under a single bypass operating mode are shown. Under these conditions, the maximum error is a rotational speed of low-pressure shaft just below 4%In this representative acceleration, deceleration simulation processed under a double bypass mode the input of the fuel flow is shown. These rotational speed, air flow, and temperature before the turbine data demonstrate that the model is able to perform an acceleration, deceleration simulation.In this representative experiment, the variable cycle engine operating mode was switched from the single bypass mode to the double bypass mode at five seconds to prevent the engine from exceeding the limited speed during the switching process, a single variable closed loop control was applied to the rotational speed of the high pressure shaft. In this assay, the rotational speed of the high pressure shaft remained nearly unchanged during the switching. Similarly, the response of the fuel flow, rotational speed, air flow, and temperature before the turbine can be observed.The acceleration, deceleration, and mode switching simulation results confirm that two dynamic simulation, the model can run correctly. Learning how to select a specific or common working equation's important, because common working equation help to set up the model correctly. Following this procedure, other types of aircraft engines or gas turbine engines models can be built.

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7.4K vues.  Nanjing University of Aeronautics and Astronautics. Cette méthode aide les chercheurs à construire rapidement un modèle de moteur d’avion avec les données existantes du moteur. Ce principal avantage de cette méthode est que n’a pas d’exigences élevées pour la technologie de programmation qui se sont produites pour la modélisation traditionnelle. Avant de commencer la modélisation, ouvrez GasTurb13 et cliquez sur Thermodynamique de base.Sélectionnez Cycle Design et cycle variable de démonstration ouvert. Les paramètres ...