Proiectarea unui sistem variabil de supraalimentare acustică

Abstract

In this graduate project it is desired to project a variable acoustical supercharging intake system. To analyze the performances of this system it must be mounted on an engine. For this it is chosen a natural aspirated spark ignition engine.

The initial dimensioning starts with the one dimensional analysis in AMESim program, also from hear it is obtained the initial dimensioning of the SI engine.

After obtaining the main dimension of the engine and the variable supercharging intake system a CAD design is made using the CATIA V5R16 and several parts of the engine will be analyzed using a FEM program to see if the parts will sustain the loads that appear in the engine and if they are right dimensioned.

Abstract

În această lucrare se urmărește proiectarea unui sitem variabil de supraalimentare acustică. Pentru a putea analiza performanțele acestui sistem, el va fi montat pe un motor cu aprindere prin scânteie aspirat natural.

Predimensionarea sistemului se face din analiza undimensională in AMESim; tot in AMESim este dimensionat si motorul.

Dupa dimensionarea motorului si a sistemului de supraalimentare acustică se realizeaza modelul CAS al acestora. Pentru analiza tensiunilor mecanice si termice se foloseseste programul Patran/Nastran din care se poate concluziona daca dimensiunile au fost corect alese.

1 Introduction

From the beginnings of automotive industry everyone wanted to obtain the best performances from the car. But to obtain the maximum power from an engine it necessary to get the maximum amount of air into the cylinder.

The variable intake system is a very interesting subject because of the improvements made by other automotive industry company, like AUDI, Opel, Nissan and even those from the F1 and Moto Gp.

In this study it is analyzed in particular the ram effect on the fore stroke internal combustion engine. It is also presented the design and calculus of a variable system that will improve the intake system of the normal aspirated internal combustion engine and further on the design of an engine based on the AMESim engine model.

The study of the variable intake system is based on the AMESim program because it can simulate the variation of the volumetric efficiency for different values of the intake manifold and lengths of the pipe.

Beside of this study of the intake system, using Catia V5R16 it will be made a 3D model of the variable intake system and of the engine on which it will be mounted this system.

Using the Patran/Nastran programs several parts of the engine will be tested to see their mechanical resistance and thermal dilatation.

2 General study of the tuned intake manifold

To be able to study the performance of the intake system and to design it, there are necessary a lot of intake and exhaust acoustics knowledge. The study of the air breath system of the engine has begun form the early twenties by Capetti A. In the late fifties, Bason continued the study on the gas-dynamics and the manifold design. At the end of nineties a complete study on the air breathes system of the engine is presented by Winterbone and Pearson.

I have chose to study the ram effect on the intake system because of the performance that can be obtain according to the results obtained on F1cars and MotoGp superbike.

Naturally aspirated engine with tuned intake system have obtained a 125% in excess volumetric efficiency and higher peak engine speeds, up to 18000 rpm.

For the F1 cars the tests war made only on one cylinder due to the high cost of the engine and the reduced time of usage, approximately two hours. The study was also made on the computer using a simulation code for the intake wave dynamics. The result obtained war compared with the one obtained experimentally on the single cylinder engine. The comparative results are shown in the following figure Fig. 2.1.