AMESIm几个例子

Technical Bulletin n°106
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Latest update: May 31st, 2001
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AMESim in the Automobile Industry: Some Case Studies 3/19 AMESim in the Automobile Industry: Some Case Studies
In this document we present so me examples of how AMESim is used in the Automobile Industry. For confidentiality reasons, we present figures and a brief description, which illustrate the applicability of AMESim.
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AMESim in the Automobile Industry: Some Case Studies
4/19
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1. Electronic fuel injection
This case study deals with the modeling of a diesel injection system known as common rail type. The objective was to build a detailed parameterized model that would allow the reproduction of measurement results.
The major features of the modeling procedure were: Ä to take into account the distortion of the needle and the
injector when they are submitted to high pressures (1400 bar) Ä to allow the study of the cavitation on the injection system.
The model developed was able to reproduce the experimental measurements with precision within a few percents for the following: Ä needle motion
AMESim in the Automobile Industry: Some Case Studies 5/19 Ä pressures
Ä instantaneous flow
Ä injected volume…
The different components of the system (pump, pressure regulator, injectors and rail) can be modeled using AMESim Hydraulic Component Design library (see Technical Bulletin: “AMESim and Common Rail”).
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AMESim in the Automobile Industry: Some Case Studies 6/19
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2. Mechanical Fuel Injection
Mechanical injection systems represent for the engineer one of the most advanced applications in the 'Fluid Power Control' field. These systems ensure, by means of
very rapid
dynamics (several milliseconds), the injection of a quantity of fuel with incredible precision. This action is repeated millions of times during the life of the injector.
The control of these systems has been achieved only by a fine understanding of the physical
phenomena having significant influence. At the functional level, we can cite the following aspects : Ä influence of fluid characteristics Ä flow rate in the control orifices taking into account evolutions of flow conditions (laminar-turbulent, cavitation influence) Ä pipe transient (see Technical Bulletin : “AMESim and Mechanical Injection”)
Certainly, engineers designing these injection systems did not wait for the availability of current numeric simulation tools to develop them. However, it is unden iable that nowadays simulation takes a significant part
AMESim in the Automobile Industry: Some Case Studies 7/19 in the design process. This is represented by different aspects:
Ä by ensuring a finer analysis of experimental situations
Ä by a capitalization of acquired knowledge
Ä by an enriched framework of acquired experience to aid in the conception of new systems (case of the common rail).
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AMESim in the Automobile Industry: Some Case Studies 8/19
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3. Automatic gearbox
This case study deals with
the development of models for the design of a
hydraulic circuit and its
control system in an automatic gearbox.
These models are made using the AMESim
Hydraulic Component Design library to construct specialist valves that are to be found on automatic gearboxes. It was validated by using experimental measurements of a benchmark. The parameters crucial in the stability of the valves and the circuit as a whole could be tuned by simulation. The design times for a gearbox are substantially reduced by using this model.
The analysis of these hydraulic circuits requires the closest reproduction of phenomena and has led to the development of mechanical components such as multidisk clutches and brakes as well as band brakes and epicycloïdal gear trains
AMESim in the Automobile Industry: Some Case Studies 9/19 present in automatic gearboxes. Due to that, IMAGINE has built the AMESim Powertrain library for automatic and manual transmissions (see Technical Bulletin: “AMESim and Powertain”).
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AMESim in the Automobile Industry: Some Case Studies 10/19
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4. Braking system
The braking circuit analyzed is classic and consists of a pneumatic vacuum booster, a master cylinder converting the booster energy into hydraulic energy and lines allowing to reach the calipers.
1.
The model of the vacuum booster, including the rubber
part, used AMESim Mechanical, Hydraulic and Pneumatic libraries. The master cylinder and the calipers have been created
with Hydraulic Component Design .
The complete model allows to predict: Ä the assistance of the booster Ä the effect of the restrictions on the output of the front and rear chambers of the master cylinder Ä the pressure on the calipers, and consequently the braking torque applied on each wheel (see Technical Bulletin : “AMESim and Braking”)
AMESim in the Automobile Industry: Some Case Studies 11/19
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5. Power steering system
An early application of AMESim
involved fault rectification of a power steering system. Bad vibrations occurred when the vehicle was stopped and the steering wheel turned. A detailed model of the hydraulic system shown above, based upon the physical sizes and characteristics of the components was built and validated by comparison with benchmarks.
A sensitivity analysis of various parameters was carried out, and tuning proposals were submitted to the manufacturer to suppress the vibrations.
For various working states, the model was linearized, and the following analyses were performed with linear analysis tools: Ä eigenvalue analysis and modal shape Ä root locus Ä transfert functions (see Technical Bulletin : “AMESim and Power steering”)
AMESim in the Automobile Industry: Some Case Studies 12/19
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6. Variable Valve Actuation
Different types of valve lift controls exist which are more or less complex. The third generation systems, which are in the process of development, allow total valve lift control: zero lift, partial or total. This concept allows to control, for each cylinder at each engine revolution, the exact quantity of air necessary for the correct combustion of the injected fuel. The prospects for the use of this technology are a 15% torque increase with a 10% reduction in consumption in the NEDC cycle.
The creation of a numerical model of an electro-hydraulic system (EHV) should allow not only to help the designer in the choice of geometric values which will allow the system to respond to the specifications, but will also allow him/her to make it evolve easily.
The method has allowed the development of a VVA system mounted on a 5-cylinder engine, 4 valves per cylinder. On each of the ten inlet valves, an EHV is mounted, the outlet valves do not have them since the benefit would be too insignificant.
AMESim in the Automobile Industry: Some Case Studies 13/19 The coupling between the simulation and the experimental tests has limited the number of physical prototypes, which is a substantial benefit in terms of time and cost (see Technical Bulletin : “AMESim and Variable Valve Actuation”).
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AMESim in the Automobile Industry: Some Case Studies 14/19
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7. Lubrication
The main interest in the modeling of such networks is to size the pump thereby ensuring sufficient pressure levels in the system and consequently to estimate the lubricant flow rates in the different branches. These flow rates are directly dependent on the rotary speed and the characteristic of the pump, the dimension of the oil canals and on the characteristics
of some specific components such
as bearings.
Flow resistance has a great influence on the design of lubricating circuits in which pressures are relatively low but flow rates are high. This is the motivation for creating the AMESim Hydraulic Resistance library. This library comprises a set of components such as T-junctions, bends, sudden expansions and contractions based on the Idel'cik formulae and experimental data, from which it is easy to model large hydraulic networks.
When an engine is started, the lubrication circuit is empty. In order to reduce friction the lubricant has to reach each working part as soon as possible. In order to evaluate the time needed to fill in the whole circuit and to evaluate the order in which the different branches composing the network will be filled, Imagine has developed the AMESim Filling . This basic element library enables the user to
AMESim in the Automobile Industry: Some Case Studies 15/19 calculate pressures, mass flow rates, type of flowing fluid and volumetric liquid fraction for the system (see Technical Bulletin: “AMESim and Lubrication”).
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AMESim in the Automobile Industry: Some Case Studies 16/19
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8. Cooling System
The main purpose of engine cooling is to avoid metallurgical damage due to h igh temperatures in the engine cylinders. Therefore, the engine cooling system has to provide during cold start or low ambient temperature conditions a controlled
increase in coolant, oil and engine material temperatures. In addition, under uphill and full-load conditions, it must provide sufficient cooling of the oil and the engine metal masses.
The AMESim Cooling System package
allows
to calculate the coolant flow rate distribution in the different branches and to check the thermal efficiency of the sy stem. The Cooling System library is composed of specific components from which complete engine cooling systems can be built. All these components are connected together using models of the Thermal-Hydraulic library. This library comprises a set of basic components such as resistance components (orifices, bends, T-junctions..), pipes/hoses components (adiabatic or with heat exchange), pump components...
A cooling system model allows to predict the distribution of flow rates of coolant and its temperature in every branch of the circuit, the levels of pressures, the operating of the thermostat and consequently the regulation of the engine outlet coolant temperature, and cavitation. The technological elements approach allows
AMESim in the Automobile Industry: Some Case Studies 17/19 easy and fast modification of each module structure: effect of different circuit architectures, influence of immersion heater, influence of the air-conditioning system (see Technical Bulletin : “AMESim and Cooling system”).
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AMESim in the Automobile Industry: Some Case Studies 18/19
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9. Vehicle thermal management
In the framework of recent and future pollutant rejection standards, car manufacturers are brought to optimize the pollution treating functions by reducing engine emissions and fuel consumption and by increasing the performances of exhaust gas post-treating systems. In addition, it is essential to enhance or at least maintain the dynamic performances of vehicles without reducing cabin comfort in order to satisfy the ever-increasing demands of customers.
From these considerations, it seems that the whole thermal management of the engine is concerned. It is essential to control the steady state and transient thermal behavior of the engine and
the exhaust line. Therefore, the sub-functions involved are cooling, lubrication, thermal exchanges in the engine block, exhaust thermal behavior, exhaust gas chemical treatment.
A complete model has been created using models of AMESim Thermal, Thermal-Hydraulic and Cooling System libraries. This model allows to simulate the engine warm-up and to study the effect of technological changes on the engine: e ngine block material, architecture of the fluid circuits (cooling, lubrication and exhaust). This model can also be used to determine the influence of topological modifications of the
AMESim in the Automobile Industry: Some Case Studies 19/19 cooling circuit: architecture of the cooling circuit, adding of extra heaters… (See Technical Bulletin: “AMESim and Vehicle Thermal Management”).
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