A calculation method has been developed to analyze and to optimize both the acoustic and performance aspects of air intake systems for internal combustion engines. The method integrates an acoustic linear one-dimensional computer code (SISASP) together with an acoustic linear three-dimensional computer code (SYSNOISE) and a one-dimensional thermodynamics analysis code (MARKPLUS XIV).
The method enables the design of complete intake systems, integrating the acoustic and performance aspects and allows the designer to optimize the design to achieve legal, subjective comfort and engine performance targets.
The results obtained from system simulations carried out in this way have been validated on a four cylinder gasoline engine and are illustrated here.
The method can be used as part of the overall integrated design of an engine and also as a tool for intake system optimization. It provides significant reduction in the time and cost of development because both thermodynamic and acoustic performance are optimized simultaneously.
In recent years, there have been increasing demands for improved engine performance and increased acoustic comfort. A trend has emerged to treat the engine as a system, to which the intake and exhaust subsystems are attached.
It has long been known that the intake system geometry affects both the engine performance and the noise radiated at the intake orifice and also that the system is a complex design.
Experienced engineers once estimated and then developed intake systems. Recently increasing system complexity and technical requirements have made this almost impossible in the allowed time. The use of predictive calculation and design systems is therefore very helpful and indeed necessary to today's engine system designer.
Increasingly obvious public concern over environmental pollution in various forms, including noise pollution, have focused attention on the definition of international requirements. There are now strict limits for the maximum noise levels generated by cars (74 dBA in the European drive-by test). The noise radiated from the intake system generally makes a significant contribution to the overall vehicle noise level.
Market demands have increasingly stressed the importance of the acoustic comfort inside the car, especially for low frequency roar but also for the overall noise quality due to the mid- and high-frequency content. This required a significant length of time to carry out and so increased the overall time and cost of the program.
There is considerable pressure to reduce this cost and to increase the design confidence level. Computer design and simulation codes are used to reduce testing. Optimized designs will be checked, not developed, on the test bed and the car.
This paper describes a computer methodology using three numerical simulation codes to predict acoustic and performance behavior of an intake system to support the design and development process.