American Journal of Vehicle Design, 2015, Vol. 3, No. 1, 6-15 Available online at http://pubs.sciepub.com/ajvd/3/1/2 © Science and Education Publishing DOI:10.12691/ajvd-3-1-2 Experimental Assessment of Noise Generation from I.C. Engine Intake and Exhaust Systems Components Sabry Allam * Automotive Technology Department, Faculty of Industrial Education, Helwan University, Cairo, Egypt *Corresponding author: allam@kth.se Received April 03, 2015; Revised April 15, 2015; Accepted April 20, 2015 Abstract Several acoustic elements are used in internal combustion engine to tune engine intake/exhaust manifold systems. Components in intake and exhaust systems that create flow separation can for certain conditions and frequencies amplify incident sound waves. This vortex-sound phenomena is the origin for whistling, i.e., the production of tonal sound at frequencies close to the resonances of a duct system. One way of predicting whistling potential is to compute the acoustic power balance, i.e., the difference between incident and scattered sound power. This can readily obtained if the scattering matrix is known for the object. For the low frequency plane wave case this implies knowledge of the two-port data, which can be obtained by numerical and experimental methods. In this paper the development of multi-port models to describe linear acoustic problems in ducts with flow is presented. From an engineering point of view this field covers many important applications ranging from ventilation ducts in vehicles or buildings to intake/exhaust ducts on IC engines and power plants.In this paper the procedure to experimentally determine whistling potential will be presented and applied to side-branch resonators and orifices. Keywords: experimental method, noise generation, resonators, engine noise, power balance, system instability, whistling Cite This Article: Sabry Allam, “Experimental Assessment of Noise Generation from I.C. Engine Intake and Exhaust Systems Components.” American Journal of Vehicle Design, vol. 3, no. 1 (2015): 6-15. doi: 10.12691/ajvd-3-1-2. 1. Introduction 1.1. Background Flow-acoustic interaction in flow duct systems could lead to intense noise, often denoted a whistle, which not only could be disturbing but also could lead to mechanical failure of the structure. Full simulations of a typical system such as a gas pipelines or automotive exhaust/intake systems are still too computationally expensive to be viable. A common simplification of the problem is to divide the system into a network of linear acoustic multi ports. Each of these “black boxes” could then be determined analytically, numerically or experimentally. This approach is widely used for studying passive system properties such as reflection and transmission of sound. For linear duct aeroacoustic problems, i.e., cases with linear wave propagation and sound generation uncoupled to the acoustic field, a multi- port represents the most general way of describing acoustic sources [1,2]. Knowledge of the multi-port data for all active (fans, flow constrictions,...) and passive (straight ducts,...) elements in a duct system, plus the radiation impedances at duct openings, enables a complete acoustic analysis. This is of course important for engineering acoustics, but to make it useful experimental or numerical methods to determine multi-port data are needed. Since 1970 most of the works done in this field have been focusing on fluid machine applications, the low frequency 1D (plane) wave range and have been experimentally validated [1]. The progress in Computational Fluid Mechanics (CFD) during the last 10-15 years has opened the possibility for the determination of both the passive and the active part via numerical methods. In particular the possibility to compute the active part is important. For fluid machines (IC-engines, compressors, fans,....) the periodic part of the spectrum can normally be obtained by so called U-RANS, but the broad-band part requires Large Eddy Simulations (LES) and is still not feasible to compute for 3D cases and realistic Reynolds numbers. An example of an area where 1-port source data determination via (1D) CFD codes today are common practice is the gas exchange analysis of IC-engines [3,4,5,6]. During the last decade efforts to also apply multi-port models to study flow generated sound in ducts and thermo-acoustics have come into focus. Aurégan and Starobinski [7] proposed an approach that provides indication for the dissipation or amplification of sound in a multi-port system. Åbom et. al. [8] investigated experimentally both the active and passive two-port data for orifice plates. De Roeck et. al. [5] investigated expansion chamber mufflers and both measured and computed the two-port data. For the active part a 2D compressible LES model was used and the analysis restricted to sound produced by low frequency Rossiter