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In this paper, a CAE methodology based on a multiphysics approach for engine gear noise evaluation is reviewed. The method comprises the results and outputs from several different analytical domains to perform the noise risk assessment. The assessment includes the source-path analysis of the gear-induced rattling and whining noise. The vibration data from the exterior surface of the engine is extended through acoustic analysis to perform the engine noise simulation and to identify acoustic hot spots contributing to the noise. The study includes simulations under different engine loading conditions with results presented in both time and frequency domains. Various sensitivity analyses involving different gear geometries and micro-geometries are investigated as well. Finally, the simulation results from three different engines are compared vis-a-vis.

The opposed piston opposed cylinder (opoc™) engine concept has been demonstrated as an engine concept with high specific power density and high power to volume ratio. The engine has several potential applications, including use as an auxiliary power unit (APU) in various commercial and military applications and as the primary power source for small unmanned air vehicles (UAVs). An engine in this power range operating on heavy fuels (e.g. JP5, JP8, DF2) is not typically available. The engine uses a two-cycle supercharged uniflow scavenging system with asymmetric port timing and will run at speeds between 8,000 and 12,000 rpm. The unique design of the opoc™ engine produces a piston speed that is half the speed of a typical crankshaft engine running at the same speed. Uniflow scavenging produces gas exchange efficiencies rivaling those of four-cycle engines. The design also leads to reduced in-cylinder heat losses. Furthermore, the opoc™ engine is fully balanced.

The shifter lever is one of the main customer contact points in the vehicle. Vibration levels at this contact point have an effect on perceived vehicle quality. For this reason, shifter lever vibration and the corresponding transfer paths from the transmission to the shifter lever need to be considered during vehicle development. On a recent program, experimental measurements identified the shifter cable to be a significant transfer path for shifter lever vibration. An integrated Computer Aided Engineering (CAE) and experimental effort was undertaken to model and optimize the shifter lever and cable assembly for reduced vibration. Experimental data was used to better understand the vibration phenomenon, set boundary conditions for the CAE modeling, and for correlation. The CAE model contains the shifter lever assembly and a detailed cable assembly model.

Numerous authors have previously published on the effects of system dynamics on gear noise in automotive applications [1,2]. It is now widely understood that the torsional compliances and inertias of propeller shafts and pinion gear sets are a controlling factor in final drive gear noise for rear wheel drive vehicles. Considerable progress has been achieved in using finite element simulations of the driveline dynamics to improve the system in regards to gear noise. However very few published results are available showing the application of dynamic simulation methods to automatic transmissions which require considerations of the complications due to epicyclical gear sets. This paper documents the successful application of finite element dynamics modeling methods to the prediction of gear noise from the gear set in a rear wheel drive automatic transmission. The model was used to investigate the effects of component inertias, stiffnesses, and resonances.

Powertrain noise is often dominated by the radiation from individual panels or covers. A structural side cover for a front wheel drive transmission represents a complex noise and vibration design problem. Amongst the NVH concerns are the radiation of structural borne sound and the sound transmission loss characteristics. This paper addresses the use of acoustic boundary elements and structural finite elements to predict the radiation of noise from a structural side cover. A comparison is made to experimental measurements, and discussion provided for practical application of these modeling methods to total side cover design.

This paper gives an overview of the analytical and experimental activities undertaken to develop an OEM vehicle system design tool for minimizing transmission gear rattle. Detailed analytical investigations were performed to develop an understanding of the important gear rattle parameters. Specialized test techniques were developed and implemented to gain an understanding of the key element of gear impacting. Results of the analytical and experimental studies were used to develop a simulation code which contains the elements required to accurately simulate gear rattle while providing greater efficiency and ease of use as compared to commercially available simulation codes.

Body acoustic sensitivity, defined as the interior sound pressure due to a unit force applied to the body, has a major influence on the powertrain and road noise of a vehicle. Body acoustic sensitivity can be predicted analytically in the design stage of a vehicle program using structural-acoustic analysis. Recognition and correction of potential problems at this stage is a cost effective approach to improving a vehicle’s NVH performance. This paper describes the structural-acoustic analysis procedure. Techniques for developing the structural and acoustic models and coupling them to form a structural-acoustic system model are discussed. An application of the procedure for prediction and improvement of body acoustic sensitivity is given for a passenger vehicle.

An overview of the analytical noise, vibration, and harshness (NVH) simulations performed to support the design and development of the Nissan Quest mini-van is presented. The use of analytical techniques on this project was unique in that analytical results were used to drive the pre-prototype design efforts, as well as to assist in the prototype development phase. Analytical models were developed, and simulations performed, prior to the release of prototype drawings. The simulation results identified necessary changes which were incorporated into the design. Once prototype vehicles became available, analytical simulations and development testing were used hand-in-hand to minimize development time as well as to optimize the cost, weight, and performance of NVH countermeasures. The extensive use of analytical simulations in the design and development process was critical in achieving the aggressive NVH performance objectives set for the vehicle.

The Integrated Closed Environmental Control System (ICECS) Program included design, analysis, fabrication and testing of an advanced environmental control system concept for military aircraft. Fuel was utilized as the primary heat sink of a vapor-cycle system with ram air augmentation. Through the use of closed-loop avionics cooling and maximum use of fuel as a heat sink, reductions in bleed air use reduced environmental control system (ECS)-related fuel penalties and, as a result, reduced life-cycle costs (LCC). Additionally, by providing a drier, more stable environment for avionics, significant reliability gains have been demonstrated when compared to the baseline open-loop ECS. The overall emphasis was to verify through test the benefits of an ICECS using primarily off-the-shelf hardware.