Morton S.,Mercury Marine |
Narasingamurthi S.,Larsen and Toubro Ltd
American Society of Mechanical Engineers, Internal Combustion Engine Division (Publication) ICE | Year: 2011
Modern, high-performance, outboard marine engines operate in severe environments. They are typically mounted to a planing boat operating at high horsepower levels due to high hydrodynamic drag. The engine also experiences high vertical impact loads in rough-water conditions. In the ocean, corrosive salt water circulates through the engine to provide necessary engine cooling. Splashing water can be ingested into the combustion air inlets on the outside of the engine cowl (engine enclosure) and must be appropriately managed. In addition, the engine often operates in very warm climates with a sealed cowl wrapped tightly around it. The warm atmospheric air that flows through the cowl inlets and into the engine compartment must first circulate around the power head in order to cool thermally sensitive components such as engine controllers and ignition coils. In some applications, the same air stream mixes with fuel then participates in the combustion process inside the cylinder. At Mercury Marine, computational fluid dynamics, CFD, is used to aid the design of outboard engines that will operate robustly in these extreme conditions. One specific application for CFD is the management of the flow and thermal aspects of engine-compartment air flow. Studies can be done with CFD to assist product design decisions that aim to balance the need to protect thermally sensitive electronics and to efficiently provide the engine with the combustion air. The CFD simulation predicts the air flow behavior from the cowl duct inlets, around the power-head, and into the throttle body inlet of the engine. The simulation also predicts air temperatures, component temperatures, and heat flow to and from the air. The CFD model typically includes rotating components such as alternators and flywheels. A recent study was conducted to validate the CFD method. The CFD model and the dynamometer experiments were conducted with a mid-size outboard 4-stroke engine. The test engine was fully instrumented to measure air temperatures, air velocities, and component temperatures. The validation exercise included a detailed comparison of these values between the CFD predictions and the experimental results. A high level of agreement was achieved and a few lessons were captured for future implementation. © 2011 by ASME.
Anderson A.,Mercury Marine
SAE Technical Papers | Year: 2012
When designing a connecting rod, one needs to pay attention to the buckling strength of the rod. The buckling strength is heavily affected by the beam section, and Johnson's buckling equation is used to estimate the buckling strength of a given beam section. This approach is acceptable if the beam section geometry is constant from the small end to the big end. But, recent expectations for light weight, low NVH, and low fuel consumption engines require optimizing the connecting rod section geometries to be progressively changing from the small end to the big end. Finite Element Analysis (FEA) is often used to evaluate the buckling strength of a rod that has complex changes in beam section. There are two primary FEA methods to do this. One is an eigenvalue method and the other is an explicit dynamic method. The eigenvalue method can obtain stable results without satisfying Courant-Friedrichs-Lewy condition that is required to control the size of the time step in the explicit dynamic method. The eigenvalue method is meant for analyzing the static (or quasi-static) problem, and is comparable to a static load test that can be done in a structural test lab. To get proper analysis results, this method requires geometry, modal analysis, interpretation of results to include a certain number of mode shapes in the buckling analysis, as well as an imperfection value. In the case of the explicit dynamic method, the time step size must satisfy Courant-Friedrichs-Lewy condition in order to obtain stable calculation results. This method can analyze quasi-static and dynamic problems, and is useful for calculating the in-situ buckling strength of a rod. An advantage of the explicit dynamic method is that simultaneous equations do not have to be solved, so memory size requirements are reduced and less computation time is used than in the eigenvalue method. Furthermore, the explicit dynamic method requires only the geometry and an input force (or velocity) to get proper analysis results. This paper shows analysis results from the eigenvalue method and the explicit dynamic method, as well as physical test results. Then, the paper discusses the pros and cons of the two methods for rod buckling analysis. Copyright © 2012 SAE International.
Scherer J.O.,Mercury Marine |
Patil S.K.R.,Mercury Marine
11th International Conference on Fast Sea Transportation, FAST 2011 - Proceedings | Year: 2011
Work has been done recently at Mercury Marine in the area of characterizing the performance of surface piercing drive systems used for outboard and sterndrive propulsion. These drive systems operate behind the boat at the air-water interface and are required to produce steering and vertical forces as well as thrust. The ability to produce these forces efficiently is a primary advantage of this type of drive system. The complexity of the physics presents a significant analytical challenge. Theoretical, experimental and computational methods are presented. The content should be of particular use to boat designers who would like to integrate these types of drive systems into vessels. Gearcase lift, drag, and side-force are reported as functions of speed, drive trim angle, drive steering angle, and drive height, including the influence of cavitation and ventilation. Some considerations for surfacepiercing propellers are reported as well. © 2011 American Society of Naval Engineers.
Austin T.P.,Fox Valley Technical College |
Chisholm P.A.,Mercury Marine |
Schreiber R.W.,Mercury Marine
SAE Technical Papers | Year: 2014
In the investigation of a collision involving recreational watercraft, analytical methods are generally limited when compared to incidents involving land-based vehicles. As is indicated in previous publications, investigators often rely on time/distance relationships, human factors, the matching of damage to determine vessel positioning at impact, and the recollections of witnesses. When applicable, speed estimates are generally based on the boat engine's revolutions. By considering the engine speed, the drive gear ratio, the propeller pitch, and the likely slip of the propeller, an estimation of the boat's travel speed can be made. In more recent publications, it has been recognized that Event Data Recorder (EDR) technology incorporated into various Electronic Control Units (ECUs) used in automotive applications can be beneficial to collision investigation and reconstruction. These devices record data surrounding diagnostic occurrences, airbag deployments, and, with respect to some heavy vehicles, "last stop" and/or "sudden deceleration" events. Formal testing of these devices has shown their accuracy and use in collision analysis. This research examines event data as recorded by specific Mercury Marine ECUs in combination with external data acquisition devices. Specifically, the study focused on validating engine speed data. In addition, recording parameters were researched, as were the effects of a powerloss condition on data files. The results of this research suggest that marine ECUs can be beneficial to accident investigation by recording specific engine parameters and operator inputs immediately prior to a collision incident. Copyright © 2014 SAE International.
Kuether R.J.,University of Wisconsin - Madison |
Deaner B.J.,Mercury Marine |
Hollkamp J.J.,U.S. Air force |
Allen M.S.,University of Wisconsin - Madison
AIAA Journal | Year: 2015
Several reduced-order modeling strategies have been developed to create low-order models of geometrically nonlinear structures from detailed finite element models, allowing one to compute the dynamic response of the structure at a dramatically reduced cost. However, the parameters of these reduced-order models are estimated by applying a series of static loads to the finite element model, and the quality of the reduced-order model can be highly sensitive to the amplitudes of the static load cases used and to the type/number of modes used in the basis. This paper proposes to combine reduced-order modeling and numerical continuation to estimate the nonlinear normal modes of geometrically nonlinear finite element models. Not only does this make it possible to compute the nonlinear normal modes far more quickly than existing approaches, but the nonlinear normal modes are also shown to be an excellent metric by which the quality of the reduced-order model can be assessed. Hence, the second contribution of this work is to demonstrate how nonlinear normal modes can be used as a metric by which nonlinear reduced-order models can be compared. Various reduced-order models with hardening nonlinearities are compared for two different structures to demonstrate these concepts: a clamped-clamped beam model, and a more complicated finite element model of an exhaust panel cover. © 2015 by H. Hafsteinsson. Published by the American Institute of Aeronautics and Astronautics, Inc.