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Arnett M.,Gamma Technologies Inc. | Papadimitriou I.,Gamma Technologies Inc. | Milios J.,Sendyne Corporation
2014 IEEE Transportation Electrification Conference and Expo: Components, Systems, and Power Electronics - From Technology to Business and Public Policy, ITEC 2014 | Year: 2014

In order to ensure high accuracy of complete hybrid powertrain simulations, it is important that models capture the temperature-sensitive behavior of the involved components and the flow of energy between subsystems. This paper presents the coupling of a battery Compact Physical Model (CPM) with a hybrid electric vehicle model, including the propulsion system and the thermal aspect of its components, as well as the entire cooling system. The resulting model can accurately predict the interactions between the various subsystems and the various energy paths and thus it can be used for thermal management analysis and control strategy optimization. © 2014 IEEE.

Kersey J.,Gamma Technologies Inc. | Loth E.,University of Virginia | Lankford D.,Aerospace Testing Alliance
AIAA Journal | Year: 2010

A methodology for simulating two-way multiphase coupling of mass, momentum, and energy was developed to investigate the effect of droplet mass and heat transfer on one-dimensional shock waves. The numerical approach employed a conservative formulation for the gas and a Lagrangian formulation for the particles. The approach was verified for one-way heat transfer, evaporation and condensation for low-speed flows, and for two-way shock attenuation for solid particles and small evaporating drops (for which breakup is not expected and internal temperature gradients are weak). Parametric studies were conducted to investigate the coupling physics, and, surprisingly, finite rate evaporation and two-way coupling were found to increase the rate of shock attenuation and reduce the postshock gas temperature for mass loadings as small as 0.5%. Larger drops led to long regions of nonequilibrium as did, unexpectedly, effects of evaporation. Copyright © 2010.

Bissett E.J.,Gamma Technologies Inc. | Kostoglou M.,Aerosol and Particle Technology Laboratory | Kostoglou M.,Aristotle University of Thessaloniki | Konstandopoulos A.G.,Aerosol and Particle Technology Laboratory | Konstandopoulos A.G.,Aristotle University of Thessaloniki
Chemical Engineering Science | Year: 2012

In the 1D modeling of flow in the channels of wall-flow monoliths used in diesel particulate filters for engine exhaust emissions control, it is common to use friction coefficients and Nusselt numbers from idealized 2D/3D channel flows with zero wall flow. This practice implicitly makes the additional approximation that the actual velocity and scalar (temperature or species concentrations) profiles within the channels are little affected by nonzero wall flow. There is extensive related research in the filtration literature for the simpler geometries of circular tubes and parallel planes that exposes much more complex and interesting effects as the wall Reynolds number, Re w, increases. Here we extend these results to the 3D geometry of square channels appropriate for wall-flow monoliths. We solve for the fully developed laminar flow, and heat transfer, within long square channels with porous walls and uniform wall velocity. Results are generated for the appropriate parameter range applicable for the diesel particulate filter application which provide the corrected friction coefficients and Nusselt numbers for nonzero Re w. Furthermore, we confirm the observation, from prior work on the simpler geometries that there exists a limiting Re w beyond which there is no fully developed flow for the inlet channels (wall suction). Implications for modeling diesel particulate filters are discussed. © 2012 Elsevier Ltd.

Harrison J.,Gamma Technologies Inc. | Aihara R.,Gamma Technologies Inc. | Eisele F.,SHW Automotive GmbH
SAE International Journal of Engines | Year: 2016

Engine and transmission oil systems are commonly pressurized by gerotor style pumps, due to their simplistic design and low cost. Gerotor pumps are designed with certain tolerances of the gears and housing, thus creating a tradeoff of lower cost with larger tolerances and higher cost with smaller tolerances. By building a detailed gerotor pump model with a 1D hydraulic flow network, engineers can evaluate pump performance with these tolerances as input and compare to find the optimal design. This paper showcases the ease of building a gerotor model in 1D by using an automated process extracting the key model inputs directly from the pump CAD file. The gerotor pump performance is predicted including flow rate, total power loss, volumetric efficiency, and total efficiency vs. pump speed, pressure rise, clearance tolerances, and temperature, and compared with experiment. A predictive friction model for gerotor pumps is proposed and total torque required to drive the pump is compared directly with experiment. Additionally, an internal leakage model for predicting volumetric efficiency taking into account physical clearance between inner and outer gears, as well as temperature is discussed. Copyright © 2016 SAE International.

Okarmus M.M.,Gamma Technologies Inc. | Keribar R.,Gamma Technologies Inc. | Zdrodowski R.,Ford Motor Company | Gangopadhyay A.,Ford Motor Company
SAE International Journal of Fuels and Lubricants | Year: 2015

Valvetrain friction can represent a substantial portion of overall engine friction, especially at low operating speed. This paper describes the methodology for predictive modeling of frictional losses in the direct-acting mechanical bucket tappet-type valvetrain. The proposed modeling technique combines advanced mathematical models based on established theories of Hertzian contact, hydrodynamic and elastohydrodynamic lubrication (EHL), asperity contact of rough surfaces, flash temperature, and lubricant rheology with detailed measurements of lubricant properties and surface finish, driven by a detailed analysis of valvetrain system kinematics and dynamics. The contributions of individual friction components to the overall valvetrain frictional loss were identified and quantified. Calculated valvetrain friction was validated against motored valvetrain friction torque measurements on two engines. The system friction was analyzed across the operating speed range and at several oil supply temperatures as well as varying component surface finishes. A good agreement was observed between simulated and measured valvetrain friction torque suggesting that the proposed analytical methodology and the tool can be very useful in guiding new engine design and enhancing the performance of a given valvetrain design. Copyright © 2015 SAE International.

Lynch B.,Gamma Technologies Inc.
ASME 2015 Internal Combustion Engine Division Fall Technical Conference, ICEF 2015 | Year: 2015

Durability is a prime concern in the design of hydraulic systems and fuel injectors [1-3] thus an accurate prediction of impact velocities between components and the flow through them is essential to assessing concepts. Simulation of these systems is difficult because the geometries are complex, some volumes go to zero as the components move, and the flow at a single operating condition generally spans Reynolds numbers less than 1 to more than 104[4-8]. As a result of these challenges, experimental testing of prototypes is the dominant method for comparing concepts. This approach can be effective but is far more costly, time consuming, and less flexible than the ability to run simulations of concepts early in the design cycle. A validated model of a fuel injector built from publicly available data [1] is used to present a new approach to modelling hydraulic systems which overcomes many of these obstacles. This is accomplished by integrating several commercially available tools to solve the physics specific to each area within the fuel injector. First, the fuel injector is simulated using a 3D CFD simulation integrated with a 1D CFD system model. The flow in various regions of the injector is then analyzed to determine if the fluid models in these areas can be simplified based on the flow regime. Based on this analysis, a combination of models is assembled to improve the quality of the simulation while decreasing the time required to run the model. The fuel injector is simulated using a multibody dynamics model coupled to a reluctance network model of the solenoid and several fluid models. The first is a 3D CFD simulation which uses novel mesh refinement techniques during runtime to ensure high mesh quality throughout the motion of components, to resolve the velocity profile of laminar flows, and to satisfy the requirements of the RNG k-ε turbulence model and wall functions. This approach frees the analyst from defining the mesh before runtime and instead allows the mesh to adapt based on the flow conditions in the simulation. Due to the highly efficient meshing algorithm employed, it is possible to re-mesh at each timestep thus ensuring a high quality structured mesh throughout the simulation duration. Then a 3D FEM solution to the Reynolds Equation and a statistical contact model is employed to solve for the squeeze films between components and to allow separation and contact between bodies in the control valve. These detailed simulations are integrated with a 1D flow model of the fuel injection system. The results from the detailed coupled simulations are compared to the results from simpler 1D models and measured data to illustrate under which operating conditions a more advanced technique incorporating 3D CFD is worth the additional computational expense versus a traditional 1D model. Copyright © 2015 by ASME.

Gundlapally S.R.,University of Houston | Gundlapally S.R.,Gamma Technologies Inc. | Balakotaiah V.,University of Houston
Chemical Engineering Science | Year: 2013

We study the effect of the substrate material (ceramic versus metallic) on the steady-state and transient performance of monolith reactors using a one-dimensional two-phase model with position dependent transfer coefficients. When the operation of the reactor is on the ignited branch, it is shown that monoliths with metallic substrate clearly lead to a superior steady-state performance compared to those with ceramic substrate. In such cases, the ignited branch extends to lower inlet gas temperatures (typically 60-100 °C in after-treatment applications) for the same catalyst loading. For transient operation where the time to light-off is important, it is shown that for the case of back-end ignition (corresponding to low inlet temperatures or low catalyst loading), metallic substrates are again superior. However, for the case of front-end ignition, ceramic converters may lead to lower cumulative emissions at lower inlet gas velocities while the converse is true at higher velocities. It is shown that the transient heating time and hence the cumulative emissions decrease with decrease in the channel hydraulic diameter and thermal capacitance of the substrate but are not monotonic with the inlet gas velocity. We present mathematical analysis and simulations to support these conclusions. Some novel results on the effect of substrate conductivity on the number of steady-states and upstream propagation of temperature fronts are also presented. © 2013 Elsevier Ltd.

Almeida F.L.,MWM International Motores Ltda. | Capana G.H.,MWM International Motores Ltda. | De Moraes H.F.,MWM International Motores Ltda. | Sokolowski D.,Gamma Technologies Inc.
SAE Technical Papers | Year: 2012

A great part of the projects in the powertrain area are focused on the development of more efficient thermal applications. In the end, efficiency is pursued, since the aim is to achieve a sustainable design with low fuel consumption. Thus, vehicles which present lower fuel consumption are demanded by customers. Additionally the emission standards have been reducing the limits of CO2 emissions to very low levels, which drive engineers to develop vehicles with lower fuel consumption. In summary, the product should now please a more demanding worldwide customer profile as the global economy grows. Vehicle design processes should consider fuel consumption sensitivity taking into account the combined engine and drive train systems at early stages. Frequently the actual fuel consumption can only be confirmed when the first prototype is assembled in order to validate the adopted solutions. On the other hand, project timing is another dominant constraint, even when using planning of experiments (DoE) not all proposed designs can be tested. In this sense, the use of numerical simulation resources has been more and more utilized to reduce project timing. A vehicle simulation of a 4 cylinder Diesel internal combustion engine (ICE) coupled with the driveline of the vehicle, including its accessories, was developed utilizing the numerical 1D model, built in GT-Suite, a Gamma Technologies, Inc. code. A multi-body dynamics method was used with explicit consideration of accessory loads and the engine, which was represented by its maps evaluated at the dyno, namely BMEP, FMEP and BSFC. The model calibration was done using some route acquired data in order to reproduce the measured fuel consumption under some specific vehicle cruise conditions and 3 accelerations ramp situations. The pedal position was assigned by a PID controller representing a virtual driver's behavior. The gear shift schedule was calculated inversely by inspection pursuing a reasonable correlation of the simulated and measured fuel rates. The aerodynamics features and the rolling resistance coefficient were adopted based on information provided by the customer and the dynamic tire radius were inversely calculated using GPS vehicle speed data, engine speed and drive line ratios. This paper presents a study of the impact of accessory loads in a physically-representative way. Their loads have been considered via their power consumption curve. Each one has been studied and modeled in order to get a representative power curve shape over the relevant speed range for the engine. Then, they were all included in the 1D dynamic model. The final numerical model presented 6% of max difference in total fuel consumption in comparison to measurements for all 6 cruise situations without the need of any calibration adjustment, which is a usual practice worldwide. The acceleration behavior of the model presented a max difference of 7% (with a minimum of 2%) in comparison to measurements in terms of acceleration times and vehicle displacements. The aforementioned results were considered excellent from the perspective of the adopted 1D approach. The model has already served as a good basis to evaluate the contribution of each accessory load on the total fuel consumption in order to provide technical basis for a system optimization, which might lead to an eventual modification of the accessory design. Last but not least, it may help with the accessory supplier competition. Copyright © 2012 SAE International.

Rodriguez J.,Gamma Technologies Inc. | Brix F.,Kaito Associates | Kumagai T.,CD adapco
SAE Technical Papers | Year: 2012

Push-belt (or Van Doorne-type) CVT systems are used for power transmission in automotive applications, including notably in engine-transmission subsystems. In order to characterize the physics of a Van Doorne CVT, two modeling options are commonly used. High fidelity models track each push-belt block as well as the dynamics of the bands that connect the blocks. The main disadvantage of this technique lies in its large number of degrees of freedom and resulting long CPU time. A second approach relies on a lesser-fidelity model with few degrees of freedom that can subsequently be used in long simulations, e.g. vehicle drive-cycles. In this work, we review different modeling techniques at this modeling level, and propose a fast-running model that overcomes some of the limitations of lesser-fidelity models yet is still suitable for long simulations. Typical fast-running models enforce kinematic constraints between the pulleys, i.e. the CVT bands and blocks are assumed to be rigid. In order to overcome some of the limitations associated with a rigid CVT, a fast-running flexible variant is proposed. The model has been implemented within a general-purpose tool in which a complete vehicle system can be modeled. Several examples are analyzed to validate the proposed model. First, a validation example and also comparison of the rigid and elastic models are presented. Next, numerical and experimental results are compared for vehicle transients. Copyright © 2012 SAE International.

Harrison J.,Gamma Technologies Inc. | Aihara R.,Gamma Technologies Inc. | Eshraghi M.,General Motors | Dmitrieva I.,General Motors
SAE Technical Papers | Year: 2014

Variable displacement vane pumps are becoming more popular for engine oil circuits due to their fuel savings over traditional fixed displacement pumps. As a result, engineers need to analyze these pumps to ensure the pump design meets the demands of the oil circuit while having good friction characteristics and avoiding issues like high pressure amplitude and resonance. By employing 1D flow simulation to these pumps, the user can analyze the most important issues surrounding vane pumps at a fraction of the time as 3D CFD. This paper showcases the prediction of several major performance quantities of a variable displacement vane pump including flow rate, pressure rise, and friction torque vs. engine speed and temperature. The simulation results show good correlation to measurement data. In addition, the pressure pulsation at several locations including in the vane chamber and at the outlet is compared directly with 3D CFD for a different pump. Furthermore, the effect of aerated oil on pump performance is also shown. Finally, a predictive friction model for vane pumps is proposed and shows good agreement with experiment. Copyright © 2014 SAE International.

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