Simerics (United States)

<div class="section abstract"><div class="htmlview paragraph">This paper presents transient, complex, moving mesh, 3-D CFD analysis of an intebrake lubrication oil circuit for predicting flow performance. Intebrake is a mechanism for improving braking performance during over speeding conditions. The mechanism briefly opens the exhaust valve at the end of a compression stroke with a small valve lift and releases the compressed gases, thereby helping in quick application of the brake. There is no fueling during the process and hence, no combustion induced pressure rise which helps in quick application of the brake. During the intebrake operation, opening of the exhaust valve is achieved by using a complex lube oil circuit inside the exhaust rocker lever. The intebrake lube oil circuit consists of various spring-operated valves with micro-sized clearances, high oil pressure generation up to ~ 250 bar, 3-D movement of the mechanism components, and it is a transient operation. The 3-D movement consists of simultaneous rotational and translational motions with dynamic motions due to net force balance between spring and fluid forces. All these factors make the simulation an absolute need as testing is extremely costly and difficult due to tight space constraints around the mechanism. The 3-D CFD model with automatic intebrake ON and OFF operations makes dynamic mesh motion more complex. In the current work, 3-D CFD simulation approach is developed which can model the intebrake operation by considering dynamic mesh, small clearances, and oil compressibility effects. The predicted intebrake lube system oil pressure is compared with transient, crank angle based test data and the results are found to be in good correlation. This approach has helped in better understanding of the intebrake response to variation of different design parameters and resolving field failures. After a single cylinder intebrake model validation, it has been extended to modeling 6-cylinders and integrated with engine 3-D CFD lube system as well.</div></div>

<div class="section abstract"><div class="htmlview paragraph">The drive unit, primarily consisting of an electric motor and a gearbox, needs to be cooled and lubricated for its long life and efficient performance. In an extreme drive cycle condition, the pickup tube to the pump may get exposed to air, leading to a substantial loss in line pressure and a drop in oil flow rate to the subsystems. An advanced Computational Fluid Dynamics (CFD) simulation can provide insights into the oil delivery system and help in improving the oil sump design, optimizing the position of the pickup tube to the pump and oil delivery lines. The current study employs a Volume of Fluid (VOF) based multiphase model implemented in a commercial CFD solver, Simerics-MP+. The drive unit lubrication system considered in the study consists of a gerotor pump, the entire oil delivery lines to the two subsystems and the drive unit casing. A multiphase simulation of the system with transient operation of the pump is computationally expensive. Therefore, a new methodology is implemented to reduce the runtime of such a simulation by simulating the gerotor pump separately, yet simultaneously, from the remainder of the drive unit by exchanging the flow and concentration distributions between the two computational models. The coupled methodology is first validated using a simplified system with a gerotor pump, and then the actual drive unit lubrication system is simulated for three different drive cycle conditions. The pump outlet line pressure compares well with the test data.</div></div>

<div class="section abstract"><div class="htmlview paragraph">This article analyzes the aerodynamic performance of Class 8 tractor-trailer geometries made available by the Environmental Protection Agency (EPA) using CFD simulation. Large Eddy Simulations (LES) were carried out with the CFD package, Simerics-MP+. A Sleeper tractor and a 53-foot box trailer configuration was considered. The configuration featured a detailed underbody, an open-grille under-hood engine compartment, mirrors, and the radiator and condenser. Multiple tractor-trailer variants were studied by adding aerodynamic surfaces to the baseline geometries. These include tank fairings and side extenders for the cabins, two types of trailer skirts, and a trailer tail. The effect of these devices towards reducing the overall vehicle drag was investigated. Mesh generation was carried out directly on the given geometry, without any surface modifications, using Simerics’ Binary-Tree unstructured mesher. Subsequently, simulations were setup considering realistic driving conditions with lateral wind, rotating wheels, and moving floor. The obtained numerical results were then compared with wind-tunnel test data, which highlighted the excellent predictive capabilities of the simulations. These accurate results, as presented in this paper, demonstrate the feasibility of using high fidelity simulation as a tool in the EPA’s SmartWay Verification Program.</div></div>

Abstract Electric vehicles are becoming increasingly common due to environmental needs. Due to this, efficiency in design process of electric motors (E-motor) is becoming critical in the industry. To assess performance capabilities for an E-motor, thermal predictions are of utmost consequence. This study describes a computational method based on unsteady Reynolds-averaged Navier-Stokes equations that resolves the gas-liquid interface to examine the unsteady multiphase flow and heat transfer in a concentrated winding E-motor. The study considers all important parts of the motor i.e., coils, bobbins, stator laminate (yolk), rotor laminate, magnets etc. The study highlights the ease of capturing complex and intricate flow paths with a robust mesh generation tool in combination with a robust high-fidelity interface capturing VOF scheme to resolve the gas-liquid interfaces. Results obtained show the dominant processes that determine the oil distribution to be the centrifugal force from rotation of the rotor, the flow rate of oil injected in the stator assembly as well as in the rotor assembly and gravity. A novel heat transfer approach (mixed time-scale coupling) is used to solve for the temperatures in the stator and rotor solids. The approach first requires achieving a quasi-steady flow solution before initiating heat transfer calculation for faster turnaround times. The approach separates the conjugate heat transfer calculation into a fluid heat simulation and a solid heat simulation while setting up a communication method to exchange the thermal boundary conditions between the two simulations. This study also considers the anisotropic nature of thermal conductivities resulting from the wound-around arrangement of the coils and the laminate nature of stator/rotor laminates in the assignment of the thermal conductivities of these solids. Results of thermal simulation show the solid temperatures to be in direct correlation with the oil distribution near those solids. This computational study was validated by comparing the computed and measured temperatures at specified locations on the coils and good agreements with experiments were found.

<div class="section abstract"><div class="htmlview paragraph">Designing an efficient vehicle coolant system depends on meeting target coolant flow rate to different components with minimum energy consumption by coolant pump. The flow resistance across different components and hoses dictates the flow supplied to that branch which can affect the effectiveness of the coolant system. Hydraulic tests are conducted to understand the system design for component flow delivery and pressure drops and assess necessary changes to better distribute the coolant flow from the pump. The current study highlights the ability of a complete 3D Computational Fluid Dynamics (CFD) simulation to effectively mimic a hydraulic test. The coolant circuit modeled in this simulation consists of an engine water-jacket, a thermostat valve, bypass valve, a coolant pump, a radiator, and flow path to certain auxiliary components like turbo charger, rear transmission oil cooler etc. A commercial CFD software, Simerics-MP+®, is used to simulate the hydraulic test for two different positions of the poppet valve of the thermostat, viz. a closed position and an 50% opening, at different speeds of the engine. In the CFD model, the complete geometrical details of water-jacket, thermostat, and pump are considered. The remaining components are approximated as pipes with flow resistance models to account for flow and pressure drop at different engine speeds. Firstly, the standalone pump performance is validated in the operating regime of interest, followed by the calibration of the resistance models for the simplified components. At the end, complete system level 3D simulations are conducted and validated for the above mentioned two positions of the poppet valve. The flow distribution and pressure drop across different components show good comparison with the hydraulic test data within 7% error band.</div></div>

<div class="section abstract"><div class="htmlview paragraph">A computational study based on unsteady Reynolds-Averaged-Navier-Stokes that resolves the gas-liquid interface was performed to examine the unsteady multiphase flow in a 4 cylinder Inline (i-4) engine. In this study, the rotating motion of the crankshaft and reciprocating motion of the pistons were accounted for to accurately predict the oil distribution in various parts of the engine. Three rotational speeds of the crankshaft have been examined: 1000, 2800, and 4000 rpm. Of particular interest is to examine the mechanisms governing the process of oil drawdown from the engine head into the case. The oil distributions in other parts of the engine have also been investigated to understand the overall crankcase breathing process. Results obtained show the drawdown of oil from the head into the case to be strongly dependent on the venting strategy for the foul air going out of the engine through the PCV system. Results also show the dynamic holdup of oil in the steady operation to be highest near the crankshaft and pistons. Results are presented to show how the rotational speed of the crankshaft affects the nature of multiphase flow inside the engine and its influence on the drawdown of oil from the head into the case. The computational study was validated by comparing the computed volume of oil in the sump in steady state operation with the experimental measurements. The computational strategy presented in this study to simulate the crankcase breathing process can be most useful in guiding the design and development of engines.</div></div>

Abstract Centrifugal compressor has widespread applications in areas such as aerospace, automotive, power and process industries and hence the prediction of its performance is crucial at the design stage. Traditional design, build and test are accelerated through numerical simulation as a virtual test bed for compressor development. In this work, a CFD methodology has been developed to predict the performance of a centrifugal compressor with its surge and choke limits. The transient, compressible flow in a moving domain with body-fitted unstructured mesh is solved in Simerics-MP. The distributed parallel solver of Simerics-MP enables to perform the complete performance map of a centrifugal compressor in a day. The phenomena of surge and choke in a centrifugal compressor is of paramount importance as it determines the limiting points of operation for a particular speed of the compressor. Surge occurs at low flow rates, and it is characterized by instabilities causing undesirable noises that lead to drop in the operational efficiency. It can also result in wear and tear of the impeller blades. Whereas choke occurs at high flow rates with no further increase in pressure and it is accompanied by aberrant vibrations. The CFD simulation predicts the instabilities occurring at surge such as pressure oscillations and flow reversal accurately, which is used as a criterion for the prediction of surge point. The choke phenomenon is characterized by fluid attaining sonic velocity in the impeller or diffuser region of the compressor. The CFD predicted results showed a fair comparison with the experimental results of pressure ratio, power, and efficiency at different speeds.

<div class="section abstract"><div class="htmlview paragraph">The present work deals with the development of a CFD method to simulate water fording/water wading for a passenger car. Water wading of automobiles in different water depths can lead to water ingestion into the air induction snorkel. This is unfavourable as this ingested water can cause the malfunction of the engine. This takes on an added importance when designing multi-terrain vehicles, where the interest could be in wading water effectively in many scenarios. The design of the snorkel, its position and height can be important in preventing water from entering the Air Induction System (AIS) and hence the engine. So, a water fording test of a vehicle is conducted to ensure the efficacy of the AIS snorkel in preventing water entering the AIS system. The ability of numerical simulations to effectively replicate testing performed in a long water tank is put to test in this paper. The CFD method development has been done using the commercial code, Simerics-MP+<sup>®</sup>.</div><div class="htmlview paragraph">In Simerics-MP+, multiphase Volume of Fluid (VOF) methodology has been used to account for capturing the water/air interaction. Simulations are performed using the explicit (VOF) multiphase approach. The simulation involves the complete vehicle CAD moving in water over a few seconds of physical time, so it can be computationally expensive. So, one of the main aims of the work is to establish a methodology that can reduce the computational time while ensuring excellent interface capturing between the water and air phases. Multiple methodologies are devised, and the results compared with each other. The numerical diffusion has been judged both qualitatively and quantitatively. The qualitative judgment has been done using the contours of volume fraction of water visualized on stream-wise planes. For the quantification of the numerical diffusion, the estimation of mass-balance error is done and is the difference of mass of water phase exiting the domain w.r.t the mass of water phase entering the domain. The developed method is used to quantify the amount of water that has entered as well as held up in the Air Induction System of the engine for a given height and car velocity. Results of the wave pattern formed around the car, and the flow around other electrical components like internal wiring and battery is also documented. The developed method has been used to simulate a passenger car wading through pool with 12 inches of water height with a speed of 10 mph. It was seen that almost negligible amount of water has entered in the AIS and ultimately engine and hence it is safe to wade the car under such conditions.</div></div>

<div class="section abstract"><div class="htmlview paragraph">This paper reports on engineering insights that can be gained from a rigorous, transient, three-dimensional CFD analysis of the complete lubrication system of automotive internal combustion engines. Building such a model is a formidable task because the computational domain of such a model is vast and includes scores of bearings as well as components such as the pump, pressure relief valve, oil filter, oil cooler, piston cooling jets etc. Thus far, the only publication on 3D CFD analysis of an engine lubrication system was for a 16-cylinder engine in which the feasibility and the potential opportunities of such a model were demonstrated. The aim of this work is to cover four engineering topics of interest in a lubrication system: 1. Showcase the capability of the CFD tool to accurately, robustly and reliably predict the engine lube system performance of a wide variety of automotive engines with no reliance on tuning the inputs. Best analysis practices were developed in order to achieve this goal by compensating for the variabilities that arise in a complex system level CFD model that connects scores of components across far flung locations in the engine lube system. The predicted pressures were validated at different locations in the lube system. Three different engines were considered, two of which were 4-cylinder and the third was 6-cylinder. 2. The paper also addresses the ability of such a model to help study dependencies of the pressure and flow rate predictions, at different components in the system, on the pump and bearing clearances. 3. One of the other points of interest addressed in this paper is the capability of such models to decide the pump to be chosen for a lubrication system. The study compares the pressures and efficiencies obtained from a system by attaching four different oil pumps and then it ranks them in the order of best to worst for that particular system. 4. Finally, the cold start priming analysis is performed on a lubrication system to estimate oil filling times and predict pressures in the system. The paper also discusses in detail the relatively similar timelines to setting up and running such a complex CFD model to that of a 1-D model. The paper illustrates the potential of 3D CFD that can be used as stand-alone alternatives or in conjunction with 1D CFD in performing engine lube system design and development.</div></div>

<div class="section abstract"><div class="htmlview paragraph">In an automotive cooling circuit, the wax melting process determines the net and time history of the energy transfer between the engine and its environment. A numerical process that gives insight into the mixing process outside the wax chamber, the wax melting process inside the wax chamber, and the effect on the poppet valve displacement will be advantageous to both the engine and automotive system design. A fully three dimensional, transient, system level simulation of an inlet controlled thermostat inside an automotive cooling circuit is undertaken in this paper. A proprietary CFD algorithm, Simerics-Sys®/PumpLinx®, is used to solve this complex problem. A two-phase model is developed in PumpLinx® to simulate the wax melting process. The hysteresis effect of the wax melting process is also considered in the simulation. The physics captured in the simulation includes the turbulent flow out of the coolant pump, turbulent mixing, heat transport, and rigorous treatment of Fluid Structure Interaction (FSI) of the circuit with the dynamic valves in the system. Two different operating sets of data are used for the analysis, case A, lower engine speed and case B, higher engine speed. The details of the model setup and the comparisons of the simulation results with experimental data are discussed in the paper.</div></div>