Refine Your Search

Topic

Author

Search Results

Video

Cooling Airflow System Modeling in CFD Using Assumption of Stationary Flow

2011-11-29
Today CFD is an important tool for engineers in the automotive industry who model and simulate fluid flow. For the complex field of Underhood Thermal Management, CFD has become a very important tool to engineer the cooling airflow process in the engine bay of vehicles. Presenter Peter Gullberg, Chalmers University of Technology
Technical Paper

Axial Fan Performance Predictions in CFD, Comparison of MRF and Sliding Mesh with Experiments

2011-04-12
2011-01-0652
Underhood Thermal Management has become an important topic for the majority of automotive OEM's. To keep combustion engines cool and manage waste heat efficiently is an important part in the design of vehicles with low fuel consumption. To be able to predict cooling performance and underhood airflow with good precision within a virtual design process, it is of utmost importance to model and simulate the cooling fan efficiently and accurately, and this has turned out to be challenging. Simulating the cooling fan in a vehicle installation involves capturing complex fluid dynamic interaction between rotating blades and stationary objects in the vicinity of the fan. This interaction is a function of fan rotation rate, fan blade profile, upstream and downstream installation components. The flow is usually highly turbulent and small geometry details, like the distance between the blade tip and the fan shroud, have strong impact on the fan performance characteristics.
Technical Paper

Effect of Rear-End Extensions on the Aerodynamic Forces of an SUV

2014-04-01
2014-01-0602
Under a global impulse for less man-made emissions, the automotive manufacturers search for innovative methods to reduce the fuel consumption and hence the CO2-emissions. Aerodynamics has great potential to aid the emission reduction since aerodynamic drag is an important parameter in the overall driving resistance force. As vehicles are considered bluff bodies, the main drag source is pressure drag, caused by the difference between front and rear pressure. Therefore increasing the base pressure is a key parameter to reduce the aerodynamic drag. From previous research on small-scale and full-scale vehicles, rear-end extensions are known to have a positive effect on the base pressure, enhancing pressure recovery and reducing the wake area. This paper investigates the effect of several parameters of these extensions on the forces, on the surface pressures of an SUV in the Volvo Cars Aerodynamic Wind Tunnel and compares them with numerical results.
Technical Paper

Cooling Airflow System Modeling in CFD Using Assumption of Stationary Flow

2011-09-13
2011-01-2182
Today CFD is an important tool for engineers in the automotive industry who model and simulate fluid flow. For the complex field of Underhood Thermal Management, CFD has become a very important tool to engineer the cooling airflow process in the engine bay of vehicles. To model the cooling airflow process accurately in CFD, it is of utmost importance to model all components in the cooling airflow path accurately. These components are the heat exchangers, fan and engine bay blockage effect. This paper presents CFD simulations together with correlating measurements of a cooling airflow system placed in a test rig. The system contains a heavy duty truck louvered fin radiator core, fan shroud, fan ring and fan. Behind the cooling module and fan, a 1D engine silhouette is placed to mimic the blockage done by a truck engine. Furthermore, a simple hood is mounted over the module to mimic the guiding of air done by the hood shape in an engine bay.
Technical Paper

Effects of Variable Inlet Valve Timing and Swirl Ratio on Combustion and Emissions in a Heavy Duty Diesel Engine

2012-09-10
2012-01-1719
In order to avoid the high CO and HC emissions associated with low temperature when using high levels of EGR, partially premixed combustion is an interesting possibility. One way to achieve this combustion mode is to increase the ignition delay by adjusting the inlet valve closing timing, and thus the effective compression ratio. The purpose of this study was to investigate experimentally the possibilities of using late and early inlet valve closure to reduce NOx emissions without increasing emissions of soot or unburned hydrocarbons, or fuel consumption. The effect of increasing the swirl number (from 0.2 to 2.5) was also investigated. The combustion timing (CA50) was kept constant by adjusting the start of injection and the possibilities of optimizing combustion using EGR and high injection pressures were investigated. Furthermore, the airflow was kept constant for a given EGR level.
Journal Article

Measurements of Energy Used for Vehicle Interior Climate

2014-11-01
2014-01-9129
Fuel consumption of vehicles has received increased attention in recent years; however one neglected area that can have a large effect on this is the energy usage for the interior climate. This study aims to investigate the energy usage for the interior climate for different conditions by measurements on a complete vehicle. Twelve different NEDC tests in different temperatures and thermal states of the vehicle were completed in a climatic wind tunnel. Furthermore one temperature sweep from 43° to −18°C was also performed. The measurements focused on the heat flow of the air, from its sources, to its sink, i.e. compartment. In addition the electrical and mechanical loads of the climate system were included. The different sources of heating and cooling were, for the tested powertrain, waste heat from the engine, a fuel operated heater, heat pickup of the air, evaporator cooling and cooling from recirculation.
Technical Paper

A 1D Method for Transient Simulations of Cooling Systems with Non-Uniform Temperature and Flow Boundaries Extracted from a 3D CFD Solution

2015-04-14
2015-01-0337
The current work investigates a method in 1D modeling of cooling systems including discretized cooling package with non-uniform boundary conditions. In a stacked cooling package the heat transfer through each heat exchanger depends on the mass flows and temperature fields. These are a result of complex three-dimensional phenomena, which take place in the under-hood and are highly non-uniform. A typical approach in 1D simulations is to assume these to be uniform, which reduces the authenticity of the simulation and calls for additional calibrations, normally done with input from test measurements. The presented work employs 3D CFD simulations of complete vehicle in STAR-CCM+ to perform a comprehensive study of mass-flow and thermal distribution over the inlet of the cooling package of a Volvo FM commercial vehicle in several steady-state operating points.
Technical Paper

Development of a Model Scale Heat Exchanger for Wind Tunnel Models of Road Vehicles

2008-04-14
2008-01-0097
During the development of the aerodynamic properties of fore coming road vehicles down scaled models are often used in the initial phase. However, if scale models are to be utilised even further in the aerodynamic development they have to include geometrical representatives of most of the components found in the real vehicle. As the cooling package is one of the biggest single generators of aerodynamic drag the heat exchangers are essential to include in a wind tunnel model. However, due mainly to limitations in manufacturing techniques it is complicated to make a down scaled heat exchanger and instead functional dummy heat exchangers have to be developed for scaled wind tunnel models. In this work a Computational Fluid Dynamics (CFD) code has been used to show that it is important that the simplified heat exchanger model has to be of comparable size to that of the full scale unit.
Journal Article

An Evaluation of Different Combustion Strategies for SI Engines in a Multi-Mode Combustion Engine

2008-04-14
2008-01-0426
Future pressures to reduce the fuel consumption of passenger cars may require the exploitation of alternative combustion strategies for gasoline engines to replace, or use in combination with the conventional stoichiometric spark ignition (SSI) strategy. Possible options include homogeneous lean charge spark ignition (HLCSI), stratified charge spark ignition (SCSI) and homogeneous charge compression ignition (HCCI), all of which are intended to reduce pumping and thermal losses. In the work presented here four different combustion strategies were evaluated using the same engine: SSI, HLCSI, SCSI and HCCI. HLCSI was achieved by early injection and operating the engine lean, close to its stability limits. SCSI was achieved using the spray-guided technique with a centrally placed multi-hole injector and spark-plug. HCCI was achieved using a negative valve overlap to trap hot residuals and thus generate auto-ignition temperatures at the end of the compression stroke.
Technical Paper

Combustion of Fischer-Tropsch, RME and Conventional Fuels in a Heavy-Duty Diesel Engine

2007-10-29
2007-01-4009
This investigation includes a comparison of two Fischer Tropsch (FT) fuels derived from natural gas and a Rapeseed Methyl Ester (RME) fuel with Swedish low sulfur Diesel in terms of emissions levels, fuel consumption and combustion parameters. The engine used in the study was an AVL single cylinder heavy-duty engine, equipped with a cylinder head of a Volvo D12 engine. Two loads (25% and 100%) were investigated at a constant engine speed of 1200 rpm. The engine was calibrated to operate in different levels of EGR and with variable injections timings. A design of experiments was constructed to investigate the effects of these variables, and to identify optimal settings. The results showed that the soot emissions yielded by FT and RME fuels are up to 40 and 80 percent lower than those yielded by the Swedish Diesel. In addition the FT fuel gave slightly lower, and the RME significant higher NOx emissions than the Swedish Diesel.
Technical Paper

Low Soot, Low NOx in a Heavy Duty Diesel Engine Using High Levels of EGR

2005-10-24
2005-01-3836
The objective of the study presented here was to examine the possibility of simultaneously reducing soot and nitrogen oxide (NOx) emissions from a heavy duty diesel engine, using very high levels of EGR (exhaust gas recirculation). The investigation was carried out using a 2 litre DI single cylinder diesel engine. Two different EGR strategies were examined. One entailed maintaining a constant charge air pressure with a varied exhaust back pressure in order to change the amount of EGR. In the other strategy a constant pressure difference was maintained over the engine, resulting in different equivalence ratios at similar EGR levels. EGR levels of 60 % or more significantly reduced both soot and NOx emissions at 25 % engine load with constant charge air pressure and increasing exhaust back pressure. However, combustion under these conditions was incomplete, resulting in high emissions of carbon monoxide (CO), unburned hydrocarbons (HC) and high fuel consumption.
Technical Paper

A Numerical and Experimental Study of Diesel Fuel Sprays Impinging on a Temperature Controlled Wall

2006-10-16
2006-01-3333
Both spray-wall and spray-spray interactions in direct injection diesel engines have been found to influence the rate of heat release and the formation of emissions. Simulations of these phenomena for diesel sprays need to be validated, and an issue is investigating what kind of fuels can be used in both experiments and spray calculations. The objective of this work is to compare numerical simulations with experimental data of sprays impinging on a temperature controlled wall with respect to spray characteristics and heat transfer. The numerical simulations were made using the STAR-CD and KIVA-3V codes. The CFD simulations accounted for the actual spray chamber geometry and operating conditions used in the experiments. Particular attention was paid to the fuel used for the simulations.
Technical Paper

Low Temperature Combustion in a Heavy Duty Diesel Engine Using High Levels of EGR

2006-04-03
2006-01-0075
The possibilities for extending the range of engine loads in which soot and NOx emissions can be minimised by using low temperature combustion in conjunction with high levels of EGR was investigated in a series of experiments with a single cylinder research engine. The results show that very low levels of both soot and NOx emissions can be achieved at engine loads up to 50 % by reducing the compression ratio to 14 and applying high levels of EGR (up to approximately 60 %). Unfortunately, the low temperature combustion is accompanied by increases in fuel consumption and emissions of both HC and CO. However, these drawbacks can be reduced by advancing the injection timing. The research engine was a 2 litre direct injected (DI), supercharged, heavy duty, single cylinder diesel engine with a geometry based on Volvo's 12 litre engine, and the amount of EGR was increased by adjusting the exhaust back pressure while keeping the charge air pressure constant.
Technical Paper

Experimental and Numerical Investigation of Split Injections at Low Load in an HDDI Diesel Engine Equipped with a Piezo Injector

2006-10-16
2006-01-3433
In order to investigate the effects of split injection on emission formation and engine performance, experiments were carried out using a heavy duty single cylinder diesel engine. Split injections with varied dwell time and start of injection were investigated and compared with single injection cases. In order to isolate the effect of the selected parameters, other variables were kept constant. In this investigation no EGR was used. The engine was equipped with a common rail injection system with a piezo-electric injector. To interpret the observed phenomena, engine CFD simulations using the KIVA-3V code were also made. The results show that reductions in NOx emissions and brake specific fuel consumption were achieved for short dwell times whereas they both were increased when the dwell time was prolonged. No EGR was used so the soot levels were already very low in the cases of single injections.
Technical Paper

Injection Strategy Optimization for a Light Duty DI Diesel Engine in Medium Load Conditions with High EGR rates

2009-04-20
2009-01-1441
Further restrictions on NOx emissions and the extension of current driving cycles for passenger car emission regulations to higher load operation in the near future (such as the US06 supplement to the FTP-75 driving cycle) requires attention to low emission combustion concepts in medium to high load regimes. One possibility to reduce NOx emissions is to increase the EGR rate. The combustion temperature-reducing effects of high EGR rates can significantly reduce NO formation, to the point where engine-out NOx emissions approach zero levels. However, engine-out soot emissions typically increase at high EGR levels, due to the reduced soot oxidation rates at reduced combustion temperatures and oxygen concentrations.
Technical Paper

Combustion and Emissions in a Light-Duty Diesel Engine Using Diesel-Water Emulsion and Diesel-Ethanol Blends

2009-11-02
2009-01-2695
The purpose of the investigation presented here was to compare the effects of fuel composition on combustion parameters, emissions and fuel consumption in engine tests and simulations with five fuels: a Diesel-water emulsion, a Diesel-ethanol blend, a Diesel-ethanol blend with EHN (cetane number improver), a Fischer-Tropsch Diesel and an ultra-low sulfur content Diesel. The engine used in the experiments was a light duty, single cylinder, direct injection, common rail Diesel engine equipped with a cylinder head and piston from a Volvo NED5 engine. In tests with each fuel the engine was operated at two load points (3 bar IMEP and 10 bar IMEP), and a pilot-main fuel injection strategy was applied under both load conditions. Data were also obtained from 3-D CFD simulations, using the KIVA code, to compare to the experimental results and to further analyze the effects of water and ethanol on combustion.
Technical Paper

Effects of Varying Engine Settings on Combustion Parameters, Emissions, Soot and Temperature Distributions in Low Temperature Combustion of Fischer-Tropsch and Swedish Diesel Fuels

2009-11-02
2009-01-2787
It has been previously shown that engine-out soot emissions can be reduced by using Fischer-Tropsch (FT) fuels, due to their lack of aromatics, compared to conventional Diesel fuels. In this investigation the engine-out emissions and fuel consumption parameters of an FT fuel derived from natural gas were compared to those of Swedish low sulfur diesel (MK1) when used in Low Temperature Combustion mode in a single cylinder heavy-duty diesel engine. The effects of varying Needle Opening Pressure (NOP), Charge Air Pressure (CAP) and Exhaust Gas Recirculation (EGR) according to an experimental design on the measured variables were also assessed. CAP and EGR were found to be the most significant factors for the combustion and emission parameters of both fuels. Increases in CAP resulted in lower soot emissions due to enhanced charge mixing, however NOx emissions rose as CAP increased.
Technical Paper

Numerical and Experimental Analysis of the Wall Film Thickness for Diesel Fuel Sprays Impinging on a Temperature-Controlled Wall

2007-04-16
2007-01-0486
Analysis of spray-wall interaction is a major issue in the study of the combustion process in DI diesel engines. Along with spray characteristics, the investigation of impinging sprays and of liquid wall film development is fundamental for predicting the mixture formation. Simulations of these phenomena for diesel sprays need to be validated and improved; nevertheless they can extend and complement experimental measurements. In this paper the wall film thickness for impinging sprays was investigated by evaluating the heat transfer across a temperature controlled wall. In fact, heat transfer is significantly affected by the wall film thickness, and both experiments and simulations were carried out to correlate the wall temperature variations and film height. The numerical simulations were carried out using the STAR-CD and the KIVA-3V, rel. 2, codes.
Technical Paper

The Effect of Charge Air and Fuel Injection Parameters on Combustion with High Levels of EGR in a HDDI Single Cylinder Diesel Engine

2007-04-16
2007-01-0914
When increasing EGR from low levels to levels corresponding to low temperature combustion, soot emissions first start to increase (due to reductions in soot oxidation), before decreasing to almost zero (due to very low rates of soot formation). At the EGR level where soot emissions start to increase, the NOx emissions are still low, but not low enough to comply with future emission standards. The purpose of this study was therefore to investigate the possibilities for moving the so-called “soot bump” (increase in soot) to higher EGR levels or reducing the magnitude of the soot bump. This involved an experimental investigation of parameters affecting the combustion and thus the engine-out emissions. The parameters investigated were: charge air pressure, injection pressure, EGR temperature and post injection (with different dwell times) for a wide range of EGR rates.
Technical Paper

Effects of Multiple Injections on Engine-Out Emission Levels Including Particulate Mass from an HSDI Diesel Engine

2007-04-16
2007-01-0910
The effects of multiple injections on engine-out emissions from a high-speed direct injection (HSDI) diesel engine were investigated in a series of experiments using a single cylinder research engine. Injection sequences in which the main injection was split into two, three and four pulses were tested and the resulting emissions (NOx, CO HC and particulate matter), torque and cylinder pressures were compared to those obtained with single injections. Together with the number of injections, the effects of varying the dwell time were also investigated. It was found that dividing the main injection into two parts lowered the engine-out particulate and CO emissions and increased fuel efficiency. However, it also resulted in increased NOx emissions.
X