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Technical Paper

3-D Numerical Study of Fluid Flow and Pressure Loss Characteristics through a DPF with Asymmetrical Channel size

2011-04-12
2011-01-0818
The main objective of the current paper was to investigate the fluid flow and pressure loss characteristics of DPF substrates with asymmetric channels utilizing 3-D Computational Fluid Dynamics (CFD) methods. The ratio of inlet to outlet channel width is 1.2. First, CFD results of velocity and static pressure distributions inside the inlet and outlet channels are discussed for the baseline case with both forward and reversed exhaust flow. Results were also compared with the regular DPF of same cell structure and wall material properties. It was found that asymmetrical channel design has higher pressure loss. The lowest pressure loss was found for the asymmetrical channel design with smaller inlet channels. Then, the effects of DPF length and filter wall permeability on pressure loss, flow and pressure distributions were investigated.
Technical Paper

A Predictive Model for the Interior Pressure Oscillations from Flow Over Vehicle Openings

1997-05-20
971906
An analytical model based on “vortex sound” theory was investigated for predicting the frequency, the relative magnitude, the onset, and the offset of self-sustained interior pressure fluctuations inside a vehicle with an open sunroof. The “buffeting” phenomenon was found to be caused by the flow-excited resonance of the cavity. The model was applied to investigate the optimal sunroof length and width for a mid-size sedan. The input parameters are the cavity volume, the orifice dimensions, the flow velocity, and one coefficient characterizing vortex diffusion. The analytical predictions were compared with experimental results obtained for a system which geometry approximated the one-fifth scale model of a typical vehicle passenger compartment with a rectangular, open sunroof. Predicted and observed frequencies and relative interior pressure levels were in good agreement around the “critical” velocity, at which the cavity response is near resonance.
Technical Paper

A Preliminary Study of Virtual Humidity Sensors for Vehicle Systems

2014-04-01
2014-01-1156
New vehicle control algorithms are needed to meet future emissions and fuel economy mandates that are quite likely to require a measurement of ambient specific humidity (SH). Current practice is to obtain the SH by measurement of relative humidity (RH), temperature and barometric pressure with physical sensors, and then to estimate the SH using a fit equation. In this paper a novel approach is described: a system of neural networks trained to estimate the SH using data that already exists on the vehicle bus. The neural network system, which is referred to as a virtual SH sensor, incorporates information from the global navigation satellite system such as longitude, latitude, time and date, and from the vehicle climate control system such as temperature and barometric pressure, and outputs an estimate of SH. The conclusion of this preliminary study is that neural networks have the potential of being used as a virtual sensor for estimating ambient and intake manifold's SH.
Technical Paper

Aerodynamic Wind Throb in Passenger Cars

1964-01-01
640797
Most automobiles, at certain speeds with at least one window open, develop a pulsating pressure which is felt mainly through the ears and is objectionable to the occupants. While this “aerodynamic wind throb” is noticeable over a range of speeds, there is a fairly pronounced peak in the effect at one speed. This problem is studied analytically and experimentally. It is established that the car is a dynamic system consisting of a Helmholtz resonator excited by an edge tone. It is shown that the trouble can be corrected by changing the natural frequency, minimizing or eliminating the excitation, or increasing damping of the system.
Technical Paper

An Analytical Method for Determining Engine Torque Harmonics for Use With Up Front CAE

1995-05-01
951248
An analytical method for determining engine torque harmonics is presented. The approach employs an engine cycle simulation model to calculate instantaneous cylinder pressure for each operating condition based on engine characteristics that can be determined experimentally and/or analytically. Cylinder pressure is converted to instantaneous torque from which harmonics are determined using an FFT algorithm. A description of the cycle simulation model, including required data, is presented. The method is validated by presenting correlation results at a number of operating conditions (i.e. engine speeds and loads) comparing analytical versus test driveline torque harmonics. Finally, limitations in the method as well as possible extensions to the method are discussed.
Technical Paper

CRC Looks at Cars, Fuels, and Vapor Lock

1965-02-01
650860
In 1962 and 1964 the Coordinating Research Council (CRC) evaluated the vapor locking characteristics of about 40 selected new model cars during centralized programs at Yuma, Arizona. Volatility tolerances were determined during acceleration following a hot soak at approximately 100 F ambient using two reference fuel series with diverse front-end volatilities. Fifty per cent of the 1962 model cars tested had a limiting vapor pressure equal to or less than 8.4 lb with the high volatility fuels and 9.7 lb with the low volatility fuels. Comparable values in the 1964 program were 8.9 lb for the high and 10.4 lb for the low volatility fuels. Analytical results obtained on vehicle tank samples for the first time during 1964 showed that limiting temperature at a given vapor-to-liquid ratio also was a useful parameter in defining car volatility tolerances.
Technical Paper

Clean Combustion in a Diesel Engine Using Direct Injection of Neat n-Butanol

2014-04-01
2014-01-1298
The study investigated the characteristics of the combustion, the emissions and the thermal efficiency of a direct injection diesel engine fuelled with neat n-butanol. Engine tests were conducted on a single cylinder four-stroke direct injection diesel engine. The engine ran at 6.5 bar IMEP and 1500 rpm engine speed. The intake pressure was boosted to 1.0 bar (gauge), and the injection pressure was controlled at 60 or 90 MPa. The injection timing and the exhaust gas recirculation (EGR) rate were adjusted to investigate the engine performance. The effect of the engine load on the engine performance was also investigated. The test results showed that the n-butanol fuel had significantly longer ignition delay than that of diesel fuel. n-Butanol generally led to a rapid heat release pattern in a short period, which resulted in an excessively high pressure rise rate. The pressure rise rate could be moderated by retarding the injection timing and lowering the injection pressure.
Technical Paper

Compensation for Road Noise in Automotive Entertainment Systems

1987-02-01
870144
Vehicle operation noise, even in the quietest cars, produces high sound pressure levels (SPL) at very low frequencies. This noise masks desired signals in and above this frequency range. A blind subjective test, using ten listeners, was undertaken to determine a frequency response equalization curve that would compensate for this noise under specific but realistic conditions. Starting with a 4 dB full-band level increase, an average of 40 listener responses showed a gentle rise in bass reaching an additional 4 dB at 50 Hz.
Technical Paper

Compound Electroformed Metal Nozzles for High Pressure Gasoline Injection

1998-02-23
980818
The objective of this research was to evaluate the effects that higher fluid injection pressures and nozzle geometry have on compound fuel injector nozzle performance. Higher pressures are shown to significantly reduce droplet size, increase the discharge coefficient and reduce the overall size of a nozzle spray. It is also shown that the geometry has a significant effect on nozzle performance, and it can be manipulated to give a desired spray shape.
Technical Paper

Cooling Inlet Aerodynamic Performance and System Resistance

2002-03-04
2002-01-0256
This report is a contribution to the understanding of inlet aerodynamics and cooling system resistance. A characterization of the performance capability of a vehicle front-end and underhood, called the ram curve, is introduced. It represents the pressure recovery/loss of the front-end subsystem - the inlet openings, underhood, and underbody. The mathematical representation, derived from several experimental investigations on vehicles and components, has four basic terms: Inlet ram pressure recovery; free-stream energy recovered when the vehicle is moving Basic inlet loss; inlet restriction when the vehicle is stationary Pressure loss of the engine bay Engine bay-exit pressure Not surprisingly, the amount of frontal projection of radiator area through the grille, bumper and front-end structure (called projected inlet area), and flow uniformity play a major role in estimating inlet aerodynamic performance.
Technical Paper

Cycle-Model Assessment of Working Fluids for a Low-Pressure CO2 Climate Control System

2000-03-06
2000-01-0578
A low-pressure CO2-based climate-control system has the environmental benefits of CO2 refrigerant but avoids the extremely high pressures of the transcritical CO2 cycle. In the new cycle, a liquid “cofluid” is circulated in tandem with the CO2, with absorption and desorption of CO2 from solution replacing condensation/gas cooling and evaporation of pure CO2. This work compares the theoretical performance of the cycle using two candidate cofluids: N-methyl-2-pyrrolidone and acetone. The optimal coefficient of performance (COP) and refrigeration capacity are discussed in terms of characteristics of the CO2-cofluid mixture. Thermodynamic functions are determined either from an activity coefficient model or using the Soave equation of state, with close agreement between the two approaches. Reductions in COP due to nonideal compressor and heat exchangers are also estimated.
Technical Paper

Determination of Vehicle Interior Sound Power Contribution Using Sound Intensity Measurement

1997-05-20
971907
For vehicle interior noise abatement and noise treatment, it is desirable to quantitatively determine sound power contribution from each vehicle component because: (1) Sound packages can be designed with maximized efficiency if sound power contribution into a vehicle is known; (2) Acoustic leakage inside a vehicle can be determined by comparing sound power contributions from adjacent vehicle components; and (3) Sound power flow information can be used to verify Statistical Energy Analysis (SEA) model. Simple sound pressure measurement does not produce any information about sound power flow and is unsuitable for these purposes. This paper describes an in-situ determination of sound power contribution inside a vehicle using sound intensity measurements. Sound power contribution from each vehicle component was determined for engine noise at idle speed. Acoustic leakage in the vehicle was also determined.
Technical Paper

Development and Validation of a Computational Process for Pass-By Noise Simulation

2001-04-30
2001-01-1561
The Indirect Boundary Element Analysis is employed for developing a computational pass-by noise simulation capability. An inverse analysis algorithm is developed in order to generate the definition of the main noise sources in the numerical model. The individual source models are combined for developing a system model for pass-by noise simulation. The developed numerical techniques are validated through comparison between numerical results and test data for component level and system level analyses. Specifically, the source definition capability is validated by comparing the actual and the computationally reconstructed acoustic field for an engine intake manifold. The overall pass-by noise simulation capability is validated by computing the maximum overall sound pressure level for a vehicle under two separate driving conditions.
Technical Paper

Development of a Fuelling System to Reduce Cold-Start Hydrocarbon Emissions in an SI Engine

1996-05-01
961119
An air-assisted fuel vaporiser (AAFV), designed to replace the conventional fuelling system has been tested on a 3.0-litre development engine under simulated cold-Start conditions. Providing the cold engine with pre-vaporised fuel removed the need for an enriched mixture during start-up. Comparisons between the AAFV and standard fuelling systems were performed. Engine-out hydrocarbon (HC) exhaust emissions were measured during cold-start and the ensuing two minutes. Fuel spray characterisation was also conducted using a steady flow test rig designed to mimic inlet port conditions of air flow and manifold pressure over a wide range of engine operation.
Technical Paper

Direct Estimation of Cyclic Combustion Pressure Variability Using Engine Speed Fluctuations in an Internal Combustion Engine

1994-03-01
940143
Cyclic variability (CV) in combustion in IC-SI engines, manifested as variation in combustion pressure, is a long term as well as a contemporary problem. CV and its relation to several areas of engine control and diagnostics are discussed. A novel stochastic model relating combustion pressure to crankshaft velocity in an IC-SI engine is presented. This model incorporates a random combustion pressure signal model composed of a deterministic waveform and a random sequence modeling cyclic variation in combustion pressure. A discrete recursion is developed relating this sequence to noisy measurements of velocity. The inverse problem of reconstructing this sequence from one measurement of velocity per combustion is solved using a signal processing deconvolution method. Experimental results using real-world engine data are presented verifying the theoretical developments for low to moderate engine speed and moderate engine load.
Journal Article

Effects of Fuel Cell Material Properties on Water Management Using CFD Simulation and Neutron Imaging

2010-04-12
2010-01-0934
Effects of fuel cell material properties on water management were numerically investigated using Volume of Fluid (VOF) method in the FLUENT. The results show that the channel surface wettability is an important design variable for both serpentine and interdigitated flow channel configurations. In a serpentine air flow channel, hydrophilic surfaces could benefit the reactant transport to reaction sites by facilitating water transport along channel edges or on channel surfaces; however, the hydrophilic surfaces would also introduce significantly pressure drop as a penalty. For interdigitated air flow channel design, it is observable that liquid water exists only in the outlet channel; it is also observable that water distribution inside GDL is uneven due to the pressure distribution caused by interdigitated structure. An in-situ water measurement method, neutron imaging technique, was used to investigate the water behavior in a PEM fuel cell.
Technical Paper

Effects of Fuel Volatility and Operating Conditions on Fuel Sprays in DISI Engines: (2) PDPA Investigation

2000-03-06
2000-01-0536
Optimal design of modern direct injection spark-ignition engines depends heavily on the characteristics and distribution of the fuel spray. This study was designed to compliment imaging experiments of changes in the spray structure due to fuel volatility and operating conditions. Use of phase-Doppler particle analysis (PDPA) allows quantitative point measurements of droplet diameter and velocity. In agreement with imaging experiments, the results show that the spray structure changes not only with ambient gas density, which is often measured, but also with fuel temperature and volatility. The mean droplet diameter was found to decrease substantially with increasing fuel temperature and decreasing ambient density. Under conditions of low potential for vaporization, the observed trends in mean droplet sizes agree with published correlations for pressure-swirl atomizers.
Technical Paper

Eliminating Piston Slap through a Design for Robustness CAE Approach

2003-05-05
2003-01-1728
Piston slap is a problem that plagues many engines. One of the most difficult aspects of designing to eliminate piston slap is that slight differences in operating conditions and in part geometries from build to build can create large differences in the magnitude of piston slap. In this paper we will describe a design for robustness CAE approach to eliminating piston slap. This approach considers the variations of the significant control factors in the design, e.g. piston pin offset, piston skirt design, etc. as well as the variation in the noise factors the system is subjected to, e.g. assembly clearance, skirt collapse, peak cylinder pressure, cylinder pressure rise rate, and location of peak cylinder pressure. Using analytical knowledge about how these various factors impact the generation of piston slap, a piston design for low levels of piston slap can be determined that is robust to the various noise factors.
Technical Paper

Experimental and Computational Analysis of Impact of Self Recirculation Casing Treatment on Turbocharger Compressor

2010-04-12
2010-01-1224
Self recirculation casing treatment has been showed to be an effective technique to extend the flow range of the compressor. However, the mechanism of its surge extension on turbocharger compressor is less understood. Investigation and comparison of internal flow filed will help to understand its impact on the compressor performance. In present study, experimentally validated CFD analysis was employed to study the mechanism of surge extension on the turbocharger compressor. Firstly a turbocharger compressor with replaceable inserts near the shroud of the impeller inlet was designed so that the overall performance of the compressor with and without self recirculation casing treatment could be tested and compared. Two different self recirculation casing treatments had been tested: one is conventional self recirculation casing treatment and the other one has deswirl vanes inside the casing treatment passage.
Technical Paper

Improving Flow Efficiency of a Catalytic Converter Using the Concept of Radially Variable Cell Density - Part I

1999-03-01
1999-01-0769
The automotive industry and emission system suppliers invest considerable efforts for the improvement of the conversion efficiency of a catalytic converter, in order to lower vehicle emission. One of the methods to improve the catalyst conversion efficiency is to use a higher cell density brick with a thinner wall to increase its geometric surface area. However, there is a significant drawback for the system - higher pressure loss along the brick. Moreover, the mechanical strength and thermal degradation of the brick become major concerns. In this paper, the concept of a brick with radially variable cell density is introduced to possibly resolve several issues. A CFD study was conducted to verify benefits in both flow efficiency and pressure loss along the brick with several different flow rates.
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