Search Results

The need to develop products faster and to have designs which are first time right have put enormous pressure on the product development timelines, thus making computer aided optimization one of the most important tool in achieving these targets. In this paper, a design of experiments (DOE) study is used, to gain an insight as to, how changes to different parameters of front suspension and steering of a passenger bus affect its kinematic properties and thus to obtain an optimized design in terms of handling parameters such as bump steer, percent ackermann error and lock to lock rotation angle of steering wheel. The conventional hit and trial method is time consuming and monotonous and still is an approximate method, whereas in design of experiments (DOE), a model is repeatedly run through simulations in a single setup, for various combinations of parameter settings.

The growing functionality and complexity of recent vehicle electronic systems have made inter-device communication (on-board LAN) technology vital to vehicle design. By field of application, the LAN (Local Area Network) systems currently in use are LIN (Local Interconnect Network) used for body systems, CAN (Controller Area Network) used for control systems, and MOST (Media Oriented Systems Transport ) used for multimedia and camera systems, and work to standardize the next-generation communication technology for each of those fields is underway. This paper provides a technical overview of the CXPI (Clock Extension Peripheral Interface) communication protocol, which satisfies the body system requirements (rapid response, system extensibility, high reliability, and low cost). It also presents the progress made on standardization at SAE and other organizations.

Due to benefits from the use of electric power, Hybrid Electric Vehicles (HEVs) and Plug-in Hybrid Electric Vehicles (PHEVs) are regarded to be superior over conventional Internal Combustion Engine (ICE) only vehicles in fuel economy and emissions. However, recent studies find out that this is not always true. On certain conditions, hybrid vehicles can be even more polluted. In order to identify these challenges and develop catalysts to meet more stringent emission requirement in the future, e.g. Euro 7, for hybrid application, as a part of our xHEV project, this study includes exclusively extensive investigation on a latest Euro 6d temp Parallel PHEV.

The aim of this paper was to describe a method of accelerated three way catalytic converter (TWC) ageing performed on the engine test bed for European On Board Diagnostics (EOBD) monitoring purposes and screening of different catalysts solutions. To accelerate the catalyst ageing process, the exhaust gas temperature was elevated to a range 1000 - 1200°C, which is typical for an ageing cycle performed using ovens. Catalyst emissions performance was checked at new condition (after degreening) and subsequently at predefined ageing intervals, based on the oxygen storage capacity (OSC) evaluation. The emission tests were performed in the laboratory on the chassis dynamometer using legislative cycles. The accelerated ageing method was found to be of use for verifying the EOBD functionality under vehicle operation with a degraded catalyst substrate.

The present work investigates the temperature distribution inside the diesel particulate filter (DPF) regeneration during the drop to idle test (DTIT), which is considered as life-threatening to the DPF. To study this scenario in detail, experiments were carried out with the filter volume of 3 liters. Initially, the experiments were done at a steady-state level, where the optimization for optimal soot loading was performed with setpoint temperature varying from 620 to 660°C. The soot loading was varied from 8 g/l to 11 g/l. The DTIT performed at a steady-state level indicated the different peak temperatures attained inside the DPF at different locations. The peak temperature was found to be in the center plane of the filter. The next peak temperature locations were found to be in downstream of the filter at different locations, which shows the non-uniformity in the soot deposition inside the filter.

The effective filtration area of a diesel particulate filter (DPF) can be improved by novel cell structure design and valuable plugging layout simultaneously without sacrificing the reduction of the inlet aperture ratio. A prototype silicon carbide DPF characterized with about more than 14 cm2/cm3 filtration area and more than 43% of the inlet aperture has been designed, optimized, and manufactured. Based on a single-cylinder diesel engine test bench, the performance of this prototype has been evaluated, such as its filtration efficiency, pressure loss, active/passive regeneration efficiency, etc.

Valve stem seals have been used for the various valve stem application of automotive engines by establishing the certain lubricating status between valve stems and valve guides. It is necessary that valve stem seals have stable controlled oil leakage characteristics relative to variables such as oil viscosity, shaft speed and shaft surface roughness. The practical aspect of the characteristics of the controlled oil leakage on valve stem seals for engine application in small size U.S. and Japanese passenger cars have been discussed in this paper.

An internal combustion engine valve stem seal is actually a precision lubricating device that allows enough lubrication to the valve stem for extended life, but limits the lubrication to provide compliance with exhaust regulations, limits valve deposits, and prevents uneconomical oil consumption. The oil leakage for lubrication can be determined using four seal lip design factors. The long term stability of the oil leakage is provided by selecting polytetrafluoroethylene (PTFE) and fluoroelastomer (FKM) rubber as the seal materials, which are bonded together during vulcanization. The PTFE provides a low friction. low wear surface, and the FKM rubber provides a stable resilient body. Validation of the design factors is accomplished by precise measurement of oil leakage using actual engine components. After long term engine testing in the laboratory or field, the leakage can be re-measured. The leakage can be expected to increase only slightly.

New emission requirements for compression ignition engines have led engine designers to review the attributes of positive valve stem seals. Federal standards for particulate emissions were initiated in 1988 for heavy duty diesel engines in the United States. Since then, the standards on particulates have been significantly reduced from .6 g/kW*hr in 1988 to .1 g/kW*hr for 1994 [1]*. Lowering particulates, improving oil economy and reducing guide wear have all become important issues in the heavy duty engine marketplace. All of these factors are affected, in part, by the amount of oil flowing thru the clearance between the valve guide and valve stem. Bench tests indicate that heavy duty valve seals could reduce overhead oil consumption by as much as 99% during idle/motoring conditions and lower particulate emission levels contributed by lube oil up to 75%. In addition, they can significantly reduce guide wear and valve stem scuffing under turbocharged conditions.

A study was conducted to reduce unburned oil fractions in diesel particulate matter (PM) by improving oil consumption. A method utilizing radioisotope 14C was developed to measure the unburned oil fractions separately for the four paths by which oil is consumed: valve stem seals, piston rings, PCV system, turbocharger. The conversion ratio of oil consumption to PM was calculated by comparing the unburned oil emission rates with oil consumption rates, which were obtained by the use of the 35S tracer method. The result in an experimental diesel engine shows the highest conversion ratio for the oil leaking through the valve stem seals. The modifications to the engine were thereby focused on reducing the leakage of the stem seals. This stem seal modification, along with piston ring improvements, reduced oil consumption, resulting in the unburned oil fractions in PM being effectively reduced.

It was presented in the previous paper (1) that oil leakage from valve stem seal (VSS) can be controlled by design and the characteristics of the newly designed composite VSS with a filled polyetrafluoroethylene (PTFE) layer lip are: a constant lower limit of oil leakage, minimal loss of power at low speed due to low friction, extended life over 300,000 km of vehicle traveled distance. It was also reported that oil leakage for lubrication can be determined by the stress distribution across the seal lip contact width touching the valve stem under a certain interference. However, the variable pressure inside Intake and Exhaust ports of an engine will affect the stress distribution of the seal lip causing the change in oil leakage. This report presents the design evaluation method and results of the improved VSS with filled PTFE layer lip which keeps the oil leakage constant even though the inside pressure of the engine port changes.

Changes in lubrication oil additive packages, increasing engine temperatures and the increased use of alternate fuels place greater demands on rubber components inside the internal combustion engine. The rubber valve stem seal, positioned in the valve train, may respond adversely to these changing conditions. Two elastomers, a copolymer, (TFE/P), and a terpolymer, having a similar propylene backbone molecular structure, (T/P/T), have been studied for their functional advantages over the standard fluoroelastomer, (FKM 1). The data presented in the paper compares the effects of various crankcase oils and crankcase fuel dilution on valve seals produced from each of the three materials. Both the TFE/P and T/P/T show improved chemical resistance over FKM 1.

As a precursor to a full leakage study on Valve Stem Seals (VSS), Finite Element (FE) Analyses were carried out using ANSYS 5.2. Two dimensional axisymmetric static models were developed, with the Mooney-Rivlin strain energy function used to describe the nonlinear behaviour of the rubber. For each analysis, elasto-hydrodynamic lubrication was assumed during valve stem reciprocation. Each model featured an alteration to a ‘standard’ design of valve stem seal (known to give excellent performance over its life cycle), the effect of these differences was then investigated. Where possible, physical measurements were made for comparison with the FE results. This research gives a first order approximation, revealing magnitude and direction of seal lip to valve stem contact.

Due to the current and future emission regulations, nearly every new internal combustion engine has to be equipped with valve stem seals. The optimal seal is designed to meet the increasingly severe emission regulations by constantly metering the oil flow to allow adequate lubrication of the valve stem/ guide while at the same time minimizing oil flow to the combustion chamber and hence minimizing emissions. The seal has to compensate for manufacturing tolerances of the cylinder head and to provide stability of the oil metering rate for all different running conditions over the life of the engine. To increase the constancy of the oil flow metered by the seals, a new stepped lip design was developed using finite element analysis.

Typically the roll propensity of a vehicle is calculated from the assumption that the vehicle is a rigid body and that its roll propensity can be determined by taking the ratio of the track width and the center of gravity height. However, a passenger vehicle is not a rigid body; it is at least two rigid bodies connected through links and springs and shock absorbers. The objective of this paper is to derive a new second order rollover metric, which will predict whether a vehicle may be susceptible to rollover from simple physical measurements of the vehicle. The validation of the derived metric using a stock and modified vehicle configuration will be presented. Further validation with several vehicles is planned and will be reported in later papers.

The assumption usually made in the safety analysis of most systems is that the failure of any one component is independent of the failure of any other. If this assumption is not valid due to the system design and implementation, the estimated Fault Tree Analysis (FTA) event probabilities will be more optimistic than what is found in practice. One of the most important modes of failure and one, which can severely degrade the actual safety, is a common mode failure. This type of failure involves the simultaneous outage of two or more components due to a common cause. Common Mode Analysis (CMA) provides evidence that the failures assumed to be independent are truly independent. In reality, this analysis is extremely complex due to the large number of common mode failures that may be related to the different common mode types such as design, operation, manufacturing, installation and others.

Occupants of off-road vehicles are very susceptible to the effects of vertical accelerations. Root mean square values normally accepted are 0.25 g's for longer duration and 0.4 g's for a shorter duration (up to two hours per day) (ref. 1). Typical off-road vehicles stiffen the suspension in order to prevent bottoming of the vehicle. This causes the ride to be extremely rough, meaning the vertical accelerations are at the limit of the human endurance. The speed of the vehicle is then limited by the endurance of the individual. By lengthening the suspension travel and tuning the spring stiffness and damping coefficients, a smooth and controllable ride is achieved thus increasing the natural limit speed. “Whoop-de-doos” are referred to by off-road drivers as a set of evenly spaced waves in the path of travel. These are often caused by repeated traffic over a soft surface. These bumps are sinusoidal in nature and are usually spaced 6 meters apart and 0.2 meters high.

Can a buckle designed with a lock for the latch when struck on the face, back, or side, also have this same feature when accelerated along the longitudinal axis? Six seatbelt buckles from various manufacturers were tested to determine their dynamic characteristics in the longitudinal direction along the mounting stalk. Patented designs of the buckles were intended to prevent inertial unlatching of the buckle. Although they may perform well in lateral and vertical directions, when force is applied along the direction parallel to the mounting stalk the buckles could be made to release. If the buckle is mounted in the vehicle with a rigid stalk, could impact pulses be transmitted to the buckle to cause release? A test apparatus was constructed where the buckle could be mounted with the stalk and webbing. The webbing could be preloaded and the buckle was accelerated by impacting the mounting point at the base of the stalk.

The homogeneous mixing flow modelling approach has been incorporated in a CFD framework to study subcooled nucleate boiling heat transfer that may occur in IC engine cooling passages. The approach is based on the assumption that vapour bubbles are small and perfectly mixed with the liquid phase (bubbly boiling flow pattern). A void faction equation has been introduced into the single phase CFD solver to describe the concentration of the vapour phase. Superheated wall heat transfer, fluid evaporation and condensation mass transfer are described by sub-models. Primary validations of the method have been conducted using channel boiling flow data from the literature over a range of flow speed, liquid subcooling and wall superheat conditions. The predicted wall heat flux and vapour concentration distributions are in satisfactory agreement with the experimental measurements.

Manifold tuning has long been considered a critical facet of engine design and performance optimization. This paper details the design, analysis and preliminary testing of a continuously variable, carbon fiber intake manifold for a restricted 2003 Suzuki GSXR-600® engine. The device achieves a large dynamic runner length range of 216-325 mm through the use of a half-tube, sliding shell design that differs substantially from traditional variable intake approaches. A combination of Ricardo WAVE® and 2D/3D Ansys Fluent® simulations were used to aid in the design of the intake along with a custom software routine to optimize restrictor geometry through fully automated CFD simulations. The sliding mechanism was actuated via a cable linkage system and powered by a small servo motor. This motor was controlled by a Microchip dsPIC® microcontroller that was embedded in a custom power distribution PCB for the 2009 Cooper Union Formula SAE® entry.