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Journal Article

Research on Measurement Method of Road Gradient and Altitude by On-Road Driving

2009-04-20
2009-01-1116
Exhaust emissions from a vehicle under road driving condition is affected by the control state of ECU (Engine Control Unit). This control state highly depends on the driving force of the vehicle. The driving force is nearly equal to the driving resistance, which is the sum of the acceleration resistance, the air resistance, the rolling resistance and the gradient resistance. Although it is essential to take an accurate measurement of the road gradient, it is quite difficult to evaluate the gradient resistance in testing on-road driving. In this study, the measurement methods of the road gradient and the altitude with GPS, gyro sensor and height sensor are reported. The road gradient under the on-road driving condition is evaluated by the combination of measuring the pitch angle with the gyro sensor and measuring the vehicle gradient with the two height sensors. Verifying of this method, the altitude of the driving test route is also evaluated.
Technical Paper

Development of the Texas Drayage Truck Cycle and Its Use to Determine the Effects of Low Rolling Resistance Tires on the NOX Emissions and Fuel Economy

2009-04-20
2009-01-0943
Trucks operating in inter-modal (drayage) operation in and around port and rail terminals, are responsible for a large proportion of the emissions of NOX, which are problematic for the air quality of the Houston and Dallas/Ft. Worth metro areas. A standard test cycle, called the Texas Dray Truck Cycle, was developed to represent the operation of heavy-duty diesel trucks in dray operations. The test cycle reflects the substantial time spent at idle (~45%) and the high intensity of the on-road portions. This test cycle was then used in the SAE J1321 test protocol to evaluate the effect on fuel consumption and NOX emissions of retrofitting dray trucks with light-weight, low-rolling resistance wide-single tires. In on-track testing, a reduction in fuel consumption of 8.7% was seen, and NOX emissions were reduced by 3.8% with the wide single tires compared to the conventional tires.
Technical Paper

Further CFD Studies for Detailed Tires using Aerodynamics Simulation with Rolling Road Conditions

2010-04-12
2010-01-0756
In an environment of tougher engineering constraints to deliver tomorrow's aerodynamic vehicles, evaluation of aerodynamics early in the design process using digital prototypes and simulation tools has become more crucial for meeting cost and performance targets. Engineering needs have increased the demands on simulation software to provide robust solutions under a range of operating conditions and with detailed geometry representation. In this paper the application of simulation tools to wheel design in on-road operating conditions is explored. Typically, wheel and wheel cover design is investigated using physical tests very late in the development process, and requires costly testing of many sets of wheels in an on-road testing environment (either coast-down testing or a moving-ground wind-tunnel).
Technical Paper

Effects of Ground Simulation on the Aerodynamic Coefficients of a Production Car in Yaw Conditions

2010-04-12
2010-01-0755
Automotive wind tunnel testing is a key element in the development of the aerodynamics of road vehicles. Continuous advancements are made in order to decrease the differences between actual on-road conditions and wind tunnel test properties and the importance of ground simulation with relative motion of the ground and rotating wheels has been the topic of several studies. This work presents a study on the effect of active ground simulation, using moving ground and rotating wheels, on the aerodynamic coefficients on a passenger car in yawed conditions. Most of the published studies on the effects of ground simulation cover only zero yaw conditions and only a few earlier investigations covering ground simulation during yaw were found in the existing literature and all considered simplified models. To further investigate this, a study on a full size sedan type vehicle of production status was performed in the Volvo Aerodynamic Wind Tunnel.
Technical Paper

A Wind Tunnel Study Correlating the Aerodynamic Effect of Cooling Flows for Full and Reduced Scale Models of a Passenger Car

2010-04-12
2010-01-0759
In the early stages of an aerodynamic development programme of a road vehicle it is common to use wind tunnel scale models. The obvious reasons for using scale models are that they are less costly to build and model scale wind tunnels are relatively inexpensive to operate. It is therefore desirable for model scale testing to be utilized even more than it is today. This however, requires that the scale models are highly detailed and that the results correlate with those of the full size vehicle. This paper presents a correlation study that was carried out in the Chalmers and Volvo Car Aerodynamic Wind Tunnels. The aim of the study was to investigate how successfully a correlation of the cooling air flow between a detailed scale model and a real full size vehicle could be achieved. Results show limited correlation on absolute global aerodynamic loads, but relative good correlation in drag and lift increments.
Technical Paper

CFD Approach to Evaluate Wind-Tunnel and Model Setup Effects on Aerodynamic Drag and Lift for Detailed Vehicles

2010-04-12
2010-01-0760
Previous work by the authors showed the development of an aerodynamic CFD model using the Lattice Boltzmann Method for simulating vehicles inside the IVK Model-Scale Wind-Tunnel test-section. In both experiment and simulation, alternate configurations of the wind-tunnel geometry were studied to change the pressure distribution in the wind-tunnel test section, inducing a reduction in aerodynamic drag due to interference between the wind-tunnel geometry and the pressure on the surface of the vehicle. The wind-tunnel pressure distribution was modified by adding so-called “stagnation bodies” inside the collector to create blockage and to increase the pressure in the rear portion of the test section. The primary purpose of previous work was to provide a validated CFD approach for modeling wind-tunnel interference effects, so that these effects can be understood and accounted for when designing vehicles.
Technical Paper

Aerodynamic Drag Simulation and Validation of a Crossover

2010-04-12
2010-01-0757
Aerodynamic simulation using commercial CFD (Computational Fluid Dynamics) codes is now an integral part of the vehicle design process. Aerodynamic prediction and vehicle development program runs in parallel. This requires a good agreement between experimental measurements and CFD prediction of aerodynamic behavior of a vehicle. The comparison between experimental and simulation results show differences, as it may not be possible to replicate effect of all the wind tunnel parameters in the simulation. This paper presents the details of aerodynamic simulation process of a Crossover and its validation with the experimental results available from the wind tunnel tests. The results are compared for different configurations such as- closing the grille openings, removing the rearview mirror, adding ski-rack and using different tyres. This study also includes the effect of different wind speeds and yaw angles on the coefficient of drag.
Technical Paper

Fuel Consumption Testing to Verify the Effect of Tire Rolling Resistance on Fuel Economy

2010-04-12
2010-01-0763
The connection between low rolling resistance tires and fuel consumption is now well established and has been successfully modeled. Previous studies have shown that fuel savings can be predicted by an empirical law tying the difference in rolling resistance force to a difference in fuel consumption while still accounting for the resulting engine efficiency change. However, accurately evaluating fuel savings in real conditions remains a crucial issue, as test uncertainty is generally close to the order of magnitude of the consumption difference. This paper proposes an analytical approach to measuring fuel economy. The test is conducted on an outdoor track using two identical vehicles at a single stabilized speed. The vehicle positions are measured by GPS devices and the absolute fuel consumption of each engine is measured with flowmeters. Specific attention is paid to numerous external parameters that influence fuel consumption, in order to minimize test dispersion.
Journal Article

Effects of Ethanol Content on Gasohol PFI Engine Wide-Open-Throttle Operation

2009-06-15
2009-01-1907
The NOx emission and knock characteristics of a PFI engine operating on ethanol/gasoline mixtures were assessed at 1500 and 2000 rpm with λ =1 under Wide-Open-Throttle condition. There was no significant charge cooling due to fuel evaporation. The decrease in NOx emission and exhaust temperature could be explained by the change in adiabatic flame temperature of the mixture. The fuel knock resistance improved significantly with the gasohol so that ignition could be timed at a value much closer or at MBT timing. Changing from 0% to 100% ethanol in the fuel, this combustion phasing improvement led to a 20% increase in NIMEP and 8 percentage points in fuel conversion efficiency at 1500 rpm. At 2000 rpm, where knocking was less severe, the improvement was about half (10% increase in NIMEP and 4 percentage points in fuel conversion efficiency).
Technical Paper

Method for the Pre-design of a Smart Droop Nose Device using a Simplex Optimization Scheme

2009-11-10
2009-01-3113
The high lift systems of modern-day commercial airplanes are highly effective systems providing the required lift during take-off and approach at low flight velocities. State-of-the-art high lift systems consist of movable control surfaces which when deployed increase high lift performance. Typical devices are slats and fowler flaps which consist of rigid parts supported and driven by complex mechanical systems. To achieve the ambitious goals defined in the strategic research agendas provided by the “Advisory Council for Aeronautical Research in Europe” (ACARE), technologies to consequently reduce drag, emissions and airframe noise will be necessary. The goals for the environment (based on the technological level of 2000) are a reduction of fuel consumption and CO2 emissions by 50%, a reduction of NOx emissions by 80 %, a reduction of perceived external noise by 50% and a reduction of the impact of production, maintenance, and disposal of the A/C [1].
Technical Paper

Reliability and Life Study of Hydraulic Solenoid Valve - Part 2 - Experimental Study

2009-04-20
2009-01-0413
The current work studies the reliability of a solenoid valve (SV) used in automobile transmissions through a joint theoretical and experimental approach. The goal of this work is to use accelerated tests to characterize SV failure and correlate the results to new comprehensive finite element models (Part 1). A custom test apparatus has been designed and built to simultaneously monitor and actuate up to four SVs. The test apparatus is capable of applying a controlled duty cycle, current and actuation frequency. The SVs are also placed in a thermal chamber so that the ambient temperature can be controlled precisely. The apparatus measures in real-time the temperature, current, and voltage of each SV. A series of tests have been conducted to produce repeated failures of the SV. The failure of the SV appears to be caused by overheating and failure of the insulation used in the solenoid coil.
Technical Paper

Automotive Roof Crush, Structural Foam Enhancement Solution

2009-04-20
2009-01-0371
Vehicle rollover is a rare event on roads, compared to other types of crashes. According to National Highway Traffic Safety Agency, USA (NHTSA), rollovers account for only 3% of crashes in a year [1]. However, one third of the fatalities occur during a rollover and the numbers of such fatalities exceed over 10,000 per annum. The fatality and the injury rate makes rollover crash an important issue in vehicle safety. As part of reducing risk of death and serious injury from rollover crashes, a proposal has been made to upgrade FMVSS No. 216, Roof Crush Resistance [2]. This upgraded regulation mandates the increase in peak load carrying capacity of the vehicle structure from 1.5 times vehicle weight to 2.5 times vehicle weight. As such, the manufacturers are required to comply to this norm even with their existing vehicles. This necessitates a change in structural design of the vehicle to be able to withstand the additional load bearing capacity.
Journal Article

Factors Influencing Contact Life and Failure Mode in Compact PCB Power Relays

2009-04-20
2009-01-0558
Compact PCB power relays were tested in repetitious on/off operations to define their reliability through a quantitative analysis of failure cycles and an investigation of relay property changes and contact erosion forms. Operation voltage was 14 V and relay temperature was 120 °C. Ten relays were used in each of two types of load test. First failure cycles were found to be high enough for practical use, 2.2 million in the lamp load (11 A) test and 7.5 million in the test using an integrated load (10 A) comprised of engine control components. Failure mode of all relays in the lamp load test revealed contact welding, while those in the integrated load test revealed significant contact resistance due to excess erosion. Wide differences between them in contact life cycle distribution and failure mode were found to be clearly distinguishable from load current characteristics.
Technical Paper

Efficient and Cost Effective Driver for HVAC Blower

2009-01-21
2009-26-0076
The Heating, Ventilation and Air Conditioning system (HVAC) blower is present in every car today. In most vehicles and especially in the mid to low cost segment, typically 250W blower motor is driven by a MOSFET used as a variable resistance. Generally seen as cost effective solution, this linear driving mode will generate a peak power loss of 80W to 100W. A more efficient way to drive a motor is to use PWM control. This solution already exists today but was always seen as too expensive for blower motors and thus reserved for mid to high range vehicles. A PWM controlled solution able to replace the existing linear module will be presented. The system cost is kept similar because no microcontroller is needed in the module embedded in or very close to the blower motor. Electrical, thermal and EMC characterization will also be shown.
Technical Paper

Numerical Investigations on Crosswind Aerodynamics and its Effect on the Stability of a Passenger Car

2009-01-21
2009-26-0059
In crosswind, or while passing another vehicle in still air, the flow around an automobile becomes asymmetric, thus altering the yawing moment, drag and lift. This paper discusses the details of crosswind aerodynamics of a typical sedan. The investigations, limited to numerical analysis, were carried out to predict the drag and lift coefficients, and the yaw moments on the selected car using a commercially available CFD software, FLUENT. The analysis was carried out for three car speeds, six crosswind angles and five crosswind velocities in various combinations. The results have shown that the drag coefficient initially decreases at 15° crosswind angle and then increases as the crosswind angle is increased. Further, the drag coefficient, lift coefficient and the yaw moment increase as the crosswind velocity increases. It is observed that the flow field around the car, especially at the rear, changes substantially with a change in the crosswind angle.
Technical Paper

Kinematic Analysis of Multi-Axle Steering System for Articulated Vehicle

2009-01-21
2009-26-0067
Steering of non-driven axles of semi-trailer results in improvement of maneuverability during negotiating sharp turn and reduces tyre drag and wear by relieving locked-in forces in comparison to non-steered axles. Among few, command steering mechanism is reported to be most efficient method of steering of articulated vehicles. In this type, the axles of semi-trailer are steered in relation with the articulation of tractor. The articulation angle of tractor is sensed by an actuation mechanism integrated on trailer at fifth wheel location and transferred hydraulically to the steering linkages. Mathematical equations have been developed based on Ackerman's Principle to estimate theoretical steering angle when Tractor-Trailer negotiate any turn. Steering linkage geometry has been conceptualised, kinematically modelled and analysed by using ADAMS. Equations developed for theoretical steering angles are incorporated in ADAMS as run time functions.
Technical Paper

A Relationship between Lift and Lateral Aerodynamic Characteristics for Passenger Cars

2010-04-12
2010-01-1025
Aerodynamic aids, such as spoilers, applied to the rear of cars can provide drag reduction to improve performance, or can enhance high speed stability by reducing lift at the rear axle. In some cases these can be conflicting demands. It has been noted, however, that when rear axle lift is reduced there is often a reduction in yawing moment which has a beneficial effect on crosswind sensitivity. Wind tunnel results from real road vehicles are presented to illustrate this effect. This beneficial relationship is further explored in a wind tunnel experiment using simple models to represent road vehicles. Force and moment coefficients as a function of yaw angle are measured for a range of vehicle geometries which generate a substantial variation in lift. It is shown that as lift is reduced, yawing moment is also reduced, while side force and rolling moment are increased.
Technical Paper

HPC-LES for Unsteady Aerodynamics of a Heavy Duty Truck in Wind Gust - 1st report: Validation and Unsteady Flow Structures

2010-04-12
2010-01-1010
Large eddy simulation based on high-performance computing technique was conducted to investigate the unsteady aerodynamic forces acting on a full-scale heavy duty truck subjected to sudden crosswind. The CFD results were applied to evaluate the effect of the unsteady external forces on a vehicle motion, as a first step toward a more reliable vehicle motion analysis. As the first report, the numerical method was validated on the DNW wind-tunnel data by comparing the time-averaged drag and lateral forces at various yawing angles up to 10 degrees. Then the method was applied to the case when the vehicle goes through the crosswind region. The time series of the aerodynamic forces were acquired and discussed through the visualization of instantaneous flow structures around the vehicle. It was observed that drastic undershooting and overshooting of the yawing moment acts on the vehicle during the rushing in and out process.
Technical Paper

One Phase Machine with DC Stator Excitation

2010-04-12
2010-01-0489
In the report, a new version of machine with DC stator excitation is discussed. A brushless one phase electrical machine has a very simple design. Rotor has no windings. In generator mode operation, stator has one winding for DC stator excitation and one output winding. In motor mode operation, there is only one sensor of rotor position and one phase H-bridge inverter. One phase machine is symmetrical. Like in dc machines, it is possible to realize here: shunt, series, and separate excitation. In motor mode, the speed control is possible by vary armature (output winding) voltage, varying current excitation, and varying resistance in armature circuit. Simplicity construction and flexibility control opportunities can find for this machine wide application in vehicles. Motor, with series excitation, leads a torque-speed characteristic that is useful for transport power circuit applications. One phase machine is the basic for design of two and three phase machines.
Technical Paper

Interference between Engine Bay Flow and External Aerodynamics of Road Vehicles

2010-04-12
2010-01-0288
This study focus on the aerodynamic influence of the engine bay packaging, with special emphasis on the density of packaging and its effect on cooling and exterior flow. For the study, numerical and experimental methods where combined to exploit the advantages of each method. The geometry used for the study was a model of Volvo S60 sedan type passenger car, carrying a detailed representation of the cooling package, engine bay and underbody area. In the study it was found that there is an influence on the exterior aerodynamics of the vehicle with respect to the packaging of the engine bay. Furthermore, it is shown that by evacuating a large amount of the cooling air through the wheel houses a reduction in drag can be achieved.
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