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This session focuses on kinetically controlled combustion. Experimental and simulation studies pertaining to various means of controlling combustion are welcome. Examples are research studies dealing with temperature and composition distribution inside the cylinder and their impact on heat release process. Studies clarifying the role of fuel physical and chemical properties in autoignition are also welcome. Presenter Hanho Yun, General Motors Company

The acoustic and performance characteristics of an automotive centrifugal compressor are studied on a steady-flow turbocharger test bench, with the goal of advancing the current understanding of compression system instabilities at the low-flow range. Two different ducting configurations were utilized downstream of the compressor, one with a well-defined plenum (large volume) and the other with minimized (small) volume of compressed air. The present study measured time-resolved oscillations of in-duct and external pressure, along with rotational speed. An orifice flow meter was incorporated to obtain time-averaged mass flow rate. In addition, fast-response thermocouples captured temperature fluctuations in the compressor inlet and exit ducts along with a location near the inducer tips.

The rotary engine provides high power density compared to piston engine, but one of its downside is higher oil consumption. A model of the oil seals is developed to calculate internal oil consumption (oil leakage from the crankcase through the oil seals) as a function of engine geometry and operating conditions. The deformation of the oil seals trying to conform to housing distortion is calculated to balance spring force, O-ring and groove friction, and asperity contact and hydrodynamic pressure at the interface. A control volume approach is used to track the oil over a cycle on the seals, the rotor and the housing as the seals are moving following the eccentric rotation of the rotor. The dominant cause of internal oil consumption is the non-conformability of the oil seals to the housing distortion generating net outward scraping, particularly next to the intake and exhaust port where the housing distortion valleys are deep and narrow.

The rotary engine provides high power density compared to piston engine, but one of its downside is higher oil consumption. In order to better understand oil transport, a laser induced fluorescence technique is used to visualize oil motion on the side of the rotor during engine operation. Oil transport from both metered oil and internal oil is observed. Starting from inside, oil accumulates in the rotor land during inward motion of the rotor created by its eccentric motion. Oil seals are then scraping the oil outward due to seal-housing clearance asymmetry between inward and outward motion. Cut-off seal does not provide an additional barrier to internal oil consumption. Internal oil then mixes with metered oil brought to the side of the rotor by gas leakage. Oil is finally pushed outward by centrifugal force, passes the side seals, and is thrown off in the combustion chamber.

In the thermal expansion valve (TXV) refrigerant system, transient high-pitched whistle around 6.18 kHz is often perceived following air-conditioning (A/C) compressor engagements when driving at higher vehicle speed or during vehicle acceleration, especially when system equipped with the high-efficiency compressor or variable displacement compressor. The objectives of this paper are to conduct the noise source identification, investigate the key factors affecting the whistle excitation, and understand the mechanism of the whistle generation. The mechanism is hypothesized that the whistle is generated from the flow/acoustic excitation of the turbulent flow past the shallow cavity, reinforced by the acoustic/structural coupling between the tube structural and the transverse acoustic modes, and then transmitted to evaporator. To verify the mechanism, the transverse acoustic mode frequency is calculated and it is coincided to the one from measurement.

The effect of aerodynamically induced pre-swirl on the acoustic and performance characteristics of an automotive centrifugal compressor is studied experimentally on a steady-flow turbocharger facility. Accompanying flow separation, broadband noise is generated as the flow rate of the compressor is reduced and the incidence angle of the flow relative to the leading edge of the inducer blades increases. By incorporating an air jet upstream of the inducer, a tangential (swirl) component of velocity is added to the incoming flow, which improves the incidence angle particularly at low to mid-flow rates. Experimental data for a configuration with a swirl jet is then compared to a baseline with no swirl. The induced jet is shown to improve the surge line over the baseline configuration at all rotational speeds examined, while restricting the maximum flow rate. At high flow rates, the swirl jet increases the compressor inlet noise levels over a wide frequency range.

This work examines the effect of valve timing during cold crank-start and cold fast-idle (1200 rpm, 2 bar NIMEP) on the emissions of hydrocarbons (HC) and particulate mass and number (PM/PN). Four different cam-phaser configurations are studied in detail: 1. Baseline stock valve timing. 2. Late intake opening/closing. 3. Early exhaust opening/closing. 4. Late intake phasing combined with early exhaust phasing. Delaying the intake valve opening improves the mixture formation process and results in more than 25% reduction of the HC and of the PM/PN emissions during cold crank-start. Early exhaust valve phasing results in a deterioration of the HC and PM/PN emissions performance during cold crank-start. Nevertheless, early exhaust valve phasing slightly improves the HC emissions and substantially reduces the particulate emissions at cold fast-idle.

Optimal material selection for a part becomes quite challenging with dynamically changing data from various sources. Multiple manufacturing locations with varying supplier capabilities add to the complexity. There is need to balance product attribute requirements with manufacturing feasibility, cost, sourcing, and vehicle program strategies. The sequential consideration of product attribute, manufacturing, and sourcing aspects tends to result in design churns. Ford R&A is developing a web based material recommender tool to help engineers with material selection integrating sourcing, manufacturing, and design considerations. This tool is designed to filter the list of materials for a specific part and provide a prioritized list of materials; and allow engineers to do weight and cost trade-off studies. The initial implementation of this material recommender tool employs simplified analytical calculators for evaluation of structural performance metrics of parts.

Torque controls for the engine and electric motors in a Powersplit HEV are keys to the success of balancing fuel economy, driveability, and battery power control. The electric variable transmission (EVT) offers an opportunity to let the engine operate at system-optimal fuel efficient points independently of any load. Existing work shows such a benefit can be realized through a decentralized control structure that translates the driver inputs to independent engine torque and speed control. However, our study shows that the decentralized control structures have a fundamental limitation that arises from the nonminimum phase (NMP) zero in the transfer function from the driver power command to the generator torque change rate, and thus not only is it difficult to obtain smooth generator torque but also it can cause violations on battery power limits during transients. Additionally, it adversely affects the driveability due to the generator torque transients reflected at the ring gear.

In an attempt to predict the responses of side crash pressure sensors, the Corpuscular Particle Method (CPM) was adopted and enhanced in this research. Acceleration-based crash sensors have traditionally been used extensively in automotive industry to determine the air bag firing time in the event of a vehicle accident. The prediction of crash pulses obtained from the acceleration-based crash sensors by using computer simulations has been very challenging due to the high frequency and noisy responses obtained from the sensors, especially those installed in crash zones. As a result, the sensor algorithm developments for acceleration-based sensors are largely based on prototype testing. With the latest advancement in the crash sensor technology, side crash pressure sensors have emerged recently and are gradually replacing acceleration-based sensor for side impact applications.

Variable amplitude torsion, bending, and combined torsion and bending fatigue tests were performed on an axle shaft. The moment inputs used were taken from the respective history channels of a cable log skidder vehicle axle. Testing results indicated that combined variable amplitude loading lives were shorter than the lives of specimens subjected to bending or torsion alone. Calculations using strain rosette readings indicated that principle strains were most active around specific angles but also occurred with lesser magnitudes through a wider angular range. Over the course of a biaxial test, cyclic creep narrowly limited the angles and magnitudes of the principal strains. This limitation was not observed in the calculated principal stress behavior. Simple life predictions made on the measured strain gage histories were non-conservative in most cases.

Two-stroke gasoline engines are known to benefit from using in-cylinder fuel injection which improves their ability to meet the strict fuel economy and exhaust emissions requirements. A conventional method of in-cylinder fuel injection involves application of plunger-type positive displacement pumps. Two-stroke engines are usually smaller and lighter than their 4-stroke counterparts of equal power and need a pump that should also be small and light and, preferably, simple in construction. Because a 2-stroke engine fires every crankshaft revolution, its fuel injection pump must run at crankshaft speed (twice the speed of a 4-stroke engine pump). An electronically controlled fuel injection system has been designed to satisfy the needs of a small automotive 2-stroke engine capable of running at speeds of up to 6000 rpm.

Vehicle sound quality has become an important basic performance requirement. Traditionally, automobile noise studies were focused on quietness. It is now necessary for the automobile to be more than quiet. The sound must be pleasing. This paper describes a development process to improve both vehicle noise level and sound quality. Formal experimental design techniques were utilized to quantify various hardware effects. A-weighted sound pressure level, Speech Intelligibility, and Composite Rating of Preference were the three descriptors used to characterize the vehicle's sound quality. Engineering knowledge augmented with graphical and statistical techniques were utilized during data analysis. The individual component contributions to each of the sound quality descriptors were also quantified in this study.

This article reports on the potential of negative valve overlap (NVO) for improving the net indicated thermal efficiency (η NIMEP) of gasoline engines during part load. Three fixed fuel flow rates, resulting in indicated mean effective pressures of up to 6 bar, were investigated. At low load, NVO significantly reduces the pumping loses during the gas exchange loop, achieving up to 7% improvement in indicated efficiency compared to the baseline. Similar efficiency improvements are achieved by positive valve overlap (PVO), with the disadvantage of worse combustion stability from a higher residual gas fraction (xr). As the load increases, achieving the wide-open throttle limit, the benefits of NVO for reducing the pumping losses diminish, while the blowdown losses from early exhaust valve opening (EVO) increase.

The windage tray effect on aeration in the engine sump was assessed by replacing much of the windage tray materials with wire meshes of various blockages. The mesh was to prevent direct impact of the oil drops spinning off the crank shaft onto the sump oil, and simultaneously, to provide sufficient drainage so that there was no significant build up of windage tray oil film that would interact with these droplets. Aeration at the oil pump inlet was measured by X-ray absorption in a production V-6 SI engine motoring at 2000 to 6000 rpm. Within experimental uncertainty, these windage tray changes had no effect on aeration. Thus activities in the sump such as the interaction of the oil drops spun from the crank shaft with the sump oil or with the windage tray, and the agitation of the sump oil by the crank case gas, were not major contributors to aeration at the pump inlet.

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.

Two-stroke cycle direct injection engines can achieve adequate stability at idle with stratified combustion at very lean overall air-fuel ratio, but exhaust temperature is very low. A rotary valve system was designed to spill charge from the cylinder into the intake tract during the compression stroke, in order to allow stable operation at lower engine delivery ratio and thereby increase exhaust temperature. Reduction of the engine delivery ratio was not achieved due to the poor scavenging characteristics of the swirl liners used, which resulted in high content of exhaust residual gas in the spill recirculation flow. Although the concept objective of higher exhaust temperature was not realized, the results indicate that the concept may be feasible if high purity of the spill recirculation flow can be achieved in conjunction with high trapping efficiency.

The presence of liquid fuel inside the engine cylinder is believed to be a strong contributor to the high levels of hydrocarbon emissions from spark ignition (SI) engines during the warm-up period. Quantifying and determining the fate of the liquid fuel that enters the cylinder is the first step in understanding the process of emissions formation. This work uses planar laser induced fluorescence (PLIF) to visualize the liquid fuel present in the cylinder. The fluorescing compounds in indolene, and mixtures of iso-octane with dopants of different boiling points (acetone and 3-pentanone) were used to trace the behavior of different volatility components. Images were taken of three different planes through the engine intersecting the intake valve region. A closed valve fuel injection strategy was used, as this is the strategy most commonly used in practice. Background subtraction and masking were both performed to reduce the effect of any spurious fluorescence.

Rapid Prototyping, Fabrication and Tooling is a process that blends a series of technologies (machines, tools, and methods) capable of generating physical objects directly from a CAD database. The process dramatically reduces the time spent during product development by allowing for fast visualization, verification, iteration, optimization, and fabrication of parts and tools. Many new techniques of tooling have been and are being developed by using rapid fabricated parts. These are having a dramatic impact on both timing and costs throughout the automotive industry. One area that these methods can be utilized to their full potential is motorsports. Of particular interest is the growing use of bridge tooling to provide first article through production intent parts that promote cost effective changes.

Multidimensional models that are used for engine computations must include spray sub-models when the fuel is injected into the cylinder in liquid form. One of these spray sub-models is the droplet interaction model, which is separated into two parts: first, calculation of a collision rate between drops, and second, calculation of the outcome once a collision has occurred. This paper focuses on the problem of calculating the collision rate between drops accurately. Computing the collision rate between drops or particles when they are non-uniformly distributed and sharp gradients are present in their distribution is a challenging task. Traditionally the collisions between parcels of drops have been computed using the same spatial grid as is used for the Eulerian gas-phase calculations. Recently it has been proposed to use a secondary grid for the collision rate calculation that is independent of the gas-phase grid, as is done in the NTC collision algorithm.