Measurement of the effect on brake performance of the intake and exhaust system components in a motorbike high speed racing engine

The paper presents a series of brake performance measurements for a high speed Road Racing Supersport motorbike engine. A modular approach consisting in a progressive assembling of each component belonging to the intake and exhaust systems is used to investigate the influence of these components on volumetric efficiency through brake torque chassis dynamometer tests. In spite of the design effort that is usually made to keep the cylinder air intake independent of each other in this kind of engines, results showed a considerable acoustic coupling between the intake primary manifolds and the upstream components. Moreover, a good correspondence is found about intake and exhaust tuning regimes between experimental results and analytical relationships proposed in the literature. The presented results can also be interpreted as representative for the overall very high speed engines category (including MotoGP and F1 ones), being the air-breathing system layout mostly independent of engine technological level within this category.     

Experimental characterization of instrument panel buzz, squeak, and rattle (BSR) in a vehicle

Among the various elements affecting a customer’s evaluation of automobile quality, buzz, squeak, and rattle (BSR) are considered to be major factors. We propose an integrated experimental method that can be used to reduce BSR in an instrument panel module in a vehicle cabin, especially during the early design stage of vehicle development. We devised a vibration triggering system consisting of a fixture and an electromagnetic shaker to generate an input load reproducing the excitation signal from the road to the instrument panel without distortion. Potential source regions for BSR were localized using a near-field acoustic holography map obtained from near-acoustic-field visualization equipment consisting of 48 intensity-type microphones, a data-acquisition system, and its analysis software. Finally, a sound quality evaluation of BSR from the detected potential source regions was performed using sound quality metrics. These experimental procedures were applied to characterize BSR from the instrument panel in a passenger vehicle. Based on our measurements and analysis, typical main source regions for BSR on the instrument panel were identified and quantitatively evaluated in terms of physical levels and sound quality metrics. These results revealed that the proposed experimental procedure can be used as a test procedure to identify BSR issues at an early stage in the vehicle development cycle, which could ultimately reduce production costs.     

An assessment of the effect of mass customization on suppliers’ inventory levels in a JIT supply chain

In some industries, mass customization requires a supplier to provide an Original Equipment Manufacturer (OEM) with a wide range of variants of a given part. We consider an OEM-parts suppliers system for an automotive supply chain where parts are delivered to the assembly line several times a day in a just-in-time environment. Simulating varying assembly schedule and parts delivery schemes, we assess the effect of mass customization on the level of inventory the supplier needs for each variant in order to prevent stockouts. We find, among other things, that as the level of mass customization increases, there tends to be an increase in the level of inventory the supplier needs to maintain for each part variant in order to prevent stockouts. Theoretical support is provided for the phenomenon. The presented framework is also useful for evaluating the levels of mass customization that will enable the manufacturer meet customers’ requirements in a cost effective manner. Furthermore, the study confirms the superiority, in terms of inventory levels, of the min–max over the min–sum optimization framework.     

Nonlinear kinematic response of premixed flames to harmonic velocity disturbances

This paper analyzes the nonlinear dynamics of premixed flames responding to harmonic velocity disturbances. These nonlinear dynamics were studied by solving a constant flame speed front tracking equation for the flame’s response to harmonically oscillating velocity disturbances. The solution to these equations is used to quantify the transfer function relating the ratio of the normalized flame area to velocity fluctuations, G = (A′/A_o)/(u′/u_o), upon the amplitude of velocity oscillations, ε = u′/u_o. Due to nonlinearities, the amplitude of this transfer function relative to its linear value decreases with increasing amplitude of velocity oscillation, u′/u_o. In contrast, the transfer function phase exhibits almost no amplitude dependence. The velocity amplitude where transfer function nonlinearities become significant depends strongly upon three parameters: a Strouhal number, St = ωL_f/u_o (where L_f is the flame length), the ratio of the flame length to width, β = L_f/R, and the flame shape in the absence of perturbations (i.e., conical, inverted wedge, etc.). In the linear case, the transfer function, G, depends only upon an algebraic combination of the first two parameters, given by St₂ = St (1 + β²)/β². In general, however, G exhibits a distinct dependence upon both parameters St and β. In particular, we show that the nonlinear response of G is an intrinsically dynamic phenomenon; i.e., its quasi-steady response (St 1) is purely linear. As such, nonlinearity is enhanced with increasing Strouhal numbers. In contrast, nonlinearity is suppressed at large β values; as such, the response of a long flame remains quite similar to its linear value, even at large ε values where the flame front exhibits substantial corrugation and cusping. Finally, we show that the response of conical flames remains much more linear at comparable disturbance amplitudes than for “V” or wedge-shaped flames. These predictions are shown to be consistent with available experimental data.     

Surface chemistry and microstructural analysis of CexZr1−xO2−y model catalyst surfaces

Cerium-zirconium mixed metal oxides are widely used as promoters in automotive emissions control catalyst systems (three-way catalysts). The addition of zirconium in the cubic lattice of ceria improves the redox properties and the thermal stability, thereby increasing the catalyst efficiency and longevity. The surface composition and availability of surface oxygen of model ceria-zirconia catalyst promoters was considered to develop a reference for future catalytic reactivity studies. The microstructure was characterized with X-ray diffraction (XRD) to determine the effect of zirconium substitution on crystalline structure and grain size. Additionally, the Ce/Zr surface atomic ratio and existence of Ce³⁺ defect sites were examined with X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) for samples with different zirconium concentrations. The surface composition of the model systems with respect to cerium and zirconium concentration is representative of the bulk, indicating no appreciable surface species segregation during model catalyst preparation or exposure to ultrahigh vacuum conditions and analysis techniques. Additionally, the concentration of Ce³⁺ defect sites was constant and independent of composition. The quantity of surface oxygen was unaffected by electron bombardment or prolonged exposure to ultrahigh vacuum conditions. Additionally, XRD analysis did not indicate the presence of additional crystalline phases beyond the cubic structure for compositions from 100 to 25 at.% cerium, although additional phases may be present in undetectable quantities. This analysis is an important initial step for determining surface reactions and pathways for the development of efficient and sulfur-tolerant automotive emissions control catalysts.     

Steady state performance evaluation of variable geometry twin-entry turbine

This paper presents the results from an experimental investigation conducted on different turbine designs for an automotive turbocharger. The design progression was based on a commercial nozzleless unit that was modified into a variable geometry single and twin-entry turbine. The main geometrical parameters were kept constant for all the configurations and the turbine was tested under steady flow conditions.A significant depreciation in efficiency was measured between the single and twin-entry configuration due to the mixing effects. The nozzleless unit provides the best compromise in terms of performance at different speeds.The twin-entry turbine was also tested under partial and unequal admissions. Based on the test results a method to determine the swallowing capacity under partial admission given the full admission map is presented. The test results also showed that the turbine swallowing capacity under unequal admission is linked to the full admission case.     

Numerical simulation and validation of SI-CAI hybrid combustion in a CAI/HCCI gasoline engine

SI-CAI hybrid combustion, also known as spark-assisted compression ignition (SACI), is a promising concept to extend the operating range of CAI (Controlled Auto-Ignition) and achieve the smooth transition between spark ignition (SI) and CAI in the gasoline engine. In this study, a SI-CAI hybrid combustion model (HCM) has been constructed on the basis of the 3-Zones Extended Coherent Flame Model (ECFM3Z). An ignition model is included to initiate the ECFM3Z calculation and induce the flame propagation. In order to precisely depict the subsequent auto-ignition process of the unburned fuel and air mixture independently after the initiation of flame propagation, the tabulated chemistry concept is adopted to describe the auto-ignition chemistry. The methodology for extracting tabulated parameters from the chemical kinetics calculations is developed so that both cool flame reactions and main auto-ignition combustion can be well captured under a wider range of thermodynamic conditions. The SI-CAI hybrid combustion model (HCM) is then applied in the three-dimensional computational fluid dynamics (3-D CFD) engine simulation. The simulation results are compared with the experimental data obtained from a single cylinder VVA engine. The detailed analysis of the simulations demonstrates that the SI-CAI hybrid combustion process is characterised with the early flame propagation and subsequent multi-site auto-ignition around the main flame front, which is consistent with the optical results reported by other researchers. Besides, the systematic study of the in-cylinder condition reveals the influence mechanism of the early flame propagation on the subsequent auto-ignition.     

Application of gaseous sphere injection method for modeling under-expanded H2 injection

A methodology for modeling gaseous injection has been refined and applied to recent experimental data from the literature. This approach uses a discrete phase analogy to handle gaseous injection, allowing for addition of gaseous injection to a CFD grid without needing to resolve the injector nozzle. This paper focuses on model testing to provide the basis for simulation of hydrogen direct injected internal combustion engines. The model has been updated to be more applicable to full engine simulations, and shows good agreement with experiments for jet penetration and time-dependent axial mass fraction, while available – radial mass fraction data is less well predicted.     

Direct numerical simulations of exhaust gas recirculation effect on multistage autoignition in the negative temperature combustion regime for stratified HCCI flow conditions by using H2O2 addition

Direct numerical simulations (DNSs) of a stratified flow in a homogeneous compression charge ignition (HCCI) engine are performed to investigate the exhaust gas recirculation (EGR) and temperature/mixture stratification effects on the autoignition of synthetic dimethyl ether (DME) in the negative temperature combustion region. Detailed chemistry for a DME/air mixture is employed and solved by a hybrid multi-time scale (HMTS) algorithm to reduce the computational cost. The effect of to mimic the EGR effect on autoignition are studied. The results show that adding enhances autoignition by rapid OH radical pool formation (34–46% reduction in ignition delay time) and changes the ignition heat release rates at different ignition stages. Sensitivity analysis is performed and the important reactions pathways affecting the autoignition are specified. The DNS results show that the scales introduced by thermal and mixture stratifications have a strong effect after the low temperature chemistry (LTC) ignition especially at the locations of high scalar dissipation rates. Compared to homogenous ignition, stratified ignitions show similar first autoignition delay times, but 18% reduction in the second and third ignition delay times. The results also show that molecular transport plays an important role in stratified low temperature ignition, and that the scalar mixing time scale is strongly affected by local ignition in the stratified flow. Two ignition-kernel propagation modes are observed: a wave-like, low-speed, deflagrative mode and a spontaneous, high-speed, ignition mode. Three criteria are introduced to distinguish these modes by different characteristic time scales and Damkhöler numbers using a progress variable conditioned by an ignition kernel indicator. The low scalar dissipation rate flame front is characterized by high displacement speeds and high mixing Damkhöler number. The proposed criteria are applied successfully at the different ignition stages and approximate characteristic values are identified to delineate between the different ignition propagation modes.     

Planning of capacities and orders in build-to-order automobile production: A review

In an attempt to achieve a competitive edge, automotive companies operate global production networks to offer an ever increasing product variety, shorter and reliable lead times as well as competitively priced products. Cars are no longer exclusively produced based on standardized product configurations and stable sales plans but are increasingly build-to-order to match the needs of individual customers. Operations Research (OR) may contribute towards successful build-to-order operations. This is likewise reflected by the appreciable number of published papers on industry specific OR applications. To provide readers with an overview about these OR models and applications we identify current and future research issues based on the review of 49 works. We focus on two important planning objects which have not been considered in prior reviews: the planning of capacities and orders. To bridge the gap between conceptual works on the one hand and quantitative contributions on the other, we provide a framework for the structuring of planning tasks. Existing models are classified according to this framework and open issues that should be addressed in OR are discussed.