Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering

The design of the chassis with an appropriate structure is thought to be an efficient way for decreasing vibration and noise since chassis vibration is one of the key causes that generates noise in the bus passenger compartment. This study uses the Frequency Response Function Method (FRFM) and Modal Participation Method (MPM) to analyze an acoustic finite element model of a bus frame model THACO TB120S. To perform the noise radiation caused by the vibration of the bus frame structure, the chassis was triggered by a diesel engine. The bus engine has a six-cylinder, four-stroke, and in-line arrangement. The triggered frequencies from the engine were operated in the range of 1–100 Hz, while the maximum engine speed was 1900 rpm. The vibration of the roof array and the noise of the bus compartment was examined analytically at four locations on the bus structure. The results show that the performance of the bus structure with respect to the noise generation was significantly improved. The resonant frequencies of noise observed from analytic results are verified by experimental measurements in terms of sound pressure. The acoustic resonance in the bus passenger compartment mainly occurs in the frequency range from 15 to 70 Hz. The peak values of the sound pressure are significantly decreased when the roof modification technique was applied. An increase in the stiffness of the roof using the structural correction method could have a positive effect on noise reduction by approximately 60%.

Increasingly stringent emissions and fuel economy standards have long remained a source of challenges for research in automobile engine technology development towards the more thermally efficient and less polluting engine. Spark ignition (SI) engines have lower part-load efficiency when compared with the diesel engines. The greatest opportunity for improving SI engine efficiency is by way of higher compression ratio, variable valve timing, low friction, reducing throttling losses, boosting, and down-sizing. Variable compression ratio (VCR) technology has long been recognized as a method for improving the fuel economy of SI engines. In order to vary the compression ratio, some method of varying the geometric compression ratio through changing the clearance volume is required. There are several ways of doing this; various patents have been filed and designs presented, including modification of the compression ratio by moving the cylinder head, variation of combustion chamber volume using a secondary piston or valve, variation of piston deck height, modification of connecting rod geometry, moving the crankpin within the crankshaft, and moving the crankshaft axis. The potential of these technologies needs to be evaluated by a trade-off between cost and consumption benefit. This paper reviews the geometric approaches and solutions used to achieve VCR, considers the results of prior research, and forecasts what benefits, if any, a VCR would bring to present engine design.

The internal-combustion Rankine cycle engine uses pure oxygen instead of air as the oxidant during the combustion process so as to preclude the creation of nitrogen oxide emissions. Carbon dioxide can be recovered from the water vapour–carbon dioxide exhaust gas mixture through condensation at a relatively low cost and, thus, an ultra-low-emission working cycle is achieved. In this paper the working process of the internal-combustion Rankine cycle was studied on the basis of bench tests on a prototype engine. An oxygen–carbon dioxide mixture was utilized to simulate exhaust gas recirculation in order to control the combustion process, and water was injected near top dead centre to determine the impact on the reaction rate and the cycle performance. The results demonstrated that water injected at a temperature of 120 °C can modulate the reaction rate and expand the area of the pressure–volume diagram through vaporization. Furthermore, combustion phasing is retarded without reducing the maximum cylinder pressure. The indicated work under the test conditions is increased by 7.8%. However, when the water-injection temperature is 20 °C, the cycle performance is reduced.

A numerical scheme for the analysis of liquids sloshing in horizontal cylindrical rigid containers is presented. The governing equations of the liquid are transformed by three continuous coordinate transformations to avoid the use of interpolation of the boundary conditions on the curved walls and capturing of the free surface, as well as to gain convergence and computational stability of numerical computation. The efficiency of the proposed method is demonstrated by numerical simulations using the finite difference method for two-dimensional circular containers and three-dimensional cylindrical containers. The method can be used to simulate the liquid sloshing under normal highway operating conditions when lateral accelerations are below the roll-over threshold. This approach can be extended to containers with walls of arbitrary shapes.

A non-linear fluid slosh analysis of a partially filled circular tank is performed to illustrate the significance of transient fluid motion on the resulting destabilizing forces and moments imposed on the tank structure and thus the vehicle. The analyses are performed on a clean bore tank of circular cross-section for various fill volumes and subject to different magnitudes of steady as well as harmonic lateral acceleration using the FLUENT software. The results of the study are presented in terms of transient forces and moments caused by the cargo slosh, which directly relate to the roll dynamic performance of the partly filled tank trucks. A relationship between the lateral force and the resulting roll moment is derived, which suggests that the roll moment could be defined as a function of the horizontal force and tank radius, irrespective of the translation of the centre-of-mass coordinates. The deviations of the forces and overturning moment from those predicted using quasi-static (QS) load shift analysis are also presented and discussed. The influence of fluid viscosity on the transient behaviour is further investigated under time-varying lateral acceleration in terms of slosh damping rate and peak responses. The results of the study suggest that the magnitude of transient roll moment could be 1.57 times larger than corresponding mean values that are very close to those predicted using the QS analysis. Analysis of the partly filled tank under harmonic lateral acceleration excitations shows that the peak values of the lateral slosh force and the overturning moment occur during the first oscillation. The magnitude of the peak overturning moment is strongly dependent upon the frequency of the lateral acceleration excitation.

Prior design optimization efforts do not capture the impact of battery degradation and replacement on the total cost of ownership, even though the battery is the most expensive and least robust powertrain component. A novel, comprehensive framework is presented for model-based parametric optimization of hybrid electric vehicle powertrains, while accounting for the degradation of the electric battery and its impact on fuel consumption and battery replacement. This is achieved by integrating a powertrain simulation model, an electrochemical battery model capable of predicting degradation, and a lifecycle economic analysis (including net present value, payback period, and internal rate of return). An example design study is presented here to optimize the sizing of the electric motor and battery pack for the North American transit bus application. The results show that the optimal design parameters depend on the metric of interest (i.e. net present value, payback period, etc.). Finally, it is also observed that the fuel consumption increases by up to 10% from “day 1” to the end of battery life. These results highlight the utility of the proposed framework in enabling better design decisions as compared to methods that do not capture the evolution of vehicle performance and fuel consumption as the battery degrades.

The work described here has been carried out to obtain a better understanding of the tooth root cracking failure mode of timing belts. Previous work has demonstrated the close dependence of this on the tooth deflections of fully meshed teeth, generated by torque transmission, but has not considered the additional distortions generated in the partially meshed conditions at entry to and exit from a pulley groove. Approximate compatibility and constitutive equations are combined with a rigorous consideration of tooth equilibrium in partial meshing to show how bending moments are generated at both exit from a driven pulley and entry to a driving pulley. Experimentally determined belt lives correlate very well with a combined measure of fully meshed tooth strain and strain due to bending at entry or exit. The analysis also shows that this strain measure reduces with increasing belt tooth stiffness, confirming the importance of a high tooth stiffness for a long belt life. Tooth force variations through the partial meshing cycle have also been predicted and compared with measurements obtained from a special strain gauge instrumented pulley. A greater pulley rotation than is predicted is required for a belt tooth to seat in a pulley groove. There is room for improvement in the modelling.

Liquefied petroleum gas (LPG) is widely used as a gaseous fuel in spark ignition engines because of its considerable advantages over gasoline. However, the LPG engine suffers a torque loss because the vapour-phase LPG displaces a larger volume of air than do gasoline droplets. In order to improve engine power as well as fuel consumption and air-fuel ratio control, considerable research has been devoted to improving the LPG injection system. In the liquid-phase LPG injection systems, the injection rate of an injector is affected by the fuel temperature, injection pressure, and driving voltage. When injection conditions change, the air-fuel ratio should be accurately controlled in order to reduce exhaust emissions. In this study, correction factors for the fuel injection rate are developed on the basis of fuel temperature, injection pressure, and injector driving voltage. A compensation method to control the amount of injected fuel is proposed for a liquid-phase LPG injection control system. The experimental results show that the liquid-phase LPG injection system works well over the entire range of engine speeds and load conditions, and the air-fuel ratio can be accurately controlled by using the proposed compensation algorithm.

For natural gas and liquefied petroleum gas (LPG), measurements of the concentrations of individual exhaust hydrocarbon (HC) species have been made under various engine operating conditions in a 2 litre four-cylinder engine using gas chromatography. Non-methane hydrocarbon (NMHC) in addition to the species of HC and other emissions such as CO₂, CO and NO_x were examined for natural gas and LPG at 1800 r/min for two compression ratios (8.6 and 10.6), various brake mean effective pressure (b.m.e.p.) values (250-800 kPa), spark timings (before top dead centre 10°-55°) and exhaust gas recirculation ratios up to 7 per cent. Fuel conversion efficiencies were also investigated together with emissions to study the effect of engine parameters on the combustion performance in gas engines, especially under the lean burn conditions.

It was found that CO₂ emission decreased with smaller C value of fuel, leaner mixture strength, higher compression ratio, higher b.m.e.p. and the ignition near the maximum brake torque spark timing. HC emissions from the LPG engine consisted primarily of propane (C₃ H₈) (more than 60 per cent), ethylene and propylene (C₃ H₆), while the main emissions from natural gas were methane (more than 60 per cent), ethane, ethylene and propane. Natural gas was shown to have less of a tendency to form ozone than LPG. This was accomplished by reducing the emissions of propylene, which has a relatively high maximum incremental reactivity factor, and propane, which forms a large portion of LPG. In addition, natural gas shows a benefit in the other emissions (i.e. NMHC, NO_x and CO₂), specific reactivity and brake specific reactivity values except fuel conversion efficiency.

The aim of this paper is to propose a power control strategy for hybrid electrical vehicles. This strategy uses a fuel consumption criterion with battery charge sustaining. It is based on an instantaneous minimization of the equivalent fuel flow. Two comparisons are performed to evaluate the proposed strategy. The first one uses the loss minimization strategy of Seiler and Schröder [1], which appears to be realistic and efficient for real-time control. This strategy is also based on an instantaneous optimization and allows the battery state of charge to be taken into account. The second comparison is made with an optimal solution found for a given driving schedule. Although not realistic for real-time control, this solution is derived through a global optimization algorithm, the well-known simulated annealing method.