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

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.

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.

This paper reports the test results of a diesel engine at different engine speeds, injection timings and emulsion ratios with water-emulsified fuel. Results show that both NO_x and smoke may be reduced significantly at the same brake specific fuel consumption (b.s.f.c.) at high engine speeds above 1400 r/min. At low engine speeds below 1000 r/min NO_x may be reduced slightly with minor penalty in the b.s.f.c. with no overall gain in use of emulsion fuel. In the tested range of water-oil ratio by volume of 0-40 there was no significant deterioration in the HC and CO emissions and the combustion stability in terms of cyclic variations of the peak cylinder pressure. It may be necessary to employ accurate electronic control of the injection timing as a function of load and speed to maintain the optimum operating condition with emulsion fuel.

The combustion characteristics of emulsified diesel fuels are investigated in a rapid compression and expansion machine (RCEM). Among the test cases, the 40 water-oil (W/O) fuel injected at 20° before top dead center (BTDC) has shown the best performance with respect to efficiency and NO_x and soot emissions. The pressure trace of the 40 W/O fuel is characterized by a longer ignition delay and a lower rate of pressure rise in premixed combustion. High-speed photographs show reduced flame luminosity and lower flame temperature with increasing W/O ratio. Microexplosions of emulsified fuel droplets, which affect the local shape and brightness of the flame, are identified in magnified flame images.

This paper presents a control architecture that simultaneously utilizes active front steering (AFS) and differential braking for vehicle lateral stability while minimizing longitudinal perturbations. This control scheme is based on the model predictive control (MPC) using the extended bicycle model that captures the lagged characteristics of tire forces and actuators. The nonlinearities of tire force are also reflected on the extended bicycle model by linearizing the tire forces at the operating points. Instead of casting the MPC problem into a quadratic program with constraints that require numerical solvers, the proposed method is designed to follow the reference states with desired inputs since the solutions of MPC problems with affine models to track desired states can be easily obtained by matrix inversion. Simulation results, obtained by the vehicle dynamics software Carsim, demonstrate that the suggested method is able to control the vehicle to track the desired path while keeping the vehicle lateral stability on various road surfaces.

Hybrid pneumatic engines, which are designed to follow the downsizing and supercharging paradigm, offer a fuel-saving potential that is almost equal to that of hybrid electric powertrains while inducing much lower additional mass and cost penalties. This paper presents a systematic optimization of the operation of such an engine system. Both two-stroke and four-stroke modes are analysed. The optimized valve and throttle actuation laws for all modes and operating areas lead to generic maps that are independent of the engine size. So far, the pneumatic hybridization of internal combustion engines was thought to require two-stroke operation. This paper presents a novel hybrid pneumatic engine configuration that entails fixed camshafts for both intake and exhaust valves while utilizing variable valve actuation for one charge valve per cylinder only. This configuration is operated entirely in four-stroke modes. Such a configuration requires a careful optimization of its operating strategy to achieve its fuel economy potential. Compared with a full two-stroke operation, only small efficiency losses result from using four-stroke modes with these new operating strategies. Initial measurement results with such an engine system are presented in this paper to confirm the validity of the principles of operation.

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.

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.

Experiments were conducted in a constant-volume combustion chamber to investigate the spray and combustion characteristics of soybean biodiesel (B100) and diesel (B0). The in-cylinder density was kept at 15 kg/m³ and the ambient oxygen concentrations of 21, 18, and 15 per cent were maintained to simulate no exhaust gas recirculation (EGR), medium EGR, and heavy EGR in diesel engines respectively. The ambient gas temperature was varied from 800 K to 1200 K. The in-cylinder pressure and heat release rate were measured and the liquid penetration, natural flame emission, and soot formation characteristics were studied via new optical diagnostics. The results show that the peak pressure decreases with increasing ambient gas temperature and decreasing oxygen concentration for B0, except that at the oxygen concentration of 15 per cent. For B100, a higher peak pressure is obtained at the oxygen concentration of 15 per cent as opposed to that of 18 per cent. A lower heat release rate is found for B100 at the oxygen concentrations of 21 per cent and 18 per cent compared to B0, while a higher value is shown at the oxygen concentration of 15 per cent. The liquid penetration increases with decreasing oxygen concentration and ambient gas temperature. As the oxygen concentration increases for B0 at the ambient gas temperature from 800 K to 1000 K, the integrated natural flame luminosity (INFL) increases, while at 1200 K, the INFL at the oxygen concentration of 15 per cent has the highest value. For B100, with increasing oxygen concentration, the INFL increases at 800 K and 900 K, but decreases at 1000 K and 1200 K. The total soot mass increases with decreasing oxygen concentration and the soot formation duration is longer at a lower oxygen concentration. B100 has a shorter soot formation duration and soot is dramatically reduced by burning B100. The peak soot mass for B100 at 1200 K is comparable to that for B0 at 800 K.

Vehicle aeroacoustic performance has a major influence on customer perception and also has importance for safety and comfort. Wind noise performance was once differentiated by the quality of sealing. Today, achieving competitive wind noise performance also depends on minimising aeroacoustic noise sources generated by the vehicle form, and on attenuation in the noise pathway from sources on the exterior to the vehicle interior. The reduction in noise transmission, especially through glazed surfaces, will continue to play an important role in controlling cabin noise, with a particular emphasis on achieving attenuation efficiently in terms of component mass. The human brain is not only sensitive towards the level of steady broadband noise, but distinctive features such as tonality or modulation draw the attention of the vehicle occupant and impact negatively on perception. Complex indices are often required to define good wind noise performance. This includes the consideration of multiple frequency bands and effects of the range of yaw angles experienced on-road. A key to achieving future vehicle refinement is bringing together an understanding of unsteady onset flow conditions, their impact on cabin sound pressure level and modulation and, in turn, the impact of noise level and modulation on psychoacoustic perception.