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The energy management strategies (EMS) for hybrid electric vehicles (HEV) have a great impact on the fuel economy (FE). The Pontryagin's minimum principle (PMP) has been proved to be a viable control strategy for HEV. The optimal costate of the PMP control can be determined by the given information of the driving conditions. Since the full knowledge of future driving conditions is not available, this paper proposed a dynamic optimization method for PMP costate without the prediction of the driving cycle. It is known that the lower fuel consumption the method yields, the more efficiently the engine works. The selection of costate is designed to make the engine work in the high efficiency range. Compared with the rule-based control, the proposed method by the principle of Hamiltonian, can make engine working points have more opportunities locating in the middle of high efficiency range, instead of on the boundary of high efficiency range.

The increasingly stringent restrictions on vehicle emissions and fuel consumption are driving the development of gasoline engines towards lean combustion. Increasing ignition energy has been considered an effective way to achieve lean operation conditions. To further improve the lean limit of engine combustion, the influence of the spark plug orientation on the combustion stability under lean operation should be explored. In this investigation, the original machine spark plug orientation, 90 degrees clockwise rotation, and 180 degrees clockwise rotation are studied to analyze the impact of spark plug orientation. The combustion experiment was carried out under the condition of low excess air ratio of the original machine and high excess air ratio with a 450 mA high energy ignition.

The internal combustion engine (ICE) is a typical complex multidisciplinary system which requires the support of precision design and manufacturing. To achieve a better performance of ICEs, tolerance assignment, or tolerance design, plays an important role. A novel multi-disciplinary tolerance design optimization problem considering two important disciplines of ICEs, the compression ratio and friction loss, is proposed and solved in this work, which provides a systematic procedure for the optimal determination of tolerances and overcomes the disadvantages of the traditional experience-based tolerance design. A bi-disciplinary analysis model is developed in this work to assist the problem solving, within which a model between the friction loss and tolerance is built based on the Gaussian Process using the corresponding simulation and experimental data.

It is well known that engine downsizing is still the main energy-saving technology for spark-ignition direct-injection (SIDI) engine. However, with the continuous increase of the boosting ratio, the gasoline engine is often accompanied by the occurrence of knocking, which has the drawback to run the engine at retarded combustion phasing. Besides, in order to protect the turbine blades from being sintered by high exhaust temperature, the strategies of fuel enrichment are often taken to reduce the combustion temperature, which ultimately leads to a high level of particulate number emission. Therefore, to address the issues discussed above, the port water injection (PWI) techniques on a 1.2-L turbocharged, three-cylinder, SIDI engine were investigated. Measurements indicate that the optimization of spark timing has a significant impact on its performance.

Port water injection is considered as a promising strategy to further improve the combustion performance of internal combustion engines for its benefit in knock resistance by reducing the cylinder temperature. A thorough investigation of the port water injection technique is required to fully understand its effects on the engine combustion process. This study explores the potential of the port water injection technique in improving the performance of a turbo charged Gasoline Direct Injection engine. A 3D computational fluid dynamics model is applied to simulate the in-cylinder mixing and combustion for this engine both with and without water injection. Different water injection timings are investigated and it is found that the injection timing greatly effects the mass of water which enters the combustion chamber, both in liquid and vapor form.

Conventionally, the engines are calibrated under the assumption that engines will be made exactly to the prints, and all the engines from the same batch will be identical. However, engine-to-engine variations do exist which will affect the engine performances, and part-to-part variations, i.e., the tolerance, is an important factor leading to engine-to-engine variations. There are researches conducted on the influence of dimensional tolerances on engine performance, however, the impact of straightness, which is an important geometric tolerance, on lubrication is an unsolved issue. This study presents a systematic method to model the straightness and to analyze its effects on the friction loss. The bearing model is built based on elastohydrodynamic (EHD) theory. Meanwhile a novel modeling method to represent any form of straightness in three-dimensional space is proposed.

High fuel injection pressure has been regarded as a key controlling factor for internal combustion engines to achieve good combustion performance with reduced emissions and improved fuel efficiency. For common-rail injection system (CRS) used in advanced diesel engines, fuel injection pressure can often be raised to beyond 200 MPa. Although characteristics of diesel spray has been thoroughly studied, little work has been done at ultra-high injection pressures. In this work, the characteristics of CRS diesel spray under ultra-high injection pressure up to 250 MPa was investigated. The experiments were conducted in an optically accessible high-pressure and high-temperature constant volume chamber. The injection pressure varied from 50 MPa to up to 250 MPa. Both non-evaporating condition and evaporating condition were studied. A single-hole injector was specially designed for this investigation.

Increasing the injection pressure in DISI engine is an efficient way to obtain finer droplets but it will also potentially cause spray impingement on the cylinder wall and piston. Consequently, the fuel film sticking on the wall can dramatically increase the soot emission of the engine especially in a cold start condition. On the other hand, ethanol is widely used as an alternative fuel in DI engine due to its sustainable nature and high octane number. In this study, the fuel film characteristics of single-plume ethanol impinging spray was investigated. The experiments were performed under ultra-low fuel/plate temperature to simulate the cold start condition in cold areas. A low temperature thermostatic bath combined with specially designed heat exchangers were used to achieve ultra-low temperature for both the impinging plate and the fuel. Laser induced fluorescence (LIF) technique was employed to measure the thickness of fuel film deposited on the impinging plate.

Electric vehicles (EVs) have become a hot research topic due to the petroleum crisis and air pollution issues, and Hybrid EVs (HEVs) equipped with engines and motors are popular nowadays due to their advantage over Pure EVs. The energy distribution between the engine and the motor is the major task of the control strategy or energy management for HEVs. Rule-based and optimization-based approaches are developed in this area, but not much work has been done for large-size super-capacitor (SC) equipped HEVs, like Hybrid buses. In this paper, a new optimization-based control strategy for a hybrid bus equipped with SCs as the energy regeneration system is presented. Considering the driving patterns of a bus that is of frequent accelerations and decelerations, it is proposed to characterize each time instant by its speed and acceleration, and the energy distribution is optimized based on these two state variables.

As the vehicle emission regulations become stricter worldwide, one way to meet the emission requirements is to engage the use of alternative fuels in engine combustion. In this investigation, the early combustion processes of regular gasoline and alternative fuels, including ethanol and butanol, were studied by simultaneously recording both the in-cylinder pressure and the crank angle-resolved high-speed flame images in a single-cylinder spark-ignition direct-injection engine. The engine was equipped with a quartz insert in the piston which provided an optical access to its cylinder through the piston. The effects of engine coolant & oil temperatures and intake air swirl ratio on the early flame development were also studied. The heat release was derived from the in-cylinder pressure measurements and the corresponding flame area characteristics were extracted from the images.

Manufacturing of the internal combustion engines (ICEs) has very critical requirements on the precision and tolerance of engine parts in order to guarantee the engine performance. As a typical complex nonlinear system, small changes in dimensions of ICE components may have great impact on the performance and cost of the manufacturing of ICES. In this regard, it is still necessary to discuss the optimization of the tolerance and manufacturing precision of the critical components of ICEs even though the tolerance optimization in general has been reported in the literature. A systematic process for determining optimal tolerances will overcome the disadvantages of the traditional experience-based tolerance design and therefore improve the system performance.

To alleviate the shortage of petroleum resources and the air pollution caused by the burning of fossil fuels, the development of renewable fuels has attracted widespread attention. Among the various renewable fuels, ethanol can be produced from biomass and does not require much modification when applied to practical engines, so it has been widely used. However, ethanol fuel has a higher heat of vaporization than gasoline, it is difficult to evaporate and atomize under cold start conditions. Besides, the catalyst has not reached the conversion temperature at this time, resulting in lower conversion efficiency. These factors all lead to higher pollutant emission levels in ethanol-gasoline blends. To solve the above problems, this research used visualization techniques to compare the effects of flash boiling and high-energy ignition technologies on the in-cylinder combustion process and pollutant emission of ethanol-gasoline blends fuel.

The proper formation of fuel-air mixture, which depends to a large extend on the complex in-cylinder air flow, is an important criterion to control the clean and reliable combustion process in spark-ignition direct-injection (SIDI) engines. The in-cylinder flow vorticity field presents highly transient complex characteristics, and the corresponding vorticity field also evolves in the entire engine cycle from intake to exhaust strokes. It is also widely recognized that the vorticity field plays a key role in the in-cylinder turbulent field because it influences the air-fuel mixing and flame development process. In this investigation, the in-cylinder vortex structure and vorticity field characteristics are analyzed using the phase-invariant proper orthogonal decomposition (POD) method.

It has been found that the spray impingement on piston for SIDI engines significantly influences engine emission and combustion efficiency. Fuel film sticking on the wall will dramatically cause deterioration of engine friction performance, incomplete combustion, and substantial cycle-to-cycle variations. When increasing the injection pressure, these effects are more pronounce. Besides, the ambient pressure also plays an important role on the spray structure and influences the footprint of impinging spray on the plate. However, the dynamic behavior of impinging spray and corresponding film was not investigated thoroughly in previous literature. In this study, simultaneous measurements of macroscopic structure (side view) and its corresponding footprint (bottom view) of impinging spray was conducted using a single-hole, prototype injector in a constant volume chamber.