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Plug-in hybrid electric vehicles (PHEVs) provide significantly improvement in fuel economy over conventional vehicles as well as reductions in greenhouse gas and petroleum. Numerous recent reports regarding control strategy, power train configuration, driving pattern, all electric range (AER) and their effects on fuel consumption and electric energy consumption of PHEVs are reported. Meanwhile, the control strategy for engine start-stop and mileage between recharging events from the electricity grid also has an important influence on the petroleum displacement potential of PHEVs, but few reports are published. In this paper, a detailed simulation model is set up for a plug-in series hybrid electric vehicle (PSHEV) employing the AVL CRUISE. The model was employed to predict the AER of the baseline PSHEV using rule-based logical threshold switching control strategy.

This research was concerned with the use of Exhaust Gas Recirculation (EGR) improving the fuel economy over a wide operating range in a downsized boosted gasoline engine. The experiments were performed in a 1.3-Litre turbocharged PFI gasoline engine, equipped with a Low Pressure (LP) water-cooled EGR system. The operating conditions varied from 1500rpm to 4000rpm and BMEP from 2bar to 17bar. Meanwhile, the engine’s typical operating points in NEDC cycle were tested separately. The compression ratio was also changed from 9.5 to 10.5 to pursue a higher thermal efficiency. A pre-compressor throttle was used in the experiment working together with the EGR loop to keep enough EGR rate over a large area of the engine speed and load map. The results indicated that, combined with a higher compression ratio, the LP-EGR could help to reduce the BSFC by 9∼12% at high-load region and 3∼5% at low-load region.

Research studies have suggested that changes to the ignition system are required to generate a more robust flame kernel in order to secure the ignition process for the future advanced high efficiency spark-ignition (SI) engines. In a typical inductive ignition system, the spark discharge is initiated by a transient high-power electrical breakdown and sustained by a relatively low-power glow process. The electrical breakdown is characterized as a capacitive discharge process with a small quantity of energy coming mainly from the gap parasitic capacitor. Enhancement of the breakdown is a potential avenue effectively for extending the lean limit of SI engine. In this work, the effect of high-power capacitive spark discharge on the early flame kernel growth of premixed methane-air mixtures is investigated through electrical probing and optical diagnosis.

Many studies show that under diesel engine operating conditions, SCR reductant sprays will impinge on the wall of exhaust pipes. In order to understand this impinging process of SCR reductant spray, and to analyze what factors affect it, a test bench was set up by means of high speed video camera. At atmospheric pressure, SCR spray was injected on a heated metal wall, the impacts of wall temperature, injection pressure, injection height and angle on developing characteristics of SCR reductant spray after impinging on the heated wall have been researched and analyzed. The results show that the heated wall temperature has a great impact on the spray developing process, when wall temperature is lower than 405K, after water evaporated the crystallized urea will remain on the wall to block exhaust pipes. When wall temperature is higher, the atomization and evaporation of SCR reductant spray will be better, and the hydrolysis process of urea will be faster.

Spray characteristics and spray wall-impingement events are the key factors for the direct injection spark ignition (DISI) engines, affecting fuel/air mixture preparation and its combustion process. Thus, the spray characteristics of a multi-hole injector for DISI engines, such as spray tip penetration and spray cone angle were investigated in an optical chamber employing the high-speed shadow photography. Furthermore, the effects of the injection pressure, ambient pressure and piston top shape on the impinging spray development were studied in the optical chamber, when the impinging distance is 26.1 mm, corresponding to about 60 CAD ATDC. In addition, the SMD and wall film thickness of the spray impinging on the piston top were studied by means of CFD technique. The results showed that the ambient pressure had the greater effect on the changes of the spray penetration and spray cone angle than the injection pressure.

To improve the cold start performance and to reduce the misfire occurrence at cold start, the start-up strategy of total stoichiometric ratio combined with local rich mixture was applied in the study. The effect of injection strategy (the 1st injection timing, 2nd injection timing, 1st and 2nd fuel injection proportion and ignition timing) on the cold start HC emissions in the initial 10 cycles were investigated in a Two stage direct injection (TSDI) gasoline engine. The transient HC and NO emissions in the initial 10 cycles were analyzed, when the fuels are injected in the only 1st cycle and in the followed all cycles. The transient misfiring HC emissions were compared between the single and two-stage injection modes. In addition, the unburned HC (UBHC) emissions in the 1st cycle are compared among the TSDI engine, Gasoline direct injection (GDI) engine, Port fuel injection (PFI) engine and Liquefied petroleum gaseous (LPG) engine at the stoichiometric ratio.

Ion current sensing, which usually employs a spark plug as its sensor to obtain feedback signal from different types of combustion in SI engines, may be applied to HCCI combustion sensing instead of a prohibitively expensive piezoelectric pressure transducer. However, studies showed that the ion current detected by a spark plug sensor is a localized signal within the vicinity of the sensor's electrode gap, being affected by conditions around it. To find out better and feasible ion probe positions, a 3D-CFD model with a detailed surrogate mechanism containing 1423 species and 6106 reactions was employed to study the effect of stratification on ion distribution in HCCI combustion. The simulation results indicate that the monitor probe 1, 8 and 9 are more stable and reliable than the others. IONmax and dIONmax are more accurate to estimate CA50 and dQmax respectively.

The weight of an exhaust system on a modern vehicle is increasing because of all kinds of reasons, like engine power's increasing, more catalysts for emission control and more NVH (Noise, Vibration and Harshness) performance requirements. After the engine starting, the exhaust system was not only bearing a cyclical load from the engine, which mainly causing the vibration of the exhaust system, but also the loads from the road, which was transferred through the wheels, the suspension system and the body. Because the exhaust system always worked in these bad conditions, its structural strength, durability and life-time were analyzed in the paper, by numerical simulation and physical correlation. By discretizing the exhaust system's CAD model, a finite element model was built. After restrict the finite element model as it in a real load condition, complete the structure stress analysis and Fatigue analysis of exhaust system's hanger with FEA analysis tools.

Reducing the pumping loss, and thus, the fuel consumption of gasoline engine at part load, a two-stage intake valve lift system was implanted into a PFI engine. A corresponding engine model was set up with GT-power as well, which can simulate the effect of two-stage intake valve lift and different EGR rates on fuel economy performance and on combustion condition of a gasoline engine. Based on simulation results, the valve lift control strategy and EGR control strategy was studied in this paper. Results showed that at low engine speed, when SMALL LIFT was used, the tumble flow and the combustion process in cylinder was improved and burn time duration became shorter, resulting in higher indicated efficiency and lower fuel consumption than by LARGE LIFT. With the introduction of the exhaust gas recirculation (EGR), lower fuel consumption was acquired.

An ion current sensor is employed in a 4 cylinder production SI engine for combustion diagnosis during combustion process, knock, and low speed pre-ignition (LSPI) detection. The results show that the ion current peak value and ion current peak phase have strong correlation with the cylinder pressure and pressure peak phase respectively. The COV of ion current integral value is greater than the COV of IMEP at the same operating condition. Results show that the ion current signal is sensitive to different lambdas. Using ion current signal, the knock in any given cylinder can be detected. Importantly, the ion sensor successfully detected the low speed pre-ignition (LSPI) about more than 20 °CA before spark ignition.

Based on high EGR rate, the low temperature combustion (LTC) has been studied widely, of which the application range is more extensive than the homogeneous charge compression ignition (HCCI) and premixed charge compression ignition (PCCI). As the high EGR rate would influence the condition of intake charge, it would also affect the combustion process and the HC emissions, thus the combustion stability of LTC would be lower than tradition diesel combustion. In this study, an ion current detecting technology was employed to explore the ion current at different EGR rates. Meanwhile, the combustion parameters were also investigated, which included the in-cylinder pressure and heat release rate. The CA50 and CAI50 were adopted as the phases of combustion and ion current, which respectively represented the crank angle of mid-point for the integrated heat release and integrated ion current. Then the correlation between CA50 and CAI50 was analysed.

A novel reciprocating engine version of oxy-fuel combustion cycle combined with water direct injection (known as internal combustion rankine cycle) is presented in this paper. Water is injected near top dead center to control the reaction rate of the oxy-fuel mixture, as well as the peak in-cylinder temperature. The evaporation of the water mist will increase the mass of working gas inside the cylinder, and enhances the thermo efficiency and MEP. Moreover, the injected water is heated up through heat exchangers by both engine coolant and exhaust gas, and the waste heat is effectively recovered this way. This study investigates the combustion and emission characteristics of ICRC under different engine loads based on a single-cylinder, air-cooled SI engine fueled with propane. An extra diesel injector is employed to inject water with high injection temperature (160°C).

The present work discusses a novel oxyfuel combustion method named internal combustion rankine cycle (ICRC) used in reciprocating engines. Water is heated up through heat exchanger by exhaust gas and engine cooling system, and then injected into the cylinder near top dead center to control the combustion temperature and in-cylinder pressure rise rate, meanwhile to enhance the thermo efficiency and work of the combustion cycle. That is because injected water increases the mass of the working fluid inside the cylinder, and can make use of the combustion heat more effectively. Waste heat carried away by engine coolant and exhaust gas can be recovered and utilized in this way. This study investigates the effect of water injection temperature on the combustion and emission characteristics of an ICRC engine based on self-designed test bench. The results indicate that both indicated work and thermal efficiency increase significantly due to water injection process.