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To improve the vehicle diesel engine performance at part-load operation, experiments on sequential turbocharging system used in a vehicle diesel engine are investigated in this paper. The brake specific fuel consumption and smoke emission of diesel engine are measured in four schemes: with the based turbocharger, with a small turbocharger, with a big turbocharger, with both small and big turbochargers. Then, a new turbocharging method named three-phase sequential turbocharging system with two unequal size turbochargers is presented by analyzing and comparing the experimental results. The experiment on a vehicle diesel engine with three-phase sequential turbocharging system shows that the brake specific fuel consumption and the smoke emission are reduced observably in complete engine speeds range, especially in the low speed operation. Finally, the transient performances of three-phase sequentially turbocharged vehicle diesel engine are analyzed by experiments.

During braking, energy regeneration for hybrid electric vehicles (HEV) is an important technique to improve their fuel economy and extend their driving range. Due to the effect of regenerative braking torque added by the electric motor, the control logic of the braking system should be adjusted. This paper presents a control strategy for an HEV braking system, which calculates the optimal target wheel slip ratio based on vehicle dynamic states; a fuzzy logic approach is applied to maintain the optimal target slip ratio so that the best compromise between hydraulic braking torque and regenerative braking torque can be obtained for the vehicle. This control strategy is implemented with an 8-DOF nonlinear vehicle model and a “Magic Formula” tire model; the simulation results show that the proposed strategy is robust and effective.

By changing the top-land radial clearance, this paper presents the effect of the piston crevice on the transient HC emissions of the first firing cycle at cold start on an LPG SI Engine. A fast-response flame ionization detector (FFID) was employed to measure transient HC emissions of the first firing cycle. At the same time, the transient cylinder pressure and instantaneous crankshaft speed of the engine were measured and recorded. The results show that increasing 50% crevice volume leads to 25% increase of HC emissions in the lean region and 18% increase of HC emissions in the rich region, however, the 50% increase of crevice volume contributes to 32% decease of HC emissions in the stable combustion region. For LPG SI engine, the HC emissions of the first firing cycle during cold start are relatively low in a wide range of the excess air ratio.

During cold start of DI diesel engine, exhaust gas comprises a great deal of unburned hydrocarbon, fuel vapor, and product of partial oxidation reaction. If these compositions are reintroduced into cylinder by EGR, the positive effects may shorten ignition delay, and thus promote ignition. Furthermore, considering thermal effect of EGR and its minor dilution effect during cold start, the combustion performance of cold start could also be promoted through introducing EGR. Through experiments conducted on a 135 single cylinder DI diesel engine, effects of EGR on combustion and emission performance during cold start process were investigated. Comparison of combustion performance between cold start processes with and without EGR suggested that it is an effective measure to improve cold startability of DI diesel engine by controlling EGR system during cold start.

The effectiveness of after-treatment systems depends on the exhaust gas temperature, which is low during cold-start. As a result, Euro III, Euro IV and FTP75 require that the emissions tests include exhaust from the beginning of cold start. It is proved that 50%∼80% of HC and CO emissions are emitted during the cold start and the amount of unburned fuel from the crevices during starting is much higher than that under warmed engine conditions. The piston crevices is the most part of combustion chamber crevices, and results of mathematical simulations show that the piston crevice contribution to HC emissions is expected to increase during cold engine operation. Based on the transient HC test data and the double zone combustion model, this paper presents the study of the crevice HC Mechanism of the first firing cycle at cold start on an LPG SI Engine. A fast-response flame ionization detector (FFID) was employed to measure transient HC emissions of the first firing cycle.

This paper presents the development of an electronic control LPG gas injection system and its application in a small SI engine. The tests results show that the developed LPG gas injection system can meet the needs for the goal of high engine power output and low exhaust emissions based on the engine bench tests. With the LPG electronic gas injection system, the air-fuel ratio can be optimized based on the requirements and CO and NOx emission levels are decreased significantly compared with the LPG mechanical mixer fuel supply system, based on the same HC emission levels. With the new gas phase LPG electronic control injection system, the HC emission level is controlled below the 300 ppm under most engine conditions and under 200 ppm when the engine speed is over 3000 r/min. The NOx emission level is under 2600 ppm in the whole range of engine operation conditions and is decreased by 2000 ppm compared with the LPG mechanical mixer system.

This paper presents an experimental study of the emission characteristics of a small Spark-Ignited, LPG engine. A single cylinder, four-stroke, water-cooled, 125cc SI engine for motorcycle is modified for using LPG fuel. The power output of LPG is above 95% power output of gasoline. The emission characteristics of LPG are compared with the gasoline. The test result shows that LPG for small SI engine will help to reduce the emission level of motorcycles. The HC and CO emission level can be reduced greatly, but NOx emissions are increased. The emission of motorcycle using LPG shows the potential to meet the more strict regulation.

This paper presents a study of LPG lean burn in a motorcycle SI engine. The lean burn limits are compared by several ways. The relations of lean burn limit with the parameters, such as engine speed, compression ratio and advanced spark ignition etc. are tested. The experimental results show that larger throttle opening, lower engine speed, earlier spark ignition timing, larger electrode gap and higher compression ratio will extend the lean burn limit of LPG. The emission of a LPG engine, especially on NOx emission, can be significantly reduced by means of the lean burn technology.

Rapid pressure build-up before acquiring the engine phase position is necessary to improve the start performance for a common rail diesel engine. This paper presents a simulation model to describe the pressure build-up process of the DENSO HP0-MD high-pressure pump, with the two pressure-control-solenoid-valves (PCV) are frequently driven in sequence. As the fuel is pumped only when one PCV is energized in its corresponding plunger supply stroke, simulation studies are carried out to analyze the pressure build-up effect of different driving frequency, and the 30Hz frequency is selected as the optimal driving frequency to achieve about 80% fuel supply efficiency for the normal cranking speed range. Additionally, when only the crankwheel signal is useful, a novel method, which checks whether the rail pressure rises in a special PCV energizing zone, is designed to assistant ascertain engine phase.

The First Firing Cycle (FFC) is very important at cold-start. Misfiring of the first firing cycle can lead to significant HC emissions and affect the subsequent cycles. This paper presents an investigation of characteristics of transient NO emissions in a small LPG SI engine with electronic gaseous injection system. To determine the optimal excess air coefficient ( λ=[A/F]/[A/F]stoic) of the first firing cycle, the emission of instantaneous NO was proposed as a useful criterion to judge if the combustion is occurred or not. A fast response NO detector- Cambustion fNOx400, based on the chemiluminescence's (CLD) method, has been employed to measure continuous, transient emissions of NO during the first firing cycle in the exhaust port of the engine. At the same time, the transient cylinder pressure, instantaneous crankshaft speed of the engine and engine-out HC emissions were measured and recorded.

This paper presents experimental studies of particulate emissions in a small SI engine fueled with LPG and gasoline fuels. A single cylinder, four-stroke, water-cooled, 125cc EFI engine with gasoline fuel is used as the baseline engine. Characteristics of the particulate emissions of the two fuels are compared. Test results show that: there are great quantities of particulate emissions for both fuels, but the total numbers of particulate emissions for the two fuels are generally in the same level. The distribution of the particulate sizes is in bimodal type for the gasoline, but for the LPG its first peak is not markedly in some conditions. The particulate sizes of the second peak for the two fuels appear at about the same size. At middle loads and 3000r/min, the particulate emissions for both of the two fuels are the greatest.

Since the vehicle AMT(Automatic Manual Transmission) has been developed to meet the requirements of high quality vehicles as well as hybrid vehicles, there are more and more tasks running on the ECU (Electronically Controlled Unit). Concerned with both function correctness and timing correctness, the scheduling of those tasks becomes important. A perfect scheduler, which distributes the proper task working during the proper time, can not only make the best use of the ECU, but also predict its capacity rationally. Compared with ordinary algorithm such as clock driven scheduler, static and dynamic priority-driven scheduler as well as round robin scheduler, this paper proposes an offline-designed Blended Timer-triggered Scheduler (BTTS) for AMT control. BTTS can coordinate periodical and event-triggered tasks in one envelope. It designates the available time slice for each task, which can make each critical task run at the proper time.

The diesel premixed low-temperature combustion mode avoids the generation of thick mixture and the high temperature region in which a great amount of NOx and PM generates. It makes a significant reduction in the emissions of both NOx and PM available at the same time. However, with the quantity of pre-injection increases and the injection time advances, the emission of HC increases significantly, which causes a decrease in the combustion efficiency. Studies have shown that the flame quench caused by too thick or too lean mixture and the oil film on the chamber is the main source for the emission of HC. As a result, understanding the mechanism of atomization and evaporation of the fuel and the formation of the mixture makes significant sense. This paper focuses on the mixture formation process. And the methods of testing the distribution of the mixture, the influential factors and control methods are studied.