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Technical Paper

Development of a Gas-Phase LPG Injection System for a Small SI Engine

2003-10-27
2003-01-3260
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.
Technical Paper

Characteristics of Particulate Emissions Fueled with LPG and Gasoline in a Small SI Engine

2004-10-25
2004-01-2901
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.
Technical Paper

Investigation of Cold-start Based on Cycle-by-Cycle Control Strategy in an EFI LPG Engine

2004-10-25
2004-01-3059
This paper presents an investigation of cold starts based on a cycle-by-cycle control strategy in an LPG EFI engine. Experiments were carried out in a four-stroke, water-cooled, single cylinder, 125cc SI engine with an EFI system. Effects of the first injection pulse width and the first combustion cycle on the characteristics of the cold-start were analyzed based on the histories of transient engine speeds and cylinder pressures. The study focuses on how to realize the controllable ignition cycle and the single-cycle and multi-cycle combustions were tested based on the single starting injection pulse width. Test results show that the first combustion cycle has an important effect on HC emission and combustion stability of following cycles at cold-start. The injection pulse width is the key factor determining the characteristics of an ignition cycle during the cold-start.
Technical Paper

Combustion and Emissions of Ethanol Fuel (E100) in a Small SI Engine

2003-10-27
2003-01-3262
An air-cooled, four-stroke, 125 cc electronic gasoline fuel injection SI engine for motorcycles is altered to burn ethanol fuel. The effects of nozzle orifice size, fuel injection duration, spark timing and the excess air/ fuel ratio on engine power output, fuel and energy consumptions and engine exhaust emission levels are studied on an engine test bed. The results show that the maximum engine power output is increased by 5.4% and the maximum torque output is increased by 1.9% with the ethanol fuel in comparison with the baseline. At full load and 7000 r/min, HC emission is decreased by 38% and CO emission is decreased 46% on average over the whole engine speed range. However, NOx levels are increased to meet the maximum power output. The experiments of the spark timing show that the levels of HC and NOx emission are decreased markedly by the delay of spark timing.
Technical Paper

Characteristics of Film Evaporation for Homogeneous Charge Preparation of Typical Fuels

2005-04-11
2005-01-1935
Fuel films of several typical fuels were investigated by means of thermal gravity analysis (TGA). To make diesel homogeneous charge by means of film evaporation, it was concluded that to get 30%∼50% evaporation of film, the wall temperature should be set between 150°C and 180°C for diesel and 40°C∼60°C for gasoline, and to get 95% evaporation of film, the wall temperature should be set between 200°C and 250°C for diesel and 50°C∼100°C for gasoline, when the thickness of the fuel film is about 40 μ m. Based on the properties of fuels, the evaporation characteristics of diesel under 100°C should be improved.
Technical Paper

In-Cycle Knocking Detection and Feedback Control Based on In-Cylinder Pressure and Ion Current Signal in a GDI Engine

2016-04-05
2016-01-0816
Due to much higher pressure and pressure rising rate, knocking is always of potential hazards causing damages in the engine and high NOX emissions. Therefore, the researchers have focused on knocking diagnosis and control for many years. However, there is still lack of fast response sensor detecting in-cycle knocking. Until now, the feedback control based on knocking sensor normally adjusts the injection and ignition parameters of the following cycles after knocking appears. Thus in-cycle knocking feedback control which requires a predictive combustion signal is still hard to see. Ion current signal is feasible for real-time in-cylinder combustion detection, and can be employed for misfiring and knocking detection. Based on incylinder pressure and ion current signals, the in-cycle knocking feedback control is investigated in this research. The 2nd-order differential of in-cylinder pressure, which means the response time of pressure rising rate dPR, is employed for knocking prediction.
Technical Paper

Evaporation Characteristics of n-Heptane Droplet Streams in a Heated Air Channel Flow

2016-04-05
2016-01-0843
An experimental study is presented on the evaporation of diluted droplet-laden two-phase jet flows within a heated air channel co-flow. In this study, n-heptane is pre-atomized by an ultrasonic nozzle to produce droplet cluster with a median diameter of about15μm, and a continuous cold air flow is applied to carry the fuel droplet cluster to emerge from a nozzle tube, producing a free turbulent jet of droplet stream. The droplet stream is then introduced as a central jet into a square-shaped channel with heated air co-flow for evaporation investigations. With flexibilities of the initial properties of droplet stream and surrounding conditions of channel flow, the axial evolution of droplet size is determined to characterize the evaporation behavior of n-heptane droplet stream under various boundary conditions. The equivalence ratios of droplet streams are varied by changing both the carrier-air flow rate and the fuel flow rate.
Journal Article

Characteristics of Lubricants on Auto-ignition under Controllable Active Thermo-Atmosphere

2016-04-05
2016-01-0889
Downsizing gasoline direct injection engine with turbo boost technology is the main trend for gasoline engine. However, with engine downsizing and ever increasing of power output, a new abnormal phenomenon, known as pre-ignition or super knock, occurs in turbocharged engines. Pre-ignition will cause very high in-cylinder pressure and high oscillations. In some circumstances, one cycle of severe pre-ignition may damage the piston or spark plug, which has a severe influence on engine performance and service life. So pre-ignition has raised lots of attention in both industry and academic society. More and more studies reveal that the auto-ignition of lubricants is the potential source for pre-ignition. The auto-ignition characteristics of different lubricants are studied. This paper focuses on the ignition delay of different lubricants in Controllable Active Thermo-Atmosphere (CATA) combustion system.
Technical Paper

Effect of Water Injection Temperature on Characteristics of Combustion and Emissions for Internal Combustion Rankine Cycle Engine

2014-10-13
2014-01-2600
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.
Technical Paper

Cycle Resolved Combustion and Pre-Ignition Diagnostic Employing Ion Current in a PFI Boosted SI Engine

2015-04-14
2015-01-0881
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.
Technical Paper

Investigations on Mixture Formation during Start-UP Process of a Two-Stage Direct Injection Gasoline Engine for HEV Application

2013-10-14
2013-01-2657
A cycle-resolved test system was designed in a Two Stage Direct Injection (TSDI) Gasoline engine to simulate the engine quick start process in an Integrated Start and Generator (ISG) Hybrid Electric Vehicle (HEV) system. Based on the test system, measurement of the in cylinder HC concentrations near the spark plug under different engine coolant temperature and cranking speed conditions were conducted using a Fast Response Flame Ionization Detector (FFID) with Sampling Spark Plug (SSP) fits, then the in-cylinder equivalence ratio near the spark plug was estimated from the measured HC concentrations. In addition, the effects of the 1st injection timing, 2nd injection timing, and total equivalence ratio on the mixture formation near the spark plug were analyzed by means of experiments.
Technical Paper

Fatigue Design and Analysis of the Vehicle Exhaust System's Hanger

2013-10-14
2013-01-2609
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.
Technical Paper

Effect of Stratification on Ion Distribution in HCCI Combustion Using 3D-CFD with Detailed Chemistry

2013-10-14
2013-01-2512
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.
Technical Paper

Study of Combustion Characteristics of a Quasi Internal Combustion Rankine Cycle Engine

2013-10-14
2013-01-2698
Internal combustion Rankine cycle (ICRC) engine uses oxygen instead of air as oxidant during the combustion process, therefore totally eliminates the emission of NOx. CO2 could be captured after separated from the exhaust gas, the latter are mainly water vapor and CO2, through condensation at a relatively low price, and thus an ultra-low emission working cycle is achieved. Moreover, water is heated up by exhaust gas and injected into the cylinder during the combustion process to control combustion temperature, and evaporation of the water mist would increase working fluid inside the cylinder, therefore enhance indicated thermal efficiency. This study investigates the combustion characteristics of a quasi ICRC on a single-cylinder SI engine fueled with propane. Gas mixture of O2/CO2 is employed to simulate EGR in order to control in-cylinder temperature.
Technical Paper

Closed-loop Control of Low Temperature Combustion Employing Ion Current Detecting Technology

2014-04-01
2014-01-1362
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.
Technical Paper

Effect of Ambient Density and Temperature on Diesel Spray Characteristics

2014-04-01
2014-01-1414
In this study, in order to form a wide range of ambient gas density, Nitrogen and sulfur hexafluoride (SF6) are employed as ambient gas. Based on the common rail and high speed imaging system, the spray characteristics in extremely high ambient density and different ambient temperature are investigated in a constant volume vessel, and the influences of gas physical property on the spray characteristics have also been analyzed. The investigation results show that: the spray tip penetration and spray cone angle vary phenomenally with the increase of the ambient gas density. Due to the generation of shock wave, the results of the spray characteristics from two ambient gas densities are different nevertheless the same densities. Furthermore, the spray tip penetrations from the different ambient gases do not vary obviously from each other until the detachment of the shock wave from the spray tip.
Technical Paper

Study of the Combustion and Emission Characteristics of a Quasi ICRC Engine Under Different Engine Loads

2014-04-01
2014-01-1202
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).
Journal Article

Impact of Control Methods on Dynamic Characteristic of High Speed Solenoid Injectors

2014-04-01
2014-01-1445
Accurate control of both the timing and quantity of injection events is critical for engine performance and emissions. The most serious problem which reduces the accuracy of the control operation in such systems is a time delay of the responsiveness for the opening and closing operation of the electromagnetic valve. Modern electronic control systems should be capable of driving high speed solenoid injectors at a very fast switch frequency with high efficiency and acceptable power requirements. In this paper, the dynamic characteristic of a high speed servo-hydraulic solenoid injector for diesel engine, with different driving circuits and control methods, is investigated. A pre-energizing control strategy based on a dual power supply is applied to speed up the opening response time of the injectors.
Technical Paper

A Novel Closed Loop Control based on Ionization Current in Combustion Cycle at Cold Start in a GDI Engine

2012-04-16
2012-01-1339
As the invalidation of the oxygen sensor in the initial cycles at cold start, the engine can not operate based on the closed loop control based on oxygen sensor. And it may result in the misfire events and higher hydrocarbon (HC) emissions during this period. To solve this problem, a novel closed loop control based on ionization current in combustion cycle is proposed. The in-cylinder combustion quality is monitored by means of the ion current detection technique; meanwhile, if the misfire event is detected in the combustion cycle, the spark re-ignition is made in the current combustion cycle. In addition, to optimize the combustion and reduce HC emissions during cold start, the fuel injection quantity and ignition timing in the next cycle are adjusted based on the current ion current signal.
Technical Paper

Transient Characteristics of Cold Start Emissions from a Two-Stage Direct Injection Gasoline Engines Employing the Total Stoichiometric Ratio and Local Rich Mixture Start-up Strategy

2012-04-16
2012-01-1068
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.
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