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Technical Paper

The Upper-Load Extension of a Boosted Direct Injection Poppet Valve Two-Stroke Gasoline Engine

2016-10-17
2016-01-2339
Engine downsizing can effectively improve the fuel economy of spark ignition (SI) gasoline engines, but extreme downsizing is limited by knocking combustion and low-speed pre-ignition at higher loads. A 2-stroke SI engine can produce higher upper load compared to its naturally aspirated 4-stroke counterpart with the same displacement due to the double firing frequency at the same engine speed. To determine the potential of a downsized two-cylinder 2-stroke poppet valve SI gasoline engine with 0.7 L displacement in place of a naturally aspirated 1.6 L gasoline (NA4SG) engine, one-dimensional models for the 2-stroke gasoline engine with a single turbocharger and a two-stage supercharger-turbocharger boosting system were set up and validated by experimental results.
Technical Paper

The Modeling and Design of a Boosted Uniflow Scavenged Direct Injection Gasoline (BUSDIG) Engine

2015-09-01
2015-01-1970
Engine downsizing of the spark ignition gasoline engine is recognized as one of the most effective approaches to improve the fuel economy of a passenger car. However, further engine downsizing beyond 50% in a 4-stroke gasoline engine is limited by the occurrence of abnormal combustion events as well as much greater thermal and mechanical loads. In order to achieve aggressive engine downsizing, a boosted uniflow scavenged direct injection gasoline (BUSDIG) engine concept has been proposed and researched by means of CFD simulation and demonstration in a single cylinder engine. In this paper, the intake port design on the in-cylinder flow field and gas exchange characteristics of the uniflow 2-stroke cycle was investigated by computational fluid dynamics (CFD). In particular, the port orientation on the in-cylinder swirl, the trapping efficiency, charging efficiency and scavenging efficiency was analyzed in details.
Technical Paper

The Dilution, Chemical, and Thermal Effects of Exhaust Gas Recirculation on Diesel Engine Emissions - Part 1: Effect of Reducing Inlet Charge Oxygen

1996-05-01
961165
This is a first of a series of papers describing how the replacement of some of the inlet air with EGR modifies the diesel combustion process and thereby affects the exhaust emissions. This paper deals with only the reduction of oxygen in the inlet charge to the engine (dilution effect). The oxygen in the inlet charge to a direct injection diesel engine was progressively replaced by inert gases, whilst the engine speed, fuelling rate, injection timing, total mass and the specific heat capacity of the inlet charge were kept constant. The use of inert gases for oxygen replacement, rather than carbon dioxide (CO2) or water vapour normally found in EGR, ensured that the effects on combustion of dissociation of these species were excluded. In addition, the effects of oxygen replacement on ignition delay were isolated and quantified.
Technical Paper

Synergy between Boost and Valve Timings in a Highly Boosted Direct Injection Gasoline Engine Operating with Miller Cycle

2015-04-14
2015-01-1262
Gasoline engine downsizing has become a popular and effective approach to reduce CO2 emissions from passenger cars. This is typically achieved in the form of a boosted direct injection gasoline engine, which are typically equipped with variable valve timing (VVT) devices on the intake and/or exhaust valves. This paper describes the synergies between valve timings and boost based on experimental investigations in a single cylinder gasoline direct injection spark ignited (DISI) engine with variable cam phasing on both the intake and exhaust cams. Two cam profiles have been tested to realize Miller cycle and compared with the standard camshaft. One cam features a long opening duration and standard valve lift for Late Intake Valve Closing (LIVC) and the other cam has a short opening duration and low valve lift for Early Intake Valve Closing (EIVC).
Technical Paper

Research and Development of Controlled Auto-Ignition (CAI) Combustion in a 4-Stroke Multi-Cylinder Gasoline Engine

2001-09-24
2001-01-3608
Controlled Auto-Ignition (CAI) combustion has been achieved in a production type 4-stroke multi-cylinder gasoline engine. The engine was based on a Ford 1.7L Zetec-SE 16V engine with a compression ratio of 10.3, using substantially standard components modified only in design dimensions to control the gas exchange process in order to significantly increase the trapped residuals. The engine was also equipped with Variable Cam Timing (VCT) on both the intake and exhaust camshafts. It was found that the largely increased trapped residuals alone were sufficient to achieve CAI in this engine and with VCT, a range of loads between 0.5 and 4 bar BMEP and engine speeds between 1000 and 3500 rpm were mapped for CAI fuel consumption and exhaust emissions. The measured CAI results were compared with those of Spark Ignition (SI) combustion in the same engine but with standard camshafts at the same speeds and loads.
Technical Paper

Reduction of Methane Slip Using Premixed Micro Pilot Combustion in a Heavy-Duty Natural Gas-Diesel Engine

2015-09-01
2015-01-1798
An experimental study has been carried out with the end goal of minimizing engine-out methane emissions with Premixed Micro Pilot Combustion (PMPC) in a natural gas-diesel Dual-Fuel™ engine. The test engine used is a heavy-duty single cylinder engine with high pressure common rail diesel injection as well as port fuel injection of natural gas. Multiple variables were examined, including injection timings, exhaust gas recirculation (EGR) percentages, and rail pressure for diesel, conventional Dual-Fuel, and PMPC Dual-Fuel combustion modes. The responses investigated were pressure rise rate, engine-out emissions, heat release and indicated specific fuel consumption. PMPC reduces methane slip when compared to conventional Dual-Fuel and improves emissions and fuel efficiency at the expense of higher cylinder pressure.
Technical Paper

Potentials of External Exhaust Gas Recirculation and Water Injection for the Improvement in Fuel Economy of a Poppet Valve 2-Stroke Gasoline Engine Equipped with a Two-Stage Serial Charging System

2018-04-03
2018-01-0859
Engine downsizing is one of the most effective means to improve the fuel economy of spark ignition (SI) gasoline engines because of lower pumping and friction losses. However, the occurrence of knocking combustion or even low-speed pre-ignition at high loads is a severe problem. One solution to significantly increase the upper load range of a 4-stroke gasoline engine is to use 2-stroke cycle due to the double firing frequency at the same engine speed. It was found that a 0.7 L two-cylinder 2-stroke poppet valve gasoline engine equipped with a two-stage serial boosting system, comprising a supercharger and a downstream turbocharger, could replace a 1.6 L naturally aspirated 4-stroke gasoline engine in our previous research, but its fuel economy was close to that of the 4-stroke engine at upper loads due to knocking combustion.
Technical Paper

Performance and Analysis of a 4-Stroke Multi-Cylinder Gasoline Engine with CAI Combustion

2002-03-04
2002-01-0420
Controlled Auto-Ignition (CAI) combustion was realised in a production type 4-stroke 4-cylinder gasoline engine without intake charge heating or increasing compression ratio. The CAI engine operation was achieved using substantially standard components modified only in camshafts to restrict the gas exchange process The engine could be operated with CAI combustion within a range of load (0.5 to 4 bar BMEP) and speed (1000 to 3500 rpm). Significant reductions in both specific fuel consumption and CO emissions were found. The reduction in NOx emission was more than 93% across the whole CAI range. Though unburned hydrocarbons were higher under the CAI engine operation. In order to evaluate the potential of the CAI combustion technology, the European NEDC driving cycle vehicle simulation was carried out for two identical vehicles powered by a SI engine and a CAI/SI hybrid engine, respectively.
Book

Laser Diagnostics and Optical Measurement Techniques in Internal Combustion Engines

2012-07-30
The increasing concern about CO2 emissions and energy prices has led to new CO2 emission and fuel economy legislation being introduced in world regions served by the automotive industry. In response, automotive manufacturers and Tier-1 suppliers are developing a new generation of internal combustion (IC) engines with ultra-low emissions and high fuel efficiency. To further this development, a better understanding is needed of the combustion and pollutant formation processes in IC engines. As efficiency and emission abatement processes have reached points of diminishing returns, there is more of a need to make measurements inside the combustion chamber, where the combustion and pollutant formation processes take place. However, there is currently no good overview of how to make these measurements.
Technical Paper

Investigation of EGR and Miller Cycle for NOx Emissions and Exhaust Temperature Control of a Heavy-Duty Diesel Engine

2017-10-08
2017-01-2227
In order to meet increasingly stringent emissions standards and lower the fuel consumption of heavy-duty (HD) vehicles, significant efforts have been made to develop high efficiency and clean diesel engines and aftertreatment systems. However, a trade-off between the actual engine efficiency and nitrogen oxides (NOx) emission remains to minimize the operational costs. In addition, the conversion efficiency of the diesel aftertreatment system decreases rapidly with lower exhaust gas temperatures (EGT), which occurs at low load operations. Thus, it is necessary to investigate the optimum combustion and engine control strategies that can lower the vehicle’s running costs by maintaining low engine-out NOx emissions while increasing the conversion efficiency of the NOx aftertreament system through higher EGTs.
Technical Paper

Investigation into Controlled Auto-Ignition Combustion in a GDI Engine with Single and Split Fuel Injections

2007-04-16
2007-01-0211
A multi-cycle three-dimensional CFD engine simulation programme has been developed and applied to analyze the Controlled autoignition (CAI) combustion, also known as homogeneous charge compression ignition (HCCI), in a direct injection gasoline engine. CAI operation was achieved through the negative valve overlap method by means of a set of low lift camshafts. The effect of single injection timing on combustion phasing and underlying physical and chemical processes involved was examined through a series of analytical studies using the multi-cycle 3D engine simulation programme. The analyses showed that early injection into the trapped burned gases of a lean-burn mixture during the negative valve overlap period had a large effect on combustion phasing, due to localized heat release and the production of chemically reactive species. As the injection was retarded to the intake stroke, the charge cooling effect tended to slow down the autoignition process.
Technical Paper

Innovative Ultra-low NOx Controlled Auto-Ignition Combustion Process for Gasoline Engines: the 4-SPACE Project

2000-06-19
2000-01-1837
The purpose of the 4-SPACE (4-Stroke Powered gasoline Auto-ignition Controlled combustion Engine) industrial research project is to research and develop an innovative controlled auto-ignition combustion process for lean burn automotive gasoline 4-stroke engines application. The engine concepts to be developed could have the potential to replace the existing stoichiometric / 3-way catalyst automotive spark ignition 4-stroke engines by offering the potential to meet the most stringent EURO 4 emissions limits in the year 2005 without requiring DeNOx catalyst technology. A reduction of fuel consumption and therefore of corresponding CO2 emissions of 15 to 20% in average urban conditions of use, is expected for the « 4-SPACE » lean burn 4-stroke engine with additional reduction of CO emissions.
Technical Paper

Impact of Port Fuel Injection and In-Cylinder Fuel Injection Strategies on Gasoline Engine Emissions and Fuel Economy

2016-10-17
2016-01-2174
As the emission regulations for internal combustion engines are becoming increasingly stringent, different solutions have been researched and developed, such as dual injection systems (combined port and direct fuel injection), split injection strategies (single and multiple direct fuel injection) and different intake air devices to generate an intense in-cylinder air motion. The aim of these systems is to improve the in-cylinder mixture preparation (in terms of homogeneity and temperature) and therefore enhance the combustion, which ultimately increases thermal efficiency and fuel economy while lowering the emissions. This paper describes the effects of dual injection systems on combustion, efficiency and emissions of a downsized single cylinder gasoline direct injection spark ignited (DISI) engine. A set of experiments has been conducted with combined port fuel and late direct fuel injection strategy in order to improve the combustion process.
Technical Paper

Experimental Study on Spark Assisted Compression Ignition (SACI) Combustion with Positive Valve Overlap in a HCCI Gasoline Engine

2012-04-16
2012-01-1126
The spark-assisted compression ignition (SACI) is widely used to expend the high load limit of homogeneous charge compression ignition (HCCI), as it can reduce the high heat release rate effectively while partially maintain the advantage of high thermal efficiency and low NOx emission. But as engine load increases, the SACI combustion traditionally using negative valve overlap strategy (NVO) faces the drawback of higher pumping loss and limited intake charge availability, which lead to a restricted load expansion and a finite improvement of fuel economy. In this paper, research is focused on the SACI combustion using positive valve overlap (PVO) strategy. The characteristics of SACI combustion employing PVO strategy with external exhaust gas recirculation (eEGR) are investigated. Two types of PVO strategies are analyzed and compared to explore their advantages and defects, and the rules of adjusting SACI combustion with positive valve overlap are concluded.
Technical Paper

Experimental Studies of a 4-Stroke Multi-Cylinder Gasoline Engine with Controlled Auto-Ignition (CAI) Combustion

2007-11-28
2007-01-2609
Controlled Auto-Ignition (CAI), also known as HCCI (Homogeneous Charge Compression Ignition), is increasingly seen as a very effective way of lowering both fuel consumption and emissions from gasoline engines. Therefore, it's seen as one of the best ways to meet future engine emissions and CO2 legislations. This combustion concept was achieved in a Ford production, port-injected, 4 cylinder gasoline engine. The only major modification to the original engine was the replacement of the original camshafts by a new set of custom made ones. The CAI operation was accomplished by means of using residual gas trapping made possible by the use of VCT (variable cam timing) on both intake and exhaust camshafts. When running on CAI, the engine was able to achieve CAI combustion with in a load range of 0.5 to 4.5 BMEP, and a speed range of 1000 to 3500 rpm. In addition, spark assisted CAI operation was employed to extend the operational range of low NOx and low pumping loss at part-load conditions.
Technical Paper

Experimental Investigation of Combustion and Emission Characteristics of Stoichiometric Stratified Flame Ignited (SFI) Hybrid Combustion in a 4-Stroke PFI/DI Gasoline Engine

2019-04-02
2019-01-0960
Controlled Auto-Ignition (CAI), also known as Homogeneous Charge Compression Ignition (HCCI), can improve the fuel economy of gasoline engines and simultaneously achieve ultra-low NOx emissions. However, the difficulty in combustion phasing control and violent combustion at high loads limit the commercial application of CAI combustion. To overcome these problems, stratified mixture, which is rich around the central spark plug and lean around the cylinder wall, is formed through port fuel injection and direct injection of gasoline. In this condition, rich mixture is consumed by flame propagation after spark ignition, while the unburned lean mixture auto-ignites due to the increased in-cylinder temperature during flame propagation, i.e., stratified flame ignited (SFI) hybrid combustion.
Technical Paper

Experiment and Analysis of a Direct Injection Gasoline Engine Operating with 2-stroke and 4-stroke Cycles of Spark Ignition and Controlled Auto-Ignition Combustion

2011-08-30
2011-01-1774
Over recent years, in order to develop more efficient and cleaner gasoline engines, a number of new engine operating strategies have been proposed and many of them have been studied on different engines but there is a lack of different comparison between various operating strategies. In this work, a single cylinder direct injection gasoline engine equipped with an electro-hydraulic valvetrain system has been commissioned and used to achieve seven different operation modes, which are 4-stroke throttle-controlled SI, 4-stroke intake valve throttled SI, 4-stroke positive valve overlap SI, 4-stroke negative valve overlap CAI, 4-stroke exhaust rebreathing CAI, 2-stroke CAI and 2-stroke SI. Their performance and emission characteristics are presented and discussed.
Technical Paper

Effects of Injection Timing and Valve Timings on CAI Operation in a Multi-Cylinder DI Gasoline Engine

2005-04-11
2005-01-0132
CAI-combustion was achieved in a 4-cylinder four-stroke gasoline DI engine, with all cylinders running in CAI-mode. Standard components were used, with the exception of the camshafts which had been modified in order to restrict the gas exchange process. Results shown in the paper are between a load of 1.45 - 2.65 bar, an engine speed of 1500rpm and at a lambda value of 1.2. As is typical with this type of combustion, reductions in emissions of NOx were recorded as well as a slight decrease in HC emissions, also there was a reduction in the brake specific fuel consumption. The effect that injection timing on factors such as start of combustion, combustion duration and heat release rate are also investigated.
Technical Paper

Effect of an ORC Waste Heat Recovery System on Diesel Engine Fuel Economy for Off-Highway Vehicles

2017-03-28
2017-01-0136
Modern heavy duty diesel engines can well extend the goal of 50% brake thermal efficiency by utilizing waste heat recovery (WHR) technologies. The effect of an ORC WHR system on engine brake specific fuel consumption (bsfc) is a compromise between the fuel penalty due to the higher exhaust backpressure and the additional power from the WHR system that is not attributed to fuel consumption. This work focuses on the fuel efficiency benefits of installing an ORC WHR system on a heavy duty diesel engine. A six cylinder, 7.25ℓ heavy duty diesel engine is employed to experimentally explore the effect of backpressure on fuel consumption. A zero-dimensional, detailed physical ORC model is utilized to predict ORC performance under design and off-design conditions.
Technical Paper

Effect of Injection Timing on Mixture and CAI Combustion in a GDI Engine with an Air-Assisted Injector

2006-04-03
2006-01-0206
The application of controlled auto-ignition (CAI) combustion in gasoline direct injection (GDI) engines is becoming of more interest due to its great potential of reducing both NOx emissions and fuel consumption. Injection timing has been known as an important parameter to control CAI combustion process. In this paper, the effect of injection timing on mixture and CAI combustion is investigated in a single-cylinder GDI engine with an air-assisted injector. The liquid and vapour phases of fuel spray were measured using planar laser induced exciplex fluorescence (PLIEF) technique. The result shows that early injection led to homogeneous mixture but late injection resulted in serious stratification at the end of compression. CAI combustion in this study was realized by using short-duration camshafts and early closure of the exhaust valves. During tests, the engine speed was varied from 1200rpm to 2400rpm and A/F ratio from stoichiometric to lean limit.
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