Refine Your Search

Topic

Author

Affiliation

Search Results

Technical Paper

Wall Temperature Effect on SI-CAI Hybrid Combustion Progress in a Gasoline Engine

2013-04-08
2013-01-1662
SI-CAI hybrid combustion, also known as spark-assisted compression ignition (SACI), is a promising concept to extend the operating range of CAI (Controlled Auto-Ignition) and achieve the smooth transition between spark ignition (SI) and CAI in the gasoline engine. In order to investigate the effect of the thermal boundary condition on the hybrid combustion, the experiments with different coolant temperatures are performed to adjust the chamber wall temperature in a gasoline engine. The experimental results indicate that increasing wall temperature would advance the combustion phasing, enlarge the peak heat release rate and shorten the combustion duration. While the capacity of the wall temperature effect on the hybrid combustion characteristics are more notable in the auto-ignition dominated hybrid combustion.
Technical Paper

Transient SI Engine Emissions Measurements on the FTP75 Drive Cycle with a Fast Response CO Instrument

2001-09-24
2001-01-3540
This paper describes the application of a non-dispersive infrared-based instrument designed to measure CO with a response time of 7ms. Spark ignition engine emission measurements recorded during the first 505 seconds of an FTP75 drive-cycle for a 4 cylinder engine are presented, including fast response hydrocarbon and NO measurements. An analysis of the engine-out (pre-catalyst) exhaust gas is provided. Data collected simultaneously with a standard emissions test stand and conventional dilution tunnel are compared to the high frequency measurements. Fast CO analysis provides new insight into cold-start fuelling calibration and cylinder-to-cylinder AFR variation. Under rich conditions, the strong dependence of CO production on the quantity of excess fuel allows a significantly faster estimate of engine stoichiometry than a UEGO sensor.
Technical Paper

Transient Gaseous and Particulate Emissions Measurements on a Diesel Passenger Car including a DPF Regeneration Event

2006-04-03
2006-01-1079
The gaseous and particulate emissions from a diesel passenger car have been studied during cold start and Diesel Particulate Filter (DPF) regeneration events occurring during the New European Drive Cycle (NEDC). During the initial phase of the cycle, Diesel Oxidation Catalyst (DOC) light-off was seen to be highly dynamic with catalyst efficiency changing dramatically with changes in catalyst temperature. Accumulation mode particulate emissions were sampled directly from the exhaust after the DPF. From cold start with a clean (regenerated) DPF, accumulation mode particle emissions were seen to be very much higher than those from a loaded DPF. This accumulation mode slip lasted only approximately 200 seconds. During regeneration of the DPF, the oxidation of trapped soot was associated with a large tailpipe emission of nucleation mode particles.
Technical Paper

Time-Resolved Measurements and Analysis of In-Cylinder Gases and Particulates in Compression-Ignition Engines

1996-05-01
961168
The extraction of small quantities of gas and particulates from diesel engine cylinders allows time-resolved gas and particulate analysis to be performed outside the engine during a short window of a few degrees crank angle at any stage of the engine cycle. The paper describes the design features and operation of a high-speed, intermittent sampling valve for extracting in-cylinder gases and particulates from diesel engines at any selected instant of the combustion process. Various sampling valve configurations are outlined. Detailed analysis of gas flow through the valve and the performance of the electromagnetic actuator and plunger are given in order to facilitate the design of the sampling valve. Finally, examples of the uses of the sampling valve in a direct-injection diesel engine are provided. These demonstrate how gaseous emissions such as NOx, uHC, CO2, and particulate emissions can be sampled at any part of the combustion process and analysed.
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.
Journal Article

The Performance Characteristics of an Production Oriented Air Hybrid Powertrain

2010-04-12
2010-01-0821
In a previous paper [ 1 ], the authors have proposed a cost effective air hybrid concept based on a proprietary intake system and cam profile switching (CPS) system [ 2 ]. It was shown through engine simulations that the pneumatic hybrid operation could be achieved with about 15% regenerative efficiency. The proposed air hybrid operation can be achieved with proven technologies and engine components and hence it represents a cost-effective, reliable and quick deployable solution for low carbon vehicles. In this work, a four-cylinder 2 litre diesel engine has been modelled to operate on refined air hybrid engine configurations and the braking and motoring performance of each configuration have been studied. Both air hybrid systems can be constructed with production technologies and incur minimum changes to the existing engine design.
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 Influence of Intake Port and Pent-Roof Structures on Reversed Tumble Generation of a Poppet-Valved Two-Stroke Gasoline Engine

2014-04-01
2014-01-1130
In order to minimize short-circuiting of the intake charge in the poppet-valved 2-stroke engine, measures are taken to generate reversed tumble in the cylinder. In this study, five different types of intake ports and three types of pent-roof geometries were designed and analysed of their ability to generate and maintain reversed tumble flows by means of CFD simulation for their intake processes on a steady flow rig. Their flow characteristics were then assessed and compared to that of the vertical top-entry ports. Results show that the side-entry port designs can achieve comparatively high tumble intensity. The addition of flow deflectors inside the side-entry ports does not have much effect on the reversed tumble ratio. The top-entry ports have the highest flow coefficient among all the intake ports examined as well as producing strong reversed tumble. It is also found that the pent-roof at a wider angle helps to strengthen the tumble intensity due to increased air flow rate.
Technical Paper

The Effects on Diesel Combustion and Emissions of Reducing Inlet Charge Mass Due to Thermal Throttling with Hot EGR

1998-02-23
980185
This paper is a complementary to previous investigations by the authors (1,2,3,4) on the different effects of EGR on combustion and emissions in DI diesel engine. In addition to the several effects that cold EGR has on combustion and emissions the application of hot EGR results in increasing the inlet charge temperature, thereby, for naturally aspirated engines, lowering the inlet charge mass due to thermal throttling. An associated consequence of thermal throttling is the reduction in the amount of oxygen in the inlet charge. Uncooled EGR, therefore, affects combustion and emissions in two ways: through the reduction in the inlet charge mass and through the increase in inlet charge temperature. The effect on combustion and emissions of increasing the inlet charge temperature (without reducing the inlet charge mass) has been dealt with in ref. (1).
Technical Paper

The Effect of Spark Ignition on the CAI Combustion Operation

2005-10-24
2005-01-3738
The present paper aims to investigate the influence of spark ignition on CAI combustion based on internal EGR strategy. Controlled Auto-ignition (CAI) combustion is facilitated in a Ricardo single cylinder engine with a pair of special camshafts, which valve lift and cam profile are modified to trap enough hot residuals. Operation regions and other detailed combustion characteristics of the CAI engine operation are analyzed and compared between pure CAI mode and the CAI mode with assisted spark ignition. The results show that spark ignition can play an important role in controlling CAI combustion ignition in low load boundary region. The low temperature chemical reaction process is shortened and the auto ignition timing is advanced due to the spark discharge. Meantime, lower fuel consumption and cycle-to-cycle variations can be achieved.
Technical Paper

The Effect of Different Ageing Conditions on Spatial Variations in Emissions Across the Radius of a Close-coupled After-treatment System

2005-04-11
2005-01-1095
Using local emissions measurements immediately downstream of a close-coupled catalyst, spatial variations in emissions have been analysed for close-coupled catalysts with different ageing histories. Comparison of the radial emissions profiles between a uniformly-aged (oven-aged) catalyst and two vehicle-aged parts suggests that the vehicle-aged parts have substantial variations in catalyst damage across the radius of the catalyst. The radial variations in damage were confirmed by bench reactor and post-mortem studies. The radial catalyst damage profiles inferred from engine-based evaluations of vehicle aged catalysts show broad correlation with high flow areas identified by CFD predictions and high temperature regions as measured during engine tests.
Technical Paper

The Dilution, Chemical, and Thermal Effects of Exhaust Gas Recirculation on Disesel Engine Emissions - Part 4: Effects of Carbon Dioxide and Water Vapour

1997-05-01
971660
This paper deals with the effects on diesel engine combustion and emissions of carbon dioxide and water vapour the two main constituents of EGR. It concludes the work covered in Parts 1, 2, and 3 of this series of papers. A comparison is presented of the different effects that each of these constituents has on combustion and emissions. The comparison showed that the dilution effect was the most significant one. Furthermore, the dilution effect for carbon dioxide is higher than that for water vapour because EGR has roughly twice as much carbon dioxide than water vapour. On the other hand, the water vapour had a higher thermal effect in comparison to that of carbon dioxide due to the higher specific heat capacity of water vapour. The chemical effect of carbon dioxide was, generally, higher than that of water vapour.
Technical Paper

The Dilution, Chemical, and Thermal Effects of Exhaust Gas Recirculation on Diesel Engine Emissions - Part 3: Effects of Water Vapour

1997-05-01
971659
Water vapour is a main constituent of exhaust gas recirculation (EGR) in diesel engines and its influence on combustion and emissions were investigated. The following effects of the water vapour were examined experimentally: the effect of replacing part of the inlet charge oxygen (dilution effect), the effect of the higher specific heat capacity of water vapour in comparison with that of oxygen it replaces (thermal effect), the effect of dissociation of water vapour (chemical effect), as well as the overall effect of water vapour on combustion and emissions. Water vapour was introduced into the inlet charge, progressively, so that up to 3 percent of the inlet charge mass was displaced. This was equivalent to the amount of water vapour contained in 52 percent by mass of EGR for the engine operating condition tested in this work.
Technical Paper

The Dilution, Chemical, and Thermal Effects of Exhaust Gas Recirculation on Diesel Engine Emissions - Part 2: Effects of Carbon Dioxide

1996-05-01
961167
This is the second of a series of papers on how exhaust gas recirculation (EGR) affects diesel engine combustion and emissions. It concentrates on the effects of carbon dioxide (CO2) which is a principal constituent of EGR. Results are presented from a number of tests during which the nitrogen or oxygen in the engine inlet air was progressively replaced by CO2 and/or inert gases, whilst the engine speed, fuelling rate, injection timing, inlet charge total mass rate and inlet charge temperature were kept constant. In one set of tests, some of the nitrogen in the inlet air was progressively replaced by a carefully controlled mixture of CO2 and argon. This ensured that the added gas mixture had equal specific heat capacity to that of the nitrogen being replaced. Thus, the effects of dissociated CO2 on combustion and emissions could be isolated and quantified (chemical effect).
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

The Combustion and Emission Characteristics of Ethanol on a Port Fuel Injection HCCI Engine

2006-04-03
2006-01-0631
With the application of valve timing strategy to inlet and exhaust valves, Homogeneous Charge Compression Ignition (HCCI) combustion was achieved by varying the amount of trapped residuals through negative valve overlap on a Ricardo Hydra four-stroke port fuel injection engine fueled with ethanol. The effect of ethanol on HCCI combustion and emission characteristics at different air-fuel ratios, speeds and valve timings was investigated. The results indicate that HCCI ethanol combustion can be achieved through changing inlet and exhaust valve timings. HCCI ethanol combustion range can be expanded to high speeds and lean burn mixture. Meanwhile, the factors influencing ignition timing and combustion duration are valve timing, lambda and speeds. Moreover, NOx emissions are extremely low under HCCI combustion. The emissions-speed and emissions-lambda relationships are obtained and analyzed.
Technical Paper

The Application of Controlled Auto-Ignition Gasoline Engines -The Challenges and Solutions

2019-04-02
2019-01-0949
Controlled Auto-Ignition (CAI) combustion, also known as Homogeneous Charge Compression Ignition (HCCI), has the potential to simultaneously reduce the fuel consumption and nitrogen oxides emissions of gasoline engines. However, narrow operating region in loads and speeds is one of the challenges for the commercial application of CAI combustion to gasoline engines. Therefore, the extension of loads and speeds is an important prerequisite for the commercial application of CAI combustion. The effect of intake charge boosting, charge stratification and spark-assisted ignition on the operating range in CAI mode was reviewed. Stratified flame ignited (SFI) hybrid combustion is one form to achieve CAI combustion under the conditions of highly diluted mixture caused by the flame in the stratified mixture with the help of spark plug.
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

Study on Layered Close Loop Control of 4-Stroke Gasoline HCCI Engine Equipped with 4VVAS

2008-04-14
2008-01-0791
Homogeneous Charge Compression Ignition (HCCI) has the potential of reducing fuel consumption as well as NOx emissions. However, it is still confronted with problems in real-time control system and control strategy for the application of HCCI, which are studied in detail in this paper. A CAN-bus-based distributed HCCI control system was designed to implement a layered close loop control for HCCI gasoline engine equipped with 4VVAS. Meanwhile, a layered management strategy was developed to achieve high real-time control as well as to simplify the couplings between the inputs and the outputs. The entire control system was stratified into three layers, which are responsible for load (IMEP) management; combustion phase (CA50) control and mechanical system control respectively, each with its own specified close loop control strategy. The system is outstanding for its explicit configuration, easy actualization and robust performance.
Technical Paper

Study of Particle Number Emissions from a Turbocharged Gasoline Direct Injection (GDI) Engine Including Data from a Fast-Response Particle Size Spectrometer

2011-04-12
2011-01-1224
A study has been conducted to measure the particle number emissions from a current-generation 1.6-liter, Euro IV-compliant turbo-charged Gasoline Direct Injection (GDI) passenger car engine. A fast-response particle size spectrometer was used along with a PMP-compliant particulate measurement system to measure the effect of various engine parameters on the particulate emissions during the New European Drive Cycle (NEDC). Overall particle number is shown along with further analysis of the transient particle emissions. The cold start clearly affects particle formation with approximately 50% of the cumulative particle number being emitted within 200 seconds of the start. Even beyond 200 seconds, the particle number emissions fall as the test progresses and are generally consistent with increases in engine coolant temperature indicating that cold engine fuel preparation issues are contributing to the particle number count.
X