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Video

Characterization and Potential of Dual Fuel Combustion in a Modern Diesel Engine

2011-12-05
Diesel Dual Fuel, DDF, is a concept which promises the possibility to utilize CNG/biogas in a compression ignition engine maintaining a high compression ratio, made possible by the high knock resistance of methane, and the resulting benefits in thermal efficiency associated with Diesel combustion. Presenter Fredrik K�nigsson, AVL Sweden
Video

Blue Bird Propane Powered Vision School Bus

2012-04-10
Propane autogas, the world?s third most-used engine fuel, powers vehicles, transit buses, and now school buses. Blue Bird has recently launched the Next Generation Vision type C school bus, powered by a ROUSH CleanTech liquid propane autogas fuel system and a Ford 6.8L V10 engine. The bus reduces operating costs by up to 40%, greenhouse gas emissions by up to 24%, and maintains the factory horsepower, torque, and towing capacity ratings. Learn about how school districts are saving over $.30 / mile using this clean, domestically-produced fuel. Presenter Brian Carney, Roush CleanTech.
Video

Propane Autogas: The Clear Choice

2012-04-10
The presentation by Tucker Perkins, President of CleanFUEL USA, provides important information to those wanting to learn about alternative fuels, specifically propane autogas. CleanFUEL USA provides liquid propane injection engine system for the 6L engine in the GM G4500 cutaway chassis used in many Type A busses. They are also developing an 8L engine in partnership with Freightliner/ThomasBuilt Bus for the Type C bus. This presentation discussed many of the advantages of propane autogas use, such as better economics, lower emissions, and inexpensive infrastructure for the fueling network. Presenter Tucker Perkins, CleanFUEL USA
Video

Powertrain Innovation Requires Infrastructure Innovation!

2012-04-10
Who are the people who know the most about the buses in your fleet? They are most likely the operators and the servicing technicians. They are also the key people whose knowledge, level of training and attitude can determine the success or failure of new powertrain technologies. Training and recruitment of both need to be held to a higher standard than we have seen in the past. I will argue that even the culture of those involved in fleet operations needs to be changed. The bar for technical competence and product knowledge needs to be raised for operators and technicians. In return managers should find ways to include them as stakeholders, investing them with both additional responsibility and accountability. This will require greater access to training and recognition of achievement. Where are the busses stored and serviced? Most likely in an all-purpose state/county/municipal service facility servicing a variety of equipment.
Video

Natural Gas for School Buses: A Case for Using the Only Domestically Produced Alternative Fuel

2012-04-10
A review of the processes that lead to the conclusion that CNG was the best solution for the fleet, including the efforts to gain public support for alternative fuels for school buses. MISD is now home for 42 CNG powered school buses (of 200). The presentation will include training and design tips for safety and smooth operations along with maintenance considerations for using CNG. Alternative fuels, the dilemma of which comes first - refueling station or operational buses ? has an impact on grant approval and funding, bearing discussion of the option of a public/private model. Unlike other alternative fuels, CNG has a national security impact Presenter Charles Stone, Mansfield Indep School Dist
Video

Development of High-Efficiency Rotary Engines

2012-05-10
In this presentation, we will explain how the traditional Miller Cycle - which has its limitations in the traditional four-stroke, Otto Cycle engine provides new opportunities for greater fuel efficiency gains and engine downsizing when incorporated in a split-cycle combustion process. Results will also be shared from studies showing how these implementations can provide both significant drops in fuel consumption and increases in power when incorporated into some of today's most economic vehicles. Presenter Stephen Scuderi, Scuderi Group LLC
Collection

Natural Gas Engines and Vehicles, 2013

2013-04-09
The 9 papers in this technical collection cover fuel injection, combustion, controls, performance and emissions of SI engines fueled with methane based fuels such as natural gas, producer gas, coke oven gas or hydrogen-natural gas blends.
Collection

Natural Gas Engines and Vehicles, 2011

2011-04-12
The 5 papers in this technical paper collection cover natural gas engines and vehicles. Topics include: sliding mode control of air path in diesel-dual-fuel engine; optimization of natural gas automotive engine cooling jacket using CFD analysis; waste coke oven gas used as a potential fuel for engines; and more.
Technical Paper

LPG and Prechamber as Enabler for Highly Performant and Efficient Combustion Processes Under Stoichiometric Conditions

2021-09-05
2021-24-0032
The European Union has defined legally binding CO2-fleet targets for new cars until 2030. Therefore, improvement of fuel economy and carbon dioxide emission reduction is becoming one of the most important issues for the car manufacturers. Today’s conventional car powertrain systems are reaching their technical limits and will not be able to meet future CO2 targets without further improvement in combustion efficiency, using low carbon fuels (LCF), and at least mild electrification. This paper demonstrates a highly efficient and performant combustion engine concept with a passive pre-chamber spark plug, operating at stoichiometric conditions and powered with liquefied petroleum gas (LPG). Even from fossil origin, LPG features many advantages such as low carbon/hydrogen ratio, low price and broad availability. In future, it can be produced from renewables and it is in liquid state under relatively low pressures, allowing the use of conventional injection and fuel supply components.
Technical Paper

Powertrain Friction Reduction by Synergistic Optimization of the Cylinder Bore Surface and Lubricant Part 1: Basic Modelling

2021-09-21
2021-01-1214
The piston assembly is the major source of tribological inefficiencies among the engine components and is responsible for about 50% of the total engine friction losses, making such a system the main target element for developing low-friction technologies. Being a reciprocating system, the piston assembly can operate in boundary, mixed and hydrodynamic lubrication regimes. Computer simulations were used to investigate the synergistic effect between low viscosity oils and cylinder bore finishes on friction reduction of passenger car internal combustion engines. First, the Reynolds equation and the Greenwood & Tripp model were used to investigating the hydrodynamic and asperity contact pressures in the top piston ring. The classical Reynolds works well for barrel-shaped profiles and relatively thick oil film thickness but has limitations for predicting the lubrication behavior of flat parallel surfaces, such as those of Oil Control Ring (OCR) outer lands.
Technical Paper

Powertrain Friction Reduction by Synergistic Optimization of Cylinder Bore Surface and Lubricant - Part 2: Engine Tribology Simulations and Tests

2021-09-21
2021-01-1217
In the present work, a system approach to the tribological optimization of passenger car engines is demonstrated. Experimental data and simulation results are presented to demonstrate the role of surface specifications, ring pack, and lubricant on the piston/bore tribology. The importance of in-design “pairing” of low-viscosity motor oils with the ring pack and the cylinder bore characteristics in order to achieve maximum reduction in GHG emissions and improvement in fuel economy without sacrificing the endurance is elucidated. Earlier motored friction data for two different gasoline engines - Ford Duratec and Mercedes Benz M133 - using motor oils of different viscosity grades are now rationalized using AVL EXCITE® piston/bore tribology simulations. The main difference between the engines was the cylinder bore surface: honed cast iron vs thermally sprayed, and the valve train type: direct-acting mechanical bucket (DAMB) vs roller finger follower (RFF).
Technical Paper

The Effects of the Specific Material Selection on the Structural Behaviour of the Piston-Liner Coupling of a High Performance Engine

2021-09-21
2021-01-1235
The materials commonly employed in the automotive industry are various and depend on the specific application field. For what concern the internal combustion engines the choice is guided by the thermomechanical performance required, technological constraints and production costs. Actually, for high-performance engines, steel and aluminium are the most common materials selected for the piston and the cylinder liner manufacturing. This study analyses the effect of possible material choice on the interaction between piston and cylinder liner, via Finite Element analyses. A motorcycle engine is investigated considering two possible pistons: one (standard) made of aluminium and one made of steel. Similarly, two possible cylinder liners are considered, the original one made of aluminium and a different version made of steel obtained by simply thinning the aluminium component in order to obtain two structurally equivalent components.
Technical Paper

Work Extraction Efficiency in a Series Hybrid Opposed Piston Engine

2021-09-21
2021-01-1242
This work investigates the development of a novel series hybrid architecture utilizing a single cylinder opposed piston engine. The opposed piston engine presents unique benefits in a hybrid architecture such as its lower heat transfer due to a favorable surface area to volume ratio and lack of a cylinder head, as well as the thermodynamic benefits of two stroke operation with uniflow scavenging. A particular focus of this effort is the work extraction efficiency of two design concepts. The first design concept utilizes a geartrain to couple the crankshafts of the engine in a conventional manner, providing a single power take-off for coupling to an electric motor/generator. In this design, the large inertia of the geartrain dampens the speed fluctuation of the single cylinder engine, reducing the peak torque required to for the electric machine. However, the friction losses caused by the geartrain limit the maximum work extraction efficiency.
Technical Paper

Under-Expanded Jets Characterization by Means of CFD Numerical Simulation Using an Open FOAM Density-Based Solver

2021-09-05
2021-24-0057
Among the others, natural gas (NG) is regarded as a potential solution to enhance the environmental performance of internal combustion engines. Low carbon-to-hydrogen ratio, worldwide relatively homogeneous distribution and reduced price are the reason as, lately, many researchers efforts have been put in this area. In particular, this work focuses on the characterization of the injection process inside a constant volume chamber (CVC), which could provide a contribution to the development of direct injection technologies for a gaseous fuel. Direct injection of a gaseous fuel involves the presence of under-expanded jets whose knowledge is fundamental to achieve the proper mixture formation prior to the combustion ignition. For this reason, a density based solver was developed within the OpenFOAM library in order to simulate the jet issued from an injector suitable for direct injection of methane.
Technical Paper

Fuel Economy Engine Oils: Scientific Rationale and Controversies

2021-09-05
2021-24-0067
Since a significant part of energy losses in the internal combustion engine comes from viscous dissipation, the trend has shifted toward low-viscosity oils from SAE 40 and 50 in the 1960s-1980s to current SAE 20 and lower viscosity grades. Use of low viscosity engine oils significantly reduces energy losses in the main bearing and piston/bore systems, while tribological stresses on the valvetrain - especially in flat-tappet cammed engines - may increase. This makes a strong argument for deploying new classes of friction modifiers and antiwear additives. However, development of a balanced formulation is not as straightforward as it appears, and numerous pitfalls may be encountered due to additive interactions. Another serious problem is that the definition of “fuel-economy engine oil” is rather vague, as it depends on choice of reference oil. Nowadays, the assessment of fuel economy is often based on the Sequence VIE or VIF tests using a 2012 3.6L GM V6 gasoline engine.
Technical Paper

Effects of EGR, Variable Valve Timing, High Turbulence and Water Injection on Efficiency and Emissions of a HD Stoichiometric Natural Gas Engine

2021-09-05
2021-24-0048
The EU recently decided to reduce CO2 emissions of commercial vehicle fleets by 30% until 2030. One possible way to achieve this target is to convert commercial vehicle diesel engines into stoichiometric natural gas engines. Based on this, a commercial vehicle single cylinder diesel engine with variable valve actuation and high-pressure EGR is converted into natural gas operation to increase efficiency and thus reduce CO2. Additionally, a water injection system is integrated. All three technologies are investigated on their own and in combination. To reduce longer combustion durations caused by Miller valve timing and charge dilution, a piston bowl with extra high turbulence generation is designed. Additionally, a swirl variation is carried out. The results show, that high swirl motion and high turbulence can lead to a disadvantage in efficiency despite faster combustion durations due to higher wall heat losses.
Technical Paper

Characterization of Cycle-by-Cycle Variations of an Optically Accessible Heavy-Duty Diesel Engine Retrofitted to Natural Gas Spark Ignition

2021-09-05
2021-24-0045
The combustion process in spark-ignition engines can vary considerably cycle by cycle, which may result in unstable engine operation. The phenomena amplify in natural gas (NG) spark-ignition (SI) engines due to the lower NG laminar flame speed compared to gasoline, and more so under lean burn conditions. The main goal of this study was to investigate the main sources and the characteristics of the cycle-by-cycle variation in heavy-duty compression ignition (CI) engines converted to NG SI operation. The experiments were conducted in a single-cylinder optically-accessible CI engine with a flat bowl-in piston that was converted to NG SI. The engine was operated at medium load under lean operating conditions, using pure methane as a natural gas surrogate. The CI to SI conversion was made through the addition of a low-pressure NG injector in the intake manifold and of a NG spark plug in place of the diesel injector.
Technical Paper

A Study on Prediction of Unburned Hydrocarbons in Active Pre-chamber Gas Engine: Combustion Analysis Using 3D-CFD by Considering Wall Quenching Effects

2021-09-05
2021-24-0049
To reproduce wall quenching phenomena using 3D-CFD, a wall quenching model was constructed based on the Peclet number. The model was further integrated with the flame propagation model. Combustion analysis showed that that a large amount of unburned hydrocarbons (UHCs) remained in the piston clevis and small gaps. Furthermore, the model was capable of predicting the increase in UHC emissions when there was a delay in the ignition time. The flame front cells were plotted on Peters' premixed turbulent combustion diagram to identify transitions in the combustion states. It was found that the flame surface transitioned from corrugated flamelets through thin reaction zones to wrinkled flamelets and further to laminar flamelets, which led to wall quenching. The turbulent Reynolds number (Re) decreased rapidly due to the increase in laminar flame speed and flame thickness and the decrease in turbulent intensity and turbulent scale.
Technical Paper

Model Development of a CNG Active Pre-chamber Fuel Injection System

2021-09-05
2021-24-0090
Natural gas as an internal combustion engine fuel is taking a predominant role as a mid-term solution to pollution due to combustion driven human activities both in the energy and transport sectors. Engine researchers and manufacturers are in the process of investigating and improving strategies that decrease emissions and fuel consumption, without compromising engine performance and efficiency; active pre-chamber configurations are to be accounted for as one of these. A relatively small amount of fuel (up to 10 % of the total fuel-energy requirement) is introduced in the confined volume of the pre-chamber and forms a close-to-stoichiometric mixture with fresh charge that is introduced from the main combustion chamber during the compression stroke. After spark-ignition the products of this early stage of combustion can ignite ultra-lean mixtures (with λ up to 2) through the Turbulent Jet Ignition mechanism, hence reducing fuel consumption as well as noxious emissions such as NOx.
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