1,721,016 research outputs found
Virtual optimization of a 2-Stroke GDI Range Extender engine
No full textVirtual optimization of a 2-Stroke GDI Range Extender engin
CFD optimization of a 2-stroke range extender engine
No full textA very promising concept for small range extenders (peak power less than 40 kW) is represented by the 2-stroke, direct injection spark ignition engine, with scavenging and exhaust ports controlled by the piston, and an external pump. The most important issue to be addressed on this type of engines is the compliance with stringent rules on pollutant emissions, which depends on combustion patterns and the quality of the scavenging process. The latter is generally hindered by the symmetry of ports timings, but this handicap can be canceled by adopting a patented rotary valve, controlling the flow through a set of auxiliary transfer ports, and using a piston pump for delivering air to the power cylinder and enhancing the balance of the crankshaft. The paper reviews the design of a virtual engine, rated at 35 kW at 5600 rpm, and developed according to the above mentioned concepts. Design has been driven by CFD simulation, using, whenever possible, experimentally calibrated numerical models, or experimental information derived from similar projects. Particular care has been devoted to characterize the scavenging process and the flow patterns within the cylinder and through the ports, analyzing the influence of the rotary induction valve. Engine performance parameters have been predicted by using a well-established commercial software (GT-Power, by Gamma Technologies), while CFD-3D analyses have been carried out by means of a customized version of the KIVA-3V code. The whole study is conceived as the basis for the construction of a physical prototype. The power target has been virtually achieved with a very light and compact engine (estimated weight without the close-coupled electric motor: 35 kg). A three-way catalyst allows the engine to comply with the most stringent emission regulations, without relevant penalizations on fuel efficiency. Furthermore, the engine can work with lean mixtures, achieving a minimum specific fuel consumption comparable to a current automotive Diesel engine (223 g/kWh). This excellent result is due to the low friction and pumping losses of the 2-Stroke engine, as well as to the compactness of the combustion chamber and the capability to stratify the charge
Optimization of the Combustion Chamber Design of a Natural Gas-Diesel Dual Fuel Engine Running at Low Load
No full textA new design concept for 2-Stroke aircraft Diesel engines
Full text linkHigh power density, low weight, compact dimensions, high efficiency as well as reliability are the key factors in designing and dimensioning piston engines for General Aviation and Unmanned Aerial Vehicle (UAV) power plants. Despite of new available technologies, conventional solutions are still struggling to fulfill simultaneously all those requirements.
The paper explores the application of a new design of 2-Stroke externally scavenged engines to aircraft. The new concept basically consists in the use of a patented rotary valve for controlling the flow through a set of inlet ports, enabling supercharging and the achievement of extremely high power densities compared to conventional solutions. The scavenging is realized by using an external pump, made up of a further cylinder, whose piston is connected to the same crankshaft. The piston pump allows the crankcase to be used as a conventional oil sump, and greatly improves the crankshaft balance. No poppet valves or camshafts need to be installed, since the flow is driven by piston-controlled ports and by two sets of reed valves.
The engine can adopt two types of combustion system: Gasoline Direct Injection (GDI) for SI operations, and Direct Injection Common Rail for Diesel cycle. The paper is focused on the last version, since it can run on standard aircraft fuel.
The Diesel engine has three cylinders and three piston pumps, for a total displacement of 1.5 liter The engine is turbocharged and inter-cooled, in order to reach a power target, at sea level, of 150 kW@4000 rpm. Another fundamental target is the minimum power of 100 kW, at the altitude of 20,000 feet.
The paper reviews the design of the engine and presents the numerical prediction of the key performance parameters
Combustion Analysis on an IDI CI Engine Fueled by Microalgae
No full textThe third generation of biodiesels, derived from microalgae, is one of the most interesting options for the replacement of fossil fuels. While the use of first generation biodiesels on different types of compression ignition engines is well documented in the open literature, much less information is available on algal fuels. As a matter of fact, the influence on combustion and pollutant emissions is not definitively assessed, depending on the combination of the specific features of both fuel and engine. The aim of this paper is to analyze the combustion process in a small industrial engine fueled by an algal Biodiesel, blended with standard Diesel fuel. The blend composition is the one typically used in most applications, i.e. 20% of biodiesel and 80% of Diesel (B20). In order to give a rigorous reference, all the experiments have been repeated with pure Diesel fuel, and with a blend made up of 20% of commercial rapeseed biodiesel, one of the most representative first generation biofuel. The experimental campaign has been carried out on an IDI 4-cylinder 1.4 liter naturally aspirated engine. It was found that the algal B20 slightly improves fuel conversion efficiency, in comparison to standard Diesel. This result is due to the different combustion rate, as well as to a more complete burning process. Differently from previous studies, no advantage has been found in terms of soot. Finally the algal B20 requires a higher fuel mass flow rate in order to compensate the lower heating value
Advances in The Design of Two-Stroke, High Speed, Compression Ignition EnginesAdvances in Internal Combustion Engines and Fuel Technologies
No full textThe most difficult challenge for modern 4-Stroke high speed Diesel engines is the limitation of pollutant emissions without penalizing performance, overall dimensions and production costs, the last ones being already higher than those of the correspondent S.I. engines.
An interesting concept in order to meet the conflicting requirements mentioned above is the 2-Stroke cycle combined to Compression Ignition. Such a concept is widely applied to large bore engines, on steady or naval power-plants, where the advantages versus the 4-Stroke cycle in terms of power density and fuel conversion efficiency (in some cases higher than 50% [1]) are well known. In fact, the double cycle frequency allows the designer to either downsize (i.e. reduce the displacement, for a given power target) or “down-speed” (i.e. reduce engine speed, for a given power target) the 2-stroke engine. Furthermore, mechanical efficiency can be strongly improved, for 2 reasons: i) the gas exchange process can be completed with piston controlled ports, without the losses associated to a valve-train; ii) the mechanical power lost in one cycle is about halved, in comparison to a 4-Stroke engine of same design and size, while the indicated power can be the same: as a result, the weight of mechanical losses is lower
2-Stroke Multipurpose Externally Scavenged Hi Efficiency Engines
No full textThis work is related to debate on potential of the 2-Stroke concept applied to Range Extender engines, proposing 3 different configurations: 1) Supercharged, Compression Ignition; 2) Turbocharged, Compression Ignition; 3) Supercharged, Gasoline Direct Injection. All the engines feature a single power cylinder of 0.49l, external air feed by piston pump and an innovative induction system. The scavenging is of the Loop type, without poppet valves, and with a 4-Stroke like lubrication system (no crankcase pump). Engine design has been supported by CFD simulations, both 1D (engine cycle analysis) and 3D (scavenging, injection and combustion calculations). The strong points found for this family of engines are: high power density (up to 122 kW/l) and power to weight ratio; low raw emissions; compactness (design integrated with the electric motor); low production costs (no valvetrain, no EGR system); excellent balance of inertia forces (thanks to the piston pump installed on the same crankshaft, at 90° from the power cylinder); mechanical reliability (no exotic solutions, effective lubrication system); low noise (low engine speed thanks to the double frequency of the cycle); low specific fuel consumption. All those characteristics would be suitable for different application: steady generator, automotive, aviation, etc
Two-Stroke Gasoline Engines for Small-Medium Passenger Cars
No full textAmong all the reciprocating internal combustion engines, gasoline two-strokes can reach the highest specific power, making this technology a natural enabler of downsizing and/or down-speeding. In addition, multi-cylinder 2-stroke engines may be an ideal match for electrical superchargers, providing very efficient power units. The paper explores through CFD-1d simulations and empirical hypotheses the potential of a 3-cylinder, 1.0 liter, GDI 2-stroke turbocharged engine featuring a patented rotary valve for the optimization of the scavenging process, the latter being of the loop type (piston-controlled ports). The lubrication system is the same of a 4-stroke engine (no crankcase pumps). The supercharging system is made up of a turbocharger and an electric compressor, serially connected. The power of the electric compressor is limited to 2 kW, in order to comply with standard automotive 12 V electric systems. The proposed engine easily achieves the goal of 95 kW at 4500 rpm, and 210 Nm at 1500 rpm, resulting also quite fuel efficient at any operating conditions (best point: 211 g/kWh, achieved with stratified charge)
Development of a High Performance Engine for a Formula SAE Racer
No full textThe paper reviews the theoretical and experimentaldevelopment of the engine powering the 2011 Formula SAEsingle seater of the University of Modena and Reggio Emilia(UNIMORE). The general design criteria followed by theUNIMORE team are discussed and compared to those chosenby other competitors. In particular, the reasons supporting theselection of the engine type (single cylinder by Husqvarna)are explained in details. The adoption of a single cylinder,instead of the more powerful four-in-line, required a muchbigger effort for getting an acceptable level of brake power.Therefore, the development was massively supported by CFDsimulation (both 1D and 3D) and by experiments. It wasfound that the most important design areas for the singlecylinder are: the intake system, including the restrictor (20mm), the intake runner and the plenum, and the muffler. GTPowerwas the main CFD tool used in the project: after theexperimental calibration of the base model, full loadsimulation have been carried out in order to optimize theengine geometric parameters, taking into account a number ofconstraints, decided by the team. The optimization goal wasnot just to have an engine as powerful as possible, but to findthe best package of both engine and vehicle.Besides full load steady calculations, also transient enginesimulations during a car acceleration have been performed.Engine-out noise was monitored too, in particular at thetesting conditions indicated by the competition rules.Finally, a complete performance characterization of theoptimized engine was predicted before starting the testing atthe dynamometer bed. These performance maps helped tospeed up the calibration process, and allowed the team also toget a rough estimation of the car fuel efficiency during theendurance event
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