Although diesel engines still power most of the heavy-duty transit buses in the United States, many major cities are also operating fleets where a significant percentage of buses is powered by lean-burn natural gas engines. Emissions from these buses are often expressed in distance-specific units of grams per mile (g/mile) or grams per kilometer (g/km), but the driving cycle or route employed during emissions measurement has a strong influence on the reported results. A driving cycle that demands less energy per unit distance than others results in higher fuel economy and lower distance-specific oxides of nitrogen emissions. In addition to energy per unit distance, the degree to which the driving cycle is transient in nature can also affect emissions.
Alcohols like methanol (CH3OH) and ethanol (C2H5OH) are well known alternative fuels. Ethanol, which replaced MTBE in California, is added to regular gasoline up to 5% without any modifications required to a normal gasoline engine. Recently E85, an ethanol-gasoline mixture of 85% ethanol and 15% gasoline derived from crude oil, got attention as an alternative fuel due to high gas prices and environmental acceptance. Therefore, it is important to understand the basics of alcohol combustion. Experimental and numerical studies are conducted on extinction of methanol and ethanol flames in premixed laminar flows. The studies are performed in a counter-flow configuration. The burner used in the experiments is made up of two opposing ducts. Two configurations are considered. In one configuration, a premixed reactant stream made up of vaporized fuel, air, and nitrogen is introduced from one duct and nitrogen from the other.
Hydrogen addition to ethylene and acetylene -air laminar diffusion flames has shown substantial reduction in soot formation. In the present study, hydrogen was carbureted in a single cylinder, naturally aspirated DI diesel engine, and combustion events and smoke emissions were studied. With hydrogen induction particularly when its energy share increased above 15%, contrary to the results reported by earlier investigators a sharp decrease in ignition delay (ID), very high peak pressure rates, increase in smoke and loss in fuel efficiency were observed. At hydrogen energy share of about 30%, ignition delay drops to nearly 0-1degree CA and peak rates of pressure rise to 25-30 bar/deg CA. Smoke emissions at low hydrogen induction rates reduced slightly but increased sharply above 15 to 20% hydrogen energy share.
Highly efficient wall-flow diesel particulate filters (DPF) are the primary means of PM emissions control in light-duty diesel vehicles. The successful commercialization of DPF technology has allowed combining attractive characteristics (good fuel economy, high low-end torque characteristics) of a diesel engine with significant PM emissions reductions to meet the stringent legislation. The design for advanced filter systems is driven by the lifetime pressure drop requirements with the accumulation of non-combustible materials (ashes) over time in the filter. More compact filter designs can be achieved by using filters with the proprietary Asymmetric Cell Technology (ACT) providing a larger inlet channel volume and therefore a higher ash storage capacity in the same space envelope without compromising the filter bulk heat capacity and mechanical integrity.
The future exploitation of global energy resources is currently being hotly debated by politicians and by sections of the scientific community but there is little guidance available in the engineering literature as to the full gamut of options or their viability with respect to fuelling the world's vehicles. In the automotive industry extensive research is being undertaken on the use of alternative fuels in internal combustion engines and on the development of alternative powerplants but often the long-term strategy and sustainability of the energy sources to produce these fuels is not clearly enunciated. The requirement to reduce CO2 emissions in the face of accelerating global warming scenarios and the depletion of fossil-fuel resources has led to the widespread assumption that some form of ‘hydrogen economy’ will prevail; this view is seldom justified or challenged.
The thermal conditions of an engine structure, in particular the wall temperatures, have been shown to have a great effect on the HCCI engine combustion timing and burn rates through wall heat transfer, especially during transient operations. This study addresses the effects of thermal inertia on combustion in an HCCI engine. In this study, the control of combustion timing in an HCCI engine is achieved by modulating the residual gas fraction (RGF) while considering the wall temperatures. A multi-cylinder engine simulation with detailed geometry is carried out using a 1-D system model (GT-Power®) that is linked with Simulink®. The model includes a finite element wall temperature solver and is enhanced with original HCCI combustion and heat transfer models. Initially, the required residual gas fraction for optimal BSFC is determined for steady-state operation. The model is then used to derive a map of the sensitivity of optimal residual gas fraction to wall temperature excursions.
Homogeneous Charge Compression Ignition (HCCI) combustion offers high fuel efficiency and some emissions benefits. However, it is difficult to control and stabilize combustion over a significant operating range because the critical compression ratio and intake temperature at which HCCI combustion can be achieved vary with operating conditions such as speed and load as well as with fuel octane number. Replacing part of the base fuel with reformer gas, (which can be produced from the base hydrocarbon fuel), alters HCCI combustion characteristics in varying ways depending on the replacement fraction and the base fuel auto-ignition characteristics. Because fuel injection quantities and ratios can be altered on a cycle-by-cycle basis during operation, injecting a variable blend of reformer gas and base fuel offers a potential HCCI combustion control mechanism.
Combustion processes employing different injection strategies in a High-Speed Direct Inject (HSDI) diesel engine were investigated using a narrow angle injector (70 degree). Whole-cycle combustion was visualized using a high-speed digital video camera. The liquid spray evolution process was imaged by the Mie-scattering technique. Different injection strategies were employed in this study including early pre-Top Dead Center (TDC) injection, post-TDC injection, multiple injection strategies with an early pre-TDC injection and a late post-TDC injection. Smokeless combustion was obtained under some operating conditions. Compared with the original injection angle (150 degree), some new combustion phenomena were observed for certain injection strategies. For early pre-TDC injection strategies, liquid fuel impingement is observed that results in some newly observed fuel film combustion flame (pool fires) following an HCCI-like weak flame.
The controlled auto-ignition1 (CAI) improves dramatically the efficiency of a gasoline engine and brings it in close competition to the diesel engine without penalties in emissions. With CAI run in part-load, the gasoline engine reaches a standard driving cycle advantage of 12% in fuel economy compared to current commercial engines operating solely in homogeneous gasoline direct injection (GDI) with a stoichiometric charge. CAI is run lean in fuel and thus limited in load similar to the second generation spray guided stratified GDI strategy that promises at least the same fuel efficiency but is plagued with high NOx emissions requiring complex after-treatment systems. Although CAI produces negligible NOx, and a simple three-way catalyst suffices, it depends strongly on judiciously operating the engine within the dynamic operating cycle. Direct injection, valve actuation flexibility and advanced controls based on combustion state sensing are indispensable for this.
Homogeneous Charge Compression Ignition (HCCI) engines offer high fuel efficiency and some emissions benefits. However, it is difficult to control and stabilize combustion over a sufficient operating range because the critical compression ratio and intake temperature at which HCCI combustion can be achieved varies with operating conditions such as speed and load as well as with fuel octane number. Replacing part of the base fuel with reformer gas, (which can be produced from the base hydrocarbon fuel), alters HCCI combustion characteristics in varying ways depending on the replacement fraction and the base fuel auto-ignition characteristics. Injecting a blend of reformer gas and base fuel offers a potential HCCI combustion control mechanism because fuel injection quantities and ratios can be altered on a cycle-by-cycle basis.
In an effort to improve the technology of motorcycle safety, we have developed an advanced motorcycle using electronic control and information communication technologies. The Motorcycle AFS (Adaptive Front-lighting System) measures the bank angle and rotates the headlight to the rolling direction. As a result, the AFS improves the visibility of a motorcycle that is cornering at nighttime. The Motorcycle Night Vision System early detects pedestrians ahead at nighttime by using an infrared camera. This system captures infrared camera images that are not visible to the naked eye, extracts the figure of pedestrians by image processing, and provides the rider with the information on the presence of detected pedestrians.
The present turbo-charged direct injection 660cm3 engine achieves low engine-out emissions and low fuel consumption with high engine output because of synergies of direct injection combined with turbo-charging. The fuel mixture in the combustion chamber is slightly stratified and is slightly richer than stoichiometric in the vicinity of the spark plug at the time of ignition, thereby yielding stable combustion. This reduces the unburned HC at cold start operation and makes is possible to retard spark timing at cold start operation, which activates the catalyst quicker and reduces exhaust emissions. Also, the stable combustion allows introduction of higher EGR(Exhaust Gas Recirculation) rates, which reduces NOx emission and improves fuel economy resulting from low pumping loss. Due to charge cooling, the compression ratio can be increased, which has inherent fuel economy advantage as well.
In an attempt for further improvement of exhaust gas purification and fuel economy, an electronically controlled fuel injection (FI) system has been applied to small size motorcycles. As compared to a similar system for cars, FI systems for small two wheeled vehicles are required to be small, lightweight and low cost. In order to meet these requirements, authors developed a new control method of determining the required quantity of fuel. This system removes the intake pressure sensor of the intake pipe that exists in the conventional FI system. From correlating the peak intake pressure in the intake pipe with the quantity of intake air closely, the peak intake pressure is estimated by using rotation change of the crankshaft. The required quantity of fuel is injected into the engine intake pipe determined by the map set up in the peak intake pressure and the fuel injection period.
An energy management strategy is needed to optimally allocate the driver's power demands to different power sources in the fuel cell hybrid vehicles. The driver's power demand is modelled as a Markov process in which the transition probabilities are estimated on the basis of the observed sample paths. The Markov Decision Process (MDP) theory is applied to design a stochastic energy management strategy for fuel cell hybrid vehicles. This obtained control strategy was then tested on a real time simulation platform of the fuel cell hybrid vehicles. In comparison to the other 3 strategies, the constant bus voltage strategy, the static optimization strategy and the dynamic programming strategy, simulations in the Beijing bus driving cycle demonstrate that the obtained stochastic energy management strategy can achieve better performance in fuel economy in the same demand of dynamic.
A Swedish MK1 diesel fuel and a European gasoline of ∼95 RON have been compared in a single cylinder CI engine operating at 1200 RPM with an intake pressure of 2 bar abs., intake temperature of 40°C and 25% stoichiometric EGR at different fuelling rates and using different injection strategies. For the same operating conditions, gasoline always gives much lower smoke compared to the diesel fuel because of its higher ignition delay; this usually allows the heat release to be separate in time from the injection event. NOx can be controlled by EGR. With dual injection, for diesel fuel, there can be significant heat release during the compression stroke because of the pilot injection earlier in the compression stroke. For a fixed total fuelling rate, compared to single injection, this reduces fuel efficiency and increases the lowest achievable level of smoke.
Study of noise radiating from an internal combustion engine is of great interest and challenge to automobile engineers. Design of low-noise engines is becoming increasingly important because of progressively stringent regulatory requirements. Further, customers are demanding products that have pleasing sound quality. As any improvement in this area will have significant impact on image of the product, addressing these concerns will prove highly beneficial. Most of the critical engine performance parameters - power, fuel economy, and emissions - impact engine noise and sound quality. Therefore, to avoid intractable engine noise and sound quality problems later, it is very imperative to deal with them upfront in the development process.
In recent motorcycles, radiation noise from engine surface dominates high percentage since enough measures have been taken for other noise sources such as intake, exhaust and drive train noise. Since most motorcycle engines consist with transmissions, the radiation noise is caused not only from combustion pressure but also from the gear meshing. Therefore radiation noise accounts for higher frequency than the other noise sources like intake and exhaust. At present, in order to reduce the radiation noise, we have to take countermeasures on actual engines since CAE is difficult to apply because of the characteristic of many high frequency components. In this study, technical build-up was made to enable the estimation of the engine radiation noise. Build-up was made of the modeling know-how of FE models capable of analyzing high frequency. We determined excitation force to the bearing housings in consideration of combustion force and gear meshing force based on the experimental data.
Damper lag and hysteresis are important parameters affecting the dynamic response of the hydraulic shock absorbers. The response of the suspension unit to road excitation strongly influences motorcycle ride comfort. Overall ride comfort of a motorcycle, under various operating conditions, is a result of very complex system dynamics, where the damper dynamics has a major share. This makes it imperative to include damper lag as a critical parameter for ride comfort optimization. Analytical models are available to predict the dynamic behaviour of a hydraulic damper, however their ability in capturing the lag and hysteretic characteristics is limited. Capturing such dynamic phenomenon through mathematical modeling can become very intricate and involved, thus making the task of analysis and simulation of ride comfort further complex. Literature available on experimental research in establishing the effect of damper lag on overall ride comfort is found to be very limited.
This paper reports the results of a fuel economy and regulated emissions survey of 15 gasoline powered generators. Tests were conducted at Environment Canada's Emission Research and Measurement Division (ERMD) facilities in Ottawa. The generators ranged in output capacity from 0.9kW to 7.0kW maximum rated output (MRO). They were obtained from a variety of sources including commercial rental companies and from other Environment Canada Divisions. The generators were operated on summer grade commercial fuel over a 6 mode test cycle when possible. The testing was designed to mimic the certification test the engines would undergo in an engine dynamometer test configuration with the exception that the loading was simulated by a load bank connected to the generators electrical output(s).