Search Results

Gasoline-ethanol blends are being used or have been considered as a fuel for spark ignition engines. The motivation for using the blends varies in indifferent parts of the world and even in regions within a country. The increasing cost of gasoline, combined with regional tax incentives, is one of the reasons for increased interests in gasoline-ethanol blends in recent years in the U.S. Many vehicular engines are not designed to use a specific gasoline-ethanol blend. Rather, the engines have multi-blend capability, ranging from E0 to about E85. It is plausible that engine-out emissions will vary depending on the blend being used which may be further impacted by the level of EGR used with the blends. The present work was carried out to investigate engine out emissions when a vehicular spark-ignition engine was operated on E0 and E85 and different levels of EGR. A 4-cylinder, 2.5 liter, PFI engine was used in the experimental investigation.

Fuel cell based powertrains are considered as potential candidates for future vehicles. Modeling of vehicle powertrains, using a combination of components and energy storage media, are widely used to predict vehicle performances under different duty cycles. This paper deals with performance analysis of a light-duty vehicle comprised of a PEM fuel cell stack, in combination with different energy storage systems using Powertrain Simulation Analysis Toolkit (PSAT). The performance of the stack was characterized by experimental data on a smaller PEM stack and was used in the simulation. The stack data was collected at controlled loading and thermal parameters. Three energy storage systems are considered in the analysis: nickel metal hydride battery storage, lithium-ion battery storage and ultra capacitor energy storage. The simulation results were analyzed for comparative evaluations and to optimize the performance of the fuel cell powertrain configurations.

Ethanol fuel has received renewed attention in recent years because of its oxygenate content and its potential to reduce greenhouse gas emissions from spark ignition engines. The economic impact on farm industry has been one of the drivers for its use in engines in the U.S. Although ethanol, in various blends, has been used in automotive engines for almost a decade the fuel has seldom been utilized in off-highway engines where the fuel systems are not well controlled. This investigation was conducted to evaluate exhaust emissions and combustion characteristics of E85 fuel in an off-highway engine used in farm equipment. A single-cylinder, four-stroke, spark ignition engine equipped with a carburetor was used to investigate combustion and exhaust emissions produced by gasoline and blends of gasoline and ethanol fuels. The engine fuel system was modified to handle flow rates required by the engine. A variable size-metering orifice was used to control air-to-fuel ratios.

A study was conducted to investigate combustion variability and exhaust emissions from high-speed, natural gas fueled engines. Two types of fuel systems were used in the investigation: a mixer and a port fuel injection. The overall engine performances were not much different at stoichiometric fuel-air ratio. But as the equivalence ratio was reduced the engine with the mixer produced higher levels of hydrocarbons and larger coefficient of variations in imep. The same engine exhibited longer flame development angle and rapid burn duration in comparison to the fuel injected engine. The differences in burn durations increased as the equivalence ratio decreased and the mixer system produced larger variations in their values at these operating points. The investigation showed the performance of the engine was better with natural gas injection system than with the mixer, particularly at lean equivalence ratios.

An experimental study was undertaken to investigate burn characteristics of homogeneous charge natural gas fueled, single cylinder, spark ignition engine. The engine was instrumented with flame detection sensors, pressure transducer, a wide-range exhaust oxygen sensor and several other devices to measure parameters associated with charge and combustion. The pressure data was used in a model to estimate mass of charge burned during the combustion events. Engine compression ratio was varied within a small range. The flame kernel development time was influenced by mixture stoichiometry, engine load and speed. Very lean equivalence ratio had pronounced effect on kernel development. The combination of light load and very lean air-to-fuel ratio provided less favorable environment for the formation of stable flame kernel. An increase in compression ratio helped to shorten flame development time.

Regulations on exhaust emissions from light- and heavy-duty diesel engines have generated interest in high-pressure fuel injection systems. It has been recognized that high-pressure injection systems produce fuel sprays that may be more conductive to reducing exhaust emissions in direct-injection diesel engines. However, for such a system to be effective it must be matched carefully with the engine design and its operating parameters. A common-rail type of fuel injection system was investigated in the present study. The injection system utilizes an intensifier to generate injection pressures as high as 160 MPa. The fuel spray characteristics were evaluated on a test bench in a chamber containing pressurized nitrogen gas. The injection system was then incorporated in a single-cylinder diesel engine. The injection system parameters were adjusted to match engine specifications and its operating parameters.

This paper provides an insight into the design of a compound combustion chamber, with square and circular cavities, for use in a direct-injection diesel engine. Automotive diesel engines using square combustion chamber design have shown improvement in oxides of nitrogen and particulate exhaust emissions. In spite of this, neither the quality of mixture formation in such chambers nor the relationship between the engine performance and combustion chamber designs have been adequately addressed. Compound combustion chambers have potential to combine attributes of square and circular chambers to provide improved engine performance. An experimental study, based on liquid injection technique (LIT), was conducted to evaluate mixture formation in compound combustion chambers of different designs. These chambers have square geometry of depth "h" at the top and a curricular cavity at the bottom, with the total chamber depth being "H."

The wider flammability limit of lean natural gas-air mixtures offers potential for operating spark ignition engines on lean air-to-fuel ratios. However, at very lean equivalence ratios, the development of the initial flame and its subsequent propagation becomes highly sensitive to physical and chemical state of the mixture. This in turn, can adversely affect engine performance, particularly the cyclic variation in the combustion process. This paper discusses the effects of lean-burn operation on the flame development durations and the cycle-by-cycle variations in a natural gas fuel injected engine. The study was conducted on a 8-cylinder, 4.6 liter, spark-ignited engine. A data acquisition system is used to acquire 300 consecutive in-cylinder pressure cycles. A heat release model was used to estimate the initial flame development time and the rapid burn duration.

An experimental study was conducted to determine potential of natural gas in lowering exhaust emissions from small spark ignition engines. A single cylinder, four-stroke, air-cooled spark ignition engine was used in the study. The investigation showed that increasing engine compression ratio from 8:1 to 10:1 reduced penalty in power normally associated with natural gas engine. The engine was able to run very stable at equivalence ratio as lean as 0.65 while the same engine could not be run at equivalence ratio below 0.85 on gasoline. Best thermal efficiency and reduced emissions of hydrocarbons and oxides of nitrogen were realized around equivalence ratio 0.75. Reducing equivalence ratio further lowered emissions of oxides of nitrogen significantly while increase in hydrocarbons was small. Most of the hydrocarbons in exhaust were of the methane type which have low ozone forming reactivity.

Small, gasoline fueled spark ignition engines are generally designed to operate at air to fuel ratios richer than stoichiometric. Consequently, they tend to emit high levels of carbon monoxide and hydrocarbons in their exhaust. This paper deals with an investigation of reducing emissions of carbon monoxide and unburned hydrocarbons by utilizing a small, metal matrix catalyst in conjunction with a thermal reactor. The experimental work was carried out on a small, single cylinder, air cooled, four stroke, spark ignition engine. The work was divided into two phases: Phase I was aimed at determining the extent to which oxidation of carbon monoxide and unburned hydrocarbons could be achieved using a two-way catalyst in conjunction with a thermal reactor. The work was later expanded to include a three-way catalyst in lieu of a two-way catalyst. In this phase controlled amounts of air from laboratory supply was used to achieve emission control.

Natural gas is one of the alternative fuels that has received considerable attention in recent years. It is believed that spark ignition engines designed to operate on natural gas may be able to meet emissions regulations of the ULEV. Natural gas has some interesting characteristics which engine designers may be able to use successfully to meet impending regulations. However, concerns have been raised on the type of suitable catalyst for such engines and whether existing catalysts designed for gasoline fuel would meet natural gas engine requirements. The work described in this paper was conducted to assess suitability of some of the existing catalysts in lowering natural gas engine emissions.

An experimental study was undertaken to investigate emissions of hydrocarbons, oxides of nitrogen, carbon monoxide, and methane hydrocarbons emitted by natural gas fueled engines and the extent of their conversion in catalysts. Two engines were used in the study: a four cylinder, 1.6 liter, spark ignition engine and a modified version of the same engine with only one of the cylinders operating at 0.4 liter capacity. Two-way and three-way catalysts were used to treat exhaust gases leaving the engine. Natural gas was supplied through gas carburetors operated at regulated pressures and supplying air-fuel ratios in the desired range. The results of the investigation showed that oxides of nitrogen could not be reduced in a three-way catalyst to the levels found in gasoline fueled engines when the operating air-fuel ratio was stoichiometric.

An experimental study was performed to determine the effects of intake air and intake charge temperature on emissions and combustion performance of a diesel engine using air atomized methanol fumigation and diesel fuel injection. A single cylinder, air cooled, naturally aspired direct injection type diesel engine was used in the investigation. Inlet charge temperature was varied over a range of 25°C to -5°C by heating and/or cooling inducted air. Decreasing inlet charge temperature reduced peak cylinder pressure and increased ignition delay period at a given methanol energy fraction supplied to the engine. Engine thermal efficiency, though it was higher than that experienced with neat diesel fuel over most of the alcohol energy fractions range, decreased as the inlet charge temperature was reduced.

An experimental investigation was conducted to measure drop sizes in the mixing region of diesel fuel spray. The spray was generated by using an experimental, electronically controlled, common rail type fuel injector. The injector incorporated an intensifier design to generate peak injection pressures as high as 140 MPa. Four different injection nozzles, with orifice diameter ranging from 0.25 mm to 0.40 mm, were used. Background gas density in the spray chamber was varied from about 1.1 kg/m3 to about 42 kg/m3 while the gas was maintained at ambient temperature. Droplets were measured by collection technique as well as by direct photography and were analyzed by computer analyses. Sauter mean diameter was found to decrease with increasing injection velocity for a given nozzle orifice and a given background gas density. The dependence of droplet sizes in the mixing region on orifice diameter as well as on background gas density was seen in the experimental results.

Compression ignition engines are required to operate over a wide temperature range and still maintain their high thermal efficiency. This requires the fuel injection system of the engine to operate at optimum conditions. It is known that fuel properties play important role in determining characteristics of fuel sprays which, in turn, influence mixing process. One of the fuel properties of interest is the fuel compressibility. Experiments were conducted to measure compressibility of diesel and methanol fuels by the P-V-T method. Fuel temperatures were varied from about -32C to +25C and fuel pressures were raised to as high as 110 MPa. The results show the compressibility of both the fuels to decrease as the fuel temperature was lowered at a constant fuel pressure. The relationship for both the fuels was almost linear over the temperature range investigated in this study.

To study diesel fuel spray behavior at high injection pressures, an experimental study was undertaken to investigate spray penetration and spray angles at constant injection pressures. Fuel spray penetration and spray angles were found to depend on the injection pressure, density of the background gas, orifice dimensions, etc. A relation, based on non-dimensional parameters, is derived to predict diesel spray tip penetration. The calculated tip penetration is found to agree well with the experimental results.

Operation of spark ignition engine under lean mixture condition is one of the several options that may be used to meet pollution and fuel economy standards. In such an operation various factors influence the combustion phenomonon. To examine these, a study is conducted in a static chamber using lean propane air mixtures of different stoichiometry. Effects of ignition energy, electrode geometry, location of ignition source and temperature profile in the initial reaction zone are investigated. It was found that increasing ignition energy accelerated flame up to a certain point; any futher increase in energy had little effect on the flame acceleration. The rate of pressure rise also showed similar pattern. Temperature in the reaction zone was lower when the ignition point was near the wall than away from it; the temperature profile was mapped using laser interferometer techniques. Round tipped electrodes showed better repeatability and yielded lower ignition energy than the flat tipped.