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This study examines the feasibility of broadening the fuel capabilities of a direct-injected two-stroke engine with stratified combustion. A three cylinder, direct-injected two-stroke engine was modified to operate on JP-5, a kerosene-based jet fuel that is heavier, more viscous, and less volatile than gasoline. Demonstration of engine operation with such a fuel after appropriate design modifications would significantly enhance the utilization of this engine in a variety of applications. Results have indicated that the performance characteristics of this engine with jet fuel are similar to that of gasoline with respect to torque and power output at low speeds and loads, but the engine's performance is hampered at the higher speeds and loads by the occurrence of knock.

Time-averaged temperatures at critical locations on the piston of a direct-fuel injected, two-stroke, 388 cm3, research engine were measured using an infrared telemetry device. The piston temperatures were compared to data [7] of a carbureted version of the two-stroke engine, that was operated at comparable conditions. All temperatures were obtained at wide open throttle, and varying engine speeds (2000-4500 rpm, at 500 rpm intervals). The temperatures were measured in a configuration that allowed for axial heat flux to be determined through the piston. The heat flux was compared to carbureted data [8] obtained using measured piston temperatures as boundary conditions for a computer model, and solving for the heat flux. The direct-fuel-injected piston temperatures and heat fluxes were significantly higher than the carbureted piston. On the exhaust side of the piston, the direct-fuel injected piston temperatures ranged from 33-73 °C higher than the conventional carbureted piston.

An investigation has been performed of some of the characteristics of di-methyl ether (DME) during high pressure injection in a diesel fuel injection system with a single hole nozzle. Recent developments in the use of DME as an alternate fuel for diesel engines are discussed. The effects of fuel compressibility on compression work are compared for DME and typical hydrocarbon fuel components. Photographs of the transient injection process into room temperature Nitrogen are given for a range of chamber pressures. For a single hole injector, spray penetrations can be predicted using existing correlations for diesel fuel, provided DME fuel properties are used.

Assisted ignition and subsequent combustion of various fuels differing in volatility and viscosity in a Diesel engine is herein described. This study was conducted to investigate the feasibility of igniting low cetane fuels at the immediate vicinity of the nozzle orifice in an attempt to produce injection rate controlled heat release. Four fuels were studied: a high viscosity, low volatility Diesel blend, a low viscosity, high volatility Diesel blend, strait gasoline, and No.2 Diesel fuel which was used as a baseline for comparison purposes. A droplet ignition delay model was used to provide insight into the various physical processes that occur when heat release is controlled by rate of injection. Split injection timing predicted by the model resulted in the successful occurrence of rate controlled heat release for all of the fuels tested.

As the incentive to produce cleaner and more efficient engines increases, diesel engines will become a primary, worldwide solution. Producing diesel engines with higher efficiency and lower emissions requires a fundamental understanding of the interaction of the injected fuel with air as well as with the surfaces inside the combustion chamber. One aspect of this interaction is spray impingement on the piston surface. Impingement on the piston can lead to decreased combustion efficiency, higher emissions, and piston damage due to thermal loading. Modern high-speed diesel engines utilize high pressure common-rail direct-injection systems to primarily improve efficiency and reduce emissions. However, the high injection pressures of these systems increase the likelihood that the injected fuel will impinge on the surface of the piston.

Dual fuel (CI) engines provide an excellent means of maintaining high thermal efficiency and power while reducing emissions, particularly in situations where the primary fuel does not exhibit good auto-ignition characteristics. This is especially true of diesel engines operating on natural gas; usually in stationary applications such as distributed power generation. However, because two fuels are needed, the reliability of the engine is compromised. Therefore, this paper describes the first phase of a project that is to eventually manufacture dimethyl ether (DME) from natural gas and supply it to the pilot injector of a dual fuel engine. A chemical pilot plant has been built and operated, demonstrating an intermediate step in the production of DME from natural gas. DME is manufactured from methanol for pilot injection into a dual fuel engine operating with natural gas as the main fuel.

The successful implementation of a clean, quiet, four-stroke engine into an existing snowmobile chassis has been achieved. The snowmobile is easy to start, easy to drive and environmentally friendly. The following paper describes the conversion process in detail with actual engine test data. The hydrocarbon emissions of the new, four-stroke snowmobile are 98% lower than current, production, two-stroke models. The noise production of the four-stroke snowmobile was 68 dBA during an independent wide open throttle acceleration test. If the four-stroke snowmobile were to replace all current, two-stroke snowmobiles in Yellowstone National Park (YNP), the vehicles would only produce 16% of the combined automobile and snowmobile hydrocarbon emissions compared to the current 93% produced by two-stroke snowmobiles.

In recent years, intensive research has been pursued throughout the world in order to find substitutes to crude oil based fuel in compression-ignition engines. Among the different fuels studied, methanol is probably the primary candidate to substitute diesel fuel in the future. The major problems encountered with methanol in diesel engines are its poor cold startability together with unstable combustion levels under low load. Forced ignition techniques such as glow plugs and spark plugs have been used to overcome these problems. The major disadvantages with the use of glow plugs are their high power requirements as well as their limited lifetime. This paper presents the results from recent work done on the feasibility of catalytically igniting methanol with the use of platinum and platinum/rhodium-coated glow plugs.

Spray angle and penetration length data were taken under cold start conditions for a Direct Injection Spark Ignition engine to investigate the effect of transient conditions on spray development. The results show that during cold start, spray development depends primarily on fuel pressure, followed by Manifold Absolute Pressure (MAP). Injection frequency had little effect on spray development. The spray for this single hole, pressure-swirl fuel injector was characterized using high speed imaging. The fuel spray was characterized by three different regimes. Regime 1 comprised fuel pressures from 6 - 13 bar, MAPs from 0.7 - 1 bar, and was characterized by a large pre-spray along with large drop sizes. The spray angle and penetration lengths were comparatively small. Regime 2 comprised fuel pressures from 30 - 39 bar and MAPs from 0.51 - 0.54 bar. A large pre-spray and large drop sizes were still present but reduced compared to Regime 1.

Droplet size and velocity measurements were taken under cold start conditions for a Direct Injection Spark Ignition engine to investigate the effect of transient conditions on spray development. The results show that during cold start, spray development depends primarily on fuel pressure, followed by Manifold Absolute Pressure (MAP). The spray for this single hole, pressure-swirl fuel injector was characterized using phase Doppler interferometry. The fuel spray was characterized by three different regimes. Regime 1 comprised fuel pressures from 6 - 13 bar, MAPs from 0.7 - 1 bar, and was characterized by a large pre-spray along with large drop sizes. The spray profile resembled a solid cone. Regime 2 comprised fuel pressures from 30 - 39 bar and MAPs from 0.51 - 0.54 bar. A large pre-spray and large drop sizes were still present but reduced compared to Regime 1. The spray profile was mostly solid. Regime 3 comprised fuel pressures from 65 - 102 bar and MAPs from 0.36 - 0.46 bar.

A computational investigation of the effects of activation energy, porosity, and pore size on the gasification of combustion chamber deposits in spark ignition engines has been performed. The oxygen in the combustion gases reacts with the carbonaceous deposit and causes the deposit to burn away. Experimentally measured deposit parameters such as heating value, surface temperature, surface pressure and porosity were used in the model. Several models for predicting the gasification of the deposit were investigated. A random pore intersection model developed by Petersen was used to predict the gasification of the deposit. The chemical reactions were modeled with a simple Arrhenius expression. The flow within the deposit was modeled using Darcy's Law. The Kozeny-Carmen equation was used to relate deposit permeability and porosity. The model was incorporated into a finite difference code that predicts the heat transfer and fluid flow through the deposit.

A thermodynamical model of the ignition and flame growth process was developed to understand and minimize cycle-to-cycle variations in pressure due to minor differences in flame kernel growth at the spark plug electrode between cycles. Initial flame kernel size after the spark breakdown process was determined by solving the one-dimensional cylindrical shock flow equation. Overall reaction rates, flame speeds including turbulence and intensity, high temperature equilibrium and other thermodynamic properties were calculated by peripheral sub-models. Relative effects of spark power, heat loss to the spark plug, and the chemical heat release were studied under varying engine conditions. Results show that breakdown energy has a significant effect on the formation and size of the initial kernel and that the effect of flame kernel velocity on subsequent combustion was considerable at specific engine conditions.

The two stroke direct injected gasoline engine is in part characterized by low temperature exhaust flow, particularly at light loads, due to the fresh air scavenging of the combustion chamber during the exhaust process. This study investigated the possibility of separating the exhaust flow into two regimes: 1) high temperature flow of the combustion products, and 2) low temperature flow from the fresh air scavenging process. Separation of the exhaust flow was accomplished by a mechanical device placed in the exhaust stream. In this way, emissions from the exhaust could be handled by two different catalysts and/or processes, each optimized for different temperature ranges and flow compositions. The first portion of this study involved validation of a computer model, using experimental data from a single cylinder engine with a stationary exhaust port and splitter.

The objective of this investigation was to identify the impingement event on a diesel piston surface. Eight fast-response, surface thermocouples were installed in one of the pistons of a 2.0 liter, four-cylinder, turbo-charged diesel engine (97 kW @ 3800 rpm). Piston temperatures were transmitted from the engine using wireless microwave telemetry. An impingement signal was identified on the piston bowl lip. A simple parameter for characterizing the impingement event is proposed. The results show an impingement signature at one of the bowl lip thermocouples, under specific operating conditions.

This investigation dealt with the experimental determination of a select chemical specie - the hydroxyl radical - present in the non-flamed end gases ahead of the flame front in a spark-ignited engine operating under conditions of both normal and knocking combustion. Concentration measurements of the hydroxyl radical present in the end gases were obtained with the technique of resonance absorption spectroscopy utilizing a broadband-output, frequency-tunable, flashlamp-pumped, organic-dye laser. The dye laser and a photographic spectrometer were placed on opposite sides of a single cylinder research engine and the combustion chamber of the engine was fitted with quartz windows that allowed the dye-laser light pulse to pass through the end gas region and into the spectrometer. The dye laser was pulsed once at a present crankangle during the combustion cycle recording the 2∑+-2∏ electronic transition absorption spectrum on film.

The effect of high pressure injection (using an accumulator type unit injector with peak injection pressure of approximately 20,000 psi, having a decreasing injection rate profile) on combustion was studied. Combustion results were obtained using a DDA Series 3–53 diesel engine with both conventional analysis techniques and high speed photography. Diesel No. 2 fuel and a low viscosity - high volatility fuel, similar to gasoline were used in the study. Results were compared against baseline data obtained with standard injectors. Some of the characteristics of high pressure injection used with Diesel No. 2 fuel include: substantially improved ignition, shorter ignition delay, and higher pressure rise. Under heavy load - high speed conditions, greater smokemeter readings were achieved with the high pressure injection system with Diesel No. 2 fuel. Higher flame speeds and hence, greater resistance to knock were observed with the high volatility low cetane fuel.

An experimental investigation of the ignition and combustion characteristics of two low cetane fuels in a spark assisted Diesel engine is described. A three cylinder Diesel engine was modified for single cylinder operation and fitted with a spark plug located in the periphery of the spray plume. Optical observations of ignition and combustion were obtained with high speed photography. Optical access was provided by a quartz piston crown and extended head arrangement. The low cetane fuels, a light end, low viscosity fuel and a heavy end, high viscosity fuel which were blended to bracket No. 2 Diesel fuel on the distillation curve, demonstrated extended operation in the modified Diesel engine. Qualitative and quantitative experimental observations of ignition delay, pressure rise, heat release, spray penetration and geometery were compared and evaluated against theoretical predictions.

An experimental investigation of the ignition and combustion characteristics of two low cetane fuels in a spark assisted diesel engine at cold starting conditions is described. A three cylinder diesel engine was modified for single cylinder operation and fitted with a spark plug located in the periphery of the fuel injection spray plume. Optical observations of ignition and combustion were obtained with high speed photography. Optical access was provided by a quartz piston crown and extended head arrangement. The low cetane fuels, a light end low viscosity fuel and a heavy end high viscosity fuel, which were blended to bracket No. 2 diesel fuel on the distillation curve, demonstrated extended operation at low temperature starting conditions in the modified diesel engine. Qualitative and quantitative experimental observations of fuel spray characteristics, ignition delay, pressure rise, heat release, and white smoke formation were compared and evaluated against theoretical predictions.

The following paper discusses alternative strategies for reducing noise and emission production from a two-stroke snowmobile. Electric, two-stroke and four-stroke solutions were analyzed and considered for entry in the Clean Snowmobile Challenge (CSC) 2000. A two-stroke solution was utilized primarily due to time constraints. Complete snowmobile competition results are provided. The electric solution, while the most effective at reducing emissions, is negatively impacted by weight and cost. A modified two-stroke solution, limited by cost and complexity, does not provide the required improvements in emissions. A four-stroke solution reduces noise and emissions and provides an acceptable trade-off between noise, emissions, performance and cost.