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Well-mixed lean SI engine operation can provide improvements of the fuel economy relative to that of traditional well-mixed stoichiometric SI operation. This work examines the use of two methods for improving the stability of lean operation, namely multi-pulse transient plasma ignition and intake air preheating. These two methods are compared to standard SI operation using a conventional high-energy inductive ignition system without intake air preheating. E85 is the fuel chosen for this study. The multi-pulse transient plasma ignition system utilizes custom electronics to generate 10 kHz bursts of 10 ultra-short (12ns), high-amplitude pulses (200 A). These pulses were applied to a custom spark plug with a semi-open ignition cavity. High-speed imaging reveals that ignition in this cavity generates a turbulent jet-like early flame spread that speeds up the transition from ignition to the main combustion event.

Detailed exhaust speciation measurements were made on an HCCI engine fueled with iso-octane over a range of fueling rates, and over a range of fuel-stratification levels. Fully premixed fueling was used for the fueling sweep. This sweep extended from a fuel/air equivalence ratio (ϕ) of 0.28, which is sufficiently high to achieve a combustion efficiency of 96%, down to a below-idle fueling rate of ϕ = 0.08, with a combustion efficiency of only 55%. The stratification sweep was conducted at an idle fueling rate, using an 8-hole GDI injector to vary stratification from well-mixed conditions for an early start of injection (SOI) (40°CA) to highly stratified conditions for an SOI well up the compression stroke (325°CA, 35°bTDC-compression). The engine speed was 1200 rpm. At each operating condition, exhaust samples were collected and analyzed by GC-FID for the C1 and C2 hydrocarbon (HC) species and by GC-MS for all other species except formaldehyde and acetaldehyde.

It is well known that ultra-lean combustion can result in higher thermal efficiency, better fuel economy, and greatly reduced NOx emissions. Accomplishing ultra-lean combustion is very difficult with a conventional spark plug, and ignition instability can be cited as one of the factors. Therefore, it is thought that ignition system innovation is important for the achievement of ultra-lean combustion in gasoline engines. This study investigated high-speed plasma ignition as a new ignition system for internal combustion engines. High-speed plasma refers to the transient (non-equilibrated) phase of plasma before formation of an arc discharge; it is obtained by applying high voltage with an ultra-short pulse between coaxial cylindrical electrodes. High-speed plasma can inherently form a multi-channel discharge, with the electrical discharge spreading over a much larger volume than a spark discharge does.

Isopentanol is an advanced biofuel that can be produced by micro-organisms through genetically engineered metabolic pathways. Compared to the more frequently studied ethanol, isopentanol's molecular structure has a longer carbon chain and includes a methyl branch. Its volumetric energy density is over 30% higher than ethanol, and it is less hygroscopic. Some fundamental combustion properties of isopentanol in an HCCI engine have been characterized in a recent study by Yang and Dec (SAE 2010-01-2164). They found that for typical HCCI operating conditions, isopentanol lacks two-stage ignition properties, yet it has a higher HCCI reactivity than gasoline. The amount of intermediate temperature heat release (ITHR) is an important fuel property, and having sufficient ITHR is critical for HCCI operation without knock at high loads using intake-pressure boosting. Isopentanol shows considerable ITHR, and the amount of ITHR increases with boost, similar to gasoline.

Previous studies have shown that fuels with higher laminar flame speed also have increased tolerance to EGR dilution. In this work, the effects of fuel laminar flame speed on both lean and EGR dilute spark ignition combustion stability were examined. Fuels blends of pure components (iso-octane, n-heptane, toluene, ethanol, and methanol) were derived at two levels of laminar flame speed. Each fuel blend was tested in a single-cylinder spark-ignition engine under both lean-out and EGR dilution sweeps until the coefficient of variance of indicated mean effective pressure increased above thresholds of 3% and 5%. The relative importance of fuel laminar flame speed to changes to engine design parameters (spark ignition energy, tumble ratio, and port vs. direct injection) was also assessed.

Homogenous Charge Compression Ignition (HCCI) is a new engine technology with fundamental differences over conventional engines. HCCI engines are intrinsically fuel flexible and can run on low-grade fuels as long as the fuel can be heated to the point of ignition. In particular, HCCI engines can run on “wet ethanol:” ethanol-in-water mixtures with high concentration of water, such as the high water content ethanol-in-water mixture that results from fermentation of corn mash. Considering that much of the energy required for processing fermented ethanol is spent in distillation and dehydration, direct use of wet ethanol in HCCI engines considerably shifts the energy balance in favor of ethanol.

The development of surrogate mixtures that represent gasoline combustion behavior is reviewed. Combustion chemistry behavioral targets that a surrogate should accurately reproduce, particularly for emulating homogeneous charge compression ignition (HCCI) operation, are carefully identified. Both short and long term research needs to support development of more robust surrogate fuel compositions are described. Candidate component species are identified and the status of present chemical kinetic models for these components and their interactions are discussed. Recommendations are made for the initial components to be included in gasoline surrogates for near term development. Components that can be added to refine predictions and to include additional behavioral targets are identified as well. Thermodynamic, thermochemical and transport properties that require further investigation are discussed.

Renewable energy sources and their integration with other power sources to support remote communities is of interest for Mars applications as well as Earth communities. The NSF, NASA, and DOE have been jointly supporting development of a 100 kW cold weather wind turbine through grants and SBIR's independently managed by each agency but coordinated by NASA. The NSF grant is specific to address issues associated with the South Pole Application and a 3 kW direct drive unit is currently being tested there in support of the development of the 100 kW unit. An NREL contract is focused on development of the 100 kW direct drive generator. The NASA SBIR is focused on development of the 100 kW direct drive wind turbine.

We have converted a Caterpillar 3406 natural gas spark ignited engine to HCCI mode and used it as a test bed for demonstrating advanced control methodologies. Converting the engine required modification of most engine systems: piston geometry, starting, fueling, boosting, and (most importantly) controls. We implemented a thermal management system consisting of a recuperator that transfers heat from exhaust to intake gases and a dual intake manifold that permits precise cylinder-by-cylinder ignition control. Advanced control methodologies are used for (1) minimizing cylinder-to-cylinder combustion timing differences caused by small variations in temperature or compression ratio; (2) finding the combustion timing that minimizes fuel consumption; and (3) tuning the controller parameters to improve transient response.

Experimental tests were conducted on a Cummins B5.9 direct-injected diesel engine fueled with biodiesel blends. 20% and 50% blend levels were tested, as was 100% (neat) biodiesel. Emissions of particulate matter (PM), nitrogen oxides (NOx), hydrocarbons (HC) and CO were measured under steady-state operating conditions. The effect of biodiesel on total PM emissions was mixed; however, the contribution of the volatile organic fraction to total PM was greater for higher biodiesel blend levels. When only non-volatile PM mass was considered, reductions were observed for the biodiesel blends as well as for neat biodiesel. The biodiesel test fuels increased NOx, while HC and CO emissions were reduced. PM collected on quartz filters during the experimental runs were analyzed for carbon-14 content using accelerator mass spectrometry (AMS).

The influence of the addition of oxygenated hydrocarbons to diesel fuels has been studied, using a detailed chemical kinetic model. Resulting changes in ignition and soot precursor production have been examined. N-heptane was used as a representative diesel fuel, and methanol, ethanol, dimethyl ether, dimethoxymethane and methyl butanoate were used as oxygenated fuel additives. It was found that addition of oxygenated hydrocarbons reduced the production of soot precursors. When the overall oxygen content in the fuel reached approximately 30-40 % by mass, production of soot precursors fell effectively to zero, in agreement with experimental studies. The kinetic factors responsible for these observations are discussed.

The results reported are from tests on July 6-8, 1999, on a limited-access 12km section of I -15 in San Diego. The tests involved 2, 3 and 4-car platoons operated and maintained by PATH personnel under the auspices of CALTRANS and utilized Buick LeSabre sedans under fully automatic longitudinal and lateral control. Multiple sensor data was acquired, including the fuel injector pulse width. We demonstrate that the fuel injector pulse width, in combination with engine RPM and forward speed, can be used to determine accurate estimates of instantaneous fuel consumption. The repeatability for total fuel consumed over a 2.4 km portion of the test path is ±1% based upon multiple single car runs over the three day period, with the major portion of the uncertainty arising from changing wind conditions. Fuel savings for individual vehicles vary from 0-10% depending upon number of vehicles, vehicle spacing, and vehicle position within the platoon.

We present the effect of EGR, at a set fuel flow rate and intake temperature, on the operating parameters of timing of combustion, duration of combustion, power output, thermal efficiency, and NOx emission; which is remarkably low. We find that addition of EGR at constant inlet temperature and constant fuel flow rate has little effect on HCCI parameter of start of combustion (SOC). However, burn duration is highly dependent on the amount of EGR inducted. The experimental setup at UC Berkeley uses a 1.9-liter 4-cylinder diesel engine with a compression ratio of 18.8:1 (offered on a 1995 VW Passat TDI). The engine was converted to run in HCCI mode by addition of an 18kW air pre-heater installed in the intake system. Pressure traces were obtained using four water-cooled quartz pressure transducers, which replaced the Diesel fuel injectors. Gaseous fuel (propane or butane) flowed steadily into the intake manifold.

A four-cylinder 1.9 Volkswagen TDI Engine has been converted to run in Homogeneous Charge Compression Ignition (HCCI) mode. The stock configuration is a turbo-charged direct injection Diesel engine. The combustion chamber has been modified by discarding the in-cylinder Diesel fuel injectors and replacing them with blank inserts (which contain pressure transducers). The stock pistons contain a reentrant bowl and have been retained for the tests reported here. The intake and exhaust manifolds have also been retained, but the turbocharger has been removed. A heater has been installed upstream of the intake manifold and fuel is added just downstream of this heater. The performance of this engine in naturally aspirated HCCI operation, subject to variable intake temperature and fuel flow rate, has been studied. The engine has been run with propane fuel at a constant speed of 1800 rpm.

The elemental composition of food consumed by astronauts is well defined. The major elements carbon, hydrogen, oxygen, nitrogen and sulfur are taken up in large amounts and these are often associated with the organic fraction (carbohydrates, proteins, fats etc) of human tissue. On the other hand, a number of the elements are located in the extracellular fluids and can be accounted for in the liquid and solid waste fraction of humans. These elements fall into three major categories - cationic macroelements (e.g. Ca, K, Na, Mg and Si), anionic macroelements (e.g. P, S and Cl and17 essential microelements, (e.g. Fe, Mn, Cr, Co, Cu, Zn, Se and Sr). When provided in the recommended concentrations to an adult healthy human, these elements should not normally accumulate in humans and will eventually be excreted in the different human wastes.

Of the many competing technologies for resource recovery from solid wastes for long duration manned missions such as a lunar or Mars base, incineration technology is one of the most promising and certainly the most well developed in a terrestrial sense. Various factors are involved in the design of an optimum fluidized bed incinerator for inedible biomass. The factors include variability of moisture in the biomass, the ash content, and the amount of fuel nitrogen in the biomass. The crop mixture in the waste will vary; consequently the nature of the waste, the nitrogen content, and the biomass heating values will vary as well. Variation in feed will result in variation in the amount of contaminants such as nitrogen oxides that are produced in the combustion part of the incinerator. The incinerator must be robust enough to handle this variability. Research at NASA Ames Research Center using the fluidized bed incinerator has yielded valuable data on system parameters and variables.

An energy-efficient lyophilization technique is being developed to recover water from highly contaminated spacecraft waste streams. In the lyophilization process, water in an aqueous waste is frozen and then sublimed, separating the waste into a dried solid material and liquid water. This technology is ideally suited to applications such as the Mars Reference Mission, where water recovery rates approaching 100% are desirable but production of CO2 is not. Candidate wastes include feces, concentrated brines from water processors, and other solid wastes that contain water. To operate in microgravity, and to minimize power consumption, thermoelectric heat pumps can be used in place of traditional fluid cycle heat pumps. A mathematical model of a thermoelectric lyophilizer is described and used to generate energy use and processing rate estimates.

This paper builds on a steady-state investigation of waste heat reuse in an Advanced Life Support System (ALSS) for a Mars mission with a low degree of crop growth. In past studies, such a system has been defined in terms of technology types, hot and cold stream identification and stream energy content. The maximum steady-state potential for power and cooling savings within the system was computed via the Pinch Method. In this paper, the next step is taken toward achieving a pragmatic estimate of costs and savings associated with waste heat reuse in terms of equivalent system mass (ESM). In this paper, the assumption of steady-state flows are discarded, and a proposed schedule is developed for activities that are of interest in terms of waste heat reuse. The advanced life support system for the Mars Dual Lander Transit Vehicle is the system of interest.

A summary is presented of experimental results obtained from a Cummins B5.9 175 hp, direct-injected diesel engine fueled with oxygenated diesel blends. The oxygenates tested were dimethoxy methane (DMM), diethyl ether, a blend of monoglyme and diglyme, and ethanol. The experimental results show that particulate matter (PM) reduction is controlled largely by the oxygen content of the blend fuel. For the fuels tested, the effect of chemical structure was observed to be small. Isotopic tracer tests with ethanol blends reveal that carbon from ethanol does contribute to soot formation, but is about 50% less likely to form soot when compared to carbon from the diesel portion of the fuel. Numerical modeling was carried out to investigate the effect of oxygenate addition on soot formation. This effort was conducted using a chemical kinetic mechanism incorporating n-heptane, DMM and ethanol chemistry, along with reactions describing soot formation.

Many studies have shown that the addition of oxygen-bearing compounds to diesel fuel can significantly reduce particulate emissions. To assist in the evaluation of the environmental performance of diesel-fuel oxygenates, we have implemented a suite of diagnostic models for simulating the transport of compounds released to air, water, and soils/groundwater as well as regional landscapes. As a means of studying the comparative performance of DBM and TGME, we conducted a series of simulations for selected environmental media. Benzene and methyl tertiary butyl ether (MTBE) were also addressed because they represent benchmark fuel-related compounds that have been the subject of extensive environmental measurements and modeling. The simulations showed that DBM and TGME are less mobile than MTBE in soil because of reduced vapor-phase transport and increased retention on soil particles.