Advanced Diesel Research Articles

Slender Tactile Sensor for Contour and Roughness Measurements Within Deep and Narrow Holes

A tactile cantilever sensor is described which was designed for quality assurance of high-aspect ratio microcomponents, e.g., spray holes of diesel injector nozzles. It was constructed as an extremely slender silicon cantilever of 1.5-5 mm in length, 30-200 mum in width, and 25-50 mum in height comprising a silicon probing tip at its free end. Close to its clamping, a piezoresistive strain gauge was integrated for signal read-out. The novel sensor was designed to be operated at high scanning speeds offering a millimeter scanning range at a micrometer lateral resolution and a ten nanometers vertical resolution. Cross sensitivity versus temperature and ambient light referred to vertical tip deflection was below 10 nm during a tactile measurement, which was performed under typical tactile probing conditions, i.e., temperature and light intensity variations of 1 K and 0.1 mW/cm 2, respectively. In form and roughness measurements with calibrated standard artifacts as well as with narrow spray holes of advanced diesel injector nozzles, we demonstrated the potential of slender cantilever sensors for high-aspect-ratio micrometrology.

Diesel Steam Reforming for PEM Fuel Cells

Different applications for the decentralized stationary or mobile power supply require the usage of liquid hydrocarbons such as fuel oil, diesel, or gas oil in fuel cell systems. Reducing the sulfur content of conventional liquid fuels such as diesel or gasoline below 10ppm, the usage of these fuels in fuel cell applications becomes increasingly promising. The first process step represents thereby the reforming, which can be carried out in different ways. One of the commonly favored gas process technologies is the steam reforming process, which is state of the art for natural gas applications. Using a proton exchange membrane (PEM) fuel cell requires a complex gas cleanup system. Using a pressurized steam reforming process offers a significant reduction of the whole system size by efficiently compressing the liquid educts. Complete PEM systems with steam reformers tend to have a higher efficiency than, for example, systems using the autothermal reforming process. Advanced diesel steam reformers for industrialization still have to be developed and improved. The Oel-Wärme-Institut gGmbH has successfully carried out research on steam reforming with variations of important parameters using a sulfur free reference fuel and desulfurized diesel. During the experiments, several parameters such as steam to carbon ratio, reformer inlet temperatures, catalysts, and fuels were varied. While running the process, a continuous product gas measurement was taken. The reformer is equipped with several thermocouples. Three of them are moveable to measure the temperature profile of the catalyst. The experiments show that product gas concentrations reach a nearly equilibrium concentration with reformer inlet temperatures ϑ>700°C of a reference fuel∕steam mixture. Hydrogen concentrations over 70% were feasible. Constant inlet temperatures of ϑ=850°C and a variation of the steam to carbon ratio only have a noticeable effect on the water gas shift equilibrium. After all experiments, carbon deposits were found in the steam reformer system and under some circumstances on the catalysts. Experiments with operating times of more than 20h were performed at a steam to carbon ratio of 4.5. The application of continuously desulfurized diesel fuel indicates a degradation of the catalyst after a few hours. For the overall system design of PEM fuel cell applications, an operation mode at a reduced steam to carbon ratio has to be developed.

New challenges for combustion control in advanced diesel engines

Against the backdrop of general discussions on the reduction of CO2 emissions, diesel engines will face new challenges in the future in order to meet future emission limits worldwide while maintaining good consumption figures, good driving characteristics, and acceptable costs. One of these challenges is that the fuel characteristics of diesel often varies greatly worldwide, and sometimes even within one country. As part of this article, we will illustrate FEV’s approach for the compensation of different fuel grades during combustion. The basic influencing factors for a possible compensation of the fuel’s influences will be demonstrated and analyzed, and first results for a suitable control concept will be presented.

The new ADEC engine management system from MTU

The increased demands on the MTU Friedrichshafen engine Series 2000 and 4000 require not just continuous development of the engine itself but simultaneously also of the engine electronics. The ADEC engine management system (Advanced Diesel Engine Control) represents a quantum leap in this respect: Apart from requirements such as more stringent emission legislation worldwide, increase in power output, reduction of life cycle costs and increase in maintenance-friendliness the possibility of use for different applications across the entire Off-Highway segment was also taken into account. Despite more stringent emission legislation, ADEC allows MTU to increase the performance of current large diesel engines. However, these possibilities also require dealing with subjects that to date were primarily found in the IT sector.

The Development of a “Pin-on-Twin” Scuffing Test to Evaluate Materials for Heavy-Duty Diesel Fuel Injectors*

In order to meet stricter emissions requirements, advanced heavy-duty diesel fuel injection systems will be required to operate at higher pressures and temperatures and in fuels that have poorer lubricity. Scuffing, as a mode of failure, severely limits injector life, and new materials and processes are required to resist scuffing in these more stringent operating conditions. Consequently, there is a need to test the ability of candidate fuel system materials to resist scuffing in fuel-lubricated environments. This paper describes a pin-on-twin reciprocating wear test in which a cylindrical specimen slides, under load, across two fixed, parallel cylindrical specimens that are perpendicular to the axis of the upper sliding specimen. Cylinders of annealed AISI 52100 were tested dry and lubricated by Jet A fuel and on-highway #2 diesel fuel. The friction force was found to give a reliable real-time determination of the onset of scuffing as verified by the morphology of the wear scar. The scar width and surface roughness profiles either did not reliably detect the onset or were difficult to carry out with this geometry. *Research sponsored by the U.S. Department of Energy, Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Office of Freedom CAR and Heavy Vehicle Technologies, under contract DE-AC05-00OR22725 with UT-Battelle LLC. Review led by Roger Melley

Effects of engine operating conditions on morphology, microstructure, and fractal geometry of light-duty diesel engine particulates

An investigation on the morphology, internal microstructure, and fractal geometry of particulate matter (PM) was conducted for a 1.7-L light-duty diesel engine. The experimental and analytical instruments used in this study include a unique thermophoretic sampling system, a high-resolution transmission electron microscope (TEM), customized digital image processing/data acquisition system, and a Raman scattering spectrometer that have been extensively used at Argonne National Laboratory. During experiments, diesel particulates were directly collected from the exhaust stream. In the morphological observations using TEM, graphitic crystallite structures were found from these light-duty diesel particulates, particularly at high engine loads. In subsequent analysis, Raman spectra revealed details of these graphitic structures quantitatively: the collected diesel PM was quite similar in atomic structures to typical graphite, and the degree of its crystalline structures increased as the engine load increased. In PM size measurements, mean primary particle diameters ( d p) are in a range of 19.4–32.5 nm and radii of gyration ( R g) in a range of 77.4–134.1 nm, respectively, across the engine operating conditions of 780–4000 rpm and 0–100% loads. From the fractal analysis, smaller fractal dimensions ( D f) (1.46–1.70) were measured for the light-duty diesel engine used in this study, compared to those of heavy-duty diesel particulates that ranged in 1.80–1.88. This result implies that more stretched chain-like particles were produced from the light-duty engine under the diffusion-limit formation mechanism. The database on the physical dimension and fractal geometry of light-duty diesel PM obtained from this study offers data for the future standards of diesel PM sizes and development of advanced diesel PM emission control technologies.

An Integrated Approach for Creating Model Diesel Fuels

This paper describes a methodology that has been developed to facilitate a detailed study of molecular composition effects on particulate matter emissions in advanced diesel engines. This includes a sophisticated numerical optimization algorithm to formulate well-characterized diesel fuel blends and an analytical method to characterize diesel fuels more accurately than previously possible. These tools are described, together with application to the formulation of test fuels with identical boiling point distribution and cetane number, but differing molecular composition. Test results are discussed from an advanced high-speed direct injection diesel engine for several of these fuels, demonstrating the improved insight and understanding available from these combined techniques.

The improvement of the efficiency of fuel cells against the elimination of harmful emissions from the internal combustion engines

There are many candidates as the prime mover of vehicles for the 21st century. Fuel cells, advanced gasoline engines, advanced diesel engines or other systems including combinations of various combustion engines with the electric motor. Overviews of the pros and cons for these prime movers are explained and the compression ignition combustion system of premixed mixtures is positively reviewed as the most promising system.

Advantages of the LV100 as a Power Producer in a Hybrid Propulsion System for Future Fighting Vehicles

The core of any hybrid propulsion system is a high power density, low weight, and fuel efficient electric energy producer. The LV100 recuperated turbine engine is such a system. This engine is well suited to provide electric power efficiently at a volume and weight significantly lower than current systems. Originally designed for vehicular use and environment to drive a Hydrokinetic transmission, the turbine’s high output speed lends itself to incorporate into the engine design an advanced generating device. This LV100 engine-based electric energy producer will provide in excess of 1MW of electric power in a volume of under one cubic meter at a weight of about 2500 pounds at fuel efficiencies comparable to advanced vehicular diesel engines. Recent state-of-the-art improvements in materials and component technology will permit further reductions in volume/weight and increase the system fuel efficiency. The technologies required to reach a volume of under one cubic meter, the system performance projections obtainable by technology upgrades and the program achievements to date are discussed. [S0742-4795(00)03103-3]

Light-Duty Diesels: Consumer Perspectives and U.S. Energy Supply Issues

An assessment of the potential for diesel engine light-duty vehicles to reduce petroleum consumption and greenhouse gas emissions is presented. Historical diesel vehicle sales behavior is presented and analyzed. Future market penetration and resultant petroleum consumption and emission reductions for advanced diesel engines are projected. Results of a survey of new vehicle buyer attitudes toward improved diesel engines are presented and analyzed. Effects of increased diesel market share on diesel fuel supply and price are estimated. Overall, the outlook for diesels in light vehicles is somewhat promising if pollution issues and consumer concerns about the earlier diesels can be addressed.

A perspective on the potential development of environmentally acceptable light-duty diesel vehicles.

Between 1979 and 1985, an international technical focus was placed upon potential human health effects associated with exposure to diesel emissions. A substantial data base was developed on the composition of diesel emissions; the fate of these emissions in the atmosphere; and the effects of whole particles and their chemical constituents on microorganisms, cells, and animals. Since that time, a number of significant developments have been made in diesel engine technology that require a new look at the future acceptability of introducing significant numbers of light-duty diesel automobiles into the European and American markets. Significant engineering improvements have been made in engine design, catalysts, and traps. As a result, particle emissions and particle associated organic emissions have been reduced by about 10 and 30 times, respectively, during the past 10 years. Research studies to help assess the environmental acceptability of these fuel-efficient engines include the development of an emissions data base for current and advanced diesel engines, the effect of diesel emissions on urban ozone formation and atmospheric particle concentrations, the effect of fuel composition, e.g., lower sulfur and additives on emissions, animal inhalation toxicology studies, and fundamental molecular biology studies.

Wear Mechanisms in Thermally-Sprayed Mo-Based Coatings

The successful development of advanced diesel engines relies heavily on piston ring coating materials which can withstand elevated temperatures and reduce friction. Traditional hard chrome plating and flame-sprayed Mo-wire materials have reached their potential in the diesel engine environment, and alternatives are needed. Thermally-sprayed Mo-based allays and composites are being evaluated for applications as next-generation ring-face coatings. The alloy development task of producing complex Mo-based alloy powders for use as thermally-sprayed coating materials requires an understanding of their wear resistance under contact stress conditions. In this paper, the wear behavior of Mo and Mo+NiCrBSi thermally sprayed coatings is examined by pin-on-disc and single-point scratch-test methods. Microstructural analysis beneath worn regions have revealed that fracture of splats and their decohesion constitute the mode of failure. Improved wear resistance and stability of low friction coefficient was obtained by p...

Piston Ring Thermal Transient Effects on Lubricant Temperatures in Advanced Engines

One class of advanced diesel engines operates with low heat rejection and high operating temperatures; piston-ring / liner lubrication is a major problem for these engines. This study attempts to illustrate the time-dependent thermal environment around the top piston ring and lubricant in these advanced engines. Particular emphasis will be placed on the maximum lubricant temperature. The analysis starts with a standard cycle simulation and a global finite-element analysis of the piston and liner in relative motion. A more detailed finite-element model, which considers variable oil film thickness on the liner, focuses on the top ring and lubricant and uses the groove and liner temperatures generated in the global analysis as boundary conditions. Results for different heat rejection engine configurations are presented. We observe that because of major transient effects, high lubricant temperature is experienced not only at top ring reversal but also down the liner to bottom ring reversal.

Ceramic Coatings for Advanced Heat Engines-A Review and Projection

This report assesses the current status and future potential for the application of ceramic coatings in advanced diesel and turbine engines. A previous report describes the authors findings in greater detail. Ceramics, in contrast with metals, generally exhibit better structural and thermal capabilities at high temperatures. In general, ceramics are more resistant to creep, oxidation, corrosion, erosion, and wear, as well as being better thermal insulators. The benefits of thermal barrier coatings on the hotter side of diesel or turbine engine components are well-documented, and thermal barrier coatings are one of several applications of ceramics that are being pursued actively for heat engines. Ceramic coatings are being considered for diesel engine cylinder liners, piston caps, valve faces and seats, piston rings, and other parts and for turbine components such as combustors, blades, stators, seals, and bearings.