Search Results

A detailed analysis of the end-gas temperature and pressure in gasoline engines has been performed. This analysis leads to a simplified zero-dimensional model, that considers both, the compression and the expansion of the end-gas by the piston movement, and the compression by the flame front. If autoignition occurs in the end-gas the sudden rise of the pressure and the heat release is calculated. The rate form of the first law of thermodynamics for a control volume combined with the mass conservation equation for an unsteady and a uniform-flow process are applied. The heat of formation in the end-gas due to the chemical activity has been taken into account. In addition, a chemical kinetic model has been applied in order to study the occurrence of autoignition and prediction of knock.

The wavelet transform is used in the analysis of the cylinder pressure trace and the ionic current trace of a knocking, single-cylinder, spark ignition engine. Using the wavelet transform offers a significant reduction of mathematical operations when compared with traditional filtering techniques based on the Fourier transform. It is shown that conventional knock analysis in terms of average energy in the time domain (AETD), corresponding to the signal's energy content, and maximum amplitude in the time domain (MATD), corresponding to the maximum amplitude of the bandpass filtered signal, can be applied to both the reconstructed filtered cylinder pressure and the wavelet coefficients. The use of the filter coefficients makes possible a significant additional reduction in calculation effort in comparison with filters based on the windowed Fourier transform.

Experimental forms of two different types of engine oil viscosity sensors have been tested that use uniformly poled disks of piezoelectric PZT ceramic. In both cases, the disks were used to form electromechanical resonators functioning as the frequency-controlling element in a transistor oscillator circuit. The simpler type of sensor used only one disk, vibrating in a radial-longitudinal mode of vibration. In this mode, a disk 2.54 cm in diameter and 0.127 cm thick had a resonant frequency of approximately 90 kHz. The second type of sensor used two such disks bonded together by a conducting epoxy, with poling directions oriented in opposite directions. This composite resonator vibrated in a radially-symmetrical, flexural mode of vibration, with the lowest resonant frequency at approximately 20 kHz. The presence of tangential components of motion on the major faces of both resonators made them sensitive to the viscosity of fluids in which they were immersed.

The single-point LIF-measurement technique has been applied to a four-cylinder spark-ignition production engine for investigation of the oil film layer between the piston, piston rings and the cylinder wall. The lubrication process was studied during engine warm-up and it was found that a scaling law could be successfully used. This scaling law enables simple scaling of the oil film thickness of the compression ring, scraper ring and on the liner during warm-up, assuming the oil film thickness and cylinder liner temperature are known for the steady-state operating condition. Thereby the value of traditional measured steady-state lubrication data is enhanced.

The purpose of our study was to investigate the effects of TAME and heavier ethers on reformulated gasoline. The research work focused on the comparison of Californian Phase 2 gasoline (CARB), current Finnish reformulated gasoline containing MTBE (RFG1), or MTBE+TAME+heavier ethers (RFG2) with non-oxygenated Eurograde gasoline (EN228). Significant reductions in exhaust emissions were achieved with all reformulated fuels when compared to the Eurograde fuel. For instance, benzene emissions were reduced as much as 40 to 50 % for all cars at two temperatures and the emissions of total toxics were reduced by 14 to 45 % depending on vehicle type and temperature. The lowest 1,3-butadiene emissions were achieved with CARB gasoline. The amount of PAH compounds in the particulate matter from the non-catalyst vehicle was lower with the reformulated fuels than with the Eurograde fuel.

Today gas engines for stationary and vehicular applications are not only faced with stringent emission legislation but also with increasing requirements to power density, while reducing operating and investment cost. The dual fuel engine is very beneficial in terms of power density and efficiency and solves the problem of reduced spark plug life. For smaller engines, however, this concept is economically unattractive due to inevitable SCR (Selective Catalytic Reduction) exhaust gas aftertreatment. The key to low NOx-production is the application of modern injection systems with maximum flexibility concerning the injection parameters. A time-controlled pilot injection system offers the best potential for combining environmental-friendly, cost-saving operation, thus making gas engines even more competitive to their diesel counterparts in many applications.

An experimental study was conducted to investigate the effect of EGR on combustion and exhaust emissions characteristics of a spark-ignited, super-charged, stoichiometric gas engine in order to achieve high BMEP equivalent to that of diesel engines. A four-stroke-cycle single-cylinder test engine was used. EGR was completely mixed with intake air before being introduced into the compressor. The results indicate that dry EGR utilizing drained exhaust gas improved the maximum mean effective pressure, as well as specific fuel consumption over the whole load due to improved knock characteristics of the unburnt mixture, increased specific heat ratio (κ), and reduced heat loss. Further experiments were conducted to identify the effect of humidity in the mixture on engine performance. The lean burn method was compared with the EGR method.

Dual-fuel pilot ignited natural gas engines have several intrinsic advantages relative to spark ignited; mainly higher thermal efficiency and lower conversion costs. The major drawback is associated with light loads. This paper discusses objectives, approaches, methods and results of the development of strategies which overcome the drawbacks and enhance the advantages. Development of a pilot fuel injection system, having a delivery of only 1 mm3 at a duration of 0.6 ms, was described in a previous paper. This paper concentrates on the results of strategies to reduce unburned methane in the exhaust and to increase the substitution of gas at light loads through skip-fire, by-passing boost air and exhaust gas recirculation techniques. Engine tests proved that with these strategies, diesel fuel replacement of more than 95% over the entire engine operating map, including idle, can be achieved and current and anticipated future emission standards satisfied.

A pressure accumulative injection rate controllable unit injector-PAIRCUI is proposed and developed. This unit injector is powered by fuel pressure accumulation controlled by an electronic control unit and its injection rate is shaped by inner valves of the injector. Inherent advantages of an accumulator type unit injector have been carried out in this new design, including sructural simplicity, totally flexible injection timing, medium common rail pressure, tolerable pump size and flow requirement. A number of decisive features have also been realized that are significant for high efficiency and low emissions of engine combustion, including higher mean effective injection pressure(MEIP), pilot injection capability and rapid end of injection. The injection pressure is independent of engine speed, but regulated upon engine load. These characteristics are beneficial in improving engine performance and fuel consumption.

The methyl esters of soybean oil, known as biodiesel, are receiving increasing attention as renewable fuels for diesel engines. Biodiesel has a high cetane number, and offers the potential of emission reduction. The properties of biodiesel vary depending on its composition, and this may affect engine performance and emissions. In this project, biodiesel fuels were prepared from feedstocks with modified compositions including the methyl esters of a low palmitic soybean oil, a partially transesterified soybean oil, a synthetic blend of saturated esters, and a commonly used methyl soyate. These esters were blended with No. 2 diesel fuel in 20% and 50% concentrations. The blended fuels were then tested in a diesel engine to investigate the effect of biodiesel composition on performance, combustion characteristics, and emissions.

Documented herein are the methods utilized to meet the performance requirements for operation in RVSM airspace. The test aircraft was equipped with an instrumented static system and a trailing cone static reference. The trailing cone was calibrated in-flight using laser range and radio altitude tower fly-by methods. Determination of the static source error and development of the static source error correction was accomplished on the instrumented aircraft. Verification of RVSM performance was accomplished on a standard production aircraft utilizing the instrumented aircraft as a pace. Additionally, test data were also obtained with perturbations on the skin near the static ports. The measured pressure changes were correlated with computational predictions. These data were used to develop skin waviness tolerances for the area around the static ports.

A personal computer based preliminary structural design system has been developed for general aviation aircraft. Structural design is coupled with other elements of the preliminary design process to provide a unique and powerful framework for the preliminary design process. Capabilities include structural layout, structural weight sizing and detailed stress analysis. All of these can be applied to a number of built-in (and user defined) structural configurations. The program is designed to reduce preliminary design time and produce an efficient well-documented structural design that complies with regulatory specifications.

Recent studies suggest that the use of ethers as fuels or fuel additives may be a key to the simultaneous reduction of both particulate and NOx emissions from Diesel engines. The present study is directed towards understanding the chemical kinetics of autoignition of ethers under Diesel-like conditions. Autoignition experiments were performed in a constant volume apparatus (CVA), that allowed independent control of temperature, pressure, and oxidizing gas composition. Hollow cone sprays of methanol, dimethyl ether (DME), CH3OCH3, and dimethoxy methane (DMM), CH3OCH2OCH3, were created in quiescent air with a standard Diesel injector, and autoignition delays were inferred from pressure-time histories. A detailed chemical kinetic mechanism was developed to describe the pyrolysis, oxidation, and autoignition of methanol, DME and DMM at high pressures. The mechanism predicts autoignition delay time under Diesel-like conditions.

The comprehensive engine simulation code, WAVE, is extended to include a knock sub-model. A hydrocarbon autoignition model based on a degenerate chain-branching mechanism that constitutes the basic kinetic framework was modified and coupled with WAVE's engine thermodynamic environment for this purpose. Making use of this modified hydrocarbon autoignition model and the flow based in-cylinder heat transfer model in WAVE, the original rapid compression machine (RCM) experiments of Shell can be reproduced reasonably well. In addition, a spatially and temporally resolved end-gas thermodynamic model was developed to allow a more accurate calculation of the end-gas temperature over the combustion chamber wall. The developed end-gas thermodynamic-driven knock model further assumes the existence of a pseudo-boundary-layer temperature profile which is linearly distributed between the unburned end-gas and the wall.

Flight Inspection is the Quality Assurance program which the Federal Aviation Administration uses to verify the performance of air navigation facilities and associated Instrument Flight Procedures. As an integral part of the National Airspace System, it is imperative that these facilities and procedures conform to the prescribed standards throughout their published service volume. This paper attempts to explain to the reader just how the FAA uses their Flight Inspection aircraft to accomplish that mission.

Recent technology advancements in hardware and software has allowed the emergence of the PC as a cost effective aircraft design/analysis platform. Software packages such as CSI-CADD, Vellum Solids, and AeroPack provide “Lockheed” class modeling tools for a wide variety of design projects. Modeling tools for airfoils, wings, and polyconic surfaces are discussed as well as data extraction methods for wetted areas, volumes, centroids, area curves, obscuration plots, meshing, and custom interfaces to design analysis programs such as GA-CAD.

This study is aimed at developing requirements for certification criteria and verification techniques for side facing aircraft seats. Presently flying side facing seats were inspected and analyzed. Results from automotive safety research were used and transferred to aircraft. For lateral strain direction, on the one hand human tolerance, and on the other hand injury criteria such as head, cervical column, thoracic/lumbar column, thorax, pelvis as well as upper and lower extremities were compiled from literature. The particularities of side facing seats were inspected with two dynamic tests, and proposals made for the requirements of certification criteria and verification techniques.

The calculation of reliable indexes of oil contamination caused by engine wear is necessary in order to use oil analysis as a failure diagnostic tool. In this paper, a method for the correction of the measurements obtained from oil spectrometric analysis is proposed. A realistic model must consider the combined effects of the oil filter efficiency, the oil consumption and the amount of fresh oil added. The concentration of contaminants is normalized taking into account all the above effects with the assumption of a constant contamination rate. At the beginning of the study the repeatability of the measuring equipment and the effect of the method of obtaining the samples were calculated. Three factors were considered: the location which the sample was taken from (the oil pan drain plug or the oil level dipstick orifice), the engine temperature (cold and warm) and the time delay from sample taking to its analysis.

This paper reports on a continuing Ohio Department of Transportation (ODOT) two year evaluation of a biodiesel blend, B20, (an 80/20 blend of diesel fuel and methyl soyate) in fleet operations. The evaluation is being conducted in two adjacent counties in northwest Ohio. The Fulton county ODOT garage has been operating all diesel powered equipment on B20 since March of 1996 and has been comparing operating results with counterpart equipment in nearby Williams county which has continued operations on diesel fuel. The results of this test are being monitored by Battelle which is collecting and analyzing detailed operational and reliability data on five (5) Navistar-International dump truck / snow plows in each county. Chassis dynamometer evaluation of engine power changes, “before/after” snap-idle smoke tests, identification of cold weather issues, and the consistency of on-site fuel blending have been conducted and are discussed in this paper.

In order to document the level of exhaust emisions from biodiesel fuels compared with conventional diesel fuels, several studies have been conducted throughout the world. The results of these studies are, however, not conclusive, and very few reports exist on the potential health risk caused by exhaust emissions from biofuels. The aim of this investigation is to examine the chemical characteristics of exhaust emissions from Rapeseed oil Methyl Ester (RME) compared with a modern diesel fuel, and to document the potential health risk associated with these fuels.