Search Results

Experimental investigations relating to the performance and emission characteristics under idling conditions of a three cylinder passenger car spark ignition engine operating on a conventional carburettor and a developed single point gasoline fuel injection system are described in this paper. The idling performance at different engine speeds was studied by carrying out comprehensive engine testing on a test bed in two phases. In the first phase, experiments were conducted on an engine fitted with a conventional carburettor whilst they were extended to the engine provided with a developed electronic single point fuel injection (SPI) system, whose fuel spray was directed against the direction of air flow. The injection timing of the SPI system was varied from 82 deg. before inlet valve opening (or 98 deg. before top dead center) to 42 deg. after inlet valve opening (or 26 deg. after top dead center).

Uncertainty about future costs and operating attributes of electric drive vehicles (EVs and HEVs) has contributed to considerable debate regarding the market viability of such vehicles. One way to deal with such uncertainty, common to most emerging technologies, is to pool the judgments of experts in the field. Data from a two-stage Delphi study are used to project the future costs and operating characteristics of electric drive vehicles. The experts projected basic vehicle characteristics for EVs and HEVs for the period 2000-2020. They projected the mean EV range at 179 km in 2000, 270 km in 2010, and 358 km in 2020. The mean HEV range on battery power was projected as 145 km in 2000, 212 km in 2010, and 244 km in 2020. Experts' opinions on 10 battery technologies are analyzed and characteristics of initial battery packs for the mean power requirements are presented.

Cycle-resolved end-gas temperatures were measured using dual-broadband rotational CARS in a single-cylinder spark-ignition engine. Simultaneous cylinder pressure measurements were used as an indicator for knock and as input data to numerical calculations. The chemical processes in the end-gas have been analysed with a detailed kinetic mechanism for mixtures of iso-octane and n-heptane at different Research Octane Numbers (RON'S). The end-gas is modelled as a homogeneous reactor that is compressed or expanded by the piston movement and the flame propagation in the cylinder. The calculated temperatures are in agreement with the temperatures evaluated from CARS measurements. It is found that calculations with different RON'S of the fuel lead to different levels of radical concentrations in the end-gas. The apperance of the first stage of the autoignition process is marginally influenced by the RON, while the ignition delay of the second stage is increased with increasing RON.

A simple set of equations has been developed to characterize automotive fuel behavior in fuel tanks, fuel vapor systems and fuel rails, particularly under hot weather conditions. The system of equations links the vapor pressure P, the temperature T, and the mass fraction evaporated Z. Parameters are determined empirically from laboratory vapor pressure and distillation tests. With appropriate values for heat capacity, heat of vaporization, and vapor composition, the equations can be used to estimate upper flammability limits, fuel weathering under hot fuel handling conditions, pressure rise in tanks, and evaporative vapor generation. The equations were developed as part of a larger fuel vapor system model.

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.