Stabilizing Excessive EGR With an Oxidation Catalyst on a Modern Diesel Engine

For diesel engines (CIDI) the excessive use of exhaust gas recirculation (EGR) can reduce in-cylinder oxides of nitrogen (NOx) generation dramatically, but engine operation can also approach zones with high instabilities, usually accompanied with high cycle-to-cycle variations and deteriorated emissions of total hydrocarbon (THC), carbon monoxide (CO), and soot. A new approach has been proposed and tested to eliminate the influences of recycled combustibles on such instabilities, by applying an oxidation catalyst in the high-pressure EGR loop of a turbocharged diesel engine. The testing was directed to identifying the thresholds of stable operation at high rates of EGR without causing cycle-to-cycle variations associated with untreated recycled combustibles. The elimination of recycled combustibles using the oxidation catalyst showed significant influences on stabilizing the cyclic variations, so that the EGR applicable limits are effectively extended. The attainability of low NOx emissions with the catalytically oxidized EGR is also evaluated.

Maritime Administration’s Formulation of a Maritime Energy and Clean Emissions Program

The Environmental Protection Agency promulgation of “Control of Emissions of Air Pollution from New Marine Compression Ignition Engines at or above 37 kW,” on December 29, 1999, marked the first time federal air pollution regulations were directly applied to marine engines for commercial U.S. ships. Perhaps surprisingly, these regulations are not having as much impact as are individual State Implementation Plans (SIP) for Nitrogen Oxides (NOx) attainment, and local political pressures. These regional plans and pressures are forcing many domestic marine operators and ports to get a quick education on the cause and mitigation of air pollution. Cases in point, include: • The State of Alaska now fines passenger vessels that enter ports with greater than allowable stack gas opacities. One cruise operator has opted to plug into shore power when its vessels are tied up to pier. • In the Ports of Los Angeles and Long Beach vessel operators have been asked to slow vessel speeds below normal while entering and exiting in a voluntary attempt to reduce NOx emissions. • Environmentalists in the San Francisco Bay Area are applying significant political pressures to ensure proposed new ferry systems emit a minimum of air pollution. • The State of Texas briefly considered stopping all industrial equipment in the Port of Houston for twelve hours per day as a method of decreasing area ozone formation. • Potential NOx emissions generated during imminent channel dredging in the Port of New York and New Jersey is impeding the development of the latest State Implementation Plan. Local pressures are likely to continue to grow, federal regulations are set to become more stringent, and international conventions loom on the horizon. However, as expected in such a competitive industry, concerns are often focused on the bottom line in which cost of operations is a pre-eminent factor. It was in view of these dynamics that the federal Maritime Administration (MARAD) recently launched the Maritime Energy and Clean Emissions Program. This paper introduces the Program, including the background, evolution, and progress of each strategic goal. This paper is intended to be an overview. Attention is paid to the potential transferability and/or development of technologies not previously deployed in the U.S. marine environment. Any of the specific projects described could become the basis for a separate technical paper.

Assessing Double Injection and Intake Air Temperature Effects on Gasoline HCCI Engine Performance and Emissions Using Fully-Automated Experiments and Micro-Genetic Algorithms

Homogeneous charge compression ignition (HCCI) is receiving attention as a new low emission engine concept. Little is known about the optimal operating conditions for this engine operation mode. Combustion at homogeneous, low equivalence ratio conditions results in modest temperature combustion products, containing very low concentrations of NOx and PM as well as providing high thermal efficiency. However, this combustion mode can produce higher HC and CO emissions than those of conventional engines. An electronically controlled Caterpillar single-cylinder oil test engine (SCOTE), originally designed for heavy-duty diesel applications, was converted to a HCCI direct-injection gasoline engine. The engine features an electronically controlled low-pressure common rail injector with a 60°-spray angle that is capable of multiple injections. The use of double injection was explored for emission control, and the engine was optimized using fully-automated experiments and a micro-genetic algorithm (μGA) optimization code. The variables changed during the optimization include the intake air temperature, start of injection timing, and split injection parameters (percent mass of the fuel in each injection, dwell between the pulses). The engine performance and emissions were determined at 700 rev/min with a constant fuel flow rate at 10 MPa fuel injection pressure. The results show that significant emissions reductions are possible with the use of optimal injection strategies.

Investigation of a Novel Fuel Injection Technology Aimed to Reduce Cold-Start Emissions in SI Engines

A novel fuel atomization device (Nanomiser™) was evaluated under laboratory conditions with respect to its ability to reduce SI engine cold-start hydrocarbon emissions. First, comparisons between the level of atomization using the conventional, pintle-type fuel injector and the novel atomizer were carried out using flow visualization in a spray chamber and particle size distribution. The novel atomizer is capable of producing sub-micron fuel droplets, which form an ultra-fine mist with outstanding non-wetting characteristics. To capitalize on these atomization characteristics, this device was compared to a conventional fuel injector in a small, two-cylinder, SI engine under a number of operating conditions. Results show a slightly enhanced combustion quality and lean limit under warm operating conditions and a dramatic reduction in unburned HC emission under cold operating conditions, with cold emissions with the Nanomiser™ matching those with a conventional injector under fully warm conditions.

Engine Failure Experience Improves the Product

There are the inevitable occasions when something goes wrong despite the great care taken when engines are designed, built, operated and serviced. Failures can lead at best to some cost and inconvenience or at the worst to a totally destroyed engine. The cost of repairs, followed sometimes by many weeks of down time, can be enormous. In addition there is the critical question of safety and the risk of injury to personnel. By analyzing failures and their causes a lot of experience can be gained and used to the benefit of all. This experience can improve future products. The paper describes some failures which have been experienced by the authors and shows how an analysis of the evidence has identified the root cause. We show how the knowledge gained improves our ability to predict engine behavior and the stress field in the components concerned. The paper goes on to describe what measures can be taken to improve the product and to prevent the circumstances from happening again. The use of Failure Mode and Effect Analysis (FMEA) is described because experience gained from failures can make this an extremely powerful tool when used during the design process.

A New Approach to Fit Bearing Performance to Advanced Gas Engine Technology

Gas engines get an increasing market share compared to four stroke engines, especially in the field of energy systems. Under these special firing conditions engine components are stressed differently than in traditional diesel engines. This particularly is the case for bearings. In order to supplement the knowledge base for bearing performance under these aggravated conditions, special test methods have been developed to find out reasons for premature bearing failure characteristics. In combination with experience from the long term behavior of different bearing types in different gas engine applications, this data allows the development of improved bearing materials as well as bearing designs. Using this knowledge in combination with advanced simulation tools, a bearing supplier can offer assistance to select adequate bearing designs, give a life time prediction and in case of unexpected phenomena, redesign recommendations. The paper presents reasons and influences for life time limitations as well as different risk factors for available bearing types and situations. Based on field experience and data from the advanced bearing test procedures, values for bearing performance are given. Data for hydrodynamic performance, tribological properties and emergency running behavior, cavitation resistance, wear resistance and last, but not least corrosion resistance against active sulfur and halogens will be given for traditional and newly developed bearing materials. A short view into the future will finish the presentation.

The Effect of Parametric Variations on Formaldehyde Emissions From a Large Bore Natural Gas Engine

Formaldehyde is a hazardous air pollutant (HAP) that is typically emitted from natural gas-fired internal combustion engines as a product of incomplete combustion. The US Environmental Protection Agency (EPA) is currently developing national emission standards to regulate HAP emissions, including formaldehyde, from stationary reciprocating internal combustion engines under Title III of the 1990 Clean Air Act Amendments. This work investigates the effect that variations of engine operating parameters have on formaldehyde emissions from a large bore natural gas engine. The subject engine is a Cooper-Bessemer GMV-4TF two-stroke cycle engine with a 14″ (36 cm) bore and a 14″ (36 cm) stroke. Engine parameter variations investigated include load, boost, ignition timing, inlet air humidity ratio, air manifold temperature, jacket water temperature, prechamber fuel supply pressure, exhaust backpressure, and speed. The data analysis and interpretation is performed with reference to possible formaldehyde formation mechanisms and in-cylinder phenomena.

A Model for Droplet Vaporization for Use in Gasoline and HCCI Engine Applications

A model for unsteady droplet vaporization is presented that considers the droplet temperature range from flash-boiling conditions to normal evaporation. The theory of continuous thermodynamics was used to model the properties and compositions of multi-component fuels such as gasoline. In order to model the change of evaporation rate from normal to boiling conditions more realistically, an unsteady internal heat flux model and a new model for the determination of the droplet surface temperature is proposed. An explicit form of the equation to determine the heat flux from the surrounding gas mixture to the droplet-gas interface was obtained from an approximate solution of the quasi-steady energy equation for the surrounding gas mixture, with the inter-diffusion of fuel vapor and the surrounding gas taken into account. The model was applied to calculate evaporation processes of droplets for various ambient temperatures and droplet temperatures.

Analysis of a 6 Cylinder Turbocharged HCCI Engine Using a Detailed Kinetic Mechanism

When analyzing HCCI combustion engine behavior, the integration of experimental tests and numerical simulations is crucial. Investigations of possible engine control strategies as a function of the different operating conditions have to take the behavior of the whole HCCI engine into account, including the effects both of the combustion process and of complex devices. Therefore the numerical simulation code must be able both to model accurately the gas-dynamic of the system and to evaluate the combustion chemical kinetics. This paper focuses on the coupling between the commercial one-dimensional fluid-dynamic GT-Power Code and our in-house detailed chemical kinetic Ignition Code. An interface has been developed in order to exchange information between the two codes: the Ignition Code considers as boundary conditions the GT-Power Code values provided for the gas composition at IVC and the pressure and temperature at every time step and passes back to GT-Power the burnt fuel fraction and stores in an external file the in cylinder gas composition. Thus the whole engine cycle can be accurately simulated, estimating the interactions between the gas-dynamics phenomena along the intake and exhaust pipes and through the valves, and the chemical processes occurring during the closed valves period. This tool makes it possible to analyze the engine behavior under duty cycle operating conditions, and therefore it represents a useful support to the experimental measurements, reducing the number of tests required to assess the proper engine control strategies.

Influence of Nucleate Boiling on the Design of Automotive Cooling Systems

With higher power ratings in automotive cooling systems the correct calculation of the heat transfer coefficient when nucleate boiling is occurring has become important. In accounting for the enhanced cooling that nucleate boiling provides, analysts can achieve two goals: more accurate metal temperature prediction at local hot spots; and an assessment of the probability that catastrophic film boiling will occur. Two correlations examined: the classic Chen correlation and the more recent Liu and Winterton correlation. The method of extending the correlations to mixtures is explained. Predictions are presented for the 50:50 mixture of water and ethylene glycol, and compared with literature data. The method of incorporating these correlations into engine CAE analysis is explained and demonstrated. The paper also considers the effect of nucleate boiling on vapor production, leading to vapor blanketing and the critical heat flux. A method of estimating critical heat flux for the mixture is described.