Experiments and Modelling of Producer Gas Based Reciprocating Engines

A 20 kW reciprocating engine is operated using producer gas derived from a modern open top downdraft re-burn biomass gasifier that has been evaluated by rigorous laboratory performance testing over several hundred hours. The engine is operated at varying compression ratio (CR) from 11.5 to 17.0 and ignition timings from 30 to 6° before Top Centre (TC). The engine – alternator system is characterised for its performance by the simultaneous measurement of gas and airflow rates, gas composition (on-line), emission levels and power delivered. It is also instrumented to obtain the in-cylinder behaviour in the form of pressure-crank angle (p – θ) diagram to assess the thermodynamic behaviour of the engine. Three-dimensional (3-D) simulation of the flow field in the combustion chamber (involving piston-bowl arrangement) through the cycle up to the start of the combustion is used to obtain inputs on the turbulence intensity (u′) and length scale (lT) for the modelling of the flame propagation process in a zero-dimensional model (0-D) designed to predict the p – θ curve. The flame propagation and heat release processes make use of eddy entrainment and laminar burn-up model. The data on u′ extracted from the 3-D flow calculations match reasonably well with experiments till compression stroke but are in contradiction with trends close to TC. This is reasoned to be due to limitation of the k-ε model to capture transient effects due to reverse squish phenomenon. The 0-D model took into account the experimental behaviour of the u′ in the post-TC period to attempt to match the observed p – θ data over a range of CRs and ignition timing advances. While these predictions match well with the experimental data at advanced ignition timing at both higher and lower CRs, the peak pressure is under-predicted at lower ignition advances; reason are traced to increase in flame area and propagation speed due to reverse squish effect. When these are accounted in the model, the p – θ curves are predicted better.

On-Board Indicated Pressure and Torque Estimation in Engines With a High Number of Cylinders

In recent years engine control development focused the attention on torque-based models, that allow improving driveability and implementing traction control strategies. The design of such a torque-based engine control strategy requires the knowledge of the torque produce by the engine, which depends on fuel injection time, spark advance, throttle opening, EGR command, … In the actual engine control strategies this is mainly done by means of static maps stored in the ECU memory. The real engine torque production under every operating condition can be evaluated by means of the in-cylinder pressure estimation, thus allowing a torque based closed loop control strategy. Many approaches are present in the literature showing the possibility of on-board estimating the actual torque produced by the engine not simply by using static maps, but estimating it through other measured signals. Most of the methodologies that do not require a specific sensor placed on the engine are based either on the engine speed fluctuations (measured by a pick-up facing the flywheel teeth) or on the engine block vibrations (measured by the knock sensor), performing better for engines with a low number of cylinders. The paper presents an original methodology based on the instantaneous engine speed fluctuations, that has been usefully applied to engines with higher number of cylinders. The methodology is based on the observation of the speed fluctuations in a crankshaft window inside the expansion stroke and on the hypothesis that there exists a strong correlation between these engine speed fluctuations and pressure inside the selected cylinder. This relationship has been characterized using Frequency Response Functions (FRF) for each steady-state engine operating condition. In the following the FRFs have been used to perform in-cylinder pressure and then indicated torque estimation under every operating condition, and a specific signal processing algorithm has been developed in order to apply the procedure during speed and load engine transients. The experimental tests have been conducted mounting a six-cylinder turbo-charged spark-ignited engine in a test cell. The application on-board a vehicle of the same methodology seems to be feasible due to the quickness of the algorithm employed and the presence on-board of all the sensors required for the implementation.

Influence of Duty Cycles and Fleet Profile on Emissions From Locomotives in Canada

Analyses were carried out of the exhaust emissions from locomotives in Canadian railway operations based on data as of the end of 2001. The authors found that locomotive technology used in the fleet significantly influenced the emission factor while duty cycles had a lesser influence. This is because despite using less fuel for the horse-power produced, the newer diesel engines produce more emissions per unit of fuel consumed. Since 1997, there has been a significant change in the locomotive fleet profile as the Canadian Class I railways replace their 1970s’ era 3,000HP SD-40 type locomotives with modern fuel-efficient 4,300 to 6,000HP locomotives. The new locomotives being introduced, or when re-manufactured, after January 1st 2000 meet the Tier 0 emission standards of the U.S. Environmental Protection Agency. Unlike the U.S.A. where the emissions limits are the subject of legislated standards, the current Canadian situation is a voluntary one aiming to keep, country-wide, locomotive emissions of oxides of nitrogen (NOx) below a cap of 115,000 tonnes per year. The authors’ analyses provide a database upon which trends and scenarios can be examined vis-a-vis the voluntary cap set by the Railway Association of Canada for the period 1995 to 2005 in its Memorandum of Understanding with Environment Canada regarding railway locomotive emissions.

Particulate Emissions From a Two-Stroke Marine Diesel Engine Operated With Heavy Fuel Oil

In these years, a problem of air pollution in a global scale becomes a matter of great concern. In such social situation, diesel engines are strongly required to reduce the NOx and particulate emission in the exhaust gas. In this paper, measurements of particulate emissions from a low speed two-stroke marine diesel engine were conducted with several kinds of diesel oil and a heavy fuel oil, to know the characteristics of particulate emissions at the present situation. The effects of engine load and sulfur content of the fuel on the particulate emission have been examined. The particulate emission from the test engine was measured by partial-flow dilution tunnel system, and particulate matter collected on the filter was divided into four components, SOF (soluble organic fraction), sulfate, bound water and dry soot, by Soxlet extraction and ion chromatograph. Results show that the particulate emission from the test engine operated with heavy fuel oil is three times as much as the value with diesel oil and that not only sulfate but SOF and dry soot concentration increase with the increase in fuel sulfur content. It is also found that the conversion rate from sulfur in fuel into sulfate in particulate matter is nearly independent of the sulfur content in the fuel and increases with the increase in the engine load.

An Analysis of the Simplified Two-Mass System of the Connecting Rod in Spark Ignition Engines

Replacing the connecting rod with a lumped two-mass system causes an error, which influences the inertia rolling moment, the thrust force between the piston and the cylinder liner, and the loading on the main bearings. Dimensionless relationships have been found that relate the inertia error due to the connecting rod simplification (the inertia error) to the errors of the forces and moments that are created by it. Additionally, the results of a statistical study of 19 SI connecting rods indicate that the mass moment of inertia of the two mass system is −2.65% to 22% higher than that the experimentally measured moment of inertia of the connecting rod, with an average error value of 9.65%.

Use of a Micro-Contact Model to Optimize SI Engine’s 3-Piece Oil Ring Profiles Regarding Wear and Lubrication

A computer model that addresses the wear behavior by calculating hydrodynamic and asperity contact pressures was used to optimize the running face of three-piece oil control rings. The model incorporates Reynolds equation to calculate the oil film thickness for two sliding surfaces under a given condition (profile and topography of the surfaces, load, speed, lubricant viscosity grade and operation temperature). Prediction of the resultant asperity contact pressures is made by Greenwood-Williamson model. More scraping ring rail profiles are better for oil control, but present more wear due to higher asperity contact pressures. This higher wear can lead to less scraping profile, increasing ring end gap and lower ring tangential load, which deteriorates long term oil consumption control, hence engine durability. In the present work, a relatively simple computer program was used to predict lube oil film thickness and wear for different rail running profiles. Ring wear was assumed to be proportional to the calculated asperity contact pressure. Different rail profiles where the running profiles had a flat portion varying from less than 0.10 mm to higher than 0.20 mm were simulated and then tested in a bench test consisting in an electrical motored engine. Except for the combustion absence, all other engine characteristics were preserved (e.g., stroke, piston-ring pack, lubrication system) in the bench test. The measured oil control ring wear correlated very well with the predicted one. The model allowed the numerical optimization of the running profile of ring rail, which has lower asperity contact pressure, hence wear, but still has a good scraping capability. Two actual ICE tests were also realized. The predicted lower wear of the optimized profile was experimentally confirmed and no differences on LOC were found.

Design and Service Experience of the Electronically Controlled ME Engine

The Norwegian shipowner Odfjell has had more than one year’s experience of operating a vessel powered by an MAN B&W 6L60MC/ME low-speed engine capable of operating by electronic valve control, without a camshaft. During that period, the engine has run in both conventional and camless modes. Valuable data has been collected on the impact of camless engine technology, on operating performance, and on operating costs. Odfjell has now ordered a 7-cylinder S50ME-C engine, featuring electronic operation, for installation on a 37,500 dwt chemical tanker newbuilding.

Theoretical Investigation of Autoignition of Combustible Gas Mixtures in Rapid Compression Machines

In any theoretical investigation of ignition processes in natural gas reciprocating engines, physical and chemical mechanisms must be adequately modeled and validated in an independent manner. The Rapid Compression Machine (RCM) has been used in the past as a tool to validate both autoignition models as well as turbulent mixing effects. In this study, two experimental cases were examined. In the first experimental case, the experimental measurements of Lee and Hochgreb (1998a) were chosen to validate the simulation results. In their experiments, hydrogen/oxygen/argon mixtures were used as reactants. In the simulations, a reduced chemical kinetic mechanism consisting of 10 species and 19 elementary reactions coupled to a CFD software, Fluent 6, was used to simulate the autoignition. The ignition delay from the simulation agreed very well with that from the experimental data of Lee and Hochgreb, (1998b). In the second case, experimental data derived from an RCM with two opposed, pneumatically driven pistons (Brett et al., 2001) were used to study the autoignition of methane/oxygen/argon mixtures. The reduced chemical kinetic mechanism DRM22, derived from the GRI-Mech reaction scheme coupled to Fluent 6, was applied in the simulations. The DRM22 scheme included 22 species and 104 reactions. When methane/oxygen/argon mixture were simulated for the RCM, the ignition delay deviated about 15% from the experimental results. The simulation approaches as well as the validation results are discussed in detail in this paper. The paper also discusses an evaluation of reduced reaction models available in the literature for subsequent Fluent modeling.

Unsteady Flows Inside the Piping Systems of Internal Combustion Engines: 1-D Simulation Modeling and Experimental Validation

The main difficulty for the one-dimensional simulation of pressure waves in the inlet and exhaust systems of Internal Combustion Engines consists in the modeling of singularities (area changes, bends, junctions, etc.). The models presented in the literature are based on the behavior of the singularity in steady flow. However the pressure losses due to the wave propagation are different from those obtained in stationary flow. The authors’ objective is to propose models with a better precision based on the non steady study of the singularities which can be found in Internal Combustion Engines. Specifically, this paper presents the investigation of the pipe wall friction factor and the sudden contraction area. The first step consists in studying the behavior of pressure waves through pipes with the Fluent CFD code. Next, a model parameterized with the Reynolds number is proposed for the pipe wall friction factor while another one with the Mach number is proposed for the sudden contraction area. These models are included in a 1-D simulation code. Finally, in order to evaluate the accuracy of the simulation program, the models are compared with experimental data. The results show a satisfactory agreement between model predictions and experimental measurements.

Application of Over-Expansion Cycle to a Larger Gasoline Engine With Late-Closing of Intake Valves

This paper presents further investigation into the effect of over-expansion cycle with late-closing of intake valves on the engine performance in gasoline engines. A larger single-cylinder test engine with the stroke volume of 650 cc was used with four kinds of expansion ratio (geometrical compression ratio) from 10 to 25 and four sets of intake valve closure (I.V.C.) timings from 0 to 110 deg C.A. ABDC. Late-closing has an effect of decreasing the pumping work due to the reduction of intake vacuum, althogh higher expansion ratio increases the friction work due to the average cylinder pressure level. Combining the higher expansion ratio with the late-closing determines the mechanical efficiency on the basis of these two contrastive effects. The indicated thermal efficiency is mostly determined by the expansion ratio and little affected by the nominal compression ratio. The value of the indicated thermal efficiency reaches to 48% at most which is almost comparable with the value of diesel engines. The improvement of both indicated and brake thermal efficiency reaches to 16% which is much higher than ever reported by the authors. A simple thermodynamic calculation could successfully explain the behavior of the indicated thermal efficiency. The brake thermal efficiency could also be improved due to the increase in both mechanical and indicated efficiencies.