Development of Pre-Turbo Catalyst for Natural Gas Engines

Distributed power generation is an efficient method for reducing CO2 emissions through the elimination of transmission losses. Co-generation has similar benefits with higher thermal efficiency. Natural gas engines are very popular for these applications. Unfortunately, these engines emit significant levels of methane, which is a greenhouse gas. Reduction of methane emissions would greatly improve the environment and provide greenhouse gas emissions credits. The exhaust temperature downstream of the turbocharger in a natural gas engine is typically below 500°C. At these temperatures, methane is difficult to oxidize with current oxidation catalysts. It would be a much better option to install the oxidation catalyst before the turbocharger where temperatures are 100–150°C higher. Pressures upstream of the turbocharger are higher than downstream and also affect catalyst conversion efficiencies. Misfiring events are common in natural gas engines. During misfiring events, the catalyst will see a sudden increase in hydrocarbon (methane). When this pulse of hydrocarbon hits the catalyst, it will be oxidized and generate a large exotherm which could lead to catalyst failure (mechanical and/or chemical). This issue is critical for a pre-turbo catalyst: 1) Mechanical failure of the catalyst could lead to catastrophic turbocharger failure, a result of the turbine blades being damaged. 2) Misfiring with catalyst installed before the turbocharger is more likely to ignite the methane pulse because of the higher temperatures in this location. High exotherms from ignition could negatively affect catalyst performance. Through careful catalyst design, one can minimize this risk and this paper will address these issues.

Transient and Unstable Torsional Vibrations on a 4-Stroke Marine Diesel Engine

Under steady state condition, unstable torsional vibration normally does not occur in shafting systems using 4stroke diesel engine due to hysteresis damping of shafting system and relative damping of standard fitted damper. However, the unstable torsional vibration occurs on marine propulsion shafting systems due to slippage of a multi-friction clutch installed between increasing gear box and shaft generator. To identify this unstable vibration and make proper counter measure, the simulation for transient torsional vibration using the Newmark method is introduced in this paper. The mechanism of this unstable vibration is verified by vibration and noise measurements of the shafting system.

A Laminar Burning Velocity Correlation for Hydrogen/Air Mixtures Valid at Spark-Ignition Engine Conditions

During the development of a quasi-dimensional simulation programme for the combustion of hydrogen in spark-ignition engines, the lack of a suitable laminar flame speed formula for hydrogen/air mixtures became apparent. A literature survey shows that none of the existing correlations covers the entire temperature, pressure and mixture composition range as encountered in spark-ignition engines. Moreover, there is ambiguity concerning the pressure dependence of the laminar burning velocity of hydrogen/air mixtures. Finally, no data exists on the influence of residual gases. This paper looks at several reaction mechanisms found in the literature for the kinetics of hydrogen/oxygen mixtures, after which one is selected that corresponds best with available experimental data. An extensive set of simulations with a one-dimensional chemical kinetics code is performed to calculate the laminar flame speed of hydrogen/air mixtures, in a wide range of mixture compositions and initial pressures and temperatures. The use of a chemical kinetics code permits the calculation of any desired set of conditions and enables the estimation of interactions, e.g. between pressure and temperature effects. Finally, a laminar burning velocity correlation is presented, valid for air-to-fuel equivalence ratios λ between 1 and 3 (fuel-to-air equivalence ratio 0.33 < φ < 1), initial pressures between 1 bar and 16 bar, initial temperatures between 300 K and 800 K and residual gas fractions up to 30 vol%. These conditions are sufficient to cover the entire operating range of hydrogen fuelled spark-ignition engines.

Exhaust Emissions of an Off-Road Diesel Engine Driven With a Blend of Diesel Fuel and Mustard Seed Oil

In the near future, crude oil based fuels must little by little be replaced by biofuels both in the region of the European Union (EU) and in the United States. Bearing this in mind, a Finnish-made off-road diesel engine was tested with a biofuel-diesel fuel blend in the Internal Combustion Engine (ICE) Laboratory of Turku Polytechnic, Finland. The biofuel was cold-pressed mustard seed oil (MSO). The engine operation, performance and exhaust emissions were investigated using a blend of 30 mass-% MSO and 70 mass-% diesel fuel oil (DFO). The injection timing of the engine was retarded considerably in order to reduce NOx emissions drastically. The main target was then to find out, whether the blended oxygen containing MSO would speed up the combustion so that the particulate matter (PM) emissions would remain unchanged or even decrease despite the injection retardation. As secondary tasks of the study, the NOx readings of the CLD and FTIR analyzers were compared, and exhaust contents of unregulated compounds were determined. Retarding the injection timing resulted in a significant decrease of NOx emissions, but in an increase in smoke, as expected. At retarded timing, the NOx emissions remained almost unchanged, but the amount of smoke decreased when the engine was run with the fuel blend instead of DFO. At retarded timing at rated speed, the number of ultra-fine particles decreased, but the amount of large particles increased with DFO at full load. At 10% load, however, the particle number increased in the entire particle size range due to retardation. At both loads, the use of the fuel blend slightly reduced larger particles, whereas the number of small particles somewhat increased. At full load at an intermediate speed of 1500 rpm, the PM results were very similar to those obtained at rated speed. At 10% load with DFO, however, the injection retardation led to a higher number of larger particles, the smaller particles being at almost an unchanged level. With the fuel blend, the particle number was now higher within almost the whole particle diameter range than with DFO. Considerably higher NO2 contents were usually detected with FTIR than with CLD. The shape of the NOx result curves were rather similar independent of which one of the analyzers was used for measurements. The NOx contents were, however, generally some ten ppms higher with FTIR. The exhaust contents of unregulated compounds were usually low.

3-Way Catalyst Testing at VTT Energy

Emissions regulations on stationary, natural gas fired reciprocating engines are becoming increasingly tighter throughout the United States. In addition to lower NOx, CO and hydrocarbon limits, regulation of HAP (Hazardous Air Pollutant) emissions has become more prevalent. Rich burn (stoichiometric) natural gas engines are widely used in the oil and gas industry, as well as in distributed power generation. Due to the low oxygen content in the exhaust, these engines are suitable for 3-Way catalyst, which simultaneously reduces NOx and oxidizes CO and hydrocarbons. A series of 3-Way catalyst tests were conducted on a small natural gas engine at the VTT Technical Research Centre in Espoo, Finland. The overall goals of the testing were to determine the ability of various 3-Way catalysts to meet California emissions regulations and to gather data on HAPs emission reductions. The testing was carried out in two phases. In phase 1, several fresh catalysts were tested at the NOx/CO crossover point (i.e., the point where CO and NOx reduction percent is approximately equal) by using an air/fuel ratio controller to keep the exhaust oxygen level constant. Detailed emissions measurements of both regulated and unregulated emissions were taken. The measurements included NOx, CO, hydrocarbon species, CH2O, N2O, NH3, and H2. In phase 2, the effects of exhaust lambda variation on NOx and CO were studied in more detail, with aged catalyst. Also, different engine loads were tested to vary the space velocity and temperature. This paper describes the testing in more detail and presents some of the resulting data.

Simulation of the Airflow Characteristics of a Two-Stroke Natural Gas Engine With an Articulated Crank

The topic of this paper is the simulation of the airflow characteristics of a large bore two stroke natural gas fueled engine. The modeling was performed with the program WAVE, a computer code developed for engine cycle simulations. The engine studied was a four cylinder Cooper GMV engine. This engine has an articulated crankshaft connecting even and odd bank cylinders. Due to the articulation, the even bank cylinders have different piston profiles, port profiles, and compression ratios than the odd bank cylinders. Due to the non-symmetric timing and articulated geometry of the odd and even banks, the gas flow processes are not the same for each cylinder bank. The different manifold and port pressure profiles result in different amounts of trapped mass in the odd and even banks. The even bank is predicted to have a smaller amount of trapped mass and slightly lower trapping and scavenging efficiencies. Finally, the model predicts that the even bank cylinders attain higher maximum temperatures, which would produce increased NOx.

Improving the Performance of Gas Engine Oils: A New Generation of Geo-Specific Additive Systems

Additive technologies able to successfully lubricate gas engines have been available for many years, but in recent years the acceleration of both commercial and technical demands placed on gas engine lubricants has highlighted the performance limits of traditional additive solutions. One of these limits is the ability to reach long and very long oil drains, required by an increasing number of operators. Since traditional additive chemistries on conventional base oil systems have reached their limits in that respect, focus has been increasingly placed on using higher performance base oils so that longer oil drains can be reached. However, traditional additive chemistries have often proved to struggle in these higher performance base oils, particularly in the aspect of deposit control — demonstrating that a new generation of additive systems for the formulation of gas engine oils is needed. The authors present one such generation of additive systems, developed around off-the-beaten-track detergent technology; providing superior control of oxidation and deposits. Such additive systems can be used either in conventional base oil systems with improved drain interval, or in high performance base oil systems with very long drain interval and excellent control of deposits. Besides the description of the chemistry involved, the authors also present a methodology of performance evaluation in the laboratory, and compare this methodology with the performance perceived in the field.

Methodology in the Development Process of Large Gaseous Fuelled Engines

High demands are placed on large gaseous-fuelled engines regarding performance, fuel consumption and emissions. Because of the different applications of gaseous-fuelled engines (block-type thermal power stations, generation of electric power in a stand alone plant, etc.) and the use of different kinds of gases (natural gas, wood gas, pyrolysis gas, dump gas, etc.), the optimization process can be seen as a very complex task. Today engines have already reached a high level of development and further improvements can only be realized with very high expenditures. Experience has shown that a purely experimental approach is no longer sufficient and therefore the application of modern simulation tools is necessary. In this paper a combined development process is described consisting of simulation, experimental investigations on a single cylinder research engine and transfer on a full scale engine as an example for the optimization of a gas-purched prechamber concept.

An Experimental and Computational Investigation on the Pre-Heating of Fuel to Improve Cold Starting of Diesel Engines

This paper describes the effect of elevated fuel temperature on cold starting operability in compression ignition engines. This study was based on the hypothesis that in a cold start condition, fuel heated to a temperature higher than the surrounding ambient air before it enters the combustion chamber would improve cold starting. Experiments on heating the injector and the fuel before the injection event were performed in a cold room facility with ambient temperatures varying from −20 degrees to 20 degrees Celsius. A computational analysis of the injector was conducted using Star-CD to more fully understand the physical phenomena involved and help explain results obtained from the experiment. Results indicated that fuel heating does affect the efflux velocity, Sauter mean diameter and the lifetime of a fuel droplet. Droplet break-up time and spray penetration are not much affected. Computational and experimental results were within 30% of each other. Results of this work should be useful in the design of improved cold starting methods of diesel fueled engines.

Performance Characteristics of a Diesel Engine Fueled With Avio-Kerosene

A comparative series of experimental tests has been performed on a 4-stroke multi cylinder indirect injection diesel engine fueled with diesel oil, pure gas-turbine fuel and gas-turbine fuel with additives. The engine has been equipped aimed at monitoring both the overall performances and the variation with time of the pressure in the pre-combustion chamber. Some key parameters have been investigated at different engine speeds and loads (ignition delay, pressure rise in the pre-combustion chamber, power output, specific fuel consumption, exhaust gas temperature) and discussed results are presented.