ARCHIVE

Michele Schiliro; Raghavendra Hegde; Iulian Vasile
Liebherr Machines Bulle SA, Bulle

Guoqing Xu
Liebherr Machines Bulle SA, Bulle/ETH, Zürich

Abstract

The gas engine manufacturers and customers are constantly seeking improvements in order to meet the stringent emission standards, lower operating cost, higher efficiency, greater robustness, longer maintenance intervals and lower maintenance cost. In the last couple of years, Liebherr Machine Bulle SA (LMB) has devoted significant amount of resources in developing a new family of gas engines G96 to meet the above-mentioned expectations.

LMB started using the innovative virtual engineering tools, such as 1D/3D engine thermodynamic/CFD simulation, 3D FEM simulation, multibody analysis to understand the physical/chemical processes and to optimize the subsystems involved. These tools were from the beginning strongly coupled with the engine design even in the concept phase. Thanks to this systematic engine development process and new concepts/technologies implemented, the G96 series of engines show a considerable increase in efficiency compared to the previous generation of Liebherr gas engines.

This led to the development of a new valve train mechanism, chamber spark plug ignition system coupled with a new cylinder head design and an optimized crankshaft for G96 gas engines. The new engine control unit (ECU) developed by Liebherr is also used in the G96 engine family. The ECU is capable of undertaking all control and protection functions of the engine.

Dr. Frederik Hahn*; Johannes Bauer; Udo Sander
MTU Friedrichshafen GmbH

Abstract

Extension of a variable speed diesel engine being in series production since 2007 to enable additional usage of gaseous fuels is described in the following. Development of the presented aftermarket kit is motivated by the increasing importance of fuel cost savings, as well as due to its potential to operate diesel only if gaseous fuels are unavailable. The contribution covers requirements and concept, technical solution, engine control and performance of the installed aftermarket kit. While emission limits are fulfilled highest diesel fuel saving are achieved especially for part load conditions typical for well servicing. This is possible using a wide range of gaseous fuels, e.g. oil accompanying gases with low treatment.

ABC`s Dual Fuel Engines in pioneering applications
L. Mattheeuws, L. Verwaeke; ABC Gent, Gent, BE

Abstract

Anglo Belgian Corporation (ABC) has over 100 years of experience in the construction of internal combustion engines. ABC was founded in 1912 with the leading principle of constructing strong and reliable engines. In marine applications, diesel or HFO has been the base fuel for the engine for many years. The last years, due to emission legislations and the belief of our customers in green maritime solutions, people start looking to new concepts. Optimizing the standard engine on diesel is one option, but fuel diversity (natural gas, methanol, …) is an alternative way that has become more and more attractive. As ABC has a long experience with dual fuel engines on land based application, it is ideal to expand the dual fuel engines to maritime applications.

ABC started with a dedicated team to develop a dual fuel engine for maritime applications and focused on a specific concept which makes it possible to have load response times even shorter than a pure diesel engine. Other topics where the decrease in pilot fuel quantity, obtaining the class approval and working on a safety concept. This made the new developed dual fuel engine available for the marine market.

The very good load impact response time of the engine together with the reliability and robustness has lead to the first project where two 12DZD-engines are installed on board of the roro ferry of TESO, the Texelstroom. The Texelstroom is a hybrid ferry with solar panels and two dual fuel engines fuelled with CNG as a clean fuel. The dual fuel engines are installed as a generator set and are used as hybrid propulsion together with a large battery pack that helps during big load demands to reduce the exhaust emissions.

Also DEME had interest in the ABC dual fuel engine concept and made an agreement to build a green dredging vessel. For this, ABC has to deliver two 16DZD engines and one 6DZD engine with LNG as clean fuel for respectively the Minerva & the Scheldt River. For the Minerva, the ABC-engines have to power as well the propulsion line, as also the dredging pump and the alternator. The ABC-engine in the Scheldt River is an auxiliary engine to power an alternator.
All these projects require high level control systems, custom made engineering and optimization on fuel consumption and emissions. This paper will describe these modifications and it will show the integration of the dual fuel engines in the vessels.

N. Böckhoff*, D. Mondrzyk, S. Terbeck
MAN Diesel & Turbo SE, Augsburg, Germany

Abstract
The demand of gaseous fuels is increasing further due to the increasing energy demand and the search for alternatives for power generation by means of liquid fuels and nuclear power. The MAN 51/60G can be used and optimized quite variously. When only peak cur-rent is required, the engine is designed for the highest possible efficiency on the output shaft. Among base load applications in Europe the gas engine is mainly applied at “Com-bined Cycle” or “Combined Heat and Power” applications. The ability to reach full load within short time makes the gas engine also attractive for e.g. replacement systems among wind power. Compared to conventional diesel power stations, gaseous fuels for use in energy generation impress by low primary emission level, especially of dust, CO₂ and NO_X. The new limit values of exhaust gas emission defined by the “TA-Luft” (Technical instructions for the air purification) and the EU directive set a challenge. There, among other emissions, the limit values for NO_X values are more than halved. In order to comply ideally with these market requirements numerous optimizations are carried out upon the 51/60G.
Within this sheet the further development of the 51/60G by MAN Diesel & Turbo is de-scribed.

Christian Trapp*, Robert Böwing, Andreas Birgel, Herbert Kope-cek, Wolfgang Madl, Albert Fahringer, Fabrizio Nota
GE Distributed Power, Jenbach

Introduction
Throughout the last decades, world energy demand has been continuously growing, driven by population and GDP growth in non-OECD countries. The worldwide energy demand increased steadily even in the years following the 2008 economic crisis. Today, we are facing a world of uncertainty, full of challenges due to slow growth in developed countries, the dramatic oil price drop and its impact on companies and nations as well as political instability across the world. Still currently available reports project an increase in world energy demand by around 25 % until 2040 compared to 2014, once again mainly driven by non-OECD countries. [1].
The period to 2040 is expected to reflect a dramatic expansion of the world’s population and the global middle class. Living conditions will improve as millions of people in countries like China, India, Brazil, Mexico, South Africa, Nigeria, Egypt, Turkey, Saudi Arabia, Iran, Thailand and Indonesia gain access to electricity, which will lead to benefits such as better education and modern healthcare.Policies to address greenhouse gas (GHG) emissions together with increased renewable deployment in many OECD countries will drive the global need for highly efficient distrib-uted power generation and combined heat and power (CHP) plants to satisfy the growing energy demand.With the introduction of the J624 and the J920 smart controlled, two stage turbocharged gas engines GE has demonstrated in the last few years how to push the gas engine tech-nology development further by focusing on key technology areas. Innovative gas engine concepts are playing an increasingly important role for base load, peaking and grid bal-ancing as well as for combined heat and power applications around the globe.This paper is discussing the technological approach to the 24 bar BMEP version of the J920 gas engine giving the customers an almost 10 % power increase and 50 % electrical efficiency (51 % engine efficiency) in the first step combined with cutting edge fast start-up capabilities, further increased lifetime and proven reliability enabling further efficiency and power growth in later steps. To reach these ambitious targets, the combustion concept for TA-Luft and EID 2012 compliance has been newly developed, the engine is using a new two stage turbo charging system with optimized air handling, model based predictive en-gine controls as well as thermo-mechanical optimization.

S. Zirngibl , M. Prager, G. Wachtmeister
Lehrstuhl für Verbrennungskraftmaschinen (LVK), Technische Universität München

Abstract
Natural gas and especially biogas combustion can be regarded as one of the key technologies on the way to a climate-neutral energy supply. Due to its wide availability, Biogas already is amongst the most important energy sources in the present energy mix. For ex-ample in stationary power plants or modern cogeneration units for combined heat and power (CHP) generation, the conversion of gaseous fuels is widely established. In addition to conventional spark plug ignition, the combustion can also be initialized by a pilot injection of liquid fuel. This ensures the ignition of the gas/air mixture under excess air conditions used in modern large bore engines in order to maximize efficiency. Apart from the basic aspects of the combustion process development, such as for example the selection of the stroke-to-bore ratio and the subsequent optimization of the combustion chamber geometry, or the definition of the valve opening and closing timings, a further essential influencing parameter must therefore be taken into consideration by the definition of the pilot injection characteristics.
The high-pressure fuel system required for the pilot injection represents a further engine subsystem. The additional complexity of the overall system at least has to be compen-sated by advantages regarding fuel consumption and efficiency, respectively. Especially with large engine sizes as well as a suitable definition of the pilot injection, advantages can be used due to a significantly faster and more efficient conversion of the gas/air mixture. Particularly in the combustion of gaseous fuels with a relatively high volumetric ratio of inert components, such as biogas, the considerably faster conversion of the cylinder charge could also justify the additional effort of the pilot injection in smaller engine sizes. For this reason, a biogas dual fuel pilot injection combustion process for a small gas engine is being investigated at the Institute of Internal Combustion Engines (LVK) of the Technical University of Munich (TUM). On the one hand, the present paper describes the experimental investigations of the pilot injection. On the other hand, this article discusses the mainly simulative adaptation and definition of the individual subsystems, such as the valve control timings, as well as the combustion chamber geometry and the geometric characteristics of the intake system including the resulting influences on the in-cylinder charge motion.

Björn Henke, Bert Buchholz*, Karsten Schleef, Christian Fink
Lehrstuhl für Kolbenmaschinen und Verbrennungsmotoren, Universität Rostock

Sascha Andree
Lehrstuhl für Technische Thermodynamik, Universität Rostock

Marius Wolfgramm, Robert Graumüller
Caterpillar Motoren GmbH & Co. KG

Abstract
Within the scope of the research project “LEDF-Konzepte” experimental investigations at a single cylinder medium speed research engine have been performed in order to analyze the impact of different parameters on the dual fuel combustion process. Apart from a variation of the µ-Pilot injection timing these investigations include a multiple injection strategy combining an early µ-Pilot, placed during compression stroke, and a µ-Pilot injection positioned in the typical time-window before TDC. While best achievable values for indicated efficiency, coefficient of variation and NOx-/CH4-emissions do not differ remarkably between the tested single and multiple µ-Pilot strategy it can be observed that these parameters behave much less sensitive against a change of the Pilot-timing for a multiple injection pattern when compared to a single injection mode.

Dr. Christoph Redtenbacher*, DI Constantin Kiesling, DI Maximilian Malin
LEC GmbH, Graz

Prof. Dr. Andreas Wimmer
LEC GmbH, Graz / Graz University of Technology

Abstract
When diesel-gas dual fuel engines are operated in gas mode, the homogeneous gas-air mixture in the combustion chamber is ignited by injecting a small amount of diesel fuel. This diesel pilot injection has a significant influence on the performance of the combustion concept. Good ignition of the lean mixture with low NOx emissions is a challenge, especially for injection systems of fully flexible diesel-gas engines that use the same diesel injector in gas mode as well as in pure diesel mode. Optimization of diesel pilot injection is thus an important starting point for improving the diesel-gas combustion concept in order

to reduce current performance deficits as compared to monovalent gas engine concepts with a gas scavenged prechamber.

This paper compares a diesel-gas engine concept with a gas engine concept with the goal of identifying the areas in which the dual fuel concept must be optimized so that its effi-ciency and combustion stability approach the level of the monovalent concept. Building on this, diesel pilot injection measures are evaluated in terms of their ability to improve the diesel-gas combustion concept. The analyses include the influences of the variable injec-tion parameters duration of injection, start of injection and rail pressure as well as influ-ences of important nozzle parameters such as the number of nozzle holes. Since it is difficult to obtain a regular spray pattern in the area of the small amount of diesel required, it is also shown to what extent a nozzle with an irregular spray pattern has an influence on engine operation as compared to a nozzle with a regular spray pattern.

The findings were obtained from a series of tests conducted on a high speed single cylin-der research engine with ≈ 6 dm³ displacement. Results from investigations in an optical spray box as well as in an injection rate measurement system on the characterization of the injection process support the interpretation of the effects observable from the engine measurements. The combination of experimental methods and a detailed analysis of en-gine operating points using engine cycle calculation make it possible to derive the requirements for the injection event in order to obtain a combustion process with favorable efficiency and emissions. A final evaluation indicates to what extent the performance of the diesel-gas engine can approach that of a gas engine through optimization of the injection event.

Lukas Virnich*, José Geiger, Dirk Bergmann, Harsh Sankhla
FEV GmbH, Aachen

Avnish Dhongde
Lehrstuhl für Verbrennungskraftmaschinen, RWTH Aachen University

Abstract
In the conflicted area between high thermal efficiency and engine operation without knock-ing combustion, while complying with the legally prescribed emission limits, the compression ratio is the essential design parameter for stationary large gas engines. Thus, determination of the most advanced knock free position of the “gravity center” of combustion is vitally important for the definition of the optimum compression ratio for a spark ignited combustion engine. In addition to the compression ratio and the air fuel ratio, the fuel composition itself has a decisive influence on the burn delay and duration, and thus on the thermodynamic state of the unburned air fuel mixture. Furthermore, the natural gas composition determines the kinetic properties of the unburnt air fuel mixture and thus also the knock limit. The wide range of available gas qualities (compositions) provides a major challenge for the determination of an optimum compression ratio.

For a more detailed analysis of the influencing variables on the knocking limit of the com-bustion process and for the simulation-assisted design of the compression ratio for a wide array of fuel compositions, a combustion and knocking model has been developed by FEV. Using a detailed chemical reaction kinetics simulation, this model identifies critical states in the unburned air fuel mixture in front of the propagating flame front.

The reaction kinetics approach considers the parameters compression ratio, air fuel ratio and fuel composition. The interactions of the influence parameters on burn delay and duration are incorporated by means of an entrainment model for the flame propagation. Furthermore, the simulation of the cyclical individual fluctuations of the variables mentioned, allows a distribution of the knocking intensities and occurrence probabilities, which corresponds to the real engine operation.

A reaction mechanism suitable for engine operation has been identified for the simulation of the chemical reaction kinetics. It models the change in the ignition delay time caused by charge dilution for different fuel compositions at the pressure and temperature conditions present inside the combustion chamber.

Björn Henke, Bert Buchholz*, Karsten Schleef, Christian Fink
Lehrstuhl für Kolbenmaschinen und Verbrennungsmotoren, Universität Rostock

Sascha Andree
Lehrstuhl für Technische Thermodynamik, Universität Rostock

Marius Wolfgramm, Robert Graumüller
Caterpillar Motoren GmbH & Co. KG

Abstract
Within the scope of the research project “LEDF-Konzepte” experimental investigations at a single cylinder medium speed research engine have been performed in order to analyze the impact of different parameters on the dual fuel combustion process. Apart from a variation of the µ-Pilot injection timing these investigations include a multiple injection strategy combining an early µ-Pilot, placed during compression stroke, and a µ-Pilot injection positioned in the typical time-window before TDC. While best achievable values for indicated efficiency, coefficient of variation and NOx-/CH4-emissions do not differ remarkably between the tested single and multiple µ-Pilot strategy it can be observed that these parameters behave much less sensitive against a change of the Pilot-timing for a multiple injection pattern when compared to a single injection mode.

Dr. Luigi Tozzi, Emmanuella Sotiropoulou*, Dr. Shengrong Zhu
Prometheus Applied Technologies, LLC Fort Collins, CO, USA

ABSTRACT

It is well known that using precombustion chambers (PCC) in lean-burn, large bore gas engines extends the lean limit and reduces the combustion variability. However, typical PCC designs require rich fuel-air mixtures to properly operate. This condition results in high NOx production and less than optimum engine efficiency (BTE)/NOx trade-off. It is also known that when this type of combustion system is used in very lean-burn engines, the vast majority of the NOx is produced in the PCC. It then follows that a substantial reduction in NOx can be achieved by either combusting leaner mixture in the PCC or by reducing the PCC volume. While this is true, attempts in trying to burn leaner mixtures in specially designed PCC have been challenging, leading in most cases to worse combustion stability. The reason for this lack of success has been the objective of extensive analytical and experimental studies.

This paper will describe a novel PCC technology developed with advanced computational flow dynamic (CFD). Unlike prior efforts in leaning the air-fuel mixture and/or reducing the volume of the

PCC, this novel PCC technology provides the reduction in NOx without compromising engine stability or BTE. This remarkable performance is due to a unique vortex flow achieved within the PCC which substantially reduces the wall quenching effect. With this type of flow dynamic, efficient and stable combustion of lean mixtures within the PCC can be sustained and results in powerful flame jets in the main combustion chamber. In fact, this paper will describe that the proper lean-burn PCC design can generate flame jets that have even more energy compared to those generated by the rich-burn PCC.

Beyond the fundamental description of the novel lean-burn PCC (LBP) technology, experimental data is presented that confirms the expectations set by the CFD regarding the benefits of the LBP. In the end, the opportunity for advancing the state-of-the-art of large bore gas engines is discussed with regard to this emerging LBP technology.

D. Neher*, S. Fieg, W. Rieb, J. Bauer, M. Kettner
Forschungsbereich Motorentechnik des Instituts für Kälte-, Klima- und Umwelttechnik (IK-KU) der Hochschule Karlsruhe

H. Biermann, N. Albrecht
Eberhardt Hoeckle GmbH

Abstract
Naturally aspirated homogeneous lean burn gas engines frequently used in small-scaled cogeneration units (Pel < 50 kWel) achieve low NOx emissions and high efficiency. While further dilution allows the engine to meet future emission limits, it reduces engine efficiency due to higher cycle-by-cycle variations as well as a further deviation of the combustion from the ideal Otto cycle. In the case of a naturally aspirated engine, leaning decreases engine power and leads to higher relative friction losses, thus reducing brake efficiency.

The presented work shows an alternative approach to improve the trade-off between engine efficiency, NOx emissions and engine power for a naturally aspirated homogenous lean burn four-cylinder gas engine. Increasing the compression ratio is here the major means for augmenting engine’s efficiency, however, it also leads to higher combustion temperatures. Consequently, NOx emissions increase, requiring additional measures to reduce process temperatures, e.g. gas exchange optimisation or cooled exhaust gas re-circulation (EGR).

In the first step, 1D-CFD engine process calculation was used to minimise residual gas fraction by varying the valve timing. A multi-body model of the valve train was used to realise the valve timings determined and to allow for engine testing with the new camshaft. Subsequently, the compression ratio was increased from 13.3 to 15.2 by designing a new piston. The designing process was accompanied by 3D-CFD calculation to study the influence on charge motion. Eventually, engine trials including EGR proved brake efficiency to increase by 1.2 %-points, while maintaining brake power and NOx emissions constant.

M.Sc. F. Rosenthal*, Dr.-Ing. Heiko Kubach, Prof. Dr. sc. techn. T. Koch
Institut für Kolbenmaschinen (IFKM),
Karlsruher Institut für Technologie (KIT), Karlsruhe, D

Dr. Ulrich Arnold
Institut für Katalyseforschung und -technologie (IKFT),
Karlsruher Institut für Technologie (KIT), Karlsruhe, D

Abstract
Actual developments for gas engines tend to more excess air or exhaust gas recirculation to reduce NOx emissions. Under these circumstances the ignition in a single cylinder research gas engine with pilot injection of highly ignitable fuels has been investigated. Two igniting fuels (2-EEE, HVO) have been selected by a systematical assessment and their properties have been analyzed. These fuels have been evaluated in their aptitude as Ignit-ing fuels and compared with diesel as reference fuel.

A higher ignitability reduced the burn delay of the ignition injection and enables the diminution of the igniting fuel fraction. A significant share of nitrogen oxide emissions have been attributed to the ignition injection, therefore minimal quantity injection is necessary to reach the targets of emission legislation. The minimal quantity injection of 2-EEE as high ignitable fuel allows lean operation with exhaust gas recirculation, offering low NOx emis-sions without disadvantages in efficiency.

Suraj Nair, PhD*, Jeff Carlson, Jason Barta, Gregory J. Hampson, PhD
Engine Systems, Woodward Inc., Colorado, USA

Abstract
Pushing gas engines to their lean / low NOx and high BMEP limits and gas-diesel dual fuel engines to high substitution rates often leads to performance-limiting abrupt uncontrolled combustion such as knock. Understanding and detection of the progression of abnormal combustion is key to engine protection. This study assesses the ability to detect the progression of uncontrolled combustion using both in-cylinder pressure and vibration knock sensors in spark-ignited and dual fuel engines.

For gas engines, the results indicate that pressure-based knock detection captures all the knock cycles while vibration-based knock detection miss a considerable percentage.

For dual fuel engines, the results indicate that the classical frequency-based detection approaches can detect severe combustion events, but do not provide a good continuously increasing signal. This makes engine control and calibration very difficult and therefore usually drives lower substitution rates in order to maintain a safety margin. This behavior is due to the diesel combustion process that creates pressure ripples in the cylinder.

As substitution rates increase beyond a certain point, it was found that the vibration-knock signature decreases. If the engine is relying on knock for protection against excessive gas substitution rates, changing gas quality, or other influences, a robust control system is needed with progressively increasing signal feedback to maximize substitution while maintaining safe engine operation.

To achieve this, a new approach of detecting uncontrolled combustion is proposed that monitors a weighted sum of pressure and heat release metrics that can accurately predict the progression of uncontrolled combustion providing a definitive control action path. With this approach, substitution rates can be maximized and maintained to a desired safety margin on a diesel dual fuel engine.

The tests reported in this paper varied the substitution rates at various speeds and loads to show the different combustion modes that can be seen in a diesel dual fuel engine. This data was used to determine a better approach to detect uncontrolled combustion in a dual fuel engine, proposing the term combustion intensity (CI). The combustion intensity metric proposed in this paper delivers a continuously increasing measure of the state of combustion to provide better controllability, while improving protection against uncontrolled combustion, since it is based upon direct real-time monitoring of in-cylinder pressure.

S. Zirngibl , F. Günter, M. Prager, G. Wachtmeister
Lehrstuhl für Verbrennungskraftmaschinen (LVK), Technische Universität München

Abstract
Given the increasing globalization and the technical progresses, the worldwide demand for energy is continuously increasing. Besides, there is a general intention in many countries observable, to increase the amount of renewable energy sources in their specific energy mix. However, even with full renewable energy supply, an energy gap remains due to climatic fluctuations. Today, since efficient storage technologies are not yet available in reasonable capacities, conventional fossil fuel based power plants are still connected to the power grid in order to compensate the residual load. A feasible approach to cover the mentioned residual load using renewable energy sources is the use of biogenic gaseous fuels. In contrast to solar or wind energy for example, the gaseous fuel can be converted into electricity on demand. Besides the above mentioned compensation of the remaining residual load, the combustion of gaseous fuels is furthermore capable to potentially con-tribute to the base load coverage. Although in this case the supply of electrical energy is mostly paramount, the combustion of biogas offers advantages when used within combined heat and power (CHP) units for cogeneration. In order to maximize the efficiency of such CHP plants, the processes of waste heat recovery from the combustion engine (e.g. from the engine coolant, the lubrication oil and the exhaust gas) have to be optimized. Therefore, this article presents a simulative approach for the investigation of thermody-namic cycles for cogeneration units. The MATLAB based code allows various combina-tions of specific components (e.g. heat exchangers and pumps, as well as steam turbines and compressors) in different cycles. The main focus of this article essentially lies on the modeling approach, as well as the comparison of thermodynamic cycles, such as for ex-ample the Joule-Brayton and the Clausius-Rankine cycle. Furthermore, potential optimiza-tions resulting from the dimensions of the considered system components as well as pro-cess the management are presented.

Wolfgang Fimml *, Jonathan Lipp, Michael Greil, Philippe Gorse
MTU Friedrichshafen GmbH

Christoph Mathey, Christoph Voser, Boris Willneff
ABB Turbo Systems Ltd

Abstract
Variable valve trains offer new possibilities for improving the performance of off-highway engines. Over recent years, MTU Friedrichshafen GmbH has successfully tested ABB Turbo Systems’ fully variable valve train technology VCM® (Valve Control Management) on its Series 4000 engines. A VCM® actuator for the intake valves was developed and tested for the purpose. This paper outlines the VCM® design process and, for the first time, presents detailed results of engine performance and durability tests conducted on stationary gas engines.

The performance tests focused on the thermodynamic potential of VCM® on a stationary gas engine. Engine load was precisely controlled via intake valve timing instead of via the throttle. Substantial improvements in efficiency were measured: 0.65 %pts on a single-stage turbocharged (L64) unit and 1.5 %pts on an emulated two-stage turbocharged sta-tionary gas engine.

Alongside improved performance, the reliability and robustness of new technologies are of major importance in large engine applications. This paper presents test results for 12 VCM® actuators that were tested for more than 7,000 hours on an MTU Series 4000 L64 gas engine that was operated in the field in a combined heat and power plant. The VCM® actuators were monitored and regularly inspected. Drift stability was excellent while cycle-to-cycle variation and wear and tear were very low.

The results obtained led to the conclusion that VCM® technology is ready for use in high-speed engines in off-highway applications.

Tobias Ehrler*, Manuel Cech, Titus Tschalamoff, Martin Wild
WTZ Roßlau gGmbH, Dessau-Roßlau, D

Abstract
The application of block-type thermal power stations as combined heat and power genera-tion plants exhibits an increased overall efficiency in the generation of electrical and ther-mal energy. With the application of a thermal driven cooling device the waste heat of the engine can additionally be used, e.g. for the cooling of the building. Thereby, the life span of the block-type thermal power station increases and so does the economic viability of the plant. Apart from the cooling of the building, the use of the generated cooling performance for the cooling of the charge air below the ambient temperature presents a further application possibility. Firstly, within the framework of the project, the Potential of the low temperature cooling of the charge air will be examined on a gas engine together with the help of an engine computer simulation and an assessment of the Potential with respect to the following command variables forwarded:

• Reduction of the NO_x emissions with a constant degree of efficiency for the achievement of future emission ratings
• Increase of the effective engine efficiency

During the following test-bed tests, the command variables are examined and the engine model validated. Further computer simulations will be carried out and the low temperature cooling is compared to the Miller cycle.

Dr. Hinrich Mohr*, Martin Abart, Ingo Koops, Dr. Rüdiger Teichmann
AVL List GmbH

Prof. Clayton Zabeu*, André Martelli, Roberto Salvador, Alexander Peñaranda, Glauber Ruy
Linhares Geração S.A.

Summary
Due to the lack of rain in Brazil during last years, most of standby thermal power plants were dispatched almost continuously. The Brazilian power plant operator Linhares Geração S.A. (LGSA), as one of the power plants in the condition mentioned above, started in 2014 a program to increase the performance and reliability of its reciprocating engine-based gensets. This would allow an optimized operation with improved economy of the 204 MW plant, which is equipped with 24 medium-speed gas engines. Therefore, a permanent knowledge of the engine conditions and a closed-loop engine control system were examined as the essential tools. AVL was involved in the discussions as independent engineering solution provider and was finally contracted to co-develop and deliver the required hardware and software as an integrated solution, coupled to the plant automation system.

The bases for this approach are two products out of the AVL large engine portfolio: the proven expert condition monitoring system AVL EPOS™ and the engine control system development services. Both were bundled, under requirements defined together by AVL and LGSA, for full integration with the respective in-house large engine competencies. Herewith also engine condition aspects can be considered for an optimized engine control strategy.

The realization at site happened in several steps: at first, one engine at the power plant was equipped with AVL EPOS™ hard- and software to prove the condition monitoring capability. Secondly, on all engines AVL EPOS™ was installed and integrated in the plant automation system. In a third step, on one engine the conventional engine control system was exchanged to the new closed-loop control system and linked to AVL EPOS™ by hard- and software interfaces – to prove the functionality and capabilities of the overall system. Based on the outcomes of this pilot phase, all engines might be modified to this system stage.

The first operational results are very promising. The integrated system acts in a very sensitive manner. LGSA is now evaluating the potentials of the new system as basis for their optimized operation strategy.

Dr. M. Schultze*, C. Drexel
Caterpillar Energy Solutions GmbH, Mannheim, D

G. Kollias-Pityrigkas
Technische Universität Kaiserlautern, D

Abstract
In this work hydrogenrich gas mixtures consisting of the main species H2, CH4, CO, CO2 and N2 were investigated as fuel for a modified TCG 2016 V08 gas engine. The engine was equipped with flame arrestors upstream of the cylinder inlets to avoid flame propagation into the intake manifold due to possible flash backs. All cylinders were equipped with high pressure sensors. Additionally low pressure sensors and optical fiber sensors were installed in the intake manifold. To facilitate comparability of the different fuel gases, in all cases a similar 50 % mass fraction burnt point was chosen. During the experimental study, engine operational parameters such as ignition timing, equivalence ratio, intake manifold temperature and pressure were varied.

Within the scope of this work the maximal achievable load and the emission of pollutants were investigated for different hydrogen-rich fuels. Main focus was on engine knocking and self-ignition of the investigated fuels.

The experimental data were used to develop and validate a numerical model based on 0D and 1D simulations and detailed chemical reaction mechanisms. This model improves the assessment of hydrogen-rich gas mixtures as fuels for gas engines.

Callahan*, D. Branyon, D. Meyers, R. Johnson,
Southwest Research Institute

ABSTRACT

US EPA Tier 4 Final (4f) emissions regulations for >560 kW engines are forcing manufacturers to use aftertreatment that needs “active control”, meaning selective catalytic reduction (SCR) to reduce NOx and/or a diesel particulate filter (DPF) to reduce particulate matter (PM). Alternatively, exhaust gas recirculation (EGR) could be used for NOx control along with a DPF. Implementation of SCR, EGR, and/or DPF adds complexity in controls, packaging difficulties for mobile applications, as well as maintenance concerns. At the same time that the market is facing these emissions regulations, there has been a growth in demand for dual fuel engines that run on pre-mixed natural gas admitted into the inlet air stream, with a diesel pilot used for ignition. The growing demand was originally driven by the price differential between natural gas and diesel fuel, but former natural gas price advantages of 30 to 70 % have greatly eroded in the last few years, although projections indicate advantages may return in the future. In SwRI’s development of large (>560 kW) dual fuel engines for mine haul trucks, it has been demonstrated that well-engineered dual fuel engines can easily meet Tier 2, and the hypothesis for this project is that dual fuel engines may potentially meet Tier 4f emissions without SCR, EGR, or DPF aftertreatment, reducing or eliminating the aftertreatment packaging issue, reducing initial engine/aftertreatment system cost, and reducing operating cost by eliminating SCR’s DEF consumption and/or regeneration fuel consumption for a DPF.

The objective of this effort was to demonstrate Tier 4f emissions using a dual fuel engine with no SCR or EGR for NOx reduction and also no DPF for PM control. A Tier 2 non-road diesel engine of 2.5 to 6 L/cyl displacement (>560 kW) was used for this project. This engine having been converted to dual fuel operation was optimized to achieve Tier 4f emission levels in this project. Injection timing, injection pressure, substitution ratio, and equivalence ratio were optimized to meet the emissions standards and provide stable and knock free operation.

The project clearly demonstrated the capability to reach Tier 4f without EGR or actively controlled aftertreatment and with very high natural gas substitution even at moderate to low speeds and loads.

Günther Gern, Geschäftsführer WTZ Roßlau