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The objective of this study was to build up an optical access into a large bore medium-speed research engine and carry out the first fuel spray Particle Image Velocimetry (PIV) measurements in the running large bore medium-speed engine in high pressure environment. The aim was also to measure spray penetration with same optical access and apparatus. The measurements were performed in a single-cylinder large bore medium-speed research engine, the Extreme Value Engine (EVE) with optical access into the combustion chamber. The authors are not aware of any other studies on optical spray measurements in large bore medium-speed diesel engines. Successful optical measurements of the fuel spray penetration and the velocity fields were carried out. This confirms that the exceptional component design and laser sheet alignment used in this study proved to be valid for optical fuel spray measurements in large-bore medium-speed diesel engines.

The development of new high power diesel engines is continually going for increased mean effective pressures and consequently increased thermal loads on combustion chamber walls close to the limits of endurance. Therefore accurate CFD simulation of conjugate heat transfer on the walls becomes a very important part of the development. In this study the heat transfer and temperature on piston surface was studied using conjugate heat transfer model along with a variety of near wall treatments for turbulence. New wall functions that account for variable density were implemented and tested against standard wall functions and against the hybrid near wall treatment readily available in a CFD software Star-CD.

The present work aims to determine the gas pressure acting in the ring pack area in a medium-speed four stroke diesel engine. The experimental part of the study was carried out as firing engine tests, with an instrumented piston, with telemetric data transmission, and an instrumented cylinder liner in a 6-cylinder test engine. The results, in terms of inter-ring gas pressure are compared with the results of computer simulations. Moreover, the computer simulations were carried out to predict and compare the effects of the piston running clearance and the ring face wear on the inter-ring pressures. The study comprises aspects on inter-ring pressures under a set of loads. The measured inter-ring gas pressures indicate steady ring operation. The simulation results show good agreement with measurement results.

Cylinder charge, cylinder flow field and fuel injection play the dominant roles in controlling combustion in compression ignition engines. Respective computational cylinder charge, initial flow field and fuel injection boundary affect combustion simulation and the quality of emission prediction. In this study the means of generating the initial values and boundary data are presented and the effect of different methods is discussed. This study deals with three different compression ignition engines with cylinder diameters of 111, 200 and 460 mm. The initial cylinder charge has been carefully analyzed through gas exchange pressure recordings and corresponding 1-dimensional simulation. The swirl generated by intake ports in a high-speed engine is simulated and measured. The combustion simulation using a whole cylinder model was compared with a sector model simulation result.

The development of diesel engines is constantly leading to greater increases in the power density. The heat load into the combustion chamber walls increases with the increased power density. Estimating correct local heat fluxes inside the combustion chamber is one of the most challenging tasks in engine simulation. In this study, the heat load of the piston was estimated with the help of the modern simulation tools CFD and FEM. The objective of the work was to evaluate the thermal stress of a research engine designed for an exceptionally high maximum and mean pressure. The local heat transfer coefficient and gas temperature were simulated with a CFD code with the standard and modified wall functions and used as boundary values for the FEM analysis. As a reference case, a model of a production engine with measured piston surface temperatures was used to validate the combined CFD and FEM analysis.

The design and testing of the valve train for a new two-stroke diesel engine concept [1,2] is presented. The gas exchange of this process requires extremely fast-acting inlet valves, which constituted a very demanding designing task. A simulation model of the prototype valve train was constructed with commercially available software. The simulation program served as the main tool for optimizing the dynamic behavior of the valve train. The prototype valve train was built according to the simulations and valve acceleration measurements were performed in order to validate the simulation results. The simulations and measurements are presented in detail in this paper.

A novel two-stroke engine concept is introduced. The cylinder scavenging takes place during the upward motion of the piston. The gas exchange valves are similar to typical four-stroke valves, but the intake valves are smaller and lighter. The scavenging air pressure is remarkably higher than in present-day engines. The high scavenging air pressure is produced by an external compressor. The two-stroke operation is achieved without the drawbacks of port scavenged engines. Moreover, the combustion circumstances, charge pressure and temperature and internal exhaust gas re-circulation (EGR) can be controlled by using valve timings. There is good potential for a substantial reduction in NOx emissions through the use of adjustable compression pressure and temperature and by using the adjustable amount of exhaust gas re-circulation.

The one-equation subgrid scale model for the Large Eddy Simulation (LES) turbulence model has been compared to the popular k-ε RNG turbulence model in very different sized direct injection diesel engines. The cylinder diameters of these engines range between 111 and 200 mm. This has been an initial attempt to study the effect of LES in diesel engines without any modification to the combustion model being used in its Reynolds-averaged Navier-Stokes (RANS) form. Despite some deficiencies in the current LES model being used, it already gave much more structured flow field with approximately the same kind of accuracy in the cylinder pressure predictions than the k-ε RNG turbulence model.

Three-dimensional diesel engine combustion simulations with single-step chemistry have been compared with two-step and three-step chemistry by means of the Laminar and Turbulent Characteristic Time Combustion model using the Star-CD program. The second reaction describes the oxidation of CO and the third reaction describes the combustion of H2. The comparisons have been performed for two heavy-duty diesel engines. The two-step chemistry was investigated for a purely kinetically controlled, for a mixing limited and for a combination of kinetically and mixing limited oxidation. For the latter case, two different descriptions of the laminar reaction rates were also tested. The best agreement with the experimental cylinder pressure has been achieved with the three-step mechanism but the differences with respect to the two-step and single-step reactions were small.

A modified version of the Laminar and Turbulent Characteristic Time combustion model and the Hiroyasu-Magnussen soot model have been implemented in the flow solver Star-CD. Combustion simulations of three DI diesel engines, utilizing the standard k-ε turbulence model and a modified version of the RNG k-ε turbulence model, have been performed and evaluated with respect to combustion performance and emissions. Adjustments of the turbulent characteristic combustion time coefficient, which were necessary to match the experimental cylinder peak pressures of the different engines, have been justified in terms of non-equilibrium turbulence considerations. The results confirm the existence of a correlation between the integral length scale and the turbulent time scale. This correlation can be used to predict the combustion time scale in different engines.

New technology for the manufacturing of copper/brass heat exchangers has been developed and the first automotive radiators are already in operation in vehicles. This new technology is called CuproBraze®. One of the essential questions raised is the external corrosion resistance with reference to the present soldered copper/brass radiators and to the brazed aluminium radiators. Based on the results from electrochemical measurements and from four different types of accelerated corrosion tests, the external corrosion resistance of the CuproBraze® radiators is clearly better than that of the soldered copper/brass radiators and competitive with the brazed aluminum radiators, especially as regards marine atmosphere. Due to the relatively high strength of the CuproBraze® heat exchangers, down gauging of fins and tubes in some applications is attractive. High performance coatings can ensure long lifetime from corrosion point of view, even for thin gauge heat exchangers.

An ultrahigh injection pressure, common rail fuel injection system was designed, fabricated, and evaluated. The result was a system suitable for high-power density diesel engine applications. The main advantages of the concept are a very short injection duration capability, high injection pressure independent of engine speed, a simplified electronic control valve, and good packaging flexibility. Two prototype injectors were developed. Tests were performed on an injector flow bench and in a single cylinder research engine. The first prototype delivered 320 mm3 within 2.5 milliseconds with a 2600 bar peak injection pressure. A conventional minisac nozzle was used. The second prototype employed a specially designed pintle nozzle producing a near-zero cone angle liquid jet impinging on a 9-mm cylindrical target centered on the piston bowl crown (OSKA-S system). The second prototype had the capability to deliver 316mm3 in 0.97ms.

The benefits of direct cylinder fuel injection to the fuel economy and exhaust emissions of small spark ignited two-stroke engines is well known. The selection of a commercially viable fuel injection solution continues to receive evaluation and scrutiny by the engine manufacturers. This paper describes the development and demonstration of an EDFI solution which is applicable to low cost and high production volume engines in several industries. The system is based on the “accumulator” fuel injection operating principle, which involves pressurizing fuel within an injection nozzle and subsequently releasing the pressurized fuel into the combustion chamber on command. This concept provides very short injection duration throughout the dynamic operating range of the engine as well as high injection frequency capability.

The potential for improving the efficiency of a heavy duty turbocharged diesel engine by closed loop Air-Fuel Ratio (AFR) management has been evaluated. Testing conducted on a 12 liter diesel engine, and subsequent data evaluation, has established the feasibility of controlling the performance through electronic control of air management hardware. Furthermore, the feasibility of using direct in-cylinder pressure measurement for control feedback has been established. A compact and robust fiber optics sensor for measuring real time in-cylinder pressure has been demonstrated on a test engine. A preferred method for reducing the cylinder pressure data for control feedback has been established for continued development.

The paper discusses objectives, approaches and results of the development of a pilot fuel injection system (FIS) for a dedicated, compression ignition, high-speed, heavy duty natural gas/diesel engine. The performance of the pilot FIS is crucial for the success of a dual fuel concept. The Servojet electro-hydraulic, accumulator type fuel system was chosen for the pilot fuel injection. An alternative pilot FIS based on the “water hammer” (WH) effect was also considered. The modifications to a stock 17 min injector is described. Three different types of pilot injector nozzle were investigated: standard Valve Covered Orifice (VCO), modified minisac and new designed, unthrottled pintle. Preliminary results from engine tests proved that the optimum pilot fuel quantity is the minimum quantity. Based on that finding, the pilot FIS design was further optimized.

Sonic flow, pulse-width-modulated electronic fuel injectors for gaseous fuels provide precise, stable and reliable service for over 1 billion cycles. Techniques for precision flow calibration are described along with dynamic response characteristics. Application techniques including pressure regulation, filtration and procedures for adjusting flow calibration for changes in gas pressure, temperature and composition are presented. Applications include single point (throttle body or mixer), multi-point constant flow and multipoint sequential strategies. Durability testing in parallel with a utility pipeline regulator fully conserves power and gaseous fuel in a simple, low cost, multiple injector test bank.

Research on the Catalytic Plasma Torch (CPT) ignition system was conducted this last year at BKM, Inc. in San Diego. The results showed that under certain conditions CPT can not only time ignition properly, but also extend the lean stability limit. This concept is based upon compression ignition of the charge in the CPT's integral pre-chamber. Compression ignition is induced by timed catalytic reduction of the pre-chamber's activation energy. This produces almost instantaneous combustion in the pre-chamber and is divided into multiple high velocity torches to rapidly ignite the main chamber charge. The timing of the ignition event is based on the location of the heated catalyst in the pre-chamber and the mass of the charge inducted into the cylinder. The base timing curve can be modified via current control which effects the catalyst activity. Dynamic modification of the timing event is accomplished by using the catalyst as an in-cylinder hot wire anemometer.

Increasing emphasis on natural gas as a clean, economical, and abundant fuel, encourages the search for the optimum approach to management of fuel, air and combustion to achieve the best results in power, fuel economy and low exhaust emissions. Electronic injection of fuel directly into the throttle body, intake ports or directly into the cylinder offers important advantages over carburetion or mixing valves. This is particularly true in the case of installations in which the gas supply is available at several atmospheres pressure above maximum intake manifold pressure. The use of choked-flow pulse- width-modulated electronic injectors offers precision control over the engine operating range with a wide variety of options for both stoichiometric and lean bum applications. A complete system utilizing commercially available components together with the application, calibration and engine mapping techniques is described.

Through the joint efforts of BKM, SPI, AFS and Belarus, an advanced, all- electronic dual fuel system has been developed for retrofit applications on the Belarus D-144, four-cylinder, 4.15 liter, 44.7 KW diesel engine. The system features all electronic control on both full diesel or up to 90 % gas with automatic and instant changeover capability. The existing mechanical diesel injection system was replaced with an all electronic, hydraulically actuated, diesel injection system coupled with timed multi-point electronic injection for the gas system. The control strategy does not utilize inlet throttling typically used on gas fueled engines. The effectiveness of this simplified control system is assumed to be the result of a degree of charge stratification. The D-144 engine is utilized in a wide variety of industrial, farm and highway applications. Special application requirements can be accommodated by programming the EPROM control chip.

An electronic fuel injection system for diesel engines has been adapted for dual fuel applications. The simplified and commercially practical system capitalizes on using standardized hardware and software modified for the dual fuel conversion kit Using the conventional diesel pump for pilot injection, electronic injectors provide timed pulses of gas for each cylinder. The system has been successfully applied to both naturally aspirated and turbocharged versions of the Mercedes OM-352 diesel engine and has been placed in service in transit bus applications. Performance data shows over 90% displacement of diesel fuel with the same power and fuel economy as the base diesel engine. Initial reports from the field indicate excellent performance and drivability as well as smoke-free exhaust when in the dual fuel mode.