bluuebunny/crossref_metadata_2025 huggingface dataset:
Vane Pump Power Split Transmission: Three Dimensional Computational Fluid Dynamics Modeling
Authors: Frosina Emma , Senatore Adolfo , Buono Dario , Stelson Kim A. , Wang Feng , Mohanty Biswaranjan , Gust Michael J.
Published: January 2016

A three dimensional CFD analysis of a novel vane pump power split transmission is studied in this paper. The model was built using PumpLinx®, a three-dimensional CFD commercial code developed by Simerics Inc.® The Mathers Hydraulics® vane pump is a double-acting vane pump with a floating ring. By coupling the floating ring to an output shaft, the vane pump becomes a hydrostatic transmission. The focus of this activity is the optimization of the vane pump analyzing the internal fluid dynamics of each part during the pump operation and redesign. The study is a result of collaboration between the University of Minnesota and the University of Naples “Federico II” research groups. The universities involved in this project worked in close cooperation on these simulations. A prototype pump will be tested on a hydraulic test bench at the University of Minnesota, and the experimental data will be used to validate the simulation model.
Control of Fuel Injection Rate for Marine Diesel Engines Using a Direct Drive Volume Control System
Authors: Sanada Kazushi
Published: January 2016

A direct drive volume control (DDVC) is applied to fuel injection control for marine diesel engine. The DDVC consists of an AC servomotor, a fixed-displacement hydraulic pump, and a hydraulic cylinder. The hydraulic cylinder pushes a plunger pump and fuel is pressurized. When the fuel pressure becomes greater than injection pressure, fuel is injected to a combustion chamber. A brief introduction of the DDVC is described first in this paper referring to conventional fuel injection systems including a cam mechanism and a common rail system. A mathematical model of the DDVC for simulation is summarized. Experiments of fuel injection shows the control function of the DDVC fuel injection system. The topic of this paper is feedback control of the quantity of fuel injection (fuel mass per injection) of the DDVC. The feedback control system is simulated using the above mathematical model. Fuel injection is stopped by switching a drive signal of the AC servomotor and retracting a piston of the hydraulic cylinder. The timing to stop injection is adjusted based on crank angle. An algorithm of updating the crank angle to stop injection is proposed so that the quantity of fuel injection follows the target value. Simulation study shows that the update algorithm works successfully.
Experimental Investigation of the Cylinder Block Movement in an Axial Piston Machine
Authors: Wegner Stephan , Gels Stefan , Jang Dal Sik , Murrenhoff Hubertus
Published: January 2016

The greatest share of hydromechanic and volumetric losses in axial piston machines are produced within the tribological interfaces piston / cylinder, cylinder block / valve plate and slipper / swash plate. Hydrostatic and hydrodynamic effects are used to minimise the sum of solid friction, viscous friction and throttle losses. Other tribological interfaces have minor influence on efficiency losses in most operating points in machines of this type.

This paper focuses on experimental investigations with the objective to acquire further knowledge on the cylinder block / valve plate contact. The investigations are part of a project funded by the German Research Foundation in which experimental and simulative investigations are combined to identify the effects influencing this tribological interface.

The experiments focus on the multi-directional movement of the cylinder block and the friction torque within the contact. Therefore a test rig was built, capable of measuring the cylinder block movement in all degrees of freedom and the friction torque between both parts. A sensor system is built around a standard rotary group of an axial piston pump with a spherical cylinder block / valve plate contact. The pump functionality is maintained and measurements under standard operating conditions up to 30 MPa are possible.

Procedures of the design process and descriptions of the measuring system are presented, followed by results of the cylinder block movement measurement, comparing the behavior under different pressure levels and speeds.
CFD Analysis of Gerotor Lubricating Pumps at High Speed: Geometric Features Influencing the Filling Capability
Authors: Altare Giorgio , Rundo Massimo
Published: January 2016

The paper presents an extensive analysis of the influence on the suction capacity of the main geometric parameters of gerotor lubricating pumps. The study was carried out using a CFD model developed with the commercial software PumpLinx®. The model of a reference gerotor unit was validated experimentally in terms of delivered flow rate in different operating conditions, in open and closed circuit configuration. In the former case different geometries of the inlet pipe were tested. In the latter the influence of the suction pressure at constant speed was analysed. After the model validation, several geometric features were changed to assess their influence on the volumetric efficiency in conditions of incomplete filling, such as the thickness and the diameter of the gears, the position of the inlet pipe with respect to the rotors (radial, axial and tangential), the shape of the port plate.
Reliable Fluid Power Pitch Systems: A Review of State of the Art for Design and Reliability Evaluation of Fluid Power Systems
Authors: Liniger Jesper , Pedersen Henrik C. , Soltani Mohsen
Published: January 2016

The key objectives of wind turbine manufactures and buyers are to reduce the Total Cost of Ownership and Total Cost of Energy. Among others, low downtime of a wind turbine is important to increase the amount of energy produced during its lifetime. Historical data indicate that pitch systems accounts for a substantial part of the downtime of wind turbines. With a focus on fluid power pitch systems; this paper presents an overview of methods relevant to assessing and increasing the reliability and availability of such systems. Four major areas are identified and covered; failure analysis, reliability and availability assessment, condition monitoring and fault-tolerant control. Within each area a brief description of the state of the art is given. On basis of the state of the art, a discussion is given on where further work is required in order to obtain a systematic framework for designing reliable fluid power.
Design and Control of Hydraulic Hybrid System for Excavators
Authors: Li Shizhen , Wei Jianhua , Fang Jinhui , Guo Kai , Liu Wei
Published: January 2016

This paper is to study on a novel recovery and release hydraulic hybrid system for excavators (HHE). The HHE uses hydraulic accumulators to recover the potential energy of the boom, the kinetic energy of the swing motor and the overflow hydraulic energy of the excavator’s main relief. The recovered energy is then utilized through a variable hydraulic motor as assistant power of the engine. The key issue of the HHE is that the operation of the boom must be similar to the conventional one about the sensing of the driver and the system must achieve higher efficiency and save more energy when comparing with the conventional system. In order to improve the recovery efficiency and while controlling the boom velocity with the similar operation, one design concept named “microcut” is proposed. When the boom drops down fast, a proportional valve is used to control the boom. While the boom goes down slowly, the recovery system is cut off. Then, the multi-way valve of the original system works to ensure good handling. An experimental prototype is designed and built in a 21-tons excavator. A 16% fuel-saving effect is obtained by weighing engine’s fuel consumption with the same amount of work, under conditions of the similar operation and higher efficiency compared with the conventional excavator.
Energy Consumption and Efficiency Measurements of Different Excavators: Does Hybridization Pay?
Authors: Hießl Arnold , Scheidl Rudolf
Published: January 2016

A series of detailed measurements of various mechanical and hydraulic system states of different excavators was performed. Main purpose of this study was to obtain a reliable information basis for assessing the potentials of hybrid drives, in particular the amount of recoverable energy. Differences concerned the size (tonnage) of the excavators and the hydraulic systems, open center versus load sensing. All machines were tested at the same set of operation scenarios, which are typical for practice, and with different operators. To this end, all test machines have been equipped with pressure, flow rate, temperature, angular and position sensors. These signals (about sixty) and several available from the machines CAN bus were recorded with a standard data acquisition system and electronically stored for later analysis. These raw data were processed to obtain the interesting data, like speeds, power flows, energies. In addition, videos of each test were recorded to facilitate the correct interpretation of the measurements and their correlation with the actual working processes.

Power flows from the combustion engine, different pumps, and at each actuator and energetic losses at the different loss sources were plotted for the different operation scenarios. Total efficiencies of the machines for different scenarios and the energy in and outflow at each actuator were computed. From the latter so called relative and absolute recovery degrees for each actuator and for the total machine in the different operation scenarios were derived. The relative recovery degree is the ratio of the total outflow energy (second and fourth quadrant) and the total inflow energy (first and third quadrant). The absolute recovery degree is the ratio of the total outflow energy of an actuator and the total energy delivered by all pumps in an operation scenario.

In most operation scenarios the total efficiency of consumed mechanical output energy at the hydraulic actuators relative to delivered hydraulic energy is in the range 15% to 25%. Reasonable recovery potentials do have the swing and the boom drive. For small machines, however, the boom drive dominates.
The Flow Dynamics of an Air-Driven Hydraulic Pump
Authors: Shi Yan , Wu Tiecheng , Plummer Andrew R. , Cai Maolin
Published: January 2016

Air-driven hydraulic pumps are widely used to pump high-pressure oil for small hydraulic systems, where it is uneconomic to set up a conventional hydraulic power pack. To obtain good performance of a small hydraulic system, input air flow and output oil flow characteristics of the air-driven hydraulic pump should be properly understood. In this paper, based on a mathematical model which has been experimentally verified, the model of an air-driven hydraulic pump is proposed. Using the software MATLAB/Simulink for simulation, the dynamic characteristics of the pumps are obtained. To set a foundation for the optimization of the pump, the influence of key parameters on the output characteristics of the pump was studied. Through analysis, it can be obtained that, firstly, with an increase in the input air pressure, output oil pressure and area ratio, the ratio of output to input volume flow rate decrease approximately linearly. Moreover, when the output oil pressure was fixed, an energy-saving method to enhance the output oil flow is to enlarge the area ratio of the pump. Furthermore, the output oil flow can be increased rapidly through increasing the input air pressure, but that may result in an increase in compressed air consumption. This research is of use in the performance and design optimization of air-driven hydraulic pumps.
Speed-Variable Switched Differential Pump System for Direct Operation of Hydraulic Cylinders
Authors: Schmidt Lasse , Roemer Daniel B. , Pedersen Henrik C. , Andersen Torben O.
Published: January 2016

Efforts to overcome the inherent loss of energy due to throttling in valve driven hydraulic systems are many, and various approaches have been proposed by research communities as well as the industry. Recently, a so-called speed-variable differential pump was proposed for direct drive of hydraulic differential cylinders. The main idea was here to utilize an electric rotary drive, with the shaft interconnected to two antiparallel fixed displacement gear pumps, to actuate a differential cylinder. With the design carried out such that the area ratio of the cylinder matches the displacement ratio of the two gear pumps, the throttling losses are confined to cross port leakage in the cylinder and leakage of the pumps. However, it turns out that the volumetric pump losses and the pressure dynamics of the cylinder and connecting pipes may cause pressure increase- or decrease in the cylinder chambers, which may seriously influence the dynamics and hence the performance during operation. This paper presents an analysis of these properties, and a redesign of the hydraulic system concept is proposed. Here the area- and displacement ratios are deliberately mismatched, causing inherent pressure build-up or cavitation in the return chamber, depending on the direction of motion. In order to avoid cavitation, a third gear pump is introduced, which provides a flow in the relevant cylinder chamber in one direction of motion, while operating in idle mode in the opposite motion direction. Together with two 2/2 way proportional valves, this design allows to control the lower chamber pressure levels, throttling excess compression flow to tank. The resulting design introduces additional losses due to throttling of excess compression flow, but also improves the dynamic properties of the system significantly. The proposed features are verified by comparison with the original pump concept and a conventional valve concept. Furthermore, significant improvement in energy efficiency is demonstrated under certain load conditions.
Novel Linear Hydraulic Actuator
Authors: Landberg Magnus , Hochwallner Martin , Krus Petter
Published: January 2016

In the area of linear motion, infinite stroke only is provided by electric actuators today, until now there has been no hydraulic alternative. The novel linear hydraulic actuator consists of two double acting cylinders with a common piston rod. The working principle of this actuator for short movements is that at least one piston is connected to the piston rod and the actuator works like an ordinary hydraulic double acting cylinder.

For longer movements one of the pistons is connected alternatively to the piston rod providing the drive. In this way the two pistons are moving the piston rod alternatingly in a kind of rope climbing motion. The critical element is the clamping mechanism which is an already known machine element but used in this new application.

Advantages of this concept are as follows: The actuator is compact. Very long strokes and piston rods are allowed without side effects of common cylinders. This property is the origin of the name “infinite cylinder”. The cylinder has small chamber volumes and so high hydraulic stiffness and low capacitance. It has also potentially no external leakage.

The cylinder can provide twice the rated force for short strokes. Applications for this feature are the plate opening stroke of injection molding machines, or presses with low work to travel stroke ratio, like a press brake.

The paper includes a detailed description of the design and the working principle. One critical component is the clamping mechanism which temporarily connects the pistons to the piston rod. The clamping mechanism together with the piston represents a new kind of machine element in the mechanical engineering field. Here the focus will be on the function and the control strategy. With simulation the proposed control strategy and function will be presented and the performance analyzed. The simulation model is backed up by first results from experiments on the early prototype.

The experiments carried out so far on the hydraulic clamping mechanism, which is the critical component in the system show very promising results that the required function can be achieved. Furthermore, the function of the whole cylinder has been simulated with good result. For the full paper results from a functioning prototype is also to be expected.
Modeling of a Pneumatic Strain Energy Accumulator for Variable System Configurations With Quantified Projections of Energy Efficiency Increases
Authors: Cummins Joshua J. , Barth Eric J. , Adams Douglas E.
Published: January 2016

The pneumatic Strain Energy Accumulator (pSEA), a device that stores the energy of compressed air in the strain energy of a rubber bladder, has recently undergone proof of concept testing showing promise in compact energy storage applications. An adequate model of the pneumatic strain energy accumulator on a systems level is needed to explore the design space in order to optimize the device. The recent success of the pneumatic strain energy accumulator on an Ankle Foot Orthosis (AFO) medical assist device serves as motivation for such a systems level model. In laboratory experiments the AFO medical assist device has reported from 25–75% energy efficiency improvement when using the pSEA depending on the various parameters of the medical device. Early measurements and calculations for a single stage independent process pSEA indicated a theoretical maximum energy efficiency increase of 33% which lies between the energy efficiency values realized on the AFO device using a single stage coupled process pSEA. A study of a lumped parameter model using measured Pressure-Volume curve data as a model input will be used to quantify energy efficiency increases for a variety of system configurations. Once complete, a set of measurement techniques and tools to successfully realize the strain energy accumulator will be ready to use in quantifying its energy savings.
Analysis of Wave Propagation Effects in Transmission Lines due to Digital Valve Switching
Authors: Kogler Helmut , Scheidl Rudolf , Schmidt Bernd Hans
Published: January 2016

In digital hydraulic systems, switching valves have opening and closing times in the range of a few milliseconds. Due to this fast switching, high bandwidth pressure pulsation is excited, which is the stimulus for airborne noise up to some kilohertz. Since the human ear is very sensitive to audible noise in this frequency range, an analysis of the influence of the valve’s opening curve on the pressure surge in the pipe system is intended. The study is based on simulations employing dynamic pipe models for linear wave propagation and laminar fluid flow. In particular, a simple pipe system with a valve at one end and a pressure boundary at the other end of the pipe is investigated. It is shown, how the valve opening characteristics of spool and seat type switching valves influences the pipe responses. Also the role of parasitic inductances due to the valve block bores is discussed and it is shown how the switching characteristics influences the dynamical effects on the pressure pulsations in the pipe system.
On the Reduction of Combustion Noise by a Close-Coupled Pilot Injection in a Small-Bore DI Diesel Engine
Authors: Busch Stephen , Zha Kan , Warey Alok , Pesce Francesco , Peterson Richard
Published: January 2016

For a pilot-main injection strategy in a single cylinder light duty diesel engine, the dwell between the pilot- and main-injection events can significantly impact combustion noise. As the solenoid energizing dwell decreases below 200 μs, combustion noise decreases by approximately 3 dB and then increases again at shorter dwells. A zero-dimensional thermodynamic model has been developed to capture the combustion-noise reduction mechanism; heat-release profiles are the primary simulation input and approximating them as top-hat shapes preserves the noise-reduction effect. A decomposition of the terms of the underlying thermodynamic equation reveals that the direct influence of heat-release on the temporal variation of cylinder-pressure is primarily responsible for the trend in combustion noise. Fourier analyses reveal the mechanism responsible for the reduction in combustion noise as a destructive interference in the frequency range between approximately 1 kHz and 3 kHz. This interference is dependent on the timing of increases in cylinder-pressure during pilot heat-release relative to those during main heat-release. The mechanism by which combustion noise is attenuated is fundamentally different from the traditional noise reduction that occurs with the use of long-dwell pilot injections, for which noise is reduced primarily by shortening the ignition delay of the main injection. Band-pass filtering of measured cylinder-pressure traces provides evidence of this noise-reduction mechanism in the real engine.

When this close-coupled pilot noise-reduction mechanism is active, metrics derived from cylinder-pressure such as the location of 50% heat-release, peak heat-release rates, and peak rates of pressure rise cannot be used reliably to predict trends in combustion noise. The quantity and peak value of the pilot heat-release affect the combustion noise reduction mechanism, and maximum noise reduction is achieved when the height and steepness of the pilot heat-release profile are similar to the initial rise of the main heat-release event. A variation of the initial rise-rate of the main heat-release event reveals trends in combustion noise that are the opposite of what would happen in the absence of a close-coupled pilot. The noise-reduction mechanism shown in this work may be a powerful tool to improve the tradeoffs among fuel efficiency, pollutant emissions, and combustion noise.
The Effect of In-Cylinder Turbulence on Lean, Premixed, Spark Ignited Engine Performance
Authors: Breaux Baine , Hoops Chris , Glewen William
Published: January 2016

The intensity and structure of in-cylinder turbulence is known to have a significant effect on internal combustion engine performance. Changes in flow structure and turbulence intensity result in changes to the rate of heat release, cylinder wall heat rejection, and cycle-to-cycle combustion variability. This paper seeks to quantify these engine performance consequences and identify fundamental similarities across a range of high-speed, medium-bore, lean-burn, spark-ignited reciprocating engines. In-cylinder turbulence was manipulated by changing the extent of intake port-induced swirl as well as varying the level of piston-generated turbulence. The relationship between in-cylinder turbulence and engine knock is also discussed.

Increasing in-cylinder turbulence generally reduces combustion duration, but test results reveal that increasing swirl beyond a critical point can cause a lengthening of burn durations and greatly reduced engine performance. This critical swirl level is related to the extent of small-scale, piston generated turbulence present in the cylinder. Increasing in-cylinder turbulence generally leads to reduced cycle-to-cycle variability and increased detonation margin. The overall change in thermal efficiency was dependent on the balance of these factors and wall heat transfer, and varied depending on the operational constraints for a given engine and application. Single cylinder engine test data, supported with three dimensional CFD results are used to demonstrate and explain these basic combustion engine principles.
Comparison of Bio-Fischer-Tropsch Fuel and Commercial Diesel Fuel Application in a 1600 CC Euro 5 Diesel Engine
Authors: Nielsen Claus Suldrup , Schramm Jesper , Ivarsson Anders , Malik Azhar , Løvås Terese
Published: January 2016

A direct injected and turbocharged Euro 5 diesel engine has been set up in a test bench where the vehicle driving conditions of the European NEDC (New European Driving Cycle) test can be simulated. The engine is operated as the engine of a corresponding vehicle, equipped with a similar engine and driving through the NEDC cycle. The regulated gaseous emissions, carbon monoxide, hydrocarbons and nitrogen oxides, as well as particulate numbers and size distributions where measured in 5 selected steady state operating points during the engine test. Fuel consumptions and carbon dioxide emissions where measured as well. The steady state operating conditions were chosen within the engine operating range during a vehicle NEDC test and representing as broad an operating range as possible during the NEDC test. A method is presented in which the NEDC test emissions are calculated from the 5 steady state measurements. It is shown that the method gives emission results that agree well with values that can be expected from the vehicle in question during an NEDC test. In this way a limited number of steady state measurements can be used to simulate vehicle emissions. The reason for carrying out engine experiments instead of vehicle measurements was to obtain well controlled engine conditions and thus better insight in the operation of the engine in the individual phases of operation, and thereby enable evaluation of the possibilities for improving engine performance with respect to emission and fuel consumption reduction.

Two different fuels where tested. These were a Fischer-Tropsch fuel, produced from biomass at the Güssing gasification plant in Austria and a commercial diesel from a fuel station in Denmark. The results of the measurements and engine modification considerations showed that bio Fischer-Tropsch fuel does have advantages with respect to particulate and also small advantages with carbon monoxide and carbon dioxide emissions. However, NOx emissions are rather a question of the injection timing of the fuel, and the NOx emissions can be adjusted to give the same level of emissions by changing the injection timing with ordinary diesel. The injection strategy was changed in order to attempt to reduce NOx emissions below the limits in the Euro 6 regulations.
High-Pressure Electronic Fuel Injection for Small-Displacement Single-Cylinder Diesel Engine
Authors: Carpenter Andrew L. , Mayo Robert E. , Wagner Jerald G. , Yelvington Paul E.
Published: January 2016

Small-displacement, single-cylinder, diesel engines employ mechanically actuated fuel injection systems. These mechanically governed systems, while robust and low-cost, lack the ability to fully vary injection parameters, such as timing, pulse duration, and injection pressure. The ability of a particular injection system to vary these injection parameters impacts engine efficiency, power, noise, and emissions. Modern, multi-cylinder automotive engines employ some form of electronically controlled injection to take advantage of the benefits of fully variable injection, including advanced strategies such as multi-pulse injections and rate shaping. Modern diesel electronic fuel injection systems also operate at considerably higher injection pressures than mechanical fuel systems used in small-bore industrial engines. As the cost of electronic fuel systems continues to decrease and the demand for high-efficiency engines increases, electronic fuel injection becomes a more viable option for incorporation into small industrial diesel engines. In particular, this technology may be well-suited for demanding and critical applications such as military power generation.

In this study, a small-bore, single-cylinder diesel was retrofit with a custom, four-hole, high-pressure electronic fuel system. Compared to the mechanical injector, the electronic, common-rail injector had a 50% smaller orifice diameter and was designed for a 4x higher injection pressure. The mechanical governor was also replaced with an electronic speed controller. The baseline and modified engines were installed on a dynamometer, and measurements of exhaust emissions, fuel consumption, brake torque, and in-cylinder pressure were made. The electronic injector led to lower smoke opacity and NOx emissions, while CO and hydrocarbon emissions were observed to increase slightly, likely due to some wall wetting of fuel with the initial prototype injector. Testing with low ignition quality fuels was also performed, and the electronic fuel system enabled the engine to operate with fuel having a cetane number as low as 30.
Large Eddy Simulation of a Turbulent Non-Reacting Spray Jet
Authors: Hu B. , Banerjee S. , Liu K. , Rajamohan D. , Deur J. M. , Xue Q. , Som S. , Senecal P. K. , Pomraning E.
Published: January 2016

We performed Large Eddy Simulation (LES) of a turbulent non-reacting n-Heptane spray jet, referred to as Spray H in the Engine Combustion Network (ECN), and executed a data analysis focused on key LES metrics such as fraction of resolved turbulent kinetic energy and similarity index. In the simulation, we used the dynamic structure model for the sub-grid stress, and the Lagrangian-based spray-parcel models coupled with the blob-injection model. The finest mesh-cell size used was characterized by an Adaptive Mesh Refinement (AMR) cell size of 0.0625 mm. To obtain ensemble statistics, we performed 28 numerical realizations of the simulation. Demonstrated by the comparison with experimental data in a previous study [7], this LES has accurately predicted global quantities, such as liquid and vapor penetrations. The analysis in this work shows that 14 realizations of LES are sufficient to provide a reasonable representation of the average flow behavior that is benchmarked against the 28-realization ensemble. With the current mesh, numerical schemes, and sub-grid scale turbulence model, more than 95% of the turbulent kinetic energy is directly resolved in the flow regions of interest. The large-scale flow structures inferred from a statistical analysis reveal a region of disorganized flow around the peripheral region of the spray jet, which appears to be linked to the entrainment process.
An Enhanced PRF Mechanism Considering Conventional Fuel Chemistry in Engine Simulation
Authors: Zhou Dezhi , Yang Wenming , An Hui , Li Jing , Kraft Markus
Published: January 2016

A compact and accurate primary reference fuel (PRF) mechanism which consists of 46 species and 144 reactions was developed and validated to consider the fuel chemistry in combustion simulation based on a homogenous charged compression ignition (HCCI) mechanism. Some significant reactions were updated to ensure its capabilities for predicting combustion characteristics of PRF fuels. To better predict laminar flame speed, the relevant C2-C3 carbon reactions was coupled in. This enhanced PRF mechanism was validated by available experimental data references including ignition delay times, laminar flame speed, premixed flame species concentrations in jet stirred reactor (JSR), rapid compression machine and shock tube. The predicted data was calculated by CHEMKIN-II codes. All the comparisons between experimental and calculated data indicated high accuracy of this mechanism to capture combustion characteristics. Also, this mechanism was integrated into KIVA4-CHEMKIN. The engine simulation data (including in-cylinder pressure and apparent heat release rate (HRR)) was compared with experimental data in PRF HCCI, partially premixed compression ignition (PCCI) and diesel/gasoline dual-fuel engine combustion data. The comparison results implied that this mechanism could predict PRF and gasoline/diesel combustion in CFD engine simulations. The overall results show this PRF mechanism could predict the conventional fuel combustion characteristics in engine simulation.
Impact of Urea Direct Injection on NOx Emission Formation of Diesel Engines Fueled by Biodiesel
Authors: Yang Wenming , An Hui , Li Jing , Zhou Dezhi , Kraft Markus
Published: January 2016

There are many NOx removal technologies: exhaust gas recirculation (EGR), selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR), miller cycle, emulsion technology and engine performance optimization. In this work, a numerical simulation investigation was conducted to explore the possibility of an alternative approach: direct aqueous urea solution injection on the reduction of NOx emissions of a biodiesel fueled diesel engine. Simulation was performed using the 3D CFD simulation software KIVA4 coupled with CHEMKIN II code for pure biodiesel combustion under realistic engine operating conditions of 2400 rpm and 100% load. To improve the overall prediction accuracy, the Kelvin-Helmholtz and Rayleigh-Taylor (KH-RT) spray break up model was implemented in the KIVA code to replace the original Taylor Analogy Breakup (TAB) model for the primary and secondary fuel breakup processes modeling. The KIVA4 code was further modified to accommodate multiple injections, different fuel types and different injection orientations. A skeletal reaction mechanism for biodiesel + urea was developed which consists of 95 species and 498 elementary reactions. The chemical behaviors of the NOx formation and Urea/NOx interaction processes were modeled by a modified extended Zeldovich mechanism and Urea/NOx interaction sub-mechanism. Developed mechanism was first validated against the experimental results conducted on a light duty 2KD FTV Toyota car engine fueled by pure biodiesel in terms of in-cylinder pressure, heat release rate. To ensure an efficient NOx reduction process, various aqueous urea injection strategies in terms of post injection timing and injection rate were carefully examined. The simulation results revealed that among all the four post injection timings (10 °ATDC, 15 °ATDC, 20 °ATDC and 25 °ATDC) that were evaluated, 15 °ATDC post injection timing consistently demonstrated a lower NO emission level. In addition, both the urea/water ratio and aqueous urea injection rate demonstrated important roles which affected the thermal decomposition of urea into ammonia and the subsequent NOx removal process, and it was suggested that 50% urea mass fraction and 40% injection rate presented the lowest NOx emission levels.
Post Injection Strategy for the Reduction of the Peak Pressure Rise Rate of Neat N-Butanol Combustion
Authors: Jeftić Marko , Zheng Ming
Published: January 2016

Enhanced premixed combustion of neat butanol in a compression ignition engine can have challenges with regards to the peak pressure rise rate and the peak in-cylinder pressure. It was proposed to utilize a butanol post injection to reduce the peak pressure rise rate and the peak in-cylinder pressure while maintaining a constant engine load. Post injection timing and duration sweeps were carried out with neat n-butanol in a compression ignition engine. The post injection timing sweep results indicated that the use of an early butanol post injection reduced the peak pressure rise rate and the peak in-cylinder pressure and it was observed that there was an optimal post injection timing range for the maximum reduction of these parameters. The results also showed that an early post injection of butanol increased the nitrogen oxide emissions and an FTIR analysis revealed that late post injections increased the emissions of unburned butanol.

The post injection duration sweep indicated that the peak pressure rise rate was significantly reduced by increasing the post injection duration at constant load conditions. There was also a reduction in the peak in-cylinder pressure. Measurements with a hydrogen mass spectrometer showed that there was an increased presence of hydrogen in the exhaust gas when the post injection duration was increased but the total yield of hydrogen was relatively low. It was observed that the coefficient of variation for the indicated mean effective pressure was significantly increased and that the indicated thermal efficiency was reduced when the post injection duration was increased. The results also showed that there were increased nitrogen oxide, carbon monoxide, and total hydrocarbon emissions for larger post injections. Although the use of a post injection resulted in emission and thermal efficiency penalties at medium load conditions, the results demonstrated that the post injection strategy successfully reduced the peak pressure rise rate and this characteristic can be potentially useful for higher load applications where the peak pressure rise rate is of greater concern.
Oxygen-Enriched Combustion for Industrial Diesel Engines
Authors: Yelvington Paul E. , Roth R. Paul , Mayo Robert E. , Carpenter Andrew L. , Wagner Jerald G.
Published: January 2016

Oxygen-enriched combustion (OEC) is used in industrial combustion applications to increase the adiabatic flame temperature. OEC has also been studied previously as a means to increase the efficiency, power density, and low-quality fuel compatibility of internal combustion engines, including diesels. Although oxygen-enriched air can be produced in a number of ways, membrane air separating is the preferred method. Under this program, a high-flux membrane was experimentally tested for this application. A small-displacement (200 cm3), single-cylinder diesel engine was also modified for OEC. The modifications included development of a custom electronic fuel injection system and changes to the inlet manifold to dynamically change the oxygen concentration in the combustion air. Membrane testing, engine dynamometer testing, and system analysis demonstrated that current air-separation membranes require excessive parasitic losses for improvement of power density and efficiency. However, OEC can enable the use of low ignition-quality fuels. OEC was also observed to decrease carbon monoxide (CO) and smoke emissions, although nitrogen oxide (NOx) emissions were observed to increase. Transient testing was also performed; a membrane-based OEC system was shown to respond to step changes in engine load with an acceptable time response.
Modifications to Improve Fuel Consumption in the Remanufacture of Spark Ignition Engines for Electric Generators
Authors: Swain Matthew Neill , Jordan Oliver Patrick , Mackey Travis Jamal , Seemann Patrick Shannon , Samarajeewa Hasitha , Swain Michael Robert
Published: January 2016

This paper describes the development of a water cooled, lean burn, gaseous fueled engine designed for distributed power installations. Electric generators have become popular because they provide a portable supply of electrical power at consumer demand. They are used in critical need areas such as hospitals and airports, and have found their way into homes frequented with power outages or homes in remote locations. Gensets are available in a wide variety of sizes ranging from 1 kilowatt (kW) to thousands of kilowatts. In the mid-range the power sources are typically spark ignition, automotive type internal combustion engines. Since engines designed for automotive use are subject to different emission regulations, and are optimized for operation at RPMs and BMEPs above that of electric generator engines, modifications can be made to optimize them for gensets. This work describes modifications which can be made during remanufacturing an automotive engine to optimize it for use as a generator engine. While the work recognizes the potential for cost savings from the use of remanufactured automotive engines over that of using new automotive engines and the majority of the design constraints were adopted to reduce engine cost, the main focus of the work is quantifying the increase in fuel efficiency that can be achieved while meeting the required EPA emission requirements.

This paper describes the seven combustion chamber designs that were developed and tested during this work. Friction reduction was obtained in both valve train and journal bearing design. The engine optimized for fuel efficiency produced a maximum brake thermal efficiency of 37.5% with λ= 1.63. This yielded an EPA test cycle average brake specific fuel consumption (BSFC) of 325 g/kW-hr. Modification of the spark advance and low load equivalence ratio to meet EPA Phase III emission standards resulted in an EPA test cycle average BSFC of 330 gm/kW-hr. When the engine used in this research was tested in its unmodified, automotive configuration under the EPA Compliant Test Cycle it’s EPA test cycle average brake specific fuel consumption was 443.4 gm/kW-hr. This is a 34% increase in fuel consumption compared to the modified engine.
Characterization and Speciation of Fuel Oil Dilution in Gasoline Direct Injection (DI) Engines
Authors: Hakeem Mohannad , Anderson James , Surnilla Gopichandra , Yamada Shuya Shark
Published: January 2016

Fuel dilution in oil is a known issue for gasoline direct injection (DI) engines especially in colder climates and for customers with short, lightly-loaded driving cycles. In this work, oil samples were generated using a cold oil fuel accumulation test. Gas chromatography (GC) was used to speciate the hydrocarbons accumulated in the oil and characterize their quantity, type, molecular weight distribution, and volatility. Further testing and analysis was done to characterize the fuel hydrocarbons that evaporate from oil during engine warm-up conditions. The results demonstrate how the wide range of gasoline hydrocarbon volatility leads to different behavior in the accumulation and subsequent evaporation phases. Lastly, a model was created to extend this analysis and estimate the evaporation of hydrocarbons from the oil.
Parametric Study of the Scavenging Process in Marine Two-Stroke Diesel Engines
Authors: Andersen Fredrik Herland , Mayer Stefan
Published: January 2016

Large commercial ships such as container vessels and bulk carriers are propelled by low-speed, uniflow scavenged two-stroke diesel engines. The integral in-cylinder process in this type of engine is the scavenging process, where the burned gas from the combustion process is evacuated through the exhaust valve and replaced with fresh air for the subsequent compression stroke. The scavenging air enters the cylinder via inlet ports which are uncovered by the piston at bottom dead center (BDC). The exhaust gas is then displaced by the fresh air. The scavenging ports are angled to introduce a swirling component to the flow. The in-cylinder swirl is beneficial for air-fuel mixture, cooling of the cylinder liner and minimizing dead zones where pockets of exhaust gas are trapped. However, a known characteristic of swirling flows is an adverse pressure gradient in the center of the flow, which might lead to a local deficit in axial velocity and the formation of central recirculation zones, known as vortex breakdown. This paper will present a CFD analysis of the scavenging process in a MAN B&W two-stroke diesel engine. The study include a parameter sweep where the operating conditions such as air amount, port timing and scavenging pressure are varied. The CFD model comprise the full geometry from scavenge receiver to exhaust receiver. Asymmetric inlet and outlet conditions is included as well as the dynamics of a moving piston and valve. Time resolved boundary conditions corresponding to measurements from an operating, full scale production, engine as well as realistic initial conditions are used in the simulations. The CFD model provides a detailed description of the in-cylinder flow from exhaust valve opening (EVO) to exhaust valve closing (EVC). The study reveals a close coupling between the volume flow (delivery ratio) and the in-cylinder bulk purity of air which appears to be independent of operating conditions, rpm, scavenge air pressure, BMEP etc. The bulk purity of air in the cylinder shows good agreement with a simple theoretical perfect displacement model.
Two-Stage Turbocharging Solutions for Tier 4 Rail Applications
Authors: Bernasconi Simone , Codan Ennio , Yang David , Jacoby Pierre , Weisser German
Published: January 2016

With the introduction of the EPA Tier 4 NOx emission limits for rail diesel engines this year, engine developers are forced to implement more advanced emission control technologies such as selective catalytic reduction (SCR) or cooled external exhaust gas recirculation (EGR). The integration and control of these systems for ensuring optimum performance throughout the operating range brings about new challenges on top of the well-known requirement for unconstrained operability in a very wide range of conditions.

As a consequence, engines and their subsystems have to be designed for maximum flexibility. The turbocharging system in particular needs to be capable of dealing with extreme ambient conditions associated with high altitudes, hot summers, severe winters, tunnel operation, etc. This flexibility must be achieved without compromising reliability and while ensuring continuous in-use compliance with the emissions standards throughout the life of the installation. At the same time, engine performance should be maintained at the highest level possible.

This study demonstrates that all of these targets can be met by combining two-stage turbocharging and EGR with suitable control elements. Two-stage turbocharging, which has become increasingly popular in other industry sectors due to its potential for improving the bsfc / NOx emissions trade-off when used in combination with correspondingly optimized valve actuation (Miller timing), is starting to be adopted also for rail applications.

A variety of EGR concepts was proposed or put into practice over the past few years, and the most important or promising of these have been taken into consideration for this study. Extensive simulations of the resulting engine and turbocharging systems have been performed using ABB’s in-house simulation platform, based on a generic engine model that can be considered representative of the rail sector.

It is shown that integration of EGR, two-stage turbocharging and appropriate control elements is highly attractive as it offers outstanding operational flexibility and very high fuel efficiency without any compromise in terms of reliability.

The selection and specification of control elements and turbocharging system components depends on the EGR concept applied. As is shown below, this can be tailored to the application to ensure optimum performance and flexibility. In view of these obvious benefits, we are very confident that such integrated EGR / two-stage turbocharging systems will be adopted more widely on railway engines.
Investigation of Cold Starting and Combustion Mode Switching as Methods to Improve Low Load RCCI Operation
Authors: Hanson Reed , Reitz Rolf
Published: January 2016

Reactivity Controlled Compression Ignition (RCCI) is an engine combustion strategy that utilizes in-cylinder fuel blending to produce low NOx and PM emissions while maintaining high thermal efficiency. The current study investigates RCCI and conventional diesel combustion (CDC) operation in a light-duty multi-cylinder engine using a transient capable engine test cell.

The main focus of the work uses engine experiments to investigate methods which can improve low-load RCCI operation. The first set of experiments investigated RCCI operation during cold start conditions. The next set of tests investigated combustion mode switching between RCCI and CDC.

During the cold start tests, RCCI performance and emissions were measured over a range of engine coolant temperatures from 48 to 85°C. A combination of open and closed loop controls enabled RCCI to operate at a 1,500 rpm, 1 bar BMEP operating point over this range of coolant temperatures.

At a similar operating condition, i.e. 1,500 rpm, 2 bar BMEP, the engine was instantaneously switched between CDC and RCCI combustion using the same open and closed loop controls as the cold start testing. During the mode switch tests, emissions and performance were measured with high speed sampling equipment. The tests revealed that it was possible to operate RCCI down to 48°C with simple open and closed loop controls with emissions and efficiency similar to the warm steady-state values. Next, the mode switching tests were successful in switching combustion modes with minimal deviations in emissions and performance in either mode at steady-state.