bluuebunny/crossref_metadata_2025 huggingface dataset:
Micro Surface Shaping for the High-Pressure Operation of Piston Machines With Water as a Working Fluid
Authors: Ernst Meike H. , Ivantysynova Monika
Published: January 2016

Oil is the main working fluid used in the hydraulics industry today — but water is nonflammable, environmentally friendly and cheap: it is the better choice of working fluid for hydraulic systems. However, there is one caveat. Water’s extremely low viscosity undermines its ability to carry load. In forest machinery, construction machinery, and aircraft systems, today’s hydraulic circuits have high operating pressures, with typical values between 300 and 420 bar. These high pressures create the need for high load-carrying abilities in the fluid films of the tribological interfaces of pumps and motors. The most challenging of these interfaces is the piston-cylinder interface of swashplate type piston machines, because the fluid must balance the entire piston side load created in this design. The low viscosity of the water turns preventing metal-to-metal contact into quite a challenge. Fortunately, an understanding of how pressure builds and shifts about in these piston-cylinder lubrication interfaces, coupled with some clever micro surface shaping, can allow engineers to drastically increase the load-carrying ability of water. As part of this research, numerous different micro surface shaping design ideas have been simulated using a highly advanced non-isothermal multi-physics model developed at the Maha Fluid Power Research Center. The model calculates leakage, power losses, film thickness and pressure buildup in the piston-cylinder interface over the course of one shaft revolution. The results allow for the comparison of different surface shapes, such as axial sine waves along the piston, or a barrel-shaped piston profile. This paper elucidates the effect of those surface profiles on pressure buildup, leakage, and torque loss in the piston-cylinder interface of an axial piston pump running at high pressure with water as the lubricant.
Optimal Control and Performance Based Design of the Blended Hydraulic Hybrid
Authors: Bleazard Tyler , Haria Hiral , Sprengel Michael , Ivantysynova Monika
Published: January 2016

Due to a growing awareness of fuel prices and government regulations on emissions there has been an expanding interest in hybrid vehicle research. Though much of these efforts have been in electric hybrid vehicles, hydraulic hybrid vehicles show great potential due to their higher power density, higher efficiency in regenerative braking, and lower cost of materials. Many different hydraulic hybrid architectures have been proposed, one of the most common being the series hybrid. The series hybrid has many deficiencies due to the hydraulic units being connected directly to the high pressure accumulator. In many operating conditions the units operate inefficiently at low displacements and high pressures. Additionally the driver’s torque demand can exceed that available from the accumulator’s current pressure. As a result additional fluid must be pumped into the accumulator to raise the system pressure. This can result in a delay on the order of seconds in meeting the driver’s demand thereby yielding an undesirably sluggish response.

To address these issues the authors’ research group previously introduced the blended hydraulic hybrid [1]. Using dynamic programming, an optimal control simulation tool, the blended hybrid showed improved efficiency and response when compared to the series hybrid [2]. This transmission achieves high efficiency and fast response partially through the inclusion of a hydrostatic transmission. In addition regenerative braking and blending of engine and accumulator power are realized through the use of actively and passively controlled valves.

With these promising results, the Maha Fluid Power Research Center has begun designing and constructing a blended hydraulic hybrid SUV. In preparation for this the authors have developed a new sizing methodology to determine transmission sizing that meets both the efficiency and performance requirements of the designer. To explore the trends in blended hydraulic hybrid sizing a full factorial combination of hydraulic unit sizes, accumulator sizes and accumulator minimum pressures were optimally controlled for the Urban Dynamometer Driving Schedule (UDDS) using dynamic programming and maximum acceleration was simulated to obtain trends in performance.
The Adaptive Robust Control of Deep-Sea Hydraulic Manipulator With Velocity Observer
Authors: Cao Xiaoxu , Luo Gaosheng , Gu Linyi , Wang Yaoyao , Xu Yihong
Published: January 2016

In this paper, the adaptive robust control method with a velocity observer is proposed to control a deep-sea manipulator. The parametric uncertainties and external disturbances make the linear controller invalid, and hydraulic actuator’s dynamics can’t be neglected because hydraulic system’s complex nonlinearity might lead to vibration. To solve the problem, an adaptive robust controller which can also compensate the interactive dynamic effects between manipulator links is developed. The deep-sea manipulators are only installed with angular sensors, so an observer providing the smooth angular velocity estimation is designed. By using the Lyapunov approach, the proposed controller can be proved asymptotically stable for trajectory tracking. The contrast experiments are conducted on a deep-sea hydraulic manipulator, experiment results show the control algorithm could provide a fast, high accuracy tracking, and guarantee the tracking performance when subjected to payload change or a range of different reference signals.
Full Vehicle Simulation of Forwarder With Semi-Active Suspension Using Co-Simulation
Authors: Braun Robert , Ericson Liselott , Krus Petter
Published: January 2016

A major concern in the forest industry is impact on the soil caused by forest machines during harvesting. A six-wheel pendulum arm forwarder is being developed. The new forwarder aims at reducing soil damage by an even pressure distribution and smooth torque control and thereby also improving the working environment. The suspension contains pendulum arms on each wheel controlled by a hydraulic load sensing system in combination with accumulator.

A natural approach is to model each part of a system in the best-suited software. In this case, the hydraulic system is modelled in the Hopsan simulation tool, while the vehicle mechanics is modelled in Adams. To understand the whole system it is necessary to simulate all subsystems together. An open standard for this is the Functional Mock-up Interface. This makes it possible to investigate the interaction between the hydraulic system and the multi-body mechanic model.

This paper describes how different simulation tools can be combined to support the development process. The technique is applied to the forwarder’s pendulum suspension. Controllers for height and soil force are optimized to minimize soil damage and maximize comfort for the operator.
On the Influence of Piston and Cylinder Density in Tribodynamics of a Radial Piston Digital Fluid Power Displacement Motor
Authors: Johansen Per , Roemer Daniel B. , Andersen Torben O. , Pedersen Henrik C.
Published: January 2016

In the past three decades an increasing amount of research has been performed in the field of tribodynamics of fluid power pumps and motors. The main incentives for this research are optimization of reliability and efficiency through the study of loss and wear mechanisms. These mechanisms are very difficult to study experimentally, whereby modeling and simulation are necessary. The modeling of tribodynamics is a multiphysics problem involving multibody dynamics, fluid mechanics, thermodynamics and solid mechanics. Consequently, the simulation durations can easily become impractical for parametric analysis or optimization. The coupling between multibody dynamics and fluid mechanics depend on the formulation of the solid body motion equations, where two approaches have historically been used. One approach is where the external forces on any lubricated joint are balanced by the fluid forces, such that solid body inertia is neglected. The other approach includes the inertia terms in the calculation of microdynamics. The inclusion of inertia terms entails a need for smaller time steps in comparison to the force balance approach, wherefore it is of interest to analyze the influence of the inertia term. In this paper the influence of the inertia term on the lubrication gaps of a radial piston motor are studied by a parametric analysis of the piston and cylinder density in a multibody tribodynamic simulation model. The motor is modeled as a digital fluid power displacement machine and a series of full-stroke displacement simulations are used as basis for the parametric analysis. From the parametric analysis a change, in the minimum film thickness as function of piston and cylinder density, is shown for certain operating modes of the digital fluid power displacement motor. This indicate a need for careful assessment of the applicability, of the force balance condition, if it is used in multibody tribodynamic simulations of radial piston digital fluid power displacement motors.
Hydraulic Die Cushions in Deep Drawing Presses: Analysis and Optimization Using Coupled Simulation
Authors: Schulze Tobias , Weber Jürgen , Großmann Knut , Penter Lars , Schenke Christer
Published: January 2016

The scientific paper proposes a method to analyze and optimize the drawing press and the deep drawing process with a virtual model. It focuses on hydraulic multi-point die cushions since they offer a wide range of possible adjustments and a high potential to increase production quality and efficiency. The operator can apply individual die cushion cylinder forces to the blankholder which enables the control of the forming process and manual die spotting can theoretically be reduced to a minimum. Utilizing the virtual model can improve the drawing press’ behavior and significantly reduce the set-up time for drawing presses during try-out of new tools or when tool sets are transferred to a different machine.

The paper presents a system simulation model of a deep drawing press including its mechanics, hydraulics, and control. It serves as a basis for developing an advanced control system which improves system performance with potentially higher slide speeds, and therefore, a more efficient production.

Another aspect in the paper is the development of a coupled simulation consisting of the machine model and a process model. This includes the elasto-static as well as the dynamic behavior of the drawing press and allows for simulations with the highest possible level of detail. The model was used to determine individual set forces for the die cushion cylinders which allowed for the production of sound quality parts without manual die spotting.
Pressure Modeling and Analysis of a Synchronized Hydraulic Press Brake With Variable-Speed Pump
Authors: Teixeira Paulo Leonel , Vianna Waldir , Penteado Ricardo D. , Krus Petter , De Negri Victor Juliano
Published: January 2016

This paper presents a theoretical–experimental pressure analysis of a hydraulic press brake with synchronized cylinders. In this machine, the motion of each cylinder is controlled by independent variable-speed electrical motors. This design has many benefits over traditional solutions using hydraulic proportional valves, such as higher energetic efficiency, nonrequirement of a heat exchanger, lower oil-cleanliness requirement, and reduced audible noise. However, a critical characteristic of the press brake is the use of double acting cylinders with large rods controlled by a pump in a closed circuit. In the studied system a cap end area roughly eleven times greater than the rod end area is used. Furthermore, the synchronized hydraulic press brake operates in six stages with particular characteristics implying in different flow rate demands and pressure behaviors. Based on experimental results, the pressures in specific parts of the circuit are analyzed and critical operational conditions are identified. A simulation model using Hopsan is validated and used to propose a hydraulic circuit modification. The proposed solution eliminates the tendency for pump cavitation and pressure surges that occur during the press break operational cycle.
Design and Stability Analysis of a QFT Pressure Controller of a Hydraulic Actuator Using Takagi-Sugeno Fuzzy Model
Authors: Esfandiari Masoumeh , Sepehri Nariman
Published: January 2016

In this paper, a robust, fixed-gain, and linear controller is designed for the output pressure of an electro-hydraulic actuator with parametric uncertainties. Quantitative feedback theory (QFT) is selected as the design technique. The objective is to satisfy specified performance criteria in terms of tracking, stability, and disturbance rejection. To design the QFT controller, the required family of frequency responses is obtained by linearizing the hydraulic nonlinear function around operating points of interest, and constructing an equivalent linear plant set. As a result, the stability of the closed-loop system is guaranteed only around the limited number of operating points, and specified values for system parameters. To overcome this limitation, Takagi-Sugeno (T-S) fuzzy modeling is employed. This way the nonlinear stability of the closed-loop system is investigated and ensured for a continuous range of parametric uncertainties and region of operating points. Having successful results from stability analysis, the QFT controller is applied on the experimental set-up. The experimental results are in accordance with the specified criteria.
Experimental Study on Low Temperature Combustion Dual Fuel Biodiesel/Natural Gas Engine
Authors: Gharehghani A. , Mirsalim M. , Jazayeri A. , Hosseini R.
Published: January 2016

Low Temperature combustion (LTC) strategies are capable of simultaneous reduction in NOx and particulate matter (PM) emissions. However, this combustion process generally leads to higher HC and CO emissions together with more cyclic variation (unstable combustion) especially at light engine loads. These emissions could drastically be reduced using certain alternative fuels like natural gas and biodiesel in LTC or PCI combustion engines. In the present research, a single cylinder compression ignition engine has been modified to operate in dual fuel mode with natural gas injection into the intake manifold as the main fuel and biodiesel as the pilot fuel to ignite the gas/air mixture. The combustion characteristics, engine performance and exhaust emissions of the reactivity controlled compression ignition (RCCI) dual fueled CNG/biodiesel engine are investigated and compared with the conventional diesel engine mode at various load conditions. The analysis of the results revealed that biodiesel as the high reactivity fuel in RCCI mode leads to higher in-cylinder pressure together with shorter heat release rate duration, compared to the common diesel engine. Experimental results indicated that combining the low temperature combustion concept and alternative fuels (e.g. biodiesel and naturals gas) causes lower levels of unburned hydrocarbon (UHC) and carbon monoxide (CO) as well as nitrogen oxide (NOx) emissions.
Late-Fuel Simulation Near Nozzle Outlet of Fuel Injector During Closing Valve
Authors: Ishii Eiji , Yoshimura Kazuki , Yasukawa Yoshihito , Ehara Hideharu
Published: January 2016

Late fuel during closing of the valve of a fuel-injector and fuel films stuck on the wall around the nozzle outlets are sources of PM. In this study, we focused on effects of the valve motions on the late fuel and the fuel films stuck on the walls around the nozzle outlets. We previously developed a particle/grid hybrid method: fuel flows within the flow paths of fuel injectors were simulated by a front capturing method, and liquid-column breakup at the nozzle outlets was mainly simulated by a particle method. The velocity at the inlet boundary of a fuel injector was controlled in order to affect the valve motions on the late-fuel behavior. The simulated late fuel broke up with surface-tension around the time of zero-stroke position of the valve, then liquid columns and coarse droplets formed after the bounds of the valve, and finally only coarse droplets were left. We found that the late fuel was generated by low-speed fuel-flows through the nozzles during the bounds of the valve. The effect of the bounds of the valve on the fuel films stuck on the wall around the nozzle outlets was also studied with a simulation that removed the bounds of the valve. The volume of the fuel films stuck on the wall of the nozzle outlets decreased without the bounds of the valve.
Evaluation of Test Bench Engine Performance Measurements in Relation to Vehicle Measurements on Chassis Dynamometer
Authors: Nielsen Claus Suldrup , Schramm Jesper , Ivarsson Anders , Malik Azhar , Løvås Terese
Published: January 2016

A 1600 cc direct injected turbocharged Euro 5 diesel engine was operated on standard diesel fuel from a gas station in Denmark for evaluation of the test bench procedure. The NEDC (New European Driving Cycle), FTP-75 (Federal Test Procedure) and WLTP (World Harmonized Light Vehicle Test Procedure) driving cycles were simulated in the engine test bench in two ways: 1) by transient engine operation were the inertia of the vehicle during deceleration was simulated by addition of power from an electric motor mounted on the crank shaft, and 2) by steady state measurements where the total driving pattern was simulated from an integration of multiple steady state measurements. The mathematical model that calculates equivalent NEDC driving cycle vehicle emissions from the engine steady state measurements in the test bench, starting with warm engine, is presented. By applying this model any driving cycle emissions can be calculated from the presented tabulated steady state measurements, starting with warm or cold engine.

Both engine test methods showed acceptable agreement with measurement in an NEDC vehicle test on chassis dynamometer where the vehicle was equipped with a similar engine as the test bench engine. The two engine test bench methods gave very similar results, but the transient engine test procedure showed a little higher emission of CO2 and NOx, results that were closest to the vehicle measurements. This is interpreted as a result of extra emissions when the engine adjusts from one operating point to the next during transient operation. These extra emissions are not caught in the steady state method. Application of the two engine test procedures on the FTP-75 procedure and the newer WLTP showed that the steady state engine test method gave significantly lower emissions of NOx and a little lower CO2 emissions compared to the transient engine test. The results indicated that this was mainly an effect of the time delay on the engines EGR system adjustment, which is not caught in the steady state method.

The advantages and disadvantages of applying the different measurement methods and test procedures are discussed in relation to introduction of new test procedures in order to reduce engine/vehicle emissions.
Effect of Valve Opening/Closing Setup on CFD Prediction of Engine Flows
Authors: Yang Xiaofeng , Keum Seunghwan , Kuo Tang-wei
Published: January 2016

In Computational Fluid Dynamics (CFD) simulations of internal combustion engines, one of the critical modeling parameters is the valve setup. A standard workaround is to keep the valve opens at a certain clearance (minimum valve lift), while imposing a solid boundary to mimic valve closure. This method would yield a step change in valve lift during opening and closing event, and different valve event timing than hardware. Two parametric studies were performed to examine a) the effect of the minimum valve lift and b) the effect of grid resolution at the minimum valve lift on predicted in-cylinder flow fields in Reynolds Averaged Navier-Stokes (RANS) simulations. The simulation results were compared with the state-of-art PIV measurement from a two-valve transparent combustion chamber (TCC-3) engine. The comparisons revealed that the accuracy of flow simulation are sensitive to the choice of minimum valve lift and grid resolution in the valve seat region. In particular, the predicted in-cylinder flow field during the intake process was found to be very sensitive to the valve setup. A best practice CFD valve setup strategy is proposed as a result of this parametric studies. The proposed CFD valve setup was applied to Large Eddy Simulation (LES) of TCC-3 engine and preliminary results showed noticeable improvement already. Further evaluation of the valve setup strategy for LES simulations is on-going and will be reported in a separate report.
Experiments on the Influence of Cooling Conditions on Thermal Balance and Thermal State for a Heavy-Duty Natural Gas Engine
Authors: Hua Shiyang , Huang Ronghua , Zhou Pei , Cheng Wei , Jia Lishui
Published: January 2016

Generally, the turbulent-flame velocity of natural gas is significantly lower than diesel in the combustion process, which results in the thermal loads of natural gas engines being significantly higher than those of diesel engines under the same stoichiometric condition without EGR. In this study, a heavy-duty natural gas engine is taken as the research object, which is used to measure the temperatures to analyze the heat transfer characteristics in the cylinder head water jacket around the valve bridges, under different speeds and loads, as well as different coolant temperatures and pressures. Twelve thermocouples are inserted by drilling through the metal in the cylinder head with different heights to measure the metal temperatures at thermally critical areas such as the valve-bridge regions. Therefore, the local heat flux and the extrapolation to coolant wall temperatures are obtained by Fourier’s Law under different engine operating conditions. In addition, the thermal balance tests of the engine are also carried out, and the energy distributions are analyzed in different parts of the engine. The results of the research show that: a) the engine cooling condition has a direct impact on the engine cylinder head temperature. If the cooling temperature is low, the temperatures of the cylinder head’s measuring points have the same increases as the increasing coolant temperature. When the coolant temperature is high, the measuring temperatures have hardly any difference from the increases in cooling temperature. With increasing cooling pressure, the temperature increase at all measuring points, and the temperature of the measuring points varies substantially under high load conditions compared with the low load condition. The results indirectly indicated that local nucleate boiling appeared in the water jacket. b) The heat transfer characteristic curve of the water jacket was obtained from the processing of experimental data. Wall heat flux increases with increasing load, and the relationship between wall heat flux and wall temperature is no longer linear. The heat transfer characteristic curve indicates that the convective heat transfer and boiling heat transfer both appeared in the cooling water jacket. c) With the decrease of engine load, the percentage of crankshaft power in the combustion heat gradually decreases, then the percentage of the heat taken away by the cooling water increases gradually. At the same time, the percentage of the heat taken away by exhaust has changed little. d) The engine cooling temperature has a substantial influence on the engine thermal balance, and the cooling pressure has little effect on the engine thermal balance. With increasing cooling temperature, the heat taken by the cooling water decreased, which lead to an increase in the proportion of crankshaft power. It can be concluded that properly increasing the coolant temperature of the engine can improve the fuel economy of the machine.
The Effects of Ester Structure on Transient Fuel Spray Characteristics Including Novel Image Analysis to Quantify Air Entrainment
Authors: Gutierrez Luis G. , Fatouraie Mohammad , Xiao Steve B. , Wooldridge Margaret S. , Han Dong , Lin He , Duan Yaozong , Huang Zhen
Published: January 2016

Achieving efficient and clean combustion of biodiesel as a renewable source of energy requires a fundamental understanding of the effects of the different thermophysical properties on the fuel injection process at conditions relevant to diesel engines. In this study, the spray characteristics of two fatty acid esters, methyl oleate and ethyl oleate, are compared to a baseline diesel fuel using high-speed imaging of the sprays in a constant volume chamber. A single hole fuel injector with a nozzle diameter of 280 μm was used with a single injection event with a duration of 1.0 ms. The spray development was investigated for fuel-rail pressures of 40, 60, 80 and 100 MPa and the chamber gas densities of 1.15 kg/m3, 5.75 kg/m3 and 11.5 kg/m3. High-speed shadowgraph imaging of the non-vaporizing sprays was performed at 15,000 frames per second. Image processing algorithms were developed to quantify the spray penetration distance, penetration rate and cone angle as a function of time for the injection process. Penetration distance and penetration rate results were similar for the esters and diesel fuel for the range of experimental conditions studied. However, diesel had a larger spray cone angle compared to both esters. Additionally a novel metric for air entrainment was developed based on the macro-scale features of the spray. The integrated mixing volume metric showed no difference in air entrainment between the fuels, which is in good agreement with the behavior expected based on spray theory.
An Experimental Investigation on the Combustion and Emissions Performance of a Natural Gas–Diesel Dual Fuel Engine at Low and Medium Loads
Authors: Guo Hongsheng , Neill W. Stuart , Liko Brian
Published: January 2016

Natural gas is an abundant and inexpensive fuel in North America. It produces lower greenhouse gas emissions than diesel fuel when burned in an internal combustion engine. It is also considered to be a clean fuel because it generates lower particulate matter emissions than diesel fuel during combustion.

In this study, an experimental study was conducted to investigate the combustion and emissions performance of a natural gas – diesel dual fuel engine at low and medium loads. A single cylinder direct injection diesel engine was modified to operate as the dual fuel engine. The diesel fuel was directly injected into the cylinder, while natural gas was injected into the intake port. The operating conditions, such as engine speed, load, intake temperature and pressure, were well controlled during the experiment. The effect of natural gas fraction on energy efficiency, cylinder pressure, exhaust temperature, and combustion stability were recorded and analyzed. The emissions data, including particulate matter, nitric oxides, carbon monoxide, and methane at various natural gas fractions and operating conditions were also analyzed. The results showed that natural gas – diesel dual fuel combustion slightly decreased brake thermal efficiency at low and medium load conditions and significantly reduced carbon dioxide and particulate matter emissions. Methane and NOx emissions increased in dual fuel combustion mode compared to diesel operation. The variation of carbon monoxide emissions in dual fuel mode depended on load and speed conditions.
Engine Capability Prediction for SI Engine Fueled With Syngas
Authors: Xu Hui , LaPointe Leon A.
Published: January 2016

There are increasing interests in converting solid waste or lignocellulosic biomass into gaseous fuels and using reciprocating internal combustion engine to generate electricity. A widely used technique is gasification. Gasification is a process where the solid fuel and air are introduced to a partial oxidation environment, and generate combustible gaseous called synthesis gas or syngas. Converting solid waste into gaseous fuel can reduce landfill and create income for process owners. However it can be very challenging to use syngas on a gaseous fueled spark ignited engine, such as a natural gas (NG) engine. NG engines are typically developed with pipeline quality natural gas (PQNG). NG engines can operate at lean burn spark ignited (LBSI), or stoichiometric with EGR spark ignited (SESI) conditions. This work discusses the LBSI engine condition.

NG engines can perform very differently when fueled with nonstandard gaseous fuels such as syngas without appropriate tuning. It is necessary to evaluate engine performance in terms of combustion duration, relative knock propensity and NOx emissions for such applications. Due to constraints in time and resources it is often not feasible to test such fuel blends in the laboratory. An analytical method is needed to predict engine performance in a timely manner. This study investigated the possibility of using syngas on a spark ignited engine developed with PQNG. Engine performance was predicted using in house developed models and PQNG as the reference fuel. Laminar flame speed (LFS), adiabatic flame temperature (AFT) and Autoignition interval (AI) are used to predict combustion duration, engine out NOx and engine knock propensity relative to NG at the target Lambda values.

Single cylinder research engine data obtained under lean burn conditions fueled with PQNG was selected as the baseline. LFS, AFT and AI of syngas were computed at reference conditions. Lambda of operation was predicted for syngas to provide the same burn rate as NG at the reference Lambda value for NG. Analysis shows that, using syngas at the selected Lambda, the engine can have less engine out NOx emissions and less knock propensity relative to NG at the same speed and load. Modifications to fuel system components may be required to avoid engine derate.
Capturing Cyclic Variability in EGR Dilute SI Combustion Using Multi-Cycle RANS
Authors: Scarcelli Riccardo , Sevik James , Wallner Thomas , Richards Keith , Pomraning Eric , Senecal Peter K.
Published: January 2016

Dilute combustion is an effective approach to increase the thermal efficiency of spark-ignition (SI) internal combustion engines (ICEs). However, high dilution levels typically result in large cycle-to-cycle variations (CCV) and poor combustion stability, therefore limiting the efficiency improvement. In order to extend the dilution tolerance of SI engines, advanced ignition systems are the subject of extensive research.

When simulating the effect of the ignition characteristics on CCV, providing a numerical result matching the measured average in-cylinder pressure trace does not deliver useful information regarding combustion stability. Typically Large Eddy Simulations (LES) are performed to simulate cyclic engine variations, since Reynold-Averaged Navier-Stokes (RANS) modeling is expected to deliver an ensemble-averaged result.

In this paper it is shown that, when using RANS, the cyclic perturbations coming from different initial conditions at each cycle are not damped out even after many simulated cycles. As a result, multi-cycle RANS results feature cyclic variability. This allows evaluating the effect of advanced ignition sources on combustion stability but requires validation against the entire cycle-resolved experimental dataset.

A single-cylinder GDI research engine is simulated using RANS and the numerical results for 20 consecutive engine cycles are evaluated for several operating conditions, including stoichiometric as well as EGR dilute operation. The effect of the ignition characteristics on CCV is also evaluated. Results show not only that multi-cycle RANS simulations can capture cyclic variability and deliver similar trends as the experimental data, but more importantly that RANS might be an effective, lower-cost alternative to LES for the evaluation of ignition strategies for combustion systems that operate close to the stability limit.
A Numerical Study of the Benefits of Electrically Assisted Boosting Systems
Authors: Burke Richard
Published: January 2016

An electric compressor and an electrically assisted turbocharger have been applied to a 2.0L Gasoline and a 2.2L Diesel engine 1D wave dynamic models. A novel approach is presented for evaluating transient response using swept frequency sine wave functions and Fourier Transforms.

The maximum electrical power was limited to 6% of the maximum engine power (12kW and 5kW respectively). The systems were evaluated under steady state and transient conditions. Steady state simulations showed improved Brake Mean Effective Pressure (BMEP) at low engine speeds (below 2500rpm) but electric power demand was lower (3kW vs 8kW) when the electric compressor was on the high pressure side of the turbocharger. This was due to the surge limitation of the turbocharger compressor. The electrically assisted turbocharger offered little opportunity to increase low speed BMEP as it was constrained by compressor map width. Re-matching the turbo could address this but also compromise high engine speeds.

BMEP frequency analysis was conducted in the region of 0.01–2Hz. This was repeated at fixed engine speeds between 1000rpm and 2000rpm. Spectral analysis of the simulated response showed that the non-assisted turbocharger could not follow the target for frequencies above 0.1Hz whereas the electrically-assisted device showed no appreciable drop in performance. When assessing the electric power consumption with the excitation frequency, a linear trend was observed at engine speeds below 1500rpm but more complex behavior was apparent above this speed where BMEP levels are high but exhaust energy was scarce.
Direct Torque Feedback for Accurate Engine Torque Delivery and Improved Powertrain Performance
Authors: Alkeilani Anwar , Wang Le Yi , Ying Hao
Published: January 2016

At the present time, both control and estimation accuracies of engine torque are causes for under-achieving optimal drivability and performance in today’s production vehicles. The major focus in this area has been to enhance torque estimation and control accuracies using existing open-loop torque control and estimation structures. Such an approach does not guarantee optimum torque tracking accuracy and optimum estimation accuracy due to air flow and efficiencies estimations errors. Furthermore, current approach overlooks the fast torque path tracking which does not have any related feedback. Recently, explicit torque feedback control has been proposed in the literature using either estimated or measured torques as feedback to control the torque using the slow torque path only. We propose the usage of a surface acoustic wave (SAW) torque sensor to measure the engine brake torque and feedback the signal to control the torque using both the fast and slow torque paths utilizing an inner-outer loop control structure. The fast torque path feedback is coordinated with the slow torque path by a novel method using the potential torque that is adapted to the sensor reading. The torque sensor signal enables a fast and explicit torque feedback control that can correct torque estimation errors and improve drivability, emission control, and fuel economy. Control-oriented engine models for the 3.6L engine are developed. Computer simulations are performed to investigate the advantages and limitations of the proposed control strategy, versus the existing strategies. The findings include an improvement of 14% in gain margin and 60% in phase margin when the torque feedback is applied to the cruise control torque request at the simulated operating point. This study demonstrates that the direct torque feedback is a powerful technology with promising results for improved powertrain performance and fuel economy.
Start-Up and Steady-State Performance of a New Renewable Hydroprocessed Depolymerized Cellulosic Diesel (HDCD) Fuel in Multiple Diesel Engines
Authors: Bermudez Eric , McDaniel Andrew , Dickerson Terrence , Luning Prak Dianne , Hamilton Len , Cowart Jim
Published: January 2016

A new Hydroprocessed Depolymerized Cellulosic Diesel (HDCD) fuel has been developed using a process which takes biomass feedstock (principally cellulosic wood) to produce a synthetic fuel that has nominally 1/2 cyclo-paraffins and 1/2 aromatic hydrocarbons in content. This HDCD fuel with a low cetane value (Derived Cetane Number from the Ignition Quality Tester, DCN = 27) was blended with naval distillate fuel (NATO symbol F-76) in various quantities and tested in order to determine how much HDCD could be blended before diesel engine operation became problematic. Blends of 20% HDCD (DCN = 45), 30%, 40% (DCN = 41) and 60% HDCD (DCN = 37) by volume were tested with conventional naval distillate fuel (DCN = 49). Engine start performance was evaluated with a conventional mechanically Direct Injected (DI) Yanmar engine and a Waukesha mechanical indirect injected (IDI) CFR diesel engine, and showed that engine start times increased steadily with increasing HDCD content. Longer start times with increasing HDCD content were the result of some engine cycles with poor combustion leading to a slower rate of engine acceleration towards rated speed. A repeating sequence of alternating cycles which combust followed by a non-combustion cycle were common during engine run-up. Additionally, steady state engine testing was also performed using both engines. HDCD has a significantly higher bulk modulus than F76 due to its very high aromatic content, and the engines showed earlier Start of Injection (SOI) timing with increasing HDCD content for equivalent operating conditions. Additionally, due to the lower DCN, the higher HDCD blends showed moderately longer Ignition Delay (IGD) with moderately shorter overall burn durations. Thus, the mid-combustion metric (CA50: 50% burn duration Crank Angle position) was only modestly affected with increasing HDCD content. Increasing HDCD content beyond 40% led to significantly longer start times.
Ability of the Methane Number Index of a Fuel to Predict Rapid Combustion in Heavy Duty Dual Fuel Engines for North American Locomotives
Authors: Van Alstine Daniel G. , Montgomery David T. , Callahan Timothy J. , Florea Radu C.
Published: January 2016

Low natural gas prices have made the fuel an attractive alternative to diesel and other common fuels, particularly in applications that consume large quantities of fuel. The North American rail industry is examining the use of locomotives powered by dual fuel engines to realize savings in fuel costs. These dual fuel engines can substitute a large portion of the diesel fuel with natural gas that is premixed with the intake air. Engine knock in traditional premixed spark-ignited combustion is undesirable but well characterized by the Methane Number index, which quantifies the propensity of a gaseous fuel to autoignite after a period of time at high temperature. Originally developed for spark-ignited engines, the ability of the methane number index to predict a fuel’s “knock” behavior in dual fuel combustion is not as fully understood. The objective of this effort is to evaluate the ability of an existing methane number algorithm to predict rapid combustion in a dual fuel engine.

Sets of specialized natural gas fuel blends that, according to the MWM methane number algorithm, should have similar knock characteristics are tested in a dual fuel engine and induced to experience rapid combustion. Test results and CFD analysis reveal that rapid or aggressive combustion rates happen late in the dual fuel combustion event with this engine hardware configuration. The transition from normal combustion to late rapid combustion is characterized by changes in the heat release rate profiles. In this study, the transition is also represented by a shift in the crank angle location of the combustion’s peak heat release rate. For fuels of similar methane number that should exhibit similar knock behavior, these transitions occur at significantly different relative air-fuel ratios, demonstrating that the existing MWM methane number algorithm, while excellent for spark-ignited engines, does not fully predict the propensity for rapid combustion to occur in a dual fuel engine within the scope of this study. This indicates that physical and chemical phenomena present in rapid or aggressive dual fuel combustion processes may differ from those in knocking spark-ignited combustion. In its current form a methane number algorithm can be used to conservatively rate dual fuel engines. It is possible that derivation of a new reactivity index that better predicts rapid combustion behavior of the gaseous fuel in dual fuel combustion would allow ratings to be less conservative.
Effects of Fuel Physical Properties and Breakup Model Constants on Large-Eddy Simulation of Diesel Sprays
Authors: Tsang Chi-Wei , Rutland Christopher J.
Published: January 2016

The Kelvin-Helmholtz/Rayleigh-Taylor (KH-RT) wave breakup model is a commonly used model in predicting primary and secondary atomization and breakup processes in Lagrangian-Eulerian Diesel spray simulations. Droplet sizes predicted by this model are dependent on several parameters. The parameters include fuel physical properties, such as density, viscosity, and surface tension, and a number of adjustable model constants, such as KH and RT time constants, KH and RT size constants, and the breakup length constant. The purpose of this study is to investigate the effects of these parameters on predicting spray motions using large-eddy simulation with the dynamic structure sub-grid stress model. The code used in this study is OpenFOAM. This study has three major parts. Firstly, effects of the model constants on the prediction of momentum exchange process were examined by comparing liquid and gas momentum fluxes. Drag Forces exerted on liquid spray by gas phase can be determined from the slopes of gas and liquid momentum fluxes plotted against axial distance. We found that the prediction of momentum exchange between gas and liquid is most sensitive to the KH time constant, B1, among the other model constants. Secondly, effects of fuel physical properties were investigated by using four different fuels in the simulations of non-vaporizing and vaporizing sprays. The four fuels used were n-dodecane, F76 fuel, n-hexadecane, and methyl tetradecanoate. The F76 fuel is a multi-component fuel containing twenty-one hydrocarbons. Global spray quantities such as liquid and vapor penetrations, Sauter mean diameter, total liquid mass, number of parcels, and breakup model quantities such as Ohnesorge number and KH wave speed were compared. The key finding is that not all of these quantities monotonically increase or decrease with fuel molecular weight. Lastly, effects of fuel physical properties on sensitivities of the breakup model constants were studied. We compared liquid penetration and vapor penetration for each fuel using different values of the model constants. We found that the prediction of vapor penetrations is more sensitive to the KH time constant B1 when a fuel with lighter molecular weight was used, and the prediction of liquid penetrations is sensitive to the breakup length constant, Cb, in all of the four fuels. The computational investigations in this study reveal some limitations of the current spray breakup model, and motivate us to develop more advanced models to overcome these limitations.
RCCI of Synthetic Kerosene With PFI of N-Butanol-Combustion and Emissions Characteristics
Authors: Soloiu Valentin , Muiños Martin , Naes Tyler , Harp Spencer , Jansons Marcis
Published: January 2016

In this study, the combustion and emissions characteristics of Reactivity Controlled Compression Ignition (RCCI) obtained by direct injection (DI) of S8 and port fuel injection (PFI) of n-butanol were compared with RCCI of ultra-low sulfur diesel #2 (ULSD#2) and PFI of n-butanol at 6 bar indicated mean effective pressure (IMEP) and 1500 rpm. S8 is a synthetic paraffinic kerosene (C6–C18) developed by Syntroleum and is derived from natural gas. S8 is a Fischer-Tropsch fuel that contains a low aromatic percentage (0.5 vol. %) and has a cetane number of 63 versus 47 of ULSD#2. Baselines of DI conventional diesel combustion (CDC), with 100% ULSD#2 and also DI of S8 were conducted. For both RCCI cases, the mass ratio of DI to PFI was set at 1:1. The ignition delay for the ULSD#2 baseline was found to be 10.9 CAD (1.21 ms) and for S8 was shorter at 10.1 CAD (1.12 ms). In RCCI, the premixed charge combustion has been split into two regions of high temperature heat release, an early one BTDC from ignition of ULSD#2 or S8, and a second stage, ATDC from n-butanol combustion. RCCI with n-butanol increased the NOx because the n-butanol contains 21% oxygen, while S8 alone produced 30% less NOx emissions when compared to the ULSD#2 baseline. The RCCI reduced soot by 80–90% (more efficient for S8). However, S8 alone showed a considerable increase in soot emissions compared with ULSD#2. The indicated thermal efficiency was the highest for the ULSD#2 and S8 baseline at 44%. The RCCI strategies showed a decrease in indicated thermal efficiency at 40% ULSD#2-RCCI and 42% and for S8-RCCI, respectively.

S8 as a single fuel proved to be a very capable alternative to ULSD#2 in terms of combustion performance nevertheless, exhibited higher soot emissions that have been mitigated with the RCCI strategy without penalty in engine performance.
Development and Validation of a Reduced Toluene/N-Heptane/N-Butanol Mechanism for Combustion and Emission Prediction in IC Engine
Authors: Xu Zhengxin , Wang Mianzhi , Hou Jie , Zhang Saifei , Liu Jingping , Chang Wayne , Lee Chia-fon F.
Published: January 2016

The present study proposed a reduced mechanism for a fuel blend of toluene reference fuel (TRF, toluene/n-heptane) and n-butanol for modeling the combustion and soot formation processes of n-butanol/diesel blend fuel. A detailed reaction mechanism for n-butanol, consisting of 243 species and 1446 reactions, and a reduced TRF mechanism, containing 158 species and 468 reactions, were reduced separately and then combined to create a new TRF/n-butanol mechanism. The new TRF/n-butanol mechanism contained 107 species and 413 reactions. A multi-technique reduction methodology was used which included directed relation graph with error propagation and sensitivity analysis (DRGEPSA), unimportant reaction elimination, reaction pathway analysis, and sensitivity analysis. In addition, a reduced 12-step NOx mechanism was combined with the TRF/n-butanol mechanism to predict NOx emissions. The proposed mechanism was also coupled with a multi-step soot model to predict the combustion and soot formation processes. The proposed mechanism was validated using available ignition delay times, laminar flame speeds and species concentration profiles from shock tubes, flat flame burner and jet stirred reactors. Good agreements were found for the above comparisons and with results from detailed mechanisms. Furthermore, multi-dimensional CFD simulations were conducted by using the KIVA-3V R2 code coupled with the preconditioned Krylov method. The effects of exhaust gas recirculation (EGR), injection timing and blending ratio of n-butanol on combustion and NOx formation were analyzed and validated experimental data. The pressure, heat release rate, NOx, and soot emissions with respect to fuel blends, EGR rates and start of injection (SOI) timings agreed well with the experimental results. With increasing n-butanol content, both experimental and calculated soot emission decreased, demonstrating that butanol additive was capable of reducing soot emission compared to pure diesel. Both experiments and models revealed that soot emissions peak occurred at SOI close to TDC. The proposed mechanism can readily be used to predict the combustion and soot formation processes of butanol-diesel blends fuel in combustion CFD simulations.