bluuebunny/crossref_metadata_2025 huggingface dataset:
The Pervasive Effect of the Calmed Region
Authors: Thomas R. L. , Gostelow J. P.
Published: November 2008

Experiments have been conducted relating to the interaction of imposed freestream wakes upon a flat plate laminar separation bubble under an adverse pressure gradient. Controlled wakes, representative of those seen in turbomachinery environments, were used to investigate unsteadiness effects upon a separating boundary layer that undergoes natural transition in the free shear layer under steady conditions. Hot-wire anemometry using a single hot-wire has shown leading edge boundary layer disturbances induced under each passing wake, which grow steadily via by-pass and natural transition methods into turbulent strips that convect with the flow. These disturbances are of such strength that the separated region is resisted and effectively swept away by the passing turbulence, momentarily giving rise to a wholly attached laminar boundary layer. Controlling the chord-wise proximity of neighboring wakes allowed for the investigation of the effect and extent of the calmed region behind each induced turbulent strip. Measurements have shown that a strong suppression of velocity fluctuations is seen related to the proximity of the turbulent strips. Turbulence level reductions of up to 40% have been demonstrated as wake spacing is reduced. Even for those cases where systematic wakes are sufficiently close together to prevent the development of a visible calmed region, very strong calming influences are seen in the wake induced turbulent domain that would have normally been occupied by the calmed flow.
Effects of Surface Roughness on Turbine Vane Heat Transfer
Authors: Boyle R. J. , Senyitko R. G.
Published: November 2008

Turbine vane surface temperatures were measured in a linear cascade using an infrared non-contact thermal detector. A thermal barrier coating (TBC) was applied to the vane surface to give a rough surface. The temperature drop across the relatively thick TBC was used to determine heat transfer coefficients. Tests were conducted over a range of Reynolds and Mach numbers, resulting in large variations in hydraulic roughness. The measured heat transfer rates were significantly higher than were expected for a smooth vane. The detector was mounted in a probe holder, and traversed in a manner similar to that used for pneumatic or hot wire probes. The results showed that this approach gave useful information, and should be considered when non-contact surface temperatures are desired.
Operation and Noise Transmission of an Axial Turbine Driven by a Pulse Detonation Combustor
Authors: Dean Anthony J. , Rasheed Adam , Tangirala Venkat , Pinard Pierre F.
Published: November 2008

Pulse Detonation Combustors (PDC’s), as part of a hybrid PDC-turbine engine, have potential thermodynamic benefits over existing Brayton-cycle gas turbines. The form of combustion is a cyclic, controlled series of detonations. These systems apply a near or quasi-constant volume combustion process that provides both heat addition and pressure. In a hybrid PDC-turbine engine, the goal of incorporating a pulsed detonation chamber upstream of a turbine is to extract more mechanical energy in a turbine that receives the products of a repeating, pressure-rise detonation process versus the constant pressure, steady-flows available in conventional gas turbines. A rig was built to investigate PDC-turbine interactions and was operated to gather data on performance, operability, and noise levels. The rig consists of a single pulsed detonation combustor firing into a partial-admission, two-stage axial turbine. This paper reports findings of critical risk areas including turbine response to PDC operation, mechanical robustness, noise and system control. At a PDC operating frequency of 5 Hz, the acoustic level near the rig was approximately 3 dB higher than from the turbine operating at the same speed with steady flow input. The noise level is 28 dB lower than a PDC with no turbine downstream operating at the same frequency and discharging directly into the room. Insights into the mechanism for noise reduction were gained via imaging experiments and CFD simulation. High speed video imaging in a 2D PDC-turbine cascade configuration showed significant shock reflection from the cascade. An unsteady, reacting flow computational study showed similar shock reflection as well as a shock system that forms downstream of the cascade. Together, these results show that shock waves are both transmitted and reflected by the turbine stages in proportions that are dependent upon turbine stage design.
The Effects of High-Pressure Injection on a Compression-Ignition, Direct Injection of Natural Gas Engine
Authors: McTaggart-Cowan G. P. , Jones H. L. , Rogak S. N. , Bushe W. K. , Hill P. G. , Munshi S. R.
Published: November 2008

The use of pilot-ignited, direct-injected natural gas fuelling for heavy-duty on-road applications has been shown to substantially reduce NOx and particulate matter emissions. The fuelling process involves the injection of pilot diesel near top-dead-center, followed shortly afterwards by the injection of natural gas at high pressure. The injection pressure of the gas and diesel will substantially affect the penetration of the fuel into the combustion chamber, the break-up and atomization of the diesel spray, and the mixing and nature of the turbulent gas jet. To investigate these influences, a series of experiments were performed on a single-cylinder heavy-duty engine over a range of engine operating conditions (exhaust gas recirculation fraction, engine speed, engine load). Due to the unique nature of the single-cylinder engine, it was possible to hold all other parameters constant while only varying injection pressure. The results indicated that injection pressure had a substantial impact on emissions and performance at high loads, where substantial reductions in PM and CO were observed, with only minor increases in NOx and no significant effect on tHC or fuel consumption. At low loads, no significant impact on either emissions or performance was detected. The effects of injection pressure, while still significant, were found to be reduced at increased engine speeds. Higher injection pressures were found to consistently reduce both the number density and the size of particles in the exhaust stream.
A Wireless Microwave Telemetry Data Transfer Technique for Reciprocating and Rotating Components
Authors: Miers Scott A. , Barna Glen L. , Anderson Carl L. , Blough Jason R. , Inal M. Koray , Ciatti Stephen A.
Published: November 2008

Wireless microwave telemetry addresses the difficult issue of obtaining transducer outputs from reciprocating and rotating components through the use of advanced electronic components. This eliminates the requirements of a direct link between the transducer and the acquisition system. Accuracy of the transducer signal is maintained through the use of a double frequency modulation (FM) technique which provides temperature stability and a 20 point calibration of each, complete system. Multiple transmitters can be used for larger applications and multiple antennas can be used to improve the signal strength and reduce the possibility of dropouts. Examples of piston temperature and automotive torque converter measurements are provided, showing the effectiveness of the wireless measuring technique.
A Simulation of the Combustion of N-Heptane Fueled HCCI Engines Using a 3-D Model With Detailed Chemical Kinetics
Authors: Liu Chengke , Karim Ghazi A.
Published: November 2008

A CFD multi-dimensional computational approach has been developed through a combination of a modified KIVA3 code together with a detailed chemical kinetics scheme for the oxidation of n-heptane in air while considering the effects of turbulence. The effects of adding different quantities of hydrogen, methane and carbon monoxide to the heptane on the combustion characteristics of the HCCI engine under different conditions were investigated both experimentally and numerically. The effects of changes in the combustion chamber wall surface temperature on the combustion characteristics of the HCCI engine were examined. It was found that the presence with n-heptane of some hydrogen, methane or carbon monoxide could delay to various extents the autoignition, while changes in the values of the combustion chamber wall temperature influence the autoignition timing and its initial location. It is suggested that the supplementing of the liquid fuel with gaseous fuels and/or application of a suitable glow-plug surface of optimum size and location fitted with temperature control may aid in controlling the combustion process of an HCCI engine while obtaining higher power output without producing knock.
Equilibrium Thermodynamics of Combustion by Means of Genetic Algorithms
Authors: Brusca S. , Lanzafame R. , Messina M.
Published: November 2008

In order to carry out an accurate heat release analysis, it is necessary to solve a non linear set of chemical equilibrium equations to calculate concentrations of the species present in cylinder gases during the combustion process. So, the thermodynamics properties of the mixture can be evaluated. The present paper deals with the study of the thermodynamics of combustion using a genetic approach. A genetic algorithm was used to solve the set of non linear equations. The goal of this method is the possibility of solving the equations set in a wide range of pressure, temperature and equivalence ratio combinations, where more traditional methods are often found to fail.
Developing Non-Gasoline Burning Outboard Motors for the UK MoD
Authors: Riis Dan
Published: November 2008

The UK Ministry of Defence (MoD) operates a wide range of small, high performance boats, used in varying environments, and locations throughout the world. These boats primarily operate using outboard motors (OBMs) due to the optimum power to size and weight ratios they provide, and the ease of maintenance compared to inboard motor boats. The use of OBMs has, with the exception of a large and heavy 27hp diesel (compression ignition) OBM, necessitated the use of Petrol (CIVGAS - F67). This dependency evolved from the difficulty encountered developing a reliable compression ignition OBM over the full power range required (20–250hp) at acceptable power to weight/size ratios. Given the lack of a perceived market for such an engine, very little development work was done in this area in the private sector. The requirement to run OBMs on CIVGAS presents a number of problems for the MoD, including logistical, availability (especially for Special Forces), and safety (especially for HM Ships required to store the fuel on the upper decks). The Marine Propulsion Systems Integrated Project Team (MPS IPT) within MoD’s Defence Logistics Organisation (DLO), was therefore mandated to develop solutions aimed at removing MoD’s reliance on CIVGAS. This resulted in a two pronged approach investigating both micro-gas turbines and multi-fuel OBMs. This paper will present the issues encountered and the development work completed to-date developing multi-fuel reciprocating OBM technology. The primary focus has been developing direct injection, spark ignition multi-fuel OBM technology, capable of using petrol, AVTUR (F34), AVCAT (F44), diesel, and marine distillate oil (MDO - F76). The paper will discuss the project plan, the technologies involved, development work, including test and trials, and the way ahead for the future.
Performance and Emission Characteristics of a Diesel Engine Using Vegetable Oil Blended Fuel
Authors: Wang Yaodong , Hewitt Neil , Eames Philip , Zeng Shengchuo , Huang Jincheng , He Yunxin , Huang Xiaodong , Li Shangping , Lin Lin
Published: November 2008

Experimental tests have been carried out to evaluate the performance and emissions characteristics of a diesel engine when fuelled by blends of 25% vegetable oil with 75% diesel fuel, 50% vegetable oil with 50% diesel fuel, 75% vegetable oil with 25% diesel fuel, and 100% vegetable oil, compared with the performance, emissions characteristics of 100% diesel fuel. The series of tests were conducted and repeated six times using each of the test fuels. 100% of ordinary diesel fuel was also used for comparison purposes. The engine worked at a fixed speed of 1500 r/min, but at different loads respectively, i.e. 0%, 25%, 50%, 75% and 100% of the engine load. The performance and the emission characteristics of exhaust gases of the engine were compared and analyzed. The experimental results showed that the carbon monoxide (CO) emission from the vegetable oil and vegetable oil/diesel fuel blends were nearly all higher than that from pure diesel fuel at the engine 0% load to 75% load. Only at the 100% engine load point, the CO emission of vegetable oil and vegetable oil/diesel fuel blends was lower than that of diesel fuel. The hydrocarbon (HC) emission of vegetable oil and vegetable/diesel fuel blends were lower than that of diesel fuel, except that 50% of vegetable oil and 50% diesel fuel blend was a little higher than that of diesel fuel. The oxides of nitrogen (NOx) emission of vegetable oil and vegetable oil/diesel fuel blends, at the range of tests, were lower than that of diesel fuel.
Performance and Emission Analysis on a Direct Injection Diesel Engine Using Biodiesel From Palm Oil With Exhaust Gas Recirculation
Authors: Udaya Kumar R. , Vijayaraj S.
Published: November 2008

At present, there is a hunt for an alternative source of fuel which should also cause less pollution. Vegetable oil is one such source, which is both renewable and biodegradable. But using straight vegetable oil lead to the clogging of the fuel injectors and there is a problem of starting especially when the engine is cold. Hence straight vegetable oils can be chemically treated to enhance its properties, after which the vegetable oil is known as biodiesel. In this work, biodiesel is prepared from Palm oil and then various tests (load test, Heat balance test and Emission test) are carried out on a Kirloskar engine (single cylinder D.I. diesel engine) by varying the percentage of biodiesel. It has been inferred from the test that performance of the engine decreases and also the various emissions (except NOx) decreases. It has also been inferred that the emissions reduction is maximum when biodiesel is blended with 60% diesel. To decrease NOx, hot EGR (15%) is adopted. Again the above tests are performed with EGR and it has been found that NOx decreases but at the same time the performance of the engine decreases further.
Detection of Combustion Chamber Deposits in Diesel Engines Through Cylinder Pressure and Exhaust Temperature Measurements
Authors: Gardiner D. , LaViolette M. , Allan W. D. , Wang G. , Bardon M. F.
Published: November 2008

This paper describes experimental research aimed at developing techniques for monitoring the growth of combustion chamber deposits in diesel engines using data obtained from cylinder pressure and exhaust temperature measurements. A naturally aspirated single cylinder research engine was operated alternately between low load “coking” conditions (2.5 bar BMEP) and higher load “decoking” conditions (5.5 bar BMEP) intended to promote the formation and removal, respectively of combustion chamber deposits. The polytropic exponent of compression was observed to increase during coking runs and decrease during decoking runs. The peak heat release rate was observed to decrease during coking runs and increase during decoking runs. The peak cycle value of the first derivative of the exhaust thermocouple signal decreased during coking runs but exhibited no clear trend during decoking runs. Conventional exhaust temperature measurements showed no consistent trend during coking runs but the exhaust temperature decreased during decoking runs.
A Study on NOx Reduction in a Medium Speed Diesel Engine Using a Charge Air Moisturizing Method
Authors: Park Hyoung-Keun , Kim Byong-Seok , Kim Jin-Won , Ghal Sang-Hak , Park Jong-Kuk
Published: November 2008

NOx forms during a combustion process and contributes to ozone, smog, acid rain, eutrophic soil, etc. The use of water to prevent NOx formation during the combustion process is well known. Adding water to the combustion process reduces the flame temperature by increasing the specific heat capacity of charge air. Moisturizing a charge air is one of the most effective methods to add water to the combustion process. In this study, the characteristics of charge air moisturizing method were evaluated on cylinder pressure, heat release rate, exhaust gas temperature, specific fuel oil consumption, NOx reduction rate, etc., using the medium speed diesel engine with a single cylinder.
Evaluation of In-Situ Synthesized Monolithic Metal-MFI/Cordierite Catalysts to Remove NOx From Lean Exhaust
Authors: Wang Tianyou , Liu Shuliang , Xu Hongjun , Li Xing , Fu Maolin , Li Landong , Guan Naijia
Published: November 2008

In this study, ZSM-5 zeolites were successfully in situ synthesized on the surface of honeycomb cordierite substrate and certified by XRD and SEM techniques. Strong interaction between zeolite and substrate has been found during in-situ synthesis, and hydrothermal stabilities of the zeolites was improved by entailing. The in-situ synthesized monolithic ZSM-5/cordierite showed superior thermal and hydrothermal stabilities. Cu-ZSM-5/cordierite was prepared by ion-exchange and impregnation methods were studied as catalysts for selective catalytic reduction (SCR) of nitrogen oxides (NOx) in a lean-burn gasoline engine. Engine test results show that NOx emission was decreased by reductants of HC and CO in the exhaust gas without any other extra reducing agents. It also exhibited high activities. Using Cu-ZSM-5/cordierite, the maximum NOx conversion efficiency to N2 reached to 64% at the exhaust temperature of 400 °C and the gas hourly space velocity (GHTV) of 25 000/h. Meanwhile, the HC conversion efficiency was about 60%, while CO was little converted. Cu-ZSM-5/cordierite also showed good duration and anti-poison properties. Furthermore, the activated temperature of the Cu-ZSM-5/cordierite was decreased and the NOx conversion was increased via addition of iridium as a modifier.
Combustion and Emission Characteristics of Biodiesel Fuels in a Common-Rail Diesel Engine
Authors: Yoon Seung Hyun , Park Sung Wook , Kim Dae Sik , Kwon Sang Il , Lee Chang Sik
Published: November 2008

A single cylinder DI (direct injection) diesel engine equipped with common-rail injection system was used to investigate the combustion and emission characteristics of biodiesel fuels. Tested fuels were conventional diesel and biodiesels obtained from unpolished rice oil and soybean oil. The volumetric blending ratios of biodiesel with diesel fuel are set at 0, 10, 20 and 40%. Experimental results show that the peak injection rate is reduced as the mixing ratio increased. The effect of the mixing ratio on the injection delay of biodiesel is not significant at the equal injection pressure. The peak combustion pressure was increased with the increase of the mixing ratio at an injection pressure of 100MPa. The ignition delay became shorter with the increase of the mixing ratio due to a higher cetane number of the biodiesel. HC and CO emissions are decreased at a high injection pressure. However, NOx emissions are increased at higher mixing ratios.
Numerical Simulation of DI Diesel Engine’s Combustion Chamber Using Several Turbulence Models During Intake and Compression Strokes
Authors: Jazayeri Seyed Ali , Mirzaei Masoud , Kheyrollahi Javad , Shadaram Abdollah
Published: November 2008

Atomization of the fuel that is injected to the combustion chamber depends on flow field characteristics during the compression process. Mixture formation, mixture preparation rate and delay period are some of the dominant factors in DI diesel engine performance and emission level. This paper presents a new CFD approach simulation of flow field during intake and compression of a four strokes IC engine. In this model a dynamic mesh is used to simulate the moving boundaries of engine parts, such as piston and valves. Computational domain, which is a precise model of one cylinder, is meshed to 300,000–500,000 cells. In our solution three different two-equation turbulence models are used. The capability of each model is highlighted and the results are compared with relevant works. The focus of these turbulence models and three-dimensional simulation of engine flow are to validate the reliability of flow characteristics. The results accurately demonstrate the three-dimensional characteristics of air motion in the swirl chamber and development of vortices.
Computational Studies on Charge Stratification and Fuel-Air Mixing in a New Two-Stroke Engine
Authors: Bakshi Shamit , Anand T. N. C. , Ravikrishna R. V.
Published: November 2008

In this paper, detailed computational study is presented which helps to understand and improve the fuel-air mixing in a new direct-mixture-injection two-stroke engine. This new air-assisted injection system-based two-stroke engine is being developed at the Indian Institute of Science, Bangalore over the past few years. It shows the potential to meet emission norms such as EURO-II and EURO-III and also deliver satisfactory performance. This work proposes a comprehensive strategy to study the air-fuel mixing process in this engine and shows that this strategy can be potentially used to improve the engine performance. A three-dimensional compressible flow code with standard k–ε turbulence model with wall functions is developed and used for this modeling. To account for the moving boundary or piston in the engine cylinder domain, a non-stationary and deforming grid is used in this region with stationary cells in the ports and connecting ducts. A flux conservation scheme is used in the domain interface to allow the in-cylinder moving mesh to slide past the fixed port meshes. The initial conditions for flow parameters are taken from the output of a three-dimensional scavenging simulation. The state of the inlet charge is obtained from a separate modeling of the air-assisted injection system of this engine. The simulation results show that a large, near-stoichiometric region is present at most operating conditions in the cylinder head plane. The state of the in-cylinder charge at the onset of ignition is studied leading to a good understanding of the mixing process. In addition, sensitivity of two critical parameters on the mixing and stratification is investigated. The suggested parameters substantially enhance the flammable proportion at the onset of combustion. The predicted P–θ from a combustion simulation supports this recommendation.
Multi-Dimensional, Transient Fluid Flow Simulations in the Manifold of a Four-Stroke Single-Cylinder Engine
Authors: Anand T. N. C. , Ravikrishna R. V.
Published: November 2008

Multi-dimensional computational fluid dynamics simulations were carried out on the intake manifold and cylinder of a four-stroke single cylinder two-wheeler engine. The complex geometry of the manifold and the engine cylinder, and the motion of the intake valve were taken into consideration. Both air flow and two-phase calculations were done to predict the trajectory of the liquid fuel and identify regions of impingement which could lead to film formation and high emissions at startup. The results show that the present geometry of the manifold is non-optimum as large recirculation zones are present. The two-phase simulations show that fuel transport is significantly affected due to the recirculation under idling conditions and significant impingement occurs. The numerical results obtained could be utilized to improve the flow in the manifold for lowering emissions.
Effect of Combustion Chamber Geometry on Emissions From a Single-Cylinder Diesel Engine
Authors: Prasad Boggavarapu V. V. S. U. , Ravikrishna R. V.
Published: November 2008

Many of the stationary power generation and agricultural pumping applications in India utilize diesel engines. Recently, as per Government regulations, these engines are required to satisfy stringent emissions norms. This forms the motivation for the present study on a stationary, direct-injection, single cylinder, 10 HP diesel engine. The selected engine was not satisfying the norms. The engine has a hemi- spherical piston bowl and an injector with a finite sac volume. The combustion chamber was made re-entrant and the injector was replaced with a sac-less injector. After these modifications, there is a significant change in emission levels. To understand clearly the effect of the combustion chamber geometry on the emission levels, three-dimensional computational fluid dynamics (CFD) simulations have been performed for the complete suction and closed-valve part of the cycle. Comparisons of turbulent kinetic energy and swirl levels of old and new geometries were systematically conducted. In contrary to the expected, that the swirl and turbulence levels are consistently less in the modified geometry than that of original geometry. A third combustion chamber was proposed and tested computationally. It was found that the in the proposed combustion chamber swirl and turbulence levels are much higher than the baseline engine. Thus, the proposed combustion chamber geometry shows significant potential for the engine to meet the prescribed norms.
Optical Investigation of HCCI Two-Stage Ignition Using Multiple Injection of Synthetic Fuels
Authors: Delebinski Thaddaeus , Eckert Peter , Merker Guenter P.
Published: November 2008

Different synthetic fuels have been investigated within a variety of optical experiments at a rapid compression machine using diverse optical set-ups. The experiments have been carried out to determine the fuel requirements for good homogenisation and a controlled ignition and heat release for HCCI combustion. A directly actuated piezo injection system, which allows a flexible multiple injection strategy has been used to inject the fuel at different times during the compression stroke. Mie-scatter and Schlieren optics have been applied to investigate the different behaviour of the synthetic fuels concerning evaporation and mixture formation. The auto ignition behaviour of the different fuels has been investigated using an intensified relay optics and combustion chamber probes utilising the two-colour-method and a photo multiplier analysis systems. A multiple injection strategy and a 13 hole injection nozzle for HCCI operation mode with diesel-like fuels have been designed and optimised using CFD simulation prior to the experimental work. The experimental results using synthetic fuels will then be used to verify advanced 3D CFD models for multi component fuels and their behaviour concerning mixture formation and HCCI two-stage ignition.
Simulation of Road Vehicle on Engine Test Bed
Authors: Vijaykumar A. , Prashanth V. , Sreehari S. , Sangappa Sunil
Published: November 2008

The objective of this paper is to simulate road loads experienced by an automobile during an urban driving cycle on an engine test bed. This is to be achieved through the use of a combined eddy-current dynamometer and flywheel arrangement, to load the IC engine on the test bed, and an automatic throttle control system, which will vary engine power under changing load conditions to obtain the desired speed-time variation. This paper is intended to provide a system which will permit engine testing under realistically simulated urban driving conditions; it seeks to avoid the use of chassis dynamometers for this purpose. The test is conducted on the IC engine/dynamometer set-up, which consists of the Maruti Omni’s 3-cylinder, 796cc, 37bhp (@5000 rpm) petrol engine with drive train coupled with an eddy current dynamometer. The paper consists of the following stages: 1. A driving cycle is defined, corresponding to urban driving conditions and tractive resistances are calculated and provided in the form of a resisting torque applied by the dynamometer on the IC engine, controlled by a microcontroller. 2. Inertial loads are calculated and applied on the IC engine via both the dynamometer and a flywheel, which is attached to the dynamometer mounted on a separately fabricated assembly. 3. Throttle control is achieved using a stepper motor, which is used to modify the existing manual throttle control setup. The stepper motor is operated using a micro controller. An interfacing circuit has been fabricated to allow this and program written is used to control the stepper motor and provide desired throttle positions through the driving cycle. 4. Torque control in the dynamometer is to be achieved by using the ‘external mode’ available on the control panel of the dynamometer. This allows communication of values from a micro controller via a parallel port, digital-analog converter, and driver circuit, in the form of voltages signals, allowing torque control to be achieved.
A Cyclic Variability Monitoring System Based Upon Cycle Resolved Exhaust Temperature Sensing
Authors: Gardiner D. P. , Bardon M. F.
Published: November 2008

This paper describes a means of monitoring cyclic variability in reciprocating engines that is an alternative to cylinder pressure measurements. The monitoring system uses robust exhaust temperature sensors that are capable of detecting cycle-to-cycle variations in the gas temperatures near each exhaust port. These variations are related to cyclic variations in combustion, and tend to increase as cyclic variability worsens. Further processing yields a combustion variability signal that is intended to reflect relative changes in the Coefficient of Variation of Indicated Mean Effective Pressure (COV of IMEP). Proof of concept experiments have been carried out using a naturally aspirated, propane fueled automotive engine equipped with laboratory grade in-cylinder pressure transducers. The results show a good correlation between the exhaust cyclic variability signal and the COV of IMEP from cylinder pressure measurements.
Friction Force Measurements Using the Instantaneous IMEP Method and Comparison With RINGPAK Simulations
Authors: Kim Myoungjin , Kiehne Thomas M. , Matthews Ronald D.
Published: November 2008

Even though many researchers have measured the piston/ring assembly friction force over the last several decades, accurate measurement of the piston/ring assembly friction force is a still challenging problem. The floating liner method is not widely used, in spite of its accuracy, due to the substantial modifications required to the engine. On the other extreme, bench tests of the piston/ring assembly cannot completely simulate the real firing condition although bench tests are rapid, consistent, and cost effective. In this study, friction forces of the piston/ring assembly were measured using the instantaneous IMEP method and compared with modeling results using Ricardo’s RINGPAK software. In this research, a flexible flat cable was used to connect the connecting rod strain gage signal to the analysis system instead of using a grasshopper linkage. Therefore, the piston/ring assembly friction force was measured with the minimum change to the engine hardware.
Further Development of a Smoke Sensor for Diesel Engines
Authors: Gould D. , Gardiner D. P. , LaViolette M. , Allan W. D.
Published: November 2008

This paper describes experimental research aimed at developing an on-board smoke sensor for diesel engines. The sensor element was similar to a conventional spark plug. Electrical heating of the insulator was used to prevent carbon fouling from the diesel soot. The sensing element created sparks within the exhaust pipe and changes in smoke levels were detected through analysis of the voltage levels of the sparks. The system was tested in a heavy duty diesel engine equipped with Exhaust Gas Recirculation (EGR)) and compared with reference measurements of the Filter Smoke Number (FSN). The experiments showed good sensitivity to step changes in smoke levels (accomplished by varying EGR levels) at smoke levels below 0.5 FSN. However, the sensor suffered from temperature induced signal drift and was unstable under some circumstances. The use of a spark plug with a smaller electrode tip diameter improved the signal stability. It is proposed that measurement and control of the electrode temperature will be necessary to control the signal drift.
Modeling HPDI Natural Gas Heavy Duty Engine Combustion
Authors: Li Guowei , Lennox Tim , Goudie Dale , Dunn Mark
Published: November 2008

CFD Modeling of the injection, the mixing, the combustion and the emission formation processes in a high pressure direct injection (HPDI) natural gas engine is presented in this paper. KIVA3V was used together with an injector model. Two sub-models had been developed that the concurrent injection, ignition and combustion of natural gas and diesel could be simulated. The gas injection was simulated with the injector model. In the injector model, the electromagnetism, the hydraulics and the mechanics were computed by solving a set of ordinary differential equations. Based on the engine experimental data, a combustion model was built in which premixed combustion of natural gas was excluded and the natural gas ignition was initiated by the pilot diesel combustion rather than a spontaneous process. The model calibration and validation are discussed. The model parameters were tuned against one set of engine test data. For the model validation, 30 engine test data were applied. The data were from HPDI engine tests at varied engine speeds, loads and injection timings with and without EGR. The model gave good agreement with the engine tests having no EGR. However, the model, in general, under-predicted the burning rate. With EGR, the model prediction errors were large and the NOx were under-predicted, though the trends were still captured.
Development of an Open Path Laser Ignition System for a Large Bore Natural Gas Engine: Part 2 — Single Cylinder Demonstration
Authors: Ahrens David L. , Olsen Daniel B. , Yalin Azer P.
Published: November 2008

Using a laser, as opposed to a conventional (electrical) spark plug, to create a combustion initiating spark is potentially advantageous for several reasons: flexibility in choosing and optimizing the spark location, in particular to move the spark away from solid heat sinks; production of a more robust spark containing more energy; and obviation of electrode erosion problems. In this paper we present the on-engine test results of the laser ignition system on a large bore natural gas engine. Test results include: mass fraction burn duration, hydrocarbon emissions data, and combustion stability comparisons to the conventional spark plug ignition system. Design and spark location considerations for the laser ignition system were presented in the first paper of this two-paper series.
Effect of Top Piston Ring Wear on Its Sealing and Scraping Performance
Authors: Ferrarese Andre , Sinatora Amilton , Almeida Fabio Luz
Published: November 2008

New engines are presenting a constant increase of mechanical and thermal loads. The engine components should guarantee similar, or superior, performance than the baseline components in spite of the unfavorable wear conditions. For piston rings, the performance is given by the ring capacity of sealing and scraping. This performance can be measured in an engine by the lube oil consumption (LOC) and the gas flow to the crankcase (Blow-by) results. The purpose of this work is to evaluate the top piston ring wear influence on its sealing and scraping performance. Two engines were tested, one Otto and the other Diesel, in a dynamometer in order to quantify the top ring dimensional variation due to wear. Numerical simulations were performed in order to evaluate the individual influences of each dimensional parameter. The results of LOC and Blow-by were compared to literature data and engine test results of each engine. A proposal of combined effects among the dimensional parameters is presented.
Development of Advanced Laser Ignition System for Stationary Natural Gas Reciprocating Engines
Authors: Bihari Bipin , Gupta Sreenath B. , Sekar Raj R. , Gingrich Jess , Smith Jack
Published: November 2008

Laser ignition is considered the prime alternative to conventional coil based ignition for improving efficiency and simultaneously reducing NOx emissions in lean-burn natural gas fired stationary reciprocating engines. In this paper, Argonne’s efforts towards the development of a viable laser ignition system are presented. The relative merits of various implementation strategies for laser based ignition are discussed. Finally, the performance improvements required for some of the components for successful field implementation are listed. Also reported are efforts to determine the relative merit of laser ignition over conventional Capacitance Discharge Ignition (CDI) ignition. Emissions and performance data of a large-bore single cylinder research engine are compared while running with laser ignition and the industry standard CDI system. It was primarily noticed that NOx emissions reduce by 50% under full load conditions with up to 65% reductions noticed under part load conditions. Also, the lean ignition limit was significantly extended and laser ignition improved combustion stability under all operating conditions. Other noticeable differences in combustion characteristics are also presented. Efforts wherein ignition was achieved while transmitting the high-power laser pulses through optical fibers showed performance improvements similar those achieved by using free-space laser ignition.
Emissions and In-Cylinder Combustion Characteristics of Fischer-Tropsch and Conventional Diesel Fuels in a Modern CI Engine
Authors: Sappok Alexander G. , Llaniguez Jeremy T. , Acar Joseph , Wong Victor W.
Published: November 2008

Derived from natural gas, coal, and even biomass Fischer-Tropsch (F-T) diesel fuels have a number of very desirable properties. The potential for emissions reduction with F-T diesel fuels in laboratory engine tests and on-road vehicle tests is well documented. While a number of chemical and physical characteristics of F-T fuels have been attributed to the observed reduction in emissions, the actual effects of both the fuel properties and in-cylinder combustion characteristics in modern diesel engines are still not well understood. In this study a 2002, six-cylinder, 5.9 liter, Cummins ISB 300 diesel engine, outfitted with an in-cylinder pressure transducer. was subjected to a subset of the Euro III 13-mode test cycle under steady-state operating conditions. Emissions and in-cylinder pressure measurements were conducted for neat F-T diesel, low sulfur diesel (LSD), ultra-low sulfur diesel (ULSD), and a blend of FT/LSD. In addition, a detailed chemical analysis of the fuels was carried out. The differences in the measured combustion characteristics and fuel properties were compared to the emissions variations between the fuels studied, and an explanation for the observed emissions behavior of the fuels was developed.
Analyzing the Effects of Three-Dimensional Cylinder Liner Surface Texture on Ring-Pack Performance With a Focus on Honing Groove Cross-Hatch Angle
Authors: Jocsak Jeffrey , Li Yong , Tian Tian , Wong Victor W.
Published: November 2008

Frictional losses in the piston ring-pack of an engine account for approximately 20% of the total frictional losses within an engine. Although many non-conventional cylinder liner finishes are now being developed to reduce friction and oil consumption, the effects of the surface finish on ring-pack performance is not well understood. The current study focuses on modeling the effects of three-dimensional cylinder liner surface anisotropy on piston ring-pack performance. A rough surface flow simulation program was developed to generate flow factors and shear stress factors for three-dimensional cylinder liner surface textures. Rough surface contact between the ring and liner was modeled using a previously published methodology for asperity contact pressure estimation between actual rough surfaces. The surface specific flow factors, shear stress factors, and asperity contact model were used in conjunction with MIT’s previously developed ring-pack simulation program to predict the effects of different surface textures on ring-pack behavior. Specific attention was given to the effect of honing groove cross-hatch angle on piston ring-pack friction in a stationary natural gas engine application, and adverse effects on engine oil consumption and durability were also briefly considered. The modeling results suggest that ring-pack friction reduction is possible if the liner honing cross hatch angle is decreased by reducing the feed-to-speed ratio of the honing tool. Reducing the cross-hatch angle increased oil flow blockage and increased the lubricant’s effective viscosity during mixed lubrication. This allowed more load to be supported by hydrodynamic pressure, reducing ring-pack friction. However, there appeared to be a potential for increased oil consumption and scuffing tendency corresponding to a decrease in honing cross-hatch angle.
Laser Ignition of Natural Gas Engines Using Fiber Delivery
Authors: Yalin Azer P. , Defoort Morgan W. , Joshi Sachin , Olsen Daniel , Willson Bryan , Matsuura Yuji , Miyagi Mitsunobu
Published: November 2008

A practical impediment to implementation of laser ignition systems has been the open-path beam delivery used in past research. In this contribution, we present the development and implementation of a fiber-optically delivery laser spark ignition system. To our knowledge, the work represents the first demonstration of fiber coupled laser ignition (using a remote laser source) of a natural gas engine. A Nd:YAG laser is used as the energy source and a coated hollow fiber is used for beam energy delivery. The system was implemented on a single-cylinder of a Waukesha VGF 18 turbo charged natural gas engine and yielded consistent and reliable ignition. In addition to presenting the design and testing of the fiber delivered laser ignition system, we present initial design concepts for a multiplexer to ignite multiple cylinders using a single laser source, and integrated optical diagnostic approaches to monitor the spark ignition and combustion performance.
Wear Model for Piston Ring and Cylinder Bore System
Authors: Qiu Yunchao , Zou Qian , Barber Gary C. , McCormick Harold E. , Zou Dequan , Mekari Milad H.
Published: November 2008

A new wear model for piston ring and cylinder bore system has been developed to predict wear process with high accuracy and efficiency. It will save time and cost compared with experimental investigations. Surfaces of ring and bore were divided into small domains and assigned to corresponding elements in two-dimensional matrix. Fast Fourier Transform (FFT) and Conjugate Gradient Method (CGM) were applied to obtain pressure distribution on the computing domain. The pressure and film thickness distribution were provided by a previously developed ring/bore lubrication module. By changing the wear coefficients of the ring and bore with accumulated cycles, wear was calculated point by point in the matrix. Ring and bore surface profiles were modified when wear occurred. The results of ring and bore wear after 1 cycle, 10 cycles and 2 hours at 3600 rpm were calculated. They coincided well with the general tendency of wear in a ring and bore system.
Considerations in the Internal Force Analysis of Slider-Crank Machines
Authors: Doughty Samuel
Published: November 2008

In the analysis of internal forces for a slider–crank machine, writing the equations of motion is just the beginning. There are many engineering analysis decisions to be made regarding the handling of the crank angular acceleration, modeling of the connecting rod mass moment of inertia, and the approach to the solution of the resulting system of equations. Over the years, each of these have been handled in various ways, not all of then entirely correct. This paper looks at the various options and makes a critical review of the various practices. The intent is to encourage all engineering analysts to review the assumptions and methods of the software that they routinely use.
Effects of Lubricant and Piston Design on Reciprocating Engine Friction
Authors: Moughon Luke , Wong Victor W.
Published: November 2008

The piston and rings generate a significant fraction of the total friction in a reciprocating engine, with comparable contributions from the rings and from the piston. In order to develop strategies to reduce overall engine friction, a piston model was used to examine the effects of lubricant, piston design, and material surface characteristics on piston friction. The analysis was performed on a large-bore reciprocating natural-gas engine. First, opportunities in friction reduction via lubricant supply and lubricant formulation were evaluated. This was done by studying how oil film thickness, viscosity, and its temperature dependence affect piston hydrodynamic and boundary-contact friction. Piston design parameters investigated include piston skirt profiles that are more realistic and varied than those previously studied. The piston material was also analyzed in terms of surface waviness. The results show how individual design parameters can be combined to generate the aggregate benefit in engine friction reduction.
Piston Ring Friction Reduction Through Surface Modification
Authors: Bolander Nathan W. , Sadeghi Farshid , Gerber Gordon R.
Published: November 2008

A numerical model has been developed to investigate the effects of surface modifications on the lubrication condition and frictional loss at the interface between a piston ring and cylinder liner. The effects of boundary and mixed lubrication conditions were included through the use of a fully deterministic mixed lubrication model, which provides detailed information of the rough contact zone throughout the stroke. The effects of non-Gaussian surface characteristics (e.g. skewness) on the cycle-average frictional performance are discussed. Surface modifications in the form of circular profile dimples were added to the cylinder liner and their effects were investigated. The modified cylinder liner was shown to reduce the cycle-average coefficient of friction by 55–65%, while total energy loss per cycle was reduced by 20–40%.
Phenomenology of Smoke From Direct Injection Diesel Engine
Authors: Aghav Y. V. , Lakshminarayanan P. A. , Babu M. K. G. , Nayak N. S. , Dani A. D.
Published: November 2008

A phenomenological model for smoke prediction from a direct injection (DI) diesel engine is newly evolved from an eddy dissipation model of Dent [1]. The turbulence structure of fuel spray is developed by incorporating the wall impingement to explain smoke formed in free and wall portions. The spray wall interaction is unavoidable in case of modern DI diesel engines of bore less than 125 mm. The new model is one dimensional and based on the recent phenomenological description of spray combustion in direct injection diesel engine. Integration of net soot rate and no need to use empirical tuning constants are the important features, which distinguish the model from existing models. Smoke values are successfully predicted using this model for an engine with heavy-duty applications under widely varying operating conditions.