bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Studies on Low Solidity Vaned Diffusers of a Centrifugal Compressor Stage
Authors: Siva Reddy T. Ch. , Ramana Murty G. V. , Mukkavilli Prasad , Reddy D. N.
Published: November 2008

Numerical simulation of impeller and low solidity vaned diffuser (LSD) of a centrifugal compressor stage is performed individually using CFX- BladeGen and BladeGenPlus codes. The tip mach number for the chosen study was 0.35. The same configuration was used for experimental investigation for a comparative study. The LSD vane is formed using standard NACA profile with marginal modification at trailing edge. The performance parameters obtained form numerical studies at the exit of impeller and the diffuser have been compared with the corresponding experimental data. These parameters are pressure ratio, polytropic efficiency and flow angle at the impeller exit where as the parameters those have been compared at the exit of diffuser are the static pressure recovery coefficient and the exit flow angle. In addition, the numerical prediction of the blade loading in terms of blade surface pressure distribution on LSD vane has been compared with the corresponding experimental results. Static pressure recovery coefficient and flow angle at diffuser exit is seen to match closely at higher flows. The difference at lower flows could be due to the effect of interaction between impeller and diffuser combinations, as the numerical analysis was done separately for impeller and diffuser and the effect of impeller diffuser interaction was not considered.
Combined 3D Fluid Dynamics and Mechanical Modelling of Brush Seals
Authors: Lelli Diego , Chew John W. , Cooper Paul
Published: November 2008

Development and application of a combined 3D computational fluid dynamics (CFD) and 3D bristle bending model for brush seals is described. The CFD model is created using commercial CFD mesh generation and solver software. A small gap is assumed between all bristles in the CFD model so as to avoid meshing problems at contact points and allow for imperfections in bristle geometry. The mechanical model is based on linear beam bending theory and allows large numbers of bristles to be modelled with arbitrary bristle-to-bristle contact and bristle to backing ring and shaft contact. Aerodynamic forces on the bristles are imported from the CFD solution. Deformed geometries may be exported directly to the mesh generation software, allowing iterative solution of the coupled aerodynamic/mechanical problem. Results from the model are presented for representative brush seal geometry. It is shown that even with initially circumferentially symmetric bristle packing and aerodynamic forces, bristle deflections tend to lead to asymmetric packing. This currently limits application of the fully coupled model, but use of the combined (but not fully coupled) model is nevertheless considered to give a powerful analysis tool. Shaft torque predictions are found to be in good agreement with measurements, and the effect of swirl in the inlet flow has been examined.
Aero-Thermal Computations With Experimental Comparison Applied to Aircraft Engine Nacelle Compartment
Authors: Balland Morgan , Verseux Olivier , Esteve Marie-Josephe
Published: November 2008

A joint Airbus & Snecma study on aero-thermal methodology applied to nacelle compartment is presented. Both partners have used their own simulation tools and compared their results with a real engine configuration to highlight the temperature heterogeneities on the engine casing and characterize equipment thermal fields. From the CFD, the structure of the flow has been consolidated in a cavity without equipments. The impact of equipment items on flow behavior has been studied in a second step. From a thermal aspect, the weight of both radiative and convective transfers has been estimated. Comparisons with engine thermocouple data show that the difference on average metal temperatures per station is less than 10% whereas the temperature gradient are underestimated in a range of [10–30]°C.
Superposition Predictions of the Reduction of Hot Streaks by Coolant From a Film Cooled Guide Vane
Authors: Jenkins Sean C. , Bogard David G.
Published: November 2008

The turbine section of a gas turbine engine is subjected to hot gases flowing from the combustor that typically have high temperature regions known as “hot streaks.” These hot streaks pass through the nozzle guide vanes, either impacting the vanes or passing through the passages between vanes. Generally the vanes are highly film cooled, and the coolant from the vanes interacts with the hot streak resulting in a reduction of the hot streak temperature. In this study, predictions of the reduction of hot streaks were made using superposition of measured temperature distributions due to coolant injection and measured temperature distributions of hot streaks. These predictions were compared to the measured hot streak reduction to determine the accuracy of the superposition technique. Results showed that the superposition predictions generally underpredicted the reduction of the peak hot streak temperature, but were within at least 20% of the peak temperature value. The superposition technique was also found to be useful for determining the hot streak reduction for different hot streak locations, and different coolant and hot streak operating conditions.
Adaptive Vaned Diffuser for Centrifugal Compressor
Authors: Ferrara G. , Ferrari L. , Baldassarre L.
Published: November 2008

Vaned diffusers are often preferred to a vaneless solution for improving maximum efficiency. The drawbacks of this choice are the reduction of stable working range and a narrower flow coefficient range at high efficiency. In this paper a solution to the above mentioned problems is presented. The solution proposed involves an adaptive vaned diffuser: the vanes can be oriented in order to find the optimum incidence by means of a mechanism moved by an oleo-dynamic piston. Several sensor typologies have been tested to find which is the best to assess the actual flow angle. The aim is to correlate the optimum vane position with sensor output in order to provide a close-loop control system. An experimental analysis was carried out on an intermediate centrifugal compressor stage to validate this approach.
Film-Cooling Characteristics of Pressure-Side Discharge Slots in an Accelerating Mainstream Flow
Authors: Kim Yong W. , Coon Chad , Moon Hee-Koo
Published: November 2008

Pressure-side discharge is commonly employed in turbine blades and nozzle guide vanes to keep the trailing edge metal temperatures within an allowable limit while minimizing aerodynamic penalties. Despite its widespread use, film-cooling data of the discharge slot are scarce in open literature. The objectives of the present experimental study were to measure detailed local heat transfer and film-cooling effectiveness from a 10x scale trailing-edge model of an industrial gas turbine airfoil in a low speed wind tunnel. To simulate the mainstream flow acceleration in vane and blade row passages, a linear velocity gradient was imposed using an adjustable top wall. The present work employed the composite slab quasi-steady liquid crystal method that allows measurements of local heat transfer coefficients and film-cooling effectiveness from two related tests. With this technique, the heat transfer measurement can be performed in a cold wind tunnel. The coolant-to-mainstream blowing ratio was varied between 0.25 and 1.0. The slot hydraulic diameter based Reynolds number ranged from 4,760 to 19,550. The coolant-to-mainstream density ratio was fixed at 0.95. Slot discharge coefficients were also measured with mainstream acceleration. Both local heat transfer coefficients and film-cooling effectiveness displayed a strong dependency on blowing ratio and mainstream acceleration. However, the discharge coefficients showed little dependency on the mainstream acceleration.
The Effect of Hot-Streaks on HP Vane Surface and Endwall Heat Transfer: An Experimental and Numerical Study
Authors: Povey T. , Chana K. S. , Jones T. V. , Hurrion J.
Published: November 2008

Pronounced non-uniformities in combustor exit flow temperature (hot-streaks), which arise because of discrete injection of fuel and dilution air jets within the combustor and because of end-wall cooling flows, affect both component life and aerodynamics. Because it is very difficult to quantitatively predict the affects of these temperature non-uniformities on the heat transfer rates, designers are forced to budget for hot-streaks in the cooling system design process. Consequently, components are designed for higher working temperatures than the mass-mean gas temperature, and this imposes a significant overall performance penalty. An inadequate cooling budget can lead to reduced component life. An improved understanding of hot-streak migration physics, or robust correlations based on reliable experimental data, would help designers minimise the overhead on cooling flow that is currently a necessity. A number of recent research projects sponsored by a range of industrial gas turbine and aero-engine manufacturers attest to the growing interest in hot-streak physics. This paper presents measurements of surface and end-wall heat transfer rate for an HP nozzle guide vane (NGV) operating as part of a full HP turbine stage in an annular transonic rotating turbine facility. Measurements were conducted with both uniform stage inlet temperature and with two non-uniform temperature profiles. The temperature profiles were non-dimensionally similar to profiles measured in an engine. A difference of one half of an NGV pitch in the circumferential (clocking) position of the hot-streak with respect to the NGV was used to investigate the affect of clocking on the vane surface and end-wall heat transfer rate. The vane surface pressure distributions, and the results of a flow-visualisation study, which are also given, are used to aid interpretation of the results. The results are compared to two-dimensional predictions conducted using two different boundary layer methods. Experiments were conducted in the Isentropic Light Piston Facility (ILPF) at QinetiQ Farnborough, a short duration engine-size turbine facility. Mach number, Reynolds number and gas-to-wall temperature ratios were correctly modelled. It is believed that the heat transfer measurements presented in this paper are the first of their kind.
Injection Coolant Isolation Curtain to Reduce Turbine Ingress Heating
Authors: Choi Dong-Chun , Rhode David L. , Sunshine Robert W.
Published: November 2008

The advanced strategy to reduce the turbine ingress heating and thus the coolant requirement by injecting a “coolant isolation curtain” was developed numerically using a 3-D CFD model under steady state conditions. The coolant isolation curtain was applied under the nozzle guide vane platform for the forward cavity of a turbine stage of a large gas turbine engine. Specifically, the isolation curtain serves to isolate the hot mainstream gas from the turbine outer region. For comparison purposes, when the baseline design and the injection curtain design have the same total coolant mass flow, the maximum temperature T*max of the injection curtain design was reduced by 0.23, 0.12 and 0.12, respectively, for the outer cavity, outer rotor adiabatic wall and outer stator adiabatic wall compared to that of the baseline design. Upon adjusting the feed slot coolant of the baseline design to match the outer cavity T*max, for example, of the injection curtain design, the reduction of dimensionless total coolant per stage from applying the injection curtain was estimated as 0.0038. Also a more uniform adiabatic wall temperature distribution along the outer rotor and stator surfaces was observed by using the coolant isolation curtain.
The Effects of Stepped Tip Gap on Performance and Flowfield of a Subsonic Axial-Flow Compressor Rotor
Authors: Lu Xingen , Zhu Junqiang , Chu Wuli , Wang Rugen
Published: November 2008

This paper investigates the flow field at the tip region of compressor rotor. In particular, the effect of stepped tip gaps on the performance and flowfield of an axial-flow compressor rotor was reviewed using both experimental and computational methods. An axial compressor rotor with no inlet guide vanes was tested under subsonic condition. A parametric study of clearance levels and step profiles was performed using eight different casing geometries. This study was aimed at comparing compressor performance in specified configurations. The experimental results showed that the inclusion of stepped tip gaps with the small clearance level gave increased pressure ratio, efficiency, and stall margin throughout the mass flow range at both speeds. However, when using medium and large clearance level, the benefits of stepped tip gaps were not noticed for all rotor operating conditions if compared with the baseline case. Steady-state Navier-Stokes analyses were performed for cases involving small clearance level and stepped tip gap geometries. They highlighted the mechanisms associated with performance improvement. The numerical procedure correctly predicted the overall effects of stepped tip gaps. Detailed numerical simulation results showed that the interaction between the stepped groove flow and blade passage flow could entrain the blockage produced by upstream tip leakage flow into the tip gap of adjacent blades of the compressor rotor. It is through this process that stepped tip gaps can help dissipating blockage that was caused by upstream tip leakage flow. Thus the path and extent of the blockage in the tip region is altered to increase the passage throughflow area and so, the rotor performance can be improved.
An Investigation of Wake-Shock Interactions in a Transonic Compressor With DPIV and Time-Accurate CFD
Authors: Gorrell Steven E. , Car David , Puterbaugh Steven L. , Estevadeordal Jordi , Okiishi Theodore H.
Published: November 2008

The effects of varying axial gap on the unsteady flow field between the stator and rotor of a transonic compressor stage are important because they can result in significant changes in stage mass flow rate, pressure rise and efficiency. Some of these effects are analyzed with measurements using Digital Particle Image Velocimetry (DPIV) and with time-accurate simulations using the 3D unsteady Navier-Stokes CFD solver TURBO. Generally there is excellent agreement between the measurements and simulations, instilling confidence in both. Strong vortices of the wake can break up the rotor bow shock and contribute to loss. At close spacing vortices are shed from the trailing edge of the upstream stationary blade row in response to the unsteady, discontinuous pressure field generated by the downstream rotor bow shock. Shed vortices increase in size and strength and generate more loss as spacing decreases, a consequence of the effective increase in rotor bow shock strength at the stationary blade row trailing edge. A relationship for the change in shed vorticity as a function of rotor bow shock strength is presented that predicts the difference between close and far spacing TURBO simulations.
Brush Seal Temperature Distribution Analysis
Authors: Dogu Yahya , Aksit Mahmut F.
Published: November 2008

Brush seals are designed to survive transient rotor rubs. Inherent brush seal flexibility reduces frictional heat generation. However, high surface speeds combined with thin rotor sections may result in local hot spots. Considering large surface area and accelerated oxidation rates, frictional heat at bristles tips is another major concern especially in challenging high temperature applications. This study investigates temperature distribution in a brush seal as a function of frictional heat generation at bristle tips. The two-dimensional axisymmetric CFD analysis includes the permeable bristle pack as a porous medium allowing fluid flow throughout the bristle matrix. In addition to effective flow resistance coefficients, isotropic effective thermal conductivity as a function of temperature is defined for the bristle pack. Employing a fin approach for a single bristle, a theoretical analysis has been developed after outlining the brush seal heat transfer mechanism. Theoretical and CFD analysis results are compared. To ensure coverage for various seal designs and operating conditions, several frictional heat input cases corresponding to different seal stiffness have been studied. Frictional heat generation is outlined to introduce a practical heat flux input into the analysis model. Effect of seal stiffness on nominal bristle tip temperature has been evaluated. Analyses show a steep temperature rise close to bristle tips that diminishes further away. Heat flux conducted through the bristles dissipates into the flow by a strong convection at fence height region.
On Vortex Formation in the Wake Flows of Transonic Turbine Blades and Oscillating Airfoils
Authors: Gostelow J. P. , Carscallen W. E. , Platzer M. F.
Published: November 2008

This paper demonstrates similarities between the vortex shedding from blunt trailing-edged transonic turbine nozzle blades and from oscillating bluff bodies. Under subsonic conditions the turbine nozzle cascade shed wake vortices in a conventional von Ka´rma´n vortex-street. This was linked with a depressed base pressure and associated energy separation in the wake. Under transonic conditions a variety of different shedding configurations was observed with vortices shedding and pairing in several different ways. Similarities are addressed between the observed structures and those from vortex shedding in some other physical situations. The authors have investigated the similarity between the vortex wakes shed from cylinders and airfoils in sinusoidal heaving motion in low speed flow and the wakes shed from the turbine nozzle cascade in transonic flow. The established field of vortex-induced vibration has provided a developed classification scheme for the phenomena observed. The paper has brought together three previously unrelated fields of investigation and, by showing that the three are essentially related, has provided the basis for a new synthesis.
The Effect of Ultrapolish on a Transonic Axial Rotor
Authors: Roberts William B. , Prahst Patricia S. , Thorp Scott , Strazisar Anthony J.
Published: November 2008

Back-to-back testing has been done using NASA fan rotor 67 in the Glenn Research Center W8 Axial Compressor Test Facility. The rotor was baseline tested with a normal industrial RMS surface finish of 0.5–0.6 μm (20–24 microinches) at 60, 80 and 100% of design speed. At design speed the tip relative Mach number was 1.38. The blades were then removed from the facility and ultrapolished to a surface finish of 0.125 μm (5 microinch) or less and retested. At 100% speed near the design point, the ultrapolished blades showed approximately 0.3–0.5% increase in adiabatic efficiency. The difference was greater near maximum flow. Due to increased relative measurement error at 60 and 80% speed, the performance difference between the normal and ultrapolished blades was indeterminate at these speeds.
Alternative Correction Factor for the Effects of Inlet Air Humidity on NOx From an Emissions Regulated Four-Stroke Medium Speed Diesel Engine and Comparison With Other Known Factors
Authors: Glenn W. Doug
Published: November 2008

With increasingly stringent emissions regulations for NOx and the known tradeoff of fuel consumption with NOx, ensuring the use of appropriate correction factors becomes increasingly significant to the OEM and customer. The Environmental Protection Agency (EPA) has specified in 40CFR Part92 that locomotive engines shall use a NOx correction factor, KNOx = f(KH), where KH is the humidity correction factor. This paper will present an alternative NOx humidity correction factor for GE Rail 4-stroke medium speed diesel engines. GE Rail’s NOx humidity correction factor will be compared with five other correction factors in a numerical exercise to assess the sensitivity to variations in ambient temperature, ambient pressure, relative humidity and A:F ratio. GE Rail’s alternative correction factor provides a 25% reduction in Line Haul Duty Cycle BSNOx variation and a mean BSNOx reduction of 3% as compared with KNOx correction factor from Part92.
The Lean Mixture Operational Limits of a S.I. Engine When Operated on Fuel Mixtures
Authors: Li Hailin , Karim Ghazi A. , Sohrabi A.
Published: November 2008

The operation of S.I. engines on lean mixtures is attractive in principle since it can provide improved fuel economy, reduced tendency to knock and extremely low NOx emissions. However, the associated flame propagation rates become degraded significantly and drop sharply as the operating mixture is made increasingly lean. Consequently, there exist distinct operational lean mixture limits beyond which satisfactory engine performance cannot be maintained due to the resulting prolonged and unstable combustion processes. The paper presents experimental data obtained in a single cylinder, variable compression ratio, S.I., CFR engine when operated in turn on CH4, H2, CO, gasoline, iso-octane and some of their binary mixtures. A quantitative approach for determining the operational limits of S.I. engines is suggested, compared and validated against corresponding experimental results of other traditional approaches. On this basis, the dependence of the values of the lean mixture operational limits on the composition of the fuel mixtures is investigated and discussed. The operational limit for throttled operation with methane as the fuel is also established.
Preliminary Energy-Efficiency Analysis on Multi-Pulse Injection Schedule in a Diesel Engine
Authors: Kumar Raj , Zheng Ming , Reader Graham T.
Published: November 2008

The multi-pulse fuel injection in a diesel engine is considered an effective way to reduce nitrogen oxides (NOx) emissions by heat-release shaping. In this research a preliminary energy efficiency analysis has been conducted for various split injection rates and schedules using the in-house and the commercial engine simulation software. Theoretical findings have been validated using experimentally obtained cylinder pressure data for various injection timings from a single-cylinder engine. The theoretical analysis on the shape of heat- release has been made to evaluate the energy efficiency of the post injection pulses on the engine exhaust temperature increases. An investigation of the cycle-to-cycle variation has also been performed for the measured cylinder pressure data.
Analysis of Cyclic Variability in a Bi-Fuel Engine by Means of a ‘Cycle-Resolved’ Diagnostic Technique
Authors: Baratta Mirko , d’Ambrosio Stefano , Spessa Ezio , Vassallo Alberto
Published: November 2008

The paper investigates cyclic variability in a fast-burn engine running on both gasoline or CNG by applying a new diagnostic technique based on a quasi-dimensional multizone model. Two different procedures were proposed for the ‘cycle-resolved’ calibration of the heat transfer correlation in the multizone model. The first procedure relates the cycle-resolved unreleased energy of the charge at the end of the flame propagation to the combustion efficiency determined from the average exhaust gas composition. The second procedure evaluates the coefficient in the heat transfer correlation through the application of the overall energy balance to the ensemble-cycle combustion and keeps them unchanged for all cycles. Both methods gave similar results, though the second procedure showed to be more physically consistent and in better agreement with the experimental results reported in the literature. The experimental matrix covered different engine speeds (n = 2000–4600 rpm), loads (bmep = 200–790 kPa), relative air-fuel ratios (RAFR = 0.80–1.60) and spark advances (SA ranging from 8 deg retard to 2 deg advance from MBT), for both CNG and gasoline operations, 100 consecutive in-cylinder pressure cycles were analyzed for each point in the test matrix and the sensitivity to cyclic variability of pressure, burn-rate and flame front position related parameters was analyzed. Main results showed that maximum pressure derivative, delay from SA of detected combustion start, NO exhaust concentration and maximum burning speed were the most sensitive parameters to cyclic variability. Strong correlations were found to hold between PFP and burned-gas temperature peak value, as well as between peak values of HRR and burning speed. On the contrary, some seemingly reasonable correlations were not assessed: for example, delay from SA of detected combustion start is related neither with PFP value nor with combustion duration. Finally, the results from mean cycle and cycle-resolved calculations were compared. Though they were usually in good agreement, in the case of NO emission and combustion interval calculation. cycle-resolved approach results in improved accuracy.
Flame Propagation Speed in SI Engines: Modeling and Experimental Assessment
Authors: Baratta Mirko , Catania Andrea E. , Spessa Ezio , Vassallo Alberto
Published: November 2008

The necessity for further reductions of in-cylinder pollutant formation and the opportunity to minimize engine development and testing time highlight the need of cycle simulation tools that have to accurately predict the effects of fuel, design and operating variables on engine performance. To develop reliable tools for indicated cycle simulation in SI engines, a correct prediction of heat release is required, which, in turn, involves the evaluation of in-cylinder turbulence generation and flame-turbulence interaction. This can be pursued by the application of a combustion fractal model coupled with semiempirical correlations of available geometrical and thermodynamical mass-averaged quantities. However, in the literature there is a lack of comparisons between the flame propagation speed obtained through these correlations and the experimental data determined under operating conditions that are significant for IC engines running on both conventional and alternative fuels. The present paper develops a new correlation that takes account of the effects of turbulence shrinking on the flame front as well as of the turbulent transfer of both species and heat across the flame front. The procedure has been applied to calculate the burning speeds in the cylinder of a naturally-aspirated bi-fuel engine for a wide range of engine speeds (N = 2000–4600 rpm), loads (bmep = 200–790 kPa), relative air-fuel ratios (RAFR = 0.80–1.30) and spark-advances (SA ranging from 8 deg retard to 2 deg advance with respect to MBT), under both gasoline and CNG operations. The computed burning speeds were compared to those obtained with the correlations currently available in the literature and to the experimental flame propagation data. These latter were extracted from measured in-cylinder pressure by means of a diagnostics technique previously developed by the authors. The results indicate that the burning speeds calculated through the authors’ procedure are in better agreement with the experimental outcomes than those derived from the correlations that are currently available in the literature.
Prediction of Peak Cylinder Pressure Variations Over Varying Inlet Air Condition of Compression-Ignition Engine
Authors: Chen Gong
Published: November 2008

Peak cylinder pressure of a compression-ignition engine can be affected by engine inlet air condition such as its temperature and pressure. The variation of peak cylinder pressure due to varying inlet air temperature and pressure is analytically studied in this paper. An analytical model is developed and thus the variations of peak cylinder pressure can be predicted along with inlet air temperature or pressure varying. It is indicated that cylinder compression ratio (CR) and intake air boost ratio (pm0/pi0) play significant roles in affecting the variation of peak cylinder pressure over inlet air temperature and pressure, and the pressure variation is proportional to CRk and pm0/pi0. The predicted results are compared to those from engine experiments, and show a close agreement. The prediction also includes the investigation of the variation in peak cylinder pressure due to varying the cylinder TDC volume. Results from the analytical studies are presented and show that the change in pmax versus a change in the volume is also affected by compression ratio. This indicates that for a certain change in the clearance volume, a higher compression-ratio configuration would produce a greater change in pmax than a lower compression-ratio would with the rest of the engine design parameters remaining unchanged.
Four Stroke Engine Geometry for Stratified Charge Combustion
Authors: Musu E. , Zanforlin S. , Gentili R.
Published: November 2008

In four-stroke engines direct injection increases power and fuel economy, which is further improved by charge stratification, due to pumping loss reduction and better combustion efficiency at partial loads. Charge stratification can be obtained by different techniques and injector designs. In every case late injection is necessary for stratification, which however is impaired by fuel dilution and spreading in consequence of burnt gas expansion, leading to incomplete combustion at very light loads. A numerical study has been carried out modifying KIVA code to handle new piston shapes. An innovative combustion chamber that is split in two volumes and allows fuel confinement during combustion has been conceived. CFD comparison has been made between a conventional combustion chamber and the proposed new one in term of combustion efficiency. Combustion is enhanced by the new design and unburnt emissions are reduced.
Exhaust Emissions From a 1,500 kW EMD 16-645-E Locomotive Diesel Engine Using Several Ultra-Low Sulfur Diesel Fuels
Authors: Fritz Steven G. , Hedrick John C. , Smith Brian E.
Published: November 2008

This paper documents results from an experimental study performed to determine the effects of several ultra-low sulfur diesel (ULSD) fuels (< 15 ppm S) on exhaust emissions from a 1,500 kW EMD 16-645-E, roots-blown, diesel locomotive engine. U.S. EPA-regulated emission levels of hydrocarbons (HC), carbon monoxide (CO), oxides of nitrogen (NOx), and particulate (PM) were measured using U.S. EPA locomotive test procedures while operating on four ULSD fuels, plus a fifth baseline fuel which was a commercially-available Federal on-highway diesel fuel (< 500 ppm). The four ULSD fuels were (1) a ULSD California motor vehicle diesel fuel (CARB fuel) with an aromatic content of less than 10 percent, (2) a ULSD “equivalent” California motor vehicle diesel fuel with an aromatic content of 24 percent, (3 and 4) two custom blended “2006 ULSD Federal” diesel fuels with relatively low Cetane Numbers and higher aromatic levels. This paper reports the changes observed in the regulated exhaust emission levels between the ULSD CARB diesel fuels and the ULSD Federal diesel fuels.
Performance and Emission Characteristics of Four Stroke D.I. Diesel Engine Fueled With Turpentine Diesel Blends
Authors: Mahalakshmi N. V. , Karthikeyan R.
Published: November 2008

Pinus product (Turpentine) has been proposed as an alternate to petro fuels since the invention of S.I. engine. In general, due to higher volatility, turpentine has been used only in the S.I. engine. But the present work proves that based on the property of turpentine (Table – 1), it is a very good substitute for diesel fuel. The low cetane number of turpentine oil had prevented the use of 100% turpentine oil in diesel engine. The present work explores the performance, emission and combustion characteristics of turpentine diesel blends and its suitability with C.I. engine. The 20% turpentine 80% diesel blend has an equal combustion and performance characteristics with that of diesel fuel. The experimental results show that some of the toxic gases like CO, UBHC and soot are decreased compared to diesel baseline. In particular around 45% to 50% smoke reduction is obtained with higher turpentine blends. Also it proves that 20% addition of turpentine into conventional diesel fuel improve the performance, combustion, and emission to a considerable limit.
Measuring the Effect of Simulated Engine Faults on the Emissions of Mechanically- and Electronically-Controlled Diesel Engines
Authors: Rubeli Brent G. , Gangal Mahe K. , Young David A.
Published: November 2008

The gaseous and particulate emissions from two diesel engines were measured while operating under simulated fault conditions in a controlled laboratory environment. The engines were representative of those typically used in light and heavy-duty mobile underground mining equipment. Faults were applied singly and in combination. Emissions data were measured using laboratory and field instruments for comparison. The development of protocols for field-testing of vehicles are discussed.
Diesel Engine NOx Reduction Using Charge Air Water Injection
Authors: Radloff Ernst , Gautier Charles
Published: November 2008

The Transportation Development Centre of Transport Canada, in collaboration with Environment Canada’s Emissions Research and Measurement Division, conducted a series of emissions tests onboard the Oceanex RoRo vessel MV Cabot operating between Montre´al, Quebec, and St. John’s, Newfoundland. The primary objectives were to verify emissions inventories and demonstrate the feasibility of installing affordable emissions reduction technology on marine vessels as well as compliance with future regulatory emissions limits. The tests also provided an opportunity for Canada to share information on emissions program and technology developments with U.S. regulatory authorities. This may lead to developing joint emissions reduction initiatives for existing marine vessels. This paper describes the field-testing of a water injection system (WIS) to reduce oxides of nitrogen (NOx) emissions from ocean-going vessels. Tests were conducted on a semi-dedicated basis during voyage and under steady-state conditions. The emissions measurements were taken in accordance with ISO 8178-4-E3 protocol and using both marine diesel oil and intermediate fuel oil, which enabled the evaluation of the impact of different fuel type and quality on emissions. An initial series of tests was carried out on the MV Cabot in March 2004, followed by a second series of tests on the same vessel in March 2005. These tests demonstrated the effectiveness of a low-cost WIS for reducing NOx emissions in marine diesel engines. They also showed that water injection reduces NOx at the expense of an increase in both particulate matter and carbon monoxide when using intermediate fuel oil. NOx reductions varied between 10 and 35 percent, and were most effective at high water injection ratios above 50 percent engine load. The test results showed no negative impact of the WIS on fuel consumption or engine operation and performance. This paper compares the results obtained from the consecutive series of tests in terms of the effectiveness of NOx reduction, and analyses the results in the context of other full-scale test results obtained from emissions control system vendors and engine suppliers. It also investigates the theoretical process and technology of water injection through charge air fumigation, and both direct water and fuel/water emulsion injection. In addition, the effects of water injection on engine emissions, operation and maintenance, and the optimization of water injection from a knowledge-based perspective are discussed. Further testing and development of the WIS are required to realize optimal emissions reduction potential and to determine the impact of water injection on fuel consumption, and engine operational performance as well as the impact of fuel quality on emissions.
On Moore’s Law and Its Application to SI Engine Technology
Authors: LaViolette Marc
Published: November 2008

Moore’s law relates how the integration of semiconductors has progressed in time. This research shows that the exponential trend shown in the electronics manufacturing industry can have applications elsewhere. This study shows that the internal combustion engine followed the same trend for over 70 years. Though not the most used engine variable, engine power density shows the same trends for engines as transistor density does for microchips. This now mature technology has ended its period of rapid growth. However the present day engine trends can show how Moore’s law can be extended to include the slower growth of long established technologies. Because exponential growth cannot go on forever, the extension Moore’s law requires that the logistic function be used. The new function also allows one to predict a theoretical value for maximum power density.
Alternate Modes Combustion Study: HCCI Fueled With Heptane and Spark Ignition Fueled With Reformer Gas
Authors: Hosseini Vahid , Checkel M. David
Published: November 2008

Homogenous Charge Compression Ignition (HCCI) combustion is an efficient operating mode for internal combustion engines operating at low specific power and has the further advantage of very low specific NOx emission rate. High Compression Lean Burn (HCLB) spark ignition (SI) provides a more conventional approach to achieving high engine efficiency. Specific NOx emission rates are low though not as low as with HCCI. Compared with HCCI engines, HCLB-SI engines have the advantage of direct combustion control, (through spark timing), and thus are able to start from cold and operate over a wider range of conditions including higher specific power than HCCI. On the other hand HCCI still has the advantage in efficiency and NOx emission rate. These trade-offs makes it desirable to develop an engine which can operate in either mode, hopefully without significantly adding to engine cost or compromising either mode. This paper presents a first exploration of a dual-mode engine which can use either HCCI or HCLB mode by operating on either a base, low-octane liquid fuel or on reformer gas (RG) produced by steam reforming or partial oxidation from the base fuel. Engine experiments with a CFR engine are used to demonstrate engine operation in both HCLB-SI and HCCI operating modes fueled with some combination of n-heptane and reformer gas. The combustion characteristics including combustion stability and cyclic variation are measured and compared for HCCI operation and RG-fueled HCLB-SI engine operation. CNG-fueled SI engine operation is also used as an additional basis for comparison.
Numerical Analysis of Flow Characteristics in a Swirl Chamber Type Diesel Engine Depending on Passage Hole Type
Authors: Choi Gyeung Ho , Kwon Tae Yun , Yun Ju Hee , Chung Yon Jong , Ha Chang Uk , Lee Jong Soon , Han Sung Bin
Published: November 2008

In a swirl chamber type diesel engine, a strong swirl is produced inside the swirl chamber during the compression stroke. By spraying the fuel into this chamber and thus forming a good mixture, the engine can obtain excellent combustion even at high speeds. Therefore, swirl chamber type diesel engines are favorable for high-speed operations, and because they can produce high power from a small size, they are used often for small, high-speed diesel engine applications. In order to simultaneously realize a reduction in harmful emissions and improvement in fuel consumption of the swirl chamber type diesel engine, reduction of the mixture formation period and complete combustion must be pursued; an optimum combustion chamber to achieve these tasks must first be designed. In this experiment, the effects of the area and the angle of the passage hole, which are the primary design factors of the swirl chamber type diesel engine, on the engine’s turbulent flow will be investigated. Using the commercial numerical analysis program the passage hole area and angle will be varied to analyze the intake and compression stages.
Effect of Internal Exhaust Gas Recycling on n-Heptane HCCI Combustion
Authors: Asad Usman , Zheng Ming , Ting David S.-K. , Reader Graham T.
Published: November 2008

Homogeneous Charge Compression Ignition (HCCI) combustion is currently limited in application due to several key issues such as a narrow operating range, high hydrocarbon and carbon monoxide emissions and lack of control over the onset of combustion. Exhaust gas recycling (EGR) has the potential to 1) provide reasonable control over the HCCI combustion process and 2) extend its operating range. In this paper, the effect of hot internal EGR on ignition timing and heat release rate of HCCI combustion fuelled with n-heptane has been investigated using the CHEMKIN 0-D closed combustion engine simulation package. An attempt has been made to study the effect of individual components of EGR on cylinder-temperature history and the rate of chemical reaction. The results indicate that combustion initiation is directly linked to the thermal energy contained in the hot EGR but the particular chemical species contained in the EGR have different influences towards ignition timing and heat release rate. This theoretical study would be substantiated by experimental work in the near future.
An Investigation of Lean Burn in a 2-Valve TJ376QE SI Engine
Authors: Liu Shu-Liang , Wang Tian-You , Su Hong-Jun , Li Xing , Li Jian-Wen , Fu Mao-Lin
Published: November 2008

The intake system of a 2-Valve TJ376QE gasoline engine was modified so that its intake swirl and tumble motions were considerably intensified. The stronger air motions are helpful to organize air and fuel mixture strength distribution. The previous port electronic fuel injection system was modified and the technique of TEFI (Twice Electronic Fuel Injection per cycle) is employed. Through regulations of the two injection timings and proportions, an adequate air and fuel mixture stratification–quasi-homogenous mixture was produced and the lean burn can be realized in a product 2-valve S.I. engine. The experimental results show that the scope of bsfc reduction can be >10 % at quite wide load range by ether 1 injection or by 2 injections. Comparing to the conventional single injection, a leaner mixture can be used by TEFI and an even more reduced fuel consumption of 5% was reached by 2 injections. The optimized values of A/F ratio can be higher by 2–3 units of A/F than that of the single injection method. The TEFI can reduce NOx emission by 35–50% than that of single injection at engine load (bmep) range of 0.20–0.75 (MPa).
Experimental Investigation of HCCI Combustion With Reduced Compression Ratio and Narrow Include Angle Injector in a Small DI Diesel Engine
Authors: Kim Myung Yoon , Lee Ki Hyung , Lee Chang Sik
Published: November 2008

An experimental investigation was performed on a small direct injection (DI) diesel engine equipped with a common-rail injection system to reduce exhaust emissions through HCCI (homogenous charge compression ignition) combustion. Recently, strict environmental standard requirements call for both lower fuel consumption and reduced emissions that could not be achieved by conventional diesel combustion. In this work experimental investigations to achieve simultaneous reduction of NOx and soot by combustion of more diluted fuel/air mixture before the start of ignition were carried out. To realize this fundamental concept, the experimental conditions including injection timing and EGR rate are varied with the different engine configurations. For reducing the deposition of early injected fuel, spray angle of injector is reduced to 60° and piston head shape also modified to fit with the new injector and to reduce the compression ratio to 15:1 for expanding the ignition delay to form diluted mixture before the ignition. Experimental results show that reduced spray angle with modified piston head allow very low NOx and soot emission level while maintaining the high IMEP of diesel combustion.
Evaluation of Biodiesel Blends in a Single-Cylinder Medium-Speed Diesel Engine
Authors: Su Fan , Payne Malcolm , Vazquez Manuel , Eggleton Peter , Vincent Alex
Published: November 2008

Biodiesel blends were prepared by mixing low sulphur #2 diesel and biodiesel of two origins (canola and frying oil) at two different concentrations (5% and 20%). They were tested in a single-cylinder four-stroke medium-speed diesel engine under three engine modes representing idle, about 50% power and full load conditions. Engine performance and emissions data obtained with the blends were compared to that of engine running with the #2 diesel. Results indicated that the 5% blends could maintain engine power and fuel economy. Frying oil based B5 provided more significant reductions on CO, THC and PM emissions and increments on NOx emissions as compared with that of the canola B5 fuel. The 20% blends reduce engine CO, PM and smoke emissions, but increase NOx emissions by up to approximately 8%. Engine cylinder pressure and injection pressure data was also collected to provide additional information for evaluation of fuel economy and emissions benefits of using the blends.
Development and Validation for Mean Value Engine Models
Authors: Jazayeri Seyed Ali , Sharifi Rad Mohammad , Azadi Shahram
Published: November 2008

Engine control algorithms are among the most important factors that affect engine performance and emission. Developing control algorithms would improve engine performance, fuel consumption and emission levels. On the other hand, time and cost reduction of controller development is becoming an ever increasing demand. To meet these demands, more advanced engine models and better controller development processes are essential. Therefore, those models with good accuracy together with high calculation speed and fewest numbers of tests for calibration are most suitable. The mean value engine models are developed to meet these criteria. The governing equations for these models are simple and relatively easy to calibrate. The main purpose of this work was to simplify the equations of such a model, decrease the number of calibration tests and improve model accuracy. Simpler equations are used for the calculation of air mass flow at the throttle body and cylinder ports. To increase the accuracy of the manifold pressure calculations, two different relations are proposed and the results are compared. Also a set of equations is presented for rotational dynamics. Then the accuracy of the developed model is examined through the experimental works carried out on the engine of a locally manufactured vehicle called Samand.
Testing of New Catalyst for Compression Ignition Engine Exhaust Treatment
Authors: Walke P. V. , Deshpande N. V.
Published: November 2008

Testing of catalytic converter with exhaust gas recirculation system for diesel engine to reduce pollute gases is chosen for present work. The emphasis is given on hydrocarbon (HC), carbon monoxide (CO) and oxides of nitrogen. The catalytic converter was developed with variations of catalyst plates. Perforated plates of copper and combination of copper oxide and cerium oxide (CeO2 +CuO2) were used as the catalyst. Copper spacer is used in between plates to vary the distance. Secondary air was injected into the converter to aid oxidization of HC and CO. Experimental study was carried out on computerized kirloskar single cylinder four stroke (10 B.H.P, 7.4 KW) diesel engine test rig with an eddy current dynamometer. The converter was tested with various combination of the exhaust gas re-circulation (EGR) system. There are some improvements in the reduction and conversion efficiency of HC & CO. Exhaust gas recirculation has proved to be effective in reducing NOx.