# Search Results

Viewing 61 to 80 of 5739
Technical Paper

### A Comprehensive Model of Piston Skirt Lubrication

1992-02-01
920483
This paper describes a comprehensive model of piston skirt lubrication, developed for use in conjunction with piston secondary dynamic analysis, to accurately characterize the effects of the skirt-cylinder oil film on piston motions. The model represents both hydrodynamic and boundary lubrication modes and applies an asperity contact pressure when surfaces are in close proximity with each other. In addition to skirt dimensions and surface roughness properties, the circumferential extent of lubrication, an arbitrary skirt profile and bore distortion are specifiable inputs to the model. The model is also extended to represent the oil starvation at the cylinder end of the skirt by allowing the axial extent of lubrication on the skirt surface to vary circumferentially and with time to satisfy continuity of oil.
Technical Paper

### A Comprehensive Model to Study the Dynamic Motion of Piston and Friction and Lubrication in I.C.Enignes

2008-01-09
2008-28-0061
The Piston assembly friction loss contributes for larger part in the engine frictional loss. In order to reduce the frictional loss due to piston assembly motion, a complete model describing the dynamics of assembly is necessary. This paper presents a model to study the primary and secondary motion of piston and also a model for determination of frictional losses in the piston assembly of an automotive Internal Combustion Engine. A mixed lubrication model based on a two-dimensional Reynolds equation is presented to use in conjunction with a piston secondary motion analysis.
Technical Paper

### A Comprehensive Piston Skirt Lubrication Model Using a Mass Conserving EHL Algorithm

2005-04-11
2005-01-1640
Elasto-Hydrodynamic Lubrication (EHL) analysis of a fully flooded piston skirt-liner conjunction is a useful methodology for design analysis of pistons. However, under typical engine operating conditions, oil present in the clearance region between the skirt and liner is sufficient to wet only a portion of the piston skirt (partial skirt lubrication). The reduction in damping due to partial skirt lubrication is an important consideration to address issues related to piston slap noise, liner cavitation and other noise and vibration aspects. The existing simulation methodology for EHL analysis of a fully flooded piston skirt uses a finite-difference scheme to solve the coupled Reynolds, Greenwood-Tripp and elasticity equations in order to calculate the nodal oil film pressures, contact pressures and elastic deformations respectively. Detection of cavitation zones within the oil film done via implementation of the Half-Sommerfeld boundary condition.
Technical Paper

### A Compressed Natural Gas Mass Flow Driven Heavy Duty Electronic Engine Management System

1993-08-01
931822
This paper describes the conversion of a stationary spark ignition engine to a heavy duty (HD) natural gas engine suitable for transportation applications, in response to the new urban truck and bus legislation of 1994 and 1998. The approach to the fuel and ignition control system is to use a microprocessor controlled engine management system based on inputs from combustion air and natural gas mass flow sensors. As the emission control system is also based on stoichiometric three way catalyst technology, it is felt that the control approach is very robust. The engine and control system were first mounted on a HD dynamometer for the development work where engine control parameters were calibrated. In addition steady state emission data were collected and estimates of the HD transient emission levels were obtained.
Journal Article

### A Computational Investigation of Piston Bowl Geometry Effects on PPCI-Diffusion Combustion in a Light-Duty GCI Engine

2023-04-11
2023-01-0275
A PPCI-diffusion combustion strategy has shown the potential to achieve high efficiency, clean gasoline compression ignition (GCI) combustion across the full engine operating range. By conducting a 3-D CFD-led combustion system design campaign, this investigation was focused on developing a next generation (NextGen), step-lipped piston design concept in a 2.6L advanced light-duty GCI engine. Key geometric features of the NextGen piston bowl were parametrized and studied with customized spray targeting. A low lip positioning design with 128° spray targeting was found to provide the best performance. Fuel injection strategy optimization was performed at a full-load operating point (OP), 2000 rpm/24 bar closed-cycle IMEP (IMEPcc).
Technical Paper

### A Computational Investigation of the Effects of Swirl Ratio and Injection Pressure on Mixture Preparation and Wall Heat Transfer in a Light-Duty Diesel Engine

2013-04-08
2013-01-1105
In a recent study, quantitative measurements were presented of in-cylinder spatial distributions of mixture equivalence ratio in a single-cylinder light-duty optical diesel engine, operated with a non-reactive mixture at conditions similar to an early injection low-temperature combustion mode. In the experiments a planar laser-induced fluorescence (PLIF) methodology was used to obtain local mixture equivalence ratio values based on a diesel fuel surrogate (75% n-heptane, 25% iso-octane), with a small fraction of toluene as fluorescing tracer (0.5% by mass). Significant changes in the mixture's structure and composition at the walls were observed due to increased charge motion at high swirl and injection pressure levels. This suggested a non-negligible impact on wall heat transfer and, ultimately, on efficiency and engine-out emissions.
Technical Paper

### A Computational Study of Hydrogen Direct Injection Using a Pre-Chamber in an Opposed-Piston Engine

2024-07-02
2024-01-3010
Combustion characteristics of a hydrogen (H2) direct-injected (DI) pre-chamber (PC)-assisted opposed piston two-stroke (OP2S) engine are investigated by 3D computational fluid dynamics (CFD) simulations. The architecture of the OP2S engine has potential features for reducing wall heat losses, as the DI H2 jets are not directed towards the piston face. To overcome the high resistance to autoignition of H2, a PC technology was implemented in order to enhance the ignition of the mixture by the multiple hot reactive jets. To further investigate the interaction between the H2 plume and the chamber walls, three different piston bowl designs were evaluated and ranked based on a merit function. For the cases under study, the flat piston design was found to be most favorable (compared to the narrow and wide pistons) due to its reduced surface area for lower wall heat losses.
Technical Paper

### A Computational Study on the Effect of Injector Location on the Performance of a Small Spark-Ignition Engine Modified to Operate under the Direct-Injection Mode

2020-04-14
2020-01-0286
In a direct-injection (DI) engine, charge motion and mixture preparation are among the most important factors deciding the performance and emissions. This work was focused on studying the effect of injector positioning on fuel-air mixture preparation and fuel impingement on in-cylinder surfaces during the homogeneous mode of operation in a naturally aspirated, small bore, 0.2 l, light-duty, air-cooled, four-stroke, spark-ignition engine modified to operate under the DI mode. A commercially available, six-hole, solenoid-operated injector was used. Two injector locations were identified based on the availability of the space on the cylinder head. One location yielded the spray-guided (SG) configuration, with one of the spray plumes targeted towards the spark plug. In the second location, the spray plumes were targeted towards the piston top in a wall-guided (WG) configuration so as to minimize the impingement of fuel on the liner.
Technical Paper

### A Computer-Controlled Poppet-Valve Actuation System for Application on Research Engines

1984-02-01
840340
A computer - controlled valve actuation system for research engines is described. The system can be used for the complete real-time control of valve motion, including valve lift, dwell, valve event overlap and valve timing. The value actuator is a fast electro-hydraulic unit, incorporating a small hydraulic actuator and a high-performance servovalve. The actuator assembly mounts over the engine valve and replaces the existing camshaft and rocker arm. An analog position-feedback controller coupled to a laboratory minicomputer provides the system control. The closed-loop step response time is 3 milliseconds with a 0.5 millisecond initial delay. The system currently operates at engine speeds less than 1000 rpm and with appropriate control software is expected to operate at engine speeds approaching 3000 rpm. The actuation system is suitable for a research environment and has many potential applications in piston engine research and development.
Technical Paper

### A Concept for a Natural Gas Fueled Locomotive that Uses a Gas Turbine

1989-08-01
891699
A concept for a natural gas fueled locomotive that uses a gas turbine for Its prime mover is presented in this paper. Additionally, the paper compares several of the economic operating aspects of the proposed motive power concept with a modified conventional diesel electric locomotive for natural gas operation. This proposed turbine powered concept is significantly different from conventional diesel driven motive power or Its natural gas derivative. In spite of this significant departure from the standard, there appears to be ample Information to support the proposed concept technical feasibility and commercial viability. The advantage of the proposed locomotive concept over the modification of conventional motive power is that in addition to reduced energy cost and Independence from the “oil supply” the proposed gas turbine locomotive can offer improvement in productivity, availability and maintain ability.
Technical Paper

### A Consideration on Piston Second Land Pressure and Oil Consumption of Internal Combustion Engine

1984-02-01
840099
Piston second land pressure, combustion pressure, and oil consumption (OC) of a four-stroke gasoline engine have been measured to investigate the relationship between 2nd land pressure and OC. Test results have revealed that OC increases when, past midway in the expansion stroke, 2nd land pressure exceeds combustion pressure and, inversely OC decreases when the 2nd land pressure is below combustion pressure. Based on both theoretical analyses and experiments, this paper describes the reason for the above observation and proposes a method for reducing OC.
Technical Paper

### A Consolidated Investigation on LPG as an Alternative Fuel for Public Utility Jeepneys

2018-04-03
2018-01-0917
This paper presents the results of a two-phase Philippine study to determine the actual mileage (km/liter) of in-use diesel and LPG (liquefied petroleum gas or Auto-LPG) public utility jeepneys plying two separate Metro Manila urban routes using both on-road and chassis dynamometer tests. Measured average load factor in on-road tests was 60-70%. Dynamometer tests at 100% load factor utilized drive cycles derived from on-road speed data. A “diesel equivalent mileage” of actual LPG mileage, deemed indicative of LPG “fuel energy conversion efficiency” relative to diesel, was calculated (based solely on fuel heating values and densities) for comparing actual mileage from both fuels. The LPG actual mileage in both on-road and laboratory tests was lower than diesel mileage. In on-road tests, the LPG actual mileage was lower than diesel actual mileage by about the same percentage LPG heating value was lower than diesel’s per liter of fuel.
Technical Paper

### A Controller for a Spark Ignition Engine with Bi-Fuel Capability

1994-10-01
942004
A bi-fuel engine with the ability to run optimally on both compressed natural gas (CNG) and gasoline is being developed. Such bi-fuel automotive engines are necessary to bridge the gap between gasoline and natural gas as an alternative fuel while natural gas fueling stations are not yet common enough to make a dedicated natural gas vehicle practical. As an example of modern progressive engine design, a Saturn 1.9 liter 4-cylinder dual overhead cam (DOHC) engine has been selected as a base powerplant for this development. Many previous natural gas conversions have made compromises in engine control strategies, including mapped open-loop methods, or resorting to translating the signals to or from the original controller. The engine control system described here, however, employs adaptive closed-loop control, optimizing fuel delivery and spark timing for both fuels.
Technical Paper

### A Coupled Tabulated Kinetics and Flame Propagation Model for the Simulation of Fumigated Medium Speed Dual-Fuel Engines

2019-09-09
2019-24-0098
The present work describes the numerical modeling of medium-speed marine engines, operating in a fumigated dual-fuel mode, i.e. with the second fuel injected in the ports. This engine technology allows reducing engine-out emissions while maintaining the engine efficiency and can be fairly easily retrofitted from current diesel engines. The main premixed fuel that is added can be a low-carbon one and can additionally be of a renewable nature, thereby reducing or even completely removing the global warming impact. To fully optimize the operational parameters of such a large marine engine, computational fluid dynamics can be very helpful. Accurately describing the combustion process in such an engine is key, as the prediction of the heat release and the pollutant formation is crucial. Auto-ignition of the diesel fuel needs to be captured, followed by the combustion and flame propagation of the premixed fuel.
Technical Paper

### A Crevice Blow-by Model for a Rapid Compression Expansion Machine Used for Chemical Kinetic (HCCI) Studies

2007-04-16
2007-01-1052
A crevice blow-by model has been developed for a Rapid Compression Expansion Machine. This device can be used to study chemical kinetics with application to Homogeneous Charge Compression Ignition and other alternative combustion processes. In order to accurately resolve the ignition conditions and understand the oxidation process, accurate models for heat transfer and crevice flow, including blow-by past the ringpack, must be utilized. Crevice flows are important when high compression ratio or boosted operation is investigated. In previous work the heat loss characteristics of the RCEM were characterized; this study concerns the crevice flows within the RCEM. A ring-dynamic model, first developed at MIT and recently modified at UIUC to account for circumferential flow pas unlubricated rings, was employed.
Technical Paper

### A Critical Evaluation of the Geared Hypocycloid Mechanism for Internal Combustion Engine Application

1988-02-01
880660
The geared hypocycloid mechanism, a kinematic arrangement that provides a straight-line motion, can be used as the basis for an internal combustion engine. Such an engine would have a number of advantages: Perfect balance can be achieved with any number of cylinders. The straight-line motion eliminates the need for a wrist pin bearing, further allowing a very short piston to be used without danger of cocking. Piston side load is virtually eliminated, and “piston slap” will not occur even with a large piston/cylinder clearance. These features make it particularly attractive for small single cylinder engine applications where vibration is undesirable, and also for the uncooled “adiabatic engines”, in which piston cylinder lubrication and friction are major concerns.
Technical Paper

### A Critical Review of Spark Ignited Diesel Combustion

1988-09-01
881317
This paper reviews previous work on spark assisted diesel engines and then goes on to discuss the results of investigations carried out at U.W. Results are given for two Army referee fuels and compared to D2 fuel results. The data concentrates on starting and low load running of Type I fuel which is a broadcut fuel with a cetane number of 20. Results are given for both two stroke and four stroke open chamber engines modified for spark ignition. The best results were obtained by directing one fuel spray at a raised central portion of the piston and spark igniting the resulting fuel cloud at a position 12 mm from the head and near the cylinder axis.
Technical Paper

### A Critique of Turbine Accessories

1969-02-01
690740
This paper is a critical discussion of various problems which one company encountered with accessories on several different makes of gas-fired turbines. These turbines are used as prime movers driving centrifugal natural gas compressors on a pipeline transmission system. The accessories covered are: ignition system, lube oil cooler, tach generator, lube oil pumps, auxiliary gearbox, thermocouples, lubricators, inlet air filter, instrument air system, cab pressurization fan, and starter.
Technical Paper

### A Current Look at the Natural Gas Fueling Infrastructure in the United States

1995-12-01
952770
The natural gas utility industry has led the development of the natural gas fueling infrastructure in the United States. Focusing primarily on compressed natural gas (CNG), the utility industry has built fueling stations to serve their own fleets and those of targeted customers. In addition, gas utility companies have formed partnerships with traditional fuel retailers to offer natural gas to a broader range of customers. This paper will: Document the history of natural gas fueling infrastructure development from the early 1980's. It will provide statistics on the current status of the fueling infrastructure, including the numbers of private and public access stations and will forecast the number of stations required to serve projected natural gas vehicles (NGVs) through the year 2010. Examine the various types of CNG fueling technologies currently being used, and will discuss the major components of fueling systems.
Technical Paper

### A Decoupled Model of Detailed Fluid Mechanics Followed by Detailed Chemical Kinetics for Prediction of Iso-Octane HCCI Combustion

2001-09-24
2001-01-3612
We have developed a methodology for predicting combustion and emissions in a Homogeneous Charge Compression Ignition (HCCI) Engine. The methodology judiciously uses a fluid mechanics code followed by a chemical kinetics code to achieve great reduction in the computational requirements; to a level that can be handled with current computers. In previous papers, our sequential, multi-zone methodology has been applied to HCCI combustion of short-chain hydrocarbons (natural gas and propane). Applying the same procedure to long-chain hydrocarbons (iso-octane) results in unacceptably long computational time. In this paper, we show how the computational time can be made acceptable by developing a segregated solver. This reduces the run time of a ten-zone problem by an order of magnitude and thus makes it much more practical to make combustion studies of long-chain hydrocarbons.