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Technical Paper

3-D Computations of Premixed-Charge Natural Gas Combustion in Rotary Engines

1991-02-01
910625
A three-dimensional model for premixed- charge naturally-aspirated rotary engine combustion is used to identify combustion chamber geometries that could lead to increased indicated efficiency for a lean (equivalence ratio =0.75) natural gas/air mixture. Computations were made at two rpms (1800 and 3600) and two loads (approximately 345 Kpa and 620 Kpa indicated mean effective pressure). Six configurations were studied. The configuration that gave the highest indicated efficiency has a leading pocket with a leading deep recess, two spark plugs located circumferentially on the symmetry plane (one after the minor axis and the other before), a compression ratio of 9.5, and an anti-quench feature on the trailing flank.
Technical Paper

High Speed Control of Damping Force Using Piezoelectric Elements

1991-02-01
910661
Semi-active suspension is one of many effective devices to improve vehicle stability, controllability and riding comfort. A practical means to realize semi-active suspension is to vary the damping force of the shock absorber. In this paper, we propose a new type of shock absorber using a piezoelectric sensor and actuator. The piezoelectric sensor and actuator are built into the piston rod which is a part of the shock absorber. The piezoelectric element provides a fast response and a high actuation force. We used the piezoelectric element in shock absorbers in order to take advantage of these two features. High level compatibility between stability, controllability and riding comfort is expected, since damping force changes very quickly using this new type of shock absorber. In this paper, several topics are discussed. First, a general description of the damping force control system with simple configuration is explained.
Technical Paper

Concepts, Materials, and Efficiencies of Piston Compounded Adiabatic Engines

1991-02-01
910895
A new practical concept for piston compounding engines is described. The calculated thermal efficiency of a fully insulated, piston compounded, overcharged diesel engine can exceed 60%. The design considerations for construction of such an engine from controlled expansion superalloys is also described.
Technical Paper

Experimental Survey of Lubricant-Film Characteristics and Oil Consumption in a Small Diesel Engine

1991-02-01
910741
Parallel measurements of lubricant-film behavior and oil consumption in two identical small production IDI diesel engines are presented. Oil consumption was measured using tritium as a radioactive tracer, and instantaneous film thickness data between the piston and liner were obtained using laser fluorescence diagnostics. The data covered single- and multi-grade lubricants and five different ring configurations (two-piece vs three-piece rings at various ring tensions). The data illustrate (a) oil-film profiles under the rings, especially around the leading and trailing edges, (b) accumulation of oil on piston lands and skirt, (c) circumferential variations around the bore, (d) observations on ring rotation, and (e) the piston-skirt oil-pumping mechanism. Effects of lubricants and piston-ring configurations on oil-film characteristics are investigated, and the oil consumption data are compared with oil-film thickness measurements.
Technical Paper

Development of Fiber Reinforced Aluminum Alloy for Diesel Piston Applications

1991-02-01
910632
A preliminary study was done to select the more adequate composite material to be used as a reinforcement at the combustion bowl of higher output diesel engine pistons. From the three types of composites produced, namely, Ceramic Reinforced Material (CRM) , Metal Reinforced Material (MRM) and Fiber Reinforced Material (FRM) (1)*, FRM was selected after preliminary tests of mechanical properties, machinability and diesel engine tests, realized in a small monocylinder diesel engine.
Technical Paper

High Frame Rate Flow Visualization and LDV Measurements in a Steady Flow Cylinder Head Assembly

1991-02-01
910473
The purpose of this work was to develop a high speed flow visualization system which could be used to observe the behavior of the air flow in a steady flow cylinder head assembly. This type of experimental rig has been used by engineers for many years to evaluate valve discharge coefficients. This study is believed to be the first high speed flow visualization of the air flow in a system of this type. Particular emphasis was placed on the characterization of intake generated swirl and tumble motions within the cylinder. A 40 watt copper vapor laser was used to expose motion picture films at 5000 frames per second. The light scattering medium was phenolic microballoons. Based on the flow visualization results, selected LDV measurements were made to quantify the visual observations. A propylene glycol aerosol was used for seeding in the LDV experiments.
Technical Paper

Uncooled Two-Stroke Gas Engine for Heat Pump Drive

1991-02-01
910456
This paper describes the design and analysis of a family of natural gas fueled, uncooled, two-stroke, lean burn, thermal-ignition engines. The engines were designed specifically to meet the requirements dictated by the commercial heat pump application. The engines have a power output ranging from 15 to 100 kW; a thermal efficiency of 36 percent; a mean time between failure greater than 3 years; and a life expectancy of 45,000 hours. To meet these specifications a family of very simple, uncooled, two-stroke cycle engines were designed which have no belts, gears or pumps. The engines utilize crankcase scavenging, lubrication, stratified fuel introduction to prevent raw fuel from escaping with the exhaust gas, use of and ceramic rolling contact bearings. The Thermal Ignition Combustion System (TICS) [1] is used for ignition to enable the engines to operate with a lean mixture and eliminate spark plug erosion.
Technical Paper

Performance of Thin Thermal Barrier Coating on Small Aluminum Block Diesel Engine

1991-02-01
910461
The cylinder of the aluminum engine block without iron sleeve was coated directly with thin thermal barrier coatings of zirconia and chrome oxide. The cylinder head and valve face and the piston crown were also coated. These three engine components were tested individually and together. The fuel consumption performance of this 84 x 70 mm direct injection diesel engine improved 10% with only coated cylinder bore. When the fuel injection timing of the coated cylinder bore engine was retarded by about 2°CA, emissions characteristics were approximately the same level as for the baseline engine with 8% improvement in brake specific fuel consumption compared with the baseline engine. At constant fuel flow rate to the engine, the exhaust and cylinder head temperatures were higher for the insulated bore case. One can summarize the combustion temperature must have been higher and heat release rates were faster in the insulated case.
Technical Paper

Ceramic Seats and Intermetallic Coated Valves in a Natural Gas Fired Engine

1991-04-01
910951
Significant reductions in valve and valve-seat insert wear have been demonstrated with the use of advanced materials for natural gas fueled engines. Total valve and insert wear was reduced by a factor of 10. It was demonstrated that the seat insert wear can be completely eliminated by using ceramic materials. All wear is then limited to the valve seat-face. The direct benefits to users of natural gas engines with advanced technology valve system materials can include reduced operating costs, greater convenience, and improved availability.
Technical Paper

DEVELOPMENT OF A CNG ENGINE

1991-02-01
910881
Impending emissions regulations for diesel engines, specifically exhaust particulate emissions have caused engine manufacturers to once again examine the potential of alternative fuels. Much interest has centered around compressed natural gas (CNG) due to its potential for low particulate and NOx emissions. Natural gas engine development projects have tended toward the use of current gasoline engine technology (stoichiometric mixtures, closed-loop fuel control, exhaust catalysts) or have applied the results of previous research in lean-burn gasoline engines (high-turbulence combustion chambers). These technologies may be inappropriate for foreseeable emissions targets in heavy-duty natural gas engines.
Technical Paper

Conversion of a Diesel Engine for Gaseous Fuel Operation at High Compression Ratio

1991-02-01
910849
A Waukesha VR 220 naturally aspirated Diesel Engine has been modified to operate with a high compression ratio fast-burn spark-ignition combustion system. Since the application of greatest interest is for Combined Heat and Power (CHP), the majority of data have been obtained with the engine operating at full throttle and 1500 rpm. The philosophy of the open chamber combustion system design is described, and this includes a discussion on the selection of the compression ratio. Results are presented for the energy balance and the emissions, for a wide range of air fuel ratios. The experiments have been conducted with natural gas and natural gas/carbon dioxide mixtures (to simulate bio-gas). Comparisons are made with the baseline engine performance data, some of which has been published earlier(1)*.
Technical Paper

Noise and Vibration Refinement of the Ford 3.8 Liter Powertrain

1991-05-01
911073
Continuous improvement of the NVH performance of current production powertrains is a necessary goal of domestic auto makers. In order to maintain a competitive product, it is necessary to re-evaluate proven hardware against demanding NVH performance targets established by the competition. This paper describes an NVH investigation of component modifications to the Ford 3.8 liter powertrain. The hardware investigated includes: ribbed and isolated rocker covers, drop-in roller fulcrums, forged steel and cast iron crankshafts, crankshaft bending damper, full skirt girdle, one piece bearing cap (bearing beam), reduced weight pistons and rods, ribbed sump, and alternate crank pulleys and water pump. At the conclusion of these investigations, a complete powertrain was assembled based on the recommendations generated in this project. The NVH features included in this “quiet” 3.8 liter engine and the rationale behind the decisions are described.
Technical Paper

Vibration Due to Piston Slap and Combustion in Gasoline and Diesel Engines

1991-05-01
911060
The paper describe investigations on the vibration characteristics of a gasoline engine due to piston slap and a diesel engine due to combustion. Engine parameters and vibration data were recorded and time series signals were obtained. The effect of speed, load and other engine parameters on vibration is investigated. Vibration due to piston slap is analysed with reference to major-minor thrust relationship, cylinder to cylinder variation, piston-slap force diagram and vibration-frequency curves. The experimental results suggest that all reciprocating engines would exhibit a complex vibration pattern due to piston slap at harmonic series of discrete frequencies, and the reason for this is analysed. The vibration transmitted by engine structure in response to the in-cylinder pressure development is termed here as ‘Vibration due to Combustion’ and is assessed from the spectrum of the Combustion Pressure curves and their derivatives in terms of time.
Technical Paper

New 150-Hour Test for SAE and MIL Specification Approval of Aircraft Piston-Engine Lubricants

1991-04-01
911000
Aviation piston engine lubricating oils undergo extensive testing prior to their approval for use. During the revision of MIL-L-22851/J-1966 specifications, it was determined that a standardized engine test would be utilized. A Textron-Lycoming TIO-540-J2BD engine was selected as the engine for the 150-hour endurance test. Federal Aviation Regulation Part 33 served as the guideline for development of a standardized test specifically aimed at lubricating oil evaluation. This paper discusses this new 150-hour endurance test for piston engine lubricants used to gain SAE and MIL approval. This new test was conducted at the University of Illinois-Institute of Aviation during 1990.
Technical Paper

The Modernization of Military Piston Engine Aviation Oil Specifications

1991-04-01
910999
In the early 1960's the U.S. Military began to gradually phase-out piston engined aircraft from it's inventory in favor of gas turbine powered aircraft. The emphasis of the aviation industry on the development of the new gas turbine engines and their attendant new synthetic lubricants resulted in the rapid decline of new oil development for aviation piston engines. As a result of this change in focus by the military and commercial engine builders, the maintenance of the MIL-L-6082 and MIL-L-22851 specifications also diminished. After years of decline, commercial interest in these specification products again developed. This paper is an attempt to document the rational used in modernizing these two specifications.
Technical Paper

Flight Test of an Improved Solid Waste Collection System

1991-07-01
911367
An improved human waste collection system was developed in 1985 using a piston and cylinder which collects, compacts, and stores in replaceable volumes human waste including cleaning material. Disposable pads on the piston face seal and clean the cylinder and occlusive air valves. Airflow provides waste entrainment and temporary retention. A series of prototypes including an automatic one-button operation unit was built and ground tested. A manually operated prototype with a number of test features including variable airflow was flown and evaluated on Shuttle flight STS-35. Performance was nominal. An airflow of 45 CFM (1.27 m3 min-1) was found to be adequate. Mean stowage volume of waste and hygienic material per use was 18.7 in3 (306cm3).
Technical Paper

LNG Vehicle Demonstration Projects

1991-08-01
911661
Liquified natural gas (LNG) may provide economic opportunities and be the preferred natural gas vehicle fuel, depending on range, fueling transfer rate requirements and gross vehicle weight (GVW) limitations. Current inexperience with LNG calls for the evaluation of demonstration projects involving LNG vehicle fueling stations and on-board vehicle storage systems.
Technical Paper

Optimized E.F.I. for Natural Gas Fueled Engines

1991-08-01
911650
Increasing emphasis on natural gas as a clean, economical, and abundant fuel, encourages the search for the optimum approach to management of fuel, air and combustion to achieve the best results in power, fuel economy and low exhaust emissions. Electronic injection of fuel directly into the throttle body, intake ports or directly into the cylinder offers important advantages over carburetion or mixing valves. This is particularly true in the case of installations in which the gas supply is available at several atmospheres pressure above maximum intake manifold pressure. The use of choked-flow pulse- width-modulated electronic injectors offers precision control over the engine operating range with a wide variety of options for both stoichiometric and lean bum applications. A complete system utilizing commercially available components together with the application, calibration and engine mapping techniques is described.
Technical Paper

Vickers New PVH Variable Volume Pumps

1991-09-01
911803
This paper outlines the design philosophy and evaluation of the new “H” series variable displacement, medium pressure, open-circuit, axial piston hydraulic pumps. The “H” series is based on previously existing, technically successful, rotating group designs, but has significant design improvements affecting the areas of: Unit Weight Envelope Size Ease of Assembly, Disassembly, Repairability and Modification Alternate Fluid Capabilities The “H” series is a family of naturally aspirated pumps nominally rated at 250 or 275 bar (3625 or 4000 psig), depending on system operating parameters. The geometric displacements of the four units in the series are as follows: 57cc (3.5 cu. in./rev.) 74cc (4.5 cu. in./rev.) 98cc (6.0 cu. in./rev.) 131cc (8.0 cu. in./rev.)
Technical Paper

Use of a Flapper-Nozzle Valve for Axial Piston Pump Control

1991-09-01
911817
A mathematical model of an axial piston pump with a flapper-nozzle valve was developed. The first stage was dynamically stable, and calculated values of first-stage gain and dynamic response agreed well with experimental values. Linearized relations were produced for each component part and were combined to form the total state-variable representation of the model. The open loop system, the combined axial piston pump and flapper-nozzle valve, exhibited dynamic instability. However, when the feedback loop was augmented by the output pressure differential, stability was achieved. From the time responses of the augmented optimal control system, we observed that an increase of input current had little effect on the system response. Doubling the discharge flow rate doubled the overshoot, and an increase in the discharge volume slowed down the system responses. Increasing rotational speed of the pump produced a higher overshoot and a slower response.
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