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Technical Paper

The Microcrystal Structure of Soot Particulates in the Combustion Chamber of Prechamber Type Diesel Engines

1990-09-01
901579
To clarify the microcrystal structure of soot particulate in the combustion chamber, we examined sampling methods which freeze the reaction of sample specimens from the combustion chamber and collected the soot particulates on microgrids. We investigated the microcrystal structure with a high resolution transmission electron microscope. The results were: the particle size distribution and the microcrystal structure of the soot particulates is little different for the cooled freezing method and room temperature sampling. The typical layer plane structure which characterizes graphite carbon is not observed in the exhaust of diesel engines, but some particulates display a somewhat similar layer plane structure. The structure of soot particulate is a turbostratic structure as the electron diffraction patterns show polycrystals. The soot particulates in the combustion chamber is similar to exhaust soot particulates.
Technical Paper

The Interaction of Fuel Spray and Air Swirl in a Diesel Combustion Chamber with Nitrogen Gas Circulation

1990-09-01
901580
A single cylinder engine was modified into a photographic test equipment. A new method-filling and cycling nitrogen gas to the cylinder-was used to keep the fuel in combustion chamber out of firing. Tests were carried out at three fuel injection pressure and three gas swirl rates. The chamber swirl rate was measured by hot-wire anemometer, the fuel spray pictures were taken by a high speed camera. By reference to the experimental results, the spray bevaviers in swiling flow were discussed both in the main injection and the end injection periods.
Technical Paper

LDA Measurements of Steady and Unsteady Flow Through the Induction System of a Heavy Duty Diesel Engine

1990-09-01
901576
Abstract LDA technique was used to investigate valve exit flow and in-cylinder flow generated by a directed intake port of a heavy duty Diesel engine under steady and unsteady conditions. The results obtained under both steady and unsteady show the flow patterns is very sensitive to the valve lift with this type of intake port. At small valve lift, flow profile around the valve periphery is relatively uniform, the corresponding in-cylinder flow is characteristic of double vortex. With valve lift increasing, the separating region appears near the valve seat in part of the valve periphery, therefore the flow pattern begins to depend on the position around the valve periphery. As a result, the valve exit flow is almost along the elongation of intake port at the maximum lift, the corresponding in-cylinder flow behaves as a solid body of rotation. The motion of valve seems to have little effects on the valve exit flow pattern.
Technical Paper

Optimum Parameters of Spool Valve Feedback to Minimize Surge Pressure

1990-09-01
901620
This paper deals with the optimum design of the stiffness and damping coefficients of the spring and dashpot used in the feedback loop of a hydraulic servovalve, to attain minimum surge pressure during the stop and reverse operations. The proportional element of the feedback represented by the lever ratio is predefined. The state space equations are derived and two objective functions based on relative and absolute pressure rise are minimized. The applied minimization technique is based on a modified gradient method.The results show a better performance and less shocks due to the optimum design of that dynamic parameters.
Technical Paper

Model to Predict Hydraulic Pump Requirements for an Off-Road Vehicle

1990-09-01
901622
This paper describes and discusses a computer model that can be used to predict the hydraulic pump requirements of an excavator necessary to meet the specified productivity levels for a given set of design conditions. The model predicts the hydraulic cylinder flow rates, pressures, and power necessary to sustain a given work cycle. The study compares the results from a simulation of the excavator with actual test data obtained from a test vehicle taken during a typical work cycle.
Technical Paper

Dynamic Properties of Single-Spool and Two-Spool Two-Stage Servovalves

1990-09-01
901621
A mathematical model of a dynamically stable flapper-nozzle pilot valve has been used in conjunction with the second stage of a flow control valve that comprises a single spool. The model has been used to calculate the valve gain and the dynamic response of the component parts. Real-time and frequency response results have been compared with those when using a two-spool version of the same type, each of the two spools being identical to the spool used in the single-spool version. It is shown that the dynamic response is improved significantly when the single-spool replaces the two-spool version.
Technical Paper

Using the Modified Lambda Ratio to Advance Bearing and Gear Performance

1990-09-01
901625
The Lambda ratio (λ) has been widely used as an indicator of the lubricant regime in an operating contact within either bearings or gear sets. λ is determined when the lubricant film thickness (h) within the contact is divided by the composite roughness (σ) of the two surfaces forming the contact. Recommendations of an appropriate film thickness equation and surface roughness values are provided to calculate modified lambda ratio (λm) that better represents the lubricant regime within bearings or gears. Bearing performance, especially as related to fatigue life, has increased significantly in recent years. This is primarily due to cleaner steels but includes the influence of better surface finishes and bearing internal geometries. With λm, and an understanding of how contact fatigue damage mode relates to a wide range of λm values, it may be possible to transfer the advances in bearing performance to other system components such as gears.
Technical Paper

Computer Simulation of Semi-Trailer Haul Truck Roll-Over Dynamics

1990-09-01
901623
Haul trucks, like other articulated heavy vehicles with high centers of gravity, have a propensity to roll over in certain situations. Variable soil conditions, high winds, significant ground slope, and shifting loads contribute to a high risk of roll over for haul trucks. The likelihood of such an event is further increased during dumping operations when the center of gravity of a vehicle is raised higher than usual. This paper develops a mathematical model of the dynamics of haul truck roll over phenomena and establishes critical performance parameters, particularly during a raised bed dumping operation.
Technical Paper

Fracture and Fatigue of High Hardness Bearing Steels Under Low Tensile Stresses

1990-09-01
901628
Tensile stresses in bearing components, particularly in rings, may be caused by conditions of manufacturing, mounting, or operation. During bearing operation, when a condition to cause tension is present, the stress cycle varies rapidly between compression when the Hertz contact stress is applied and tension when the contact stress has passed. Analysis of 14 bearing failures indicates that tensile stresses as low as 140 to 200 MPa (20 to 30 ksi) are sufficient to cause cracks to grow in fatigue. When tensile stresses drive the crack in a radial direction, fracture rather than spalling will occur.
Technical Paper

The Influence of Bearing Run-In on Lambda Calculations

1990-09-01
901626
This paper examines surface roughness effects and the inaccuracy introduced by changes in roughness resulting from normal run-in. While factors such as the ‘Oil Film Thickness to Composite Surface Roughness ratio’, Lambda, are being used, their reliability is dependent on the accuracy of the input data. Studies were conducted on cylindrical roller bearings (40 mm bore) at two calculated Lambda levels, 1.5 and 0.04, to evaluate changes in surface texture during short running time increments. The conclusion of the study offers recommendations for improving the methods used to predict bearing fatigue life.
Technical Paper

The Design of High Speed Grease Lubricated Spindles for Machine Tool Production Equipment

1990-09-01
901631
The use of high quality grease in conjunction with precision spindle bearings permits high rotational speeds. This paper will address the parameters which must be met to achieve such operating speeds: grease type, grease quantity, run-in procedure, maximum operating temperatures, overall bearing arrangement, and abutment dimensions. Guidelines will also be provided giving realistically attainable speeds.
Technical Paper

Performance of Ceramic Bearings in High Speed Turbine Application

1990-09-01
901629
High speed precision ball bearings, like those used in machine tool spindles, can have serious problems associated with spin or gyroscopic moment of the rolling elements. The use of low density, silicon nitride ceramic rolling elements reduces these problems. This report presents performance test results of bearings with silicon nitride balls, and steel balls, in a high speed turbine application, using oil jet, and oil mist lubrication methods.
Technical Paper

The Development of an Automated L-42 Test Stand to Evaluate the Anti-Score Properties of Gear Lubricants

1990-09-01
901634
Abstract This paper describes the development of a computer-based control and data acquisition system for the L-42 Performance Test for Evaluating the Load Carrying Capacity of Automotive Gear Oils Under Conditions of High Speed Shock Loading. The L-42 test is a procedure that is used in determining the anti-score properties of gear lubricants and is one of the required tests for API GL-5 and U.S. Military MIL-L-2105D designations. Data will be presented to compare the computer system with a human operator.
Technical Paper

Effect of Surface Roughness of Impeller Channel in Centrifugal Compressor on Its Performance

1990-09-01
901632
Abstract Influences of the surface roughness of a centrifugal compressor on its performance were examined. The experiments were conducted by varying the surface roughness within the impeller channel as well as Reynolds number. The surface roughness of the pressure, suction and hub walls were varied by means of sticking the sand of a definite grain size onto the walls, while that of the shroud wall was roughened by machining it with a lathe. Reynolds number was varied by changing air pressure in a closed circuit of duct containing the compressor. Efficiency of the compressor decreased gradually as the surface roughness was increased, and the reduction of the efficiency amounted to about five percent when the relative roughness was increased from 3.2X10-3 to 14.0X10-3. Shifting of the critical Reynolds number was not affected so much through the variation of the roughness.
Technical Paper

Hydraulic Pump Performance-A Basis for Fluid Viscosity Classification

1990-09-01
901633
A series of polymer-containing fluids was evaluated in a modified ASTM D 2882 pump loop to determine both permanent viscosity loss and flow rate as a function of test time. Flow rate did not change over the course of the test. It correlated equally well with either new oil high-shear-rate viscosity or used oil kinematic viscosity. The current ISO viscosity classification system provides no means to differentiate the levels of performance observed. It is proposed that a new, more meaningful viscosity classification system be adopted for hydraulic fluids. This system should maintain continuity with the current system, but should account for permanent viscosity loss of polymer-containing fluids. Measured low temperature properties should also be part of any new viscosity classification.
Technical Paper

A Study of an Outline of Combustion for a Direct Injection Stratified-Charge Rotary Engine

1990-09-01
901600
In order to investigate the combustion process of a Direct Injection Stratified Charge Rotary Engine (DISC-RE), a statical model combustion chamber was made and 2 stroke diesel engine was used as a Rapid Compression Machine (RCM) for the purpose of fundamental study of some characteristics of DISC-RE operation. This paper present some data on air flow in the model combustion chamber, some films of fuel injection spray, combustion flame propagation, using high speed camera, and test datas of combustion characteristics. From these films, it was clarified what happen inside of the rotor pocket. Generally to take a photograph inside of combustion chamber is very difficult using actual engine, because the combustion chamber moves toward rotational direction, so, using the static combustion chamber is very effective in the study of the fundamental process.
Technical Paper

A Visualization of Spray of Gasoline Injection

1990-09-01
901606
The good relationship between the spray condition in the intake manifold and the combustion characteristics is required. Firstly by this report it was tried the visualization and observation of spray of gasoline injection. It was mainly photographed when injection just began and the spray impinged on a intake valve. The photographs of fuel spray were taken by a image converter type high speed camera. The characteristics of the fuel spray injected in early injection period is influenced with fuel pressure and flow rate of fuel. The atomizing phenomenon of tip fuel of spray could be visualized. The atomizing process in early injection period are differ from that in stady-state spray. And the picture of spray at impingement on the intake valve was shown too. The atomizing condition on the valve surface could be observed visually.
Technical Paper

Exploratory Development of Low NOx and High Combustion Load Combustor

1990-09-01
901604
A low emission and high combustion load combustor is developed. The combustor reduces both NOx and unburnt fractions using rich-lean staged combustion. NOx is suppressed by fuel-rich combustion in the primary combustion chamber. Unburnt fraction is oxidized by the transition from rich to lean combustion. To avoid NOx formation, residence time nearby stoichiometry is shortened. NOx is less than 24.8 ppm(16 % O2 equivalence) or 2.26 g/kg throughout the experiments. Combustion efficiency is high regardless of the wide operating range. Specific combustion load is up to 33.6 MW/m3 without excessive NOx emission under atmospheric air condition.
Technical Paper

The Development of an Electronic Governor for the Power Generator System

1990-09-01
901603
Abstract An electronically controlled governor was developed for a generator equipped with a medium size gasoline engine. Among the available control methods, LQ and PID were considered since they are high practical and require less computations. Based on a numerical simulation, the PID control method was chosen for the governor system because of its simplicity in tuning the control parameters. To ensure the reliability of the governor system for volume production, the system has been tested with regard to the influence of environmental changes, and the deviation of engine performance and its deterioration. Under all of the above severity tests, the governor system has been confirmed to provide an excellent performance and stability in the power output far exceeding the ISO-A1 standards.
Technical Paper

Numerical Study for Free-Stream Turbulence Effects on a Single Droplet Vaporization

1990-09-01
901607
This investigation reports on the study of the ambient turbulent effects on the droplet vaporization in the fuel spray combustion. For tractability, this discussion considers a single droplet in an infinite turbulent flow. In this numerical study, the low-Reynolds-number version of k- ε turbulence model was used to represent the turbulence effects. The set of two-dimensional conservation equations which describe the transport phenomena in turbulent flow using the mean flow quantities including the droplet internal laminar motion, are solved numerically with the finite difference procedure of Patankar(SIMPLER). The evaluation of the computational model is provided by two limiting cases: turbulent flow over the solid sphere and the laminar flow over a liquid drop. The results show that the turbulence effects are noticeable for the vaporization at high turbulence intensity (10-50%) which is encountered in a typical spray.
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