Alternative eco-friendly lubes for clean two-stroke engines

High performance lubricant for clean two-stroke engines operating with ethanol-containing fuels was developed by the selection of the optimal synthetic esters base oil followed by an improvement of the additives composition. The developed lubricant has very good wear resistance, ashless and low carbon soot deposit formation. The lubricant has low toxicity for aqueous organisms (algae and Daphnia Magna) and high biodegradability. Good wear resistance and low friction were achieved because of formation of a protective transparent friction lacquer on the contact surface due to tribochemical reactions.     

Behavior of piston rings passing over cylinder ports in two-stroke cycle engines

In two-stroke cycle engines, the piston and piston ring slide over not only the cylinder wall but also the cylinder ports. This study investigates whether piston rings project and get caught in the cylinder ports. We installed strain gauges, on the bottom sides of piston rings, over the intake and exhaust ports, and plotted the variation of strain per cycle, while running the engine. By examining the variation in strain on the bottom of the piston ring, we clarified that our piston ring indeed became momentarily caught in the cylinder ports.     

Some experimental studies of lubricants in a two-stroke methanol engine

A two-stroke cycle scooter engine modified to operate on methanol fuel has been tested. Castor and synthetic oil formulations were identified as potential lubricants. A formulation based on polypropylene glycol (PPG) has demonstrated excellent miscibility in methanol fuel. It also performed well in engine tests, especially with reference to piston tightening and deposit forming tendencies.     

Design approach for single piston hydraulic free piston diesel engines

The operating characteristics of a single piston hydraulic free piston diesel engine differ significantly from conventional diesel engines and this provides a theoretical basis for controlling and optimizing the design of the engine. The design of the proposed engine intended as a power supply for a hydraulic propulsion vehicle is presented. An engine performance forecast model was generated in AMESim. The performance of the prototype engine is predicted and the predictive results are verified with experiments. The particular features of the engine are discussed. The dynamic characteristics of the prototype engine are analyzed and the results indicate the rationality and feasibility of the engine design parameters. The features of the controllable working frequency and the intermittence output flows are provided. The flow capacity characteristics of the hydraulic valves on the prototype engine are offered. The methods for starting and the operation after misfire are presented.     

Design approach for single piston hydraulic free piston diesel engines

The operating characteristics of a single piston hydraulic free piston diesel engine differ significantly from conventional diesel engines and this provides a theoretical basis for controlling and optimizing the design of the engine. The design of the proposed engine intended as a power supply for a hydraulic propulsion vehicle is presented. An engine performance forecast model was generated in AMESim. The performance of the prototype engine is predicted and the predictive results are verified with experiments. The particular features of the engine are discussed. The dynamic characteristics of the prototype engine are analyzed and the results indicate the rationality and feasibility of the engine design parameters. The features of the controllable working frequency and the intermittence output flows are provided. The flow capacity characteristics of the hydraulic valves on the prototype engine are offered. The methods for starting and the operation after misfire are presented.     

Some comments on models for field enhancement

To estimate the apex field-enhancement factor gamma(a)associated with a pointed protrusion on a flat planar surface, the simple physical models of a 'floating sphere at emitter-plane potential' and a 'hemisphere on a post' are often discussed. The corresponding mathematical expressions have the form: gamma(a)=m+h/rho, where rho is the sphere or hemisphere radius, h is its 'height above the emitter plane', and m is a constant variously taken as 0, 2 or 3. Recent numerical simulations for the 'hemisphere on a post' model, reported elsewhere by two of us (CJE and GV) and by Kokkaris, Modinos and Xanthakis, have shown that all of these simple formulae significantly overpredict gamma(a) if h/rho is large. This article first reexamines the basis of these simple formulae and confirms that they are less secure than is sometimes thought. The formulae reported elsewhere as fits to the numerical results are then quoted and compared with the simple formulae, and with the known exact analytical result for the 'hemi-ellipsoid on a plane' model. Discrepancies can be rationalised. Some general conclusions are drawn.     

Some experience with ferrography in monitoring the condition of aircraft engines

Experience of the use of ferrography in conjunction with spectrographic oil analysis procedures in the condition monitoring of aircraft engines is reported. Some advantages of ferrography are outlined and the benefits of using both techniques are discussed.     

The ``limits of lubrication' concept applied to thepiston ring zone lubrication of modern engines

The ``limits of lubrication' concept is used to consider thephysical and chemical results obtained from bore wall and pistonring zone sampling for the CAT 3406 B and Petter AA-1 dieselengines. It is shown that the mass of lubricant in the pistonring zone has declined substantially and also that the residencetime of that lubricant has increased by an order of magnitude,due to changes in piston ring pack design. The composition of thelubricant also changes as it moves up through the ring pack. Theinfluence of surface finish is discussed and it is shown that the``ideal' surface for lubricant transport control is not defined,moreover, that the ``ideal' initial manufactured surface mayneed to be defined in terms of the ``ideal' running surfaceobtained by wear. The lubricant regime in the piston ringzone/bore interface is also discussed and shown to be closest toboundary lubrication.     

Some considerations concerning lubrication in high‐performance internal combustion engines

The increasing rotational speeds and the weight reduction of high‐performance internal combustion engines are accompanied by problems of lubrication, heat transfer, and vibration that are mostly negligible in medium‐ and low‐performance engines. To deal with such phenomena under demanding operating conditions necessitates a specific design. The dynamics of the power system between crankshaft and related sub‐components, e. g., bending and torsional vibrations of the connecting rod, ovalisation of the head and eye of the connecting rod, and vibrations of thin cylinder liners, are critical for the lubrication system in general, and for oil film pressure fields in particular. In some cases, no information on these features has existed until now, so no quantification of the variables involved has been possible. Over the last few years a systematic investigation has been performed to take into account the critical points and their fundamental importance in the design of such engines. The present paper considers some of the phenomena related to lubrication in high‐performance engines. The need is highlighted for further investigations using computational and experimental methodologies.     

Advanced lubricants for heat engines

An advanced liquid lubricant for heat engines has been developed and tested successfully in a prototype engine. The lubricant possesses superior oxidation stability and high temperature stability. With the advent of new engine designs, stability should be measured in terms of both the temperature and the time for which the lubricant is subjected to it. This lubricant is designed to provide friction and wear protection for three to five minutes at 425°C (800°F) at the ring zone and maintains stability at an oil sump temperature of 171°C. The lubricant has been evaluated by the Cummins Engine Company. Out of a field of several dozen lubricants, six lubricants were selected for a prototype 200 h endurance tests. The NIST lubricant was one of the two lubricants that successfully finished the endurance testing. This paper provides an overview of the key lubricant design considerations, including oxidation and thermal stability, volatility, and deposit control, the prototype engine test conditions and the results.     

A new approach for assessing the cleanliness characteristics of two-stroke engine oils

The frictional characteristics of two-stroke engine oils have been studied in a high speed disc machine. Engine cleanliness index, calculated on the basis of the average coefficient of friction at six different temperatures, was found to correlate well with engine cleanliness characteristics.     

A new method for assessing the lubricating ability of two-stroke engine oil

Evaluating the lubricating ability of two-stroke engine oils in laboratory test machines is difficult because of the lack of correlation with the engine test results. A high speed disc machine has proved its value as an effective screening method for this purpose: this paper describes the technique and its correlation with engine performance     

Some simple elastohydrodynamic lubrication deformation models

By assuming that the elastic deformation taking place in an elastohydrodynamic lubrication (EHL) contact can be described by a polynomial function, the corresponding pressure function can be determined by solving a linear integral equation. Some EHL models derived from applying this approach are described and briefly discussed.     

Some fast mono multi-processor configurations for a single multi-parameter multichannel analyzer

Some single, multi-parameter multichannel analyzer configurations are reported. The analyzer is especially suitable for time and/or pulse-height spectra measurements from high counting rate sources. The various analyzer configurations arise from the need to reach a compromise between measurement requirements and analyzer speed and cost. The main element of each configuration is the Analog Devices 21060, a fast and flexible digital signal processor (DSP). The DSP takes part in the control of data acquisition, and updates spectra in real time without taking Host computing and Input/Output resources, so shortening the dead time of the whole spectrometric system. The instrumentation peculiar characteristics are as follows: (1) the true acquisition phase is an autonomous one; (2) the maximum count capacity is equal to 2³²−1 counts/channel; (3) the conversion gain is programmable. The maximum achievable value is 2¹⁰⁰; (4) spectra may be transferred from the instrumentation to the Host computer either at the measurement end or in the course of the measurement to display data during the accumulation process; (5) the maximum acquisition rate depends on the configuration. The monoprocessor configuration is able to acquire data and to update spectra without interruption at 10 MHz rate. Multi-bus configuration is recommended in the case that high conversion gain and/or fast multichannel structures are dealt with. Multi-bus configuration is needed if the spectrum must be transferred to the Host in the course of the measurement without interrupting the acquisition. (6) The instrumentation makes use of commercially available components. Their high integration and speed have led to powerful, compact, flexible, and modular instrumentation.     

渐开线齿轮单齿啮合区的齿形系数

本文对范成法加工的渐开线圆柱齿轮，在单对齿啮合受载时，按轮齿危险截面形状（分平截面法和折截面法）、加工方法（分齿条刀类和插齿刀类），给出四组齿形系数的计算式。此式既可计算标准（或非标准）齿轮齿顶受载时的齿形系数，又可计算标准（或非标准）齿轮齿廓任意点受载时的齿形系数，还可计算具有非标准齿廓参数的渐开线齿轮任意点受载的齿形系数，为精确计算轮齿齿根弯曲强度提供了依据。     

Uncooled choked-flow turbine for limited-power turbine engines

The gas dynamics of a choked-flow turbine is considered. An uncooled choked-flow turbine may be used in a limited-power gas-turbine engine without marked impairment of its mass and size and with considerable decrease in cost.     

A knowledge-based diagnosis system for automobile engines

A newly-developed knowledge-based diagnosis system for automobile engines is described in this paper. The system is based on the Hierarchical Diagnosis Principle, suggested by the authors. According to this principle, a complex diagnostic task can be divided into several simple ones and then solved step-by-step. Both deep and shallow knowledge are used in the system, and organised in two different knowledge bases:

Thrust stand for low-thrust liquid pulsed rocket engines

A thrust stand is developed for measuring the pulsed thrust generated by low-thrust liquid pulsed rocket engines. It mainly consists of a thrust dynamometer, a base frame, a connecting frame, and a data acquisition and processing system. The thrust dynamometer assembled with shear mode piezoelectric quartz sensors is developed as the core component of the thrust stand. It adopts integral shell structure. The sensors are inserted into unique double-elastic-half-ring grooves with an interference fit. The thrust is transferred to the sensors by means of static friction forces of fitting surfaces. The sensors could produce an amount of charges which are proportional to the thrust to be measured. The thrust stand is calibrated both statically and dynamically. The in situ static calibration is performed using a standard force sensor. The dynamic calibration is carried out using pendulum-typed steel ball impact technique. Typical thrust pulse is simulated by a trapezoidal impulse force. The results show that the thrust stand has a sensitivity of 25.832 mV/N, a linearity error of 0.24% FSO, and a repeatability error of 0.23% FSO. The first natural frequency of the thrust stand is 1245 Hz. The thrust stand can accurately measure thrust waveform of each firing, which is used for fine control of on-orbit vehicles in the thrust range of 5-20 N with pulse frequency of 50 Hz.