Four-stroke Cycle Research Articles

Measuring Methods of Swirl in a Four-Stroke Cycle Engine

Measuring Methods of Swirl in a Four-Stroke Cycle Engine

Navier-Stokes Solutions of the Flowfield in an Internal Combustion Engine

The flowfield inside the cylinder of a reciprocating internal combustion engine is calculated by solving the complete Navier--Stokes equations by use of a time-dependent finite-difference technique. The main problem is to solve these equations, including multicomponent diffusion and finite-rate chemical reactions (for H-C-O-N chemistry), and obtain a complete solution for the velocity, pressure, temperature, and chemical composition of the flowfield throughout the four-stroke cycle of a piston-cylinder arrangement. At present, this total problem is a horrendous task, and its exact numerical solution will most likely be an evolutionary process over a long period. The flowfield between the top of the cylinder and the face of the piston is computed as a function of space and time as the piston moves through the conventional 4-stroke cycle, with the inlet and exhaust valves opening and closing appropriately. Combustion is not considered in detail. Solutions are obtained for 2-D geometry (infinite aspect ratio engine) and low Reynolds number.

Harry Ralph Ricardo, 26 January 1885 - 18 May 1974

Harry Ralph Ricardo was born at a time when mechanical engineering was developing from a craft into a technology. The steam engine, the prime mover of the day, was only beginning to be threatened by the steam turbine, and the internal combustion engine was in its infancy. This engine was to become his lifelong interest. He brought to it not only the skill of an outstanding designer, which was soundly based on personal craftsmanship, but also a long lasting curiosity and originality in engineering research. His contributions to the understanding of the ignition, combustion and detonation processes in spark- ignition and diesel engines were of the greatest importance; he gave the world the concept of the octane number as a means of rating the tendency of fuels to detonate. His application of this knowledge and his ability in design is seen not only in his early engines, for example in the two-stroke cycle Dolphin and the four-stroke cycle engine for the tanks in 1917, but in his light high speed diesel engines, the prime mover of the modern truck, and the sleeve valve aero-engines which were the last and best of the large British piston engines for aircraft.

A simulation model including intake and exhaust systems for a single cylinder four-stroke cycle spark ignition engine

A comprehensive simulation model is presented for a spark ignition engine including intake and exhaust systems. The power cycle simulation requires only one empirical factor to correct for turbulent speed of the flame front in order to complete the cycle calculation including NO. The exhaust pipe gas dynamics include chemical reactions along path lines. Calculations are presented which compare well with experimental results. The model predictions compare favourably with previous work.

Application of Exhaust Gas Ejector to Engine Cooling

Although exhaust gas ejectors have been little utilized in engines, their application is worthy of consideration because of their basic simplicity. An application for engine cooling has been investigated using a four-stroke cycle Diesel engine and an air model. Following results are obtained : (1) The cooling air for an engine may be supplied only from the ejector which is well designed. Fuel consumption can be decreased by using the ejector together with a fan for engine cooling. (2) Flow rate of air induced into the ejector becomes larger with an increase in engine load. However, flow rate per unit horse power becomes smaller. (3) Flow rate of secondary fluid for the ejector, whose driving fluid is intermittently supplied, is much larger than that for the ejector of steady state, because the inertia effect of fluid in the ejector is a useful factor to draw the secondary fluid.

Developing a High-Powered Diesel Engine for Railway Traction

The paper deals, first of all, with the design criteria for the new Sulzer four-stroke locomotive engine being developed by the author’s firm and how some of these derived from two experimental engines which, although identical in construction, were operated on the four-stroke and two-stroke cycle, respectively. Field research as well as elaborate bench test facilities have been provided to perfect the new locomotive diesel engine. The work that has recently been carried out on some of the more important components of this is described. Some mention is made of the problems encountered with combustion and pressure charging at the high specific loads to which this engine type is being taken.

Relation between Inlet-Valve Closing Time and Volumetric Efficiency of Four-Stroke Cycle Engine

Relation between Inlet-Valve Closing Time and Volumetric Efficiency of Four-Stroke Cycle Engine

Paper 4: High-Output Medium-Speed Diesel Engine Air and Exhaust System Flow Losses

This paper gives the results of air-flow tests through two-stroke cycle and four-stroke cycle diesel engine cylinder heads and ports on steady-flow low-pressure air flow rigs.An analysis is made of the pressure drop through a diesel engine cylinder head inlet port system which shows the effect of the various parts of the system on flow loss. This also includes the effects of valve lift, valve seat angle, and valve shape on isentropic area.A comparison is made between tandem and Siamese porting on a four-stroke cycle engine cylinder head. The results of tests on uniflow scavenged two-stroke cycle inlet ports and exhaust valves are also included.

The Origin of the Four-Stroke Cycle

In an earlier paper1 on the genesis of a gas engine built by Nicolaus August Otto in 1876, I tried to follow the course of Otto's thought and to explain the success of his engine. Otto attributed his success to what he called the stratified charge, a special way he devised of mixing the fuel and air in his cylinder. His theory was wrong, but guided by this theory he built a remarkably successful and influential engine, the earliest recognizable ancestor of today's automobile engine. I should now like to argue that Otto's engine of 1876 was the first to use the four-stroke cycle. The four-stroke process, which first made it practical for a gas engine to use compression, was a key idea in the evolution of the internal-combustion engine, and the question of priority in its use was once a matter of critical importance: fortunes were at stake, or at least the owners of the patents involved thought so. Now the patents and the inventors are dead, and all that is at stake is credit for the invention. But the historical literature on early engines still reflects the confusion and disagreement of the old patent litigation, and perhaps it would be a service to review and evaluate the competing claims now that no money is at stake. Four men are said to have used the four-stroke cycle before 1876. All of these claims arose in the course of patent litigation from ten to forty years after the time of the invention, and they all still appear from time to time in the literature. None is supported by substantial contemporary evidence. In 1862, the French engineer Beau de Rochas expressed the idea of the four-stroke cycle, but there is no evidence that he built an engine of this type or had any influence on anybody who did. The Munich watchmaker Reithmann and the famous Vien-

Nominated Lecture: Performance and Operation of Spark-Ignited Gas Engines

The author discusses the application of spark-ignited gas engines to such services as gas transmission, gas gathering and chemical processing with integral angle engine-compressors as well as directly coupled units. The author also treats such performance aspects of two-and four-stroke cycle spark-ignited gas engines as: fuel consumption, cyclic dispersion in combustion, accommodation of ambient temperature variation, load variation and altitude. There is an extended discussion of pulse and constant pressure turbocharger characteristics and their influence on engine performance. Important hardware considerations are given, such as design of valves and valve inserts, cylinder heads and pistons.

The Silent Otto

The story of the gas engine that I am calling the Silent Otto-the first engine to operate on the four-stroke cycle, and the first to achieve compression of the charge within the working cylinder-has been told before.1 But I should like to go over it again in order to consider a question that still seems significant to a historian interested in technology and culture: Why was this engine suddenly successful after seventyfive years of rather fumbling efforts to develop an internal-combustion engine? Nicolaus August Otto (1832-91) built the first Silent Otto in 1876 in the Gasmotorenfabrik Deutz near Cologne (Fig. 1). In its original form the engine had one horizontal cylinder, drew in a charge of illuminating gas and air through a slide valve, compressed it within the cylinder with a compression ratio of about 2 :1, and ignited it with a flame. The engine developed about three horsepower at a speed of 180 revolutions per minute, had a thermal efficiency of about 14 per cent (two or three times as good as a comparable steam engine), and weighed about a ton per horsepower.2 They called it silent not because you could not hear it when it was running-you certainly could -but because it ran much more smoothly and quietly than its immediate predecessor, the Otto and Langen, is a one-cylinder atmospheric gas

Paper 5: The Hillman 875 cm3 Engine

The paper covers the constructional considerations, design and development of the engine to be installed in a rear-engined vehicle. The need for minimum weight and size coupled with adequate power output resulted in the decision to use light alloy diecastings wherever possible. The various methods of diecasting are considered and the methods used for the various components are discussed with the reasons for their use. Problems with cast-in cylinder liners, machining considerations and the implications of laying the engine at an angle in the car are covered. With regard to performance, several factors are discussed: the reasons for adopting the four-stroke cycle, four cylinders, water cooling; determination of capacity from power required data; the use of a single overhead camshaft; combustion chamber shape and compression ratio; port shapes and determination from air flow research. Then follow the various stages of development work and endurance testing.

The Influence of Volume and Period of Gas-Sampling upon the Accuracy of the Measurement of Scavenging Efficiency

As for the measurement of scavenging efficiency by means of chemical analysis of sampled gas, here will be discussed the proper volume and period of gas-sampling. In this investigation, two valves were specially installed on the cylinder head of a two-stroke cycle engine, and gases were sampled through the valves by operating this engine continuously as of four-stroke cycle. The following experimental results were obtained. 1. The volume of sampled compression gas should be more than 20 percent of the effective cylinder volume. 2. If the volume cannot be over 20 percent, the gas should be extracted near the top dead center. 3. The expansion gas should be extracted in a small volume in the period just before scavenging. 4. It was found that the relative charge amounts to 0.65 to 0.75. The author would like to express his sincere appreciation to Dr. F. Nagao, professor of Mechanical Engineering, Kyoto University, for his valuable suggestions and guidances throughout this investigation.

A Method of Measuring Scavenging Efficiency and its Application

The paper deals with a new method of measuring the scavenging efficiency in a loop-scavenged two-stroke cycle diesel engine and its assessment on a test engine. The two valves installed on the cylinder head are to be timely opened by the overhead cam shaft driven at half an engine speed, and to extract the gases of the same cycle before and after the scavenging, giving the possibility of determining either the scavenging efficiency when the engine is operated as fourstroke cycle, or the trapping efficiency when done as two-stroke cycle. The experments employing this apparatus revealed a great deal of valuable information for improving the scavenging system, and also indicated that the scavenging efficiency in a well-designed cylinder could reach over 90% at a delivery ratio of 1.3∼1.4, which does not seem to be inferior to that obtained in the uniflow scavenged system.

The Influence of Volume and Period of Gas-Sampling upon the Accuracy of the Measurement of Scavenging Efficiency

Two valves were specially installed on the cylinder head of an engine of two-stroke cycle, and gases were sampled through these valves, while this engine was operated continuously as of four-stroke cycle for this investigation. The result of this experiment are as follows : 1. The volume of sampled compression gas must amount to more than 20 percent of effective cylinder volume. 1'. If the volume cannot be over 20%, the sampling must take place near the top dead center. 2. The expansion gas must be extracted at the period just before scavenging, and its volume has to be small. 3. In addition, it was found that the relative charge equals 0.65 to 0.75. The author would like to express his sincere thanks to Dr.F. Nagao, professor of Mechanical Engineering, Kyoto University, for his valuable suggestions and guidances throughout this investigation.

On the Ineffective Lift of Poppet Valves in Internal Combustion Engines

To examine the effects of various factors on the ineffective angle or the corresponding valve lift, the authors carried out some experiments with two model pieces of piston head and a regular one in an air-cooled, single cylinder, four-stroke cycle engine. A summary of the results is as follows; a) If the ineffective valve lift be used instead of the ineffective angle, it is not necessary at all to consider the values of tappet clearance and the kinds of valve lift curve. b) It is possible to estimate the ineffective lift not only by the measurement of air flow, but also by the analysis of pressure diagrams. c) The ineffective lift increases with the engine speed, but decreases as the pressure difference between suction and exhaust ports increases. d) The minimum value of the ineffective lift remains constant irrespective of the engine speed and the pressure difference.

Dynamic Strength of Single Cylinder Marine Diesel Engine Crank Shaft

In these few years the systematic studies have made clear the stress distributions on diesel engine crank shafts under static load conditions. However very little is known about the stress conditions in operating engines, mainly because of difficulties of measurment.Authors carried out the dynamic stress measurments in a four-stroke cycle marine diesel engine during operating condition. The stresses were measured by means of wire and foil type electric resistance strain gauges. Electric connections between gauges and recorder were made through sliprings. Measured points were crank pin corner, web, connecting rod and crank pin bolt. Stress calculations by conventional methods were made on the basis of cylinder gas pressure and inertia forces of moving parts, taking into account of static test results. Good agreement was observed between calculated and measured stresses.Distance between support points of journal bearings seems to be constant under operating conditions, and no additional assumption was necessary.It is concluded that dynamic stresses of single-throw diesel engine crank shaft can be calculated with good accuracy by conventional methods already known.

A Method for Calculating the Energy Available in the Exhaust Gas at the Inlet End of an Exhaust Pipe of a Two- or Four-Stroke Cycle Engine

The Nature of the flow in the exhaust pipe of a turbo-charged two- or four-stroke cycle engine is in general so complex that practical tests on running machinery are necessary to compare the merits of one exhaust system with another. The analysis of the results of these tests is rendered somewhat difficult by the lack of reliable methods for measuring accurately the transient temperatures in the exhaust pipe. Indicator diagrams have therefore to be used in conjunction with empirical methods for computing the exhaust energy, these methods being associated with the measured exhaust pyrometer temperature. In calculating the theoretical possibilities of different exhaust pipe configurations for four-stroke cycle engines Jenny has suggested that the total energy was the sum of the internal and kinetic energies of the gas entering the pipe. In the present treatment it is suggested that a better criterion is the enthalpy available if the gas expands isentropically from stagnation conditions to atmospheric pressure, the justification being that this would be the energy utilised in the turbine.

Nikolaus August Otto, 1832–1891

AMONG the names of the hundreds of inventors through whose individual efforts the internal combustion engine has reached its present state of efficiency, that of Nikolaus August Otto will always be associated with the invention of the atmospheric gas engine and with the introduction of the four-stroke or Otto cycle for gas engines, which formed the subject of his German patent of Aug. 4, 1877. Since then, the Otto cycle has been applied to internal combustion engines to an extent little dreamt of by the inventor, and it has proved of such fundamental importance that it may almost be compared with the invention of the separate condenser for the steam engine by Watt about a hundred years earlier. There are, it is true, many internal combustion engines running on the two-stroke cycle, but the vast majority of the millions of engines found in power-houses, factories, ships, motor cars, and aeroplanes to-day work on the four-stroke cycle.

Heavy-Oil Engines

THE James Forrest Lecture for 1925 was delivered by Capt. H. Riall Sankey before the Institution of Civil Engineers on May 5, and dealt with some outstanding questions relating to large engines of the self-ignition type. The discussion was limited to engines working either on the two- or the four-stroke cycle, and compressing air to a temperature sufficient for the self-ignition of an injected fuel of not less than 0.82 specific gravity.