Yutaro Wakuri

Piston ring friction in internal combustion engines

Abstract The tribological phenomena of the sliding surfaces between piston rings and cylinder liners may be among the most complex in internal combustion engines, and could become even more severe with an increase of the engine power. The friction between the piston rings and the cylinder liner significantly contributes to the mechanical power losses of the engine. The calculations of friction force for a piston ring pack are conducted based on hydrodynamic lubrication theory. The oil starvation within the piston ring pack is considered in the calculation of oil-film thickness. The friction characteristics of piston rings are evaluated with the frictional mean effective pressure. The instantaneous friction force of a piston assembly under firing engine conditions is measured by an improved floating liner method in which the cylinder liner is supported by means of hydrostatic bearings. The friction characteristics are made clear by analyses and experiments.

Improvement of Lubrication for Cam and Follower

In order to improve the lubrication between cam and follower of internal combustion engines, the influences of materials or oil viscosity and additives on the friction and scuffing characteristics have been examined with a test rig by increasing the contact load at a constant revolution speed. Also the effects of oil supply through the oil-hole of the camshaft on the reduction of friction and the prevention of scuffing have been examined. From the experiments the following results were made obvious. Firstly, the effect of the material on the reduction of friction or the prevention of scuffing is dependent upon the combination of cam and follower materials. The follower material of hard sintered metal or silicon nitride ceramics is superior in both effects to chilled cast iron when mating with the cam material of hardened S48C steel cam. Secondly, as the viscosity of base-oil becomes low, the friction increases or decreases depending on oil additives, but the scuffing resistance always becomes small. The o...

PREDICTION OF IN-CYLINDER GAS MOTION IN ENGINES BY AN ENERGY METHOD.

A simple new method to predict in-cylinder gas motion during the compression stroke is presented for both flat piston and bowl-in-piston type combustion chambers. The method is principally based on the decay law of kinetic energy of the gas flow in an engine cylinder. Comparison of predicted and measured values shows fairly good agreement for different engine variables. Calculations for a flat piston type combustion chamber show that the velocity at TDC (top dead center) varies proportionally to the 1.15th power of the engine speed and to the -0.50th power of the compression ratio (CR). For the bowl-in-piston type combustion chamber, the ratio of the velocity in the bowl at TDC to that at the intake valve closure increases with a decrease in the CR, initial velocity, height of the bump clearance, and combustion bowl diameter, and with an increase in the engine speed.

Visuelle Untersuchung der Verbrennungseigenschaften von Schweröl in Dieselmotoren

Schwerol ist haufig der Kraftstoff fur Stationar- oder Schiffsdieselmotoren. Bisher war die Zundqualitat einzig relevantes Verbrennungskriterium. Dabei sind der Verbrennungsprozess und die Bildung des Kraftstoffstrahls ebenso wichtig fur eine emissionsarme und wirtschaftliche Verbrennung. Neue Erkenntnisse liefert eine gemeinsame Untersuchung an den Universitaten Hannover und Kyushu/Japan.

Studies on the measuring method of the total friction loss of internal combustion engines

Abstract In the present study a new test method is investigated to measure the total friction loss of engines over the whole range of speed and load. It is based on the idea that the friction loss close to the true one of fired and braked engines can be measured by the run-out method because the temperature mainly influencing the friction loss is almost stable for the short run-out test duration. From the test results and the comparison with those measured by other conventional test methods, the following becomes evident: 1. (1) The total friction mean effective pressure slightly increases as the revolution speed becomes high, but it decreases as either the load or the cooling water temperature becomes high. 2. (2) The total friction mean effective pressure measured by the present method is smaller than that measured by the run-out method, the motoring method or Willans-line method, but it is larger than that measured by the indicated pressure diagram method.

Analyses of the Influence Degree of Principal Particulars on the Engine-Mass and Simplified Engine-Mass Estimation Method for Optimum Planning on the Four-Stroke Cycle, Medium Speed, V-Type Diesel Engines (Supplemental Report)

When developing a new four-stroke cycle, medium speed, V-type diesel engine, it is desirable to establish suitable target of the engine-mass in early stage of initial planning. Since the engine-mass is closely related to the engine manufacturing cost. By the way, some of the principal particulars to be selected in this stage side by side have the great influence on the engine-mass. So if the influence degree of each principal particular is cleared in advance by analyzing, it will be possible to select the most suitable principal particulars rationally and efficiently. The authors developed mass estimation and evaluation simulating method for optimum planning on the same type above-mentioned engine, and reported before. This time, the authors present on the results of analyses of the influence degree of principal particulars on the engine-mass using the above-mentioned method and the simplified engine-mass estimation method applicated with these above results of analyses as a supplemental report.

Analysis of Principal Particulars of Two-Stroke Low-Speed Marine Diesel Engines

By Tetusya Oyamada, Yutaro Wakuri, Yoshinori Hirayama, Keijiro Tayama and Shigemi Ono When developing new engines, it is always an important subject for designers to realize lightweight and compactness while ensuring required performance and reliability of engines. Factors which contribute to the lightweight and compactness of engines are considered to roughly be classified into two. One is a factor related to engine particulars and the other is a factor related to engine structure. Once the authors proposed a method of estimating engine weight using numerical formulas into which related principal particulars were incorporated to this society. This paper reported the results of analysis on the degree of contribution of the abovementioned two factors by this method paying attention to actual data on the realization of the lightweight and compactness of two-stroke low-speed marine diesel engines which have been developed to date. These results of analysis are considered to become useful references for establishing the target values of lightweight and compactness when new engines are developed in future.

An Experimental Study on the Fuel Spray Distribution and Combustion Characteristics in a Diesel Engine with Side-Injection System

The fuel spray distribution and combustion characteristics in side-injection system have been investigated by making use of the special test engine equipped with a variable angle swirler. As the results of experiments, following items have been clarified. In side-injection system, higher swirl intensity is necessary at combustion stage than central-injection system. Therefore the swirl acceleration by piston bowl during compression stroke is effective to improve the combustion characteristics. For the optimization of combustion system, it is important to find out the optimum combination of shape of combustion chamber and initial swirl intensity. When the residual fuel is used, optimization of sharp of combustion chamber becomes more important. For example, spherical bowl type combustion chamber can achieve better specific fuel consumption with smaller initial swirl intensity than flat-bottom bowl type.

On the Load Carrying Capacity of Crosshead-pin Bearing with Eccentric Journal

This paper refers to a new investigation to improve the load carrying capacity of the crossheadpin bearing in a 2-stroke cycle diesel engine. By using a specially equipped journal with a pair of eccentric sections the oscillating bearing can be forced to move up and down just like a piston-pin bearing in a 4-stroke cycle engine. Such a squeeze motion of the oil-film between a journal and a bearing has an ability to increase the oil-film thickness. Then, from the theoretical analyses on effects of various bearing shapes the following features and optimums for design became evident.(1) According to the change of an oscillating direction each sliding face is alternatively unloaded and the oil-pumping ability is generated.(2) In order to keep the oil-film pressure lower than the elastic flow pressure of a bearing metal and make the oil-film thickness as large as possible the next designing points are needed.(i) The ratio of a radial clearance to the radius is about 5 × 10-4 .(ii) The eccentricity between journals is as large as the radial clearance.(iii) The width ratio of a main journal to the whole bearing is about 0.7.