Paper 23: The Collision of Drops with Dry and Wet Surfaces in an Air Atmosphere

This paper describes an investigation into the behaviour of drops which impinge upon dry and wet surfaces. This is of particular interest in the context of the wet steam turbine. Two approaches have been made in the studies; these are: (1) Drops were made to impinge normally on to various types of dry, stationary surfaces. The drops were in the size range 300–1500 μm diameter with velocities of 2–9 m/s. (2) Drops were made to impinge on to surfaces moving with considerable velocity at right angles to the motion of the drop. Surface velocities ranged up to 45 m/s. The latter study is of direct interest for the splashing of drops on turbine casings at small glancing angles, as occurs near drainage belts. Analysis of the mechanisms involved is made from the records of high-speed ciné photography.

Paper 21: Planning for Failures

When a serious failure situation has developed, an expensive crash programme is usually required. If in-service data are analysed as a routine, then impending trouble may be foreseen and management decisions made to minimize the cost. A reliability analysis can help to establish a failure pattern compatible with intuitive engineering assessment so that, from a realistic prediction, alternative courses of action can be considered. A recent gas-turbine engine problem which has caused six component failures is analysed, and alternative replacement strategies are considered. It is suggested that to adopt the intuitive compromise strategy could be the most expensive in this case.

Paper 15: Recent Research and Development in Truck Engine Cooling

To improve economically the cooling performance of trucks an analytical approach was used to assist development. The component tests undertaken included the complete net pressure and power characteristics of two engine water pumps and four engine fans, the heat transfer and pressure drop performances over appropriate flow ranges of some 14 radiators, the additional resistance to air flow offered by two noise shields, and studies of the effects of pump speed, coolant temperature, system pressure, thermostat resistance, and by-pass resistance on radiator water flow with three different engines. The apparatus and methods used for each type of test are outlined. Using the above and other existing data, cooling performance was predicted for some 80 different configurations and conditions, and fan power consumption was predicted for several of these. These results enabled component design and manufacturing problems to be identified and the selection of the most promising configurations for actual development testing. The agreement between the predicted and actual cooling performances is discussed. The use of computer programmes in component testing and analytical prediction is mentioned, and various possible developments in future cooling systems of still higher performance are discussed.

Current Design Activities on British Railways

With the identification of profitable freight areas and the selection of growth traffics for development has come the need to review in detail the running gear and, in particular, the suspensions of both 4-wheeled and bogie vehicles. This design review has been aimed at ensuring a high-speed capability for all new freight vehicles coupled with safety at all times, low maintenance costs, and maximum availability. After reviewing traditional suspensions, in wide use, with reference to their known strengths and weaknesses, the paper discusses in some detail the philosophy now being applied in B.R. design offices to new freight running gear, for both 4-wheeled and bogie vehicles, to ensure satisfactory achievement of technical objectives. Examples of new developments are provided, together with comments on progress to date.

Re-Orientation of Moving Letters

Several areas of every item must be examined in any automatic mail processing system. This introduces the necessity for mechanisms to turn and twist items so that the appropriate areas are brought into view of the various scanning devices. This paper studies the basic movements and offers solutions.

IP Dynamic Anti-Rust Test, Lubricating Greases

The Institute of Petroleum has recently published a test method (IP 220/67) for assessing the rust-prevention characteristics of greases. Specially selected and preserved double-row, self-aligning ball bearings are used as test specimens. The test, which lasts for 164 1/2 h, is dynamic, the grease film being produced and part of the test being performed with the bearings rotating partially submerged in distilled water. The performance of the grease is assessed by estimating the area of rust on the outer races of the test bearings. The precision of the test method was established by an extensive international correlation programme involving 30 laboratories from five European countries. This showed a precision which varied according to the performance level of the test greases. The results of tests with greases affording very good protection and with greases affording very poor protection against rusting gave better precision than results from greases with intermediate performance levels.

A Spray-Droplet Model for Diesel Combustion

A spray-burning model (based on single-droplet theory) for heat release in a diesel engine is presented. Comparison of computations using this model and experimental data from an operating diesel engine indicate that heat release rates are not adequately represented by single-droplet burning rates. A new concept is proposed, i.e. a burning coefficient for a fuel spray. Comparisons between computations and experimental data indicate that the numerical value of this coefficient is nearly independent of engine speed and combustion-chamber pressure. However, the instantaneous value of the spray burning coefficient is approximately proportional to the instantaneous mass-averaged cylinder gas temperature to the one-third power.