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The droplet velocity, size and distributions of iso-octane fuel from single hole and twin jet air-assist injectors have been measured by phase Doppler velocimetry in the pent-roof for two cylinder head designs of firing four-valve engines running at 1500 rpm, together with the airflow during induction and compression. The use of the twin jet air-assist injector together with the introduction of a transfer-passage between the two intake ports of a Honda VTEC-E valve train arrangement resulted in reduction in ISNOx and COV-1mep of the order of half of those with the single hole injector design without a transfer passage. Droplets, for both heads and injectors, having passed the inlet valves, impinged directly onto the sleeve opposite to their entry without striking the exhaust valves and had velocities up to 30 m/s and Sauter mean diameters which varied from 20 to 50pm.

Measurements are presented of droplet characteristics and air velocity in the cylinder of a 0.36 litre four valve engine, equipped with an sohc VTEC-E valve train and port injection. The results show that injection at crank angles, θinj(s), when the inlet valve is open results in most of the liquid volume flux being in the form of droplets with Sauter mean diameter between 20 and 30 mm which strikes the sleeve up to about 2.5 cm below the exhaust valves, thus generating a locally rich cloud there. The amount of liquid phase gasoline passing through the plane 16 mm below the spark plug gap increases with θinj(s) up to 50 CA after intake TDC and this, together with the crank angle of droplet arrival and vapour generation, controls stratification of the gaseous fuel phase. The optimum injection time is when the fuel-rich cloud is generated so that the tumble vortex convects it to the spark plug at the time of ignition.

The performance of a four-valve engine operating with combustion in all cylinders has been determined in terms of indicated mean-effective pressure, drivability and concentrations of unburned hydrocarbon in the exhaust gases with a stoichiometric mixture of gasoline and air and four injectors including two with air assist. In addition, size and velocity characteristics of the fuel sprays were measured with a phase-Doppler velocimeter outside and inside the engine. With operation at a steady rotational speed of 1200 rpm, the indicated mean- effective cylinder pressure and its covariance were found to be nearly constant with the initiation of injection from 150 to 600 degrees of crank angle after top-dead-centre of intake.

Previous measurements of the velocity, size and number density of droplets have been reported in one cylinder of a production two-valve engine as a function of position, crank angle, injection timing, rotational speed, load and cooling water temperature. In this paper, similar measurements are reported in two cylinders of the same engine, this time with four cylinders firing, and with two manifolds and injectors. They were obtained with a phase-Doppler velocimeter with measurements ensembled in relation to an optical shaft encoder. The engine was also instrumented to provide air and fuel flow rates and temperatures. The results show that most of the droplets emerge in a comparatively small region of the inlet valve and that the characteristics of the spray are important mainly when injection takes place with the inlet valve open.

A method is described of calculating the flow, temperature and turbulence fields in cylinder configurations typical of a direct-injection diesel engine. The method operates by solving numerically the Navier Stokes equations that govern the flow, together with additional equations representing the effects of turbulence. A general curvilinear-orthogonal grid that translates with the piston motion is used for the calculations in the complex-shaped piston bowl, whilst an expanding/contracting grid is used elsewhere. Predictions are presented showing the evolution of the velocity and turbulence fields during the compression and expansion phases of a motored engine cycle, for various shapes of axisymmetric piston bowl and various initial swirl levels. These results illustrate the strong influence of these factors on the TDC flow structure.

Measurements of cylinder pressure and flame travel velocity have been obtained in a single cylinder engine with two arrangements of port geometry and with mixture equivalence ratios from 0.68 to 0.9. They are complemented by photographs of the flame development and measurements of local velocity. The investigation compares the combustion processes in terms of the maximum pressure, flame speed and in-cylinder flow velocity without and with an intake shroud which increased both the tumble and swirl ratios. The extent to which residual burned gas retarded the combustion rate and increased cyclic variability are quantified. The photographic studies confirm the dominant effect of the swirling flow on flame propagation and deviations of the flame kernel from spherical as the air-fuel ratio is increased, with much higher probability of influence of velocity fluctuations.

This paper is concerned with prediction and comparison with measurement of the temperature field in a motored four stroke reciprocating engine, the Ricardo E6, in which an artifical hot spot has been created through electrical heating of the exhaust valve. The purpose is to ascertain the extent to which hot spots affect the temperature field and the implications of this for knock. The calculations are perfomed using the EPISO finite volume solution procedure with a compressible flow version of the k-ϵ model. In the energy variance equation, which is added to the usual k -ϵ equation set, turbulent flux and volume expansion terms and the dissipation rate are obtained from simple algebraic relationships. The experiments use Freon as a working fluid, in order to obtain Reynolds number similarity with air motion, but at much lower engine speed. A thin film resistance thermometer is used for temperature measurement.

Results of a case study in which an unusual liner wear pattern is seen to form within the cylinders of a large marine diesel engine are presented. Analysis of the wear patterns and the wear surfaces are also presented which reveal that the maximum wear corresponds to regions on the liner where “varnish” or “lacquer” films appear to build up from decomposition products of the fuel and lubricants employed. Possible reasons for such wear and film formation are discussed, and compared with frictional and thermal analyses of the ring-liner contacts under operating conditions, with and without the presence of lacquer films. Preliminary results suggest that such films can act as insulation layers to frictionally generated heat between rings and liner, and if allowed to become thick enough can lead to scuffing.