Brian E. Milton

AIR FLOW AND HEAT TRANSFER IN VENTILATED DISC BRAKE ROTORS WITH DIAMOND AND TEAR-DROP PILLARS

This study is part of an ongoing research project investigating the airflow and heat transfer of different disc brake rotors. This article reports on three geometries: straight radial vane (SRV) rotor; SRV rotor with rounded vanes (SRV-R); and a rotor with diamond and teardrop pillars (DTDP) instead of vanes. The total heat transfer from the SRV-R and DTDP passages is up to 20% greater than that for the SRV rotor. As much as 35% more heat is lost from the free side friction surface than the hub side friction surface. Flow development through the DTDP rotor passages is also noted.

Characteristics of impact driven supersonic liquid jets

Abstract In this paper, a technique for the generation of supersonic liquid (water and diesel fuel) jets is presented. The supersonic liquid jet is generated by the use of a purpose-developed vertical, single-stage powder gun. The characteristics and behavior of supersonic liquid jets were obtained by visualization using the shadowgraph technique. The visual evidence related to supersonic liquid jets (velocity around 2000 m/s) generated from a variety of nozzle types is presented and the effects of nozzle parameters on the jet behavior are described. The characteristics of the leading edge shock wave and jet shape were found to be significantly related to the nozzle geometry. A one-dimensional analysis of the multiple, reflected shock waves inside the liquid sac and nozzle during the process of supersonic jet generation is presented. The method allows impact pressure, particle velocity and effect of shock wave reflections inside the nozzle cavity on the liquid jet velocity to be obtained. Jet shock waves obtained from the shadowgraph image and CFD simulation are also compared. The jet outflow characteristics and its leading edge shock wave in air were assessed for their potential for auto-ignition using fuel with cetane numbers from 50–100. The contribution of the strong leading edge shock wave to the auto-ignition is discussed.

Fuel deposition and re-atomisation from fuel/air flows through engine inlet valves

The two-phase fuel/air flow through an internal combustion engine inlet valve has been studied experimentally in a specially designed rig. The separated flow associated with fuel films on the inlet port and large droplets on the valve stem can be readily seen. Injector location, valve lift and air stream velocity all influence the subsequent re-entrainment and secondary atomisation of the fuel. Deposition into discrete regions below the valve occurs. Numerical simulation of the airflow shows good agreement with the experiments.

NUMERICAL SIMULATION OF THE GAS/DIESEL DUAL-FUEL ENGINE IN-CYLINDER COMBUSTION PROCESS

ABSTRACT An alternative fuel such as natural gas may be used in a dual-fuel engine for both economic reasons and emission advantages. However, the performance at relatively light load and idling conditions has been quite poor, while at very high load, engine knock is often encountered. In this study, a three-dimensional, dual-fuel, in-cylinder model has now been developed. This is used to provide an improved understanding of the operational features arising from the interaction between the gaseous fuel and the pilot fuel, the preignition processes, and subsequent combustion of the pilot fuel and gas during the piston movement.

DUAL-FUEL COMBUSTION MODEL FOR PREMIXED NATURAL GAS WITH DISTILLATE IGNITION IN A QUIESCENT BOMB

Dual-fuel engines using a low cetane number primary fuel such as natural gas (NG) ignited by a pilot distillate spray have been in existence for a considerable period. However, there are still many unknowns related to the fundamentals of the combustion process of the two fuels. This article reports on the development of a simulation model of the dual-fuel combustion process calibrated using constant-volume combustion bomb tests, the bomb being specifically developed for this application. Both global and local variations in the combustion process are studied parametrically.

Experimental Study of Ignition over Impact-Driven Supersonic Liquid Fuel Jet

This study experimentally investigates the mechanism of the ignition of the supersonic liquid fuel jet by the visualization. N-Hexadecane having the cetane number of 100 was used as a liquid for the jet in order to enhance the ignition potential of the liquid fuel jet. Moreover, the heat column and the high intensity CO2 laser were applied to initiate the ignition. The ignition over the liquid fuel jet was visualized by a high-speed digital video camera with a shadowgraph system. From the shadowgraph images, the autoignition or ignition of the supersonic liquid fuel jet, at the velocity of 1,186 m/s which is a Mach number relative to the air of 3.41, did not take place. The ignition still did not occur, even though the heat column or the high intensity CO2 laser was alone applied. The attempt to initiate the ignition over the liquid fuel jet was achieved by applying both the heat column and the high intensity CO2 laser. Observing the signs of luminous spots or flames in the shadowgraph would readily indicate the presence of ignitions. The mechanism of the ignition and combustion over the liquid fuel jet was clearly clarified. Moreover, it was found that the ignition over the supersonic liquid fuel jet in this study was rather the force ignition than being the auto-ignition induced by shock wave heating.

Modelling HEUI injector In MATLAB Simulink

The present work describes the development and partial validation of a mathematical model of a hydraulically actuated electronically controlled unit injector (HEUI). The HEUI analyses include submodels of the solenoid, hydraulic differential valve (HDV), intensifier and injector subsystems. It has been implemented using the MATLAB/SIMULINK graphical software environment. The modeled HEUI is a compact, flexible diesel injector developed at the University of New South Wales in conjunction with local industry. The work undertaken is part of a wider study aimed at optimization of the design of the HEUI for dual-fuel systems.

A Blunt Body Analogy for Bow Shock Characteristics in Front of a Supersonic Liquid Jet

The unique characteristics of high-speed liquid fuel jets suggest that they have the potential to be applied to high performance diesel engines, SCRAM jets and other combustion applications where small combustion residence times are required. When a liquid jet is injected at supersonic speed, with respect to the surrounding medium, a bow shock wave is produced. The ability of such jets to increase atomisation rates and decrease ignition times has led to interest in the liquid jet head - bow shock region. The use of CFD to study this region is advantageous as experimental studies are unable to take many measurements without being intrusive. This paper investigates the effect of the dynamic jet shape on the bow shock stand-off distance and shape using contemporary CFD methods. The shock wave characteristics in the shock layer are also presented.

Fundamentals for Optimizing the Use of Natural Gas in Diesel Engines

For fueling diesel engines with gaseous fuels, combined gas/diesel in-cylinder injection systems have many advantages over traditional systems with carburetted manifolds. However, understanding mixing phenomena within an engine is difficult. Here, it has been studied in a rig under atmospheric conditions. Shadowgraph and schlieren techniques were employed to identify mixing regions between diesel and natural gas injected simultaneously into a chamber. The results were used to calibrate a CFD model for simulating injection into an engines cylinder. The optimum orientation of the jets relative to each other was determined and then the best staging of the jets was estimated.

Visualization of supersonic diesel fuel jets using a shadowgraph technique

High-speed liquid jets have been widely used to cut or penetrate material. It has been recently conjectured that the characteristics of high-speed fuel jets may also be of benefit to engines requiring direct fuel injection into the combustion chamber. Important factors are combustion efficiency and emission control enhancement for better atomization. Fundamental studies of very high velocity liquid jets are therefore very important. The characteristics and behavior of supersonic liquid jets have been studied with the aid of a shadowgraph technique. The high-speed liquid jet (in the supersonic range) is generated by the use of a vertical, single stage powder gun. The performance of the launcher and its relation to the jet exit velocity, with a range of nozzle shapes, has been examined. This paper presents the visual evidence of supersonic diesel fuel jets (velocity around 2000 m/s) investigated by the shadowgraph method. An Argon jet has been used as a light source. With a rise time of 0.07 microseconds, light duration of 0.2 microseconds and the use of high speed Polaroid film, the shadowgraph method can effectively capture the hypersonic diesel fuel jet and its strong leading edge shock waves. This provides a clearer picture of each stage of the generation of hypersonic diesel fuel jets and makes the study of supersonic diesel fuel jet characteristics and the potential for auto-ignition possible. Also, in the experiment, a pressure relief section has been used to minimize the compressed air or blast wave ahead of the projectile. However, the benefit of using a pressure relief section in the design is not clearly known. To investigate this effect, additional experiments have been performed with the use of the shadowgraph method, showing the projectile leaving and traveling inside the nozzle at a velocity around 1100 m/s.