Various aspects of the method of impinging-streams, which proved to be one of the most efficient methods for performing the gas-solid operations in Chemical Engineering, are discussed. The aim of the review is to bring the method of impinging-streams and its possibilities to the attention of the Chemical Engineering community, to stimulate further research in the field and to encourage the technological applications of this method. KEYWORDS: Impinging streams, Impinging jets, Impingement zone, Opposed jets

Applications of impinging-streams in chemical engineering processes—review

Utilisation of biomass for motive power generation — gasifier engine system

In der letzten Dekade haben mehrere experimentelle Untersuchungen gezeigt, dass wahrend der voll- oder teilhomogenen Dieselverbrennung, im Vergleich zur konventionellen Dieselverbrennung, weniger Rus- und Stickoxidemissionen im Brennraum entstehen. Da der spezifische Kraftstoffverbrauch bei teillhomogener Dieselverbrennung nicht hoher ist, als bei konventionellen Dieselbrennverfahren, ist somit im Teillastbereich eine verbrauchsneutrale, innermotorische Schadstoffreduktion moglich. Aufgrund der je nach Verfahren unterschiedlich starken Entkopplung von Einspritzzeitpunkt und Brennbeginn sind teil- und vor allem vollhomogene Brennverfahren jedoch nicht einfach zu realisieren, insbesondere im Transientbetrieb. Es sind daher weitere Entwicklungsarbeiten notwendig bis eine serientaugliche Applikation vorliegt, bei der im Teillastbereich voll- und teilhomogene Brennverfahren zum Einsatz kommen. Mangels eines geeigneten vorhersagefahigen Brennratenmodells konnen die Potentiale der Arbeitsprozessrechnung dazu bisher nur unzureichend genutzt werden. In dieser Arbeit wird ein solches Modell vorgestellt, welches nach einer Abstimmung an den jeweiligen Motor alle relevanten voll- und teilhomogenen Betriebsarten (HCCI, HCLI und HPLI) vorhersagefahig abbilden kann.

In Summe kann uber alle Betriebsarten der Umsatzwirkungsgrad und auch der indizierte Mitteldruck mit einer Genauigkeit von ±10% vorhergesagt werden. In dem Betriebsbereich mit Einspritzbeginnen um den oberen Totpunkt, der aktuell besonders im Entwicklungsinteresse steht, betragt die Genauigkeit ±5%. Die Rechenzeit fur ein Arbeitsspiel betragt auf einem aktuellen Buro-PC weniger als zwei Sekunden. Damit ist das Modell fur den taglichen Einsatz auch im Rahmen einer 1D-Stromungssimulation geeignet. 
In the last decade many experimental researches have proven that during homogenous- or partly-homogenous Diesel combustion less soot and nitrous gases are formed compared to conventional CI combustion mode. Furthermore it has been shown that the specific fuel consumption of partly-homogenous Diesel combustion is comparable to conventional CI combustion. Consequently at part load in-cylinder pollutant reduction is possible without disadvantages regarding to fuel consumption. But partly- and even more full-homogenous Diesel combustion is not easy to implement due to the strong decoupling of injection timing and start of combustion depending on the combustion mode especially in transient operation. For that reason further efforts are necessary until an application suitable for series production exists, with full- or partly-homogenous Diesel combustion at part load. Until now the capability of working cycle simulation couldn't be used to improve the situation because no suitable predictive burn rate model exists. In this dissertation such a model shall be presented which has the predictive capability to reproduce the burn rate of all relevant full- or partly-homogenous combustion modes (HCCI, HCLI and HPLI) inside the working cycle simulation after calibration on a specific engine.

In total IMEP and combustion efficiency can be predicted with an accuracy of ±10% over all operating modes. At modes with start of injection near FTDC the accuracy is ±5%. The computation time for one working cycle is less than two seconds on an up-to-date office-PC. Therefore the model is suited for daily use in the context of 1-D flow simulations.

Modell zur Vorhersage der Brennrate bei homogener und teilhomogener Dieselverbrennung

An ultra-low carbon steel is studied and the temperatures at which the austenite to ferrite transformations begin and are complete are determined. The methods of measurements of the temperatures are discussed. The effects of the cooling rate, initial austenite grain size, prestrain, residual strains, static recrystallization, and the mode of deformation on phase transformation temperatures are determined and discussed.

Phase Transformation Temperatures of an Ultra-Low Carbon Steel

Continuous cooling curves of an extra-low carbon steel under three cooling rates are measured. The flow stress of the steel is established in compression tests during which the temperature is continuously decreasing. The phase transformation temperatures are determined from the cooling rate curve. The latent heat during phase transformation is calculated. A new variable, related to the volume fraction of transformation, is defined. Experimental results show that the relationship between the softening ratio of the flow stress due to phase transformation and this new variable may be described by a quadratic relationship. Based on this relationship and the continuous cooling curves, the flow stresses in the two-phase region are successfully predicted.

The Prediction of the Flow Stress of an Extra-Low Carbon Steel in the Two-Phase Region Using Continuous Cooling Curves

Study of Heat Transfer Phenomena in Quenching of Steel (An Analysis of Cooling Curves Accompanied wth Phase Transformation)

This paper deals with the jet flames of rich propane-air mixtures in a counter air stream. At a constant jet nozzle pressure a stable combustion can be obtained within the appropriate ranges of the air-fuel ratio of the jets and the velocity of the counter air streams. In order to examine the fundamental characteristics of the flames, the behaviour of some typical flames within the stability curve is studied by means of visual observation and temperature and concentration measurements. A concept of similar flame based on the temperature profile at the maximum temperature section is introduced and confirmed experimentally. By using this concept a dimensionless flame stability curve can be obtained. The temperature, concentration and heat release rate profiles give a good explanation of the estimated relationship between the flame and flow pattern.

Jet Flames Stabilized by a Counter Air Stream

It is well known that diesel knock intensity can be reduced by appropriate double injection. The authors have made an optical and theoretical investigation of the combustion mechanism of the pilot fuel. It is known that the pilot fuel burns with a different mechanism corresponding to the injection timing. In the case of retarded pilot injection, e. g., 30°BTDC or later, the ignited mixture initially burns rapidly with intense luminosity under near-stoichiometric conditions. However, the amount of fuel is so small that pressure rise is not sufficient to cause diesel knock. When the pilot injection timing is earlier, weak luminosity is observed because of the relatively weak mixture and low burning velocity, but the flame has enough energy to ignite the main fuel. When the pilot fuel is injected at the scavenging top dead center, intermediate products which show no luminosity shorten the ignition lag of the main fuel.

An Optical Investigation of Combustion on a Double Injection Diesel Engine

We studied the effects of double injection by a single nozzle on fuel consumption and noise level of a single cylinder 4-stroke direct injection diesel engine. It was observed that, within a certain range of fuel quantity of pilot injection, the combustion noise was reduced considerably. This range of the fuel quantity depends on the timing of the pilot injection. In view of the fuel consumption, it was found desirable to inject pilot fuel at the end of exhaust stroke of the previous cycle or just before the main injection. Furthermore, a thermodynamic analysis was made to explain qualitatively the mechanism of the effects of pilot injection.

Tadasu Maki

Papers

Study of Heat Transfer Phenomena in Quenching of Steel (An Analysis of Cooling Curves Accompanied wth Phase Transformation)

Jet Flames Stabilized by a Counter Air Stream

An Optical Investigation of Combustion on a Double Injection Diesel Engine

Effects of Pilot Injection with a Single Fuel Nozzle on a Direct Injection Diesel Engine

対向流によって安定化された噴流火炎の研究 : 第2報、主として濃度分布による考察