– a perspective from Klaus Hein, former IFRF Investigator, former Joint Committee/Council member and current member of the German Flame Research Committee

Hello MNM readers,

Having finished my engineering degree at the Technical University of Aachen in Germany in 1965 and following a one-year exchange scholarship at Imperial College London in the UK, in early 1966 I approached Professor Quack – a highly reputed engineer and scientist in energy and power technology at the University Stuttgart – seeking a position as a PhD student at his Institute.  At that time, Prof. Quack was a member of the Joint Committee of IFRF and he suggested a position at the Research Station in IJmuiden which I accepted with great pleasure as it fitted well with my intention to work on experimental research in an international context.  This decision was to influence my whole professional life!

I started work at IFRF in August 1966 with Mr Jaques Chédaille as the Head of Station and Klaus Hemsath, Yves Braud, John Mineur, Wolfgang Leuckel and Allan Chesters as my fellow investigators.  My first task was to evaluate analytical data from samples taken during recent coal trials.  Soon I was participating in the shift working system that we adopted during combustion trials, initially on the latest oil trials (‘O-16’) and then in preparing for the ‘C-13’ coal trials (scheduled for October-December 1966).  The objective of these trials was to study the effect of swirl on the ignition and combustion performance of anthracite coal – one of the most difficult low-volatile solid fuels utilised in utility boilers and cement kilns.  During these trials the recently developed (by Wolfgang Leuckel) ‘moving-block swirl generator’ was applied to the secondary air (in boiler-type burners) or to part of the primary air (in cement kiln-type burners).  Detailed observation and measurement of local flame properties confirmed the expected improvements in ignition stability and reduced burn-out length, even for low-volatile coals, due to the fast entrainment of externally recirculated matter and the corresponding cross-mixing achieved.  Details of these trials are given in the following reports available from the IFRF Archive:

• The effect of swirl on pulverized anthracite flames – IFRF trials C-13  (Leuckel, Hein),IFRF doc. no. F 32/a/38, 1967
• Results of detailed measurements carried out in swirling pulverized anthracite flames during the series of trials C-13 (Hein, Leuckel),IFRF doc. no. F 32/a/39, 1970

Based on these results, it was decided to conduct a similar series of trials (‘C-14’) in October-November 1967 on swirling boiler-type flames only, with anthracite and high-volatile coal, and investigating additional parameters such as variable swirl intensity, air preheat and furnace cooling load.  These tests revealed that for high-volatile coal flames ignition was secured at the burner face beyond a certain swirl intensity, while even for anthracite flames visible ignition (i.e. inflammation of liberated volatiles) was obtained as a result of particular mixing condition in the root of the flame.  The full report is available as:

• Further studies on the effect of swirl on pulverized coal flames – Trials C-14 (Hein, Leuckel),  IFRF doc. no. F 32/a/40², 1969

In 1967-68 two series of trials (‘O-17’ and ‘O-17A’) were performed on luminous oil and gas flames with burners comparable to those used in industry.  These trials were specifically aimed at the formation and combustion of soot as a key mechanism for the heat transfer by radiation in industrial furnaces and boilers.  Since this topic had not been investigated at IJmuiden previously, it was necessary to develop appropriate measuring methods and instruments such as a probe for point sampling in the first ‘wet’ part of oil flames to separate liquid, solid and gaseous components.  Also, in order to determine the local ‘extinction coefficient’ (necessary to correlate radiation with concentration and properties of solids at any point within a flame), another new instrument designed by Wolfgang Leuckel – the so-called suction radiometer – was applied.  The description and operation of these new instruments, together with the results of local flame point measurements and their interpretation, can be found in the following documents and publications available from the IFRF Archive:

• Programme of main trials O-17 (Leuckel),  IFRF doc. no. D 07/a/22, 1967
• Programme of trials O-17A  (Leuckel), IFRF doc. no. D 07/a/26, 1968
• Recent results on the formation and combustion of soot in turbulent fuel-oil and gas flames (Hein),IFRF doc. no. G 07/a/1, 1970
• The formation, combustion and radiation of soot in luminous fuel-oil and gas diffusion flames (Hein, Leuckel), IFRF doc. no. Tg K 20/a/46, 1970
• Untersuchungen zum strahlungsverhalten von heizöl- und gasflammen mit verschiedenen Brennersystemen (Hein), IFRF doc. no. K 20/a/53, 1970

In order to support further interpretation of the previous coal trials, in particular the swirl-induced mixing pattern and the consequences on ignition of anthracite flames, the decision was taken to switch to a ‘cleaner’ fuel – namely natural gas (which was then available from the Groningen field in the Netherlands).  The first series of trials with this new fuel (‘NG-1’) took place in November-December 1968 in IFRF’s No. 1 Furnace, with a similar swirl burner arrangement used for the boiler-type burner during the ‘C-13’/’C-14’ coal trials but modified for natural gas and with a much wider variety of burner-side parameters.  Because of this new fuel, the high uncertainty concerning the ignition and combustion behaviour, and the corresponding safety aspects, Neil Fricker (who had joined the team in 1968) and I spend many day- and night-shifts running through a large number of flame root patterns by essentially varying the burner exit configuration, swirl intensity, as well as gas and air throughput.  In this way we came up with four visibly distinguishable forms of flame appearance (later reduced to two), which served as the basis for the development of an IFRF ‘flame classification system’ used subsequently in all flame research studies both in-house and beyond.  The detailed measurements conducted in the ‘NG-1’ trials established the importance of the interaction between the swirl-induced reverse flow and a jet of centrally-injected fuel gas.  The full report of this trial is available from the IFRF Archive:

• Flow and mixing patterns in gas flames with swirl in the annular air stream: Results from the NG-1 trials (Fricker, Leuckel),  IFRF doc. no. G 02/a/18², 1969

An overview of the results of the coal trials in 1966-67 and the first gas trials in 1968 is also available:

• The effect of swirl on the ignition characteristics and combustion intensity of pulverized coal and natural gas flames (Leuckel, Fricker, Hein), IFRF doc. no. Tg K 20/a/45, 1970

Further trials on coal flames were conducted in March and May-June 1969, supplementing previous coal trials.  These trials (‘C-15’) aimed to provide a better understanding of the fundamental processes in a coal flame such as devolatilisation, and the combustion of volatiles and the remaining solids.  For this purpose, only three non-swirling flames were chosen for closely-spaced point measurements, in particular in the first flame zone.  From these measurements, reaction rate data were obtained, and these were subsequently validated by the findings of other researchers outside of IFRF.  The full report of these trials can be found in the IFRF Archive:

• Investigations into the combustion and devolatilisation behaviour of the non-swirling pulverized coal flames studied in the C-15 trials (Hein), IFRF doc. no. F 32/a/41, 1971

Staffing of the three work shifts with the necessary number of investigators during these various measuring campaigns could prove problematic and the Research Station had to deal with severe personnel shortages at times.  This was certainly the case from the autumn of 1966 through to the summer of 1967:  The departure of the last members of Mr Chédaille’s team during the second half of 1966 with the new investigators not arriving before 1968 left only Wolfgang Leuckel as Head of Station and myself as the sole Investigator!  Fortunately, several IFRF member organisations ‘loaned’ experimenters from their own staff to IJmuiden during trial campaigns in this period, enabling us to staff the pattern of shifts.  Worthy of a mention in this regard is the very valuable assistance we had from Peter Roberts from British Steel, Terry Johnson from the University of Sheffield, Wolfgang Richter from the University of Stuttgart, George Szpindler from CSIRO in Australia, Horace Whaley from the Canadian Combustion Laboratories and Keith Wilkinson from BCURA, UK.

May 1969 also saw the launch of a new initiative for IFRF with the organisation of the first ‘Members Conference’, held at IJmuiden.  Around 120 participants attended this highly successful event, listening to 18 presentations (including five papers on results from the Research Station).  Thus began the series of IFRF conferences on an approximately triennial basis – an IFRF tradition that has continued to this day with the 19^th such conference (also attracting 120 participants but with 50 presentations) earlier this year.  The full documentation of the first IFRF conference is available from the IFRF Archive as:

• Proceedings of the 1^st IFRF Members Conference, IJmuiden, 22-23 May, 1969

Finally a personal appreciation.

I left the IFRF Research Station at IJmuiden in February 1971.  The experience I gained at IFRF was the basis for my next role in industry as the head of a research group at German utility RWE.  Throughout my whole industrial and academic career, IFRF has been an important partner in my many international engineering and research projects.  The exceptional team spirit experienced at IJmuiden became a guideline for most of my projects in industry and academia, and the friendship with my co-investigators and their families – which I thoroughly enjoyed during my time there – is still pleasantly alive to this day.  In my opinion IFRF was – and still is – a great experience and one that is sustainable for a full lifetime!

Klaus Hein

[Ed. – thank you, Klaus, for your excellent contribution.  Having organised the 19^th ‘IFRF Conference’ in May this year, it was interesting to read about the first of the series almost exactly 48 years earlier (which, interestingly, attracted the same size number of participants).  Thank you too for over 52 years of invaluable input to IFRF!]