The Kaveri Engine Project revisited                                                 Prodyut Kumar Das  

08/06/2020

There are times in the course of a project when the solution to the problems of development shift from engineering and technology to old wives tales and black magic i.e. uncodified engineering practices. The Kaveri Engine programme has entered such a phase.No timely solution to the Kaveri’s problem will be found if examined from a pure technology algorithm. Indeed the Kaveri’s “technical” problems should be viewed as a deeper malaise. Treating the Kaveri’s technical problems will be akin to symptomatic treatment. Elaborate plans for the “future” has and will remain “music in the distance”. Yet much can be done by an “intuitive” and “illogical” approach.

To avoid a repeating of the self created problems in the Kaveri’s development new readers may read “The Lessons of the Kaveri” which was put on my blog profprodyutdas.blog in 2013. It had also appeared in Vayu Aerospace III/2014.

The Kaveri project after several years in the doldrums has come back to the limelight with the Indian Air Force rightly insisting on having an Indian engine on the AMCA. This is a crisis because the engine will not be ready.

The hitch is not just that necessary engine test facilities are not ready. We have not displayed  the culture of enterprising use- to the hilt of the facilities and resources we have. Unless we use the crisis as an opportunity to overhaul our processes we will again fail.

My pitch is different; even if we had the facilities we would not have succeeded because we did not have the Right Stuff”. Indeed it is because we did not have the Right Stuff then that we do not have the facilities now.

What do I mean by “The Right stuff”? I give two examples: The prototype Olympus engine, at that time the most powerful jet engine in the world, was on the test bed for its very first run. It was idling and its designer Hooker was, naturally, there. There happened to be an important customer present who was seeking a Bristol license. Hooker edged away the fitter in charge of the throttle- so that Hooker could take the responsibility if there was failure- and then he “slammed” the throttle of the prototype not once but twice. The engine could have surged but Hooker knew his engine - he was the design leader- as well as the Director of Engineering, Bristol Siddeley- and a “hands on” engineer (Note 1) and the prototype behaved impeccably. The customer, impressed far beyond any sales talk, bought the License.

 The Right stuff is that- “hands on” knowledge, passion, courage and curiosity to see the proof and the willingness to act on knowledge based impulse.  I have not seen these qualities in Research Establishments and the lack of these have been a bigger factor in delay than is realized. Our Project leaders are chosen for a different set of attributes though one hopes and expects that the new “under 35” scheme launched by DRDO will raise a better vintage.

The Right Stuff also makes a little money go a long way as R&D funds is always clamorously short. When Pratt & Whitney was setting up its Wilgoos Turbine Test Lab, in the late 1940’s – prior- it may be noted- to getting into competitive jet engine development - amongst the many things they need was a 20,000 shp drive for their compressor test. They got it- at throwaway prices and with immediate delivery- from the propulsion system of a WWII destroyer that was being scrapped. Engineers will appreciate how enterprising, resourceful and “turned on” the decision makers were. We need to study the human aspects in product development which- at this stage of the Kaveri- is as important as technology. Indeed the technical problems are the symptoms of a deeper disease.

Kaveri 2020

Prima Facie the Kaveri project, stuck at the usual “last mile”, is really not too bad. If the data is true it is possibly a “black magic “ case. We have an engine which is:

i)                    Delivering 90 percent of its design thrust.

ii)                  The engine is shedding blades

iii)                The afterburner operation is unstable

iv)                The total number of engine test hours is around 2200 hrs

v)                  The above includes 72 flight hours

None of the above except iv) and v) are unusual if you are trying axials for the first time. (note2) Axial Engines do fail initially to meet specifications (but, with tinkering, end up giving almost double the power), shed blades and have afterburner unreliability. The situation is promising.

 That further engine tests have not been done does not square up with common sense. The reluctance and tardiness to run the Kaveri tests could indicate that things are much more of a mess than is being publicly acknowledged and GTRE has reached a dead end.

The following are my conjectures:

i)                    The engine to engine test data shows very high variation.- possibly only one of the six prototypes may have reached the thrust reported.

ii)                  The engines are mechanically unreliable and there are not sufficient “spares” of critical items to continue with the tests.

iii)                The original “champion” has retired and the rest could not be bothered too much to carry on with someone else’s “folly” with the necessary zeal. (Note 3).

Little else can explain the reluctance to test. GTRE has reached a dead end.

The engine has to be run- you can’t make an omlette without breaking the egg. Unfortunately in the Government Research Laboratories anyone who “bends” an engine is taken by his colleagues to be a fool who unnecessarily puts his career and peace of mind at risk. Even progress that is possible is held up because of the culture. The smallest risks are not taken and indeed the culture is to avoid “unnecessary” risk in a field where wise risk taking is as inherent as a fisherman who has to put to sea.

That is not the fault of any individual or group. Overly bureaucratic structures forget engineering and emphasise administrative stability. (Note 4) They consequently tend to take failures too seriously to do any good to the project. Failures are blamed and accountabilities fixed or hushed up rather than being celebrated. Edison’s nine ninety nine way of how not to do the thing is more of a bon mot at seminars rather than a guiding philosophy.

The Kaveri Technicals- an alternate “black magic “construct.

For the present we have no alternative but to try and use old wives tales and black magic approach if only because it is the only possibility available at the present and does not need much funds or time as the current “correct” and “formal” methods being followed will not deliver!

Actually the problems i) ii) and iii), if they are really the only problems, namely:

i)                    Delivering 90 percent of its design thrust.

ii)                  The engine is shedding blades

iii)                The afterburner operation is unstable

are probably different symptoms of the same one flaw or trouble i.e. excessive resistance to airflow and micro instability of flow through the compressor- a phenomena that gets worse as the compression ratio rises so that the usual old “trick” no longer work and new “trick” have to be found to get the highly compressed air flow against a very adverse pressure gradient to behave. It is here a “feel” based approach may work.

Visualizing the problem

The Jet engine is a very interesting case of airflows. The axial flow from the inlet lip up to the turbine nozzle entry is actually low subsonic i.e. about 0.3 Mach. The radial flow at the tips is transonic/ supersonic but as compression increases per stage, it becomes subsonic. At the roots the flow is low subsonic in both axes at all times. The singular peculiarity of the flow is it is taking place in a situation of very high ratio of wetted area to passage area and that too in a cascade and with “shuttering” i.e. the passage areas keep varying along any arbitrary line and is a cause of powerful vibrations because of the very condensed air.

 As an example, for the AL31F, the passage area at the periphery of the final stage is for one pitch 5 sq. cms and the perimeter is 10 cms; at the roots it is almost all wetted area!  To this we combine the fact that the flow is taking place in an adverse pressure gradient. The possibility therefore exists of:

i)                    Due to micro variation of blade surface finish, fit between the discs (which is why the “blisk” is better beyond a certain compression ratio) and the boundary layer thickness the through flow area is affected; the flow distribution around the perimeter is uneven and can cause full or incipient rotating stall- common enough in axial flow compressors under development.

ii)                  The same takes place due to variations in the thicknesses of the blading.

iii)                These singly and together not only cause the axial mass flow but also the peripheral distribution of flows to be uneven and unstable and which will cause surging leading to blade breakage as  (note 5) the blading is already under high axial and bending loads and is working close to its upper temperature limits.

iv)                These pulsations will also cause afterburner blow out for the same reasons it is difficult to light a cigarette outdoors on a gusting  wind.

The divergence in thinking between “safe/logical” and “the right stuff” is at this point. Should we use snubbers on the blades or should we see if better fit, finish and assembly techniques to overcome the problem? Snubbers used to be a common fix and “safe” in official thinking but they will need considerable funding, design mods. , a new engine and two years of time at least. No one will ”risk” or spend time exploring finish and process technique to effect the improvement though I feel that is worth a serious try. The psychological problem is that a “consensus” decision is organizationally safer even if it will lead nowhere an intuitive effort is always risky for the proposer and unlikely to benefit the proposer should he succeed.

To develop the case of a need for a “cultural revolution” (no, not of that kind!) we now have to break off and go to look at how the Kaveri was produced.

There used to be a joke in the GTRE canteen of the ‘80s that the people on the project bought a very large map of the world and, so the story went, this was used to select vendors farthest away from Bangalore to develop the aggregates and BOC items  so that the project people could make visits for “inspection”. Foreign visits were prized in Socialist India. Long distance foreign visits were extremely difficult to organize- there was a perennial foreign exchange shortage ( think of the ‘80s and 90s) and so vendor interactions was almost a ceremonial  to sign the acceptance papers rather than a steady and continuous build up of competence. Where people were put in situ –since these visits were prized-good conduct and seniority were often factors in deciding who went. I have seen happen elsewhere.

When it came to assembly the job was because of “tribal thinking”, led by GTRE. The number of engines they had assembled even till today can be counted on the fingers of one hand. It did recruit skilled assemblers but it is a reflection on the quality of leadership that reportedly overhaul assemblers were recruited. Overhaul assembly is a routine job; experimental jet engine assembly is not. “Putting together” no matter how meticulous, is quite different from assembling and mentally noting features which will be compared when the test bench results come in. To understand and use the test bench results the Project engineers must be perched on the engine along with the fitters –all the time! It is unlikely that this happened every time and always.

There is a physiological explanation for my stress on “hands on” Most of our sensory nerve endings –some 14,000 of them end up in our hands. This is why we instinctively reach out to something and say “Show” when we see something interesting. We “see with our hands” getting a huge load of informal data that the brain processes at leisure. These visual and tactile experiences can come only from intelligent, rather than calendar, experience and curiosity. In India this unrecorded experience was not valued. There was no “market” for it in the “License permit Raj” In the Industry both in the private and public sectors  one often found engineers who are unable or uncomfortable in assembling something they themselves have designed. There is too often a real shying away and even horror of getting ones hands dirty touching greased or oily components!

Getting foreign experts, or even collaboration,  unless recruited “lifetime” as the defeated Germans in Soviet Russia, will not help. They are unlikely to pass on the old wives tales of the engine assembly or else the Chinese would be selling cut price AL 41 Fs on the pavements of Hong Kong by now. I personally know that two of the most severe problems of the HF 24- cockpit vibration during four gun firing and the tendency of the Fairey aileron jack to lock in full fire out were easily rectifiable. These were not corrected by the foreign consultants. They had a job to keep perhaps. My take is that the Russians recruited by the Chinese simply did not have the “black magic” of very high compression engines. It is possible that even with the collapse of the USSR people with such “black magic” skills were not allowed to migrate.

In defence

A reasonable question is what is my justification? I cannot ‘prove’ what I have said. I base my prognosis of the lack of the elusive “soft skills” from my own experiences of product development in the Indian Industry in both the private and public sectors. The technical diagnosis is from my  experience of flows through ducts, nozzles and rotodynamic machines in various Industries and the sensitivity they show to the factors mentioned above.

I will recount a few examples of organizational behavior which I have repeatedly observed:       

i)                    Faced with a nagging problem in the product engineers stop thinking. This partly a fault of our education system which has given stress in achieving the numerical correct answer (note 5). There were several occasions when engineers with many calendar years of experience would confidently swear that there could be no improvement in a particular situation or the correction proposed was impossible-only to be easily proved wrong! (Note 6) It is my expectation that the present Kaveri impasse is just such another such occasion. I have seen it happen.

ii)                  The planning of development testing is often a formality. Insufficient thought is given to what kind of information is being sought from the tests and results in poor feedback. 

I will relate two occasions.

 The first was at a PSU in the testing of a cold air unit- India’s first Turbo cooler where the turbine did 93,000 rpm at great number of decibels! A foreign trained and returned engineer wrote out the Test Schedule and being something of a “Boss” would not brook any discussion. We were ordered to test and despite voicing misgivings about the what the quite complicated tests were supposed to achieve we were shushed but carried out the schedule faithfully. It turned out that we had, by a process I cannot now remember, tested the Test Rack rather than the turbo-cooler. “Well” said my boss” we needed to do that anyway” thus proving he was human after all.

In another occasion at a much respected Private sector Automotive R&D establishment there was a project “Field Trials of recycled Lubricating oils”. It was quite a bustling project with the sample dozen off road diesel engines being brought in from the field every fortnight, stripped and both the Lubricating oil and the engine components beings being very laboriously measured with the very latest equipment CMS etc. Phrases and acronyms such as TAN, TBN, motility, factorial testing and AL, Si, Cu, Fe etc still float around in my mind. A year into the project  the “champion”- incidentally with almost a decade of previous R&D Centre experience in a national Oil company and the author of books and publications  left after about a year and since the project was Govt. Funded the thing came up to me for closure. Very preliminary studies on my part to educate myself for the task soon revealed that Lubricating oils have to be tested under hermetic atmospheric conditions as the minerals in the field would contaminate the results. “Put an honourable closure to it” was my brief from “Doc” our dear and well loved Head of the Centre .  

All the examples are quite true!

Refusal to look for fundamentals based solutions, blind following of procedures rather than “designing” the tests and sometimes, fundamental or conceptual errors are more common than imagined and stems from a refusal to think. My experience suggests that caution is advised in believing Officials and Official Reports- especially if it does not sound right to common sense. Being Official they do not tell lies but they do not tell the necessary truth either! One can never be sure what is going on just because A or B or C says or swears by something. Wade in and get your hands dirty is my suggestion to anyone who will listen.

The next steps

If the above prognosis- that “inexpert” or unstrategized  assembly and testing is the cause for the Kaveri’s problems are roughly right the engine test bed results will show a scatter much higher than +/- 2% of production ready engines. This is the simple “go /No go” gauge for the next decisions which will logically follow. Perhaps if Silos are broken and the brightest and best engine fitters and engineers sit together and work out an assembly plan that goes beyond the routine and sets out causes and effects plans and compare them with the results. We will have startling clarity. Two outcomes are likely, again from my experience:

i)                     Surprisingly easy solutions will emerge providing considerable or total improvements at no or little cost / time.

ii)                  Or we will know exactly where we are stuck and how badly.

The uncertainty will disappear and we will be forced to think of positive alternatives instead of sitting around and commiserating with each other about the situation.

Thinking from a zero base

From a larger perspective our problem has to be redefined. Our problem is not the Kaveri’s performance. Our problem is to be able to produce – without crippling dependence on foreign sources- effective combat aircraft.

If the Kaveri design has consistently reached 90% of its design thrust at a lower TET the designers should be commended and logically the next step is to “authorize” them to “blow” an engine ,if necessary, to find out how much she will stand before brewing.

There can be no “catching up”. Already the Jet Engine development ecology in the West is exploring CP.Rs of 70:1. I don’t think we need to follow that act.

The Jet Engine Design Ecology in India should tell the customer what is the best they can do with reasonable i.e. plus minus one year of promised date, dependability. The private sector should be included as design leaders and there can be none of the past “socialism” mantra which is responsible for a lot of the present situation.

 We should re- examine our own capabilities vis a vis the customer’s requirement. The Air Force has to explain why it needs aircraft capabilities that in turn require engines of international specifications or rather it should come to what are the very minimum as regards engine specifications and if any shortcoming in one area can be met by some capability in another area. The Russians for example are formidable in imaginative mechanical engineering- thrust vectoring, pressure rise per stage and mechanisms but lag when it comes to TTL and TBO which they accept. The figures have been arrived at by experts on both sides working in an atmosphere of mutual respect.

  The choice for the country is between self reliance and sustainability in dissuasion capability or being open to embargoes and price twisting and the consequent unrealistic fleet sizes.

Different engine concepts?

If the TET for example is the crux of the Kaveri’s engine’s problem is there an alternative solution? The TET is used to power the compressor via the turbine and the residue is used to energize the jet giving thrust. Keeping the Jet energy the same we can explore the possibility of finding a “sweet spot” using a lower compression ratio and therefore  lower compressor power and hence lower TET? The fuel efficiency will be lower prima facie but since fuel efficiency is a reciprocal of the CR we may find some area which is within our experience and therefore more likelihood of having the “necessary black magic”. I raise the point because most of our experience is in the relatively lower compression ratio engines in the range of 10-12 i.e. R 25, Adour etc and the Reynolds numbers and the associated finishes are of a lower order.

Given our predicament, we also have to consider a solution where the engine plus the fuel plus the system can be evaluated to achieve an acceptable compromise. A lighter, cheaper and simpler engine has its points.

Mixed Power Plants

 The third alternative is mixed power plants. This was a concept which found much favour when the West, like us, was foxed with the development of high power turbojets afterburners for supersonic flight. Particularly in Europe both France and Britain had a number of such projects e.g. Durandal/ Trident/ Saro P177 until a stupid policy change- no manned aircraft after the Lightning in Britain and successful development of the ATAR afterburner put an end to the efforts. ISRO should be brought in if their expertise in vernier rockets can be used to solve the problems of Thrust Vectoring or afterburner much in the same style as the  SEPR and the Stentor  of the ‘fifties but with the latest proven ISRO technology giving a better product than what was developed seventy years ago. We need thrust vectoring and Afterburner perhaps no more than two or three minutes and a re-examination of mixed power plants is certainly called for with ISRO/DRDO cooperation. For ISRO the development of a60 kN / 60 seconds Thrust Vectoring would be familiar grounds and yet would allow our Jet engine designer great reduction of the challenges and a real opportunity to optimize the engine for the cruise conditions resulting in a simpler lighter engine.

Conclusions

Jet engine development is not easy because it depends on many hundred different technologies. The turbine blade alone needs about a dozen new technologies. In India the problem is that we still have an inefficient centralized process which moves because of funding rather than moving because of the passion of those involved. This is possibly the reason why the Chinese and the Russians despite having funding and facilities still lag behind the West in engine parameters. Jet engine development has a large element of “black magic” which can be exercised only in a  ”free enterprise” society. The fact that the Russians and the Chinese have a legacy of Totalitarian State-ism is no coincidence and lends credence to my argument.

What is needed is a  ”society’ where various groups for their own “interest and profit” collaborate to solve the problems by innovating processes and products that can be applied to the problem of the Jet engine. A Government is far too busy elsewhere to solve, to a usable time scale, the problems of “plus ultra” technologies and in any case a majority of the total development structure is simply not interested in the outcome. We have an unfortunate- and remarkably unjustifiable –legacy of State control where the Government fettered the creativity of the most mercantile and enterprising civilization on earth. Our jet engine development has to be profit based than dole based at present with DARPA style funding to only those who are likely to succeed.

The development of “plus ultra” technologies such as modern jet engines is an area which has to bear the burden of faulty ideological policies of the Governments past. The idea that we can develop an international standard jet engine or bring the Kaveri up to scratch by 2026 without rebuilding the development process is a waste of time. The main obstacles are not physical.

Note 1

Actually Stanley Hooker was an Oxford Mathematician who took supplementary courses in Engineering Drawing and Fluid Mechanics. Starting off with high explosives he applied for a job with Rolls Royce where somewhat to his surprise he was offered a job by the legendary manager of RR Derby, Hives (Hs). During the interview Hs reportedly commented “You’re not much of an engineer, are you?”. Hooker who ws one of the very rare “green thumbs” of an engineer had the wit and humour to title his very readable autobiography “Not much of an Engineer”.

Note 2

Rolls Royce and the brilliant Stanley Hooker had enormous problems getting their first axial .the Avon to behave which the finally got by a variable inlet stator and air dump valves. In comparison the smaller and less endowed Armstrong Siddeley’s Saphire of roughly same power went along swimmingly. The Sapphire lost because funding for its development was cut by lobbyist which reminds one of the old swon “It’s the syme the whole world over!”

Note 3

Project stalling when the “original” champion retires or is transferred is very common. I observed this happen with the NAL Hansa (which with a modest development can still be significantly improved) and yet again in Kolkata in 2014 when I was looking for a wind tunnel to try out one of my ideas. To my surprise I found eleven wind tunnels in the region of which only two were working and only one was up to date. The remaining ,some dating back to the ,fifties were in various states of disrepair. One, a variable cross section tunnel had been used only once and had become a residence of pigeons. The up to date tunnel was of course “unapproachable” being jealously guarded I suppose. The point is many projects start as personal projects and they end with the retirement and transfer of the person concerned. There is no follow up and so the funding is wasted.

Note 4

The Right Stuff can cause “problems” for administrators who are ill equipped to meet their technical ploys. The legend goes that Dr. William (?) McLean .the “inventor” of the Sidewinder made the prototype missile from scrap he scrounged from the China Lake Test Station junkyard. This led to difficulties for a visiting US General who saw the cheap and simple missile a “threat” (Yes! Aren’t they all the same!) to the “official” Falcon missile which was at that time up to its eyebrows in unreliability. He wanted to cancel the project immediately only to discover that the project was not even funded!

Note 5

The other was the very cheap engineering education (with no commensurate coordination to employ them in India!) led to  intelligent and capable people but with no special aptitude for engineering joined the profession though the vast majority went on to management. Being competent the could do the job but not beyond it which was what is required in jet engine development.

Note 6

In a multi-layer blown film plant of the customer created a shock by asking for a tolerance of 40+/- 2 microns on the film when the going tolerance was 65 +/- 7 microns. The order was prestigious and trend setting. All the “greybeards” of the company with decades of experience declared this was impossible though perhaps a few square meters here and there could achieve the specifications. Considerable sums were offered as bets- this was a surprisingly modern Private sector company.

One it was established that +/- 2 micron was a genuine requirement- it helped to get a much better quality of printing on the film- it was possible from examining the process to achieve the desired results with no expenditure but with considerable thinking. I don’t remember collecting the bets but the celebratory party was fabulous. Packaging films is not jet engines but the unwillingness to believe that there can be simple solution stops the search for such solutions even when they exist.

Note 7

Just as an illustration : Some of you may have noted the soft “brr…brrr…brr” noise made by a gas burner if the perforated lid’s passage area is not matched to the gas flow and thelid sits too tight on the annulus to let the excess gas leak off the fluctuations. This happens at a supply pressure of perhaps a few inches of water gauge pressure.  Imagine the energy of fluctuations at 24 bars pressure!

Note 8

Whether that will happen is a matter of conjecture. There exists a powerful a well organized import lobby as well as a ‘state control” lobby. Reducing their clout is a formidable and time consuming task even given political will. The delay observed in placing orders for items already developed by the local industry is an effective way of finally edging out the private sector and is unfair in terms of a level playing field . The pity is there is more than enough market and work for both sectors but the agenda of the lobbies is different.