[Stoves] "Those of us who believe that the WBT is critical to stove improvement"

Crispin Pemberton-Pigott crispinpigott at outlook.com
Thu Dec 7 16:55:24 MST 2017

Dear Andrew

I got a chuckle out of your last point. Yup, that's the way they cheat now. 

I agree the programming trick was cheating, the point is the drafters of the Standard made is so easy. It is important to understand how these documents get written. The working groups can be individual members of the compliance office of Mercedes and Toyota. These things are not written by 'government'. They are written by who shows up. 

We had an LPG association guy show up to the first few kerosene stove standard meetings during which it became clear he was intent on making the requirements nearly impossible to meet 'in the name of safety' with requirements that were not placed on LPG appliances! It was mooted that his suggestions should be applied equally to gas stoves and he vanished. 

There are private, corporate, extended bun fights in these WG's. It was a pleasure to work all these years with someone as even-handed as Prof Lloyd from Cape Town. For one thing all the drafting rules and conventions were followed which was refreshing and good training. The WG and the TC (SABS TC 1054)‎ went to great trouble to accommodate novel products and to ensure it was difficult to evade the intention of the requirements and still be a simple test to conduct (a series of tests actually).

Re the diesel and NOx, I think there is the expectation that the air is in excess in a diesel under all conditions otherwise it smokes like crazy. Not so?

We were testing a crossdraft low pressure boiler today at CAU and ‎observed something identified by Dr Chunyu Xue from BUCT (sp?). He noted in a presentation to out annual October meeting of experts that the NO was being reduced in the coke bed. Remember that brief conversation? Today (I guess it was yesterday because it is early morning in Urumqi) we calculated the undiluted concentration of NO as the fire bed evolved. 

When the fire was about 1/3 lit (but strong flames) it was 583 ppm(v). This is calculated by multiplying the measured vale times (CO2max/CO2measured) to give an undiluted concentration. 

As the fire ‎developed across the grate back to the door, covering the underside of the hopper, the NO dropped as the active coke bed lengthened (horizontal distance) even as the intensity of the fire rose (a lot).

It dropped from 583 to 525, 480, 420, 380, 320, 290 and so one every few minutes. After it was fully lit and blasting away, it was 200 ppm. To me, it serves as a proof of concept. ‎The NO was reduced to N2 and O2. Very obvious and very interesting. It is literally a low NOx burner. Who knew?


The On Thu, 7 Dec 2017 19:26:04 +0000,Crispin Pemberton-Pigott
<crispinpigott at outlook.com> wrote:

>The requirement is decontextualised and based on the maximum possible value, which is of course 'full throttle'. The computer on board was programmed to detect when it was being tested and redefined what 'full' means.

We'll have to disagree on whether it was right or wrong to take
advantage of a loophole, especially when the software was so deviously

In fact I suspect that there is more NOx formed at a bit less than
full throttle because the formation depends on the presence of excess
oxygen as well as heat and pressure, at lower throttle settings (where
diesel conversion efficiency excels) the combustion has lower
temperature. Spark ignition engines are inherently lower in NOx
because they run with the right, premixed, air:fuel ratio. This may
not be the case with lean burn, stratified charge engines.

My concern would be that if such a loophole existed in the engine
scenario what makes you think that the same would not happen in the
stove context.What's at stake isn't the livelihood of indigenous
stove manufacture but rather access for funding from the various
quangos Nikhil rails against.

Incidentally, and off topic for stoves, the diesel engine used in the
best selling UK assembled car has been independently tested in the
real world and found to be worse polluting than a 20 year old VW Golf
diesel which would not be able to be sold here again, yet the new
engine passes the euro 4 or 5 standard


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