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Aircraft Topics related to WWI aircraft, aircraft engines and armament

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Old 2 January 2011, 03:36 AM   #1
tartle
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'Increasing the Charge'

This is my interpretation of the supercharger story and so feedback that corrects and improves will really help... thats why I'm doing it here!

The start of interest in supercharging really came about as the Military realised that altitude and power were necessary for the 'war in the air'.

Back in 1909 Alec Ogilvie realised that his sport aeroplane, one of the batch of Short-Wright Flyers needed a powerful prime mover to keep him in the air at air displays and races that were springing up. He was attracted by the work of G. F. Mort who was in the process of designing two-stroke vertical twin and four cylinder engines that promised to deliver more power per lb than other developers. This engine used a Roots blower to scavenge exhaust gases and 'ram a fresh fuel/air charge into the cylinders. Not strictly a supercharger it is one of the first instances I have found of an aero engine with a 'rammed' charge.
Ogilvie worked with Mort's New Engine Company to develop and install a V4 version in his recently acquired Wright 'Baby' of 1911. Flight published a picture here.
The New Engine Company, based in London, manufactured a very simple engine which showed considerable promise but which ultimately proved too severely handicapped by its heavy fuel consumption. Known as the N. E. C. the engine was produced initially in 2 or 4 cylinder water-cooled vertical two-stroke versions. The 4 cylinder versions weighed in at 20 lbs and generated 40 hp. Alec Ogilvie worked with N. E. C. to develop a version suitable for his Wright ‘Baby’ ; in 1911 he installed a V4 engine. Construction of body, cylinders and pistons was cast iron and cooling jackets were electrodeposited copper.
The V4 weighed 155 lb without radiator or flywheel and developed 50 hp at 1250 rpm. Total weight without flywheel, but with radiator, water and plumbing was 205 lb giving a wt/hp at 1200 rpm was 4.28 lb/hp.
A vertical 6-cylinder prototype was shown in 1912 but ultimately development was thwarted by the lack of technological understanding in materials, fuels and manufacturing to bring a satisfactory 2-stroke to the market. Although a relatively reliable engine it was severely handicapped by its heavy fuel consumption, even in the ‘age of the rotary’.
Ogilvie's engine survives in the Science Museum Here are a couple of shots taken by Asquith (thanks!)



Flight published a picture of the 100 hp vertical six here and reported on the use of the Roots blower:
'It will be understood, as matter that is self-evident, that the explosive mixture must be forced into the cylinders of an engine that is working on the two-stroke principle. In an engine that is working on the four-stroke principle, the piston during one of its idle strokes acts as a suction pump for the performance of this duty. That particular idle stroke, having, in the two-stroke principle, been converted into a working stroke, is no longer available for suction purposes, and means have, therefore, to be found for substituting an equivalent effect.
On the N.E.C. engine, a modified type of Roots blower is employed to this end. The Roots blower, in principle, may be regarded as a pair of meshing gear-wheels, the teeth of which form a perpetually closed door where they touch in the centre, and an endless succession of moving paddles as they move in proximity to the walls of their casing. The device is used frequently on motor car engines in the form of pumps for the circulation of water and oil. The blower on the N.E.C. engine is divided into two main parts, one dealing exclusively with pure air and the other with carburated air, that is to say a mixture of air and petrol vapour, of a richness above the normal. The object of that part of the pump which deals with the pure air is to blow a blast into the cylinders directly the descending piston uncovers the inlet port and thus scavenge the cylinder ol burnt gases and leave it full of pure air. Immediately following thereon, the second part of the blower delivers its over-rich charge of fresh mixture, which diffuses through the fresh air and is finally compressed into a homogeneous explosive charge as the piston returns on its upward stroke. For the purpose of timing the entry of the gas, a rotary valve is interposed between the blower and the cylinders. These valves are simple cylindrical shafts running on ball bearings and are not in the least comparable with valves of the poppet type.'

Last edited by tartle; 2 January 2011 at 04:19 AM.
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Old 3 January 2011, 09:42 PM   #2
Bletchley
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Thank you tartle, that is very interesting

The link from "reported" refers back to the Asquith thread, not to Flight.

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Last edited by Bletchley; 3 January 2011 at 09:47 PM.
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Old 4 January 2011, 11:52 AM   #3
tartle
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link to roots blower description

Thanks Bletchley .. for some reason I can't edit the link so here it is ..."Flight published a picture of the 100 hp vertical six and reported on the use of the Roots blower:..."
Since writing about the N.E.C. I shall have to define its place in history as the first British and probably the world's first supercharged aero engine to actually fly. This is because my researches on the process of technological invention that led to the Gnome Omega rotary has thrown a light on Charles Benjamin Redrup who has a legitimate claim to have demonstrated the first supercharged aero engine in 1906. More on that shortly.
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Old 5 January 2011, 02:38 AM   #4
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Redrup's 'Reactionless' Aero engine

Charles Benjamin Redrup (The Knife and Fork Man)was an engineer who designed and built one of the first rotary engines intended for use in a motorcycle or motor car. (A later claim to fame was a project for the Lancaster: The hydraulic drive for the spinning "Dam Busters" bombs.)
The two-cylinder rotary went into production in 1904 for the Barry motor cycle. The Barry was offered in two versions- a 3 hp at 16 guineas and six hp at 26 guineas. Redrup had adopted the rotary principle to address the shortcomings of more conventional engines of the time.
This picture from "The Knife and Fork Man" shows one of the original bike engines:



By 1905 Redrup had improved the engine and one version tailored for aeronautical use, was demonstrated at the Royal Balloon Factory, Farnborough in 1906 as a possible powerplant for the new Nulli Secondus semi-rigid airship being built at that time. The ‘Reactionless' engine as it was known was a modification of the Barry motorcycle engine that enabled the crankshaft to rotate in one direction and the engine block in the opposite direction.
This is a picture of the Aero engine from the book:


The intention was to create a more efficient high revving engine that could drive two propellers at half engine speed not compromising their efficiency also was not compromised. The picture from the book ‘The Knife and Fork Man- The Life and Work of Charles Benjamin Redrup' shows the demonstrator with a paddle at each end to represent the propellers. The idea of contra-rotation was to eliminate torque forces on the surrounding structure that usually accompanied a rotary engine.

In 1904 Richard Benjamin Redrup applied for a rotary engine patent which was granted as GB 13314 in 1905. It contains drawings and description of the engine.




“ ... ...In carrying the invention into effect as illustrated in the accompanying drawings, the central chamber c and the cylinders at their inner ends are used as a pump, the pistons acting as the plungers, and on the inward strakes compressing a charge which was previously admitted through the hollow trunnion or crankshaft d from the carburettor which is connected thereto by means of a pipe at p, and is forced into the storage chamber or reservoir q which is provided. This storage container q is connected by means of pipes r to the inlet valve casings, or to the inlet of the respective motor cylinders a and b, and is utilised for the purpose of storing the combustible mixture forced therein as hereintofore described, the mixture being compressed within the storage container through the action of the pump, whereby a constant feed of the explosive mixture at a uniform pressure is admitted upon the opening of the inlet valves.
It will be understood that the combustible mixture thus enters the respective cylinders under compression, and on the compression stroke is subjected to further compression, so that on upon ignition it explodes with great force, producing increased power and effect.”

The patent describes the motor construction:

“The hollow crankshaft or trunnions d are mounted in bearings e fitted centrally in the walls of the crank chamber casing c so that the frame constituted of the cylinders and their connections may rotate upon the trunnions or crankshaft may be held stationary on the frame of the cycle or vehicle in any suitable and convenient manner.
The piston rods f are directly connected to the crankpins g. Exhaust valves h are provided on opposite sides of the respective cylinders a and b which by arrangement before described it will be understood are out of line although oppositely disposed in parallel planes, the valves being accommodated in the spaces which result by reason of the disposition of cylinders a and b as illustrated in Figure 1, a very convenient arrangement being thus secured.
The exhaust valves h and the inlet valves are operated by cams k and they are preferably held closed normally under the action of spiral springs l and are positively operated by the cams aforesaid, which are mounted upon a spindle m upon which also a toothed wheel n is mounted gearing with a toothed pinion v fixedly secured upon the trunnion d or upon a fixed frame, the gear being a two to one gear such as will cause the operation of the exhaust valve and the inlet valve as required according to the four stroke cycle of operation of the respective cylinders .....”

The negotiations with the Balloon Factory did not result in an order, an Antoinette 35hp being fitted to the airship.

Redrup went on to develop larger versions of the 'reactionless' and then a radial (Hart) but without supercharging they do not belong in this story (See the book for further stories). We will move on to the Royal Aircraft Factory.
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Old 5 January 2011, 04:08 PM   #5
dirtyshirt
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Good evening,

Keep it coming, tartle, I'm tempted to dump the plastic and make one of these 2-stroke rotaries, of which I knew nothing about, in my shed. As they used to say "we have the technology".
I look forward to your revelations on 1916 / 1919.

With regards and much appreciated.
Mike.
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Old 5 January 2011, 10:05 PM   #6
Bletchley
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This is really very good, tartle - I know next to nothing about these very early motors, other than a few brief references in other books. I look forward to any thing you have to say on the RAF engines

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Old 6 January 2011, 05:21 AM   #7
tartle
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Forgot to cover Buechi!

Thanks for feedback! But before the RAF we should mention two other significant technology influences:
Buechi and Rateau.

Alfred Büchi – father of the turbosupercharger


The compound engine patented in 1905 is generally recognised as the starting point for exhaust gas turbocharging.
‘The Swiss engineer we have to thank for the 1905 patent is Alfred Büchi, who at the time was working with Sulzer. In it he describes a “highly supercharged compound engine” with a four-stroke diesel engine, multi-stage axial compressor and multi-stage axial turbine mounted on a common shaft.'
Born on 11 July 1879, Büchi, who died on 27 October 1959, worked as an engineer in the Swiss town of Winterthur. His idea was not just to pre-compress the air flowing into the engine, but also to use the kinetic energy coming out in the exhaust gas under high pressure, which otherwise was simply wasted. So he used the exhaust gas flowing out after the combustion process to drive a turbine serving, in turn, to drive a compressor pre-compressing the intake air and boosting the air charge in the engine. This marked the birth of the turbocharger.


GB 24,980. Büchi, A. Nov. 13, 1905, [date applied for under Patents Act, 1901].
Revolving - cylinder type; elastic - fluid turbines. -An internal-combustion engine comprising a number of radial cylinders a works on a four stroke cycle and drives the shaft b by the pressure of the piston - rods d on an eccentric e. The exhaust passes into a collecting - channel o and thence through a turbine p on the shaft b. The charges may be supplied to the engine under pressure, preferably by a turbo-compressor, and cooled in a cooler k. The compressor and turbine may work in stages, and the cylinder a may revolve about a stationary shaft.

Further work by Büchi at Sulzer eventually led to publication in 1909 of his idea for a freewheeling turbocharger (it would nevertheless be a while before anyone would follow this up) and later, in 1915, to his important ‘scavenging patent'. Alfred Büchi soon approached the Brown Boveri Company in the hope of turning his “highly supercharged compound engine” into reality. Some reservations on the part of BBC lasted until 1920 when the firm agreed to work with Büchi. It marked the beginning of a remarkable Swiss success story.
Parallel developments

Around the same time, work on supercharging aircraft engines was going on in France under Auguste Rateau and at General Electric in the USA under Sandford Moss.
In a 1916 patent (which was not published until 1921) Rateau, who had collaborated with Brown Boveri in gas turbine development in the early 1900's, described devices for regulating a supercharging compressor driven by an exhaust gas turbine, and in 1917 manufactured and tested such a device. Aircraft with turbocharged engines were in use towards the end of and after World War I, but development proceeded much more slowly post-war. Alfred Büchi and others later acknowledged that Rateau should take the credit for having manufactured the first turbocharger.'
We will return to Rateau later.

Last edited by tartle; 7 January 2011 at 01:18 AM.
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Old 7 January 2011, 09:57 AM   #8
tartle
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From RAF1a to R-R Griffon and Napier Nomad Turbo compound

British supercharger development can be put into two camps:
1) Mechanically driven, and
2) Exhaust-turbine driven, i.e. the turbo supercharger or turbocharger for short.
The story involves about twenty steps 1915-1945, so only those that take us upto the end of WW! technology in the mid-twenties is appropriate for this forum. This really spans the RAFactory, later RAE, career of James Edwin Ellor and associated aero engine company efforts, both influenced by developments abroad.
So we will follow around ten of the steps that will take us through the turbo story until Ellor joins Rolls-Royce and a new post-WW1 generation of engines take over. It is from then on, in Britain, that mechanically driven supercharging takes precedence driven by two crucial lines of thought:
a) It is the powerplant that provides power for flight and this means integrated thinking about cooling, propellers, supercharging and exhaust gas power recovery.
b) gearbox technology was proceeding apace and could be used in supercharger design; the challenge of developing and matching a hot turbine and a cooler compressor with interesting metallurgical and design challenges was a step too far in British aviation circles.
So on with the story.....
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Old 7 January 2011, 10:37 PM   #9
Bletchley
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Great stuff, tartle, keep it coming! This is a really interesting essay on early aero engine supercharger development. Do you have references or links to further reading for the Rateau and Büchi section?

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Old 8 January 2011, 03:10 AM   #10
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A most interesting thread - even to us non-engineers that just appreciate a bit of technical gen, up to their level of understanding.
When Formula One went to their Turbo formula there was such a massive amount of blow-ups, and even although oils had had such development over the years.
Can you say how the turbo bearings of WW1 survived the heat involved - with the oil technology of that time?

Cheers

Al
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