Renaults Hungarian Sidepod Fire

The silver canister is visible towards the front lower of the sidepod - via nextgen-auto.com

Update: Lotus Renault GP, have provided me with this response from Technical Director James Alison.

Three days after the incident on Nick’s car, has the team identified the reason why it caught fire after the pitstop?
J.A.: As with most accidents, several incidents combined to cause the fire that Nick suffered in Hungary. First of all, we ran a slightly different engine mapping strategy in qualifying, which produced hotter than normal exhausts. We believe that this elevated temperature and caused a preliminary crack in the exhaust pipe. We presume that the crack then propagated during the laps to the pitstop – this was not evident to us as we believe that the failure occurred upstream of the place where we have a temperature sensor. We believe that Nick then came in with a partially failed exhaust. This pitstop took longer than normal, the engine was left at high rpm for 6.3 sec, waiting for the tyre change to be completed. Under these conditions, a lot of excess fuel always ends up in the exhausts and their temperature rises at around 100°C/sec. This temperature rise was enough to finish off the partially failed pipe and to start a moderate fire under the bodywork.

There was an explosion shortly after Nick got out of the car, on the left. What was it?
J.A.: This was caused by the air bottle which supplies the air valves in the engine. It has overheated in the fire and failed.

Will you have to modify the car before Spa and if yes, is the August factory shutdown a handicap?
J.A.: The incident was highly undesirable, as it has caused us to write off a chassis. We will take steps prior to the next race to reduce the likelihood of a further fire and to ensure that the air bottle cannot overheat. We are in touch with the FIA both to provide them with a full report of the incident and also to explain to them the actions we are taking to prevent a reoccurrence.

As Nick Heidfeld made a pit stop at the Hungarian GP, there was a problem with one of his wheel nuts. This kept the car stationery for an extra 10-12 seconds. In readiness to leave the pit, Heidfeld kept the engine pegged at maximum revs. This extra delay was enough for the exhaust to start to overheat the surrounding bodywork. Without the usual pit fans blowing air over the bodywork, the carbon fibre soon started to smoke and then caught fire. Heidfeld was then released from the pit, as the wheel nut was properly fastened. Sparks were being blown from the car as he sped down the pitlane, this was the action of the exhaust blowing the fragments of the burning carbon fibre bodywork and not electrical sparks as some have speculated. The airflow over the bodywork only fed the flames and by the time he was at the pit lane exit his sidepod was well alight. As it was the bodywork itself that was on fire, the flames were on the outside of the sidepod and looked perhaps more alarming than was actually the case. Bodywork fires are not uncommon and teams have well rehearsed drills to meet the car in the pitlane with the pit fans and a precautionary fire extinguisher. Although it’s fair to say these sorts of fires are normally prevented by detail work to the shape and heat shielding of components early in the cars testing. Particularly around the exhaust which is the greatest source of heat within the sidepod. This year’s unusually long faired-in exhausts contribute a greater risk and the Forward exhaust exit (FEE) of the Renault only adds to the proximity of the exhaust to bodywork. With more conventional exhaust blown diffusers (EBDs), the exhausts are run along the floor to ahead of the rear tyre; these are slightly easier to manage. Additionally the heat shielded ducting for the Renault FEE, also provide a route for flames to exit out of the front of the sidepod, making the flames in closer proximity to the driver. This isn’t to say the Renault FEE is inherently unsafe. Any F1 cars bodywork left to overheat will see the flames rapidly spread across the skin of the cars sidepod bodywork.

http://youtu.be/s9tF7g3CwK8

What made Heidfelds fire more concerning was the apparently explosive moment when debris and gasses were blown out from the cars sidepod as the marshals sprayed extinguisher foam over the burning bodywork.

As the R31 came to rest, the driver jumped out and the fire marshals arrived from a post a few meters up the track. Two marshals tackled the blaze, running from behind the car to around the front to direct foam over the sidepods. As the first marshal carried on towards the rear of the car, the second marshal arrived at the front of the sidepods. Then there was this burst of debris and gas from the front of the sidepod. This appeared to slightly injure the marshal who limped around to the rear of the car. Renault have confirmed “he is ok. No injury. We are sending him a nice gift”. Shrapnel from the burst lay several meters away from the car in the pitlane exit lane. As we’ve seen fire’s are relatively rare in F1, oil fires being the more common and spectacular, but it’s very rare for a burning car to have this sort of violent moment.

Sidepods contain a multitude of systems; many items being solely in the left or right hand sidepods, rarely are any internals symmetrical left to right.

Typical components in this area are.

• Water radiator (LHS)

• Oil radiator (RHS)

• Hydraulic reservoir (varies)

• Nitrogen cylinder for the engine Pneumatic valve return system (varies)

• KERS battery water radiator (RHS)

• SECU, PCU, Battery, Lap time beacon (typically RHS)

• KERS PCU (RHS)

It’s important to note, sidepods do not contain the KERS batteries or the MGU. Also the gearbox oil and hydraulic fluid coolers are mounted atop the gearbox. There is very in the of little hydraulic systems being in the front of the sidepods, only the lines for the power steering passes this far forward in the car.

Seeing the explosion was not backed up with a further blaze of burning oil or steam from water radiators, its unlikely these burst in the fire. Then as most of the electronics are in the right hand sidepod, again these can be discounted. This leaves the obvious exception of the nitrogen cylinder. This is required as F1 engines do not use valve springs but instead a pneumatic pressure keeps the valves pressed open against the cam. In order to provide this pressure and as the system loses a little pressure during the race, a pressurised chamber maintains the required pressure. This comes in the form of a ~half litre aluminium cylinder. (Circled red – twitpic.com/5yycsi )

On most F1 cars and indeed Renaults all the way up to last year’s R30, teams mount these small cylinders inside the cockpit to protect them from crash or fire damage. Renaults R30 placed this on the hand side of the car, down on the small amount of floor between the driver’s seat and the side of the monocoque. But this location is not mandated by the regulations. Pictures of the R31 left-hand sidepod without bodywork, show there is an aluminium cylinder placed in the front section of sidepod. This transpires to be the nitrogen cylinder for the engine pneumatic valves. Probably because Renault had to create a slimmer monocoque to claw back the radiator volume lost to the routing of the FEE, they slimmed the monocoque and fond no space next to the driver’s seat to mount the cylinder and placed it outside on the radiator ducting instead. When this aluminium cylinder was heated in the flames and then suddenly cooled by the marshals extinguisher, the casing shattered sending the pressurised gas out in a hail of debris. This failure of a pressurised aluminium structure could also be the water radiator failing, while some rumours point to this the lack of the plume of steam ejecting from the sidepods after the initial blast, suggests to me this is unlikely. But to be clear, this wasn;t a chemical explosion, merely the failure of the casing of a pressurised vessel. as nitrogen is both intert and not liable to high rates of the thermal expansion

Comment by the team to news websites seems to back this theory up http://www.gpupdate.net/en/f1-news/265636/heidfeld-s-fire-caused-by-overheating-exhausts/ . Although I have yet to have direct confirmation from a source within Renault.

Seeing this was the first instance of such an occurrence that I can recall, I would imagine this might be examined by the FIA and technical directive issues asking teams to place this item in a more secure position to protect it and track officials from a similar incident.

More analysis of Renaults Front Exit Exhaust

http://scarbsf1.wordpress.com/category/front-exit-exhaust/

Renault – Front Exit Exhaust Details

Copyright Sutton Images via Formula1.com

Although we almost didn’t believe it when the rumours emerged at the launch of the Renault R31, The car does indeed have exhausts that exit at the front of the sidepods. We (@f1fanatic.co.uk and I) managed to see, understand and get the first pictures of the unique set up (http://scarbsf1.wordpress.com/2011/02/01/renault-r31-front-exit-exhausts-fee-explained/). Now the car can be seen stripped in the pit garage, we can see exactly how the Renault packages the exhaust.

The exhaust system routes the four pipes into a collector which then continues to point forwards and direct the secondary pipe low underneath the radiator to the front of the sidepods. As the exhaust routes gasses at up to 1000-degrees C, it needs insulating to protect the other equipment housed in the sidepods. Renault appear to have fitted an insulated jacket around the main length of pipe in the sidepods. What is clear from the set up is that Renault had to raise the radiators to allow the pipe to ass underneath. The R31 has unusually large sidepod inlets and this might to cope with the ducting of the cooling airflow to the laid down radiator.

Copyright: Andrew Robertson (@JarZ)

From these pictures via Andrew Robertson (@Jarz) we can see the front detail around the sidepods. Although the exhaust outlets are not seen here, the problem of the final routing is apparent. Teams need to fit beams to the side of the monocoque for side impact protection. Known as Side Impact Tubes (SITs) there are two pairs to share the load, with one upper pair and a lower pair. As these SITs are heavy, the majority of the work is down by the lower pair, to keep the weight low in the car. Correspondingly the lower SITs are larger and the exhaust needs to pass over these and down to exit sideways.

Copyright: Andrew Robertson (@JarZ)

Renault has packaged these lower SITs into a narrow front and wider rear Tube. The exhaust will angle down along the front tube to blow still pointing downwards across the lower leading edge of the floor. We can see the metallic heat protection on the SITs.

Copyright: Andrew Robertson (@JarZ)

More info on Front Exit Exhausts and how they work – http://scarbsf1.wordpress.com/2011/03/22/trends-2011-exhausts-and-diffusers/

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Trends 2011 – Exhausts and Diffusers

This year the technical talk has largely been about exhausts.  How teams have adapted to the ban on double diffusers and the added restriction on Exhaust blown diffusers. Just to aid understanding going into the new season, I have explained how these solutions work and how they look from beneath.

Double Diffusers

Force India 2010 Double Deck Diffuser (DDD)

Since 2009 the regulations regarding the floor have been interpreted in a literal sense to allow the double deck diffuser (DDD). Indeed the very same rules were exploited to a lesser extent under the previous rules, but this only produced small extra channels in between the outer and middle diffuser tunnels. With the major cut in aerodynamic aids for 2009, several teams sought to find a way to gain more expansion ratio from the smaller diffusers. In essence the loophole exploited the definition of surfaces formed between the step and reference planes. Multiple surfaces allowed fully enclosed holes, which fed the upper diffuser deck that sat above the 175mm lower diffuser. This allowed diffuser to be significantly larger in order to create more downforce. Notably Brawn, Williams and Toyota launched 2009 cars with DDDs. Other teams soon followed suit in 2009 and last year every car exploited the same loophole. Over the winter the FIA acted to close the loophole, by enforcing a single continuous surface across a 90cm span under the floor. In a stroke this banned the double diffuser, there being no scope to create any openings in the floor to feed the upper deck.

Single Diffuser

Double Diffuser

 

Exhaust Blown Diffusers
Another approach to regain lost downforce was the re-invention in 2010 of the exhaust blown diffuser (EBD). This used high energy exhaust gasses to blow the diffuser, the faster throughput of flow under the floor increased downforce. Two methods of EBDs were used in 2010, one blowing over the diffuser and the second blowing inside the diffuser. This latter solution was more effective at driving flow through the diffuser and created more downforce. However this necessitated a hole made into the diffuser to allow the exhaust gas to enter, I‘ve termed this method an ‘open fronted diffuser‘.

2011: No openings allowed in the yellow 90cm zone, outside certain holes are permitted

A by product of the 2011 rules intended to ban the DDD, also stopped this open fronted diffuser solution. However the rules enforced the continuous surface only across a 90cm width of floor and the diffuser is allowed to be 100cm wide. Thus a 5cm window was allowed each side of the diffuser.

Outer Blown Diffuser – Solution

Red Bull Diffuser: Flow passes under the outer 5cm of floor into the diffuser

Red Bull and Ferrari appear to have found this loophole simultaneously. Recently Sam Michael pointed out this was probably the most efficient way to blow the diffuser under the new rules. As Red Bull appeared with this set up first, its often termed the Red Bull Blown diffuser.

What these teams have done is to open up the floor 5cm either side of the diffuser, then route the exhaust towards this opening. The exhaust gas gets collected by the coved section of floor and this directs the high energy gasses under the diffuser, to recover some of the losses from the more open diffuser allowed last year.

Front Exit Exhaust

Renault Front Exit Exhaust: Flow passes wide around the floor before entering the diffuser

Renault meanwhile turned the problem on its head. As the aim of the EBD is to increase flow under the car, they pointed their exhaust at the front of the floor. I’ve had it confirmed to me by two ex-Renault sources that the exhaust does indeed mainly flow under the floor.

The exhaust pipe outlet sits above the step plane just ahead of the leading edge of the floor. This is not simply blowing out horizontally and across the floor, but is ducted slightly to blow downwards and backwards, this is roughly in line the with the flow trailing off the “V” shape above the splitter. Along with the strong vortices set up by the splitter, vanes and bargeboards, this makes the floor appear wider than it is. The flow will go out beyond the floor and then curl back in and under the floor. Some flow will inevitably pass over the floor, but the most of the energy will be driving more flow under the floor to the diffuser.

McLarens Slit Exhaust

The slit above the floor is visible. Copyright: Liubomir Asenov

No conversation about exhausts this year, would be complete without some speculation about McLaren. Amongst the several exhaust systems run by McLaren over the pre-season tests was a “slit” exhaust. This appeared at the first Barcelona test, but did not seem to appear for the second Cataluña test. The exhaust collector could be seen to duct towards a double thickness section of floor ahead of the rear wheels. This section was also interesting for its longitudinal slot, this slot was not large enough to be the actual exhaust outlet, This might be a cooling slot, or to improve the flow from above to beneath the floor.  I beleive the Exhaust is actually below the floor.  As when the car ran the same floor with a conventional exhaust outlet, there appeared to be a removable section of floor ahead of the rear wheels. Being just outside of the 90mm opening rule, the floor ‘could’ be opened to allow an exhaust to blow through to underneath. If sculpted correctly, the exhaust could be ducted back inboard and blow towards the diffuser from under the floor. It’s possible that this could be in interpretation of a legal opening, assuming it met the maximum fillet radius rules.
I’d expect the resulting exhaust outlets to be a long wide slot, this wider outlet would be needed to meet the maximum radius rules and also reduce the back pressure from the tight curve of the exhaust outlet. As the exhaust would have a tortuous bend, to curl back under itself to direct the flow inboard, rather than out wide around the rear tyre.

Mac Slit: The exhaust might exit beneath the floor in a long narrow outlet

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Renault R31 – Cooling solution and diffuser performance

Renault are not only unique in their exhaust location, but also their sidepod cooling set up. Its possible that the two solutions are related.

Teams have to find the most efficient way to vent hot air from within the sidepods. This air has to pass through the radiators and coolers, as it passes from the sidepod inlet to the tail of the coke-bottle shape. In order to keep the car as slim as possible for reduced and drag and better airflow to the diffuser and beam wing, teams adopt different cooling outlet solutions to work with the other aero flow structures around the car. In Renaults case the majority of the outlet area is in three places: a tall narrow outlet above the gearbox and two low and wide vents either side of the gearbox. We can see the gearbox oil cooler within the upper outlet, so some of its volume is used for venting this heat. Reducing its ability to vent air from the sidepods.

Renault appear to have chosen the two lowwide outlets in order to boost airflow to the beam wing. The compromise in doing this, is the airflow over the diffuser. Airflow over diffusers might be considered as unimportant, as its the flow underneath creates the low pressure and hence downforce. But with a restricted diffuser height , the use of directing high energy airflow over the top of the diffuser and its trailing edge gurneys, helps the airflow beneath. Effectively making the diffuser act like its larger than it is. With other teams, they use the exhaust gasses or very narrow sidepods to direct as much high energy flow as possible over the diffuser. In Renaults case, the airflow running along the floor does not flow directly over the top surface of the diffuser, as these wide vents are in the way. Some people have suggested the teams are directing the heated airflow from within the sidepods out of these vents and over the diffuser for greater aerodynamic effect. However the reality is different, the air coming out of these vents will be of low energy, having passed through the various cooler matrices. Thus its effect in aiding the diffuser is much reduced.

So why have Renault thrown away some aero gains in this area? Probably because of the exhaust solution, As the flow under the diffuser is accelerated by the exhaust gasses passing under the floor, the diffuser does not need the effect of airflow blowing over the top. Thus they moved to the sidepod outlets to this area and played better airflow over the beam wing.

So far no other team have gone for low wide cooling outlets, but equally contrary to the rumour mils no teams has adopted front exit exhausts either. It will be interesting if any team follows Renaults solution in either of these areas.

McLaren MP4-26 exhaust – is the “U” bend a Front Exit?

 

MP4-26 - the "U" bend is visible between the diffuser and suspension

McLaren lead the way with innovations in 2010 with the F-duct, but they were late to debut their double diffuser and blown diffuser. In 2011 McLaren appear to be right on the tail of this year’s novelty the front exit exhaust.
So far in testing, the MP4-26 has been seen completing a diligent aero programme with the car appearing with two different format exhausts. One conventional set up which blows over the diffuser and another which appears to have a “U” bend in the system. This latter solution is believed to be a front exit exhaust as used by Renault (http://scarbsf1.wordpress.com/2011/02/01/renault-r31-front-exit-exhausts-fee-explained/).

But as yet there is no sighting of the actual exhaust outlet.

Last year teams started to blow the exhaust over or through the diffuser to produce more downforce. With the method of opening the front of the diffuser up and letting the fast moving exhaust blow inside the diffuser, being the most effective route for more aero grip. Rule changes for 2011 prevented teams opening the front of the diffuser up (aside from a 5cm outer section of floor). So teams are faced with either blowing less efficiently over the floor or finding a new way. Renault have exploited another way, by leading the exhaust forward and pointing it under the front of the floor. Blowing the exhaust at the leading edge of the floor effectively creates more flow under the floor, which in turn creates more downforce. This front exit is a good aero solution, but packaging the duct from the main exhaust to the front of the sidepod is difficult due to the space constraints within the sidepod and heat rejected from the exhaust duct itself.

MP4-26 the conventional exhaust exits at the rear and blows over the diffuser

With McLaren’s conventional exhaust the four pipes merge into the collector and the secondary exhaust pipe points backwards to blow flow over the ramped outer section of diffuser. This set up has been used on and off consistently through the test. It also appears to the baseline configuration. As a lot of the aero tests using pressure rakes, flow-viz and long runs, are being completed with the conventional exhaust.

MP4-26 with the conventional exhaust exposed, the "U"bends crease in the floor can be seen

However other tests have been completed where the sidepod is revised. The sidepod features a bulge at the rear of the coke bottle, the bulged section appearing to house a revised exhaust system. Looking from the rear where the normal exhaust outlet can be seen is instead a “U” bend of exhaust tubing. With this set up the exhaust exit cannot be seen. Although several photos of sensors and cabling around the sidepodsplitter have prompted some fans and media to propose they are exhausts. In my opinion no photo as yet exposed the real exhaust outlet. With both systems, the rear of the floor and diffuser are the same.

MP4-26: This is how the "U" bend exhaust might look

Knowing the “U” bend system exists, I’ve tried to find proof for a front exit. One bit of evidence is on the launch car, which was initially unveiled without bodywork. Clearly a lot on the car was missing, but the floor appears definitive enough and just below the normal exhaust collector was a crease in the floor. This niche moulded into the floor is in the same location as the bulge in the sidepod when the “U” bend is run. Looking at its shape, I’d suggest this is where the collector and secondary pipe sit when the “U” bend exhaust is fitted. We can roughly predict that the collector sits further outboard and a little lower. The secondary pipe then curves inboard and then forward under the branch of four primary pipes (see illustration). Of course from here we don’t know where the exhaust routes, so we can’t confirm if it does blow back under the floor.

MP4-26: this is the aero rake used to measure flow accross the floor

Amongst the various aero rake tests McLaren have run, some tests features a huge array of pressure sensors in a rig mounted behind the diffuser. A later test had a simpler rig, which passes the floor ahead of the rear wheels. Initially this system ran with a conventional exhaust, and then later the rake was run with the “U” bend. I believe the rake was used to look at the pressure distribution under the floor. The two runs were used to map the different between the conventional exhaust and the improved flow of the front exit. So this suggests they are running some form of front exit.

MP4-26: the aero rake and "U" bend being run simultaneously

So where is the exit? I’ve looked at every picture I can find of the MP4-26 and I have yet to see any evidence of the front exit. I do believe its there, hidden behind the bargeboards somewhere below the sidepod inlet, or routed inside the splitter and blowing backwards. Other journalists at the Jerez test have confirmed some form of exhaust exit appears to be in there, kept out of sight both by other bodywork and the huddle of mechanics around the front of the car with the portable blowers to keep things cool when it returns to the pits. Also I’ve heard that the switch for one system to another takes 2 hours, which has reduced the McLarens track time.

But until we see a photo of the exit we can only speculate.

Notes:

This is not an exhaust

 

This is not an exhaust

 

This is not an exhaust

Renault R31 Front Exit Exhausts (FEE) – Explained



Renault have found a new solution to the blown diffuser concept. In fact they’ve turned it on its head. With an exhaust that exits at the front of the sidepods.

Last years teams reintroduced the blown diffuser concept, either by blowing exhaust gasses over the top of the diffuser, or by creating an opening into the diffuser to blow inside the diffuser. Both solutions created more downforce. With the latter solution now banned, it seemed the less effective over-blown solutions are all that’s left to race. However LRGP have found another way, blowing the front edge of the floor.

For a diffuser to create downforce it needs as much flow to pass through the venturi as possible. Teams arrange bargeboards and other aero devices to build up a high pressure region ahead of the floor to ensure the greatest mass flow underneath. Its then down to the expansion ratio of the diffuser to pull that flow through. Last years blown diffusers improved the expansion ratio, but not the flow ahead of the floor. What Renault have done in to lead the exhausts forward through the sidepods (about 1 meter) in-between the chassis and the radiators, then turn the exhaust 90-degrees to point it down towards the leading edge of the floor. The exhausts gasses follow the curved leading edge and round underneath the floor. This accelerates the flow under the floor for more mass flow and hence more downforce.


Problems with this solution are mainly to do with heat and engine mapping. With exhaust temperatures of 6-800c some clever insulation solutions are needed to keep hits heat from the fuel tank, radiators and a electronics. Then the Renault engine team lead by Rob White need to design exhaust tuning to deal with a far longer secondary pipe. typically longer pipes are better for low revs, somewhat contrary to the needs of an engine running at 18000rpm. Renault placed their KERS MGU and Battery underneath eh fuel tank, this was clearly to allow the packaging of the FEE. Unlike the McLaren F-duct, it is possible for this solution to be copied as no monocoque alterations are required.