2014 Power Unit - Thermodynamics

With the introduction of Hybrid power trains for the 2014 FIA Formula 1 season, I thought it’d be the perfect time to introduce the ‘Thermodynamics’ subject, and how crucial understanding it is to a powerful, thermally efficient hybrid power train.

Thermodynamics is the study of energy. We use thermodynamics in power units to understand how to maximise efficiency. Maximising efficiency is achieved by reducing energy losses across a system.

If we maximise Power Unit efficiency in our Formula 1 scenario, we can use a lower volume (therefore lower mass) of fuel but still achieve the same levels of power output from the power unit. By reducing fuel consumption as much as possible whilst maintaining power output, it means that less fuel needs to be put into the car to complete a race distance. Less fuel means less weight, less weight equates to better lap-times from better tyre management and better power to weight ratio.

Throughout the 2014 season, FOM have treated us F1 viewers to live fuel consumption data. Every occasion that the data has been shown, we have seen that the Mercedes Power Units have used less fuel (at that particular point in the race) than their rival Renault Power Units.

There are different ways that thermodynamic calculations can be applied to a system, from Rankin cycles to PINCH technology. I won’t progress into any form of calculations because the level of understanding required! Even I would struggle to do calculations on the very complex 2014 PU!

When I refer to a ‘system’, I am talking about a cycle of some sort. For example, if I will quickly demonstrate the energy cycle of a turbocharger:

• To begin with, I’d like to add that this is not a fully accurate representation of a turbocharger system; I have drawn this diagram to demonstrate what happens in the ‘cycle’.
• The lines connecting the components together represent pipework for the working fluid, which in this case is air. Air is the fluid used in this system to produce WORK.
• The circuit is broken at stage three because the working fluid, air, is rejected from the system via the exhaust pipe. The compressor then brings clean, cold air back into the system ready for another cycle.

W = WORK (A useful form of energy we can use mechanically)

Q = HEAT FLOW

Step 1:

Cold compressed air enters the ICE combustion chamber. The combustion process adds heat into the system, Qin. This means that our working fluid has absorbed heat energy (hot exhaust gases).

Step 2:

Used gases are expelled from the ICE. Usually they would be released into the atmosphere through the exhaust pipe, but that would be very inefficient because the hot, high velocity gases still possess a lot of thermal energy. This thermal energy can be used to do something useful to increase the efficiency of the powertrain…

The exhaust gases from the ICE are sent to a turbine, the job of the turbine is to create work,         W-out by removing energy from the working fluid (exhaust gas). Can you see how we used energy that would’ve been wasted to make it into something useful?

Step 3:

The gases that spun the turbine to create work have now been discharged through the exhaust tail pipe. These gases are of lower energy which results in lower decibel level of sound as they escape into the atmosphere!

The work produced by the turbine is now used to run the compressor. The compressor compresses fresh air taken in from the air intake above the drivers’ heads, work is being put into the system,  W-in, as the working fluid (fresh air) is being compressed.

Step 4:

Pressure is proportional to temperature; therefore our compressed air (high pressure) is now also very hot. If this hot compressed air is put straight into the combustion chamber, it would result in inefficient combustion and be detrimental to the materials used for the engine’s components, so the air needs to be cooled somehow.

The intercooler cools the compressed air so that it is a suitable temperature for combustion; the engineers have to compromise intercooler size with aerodynamics. The aerodynamicists will desire small side pods, therefore small intercooler, but the engineers will want a large intercooler to increase the cooling levels of the gases.

Step 1:

The cooled compressed air is ready for combustion and the cycle continues.

Efficiency:

If this was an example of a steam power plant, the engineers would want as much W-out as possible but for the smallest W-in as possible. More W-out means that the power plant can use that work to create more electricity to sell, whereas W-in requires money to be spent (powering the machines providing work into the system).

In this case of an F1 turbo, W-out is not wanted for money; W-out is wanted to power the compressor as much as possible. We don’t desire a low amount of W-in to the system because we want to compress the air as much as possible.

Therefore, the aim of the turbo designers is to maximise both W-out and W-in to gain as much performance as possible. This means that the turbine and compressor need to be designed for 100% efficiency to prevent losses, but of course, there are turbo size restrictions that limit the maximum power the engineers can get out of the turbo.

The actual inclusion of the turbo into the power unit provides the largest efficiency increase. The exhaust gasses that would otherwise be wasted are now used to create work. That work created is used to power the compressor, which in turn provides better combustion for the ICE.

This has been a very basic example as it doesn’t include any hybrid features such as the MGU-H etc. I just wanted to demonstrate what efficiency actually is and how it can be increased by not wasting anything that still holds some energy, in this example it is the ICE waste gases running a turbocharger.

If you enjoyed this different take on the 2014 Power Unit please share it, or retweet it on Twitter. Don’t forget to follow @HybridAliF1. Thank you for reading!

Ali

Canadian GP – Team Overview

Hey guys,
Let me know what you thought of this 'overview' type blog. If you liked it, I'd appreciate a share or a retweet on Twitter - @HybridAliF1.

Thanks for reading!
Ali


Red Bull

Red Bull Racing
	Qualifying	Race
Vettel	3	3
Ricciardo	5	1

On Sunday morning, it was likely that Red Bull were praying for one of their drivers to occupy the final step of the podium in a few hours time. Having been constantly reminded that this was their worst circuit on paper, and that the Mercedes Power Unit would dominate them on the straights, they pulled off the most unlikely win seen by F1 in years.

Vettel’s race was hampered by his strategy, if it wasn’t for this, he would’ve been the driver on the top step. Vettel’s problems came about when exiting the pits, both for his second and third stints. Unfortunately, he’d found himself slot behind the equally as quick, one-stopping Force India cars. Due to the nature of the Montreal Circuit Vettel’s Renault PU could not muster up enough power to get past the Mercedes driven Force India cars.  

On the contrary however, Vettel’s team-mate Daniel Ricciardo found that he was in good positions after his pit stops. Vettel’s second and final pit stop came at around lap 37, and again he found him-self behind a Force India car. Ricciardo meanwhile pitted during lap 38 and exited just in front of the Force India and Vettel train of cars. This showed how much time Vettel lost being stuck behind the cars ahead of him.

Sergio Perez led Ricciardo then Vettel for a number of laps until his tyres began killing his pace, this was due to his one stop strategy. Ricciardo soon dispatched the Force India before storming past the injured Mercedes-Benz taking an incredible win. Vettel meanwhile kept his wits about him to secure third place as he dodged Massa’s Williams as it came hurtling towards him going into turn one.

Mercedes AMG

Mercedes
	Qualifying	Race
Rosberg	1	2
Hamilton	2	Ret

The race start saw bought no surprise as the two Mercedes cars quickly hurried away from the rest of the field. Hamilton challenged Rosberg for the lead on a few occasions but was unsuccessful on all attempts.

The drama started on lap 37 where Hamilton reported to his engineers that he’d lost power. His lap-times suffered massively as a result of this which meant Rosberg’s lead increased. It  was around a lap later when Rosberg also lost power, and the gap between the Mercedes car neutralised as both cars developed the same problem. Although the gap between the two front runners neutralised, the rest of the field began to catch up at a terrifying rate.

The problem was a KERS failure. It is to my understanding that the KERS on both cars ceased to harvest energy. When the KERS isn’t harvesting energy, it isn’t contributing to the deceleration of the cars velocity as it should be. This meant that the smaller and ‘weaker’ rear brake discs had to be worked harder to make up for the lost braking power that the KERS harvesting provided.

Unfortunately on lap 45, by the time the engineers had realised what was fully going on, Hamilton’s rear brakes had been overwhelmed with responsibility where they failed due to the carbon ceramic material overheating.

Tony Ross (Rosberg’s Race Engineer) saw Hamilton retire and quickly told Rosberg to change KERS settings and adjust the brake bias forwards. From here Rosberg managed to hold out until the end of the race for P2.

Ferrari

Ferrari
	Qualifying	Race
Alonso	7	6
Raikkonen	10	10

Ferrari had a very poor race in Montreal. Alonso fell back a place from his starting position, even with three retirements from the front of the field; it could have been a lot worse.

Raikkonen continued to have his usual troubles. Spinning in the low speed chicane confirmed that he was destined for a disastrous race. The spin most likely occurred due to bad mechanical grip and set up. Recently the Ferrari has been struggling to get its tyres into the operating window within an acceptable period of time; this could be due to the pull-rod suspension geometry settings.

(Which I have discussed in a previous blog! - http://ali-f1.blogspot.co.uk/2014/06/suspension-geometries.html)

Force India

Force India
	Qualifying	Race
Hulkenberg	11	5
Perez	13	11

There is no doubt about the potential of the VJM07, both drivers have shown promising pace since the beginning of the year.

Force India showed extreme confidence in their tyre wear management by opting to run a one stop strategy on both of their cars. This decision was most definitely the correct one because the two Force India cars were constantly at the front end of the field despite their bad results in qualifying. Hulkenberg started on the soft tyre and pitted for the softer option on lap 42, whereas Perez did the opposite starting on the super soft and pitting on lap 35 for the soft (harder) compound.

Both strategies would’ve resulted in similar finishing positions. Perez’ soft tyres had begun to perish by the end of the race, as Ricciardo and then Vettel overtook him. Massa was next in line but for the eye watering accident that occurred a few seconds later. Either way it looked as if he was going to finish in 4^th position. By this time, Hulkenberg had went almost double the time everyone else did on their own super soft tyres, therefore he had no chance whatsoever of any further overtaking opportunities.

McLaren

McLaren
	Qualifying	Race
Button	9	4
Magnussen	12	9

McLaren did not progress performance-wise through the Canadian GP. Although Button finished a fantastic P4, it was mainly down to the three retirements up front and a mistake from Alonso on the final lap. Magnussen made up 3 places through the race, but again it was due to the three retirements at the front of the field.

McLaren’s problems go on with no let up from Button’s lucky fourth place finish.

Williams

Williams
	Qualifying	Race
Massa	5	12
Bottas	4	7

Williams showed that they have a car that is good enough to be on the podium consistently. Massa also had the greatest opportunity to win the race, but it was all over when a slow pit stop meant he was released behind his team mate and Niko Hulkenberg. Massa still had a good chance to challenge the win as he approached: Rosberg, Perez, Ricciardo and Vettel. Unfortunately he made a mistake at the hairpin before the back straight and couldn’t catch Vettel that lap, then the next lap he either forgot to activate his DRS or there was a DRS failure when he was trying to overtake Vettel on the straight.

Regarding the final lap accident, I believe that both Massa and Perez were at fault. Perez definitely cut across Massa (to defend position) but it was a bit too late as Massa was already very close to the Force India. Massa also steers right (into Perez) as if he was trying to get back onto the racing line, but he did this without noticing that Perez had turned into his path.

Valterri was plagued with various problems and his main aim was to bring the car home without pushing it over the limit.

Toro Rosso

Toro Rosso
	Qualifying	Race
Vergne	8	8
Kvyat	15	Ret

 Kvyat also ran into a lot of trouble, he span early on in the race before eventually retiring with a drive train issue.

Vergne had a weekend he’ll be very proud of considering how unlucky he has been this year. He was much quicker than his talented team mate and dominated him all weekend.

 Lotus

Lotus
	Qualifying	Race
Grosjean	14	Ret
Maldonado	17	Ret

Lotus’ woes continue as both cars retired with mechanical problems. Maldonado retired with engine issues and Grosjean retired when his rear wing end plate broke at the bottom mount.

Marussia

Marussia
	Qualifying	Race
Bianchi	19	Ret
Chilton	18	Ret

After having the best weekend of the team’s history, the only way the Canadian GP could’ve went any worse for Marussia is if Caterham or Sauber scored a point or two here.

As the back of the pack filtered in to turn three on the first lap, Max Chilton experienced a major case of oversteer as he clattered into Bianchi, sending him into the concrete wall of turn four, and demolishing his rear end. Chilton’s mistake saw the end of the only achievement in his F1 career, to have finished every race he’d competed in.

Sauber

Sauber
	Qualifying	Race
Sutil	16	13
Gutierrez	22	14

Sauber had a rather uneventful weekend as Sutil started from the pitlane to bring the car home in P13. Gutierrez retired with a battery issue but finished last of the finishers.

Caterham

Caterham
	Qualifying	Race
Kobayashi	21	Ret
Ericsson	20	Ret

The situation at Caterham does not look any better as they were the slowest team at the Canadian GP. With the amount of retirees throughout the GP, Caterham could have had a very acceptable weekend, unfortunately though, mechanical failures doomed them to double retirement. 

Vehicle Dynamics - Suspension & Geometries

The suspension system is critical to an F1 car because it is the link between how the tyres work with the chassis. In recent races, we’ve been hearing how the teams have been struggling to turn the tyres on, or it is taking a while for the drivers to get the tyre in an optimum operating window.  The problem is that teams are trying to balance extracting the maximum amount of friction from the tyres whilst also attempting to keep wear rates as low as possible.  Another factor may be that teams are being too conservative with geometry so that they don’t wear their tyres too quickly during races, but because of this, the car isn’t putting as much load and forces into the tyre and therefore, it is taking the driver a lot longer to get the tyre into its operating window. This area is very complex and there is no set ‘perfect’ geometry.

Suspension geometries are an important branch of vehicle dynamics. Suspension geometries determine how the sprung mass (car chassis) and un-sprung mass (wheel/hub/brake discs etc) connect to each other. The angles and positions of the suspension members dictate how the body of the car behaves as the car corners and the suspension systems are loaded up.

Degrees of Freedom:

The wheels of an F1 car need to be restrained in some way so that the contact patch of the tyre is maintained at a maximum. There are various suspension design layouts that can be chosen to restrict wheel movement, but for open-wheeled F1 car, we can only use a double wishbone system.

The double wishbone system consists of an upper and lower A shaped arm (wishbone) that connects the wheel to the chassis / car body and a push or pull rod to dampen the vertical motion of the wheel.

Camber:

Camber is one of the geometry settings most mentioned on TV. The point of camber adjustment is to maximise the contact patch of the tyre as it corners. Taking a front view of an F1 car (looking at the front wing), camber is the vertical angle of the tyre relative to the floor. Therefore, a tyre sat perpendicularly to the floor has 0 camber. When the tops of the two front tyres (or the two rear tyres respectively) are a closer distance to each other than the bottoms of the tyres, this is called negative camber.

The front tyres are always set to negative camber. A few degrees of negative camber counter acts the body roll and tyre sidewall flex during high down-force cornering. This means that mid corner, the car’s motion will have rolled the negative cambered outside tyre into a neutral camber therefore maximising the contact patch and maximising grip mid corner.

Instant Centre:

In this example, I will only be looking at the front view instant centre. There is also a side view instant centre which is just as important, but for this blog we’ll only look at front view.  Front view instant centre determines important things such as: the roll centre height of the car, change of camber rate and lateral tyre scrub.

This example looks at a simple rear end of an opened wheel car. In the image you can see the two tyres on the left and right, with wishbones connecting the wheels to a ‘body’ of some sort in the middle. (It looks messy, but this is a simple example!)

The instant centre is a point where lines are drawn from one side’s suspension linkages until they intersect each other at some point. The engineer decides to place the IC wherever they want it to be.

As I was the engineer in this example, I had decided to place my instant centres in the middle of the outside wall of the opposite tyre.

For example:

Starting from the left tyre and wishbones, extrapolated lines are drawn from the upper and lower wishbones across to the right hand side until they intersect each other. Where these two lines intersect is the instant Centre, and as said earlier, the instant centre was deliberately placed. Using some simple trigonometry, the angles of the two left hand side wishbones were found to be 3.55° from the horizontal axis. (Both upper and lower have equal angles for simplicity, but in real life they will probably be different)

As the car is symmetrical, both IC’s have been identified and now we can find the roll centre height.

Roll Centre Height:

Roll centre determines where the rolling moment of the cornering car will be and what effects that will bring. (A moment is a ‘Twisting’ force, Moment = Force x Distance)

Roll centre height is found by drawing a straight line from the centre of the tyre’s contact patch to its respective instant centre. Drawing two lines from the contact patch of each to their IC’s makes the lines intersect each other, where the lines intersect shows where the roll centre is. The distance between the floor (bottom of the tyres) to the roll centre is the roll centre height.

In this example, the RCH is 11.5cm from the floor.

When a car is cornering, the lateral force at the centre of gravity can determine the moment about the roll centre. The higher the roll centre height, the smaller the moment about the moment about the roll centre.

The high nosed 2013 F1 cars naturally bought with them a high roll centre height. The steep front wishbones of the cars meant that high instant centres were necessary and therefore, the consequence was a high roll centre. This high roll centre bought with it relatively low moments about the RC. This low moment means that the car isn’t rolling about laterally so it is very stable.

In contrast, this year’s 2014 cars have much lower angled wishbones due to the lower nose/bulkhead height. These smaller angles mean that the roll centre height must be lower on this year’s cars. Although corner speeds are lower this year due to lower amounts of down-force, the rolling moment about the RC is higher because the roll centre height is lower down than in 2013.

The higher moment about the roll centre means the cars aren't as laterally stable as they were last year, and this is most evident in medium speed direction changes where down-force isn't available to plant the car into the floor.

For example, this weekend in Canada we have seen: Gutierrez crash between turns three and four, Ericsson crash between 8 and 9, and Chilton causing a crash by drifting across turn three into his team-mate Bianchi. The leading constructor Mercedes also saw lateral instability, during the race we saw Rosberg make an incredible catch coming out of turn 4 to save his race. This shows that it isn't just the smaller teams struggling with suspension and geometries.

This is a very brief insight into suspension geometries, I hope that you enjoyed reading about it and would like to learn more like I do! Keep an eye out on future vehicle dynamic blogs of mine.

Ali