At the opening of Ricardo’s new Vehicle Emissions Research Centre (VERC), Calum MacRae sat down to discuss future powertrain developments with Ricardo’s Professor Neville S. Jackson who serves as the engineering consultancy’s Chief Technology and Innovation Officer.
What does your job mean on a day-to-day basis?
It is the best job in the world, because my focus is on the future and where technology is going and what is important. To do that I need to learn. I need to go and listen to people, share views, learn about all sorts of things going on in different sectors. What is happening in healthcare, for example, some of the stuff we are doing on cryogenics (the CryoPower split cycle engine) came from healthcare, what is going on in artificial intelligence. How does it affect our business. I live in a world of technology and it is faster moving now than it has ever been.
In terms of the technology you see coming down the line for light vehicles in terms of CO2 many of the lower-cost solutions are on the market already. What’s next?
The lower cost solutions are downsizing coupled with ever-increasing degrees of electrification. So moving from the 12-volt electric system to slightly more volts, 48-volts maybe, and being able to produce 12-15kW of electric power in that system. Not only recovering that amount of power but also redelivering it back in to the powertrain when you need it. That equates to in the region of 100Nm of torque. Now a little turbocharged one-litre engine produces 200-250Nm of torque, if I can get 100Nm instantaneously at launch from an electric motor that transforms the driveability and you can make the engine smaller and get even more fuel efficiency.
So from here you could change the transmission as well?
Transmissions are another issue and a lot more complicated. The trend recently, particularly for autos, has been more gears so 8-, 10- and even more speeds. Primarily that is there to try and keep the engine operating at its optimum operating condition. The new engines we are making, designing and developing, have a much broader range that they can operate in optimally. So you do not need so many gears. The interesting thing is are we going to stick with ten gears because they are fashionable and they are what drivers expect? Or can we go back to five- or six- gears? It could be less expensive to build a vehicle with fewer gears.
I was told that four would be the optimum number of forward gears for the transmission in the future?
It might be. However, what we have been looking at it might not be the number of speeds, maybe they need to be torque ratios as well. With a light duty engine and a light duty transmission you’ve got to size the transmission to take the full torque, but most of the time you’re operating at 30Nm but it’s got to take 200-250Nm, while your engine produces 100kW but driving along the road at 30mph you only need 2.5kW and at 70mph you need 18kW, but you’re carrying all the infrastructure for a 100kW event that’s hardly ever required. Engines we are making ever smaller, but downsizing a transmission? The issue is we need an efficient transmission at relatively light torques, but because of the size of your gears, bearings, seals, larger shafts etc. you need for the absolute potential of the engine the only way we think you can do it is make everything smaller for the torque required and go totally modular but with only 5-speeds. If you need more torque handling capability it is the same transmission but with larger gears etc.
Conversely, with electric vehicles it has always been thought only one-speed is required but now there is multi-speed electric vehicle transmission development?
Again, it is about efficiency. All machines have an area where they are most efficient and you need to operate in that space as much as you can. The complexity of adding more gears can deliver you an improvement in overall system efficiency because you are operating in that more efficient area of the electric motor for a longer period of time of the vehicle operation. So sometimes it is worth doing. It does depend on the motor design as they do have different characteristics.
Can you increase range or have a smaller battery by having more gears for electric vehicles?
Not really. The range is about energy. Therefore, it is not going to give any more range unless we are talking about a massive impact on efficiency. With more gears, we are only talking about 4-5%, so a 100 mile range becomes 105 miles – that is not enough to persuade the average consumer.
Improving efficiency does improve range, particularly on the electric motors. Electric motors are pretty efficient anyway – over 90% efficient over most of the operating range, so we’re talking going from the early 90s to the mid-90s over a wider operating range which could potentially give you a bit more range but it would be changing from a 100 miles to 105 miles again. It is the right thing to do, but is it going to change consumer perception? Probably not.
In terms of engines the low-hanging fruit has been taken, where are we going next?
It depends how far you are looking ahead! The direction we are going on downsizing has a long-way to go, there are more and more things we can do. Particularly mixing in the low-power electrical systems, downsizing, boosting, and thermal-efficiency kind of approach. That is probably going to continue to develop for the next 10 or 15 years. The next step really is what we can do to recover more exhaust energy – e-turbines, a bit like those in Formula 1 now – how do we use heat to generate electricity directly. Thermoelectric generators are relatively expensive at the moment but we have a big programme to reduce costs. After that the next step is can we modify the thermal dynamic cycle on which the internal combustion engine generates? Now we have suck, squeeze, bang, blow of the four-stroke cycle but we have been looking at can you do that differently and do it more efficiently.
Would that solution involve two-stroke engines or are you referencing split cycle engines?
We are not talking about two-strokes, but they do have some advantages and some disadvantages too. Our recent work, and we are talking ten years ahead, is on split cycle work where you have one cylinder that does intake and compression and another that does combustion and expansion. In our work on split cycle engines, we are looking at recovering a large part of the exhaust energy in to the cycle. The potential to improve the thermal efficiency is by half – so going from 40% to 60% thermal efficiency. The highest efficiency point you have now for a light duty engine – stoichiometric gasoline engine, lambda 1, three-way catalyst – is 35-36%. A diesel engine reference point is early 40s. If we run the gasoline engine lean, like we do with the diesel, the efficiency is going to be similar to the diesel. That is probably where we will go next with gasoline in the next ten years. Downsize and run it lean like the diesel.
Does that mean the HCCI engines?
We might not call it that. HCCI is largely about NOx emissions rather than efficiency. NOx is formed because you are burning too hot. If you can keep combustion temperature below 2000 degrees kelvin, you do not produce NOx. Therefore, we want to develop a relatively low temperature combustion system. That is difficult because you have to make the burn almost homogeneous – you cannot have little bits that are running hot and little bits that are running cold. HCCI is a method of doing that. However, controlling combustion so you also get good efficiency is a real challenge. The way HCCI is done gives you very little control of where combustion occurs in the cycle. There are other ways of achieving the low-temperature combustion – which is the prime objective – but where we can have control over ignition. The other means are a better combination of how you inject the fuel, when you ignite it, how you ignite it, what the constituent gases are going on, how much recirculated exhaust gas, what the temperature is. Spray guided direct injection helps run it cooler, but it is employed stoichiometrically at the moment. If I want to get better efficiency from the engine that means running it lean, but if I run it lean how do I get to a temperature that does not produce NOx.
One of the developments being reported is that Mazda is looking at adiabatic engines as the third generation development of their Skyactiv engines. Does that report reflect the need to change the thermoefficiency of the engine?
It does. When I first joined Ricardo, in the mid- to late-1980s, I did a whole load of work on ceramics in engines and thermo insulation and what it could deliver. It is very complicated to implement. It is not necessarily what you want to do. The challenge again is you do not want combustion temperatures to get too high, so if you thermally insulate everything you make the combustion temperature high but what we want to do is relatively cool temperature combustion but not lose heat through the cylinder walls and piston when the gas is expanding. Because that is energy lost.
Effectively we want zero heat transfer, so expanding gas is just pushing the piston down and we do not lose pressure because we are losing heat through the walls. So adiabatic engines are very complicated to implement. We are experimenting with thermal coatings that have very high thermal diffusivity – they change temperature very fast. What we really like is the wall temperature to be the same as the gas temperature. When you put the intake charge into the engine you want the walls to be cold, because if they are hot they warm the gas up and reduce its volumetric efficiency. When you combust you want the wall temperature to be the same temperature as the gas so it does not lose heat.
We have talked a lot about gasoline engines. What about diesel engines, do you see there is a future for them with all the negative noise that is coming from Paris and London on their environmental impact?
Particulates are interesting. Since 2007, they have been fitted with particulate traps so particulate emissions from diesel are now lower than gasoline. The issue is more associated with the legacy fleet. With NO2 it is slightly different, because as we have improved our efficiency we are producing a bit more NO2 from engines, but Euro 6 and Euro 7 will substantially reduce NO2. Therefore, we think the diesel issue now is a phase we are going through because of legacy issues we have. We’ve made huge strides in reducing CO2 emissions, a lot of which has come from diesel penetration, but air quality from diesels in legacy is not as good as gasoline but in the future the air quality will be as good from diesel.
In the UK, we have recently had a budget that has stripped away the differentiation in road taxes by CO2 band, were you surprised by that move?
Yes. There is a trade-off between two opposing views. One is the whole system was very complicated and there is a need to simplify it, make fewer bands etc. The other is the need to encourage people to buy low emission vehicles. How do you get the two to work together? Somewhere in the middle there is a balance, but the changes are a little bit too far towards the simplification argument.
We are seeing GPS used as part of the toolkit for reducing CO2, so how do you see vehicle connectivity affecting the business of reducing CO2?
It is a huge area. It impacts all of our businesses. There is vehicle technology, there is also the business of mobility – what is going on with Uber – what is the next part of the mobility ecosystem to be “Ubered”? That is a good question. What is the impact of the technology on vehicles? In addition, how will the technology develop? Then there is also connected vehicle technology where information is pulled in and sent out about where the vehicle is, what it is doing, where it is going, how it is performing – that gives us a huge opportunity to better manage the whole transport system and the question of taking responsibility away from the driver. The single most cost-effective thing we could do in terms of fuel economy is teach drivers how to drive efficiently. That will be difficult to implement. Therefore, we can design a system that will get them to drive as efficiently as possible based on external data. We can do it, but how acceptable will it be to the consumer?
One area that can really be described as “low-hanging fruit” is platooning for trucks. They already do it informally and independently on the motorways, but maybe not as safely as they could. If you were to couple those vehicles electronically, with a train driver at the front, you would get aerodynamic efficiency and safety benefits. And that is cheaper than investing in the rail network, which just does not work on a CO2 benefit basis.
Finally, what will the average driver be driving in Europe in terms of fuel, engine size, technology etc. in 2030?
It will be a lower carbon liquid that behaves pretty much like gasoline, it will have more electrification, but the majority of vehicles will still have an internal combustion engine. The power output will depend on how well we do with lightweighting. Specific power will go up because the engines will get smaller. Actual total power of the vehicle will probably go up a bit, but not substantially. The average car will still have 100kW+ of power, per litre the power will probably be over that mark.