[RahulNagaraj]

Speed of Air - an engine technologies company is said to have come up with a new design for their pistons which could help diesel engines to reduce particulate filters while also improving efficiency and performance. According to a media report, Speed of Air (SoA) is said to have taken inspiration from golf balls and introduced diesel engine pistons with dimples.



Dimples on a golf ball create a boundary layer by producing small turbulences at the surface. This boundary layer is what helps the golf ball reduce drag & retain its speed; translating to a longer distance of travel compared to a smooth ball. Similarly, in a combustion chamber, the dimples create a boundary layer with the fluids, which helps keep the fuel in suspension with the air, which leads to a better air-fuel mixture for burning.

The company has been experimenting with different textured pistons for quite a long time, before concluding that the dimpled texture of a golf ball works best. Today the company relies on computational fluid dynamics (CFD) to optimise its designs before using them in Powerstroke, Duramax and Cummins engines for medium-duty vehicles. SoA has further improved the design by having pressure release slots machined into the crown of the piston, which helps accelerate the burn of the air-fuel mixture and offers a quieter running engine in the process.

To prove it's working, the company compared a stock Cummins 5.9-litre engine to one with its pistons installed. The result was that the engine with SoA's dimpled pistons produced 15.5% more horsepower and a 15.2% rise in torque. The reports also stated that brake-specific fuel consumption was reduced by 3.2%, the opacity of exhaust dropped by 77.6%, NOx levels went down by 61%, exhaust hydrocarbons dropped by 32.5%, and CO2 levels were cut down by 41.4%.

Speed of Air is currently said to be concentrating on the commercialisation of its medium-duty engines. However, they could expand to offering petrol and racing engines with dimpled pistons in the future as well.

Source: MotorTrend

Link to Team-BHP news

[Turbohead]

Amazing concept! Wonder how it'll perform in the long run with deposit of soot on the surface. Will the dimples get covered completely thereby nullifying all the gains? Wonder what SoA got to say about it.

[NT_GT]

Originally Posted by RahulNagaraj

To prove it's working, the company compared a stock Cummins 5.9-litre engine to one with its pistons installed. The result was that the engine with SoA's dimpled pistons produced 15.5% more horsepower and a 15.2% rise in torque. The reports also stated that brake-specific fuel consumption was reduced by 3.2%, the opacity of exhaust dropped by 77.6%, NOx levels went down by 61%, exhaust hydrocarbons dropped by 32.5%, and CO2 levels were cut down by 41.4%.

Link to Team-BHP news

This is fantastic (and slightly unbelievable) improvement in every aspect. I am sure the idea is not new. The physics of the dimpled golf ball is taught to every science undergrads. The famous Mythbusters' dimpled car is also there. SoA must have added something extra.

[NiInJa]

Something does not seem right here. The performance gain and reduction in pollutants is too good for a such a simple solution that was missed by tech experts for more than 50-60 years of diesel engine's existence!

This tech should have been around before humans landed on the moon or before VW decided to rig their diesel vehicle's ECUs

[Kakashi91]

Just curious, as to how much would it increase the clearance volume in the cylinder. Ideally, one would want a clearance volume close to zero, but since it is not possible, one would try and reduce it as much as possible.

Clearance volume directly affects the compression ratio in the engine. So, with these indentations, the clearance volume would increase thereby reducing the compression ratio. Although, I understand that the negative effect from this would be offset from the better mixing of fuel and air in the cylinder.

But, what I don't understand is that the reduction in the NOx is said to be reduced by 61%! Now, NOx and other pollutants are not just measured at one condition, but with different duty cycles. Is this reduction by 61% compared to the current limits? Because that seems too good to be true. Also, it is accompanied by a huge reduction in the unburnt hydrocarbons. Now, both these pollutants are produced at exactly opposite conditions. In general, NOx would be produced when there is good combustion leading to high temperatures in the cylinder. Whereas, hydrocarbons would be left out through exhaust in case of incomplete combustion. One can't reduce both just through in-cylinder technololgy and one would need after-treatment devices. Anyways, that's my thought and would be more than eager to know your thoughts too!

[Sankar]

In 1999-2000 I did something similar to my then ride, dad's and now mine mighty 2 port 2-stroke bajaj chetak which was a daily as well as a sleeper test bed. My friends had 2stroke bikes (samurai, shaolin, shogun, RX100, KB125 etc) and had to keep up you know. The golf balled piston was one of the mods that I did (well, the thought behind it was the same golf ball theory) but it took too much work and effort to put a number of dimples on the piston with my then available hand tools. In the end with a host of many other mods (all internal nothing outside) including the dimpled piston the chetak did gallop and was quick and could easily clock its speedo fast.

Some tuners do the same on the intake manifold (to increase intake velocity by using boundary layer formation due to the dimples) and the runners and for the same reason. Regarding soot formation and carbon deposits it seems that the dimples aid in a cleaner combustion resulting in less soot formation and thus lower carbon deposits on the piston. This is by creating turbulence in the combustion chamber aiding better mixing of air and fuel.

Btw why is this news popping up now? This came up couple of years ago https://www.dieselarmy.com/tech/can-...oving-forward/

Btw also read about Somender Singh in the below link. He has been mentioned in Tbhp before but the topic is related ie., combustion chamber modification. https://somender-singh.com/