Here's some interesting gas-flow tech: http://www.chengfluid.com/flow_conditioner/
Click on 'LAD' ( large angle diffuser) - it appears this design would enable much more compact tuned pipes for 2Ts.
Muniix wrote: You seem to be completely forgetting how one would approach the design of an engine with a Bishop Rotary valve.
Given the extensive knowledge gained during the CFD analysis of the BRV, the windows will be the full length of the bore minus a few mm, and the width will be determined by flow requirements for the engines operating range. The flow coefficient is the important issue, it is not just port area.
One would have again done some CFD to optomise this. But essentially is depends on the flow coefficient through the window and the valve as a whole, that is why the BRV has the throat to increase the pressure to avoid seperations as it turns around to flow into the cylinder.
Something that has never been done on your rotary valve, If I were you I'd be setting up Stanfords SU2 cfd code and doing some optimisation, You really need to work out how to get the air flow turned into the cylinder through your valve without restricting it. Some streamlines and a real idea of what the flow will actually look like, and its coefficient. Bishop valves actually flow better in higher bsr engines at equal cc's.
tuned pipes require inconvenient path lengths because the path lengths determine the time taken for each stage of the 'tuned exhaust' pressure cycleJ.A.W. wrote:Here's some interesting gas-flow tech: http://www.chengfluid.com/flow_conditioner/
Click on 'LAD' ( large angle diffuser) - it appears this design would enable much more compact tuned pipes for 2Ts.
Tommy Cookers wrote:tuned pipes require inconvenient path lengths because the path lengths determine the time taken for each stage of the 'tuned exhaust' pressure cycleJ.A.W. wrote:Here's some interesting gas-flow tech: http://www.chengfluid.com/flow_conditioner/
Click on 'LAD' ( large angle diffuser) - it appears this design would enable much more compact tuned pipes for 2Ts.
so there's no scope for shortening the exhaust system
Some interresting idea may be to use the Mahle Jet Ignition, should work on both two stroke and four, it just needs the right pressure action to exhange the gasses between pre and main chambers. Of note the Mahle TJI was developed by Oz engineer Dr. William Attard here is Oz for some time and then completed at Mahle powertrain in the UK. He also worked at Bishop on the rotary valve, the person who did the CFD on the Bishop now works at Memjet creators of the worlds fastest colour inkjet printer (one a4 page / second) he was also the first to successfully model tumble breakdown to turbulence showing the energy cascade theory. The advantage of the TJI is its ultra lean combustion at lambda's up to 1.85 with no loss of bmep and sustains combustion to 2.1 and 2.35 with liquid petroleum gas, has a thermal efficiency up to 46% thou that includes pumping improvements through reduced intake throttling due to increased intake volume, one paper quotes ~38%.J.A.W. wrote:This current 2T research project into 'clean,green' DI developments gives some useful data..
http://www.mtukrc.org/download/idaho/id ... r_2016.pdf
Yeah, if of interest, check back to page 66 of this thread, ( 'bout 1/2 down) I linked an Australian ( RMIT) academic paper considering the potential value of 'jet ignition' DI - for 2T use.Muniix wrote: Some interesting idea may be to use the Mahle Jet Ignition, should work on both two stroke and four, it just needs the right pressure action to exhange the gasses between pre and main chambers. Of note the Mahle TJI was developed by Oz engineer Dr. William Attard here is Oz for some time and then completed at Mahle powertrain in the UK. He also worked at Bishop on the rotary valve, the person who did the CFD on the Bishop now works at Memjet creators of the worlds fastest colour inkjet printer (one a4 page / second) he was also the first to successfully model tumble breakdown to turbulence showing the energy cascade theory. The advantage of the TJI is its ultra lean combustion at lambda's up to 1.85 with no loss of bmep and sustains combustion to 2.1 and 2.35 with liquid petroleum gas, has a thermal efficiency up to 46% thou that includes pumping improvements through reduced intake throttling due to increased intake volume, one paper quotes ~38%...
The CFD analyses of the BRV showed exactly how it would flow and did flow and the difference was less than 1% to experimental. Nowhere was a rpm of 30,000 mentioned, 20K rpm was the highest. They knew exactly what size valve was needed to support peak torque at a specific rpm. CFD and experimental matched up at speeds they were done at, giving the correct cylinder pressure and flowrate. CFD was very accurate and successfull.manolis wrote:Hello Muniix
You write:
“You seem to be completely forgeting how one would approach the design of an engine with a Bishop Rotary valve.
Given the extensive knowledge gained during the CFD analysis of the BRV, the windows will be the full length of the bore minus a few mm, and the width will be determined by flow requirements for the engines operating range. The flow coefficient is the important issue, it is not just port area.
One would have again done some CFD to optomise this. But essentially is depends on the flow coefficient through the window and the valve as a whole, that is why the BRV has the throat to increase the pressure to avoid seperations as it turns around to flow into the cylinder.
Something that has never been done on your rotary valve, If I were you I'd be setting up Stanfords SU2 cfd code and doing some optimisation, You really need to work out how to get the air flow turned into the cylinder through your valve without restricting it. Some streamlines and a real idea of what the flow will actually look like, and its coefficient. Bishop valves actually flow better in higher bsr engines at equal cc's.”
The CFD analysis is useful, but not a panecea.
Unless I am wrong, according the theoretical analysis of the Bishop rotary valve, their engine would breath freely till 30,000 rpm.
In practice the limit was by far lower (a little more than 20,000rpm).
On this reasoning, the specific CFD analysis was not a successful one.
Nevertheless, the Bishop rotary valve engine proved in practice substantially better, as regards the peak power, than the best poppet valve engines.
Worth to mention: besides the port area and the flow coefficient it is also important the compact shape of the combustion chamber and the central location of the spark plug(s), which are not among the characteristics of the Bishop BRV.
Despite the superiority of the BRV in the F1, it is disappointing that the Bishop rotary valves (which is a version of the Cross rotary valve) was never used in a car or motorcycle.
The PatRoVa:
http://www.pattakon.com/PatRoVa/PatRoVa_ports.jpg
combines large port area with good coefficient of flow, with compact combustion chamber, with central location of the spark plug and/or injectors, etc.
Thanks
Manolis Pattakos
Thanks for everything, I've looked at your spreadsheet and put in the changes, one thing i've noticed is it is effectively rotating backwards, which on a normal non offset engine being symetrical at least either side of tdc until the pistons reach half stroke, long before 90 degrees, peak speed is around 77degrees, the con rod is moving away equally in each direction of rotation. I coded to be observing the left crankshaft clockwise starting from tdc.J.A.W. wrote:Here is a patent of a twin crank/rod single piston set up: http://www.google.com/patents/US5595147
The inventor was familiar with blade & fork conrods from Harley-Davidson engines ( he did a V-triple version).
AFAIR, the rod angularity proved problematic, even when others tried rods curved like a sabre's blade.