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Modifications on 125hp Rand Cam Sliding-Vane Rotary Engine Nearing Completion

Ebco Industries, under contract to REGI US, is implementing the same set of modifications done on the 42hp Rand Cam sliding-vane rotary engine on the diesel, 125hp version of the Rand Cam. (Earlier post.)

The modifications include vane design to eliminate sealing and six additional cam designs with a special coating to ensure durability. The company expects these to be complete within 30 days, and will then begin an engine testing program to assess endurance, maintenance factors and fuel efficiency.

The 42hp version earlier entered testing for a genset application for a series hybrid vehicle and for an unmanned aerial application.

Invented by James McCann in 1983, the Rand Cam uses a disk-shaped rotor with two or more axial vanes mounted perpendicular to the direction of rotation. The vanes slide back and forth against cam surfaces to alternatively expand and contract the chamber volume.

Through the process of these sliding vanes, combustion chambers form between the rotor, stator walls and vanes where the fuel/air mixture is injected, compressed, combusted and exhausted. (Sealing is an issue that Rand Cam is working to resolve with the modifications.)

Increasing the number of vanes increases the number of combustion events throughout a revolution. The original Rand Cam had two; the current version has 12.

The engine operates at lower speeds than a typical Wankel engine (less than 2,000 rpm) and at higher compression ratios: 15 and 20 to 1.

The engine is compact (the 42hp diesel is 6" in diameter and 6" long), and offers 30% volume efficiency, according to the company, compared to the Wankel engine’s 10% volume efficiency.

Comments

Rafael Seidl

A very interesting design, but there are an awful lot of sliding surfaces that all have to seal well to maintain a compression ratio as high as 20.

Oiling will have to happen by adding a small amount to the fuel, as with two-strokes gasoline and all Wankel rotary engines. This leads to a rather high consumption of light oil. Coking of the exhaust port could be a problem. Confusingly, their animation implies the chamber ends featuring the undulating surfaces are rotating - while designating the central portion as the rotor (which it presumably is).

The are also hush-hush about their injector geometry - the tips are each passed 12 times per rotation by the ends of the vanes, which drag thin oil films which would be prone to coking. The quality of the seal near the injector tip would be reduced. Of course, they may have chosen indirect injection or even an HCCI combustion process.

Another issue is how the rotor and its vanes are cooled. All in all, this is a daunting engineering challenge.

Robert Schwartz

Has anybody seen a live working engine?

Nick

Got the their website; they have a video of a bench test.

Ash

But what does it weight?

tom deplume

Wouldn't the 350 bar pressure of diesel injectors easily prevent coking from clogging injectors? A buildup of a thin layer of graphite could be the vane lube strategy.

Barry R. Guthrie

Another big problem with this engine is the combustion duration is very short and incapable of complete combustion before the exhaust.

Heat transfer into the rotor structure is very difficult. There would be thermal expansion problems.

The friction from all the sealing surfaces plus 12 vanes is vary large.

The centrifugal radial forces plus axial vane forces produce high degree of stress on the vanes and new cams.

I don't see any benefits to this engine except that it could have a very small diameter for military UAV applications, but the surface cooling, exhaust, and friction losses would reduce the BTE so much that any utility would still be questionable.

jb


Oiling will have to happen by adding a small amount to the fuel, as with two-strokes gasoline and all Wankel rotary engines.

I thought modern wankels such as the ones used in the mazda sportscars have solved this problem by having IIRC ceramic rotor edges.

Osama Al hawaj

There is an alternative design to this engine concept whereby the intake, exhaust ports and injectors are supplied through a central stationary core rather than through the cam surfaces ( see US patent application by Al hawaj). These improvements simplify manufacturing and prenvents possible coking of injectors.

Juan

Siendo niño alla por los años 60 empece a dibujar un motorcito de paletas basado en la turbina Convac
Pronto me di cuenta que no podia ser de un solo rotor tenia que ser por lo menos dos Uno grnade para admision y compresion y otro para combustion y fuerza . Bien Nunca lo pude construir ,hice uno que aun esta inconcluso . Razones de tiempo plata y ganas no me permitieron terminarlo Se que funcionaria ,pues cumple con los 4 tiempos del ciclo de otto Es un primo hermano de la turbina de gas axial En el mismo eje monta el compresor asi como el rotor motor
El encendido es por chispa y un carburador suministra los gases al compresor . Se puede hacer una version "diesel "inyectando elcombustible directamente en la camara de combustion Si alguien tuviera interes en esto que se contacte conmigo Gracias Juan

Juan

Siendo niño alla por los años 60 empece a dibujar un motorcito de paletas basado en la turbina Convac
Pronto me di cuenta que no podia ser de un solo rotor tenia que ser por lo menos dos Uno grnade para admision y compresion y otro para combustion y fuerza . Bien Nunca lo pude construir ,hice uno que aun esta inconcluso . Razones de tiempo plata y ganas no me permitieron terminarlo Se que funcionaria ,pues cumple con los 4 tiempos del ciclo de otto Es un primo hermano de la turbina de gas axial En el mismo eje monta el compresor asi como el rotor motor
El encendido es por chispa y un carburador suministra los gases al compresor . Se puede hacer una version "diesel "inyectando elcombustible directamente en la camara de combustion Si alguien tuviera interes en esto que se contacte conmigo Gracias Juan

Juan

Siendo niño alla por los años 60 empece a dibujar un motorcito de paletas basado en la turbina Convac
Pronto me di cuenta que no podia ser de un solo rotor tenia que ser por lo menos dos Uno grnade para admision y compresion y otro para combustion y fuerza . Bien Nunca lo pude construir ,hice uno que aun esta inconcluso . Razones de tiempo plata y ganas no me permitieron terminarlo Se que funcionaria ,pues cumple con los 4 tiempos del ciclo de otto Es un primo hermano de la turbina de gas axial En el mismo eje monta el compresor asi como el rotor motor
El encendido es por chispa y un carburador suministra los gases al compresor . Se puede hacer una version "diesel "inyectando elcombustible directamente en la camara de combustion Si alguien tuviera interes en esto que se contacte conmigo Gracias Juan

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