Engine derived from air-con compressor design

[Leo]

The rotary air-con compressor in our car is more efficient and compact as compared to the old design (20+ years ago) that was similar arrangement as in RC engine (piston movement is 90 degrees wrt the shaft).
The rotary air-con compressor is actually without the rotor as in those rotary engine in Mazda RX8, instead they got 3 pairs of pistons (6 pistons) moving in the direction along with the shaft via some cam arrangement.

The point is,

Why RC engine can't be derived from the same design? Leave the efficiency aside, at least they could obtain the compactness as in elec motor.

Pls advise

[Adrianli]

Fuel Consumption =

Many moving parts =

More maintenance =



Sweet sound of rotary engine =


I love the sound of screaming engines!!! But never the cleaning upo after.

[cdckjn]

Wankel engine

extracted from http://en.wikipedia.org/wiki/Wankel_engine

Wankel engines have several major advantages over reciprocating piston designs, in addition to having higher output for similar displacement and physical size. Wankel engines are considerably simpler and contain far fewer moving parts. For instance, because valving is accomplished by simple ports cut into the walls of the rotor housing, they have no valves or complex valve trains; in addition, since the rotor is geared directly to the output shaft, there is no need for connecting rods, a conventional crankshaft, crankshaft balance weights, etc. The elimination of these parts not only makes a Wankel engine much lighter (typically half that of a conventional engine of equivalent power), but it also completely eliminates the reciprocating mass of a piston engine with its internal strain and inherent vibration due to repeated acceleration and deceleration, producing not only a smoother flow of power but also the ability to produce more power by running at higher rpm.

Yes your fuel consumption is higher due to the higher power per CC compared to the normal 4-stroke Otto engine. Not really so many moving parts as it has only one big moving part, maintenance is necessary to ensure proper sealing as the rotor rotates in the chamber.

Fuel Consumption =

Many moving parts =

More maintenance =



Sweet sound of rotary engine =


I love the sound of screaming engines!!! But never the cleaning upo after.

[Leo]

The RCV engine (JH had them before) is by far the closest of what I want, still used the conventional round piston, hence without the leaking problem of Wankel rotary.
However, the RCV used gear 2:1 to convert the piston reciprocating along the shaft and valve timing for 4 strokes. Due to the gear ratio, they need very big prop, beside the noise from the gear is not very pleasant.

[Leo]

The RCV engine (JH had them before) is by far the closest of what I want, still used the conventional round piston, hence without the leaking problem of Wankel rotary.
However, the RCV used gear 2:1 to convert the piston reciprocating along the shaft and valve timing for 4 strokes. Due to the gear ratio, they need very big prop, beside the noise from the gear is not very pleasant.

Oh, I found the compressor cross section

[Leo]

Question is too difficult to have an reasonable answer?

[Leo]

Question is too difficult to have a reasonable answer?

[X34]

The layout you wanted would be very similiar to a radial engine. Available from OS, 3W. All you need is to built larger models to accomodate the engines.

Secondly, there is a heat problem, aircon compressor generate heat by compression and engines generate heat by chemical reaction which is much higher temp than compressing gas.

Is just a question of price/performance.

As to the RCV gear noise - some shims to get the gear meshing correct will help reduce the noise.

I hope the above answers your question.

Cheers

[AceViperX]

The rotary air-con compressor in our car is more efficient and compact as compared to the old design (20+ years ago) that was similar arrangement as in RC engine (piston movement is 90 degrees wrt the shaft).
The rotary air-con compressor is actually without the rotor as in those rotary engine in Mazda RX8, instead they got 3 pairs of pistons (6 pistons) moving in the direction along with the shaft via some cam arrangement.

The point is,

Why RC engine can't be derived from the same design? Leave the efficiency aside, at least they could obtain the compactness as in elec motor.

Pls advise

An aircond compressor doesn't create kinetic energy from other source but rather its the opposite. It uses kinetic energy to compress the expanded freon gas in the aircond pipes back into liquid state. So how this can be applicable for RC use I don't know. It can't be compared to a piston combustion engine.

[Leo]

An aircond compressor doesn't create kinetic energy from other source but rather its the opposite. It uses kinetic energy to compress the expanded freon gas in the aircond pipes back into liquid state. So how this can be applicable for RC use I don't know. It can't be compared to a piston combustion engine.

Of course we understand how the aircon system and compressor works. Thks anyway.

Sorry I didn't make it clear what I mean. I am exploring some new ideas of new engine layout with compactness.
In principle, Engine and Compressor are the same but reverse in the process. i.e Hot expansion air pushes the piston vs move the piston to compress the air. Hence the engine and compressor should be able to have the same layout.

Normal round piston engine, the piston reciprocating direction is "L" shaft axis. This is the same for the OS radial engine ( Many "L" with common shaft). The piston rod and crank will then translate the piston reciprocating direction to shaft rotation (Linear to rotation)

Whereas in the aircon rotary compressor layout, the piston reciprocating along the shaft axis and there is not crank to translate the rotation to linear motion, but instead they use a tilted disk for the same function(see my attach. section view for better understanding).

So the key points are,
1. normal engine uses crank -> engine layout is "L" (radial engine layout is "T")
2. rotary aircon compressor uses tilted disk -> the layout is "="

Heat is the same problem for all engines, so as long as the engine body designed with sufficient fin (same as in RCV engine), problem could be solved.

Anyway, thks for all the inputs.