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THERMAX - cost effective hydrogen hybrid engine

THERMAX is a dedicated hybrid system of the future able to consume the most abundant element in the universe, which is hydrogen.

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THERMAX - cost effective hydrogen hybrid engine

  1. 1. 1 Cost effective hydrogen hybrid engine-THERMAX Introduction Generally, current hybrid vehicles have a high cost due to the very complex construction or the combination of a conventional or slightly modified powertrain with an additional electric transmission. Most systems use a gearbox or a dedicated power split mechanism that is complicated and expensive. In most cases, the additional cost of technology is not recovered even at the end of the vehicle's life. Also the current hybrids use conventional fuels and are not adapted to the “zero emission future”. For these reasons, hybrid vehicles still have a limited spread although they are advantageous in terms of emissions and fuel consumption compared to conventional ones. In conclusion it is necessary to design a dedicated hybrid system of the future to consume the most abundant element from the universe, which is the hydrogen. THERMAX in range extender applications THERMAX has a similar configuration with a “conventional” free piston engine but modified to transmit its power to a rotating electric machine in order to create an attractive new type of range extender.
  2. 2. 2 THERMAX employs two axially disposed stepped pistons, connected between them by a stiff rod and forming as such an innovative type of two-headed piston. The solid piston transmits its reciprocating motion by a single conventional connecting rod to a conventional crankshaft located in the space formed between the two stepped pistons, respectively in the middle zone of the engine. The crankshaft has its axis perpendicular on the axis of the two stepped pistons. The small portion of every stepped piston, named motor piston, works in a conventional way as the movable wall of the combustion chamber. The stepped or enlarged diameter portion named pumping piston, operates in an axially aligned cylinder, named pumping (supercharging) cylinder. The fresh air enters the pumping cylinder on the “down- stroke” of the piston using some flexible inlet valves and is compressed on the “up-stroke”, being delivered through a transfer pipe. The transfer pipe makes the connection with the combustion chamber of the opposite cylinder.
  3. 3. 3 The rotating masses of the engine are balanced by means of counterweights which oppose the centrifugal force. The inertia forces, caused by the solid piston (or the oscillating masses), are mostly balanced by the pressure existent in the opposite combustion chamber and by the compression pressure existent in the opposite pumping cylinder. These forces are directly transmitted from one stepped piston to the other using the stiff rod(s). Consequently, the connecting rod and the crankshaft are forced to transmit the useful work of the engine and can be sized properly with this considerable diminished stress (the connecting rod and the crankshaft are solicited by the inertia forces only in the starting conditions when the engine speed is very low and these forces are proportionally lower). Due to the special balancing solution, the mass of the solid piston does not limit the engine speed and consequently it can obtain a high level of power density. It is a very simple and cost-effective solution because every two stepped piston uses only one connecting rod and the crankshaft has only one crankpin (only three parts in motion). The stroke to bore ratio can be achieved in the range of 0.7-2 because the pistons are interconnected in the most convenient zone, respectively using the stepped portion which has a large diameter. The connecting rod and the crankshaft transmit the useful work of the engine and can be sized properly. Having an efficient scavenging process this engine can operate with hydrogen “lean” mixture and the fuel consumption can be significantly lower. The scavenging pump
  4. 4. 4 and the crankshaft mechanism are separated and consequently the lubrication problem disappears. There is no oil burned in the cylinder, lowering the HC emission and the soot deposits. Slide bearings for crankshaft and connecting rod can be used. Also using the stepped pistons and the control of the exhaust timing a supercharger effect is obtained and consequently the power density is increased. The foot print of the engine becomes much smaller and the weight, the engine’s cylinder displacement and combustion chamber volume can be reduced. The size of the engine is greatly reduced relative to the size of the vehicle in order to minimize the effect of the engine friction losses. This in turn improves vehicle fuel economy. The number of the main parts in motion (only 3 for each double cylinder) are reduced which improves the durability and reliability of the engine and respectively that of the range extender. The THERMAX hydrogen range extender can be used in many applications in aerospace, automotive or naval sectors, as well as for stationary constructions. Series-parallel hybrid THERMAX for automotive applications With THERMAX we propose a series-parallel plug-in hybrid system replacing the traditional transmission and adding the benefit of pure EV mode. What is unique is that the system manages to create direct drive to motor axle from the combustion engine, positioned transversally with its crank, without the need of multitude gears or other traditional types of variable transmissions, with inherently
  5. 5. 5 high energy losses. In this case the differential, beside its basic role, represents also the splitting mechanism. In parallel with THERMAX the system uses two reversible electric machines and a battery which supply the system when the IC engine is interrupted. The electric machines and the IC engine are arranged, in conjunction with control circuitry, to effect the starting and running of the vehicle at both its slower and higher speeds or when the battery is more than 1/2 charged, whereas the IC engine is adapted to take over and operate the vehicle at predetermined higher speeds in those circumstances where the battery is less than 1/2 charged. Charging of the batteries is normally effected by the use of commercial electricity, but may also be effected by the electric machine powered from the internal combustion engine, while in
  6. 6. 6 motion or stationary. A pure electric operation is also available for short distances (50 km). The described hybrid propulsion system can be used on autonomous or semi- autonomous vehicles as they allow the torque to be adjusted automatically according to the outside conditions or/and the user's desire. The new plug-in series-parallel hybrid powertrain eliminates the gear box or any power-split dedicated device without affect the performance of the vehicle. This allows reducing cost which is one of the biggest issues for the hybrids commercialization. The new drive system is less complex and requires a low maintenance level. The energy utilization of the vehicle and the thermal efficiency of the engine is high, the mechanism of the vehicle is simplified, for example a pedal clutch, a transmission and a transfer case are cancelled, and therefore the failure rate and manufacturing cost of the vehicle and the complexity of a control system are reduced, the safety factor is improved, and the product has high performance cost ratio. Contacts: liviu.giurca@micortec.com michael.soimar@micortec.com URL: https://micortec.com/quasi-free-piston-range-extender/

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