construction and working of a torque convertor in an automobile | torque convertor a type of fluid coupling

Torque converter

Torque converter is a type of fluid coupling that uses a fluid to transmit turning effort from the one shaft to another. It is a device which performs a function similar to that of a gear box, namely, to increase the torque while reducing the speed. A gear box provides only a small number of fixed ratios, but the torque converter provides a continuous variation of ratio from the lowest to the highest.The torque convertor is somewhat similar to a fluid fly wheel, but differs from it in one aspect, namely it has three principal components instead of only two.

01 - construction and working of a torque convertor in an automobile  - TORQUE CONVERTER OF AN AUTOMOBILE AN ESSENTIAL PART

Torque converter consists of

(i) The driving element or impeller or pump which is connected to the engine.

(ii) The driven element or rotor or turbine which is connected to the propeller shaft and

(iii) The fixed element or reaction member or stator which is fixed to the frame. The fixed element is responsible to cause a change of torque between input and output shafts. The fluid flywheel does not have any fixed member, as such cannot produce any change of torque.

Working of a torque converter

The three element torque converter can be seen in the picture. In the torque converter, torque multiplication take place in the following way. The oil leaving vanes hits the stator vanes. This oil is redirected into the pump vanes in a direction which helps the pump operation. This oil is again thrown into the turbine by the pump. In fact, this is a continuous process. The fluid pushing repeatedly on the turbine vanes increases the torque on the turbine. In many designs of torque converters, the torque is almost doubled. However, as the speed of the turbine approaches the speed of the pump, the increase in torque falls of gradually till it becomes 1:1. At this stage, the oil starts striking the rear faces of the vanes in the stator, thus making the stator to turn. Now the stator does not take part in torque converter action. Under these conditions, the torque converter simply acts as a fluid fly-wheel.

01 - TORQUE CONVERTER OF AN AUTOMOBILE - construction and working of a torque convertor in an automobile

The over running clutch or freewheeling device is used for mounting the stator. The spring loaded rollers in the freewheel allow the stator to freewheel when the oil starts striking the rear of the stator vanes. On the other hand, when the oil strikes the front of the stator vanes, it attempts to rotate the stator in the opposite direction. But this action locks up the freewheeling device and thus holds the stator stationary. Under such condition, the stator acts as a reaction member, and directs the oil leaving the turbine trailing edges in the proper direction before it enters the pump vanes.

construction and working of pistonless pump | pistonless pumps in aerospace technology

In-space propulsion systems generally use pressure fed systems that drive up tank cost and mass and limit engine performance and design choices. This paper describes a low cost pump technology, the pistonless pump, to improve performance and design flexibility and increase damage and fault tolerance.

Pump description

The pistonless pump is similar to a pressure fed system, but instead of having the a main tank at high pressure (typically 300-500 psi) the proposed pump system has a low pressure tank (5 -50 psi) which delivers propellant at low pressure into a pump chamber, where it is then pressurized to high pressure and delivered to the engine.

01 - LATEST SPACECRAFT TECHNOLOGY PISTONLESS PUMPS - CONSTRUCTION AND WORKING OF PISTONLESS PUMPS

Two pumping chambers are used in each pump, each one being alternately refilled and pressurized. The pump starts with both chambers filled. One chamber is pressurized, and fluid is carried to the rocket engine from that chamber.

(Step 1) the level gets low in one chamber. Then other chamber is pressurized and flow is thereby established from both sides during a short transient period.

(Step 2) until full flow is established from the other chamber. Then the nearly empty chamber is vented and refilled.

(Step 3) Finally the cycle repeats. This outcomes in steady flow and pressure. The pump is powered by pressurized gas which acts directly on the fluid. Initial tests showed pressure spikes as the pump transitioned from one chamber to the other, but these have since been eliminated by adjusting the valve timing.

This pump is more robust than a piston pump in that it has no high pressure sliding seals, and it is much less expensive and time consuming to design than a turbopump and a system which uses the pump has far lower dry mass and unusable residuals than turbopumps do.

Pump Technology Readiness Level

. It has been tested with water at 450 psi and 20 gpm, it has been tested 150 psi, and it has been used to pump kerosene at 485 psi and 20 GPM in an Atlas Vernier rocket engine test. Valves and sensors have been specified. Materials and manufacturing processes (standard welding and machining processes) have been identified, and vendors to fabricate such a system have been qualified .

Spacecraft Applications of the Pump

01 - LATEST SPACECRAFT TECHNOLOGY PISTONLESS PUMPS - CONSTRUCTION AND WORKING OF PISTONLESS PUMP

This pump offers substantial performance and flexibility improvements for a space vehicle such as the Crew Exploration Vehicle. Space vehicles currently use spheroidal tanks pressurized to 200-300 psi. These tanks are somewhat heavy, are very expensive and require propellant management devices to keep liquid propellant at the tank outlet for engine starting in a zero gee environment. The pump allows for lightweight, low-pressure tanks and the pump can be stopped with one chamber full of fuel so that when the spacecraft starts, the fuel will settle to the bottom of the tank and no PMDs are required in the tank. The spacecraft tanks need not be spheroidal, and options such as low pressure drop tanks, flexible composite tanks etc. become feasible. The low-pressure tanks can be lifted to LEO empty and then filled from the upper stage, thereby limiting the structural loads on the tanks. Low-pressure tanks can also be more easily jettisoned or connected, and low-pressure plumbing, valves and fittings are lighter, less expensive and more reliable. For lunar and mars missions, fuel can be pre-positioned by robotic spacecraft at the destination for the return trip. These tanks can be more easily integrated with the spacecraft, and the dangers associated with handling propellant tanks and transferring propellant are lower at low pressures. We imagine a system that utilizes aircraft drop tank style operations. Since ascent stages from the moon or Mars need not be streamlined, concepts for use of propellant produced locally on the moon or Mars may benefit from fiber reinforced external flexible bladder tanks. This will reduce delivered vehicle size and mass.

The pump works well at flow rates from zero to full flow, so it can be used to provide pressurized propellant for attitude control or for landing rockets, as well as for main engine burns. Because the flow and pressure are decoupled the pump uses no pressurant at zero flow. The pump can also be vented to a low pressure so as to reduce loads on propellant valves with seals subject to creep or degradation for long.

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