Construction and Working of Piston-less Pump | Piston-less Pumps in Aerospace Technology


Tags: Pump Chamber, Construction and Working of Piston-less pump, Piston-less pumps in Aerospace, Latest Spacecraft Technology Piston-less pump, How does a Piston-less pump works, Spaceship Propulsion, New Space Travel Technology


In-space propulsion systems generally use pressure fed systems that drive up tank cost, mass, limit engine performance and design choices. This concept describes a low cost pump technology “the piston-less pump” to improve performance, design flexibility. It also reduce damage and fault tolerance.

Latest spacecraft Technology Piston-less Pump description

The piston-less pump is similar to a pressure fed system. 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

How does a Piston-less pump works

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 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 turbo pump and a system which uses the pump has far lower dry mass and unusable residuals than turbo pumps do.

Pump Technology Readiness Level

Pump 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 Piston-less 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 and very expensive. It require propellant management devices to keep liquid propellant at the tank outlet for engine starting in a zero gravity environment. The pump allows for lightweight, low-pressure tanks and the pump stopped with one chamber full of fuel so that when the spacecraft starts, the fuel 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 lifted to LEO empty and then filled from the upper stage, thereby limiting the structural loads on the tanks. Low-pressure tanks more easily connected, and low-pressure plumbing, valves and fittings are lighter, less expensive and more reliable. For lunar and mars missions, fuel pre-positioned by robotic spacecraft at the destination for the return trip. These tanks more easily integrated with the spacecraft. 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.

Latest Space Craft technology

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 altitude control / landing rockets / main engine burns. Because the flow and pressure decoupled the pump uses no pressurant at zero flow. The pump vented to a low pressure. So as to reduce loads on propellant valves with seals subject to creep or degradation for long.

fluid flywheel of an automobile | construction and working of fluid coupling of an automobile

Fluid flywheel or fluid coupling

A liquid coupling is used to transmit engine turning effort (torque) to a clutch and transmission. The coupling is always a major part of the engine flywheel assembly. As such it is sometime called a fluid flywheel.

Construction of flywheel

The fluid flywheel details can be seen in the picture. It consists of two half dough nut shaped shells equipped with interior fins. The fins radiate from the hub, and thereby form radial passages. The areas of these passages, perpendicular to their centre line, are kept constant by a suitable design. Since the circumferential width of the opening close to the hub is less than that at the periphery, the radial size of the opening, close to the hub is made greater than that at the periphery.

01 - CONSTRUCTION AND WORKING OF A FLUID COUPILNG - HOW DOES A FLUID FLY WHEEL WORKS

One of the shells is fixed to the crankshaft of the engine and the other to the clutch/gearbox shaft. The two shells are mounted very close, with their open ends facing each other, so that they can be turned independently without touching. Housing surrounds both units to make a closed assembly. About 80 percent of the interior of the assembly is filled with oil.

Working of fluid flywheel

The driving unit, called impeller, is linked to the engine crankshaft. When the engine throttle is opened, the oil in the impeller starts moving. Due to the force of the rotating, trapped oil impinges on the fins of the driven unit called runner and causes it to move. In this way, the moving liquid transmits the engine power to the clutch driving plat or to any other unit to which the runner is attached. This happens without any metal contact.

In the actual units, the runner speed becomes almost equal to that of the impeller only under the best operating conditions, when the efficiency of liquid coupling is highest. But usually the runner speed is less than that of the impeller. The (speed) lag of the runner behind the impeller is known as slip. This (speed) slip varies with many factors such as engine speed, vehicle speed and engine and vehicle load.

01 - CONSTRUCTION AND WORKING OF A FLUID FLY WHEEL - HOW DOES A FLUID FLY WHEEL WORKS

Flywheel Torque

The slip is greatest with the vehicle at rest (ie runner stationary), and the engine throttle being opened to cause the impeller to start circulating the oil. Under these conditions, the oil moves in two general directions at the same time. It rotates at right angles to the shafts, i.e., undergoes rotary flow. The oil also circulates between the impeller and runner, i.e., undergoes vortex flow. When the rotary flow attains sufficient force and volume, it causes the movement of the runner.

The vortex flow is at right angles to the rotary flow. The vortex flow is produced by the oil trapped in the fins of the impeller. The oil flies out against the curved interior, because of centrifugal force. The centrifugal force directs the oil across to the runner, thereby returning it to the impeller in the region of the hub.

The vortex flow is maximum when the slip is 100 percent (runner stationary), and decreases as the runner speed approaches that of the impeller. This results from the centrifugal force produced by the oil in the runner, which moves out and opposes the vortex flow. At cruising speeds, there is little or no vortex flow because the centrifugal forces produced in the impeller and runner are almost equal. As such, the efficiency of coupling increases rapidly from zero at rest to nearly 99 percent at higher speeds.

Fluid Flywheels of an Automobile

The torque or turning effort delivered to the runner through the liquid is equal to the torque applied to the impeller by the engine. But the power received by the runner is always less than that furnished by the engine. The power losses in the coupling appear as heat, which is dissipated as the assembly revolves.

01 - CONSTRUCTION AND WORKING OF A FLUID COUPILNG - HOW DOES A FLUID FLY COUPLING

Advantages of fluid flywheel

An ordinary friction clutch would be damaged by prolonged slipping, with increased fuel consumption. But by prolonged slipping, the fluid flywheel will not suffer any mechanical damage. Although it may become so hot as to burn one’s hand if one touched it.

When a liquid coupling is used with a conventional clutch and transmission, it enables the driver to use the clutch and gears with less skill and fatigue than with an all mechanical linkage. Unskillful clutch engagement or selection of the improper gear will not produce any chattering and bucking. Any sudden load is cushioned and absorbed by the coupling so that dynamic stresses on the gear teeth of the transmission and rear (drive) axle are greatly reduced.

Liquid coupling at low speeds are not as efficient as mechanical clutch. As such it reduces engine braking when slowing down the vehicle speed, particularly during coming down a hilly track. Further, it requires higher speeds to start a vehicle by pushing or towing it.