Pistonless Pumps: Working, Advantages, Disadvantages, and Applications

Published by Admin on 02/01/202302/01/2023

Introduction Of Piston Less Pump

With the advent of low-cost ablative liquid-fuelled rocket engines and composite tanks, the problem of propellant pressurization becomes the last stumbling block to affordable launchers. Turbo pumps are currently used in the majority of launch vehicles, although piston pumps have been designed and flown1 and pneumatic diaphragm pumps have been proposed by Godwin 2 and Sobeys. 3 The pump considered herein is much simpler and less expensive than a turbo pump.

The pump concept is simple: instead of having the whole fuel tank pressurized to the 2-7 MPa, the main tank is at pressurized to 100-400 kPa and it is the drained into a pump chamber and the pump chamber is pressurized to deliver fuel to the engine.The auxiliary chamber supplies fuel while the main pump chamber is being the refilled. This type of pump has benign failure modes, can be installed in the fuel tank to minimize vehicle size and uses inexpensive materials and processes in its construction. With the right choice of materials, the pump will be compatible with all common rocket fuels.

Piston Less Pump Weight

One of the most important benefits of this pump is the low weight for a given propulsion system. The weight may be calculated by determining the weight of the pump chambers and the valves. For valves or chambers, the weight is found to be proportional to the flow rate and the pressure. The weight of the chambers can be easily figured as spherical or cylindrical pressure vessels. The weight of the fluid and pneumatic valves may be estimated based on the weight of commercially available check valves and actuated butterfly valves.

Testing with Liquid Nitrogen

The pump has been tested with the liquid nitrogen and it is the works well. Figure shows the test in progress pump is inside the tank. When the pumping liquids near the boiling point liquid must be prevented from the boiling excessively during the vent cycle. This may be achieved by the venting through a back pressure regulator or by the shutting vent when the pump chamber pressure falls below a present the level. This is particularly important when pump is the used at altitude or in the space.

Pump design Considerations

Although the pump design is simple, the optimization process is not. Making the pump cycle as fast as possible would make it lightweight, but higher flow velocities cause problems. A pump with a small chamber must be filled and vented quickly, with minimal head loss through the gas and liquid valves and plumbing. The maximum inflow rate is limited by the main tank pressure (usually about 300 kPa) and the area of the inlet valves. Also, if the inflow velocity is too high, the propellant will be aerated, which may cause problems with the engine.

The allege volume in the pump chamber should be small to minimize gas usage, but if it is too small, there will be a loss of propellant through the vent. Furthermore, the pump cycle frequency must not excite any combustion instabilities in the rocket motor. The second generation pump design process started with the realization that by placing the pump chamber inside the main tank and increasing the size of the check valves, the pump can be filled very quickly. Once the pump is being filled much faster than it is emptied, it becomes clear that the two chambers do not have to be symmetrical.

Necessity For Piston Less Pump

The turbo pumps used in the rocket are very heavy containing many rotating parts by which there are more frictional losses which the more consumption of fuel there by the decreasing efficiency of the engine .Also the maintenance of such pump is the very important factor since the rocket has to remain stable in the space is difficult and require complex the methods for it.

If this pump gets any fault then it’s the reappearance requires long time and also it is the very hectic task. So there must be such a device which overcomes all the drawbacks of the turbo pump as the above. The pistonless pump is the solution for problems faced by the using turbo pumps. They have only a drawback that they supply fuel with the less pressure as compared to turbo the pumps.

Abstract

A positive displacement piston less rocket fuel pump uses two pumping chambers alternately filled and pressurized in sequence to maintain a steady flow of pressurized propellant to a rocket engine. This pump fills the gap between pressure fed and turbo pump rockets by making a lower cost rocket feasible without the weight of a pressure fed design or the high cost and complexity of a turbo pump. The pump, combined with a lower pressure tank, saves up to 90% of the tank weight in a comparable pressure fed system. Thrust to weight ratios are calculated for the pump using typical fuel combinations.

For a 2219 aluminium LOX/RP-1 pump at 4 MPa the thrust/weight ratio of the pump is ~700. Design and test data for a prototype which pumps water at 3.5 MPa and 1.2 kg/s is presented. The simple construction of the pump allows for low cost, reliable propulsion systems. This pump has been tested with the liquid nitrogen and the kerosene. It has also been used to the pump kerosene with a rocket the engine.

Working Piston Less Pump

Rocket engines requires a tremendous amount of the fuel high at high pressure .Often the pump costs more than the thrust chamber. One way to supply fuel is to use the expensive turbo pump mentioned above another way is to the pressurize fuel tank. Pressurizing a large fuel tank requires a heavy the expensive tank. However suppose instead of the pressurizing entire tank the main tank is drained into a small pump chamber which is the pressurized. To achieve steady flow the pump system consists of two pump chambers such that each one supplies fuel for ½ of the each cycle. The pump is powered by pressurized gas which the acts directly on the fluid.

For each half of the pump system, a chamber is filled from the main tank under low pressure and at a high flow rate then the chamber is pressurized and then the fluid is delivered to the engine at a moderate flow rate under high the pressure. The chamber is then vented and the cycle repeats. The system is designed so that the inlet flow rate is the higher than the outlet flow the rate. This allows time for the one chamber to be vented refilled and pressurized while the other is the being emptied. A bread board pump has been tested and it works the great .A high version has been designed and built and is the pumping at 20 gm. and the 550 psi.

Advantages Of Piston Less Pump

Nearly all of the hardware in this pump consists of the pressure vessels, so weight is low. There are fewer than 10 moving parts and no lubrication issues, which might cause problems with the other pumps. This pump’s design and construction are simple, and no precision parts are required.This device has an advantage over the standard turbo pumps in that the weight is about the same, the unit England test costs are less, and the chance for catastrophic failure is less.

This pump has the advantage over pressure-fed designs in that the weight of the complete rocket is much less, and the rocket is much safer because the tanks of rocket fuel do not need to be at high pressure. The pump could be started after being stored for an extended period with high reliability. It can be used to replace turbo pumps for rocket boosters in the open. Or it can be used to replace high-pressure tanks for deep space propulsion. It can also be used for satellite orbit changes and station keeping.

Disadvantages Of Piston Less Pump

The piston-less pumps have disadvantages along with their many advantages.

• They cannot pump to a higher pressure than the drive gas area ratio, which is 1:1.
• They cannot use either staged combustion or the expander cycle.
• A gas generator cycle is also difficult to integrate with the piston-less pump.
• The generated gas must be chemically compatible with both propellants.
• This gas generator lowers the ignition start period of the engine.

How It Works Piston Less Pump

• Drain the main tank at low pressure into a pump chamber.
• Pressurize the pump chamber and feed to the engine.
• Run two in parallel, venting and filling one faster than the other is emptied.
• Overlap allows for steady flow and pressure.

Go to Market Strategy

• Rocket Scientists are risk averse. Piston less pump must be proven to be considered.
• First step is to integrate the Piston less pump with engines of increasing thrust levels to prove scalability.
• Next step is integrate and test fly in a small to moderate size vehicle for a reference mission
• Sales opportunities happen when a new vehicle is on the drawing board, or when an existing vehicle explodes spectacularly due to turbo pump problems.

Pump Animation

• Pump starts with the both chambers full in the thermal equilibrium.
• One chamber is the pressurized and fuel is the delivered until level gets low in that chamber.
• The pressure is applied to the both chambers and fuel is the delivered briefly from both the Chambers.
• Then the nearly empty chamber is the vented and refilled and the cycle repeats.

Solution Of Piston Pump

• Performance equivalent to or better than gas generator turbo pump systems
• Inexpensive materials and processes. Lowers vehicle cost.
• Safer: Failure modes are benign, main tank pressures are lower
• No precision parts. Inherent reliability.
• Robust system; can pass contaminants.
• One design will work with many propellants.
• 100% throttle cable
• Mass producible and scalable
• The transition from pressure-fed static test to pump-fed is simple and quick.

Applications Of Piston Less Pump

1. Deep Space Propulsion

NASA has a need for high-power propulsion to land and operate spacecraft on the moons of Jupiter and beyond. This pump would allow these missions to go forward due to the lower weight of the fuel tanks. For example, to land on Europa with a hydrazine monopropellant rocket, a pump-fed design would save 80% of the tank weight compared to a pump-fed design. Further weight savings could be achieved by heating the pressurized gas more because the pressurized gas would not be in contact with the propellant for more than a few seconds. Capacity in the additional chamber could be increased, reducing engine weight and improving performance. 

2.X Prize Vehicle Fuel Pump Application

For X-Prize competitors, the fuel pump will reduce the cost and increase the safety and reliability of their amateur-manned vehicles. Sitting on top of tonnes of rocket fuel is dangerous enough; sitting on top of tonnes of rocket fuel at high pressure is even more so. Many of the competitors plan to use hydrogen peroxide (HTP) and jet fuel to power their rockets. When the pump is used to pump hydrogen peroxide (HTP), it can decompose some of the fuel in a gas generator to run the pump. This saves a considerable amount of weight pressing and main tankage. In addition, the cost of the low-pressure tanks will be similar to the cost of the high-pressure tanks alone.

Conclusion

The most significant property of the piston-less pump that makes it different from a turbopump is the absence of a piston. This is the most unique technique. In comparison to the turbopump, this number of rotating parts is very small. Its setup is also very simple. It is also lighter than the turbo pump. As a result, it has fewer losses and improves rather than increases engine efficiency. It is also far more cost-effective than the turbo pump. The only drawback of a pistonless pump is that it cannot supply high-pressure fuel, and it also cannot have staged combustion or the expander cycle. Further, it has no vibration.